TWI891704B - Lance for immersion of a probe into molten metal, sublance and protective device - Google Patents

Abstract

The present invention concerns a lance composed of a top lance (1t) and of a sublance (2) coupled to the top lance (1t), which forms a shoulder (1s) between the top lance and the sublance. The sublance (2) of the present invention is provided with a protective device (3) comprising a coupling end (2c) opening to the cavity (2v), wherein, ● when at rest, the protective device (3) is in an initial configuration characterized by an outer maximum diameter (D3o) which is not more than 10% larger than the diameter (D2) of sublance (2) (D3o≤1.1D2), ● when the sublance (2) is coupled to the lance the protective device (3) contacts the shoulder (1s) and is deformed into a deformed configuration, forming a surface impervious to molten metal and slag, which spans over a whole area of the shoulder (1s).

Description

Blowpipe, auxiliary blowpipe and protective device for immersing the probe into molten metal

The present invention relates to a blowpipe for immersing a probe into molten metal contained in a metallurgical vessel, such as a converter for steel production. Types of blowpipes include a reusable top blowpipe that is not in contact with the molten metal, and an auxiliary blowpipe coupled to the top blowpipe and holding at its free end a probe for measuring a parameter of the molten metal, and/or a sampling tool for collecting a sample of the molten metal. In use, the auxiliary blowpipe is partially immersed in the molten metal and is disposable. Since the diameter of the top blowpipe is larger than the diameter of the bottom blowpipe, the connection between the top blowpipe and the auxiliary blowpipe defines a shoulder. If molten metal splashes onto the shoulder of the top blowpipe, once solidified, it can jeopardize the coupling of a new auxiliary blowpipe to the top blowpipe. This invention proposes a secondary blowpipe equipped with a protective device that prevents molten metal or slag from splashing onto the shoulder area of the top blowpipe. To facilitate storage of the secondary blowpipe in an existing material rack and to enable manipulation of the secondary blowpipe by a robot arm without requiring changes to the robot arm's programming, the diameter of the protective device stored in the material rack is similar to that of the secondary blowpipe.

Metal production processes take place at high temperatures in metallurgical vessels, where the molten metal and/or slag undergo chemical or physical reactions, whether desired or undesirable, during the residence time or transfer from one vessel to another. Since the properties of the final metal product produced thereby depend largely on the process conditions, including temperature, pH and whether desired or undesirable chemical or physical reactions occur, it is important to measure such parameters and collect samples in situ for further characterization. This is usually done with a blowpipe, which comprises a top blowpipe that is retained away from the molten metal or slag and a secondary blowpipe coupled to the top blowpipe and provided with a probe and/or sample collector at its free end. The top blowpipe is usually made of metal or polymer and is reusable. The secondary blowpipe, on the other hand, is usually made of cardboard and is disposable.

For example, steel can be produced from carbon-rich molten pig iron by the oxygen converter process, in which oxygen is blown through the molten pig iron using a blowpipe (12) to reduce the carbon content of the alloy and turn it into low carbon steel (see Figure 1). In this process, at least during the oxygen blow (sometimes called the blow-in blowpipe) and after the oxygen blow (sometimes called the end blow-in blowpipe), samples are collected and melt parameters are measured using different blowpipes to ensure that steel of the desired quality is obtained. The blow-in blowpipe is typically equipped with sensors that can measure the temperature and liquid phase of the molten metal, and is equipped with a sample collector for recovering the metal sample. The end blow-in blowpipe is typically equipped with sensors that can measure the temperature and oxygen content of the molten metal, and is equipped with a sample collector for recovering the metal sample.

A new auxiliary blowpipe is inserted into the coupling part of the top blowpipe until it reaches the shoulder formed by the manipulator part of the top blowpipe, the diameter of which is greater than the diameter of the auxiliary blowpipe. Due to vibrations during use, the auxiliary blowpipe may lose contact with the shoulder and a small gap may form. The molten metal (11) or the slag floating on its surface may be disturbed because the vessel is in motion or, in the case of a steelmaking converter, because of the injection of oxygen, thereby generating splashes (11s) that may reach the auxiliary blowpipe or even the top of the shoulder, or, if applicable, a gap may be created between the shoulder and the top of the auxiliary blowpipe. The metal or slag splashes solidify at the level of the gap on the surface of the shoulder and/or the coupling part and form a hard crust. When retrieving the current secondary blowpipe from the top blowpipe and disposing of it, it is important to scrape off any solid metal crust from the shoulder and the surface of the coupling portion of the top blowpipe to prevent the next secondary blowpipe from being properly coupled to the top blowpipe.

US4566343 and EP3588052 describe solutions for preventing metal crusting in the gap between the secondary blowpipe and the shoulder. US4566343 describes an elastic ring seal between the immersion end of the top blowpipe shoulder and the top of the secondary blowpipe to reduce the accumulation of frozen metal at the joint between the top blowpipe and the secondary blowpipe. EP3588052 describes a similar solution using two elastic ring seals disposed at the end of the secondary blowpipe. The two elastic ring seals are arranged circumferentially overlapping each other to seal the space between the coupling tap and the end of the secondary blowpipe. These solutions protect the gap between the secondary torch and the shoulder from metal or slag splashes. As mentioned above, this gap does not necessarily occur, and these solutions do not protect the shoulder from metal splashes.

KR101597688 proposes a solution for protecting the shoulder of the top blowpipe from metal splash. The top of the auxiliary blowpipe is equipped with an anti-stick cover formed by an inner ring and an outer ring. The inner ring contains an internal channel adapted to engage the coupling portion of the top blowpipe. The outer ring is coaxial with and separate from the inner ring. The outer ring has a larger diameter than the inner ring, matching the diameter of the shoulder and protecting it from metal splash. The problem with this solution is that the outer ring's diameter is substantially larger than that of the auxiliary blowpipe. Without modifying the dimensions of the receiving mechanism to match the dimensions of the anti-stick cover, the racks traditionally used to store new auxiliary blowpipes awaiting use would no longer be usable. Furthermore, the geometry of the auxiliary blowpipe's top end, altered as the anti-stick cover is coupled, would require changes in the programming of the robotic arm used to manipulate the auxiliary blowpipe and couple it to or retract it from the top blowpipe.

The present invention proposes a solution for protecting the shoulder of the top blowpipe and any gap formed between said shoulder and the secondary blowpipe, thereby maintaining the geometry of the top of the secondary blowpipe essentially unchanged. This solution has the advantage that it can be implemented by replacing existing secondary blowpipes one-for-one, without requiring any design changes to the existing racks used to store them, or to the programming of the robotic arms used to manipulate them. This solution also has the advantage that the conformity of the protective device to the surface of the top blowpipe and to the surface of the secondary blowpipe is a result of deformation of the entire device, rather than deformation of the surface of the elastic material. The advantage of this solution is that the expandable radial guard only expands after the top blowpipe and the auxiliary blowpipe have been axially engaged, thereby reducing the possibility of damage during handling and assembly. These and other advantages of the present invention continue to be presented.

The invention is defined in the accompanying independent claims. Preferred embodiments are defined in the dependent claims. In particular, the invention relates to a torch for immersing a probe into molten metal, comprising: (A) a top torch comprising: ● a steering portion extending along a longitudinal axis (X) and comprising a distal end, the cross section of which is orthogonal to the longitudinal axis (X) of a diameter (D1), the distal end being provided with ● a coupling portion extending coaxially with the longitudinal axis (X) and having a maximum diameter (d1), with D1>d1; (B) A secondary blowpipe formed by an elongated tubular member extending along a longitudinal axis (X) and including a bore configured to snugly receive a coupling portion, wherein the bore is substantially cylindrical having a diameter (d2), where d1≲d2, and extends along the longitudinal axis (X) from an immersion end having a probe and/or a sample collector to a proximal end coupled to a shield including a coupling end that opens into the bore, wherein: ○ the elongated tubular member has a cross-section having an outer diameter (D2), where d1<d2<D2<D1, and ○ the shield is deformable when a force is applied thereto along the longitudinal axis (X), and ○ the coupling portion is inserted into the bore of the secondary blowpipe, and the shield contacts the shoulder, wherein ● When stationary, the guard is in an initial configuration characterized by a maximum outer diameter (D3o) that is not larger than D2 by more than 10% (D3o≤1.1D2), preferably not larger than D2 by more than 5% (D3o≤1.05D2), and more preferably D3o=D2; ● When the auxiliary blowpipe is coupled to the blowpipe and the coupling portion is inserted into the cavity, the guard contacts the shoulder and deforms into a deformed configuration, forming a surface impermeable to molten metal and slag, which spans an area inscribed in a circle that is orthogonal to the longitudinal axis (X) and has a diameter (D3d) and covers the entire shoulder area, and D3d D1.

In a first embodiment, the protective device comprises: an inner tube that is deformable when a compressive force is applied thereto along a longitudinal axis (X), the inner tube extending along the longitudinal axis (X) and forming an inner channel having a diameter (D3i), wherein D3i d1, the inner layer comprises a plurality of inner slits separated from each other and distributed on the circumference of the inner tube; ● an outer tube, deformable when a compressive force is applied thereto along the longitudinal axis (X), the outer tube tightly surrounds the inner tube, and comprises a plurality of outer slits separated from each other and distributed on the circumference of the outer tube; ● optionally, one or more peripheral tubes, deformable when a compressive force is applied thereto along the longitudinal axis (X), and which are inserted into each other and tightly surround the outer tube (3 o), and wherein each of the more than one peripheral pipes includes a plurality of peripheral slits separated from each other and distributed on the circumference of each of the more than one peripheral pipes, wherein the peripheral slits of two adjacent peripheral pipes do not overlap with each other at any point, and wherein the outer slit (3so) does not overlap with the peripheral slit of the peripheral pipe of the adjacent outer pipe at any point; and wherein the intermediate inner slit (3si) and the outer slit (3so) do not overlap with each other at any point.

Preferably, the inner and outer slits extend preferably parallel to the longitudinal axis (X). In an alternative embodiment, the inner and outer slits extend transverse to the longitudinal axis (X) but not orthogonal thereto, and wherein the inner and outer slits form an angle with the longitudinal axis preferably comprised between 10° and 50°, more preferably between 25° and 45°. The inner and outer tubes may be made of an elastomeric material or of a plastically deformable metal, or may be in the form of a woven or non-woven fabric made of ceramic, polymer or metal fibers. In order to enhance the reproducibility of the deformation of the guard, the inner and/or outer tube may be provided with folding lines to control the deformation of the guard (3) for folding in a reproducible manner. The inner and outer tubes may have different heights measured along the longitudinal axis (X).

In a second embodiment, the protective device may include a tube capable of deforming when a compressive force is applied thereto along a longitudinal axis (X). The tube extends along the longitudinal axis (X) and defines an internal passageway having a diameter (D3i), where D3i ≥ d1. The tube includes a plurality of slits spaced apart from one another and distributed around the circumference of the tube. In a preferred embodiment, the slits are arranged in two groups: ●     an upper group extending from a location adjacent to the coupling end to a location halfway along the longitudinal axis (X), and ●     a lower group extending from a location adjacent to the fixed end opposite the coupling end to a location halfway along the pipe height, wherein the slits in the upper group are offset relative to the slits in the lower group.

The protective device of the first and second embodiments may be cylindrical, or may include one or more cylindrical portions and one or more tapered or curved portions distributed along the longitudinal axis (X).

In a third embodiment, the guard comprises: ●     A support ring coupled to the proximal end of the elongated tubular member, and ●     A plurality of L-shaped plates, each L-shaped plate comprising an outer portion joined to an inner portion at the level of a corner of the L, the L-shaped plates being rotatably mounted at or adjacent the corner of the L-shaped plate and hingedly arranged around the circumference of the support ring such that: ○     In an initial configuration of the guard, each L-shaped plate is biased to rotate such that the inner portion extends radially inwardly substantially perpendicular to the longitudinal axis (X), at least partially obstructing the bore, and the outer portion rests against the outer surface of the secondary blowpipe, and ○    The L-shaped plate is configured to pivot the hinge (3h) from an initial configuration to a deformed configuration when the coupling portion (1c) is inserted into the cavity to couple the auxiliary blowpipe to the top blowpipe, wherein in the deformed configuration the inner portion is aligned parallel to the longitudinal axis (X) and the outer portion extends radially substantially perpendicular to the longitudinal axis (X) and overlaps each other to form a continuous screen to prevent splashing when the guard is brought into contact with the shoulder.

Preferably, each outer portion has a free edge greater than the corner measured perpendicular to the longitudinal axis (X), and wherein each outer portion is curved with a curvature matching the outer diameter (D2) of the coupling end so that when the guard is in the initial configuration, each outer portion mates with the outer surface of the secondary blowpipe.

Similarly, it is preferred that each inner portion has a free edge shorter than the corner measured perpendicular to the longitudinal axis (X), and that each inner portion is bent with a curvature matching the maximum diameter (d1) of the coupling portion, so that when the coupling portion is inserted into the cavity and the L-shaped plate is pivoted on its hinge, the inner portion is pressed against the wall of the cavity and forms an internal channel with a diameter (D3i), and D3i ≥ d1, allowing the coupling portion to be inserted.

The L-shaped plate is preferably sufficiently rigid so as not to deform substantially during normal use of the device, and is preferably made of metal, preferably steel or aluminum, or a ceramic material, or a polymeric material.

The present invention also relates to an auxiliary blowpipe for coupling to a coupling portion of a blowpipe as described above. The auxiliary blowpipe is formed by an elongated tubular member extending along a longitudinal axis (X) and comprising a cavity configured to snugly receive the coupling portion, wherein the cavity is substantially cylindrical with a diameter (d2), where d1≲d2, extending along the longitudinal axis (X) from an immersion end provided with a probe and/or a sample collector to a proximal end coupled to a protective device (3) comprising a coupling end (2c) leading to the cavity (2v). The auxiliary blowpipe is characterized as follows: ●     The elongated tubular member has a cross-section with an outer diameter (D2), wherein d1 < d2 < D2 < D1, and ●     The guard is deformable when a force is applied thereto along the longitudinal axis (X), and ●     The coupling portion is inserted into the bore of the auxiliary blowpipe, and the guard contacts the shoulder. ●     When at rest, the guard is in an initial configuration, characterized by a maximum outer diameter (D3o), which is no greater than D2 by more than 10% (D3o ≤ 1.1D2), preferably no greater than D2 by more than 5% (D3o ≤ 1.05D2), and more preferably D3o = D2; ●    When the auxiliary blowpipe is coupled to the blowpipe and the coupling portion is inserted into the bore, the guard contacts the shoulder and deforms into a deformed configuration, forming a surface impermeable to molten metal and slag, which spans an area inscribed in a circle having a diameter (D3d) and covering the entire shoulder area, where D3d ≥ D1, and the shoulder extends perpendicular to the longitudinal axis (X) at a distance from the longitudinal axis (X) that is at least ½ D1.

The protective device is preferably as defined in the first, second or third embodiment above.

The present invention also relates to a protective device for preventing splashing at a shoulder formed between the distal end of the manipulator portion and the auxiliary blowpipe of the blowpipe as described above. The protective device comprises: an inner tube that can be deformed when a compressive force is applied thereto along the longitudinal axis (X), the inner tube extending along the longitudinal axis (X) and forming an inner channel having a diameter (D3i), wherein D3i d1, the inner layer comprises a plurality of inner slits separated from each other and distributed on the circumference of the inner tube; ● an outer tube, which is deformable when a compressive force is applied thereto along the longitudinal axis (X), the outer tube tightly surrounds the inner tube and comprises a plurality of outer slits separated from each other and distributed on the circumference of the outer tube; ● optionally, one or more peripheral tubes, which are deformable when a force is applied thereto along the longitudinal axis (X), and which are inserted into each other and The outer tube is snugly surrounded by the outer tube, and wherein each of the one or more peripheral tubes includes a plurality of peripheral slits separated from each other and distributed around the circumference of each of the one or more peripheral tubes, wherein the peripheral slits of two adjacent peripheral tubes do not overlap with each other at any point, and wherein the outer slit does not overlap with the peripheral slit of the peripheral tube adjacent to the outer tube at any point; and wherein the inner slit and the outer slit do not overlap with each other at any point.

The protective device is preferably as defined in the first, second or third embodiment above.

The invention relates to a blowpipe for immersing a probe into molten metal. The blowpipe comprises a top blowpipe (1t) and a disposable auxiliary blowpipe (2), wherein the auxiliary blowpipe (2) holds the probe and is coupled to the top blowpipe (1t).

The top blowpipe (1t) comprises a reusable manipulator portion (1h) and a coupling portion (1c) coupled to the distal end of the manipulator portion (1h) or at least partially integral with the manipulator portion (1h). The manipulator portion (1h) extends along a longitudinal axis (X) and comprises a distal end, the substantially circular cross-section of which is generally orthogonal to the longitudinal axis (X) of diameter (D1). The distal end is provided with a coupling portion (1c) extending coaxially with the longitudinal axis (X) and having a maximum diameter (d1), wherein D1>d1. The coupling portion is typically formed by: a fixing element (1f) fixed to or integral with the distal end of the manipulation portion (1h) and defining an exposed area of the distal end forming a shoulder (1s); and a probe holder (1p) extending along a longitudinal axis (X) and comprising a proximal end reversibly coupled to the fixing element (1f).

The known probe holder can be used multiple times without replacement, but due to the harsh conditions of use to which it is exposed, it degrades rapidly and, unlike the operating part (1h) and the fixing element (1f), the probe holder needs to be replaced regularly.

The auxiliary blowpipe (2) is disposable and is formed by an elongated tubular member (2t) extending along a longitudinal axis (X) and includes a cavity (2v) configured to snugly accommodate a coupling portion (1c). The cavity is substantially cylindrical with a diameter (d2), where d1 < d2, and extends along the longitudinal axis (X) from an immersion end provided with a probe (2p) and/or a sample collector to a proximal end coupled to a protective device (3) including a coupling end (2c) leading to the cavity (2v). The elongated tubular member (2t) has a substantially circular cross-section with an outer diameter (D2), where d1 < d2 < D2 < D1. The guard (3) is deformable when a force is applied thereto along the longitudinal axis (X). The auxiliary blowpipe (2) can be reversely coupled to the top blowpipe (1t) to form the blowpipe. The auxiliary blowpipe (2) is coupled to the top blowpipe (1t) to form the blowpipe of the present invention by inserting the coupling portion (1c) of the top blowpipe (1t) into the cavity (2v) of the auxiliary blowpipe (2), and the coupling end (2c) of the guard (3) contacts the shoulder (1s).

The gist of the invention is to provide a protective device which, on the one hand: ●     does not substantially alter the geometry of the coupling end (2c) of the separate (uncoupled) secondary blowpipe, thereby allowing the use of existing racks for storing the secondary blowpipes and allowing the use of the robot arm without modifying its programming, and, on the other hand, ●     covers and protects from splashing the entire area of the shoulder and any gap formed between the shoulder (1s) and the secondary blowpipe (2) when the secondary blowpipe is coupled to the blowpipe.

This is achieved by designing the guard so that: ● when at rest, the guard (3) is in an initial configuration characterized by a maximum outer diameter (D3o) that is not more than 10% greater than D2 (D3o≤1.1D2), preferably not more than 5% greater than D2 (D3o≤1.05D2), and even more preferably D3o=D2; and ● When the auxiliary blowpipe (2) is coupled to the blowpipe and the coupling portion (1c) is inserted into the cavity (2v), the shield (3) contacts the shoulder (1s) and is deformed into a deformed configuration, forming a surface impermeable to molten metal and slag, which spans an area inscribed in a circle perpendicular to the longitudinal axis (X) and having a diameter (D3d), where D3d ≥ D1; in this deformed configuration, the shield (3) covers the entire area of the shoulder (1s) and extends perpendicular to the longitudinal axis (X) at a distance of at least ½ D1 from the longitudinal axis (X). Top blowpipe (1t)

As shown in Figure 1, the top lance (1t) is a hollow rod long enough to be inserted into a metallurgical vessel. For example, for a steelmaking converter, the top lance (1t) can be 10 to 20 meters long, or even longer, depending on the size of the metallurgical equipment. It is manipulated by a robotic arm designed to pull the lance downward into and upward out of the metallurgical vessel. The top lance is formed by a manipulation portion (1h) and a coupling portion (1c).

The manipulating portion (1h) extends along the longitudinal axis (X) and includes a distal end having a substantially circular cross-section of diameter (D1) perpendicular to the longitudinal axis (X). In most cases, the cross-section of the distal end is circular, but in non-circular cases, similar features of the cross-section may be achieved by replacing the diameter (D1) with a hydraulic diameter (Dh1) (not shown in the drawings), where Dh1 = A1/P1, and A1 and P1 are the area and perimeter of the cross-section of the distal end perpendicular to the longitudinal axis (X). The circularity of the cross-section of the distal end of the manipulating portion is not essential to the present invention. But in reality, it is usually round.

The operating part (1h) can be made of metal or polymer or fiber-reinforced polymer composite. It is designed to continue in service for a considerable period of time without modification. It can be considered an integral part of the metallurgical equipment.

As shown in Figure 2(b), the coupling portion (1c) extends coaxially with the longitudinal axis (X) and has a maximum diameter (d1), where D1>d1. Thus, a shoulder (1s) having a width of (1/2(D1-d1)) is formed by the distal end of the manipulation portion (1h) and the coupling portion (1c).

As shown in FIG2(a), the coupling portion (1c) is generally formed by: ● a fixing element (1f) fixed to or integral with the distal end of the manipulation portion (1h) and defining an exposed area of the distal end forming a shoulder (1s); and ● a probe holder (1p) extending along a longitudinal axis (X) and comprising a proximal end reversibly coupled to the fixing element (1f).

Like the operating portion, the coupling portion is typically hollow and defines a passage for accommodating any wiring required by the probe (2p) positioned at the free end of the auxiliary blowpipe (2). The free end of the coupling portion (1c), in particular the free end of the probe holder (1p), may be provided with an electrical connection (1e) (e.g., a male plug or a female socket) for coupling to a corresponding electrical connection (2e) of any wiring of the probe (2p) when the auxiliary blowpipe (2) is coupled to the top blowpipe (1t), thereby forming a continuous conductive connection extending from the probe (2p) along the passage through the top blowpipe to any controller for recording the measurement value of the probe (2p). Since the electrical connections (1e) of the probe holder (1p) can be damaged by repeated connection/disconnection with the new auxiliary blowpipe (2) and the harsh working conditions inside the metallurgical vessel, where it is very close to molten metal at very high temperatures and is often exposed to vibrations, the probe holder (1p) must be replaced regularly to ensure good connections of all wires.

The probe holder (1p) can be reversibly coupled to the fixing element (1f) by a mechanical mechanism such as a thread, a bayonet, a snap-fit portion, etc. as shown in Figures 4(a) and 6(a) to form a coupling portion (1c). Auxiliary blowpipe (2)

The auxiliary blowpipe (2) extends along a longitudinal axis (X) and includes a bore (2v) configured to snugly receive the coupling portion (1c). The auxiliary blowpipe (2) is composed of at least the following: an elongated tubular member (2t) including an immersion end and a proximal end, a probe (2p) and/or a metal or slag sample collector coupled to the immersion end of the elongated tubular member (2t), and a protective device (3) coupled to the proximal end of the elongated tubular member (2t).

The cavity is substantially cylindrical with a diameter (d2), where d1≲d2, and extends along a longitudinal axis (X) from an immersion end at least partially closed by a probe (2p) to a coupling end (2c) of a protective device (3), which leads to a cavity for accommodating a coupling portion (1c) of a top blowpipe (1t). The coupling portion (1c) of the top blowpipe (1t) may include a clamping mechanism that contacts the wall of the cavity (2v) and locks the auxiliary blowpipe (2) by friction. The auxiliary blowpipe (2) may also be locked to the coupling portion by a mechanical mechanism, such as a thread, a bayonet, a snap-fit portion, etc.

The electrical connection portion (2e) that matches the electrical connection portion (1e) of the coupling portion (1c) of the top blowpipe can be fixed at a corresponding position in the cavity (2v), so that when the auxiliary blowpipe (2) is coupled to the top blowpipe (1t), electrical communication is established through the electrical connection portions (1e, 2e) connecting the top blowpipe (1t) and the auxiliary blowpipe (2). In this way, the probe (2p) can be electrically coupled to an external controller (not shown).

The elongated tube (2t) is usually made of a paperboard, which is sealed at its immersion end by a probe. The coupling end (2c) of the elongated tube (2t) of the auxiliary blowpipe (2) usually has a substantially circular cross-section with an outer diameter (D2), where d1<d2<D2<D1. If the cross-section of any of the coupling portion (1c), the cavity (2v), the coupling end (2c) of the auxiliary blowpipe (2) or the distal end of the operating portion (1h) is not circular, the cross-section can be defined by the corresponding hydraulic diameter dh1<dh2<Dh2<Dh1, where the hydraulic diameter is defined as the ratio of the area (A) of the corresponding cross-section to the perimeter (P) (Dh=A/P).

The gist of the invention consists in providing a guard device (3) fixed to the coupling end of the auxiliary blowpipe (2). When at rest, the guard device has an initial configuration that does not substantially change the external geometric dimensions of the auxiliary blowpipe. The guard device can be deformed into a deformed configuration when a force is applied to it parallel to the longitudinal axis (X). The force used to deform the guard (3) must not substantially exceed the force normally applied to couple the auxiliary blowpipe (2) to the top blowpipe (1t), and the guard must be deformed from the initial configuration to the deformed configuration when the coupling portion (1c) of the top blowpipe (1t) is inserted into the cavity (2v), until the free end of the guard (3) contacts the shoulder (1s) of the top blowpipe (1t), and, depending on the embodiment, when the coupling portion (1c) is inserted deeper into the cavity (2v).

According to the present embodiment of the invention, the coupling of the various components of the blowpipe (1) can include coupling the probe holder (1p) to the fixed element (1f) to form a coupling portion (1c). The probe holder (1p) can be locked to the fixed element (1f) by means of threads, bayonet, snap-fit, etc. The coupling portion (1c) of the top blowpipe (1t) can then be coaxially inserted into the bore (2v) of the auxiliary blowpipe (2) like a sword into a sheath until the guard (3) contacts the shoulder (1s) in the initial configuration. When a force is applied to the guard (3) along the longitudinal axis (X), the guard reaches the deformed configuration. It is important for the present invention that when the coupling between the auxiliary blowpipe (2) and the top blowpipe (1t) is completed, the protective device (3) has reached the deformed configuration.

As shown in Figures 2(d), 4(d) and 6(d), when the auxiliary blowpipe (2) is coupled to the top blowpipe (1t), the guard (3) is in a deformed configuration in which the free end of the guard contacts the shoulder (1s) and radially extends over an area inscribed in a circle which is orthogonal to the longitudinal axis (X) and has a diameter (D3d) and covers the entire area of the shoulder (1s), and D3d D1. In the modified configuration, the shoulder (1s) is protected from any molten metal splashes (11s) by the guard (3) and there is no need to scrub and scrape to remove any solidified metal from the surface of the shoulder (1s). Such cleaning operations must be performed manually and can be very troublesome.

Protective device (3) - double pipe fittings

In the preferred embodiment illustrated in Figures 3(a) to 3(e), the protective device (3) comprises: an inner tube (3i) which is deformable when a compressive force is applied thereto along the longitudinal axis (X), the inner tube extending along the longitudinal axis (X) and forming an inner channel having a diameter (D3i), wherein D3i d1, the inner layer (3i) comprises a plurality of inner slits (3si) separated from each other and distributed on the circumference of the inner tube (3i), an outer tube (3o) deformable when a compressive force is applied thereto along the longitudinal axis (X), the tube tightly surrounding the inner tube (3i) and comprising a plurality of outer slits (3so) separated from each other and distributed on the circumference of the outer tube (3o), wherein the inner slits (3si) and the outer slits (3so) do not overlap each other at any point.

The protective device (3) may optionally include one or more peripheral pipes that can be deformed when a compressive force is applied thereto along the longitudinal axis (X), and which are inserted into each other and tightly surround the outer pipe (3o), and each of the one or more peripheral pipes includes a plurality of peripheral slits that are separated from each other and distributed on the circumference of each of the one or more peripheral pipes, wherein the peripheral slits of two adjacent peripheral pipes do not overlap each other at any point, and wherein the outer slit (3so) does not overlap with the peripheral slit of the peripheral pipe adjacent to the outer pipe at any point.

As shown in FIG4(e), non-overlapping inner and outer slits (3si, 3so) are essential to the present invention for the following reasons. In the initial configuration, the guard has a maximum outer diameter (D3o) resulting in a perimeter Pi = π × D3o, and is formed by a plurality of material strips having a strip width measured tangentially (i.e., perpendicular to the longitudinal axis (X) and the radial direction) defined between two adjacent slits of the initial slit width. In the modified configuration, the guard (3) forms a surface spanning an area inscribed in a circle having a diameter (D3d), with D3o < D3d, thus resulting in a perimeter Pd = π × D3d > Pi. Since the width of the strip of material remains constant when it is bent, Pd can be made greater than Pi simply by increasing the slit width accordingly. The problem with having locally wider gaps (3si, 3so) is that the surfaces formed through these openings are impermeable to molten metal and slag splashes (11s). For this reason, it is required that both the inner tube (3i) and the outer tube (3o) have inner slits (3si) and outer slits (3so) that do not overlap each other at any point, so that any locally wider slits of the inner or outer tube are always covered by the strip of material of the outer or inner tube, respectively, thus defining a surface that is impermeable to metal or slag splashes (11s).

As illustrated in Figures 3(a) to 3(e), the inner slit (3si) and the outer slit (3so) may extend parallel to the longitudinal axis (X). Alternatively, as shown in Figure 3(f), the inner slit (3si) and the outer slit (3so) may extend transverse to the longitudinal axis, but not orthogonally to the longitudinal axis. In this embodiment, the inner slit (3si) and the outer slit (3so) may form an angle with the longitudinal axis comprised between 10° and 50°, preferably between 25° and 45°.

FIG3( c ) illustrates an embodiment in which the inner tube ( 3 i ) and/or the outer tube ( 3 o ) are provided with folding lines ( 3 f ) to control the deformation of the guard ( 3 ) for folding in a repeatable manner. The folding lines ensure that the tubes are preferentially deformed along the folding lines ( 3 f ). The folding lines ( 3 f ) can be formed by point perforations of the tubes, or by locally thinner wall thicknesses of the inner tube and/or the outer tube, whereby the folding lines are defined by corresponding grooves. Since the guard (3) is coupled to the proximal end of the elongated tube (2t) at one end and to the coupling portion of the top blowpipe (1t) at the coupling end (2c), the fold line (3f) can extend adjacent to and parallel to the one end and the coupling end (2c) of the guard (3). The fold line (3f) can also extend circumferentially at approximately the mid-height of the guard (3) to ensure that the guard (3) spans the entire area of the shoulder in the deformed configuration. The preferred position of the fold line (3f) as described above is illustrated in Figures 3(c) and 4(e).

As shown in FIG3( d ), the inner tube ( 3 i ) and the outer tube ( 3 o ) may have different heights measured along the longitudinal axis (X). In the embodiment of FIG3( d ), the outer tube ( 3 o ) is approximately half the height of the inner tube ( 3 i ). In the embodiment of FIG3( d ), the outer slit ( 3 so ) of the outer tube opens at the free edge of the outer tube ( 3 o ) located closest to the coupling end ( 2 c ). The outer slit ( 3 so ) opened at the free edge of the outer tube ( 3 o ) located closest to the coupling end ( 2 c ) may also be applied to any outer tube ( 3 o ) that has a height comprised between 50% and 100% of the height of the inner tube ( 3 i ). With this construction, the inner tube folds into two parts and unfolds a free strip of material of the outer tube, which opens like the petals of a flower. The space between two adjacent strips (= petals) of the outer tube is protected by strips of material of the inner tube (3i), which are offset relative to the strips of material of the outer tube.

The protective device (3) may be cylindrical as shown in Figures 3(a) to 3(d) and 3(f), or it may include one or more cylindrical parts and one or more tapered or curved parts distributed along the longitudinal axis (X), an embodiment of which is illustrated in Figure 3(e).

The inner tube (3i) and the outer tube (3o) may be made of an elastomeric material or a plastically deformable metal, or may be in the form of a woven or non-woven fiber fabric made of ceramic, polymer or metal fibers.

Figures 4(a) to 4(d) illustrate the various steps for installing the blowpipe according to this embodiment of the invention, and the deformation of the protruding protection device (3) when coupling the auxiliary blowpipe (2) to the top blowpipe (1t). Figure 4(a) shows how the probe holder (1p) is coupled to the fixing element (1f) to form the coupling portion (1c) of the top blowpipe (1t). In Figure 4(a), the thread used to couple the probe holder (1p) to the fixing element (1f) is illustrated. As mentioned above, other coupling mechanisms, such as bayonet or snap-fit parts, can be used without affecting the present invention. As shown in Figures 4(b) and 4(c), the coupling portion (1c) of the top blowpipe (1t) is inserted into the bore (2v) of the auxiliary blowpipe (2) like inserting a sword into a sheath until the coupling end (2c) of the guard contacts the shoulder (1s), while the guard, which is still in its initial configuration, is not deformed. The guard (3) illustrated in Figures 4(b) to 4(e) is of the type illustrated in Figure 3(b) or 3(c), but the same principles apply to any of the embodiments illustrated in Figures 3(b) to 3(f). At this stage, as illustrated in Figure 4(c), the auxiliary blowpipe (2) is not yet fully coupled to the top blowpipe (1t). In order to complete the coupling, the coupling portion (1c) must penetrate further into the cavity, which applies a compressive force along the longitudinal axis (X) to the deformed guard (3) to achieve the deformed configuration. By comparing Figures 4(d) and 4(e), it can be seen that when a compressive force is applied along the longitudinal axis (X), the two tubular, substantially cylindrical guards bend at the mid-height (measured along the longitudinal axis (X)), forming a geometry of this type consisting of two inverted funnels joined to each other at the wide end of each funnel. The diameter (D3d) at the level of the fold of the material strip must be at least equal to the diameter (D2) of the distal end of the top blowpipe (D3d≥D2). Therefore, the height of the guard (3) measured along the longitudinal axis (X) must be greater than twice the radial width (=1/2(D1-D2c)) of the shoulder (1s) formed between the top blowpipe (1t) and the auxiliary blowpipe (2), where D2c is the diameter of the coupling end (2c) of the guard (3). Guard (3) - Single pipe

In an alternative preferred embodiment illustrated in Figures 7(a) and 7(b), the guard (3) comprises a single tube that is deformable when a compressive force is applied thereto along a longitudinal axis (X). The tube extends along the longitudinal axis (X) and forms an internal passage having a diameter (D3i), where D3i ≥ d1. The tube (3i) comprises a plurality of slits (3s) separated from one another and distributed around the circumference of the tube.

In the embodiment illustrated in FIG. 7( a ), the slit extends over at least 70%, preferably at least 80%, and more preferably at least 90% of the height of the tube measured along the longitudinal axis (X).

In the embodiment illustrated in FIG. 7( b ), the slits ( 3 s ) are distributed in two groups: an upper group extending from a position adjacent to the coupling end ( 2 c ) to a position adjacent to half the height of the pipe as measured along the longitudinal axis (X), and a lower group extending from a position adjacent to the fixed end opposite to the coupling end ( 2 c ) to a position adjacent to half the height of the pipe, wherein the slits ( 3 s ) of the upper group are offset relative to the slits ( 3 s ) of the lower group.

The slits (3s) may extend parallel to the longitudinal axis (X), or alternatively they may extend transversely to the longitudinal axis (X), but not orthogonally thereto. In the latter embodiment, the slits (3s) form an angle with the longitudinal axis preferably comprised between 10° and 50°, more preferably between 25° and 45°. In all cases, the slits are preferably parallel to one another, or at least never cross one another.

As shown in Figures 7(a) and 7(b), the tube is preferably provided with a folding line (3f) to control the deformation of the guard (3) for folding in a reproducible manner. For example, the folding line (3f) may extend circumferentially at half the height of the tube.

The tube may be cylindrical or may comprise one or more cylindrical portions and one or more tapered or curved portions distributed along the longitudinal axis (X). The tube is preferably made of an elastomeric material or a plastically deformable metal, or is in the form of a woven or non-woven fiber fabric made of ceramic, polymer or metal fibers.

Protective Device (3)-Lotus

In the alternative preferred embodiment illustrated in Figures 5(a) to 5(e), the protective device (3) comprises: ● a support ring (3r) coupled to the coupling end (2c) of the auxiliary blowpipe (2), and ● a plurality of L-shaped plates (3p), each L-shaped plate (3p) comprising an outer portion (3po) joined to an inner portion (3pi) at the level of the corners of the L-shaped plate (3p) (see Figure 5(a)).

The L-shaped plate (3p) is rotatably mounted by hinges (3h) at or near the level of the corners of the L-shaped plate (3p) and distributed around the circumference of the support ring, so that the guard (3) can be changed between the initial configuration and the deformed configuration by rotating the L-shaped plate (3p) around its respective hinge (3h) as shown in Figure 5(b).

In the initial configuration of the guard (3) illustrated in FIG5(c), each L-shaped plate (3p) is biased to rotate so that the inner portion (3pi) extends radially in a direction substantially perpendicular to the longitudinal axis (X), at least partially blocking the cavity (2v), and the outer portion (3po) rests against the outer surface of the auxiliary blowpipe (2). In the initial configuration, the inner portion (3pi) forms an inner channel with a diameter (D3i), where D3i < d1. The bias can be caused by a spring that forces the L-shaped plate (3p) into the initial configuration. However, the bias can be more simply caused by moving the center of gravity of the L-shaped plate (3p), so that the L-shaped plate (3p) naturally rotates due to gravity to achieve the above configuration. Note that the secondary blowpipe is usually stored, manipulated, and used with the longitudinal axis (X) substantially vertical so that the effects of gravity can be easily controlled.

As shown in FIG5(b), the L-shaped plate (3p) is configured to pivot from the initial configuration illustrated in FIG5(c) to the modified configuration illustrated in FIG5(d) around the hinge (3h) when the coupling portion (1c) is inserted into the cavity (2v) to couple the auxiliary blowpipe (2) to the top blowpipe (1t). As shown in FIG5(d), in the modified configuration, the inner portion (3pi) is aligned parallel to the longitudinal axis (X), and the outer portion (3po) extends radially substantially orthogonal to the longitudinal axis (X) and overlaps each other to form a continuous shield to resist metal splash when the guard (3) contacts the shoulder (1s).

As can be seen in Figures 5(a) and 5(d), each outer portion (3po) preferably has a free edge that is larger than the corner and is measured in the tangential direction (i.e., perpendicular to the longitudinal axis (X) and the radial direction). In this way, when the L-shaped plate (3p) rotates around its hinge to achieve a deformed configuration (like a blooming lotus), all L-shaped plates (3p) will contact adjacent L-shaped plates (3p) located on either side thereof, thus forming a continuous shield that protects the shoulder (1s) from splashing.

Each outer portion (3po) is preferably curved with a curvature that matches the outer diameter (D2) of the coupling end (2c), so that when the guard (3) is in the initial configuration, each outer portion (3po) fits the outer surface of the auxiliary blowpipe (2). This is illustrated in Figures 5(c) and 5(e), so that the maximum diameter (D3o) of the guard (3) is not greater than D2 by more than 10% (D3o 1.1D2).

In a preferred embodiment, each inner portion (3pi) has a free edge that is shorter than the corner and is measured orthogonally to the longitudinal axis (X), as can be seen in Figures 5(a) to 5(c). In this way, when the guard (3) is in the initial configuration and the inner portions (3pi) are extended radially inward, they do not overlap each other. They do not need to form a continuous shield because, in the initial configuration, the secondary blowpipe is not coupled to the top blowpipe and is therefore not in use. When the L-shaped plate (3p) pivots to reach the deformed configuration, they contact the wall of the cavity and should preferably not overlap each other to allow the cavity opening to be as large as possible to allow the coupling portion of diameter (d1) to enter the cavity (2v).

Each inner portion (3pi) is preferably curved with a curvature matching the maximum diameter (d1) of the coupling portion (1c), so that when the coupling portion (1c) is inserted into the cavity (2v) and the L-shaped plate (3) is pivoted on its hinge, the inner portion (3pi) is pressed against the wall of the cavity (2v) and forms an inner channel with a diameter (D3i), and D3i d1, thus allowing the coupling part (1c) to be inserted.

The L-shaped plate (3p) is preferably sufficiently rigid so as not to be substantially deformed during normal use of the device. In particular, when the coupling portion (1c) is introduced into the cavity (2v) and pressed onto the inner portion (3pi) of the L-shaped plate (3p), the inner portion does not need to be (substantially) bent, and must be sufficiently rigid to drive the L-shaped plate (3p) to rotate without bending. The L-shaped plate (3p) is preferably made of metal, preferably steel or aluminum, or made of ceramic material, or made of polymer material, preferably not made of rubber-like polymer.

Figures 6(a) to 6(d) illustrate the various steps for coupling the various components of the blowpipe according to this embodiment of the invention, highlighting the deformation of the protective device (3) when coupling the auxiliary blowpipe (2) to the top blowpipe (1t). Figure 6(a) shows how the top blowpipe (1t) is formed by coupling the probe holder (1p) to the fixing element (1f) to form the coupling portion (1c). Figure 6(a) illustrates the thread used to couple the probe holder (1p) to the fixing element (1f). As mentioned above, other coupling mechanisms, such as bayonet or snap-fit parts, can be used without affecting the present invention. As shown in Figures 6(b) and 6(c), the coupling portion (1c) of the top blowpipe (1t) is inserted into the bore (2v) of the secondary blowpipe (2) like inserting a sword into a sheath. In the initial configuration, the inner portion (3pi) of the L-shaped plate (3p) extends radially inward, partially blocking the opening of the bore (2v), leaving an opening with a diameter smaller than the diameter (d1) of the coupling portion (1c). Therefore, when the coupling portion (1c) contacts the inner portion (3pi) of the L-shaped plate (3p), it applies a force along the longitudinal axis (X) to the inner portion, pushing it downward against the wall of the bore (2v), thereby driving the tilt of the L-shaped plate (3p) and simultaneously lifting the outer portion (3po) away from the outer wall of the secondary blowpipe (2). At the stage illustrated in FIG6( c ), the protective device may or may not have reached the deformed configuration, depending on the distance to which the inner portion ( 3pi ) is pushed against the wall of the cavity ( 2v ). At this stage, the auxiliary blowpipe ( 2 ) is not fully coupled to the top blowpipe ( 1t ) because the coupling end ( 2c ) of the auxiliary blowpipe ( 2 ) is not in contact with the shoulder ( 1s ). In order to complete this coupling, the coupling portion ( 1c ) must penetrate further and deeper into the cavity. It is important for the present invention that the protective device ( 3 ) has reached the deformed configuration when the coupling between the auxiliary blowpipe ( 2 ) and the top blowpipe ( 1t ) is completed. In order to fully open the "lotus" and form a continuous shield with the outer part (3po) side by side, the coupling part (1c) can be gradually tapered, and the diameter of the coupling part can be increased until it reaches the maximum diameter (d1) at the top section adjacent to the operating part (1h), so as to completely press the inner part against the wall of the cavity (2v).

Concluding remarks

The various aspects of the present invention including the top blowpipe (1t), the auxiliary blowpipe (2) and the protective device (3) have in common the protective device, which is characterized in that: ● When at rest, the protective device (3) is in an initial configuration, the initial configuration being characterized by a maximum outer diameter (D3o) that is not greater than D2 by more than 10% (D3o 1.1D2), preferably no larger than D2 by more than 5% (D3o 1.05D2), preferably D3o=D2, ● When the auxiliary blowpipe (2) is coupled to the blowpipe and the coupling portion (1c) is inserted into the cavity (2v), the guard (3) contacts the shoulder (1s) and is deformed into a deformed structure to form a surface impermeable to molten metal and slag, which spans an area inscribed in a circle having a diameter (D3d) and covering the entire area of the shoulder (1s), and D3d ≥ D1, and the shoulder (1s) extends perpendicular to the longitudinal axis (X) at a distance from this longitudinal axis (X) that is at least equal to ½ D1.

This apparently simple solution offers great advantages in terms of maintenance of the blowpipe, since there is no need to scrape off any solidified metal or slag splashes that may soil the shoulder (1s) of the top blowpipe (1t). At the same time, the auxiliary blowpipes of the prior art can be replaced by the auxiliary blowpipe (2) of the invention without requiring any modifications in the process, neither a rack for storing spare auxiliary blowpipes (2) nor programming of the robot arm that operates the auxiliary blowpipe. This is possible because, in its initial configuration, the protective device (3) does not substantially modify the geometry of the auxiliary blowpipe. This solution is also very cost-effective to implement.

1: Blowpipe 1c: Coupling section 1e: Electrical coupling section of disposable probe holder 1f: Fixing element 1h: Operating section 1p: Disposable probe holder 1s: Shoulder 1t: Top blowpipe 2: Secondary blowpipe 2c: Coupling end of secondary blowpipe 2e: Electrical coupling section of secondary blowpipe 2p: Probe 2t: Long tube 2v: Bore 3: Guard 3f: Folding wire 3h: Hinge 3i: Inner tube 3o: Outer tube 3p: L-shaped plate 3pi: Inner portion of L-shaped plate 3po: L-shaped plate =Exterior of the coupling 3r: Support ring 3si: Inner slit 3so: Outer slit 10: Metallurgical vessel (e.g., converter) 11: Molten metal 11s: Spatter 12: Gas lance (e.g., oxygen lance) d1: Maximum cross-sectional diameter of the coupling section D1: Cross-sectional diameter of the distal end of the manipulator d2: Diameter of the bore D2: Outer diameter of the coupling end D3d: Maximum outer diameter of the deformed guard D3i: Diameter of the inner channel of the guard D3o: Maximum outer diameter of the undeformed guard X: Longitudinal axis

For a more complete understanding of the nature of the present invention, reference is made to the following detailed description in conjunction with the accompanying drawings, wherein: Figure 1 shows a steelmaking converter having an oxygen lance and a lance according to the present invention. Figure 2(a) shows the control portion and the separated coupling portion of the lance according to the present invention. Figure 2(b) shows the top lance according to the present invention, which is formed by coupling the control portion and the coupling portion of Figure 1(a) together. Figure 2(c) shows the auxiliary lance according to the present invention. Figure 2(d) shows the lance according to the present invention, which is formed by coupling the auxiliary lance of Figure 2(c) to the top lance of Figure 2(b). Figure 2(e) shows the auxiliary lance according to the present invention. Figure 3(a) shows an exploded view of an embodiment of a protective device according to the present invention. Figure 3(b) shows the protective device of Figure 3(a) in assembled form. Figures 3(c) to 3(f) show alternative embodiments of the protective device according to the present invention. Figure 4(a) shows details of the coupling of the coupling portion to the operating portion used to form the top blowpipe of the present invention. Figure 4(b) shows details of the assembled top blowpipe of Figure 4(a) above the auxiliary blowpipe equipped with a protective device of the type illustrated in Figures 3(a) to 3(f). Figure 4(c) shows the secondary blowpipe of Figure 4(b) partially inserted into the coupling portion of the top blowpipe of Figure 4(b), with the top surface of the guard contacting the shoulder but remaining undeformed in its initial configuration. Figure 4(d) shows the secondary blowpipe of Figure 4(c) fully inserted into the coupling portion of the top blowpipe of Figure 4(c), with one embodiment of the guard deformed into a deformed configuration and protecting the shoulder from splashing. Figure 4(e) shows a partially deformed guard of the type illustrated in Figures 3(a) to 3(f). Figure 5(a) shows an exploded view of a second embodiment of the guard of the present invention. Figure 5(b) shows a side view of the second embodiment of the guard of Figure 5(a) in assembled form. Figure 5(c) shows the second embodiment of the protective device of Figure 5(b) in its initial configuration. Figure 5(d) shows the second embodiment of the protective device of Figure 5(b) in its modified configuration. Figure 5(e) shows a secondary blowpipe according to the present invention having the protective device of the second embodiment of Figure 5(a). Figure 6(a) shows details of the coupling of the coupling portion to the operating portion of the top blowpipe of the present invention. Figure 6(b) shows details of the assembled top blowpipe of Figure 6(a) above the secondary blowpipe equipped with a protective device of the type described in Figures 5(a) to 5(e). Figure 6(c) shows the secondary blowpipe of Figure 6(b) partially inserted into the coupling portion of the top blowpipe of Figure 6(b), leaving the top surface of the second embodiment of the guard still separated from the shoulder and already at least partially deformed by the insertion of the coupling portion. Figure 6(d) shows the secondary blowpipe of Figure 6(c) fully inserted into the coupling portion of the top blowpipe of Figure 6(c), with the second embodiment of the guard deformed into a deformed configuration and protecting the shoulder from splashing. Figures 7(a) and 7(b) show alternative embodiments of the guard according to the present invention.

1: Blowpipe

2: Secondary Blowpipe

3: Protective device

D3d: Maximum outer diameter of the deformed protective device

X: longitudinal axis

Claims (17)

A blowpipe (1) for immersing a probe into molten metal, comprising: (A) a top blowpipe (1t) comprising: a manipulation portion (1h) extending along a longitudinal axis (X) and comprising a distal end, the cross section of which is orthogonal to the longitudinal axis (X) of a diameter (D1), the distal end being provided with a coupling portion (1c) coaxial with the longitudinal axis (X) (B) an auxiliary blowpipe (2) formed by an elongated tubular member (2t) extending along the longitudinal axis (X) and comprising a cavity (2v) configured to snugly receive the coupling portion (1c), wherein the cavity is substantially cylindrical with a diameter (d2), and d1>d1; d2, and extending along the longitudinal axis (X) from an immersion end provided with a probe (2p) and/or a sample collector to a proximal end, the proximal end being coupled to a protective device (3) comprising a coupling end (2c) leading to the cavity (2v), wherein: ○ the elongated tube (2t) has a cross section having an outer diameter (D2), wherein d1<d2<D2<D1, and ○ the protective device (3) is capable of applying a force along the longitudinal axis (X) and ○ the coupling portion (1c) is inserted into the cavity (2v) of the auxiliary blowpipe (2), and the protective device (3) contacts a shoulder (1s) formed between the top blowpipe (1t) and the auxiliary blowpipe (2), characterized in that ● when stationary, the protective device (3) is in an initial configuration, characterized in that the initial configuration is characterized by a maximum outer diameter (D3o) that is not larger than D2 by more than 10% (D3o 1.1D2), preferably no larger than D2 by more than 5% (D3o 1.05D2), preferably D3o=D2; ● When the auxiliary blowpipe (2) is coupled to the blowpipe and the coupling portion (1c) is inserted into the cavity (2v), the protective device (3) contacts the shoulder (1s) and is deformed into a deformed structure, forming a surface impermeable to molten metal and slag, which spans an area inscribed in a circle that is orthogonal to the longitudinal axis (X) and has a diameter (D3d) and covers the entire area of the shoulder (1s), and D3d D1. The blowpipe of claim 1, wherein the protective device (3) comprises: an inner tube (3i) that is deformable when a compressive force is applied thereto along the longitudinal axis (X), the inner tube extending along the longitudinal axis (X) and forming an inner passage having a diameter (D3i), wherein D3i d1, the inner tube (3i) includes a plurality of inner slits (3si) separated from each other and distributed on the circumference of the inner tube (3i); ● an outer tube (3o) that can be deformed when a compressive force is applied thereto along the longitudinal axis (X), the outer tube tightly surrounds the inner tube (3i) and includes a plurality of outer slits (3so) separated from each other and distributed on the circumference of the outer tube (3o); ● optionally, one or more peripheral tubes that can be deformed when a compressive force is applied thereto along the longitudinal axis (X), and their relative The outer tube (3o) is inserted into each other and tightly surrounds the outer tube (3o), and each of the one or more peripheral tubes includes a plurality of peripheral slits separated from each other and distributed on the circumference of each of the one or more peripheral tubes, wherein the peripheral slits of two adjacent peripheral tubes do not overlap with each other at any point, and wherein the outer slits (3so) do not overlap with the peripheral slits of the peripheral tube adjacent to the outer tube at any point; and wherein the inner slits (3si) and the outer slits (3so) do not overlap with each other at any point. The blowpipe of claim 2, wherein the inner slits (3si) and the outer slits (3so) extend parallel to the longitudinal axis (X). The blowpipe of claim 2, wherein the inner slits (3si) and the outer slits (3so) extend transversely to the longitudinal axis (X) but are not orthogonal to the longitudinal axis (X), and wherein the inner slits (3si) and the outer slits (3so) form an angle with the longitudinal axis preferably comprised between 10° and 50°, more preferably between 25° and 45°. A blowpipe as claimed in any one of claims 2 to 4, wherein the inner tube (3i) and the outer tube (3o) are made of an elastomeric material or a plastically deformable metal, or are in the form of a woven or non-woven fiber fabric made of ceramic, polymer or metal fiber. A blowpipe as claimed in claim 2, wherein the inner tube (3i) and/or the outer tube (3o) are provided with folding lines (3f) to control the deformation of the protective device (3) for folding in a reproducible manner. The blowpipe of claim 2, wherein the inner tube (3i) and the outer tube (3o) have different heights measured along the longitudinal axis (X). The blowpipe of claim 1, wherein the guard (3) comprises a tube that is deformable when a compressive force is applied thereto along the longitudinal axis (X), the tube extending along the longitudinal axis (X) and forming an inner passage having a diameter (D3i), wherein D3i d1, the pipe (3i) includes a plurality of slits (3s) separated from each other and distributed on the circumference of the pipe, wherein the slits (3s) are preferably distributed in two groups, an upper group extending from a position adjacent to the coupling end (2c) to a position half of the height of the pipe measured along the longitudinal axis (X), and a lower group extending from a position adjacent to the fixed end opposite to the coupling end (2c) to a position adjacent to half of the height of the pipe, wherein the slits (3s) of the upper group are offset relative to the slits (3s) of the lower group. A blowpipe as claimed in claim 2, wherein the protective device (3) is ● cylindrical, or ● comprises a plurality of cylindrical parts, or ● comprises one or more cylindrical parts and one or more conical or curved parts distributed along the longitudinal axis (X). A blowpipe as claimed in claim 1, wherein the guard (3) comprises: a support ring (3r) coupled to the proximal end of the elongated tube (2t), and a plurality of L-shaped plates (3p), each L-shaped plate (3p) comprising an outer portion (3po) joined to an inner portion (3pi) at the level of a corner of the L-shaped plate (3p), the L-shaped plates (3p) being rotatably mounted and distributed around the circumference of the support ring by hinges (3h) at the level of or adjacent to the corner of the L-shaped plate (3p) so that: in an initial configuration of the guard (3), each L-shaped plate (3p) is biased to rotate so that the inner portions (3pi) are substantially perpendicular to the longitudinal axis (X ) extends radially inwardly to at least partially close the cavity (2v), and the outer portion (3po) is stationary against the outer surface of the auxiliary blowpipe (2), and the L-shaped plate (3p) is configured to be used for winding around the hinges (3h) when the coupling portion (1c) is inserted into the cavity (2v) to couple the auxiliary blowpipe (2) to the top blowpipe (1t). The initial configuration pivots to the deformed configuration, wherein in the deformed configuration the inner portions (3pi) are aligned parallel to the longitudinal axis (X) and the outer portions (3po) extend radially substantially perpendicular to the longitudinal axis (X) and overlap one another to form a continuous screen to prevent splashing when the guard (3) is brought into contact with the shoulder (1s). The blowpipe of claim 10, wherein each outer portion (3po) has a free edge greater than the corner measured perpendicular to the longitudinal axis (X), and wherein each outer portion (3po) is bent with a curvature matching the outer diameter (D2) of the coupling end (2c), so that when the guard (3) is in the initial configuration, each outer portion (3po) is engaged with the outer surface of the secondary blowpipe (2). A blowpipe as claimed in claim 10, wherein each inner portion (3pi) has a free edge shorter than the corner measured perpendicular to the longitudinal axis (X), and wherein each inner portion (3pi) is bent with a curvature matching the maximum diameter (d1) of the coupling portion (1c), so that when the coupling portion (1c) is inserted into the cavity (2v) and the L-shaped plate (3p) is pivoted on its hinge (3h), the inner portions (3pi) are pressed against the wall of the cavity (2v) and form an inner channel having a diameter (D3i), and D3i d1, allowing the coupling part (1c) to be inserted. The blowpipe of claim 10, wherein the L-shaped plate (3p) is sufficiently rigid so as not to be substantially deformed during normal use of the device, and is preferably made of metal, preferably steel or aluminum, or a ceramic material, or a polymer material. A secondary blowpipe (2) for coupling to a coupling portion (1c) of a blowpipe (1t) as claimed in any one of claims 1 to 13, wherein the secondary blowpipe (2) is formed by an elongated tubular member (2t) extending along the longitudinal axis (X) and comprises a cavity (2v) configured to snugly receive the coupling portion (1c), wherein the cavity is substantially cylindrical with a diameter (d2), and d1 d2, extending along the longitudinal axis (X) from an immersion end provided with a probe (2p) and/or a sample collector to a proximal end, the proximal end being coupled to a protective device (3) comprising a coupling end (2c) leading to the cavity (2v), wherein: ● the elongated tube (2t) has a cross section with an outer diameter (D2), wherein d1<d2<D2<D1, and ● the protective device (3) is capable of being inserted along the longitudinal axis The coupling portion (1c) is inserted into the cavity (2v) of the auxiliary blowpipe (2), and the guard (3) contacts the shoulder (1s), characterized in that when at rest, the guard (3) is in an initial configuration, characterized in that the maximum outer diameter (D3o) is not greater than D2 by more than 10% (D3o 1.1D2), preferably no larger than D2 by more than 5% (D3o 1.05D2), preferably D3o=D2; ● When the auxiliary blowpipe (2) is coupled to the blowpipe and the coupling portion (1c) is inserted into the cavity (2v), the protective device (3) contacts the shoulder (1s) and is deformed into a deformed structure, forming a surface impermeable to molten metal and slag, which spans the area of an inscribed circle having a diameter (D3d) and covering the entire area of the shoulder (1s), and D3d D1, and the shoulder (1s) extends perpendicular to the longitudinal axis (X) at a distance from the longitudinal axis (X) that is at least equal to ½ D1. The auxiliary blowpipe (2) of claim 14, wherein the protective device (3) is defined as any one of claims 2 to 7, claims 8 and 9, or any one of claims 10 to 13. A protective device (3) for preventing splashing at a shoulder (1s) formed between a distal end of a manipulation portion (1h) and an auxiliary blowpipe (2) of a blowpipe as claimed in claim 1, wherein the protective device (3) comprises: an inner tube (3i) deformable when a compressive force is applied thereto along the longitudinal axis (X), the inner tube (3i) extending along the longitudinal axis (X) and forming an inner channel having a diameter (D3i), wherein D3i d1, the inner tube (3i) includes a plurality of inner slits (3si) separated from each other and distributed on the circumference of the inner tube (3i); an outer tube (3o) deformable when a compressive force is applied thereto along the longitudinal axis (X), the outer tube tightly surrounding the inner tube (3i) and including a plurality of outer slits (3so) separated from each other and distributed on the circumference of the outer tube (3o); ● Optionally, one or more peripheral tubes can be deformed when a force is applied thereto along the longitudinal axis (X), and they are inserted into each other and tightly surround the outer tube (3o), and each of the one or more peripheral tubes includes a plurality of peripheral slits separated from each other and distributed on the circumference of each of the one or more peripheral tubes, wherein the peripheral slits of two adjacent peripheral tubes do not overlap with each other at any point, and wherein the outer slits (3so) do not overlap with the peripheral slits of the peripheral tube adjacent to the outer tube at any point; and wherein the inner slits (3si) and the outer slits (3so) do not overlap with each other at any point. The protective device of claim 16, which is defined as any one of claims 2 to 7 and 9.