JPH0570546B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for melt cutting a steel material with a rectangular cross section such as a slab or a bloom, and a preheating and melting start method when melt cutting the upper, lower and both side surfaces of the steel material with a rectangular cross section in the longitudinal direction. It is related to the improvement of [Prior Art] Steel materials having a rectangular cross section, such as slabs and blooms, are materials for various rolled products, and surface defects that cause surface flaws in the rolled products are removed by a cutting device before rolling. As a fusing device, there are a partial fusing device and a so-called full surface fusing device for cutting the entire upper, lower, and both side surfaces of a steel material having a rectangular cross section. Conventionally, the upper, lower, and both sides surfaces of a steel material having a rectangular cross section are machined by a full-surface melting machine using a method called surface start, as shown in FIG. The fusing units 20a to 20d were arranged along the ridge, and the cutting was started at the same time. In the method called surface start, a preheating position is set at a predetermined width position _D1 near the ridge 6a at the longitudinal end within the upper and lower and both side surfaces 5a to 5d of the rectangular cross-sectional steel material 3, and the melting start position after preheating is set as the preheating position. That is. This is because when the cutting starts after preheating, when the oxygen jet flow 10a collides with the cutting start position _D1 from the cutting nozzle 1a of the cutting unit 20a, the divided flows 11a, 12
a is generated, and a part of the slag is blown far backward along the longitudinal end 4a by the branch flow 12a, and the melting nozzle 1 of the melting unit 20c on the lower surface side is blown away.
This is because slag can be prevented from entering and adhering to the preheating nozzle 7c and the preheating nozzle 7c. Another example is the edge start method introduced in Japanese Patent Application Laid-open No. 130677/1983. In this method, as shown in Fig. 5a, a flame 9a from a preheating nozzle 7a is used to heat the steel material by 20 to 70 mm from a ridge 6a that intersects the longitudinal tip of the steel material and the upper, lower, and both side surfaces, that is, the surface to be cut (only 5a is shown). Distant machined surface
D ₂ is preheated, and when it melts, the position of the preheating nozzle 7a is moved relatively to the ridge 6a side as shown in Fig. 5b to widen the melting width, and then the oxygen jet 10a is injected from the cutting nozzle 1a. The intention is to start cutting from approximately the edge 6a. [Problem to be Solved by the Invention] However, in the former surface start method of the prior art, the longitudinal ends 4a of the upper and lower and both side surfaces 5a to 5d of the steel material 3 remain as uncut zones 21, and the rolled product is Position D ₁ where surface flaws occurred and melting started
As shown in FIG. 4c, a deep cut portion called gauging 22 is formed, which causes a portion with insufficient width in the rolled product and significantly lowers the yield. In addition, in the latter edge start method of the prior art, the edge 6a at one end in the longitudinal direction of the upper and lower and both side surfaces of the rectangular cross-sectional steel material 3 is used as the continuous preheating position and the melting start position after preheating, so as shown in FIG. As shown in c, when the oxygen jet flow 10a from the melting nozzle 1a of the upper surface side melting unit 20a collides with the melting start position, it splits upward and downward into streams 11a and 12a, and the split stream 12a causes a part of the molten slag to is the longitudinal end surface 4 of the steel material
It is blown away along the direction a, and enters and adheres to the melting nozzle 1c and the preheating nozzle 7c of the lower surface side welding unit, making it impossible to perform welding. The present invention provides a method for cutting a steel material with a rectangular cross section, which solves the above problems. [Means for Solving the Problems] The present invention is characterized in that when the upper and lower and both side surfaces of a steel material having a rectangular cross section are used as the surfaces to be cut, and the surfaces to be cut are cut from one end to the other end in the longitudinal direction, The collision surface of the oxygen jet from the cutting nozzle of the cutting equipment is set at the inner surface of the tip in the longitudinal direction of the rectangular steel material, parallel to the ridge where the tip surface intersects the surface to be cut, and has a predetermined width. The collision surface of the flame flow from the preheating port of the device is set within the surface to be cut of the steel material having a rectangular cross section and parallel to the ridge that intersects the surface to be cut and the tip surface with a predetermined width. Start preheating by colliding a flame stream from a preheating crater against a set collision surface, and after the surface to be welded from the collision surface to the immediate vicinity of the ridge is melted, an oxygen jet flow is set from the cutting crater of the fusing device. A steel material having a rectangular cross section, characterized in that the steel material having a rectangular cross section is caused to collide with an impact surface, and the steel material having a rectangular cross section and a cutting device are moved relative to each other, and the oxygen jet impact surface is moved from the set impact surface to the preheated surface to be cut, and melt cutting is started. It's in the cutting method. [Operation] The operation of the above-mentioned means of the present invention is shown in Figures 1 a to e.
The explanation will be as follows. FIG. 1a shows an oxygen jet impinging surface 2 from a cutting nozzle 1 of a cutting device 20 within a longitudinal tip surface 4 of a steel material 3 having a rectangular cross section, and intersects the tip surface 4 and the surface to be cut 5. Set a predetermined width W ₁ parallel to the edge 6,
The flame flow collision surface 8 from the preheating nozzle 7 of the fusing device 20 is predetermined in parallel within the surface to be cut 5 of the steel material 3 having a rectangular cross section and along the ridge 6 that intersects the surface to be cut 5 and the tip surface 4. Shows the width W set to ₂ . In the setting state shown in FIG. 1a, the cutting device 20
A flame stream 9 is injected from the preheating nozzle 7 onto the collision surface 8 to start preheating. By this preheating, the temperature of the collision surface 8 and the space between the collision surface 8 and the edge 6 is raised to a temperature at which melting is possible, and a molten layer 13 is generated. Next, as shown in FIG.
The oxygen jet flow 10 is preliminarily divided 1 into the ridge 6 side and the center side of the tip surface 4 by colliding with the set collision surface 2 in the end surface 4 of the
I'll let you do 1, 12. In parallel with this, the melt cutting nozzle 1, the steel material 3, and the steel material 3 are moved relative to each other in the longitudinal direction to bring the ridge 6 side of the collision surface 2 closer to the ridge 6, as shown in Fig. 1c. Match. Subsequently, as shown in FIG.
By shifting to the 3 side, the ridge 6 side branch 12 of the oxygen jet 10 is always maintained and transferred to the molten layer 13, so that the collision surface 2 of the oxygen jet 10 shown in FIG. During the transition, there is no chance of the molten slag getting caught up on the tip surface 4 side and causing it to scatter.
The entire amount of molten slag is blown onto the front, uncut surface 5 to be cut, and the cutting is carried out smoothly and satisfactorily. In this way, the melting nozzle 1 of the melting device 20,
This prevents molten slag from entering and adhering to the preheating nozzle 7, and also makes it possible to melt the entire length of the upper, lower, and both side surfaces of the steel material 3 with a rectangular cross section in the longitudinal direction without leaving any uncut parts. It is. [Examples] Examples of the present invention will be described below. Fig. 2 is a drawing showing an example of melt cutting of slab 15, and shows slab 15 [carbon steel, 180~350mm thickness, 750~
2160 mm width, 4 to 10 m length, temperature: room temperature to 950°C] shows the melt cutting device 20 (8 units arranged in series) on the upper surface 5A side, the lower surface (8 units), and both sides (1 unit each). Although the cutting devices are omitted, the setting conditions for each of them are the same as those of the cutting device 20 on the upper surface 5A side. The setting conditions of the upper surface side fusing device 20 are as follows. Flame flow from preheating vent 7: LPG: 0.9N
^m3 /min (back pressure: 0.8~1.1Kg/ ^cm2 ) _O2 : 4.7N
m ³ /min (back pressure: 3.0 to 4.4 Kg/cm ² ) Angle Θ ₁ at which the flame flow 9 from the preheating nozzle 7 collides with the upper surface 5A of the slab 15: 43 to 49° Flame flow from the preheating nozzle 7 Width W ₂ of the surface 8 where the flame stream 9 collides with the upper surface 5A of the slab 15 W 2 : 30 to 60 mm Distance between the tip of the preheating crater 7 and the collision surface 8 of the flame stream 9 L ₁ : 111 to 135 mm Flame stream from the preheating crater 7 Width W ₃ between the rear end of the collision surface 8 of 9 and the ridge 6 that intersects the slab upper surface 5A and the tip surface 4 on its extension: 2 to 30 mm Oxygen jet flow from the preheating crater 1 10: 1.8~2.0
Kg/cm ² Angle Θ ₂ at which the oxygen jet flow 10 from the cutting nozzle 1 collides with the tip surface 4 of the slab 15 : 32 to 35° The oxygen jet flow 10 from the cutting nozzle 1 collides with the tip surface of the slab 15 Width _W of surface 2 that collides with 4: 5~
7.3mm The tip of the melting nozzle 1 and the collision surface 2 of the oxygen jet flow
Distance L ₂ : 176 to 183 mm The collision surface 2 of the oxygen jet flow from the melting nozzle 1
Width W 4 between the upper end and the ridge 6 where the slab tip face 4 and the upper surface 5A intersect on the extension thereof: ₆ to 31
mm After setting the various conditions for the entire fusing equipment in this way, the flame stream 9 is started to be injected from the preheating nozzle 7 onto the upper surface 5A of the slab 15, and the impact surface 8 is heated, and by this heating, the front and ₃ parts of the width W of is heated by conduction. This heating melts the collision surface 8 to a depth of about 5 to 10 mm, and also melts the collision surface 8 to a depth of about 5 to 10 mm, and
Melt W ₃ to a depth of about 2 to 6 mm to make it ready for cutting. When this preheating is completed, at the same time as stopping the injection of the flame stream 9 from the preheating nozzle 7, or continuing the injection of the flame stream 9 for a predetermined period of time, oxygen is removed from the melting nozzle 1 at an appropriate timing during the continuation. At the same time, the jet flow 10 is started to be injected onto the collision surface 2, and the slab 15 is moved in the direction of the arrow K in the speed pattern shown in _FIG . Simultaneous longitudinal cutting of the top, bottom, and both side surfaces of the slab 15 was started by passing through the collision surface 8 during internal and preheating. As a result, the entire area of the upper and lower sides and both side surfaces of the slab 15 from one end to the other end in the longitudinal direction could be satisfactorily machined in one bath without leaving any uncut parts. Regarding the velocity pattern, in particular, the velocity pattern from the time when the oxygen jet flow 10 passes through the collision surface 2 from the slab tip surface 4 through the ridge 6 to within the width W ₃ and to the collision surface 8 during preheating. The gradient of the initial velocity is preferably 3 to 6 m/min/sec. That is, 3
If it is less than m/min/sec, it is too slow and when the collision surface 2 of the oxygen jet flow 10 passes the ridge 6, a phenomenon occurs in which molten slag near the ridge 6 is trapped on the slab tip surface 4 side. . Also, if it is 6m/min/sec or more,
Although the phenomenon in which the molten slag is trapped in the slab end face 4 side does not occur, the melting process is performed too quickly, and an uncut part may be generated in the front part of the collision surface 8 during preheating. In addition, the timing between the time when the slab starts moving and the time when the oxygen pressure rises when the oxygen jet flow 10 starts to be injected from the melting nozzle 1 to the collision surface 2 is such that the time when the oxygen pressure rises is from the time when the slab starts moving. 0~+0.5sec
(O ₂ pressure: 0.3 Kg/cm ² /sec). Table 1 shows specific examples of the present invention.

〔Effect of the invention〕

As explained above, in the present invention, after setting the fusing device at a predetermined position, first, a flame stream is injected from the preheating nozzle onto the impingement surface of the material to be cut to preheat the impingement surface and the impingement surface. The temperature between the surface and the ridge is raised to a temperature that can be cut by this preheating, and a molten layer is generated. After that, an oxygen jet stream is applied from the cutting mouth of the cutting device to the set collision within the end face of the steel material with a rectangular cross section. The oxygen jet flow is divided into the ridge side and the center side of the end surface in advance by colliding with the surface, and in parallel with this or just before this, the melting nozzle and the steel material are moved relative to each other so that the ridge side of the oxygen collision surface is Since the slag is brought close to the ridge and coincident with the molten layer of the surface to be cut, the molten slag is not rolled up to the end surface and scattered, and the entire amount of molten slag is blown onto the surface to be cut on the unmelted side in front while the solvent is being transferred. Implemented smoothly and well. This prevents molten slag from entering and adhering to the cutting nozzle and preheating nozzle of the fusing equipment, and also leaves uncut portions of the upper, lower, and both side surfaces of the rectangular steel material in the longitudinal direction. The steel material is melt-cut without cutting, and it is possible to improve the yield and quality of steel materials.

[Brief explanation of the drawing]

Figures 1 a, b, c, d, and e are explanatory diagrams showing the effects of the present invention in order, Figure 2 is an explanatory diagram showing the initial setting state of the cutting machine in one embodiment of the present invention, and Figure 3 is A drawing showing the relationship between the preheating of the cutting equipment, the preheating flame for cutting, the injection pattern of cutting oxygen, and the slab moving speed pattern in one practical example of the present invention, FIG. 4a,
FIGS. 5b and 5c are explanatory diagrams showing the conventional surface starting method and its results, and FIGS. 5a, b, and c are explanatory diagrams showing the conventional edge starting method and its results. 1... Crater for melt cutting, 2... Collision surface of oxygen jet stream, 3... Steel material with rectangular cross section, 4... Tip surface of steel material,
5... Surface to be melted, 6... Edge, 7... Preheating crater,
8... Flame flow collision surface, 9... Flame flow, 10... Oxygen jet flow, 11, 12... Divided flow, 13... Molten layer, 20... Cutting device.

Claims (1)

[Claims] 1. When cutting the top, bottom and both sides of a steel material with a rectangular cross section as the surfaces to be machined from one longitudinal end of the surface to the other, the impact surface of the oxygen jet from the cutting mouth of the cutting equipment is A predetermined width is set parallel to the inner surface of the tip in the longitudinal direction of the steel material with a rectangular cross section and along the ridge where the tip surface intersects with the surface to be cut. It is set in parallel with a predetermined width within the surface to be cut and along the ridge that intersects the surface to be cut and the tip surface, and then a flame stream is made to collide with the set collision surface from the preheating mouth of the cutting device to start preheating. After the surface to be cut from the collision surface to the immediate vicinity of the ridge is melted, an oxygen jet stream is made to collide with the set collision surface from the cutting mouth of the cutting device, and the steel material having a rectangular cross section and the cutting device are moved relative to each other. A method for melt cutting a steel material having a rectangular cross section, characterized in that melt cutting is started by moving an oxygen jet impingement surface from a set impingement surface to the preheated surface to be cut.