JPH0788511A - Mandrel for manufacturing seamless steel tube and device for forming hardened layer - Google Patents

Abstract

PURPOSE:To provide a mandrel for manufacturing a seamless steel tube, of which the outside diameter is uniform and the life is extended with the formed hardened layer firmly stuck to the base material, and a device for forming a hardened layer in order to manufacture this mandrel. CONSTITUTION:A first head 15 is supported in a freely ascendable and descendable state on a guide post 13 which is fixed on a freely running truck 12, an arm 16 is supported freely movably on the first head 15 along a direction crossing the travelling direction of the truck 12; and a vibrator 17 is supported freely rotatably on the axis in the direction nearly perpendicular to a part of the arm 16. A second head 18 is attached to this vibrator 17, and an electric discharge machine 23 is held on the second head 17 through a holding member 19. An object to be machined 1 is worked with the electrode of the electric discharge machine 23 at a proper interval and the machine 23 is actuated, simultaneously the machine 23 is vibrated by the vibrator 17, and an electric discharge machining is performed while the truck 12 is run, forming a hardened layer 3 on the surface of a base material 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a core rod used for manufacturing a hot seamless steel pipe, and a hardened layer forming apparatus suitable for processing the structure.

[0002]

2. Description of the Related Art A core rod (mandrel bar) is used to form an inner circumference in the production of a hot seamless steel pipe. The material of this mandrel bar is generally made of special steel, which is machined to suit the diameter of the steel pipe to be manufactured, and is then hardened by heat treatment (quenching). .

When using a mandrel bar,
Carbon is applied to the surface of the core rod as a lubricant to reduce friction between the inner surface of the manufactured steel pipe and the core rod.

[0004]

However, in the above-mentioned conventional lubricant application, since the surface of the core rod has a smoothness by the grinding process, it is difficult to fix the applied carbon and the carbon is easily peeled off. There is a risk that Further, there is a possibility that the adhesion may become uneven in the applied state, and the outer diameter of the core rod may become non-uniform.

In the conventional core rod, the use limit is 1,
It is about 000 to 1,200 times, and the core rod that has reached the end of its life is diverted for small-diameter steel pipe by re-cutting the surface and then subjecting it to heat treatment.

Therefore, an object of the present invention is to improve the surface of the core rod so as to make the outer diameter uniform and to extend the life of the core rod for producing a seamless steel pipe, and to process the core rod. It is to provide a hardened layer forming apparatus.

[0007]

As a technical means for achieving the above object, a core rod for producing a seamless steel pipe according to the present invention is made of a special steel which is ground to suit the diameter of a steel pipe to be produced. It is characterized in that a hardened layer made of refractory metal, chromium carbide, tungsten carbide or the like is formed on the surface of the base material which is heat-treated and processed.

The hardened layer forming device for manufacturing the core rod for producing seamless steel pipe is movable in a predetermined direction, and a carriage to which a guide column is fixed and a vertically movable body along the guide column. A first head supported by a guide pillar, an arm supported by the first head so as to be movable along a direction intersecting with a moving direction of the carriage, and a parallel position with the guide pillar at an appropriate position of the arm. A vibrator that is rotatably supported with respect to the arm about a direction, a second head that is supported by the vibrator, and a second head that is detachably attached to the second head and that is used for electrical discharge machining on a workpiece. And an electric discharge machine for forming a hardened layer made of refractory metal, chromium carbide, tungsten carbide, etc. Pair with the first head Steel pipe to be manufactured by the electric discharge machine while adjusting the moving position of the arm and the rotating position of the vibrator with respect to the arm to vibrate the second head by the vibrator and move the carriage. It is characterized in that the hardened layer is formed on the surface of the base material processed by subjecting the special steel that is ground and adjusted to the above diameter to a heat treatment.

If a suitable number of electric discharge machines are detachably attached to the second head, a wide range of machining can be performed by one machining operation. In addition, the electric discharge machining may be performed on the workpiece while the arm is reciprocally moved with respect to the first head as necessary.

That is, the present invention is, as a hardened layer forming apparatus, a carriage which is movable in a predetermined direction and to which a guide pillar is fixed, and a first head which is supported by the guide pillar so as to be vertically movable along the guide pillar. An arm supported by the first head so as to be movable along a direction intersecting with a moving direction of the carriage, and an arm at an appropriate position of the arm about an axis substantially parallel to the guide column. A vibrator rotatably supported, and a second head supported by the vibrator,
And an electric discharge machine which is detachably attached to the second head and which performs electric discharge machining on the workpiece to form a hardened layer made of refractory metal, chromium carbide, tungsten carbide or the like. The positional relationship of the electric discharge machine is adjusted by the raising / lowering position of the first head, the moving position of the arm with respect to the first head, and the rotating position of the vibrator with respect to the arm, and the second position is adjusted by the vibrator.
The hardened layer is formed on the surface of the workpiece by the electric discharge machine while the head is vibrated and the carriage is moved.

[0011]

The hardened layer formed on the surface of the ground material which has been ground and heat-treated is firmly fixed to the base material to make the outer diameter uniform. Further, since the adherence is strong, it is not easily peeled off and the life of the steel pipe manufacturing core rod is extended.

Further, the work piece for the core rod is arranged in the traveling range of the carriage, and the respective positions of the first head, the arm and the vibrator are adjusted, and the electrode of the electric discharge machine and the work piece are adjusted. The gap between and is a predetermined one. Then, a hardened layer made of refractory metal, chromium carbide, tungsten carbide, or the like is formed on the workpiece by electrical discharge machining. At this time, the work is performed while appropriately rotating the base material which is the workpiece. Then, by vibrating the electric discharge machine with an appropriate amplitude by the vibrator, the hardened layer can be formed evenly on the surface of the workpiece. Further, the hardened layer can be formed in a predetermined range of the workpiece by moving the cart.

By performing the working operation while reciprocally moving the arm with respect to the first head, the working range can be further widened and the hardened layer can be formed on the surface of the flat plate or the curved plate. .

[0014]

EXAMPLES A core rod for producing a seamless steel pipe and a hardened layer forming apparatus according to the present invention will be specifically described below with reference to the illustrated examples.

FIG. 2 is a cross-sectional view of the end of the mandrel bar. The work piece 1 is composed of a base material 2 which has been heat treated by quenching by grinding the surface of a solid cylinder made of special steel by machining. . A hardened layer 3 made of refractory metal, chromium carbide, tungsten carbide or the like is formed on the surface of the base material 2 by electric discharge machining.

1 and 3 to 5 are schematic views of an apparatus for forming a hardened layer 3 on the base material 2 by electric discharge machining. As shown in FIGS. 1 and 3, a rail 11 is laid at a work place, and a carriage 12 is guided by the rail 11 to travel. A bearing portion 12a is attached to the upper surface of the dolly 12, and a rotor 12b is rotatably supported by the bearing portion 12a about a vertical axis. A pair of guide columns 13 extending to an appropriate height are fixed to the upper surface of the rotor 12b, and a drive unit 14 accommodating a drive mechanism is attached to the upper end of the guide columns 13. The first head 15 is suspended from the drive section 14 by the drive chain 15a.
Is guided by the guide column 13 and is movable up and down.

An arm 16 is movably supported on the first head 15, and the moving direction of the arm 16 is the carriage.
It is along the direction that intersects with the 12 movement directions.
A shaft portion 17a rotatable about the arm 16 is supported at the tip of the arm 16 about an axis substantially parallel to the guide column 13, and a vibrator 17 is attached to the lower end of the shaft portion 17a. It is installed. The vibrating portion 17b of the vibrator 17 supports a second head 18 having a substantially triangular shape.
The operation of 17 vibrates in the arrow P direction shown in FIGS. The second head 18 is assembled into a frame shape by a band material, an angle material, etc., and the lower surface is formed by a pair of band materials 18a arranged at appropriate intervals as shown in FIG. A support hole 18b is formed by a long hole extending in the longitudinal direction.

A holding member 19 is detachably attached to the lower surface of the second head 18. This holding member 19
As shown in FIG. 5, the angle member and the band member are formed into a substantially right-angled triangle, and a pair of mounting bolts 20 are planted on the other side with its oblique side being the lower side. The holding member 19 is attached to the second head 18 by inserting the attachment bolt 20 into the support hole 18b and tightening the nut at the end. Then, the mounting position of the holding member 19 is changed by changing the position of the mounting bolt 20 with respect to the support hole 18b.

A guide rail 19a is provided on the outer surface of the oblique side of the holding member 19 along the oblique side, and the slider 21 is guided by the guide rail 19a so as to be movable.
Is provided. An electric discharge machine 23 having an electrode 24 at its tip is detachably attached to a holding plate 21a formed under the slider 21 by a holding band 22 or the like.

On the other hand, as shown in FIG. 1, a work piece 1 which is a core rod of a seamless steel pipe is mounted on a work table 4 arranged in the vicinity of both end portions of the guide rail 11 on both ends of the work piece 1. The unit is held and rotated by the work table 4 at an appropriate speed about the longitudinal direction.

The operation of producing a core rod for producing a seamless steel pipe by the hardened layer forming apparatus according to the present invention constructed as described above will be described below.

With respect to the work piece 1 held on the work table 4, the electrode 24 of the electric discharge machine 23, as shown in FIG.
The position of the holding member 19 is adjusted so that the center of the work piece 1 is located on the extension of. For this adjustment, the direction of the electrode 24 with respect to the workpiece 1 is such that the vibrator 17 is attached to the arm 16 and the shaft portion 17a.
The first head 15 is moved up and down with respect to the guide column 13 for the height relationship, and the arm 16 is moved to the first head 15 with respect to the positional relationship in the direction intersecting the longitudinal direction of the workpiece 1. This is done by moving it to the other side.

When the position adjustment is completed, the electric discharge machine 23
Operate. Next, the vibrator 17 is operated to vibrate the second head 18 in the direction of the arrow P in FIG. When the electric discharge machine 23 operates, the refractory metal, chromium carbide, tungsten carbide and the like are sequentially fixed to the surface of the base material 2 to form the hardened layer 3.

Although the electrode 24 is worn as the hardened layer 3 is formed, the gap between the electrode 24 and the workpiece 1 is kept constant. That is, the holding portion plate 21a holding the electric discharge machine 23 is formed on the slider 21.
Reference numeral 21 is adapted to slide on the guide rail 19a. Since the slider 21 is provided on the oblique side of the holding member 19, the guide rail 19a is obliquely arranged, and the lower end portion thereof is the work 1 side. Therefore, the electric discharge machine 23 moves to the work piece 1 side by its own weight, and when the electrode 24 wears, the gap between the work piece 1 and the work piece 1 becomes large. This maintains the gap at a predetermined size.

Next, a case where a flat plate is used as the workpiece 1 and the hardened layer 3 is formed on the surface thereof will be described with reference to FIG. In the case of a flat plate, unlike the case of a core rod, the workpiece 1 cannot be rotated and the processing range is widened.
For this reason, as shown in FIG. 3, the direction of the second head 18 is set to a state in which the direction of the second head 18 is rotated by approximately 90 degrees when processing the core rod for manufacturing the steel pipe. During processing, the arm 16 is reciprocated with respect to the first head 15 in addition to the vibration of the vibrator 17 and the traveling of the carriage 12, so that the electrode 24 can be moved over the entire surface or a predetermined portion of the workpiece 1. To face.

The number and the mounting position of the electric discharge machine 23 required for machining are determined by the width of the flat plate and the moving distance of the arm 16.

Further, depending on the shape of the workpiece 1, the rotor 12b is rotated with respect to the bearing portion 12a so that the hardened layer is formed with the arm 16 parallel to the rail 11. You can also

[0028]

As described above, according to the core rod for producing a seamless steel pipe according to the present invention, since the hardened layer is formed on the surface, the outer diameter of the core rod can be made uniform. , The life can be extended.

Further, according to this hardened layer forming apparatus, when a hardened layer is formed on the surface of a base material for producing a core rod for producing a seamless steel pipe, the hard material is formed at a constant speed with respect to the base material. Since the cured layer is formed while vibrating the electrodes, the thickness of the cured layer can be made uniform and the outer diameter of the core rod can be made uniform. Moreover, since the hardened layer is formed by electric discharge machining, it is firmly fixed to the base material and is not easily peeled off, and the life of the core rod can be extended.

Further, when the hardened layer is formed, the hardened layer can be formed even on a workpiece having a large width by performing work while reciprocally moving the arm of the hardened layer forming apparatus. According to the requirements, a hardened layer can be formed on the surface of the flat plate.

[Brief description of drawings]

FIG. 1 is a front view showing a state in which a surface of a work piece is processed by a hardened layer forming device according to the present invention to manufacture a core rod for producing a seamless steel pipe.

FIG. 2 is a sectional view of a part of a core rod for producing a seamless steel pipe according to the present invention.

FIG. 3 is a side view of this apparatus for forming a hardened layer, showing a case where a hardened layer is formed on a flat plate.

FIG. 4 is a schematic view taken along the line AA in FIG.

5 is a schematic view taken along the line BB in FIG.

[Explanation of symbols]

 1 Workpiece 2 Base material 3 Hardened layer 12 Carriage 13 Guide column 15 First head 16 Arm 17 Vibrator 17a Shaft part 18 Second head 19 Holding member 19a Guide rail 20 Mounting bolt 21 Slider 23 Electric discharge machine 24 Electrode

Claims (3)

[Claims] 1. A surface of a base material, which is processed by heat-treating a special steel that is ground and adapted to the diameter of a steel pipe to be manufactured,
A core rod for producing a seamless steel pipe, characterized in that a hardened layer made of a refractory metal, chromium carbide, tungsten carbide, etc. is formed. 2. A dolly which is movable in a predetermined direction and to which a guide pillar is fixed, a first head which is supported by the guide pillar so as to be vertically movable along the guide pillar, and intersects with the moving direction of the dolly. An arm movably supported by the first head, and a vibrator rotatably supported on the arm at an appropriate position on the arm about a direction substantially parallel to the guide column. And a second head supported by the vibrator, and detachably attached to the second head, and a workpiece is subjected to electric discharge machining to form a hardened layer made of refractory metal, chromium carbide, tungsten carbide, or the like. The electric discharge machine has a positional relationship with respect to the workpiece. The vertical position of the first head, the moving position of the arm with respect to the first head, and the rotation of the vibrator with respect to the arm. Rank And the second head is vibrated by the vibrator, and the electric discharge machine is used while moving the carriage.
A hardened layer for producing a core rod for producing a seamless steel pipe, characterized in that the hardened layer is formed on the surface of a base material processed by heat-treating a special steel that is ground and adapted to the diameter of the steel pipe to be manufactured. Forming equipment. 3. A carriage which is movable in a predetermined direction and to which a guide pillar is fixed, a first head which is supported by the guide pillar so as to be vertically movable along the guide pillar, and intersects with the moving direction of the carriage. An arm movably supported by the first head, and a vibrator rotatably supported on the arm at an appropriate position on the arm about a direction substantially parallel to the guide column. And a second head supported by the vibrator, and detachably attached to the second head, and a workpiece is subjected to electric discharge machining to form a hardened layer made of refractory metal, chromium carbide, tungsten carbide, or the like. The electric discharge machine has a positional relationship with respect to the workpiece. The vertical position of the first head, the moving position of the arm with respect to the first head, and the rotation of the vibrator with respect to the arm. Rank And the second head is vibrated by the vibrator, and the electric discharge machine is used while moving the carriage.
An apparatus for forming a hardened layer, wherein the hardened layer is formed on the surface of a workpiece.