JP2001191180A - Method of flash butt welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of flash butt welding which gives a welded zone of high quality by preventing the generation of a gap on joined faces as far as possible in a flash butt welding where members having a large sectional area and having high temperature are used as welded members. SOLUTION: An upset is performed by placing the joining faces of welded members non-parallel with each other in the process of upsetting for a flash butt welding. In this case, the joining face of the welded members are inclined by operating the operation mechanism for upsetting disposed on both sides of the welded members, while a deviation is given to the mechanism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flash butt welding method, and more particularly to a flash butt welding method suitable for a case where a member to be welded is a high-temperature large-area member.

[0002]

2. Description of the Related Art In flash butt welding, a voltage is applied between two members to be welded to generate a flash, the end surface of the member to be welded is heated and melted (flash process), and the end surface is sufficiently heated. The welding is performed by rapidly pressing each other (upset process), and the upset process is performed simultaneously with the end of the flash process.

In the upset process, an upset operation is performed by one or more upset cylinders, but the upset is performed so that the contact surfaces of the members to be welded are always parallel. This is because if the welding is not performed with the contact surfaces of the members to be welded parallel to each other, the member after welding is bent at the joint surface. In order to make the contact surfaces of the members to be welded parallel to each other, for example, when performing an upset operation with one upset cylinder, the guide of the movable head holding the member to be welded on the movable side should be of a high rigidity. In order to maintain parallelism and to operate with multiple upset cylinders, synchronize the movement of each cylinder and control so that the direction vector of the upset operation is always perpendicular to the joint surface I have.

[0004] Further, a plurality of depressions are formed on the end face of the member to be welded after the flash step is completed by an arc generated at the time of flashing. However, this is usually buried by deformation due to a large pressure that presses the end surfaces of the members to be welded at the time of upset, and a gap is rarely left on the joint surface.

[0005]

However, when flash butt welding of a member having a high temperature and a large cross-sectional area as a member to be welded, a large diameter deformation of the member to be welded occurs at the time of upsetting, so that a sufficient welding pressure cannot be obtained, so There is a problem that voids remain on the surface. This is a problem particularly in a high-temperature large-area member having a member temperature of 1,000 ° C. or more and a joint having a sectional area of 10,000 mm ² or more.

For example, in the case of a carbon steel member having a diameter of 200 mm, as shown in FIG. 7, when the member temperature is 950 ° C., the contact pressure reaches 70 MPa sufficient for welding with an increase in the upset amount (member pressing distance). But the member temperature is 1,
In the case of 150 ° C, 40 MPa even if the upset amount is increased
Surface pressure can only be secured.

For this reason, when upsetting a high-temperature large-area member, it is impossible to apply a sufficient surface pressure to deform the end face of the member to be welded. It will remain on the surface and the quality of the weld will be reduced. This phenomenon becomes more conspicuous as the member temperature increases and the cross-sectional area of the joint increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. When flash butt welding of a high-temperature large-area member as a member to be welded, particularly when the temperature of the member is 1,000,
0 ° C. or higher and the cross-sectional area of the joint is 10,000 mm ²
It is an object of the present invention to provide a flash butt welding method that can minimize the occurrence of voids on a joint surface and obtain a high-quality weld even when the above-described high-temperature large-area members are subjected to flash butt welding.

[0009]

The above object is achieved by the following invention. [1] A flash butt welding method in which, in an upset step of flash butt welding, upsetting is performed with the joining surfaces of the members to be welded in a non-parallel state. [2] In the above [1], the joining surface of the member to be welded is set at 5 °
A flash butt welding method characterized by inclining at an angle within the range. [3] The method according to [1] or [2], wherein the temperature is 1,0.
The temperature is over 00 ° C and the cross-sectional area of the joint is 10,000mm
A flash butt welding method comprising welding ^two or more members to be welded. [4] The flash according to the above [1] to [3], wherein the upset operating mechanism arranged on both sides of the member to be welded is operated with a deviation to incline the joint surface of the member to be welded. Butt welding method.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In flash butt welding, a voltage is applied between two members to be welded to generate a flash, the end surface of the member to be welded is heated and melted (flash process), the end surface is sufficiently heated, and The welding members are rapidly pressed together (upset process) for welding.

FIG. 1 is an explanatory view of a flash butt welding method according to the present invention. Here, one of the members to be welded 1
The (fixed-side welded member) is gripped and fixed by a fixed-side head 3 having a member gripping mechanism, while the to-be-welded member 2 (movable-side welded member) is a movable-side head 4 having a member gripping mechanism.
Is gripped by The movable head 4 is provided with upset operating mechanisms 5 and 6 on both sides of the member 2 to be welded, and its operation is independently controlled by the upset control means 7. That is, the operation control of the member to be welded during welding is performed by the upset operation mechanisms 5 and 6 whose operations are independently controlled by the upset control means 7.

As the upset operation mechanisms 5 and 6, for example, hydraulic cylinders can be used.

In the flash butt welding method according to the present invention having the above-described structure, the joining surface of the member 2 to be welded is placed in a non-parallel state (inclination angle θ) as shown by a solid line in FIG.
Upset is performed while

As described above, since the joining surface of the member to be welded is set up in a non-parallel state, the pressure is applied from the end of the contact surface of the member to be welded. The metal or softened metal flows more easily. As a result, the depression created by the arc in the flash step is easily filled, and the gap after welding is dramatically reduced.

Such an effect is obtained when the member temperature is 1,000 ° C. or more and the sectional area of the joint is 10,000.
This is particularly noticeable when a high-temperature large-area member of 0 mm ² or more is used.

To make the joint surfaces of the workpieces 2 non-parallel at the time of upset, a predetermined deviation is provided in the operation commands given to the upset operation mechanisms 5 and 6, and the movable-side workpieces are operated.

This is, for example, the upset operation mechanism 5,6
This can be achieved by giving a time difference to the operation command given to. That is, by giving a time difference to the operation commands given to the upset operation mechanisms 5 and 6, the joint surfaces between the members to be welded at the time of the upset are not parallel, and the joint surfaces of the members 2 to be welded are the joint surfaces of the members 1 to be welded. With a predetermined inclination angle θ.

When a hydraulic cylinder is used as the upset operating mechanism, the switching valve is operated with a time difference as shown in FIG. 2 so that the displacement of each cylinder becomes a constant distance deviation as shown in FIG. Move with ΔX. This method is effective when a constant flow rate switching valve is used, and the configuration is simple because only opening / closing timing needs to be controlled.

The inclination θ of the contact surface of the member 2 to be welded can be obtained by the following equation from the distance between the cylinders, that is, the ratio ΔX / Y between the distance Y between the connection points between the cylinders and the movable head and ΔX. θ = tan ⁻¹ (ΔX / Y) (1)

Here, at the end of the upset process, the distance deviation ΔX of each cylinder is set to zero, and the center line between the members to be welded is aligned, whereby bending at the joint surface can be eliminated.

Note that the inclination angle θ is preferably within 5 °, more preferably 2 ° to 5 °. When the angle θ exceeds 5 °, not only does the structure of the welding machine body become complicated, but also when performing the operation of aligning the center line at the end of the upset process, a large force in the shear direction is applied to the joint of the members to be welded, This is because a defect such as a crack may occur in the welded portion.

As another method of operating the operation commands given to the upset operation mechanisms 5 and 6 with a predetermined deviation,
There is a method of giving an operation speed command while feeding back the position deviation shown in FIG. 4, or a method of giving a difference in the upset operation speed characteristics, for example, the valve opening degree shown in FIG.

In the method of feeding back the position deviation, the upset can be performed while maintaining a constant position deviation even when the valve opening changes with time. For this reason,
Upset can be performed at higher speed, and stable quality can be obtained.

The method of giving a difference in the upset operation speed characteristics is a method in which the upset operation mechanisms 5 and 6 are given in advance an operation speed characteristic capable of giving a predetermined deviation, and compared with the method of feeding back the position deviation. It is also possible to use control means with a slow processing speed.

Table 1 shows that the temperature of the member to be welded was 1150 ° C. and the cross-sectional area of the joint was 30,000 m by the method of the present invention.
porosity on the joint surface when flash butt welding is performed for the m ² (area of void / area of joint surface × 1)
00) is the result of the experiment.

[0026]

[Table 1]

As shown in Table 1, when the inclination of the joining surface is 2 ° or more and 5 ° or less, the porosity is 0.20% or less, which is a good result.

The relationship between the inclination of the joining surface and the porosity in the experimental results shown in Table 1 differs depending on the temperature of the member to be welded, the sectional area of the joint, and the sectional shape of the joint.

[0029]

As described above, according to the method of the present invention,
In the upset process at the time of flash butt welding, by setting up the joining surface of the members to be welded in a non-parallel state, even if the member to be welded is a high-temperature large cross-section member, the occurrence of voids on the joining surface is minimized, High quality welds can be obtained.

Further, by setting the inclination of the joining surface of the members to be welded in a non-parallel state to 5 ° or less, a higher quality welded portion can be obtained.

The above effect is obtained when the member temperature is set at 1,000
0 ° C. or higher and the cross-sectional area of the joint is 10,000 mm ²
This is particularly noticeable when the above-described high-temperature large-section-area member is used.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a flash butt welding method according to the present invention.

FIG. 2 is a diagram showing operation timing of a switching valve when a hydraulic cylinder is used.

FIG. 3 is a diagram showing displacement of a hydraulic cylinder.

FIG. 4 is an explanatory diagram of a method of performing an operation speed command while feeding back a position deviation.

FIG. 5 is an explanatory diagram of a method for giving a difference in operating speed characteristics, for example, a valve opening degree.

FIG. 6 is a diagram showing a relationship between a member pressing distance and a surface pressure when a carbon steel member is used.

[Explanation of symbols]

 1, 2 Welded member 3 Fixed side head 4 Movable side head 5, 6 Upset operation mechanism 7 Upset control means

Claims (4)

[Claims] 1. A flash butt welding method in which, in an upset step of flash butt welding, upsetting is performed with the joining surfaces of the members to be welded in a non-parallel state. 2. The flash butt welding method according to claim 1, wherein the joining surface of the member to be welded is inclined within an angle range of 5 ° or less. 3. The flash butt according to claim 1, wherein a member to be welded having a temperature of 1,000 ° C. or more and a cross-sectional area of a joint portion of 10,000 mm ² or more is welded. Welding method. 4. The apparatus according to claim 1, wherein the upset operating mechanisms arranged on both sides of the member to be welded are operated with a deviation so as to incline the joining surface of the member to be welded.
A flash butt welding method according to claim 3.