JPS5933475B2 - Automatic gas pressure welding method - Google Patents

Description

[Detailed description of the invention] The present invention relates to an automatic gas pressure welding method.

The gas pressure welding method does not require a power source and can produce joints with high joint strength S, so it is widely used for on-site work on reinforcing bars and rails.

There is also a method in which the pressure welding process is divided into a plurality of steps and the steps are sequentially executed by sequence control to automatically perform the work. FIG. 1 shows an example of an automatic gas pressure welding device, in which a main body 6 of the pressure welding device 5 is supported by a workpiece 1 via a fixed chuck 7. As shown in FIG.

The main body 6 is equipped with a ring-shaped burner 8 and a sliding block 10 that eject gas flames from a plurality of nozzles 9 to heat the joint 3. It is attached. A movable chuck 11 provided on the sliding block 10 grips the other workpiece 2 . The sliding block 10 moves along the axis of the materials to be joined 1 and 2 by the action of a hydraulic cylinder 12 connected thereto, and the materials to be heated 1 and 2 whose joint portions 3 are heated by the burner 8 Apply strong pressure to join. The operation of the device is controlled by a controller (not shown) including a microcomputer. In the above-mentioned automatic gas pressure welding, conventionally, after the joint part 3 is heated to the pressure welding temperature, the workpieces 1,
2 was pressurized.

That is, the hydraulic cylinder 12 is driven and pressurized as described above, but at this time, when the amount of upset reaches a required value, the pressurizing force is immediately released, or the pressurizing force is maintained as it is for an appropriate period of time. . However, if the pressing force is immediately released, a tensile force f acts on the joint 3, and solidification cracks R occur as shown in FIG. 2A.

Furthermore, if the pressing force is maintained as it is, the upset will proceed further and the joint 3 will buckle as shown in the opening in FIG. 2, and further surface cracks S will occur. This invention was made to solve the above-mentioned problems in conventional automatic gas pressure welding, and aims to provide an automatic gas pressure welding method that can obtain joints in good shape without defects such as cracks. It is something.

In this invention, after the amount of upset reaches a set value, the materials to be joined are pressed and held by a cut pressure smaller than the pressure applied during upset.

When the bonded portion solidifies and contracts, the above-mentioned pressurizing force gives the materials to be bonded a displacement commensurate with the contraction, so that the bonded portion does not generate any tensile force, and therefore no solidification cracking occurs. Further, since the magnitude of the pressing force is smaller than the pressing force at the time of upset, an excessive compressive force is not generated in the joint, and the joint does not buckle or crack the surface. This invention will be explained in detail below.

FIG. 1 shows a pressurization control system used in carrying out the present invention.

A hydraulic pump 14 is connected to the hydraulic cylinder 12 via a conduit 13. Electromagnetic switching valves 15, 16, and 17 are connected to the conduit 13 in parallel, respectively. Relief valves 18 and 19 are provided on the outlet sides of the switching valves 15 and 16, respectively.
are connected, and the set pressure of the former relief valve 18 is set higher than that of the latter relief valve 19. The switching valve 17 is for releasing hydraulic pressure. Any one of these three switching valves 15, 16, 17 is in an open state,
The other two are closed. An offset amount detector 20 is attached to the main body 5 of the pressurizing device, and the detector 20 detects the displacement of the sliding block 10, that is, the offset amount using a direct acting potentiometer 21. The output of the detector 20 is input to an operational amplifier 22. An upset setter 23 is connected to the input side of the operational amplifier 22, and the output side is connected to the base of a transistor 24. An electromagnetic coil 25 of a relay is connected to one side of the emitter of the transistor 24, and a switch 25a is switched by excitation of the electromagnetic coil 25. FIG. 3 shows an example of the automatic gas pressure welding process of the present invention, and the process consists of 10 steps.

A and B are periods during which oxygen and acetylene gas are ejected from burner 8 (see FIG. 1), respectively. C indicates a period during which the burner 8 vibrates or moves in the axial direction of the welded materials 1 and 2, and D indicates a period during which the burner 8 swings around the axis. Further, E is a period during which the hydraulic pump operates to supply pressure oil to the hydraulic cylinder 12, and F is a period during which pressure oil is released from the hydraulic cylinder 12 and the pressure on the joint portion 3 is released. Furthermore, G is the hydraulic cylinder 1
2 indicates the pressurizing pattern of the joint portion 3 due to the operation, and H indicates the amount of compression of the joint portion 3 due to pressurization. In the above pressure welding process, the joining part 3 is heated during steps 3 to 6.
When the temperature reaches the proper temperature (time a), the hydraulic pump 14 is activated.

At this time, since the switching valves 16 and 17 are closed, the hydraulic cylinder 12 is pressurized to the set pressure of the relief valve 18. As a result, the joint portion 3 is pressed, and the amount of compression, ie, the amount of upset, gradually increases as shown by H in FIG. When the offset amount reaches the set value M (time b
), the heating is stopped and the pressing force is lowered, and this state is maintained until the solidification of the joint 3 is almost completed. The level of the lowered pressure may be such that the joint 3 can solidify and shrink smoothly, and should be about 50 to 80% lower than the pressure before lowering.
%.

The above-mentioned switching of the pressing force is automatically performed as follows.

In FIG. 1, the difference between the upset signal from the detector 20 and the target value from the setter 23 is amplified by an operational amplifier 22, and its output is input to a transistor 24 as a base current. When the output of the transistor 24 reaches a certain value in accordance with the base current, the electromagnetic coil 25 is activated and the switch 25a is switched from contact b to contact a. This results in
The switching valve 15 is closed, the switching valve 16 is opened, and the pressure in the hydraulic cylinder 12 becomes the pressure set in the relief valve 19.
Pressure force becomes lower. Note that the pressing force is released by opening the switching valve 17. Next, to explain an embodiment of the present invention in comparison with a conventional example, the material to be joined is a steel pipe (SG
P5OA6O. The heating time was 60 seconds. Table 1 shows the results of gas pressure welding under different pressure conditions. As shown in Table 1, according to the method of the present invention, there were no defects in the joints, and joints with good shapes were obtained.

[Brief explanation of the drawing]

Fig. 1 shows an example of an apparatus for carrying out the method of the present invention, and Fig. 2 shows a schematic diagram showing the state of the joint according to the conventional method, and Fig. 2 shows the state of the joint according to the present invention. 3 and 3 are diagrams showing the gas pressure welding process of the present invention. 1, 2... Material to be joined, 3... Joint part,
5...Pressure device, 7, 11...Chuck, 8...Burner 12...Hydraulic cylinder, 14...Hydraulic pump, 15, 16, 1
7... Switching valve, 18, 19... Relief valve, 20... Abset amount detector, 22 Operational amplifier, 24... Transistor, 25...
...Electromagnetic coil.

Claims (1)

[Claims] 1. An automatic gas pressure welding method characterized in that after the amount of upset reaches a set value, the pressurizing force subsequently applied to the materials to be welded is made weaker than the pressurizing force during the upset and the pressure is maintained.