JPS6039466B2 - Plasma arc cutting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cutting steel pipes with high efficiency using a plasma torch (cutting torch).

Conventionally, square steel pipes, rectangular steel pipes, and round steel pipes manufactured using steel pipe manufacturing equipment, press equipment, or welded structures have closed cross-sectional shapes, so circular saws such as mirror cutters or segment saws are used as cutting equipment. It's here.

For example, in the former type of saw, a disk with mirror-shaped gears cut on its outer periphery is rotated at high speed by an electric motor, and the saw blade is sent by a hydraulic cylinder, etc., and this occurs when the saw blade comes into contact with the material to be cut. Cutting was performed using frictional heat.

This saw cutter has the following features: {1) It is possible to cut objects with an open cross section using a single disc.

■ Although it has the advantage of being able to cut at a high speed of up to 200 ribs/sec, in view of the working environment, which has become increasingly harsh in recent years, ■ The cutting noise can reach 120 to 13 MB, resulting in large costs. Even if you install soundproofing equipment, the problem cannot be completely resolved.

■ Molten iron powder is scattered around, causing environmental deterioration.
Great personal risk.

■ If the cutting conditions are not met, the saw blade will be damaged and there is a high risk of personal injury.

■ Cutting quality was poor, with burrs remaining during cutting, which not only required maintenance and labor in post-processes, but also caused human accidents due to these burrs.

The latter type of segment saw has the same mechanical structure as a saw cutter, but has the disadvantages of attaching a carbide tip to the mirror blade to perform the cutting work, cutting surface quality, noise, human danger, etc. Although it was superior to mirror cutting machines, the biggest problem was that the cutting speed was slow.

Plasma cutting equipment is available as a method for cutting square steel pipes and rectangular steel pipes very efficiently, eliminating the drawbacks of the conventional techniques.

However, in this plasma cutting, if the corner R part is cut at the same speed as the flat plate part, the corner R part will be cut off, and if the corner R part is cut at a speed that completely cuts the corner R part, the entire corner R part will be cut. There was a problem that the cutting time was extremely long.

An object of the present invention is to provide a method for eliminating such drawbacks and completely cutting corner R portions of rectangular woven pipes and the like with high efficiency.

FIG. 1 shows an example of a cut section A and a speed pattern B in conventional constant speed cutting, where 1 shows a square steel pipe, 2 a plasma cutting torch, 3 a corner R part of a square steel pipe, and 4 a flat plate part of a square steel pipe.

According to this constant speed cutting, when attempting to completely cut a corner R part, as is clear from the speed pattern in Figure 1, it is possible to cut only at a low speed, and as a matter of course, the cutting time becomes longer. For example, if this type of equipment is used to manufacture continuous-stitched steel pipes, it will be extremely inefficient as the steel pipes will have to be cut long or the line speed will be slowed down.

Furthermore, if a certain distance cutting is performed to cut the flat plate portion, an uncut portion 5 will be generated inside the corner R portion as shown in FIG. 2, and the function will not be fully achieved.

FIGS. 3A and 3B show examples of cutting surfaces and speed patterns in speed controlled cutting according to the present invention, and one embodiment of the present invention will be explained with reference to these figures. In the figure, reference numeral 11 indicates a square steel pipe, and reference numeral 12 indicates a plasma cutting torch, and the plasma cutting torch 12 is movably disposed in a plasma cutting device (not shown).

Four plasma cutting torches 12 are arranged corresponding to each side of the square steel pipe 11, and each side is cut simultaneously. In cutting each surface, each plasma cutting torch 12 (hereinafter simply referred to as the torch 12) is moved linearly from the torch movement starting point 15 and the distance from corner R low speed cutting range 16 to 17 is linearly moved at low speed. Cut while moving, cut while moving at high speed from flat part high speed cutting range 18 to 19, further cut while moving at low speed again from corner R part low speed cutting range 20 to 21, and then cut while moving at low speed again, and then cut while moving at high speed from flat part high speed cutting range 18 to 19. to complete the cutting. In this case, the four sides of the square steel pipe 11 are simultaneously cut by moving the four torches 12 linearly along the flat portion of the material to be cut. Accordingly, the present invention was tested and the following results were obtained. That is, a test was conducted on a 30-degree square steel pipe with a board size of 12.7 fences, keeping conditions other than the cutting speed constant.

As a result, the cutting speed for the flat plate section was 42 sails/sec, the speed for completely cutting the corner R section was 23 sails/sec, and the average speed at which complete cutting was possible by controlling the torch speed was 35 sails/sec.
was obtained, and it became possible to cut the cutting time of a square steel pipe of 30 seconds by about 5 seconds compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1A is an example of a cutting plane in conventional constant distance cutting, FIG. 1B is a speed pattern diagram in FIG. 1A, FIG. 2 is a plan view of a cutting part, and FIG. 3A is a cutting plane in the method of the present invention. An example diagram, FIG. 3B, is a speed pattern diagram in FIG. 3A. Soup Z diagram ga' diagram) O diagram (8) Outside 3 diagram of 3 diagram (B)

Claims (1)

[Claims] 1. When cutting a material to be cut with a plasma cutting torch that has a corner portion, a plurality of plasma cutting torches arranged with their injection ports directed toward the material to be cut are each moved linearly in a direction parallel to the cutting flat portion of the rectangular material to be cut. A plasma arc cutting method characterized in that the absolute moving speed of the material is changed to a low speed in the corner portions of the material to be cut and a high speed in the flat portions of the material to cut the material.