JPS5934478B2 - ERW steel pipe manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for producing an electric resistance welded pipe in which a welding atmosphere is adjusted during the production of an electric resistance welded steel pipe in which strip-shaped skelps are continuously formed into a tubular shape and welded.

In the electric resistance welded steel pipe manufacturing method, for example, high-frequency induction welding, the skeleton 1 (
The edge portion 3 of the tubular skelp (hereinafter referred to as a tubular skelp) is heated to a welding temperature by an eddy current induced by a high frequency current flowing through the work coil 2, and is pressure welded by a welding roll 4.

During this heating process, oxides of the constituent elements constituting the steel are generated at the edge portion 3 of the tubular skelp 1, and the generated oxides are extruded from the welded portion 5 by the pressurizing action of the welding roll 4. In addition, foreign matter such as a paste-like substance (hereinafter referred to as metal powder paste), which is a mixture of water, lubricating fluid such as soluble oil used in the molding process, and metal powder generated in this process, adheres to the edge portion 3 of the tubular skeleton 1. are doing. Normally, most of the lubricating fluid adhering to the edge part 3 evaporates during the heating process, and its residue and metal powder paste are also pushed out from the weld part 5 by the pressurizing action of the welding roll 4 together with the oxides generated on the edge part 3. Ru. However, as the proportion of elements such as Cr, Si, and Mn in the steel increases, the oxides generated at the edge portion 3 become difficult to be extruded even by the pressurizing action of the welding roll 4, resulting in weld defects called so-called penetrators. There are many cases.

Therefore, when manufacturing high-grade steel or alloy steel containing many elements such as Cr, Si, and Mn, the welding atmosphere is adjusted to an inert or reducing non-oxidizing atmosphere, and the edges of the tubular skeleton are It is considered that one of the most effective means is to prevent the generation of oxides. As a technical solution, for example, US Pat. No. 2,800,561 and US Pat.
No. 991,345 discloses blowing a jet of inert gas from a nozzle onto the welding area, but this cannot be said to be an effective method since ambient air is drawn into the gas jet.

In addition, as mentioned above, the lubricating fluid, metal powder paste, etc. that adhere to the tubular skeleton edges, which do not cause welding defects in ordinary electric resistance welding of carbon steel, are also caused by high-grade steels and alloys containing a large amount of elements such as Cr, Si, and Mn. In electric resistance welding of steel, even if the welding atmosphere is controlled using inert gas or the like, if these enter the area where the atmosphere is being controlled, the effect of the atmosphere control will be impaired.

In addition, metal powder paste in particular adheres and accumulates on the sealing device, causing welding defects and damage to the sealing device. Tokuko Showa 5
In Publication No. 0-6424, a pair of shutters with fins are arranged inside and outside the tube upstream of the welding part to form a cavity surrounding the heated part of the tubular skelp, and the inside of the cavity is filled with an inert gas or the like. It is proposed to prevent ambient air and lubricating fluid from entering the cavity by maintaining the pressure at a high level and leaking an inert gas or the like from the cavity to the surroundings.

However, even this method is insufficient as a means for solving the above problem.

This is because the metal powder paste adhering to the tubular skelp edge portion adheres to the fins provided between the edges and gradually accumulates, eventually causing a short circuit phenomenon between both edges and causing welding defects. Also, during operation of the tube-making mill, the cross-sectional shape of the tubular skelp may change due to the eccentricity of the welding roll, the camber of the skelp, etc. In this case, the metal powder paste etc. deposited on the edges and fins may flow into the cavity. It is easy to penetrate and cause welding defects. US Patent No. 27
In the specification of No. 94108, a hood equipped with a gas supply pipe to protect the tubular skelp edge portion and the welded portion is disposed inside and outside the tube, and in order to purify the edge portion of the tubular skelp passing inside the hood, a hood is provided between the edge portions. It is shown that a tooth-shaped tool made of hardened steel is placed so as to press against the edge.

However, in this method, the tool is heated by the welding current, and the resulting debris accumulates in the hood, causing short circuits between the edges and contamination of the weld. There is a problem that welding defects occur.

An object of the present invention is to provide an atmosphere electric resistance welding pipe manufacturing technique that does not cause welding defects when forming high-grade steels and alloy steels containing large amounts of Cr, Sl, Mn, etc. by electric resistance welding.

In the present invention, a weir is provided at an intermediate position between the final forming roll and the gas sealing device so as to shield the internal cross section of the tubular skelp, and a suction port is provided so as to cover the edge portion of the tubular skelp in the immediate vicinity of the weir and the vicinity thereof. A foreign matter removal device is installed on the downstream side of the pipe to remove foreign matter adhering to the tubular squelp edge portion and its vicinity, and then a gas seal device is used to remove foreign matter from the heated zone of the tubular squelp edge portion. and adjusting the atmosphere of the welding area.

The configuration of the present invention will be explained in detail below with reference to FIG.

A weir 8 made of a non-metallic elastic material such as a rubber plate or sponge is attached to the in-heater mandrel 7 so as to shield the inner cross section of the tubular skelp 1. The outer diameter of the weir 8 is determined by the amount of compressive deformation of the material constituting the weir 8. Although it varies depending on the case, the inner diameter of the pipe is 1.1~
About 1.5 times is preferable, and the longer the length of the weir 8 in the pipe flow direction, the more effective it is. A suction port 9 made of a non-metallic insulating material such as nylon or Bakelite is disposed so as to cover the edge portion 3 of the tubular skelp 1 closest to the weir 8 and the vicinity thereof.
is shaped so as to be in close contact with the tubular squelp 1, and is connected to a suction pump (not shown) by a suction tube 10.

A foreign matter removal device disposed on the downstream side of the suction port 9 wipes a strip-shaped wiping cloth 11 made of a highly hygroscopic material such as animal and plant fibers or chemical fibers from the outer surface and edges of the tubular skelp 1. It is composed of a wiping roll 12 made of a non-metallic material shaped to be pressed against the part 3, a winding motor (not shown in the figure) for continuously winding up the wiping cloth 11, and a holding mechanism for these. Ru.

FIG. 3 shows the interrelationship of the wiping cloth 11, the wiping roll 12 and the tubular skelp 1.

The wiping cloth 11 always follows the shape change of the tubular skelp 1.
An elastic layer 12a made of a non-metallic elastic material such as sponge is adhered to the surface of the wiping roll 12 that contacts the wiping cloth 11 so that the tubular skelp 1 and the edge portion 3 are in a sliding state. The wiping cloth 11 is pressed against the tubular skelp 1 by a wiping roll 12, and is wound up by a winding motor while sliding on the outer surface and edge portion 3 of the tubular skelp 1. The metal powder paste adhering to the inner surface of the tubular skelp 1 and the lubricating liquid used in the molding process and flowing inside the tubular skelp 1 are restricted from flowing downstream of the pipe by the weir 8.

The lubricating fluid, etc. dammed up by the weir 8 overflows from the groove formed by the edge part 3 of the tubular skelp 1, and some of it flows to the downstream side of the pipe together with the tubular skelp 1, so it is collected by the suction pump. and suction from the suction port 8.

Since metal powder paste and the like are still attached to the edge part 3 after passing through the suction port 9, the wiping cloth 11 is pressed against the tubular skelp 1 and the edge part 3 by the wiping roll 12 and wound by the winding motor. Wipe off any adhering metal powder paste, etc.

This series of processes removes lubricating fluid, which is harmful to ERW pipes.
Metal powder paste etc. are completely and continuously removed from the tubular skelp 1 and the edge 3.

A sealing device arranged to adjust the atmosphere of the heated zone and welding area of the edge portion 3 of the tubular skelp 1 includes a seal cover 15 made of a heat-resistant non-metallic insulating material such as mickeyx, quartz, etc.; 15, and a reverse blow seal cover 17 and its reverse blow seal gas inlet pipe 18 for preventing air from entering from the upstream side of the pipe due to movement of the tubular squelp 1. Ru. The surface of the seal cover 15 in contact with the tubular squelp 1 is formed to be in substantially close contact with the tubular squelp 1, and is held by a method not shown.

A reverse blow seal cover 17 is attached to the seal cover 15. In the present configuration, the foreign matter removal device for removing metal powder paste etc. attached to the edge portion 3 rotates a brush roll to remove the metal powder paste attached to the edge portion 3 instead of using the wiping cloth 11, and uses a suction pump. It may be recovered by

FIG. 4 shows an example of a foreign matter removal device using a brush roll. The rolled brush 19 is shaped so as to slide on the tubular skelp 1 and the edge portion 3 by means of brush holders 20a and 20b made of non-metallic material.

Effective materials for the rolled brush 19 include nylon, polypropylene, etc., or mixtures thereof with the mineral 3 powder. The rolled brush 19 is rotated by a rotating shaft 21 connected to a motor (not shown).

This rotating shaft 21 is rotatably attached to the suction cover 22. The suction cover 22 is made of a non-metallic insulating material.
It is connected to a suction pump (not shown), which suctions and removes foreign matter removed from the tubular skelp 1 and edge portion 3 by rotation of the mouth-shaped brush.

Hereinafter, an embodiment of the present invention according to the configuration shown in FIG. 2 and manufacturing results by a conventional method will be described. Welding equipment Vacuum tube type high frequency induction welding equipment Frequency 150KIIz Output 600kW Pipe material Pipe manufacturing dimensions 50.8φMm x 3.2tm7! L
Steel component tube manufacturing speed 40m/Milt Squeeze amount 2.0m71L Seal conditions Seal range Type of sealing gas in heated zone of tubular skelp and welding area Ar Seal gas flow rate Seal cover: 6001/Mm Reverse blow seal cover: 501/MUl or more In the case of the present invention, the conditions of the weir are constant.
Material Urethane rubber Outer diameter 52mm Suction pump Air volume 4.9m3/m or suction pressure 2
700mm foreign matter removal device wiping cloth Vegetable fiber winding speed was set to 5m/Mm to clean the tubular skelp edge.

Destructive inspection of the welded parts of the resulting products was performed, and the incidence of welding defects was compared, as shown in FIG. Destructive inspection of the welded parts of pipes manufactured by atmospheric welding without purification or gas sealing of the tubular skelp edges revealed that 82% per meter of inspection length.
Welding defects occurred, and the ratio of the welding defect fracture surface length to the destructive inspection length was about 24%. The size of one welding defect fracture surface is in the range of 0.5 mm to 25 mm. In normal atmospheric resistance welding pipe manufacturing where only gas sealing is performed without purifying the tubular skelp edge, the destructive inspection length of the welded part is 1.
The occurrence of welding defects per meter is approximately 17, which is 1/1 of that of atmospheric welding pipe manufacturing.
5, but the ratio of the weld defect fracture surface length to the destructive inspection length is only about 12%, or 1/2. Purification and gas sealing of the tubular skelp edge according to the present invention In atmospheric resistance welding pipe manufacturing, the occurrence of weld defects is 0.015 per meter of destructive inspection length of the weld.
What is more important is that the size of each welding defect is minute, less than 0.5 degrees, so even if JIS G3462, which is applied to seamless pipes, is applied, The flattening ratio fully satisfied the standards, and a product that could be put to practical use was obtained. In this way, in conventional atmospheric resistance welding pipe manufacturing, metal powder paste generated during the forming process adheres to the sealing device.
Although a relatively large welding defect occurs due to the accumulation, the atmosphere electric resistance welding method according to the present invention combines cleaning the tubular scallop edge and adjusting the atmosphere of the heated zone of the tubular scallop edge. In tubes, Si, M
Welding defects, which were thought to always occur in ERW pipes made of high-grade steels and alloy steels that contain large amounts of elements such as n and Cr, have been drastically reduced, and ERW steel pipes that are comparable to seamless steel pipes have been produced. can.

[Brief explanation of the drawing]

Fig. 1 is a simple perspective view of the ERW welding pipe manufacturing method, Fig. 2 is a simple perspective view of the atmospheric ERW welding pipe production method according to the present invention, and Fig. 3 is a foreign object at A-A'' in Fig. 2. A cross-sectional view of the removal device, FIG. 4 is a diagram equivalent to FIG. 3 when using a roll brush,
FIG. 5 is a diagram comparing the results of destructive inspection of welded parts of products by manufacturing method. 1: Tubular scalp, 2: Work coil, 3: Edge part,
4: Welding roll, 5: Welding part, 6: Impeder, 7 Reimpeder mandrel, 8: Weir, 9: Suction port, 10: Suction pipe, 11: Wiping cloth, 12: Wiping roll, 13: Wiping roll Holder, 14: Wiping roll rotation shaft, 15: Seal cover, 16: Seal gas introduction pipe, 17: Reverse blow seal cover, 18: Reverse blow seal gas introduction pipe, 19: Rolled brush, 20a, 20b: Brush presser foot, 2
1: Rotating shaft, 22: Suction cover.

Claims (1)

[Claims] 1. When manufacturing ERW steel pipes, in an atmosphere ERW pipe manufacturing equipment that has a gas seal device that adjusts the atmosphere around the heated zone of the tubular scalp edge, the internal cross section of the tubular skelp is placed at an intermediate position between the final forming roll and the gas seal device. A weir made of a non-metallic elastic material is fixedly arranged on an impeder mandrel or the like so as to shield the weir, and a suction port is provided so as to cover the tubular squelp edge part and its vicinity immediately adjacent to the weir position, and a suction port is provided on the downstream side of the pipe of the suction port. ERW steel pipe manufacturing equipment, characterized in that a foreign matter wiping cloth, brush, etc. is disposed on the upstream side of the gas seal device so as to slide on a portion of the tubular skelp covered by the gas seal device. .