JPH07110371B2 - Manufacturing method of welded steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a welded steel pipe, and more specifically to a gas shielded arc made of a high alloy steel strip such as stainless steel in which welding beads do not protrude on the inner and outer surfaces. The present invention relates to a method for manufacturing a welded steel pipe.

[Conventional technology]

To produce gas shielded arc welded (usually TIG welded) steel pipes made of high alloy steel strips such as stainless steel, especially welded steel pipes with no weld bead protruding on the inner or outer surface, The outer surface welding bead between the welding torch and the constant diameter roll group is removed by cutting or grinding means, and then the inner surface welding bead is inserted and arranged in the pipe, for example, a cylindrical jig made of tool steel such as JIS-SKD11 and the outer surface. The erasing is performed by using a restraint roll and rolling while supplying a lubricant so that the pipe insertion jig does not stick to the inner surface of the pipe.

Therefore, in order to improve the production efficiency, if it is attempted to perform a required heat treatment or the like in a pipe mill line, it is indispensable to remove the lubricant used in the erasing and rolling of the inner weld bead from the viewpoint of carburizing prevention and the like. However, it is physically impossible to remove the lubricant adhering to the inner surface of the pipe in the pipe mill mill line.

Therefore, conventionally, there is no method other than removing the lubricant outside the pipe mill line, and therefore the manufacturing method has to take the step shown in FIG. That is, in the pipe milling line, the outer / inner weld beads are removed / erased by the above means (,), the outer diameter finish rolling by the constant diameter roll group, the desired product length provisional cutting by the traveling pipe cutting machine, and the required number of units. Only perform lot consolidation.

After that, outside the pipe mill, degreasing and removing the lubricant in the degreasing and cleaning tank in the unit of the integrated lot, required heat treatment in the heat treatment furnace, pickling descaling and bending correction of the scale generated during heat treatment in the pickling tank, finishing The final finishing processes such as cutting, flaw inspection, dimensional inspection, etc. are batch processed in the above order.

[Problems to be solved by the invention]

However, in the conventional manufacturing method adopting the above-mentioned steps, not only the productivity cannot be expected to be improved, but also the work outside the pipe mill line is carried out in lot units by carrying equipment such as cranes or carts between each processing. Since this is a batch process involving transportation, there is a problem that many surface defects such as hits are generated during the transportation, and a large number of man-hours and costs are required for the maintenance. Further, since the oxide scale generated during the heat treatment is removed by the dipping and pickling means using a pickling tank, there is a problem that only a product having a rough acid surface and a low commercial value can be obtained.

Furthermore, a degreasing cleaning tank provided outside the pipe mill line,
In addition to the need to allocate a dedicated worker to the operation of the heat treatment furnace and the pickling tank, there has been a problem that a large number of man-hours and costs are required for the maintenance and management thereof, resulting in a high manufacturing cost.

The present invention has been made in view of the above circumstances, and the purpose thereof is not only improvement of productivity but also a novel production capable of inexpensively supplying a product of high commercial value without exhibiting an acid rough surface. To provide a method.

[Means for solving problems]

In order to achieve the above object, the present invention is to perform the erasing rolling of the inner surface welding bead by the pipe insertion jig and the outer surface restraining roll in a pipe milling mill line without using a lubricant, and from a constant diameter roll group. A heating / cooling means is installed in the pipe mill line on the downstream side to perform the required heat treatment, and then a mechanical scouring means is installed to continuously perform the external surface descaling polishing treatment, and then the required length. After cutting, the lots were integrated, and as the work outside the pipe mill line, only the final refining process was performed.

[Action]

According to the manufacturing method of the present invention, by performing the erasing rolling of the inner surface welding bead without using the anti-seizure lubricant, the degreasing step is omitted and the required heat treatment and outer surface descaling polishing are performed in the pipe mill line. Since it is performed in step 1, it is possible to inexpensively manufacture a welded steel pipe with a high efficiency and a weld bead that does not project on the beautiful inner and outer surfaces of the outer surface.

〔Example〕

Hereinafter, a manufacturing method according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a manufacturing process of the present invention, and FIG. 2 is a schematic diagram showing an example of a pipe mill line used for carrying out the process.

As is apparent from FIG. 1, in the manufacturing method of the present invention, the erasing rolling process of the inner surface weld bead, which has been conventionally carried out in the pipe mill line, is carried out under a non-lubricated state, and After the diameter rolling step, the heat treatment step and the outer surface descaling step are successively performed in the pipe manufacturing mill line in the above-described order, and the product is transferred to the outside of the pipe manufacturing mill line through the cutting process and the lot integrating process. Then, only the final refining step is performed outside the pipe mill line.

The method of the present invention is carried out by constructing the pipe making mill line as shown in FIG.

That is, a belt (1
The inner bead rolling device (11) shown in FIG. 3 and whose structure will be described in detail later is used as the means for erasing and rolling the inner weld bead to be provided in the subsequent stage of (0). Then, a sizing roll group (12) for finishing to a predetermined size and a frying cutter (18) for cutting the continuously supplied welded pipe (P) into a predetermined length.
4, an induction heating coil (13) as a heat treatment means, a cooling water injection header (14), and front and rear restraint rolls (16), (16) as outer surface descaling means are shown in FIG. A pipe-making mill line configuration in which a blasting / cleaning device (15) whose structure will be described later in detail is installed in the above order from the upstream side to the downstream side.

In FIG. 2, (1) is an uncoiler, (2) is a shear, (3) is a bat welder, (4) is a pinch roll, (5) is a looping pit, (6) is a side guide roll, and (7). ) Is a forming roll group, (8) is a squeeze roll, (9) is a welding torch, (17) is a straightener,
(W) is a steel strip, and (P ₁ ) is a tube that is cut into a predetermined length and lot-collected.

The inner bead rolling device (11), which can perform rolling without seizure under non-lubricated conditions, is unlikely to cause seizure of jigs, specifically plugs, mandrels or rollers, to be inserted and arranged on the inner surface of the pipe, with stainless steel. Special tool steel made of ceramics or WC cemented carbide, etc. Fig. 3 (a) ~
The three types shown in (c) are selectively used.

The model shown in Fig. 3 (a) is a core bar (110a) (110a) (indicated and extended into the pipe through the gaps on both side edges of the bent steel strip (W) in the subsequent stage of the forming roll group (7). This cored bar is provided with an inert gas supply pipeline to the opposing tube of the welding torch (9) and a pair of front and rear seal rings), and has a diameter at the central portion in the axial direction slightly smaller than the inner diameter of the welded tube (P). In addition, the ceramic plug (110b) whose diameter gradually decreases toward both ends is elastically mounted by the spring (110c), while the outer diameter of the welded pipe (P) is slightly larger than that of the welded pipe (P). Steel outer surface restraint rolls (110e) and (110e) having a large caliber groove (110d) and the same outer diameter are fixedly arranged vertically with a constant gap.

In the case of such an inner bead rolling apparatus, even if the protrusion height of the inner weld bead (WB) in the axial direction varies, the position of the plug (110b) fluctuates in the axial direction against the elastic force of the spring (110c). The weld bead (WB) can be erase-rolled so that the welded portion always has a constant thickness.

The model shown in Fig. 3 (b) is a barrel-shaped roller (111b) made of ceramics, which is formed at the tip of the cored bar (110a) with a radius of curvature slightly smaller than the inner radius of the welded pipe (P),
The shafts are arranged vertically opposite to each other in the direction orthogonal to the axial direction of the welded pipe (P), and the spring (111c) is used to elastically bias the upstream side so that the position can be changed in the axial direction of the welded pipe (P). The inner roller header (111d) is fixedly mounted, while the outer surface restraint rolls (110e) and (110e) similar to the type shown in FIG. 3 (a) are arranged in the same manner on the outer surface of the welded pipe (P). Is.

In the case of such an inner bead rolling device, the erase rolling of the inner weld bead (WB) can be performed in the same manner as the model of FIG. 3 (a), and in the case of this model, the barrel roller (111b) is used. ) No seizure occurs because it rotates itself.

The model shown in FIG. 3C is a ceramic mandrel (112b) having the same diameter in the axial direction, which is relatively long at the tip of the core metal (110a) and slightly smaller than the inner diameter of the welded pipe (P). While the mandrel (112b) is mounted on the outer surface of the welded pipe (P), the mandrel (112b) is reciprocally movable in the axial direction of the mandrel (112b). B) An outer surface restraint roll (110e) similar to (b) is provided so as to be reciprocally movable only in the axial direction of the welded pipe (P), and the outer surface restraint roll is located on the weld bead (WB) side, in other words, on the upper side. It has the same caliber groove (112d) as (110e), but its roll diameter is smaller.
2e) is provided so as to be reciprocally movable in two directions of the axial direction of the welded pipe (P) and a direction orthogonal to the axial direction.

In the case of such an inner surface welding bead rolling device, the vertical position of the outer surface restraining roll (112e) on the upper side is adjusted according to the variation of the protruding length in the axial direction of the inner surface welding bead (WB) to adjust the welded portion. The weld bead (WB) is erase-rolled so that its thickness is constant in the axial direction, while the upper and lower outer surface restraint rolls (112e), (110e) and the mandrel (112b) are welded in the axial direction of the welded pipe (P). Since rolling is performed while reciprocally moving in opposite directions, heat dissipation is promoted and rolling can be performed without causing seizure.

The induction heating coil (13), which is a heat treatment process after the sizing roll group (12), can be replaced with a barrel furnace that burns gas or liquid fuel.
In addition, the cooling water injection header (14) can be replaced with a steam-water mixed (mist) refrigerant injection header or the like, and the cooling water injection header (14) is omitted when cooling is not necessary depending on the heat treatment content. be able to.

Next, a desirable polishing / cleaning device (15) used in the outer surface descaling step will be described with reference to FIG. 4 (a) is a partially cutaway front view, and FIG. 4 (b) is A in FIG. 4 (a).
-A line arrow view.

In the figure, (150) is a cylindrical casing main body, and the casing main body (150) is arranged in front of and behind the casing 1.
2 in the circumferential direction between the pair of annular flanges (150a), (150b)
One of the divided cover bodies (150c) and (150d) is fixed by interposition, and the other can be attached and detached with a bolt (150e). In addition, the annular flange (150
Hollow shafts (150f) and (150g) are projectingly fixed to a) and (150b), respectively, and are supported by bearings (not shown), and pulleys (150h) are fixed to the hollow shaft (150g) with a key (150h). 150i), a belt (15) suspended on the pulley (150i)
The casing main body (150) is rotated by a motor (not shown) via 0j).

On the other hand, inside the casing main body (150), there are provided semi-cylindrical movable pieces (151a), (151b) which are divided into two in the circumferential direction, and these movable pieces (151a), (151b) are provided. Is penetrating through the holes formed in the cover bodies (150c) and (150d), and the tip portion thereof projects to the outer surface of the casing body (150), and weights (152a) and (152b) of arbitrary weight are attached to the projecting tip portion. The guide lots (151c) and (151d) that can be replaced are detachably screwed. Further, between the movable pieces (151a) and (151b) divided into two, a polishing body (153) having a cylindrical elasticity is fixedly provided inside the movable pieces (151a) and (151b).

According to the blasting / cleaning apparatus (15) having such a structure, when the casing body (150) is rotated, the movable pieces (151a) and (151b) are separated by centrifugal force in opposite directions, and are fixed to the cylindrical shape. The polishing body (153) is deformed into an elliptical shape and rotated around the pipe axis with its inner surface in contact with the outer surface of the welded pipe (P), so that oxide scale generated during the heat treatment in the previous step is removed and it is beautiful. It is possible to polish finish on various surfaces.

The blasting condition can be changed by appropriately adjusting the weights of the weights (152a) and (152b) and / or the rotation speed of the casing body (150).

By the way, if comparing the manufacturing cost and the number of man-hours required per defect when manufacturing a product made of SUS304 with an outer diameter of 34 mm and a wall thickness of 1.2 mm by the manufacturing method of the present invention and the conventional manufacturing method, As shown in the table.

The results shown in Table 1 are based on the case of the method of the present invention.
Compared as 100.

As is clear from the results shown in Table 1, it can be seen that each of the cases according to the method of the present invention is superior in each step.

〔The invention's effect〕

As described above, according to the present invention, not only it is possible to manufacture a product with high surface quality and high commercial value at low cost, but also a batch processing facility such as a degreasing cleaning tank is not required, so that a more compact factory There is also the side effect of making the design feasible, and its economic benefits are enormous.

[Brief description of drawings]

FIG. 1 is a flow chart showing steps of the manufacturing method according to the present invention, FIG. 2 is a schematic view showing an example of a pipe mill line used for carrying out the manufacturing method according to the present invention, and FIG. ) To (C) are schematic diagrams of an inner bead rolling device that erases and rolls the inner weld bead in a non-lubricated state, and FIG. 4 (A) and (B) are diagrams showing a polishing and cleaning device that descales the outer surface of the pipe. , FIG. 5 is a flow chart showing a conventional manufacturing method. In the figure, 11 …… Internal bead rolling device 13 …… Induction heating coil 14 …… Cooling water jet header 15 …… Brushing device

Claims (1)

[Claims] Claim: What is claimed is: 1. A steel pipe which is continuously supplied is bent into a tubular shape by passing through a forming roll group, and the abutting edge of the bent steel strip is gas shield arc welded to form a welded steel pipe. The method for producing a welded steel pipe is characterized in that the following treatments are sequentially performed on the pipe making mill line. I. The outer weld beads are cut or ground away. B. The inner surface welding bead is smoothed in the circumferential direction of the inner surface of the pipe by rolling with a pipe insertion jig and an outer surface constraining roll without using a lubricant. C. Finish the required outer diameter by passing through a group of constant diameter rolls. D. Perform the required heat treatment. E. The external oxide scale generated during the heat treatment is removed by a scavenger. What. Cut to the required length.