JP2009208102A - Welding method of steel tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a butt-welding method capable of shortening the required time for welding and executing the excellent welding even when the sectional shape of a steel tube is slightly flattened even when the steel tube has a large diameter and large wall thickness. <P>SOLUTION: When executing the butt-welding of a steel tube 3A and a steel tube 3B, a band socket 1 is arranged across butt-ends of both steel tubes. After welding ends of the band socket, both steel tubes and the band socket are fillet-welded over the entire circumference. A substantially C-shaped band socket is formed by roll-working and bending a rectangular steel plate. The band socket is arranged across butt-ends of both steel tubes, and the band socket in this state is fastened, and then, the band socket and both steel tubes are preferably fillet-welded to each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for welding a steel pipe such as a stainless steel pipe, and more particularly to a method suitable for welding a steel pipe having a large diameter and a cross-sectional shape that is not a perfect circle and is slightly flat.

In manufacturing factories of semiconductor devices, liquid crystal display elements, etc., a large amount of dry air, nitrogen gas or the like is used for the production, and pipes welded with steel pipes such as large diameter stainless steel pipes are used for the supply. Yes.
A thin-walled steel pipe is generally used for this type of gas supply pipe. If the steel pipe has a large diameter, even if it is a thin-walled steel pipe, its thickness is inevitably thick. In such a butt welding of a thick steel pipe, a method is adopted in which the end face of the steel pipe is processed into a V-shape and a U-shape, and then the end face is welded and then weld welding is performed using a filler rod.

  However, this method has a disadvantage that it takes a very long time for the groove processing time and the welding time. In addition, a large diameter steel pipe is heavy and difficult to handle, and it takes time to align the ends of the steel pipe.

In general, the cross-sectional shape of a steel pipe is not a perfect circle but is slightly flattened, and the flattening amount increases as the diameter increases and the wall thickness decreases. The flatness is defined in JIS G 3468.
For this reason, when the end surfaces of two steel pipes are abutted, the end surfaces of both steel pipes do not exactly match, and the angle of the groove does not exactly match, so the welding arc is not constant and good. There is also a disadvantage that welding cannot be performed.
Japanese Patent Laid-Open No. 11-50449 JP 2001-179441 A

  Therefore, the problem in the present invention is that even in the case of a large-diameter and thick steel pipe, it is possible to shorten the time required for welding and eliminate the need for groove processing in the butt welding, and the cross-sectional shape is slightly flattened. Is to enable good welding.

To solve this problem,
When the invention concerning Claim 1 butt-welds a steel pipe and a steel pipe,
Welding of steel pipes, characterized in that band sockets are arranged so as to straddle the butted ends of both pipes, and then the ends of the band sockets are welded, and then both steel pipes and band sockets are fillet welded over the entire circumference. Is the method.

  According to a second aspect of the present invention, the band socket is a substantially C-shaped one obtained by rolling and bending a rectangular steel plate, and the band socket is disposed so as to straddle the butted ends of both steel pipes. The steel pipe welding method according to claim 1, further comprising tightening the band socket in this state and welding the end portion thereof.

  The invention according to claim 3 is the steel pipe welding method according to claim 2, wherein the inner peripheral length of the band socket is 1 to 1.05 times the outer peripheral length of the steel pipe.

When the invention concerning Claim 4 butt-welds a steel pipe and a steel pipe,
The end of one steel pipe is abutted and fixed to one end face of the weld ring, and then the end of the other steel pipe is abutted and fixed to the other end face of the weld ring, and both the steel pipe and the weld ring are joined together. A steel pipe welding method characterized in that fillet welding is performed over the entire circumference.

  The invention according to claim 5 is the steel pipe welding method according to claim 4, wherein the weld ring is provided with a projection on the end face thereof for temporarily placing the steel pipe.

  According to the present invention, groove processing is unnecessary, and accurate alignment of the end surface is not necessary. In addition, since both steel pipes are welded via a band socket or a welding ring, even if the steel pipes are somewhat flat, accurate alignment is not necessary, and the work time until welding can be shortened.

  In addition, since the end of the steel pipe is not welded directly, it is welded between the steel pipe and the strip socket or weld ring, so that fillet welding is possible and the strength of the welded part, which has no practical problems, can be secured, and the work is highly skilled. Even if it is not a person, welding is possible.

1 to 8 show a first example of the welding method of the present invention in the order of steps.
First, a band socket 1 as shown in FIG. 1 is prepared. This band socket 1 is formed by rolling a rectangular (band-shaped) steel plate into a substantially C-shaped cross section, and is not a completely closed circle, but has an opening 2 of about 10% of the outer diameter. It is what remains.

  The length of the steel plate is 1 to 1.05 times the outer peripheral length of the steel pipe to be welded, and the width is 50 to 100 mm. Therefore, the inner peripheral length of the band socket 1 has a slight margin with respect to the outer peripheral length of the steel pipe, and can be easily inserted even if the steel pipe is slightly flattened. In principle, the material of the steel plate forming the band socket 1 is the same as that of the steel pipe to be welded, but may be different as long as welding is possible.

Next, as shown in FIG. 2, two steel pipes 3A and 3B to be welded are prepared. The material of the steel pipes 3A and 3B is not particularly limited, but a stainless steel pipe such as SUS304 is mainly used. Moreover, as a diameter of a steel pipe, a large diameter having a nominal diameter of 500 A or more is mainly used, but a diameter of less than this may be used.
In this welding method, since the end portions of the steel pipes 3A and 3B to be welded are not directly welded, it is not necessary to perform groove processing.

  The band socket 1 is inserted into one steel pipe 3A, and then, as shown in FIG. 3, the end of the other steel pipe 3B is flush with the end of one steel pipe 3A, and as shown in FIG. It moves and the position is determined so that the strip socket 1 may straddle the ends of both steel pipes 3A and 3B. At this time, both ends of the steel pipes 3A and 3B may be in contact with each other or may be separated from each other, and FIG. 4 shows a separated form.

Next, as shown in FIG. 5, the band socket 1 is tightened in the circumferential direction by using a chain block or the like so that the opening 2 of the band socket 1 is closed and there is no gap. By this tightening, flatness at both ends of both steel pipes 3A and 3B is corrected.
While maintaining this state, as shown in FIG. 6, the both ends of the strip socket 1 and the outer peripheral surfaces of both the steel pipes 3A and 3B are spot welded over the entire circumference to perform temporary attachment.

  Furthermore, after releasing the tightening state, as shown in FIG. 7, after welding the portion where the opening 2 of the band socket 1 is closed, as shown in FIG. 8, both ends of the band socket 1 and both steel pipes are welded. The outer peripheral surfaces of 3A and 3B are fillet welded over the entire circumference, and the welding of both steel pipes 3A and 3B is completed.

  In such a welding method, as shown in FIG. 9, the end surfaces of the two steel pipes 3A, 3B may not be in direct contact, and in this case, the band socket 1 is located on the outer peripheral side of the steel pipes 3A, 3B. Thereby, the small recessed parts 4 and 4 are formed. For this reason, there is a possibility that dust adheres to and accumulates in the concave portion 4. However, if the gas flowing in the pipe is dry air, nitrogen or the like, the dust hardly poses a problem.

  In such a welding method, it is not necessary to groove the ends of the steel pipes 3A and 3B, it is not necessary to set a clearance between the ends, and the time required for aligning the steel pipes can be omitted. it can. Further, by tightening the steel pipes 3A and 3B with the band socket 1, the flatness of the steel pipe can be corrected, and the time required for correcting the unevenness between the steel pipes can be shortened.

  Furthermore, since the two steel pipes 3A, 3B and the strip socket 1 are fillet welded, the welding can be given only one round, and the required strength can be given, and no advanced welding technique is required. Even an operator who is not expensive can perform the welding work.

10 to 15 show a second example of the welding method of the present invention in the order of steps.
In this example, a welding ring 5 as shown in FIG. 10 is prepared. The welding ring 5 is an annular ring made of a steel plate.
The outer diameter of the weld ring 5 is a dimension obtained by adding the wall thickness to the outer diameter of the steel pipe to be welded, or a dimension obtained by adding 1.5 times the wall thickness to the outer diameter. It is a dimension obtained by subtracting the wall thickness from the inner diameter or a dimension obtained by subtracting 1.5 times the wall thickness from the outer diameter, and has a plate thickness of 10 to 30 mm.

  A projection piece 6 is attached to one end face of the welding ring 5. This projection piece 6 is for temporarily placing a steel pipe to be welded on the welding ring 5 and is a claw-like piece made of a lightly curved steel plate having a width of about 50 mm and a length of about 5 mm, and its concave portion is directed inward. The welding ring 5 is welded and attached to a position on the outer peripheral side.

  The protruding piece 6 also functions as a guide when aligning the welding ring 5 and the steel pipe to be welded. Further, the length from the inner surface of the protruding piece 6 to the inner peripheral surface of the weld ring 5 is set to a length obtained by adding an error tolerance to the thickness of the steel pipe, and the error defined in JIS G 3468 is taken into account at that position. If the inner peripheral dimension of the weld ring 5 is determined on the assumption that the is disposed, the inner peripheral surface of the weld ring 5 always protrudes inward from the inner peripheral surface of the steel pipe.

Then, as shown in FIG. 11, the end of one steel pipe 3A to be welded is placed on the protruding piece 6 of the welding ring 5 and temporarily placed, and as shown in FIG. And fixed in this state.
Subsequently, as shown in FIG. 13, the end of one steel pipe 3 </ b> A and one end face of the welding ring 5 are spot welded to perform temporary attachment.

Next, as shown in FIG. 14, the end portion of the other steel pipe 3B is fixed to the other end face of the temporarily welded ring 5, and temporary attachment is performed in the same manner. Further, as shown in FIG. 15, both end faces of the weld ring 5 and the outer peripheral surfaces of both the steel pipes 3A, 3B are fillet welded over the entire circumference, and the welding of the two steel pipes 3A, 3B is completed.
The protruding pieces 6 may be provided on both surfaces of the welding ring 5. Instead of arranging the steel pipe 3A (3B) on the protruding piece 6, the protruding piece 6 may be hooked on and brought into contact with the upper end of the steel pipe for temporary attachment, and further fillet welding may be performed.

  When one or both of the steel pipes 3A and 3B are short, as shown in FIG. 13, after temporarily attaching one steel pipe 3A to the weld ring 5, this portion is fillet welded and the main welding is performed. The weld is rotated so that the weld ring 5 faces upward. In this state, the end portion of the other steel pipe 3B is placed on the end face of the weld ring 5, the end face of the weld ring 5 and the other steel pipe 3B are spot welded, temporarily attached, and further fillet welded for main welding. Can also be adopted.

Also in such a welding method, as shown in FIG. 16, the outer peripheral surface of the weld ring 5 protrudes outward from the outer peripheral surface of the steel pipes 3A and 3B, and the inner peripheral surface of the weld ring 5 is the inner peripheral surface of the steel pipes 3A and 3B. It may be in a state protruding more inward.
Also in this case, there is a possibility that a plurality of small recesses 4... Are formed between the ends of the steel pipes 3 </ b> A and 3 </ b> B and the welding ring 5, and dust may adhere to and accumulate on the recesses 4. However, if the gas flowing in the pipe is dry air or nitrogen, the dust hardly poses a problem.

  Even with the welding method of this example, it is not necessary to bevel the ends of the steel pipes 3A and 3B, and it is not necessary to set the clearance of the end parts, so that the time required for aligning the steel pipes can be omitted. Moreover, since it welds to the welding ring 5, it is not necessary to consider the flatness of a steel pipe. Furthermore, since the two steel pipes 3A and 3B and the weld ring 5 are fillet welded, the welding can be given only one round, so that the necessary strength can be given and no advanced welding technique is required. Even an operator who is not expensive can perform the welding work.

It is a schematic block diagram which shows the 1st example of this invention in process order. It is a schematic block diagram which shows the 1st example of this invention in process order. It is a schematic block diagram which shows the 1st example of this invention in process order. It is a schematic block diagram which shows the 1st example of this invention in process order. It is a schematic block diagram which shows the 1st example of this invention in process order. It is a schematic block diagram which shows the 1st example of this invention in process order. It is a schematic block diagram which shows the 1st example of this invention in process order. It is a schematic block diagram which shows the 1st example of this invention in process order. It is a schematic sectional drawing which shows the cross section of the welding part obtained in the 1st example of this invention. It is a schematic block diagram which shows the 2nd example of this invention in process order. It is a schematic block diagram which shows the 2nd example of this invention in process order. It is a schematic block diagram which shows the 2nd example of this invention in process order. It is a schematic block diagram which shows the 2nd example of this invention in process order. It is a schematic block diagram which shows the 2nd example of this invention in process order. It is a schematic block diagram which shows the 2nd example of this invention in process order. It is a schematic sectional drawing which shows the cross section of the welding part obtained by the 2nd example of this invention.

Explanation of symbols

1 .. Strip socket, 2 .... Open, 3A, 3B ... Steel pipe, 4. Recess, 5 .... Weld ring,
6. Projection piece

Claims (5)

When butt-welding steel pipes and steel pipes,
Welding of steel pipes, characterized in that band sockets are arranged so as to straddle the butted ends of both pipes, and then the ends of the band sockets are welded, and then both steel pipes and band sockets are fillet welded over the entire circumference. Method.   The band socket is a substantially C-shaped one obtained by rolling and bending a rectangular steel plate, and the band socket is disposed so as to straddle the butted ends of both steel pipes. The steel pipe welding method according to claim 1, wherein the ends are welded by tightening.   The steel pipe welding method according to claim 2, wherein the inner peripheral length of the band socket is 1 to 1.05 times the outer peripheral length of the steel pipe. When butt-welding steel pipes and steel pipes,
The end of one steel pipe is abutted and fixed to one end face of the weld ring, and then the end of the other steel pipe is abutted and fixed to the other end face of the weld ring, and both the steel pipe and the weld ring are joined together. A steel pipe welding method characterized by welding fillet along the entire circumference.   5. The method for welding a steel pipe according to claim 4, wherein the welding ring is provided with a protrusion capable of temporarily placing the steel pipe on an end surface thereof.

Images