JP2001179453A - Welding method for cylindrical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method capable of obtaining a stable initial layer back bead by a highly efficient MAG welding only without generating a welding defect of a shortage of penetration, etc., and by using a low cost shield gas (e.g. CO2). SOLUTION: In a back bead welding in which end faces of cylindrical members 1, 2 with machined grooves 1A, 2A are butted on each other and groove parts are successively welded, one round periphery is welded while cutting off a fixed section of a welded part from a welding start part liable for a welding defect, successively, the cut off section F is welded, thus, a stabilized initial layer back bead is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to backwashing of two cylindrical members, and in particular, requires precision of coaxiality and cylindricity such as flowing a fluid into a cylindrical portion such as a cylinder tube of a hydraulic cylinder. This is related to single-sided uranami welding that requires consideration of contamination.

[0002]

2. Description of the Related Art For butt welding of carbon steel pipes or special steel pipes such as alloy steel and heat-resistant alloy steel, see, for example,
A welding method disclosed in Japanese Patent No. 24580 is known. In this publication, MIG welding using an inert gas (for example, Ar) is described as an example.

[0003] In butt MIG welding, the first layer welding is generally performed by forming a back bead or by using a backing material. When forming a back bead and welding, in MIG welding, the shape and position of the arc point of the electrode wire are constantly changing, which causes some spattering, and the arc shifts to a stable state in which the arc is sprayed and blows out. It takes time.

Therefore, stable welding cannot be obtained from the start of the arc, and it is difficult to form a uniform and good back bead at the start of the arc. Therefore, even when the back bead at the end of the first layer welding is joined to the bead at the start of the arc, a good back bead is not formed. For example, in the arc start part, FIG.
As shown in (C), a part of the molten metal hangs down inside, and a bead burn-through A occurs. As a result, at the end of the first layer, as shown in FIG. 2 (D), the seam B between the weld start portion and the bead is shifted, and the back bead becomes uneven.

When the welding current is reduced to prevent the bead burnout at the start of the arc, as shown in FIG. 2 (E), the back bead is insufficiently sagged C, and therefore, at the end of the first layer, As shown in FIG. 2F, part of the molten metal is likely to hang inside. As described above, in MIG welding, it is difficult to form a stable weld at the welding start portion, and formation of a good back bead from the welding start portion is an important issue.

In order to solve the above-mentioned problem, in the welding method disclosed in the above-mentioned publication, as shown in FIG. 2 (A), Uranami welding is performed in a predetermined section at a welding start portion by TIG welding Tw. In this case, the length of the TIG welding Tw is a length necessary for stabilizing the MIG welding Mw after the disclosure as described below, and a minimum of 50 mm is sufficient. Next, the MIG welding is started from the intermediate portion M of the TIG welding Tw, the arc is stabilized, and the first layer backside wave welding is performed. In TIG welding, since the shape of the tungsten electrode is constant, the arc is easily stabilized, and stable welding can be performed from the start of welding.

[0007] Even in the final portion E of the first layer shown in FIG. 2B, since the TIG welded portion Tw formed stably is welded to the bead, a uniform connection of the back bead can be achieved. This method can be easily carried out when an operator manually performs a welding operation, and of course, the shielding gas, electric current, welding speed, TI
The supply of the axis for G and the supply of the electrode wire for MIG can also be carried out in the case of automatic welding through a program.

In the above-mentioned program welding, a shielding gas is supplied by a welding start signal, and thereafter, a welding current is increased and TIG welding is started. The cylindrical member is TIG
Rotational movement is started at the same time supply of the core tip is started, and M
Distance required to stabilize the arc of IG welding (about 50m
m) Rotate to end TIG welding.

Next, the cylindrical member is rotated in the reverse direction, the welding tip is returned to the center of the length of the back bead formed by TIG welding, and the shield gas is supplied again by the start signal. Then, when the welding current rises and an arc is generated, MI
The electrode wire for G is supplied and the M
Start IG welding.

[0010] After the start of the MIG welding, the welding conditions are not stable and the beads are not uniform in a predetermined section. However, since the welding is performed from the top of the uniform back bead formed in advance by TIG welding, the back bead is not affected. do not do. At the time when MIG welding has progressed to the point where the back bead of TIG welding is interrupted, MI
Because the G welding conditions are stable, butt welding is performed over the entire circumference of the pipe while forming a stable back bead by MIG welding. At the end of the first layer welding, it is connected to the bead at the welding start point, but since a normal back bead is made by TIG welding in this section, TIG
The seam welding with the welded portion enables uniform connection of the back bead. On the other hand, for welding cylindrical members made of carbon steel, MAG using an economical active gas (eg, CO2) is used.
It is also known to employ welding.

[0011]

However, according to the welding method disclosed in the above-mentioned publication, TIG welding is performed on the initial layer welding start portion where it is difficult to obtain a back seam by MIG welding to form a back seam at the welding start portion. Therefore, since the TIG welding and the MIG welding are used together, the process is duplicated, and both equipments are required, and the equipment cost increases.

When the cylindrical member is welded by MAG welding, as shown in FIG. 3A, the back bead is not sufficiently drooped at the welding start portion, as in the case shown in FIG. 2E. E1 occurs, and as a result, at the end of the first layer, FIG.
As shown in (B), there is a problem that a portion E2 where welding is not performed occurs.

[0013] Therefore, an object of the present invention is to provide a first layer backwash that is stable only by high-efficiency MAG welding without using welding defects such as insufficient dripping and using inexpensive shielding gas (eg, CO2). The aim is to provide a welding method that can be obtained.

[0014]

Means for Solving the Problems In order to solve the above-mentioned problems, a means adopted in the present invention is to perform MAG welding by continuously abutting the end faces of a grooved cylindrical member and continuously forming the groove. In Uranami welding, it is to form a stable first layer Uranami by welding one round while cutting off a welded part of a certain section from a welding start part where a welding defect is likely to occur, and subsequently welding the cut off section.

In this case, for example, when welding cylindrical members of a product that dislikes contamination such as a hydraulic cylinder, the end contact portions of the grooved cylindrical member are pressed from both sides to reduce the gap between the contact portions. It is desirable to prevent welding spatter and cut chips from entering the inside of the cylindrical member.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A welding method according to the present invention will be described based on an embodiment shown in FIG. The same parts as those in the related art are denoted by the same reference numerals, and description of parts that are not particularly necessary is omitted. In the prior art, MIG welding using an inert gas (for example, Ar) that can also weld special steel is illustrated and described. However, regarding welding of a cylindrical member made of carbon steel, which is the object of the present invention, Since MAG welding using a more economical active gas (for example, CO2) is common, it will be described below as MAG welding.

First, as shown in FIG. 1A, the groove 1A is machined except for the contact portion 1B which is a part of the one cylindrical member 1. Similarly, the groove 2a is machined on the other cylindrical member 2 while leaving the contact portion 2B.

Next, the end faces of the contact portions 1B and 2B (0.5 to 2 mm thick) of the two grooved cylindrical members 1 and 2 are butted against each other, and a pressing force is applied to the contact portions from both directions. While clamping to the welding machine with the required precision without gaps.
In this state, as shown in FIGS. 1B and 1D, the initial welding a is welded to an arbitrary range by MAG welding that is more efficient than the first layer. At this time, as described in the related art, FIG.
Since a stable back seam is not formed at the welding start portion F shown by the hatched portion in (D), the welded portion of the welding start portion F (about 20 mm from the welding start portion) where the back seam is insufficient is shown in FIG. And (E), the notch b
In addition to cutting along the groove shape, Uranami welding is continuously performed over one or more rounds (one round from the welding start part + the cut length), including the notch b. As a result, the weld C
Will weld the portion corresponding to the above-mentioned welding start portion F to eliminate defects such as insufficient initial dripping. Therefore,
It is possible to perform stable Uranami welding over the entire circumference of the first layer. Subsequently, the groove was continuously welded to the second and third layers,
Join two cylindrical members.

According to the present invention, in uranami welding by MAG welding, a welded portion in a certain section from a welding start portion where a welding defect is apt to occur is cut off so as not to penetrate inward along a groove shape,
By welding one or more rounds (one round from the welding start part + cutting length), a stable first layer reverse wave can be formed, and the contact parts 1B and 2B
Since there is no gap between them, a backing material is not required, and inexpensive backside welding can be performed.

Further, since the rim welding is performed over the entire circumference while pressing the end faces of the contact portions 1B and 2B from both sides, no welding spatter or cutting chips enter the inside of the cylindrical member, so that the inside is kept clean. On the other hand, since good backside welding can be performed only by MAG welding, there is no need for TIG welding and equipment related to TIG welding, and highly efficient backside welding can be performed with inexpensive equipment.

Further, in this welding method, since the abutment portions are pressed from both sides to perform the backwash welding, joining accuracy such as cylindricity and coaxiality can be obtained with high accuracy by a welding jig.

[0022]

As described above in detail, according to the first aspect of the present invention, a welded portion of a certain section is cut along a groove shape from a welding start portion where a welding defect is liable to occur, and one or more rounds (welding start portion) (1 round + cutting length) By welding, it is possible to form a stable first layer back seam, so that a backing material is unnecessary and inexpensive back seam welding can be performed. Further, welding can be performed in one process such as MAG welding, and the welding equipment can be simplified.

According to the second aspect of the present invention, since the uranami welding is performed over the entire circumference while pressing the contact portions from both sides, no welding spatter or cutting chips enter the inside of the cylindrical member. On the other hand, since good backside welding can be performed only by MAG welding, there is no need for TIG welding and equipment related to TIG welding, and highly efficient backside welding can be performed with inexpensive equipment.

[Brief description of the drawings]

FIGS. 1A, 1B, 1C, 1D, 1E, and 1F are process diagrams of a cylindrical member and a welding method according to an embodiment of the present invention.

FIG. 2 is a process diagram of a conventional method for welding a cylindrical member.

FIG. 3 is a process chart of a cylindrical member welding method according to another conventional technique.

[Explanation of symbols]

 F Welded part (cutting section) in a certain section from welding start part 1, 2 Cylindrical member 1A, 2A Groove 1B, 2B Contact part a Initial weld b Notch c Welded part delayed by one round

Continued on front page F term (reference) 4E001 AA03 BB12 CC03 CC04 DD04 DF05 DF09 DG05 4E081 AA02 AA12 AA14 BA19 BA26 BA27 BB15 CA09 DA01 DA05 DA11 DA42 FA01

Claims (2)

[Claims] 1. In Uranami welding, in which end portions of a cylindrical member having a groove formed thereon are joined to each other and the groove portion is continuously welded, a welded portion in a predetermined section is cut from a welding start portion where a welding defect is likely to occur. A method of welding a cylindrical member, characterized in that a stable first-layer back seam is formed by welding one circumference while continuously welding a cut section. 2. An end face contact portion of a cylindrical member having a groove formed therein is pressed from both sides, and welding is performed without a gap between the contact portions, so that welding spatter and cut chips enter the inside of the cylindrical member. 3. The method according to claim 1, wherein
3. The method for welding a cylindrical member according to claim 1.