JP5548545B2 - Backing metal for arc welding - Google Patents

Description

  The present invention relates to a back metal for arc welding, and more particularly to a back metal for welding used when welding a base material to another base material by arc welding such as MAG (Metal Active Gas) welding.

  In assembling a building steel frame, when two base materials such as beam flanges are welded to each other by an automatic arc welding machine, the end of one beam flange is formed as an inclined end surface, that is, an open end surface by groove processing, and the other beam flange The end face of is formed as a vertical end face. Both beam flanges are arranged so that the open front end surface of one beam flange faces the vertical end surface of the other beam flange and a groove groove having a substantially V-shaped cross section is formed therebetween. A welding backing metal is applied between the bottom surfaces of the end portions so as to be the bottom portion of the groove portion. The welding backing metal is longer than the length of both groove grooves, and both ends of the welding backing metal for this purpose are projected from the side surfaces of the ends of both beam flanges. The end tab is disposed so as to close the end of the groove portion.

  Next, the automatic arc welding machine is operated, whereby the feeding head for the welding wire is moved to one end of the groove groove, that is, the first end, and is positioned at a predetermined height. Next, when the welding wire is fed from the feeding head and the tip thereof is brought into contact with the bottom portion on the first end side of the groove portion, a predetermined voltage is applied between the base material side and the welding wire. Therefore, an excessive short-circuit current flows during that time. When a short-circuit current is passed through the welding wire, its tip melts for heating and an arc is generated in the meantime, thereby starting the welding operation. That is, while the welding wire is fed from the feeding head at a predetermined feed amount, the feeding head is moved toward the other end side of the groove groove portion, that is, the second end portion side, thereby the groove groove portion. An initial layer of molten metal, that is, a first molten metal layer is formed at the bottom of the substrate. When the feeding head reaches the second end side of the groove portion, the feeding head is raised by a predetermined amount, and then the movement of the feeding head is reversed. That is, the feeding head is moved from the second end portion side of the groove portion toward the first end portion thereof, thereby forming a second molten metal layer on the first molten metal layer. The By repeating such a welding operation, a molten metal layer is sequentially laminated in the groove groove portion, whereby the groove groove portion is filled with the molten metal to form a weld bead.

  In the above-described example, the molten metal layer is sequentially laminated while reciprocating the arc between the first and second ends of the groove groove portion. However, after the first molten metal layer is formed, the arc The generation is temporarily stopped, and the feeding head is returned from the second end side of the groove groove to the first end side, where an arc is generated again to move toward the second end of the groove groove. Then, the welding operation may be resumed to form the second molten metal layer on the first molten metal layer.

  As described above, when the molten metal layer is sequentially laminated in the groove portion having a substantially V-shaped cross section, the width of the molten metal layer increases as the molten metal layer becomes an upper layer. Therefore, in order to make the thickness uniform when each molten metal layer is formed, when the feeding head is moved between the first and second end sides of the groove groove, the feeding head is moved to the groove groove. The arc is shifted in a zigzag manner along the groove portion by oscillating in the width direction, and the amplitude of the zigzag transition of such an arc is gradually increased as the molten metal layer becomes an upper layer.

  By the way, in the conventional arc welding method described above, there is a problem that welding defects are likely to occur at the welding start portion (in the above-described conventional example, the first end side bottom portion of the groove portion). The main type of such a welding defect is a gap generated at the welding start location, particularly at the bottom region of the groove groove adjacent to the end tab, which is caused by unstable arc generation at the start of welding. In addition, the temperature of the base material and the end tab is too low at the start of welding, which is also caused by the poor penetration of the molten metal into the base material and the end tab.

Patent Document 1 discloses that in order to stabilize arc generation at the start of welding, the occurrence of welding defects is prevented by appropriately controlling the balance of current and voltage immediately after starting arc welding. There is a problem that it is relatively difficult and troublesome to properly control the balance of current and voltage at the time of arc generation. Patent Document 1 does not mention anything about improving the penetration of the molten metal into the base material at the start of welding.
JP2000-102867

Patent Document 2 discloses a circumferential multi-layered arc welding method for joining open end surfaces formed at the ends of two steel pipes to each other, and includes grooves along the inner side surfaces of the ends of both steel pipes. A circumferential multilayer prime arc welding method is disclosed in which a welding backing metal is applied to form a good initial molten pool in the groove of the grooved welding backing metal. Therefore, an end tab is not used in this circumferential multilayer prime arc welding method. In short, the technique disclosed in Patent Document 2 is free from welding defects such as gaps generated at the welding start location as described above, particularly at the bottom region of the groove portion adjacent to the end tab.
JP 06-015104

Patent Document 3 discloses that the initial welding current value is set to a value higher than the steady-state current value during arc welding to increase the temperature at the welding start location and improve the penetration of the molten metal into the base material. However, Patent Document 2 makes no mention of the elimination of welding defects such as gaps generated at the welding start location as described above, particularly the bottom region of the groove portion adjacent to the end tab.
JP-A-57-079073

  Accordingly, an object of the present invention is a welding backing metal used when welding a base material to another base material by arc welding such as MAG (Metal Active Gas) welding, and the welding start point as described above. In particular, it is to provide a welding backing metal configured to surely eliminate the occurrence of welding defects such as a gap generated in the bottom region of the groove portion adjacent to the end tab.

The above object is achieved by the welding backing metal according to the present invention having any one of the following configurations (1) to (3).
(1)
When the groove tip is faced to another base material, a groove groove is formed between them, and the groove is filled with molten metal by arc welding to perform welding. A welding backing metal disposed over both the base materials to form the bottom of the groove,
A length corresponding to the length of the groove portion, which is made of steel, and after welding, is removed from at least one end of the backing metal body welded to the two base materials. Extending in the width direction, extending in the width direction on the back surface of the run-up forming portion for forming the first layer run-up portion of the molten metal, and only the outer portion adjacent to the critical portion of the backing metal body and the run-up forming portion. A welding backing metal provided with a functional groove for preventing stress that may be generated in the run-up forming part due to an earthquake or the like from being transmitted to the base material.
(2)
The welding backing metal according to (1), wherein a plurality of the functional grooves are formed.
(3)
The welding backing metal according to (1), wherein the two functional grooves are formed.

  According to the present invention, the starting formation portion for introducing the first layer of molten metal as described above is provided in the backing metal, and the molten metal of the first layer is started from here, so the start portion of the first layer is good. In addition to being formed, the provision of the functional grooves facilitates the separation of the run-up forming portion after welding, and has the effect of not transmitting stress that may occur in the run-up forming portion due to an earthquake or the like to the base material. is there.

It is a perspective view which shows embodiment of the backing metal for welding by this invention. It is a perspective view which shows 1 process of the arc welding method using the backing metal for welding of said embodiment.

  FIG. 1 is a perspective view generally showing a welding backing metal 10 according to an embodiment of the present invention. The welding backing metal 10 is used for arc welding the two base materials 11 and 12 to each other as shown in FIG. 2, and each of the base materials 11 and 12 is configured as a beam flange.

  One end of the beam flange 11 is preliminarily grooved to form an inclined end surface, that is, an open end surface 11a. The beam flange 11 is disposed so that the open end surface 11a thereof faces the vertical end surface 12a (FIG. 2) of the beam flange 12, and a groove groove 13 having a substantially V-shaped cross section is formed between the both end surfaces 11a and 12a. Is done.

  The welding backing metal 10 is applied to the lower surfaces of the beam flanges 11 and 12 so as to form the bottom of the groove groove 13 when welding is performed by filling the groove groove 13 with molten metal by arc welding. .

The welding backing metal 10 is made of steel , and has a length corresponding to the length of the groove 13 and a outwardly extending from at least one end of the backing metal body 10a. , Provided to extend integrally with the backing metal main body 10a, and includes a run-up forming portion 10b for forming a first-layer run-up portion of molten metal. The backing metal body 10 a is welded to both base materials 11 and 12.

  And this backing metal 10 was provided to extend in the width direction on the back surface of the critical part of the backing metal main body 12a and the run-up forming part 12b or in the vicinity of the critical part of the run-up forming part. At least one functional groove 14 is formed (two are shown in the figure).

  This functional groove 14 can be used for separating the run-up forming portion 10b after welding, if necessary, and has a function for preventing stress generated in one of the backing metal body 10a and the run-up forming portion 10b from being transmitted to the other. I have.

  Most preferably, one functional groove 14 is formed. This is because it is easy to separate the run-up forming portion after welding.

10: Backing metal for welding 10a: Backing metal body 10b: Run-up forming part 11: Beam flange 11a: Opening end face 12: Beam flange 12a: Vertical end face 13: Groove groove part 14: Functional groove

Claims (4)

When the groove tip is faced to another base material, a groove groove is formed between them, and the groove is filled with molten metal by arc welding to perform welding. A welding backing metal disposed over both the base materials to form the bottom of the groove,
A length corresponding to the length of the groove portion, which is made of steel, and after welding, is removed from at least one end of the backing metal body welded to the two base materials. Extending in the width direction, extending in the width direction on the back surface of the run-up forming portion for forming the first layer run-up portion of the molten metal, and only the outer portion adjacent to the critical portion of the backing metal body and the run-up forming portion. A welding backing metal provided with a functional groove for preventing stress that may be generated in the run-up forming part due to an earthquake or the like from being transmitted to the base material.   The welding backing metal according to claim 1, wherein one functional groove is formed.   The welding backing metal according to claim 1, wherein a plurality of the functional grooves are formed. The welding backing metal according to claim 3, wherein the two functional grooves are formed.

Images