JPH0335880A - Automatic welding method - Google Patents

Abstract

PURPOSE:To obtain satisfactory weld zone quality without a tab plate at the welding starting end by igniting an arc at a specified distance from one end of a butt line of steel plates and starting the arc movement after attaining a specific thickness of depth of penetration. CONSTITUTION:The arc is ignited at the position within 15mm from one end of the butt line of steel plates and the arc movement is started after the depth of penetration is attained to >=1/2 of plate thickness. The arc movement is then stopped at the position within 15mm from the other end of the butt line of steel plates and the arc is extinguished after a bead is swollen from the plate surface. By this method, even if the tab plate and a press plate, etc., similar to this are not used, the satisfactory weld zone quality can be given to the welding starting end and finishing end.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an automatic welding method that does not require tab plates.

(Prior Art) Conventionally, submerged arc welding has been widely used in the production of welded steel pipes.In the production of welded steel pipes by the submerged arc welding method, after forming a bottom shape of a steel plate into a tubular shape, the IU
Weld the metal wire from one end to the other. In that case,
Sufficient penetration is not obtained at the welding start end, and craters due to underbeads occur at the welding end, resulting in poor welding at both ends. For this reason, before welding, a temporary temporary tab called a tab plate is installed on the extension of both ends of the steel plate butt line, and welding is started and finished on this tab plate to ensure the quality of the welded part of the steel pipe over its entire length. .

In addition, some progress is being made in the development of welding methods that can ensure the quality of welded parts of steel pipes without using tab plates. As such welding methods, a method in which welding conditions are changed during seam end welding is disclosed in JP-A-61-140372, and a method in which pressing a metal plate instead of attaching a tab plate is disclosed in JP-A-57. It is disclosed in Japanese Patent No.-81990.

[Invention tries to solve! IN! l) Among conventional welding methods, welding methods that require the use of tab plates take time to attach (tack welding), and require a process to remove the tab plate after welding, which reduces work efficiency. This is causing a decline.

Even with the welding method in which a metal plate is pressed instead of the tab plate, it takes time to align the metal plates, etc., and it cannot be expected to significantly improve efficiency compared to the welding method in which the tab plate is attached. For long pressing, equipment is also required.

Furthermore, welding methods that change conditions at the time of end welding not only have restrictions that can only be applied to the end of the weld, but there is also a high possibility that the weld itself will be sacrificed due to changes in welding conditions, making it impractical. .

The present invention solves all of these problems, and its purpose is to provide an automatic welding method that can weld steel plates with good quality from one end to the end of the butt line without using a tab plate. be.

[Means to solve the problem]

The automatic welding method of the present invention ignites an arc at a position within 15 degrees from one end of the steel plate butt line, starts arc movement after the penetration depth becomes 1/2 or more of the plate thickness, and The arc movement is stopped at a position within 15 mm from the other end of the butt line, and the arc is extinguished after the bead rises above the plate surface.

[For production]

In the automatic welding method of the present invention, an arc is ignited near one end of the steel plate butt line, and arc movement is started after securing a sufficient penetration depth at that position. By doing so, good weld quality can be imparted to the welding start end even without a tab plate.

The arc ignition position is related to welding, and by setting this position within 15 mm from one end of the steel plate butt line, deterioration of the quality of the welded part due to insufficient penetration can be prevented.

The time from arc ignition to the start of arc movement is adjusted so that the penetration depth at the arc ignition position is 1/2 or more of the plate thickness.6 The specific time depends on the plate thickness, welding conditions, etc. Since it varies, it cannot be generally specified, but for reference, in the case where the plate thickness is 6 to 16 mm, this penetration depth is secured in about 0.5 seconds or more. however,
If this time exceeds 5 seconds, the penetration will be excessive.

After arc movement starts, arc movement continues at the set speed.

When the arc reaches the vicinity of the other end of the steel plate butt line, the movement of the arc is stopped, additional reinforcement is applied to this position, and then the arc is extinguished. By doing this, good weld quality can be imparted to the weld end without the need for a tab plate.

The reason why the arc movement stop position, that is, the arc extinguishing position, was set within 15 m from the other end of the steel plate butt line is the same as the reason for setting the arc ignition position.

The time from the stop of arc movement to the extinguishment of the arc is adjusted so that the arc at the stop position of the arc rises above the plate surface. The specific time varies depending on the plate thickness, welding conditions, etc., and when the plate thickness is 6 to 16 mm, this overfilling is performed in about 0.2 seconds or more, and the crater is eliminated. However, if this time exceeds 10 seconds, the excess will become excessive.

Welding conditions are appropriately set depending on the material, thickness, etc. of the steel plate. It is not necessary to change the arc generation conditions from arc ignition to arc extinguishment; the only condition that needs to be changed is the arc movement condition, and that is only when the arc movement is stopped at the arc ignition position and the arc extinguishment position. This is an extremely simple method in which the arc is generated while the arc is moving, and there is no need to change the moving speed while the arc is moving, allowing constant speed running.

〔Example〕

The present invention will be explained in detail below.

When butt welding carbon steel plates with a thickness of 91 m using the submerged arc welding method under the conditions of 650A-32V-0.5M/min, the arc ignition position, arc extinguishing position, and arc movement stopping time at each position were varied. Table 1 shows the welding results when changed.

In the table, the movement start position and movement stop position are expressed as distances from the tip of the steel plate butt line. The number indicating the quality of the weld at the starting end represents the penetration rate (%) relative to the plate thickness, and the number indicating the quality of the weld at the end indicates the protrusion of the bead from the plate surface!
(m), that is, it represents the amount of surplus.

kl ignites an arc at a position 6 m from one end of the steel plate butt line, continues arc generation at that position for 1.5 seconds, then starts arc movement, and at the welding end, the arc is ignited at a position 6 m from the other end of the steel plate butt line. After stopping the arc movement at
This is an example in which arc generation continued for 3.5 seconds at that position. The arc generation conditions are the same from arc ignition to arc extinction (650A-32V), the arc movement speed is constant (0.5M/min) during the movement period, and the weld quality is good at both the start and end ends. be.

For No. 2, the arc movement start position is 13m from one end of the steel plate butt line.
This is the case of g. The quality of the weld at the starting end is as good as in No. 1.

Case 3 is an example in which the arc movement starting position was 16n, which was too far from one end of the steel plate butt line, and a welding defect occurred at the starting end.

N[L4 is a case where the arc movement start position is appropriate, but the time from arc ignition to movement start is excessive (5 seconds). As a result, weld leakage occurred at the starting edge.

Case 5 is an example in which this time is not secured, that is, an example in which arc movement is started at the same time as arc ignition. The starting edge melting rate does not reach 1/2 of the plate thickness.

Magnet 6 is an example in which this time is 1 second, but the penetration rate is sufficient.

\7 is a case where the arc movement stop position at the welding end is 13 m, and the quality of the welded part at the end is good.

Shame 8 has a welding defect at the end because this position is too large (16M).

14I19 is an example in which the time from arc movement stop to arc extinction at the welding end is 8 seconds. The amount of surplus at the end is 3.0, which is within the allowable range.

For llll110, this time is too long (15 seconds), resulting in excessive weld leakage at the end.

1 kll is an example in which this time is not secured, that is, the arc is extinguished at the same time as the arc stops moving.

Although the arc movement stop position was appropriate, a dent (a dent amount of 0.5 square meters) was formed at the welding end.

Although the above example shows single-electrode submerged arc welding, the automatic welding method of the present invention is applicable to MIC5MAG, TI
It can be applied to G welding and also to multi-electrode welding.

〔Effect of the invention〕

The automatic welding method of the present invention can provide good weld quality at the weld start and end without using a tab plate or a similar pressing plate. Therefore, tab plates and similar pressing plates can be omitted, and welding workability can be significantly improved.

In addition, there is no need to change welding conditions during welding, so
Welding work is easy, and deterioration in weldability due to changes in welding conditions can be prevented.

Claims (1)

[Claims] 1. Ignite the arc at a position within 15 mm from one end of the steel plate butt line, and start arc movement after the penetration depth becomes 1/2 or more of the plate thickness, and 15 mm from the other end of the steel plate butt line. An automatic welding method characterized by stopping the arc movement at a position within 100 degrees and extinguishing the arc after the bead rises above the plate surface.