JPS59179294A - Multielectrode submerged arc welding method and welding wire used therein - Google Patents

Abstract

PURPOSE:To assure the fluidity of slag and to suppress generation of welding defects in multielectrode submerged arc welding by using a cored wire contg. a specific amt. of Al and Al-Mg alloy powder as a slag forming agent. CONSTITUTION:A cored wire contg. 0.5-7wt% powder of Al, Al-Mg alloy or a mixture composed thereof as a slag forming agent is used for at least one of welding wires in multielectrode submerged arc welding of a thin walled large diameter pipe, etc. The properties over the entire part of slag are maintained at a high viscosity by using such wire. A thermit reaction is caused in at least a part of a molten pool and the fluidity of slag is assured by utilizing the heat generated by the same, by which the generation of welding defects such as an undercut and slag inclusion is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-electrode latent arc welding method used for manufacturing and welding thin-walled, large-diameter pipes, and a welding wire used therefor.

The multipolar submerged arc welding method allows the use of large diameter welding wires, has high welding ability, and generates an arc under conditions covered by 7 ranks, so there are no countermeasures against arc light, fumes, etc. It is not necessary and is convenient for managing the working environment.In particular, multi-electrode types have each electrode arranged in tandem, that is, a so-called degging electrode with a degging function that determines the penetration depth. The penetration shape, surface texture, etc. of the weld bead can be arbitrarily set by setting suitable welding conditions for the electrode, which has a smoothing function that adjusts the bead surface properties, and the subsequent smoothing electrode. Although it has excellent properties, it has the disadvantage that welding defects such as slag entrainment and undercant are likely to occur during high-speed welding.

Conventionally, countermeasures to this problem include reducing the welding speed, finely adjusting the electrode spacing, current, and voltage, or adjusting the particle size distribution of the flux. However, all of these methods have the disadvantage that they are empirical methods, lack certainty, and have unsatisfactory effects.

The present invention @ conducted an experimental study on the relationship between welding defects such as undercuts and slab entrainment in multi-electrode submerged arc welding and the flux used, and found that undercuts occur when fluxes with high viscosity Noslag physical properties are used. It was also found that the lower the melting point of Franks, the less slag entrainment occurs. This is because when the slag physical properties are high, the flow of the molten metal is suppressed, so the molten metal does not retreat from the groove, and as a result, the occurrence of undercuts is prevented and the flux is reduced. It is thought that this is because when the melting point is high, the fluidity of the slag in the molten pool is high and the slag easily floats even if it gets caught, and as a result, the occurrence of slag entrainment is prevented.

Therefore, for example, when using a flux that seals the physical properties of high-viscosity slag for the purpose of preventing undercuts, it is possible to prevent slag entrainment by increasing the fluidity of the slag in at least a portion of the molten pool where slag entrainment is likely to occur. This makes it possible to eliminate both undercut and slag entrainment defects.

The present invention was made based on such knowledge, and its purpose is to use the late I1i7 slag having high viscosity physical properties, while at least one of the welding wires is made of Ae, Kl-Mg alloy. .

Alternatively, by using a cored wire containing 0.5 to 7% by weight of powder of these mixtures as a slab forming agent, a thermite reaction can be generated in at least a part of the molten pool while maintaining the physical properties of the entire slag at a high viscosity. A multi-electrode submerged arc welding method that utilizes the generated heat to raise the slag temperature and ensure the fluidity of the slag, thereby suppressing the occurrence of welding defects such as undercuts and slag entrainment. The present invention provides a creepage wire used for this purpose.

Polyelectric 4Ii submerged arc welding method AJ or 4 according to the present invention
4? It is characterized by using at least one cored wire containing powder of -J alloy or a mixture thereof as a slag forming agent in an amount of 0.5 to 7%.

Note that the powder of Al or Al-Mg alloy or a mixture thereof causes a chillmint reaction in the molten pool, increases the temperature of the molten metal and slag, improves their fluidity, and promotes the floating of the slag involved. This is used to prevent the occurrence of slag entrainment, and the content is 0.5 to 7% by weight as a slag forming agent. This is due to the fact that the heat generation effect is not sufficient, and if it exceeds 7%, creeping workability will deteriorate significantly.

The present invention will be specifically explained below based on drawings showing its implementation state. FIG. 1 is a structural side view showing a state in which the method of the present invention is carried out using a welding wire according to Zero Shot (7), in which M is the tube base material, M a is the edge portion, 1. ;2.
311i: Electrode for submerged arc welding, F indicates 7 lux. The edge portion Ma of the tube base material M is abutted with an appropriate 9J beveling process, and the electrode 1.2.8 is placed on the abutted edge portion Ma. The electrodes 1, 2, and 8 are arranged in a line in the direction of welding progress indicated by the open arrow, and are spaced apart from each other so as to form a single molten pool, and are connected to the welding wire Ia, respectively.

2a and 3a are inserted into Franks F. Leading pole located at the forefront in the direction of welding progress,
That is, the first electrode 4 & 1 mainly has a digging function that determines the digging depth, and the subsequent electrode 'f; 2
The electrode 2 has a digging function and a smoothing function to adjust the bead surface properties, and the third electrode 3, which is the electrode in the last row, has a smoothing function (fi# is set to the most appropriate welding conditions). Welding wire Ia, 2a
, 8a, the welding wire Ia is supplied from the first and second electrodes 1.2.

2aFi both solid wires but still the 8th electrode 3
A cored wire is used as the welding wire 3a supplied from the welding wire 3a. Cored Soyer is a slag forming agent with a weight ratio of 0.5 to 7% AI! 1 or AJ-Mg alloy or a mixture of both as powder. By supplying the core wire from the last row of electrodes, the levitation of the slag is promoted in the region where entrainment is most likely to occur, and as a result, the occurrence of slag entrainment can be effectively prevented. Of course, as other welding wires Ia and 2a, cored
It goes without saying that you can use wire.

As long as the slag physical property is high viscosity as 7 lux F, a commercially available slag may be used as is. Figure 2 is a schematic cross-sectional view showing another implementation state of the method of the present invention. The required angle θ (0~
2°) so that the welding direction is diagonally downward. The other configurations are the same as the embodiment shown in FIG. 1, and corresponding parts are given the same numbers. By making the welding direction diagonally downward in this way, the retreat of the molten metal in the molten pool, that is, the flow backward with respect to the welding direction, is suppressed, and the spread in the width direction is promoted, and the weld metal is wide and high. A low bead is formed, and the occurrence of undercant is effectively prevented. If the inclination angle θ is 0 to 2° and the angle exceeds 0°, that is, the direction of g-tangential movement is diagonally upward, the molten metal will be forced to retreat due to self-injection (and its spread to the left and right will be insufficient). death,
If the bead is narrow (1111+1), it becomes high and undercant is likely to occur.If θ exceeds 2 degrees, the forward movement of the molten metal increases, causing an overramp bead and slag entrainment. This is because it results in frequent occurrence of

Next, examples of the method of the present invention will be described.

The test steel sheet was 5M4 with the lj component 2 composition shown in Table 1.
1 Made of A material, thickness 12m+n, width 200mm.

A steel plate having a length of 1500 mm was welded using an 8-electrode latent arc welding method using a bead-on-plate.

The first electrode of the three welding voltages was DC, 950A.

36V1 second electrode is AC, 800A, 42V, third
The electrode was AC, 750A, 46V1, and the welding speed was 2.
．． 3Ill/min, the distance between the electrodes is between the first and second electrodes: 2
0mm.

The distance between the second and third electrodes was 20 mm, and the chip height was 85 mm.

The flux used is a commercially available S102-Mn0-CaO system having high viscosity slag physical properties, and has grain IW and mesh size of 28 or less.

The components of the cored wire are as shown in Table 2.

The composition was used. Note that wires marked with * in Table 2 are wires that do not belong to the present invention and were used as a reference. The composition shown in Table 2 is shown in the weight ratio as a slag forming agent in the upper row)
In addition, the weight ratio of the hoop of the cored wire to the 7 lux is shown in parentheses at the bottom.The weight ratio of the hoop to the 7 lux in the cored wire is 85:15, but depending on the thickness and shape of the hoop material. Table 3 shows the combination of welding wires and the inclination of the welding direction that were changed at 60:40t. The results were obtained by performing X-ray inspection on a bead length of 60 cm, excluding the welding start point and immediately after, and the busy turret part.

In Table 8, (LJ, *#J indicates the case where there is no welding defect, ○ indicates the case where it is also a decimal, Δ indicates the case where it is normal, and × indicates the case where there are many welding defects. In Table 3 * Those marked with ``mark'' indicate cases in which the conditions of the method of the present invention are not met.

From Table 3, methods other than the ``Manly, Wood-starting'' method (N8
．． ], 8', 10), whereas crack welding defects frequently occur due to the method of the present invention (Nos. 2 to 7, 9).
It can be seen that the occurrence of undercant and slag entrainment is either non-existent or remains small. In addition, when the welding progress direction is 1.2 degrees downward, slab entrainment may occur frequently when using the present invention, but when using a cored wire, It can be seen that it can be easily redeployed by changing A.

As described above, in the method of the present invention and the zero-starting one product, in multi-electrode submerged arc welding, at least one of the welding wires used is a cored wire, and this cored wire has a weight ratio of slag forming agent of 0. .5-7% of Al, Af-Mg alloy, or a mixture of both is added as a powder as a built-in slag forming agent, which keeps the entire slag highly viscous during the welding process, so that it is in the opposite direction to the welding direction of the molten metal. The present invention has excellent effects such as suppressing and controlling the flow in the direction, increasing the slag temperature in the part still facing the cored wire, improving fluidity in the molten pool, and eliminating welding defects such as undercuts and slag entrainment. It is something that plays.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an implementation state of the method of the present invention, and FIG. 2 is a schematic diagram showing another implementation state of the wood selling method. 1.2.3... Electric 4dila, 2a, 3a - Welding thread M... Pipe base material F... Franks Special K Applicant: Sumitomo Metal 11" 4 Industrial Company Representative Patent Attorney Kawa Wild climbing dog

Claims (1)

[Claims] 1. At least one cored wire containing powder of Al or Af-Mg alloy or a mixture thereof as a slag forming agent in a weight ratio of 0.5 to 7% is used. Multi-electrode submerged arc welding method. 2. Using AJ or Al-Mg alloy powder or a mixture thereof as a slag forming agent, the ET ratio is 0.5 to 7.
Welding wire characterized by containing 0%