JPS60148679A - Submerged arc welding method - Google Patents

Abstract

PURPOSE:To prevent generation of an undercut, to increase a welding speed, and to improve a productivity by making a force of a reverse direction operate on a molten metal flow by an electromagnetic force of a moving magnetic field against a molten metal, in case of a horizontal submerged arc welding. CONSTITUTION:In case of a large heat input welding or a high speed welding, a molten pool 5 becomes long and large, and flows 6 in the rear of an arc. A force 11 for obstructing a metallic flow is operated by providing a moving magnetic field generating device 7 just behind an arc fusion zone 10. By this force 11, a good welding state is obtained by preventing generation of an undercut part of a weld zone, and a work efficiency can be improved by further increasing a welding speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to ordinary horizontal submerged arc welding, such as a submerged arc welding method for manufacturing straight seam welded steel pipes and joining various types of steel plates.

(Prior art) In conventional horizontal submerged arc welding, various methods have been proposed to speed up the welding of straight seam steel pipes. Welding speed has been increased by improving the welding wire, flux, groove shape, and welding conditions, such as the I-groove high-speed submerged arc welding method (Japanese Patent Publication No. 56-52672).

(Problems with the conventional technology) As shown in Figure 1, in the conventional technology, the arc force determined by the welding conditions and the difference between slag and metal (solid).

The relative relationship between the molten metal retraction distance 3 and the solidification start position 4 at the toe of the peed is determined by the molten metal flow generated by the interfacial tension of the liquid (1) gravity, etc., thereby achieving the maximum welding speed at which welding defects such as undercuts do not occur. The limits were set.

(Objective of the Invention) The object of the present invention is to obtain a submerged arc welding method that can further improve the maximum welding speed limit compared to conventional methods without causing welding defects such as undercuts.

(Structure 0 Effect of the Invention) In the submerged arc welding method according to the present invention, by applying an electromagnetic thrust by a moving magnetic field to the molten metal generated during welding in horizontal submerged arc welding,
The maximum welding speed can be increased by controlling the molten metal retreat distance.

In welding where the molten pool is long, such as high heat input welding or high-speed welding, the molten metal flows toward the rear of the arc and solidifies. In the welding method of the present invention, for example, as shown in FIG. 2(a), a moving magnetic field generating device 7 is installed parallel to the weld metal before solidification, so that no current is induced by the moving magnetic field generated. The interaction between the molten metal and the moving magnetic field applies thrust to the molten metal, solidifying the weld bead into an arbitrary shape.

What is shown in FIG. 2(b) is a device in which a moving magnetic field generating device 7 is installed on the back side of the welding part, and a magnetic field is applied from the back side of the welding part in the same manner as described above. In this embodiment, compared to the above embodiment in which the magnetic field generator 7 is provided directly on the surface of the molten metal,
Although the effectiveness is reduced, there are no obstacles on the equipment, so this may be more advantageous in terms of equipment design.

Although single-electrode submerged arc welding is illustrated in FIG. 2, the same effect can be obtained even when applied to multi-electrode submerged arc welding.

Next, the effect of the method of the present invention will be described in more detail. For example, in Fig. 2, when no moving magnetic field is applied, the molten metal flows in the opposite direction to the welding progress direction, but when high-speed welding is performed, the molten metal recedes distance becomes large, and as shown in Fig. 3 (b).
), an undercut 12 occurs. At this time, the transfer retreat distance shown in FIG. 2 becomes small, undercutting is prevented, and a good bead as shown in FIG. 2(a) can be obtained.

(Example) Table 1 shows examples of the present invention. The test material used was a flat steel plate, and when welding was carried out at a speed exceeding the maximum welding speed limit of the conventional method, the conventional method applied no thrust due to the moving magnetic field, and the present method applied thrust due to the moving magnetic field. Submerged arc welding was carried out for this.

As is clear from the results shown in Table 1, undercuts occurred in the conventional method, but such defects did not occur in the method of the present invention, and a good weld bead could be obtained.

Table 1 As mentioned above, the maximum welding speed is limited by the molten metal flow caused by the welding arc and the balance of the molten head, as well as the molten metal retreat distance and the bead top solidification start position. By artificially applying thrust to the molten metal during welding using a magnetic field, it is possible to freely control the bead shape and improve the maximum welding speed limit.

(Effects of the Invention) As explained above, according to the method of the present invention, the maximum welding speed can be improved, productivity is improved, and the invention is industrially very valuable.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the retreat distance of molten metal and the solidification start position of the upper end of the bead. FIG. 2 is an explanatory diagram of the method of the present invention, in which (a) shows the case where the electromagnetic thrust is applied to the molten metal from the front side of the bead using a moving magnetic field generator, and (b) shows the case where the electromagnetic thrust is applied from the back side. FIG. 3 shows a cross-sectional view of a welded part, in which (a) shows a proper bead shape before welding, and (b) shows a bead shape in which an undercut has occurred. 1... Base material, 2... Pead, 3... Molten metal retreat distance, 4... Bead toe solidification start position, 5... Molten metal, 6... Molten metal flow, 7 ... Moving magnetic field generator, 8... Electrode, 9... Wire, 10... Arc, 11... Moving direction of magnetic field, 12... Undercut. Agent: Patent attorney Masamitsu Akizawa and 2 others

Claims (1)

[Claims] (1) A submerged arc welding method characterized by applying electromagnetic thrust by a moving magnetic field to molten metal generated during horizontal submerged arc welding.