JPS6233072A - Submerged arc welding method - Google Patents

Abstract

PURPOSE:To prevent the generation of a high temp. crack, shrinkage cavity, etc. by pressing the toe of weld part of a welding bead from both side faces by a cooling shoe at the downstream of an electrode and by performing the rolling reduction of the apex part and toe weld part of the welding bead with the rolling reduction roll at the downstream thereof. CONSTITUTION:A pair of cooling shoes 30 are arranged in opposition each other by pinching a welding bead 9 around the unsolidification of a slug 8 at the downstream side of an electrode 3. On the cooling shoe 30 the passage 32 of a refrigerant for cooling a bead with its inclined tip part 31 for conducting a welding bead 9 is provided. The cooling shoe 30 gives a pressure to the toe weld part 93 of the welding bead 9 and performs as well the forcible cooling of the welding bead 9. The shape of the bead toe end part 93 is therefore controlled forcibly. With the shape control thereof the inclination of the dendrite 91 of the toe weld part 93 is forcibly controlled to prevent a high temp. crack. The welding bead 9 is shaped by providing a rolling reduction roll 40 on the welding bead 9 at the downstream side of the cooling shoe 30 and by applying the rolling reduction on the apex part and toe weld part of the welding bead 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a submerged arc welding method aimed at preventing hot cracking of a weld bead.

(b) The conventional submerged arc welding method is as shown in Figure 5.
7Lux 2 is sprinkled on the base metal L, the welding electrode 3 is submerged in the 7LUX2, and an arc 4 is thrown between the electrode 3 and the base metal L, and a part of the electrode 3 and the base metal L is is melted and welded. The welding direction at this time is the direction of arrow 5. In this case, move the base material 1 in the direction opposite to the arrow 5 direction, or
Alternatively, move the electrode 3 in the same direction as the arrow 5.

In FIG. 5, 6 indicates a liquid phase portion of the weld metal, 7 indicates a solid phase portion of the weld metal, and 8 indicates a molten slag.

A cross section of the solid phase portion 7 of the weld metal is shown in FIG.

In the figure, 9 indicates a weld bead. In the weld bead 9, dendrites (columnar crystals) 91 and equiaxed crystals 92 grow during transformation from a liquid phase to a solid phase.

Now, in the cross section of the weld bead 9, the angle formed by the dendrite 91 with respect to the horizontal direction is called the inclination angle θ (FIG. 4). At the toe 93 of the weld bead 9, the inclination angle θ is 7.
Hot cracking occurs in the region of 0 to 90''. Also, shrinkage cavities occur in the equiaxed crystals 92 near the surface of the weld bead 9.

In order to prevent these hot cracks and shrinkage cavities, conventional methods have controlled welding conditions such as current and voltage, and adjusted the composition and particle size of flux to adjust the shape of the weld bead. However, with this method, the shape of the weld bead was not constant, and the effect of preventing weld bead defects was unstable.

0→ Problem to be solved by the invention The problem to be solved by the invention is to stably prevent internal defects such as hot cracks and shrinkage cavities that occur in the weld bead during submerged arc welding. The objective is to obtain a submerged arc welding method.

2) Means for solving the problem The submerged arc welding method of the present invention
To provide a pair of cooling shoes that sandwich the weld bead and face each other near the unsolidified slag position on the downstream side of the welding electrode in the welding direction during arc welding, and to collect flux on the weld bead near the cooling shoes. , applying a pressing force to the toe of the weld bead with the cooling shoe and performing forced cooling; providing a reduction roll on the weld bead on the downstream side of the cooling shoe with respect to the welding direction; The above problem is solved by shaping the weld bead by applying pressure to the toe.

When carrying out the above method, even more reliable effects can be obtained by carrying out it in an inert atmosphere.

(E) Example The submerged arc welding method of the present invention will be specifically explained with reference to FIGS. 1 to 4.

FIG. 1 is a plan view of a groove portion IL welding progressing portion 12 and a welding completed portion 13 of the base material 1 to be welded.

The welding electrode 3 is disposed on the most upstream side in the welding direction 5, and the 7 lux slag collector 20, the cooling shoe 30, and the reduction roll 4o are sequentially disposed on the downstream side thereof. Note that an inert gas atmosphere chamber 50 surrounding the 7 lux slag collector 20 and the cooling shoe 30 may be provided as necessary.

As shown in FIGS. 1 and 4, the cooling shoe 30 is
They are arranged downstream of the welding electrode 3 in the welding direction 5 near the unsolidified slag 8 so as to face each other with a weld bead 9 in between.

The cooling shoe 30 is connected to the weld bead 9 as shown in FIG.
The distal end 31 is inclined in order to smoothly guide the
In addition, in order to provide a cooling function, a cooling medium (for example,
A conduction path 32 for circulating water (water, etc.) is provided. moreover,
The entire cooling shoe 30 is made of copper, and only the portion that contacts the weld bead 9 is made of tungsten to provide heat and wear resistance functions.

The cooling shoes 30 have a function of opening and closing in opposition to each other, and the interval between them can be adjusted within a range of, for example, 10 to 30 mm. The pressure with which the cooling shoe 30 clamps the weld bead 9 is 1 to 5 degrees.

The flux/slag collector 2o is arranged on the inlet side of the cooling shoe and collects most of the flux used during welding and the slag generated during welding.

Another flux is sprinkled onto the weld bead 9 downstream of the flux slag collector 20 and sandwiched between the cooling shoes 30. This flux may be either a bond type or a sintered type. This flux reacts with the slag metal to adjust the weld metal components, and also generates gas to shield the weld metal surface with the gas.

As shown in FIGS. 1 and 4, the cooling shoe 30 applies a pressing force to the toe 93 of the weld bead 9 and performs forced cooling. By applying a pressing force to the toe 93, the shape of the bead toe 93 is forcibly controlled. This shape control forcibly controls the inclination angle θ of the dendrite 91 of the toe portion 93 to prevent hot cracking.

By forcibly cooling the toe 93 of the bead 9 by the cooling shoe 30, the growth of the dendrite 91 is promoted and a sufficient liquid phase is supplied to the equiaxed crystal 92.

When suppressing the cooling shoe 30, an inert gas atmosphere chamber 50 can be provided as necessary to keep the weld metal warm and protect it. Argon gas, nitrogen gas, etc. are used as the inert gas.

A reduction roll 40 is provided on the weld bead 9 downstream of the cooling shoe 30. The weld bead 9 is shaped by applying pressure to the top and toe of the weld bead 9 using a reduction roll 40 . The reduction roll 40 preferably has flanges 41 on both ends and a concave crown on the body 42, as shown in FIG.

7. The flange 41 also connects the toe 93 of the weld bead 9 to the body 4.
2 shapes the top of the bead 9, respectively.

(f) Effects According to the method of the present invention, the shape of the weld bead is shaped,
The dendrite inclination angle θ was lowered to 60 degrees, and there was no occurrence of hot cracking. In the conventional method, the weld bead shape was poor, the dendrite inclination angle θ was 90 degrees, and the incidence of hot cracking was 10 degrees.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view of a line showing an example in which the submerged arc welding method of the present invention is applied to an actual welding line. FIG. 2 is a plan view of a cooling shoe used in the method of the present invention. Third
The figure is a plan view of a reduction roll used in the method of the present invention. FIG. 4 is a cross-sectional view of the weld bead section taken along line IV--IV in FIG. 1. FIG. 5 is a schematic explanatory diagram of a conventional submerged arc welding method. FIG. 6 is a drawing similar to FIG. 4, and is a cross-sectional view of the weld bead section taken along the line W--■ in FIG. 5. l: Base metal 2: Flux 3: Welding electrode
4: Arc 5; Welding direction 6: Liquid phase portion 7: Solid phase portion 8: Molten slag 9: Welding bead 20: Flux/slag collector 30: Cooling shoe 40; Reduction roll 50; Inert gas atmosphere chamber (outer 5 name

Claims (1)

[Claims] During submerged arc welding, a pair of cooling shoes are provided near the unsolidified slag position on the downstream side of the welding electrode in the welding direction, sandwiching the weld bead and facing each other, and collecting flux on the weld bead near the cooling shoe. applying a pressing force to the toe of the weld bead with the cooling shoe and performing forced cooling; providing a reduction roll on the weld bead downstream of the cooling shoe in the welding direction; A submerged arc welding method that involves shaping the weld bead by applying reduction to the top and toe of the weld bead.