JPS6363571A - Horizontal submerged arc welding method - Google Patents

Abstract

PURPOSE:To prevent the blow hole defect caused at the inner part of the final welding metal in a horizontal submerged arc welding by specifying the rising angle at the end part of the upper part of the final welding metal. CONSTITUTION:The angle theta made by the tangent to the final welding metal 3 at the part where the surface of a steel plate 1 and the final welding metal 3 are intersected and the surface of the steel plate 1 is taken as the rising angle theta of the end part of the upper part and the welding is performed so that this angle theta attains to 3 deg.-20 deg.. The generation of a blow hole can thus be prevented.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to horizontal arc welding for the purpose of preventing blowhole defects that occur inside the final weld metal during horizontal arc welding in the manufacture of cylindrical tanks, etc. This invention relates to an arc welding method.

(Prior art) In recent years, cylindrical tanks such as crude oil tanks and LPG tanks have been constructed in various places, and the steel plates are made of mild steel to HT6.
0kg steel, low-temperature steel is used; rL, one-way circumferential joint, V, t horizontal submerged arc welding method using melt flux or Zend flux is widely used.

This horizontal submerged arc welding has an unnatural welding position compared to downward submerged arc welding, so the weld bead tends to hang down.
To prevent this, welding is usually done using dwarf heat. In particular, the final layer becomes a finishing bead and it is necessary to keep the bead appearance smooth, and for this purpose a method is adopted in which welding is performed by lowering the welding voltage and increasing the welding speed.

(Problems to be Solved by the Invention) By the way, slag entrainment has conventionally been a problem that occurs in horizontal open welding. Regarding this slag entrainment, it is disclosed in JP-A-56-92000 that defects can be prevented by examining the flux composition. However,
Recently, minute blowhole defects discovered in magnetic particle testing have come to be seen as a problem.

In other words, this defect occurs at a position several millimeters below the bead surface, especially at the top few edges of the final layer (7).The size of the defect is 0.3- to 3-cm spherical or half-moon, so it is 5% This problem is easily caused by low-voltage, high-speed welding, and is difficult to solve with the conventionally proposed flux combination BT.

The present invention utilizes this technique for horizontal submerged arc welding. I11. The purpose is to prevent blowholes near the pressure area near the leprosy.

(Means for Solving Problems) The gist of the present invention is to perform welding so that the rising angle IIjL of the upper ridge end of the final weld metal is 3° to 20°. -This is a distinctive horizontal submerged arc welding method.

Here, the rising angle is the angle θ between the tangent to the final weld metal 3 and the surface of the steel plate 1 at the intersection of the surface of the steel plate 1 and the final weld metal 3 in the macro cross section of the weld shown in FIG. It is.

(Function) The present inventors have conducted detailed studies in order to provide a method for preventing horizontal submerged arc welding defects that produces good weld metal without blowholes. As a result, blowholes that occur in the vicinity of the final layer top and bottom droplets, as shown in Figure 2, are caused by gas in the arc cavity due to changes in the arc length due to droplet transfer or by fluctuations in the molten pool. It is mixed into the molten metal, dispersed, and becomes foamy.
It was concluded that this gas remained on the upper side of the bead during solidification, and that it was difficult to float this gas using normal welding methods. In horizontal submerged arc welding, the sheets are usually laminated from the bottom outward and upward with a groove. final weld metal and ri.

This refers to the uppermost surface weld bead on both sides as shown at 3 in Figures 1 and 2. That is, in the final layer shown in FIG. 2, low voltage and high speed welding is used to prevent the bead from sagging, so the bead cross section has a deep bathing depth relative to the bead width. Therefore, since the rising angle θ of the upper ridge end of the bead is large and the wall thickness is large, the injected constant gas is difficult to escape upward and remains as a blowhole.

If it takes on a half-moon shape, it is thought that the gas pressure was low and it was crushed by the molten metal.

Therefore, as a result of various studies to prevent this blowhole defect, we found that in order to fully float the gas, the rise angle θ of the upper ridge end of the final bath welded metal should be made small, as shown in Fig. 1. It was found that forming a smooth bead shape makes it easier for gas to float and is effective in preventing blowhole defects.

FIG. 3 shows the relationship between the number of blowhole defects and the rising angle of the upper restraint portion. When the rising angle θ of the upper ridge end exceeds 20°, the thickness of the upper ridge becomes large;
The gas that has been sucked in is difficult to escape upward and increases to Ml as a blowhole. Also, the bead shape becomes a convex bead, which makes the appearance confusing. On the other hand, when the rising angle θ of the upper part 1 part is less than 3 degrees, the wall thickness of the upper W+h edge becomes thinner, the m gas that is mixed in is easy to float, and the blowhole μ does not occur, but the bead hangs down and the under Cuts occur and a good bead appearance cannot be obtained.

In other words, in order to obtain a good weld metal without undercut or blowhole defects in the final welding, it is necessary to set the rising angle θ of the upper dance edge to 3° to 20° and to allow all of the gas to float to prevent defects. It is extremely effective against.

(Example) The steel plate was regulated according to JIS G3106 with the components shown in Table 1, and was made of SM50 B steel (thickness: 16mm, length: 1000+aI).
Then, using the same wire with the components shown in Table 1,
The groove angle shown in FIG. 4 [X=45°.

The depth in the plate thickness direction is d = 81111, the flux is 11, S 102 = 25 qb, Mn0 = 11%
, A1203=20%, 0aO=20aj), 0
aF2=20qb, other 3% melt type (particle size 2
0x65 Metsunyu) and was made into a 21m pile. The electrode angle Y
1Z is shown in Figure 5. Electrode angle Y = 30°, welding direction Electrode angle 7, = Q ~ l 50, using a DC power source, welding the first layer under the same conditions, welding conditions for the second layer Metal Kae 90 Evaluation of the welded part is The rise angle θ of the upper ridge end of the final weld metal was examined by taking a macro cross-section, and for blowholes, the bead excess was polished down to the base metal, and a magnetic particle test was conducted to check for defects and the number of defects. . Dimensions,
The presence or absence of undercuts was also investigated.

These results are shown in Table 2 together with the welding conditions.

First, for H1 and H2, which have lower voltages in consideration of undercut, the rising angle θ of the upper ridge end is 23° and 26°,
A blowhole defect occurred. On the other hand, the voltage was increased and the rising angle θ of the upper ridge end was 18°.

H3, 84, which was smoothed to 10', had no defects and was in good condition.

Next, for H6 and H7, which used thick wire to increase the bead width and create a smooth bead shape, the rising angle θ of the upper ridge end was smooth at 13° and 5°, and there were no defects. It was in good condition. On the other hand, H5 of the small diameter wire is
A blowhole occurred when the rising angle θ at the end was 23°. Furthermore, when the electrode angle Z was changed, the penetration of 1-19, 810 and the first stitch 1ri became shallower, and the upper dance end stood -1.
- The angle θ was also 14°% 8°, 3°, and was good with no defects. The H8H bead shape is convex.

Gas release was poor, and a defect occurred when the rising angle θ of the upper leg end was 23°.

As mentioned above, in the method of the present invention, by setting the rising angle θ of the upper edge of the final weld metal to 3° to 211f, no blowholes will occur in the final layer.

Table 1 (Effects of the invention) Method U of the present invention is a horizontal submerged arc welding method with no blowhole defects in the final layer and a pleasing bead appearance.It also improves welding efficiency and has extremely high industrial value. .

[Brief explanation of the drawing]

′? Figure 51 is a sectional view showing the bead shape according to the method of the present invention;
Figure 2 is a cross-sectional view showing the bead shape and blowhole defect position in the conventional method, Figure 3 is a diagram showing the relationship between the number of blowholes generated and the rising angle of the upper part of the final layer - the F end, and Figure 4 is a cross-sectional view showing the bead shape and blowhole defect position of the conventional method. Cross-sectional view showing tip shape and lamination method, Fig. 5 fat is a plan view showing electrode arrangement, Fig. 5 horizontal angle I of tblμ'\1L pole
It is a side view which shows f. 1... Steel machine, 2... Pole, 3... Final weld metal. Agent: Patent attorney Masamitsu Akizawa and 1 other person

Claims (1)

[Claims] (1) Set the rising angle of the upper toe end of the final weld metal to 3°.
A horizontal submerged arc welding method characterized by welding at an angle of ~20°.