JPS5849352B2 - Yokomukikiyoukaisakia - Kuyousetsuhou Oyobi Sonosouchi - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a horizontal narrow groove arc welding method, and its purpose is to reduce the lack of fusion that occurs between the base material groove surface and the weld metal, and to reduce the high temperature that occurs in the center of the weld metal. The object of the present invention is to provide a useful welding method that does not cause cracks.

Conventionally, horizontal position welding joints such as joints between architectural steel columns, horizontal joints of shell panels in shipbuilding, circular joints of storage tanks or steel towers, etc., are generally welded at an angle of 35 to 60 degrees to the upper steel plate.
Manual welding, non-gas semi-automatic welding, carbon dioxide gas arc welding, etc. were performed on V- or K-shaped welds with a bevel angle.

However, with the recent increase in the size of welded structures, the cross-sectional area within the groove increases in proportion to the square of the plate thickness, resulting in an increase in the amount of welding and the need for multiple welding tasks. It took a lot of time and was not economical.

In order to solve this problem, a high heat input welding method has been developed that increases the amount of metal deposited per unit time.

However, in this method, when the weld is placed in a horizontal position, the weld metal sag and spoil the appearance of the bead, and the structure of the heat-affected zone of the base material becomes coarse and brittle, and furthermore, the welding operation cannot be said to be simple.

A narrow gap gas shielded arc welding method using a solid wire method is known as a method for dealing with these problems.

This method uses a small groove angle of 0 to 10 degrees, reduces the groove cross section, and uses the same amount of welding heat per pass as conventional methods. The cross-sectional area of the groove is approximately 1/3 that of the conventional method, which is efficient and economical, and there is no embrittlement of the heat-affected zone.

However, in narrow gap welding, because the groove is narrow, insufficient fusion tends to occur between the base material groove surface and the weld metal. The final solidified part of the metal is concentrated at the center of the weld metal cross section, and hot cracking due to solidification shrinkage is likely to occur there.

Therefore, the generally used narrow gap gas shielded arc welding method uses a narrow gap gap consisting of a lower base plate 11, an upper base plate 12, and a backing material 13, as shown in Figure 1 of the drawing. To,
Penetration in the base material direction is ensured by a two-pass method for each layer, which is divided into a lower pass 14 and an upper pass 15.

However, according to experiments, with this method, the gap between grooves is 15 mm.
In the following, when welding the upper pass as shown in Fig. 2, the groove shape formed by the lower bead and the groove surface of the upper plate 12 is extremely narrow, so the arc generation position is very limited. For example, if an arc occurs at point A on the upper plate 12 side, the penetration into the upper plate 12 becomes extremely narrow, resulting in a so-called pear-shaped bead shape, as shown in Fig. 8. Hot cracking occurs at the center of the bead in the upper pass 15.

On the other hand, when the arc generation point is set at point B on the center side of the bead, there is a drawback that there is no penetration into the upper plate 12, and insufficient fusion occurs on the upper plate 12 side as shown in FIG.

Regarding this method, it may be possible to solve the drawbacks by increasing the groove spacing to about 15 to 18, but since the groove spacing becomes large, problems remain in terms of efficiency and economy. Moreover, since each layer is divided into two passes, the arc generation position must be changed for each pass, making the welding work complicated, which still remains a problem.

This invention has been proposed to address the above-mentioned conventional problems.

The present invention will be described below with reference to the illustrated embodiment. As shown in FIG. A solid wire 4 of a narrow gap arc welding device is continuously supplied between the grooves from the front side of a narrow gap welding joint in which the upper surface 1a and the lower surface 2a of the base material upper plate 2 are arranged substantially parallel. A shielding gas G is supplied by a welding torch 5 having a structure to perform gas shielded arc welding.

At this time, the welding torch 5 is set at a predetermined angle with respect to the vertical line, that is, the weaving angle α, the weaving width W, and the locus L as shown in the weaving cycle is drawn so that the weaving motion continues without stopping. Weaving welding is performed in multiple layers in the thickness direction, with each layer being welded in one pass.

Here, in the case of FIG. 5, the weaving angle α is an angle inclined backward in the clockwise direction, that is, the weaving angle
As shown in the figure, the line l0 connecting the apex T of the waveform and the midpoint between the bottom points B and B is the angle made with the vertical line lo, and the welding torch 5 is welded at such a weaving angle α. Line L.

By vibrating by the weaving width W while moving along the welding direction, a waveform locus L in which the apex T is shifted in the opposite direction to the welding progress direction is obtained.

Figure 6 shows a joint with a plate thickness of 32vrLm and a groove spacing of 9mm.
Weaving width W = 3111 m under the conditions of 340 A (converted to constant current of current density: 170 A/interval 2) and 36 V using 1.6 mm diameter solid wire for HjT50.
, cycle C=45 cycles/minb and welding speed 3
Arc welding is performed at 0 CIIL/min, and the ratio H/W of the bead height and bead width to the weaving angle α, penetration du + dL) and the angle between the groove surface and the bead (θU
+θL).

From this figure, at weaving angles of 300.45° and 60°, the ratio H/W of bead height to bead width is smaller than that at weaving angle O0, and the base material penetration (du+
dL) is large, and the angle between the twisted groove surface and the bead (θU+
It turns out that θL) has become large.

This shows that at these angles, defects such as hot cracking and insufficient fusion caused by narrow gap welding are less likely to occur, and it is effective to maintain the weaving angle.

An actual example is shown in FIG. 10, and the above-mentioned tendency is clearly seen.

In FIG. 10, A-0, A-30, and A-45 indicate weaving angles of 00, 30°, and 45°, respectively.

On the other hand, as a result of similar experiments and studies with various weaving widths and weaving cycles, the optimal weaving width changes depending on the groove spacing, and groove spacing G = 9 mm -> weaving width = 1 to 4 mm (G
- W value is minimum 5 rudder 0 G = l l G → weaving width = 2~61n1n
(G-W value is minimum 5 fights) G-13 → Weaving width -4 to 8 (G-W value is minimum 5 mm) G = 14 mi → Weaving width = 5 to 9 mrIL (G-
By the way, when using the welding method according to the present invention, the weaving angle is set at a weaving angle of 15 to 60 from the vertical line in the opposite direction to the welding direction.
The reason for setting the value to 0 is that within this range, as described above and shown in FIG. 6, hot cracking and insufficient fusion can be prevented and good welding can be performed.

More specifically, if it is within this range, firstly, as weaving is performed, the rate of welding the base metal will increase as the momentum increases, and secondly, the weaving angle will change in the direction of welding progress. Since the direction is opposite, when the arc moves from below to above as the torch moves, it pushes up the weld metal that tends to sag from below, improving the bead shape. Thirdly, the arc moves downward. Although the advancing speed increases relative to the standing plate, a good bead shape can be obtained only if the penetration depth is within the above range.

If the angle is less than 15°, these effects will not be achieved, resulting in insufficient fusion and hot cracking.

If the angle is more than 60 degrees, firstly, the momentum applied to the arc groove will be too large, making the arc unstable. Secondly, the molten metal will become large and the bead shape will become defective. .

By the way, the welding conditions of this invention are 300 to 400 A for 1.6φ solid wire, and the welding speed is 20 to 50 A.
crn/min is a desirable range for performing good welding.

1 weaving cycle is 20-60 cycles/mi
n was appropriate.

Outside these ranges, insufficient fusion and high-temperature cracking tended to occur.

FIG. 7 shows the applicable range of groove spacing and arc voltage V in narrow gap gas shield welding welding of the present invention.
Welding conditions Using 1.6mmφ solid wire for H-T50, constant current of 350A (current density 175A/am2) and speed 35cfIl/min, weaving conditions, weaving conditions, weaving angle α = 45 ° cycle 45 cycles/mi
This was determined from the results obtained by welding under n.

FIG. 3 shows the laminated state according to the conventional example, but also shows the results obtained by a one-pass welding method for each layer without weaving.

FIG. 7 shows that the welding method of the present invention has a wide range of appropriate conditions, such as a groove spacing of 7 to 14 V and an arc voltage of 33 to 38 V, and is extremely practical.

On the other hand, a one-pass welding method for each layer in which weaving is not performed is impractical because the appropriate range of groove spacing is narrow.

11 and 12 show an example in which the welding method of the present invention is applied to a thick plate, and respectively show the cross section p and the results of side bending performed three times.

The welding conditions are as follows.

Welding wire: Solid wire for H-T50 (1.6
mm) Shielding gas: CO2 Base material: SM-5OA, plate thickness 70mm Groove spacing: 117717+! Welding conditions: Current = 35OA (current density 175A/
Inm2) constant current voltage = 36V Welding speed = 35CV'min Weaving conditions: Weaving angle = 45° Weaving width - 4mm Weaving cycle - 45 cycles/min In this photo, no defects were observed and there was only one thermal effect. It has been confirmed that this welding method is useful even for very small, extremely thick plates of 7Qmm.

Although carbon dioxide gas is used as the shielding gas in the above embodiments, the shielding gas used in the present invention is not limited to this, and for example, a mixed gas of argon and carbonic acid gas can also be used.

As described above, according to the welding method of the present invention, in narrow-gap welded joints with a groove interval of 14 mm or less, insufficient fusion occurs between the base metal groove surface and the weld metal, and fusion occurs in the center of the weld metal. It is possible to weld each layer in one pass without causing hot cracking, which has a wide range of application, and is much more efficient and economical than conventional methods.

Further, in detail, according to the present invention, the weaving angle is 15° to 60°, and the weaving angle is 170A゛/mi to 1
Since weaving is performed continuously without changing the current value during welding using a high current density arc of 75 A/mW2, the weaving angle is 1 as shown in Figure 6.
In the range of 5° to 600°, H/ clearly shows a bead shape.
Decrease in W value/Amount of penetration into groove side wall (base material) (du+d
L) increase and the angle between the groove surface and the bead (θU, θL)
It is possible to obtain an increase in

In other words, these effects are due to the pushing up of the molten metal by the arc force of high current density, which prevents hot cracking, poor penetration, and prevents poor penetration during the next pass welding. Welding (30~35c
rrL/min).

Furthermore, the present invention is applied to a narrow gap where the lower surface of the upper plate of the base material and the upper surface of the lower plate are arranged nearly parallel to each other, and there is no need to process the base material into a flat shape. It is considered to be a welding groove.

[Brief explanation of drawings]

1, 2, and 3 are cross-sectional views showing a conventional narrow-gap gas-shielded arc welding method, and FIG. 4 is a cross-sectional view showing an embodiment of the narrow-gap arc welding method of the present invention. Fig. 5 is a schematic front view showing the weaving operation, Fig. 6 is a characteristic correlation diagram given by the weaving angle, Fig. 7 is a comparative correlation diagram of the applicable range of the welding method of the present invention and the conventional welding method, 8 and 9 are cross-sectional photographs showing defects caused by conventional arc welding, and FIGS. 10, 11, and 12 are cross-sectional photographs showing the results of welding according to the present invention. 1... Base material lower plate, 2... Base material upper plate, 3
... Backing material, 4... Shield wire,
5... Welding torch, 11... Base material lower plate, 12
...Base material upper plate, 13... Backing material, 14...
...Lower pass, 15...Upper pass.

Claims (1)

[Claims] 1. A type 1 horizontal groove welded joint consisting of an upper matrix plate, a lower plate, and a backing material, in which the lower surface of the upper base plate and the upper surface of the lower base plate are arranged almost parallel, The groove spacing is 7 to 14r.
/L7IL, and a weaving angle of 15-60°, 1 to 97rL7/L, where the apex of the weaving is tilted back from the vertical line to the south of the welding direction when viewed from the front of the welded joint. While performing continuous weaving without stopping the motion with a weaving cycle of 20 to 60 cycles/min, gas shielding is performed in multiple layers in the thickness direction with one pass for each layer using a high current density arc of 170 to 175 A/1 Ilm. A horizontal narrow gap arc welding method characterized by arc welding.