JPS60187478A - Welding method - Google Patents

Abstract

PURPOSE:To perform welding in a way as to provide excellent resistance to stress corrosion cracking in welding of a stainless steel by providing a nozzle for ejecting cooling water toward the direction opposite from welding at a specific distance backward of a welding arc and cooling quickly the weld zone at the method to avoid intrusion of water into the molten pool. CONSTITUTION:A nozzle 12 for ejecting cooling water of which the top end faces the direction opposite from welding is provided at 20-40mm. backward of a welding arc 5 and further a copper plate 10 and stainless steel wire brush or glass fiber board 11 which are bent backward to avoid intrusion of cooling water 13 into a molten pool 6 are provided. The weld zone and weld metal 7 are quickly cooled, by which the stress corrosion cracking liable to arise in stainless steel welding is prevented and the increased yield strength and improved weld zone are obtd. The harzard of the cooling water is further prevented if a base metal 8 is inclined theta.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of welding stainless steel such as EIU8504, 516, and in particular, the welding itself stabilizes the arc,
The present invention also relates to a welding method that increases the welding heat input to perform well, cools the welded metal immediately after welding with cooling water, speeds up the cooling rate of the weld heat affected zone, and improves the stress corrosion cracking resistance of the welded material. .

When welding stainless steel, parts that receive welding heat are susceptible to stress corrosion cracking. The larger the welding heat input and the slower the cooling rate of the heat affected zone, the higher the susceptibility to stress corrosion cracking.

For this purpose, the welding heat input is limited and the cooling rate is increased by using water, M, or gas from the back side of the weld.

However, limiting welding heat input is problematic from an efficiency standpoint, and methods of spraying water, N, or gas from the back side have little cooling effect on thick plates.

The present invention has been made for the purpose of increasing heat input or shortening the time for maintaining interlaminar temperature in order to improve the efficiency of welding.

In the stainless steel welding method of the present invention, a cooling water spray nozzle is installed at a position 20 to 40 meters behind the welding arc, and after the welding arc is generated, the cooling water is directed into a jet stream from the spray nozzle so as to face the opposite side of the welding direction. This is a welding method that is characterized by spraying on the welded metal.

The main points of the method of the present invention can be summarized as follows.

(1) Set a nozzle for spraying cooling water behind the T-work G, M-work G or plasma welding torch, and spray cooling water onto the bead after welding arc occurs.

(2) For cooling water spraying, the nozzle opening should be shaped like a slit with a longer groove in the width direction, and be curved in the opposite direction to the welding torch, so that the cooling water does not flow into the molten pool.

[3] Cooling water spraying can be done by attaching a copper plate that matches the curve of the nozzle to the torch side of the nozzle, and hanging a heat-resistant cloth such as a stainless steel brush or glass fiber over the bead surface like a curtain between the copper plate and the nozzle. This allows the cooling water sprayed from the cooling water spray nozzle to fall smoothly onto the bead.

(4) Top welding can be performed by tilting the material to be welded so that cooling water does not flow into the molten pool.

An overview of an embodiment of the method of the present invention is shown in FIG.

In the figure, reference numeral 1 denotes a nozzle of a welding torch, and in this figure, T-type welding is used, but MIG welding or plasma welding may also be used.

2 is a collet for holding a tungsten electrode, 3 is a tungsten electrode, 4 is a shielding gas, 5 is a welding arc, 6 is a molten pool, 7 is a weld metal (also called a bead), 8 is a base metal, these 1 to 8 is also used in the conventional method.

9 is a floor surface, and the base material 8 has a slight inclination angle θ so that the welding direction is upwardly sloped. This θ may be 0 as long as the cooling water 13 does not flow into the molten pool 6. In addition, in the case of circumferential welding, the nozzle 12 for cooling water spray is connected to the nozzle 1 of the welding torch.
It may be provided at a lower position (this mode is shown in FIG. 2).

A copper plate 10 is attached to the rear of the welding torch, and its lower end is bent with a radius R so as to face the welding rear. 11 is a partition material made of stainless steel wire brush, glass fiber, or the like.

The nozzle 12 for spraying cooling water is a steel pipe formed with a flat tip so that the cooling water flows out in a curtain shape. In addition, the tip is bent with the same curvature as the copper plate 10, and the stainless steel wire brush or glass fiber partition material 11 is sandwiched between the copper plate 10 and the cooling water spray nozzle 12, so that the partition material 11 also moves backward. Curvature is added.

The closer the cooling water spray nozzle 12 is installed to the arc point, the greater the effect, but even if the cooling water spray nozzle 12 is installed closer to the arc point, the cooling water 1 will not reach the molten pool 6.
3 is included. In addition, the distance from the arc point to the end of the molten pool 6 varies depending on the welding conditions, but is generally about 10 to 20 meters, so the installation position of the cooling water spray nozzle 12 should be about 15 to 40 meters behind the welding arc. It is preferable to do so.

The copper plate 10 described above is used to maintain the shape of the partition material 11 and to prevent the partition material 11 from being damaged by welding heat.Of course, when the partition material 11 is not used, the copper plate 10 is also no longer necessary.

Further, the thickness of the copper plate 10 is preferably about Q, 1 to 1w in order to maintain the above-mentioned effect, and the thickness of the partition material 11 is preferably about 1 to 1w.
It is generally preferable that the thickness be approximately α3 to 2−, since flexibility is required to adapt to the shape of the groove wall and bead, and since it is used in a narrow groove.

Note that the copper plate 10 is not limited to a copper plate, and may be made of stainless steel, brass, or the like, as long as it can perform the above-mentioned functions, and even a net-like material may be used without any problem.

Even if the base metal 8 is submerged in water, the welding arc 5 can blow away the water immediately below the tungsten electrode 3 to the surrounding area by the gas flow velocity of the shielding gas 4 from the welding torch, and even if the submergence depth increases. By increasing the flow rate of the gas 4, the water immediately below the tungsten electrode 5 can be drained away, which causes trouble. Once the arc 5 is generated, the water is drained by the arc force, so welding is possible even if there is only a certain number of floods. It is a well-known fact that welding can be performed underwater if high-pressure water or a brush is placed around the welding torch and a cavity is locally formed within the welding torch.

In the method of the present invention, the cooling water 13 is forcibly sprayed onto the weld metal 7 only at the rear of the welding torch to increase the cooling rate of the weld heat affected zone, and the cooling water 13 and the molten pool 6 are separated by a partition material 11), the cooling water may be sprayed by setting the spraying angle to the nozzle 12 and spraying the cooling water 13 backward, and even if the cooling water flows to the molten pool 6 side, the above-mentioned Since the water can be blown away by the shielding gas flow rate and arc force, the welding arc 5 does not become unstable and good welding can be performed.

Moreover, when the base material 8 is tilted, the cooling water 1 is further poured into the molten pool 6.
3 can be prevented from flowing in.

Table 1 shows an example of the results of measuring the cooling rate and cooling time of the bond part when a welding test was conducted using the method of the present invention with a cooling water spray nozzle installed at a position approximately 50 mm behind the welding torch. This is shown in comparison with the case of .

Table 1 1) Welding conditions: T work G 100mm-12V-10e
V'm1n2) Cooling water amount: 5 to 4 t/xn i
nS) Inclination angle #: 1o' 4) Base material: 5trsso4 (thickness 5 dew) As is clear from Table 1, according to the method of the present invention, even at a position 30 wI away, the cooling rate is about 2 The cooling rate is more than double that.

Furthermore, if the partitioning material according to the present invention is installed at a position several distances away from the molten pool, the distance between the nozzle and the torch for cooling water spraying can be further shortened, and the cooling rate can be further increased. The lower the temperature of the cooling water, the better, so using a heat exchanger to spray low-temperature water will improve the effect.

As described in detail above, according to the method of the present invention, the cooling rate can be increased, thereby improving stress corrosion cracking resistance, and industrially useful welding can be performed.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams showing one embodiment of the method of the present invention. Sub-agents 1) Meifu agent Ryo Hagiwara - Commissioner of the Japan Patent Office Kazuo Wakasugi 1. Display of the case Patent Application No. 41227 of 1982 2, Name of the invention Welding method 3, Person making the amendment Relationship with the case Patent applicant address Hyogo Prefecture Ministry 116゛Mitsuyoi'8-254 Agent address Toranomon-chome-16-2, Minato-ku, Tokyo Target of Z amendment (1) Application (2) Specification (3) Drawings (4) Power of attorney a Contents of amendment (1) Engravings of application, specification, and drawings (respectively) , no changes in content) will be supplemented. (2) We will supplement the power of attorney. 9 List of attached documents (1) Power of attorney 3 copies (2)

Claims (1)

[Claims] In the stainless steel welding method, the welding arc rearward 20
A welding method characterized in that a cooling water spray nozzle is installed at a position of ~40 m, and after a welding arc is generated, the cooling water is sprayed onto the weld metal by a jet stream from the spray nozzle so as to face the opposite side to the welding direction.