JPS6117370A - Gas shielded arc welding - Google Patents

Abstract

PURPOSE:To prevent lowering of toughness of welded metal due to absorption of oxygen in gas shielded arc welding by adopting double gas shielded welding, and using a filler wire blended with a deoxidizer, and at the same time, magnetically agitaing molten metal. CONSTITUTION:Steel for low temperature such as 3.5% Ni steel, 9% Ni steel etc. for which low temperature toughness is required is welded by gas shielded a arc welding such as TIG welding and MIG welding. In the case of TIG welding, a filler wire 7a blended with Al, Ti, Si, Mn etc. as deoxidizer is used. Further, secondary shielding gas 10 composed of reducing H2 gas is supplied to outside of primary shielding gas 6 of Ar etc. as shielding gas. O2 intruding from the open air becomes H2 O by H2 of the secondary shielding gas and is discharged. Further, molten metal 8 is magnetically agitated by an exciting coil attached to a shield nozzle 5 to accelerate deoxidizing reaction of the molten metal. Thus, welding of Ni group alloy having small O2 content and excellent in toughness can be performed. Similar method can be adopted in the case of TIG welding.

Description

[Detailed Description of the Invention] [Industrial Field of the Invention] The present invention is applicable to low-temperature containers such as ethylene, LPG, LNG plants, LPG, LNG ships, LPG/DNG tanks, and welded structures using active metals. Regarding the applicable gas shielded arc welding method. Further, the present invention mainly relates to a gas shield arc welding method for low temperature steels such as 45% Mi steel and 9% Ni steel that require low temperature toughness.

[Conventional welding technology]

5% Mi steel and 9%ll steel that requires low-temperature toughness
T-work Q welding is used for low-temperature steel co-heavy welding such as I-steel.

Gas-shielded arc welding methods such as MIG welding and plasma welding have been conventionally used.

Among these, the conventional T' construction method welding method is shown in FIG.

In this figure, 1 is the base steel plate, 2 is the weld metal, 3 is the power supply tip, 4 is the tungsten electrode, 5 is the shield nozzle, 6 is the shield gas (inert gas such as mulch), 7 is the filler wire, 8 is molten metal.

Furthermore, the conventional M-G welding method is shown in FIG.

In this figure, 1 is the base steel plate, 2 is the welding metal, 3 is the power supply tip, 7' is the welding wire, 5 is the shield nozzle, and 6
7 is a wild gas (inert gas such as molten metal), and 8 is a molten metal.

[Disadvantages of the above conventional welding technology]

In the gas-shielded arc welding methods such as the above-mentioned conventional τ-G welding method and M-G welding method, atmospheric oxygen is involved during welding. It has the disadvantage that it absorbs oxygen from the base metal, welding material (wire), etc., and as a result, it causes a decrease in the toughness of the weld metal.

Therefore, in welded structures with strict performance requirements, even higher grade welding materials (for example, high N1 alloys) are used, resulting in a significant increase in material costs.

By the way, today there is a great demand for welded structures that require low-temperature toughness, such as plants, ships, and tanks that handle LNG, LPG, ethylene, etc., and high-quality welding methods that can stably obtain high toughness at low cost are needed. is currently in strong demand.

[Object of the present invention]

An object of the present invention is to provide a gas-shielded arc welding method for low-temperature steel, etc. that meets the above requirements. Specifically, the present invention is capable of preventing the absorption of oxygen into the weld metal and forcibly removing oxygen in the weld metal caused by oxygen in the welding wire, filler wire, or base steel plate. The purpose of this invention is to provide a gas-shielded arc welding method for low-temperature steel, etc.

[Configuration of the present invention]

The present invention, as a means to achieve the above object, employs a double shielding gas system, uses a welding wire or filler wire mixed with a deoxidizing agent, and magnetically stirs the molten metal. .

That is, the present invention provides a gas-shielded arc welding method in which a secondary shielding gas consisting of a reducing gas is supplied to the outside of a primary shielding gas consisting of an inert gas, and a welding wire or welding filler containing a deoxidizing agent is supplied to the outside of the primary shielding gas consisting of an inert gas. This is a gas-shielded arc welding method that uses a wire and magnetically stirs the molten metal.

The present invention employs a double shield gas system. To explain this in detail, a secondary shield gas consisting of an orphan gas is placed outside the primary shield gas consisting of an inert gas such as Ar or He. It supplies gas. It is best to use hydrogen (Hi) as this reducing gas.

Further, in the present invention, a welding wire or filler wire containing a deoxidizing agent is used, and the deoxidizing agent includes:
At, Ti, Zr, B, V.

81, Mn, etc. are preferred.

Furthermore, in the present invention, the molten metal is magnetically stirred, and in order to promote the deoxidation reaction, specifically, a low frequency alternating current (1!) is applied to the excitation coil provided at the tip of the torch. The molten metal R is stirred at 1 to 20 H2 by the Lorentz force generated by the magnetic field and welding current.

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. Fig. 1 is a diagram for explaining the case where the present invention is applied to T-work G welding, and Fig. 2 is a diagram for explaining the case where the present invention is similarly applied to M-work G welding. code 1
~6.8 shows the same parts and has the same effect as the conventional TIG welding method and the conventional M/G welding method explained based on FIGS. 4 and 5, so here, A description of the common parts will be omitted, and only the different parts will be described.

In Figures 1 and 2, 9 is a secondary shield nozzle;
10 is secondary shielding gas (reducing gas Hz), 11
1 is an excitation coil, 12 is a low frequency AC excitation power source, 13 is a welding power source, 14 is a water cooling pipe, and 15 is cooling water.
゛In Fig. 1, 7a is a filler wire, which contains a deoxidizing agent (AL, Ti, Zr, B.

V, B1. Furthermore, in FIG. 2, 4' is a welding wire, which also contains a deoxidizing agent.

To fully explain the operation of the welding method according to FIGS. 1 and 2, when oxygen in the atmosphere tries to enter the shielding gas, this oxygen reacts with H2 as a secondary shielding gas of 1°, causing HI
It becomes O and is discharged. Also, in case - next shield gas 6
If the filler wax enters the molten metal 8 and is absorbed into the molten metal 8,
Deoxidizing agents (At, Tl, Zr, B, V, si, Mn) mixed in the wire 7a or the welding wire 4'
etc.) to produce oxide Mmon such as Al40s.

The solubility of this oxide in the molten metal 8 is low, and it separates and floats to the surface of the molten metal 8 and is deoxidized.

Further, the molten metal 8 is heated by magnetic stirring by the excitation coil 11.
The reaction rate is increased by stirring, and sufficient deoxidation can be achieved even in short-time reactions such as welding phenomena.

In this manner, the present invention allows H2 to flow as a reducing gas into the secondary shield nozzle 9 provided outside the primary shield nozzle 5, thereby preventing oxygen from entering the atmosphere and reducing the oxidized surface. Furthermore, a dispersing agent mixed in the filler wire 7a or the welding wire 4' is reacted with oxygen in the molten metal 8, and in order to further enhance the effect, an excitation coil 11 provided at the tip of the torch is used to remove the molten metal. 8 can be stirred and the deoxidation reaction can be promoted.

If oxygen is included in the molten metal 8, the toughness of the weld metal will be reduced, and this relationship is shown in FIG. 3. FIG. 3 is a diagram showing the relationship between the amount of oxygen (ppm) in the weld metal and the absorbed energy VX. As is clear from this figure, as the amount of oxygen in one weld metal decreases, the absorbed energy increases and the toughness improves.

Although the present invention has been described in detail above, the present invention will be explained in more detail by giving specific examples of the present invention.

〔Concrete example〕

A specific example in which the present invention is applied to alloy welding of 9-inch N1 steel is shown in the following table in comparison with the conventional method and Comparative Examples 1 and 2.

As is clear from the table above, in the conventional method, when the oxygen content in the weld metal was 400 ppm, the toughness was below the standard value (71-196℃).
≧15kyf-m), but with the method of the present invention, F! , 30 ppH, 20 to 9 f-m, and good results have been obtained. In addition, in the welding method (Comparative Example 1) in which secondary shielding is performed but no deoxidizing agent is added and no magnetic stirring is performed, the amount of oxygen in the weld metal is 50%
ppm, the toughness is 15 to 9 f-m, and even when a dispersing agent is mixed and magnetic stirring is performed but no secondary shielding is performed (Comparative Example 2), the toughness is 50 ppm and 15 kp.
It was f-m.

[Effects of the present invention]

As detailed above, the present invention supplies a secondary shielding gas made of a reducing gas to the outside of the conventional shielding gas made of an inert gas, thereby preventing oxygen from the atmosphere from getting mixed in. In addition, even if it is mixed in, the effect of being reduced by the reducing gas used as the secondary shielding gas is produced. tfr, Since the present invention uses a welding wire containing a deoxidizing agent, the effect of separating and removing oxygen in the molten metal is produced by the action of the deoxidizing agent. Furthermore, in the present invention, since the molten gold layer is magnetically stirred, the effect of promoting the deoxidation reaction of oxygen in the molten metal is produced.

As described above, the present invention employs a double shield gas system,
It has the effect of preventing oxygen from entering the atmosphere during welding, and also has the remarkable effect of forcibly removing oxygen from the molten metal through the use of a deoxidizing agent and the action of magnetic stirring. .

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the case where the present invention is applied to '1 TIG welding, and FIG. 2 is a diagram for explaining the case where the present invention is applied to M/G welding. FIG. 3 is a diagram showing the relationship between the amount of oxygen in the weld metal and absorbed energy (toughness). FIG. 4 is a diagram for explaining the conventional T-work G welding method, and FIG. 5 is a diagram for explaining the conventional M-work G welding method. 1... Base steel plate 2... Weld metal 3... Power supply tip 4... Tungsten tti 5... Shield nozzle 6... Shield gas 7... Filler wire 7'... Welding Wire 9...Secondary shield nozzle 10...Secondary shield gas 11...Excitation coil 12...Low frequency AC excitation power source 13...Welding power source 14...Water cooling pipe 15...Cooling water Sub-agents 1) Meifuku agent Ryo Hagiwara -

Claims (1)

[Claims] In the gas shielded arc welding method, a secondary shielding gas consisting of a reducing gas is supplied to the outside of the primary shielding gas consisting of an inert gas, a welding wire or filler wire containing a deoxidizing agent is used, and , a gas-shielded arc welding method characterized by magnetically stirring molten metal.