JPS6117371A - Gas shielded arc welding - Google Patents

Abstract

PURPOSE:To prevent lowering of toughness of weld metal by absoption of oxygen by controlling flow rate of gas, addition of deoxidizer and magnetic agitation by analysis of arc light while making addition of deoxidizer and magnetic agitation of molten metal by double shielded gas system in gas shielded arc welding. CONSTITUTION:Low Ni content steel for which low temperature toughness is required is welded by gas shielded arc welding. For instance, in the case of MIG welding, secondary shielding gas 11 such as H2, Ar etc. is supplied outside of Ar gas as the primary shielding gas 6, and at the same time, powder of deoxidizer such as Al, Ti, Zr, Si, Mn etc. 21 is supplied to a welding wire 7 by a pipe P, and deoxidizing reaction is accelerated by magnetically agitating molten metal 8 by an exciting coil 12. In this case, the arc 22 is sent to a spectroscopic analysis type monitor 16 through a condenser 14. The quantity of O2 in the molten metal 8 is detected by the result of spectroscopic analysis of the arc 22, thereby flow rate of the two shielding gases 6, 11, quantity of addition of deoxidizer 21 etc. arc controlled properly. Thus, O2 content in the molten metal 8 is lowered as far as possible, and lowering of toughness of weld metal is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas-shielded arc welding method that is applied to low-temperature containers such as ethylene, LPG, and LNG plants, LPG and LNG ships, and LPG and LNG tanks, as well as welded structures that use active metals. . The present invention also relates to a gas-shielded arc welding method for low-temperature steels that require low-temperature toughness, such as mainly 55th grade Mi steel and 996M1 steel.

[Conventional welding technology]

A5S Ni steel and 99611 that require low-temperature toughness
For low-temperature steel co-heavy welding such as 1 steel, T-work G welding, MX
Gas shielded arc welding methods such as G welding and plasma welding are conventionally used.

Among these, the conventional T welding method and G welding method are 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 Ar), 7 is the filler wire, 8 is the 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
is a shielding gas (inert gas such as Ar), and 8 is a molten metal.

[Disadvantages of the above conventional welding technology]

In gas-shielded arc welding methods such as the conventional L'lG welding method and MiG welding method described above, there is no need for shielding from wind etc. during welding.
This method has the drawback that it generates hydrogen gas, entrains oxygen from the atmosphere, and increases the amount of oxygen in the weld metal, resulting in a decrease in the toughness of the weld metal.

Therefore, in welded structures with strict performance requirements, welding materials such as high 1ti alloys, which are less affected by oxygen contamination, 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 XRU, A, LLA, 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 provides a gas-shielded arc that can prevent the absorption of oxygen into the molten metal and forcibly remove oxygen in the weld metal caused by oxygen in the welding wire and base steel plate. Welding method t - For the purpose of practicing.

Furthermore, in the gas-shielded arc welding method for low-temperature steel, etc., which requires low-temperature toughness, when a shield failure occurs due to wind etc., this invention is detected by a sensor, and the shielding gas flow rate and deoxidation The objective is to provide a gas-shielded arc welding method that automatically controls the amount of additive added.

[Configuration of the present invention]

As a means to achieve the above object, the present invention adopts a double shielding gas method, adds deoxidizer powder and welds the molten metal while magnetically stirring it, and spectroscopically analyzes the arc light of this welded part. Based on the results, the flow rate of the shielding gas, the amount of deoxidizer powder added, and the magnetic stirring are automatically controlled. That is, the present invention supplies a secondary shielding gas consisting of a reducing gas to the outside of the primary shielding gas consisting of an inert gas, adds a deoxidizer powder, and performs welding while magnetically stirring the molten metal. A gas shield characterized in that the arc light of this welding part is spectroscopically analyzed, and the flow rate of the primary and secondary shielding gases, the amount of deoxidizer powder added, and the magnetic stirring are controlled based on the spectroscopic analysis results. This is an arc welding method.

In the present invention, the inert gas used as the secondary shielding gas is Ar, He, etc., and the reducing gas used as the secondary shielding gas is hydrogen (H
2”) is suitable.Also, the deoxidizer powder and shite are
, Ti,' Zr, B, V.

It uses Si, Mn, etc.

In addition, in the present invention, molten metal is welded while being magnetically stirred, but this is to promote the deoxidation reaction in the molten metal, and specifically, the excitation coil provided at the tip of the torch A low-frequency alternating current is passed through the molten metal, and the molten metal is heated by the Lorentz force generated by the magnetic field and welding current.
In addition, in the present invention, when a shield failure occurs due to wind, etc., this is detected by an arc light sensor, and the shielding gas flow rate is increased, the amount of deoxidizer powder added is increased, and melting is performed. This automatically increases the magnetic stirring of metal.

Embodiments of the present invention will be described below with reference to FIG. 1st
The figure is a diagram for explaining the case where the present invention is applied to MIG welding.
Since this method shows the same parts and has the same function as the conventional M-G welding method explained based on FIG. do.

Figure 1 Ki? 9 is a magnetic conductor, 10 is a secondary shield nozzle, 11 is a secondary shielding gas (reducing gas H2 or inert gas), 12 is an excitation coil, 13#i low frequency AC excitation power supply, 14ij condenser lens, 15ij optical fiber,
16 is a spectroscopic shield status monitor/control device, 17
is a valve drive device, 18Fi powder addition amount control valve, 19 is a valve drive device, 20 is a secondary shield gas flow rate control valve, 21 is a deoxidizer powder, 22 is an arc, 23 is an arc light, 24 is a welding power source, P is a conveyor tube for transporting the deoxidizer powder 21, and the tip of the conveyor vibrator 21 is open to face the tip of the filler wire 7.

To explain the action of the welding method shown in Figure 1, when oxygen in the atmosphere enters the shielding gas due to disturbances such as wind, arc light 2
3, light with a unique wavelength caused by oxygen and nitrogen in the air increases. This is collected by a condensing lens 14 provided near the arc 22 and guided to a spectroscopic shield condition monitor control device 16 through an optical fiber 15.

Figure 2 shows an example of the results of spectroscopic analysis of arc light. The amount of oxygen in the weld metal 2 is estimated based on the relationship between the amount of oxygen in the weld metal 2 and the spectral intensity of the specific wavelength shown in FIG.

Next, the oxygen amount reduction measures input in advance, the increase in the secondary shielding gas flow rate, and the addition signal of deoxidizer powder are outputted, and the powder addition amount control valve 1 is outputted through each valve drive device 17.19.
8 and the secondary shield gas flow rate control valve 20 are opened, and magnetic stirring is also performed through the excitation coil 124.

This effectively and automatically prevents oxygen from entering the shielding gas and deoxidizes the oxygen absorbed into the molten metal. In this way, the present invention monitors the shielding status using arc light, and when a shielding failure occurs, increases the amount of reducing gas H3 and inert gas from the secondary shielding nozzle provided outside the secondary shielding nozzle, and removes oxygen. It is possible to automatically add a deoxidizing agent to the molten metal, stir it, and remove the absorbed oxygen.

When oxygen gets mixed into the molten metal 8, the toughness of this weld metal decreases, l! : This relationship is shown in Figure 4. As is clear from this figure, the amount of oxygen in the weld metal is reduced and the co-trap absorption energy is increased, resulting in improved toughness.

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 9%N1 steel alloy M/G welding is shown in the following table in comparison with the conventional method and Comparative Example 1.2.

As is clear from the table above, in the conventional method, the oxygen content in the weld metal is 500 ppm, and the toughness is below the standard value (vlc-1
96℃≧xskgf-m)? However, with the method of the present invention, l'i is 30 ppm, 20 kl/f.
-m, good results were 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 and the toughness is 15 kl? In addition, when a deoxidizing agent is added and magnetic stirring is performed but no secondary shielding is performed (Comparative Example 2), 50 ppm
, 15 to 9 f-m fco [Effects of the present invention] As detailed above, the present invention adopts a double shield gas system, adds deoxidizer powder, and magnetically stirs the molten metal. The method automatically controls the above-mentioned shielding gas flow rate, amount of deoxidizing agent powder added, and magnetic stirring based on the spectroscopic analysis results of the arc light in the welding area, so that the oxygen in the atmosphere during welding can be controlled automatically. This has the remarkable effect of automatically preventing the contamination of molten metal and automatically forcibly removing oxygen from the molten metal.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the case where the present invention is applied to M/G welding. Figure 2 shows an example of the results of spectroscopic analysis of arc light according to the present invention, Figure 3 shows the relationship between the amount of oxygen in the weld metal and the spectral intensity of a specific wavelength, and Figure 4 shows the relationship between the amount of oxygen in the weld metal and the spectral intensity of a specific wavelength. FIG. 3 is a diagram showing the relationship between the amount and absorbed energy (toughness). FIG. 5 is a diagram for explaining a conventional T-type G welding method, and FIG. 6 is a diagram for explaining a conventional M-type G welding method. 1...Base material steel plate 2...Weld metal 511@-Feeding tip 4-ElI fist tungsten electrode 511--Shield nozzle 6@Medium...Shield gas 7--Filler wire 7' 90 Welding wire 8... Molten metal 9... Magnetic conductor 10iIII*l Next shield nozzle 11110111 + Secondary shield dregs 12-・1111 Excitation coil 15... Age・Low frequency AC excitation power source 14・116・Condensing lens 15-#... Light 7 Eyeper 16, Hand number spectroscopic analysis type shield status monitor/control device 17...-9 Valve drive device 180e, Powder addition amount control valve 19... Valve drive device 20. ...Secondary shield gas flow control valve 21-...
Deoxidizing agent powder 22 e @ II @ arc 25 mamm arc light 24... Welding power source p e * ea Transport pipe sub-agent 1) Meifuku agent Ryo Hagiwara - Figure 2 Figure 3 Some skin! 02 amount in weld metal (PPm)

Claims (1)

[Claims] A secondary shielding gas consisting of a reducing gas is supplied to the outside of the primary shielding gas consisting of an inert gas, deoxidizer powder is added, and the molten metal is welded while being magnetically stirred, and the arc light from this welded part is analyzed by spectroscopy. A gas-shielded arc welding method characterized in that the flow rates of the primary and secondary shielding gases, the amount of deoxidizer powder added, and the magnetic stirring are controlled based on the spectroscopic analysis results.