KR20110076014A - Method of arc melt-in welding using ar and nitrogen gas - Google Patents

Abstract

PURPOSE: An arc fusion welding method using argon and nitrogen gas is provided to improve the hardness of weld metal by mixing nitrogen gas with protective gas. CONSTITUTION: An arc fusion welding method using argon and nitrogen gas is used for welding manganese steel or stainless steel. The arc fusion welding method uses mixing gas of argon and nitrogen as protective gas. The nitrogen content of the protective gas is 2~8 v/v%. The argon gas and the nitrogen gas are exhausted from a mixed gas bombe and are mixed using a mixer.

Description

Method of Arc Melt-in Welding using Ar and nitrogen gas}

The present invention relates to an arc welding method for preventing ductility degradation of welds and at the same time providing high hardness weld steel, and more particularly, using a mixed gas of argon gas and nitrogen gas as a protective gas. It relates to an arc welding method.

In the automotive industry, materials are becoming increasingly strong due to the strong demand for lighter body weight and improved collision stability. However, as strength increases, elongation generally decreases, so there is a limit to manufacturing parts. In order to overcome these limitations, efforts have been made to develop high strength and high elongation steels, and as a result, so-called TWIP (Twin Induced Platicity) steel containing more than 15% of Mn is expected to be commercialized. This TWIP steel has an abnormal combination of tensile strength of 1000 MPa or more and elongation of 50% or more, and can be applied to parts requiring excellent formability and high strength.

Weldability is basically a required feature in manufacturing parts. In recent years, while designing a high rigidity vehicle body, the demand for high-strength steel tubing products is increasing. Tube welding of ordinary carbon steel is mostly manufactured by the highly productive welding method called ERW. ERW has a problem that welding is difficult in the case of non-magnetic materials such as TWIP steel such as 300-based stainless steel by converting electrical energy into heat energy by electromagnetic induction.

In general, 300 series stainless steel is manufactured by TIG welding or plasma welding. In recent years, the tube making method using the laser welding with excellent weld quality has been applied, but there is a disadvantage in terms of economic efficiency due to the initial investment and maintenance cost of the laser welding machine. Therefore, it is thought that it is advantageous in terms of economical efficiency to make TWIP steel by TIG welding (tungsten inert gas welding) or plasma welding. However, the welded portion of the TWIP steel welded by the conventional TIG welding method has a lower hardness than the base metal as it is melted and solidified in the absence of phase transformation. Figure 1 shows the hardness distribution and the Ericsson test results of the weld by the conventional TIG welding, the weld hardness is more than 50Hv lower than the base material, it can be seen that the fracture occurs in the weld metal in the Ericsson test. The tubular material having the welded portion of this characteristic has a difficulty in being applied as a structural material.

The present invention has been made to solve the above problems, arc melting to prevent the weld ductility degradation by using argon-nitrogen mixed gas containing a small amount of nitrogen as a protective gas instead of using a conventional pure argon protective gas The purpose is to provide a welding method.

In the conventional TIG or plasma melt welding, it is common to use an inert gas such as argon as a protective gas in order to block the mixing of oxygen and nitrogen in the outside air. In this case, the present invention has been newly completed to prevent a decrease in ductility of the weld and increase the hardness of the weld metal as nitrogen is dissolved in the weld metal.

By mixing nitrogen gas as the protective gas, it is possible to prevent a decrease in ductility of the weld, and as nitrogen is dissolved in the weld metal, the hardness of the weld metal may be increased.

The present invention relates to an arc welding method comprising using a mixed gas of argon and nitrogen as a protective gas.

In the present invention, the content of nitrogen in the protective gas is preferably 2 to 8v / v%, more specifically 2 to 5v / v%. If it is less than 2v / v%, the nitrogen property to the base metal is not enough to exhibit the desired physical properties. If it exceeds 8v / v%, the hardness is increased due to nitride precipitation, but brittleness may be increased.

The arc welding method of the present invention can be used to weld manganese steel and stainless steel, and is particularly useful for welding high manganese steel having a manganese content of 10% or more.

In the present invention, the argon gas and the nitrogen gas may be discharged from the mixed gas cylinder, or the gas discharged from the argon gas cylinder and the nitrogen gas cylinder may be used in combination with the mixer.

In the present invention, TIG welding is a kind of inert gas arc welding and is also called tungsten inert arc welding. As a welding method for preventing oxidation and the like by covering the arc with an inert gas such as helium or argon gas, a method of generating an arc between the tungsten electrode having the highest melting point and the base metal is used, and generally used for welding nonferrous metals.

In the case of mixing a small amount of nitrogen gas as a protective gas as in the present invention, there is an advantage that the hardness of the weld metal can be increased as nitrogen is dissolved in the weld metal while preventing a decrease in ductility of the weld.

Hereinafter, the present invention will be described in more detail through examples according to the present invention, but the scope of the present invention is not limited to the examples given below.

≪ Example 1 >

The TWIP steel with a tensile strength of 1000 MPa and a thickness of 1.4 mm was subjected to TIG welding using an argon-nitrogen mixer at a welding speed of 1 m / min and a welding current of 200 A under a mixed gas of 2, 5, or 10% nitrogen. The result showed the best dome height and fracture load when nitrogen was mixed at 2% and 5% (see FIG. 3). Dome height was nearly doubled compared to pure argon. However, when the nitrogen concentration was 10%, the dome height and the breaking load were decreased.

Figure 1 shows the weld hardness distribution and Ericsson fracture characteristics in the conventional welding conditions.

2 is an exemplary view of a TIG welder.

Figure 3 shows the weld Ericsson measurement results according to the protective gas composition.

Claims (6)

Arc welding method characterized by using a mixture of argon and nitrogen as a protective gas. The method of claim 1 Arc welding method characterized in that the content of nitrogen in the protective gas is 2 to 8v / v%. The method of claim 1 Arc welding method characterized in that the content of nitrogen in the protective gas is 2 to 5v / v%. The method of claim 1 Arc welding method characterized in that the arc welding is used for welding of manganese steel or stainless steel. The method of claim 4 Arc welding method characterized in that used in the welding of high manganese steel content of more than 10% of the manganese in the manganese steel. The method of claim 1 And argon gas and nitrogen gas are discharged from the mixed gas cylinder, or each of the gas discharged from the argon gas cylinder and nitrogen gas cylinder is mixed and used as a mixer.

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