INERT GAS AND METHOD OF METAL INERT-GAS WELDING FOR POLLUTANT REDUCTION

Abstract

A method of metal inert-gas welding is proposed, a method in which a welding filler (1) is fed to a welding torch (10) and a welding current of a welding current source (30) is applied via a welding current connection (5), whereby an arc (7) is formed and, in a welding region, material of the welding filler (1) is transferred to a workpiece (20) consisting at least in the welding region of an alloyed high-grade steel. By means of the welding torch (10), an inert gas that includes a content of 0.5 to 3.0 percent by volume of at least one oxidizing component and a content of 0.1 to below 0.5 percent by volume of hydrogen is fed to the welding region. A method of reducing the content of nickel oxides and chromium (VI) compounds in welding fumes of such a welding method, a corresponding inert gas and the use of a gas mixture as an inert gas are likewise the subject of the present invention.

Claims

1. A method for metal inert gas welding, in which a weld filler is fed to a welding torch and via a welding current connection is subjected to a welding current of a welding current source, as a result of which an arc is formed and material of the weld filler in a welding region is transmitted onto a work piece which at least in the welding region consists of alloyed stainless steel and an inert gas is fed to the welding region by means of the welding torch, which inert gas has a content of 0.5 to 3.0% by volume of at least one oxidising component, characterized in that the inert gas additionally has a content of 0.1 to below 0.5% by volume of hydrogen.

2. The welding method according to claim 1, in which the inert gas has a content of 1.2 to 2.5% by volume of the at least one oxidising component.

3. The welding method according to claim 1, in which the inert gas has a content of 0.5 to 0.4% by volume of hydrogen.

4. The welding method according to claim 1, in which the inert gas in the remaining proportion contains argon and/or helium.

5. The welding method according to claim 1, in which a welding filler selected from the group consisting of a high-alloyed nickel and/or chromium-containing iron material is used.

6. The welding method according to claim 1. in which a work piece selected from the group consisting of a high-alloyed nickel and/or chromium-containing iron material is used.

7. The welding method according to claim 1, in which the inert gas is mixed out of at least two inert gas components.

8. The welding method according to claim 1, in which the inert gas is provided in premixed form.

9. A method for the reduction of a content of nickel oxides and/or chromium (VI) compounds in a welding fumes of a method for the metal inert gas welding, in which a weld filler is fed to a welding torch and via a welding current connection is subjected to a welding current of a welding current source, as a result of which an arc is formed and material of the welding filler in a welding region is transferred onto a work piece which at least in the welding region consists of an alloyed stainless steel and by means of the welding torch an inert gas is fed to the welding region, which inert gas has a content of 0.5 to 3.0% by volume of at least one oxidising component, characterized in that the inert gas additionally has a content of 0.1 to below 0.5% by volume of hydrogen.

10. An inert gas which has a content of 0.5 to 3.0% by volume of at least one oxidising component and a content of 0.1 to below 0.5% by volume of hydrogen.

11. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWING

[0037] In the following, the invention is explained in more detail making reference to the attached drawing. In this drawing FIG. 1 illustrates the bases of the formation of chromium (VI) compounds by way of a schematic representation of a welding torch.

COMPREHENSIVE FIGURE DESCRIPTION

[0038] FIG. 1 illustrates the chemical bases of the formation of chromium (VI) compounds by way of a schematic representation of a welding torch. The view in its entirety is marked with 100.

[0039] In the view 100, the welding torch 10 is shown in part view in longitudinal section. The welding torch 10 is designed as a metal inert gas welding torch. It is equipped in order to guide a wire-shaped welding filler 1 in the shown section and to this end comprises corresponding guide means 2, for example a guide sleeve with a suitable inner diameter. The welding torch 10 is directed at a work piece 20.

[0040] The guide means 2 are surrounded by a nozzle 3, which defines an annular process gas duct 4, which runs concentrically about the guide means 2 or the welding filler 1. By wav of the process gas duct 4, a suitable inert gas can be supplied by way of a suitable inert gas device (not shown), which covers a region 6 between the welding torch 10 and the work piece 20.

[0041] As metal inert gas welding torch, the welding torch 10 is designed in order to subject the welding filler 1 to a welding current. To this end, the guide means 2 are connected, by way of a welding current connection that is only schematically illustrated, with a pole of a suitable welding current source 30. The welding current source 30 is preferentially equipped for providing a direct and/or alternating current. In the shown example, the work piece 20 is connected to the other pole of the welding current source 30, as a result of which an arc 7 can be formed between the welding filler 1 and the work piece 20 (transmitted arc). In the same way, another element of the welding torch 10 however can also be connected with the other pole of the welding current source 30, so that between welding filler 1 and this other element of the welding torch 10 an arc is formed (untransmitted arc).

[0042] By way of a schematically illustrated feeding device 8, the welding filler 1 can be provided to the guide means 2 and conveyed at a suitable speed. By feeding the material 20 relative to the welding torch 10 or vice versa, a gradually solidifying weld seam 21 is formed.

[0043] The shown arrangement can also be surrounded by further nozzles, which can be used for feeding additional process gases. By way of a further annular process gas duct, a plasma gas can for example be fed in and a focussing gas via another annular process duct, so that by means of the welding torch 10 a plasma method can also be realised.

[0044] The liberation of chromium (iii) compounds (combined by Cr.sup.III) from the welding region, i.e. the region of the arc 7, is illustrated by a corresponding arrow. By way of a reaction with the likewise formed ozone (O.sub.3) the further oxidation to form chromium (VI) compounds (combined by Cr.sup.VI) occurs.