Laser manual welding process for metal materials under shielding gas

Abstract

In a laser manual welding process for metallic materials, in particular austenitic steels, a shielding gas is used according to the invention, which consists of 1 vol.% to 20 vol.% hydrogen, the remainder being argon and / or nitrogen.

Description

[0001] The invention relates to a method for manual laser welding of metal materials, in which surfaces of two workpieces to be joined are melted by applying a laser beam from a hand-held laser welding gun and a protective gas is supplied to the melted area.

[0002] Laser welding uses monochromatic, coherent radiation as the heat source to melt the workpiece material. This radiation is focused by an optical arrangement. To protect the weld seams from oxidation, a shielding gas is often used in laser welding.

[0003] While automated laser welding has been established for many years, manual laser welding has only been available as a new welding process for a few years. This process uses a manually operated laser welding gun to join materials. Nd:YAG lasers or fiber lasers are typically used as the laser source. Manual laser welding is distinguished from other manual welding processes by its high precision, high speed, low heat input, and ease of handling, making it particularly suitable for small batches and / or for welding small structures. The comparatively inexpensive welding guns and the option of manually guiding the equipment make manual laser welding very cost-effective and efficient compared to automated laser welding.

[0004] When using a handheld laser gun, the shielding gas is applied to the welding area—the junction between the surfaces of the workpieces to be joined—during the welding process. To supply the shielding gas, handheld laser welding guns often have a nozzle that can be connected to a hose and is directed toward the welding area when the welding machine is in use.

[0005] To date, the shielding gas used in manual laser welding of metallic materials, especially austenitic materials, has primarily been high-purity argon, and to a lesser extent, nitrogen. Argon often causes porosity, while nitrogen results in comparatively low penetration.

[0006] The object of the present invention is to provide a welding shielding gas suitable for manual laser welding of metallic materials, which has good penetration properties and which, when used, results in a significantly reduced formation of pores compared to the use of argon.

[0007] The object of the invention is achieved by a method for manual laser welding of metal materials having the features of patent claim 1. Advantageous embodiments of the invention are claimed in the subclaims.

[0008] The gas mixture used as a shielding gas in the method according to the invention for manual laser welding of metallic materials is characterized by a proportion of 2 vol.% to 20 vol.% hydrogen. A preferred hydrogen proportion is between 2 vol.% and 10 vol.%, particularly preferably between 2 vol.% and 7 vol.%. Otherwise, the shielding gas consists of argon or nitrogen or a mixture of argon and nitrogen with any desired composition. In a particularly advantageous embodiment of the invention, however, the shielding gas used according to the invention is a binary gas mixture consisting of nitrogen and hydrogen, the hydrogen proportion of which corresponds to the proportions mentioned above. For example, the shielding gas consists of 97 vol.% nitrogen and 3 vol.% hydrogen, or of 95 vol.% nitrogen and 5 vol.% hydrogen, or of 93 vol.% nitrogen and 7 vol.% hydrogen.

[0009] Surprisingly, it has been found that pore formation is drastically reduced when using a shielding gas according to the invention during manual laser welding of metallic materials, especially austenitic steels, compared to using pure argon as the shielding gas. At the same time, with all other process parameters remaining the same, the weld exhibits deeper penetration than when using pure nitrogen as the shielding gas.

[0010] The method according to the invention is therefore preferably used in manual laser welding for joining two workpieces, at least one of which is made of an austenitic steel.

Claims

[1] A method for manual laser welding of metal workpieces, in which surfaces of two workpieces to be joined are melted by applying a laser beam from a hand-held laser welding gun and a protective gas is supplied to the melted area, characterized by that a gas mixture is used as the protective gas, which consists of a proportion of 1 vol.% to 20 vol.% hydrogen, the remainder nitrogen and / or argon. [2] Method according to claim 1, characterized by that the hydrogen content in the protective gas is between 2 vol.% and 10 vol.%, preferably between 2 vol.% and 7 vol.%. [3] Method according to one of claims 1 or 2, characterized by that a binary gas mixture consisting of nitrogen and hydrogen is used as the protective gas. [4] Method according to one of the preceding claims, characterized bythat at least one of the workpieces to be welded together is made of austenitic steel.