DD263480B1 - PROCESS FOR PREPARING TIG APPLICATION WELDING OF HIGH-WELD MATERIALS ON SMALL DIMENSIONS OF STEEL BODY - Google Patents

Abstract

The method is applicable to machine component parts with edges prone to overheating, for example, hammer hammers and putty scrapers. According to the invention, the steel bodies are provided with a galvanically applied copper layer, with a thickness of at least 5 .mu.m, and heated until the complete color change of the copper layer before the build-up welding.

Description

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Field of application of the invention

The invention includes a method for preparing TIG build-up welding of refractory materials to steel bodies, such as engineering small parts, in which heatectau and thus scaling occurs during welding and for which TIG build-up welding could not previously be used. The method is particularly suitable for hammering jaws for hammering machines, with which tungsten and molybdenum rods are processed.

Characteristic of the known state of the art

In TIG build-up welding, small parts are preheated to about 300 ° C and hot-worked by application of the listed method.

As a result of the arc heat, the parts reach white heat within a very short time and start to scale up especially at the edges. When welding the edges or corners of the scale must be melted and there is a risk that it is flushed into the molten bath and leads to defects.

The structure of the scale layers begins already during the preheating without inert gas purging, the parts can then already make trouble when placed on the welding table due to insufficient electrical contact.

Already in DE-PS 362591 it is proposed, when welding sheet metal, to protect the areas exposed to overheating by a protective coating or spreadable paste from the ingress of air. As a protective layer aluminum is proposed.

On a protective layer of aluminum, however, Al ₂ O _{3 forms} , thus no exact approach of the arc is guaranteed and the TIG welding process is not applicable.

The arc is ignited unstable in these cases, which can already lead to scrap in sensitive small parts.

From DE-PS 2004738 intermediate layers, such as chromium, nickel, cobalt or tungsten are known, which are applied by a galvanic process with the aim of Verri.iischungshemmung in the weld transition zone.

Dieoe layers have the disadvantage that during the warm-up and welding process, the oxygen of the air leads to firmly adhering scale layers, which are melted into the weld metal and produce defects. Although chromium and nickel layers appear to be particularly suitable in the literature, the practical experiments of electroplated chromium or nickel layers led to strong scaling.

Object of the invention

The object of the invention is to find an effective material-saving method of preparation in order to apply highly heat-resistant wear-resistant layers, for example cobalt alloys by TIG build-up welding, to machine parts of complicated shape.

Explanation of the essence of the invention

The invention has for its object to prevent the resulting from arcing heating change at heat endangered edges in compli 'rt shaped small steel bodies, such as hammers jaws, and to ensure a good contact up to thin edges.

According to the invention the object is achieved in that the steel body is provided with a plated copper layer of a thickness of at least 5pm and heated to build-up welding to complete color change of the copper layer.

Surprisingly, the Verzoberungsproblcme were solved by this electroplated copper protective layer.

Thin edges are particularly endangered by you »scaling. In the galvanic bath occurs at these edges, the largest current density and thus the strongest deposition, so that these edges are protected by thicker copper layers than the rest of the steel body.

Another advantage is the fact that the copper layer having sufficient warming in the preheating a color change. During build-up welding, this allows the welding part to make immediate contact with the electrically conductive welding table, without causing e.g. By copper plates too much heat dissipation takes place.

The copper protective layer thus allows a free manipulation of the aufzuschweißenden part and the protective effect of Argon stream can z. B. fully utilized in suitable parts with far protruding electrode to protect the molten bath

become.

Due to the copper protective layer and the resulting manipulation, it is possible to expensive, highly effective Hardfacing materials, e.g. Cobalt alloys, use material saving. It is thus possible to use cheap, easily machined material body and refine them by welding. It is also possible to carry out job cheating on old parts that have previously been rejected by scaling

had.

exemplary The invention will be explained in more detail with reference to two embodiments

Fig. 1: shows a Hämmerbackenkörper Fig.2: shows a Kittabstreifer.

By means of impact jaws rods are stretched and hardened in the preheated state on hammer machines. The Hammer hammers are made of high-temperature resistant materials that must have high impact resistance. These parts

For the production of refractory metals, such as tungsten and molybdenum, wear parts represent a high

Tying up expenditure on cutting capacity. The Hämmerbackengrundkörper laus carbon steel is provided with a groove-shaped longitudinal groove at the top Finally, the overheating endangered edges 2 are located and in the longitudinal groove by TIG-Auftragschweißnut

multilayered the application material 3 introduced.

The dimensions are kept so that the side uno uangsflächen during a TIG build-up welding freely transverse and

can shrink longitudinally.

Before welding, the parts are cleaned and provided with a copper layer in the galvanic pad. The overheating-prone edges are provided by high current concentration with a stronger copper protective layer. Subsequently, the parts are preheated in an oven (about 2 hours at 300 ° C) until the complete Color change of the copper layer took place. Thereafter, the cobalt alloy welding is performed in a plurality of layers with a 3 mm tungsten electrode Given the diameter of the component. The channel-shaped longitudinal groove acts during the welding as gas protection, so that the protruding electrode can be good

be manipulated, and it is a favorable Kantenaufschmelzung possible.

After welding and subsequent reheating of the parts, the copper oxide layer can easily be brushed

be removed. Equally good results have been achieved with the scraper, whose edges are subject to special wear. Even with these parts occurs at the edges of the risk of overheating. These edges are provided in the galvanic bath with a stronger copper protective layer than the rest of the part and then treated as well as the hammers.

Printed pamphlets: DR-PS 262591 (49h, 34/01)

Claims (1)

claims: Method for preparing a TIG hard facing of high temperature resistant materials on small-sized steel bodies, in particular on impact hammers of wire hammers, using a metal application applied to the superheated areas, characterized in that the steel bodies are provided with a plated copper layer at least 5 μm thick provided and heated to build-up welding to complete color change of the copper layer.