CS263600B1 - The way to prepare steel components before welding with media and its alloys - Google Patents

Abstract

' The solution concerns the preparation of steel components before welding copper and its alloys and solves the problem of preventing the occurrence of under-weld defects of the type of intercrystalline leakage of the welded metal into the steel. The formation of these defects is a typical accompanying phenomenon for welding copper and its alloys onto steel, especially when welding onto steel of higher strength. The essence of the solution lies in the fact that before welding copper or its alloys onto steel, compressive stresses are induced in its surface layer intended for welding.

Description

The invention relates to a method of preparing steel components prior to welding of media and its alloys, and to the problem of preventing the occurrence of intercrystalline type defects of the type intercrystalline by pouring welded metal into steel. The formation of these defects is a typical accompanying phenomenon for the welding of media and its alloys to steel, especially when welding on steels of higher strengths. .

The welding of the alloy and its alloys to the steel components is carried out in order to create functional surfaces of special properties, for example for sliding bearing, corrosion and cavitation resistant surfaces and the like.

Until now, the welding of media and its alloys to steel components is most often carried out by mechanized welding, namely by welding under the flux with a strip electrode and welding with a semi-automatic or iautomatic melting electrode in protective atmospheres. These methods of welding • have considerable productivity, but they are melting the surface of the vinegar part, which increases the number and depth of underfloor defects.

More preferred is a non-melting tungsten electrode in a protective atmosphere without melting the base material or plasma welding, wherein the welded metal is mechanically added to the arc. Even in these cases, however, the occurrence of underfloor defects is not dialed. The intercrystalline penetration of the welded medium or its alloy occurs mainly due to the existence of tensile stresses in the weld deposit area, among other effects, such as the surface roughness, its fusing during welding, the type of the basic weld material and the like. These stresses are either as residual stresses or as a result of the welding process.

Examples of solutions are known in which the selected base material is ferritic with a chromium content of 16% or nickel alloys with a nickel content of more than 60%, or these materials are pre-welded to the steel surface as interlayer to avoid the formation of underfloor defects. However, these solutions are economically very demanding. Underfloor welding defects can cause fracture failure of the base component during prevailing cyclic loading.

These drawbacks are eliminated by the method of preparation of steel components before welding ^! The invention is characterized by the fact that compressive stresses are induced in the surface layer of the parts to be welded on.

Claims (1)

SUBJECT . Method of preparation of steel parts before welding of the media and its alloys prior to the occurrence of underfloor defects The advantage of the method of welding of the media and its alloys to the steel according to the invention is that it is not necessary to choose high-alloy materials such as ferritic steels with a chromium content of at least 16%. Alternatively, nickel alloys having a nickel content of at least 60%, may be welded between layers of these materials. Higher effect is achieved 1 when welding medium and its alloys on low carbon steels, where the occurrence of underfloor ‘defects tends to be lower than in alloy steels, especially higher strength steels. An example of a welding method according to the invention is welding to a 120 mm steel tube (30 Cr 2MnV type steel) where the outer surface is welded with an alloy medium (CuSn6 type). The workpiece is subjected to high-frequency heating above the Ac3 conversion temperature to a depth of 3 mm and vigorous cooling with a water spray after mechanical treatment at the weld deposit point, resulting in pressure stresses on the surface of the scaffold component followed by welding of the alloy alloy layer in the example. by a mechanized method of welding with a non-melting tungsten electrode in a protective atmosphere of argon. The defectoscopic examination and metallographic evaluation showed that there was no occurrence of underfloor defects that were otherwise common without the application of this method. Another embodiment of the welding method according to the invention is the welding of the equatorial component as in the previous example, except that the component after mechanical treatment is preheated to a temperature of 250 to 350 ° C and at this temperature a deformation treatment of the surface is performed by roller. followed by welding. By this treatment, the desired surface stresses are achieved in the surface layer of the component. The resulting effect is similar to the previous example. The invention can be used in all examples of welding of media and its alloys to steel by wound welding technologies, for example under argon shielding by a non-melting tungsten electrode, under a flux wire or strip electrode, semi-automatically in protective atmospheres and the like bearings, pistons of hydraulic machines, corrosion and cavitation resistant layers, different sliding pairs and the like, especially in the case of dynamically stressed components.