Solder and Repair Welding Method for Casting Defects of K418b Superalloy Guide

Abstract

The invention belongs to the field of welding technology, and relates to a solder used for casting defects of a K418B superalloy guide and a repair welding method; the solder composition and mass percentage are: C: 0.03-0.07; Cr: 21.5-24.0; Nb: 3.2-4.2 ; Mo: 8.5~10.5; Ti: 0~0.5; Al: 0~0.5; P: ≤0.015; S: ≤0.015; O: ≤0.015; N: ≤0.01; Frequency pulse argon arc welding technology, supplemented by pre-weld preheating, post-weld slow cooling and post-weld spot shot peening, can repair casting defects on the guide, and can be used for K418B casting superalloy casting shrinkage porosity, shrinkage cavity, Repair welding of defects such as undercasting, wear and cracks; the welding fluidity of the solder is good, the weld shape is good, the repaired welding joint has no cracks and unfused defects after fluorescence and X-ray inspection, and the average strength of the repaired welding joint at room temperature reaches 885MPa, It is better than the technical requirements of the part material standard.

Description

technical field [0001] The invention belongs to the technical field of welding, and relates to a solder used for casting defects of a K418B superalloy guide and a repair welding method. Background technique [0002] K418B alloy is a modified cast nickel-based superalloy of K418. Compared with K418 alloy, its carbon and titanium contents are lower, the room temperature plasticity and impact toughness are obviously improved, and the microstructure stability is better. The alloy composition is relatively simple and the price is relatively cheap. It has high creep strength, thermal fatigue and oxidation resistance below 900℃. It is suitable for making gas turbine guide vanes and rotor blades working below 900℃, as well as integral casting turbines. However, large-sized and complex-shaped parts are prone to defects such as shrinkage porosity, shrinkage cavities, under-casting and cracks during the casting process, and welding technology needs to be used to repair the defects. ...

AI Technical Summary

Problems solved by technology

[0004] On the other hand, the guide is a ring-shaped closed structure with a large degree of self-constraint, which will cause large repair welding thermal stress and residual stress, and increase the tendency of welding thermal cracks and strain failure cracks

The structure of the guide is complex, including blades and inner and outer rings. The size difference between the inlet and outlet edges of the blades is large, and there is a sudden change in section at the transition connection between the blades and the inner and outer rings, which will not only cause uneven structure and composition of the casting, but also cause stress. Concentration, increasing the tendency of cracking during repair welding

[0005] There are many factors affecting the repair welding cracks of castings. Welding materials, process parameters, heat treatment status, repair welding parts, etc. all have an impact on the occurrence of cracks, and the interaction between different factors is complex.