The assessment of the effects of wet melting on the stress-strain state of the shaft

Abstract

Welding is a progressive and highly productive way of repairing worn working surfaces of parts. One of the most widespread technologies of the reconstruction of the diameter of the shafts is their surfacing in the environment of protective gases. However, with such repairs of small diameter and longitudinal shafts there are significant deformations, and the casting shortenings are associated with excessive heating in the process of surfacing. Uneven local heating of the metal during surfacing, change in its volume, due to temperature expansion and structural transformations, cause the appearance of welding stresses and deformations, which in some cases cause changes in the shape and size of the product, and make it unfit for further use. This is especially true of the process of surfacing small diameter shafts, which often passes through their heating to temperatures above 600 ºС. As you know, the boundary of steel steels with a temperature rise above 500 ºС drops sharply. In this connection, the shaft fastening in the centers gets axial shrinkage, and details with one-way fastening can deform due to its own weight. One of the methods to prevent the rise in temperature is the use of various methods of cooling, including water.

The paper proposes the technology of wet surfacing, which consists of partially immersing parts in water and allows to minimize heating during surfacing, and accordingly all negative consequences are connected with it. The proposed technology of wet surfacing allows the components to be restored without overheating, and as a result, reduce current deformations by 60-70%, and the residual is almost doubled. The microstructure and hardness of the coatings obtained by wet surfacing were also studied in this work. The coatings welded with low-carbon wire Sv-08G2S with an additional blown carbon dioxide have a structure similar to athermal martensite and low porosity. Measurements of microhardness have shown that only the surface layers have relatively high hardness that goes down to the depth of the coating.