Metallurgical and technological features of forming the connection zone between the welded layer and base metal during repair welding of cast iron parts with carbon dioxide and oxygen

Abstract

A new technology has been developed for restoring worn cast iron parts using electric arc surfacing. This technique uniquely combines the simultaneous introduction of filler materials, both as seamless wire and powder alloys, directly into the weld pool. Additionally, oxygen is supplied to the surfacing zone to decarburize the weld pool. The powder alloys used are enriched with graphitizers and carbide-forming elements to protect the melt during the crystallization process. Research has found that the connection zone between the original material and the added layer consistently features a transition layer, regardless of the specific gases and powder materials used. Notably, the use of NPCh‑3 powder, together with the supply of oxygen and carbon dioxide into the weld pool is 2.0–2.7 times thinner than those produced with either PG-12N-01 or PG-10N-04 powders. This method significantly enhances the quality of the deposited layer by increasing the proportion of finely dispersed complex carbides, obtaining an equilibrium structure of fine-plate pearlite with finely dispersed graphite deposits. This results in minimal porosity and the elimination of microcracks, while also reducing cast iron microhardness in the heat-affected zone by 2.1 times. A technology has been developed for restoring cast iron parts through electric arc gas-electric surfacing. This approach has been tested in industrial settings, demonstrating its ability to reduce metal scattering, porosity, and hardness of the deposited layer and the transition zone,. Furthermore, it significantly lowers the likelihood of crack formation, all while minimizing the expenditure on.