Restoration of Metal Molds for Centrifugal Casting of Pipe From High-Strength Iron by Arc Welding

Abstract

Currently, metal molds for casting cast-iron pipes operate under severe temperature and deformation conditions, as a result of which they fail due to wear of their inner surface and the formation of cracks and a mesh of heat in the same place. (Research purpose) The research purpose is studying the possibility of defect-free restorative surfacing of the inner surface of metal molds without preheating in the environment of protective gases. (Materials and methods) All work on the development of the metalform surfacing technology was carried out on samples cut from the original metalforms. The method of arc surfacing in the environment of protective gases was taken as a basis. Various welding wires and protective media were tested for surfacing. Assessment of the surfacing quality for the presence of pores and cracks before and after mechanical treatment was carried out visually, followed by determination of the chemical composition and hardness of the deposited layer. (Results and discussion) Surfacing was carried out on the inner surfaces of the samples without preheating them. Various wires were tested for surfacing: Sv-18XGS, Sv-18XM and Np-30XGSA based on obtaining a composition close to the composition of the base metal in the deposited layer. As a result, Sv-18XMA welding wire with a diameter of 2.0 millimeters was chosen for the restorative surfacing, and a welding mixture was used as a protective medium, ensuring satisfactory formation of the deposited layer without pores and cracks with minimal splashing in the selected modes. Studies were carried out to determine the hardness and chemical composition of the deposited layer and the base metal of metal forms. (Conclusions) Proposed a technology for reducing the surfacing of the inner surface of metal molds without preheating. A comparative analysis of the hardness and chemical composition of the deposited layer and the base metal of the metal forms showed a comparable level of hardness and alloying elements in them, which will ensure the necessary wear and heat resistance of the restored metal forms