Investigation Of Gas Shielded Arc Welding Of Hsla Steel Blade Wheel

KMN steel is a kind of high-strengh low alloy steel, which is developed for centrifugal compressor blade wheel in Italy Nuovo Pignone Company, and is imported by Shenyang Blower Works Group Co., Ltd. This steel is mainly applied in the manufacture of centrifugal air-blower and compressor blade wheel. Due to its high carbon equivalent, it has high harden-ability and cold cracking tendency. Though the manual arc welding applied in this steel is simple and convenient, but the low quality and high repair difficulty lead to low manufacture efficiency.In the present paper, Ar/CO₂ mixed gas shielded arc welding technology is applied to the welding of KMN steel. According with the welding principle, different experiments with CHW-62B₃ solid cored wire, TWE-911B₃ and K-91TB₃ flux-cored wire are carried out. The welding ability of KMN steel and metallography of welding joint in different wire and heat input are fully studied. Moreover the mechanical properties of the welding joint is tested by tensile and impact test. All these results provide a clear direction for the application of KMN steel on the blade wheel of blower.As though the welding ability of KMN steel is not good, the results show that by adjusting the technique parameters, the KMN steel can obtain good welding quality in Ar/CO₂ mixed gas shielded arc welding process with both solid cored and flux-cored wire. And no crack is observed in the welding joint. As though the heat input can affect the welding joint, the mechanical properties of welding joints obtained by different welding wires almost have the same trendency. With the increase of the heat input, the tensile strength and yield strength of the welding joint increase firstly and then drop, but the elongations just change a little. The welding joint of solid cored welding wire CHW-62B3 owns the best tensile properties. The observations on the welding joint find that the different welding wires have different effects on the heat affected zone. The heat-affected zone of solid cored wire CHW-62B3 is mainly bainite; while the heat-affected zone of flux-cored wire is mainly sorbite. According to the results, it can be concluded that the welding joint obtained by solid cored welding wire has the best properties.The testes on the KMN steel blade wheel of blower prepared by 80%Ar+20%CO₂ mixed gas shielded arc welding with CHW-62B₃ solid cored wire show that the products can well meet the requirements of applications.