Research On Key Technology And Mechanical Property Material Of ESC Diaphragm Pump Crankshaft

The diaphragm pump is a kind of updating product for the traditional mud pump, whose heart component is crankshaft. Ever before, the crankshaft of the diaphragm pump was prepared through forging, resulting in long production period and low metal utilization ratio, and the crankshaft crack accidents often occur. However, instead of forging, the electro-slag casting (ESC) method can provide higher purity of the steel and more compacted microstructure, which can be considered to be an efficient approach to enhance the production property. The paper studied the key processing technology of the ESC method and the heat-treatment of 42CrMoA steel, having obtained high quality and performance crankshaft rough part.The key processing technology of the ESC method indicates that: (1) the long flowing distance of the metal liquid can be carried out by the way of slope-changing of the crankshaft mould cavity. (2) The surface forming quality and inner quality can be improved by proper electrode controlling. (3) According to the data collecting and tiding,_a relatively accurate crystal current density and working voltage equation was obtained, optimizing the process parameters for the crankshaft casting. The crankshaft rough part adopting the above method obtained a relatively high surface forming quality and inner quality.The metallurgy quality result analysis indicates that: the chemical elements of 42CrMoA steel distribute uniformly, Harmful elements S, P lower, and the nonmetal inclusions were reduced greatly and their figures take on small particles.Heat-treatment investigation indicates that: (1) On 920℃annealing and 900℃normalizing and 870℃quenching and 580℃tempering, 42CrMoA electroslag steel performs optimum comprehensive properties,whose tensile strength is 975MPa, yield strength is 880MPa, elongation is 16.5%, contraction of area is 55%, impact toughness is 82J of the A_kv index and hardness is 309 of the HB index, conforming to the requirement of JB/T6396-92. Furthermore, compared the fatigue property of 42CrMoA electroslag steel with that of 42CrMoA forging steel by adopting the heat-treatment method, having a considerable tension fatigue performance, and normal property equal to the hardened and tempered steel.(2) On heat-treatment, the micro-organization are almost tempered martensite, and the cementite distributes dispersively to strengthen the microstructure. At the meaning time, on high temperature tempering, the matrix restores and re-crystals, the cementite deposits, and the inner stress disappears, resulting in the higher strength and plasticity of the electroslag steel.Now the Crankshaft of electroslag casting is used on Diaphragm Pump, achieve the purpose of compact, and beginning production capacity.