Performance Analysis Of Alloy Steel Material And Its Welded Joints Used For Blower Impeller

With the rapid development of the country's industrialization, blower industry has got speedy development. Blower is widespread used to national production and daily life, such as medicine, paper making, textile, chemical fiber, glass, coal, grain, construction industry, tobacco, military, brewing, steel, power generation, cement, petrochemical, sewage treatment and other important industries. The impeller as a component of blower is so important that its quality directly impacts on the work environment and the service life of blower. In order to expand the field of application, especially the application under low-temperature working condition, to improve the overall quality and extend the service life of blower, at the same time to widen the applied range of existing materials, the properties of base metal and welded joints of blower impeller made from two kinds of high-strength alloy steel (40CrNiMo7, 25Cr2Ni4MoV) have been studied respectively.In this paper, mechanical properties, especially the properties in low temperature, of two kinds of alloy steel under different heat treatment processes were studied. The influence of different heat treatments on the microstructure and the performance of base material have been researched with several test methods, such as microstructure observation, the impact fracture analysis, hardness test and tensile test. Through comparing the overall properties of two kinds of base metals, one with better low temperature performance was chosen, and meanwhile the heat treatment process which matches with the chosen base metal was determined. Then, the welding experiments were carried by the use of selected base metal and existing welding material and the performance deficiency of existing welding material was shown from the tests results. Finally, aiming at the application under low-temperature working condition, the research approach of new welding material matching with the selected base metal was put forward.Through the research of different heat treatments to two kinds of base metals, the following conclusions can be drawn.First of all, with the heat treatment processes of 850℃for 30min oil quenching and then at 650℃for 100min water-cooled tempering,40CrNiMo7 has a better comprehensive properties.Secondly,25Cr2Ni4MoV can obtain comprehensive properties, especially the property in low temperature though the heat treatment processes of 860℃for 40min oil quenching and then at 630℃for 120min air-cooled tempering.From the welding test of 25Cr2Ni4MoV steel, it was shown that the properties of welded joints treated with the process of whole postweld heat treatment surpass the welded joints obtained by combining with the processes of welding pre-weld heat treatment and post-treatment process. In guarantee of the intensity of welded joints, the idea of developing the matching welding materials was to increase the low temperature toughness of welding seam by adding alloy elements Ni, Mn, Mo etc and to purify the crystal boundary and refine the grain by adding the micro-alloy elements Ti, B, Re.