| Since the environment of mine rescue capsule is relatively bad, it is required that the mine rescue capsule plate steel should have sufficient strength, toughness, impact resistance, corrosion resistance and fire resistance. Currently, the steels of mine rescue capsule cabin commonly employ Q235, Q345, Q460and Q550and other ordinary structural carbon steel and low alloy high strength steel, the yield strength of these materials are235～600Mpa, the properties of toughness and bending and other indicators meet the basic requirements. But given the impact of the underground gas explosion generating the instantaneous temperature, methane and H2S and other corrosive environment, lighter weight and higher strength and other higher repuiring aspects, the existing mine rescue capsule cabin materials are difficult to meet the used requirements. Therefore, starting from the steel of the mine rescue capsule, developing a special kind of hot rolled plate steel for coal mine machinery, which has high yield strength, good impact resistance, high temperature resistance, corrosion resistance, good weldability and other comprehensive properties is an important task and urgent problem to be solved for the scientific and technological workers. Low carbon bainite steel has the advantages of high strength, high toughness and excellent welding performance, which is widely used in the fileds of engineering machinery, mine equipment, shipbuilding, marine facilities, oil and gas pipeline steel and so on. Aiming at the technical characteristics of high strength steel used in coal mine machinery, adopting reasonable composition design, the TMCP technology, the low carbon bainite steel with the tensile strength level of800to1000Mpa was obtained under different cooling system. We studied its strength, heat resistance, toughness and welding performance comprehensively. This thesis also studied the microstructure morphology and strengthening mechanism of the steel by metallographic microscope, scanning electron microscopy, transmission electron microscope. The main experiment and achievements in this thesis shown as follows:(1) Aiming at specific service environment and technical characteristics of coal mine machinery high strength steel, on the premise of exploring the effects of each alloy element, combined with the production and technical indicators of high strength steel applied in domestic steel coorperations, three ingredients steels were designed and code-named C56, C78and C89.(2) Through the single press test on the thermal simulation experimental equipments, the stress-strain curve of the test steel C89was measured, the influence of the deforming temperature, deforming rate and deforming degree on the deformation resistance of the steel was studied, and the C89’s mathematical model of deformation resistance was established.(3) Through the double press test on the thermal simulation experiment, the influence of different deformation temperature and the time interval of the pass on static recrystallization of the steel were researched. The static recrystallization activation energy of C89was400.89kJ/mol, and the static recrystallization kinetics equation was regressed.(4) Expansion experiment was used to measure static CCT curves and dynamic CCT curves of test steel. Austenite transformation law under different cooling conditions of the test steel C89was studied and analyzed.(5) On the basis of the thermal simulation experiment, through laboratory hot rolling experiments of different rolling and cooling process, microstruture observation and performance testing C56, C78and C89were conducted, and we obtain the production technology of coal mine machinery high strength steel with the tensile strength level of800to1000Mpa, which will provide reference and basis for in-depth research in the future.(6) A preliminary discussion was made on the welding performance of the steel C89. When the welding line energy is12.5～12.5kJ/cm, the microstructure and mechanical properties of weld seam and heat affected zone were measured, we get the welded joint matching the base metal, which will lay the foundation for the in-depth research of welding performance. |
PDF Full Text Request