The Strength-toughening Mechanism Of A Intensive Quenched Low Carbon Alloy Steel

In this work, The steel20CrMnTi were treated by intensive quenching process incombining the calcium bichloride with liquid nitrogen, then we got the steel with residualstress gradient from the heart to the surface. It observed microstructure and austeniticrecrystallization of20CrMnTi steel treated by intensive quenching craft processing using themetallography microscope, the scanning electronic microscope, X-ray diffraction analyzerand transmission electron microscope.20CrMnTi steel mechanical properties and residualstress and physical phase was determined by vickers microhardness and X-ray diffraction. Itanalyses the intensive quenching craft’s influence to the mechanical properties and theorganization.The results show that: the steel of20CrMnTi existed the residual stress gradient andhardness profile after intensive quenching processing; the grain boundary of parent austenitein the steel20CrMnTi existed the phenomenon of austenitic recrystallization. The surfacerecrystallization degree is obviously higher than the heart; there are dispersion, even and fineseparation phase (Cr₇C₃、C₂₃C₆、Mn₂₃C₆、Ti₂C_0.06、Fe₃C、Fe₅C₂、Fe₇C₃) which are along withthe quenching the change of time carbide present metastability and steady state changes in theintensive quenching organization. the micro hardness, impact toughness, tensile properties,service life all have greatly enhanced after intensive quenching. The service life of theworkpiece after intensive quenching is1³times longer than the workpiece afterconventional quenching, and the impact toughness of the workpiece after intensive quenchingis1.15times bigger than the workpiece after conventional quenching.After analysis, we can get intensive quenching organizations after intensive quenchingwhich is in CaCl₂solution and liquid nitrogen compound for quenching medium quenchingprocess. Quenching cracks were inhibited by residual stress which repaired some microcracks at the sample surface and effectively improved the service life; The micro hardnessgradient distribution can effectively absorb impact energy, improve the impact toughness; Theoriginal austenitic grain boundaries happen recrystallization phenomenon, that after a switchmartensite organization super refinement, thus produce fine-grain strengthening, and improvethe strength of the material and toughness;The separation phase after intensive quenching temperature after tempering is more diffuse and small, and improves the strength of thematerial. The uniform distribution of Cr, Mn, Ti, Fe carbide which is high hardness and highmelting point can improve the strength of steel, hardness and wear resistance.