Study On High Temperature Behavior And Hot Workability Of 301L Stainless Steel

301L is a metastable austenitic stainless steel.Due to its high strength and good toughness,and widely used in the body structure of rail vehicles.it is particularly important to obtain excellent austenite structure,control the high-temperature behavior of the material and prevent the occurrence of cracks by hot working of 301 stainless steel casting billet.The plastic deformation characteristics of 301L stainless steel at high temperature and the determination of reasonable hot working conditions to prove the dissolution behavior of delta ferrite at high temperature In the range of⁵0s^-1,The hot compression deformation behavior of 301L stainless steel was measured,and the high temperature heat treatment furnace was used to anneal the 301L stainless steel billet samples in the range of 1210?¹300?and 10min⁶0min.The research shows that according to the stress-strain curve of the 301L stainless steel casting billet,The discontinuous dynamic recrystallization and continuous dynamic recrystallization behavior of the material under high temperature,low strain and high strain conditions are significant.Using the stress-strain curve data and the hyperbolic sine model proposed by Sellars and Tegart,The constitutive equations of301L stainless steel billet during uniaxial compression were established.The constitutive equation at a strain of 0.1 is:?=7.621x10¹⁴[sinh?0.0089??]^5.375exp?-400.135/RT?,The equation reflects the interrelationships between the kinematics?,dynamics?and thermodynamics T of 301L stainless steel.The results of the calculation and fitting of the constitutive equation are in good agreement with the experimental results.The constitutive equation was established to determine the thermal deformation activation energy Q of the material between 400⁴69 KJ/mol under different strains,and the strain hardening index n between 5.537⁶.030.the data obtained from the experiment was calculated by using the cubic spline interpolation method to calculate the strain sensitivity index m,and the power dissipation factor?and the instability criterion????were determined by the formula.The analysis of the thermal processing chart drawn by the origin software shows that within a certain range,the reasonable area for hot working of 301L stainless steel slabs is concentrated in the high temperature and medium and high strain rate regions.That is,the area surrounded by the temperature is 1075?¹240?and the strain rate is 5.0s^-150s^-1.the increase of the strain variable has a greater impact on the range of the machinable zone.As the strain variable increases,the 301L stainless steel instability zone gradually expands from a low strain rate region to a high strain rate region.The effect of strain rate on the non-machinable area is significant.The smaller the strain rate,the worse the material's hot workability.The effect of temperature on the non-machinable area is reflected in the low temperature,and the instability of the material is more serious.The effect of microstructure on the material is analyzed.The results show that as the temperature increases,the?ferrite content on the austenite matrix decreases first and then increases,and the equilibrium?ferrite dissolves in Austria.for austenite,the non-equilibrium?ferrite at the node grows for a second time,and some?is transformed into austenite after passing the solid phase transition point.With the increase of strain rate,the tendency of?ferrite to develop laterally decreases.finally,the subject studied the?ferrite annealing process of 301L stainless steel slabs and found that at the initial stage of dissolution,more than half of the?ferrite dissolved rapidly.with the increase of annealing time and temperature,the 301L slab solids the?ferrite content decreases from 12%to 0.7%.The higher the temperature,the morphology of the equilibrium?ferrite at the nodes gradually spheroidizes,and the grain size decreases to 2³?m,which can reduce the additional stress at the?/?interface.conducive to rolling.at1210?,the dissolution parameter is 0.26,the diffusion coefficient is 4.87x10^-1010 cm²/s,and the activation energy Q=6.86KJ/mol.the change in grain size of?ferrite is related to the diffusion of Ni element,and it is proportional to the annealing time t^1/2with time.