Effect of rolling process on microstructure and properties of chrome-molybdenum steel rebar
In order to solve the problem of rolling process parameters setting of chrome-molybdenum steel rebar,the effects of heating temperature,deformation temperature,temperature on cooling bed and cooling rate on the micro-structure and mechanical properties of chrome-molybdenum steel rebar were studied by high temperature confocal microscope,Gleeble thermal simulator,metallographic microscope,tensile testing machine,Vickers hardness tester and other equipment,and combined with small-size sample tensile test.The continuous cooling phase change behav-ior of test steel was analyzed,and the CCT(Continuous Cooling Transformation)curve of test steel was measured.The trial production of 20 mm diameter chrome-molybdenum steel rebar was completed in the industrial production line.The results show that,during the continuous cooling of test steel undercooled austenite,the ferrite and bainite phase transitions mainly occur.With the increase of cooling rate,the ferrite content decreases,while the bainite content increases,and the hardness increases.Rolling process parameters affect the structure type,grain size and proportion of steel rebar,and then affect the strength and plasticity of steel rebar.With heating temperature of 1 150-1 200 ℃,hot rolling temperature of(1 020±10)℃,cold bed temperature of 850-900 ℃,and cooling rate of 1 ℃/s,the produced steel rebars exhibit a microstructure of ferrite and bainite,of which the proportion of ferrite is 48.56％,the average particle size is 18.34 μm,and the yield strength is greater than 430 MPa,the tensile strength is greater than 630 MPa,the elongation after fracture is more than 20％,and the product of strength and elongation is greater than 12 GPa·％.The results provide data support for the industrialization of chrome-molybdenum corro-sion resistant steel bar.
rolling processchrome-molybdenum steel rebarferritebainiteproduct of strength and elongation
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