| The environmental conditions are more and more strict to the properties of the structural steel.Therefore,the demand for steel materials with high comprehensive performance is increasing.Uniform fine grain of ultrafine grained materials and nanocrystalline materials have more excellent performance than the coarse grained material.By conducting SEM,EBSD and tensile experiment on different medium carbon steel and industrial pure iron after enduring warm rolling at 600? and heat treatment,we studied their organization state's influence on the mechanical properties.Experimental results are as follows:The original microstructure of ferrite + pearlite medium carbon steel was rolled with the reduction rates of 80%,85% and 90%,respectively.The ferrite grain of sample that was rolled at the reduction rate of 85% and then holded in 650? for 4 h was completely equiaxed and the grain size was 0.73 ?m.The hardness of samples when it was annealed4 h at 650?,reduce to 163.833 HV,the yield strength reduce to 413 MPa,the yield ratio is 0.7634,the total elongation increase up to 17.78%.The average grain size of ferrite is 0.65 ?m of the medium carbon martensite steel after the reduction rate is 85% and anneals for 4 h at 650?.Simultaneously,when the steel anneals 4 h at 650?,the hardness reduces to 165.167 HV,the yield strength and tensile strength reduce to 529 MPa and 607 MPa respectively,the yield ratio is 0.8715,the total elongation increase up to 14.55%?The average ferrite grain size of industrial pure iron that was rolled at the reduction rate of 85% was 35.03 ?m.And then when the samples holding for 5 mins in 650?,the gain size is 13.2 ?m.Annealed 5 mins,the hardness is reduced to 96.517 HV,the tensile strength decreases to 334 MPa,the yield ratio is 0.7186,and the total elongation increases to 24.88%.The tensile fracture surface of the three kinds of steel had dimples with different sizes,which belongs to the ductile fracture in ductile fracture.Figure52;Table9;Reference 61... |
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