Double Vacuum Melting Phase Change,Organization And Properties Of 9315 Steel

This paper,based on the research status of carburizing steel abroad,with a good performance of the alloy carburizing steel SAE9315 steel,to its reference refining furnace 24 different alloy composition test of steel.The melting process,ingot casting,forged again on the tensile test,impact test,and the quenching experiments.Determined the carbon content is 0.15%.According to the experimental results of other alloying elements on the comprehensive performance of 9315 steel plays a very important role,respectively,Cr1.17 Ni3.12 % %,Mo0.13 %,Mn0.51 %,Si0.34 %.Using Thermo Calc software and related database(TCFE3)to calculate the equilibrium phase diagram of steel vertical section.With double vacuum(VIM + VAR)smelting process of refining the steel 9315 experiment.Using the high precision measure the expansion of the different cooling speed curve of inflation,by dilatometric curve result shows that steel Ac1,Ac3,Ms and Mf points,respectively,700 ?,800 ?,400 ?,200 ?.Using metallographic microscope to observe the sample under different cooling rate of the microstructure morphology,determine the organization transformation type(high temperature,the ferrite transformation temperature for the bainite transformation,low temperature zone of martensitic transformation)calculated the change of phase transformation point of different types of organization,and then combined with the microstructure and linear expansion curve plotted SAE9315 CCT curve of steel.Finally,determine the sample under different cooling speed of microhardness verified the reliability of CCT curve.Will impact and tensile test steel blank sample at 920 ? is the fire,after 1 h after different quenching temperature and tempering time,different tempering temperature and tempering heat treatment time,then the tensile test and impact test.The result shows that the strength of the 780 ? quenching hardness is lower;Under 805 ? and 815 ? quenching,the 9315 test of steel strength,hardness,wear resistance,fatigue strength and toughness obviously strongest;Mechanical properties of 825 ? and 850 ? quenching ShiGang variation;With tempering temperature,the material strength rise,when the tempering temperature over 200 ?,tensile strength began to decline,quenching and tempering time impact on the mechanical properties of the weak,according to the results of the experiment to determine 9315 testing system of steel quenching and tempering heat treatment(820 ?)x 1 h + oil cooling,(150 ?-200 ?)x 3 h + air cooling.For practical analysis after carburizing treatment,carburizing layer in the different levels of carbon parts of the organization evolution and performance,based on the chemical composition of 9315 steel smelting in the three different furnace carbon content(0.5%,0.79%,0.93%)of the test steel,respectively corresponding to the 9315 steel carburized after three different carbon concentration in carburized layer,this simulation study organization transformation regularity of 9315 steel carburized layer.To map the 9315 steel carburized layer simulated CCT curve of steel.Determine the microhardness of the sample under different cooling speed.Integrated all the result of basic research,to develop industrial optimization under the condition of heat treatment process scheme to provide important reference basis,to realize the industrialization of the 9315 steel application is of great significance.