The Optimization Of Composition And Heat Treatment Process Of Bogie Steel

As the requirement of transportation railway in increasing speed and heavy load in the new period,the existing bogie steel has been unable to meet the requirement on the performance in our country,and the existing high performance alloy cast steel means high production costs,so it is necessary to develop a new bogie steel with high performance and reduce production costs.During this subject,we successfully developed a new cast steel and formulated the best heat-treatment temperature of cast steel by studying the influences of the contents of C,Mn,Cr and Ni and heating temperature on the microstructure and mechanical properties of cast steel based on the composition of B+ steel in north American AAR standard grade,and we established the mathematical model between the composition,microstructure and performance of cast steel.The properties of the cast steel were close to that of grade C steel;On this promise,we reduced the cost of production effectively.The results show that,with the increase of Mn content in cast steel,the content of pearlite is elevated,and the spacing decreasing,and the strength of the cast steel is elevated,but plastic toughness decreasing.When the content of Mn is 0.9 wt.%,the cast steel has a best combination of strong toughness.The element of Ni in the cast steel can effectively refine the matrix organization and strengthen the performance of cast steel;But when the content of Ni in cast steel is more than 0.3 wt.%,the strengthening effect on properties of cast steel is not obvious with increasing of Ni content.With the increasing content of Cr in cast steel,the content of pearlite and the strength and hardness of the cast steel are increased,and when the content of Cr is 0.3 wt.%,the best combination of strong toughness of cast steel is reached.With the increase of C content in cast steel,strength,hardness and content of pearlite of cast steel are increased.When the content of C increases from 0.25 wt.% to 0.31 wt.%,tensile strength of cast steelis increased from 545 MPa to 616 MPa,but sharply destroy toughness of cast steel and elongation rate reduces from 31.4 % down to 24.8 %;the final components of cast steel is that: content of C is 0.27 wt.%,Mo is 0.1 wt.%,Si is0.4 wt.%,Mn is 0.9 wt.%,Cr is 0.3 wt.% and Ni is 0.3 wt.%,At this point,the carbon equivalent of cast steel is 0.56(CE = 0.56),and can meet the requirements in welding performance of cast steel.Making heat treatment in different heating temperature of cast steel,the results show that: with the increase of quenching heating temperature,the strength,hardness and impact absorption function of the cast steel are lower after rising first,elongation is almost the same;When the normalizing heating temperature is 900 ?,the strength of the cast steel is highest,strong toughness combination achieves the best.The tensile strength of the cast steel is 652.3 MPa,yield strength is 438.2 MPa,the elongation is 24.3 %,and sharp v-notch specimen at-18 ? impact absorption energy is 34.3 J in this time.The properties of the cast steel are close to that of grade C steel.