The Research On The Organization And Property Of The 960MPa Non-quenching&Tempering High Strength Steel

This study based on micro-alloying and controlled rolling technology of controlled cooling,with phase transformation strengthening as the main strengthening mechanism,martensite and bainite at low temperature for ideal organization,the development of a kind of strength level of 960MPa grade of non-quenched and tempered carbon alloy steel.High strength steel should have enough plastic and toughness in some degree,at the same time,and we should ensure that the material has a certain application prospect.By S960&1#component system,researchers take the martensite as the main organization of the material and produce a kind of new material whose yield strength more than 900MPa grade and have good plastic toughness.By S960&2#?S960&3#?S960&4#component system,researchers take the Low bainite as the main organization of the material and produce a kind of new material whose yield strength more than 800MPa.Research shows that in the present alloy system,the material whose main organization is the low bainite is unable to guarantee the materials has high strength and good plastic toughness at the same time.In order to ensure the materials has a good comprehensive performance,we should optimize the composition system.In the study,researchers through the phase change instrument experiment get the main phase transition point,mapped the CCT curve,design rolling plan;Through the Thermo-Calc software,and we know precipitated phase at different temperatures;Through metallographic microscope,scanning electron microscope and electron probe,we analyze the identity of the microstructure;Using Klemms corrosive liquid to analyze the residual austenite;Through the tensile,impact pendulum experiment to test the identity of the mechanical properties of the experimental materials,and analyze the parameters such as finishing,tempering,coiling temperature on the properties of ceramic materials;By scanning electron microscope(SEM),we analyze the impact fracture surface,and study the impact of the finish rolling and coiling temperature on DBTT;Through the analysis of the composition,we study the impact of the Mo?Cr alloy elements on the properties of experimental materials.Finding are as folllows:For S960&1#composition system,with the improvement of finish rolling,deformation zone gradually disappear in the organization,and the strength of materials decrease,impact toughness increase after lower first.when the finishing temperature is 890?,the toughness of materials is the best and DBTT<-40?;For S960&2#?S960&3#?S960&4#component system,as the coiling temperature increase,the increase of granular bainite,grain anisotropy is no longer obvious,when the finishing temperature is lower,the bainite organization is finer;Raise S960&2#Mo element content in the composition system,material hardness,strength,plasticity and toughness at low temperature will improve;Raise the Cr content of S960&3#composition system,material strength,hardness will be increased,plasticity and toughness at low temperature would be reduced.In a alloy system that the Cr cotent is high,when the temperature dropped to below 400?,the types of precipitated phase will change obviously.By Thermo-Calc we know that the improvement of Mo element content,the content of M7C3 increase;Increase the content of Cr,carbide precipitation increases and the precipitation strengthening effect is enhanced;In order to ensure the material plastic and toughness,we should avoid Cr carbide precipitation excessively.