Connection Of Microstructures Parameter And Mechanical Properties And Work Hardening Of Pearlite Steel Under The Super-Cooling Technology

In this paper, the high carbon steel of SWRS82 B had been treated as the research object, first using the expansion method and metallographic method to draw the experiment SWRS82 B pearlite steel isothermal transformation TTT curve, to study the kinetics of pearlite transformation related content; Secondly, combining with SWRS82 B pearlite steel isothermal transformation TTT and continuous cooling CCT curve, set the contrast experiment, DIL-805A/D dynamic and static transformation instrument used for carrying out the accurate heat treatment, studied the feasibility of the super-cooling technology; Finally, the use of salt bath isothermal process to replace the traditional lead bath, salt bath super-cooling technology was carried out, by OM, SEM and TEM morphology observation, MTS Landmark tensile properties test, Image measurement tool software microstructure(grain) size, Origin software drawing analysis, linear regression analysis method of SPSS software and so on, the change of pearlite microstructure and mechanical properties were researched deeply and systematically under different super-cooling technology parameters, and the empirical equation of pearlite microstructure parameter and mechanical properties and work hardening index were established, and analyzed the contact between, get the following main conclusions:(1) Compared with the traditional isothermal treatment, the super-cooling technology can significantly increase the rate of pearl shape nuclear, when an increase of 250(instantaneous) super-cooling degree, pearlite(nucleation) volume increased by nearly 50%, facts proved that the super-cooling technology is feasible.(2) The lower the super-cooling temperature is, the bigger undercooling degree and instantaneous nucleation rate are, the pearlite colony is refined significantly and nanoscale cementites are easy to appear. With super-cooling time increases, both the colony size and interlamellar spacing are increased, and the dislocation density of two-phase interface in ferrite and cementite is dropt. Further extension of time, the size of pearlite colony and interlamellar spacing is diminished, the continuity of substructure is improved and the bainites organization are appeared.(3) When the super-cooling temperature at 300? and the super-cooling time for 3s, the size of pearlite colony and the interlamellar spacing are the smallest, respectively 2.39 um and 62.11 nm, and there is large number of nanoscale cementites of size range 55 nm. The mechanical properties is mainly determined by interlamellar spacing and colony size, But also by the nanoscale cementites, dislocation, the continuity and the bainite structure, etc.(4) When the supercooling temperature at 300?,the substructure of pearlite is the smallest,and the test specimen has a better comprehensive mechanical performance.Take into account the fully pearlite steel is best raw material of the cold drawing wire steel and eliminate the influence of the mixed phase organization such as the bainite, and in combination with actual production application, the optimal process parameters for 300?- 3s-550?.(5) by using SPSS software pluralistic regression fitting, with the result of the experiment established the pearlite microstructure parameter(grain size) and the mechanical properties and strain hardening index empirical equation, the tensile strength and deformation hardening index was mainly affected by interlamellar spacing, at the same time are greatly influenced by group size, almost not influenced by grain size, and reduction of area is mainly affected by colony size, less affected by the grain size, basic is not affected by interlamellar spacing.