The Compasite Strengthen-Toughene Process And Its Microstructural Of Drawing Die Of Muffler Plate

This paper analyzed the drawing die working conditions,failure modes.Analysis shows that those kind of die not only requires that the surface has a high wear resistance,high hardness and nocorrosice,and whose substrate has good strength and toughness.Choosing 9SiCr steel make die,was preprocessed firstly by refining carbide and strengthed-toughnessed by isothermal quenching,and then which was surface hardened by solid boride method and electrospark surface strengthening.In the last optimizing two composite strengthened -toughened to offer industrial production.Observing metallographs by SEM and metallographic microscope,testing hardness by rockwell tester and micro hardness tester when 9SiCr steel was treated by above-mentioned.and obtain the following conclusions:(1) There is obviously crassitude,closed angle carbide in the Pearlite in the last two when 9SiCr steel is treated through isothermal spheroidizing,cyclic spheroidizing, high temperature solid solution.But the carbide is small,fine, homogeneous and the effect of spheroidizing is better in the Pearlite, when the temperature of solid solution is 1050℃,and then tempered at 680℃to 9SiCr steel.(2) The 9SiCr steel sample can obtain the duplex structure which is composed of lower bainite+martensite+little carbide whose Rockwell hardness is 63.6HRC after it was treated by isothermal quenching whose process is 860℃×30min+200℃×8min→Hydrocooling.(3) The thickness is 54.8μm and the microhardness is 1410Hv of borided layer of 9SiCr steel sample,when 9SiCr steel sample is treated by boriding whose prodess is 880℃×4h.(4) It can obtain lower bainite+martensite+little carbide when the 9SiCr steel was treated by processing of compasite strengthen-toughene which is→1050℃solid solution + tempered at 680℃→880℃×4h(boronizing)→isothermal quenching (860℃×30min+200℃×8min→hydrocooling)in the matrix,whose Rockwell hardness is above 63HRC.Not only the strengthen layer which is produced by boronizing whose thickness is 52.5μm,hardness is 1440Hv,the matrix have good strength and toughness too, The hardness profile between matrix and strengthen layer is gently.(5) Not only can it obtain the strengthen layer whose thickness is 43.5μm, hardnessis 1395Hv and good surface quality,the matrix have not too much deformation and still keep good strength and toughness,when 9SiCr steel was treated by processing which is 860℃×30min+200℃×8min→hydrocoolingand then was compasite strengthened-toughened by twice electrospark process whose power grade is 6×2 min/cm2+ power grade is 1×1min/cm2.At the same time, The hardness profile between matrix and strengthen layer is gently.