Study on Control Rolling and Control Cooling ( CRCC) of 60Si2Mn Spring Steel Wire Rod Applied for Automatic Industry

摘要

60Si2MnA spring steel wire is mainly used for suspension springs, which is used in car manufacture and needs a good cold workability in the production of spring to present brittle fracture. By measuring the undercooled austenits transformation curve(CCT)in different deformation temperatures of 950C , 900C and 850C , we find that with the decrease of deformation temperature and the acceleration of cooling rate,the proportion of proeutectoid ferrite in microstructure is decreased,interlamellar pearlite spacing reduce gradually and the proportion of sorbite increase proportionately. Combining dynamic CCT curve and equipment capacity the wire production line process is adjusted by reducing the beginning temperature an increasing the amount of cooling water to control the final rolling temperature at 850C and grains refinement. In forepart of the Stelmor cooling line, through the speed adjustment of roller,fan opening and air volume controlling,thermal insulation cover opening and other means to control the cooling rate 040C/s. Spring wires are quickly cooled to 700C and then cooled with a slow cooling rate at the rear end ol Stelmor cooling line. Inis process can make phase tran storm all on through the eutectoid ferrite phase transformation aone quickly and prevent the semi-reticulate ferrite formation. The average of thickness of Lamella Pearlite reduced from 0. 30um to 0. 15um and the average rate of reduction of area reduce from 31% to 39. 7%. After half a year' s process stability and mass production, cold workability of spring wire has been greatly improved and brittle failure never occurs in work process.