Research On Water Spray Quenching Equipment&Technology Of Large-size Stainless Plastic Mould Steel Block

In recent years，with the development of manufacturing industry，the demandof mould is growing.So the varieties and specifications of mould steel are moreand more needed，quality requirement of heat treatment for it is more strictly.In thecondition of present heat treatment technology both in and abroad，the heattreatment of medium and small-size high alloy mould steel block with thelargest-size of200mm was main quenched by air or oil.Deformation and crackwere easily caused in block when quenched by water though it was clean andenvironment friendly，so it had not been adopted in actual project.However，thelarger differences in microstructurals and properties for mould steel block wereformed when quenched by air or oil because of slow cooling speed.Morever，quenching oil was easy to burn and pose a safety hazard，production cost was surelyincreased with the consumption of oil.Researching and developing low-carbongreen heat treatment equipment and process in large-size for high alloy mould steelblock with the smallest-size of200mm while there is little deformation or crack，microstructural and hardness distribution are even，quenching cooling speed isstepless adjustable between water spray cooling and air cooling is imminent.In this thesis，a large spray quenching device was conceived and selfmadeaccording to the demand and technology characteristic of heat treatment forlarge-size plastic mould steel block(main martensitic steel).The device which hadfour rows of nozzles for water spray quenching to block met the basic action andcooling requirements of spray quenching for large-size high alloy mould steelblock.Bending distortion，crack and other defects were avoided to appear inblock.The production process was achieved with clean，low carbon and nopollution.4Cr13large-size block was used as the research object for hot testing to selfmade spray quenching device，ralating temperature was measured.Quenchingtemperature field finite element calculation model of large-size block wasestablished in the way of heat transfer theory on that basis.It was confirmed thatthe heat transfer coefficient of spray quenching was0.6times of water immersionquenching when working pressure was0.3MPa and the flow was100m3/h throughthe way of combining finite element simulation with trial-error method.The temperature field distribution and cooling curve of key points in sprayquenching process of five specifications4Cr13blocks were simulated by usingquenching heat transfer coefficient getted from finite element analysis. The leastcooling time was respectively confirmed while pearlite and non-hardenedmicrostructurals were not appeared in the centre of various specifications blockscombining with CCT curve of4Cr13.The specific quenching process was spraycoolingâ†'air coolingâ†'spray coolingâ†'air cooling，accumulative total water spraytime was controlled.Adjusting quenching cooling speed in a larger range throughintermittent water spray could be realized in this device，quenching crack andbending deformation were avoided at the same time.The largest-size block of4Cr13was dissected to inspection for quenching results.Inspections showed thatthe hardness difference for block between surface and centre was less than2HRC inspray quenching，metallographic microstructural was tempering martensite anddistribution was normal which complied with the pre-hardening requirements forplastic mould steel.The way of spray quenching heat treatment and technology for large-sizestainless mould steel block was firstly put forward in this thesis.Cooling speed ofblock was adjustable in the process of spray quenching， and there wasnon-pollution.Bending deformation was not appeared in blocks，microstructuraland hardness distribution were even after quenching.Poor microstructuralperformance，deformation and crack defects could be avoided on mould steel block when quenched by air，oil or water.Spray quenching has higher promotional value.