Effect Of Heat Treatment On Microstructure And Property Of Low Carbon Si-Mn TRIP Steel Of Bolt

Through finite element simulation analysis, we verify the larger stress of the boltposition and the fault location in actual working condition under the different action oftensile stress.At the same time, according to the current main bolt support theory,it putsforward the higher request with the higher strength and the higher elongation.This paper analyzes mechanical properties, microstructure, the tensile fracture andimpact fracture by tensile, impact, hardness, microstructure observation X ray diffractionand scanning electron microscope (SEM) under the different heat temperature, isothermaltemperature and isothermal time for the main components0.25C-1.35Si-1.71Mn steel.The experimental result show that it got the best overall performance σb×δ1025377.6MPa×%, when the samples are heated at800℃for30min, being isothermal at380℃for20min and cooling to room temperature. The tensile strength σband theelongation δ10are816MPa and31.3%respectively.The impact and hardness are51J/cm2and242HB. After heat treatment process, we can get the ferrite, bainite and retainedaustenite organization.When heat temperature increasing, the volume fraction of retainedaustenite increases. Once isothermal temperature increasing the volume fraction of retainedaustenite increases first and then decreases.With increasing isothermal time, the volumefraction of retained austenite increases first and then decreases.When the samples areisothermal at380℃for20min, the volume of bainite is the maximum and the volumefraction of retained austenite is also maximum14.07%.When matrix exists a certainamount of retained austenite, the stress and strain induce TRIP effect.the more the volumefraction of retained austenite is, the better the comprehensive mechanics performance ofthe material is.Through tensile fracture of the macroscopic and microscopic, the fracturestyle of the steel is the ductile fracture in this test method.The microscopic mechanism ismicroporous gathering fracture and the fracture process is influenced by the volumefraction of retained austenite and the carbon content of austenite and so on.Through marketresearch, this experiment steel is produced the bolt for cost of steel and mainly used bolt incontrast with the mechanical properties.The experimental results show that the test of low carbon Si-Mn TRIP steel for boltnot only has high mechanical properties, but also low production cost, simple productiontechnology. It has important guiding significance for the development and application ofhigh strength and high plasticity bolt.