Effect Of Ni Content On Strength Plasticity Of High Strength Wear Resistant Steel

Aiming at 20Si-Mn-Cr-Ni-Mo high strength wear-resistant steel,in order to find out the best alloy element ratio and the best heat treatment process,in the experimental process,through the relationship between the microstructure and the macro mechanical properties,the experimental research on different heat treatment processes was carried out,the microstructure was observed,and the macro properties were measured,so as to determine the optimal heat treatment process temperature and adjust the temperature Through the observation of microstructure and the test of mechanical properties,the relationship between Ni content and properties was explored,and the best Ni content was determined.The test contents and conclusions are as followsThe test steel was melted in 30 kg vacuum induction furnace,ingot cast and forged,and the column with length and width of 30 mm was obtained.After hardness reduction annealing,the samples were cut into heat treatment samples.The test steel was austenitized at 950 ? and then quenched by PAG,and then tempered at 220 ?,240 ?,260 ?,280 ?,300 ? and 320 ? for 3 h.The results show that when the tempering temperature is 260 ?,the test steel has the best comprehensive mechanical properties,with impact value of Akv 78.9J,hardness of 43.8HRC,tensile strength of1349.9MPa,yield strength of 1282.4MPa,elongation after fracture of 11.5% and reduction of area of 54.6%.Through the observation of microstructure and fracture scanning,it is found that most of the microstructure is lath martensite with special fracture characteristics The fracture is ductile.The composition of Ni in the test steel is adjusted and divided into six kinds.The Ni content is 0.2%,0.5%,0.8%,1.0%,2.0% and 3.0% respectively.The heat treatment process is still PAG quenching after austenitizing at 950 ? and then tempering and holding.The tempering temperature is fixed at 260 ? and holding time is 3h.The results show that when the Ni content is 1.0%,it has the best comprehensive mechanical properties,such as impact value Akv 74.7J,hardness 43.8HRC,tensile strength1362.4MPa,yield strength 1302.3MPa,elongation after fracture 11.5% and reduction of area 55.7%.It is found that with the increase of Ni content,the lath bundles gradually have directionality,and the lath martensite content increases,and the microstructure is more delicate.However,with the increase of Ni content,the diffusion coefficient of carbon atoms in the steel increases,which leads to the increase of martensite content.At this time,the content of retained austenite also increases,so the strength of the steel decreases.The scanning fracture test shows that all the Ni content is ductile fracture,but with the increase of Ni content,the number of dimples increases obviously and the dimples become deeper gradually,and some equiaxed dimples appear when the Ni content reaches 1.0%.The macro fracture shows that the area of ductile area increases with the increasing of Ni content.It is found that there is a positive correlation between the area of ductile area and impact energy,so the impact value increases.