The Effect Of Heat Treatment On Microstructure And Mechanical Properties Of Wear-resistant Steel Ball

With the continuous development of grinding industry, puts forward the higher comprehensive performance requirements to grinding ball.The research object of this paper are B2 steel Φ120mm forged ball and 269 B steel Φ80mm rolling ball. The research mainly aimed at the cracking and broken phenomenon of two kinds of grinding balls,explore the cracking reasons and optimize the performance of grinding ball with heat treatment process.Using matlab software to simulate quenching temperature field of the quenching specimen and grinding ball,and through the contrast test and material analysis method to explore the influence of different heat treatment parameters on the microstructure and properties of the grinding ball.Research show that:(1) for B2 steel Φ120mm forged ball, there are two reasons for early broken in using.On the one hand,forging heating temperature as high as 1100 ℃ cause original austenitic grain bulky and reduce the toughness of the grinding ball.On the other hand,the internal temperature is higher than surface temperature of grinding ball when quenching,resulting the organization from surface to center change quickly,especially on the 20mm~30mm from surface of the ball,hardness from 62.5HRC steeply drop to47 HRC,increased the cracking tendency of here.(2)For 269 B steel Φ80mm rolling ball, the reason of crack after quenching is quenching temperature higher than 720 ℃,water-cooled70 s the temperature of the center higher than Ms.Causing the martensitic transformation of center did not occur in water cooling phase, this increase the asynchronism of martensitic transformation.And 269 B steel has center porosity,combined two aspects makes the ball cracking under the action of stress.According to the results of this study, the B2 steel grinding ball by reheated quenching process can significantly improve the crushing resistance ability in using,which is air cooling to 200 ℃ and put into 820 ℃ resistance furnace for heat preservation of three hours,then water cooled two minutes and get on low temperature tempering.Result show that,on the 20mm~30mm from surface of the ball,hardness from 57 HRC drop to50 HRC,falling ball number more than 3000 times,meet the performance requirements. 269 B steel grinding ball are air cooling after rolling to 700 ℃ ~ 720 ℃, then cooling 70 s in45 ℃ water and carry on the 200 ℃ low temperature tempering.The center hardness of theball can reach 55 HRC and without cracking,comprehensive performance meets the requirement.