Research On Hign Carbon-medium Chromium Steel For Grinding Rod

According to the service conditions and demands of grinding rod performence,three kind of test steels were designed in this paper.The effect of heat treatment process on microstructures and properties of test steels was studied by the way of SEM,XRD,etc.Meanwhile,a series of research was carried out on the Fe-Cr-C ternary system phase equilibriumm calculation.The variation of composition of austenite and M₇C₃ carbides with temperature was calculated by means of programming with matlab language within two phases zone of the test steels.Research showed that:?1?The microstructure of high carbon medium chromium steel could be remarkably refined by large forging ratio?forging ratio>4?,austenite gain size level of test steel was increased 5 level above when forging ratio was changed from 1.2 to 4and the toughness of the test steel was increased significantly.?2?2#test steel with content of higher chromium?wt.6.7%?and lower molybdenum?wt.0.35%?had better hardenability therefore?100mm test steel bar was characteristized with the microstructure of martensite+little retained austenite+carbide,and the high hardness was higher than 57HRC after austenizing?880??following by air-cooling.Compared with 2#test steel,1#test steel with low content of chromium?wt.3%?,?100mm test steel was with the microstructure of a large amount of perlite and bainite,and the hardness was about 42⁵2HRC after air-cooling.However 3#test steel just with high chromiun?wt.6.3%?,it had worse hardenability leading to its microstructure with perlite dominantly and hardness lower than 42HRC after treated.?3?The refinement of martensite and the nanoscale M₇C₃ carbide distributed uniformly in matrix had been observed,with the hardness greater about 58HRC in 2#test steel after treated by the improved heat treatment process.Using the same process of 1#,the refinement of martensite was observed on the condition of forced-air and added-water cooling,and the hardness as high as 61HRC.Whereas 3#after treated by added-water and forced-air cooling,less martensite was observed with lower hardness due to worse hardenability.?4?1#and 2#test steel was with high tempering resistance therefore the hardness can be reached 53HRC,and impact energy was as high as 64J?1#?and 96J?2#?as tempering temperature decreased to 300?.?5?Wear resistance test showed that,the wearability of 2#was better than 1#.?6?The variation of carbide quantity and the composition of austenitic matrix had been analysised quantitatively with the temperature through the thermodynamics analysis of the two phase equilibrium?austenite+M7C3?in Fe-Cr-C ternary system.The 1#and 2#test steel could obtain fine and uniform microstructures and well mechanical properties as well as high wear resistance under the condition of slow cooling.The wear resistance was twice of current grinding rod,so this new type of steel for grinding rod production has an important practical significance.