Exploitation Of New-style Hot Work Die Steel 4Cr2MoWVNi And Its Applicable Studies Of Cummins Connecting Rod Dies

Although traditional hot work die steels such as 5CrNiMo, 4Cr5MoSiV, 4Cr5MoSiVl and 3Cr2MoWVNi are of good mechanical performance in high temperature condition when working, such phenomena as serious hot wear, thermal fatigue, and local deformation occur in condition of temperature higher than 600 degree especially in the area of heat focused, which lead to die failure directly. So we have studied the new-style hot work die material 4Cr2MoWVNi on heat treatment process and mechanical performance aspects in terms of test to learn its effect on hot die-forging presses.After having researched heat treat process's effect on the material, we worked out the optimum heat treat process that is 1000℃ oil quenching and 590℃ twice tempering. Hardness of dies used on presses is recommended to be 42-49 HRC. Quenching microstructure is the mixture of lath martensite, granular carbide and a small quantity of residual austenite. Tempering microstructure is tempering sorbitic pearlite plus granular carbide, and carbide particles are well distributed and small. Its hot stability and toughness are superior compared to H11 steel. Serve life of Cummins connecting rod dies made of the material is enhanced 65 percent more thanHll steel.Another content of the article is to research surface performance of 4Cr2MoWVNi steel after ion nitriding process, and we designed a hot wear testing device specially to do impact simulation test of superficial hot wearability. The result indicates that the optimum ion nitriding process of 4Cr2MoWVNi is 520°C heat preservation plus 18 hours heat preservation time, and corresponding total nitriding layer depth is 0.15~0.20 millimeter. In same conditions, no matter samples are tackled with ion nitriding, wearability of 4Cr2MoWVNi steel is better than that of Hll steel, wear rate declines 50-122 percent. Tackled with ion nitriding, serve life of dies made of whether 4Cr2MoWVNi or HI 1 is enhanced about 50 percent.The last content is to research the effect on Cummins connecting rod dies made of 4Cr2MoWVNi steel, and analyzed failure causation of dies. The result obtained indicates that no matter dies are tackled with ion nitriding, their normal failure styles are all hot wear. Main cracking reason of dies is that serious component segregation and quantities of sulfides exist in microstructure.