Ultra High Strength Maraging Stainless Steel Tenacity Technology Research

OOCr11Ni11MoTi is Co-free high-strength maraging stainless steel strengthened by Ti. Through solution treatment the steel acquires martensite, and it is additionally strengthened by the precipitation of intermetallic in the martensite after aging, which is similar to the strengthen mechanism of traditional maraging steel. However, compared to the traditional maraging steel the strengthening and toughening mechanisms of maraging stainless steel are more complicated. Until now, the research of the alloying and improving strength and toughness is not enough. Therefore, in this paper the following three aspects were investigated:â‘ The effect of solution treatment on structure inheritance, the solution of excess-phase and the strength-toughness of the steel.â‘¡The effect of compositions of Cr and Ni on microstructures and mechanical properties.â‘¢The effect of a combination of cold rolling deformation and aging on mechanical properties was investigated to explore new ways to raise their strength.The influence of the contents of Cr and Ni on the mechanical properties of OOCr11Ni11MoTi maraging stainless steel was investigated. The results have shown that the impact toughness is the most sensitive to the changes of the contents of Cr and Ni. Namely, the sensitivity to aging temperature of impact toughness drops with an increase in concentrations of Cr and Ni. To sum up, with an increase in concentrations of Cr and Ni there is a change in the aging behavior of the steel due to the formation adequate retained austenite after the solution treatment. In addition, Cr and Ni, especially Cr, could lower the formation temperature of reversed austenite and increase the overaging inclination.The effect of solution treated temperature on strength-toughness of OOCr11Ni11MoTi maraging stainless steel was studied. The results have shown that many complex processes took place in solution treatment, including non-diffusion reverse α’â†'γ transformation in the austenite, recovery, recrystallization, the growth of grain, and the precipitation/solution of excess-phase. The changes of austenite have a direct impact on morphology and substructure of martensite, the amount of reversed austenite and strength-toughness of the steel.OOCr11Ni11MoTi maraging stainless steel could be processed into strips by cold rolling deformation after solution treatment. There was a sharp rise in yield and tensile strength after whether underaging, peakaging or overaging. The observations with regard to fractography have shown that the fracture occurred by microvoid coalescence after standard aging or over aging. This demonstrates that the strip still posses high toughness. The result demonstrated that it is principally possible to further raise the strength of OOCr11Ni11MoTi maraging stainless steel by this combination technology.