.12% Cr Steel Forging Crack Theory And Experimental Research

Most of large forings are the key components of machinery and equipment. In particular, there are stringent requirements for quality for large forings, which reflected in quality mainly: excellent metallurgical quality, dense uniform organizational Structure, good dimensional accuracy, qualified mechanical properties, and defects in as little as possible. We must find ways to avoid defects in the production, and propose appropriate solutions. Crack is the hot and difficult issue in the forging industry, and is the outstanding problem that affect the development of forging production and forging quality. In this paper, the ultimate goal is to find the quantitative criteria to predict the time and location of the fracture to guide production. In this paper, in view of the problem of supercritical rotor steel 12%Cr easy to crack, the research was unfolded, in order to avoid cracks, optimize organization and improve overall performance, by high-temperature diffusion experiments, Deform numerical simulation, thermal simulation tension and upsetting test.We must search for the major impact factors of crack formation of 12%Cr to sum up the conditions and methods that control crack extension by research the factors of forging cracks. It carries on the observation of metallographical through the high temperature diffusion experiment, and summarizes the dissolution regularity of the second phase and the variation regularity of sonims. We established basic parameters model of 12%Cr, and came to high temperature plastic law of 12%Cr. The elongation and surface shrinkage of 12%Cr steel increased monotonously, that is, the plastic increased with the increase of test temperature when the deformation temperature is between 900℃and 1100℃. The elongation and surface shrinkage of 12%Cr steel reduced, that is, the plastic reduced with the increase of test temperature when the deformation temperature is between1100℃and 1200℃. The surface shrinkage and fracture strain increased with the increase of strain rate and temperature. But the gap of surface shrinkage and fracture strain is small caused by strain rate in the lower temperature range. The gap of surface shrinkage and fracture strain is large caused by strain rate in the high temperature range. The starting point of necking can be used as hole nucleation starting point. Breaking strain can be used as the hollow polymer strain. In view of the 12%Cr steel, we can get the damage threshold of the ductile fracture criterion; and its variation with the temperature; and the predicted results of various ductile fracture criterion. We have also done the physical verification experiments in order to verify the accuracy of the conclusions of prediction, and select the most suitable ductile fracture criterion for this material(Brozzo criterion), which can be used to guide the actual production.