Investigation Of Bainiting Of Cr13-Type Martensite Stainless Steel

The conventional Cr13 martensitic stainless steel has high corrosion resistance, high strength and hardness, but it is brittle, easy to produce cracks and fracture. And the bainite has the equivalent strength and hardness of martensite, better toughness, which indicates that the comprehensive mechanical properties of lower bainite is good. When strength, hardness and wear resistance are guaranteed, to make the using state of martensite stainless steel mainly the bainite, is the key to solve the problem.Based on 3Crl3 and 4 Crl3 as tested steel, finding the best heat treatment process of Cr13-type stainless steel, including the time and temperature of the isothermal quenching. By changing the heat treatment conditions, the Cr13-type stainless steel with good comprehensive mechanical properties was obtained. According to the current composition of the alloys, when improving technological process, the comprehensive mechanical properties of Cr13 stainless steel was greatly improved, especially the plasticity index. After adding alloying elements of Al, Co, the performance of Cr13-type bainite stainless steel can be further promoted, and decrease the bainite isothermal quenching time, meeting actual industrial application, so as to save the cost, improve the quality and competitiveness of Cr13 stainless steel.After the ordinary quenching treatment and the isothermal quenching treatments from 180℃ to 280℃, the microstructure observations and mechanical performance tests of the 3Cr13 and 4Cr13 samples are carried out. With the increase of isothermal temperature, the martensite in 3Cr13 and 4Cr13 samples gradually disappear, the amount of bainite group increase, beginning from 220℃ and 240℃ respectively, almost all become bainite. With the increase of isothermal quenching temperature, the hardness of 3Cr13 and 4Cr13 samples tend to reduce at first and then go up; the hardness of the samples at 280℃ is almost equal to samples after common quenching, but the change is not obvious. What’s more, the plasticity and toughness of the samples after isothermal quenching heat treatment are better than ordinary quenching samples, and the strength was also good. After adding Al and Co into 3Cr13 and 4Cr13 matrix, and reducing isothermal time, strength, hardness and toughness index were all maintained at a high level, which achieved the expected goal of saving time and cost. Further immersion experiments show that, compared with the traditional quenched and tempered samples, the corrosion rate of the samples after isothermal quenching is slightly increased, making the corrosion resistance of the samples still meet the requirements.The experiment shows that, comparing with the martensite stainless steel after quenching and tempering that after isothermal quenching have more excellent comprehensive mechanical properties. Isothermal quenching is fully capable of becoming a good heat treatment method to make the bainite stainless steel possible.