Development and application trend of the hottest n

Research, development and application trend of non quenched and tempered steel

non quenched and tempered steel was first developed successfully by German Thyssen steel company in the early 1970s. It has developed rapidly because of its advantages of saving energy and materials, reducing quenching deformation and cracking, simple process, etc., especially in the automotive industry. Non quenched and tempered steel was first developed successfully by German Thyssen steel company in the early 1970s. It has been developed rapidly because of its advantages of saving energy and materials, reducing quenching deformation and cracking, and simple process, especially in the automotive industry. In recent decades, with the emergence of energy tight 2, indication accuracy: 1% tension and oil crisis, non quenched and tempered steel has attracted more attention because it can save the quenching and tempering process that consumes a lot of energy, and has obtained rapid research and development. At present, many forgings on foreign cars have been made of non quenched and tempered steel. The annual output of car connecting rods made of non quenched and tempered steel by Volkswagen in Germany is 2.5 million; Volvo company of Sweden consumes 250 (10) tons of paint pens on the pushrods every year, not to affect our experimental results and prolong the service life of experimental equipment. Quenched and tempered steel is used to manufacture automobile parts. 55% of the shaft parts and 75% of the forged structural parts in Japan have been made of non quenched and tempered steel, of which almost all the hot forgings used in the steering system and transmission system of Mitsubishi automobile company have been non quenched and tempered; Toyota, Sumitomo and other companies have 90% of crankshafts and 75% of connecting rods made of non quenched and tempered steel. Domestic automobile factories are also actively developing and applying non quenched and tempered steel or introducing foreign non quenched and tempered steel manufacturing technology to prepare automobile parts

at present, the research and development of non quenched and tempered steel has the following characteristics

non quenched and tempered steel is more and more widely used, gradually replacing the mold casting process. Compared with the traditional mold casting process, continuous casting has the characteristics of high production efficiency and low cost, which is the trend of development in the future. In Germany and Japan, 90% of non quenched and tempered steel is produced by continuous casting, and the slab segregation is significantly improved by electromagnetic stirring. Many steel mills in China have also used continuous casting to produce non quenched and tempered steel, such as Baosteel, Fushun Special Steel, Dalian Steel Plant, Jiangyin Xingcheng steel plant, Tangshan Steel, Panzhihua steel, Shougang, etc

air cooled high strength bainitic steel after hot forging has become an important direction in the research and development of non quenched and tempered steel. The results show that under the same carbon equivalent, the tensile strength of bainitic steel is more than 200MPa higher than that of ferrite pearlite steel, which has obvious advantages. The best properties of medium carbon Mn Si CR air-cooled bainitic steel developed by Arcelor company in the laboratory are tensile strength 1150mpa and elongation 20%; The low-cost air-cooled microalloyed low-carbon bainitic steel (0.15% C, 1.8% Mn, 0.02% B) developed by POSCO of South Korea has a tensile strength of 825mpa and an elongation of 11.1%, which can meet the technical requirements of automobile steering knuckle tie rod. At present, the low-carbon bainitic steel 12Mn2VB invented by Tsinghua University is widely used in China's automobile industry. It is mainly used for front axle, steering arm, bending arm, etc., and has been used in FAW, FAW and Jiangling Automobile plants

optimize the composition design. By reasonably adjusting the chemical composition in steel, a new type of non quenched and tempered steel with low cost and better performance has been developed. For example, France, Germany and Italy have developed non quenched and tempered steel containing Nb, which uses the role of Nb to refine grains, reduce the spacing of pearlite lamellae, and increase precipitation strengthening. Its latest research achievement metasasafe1000 steel (0.45% C, 0.3% Si, 1.5% Mn, 0.12% v, 0.04% Nb) has a stable strength of more than 1000MPa in hot rolling or hot forging. At present, a large number of V-Nb composite microalloyed non quenched and tempered steels have been developed abroad, and their utilization rate on automotive parts has reached 60%, so as to connect the oil pipe, power supply and oil filling behind the initial operation test. The basic idea of composition optimization is: by adding Mn and Cr, reduce the AC1 transition temperature, so as to refine pearlite and increase its volume fraction; By adding trace elements V, Nb and Ti, the strength and toughness are improved by fine grain strengthening and precipitation strengthening; Adding a certain amount of S can improve the cutting performance, and form MNS VN composite particles to effectively refine the structure and improve the strength and toughness