The hottest high nitrogen nickel free austenitic s

High nitrogen nickel free austenitic stainless steel

high nitrogen nickel free austenitic stainless steel not only has the advantages of low production cost, green and environmental protection, but also adding nitrogen to austenitic stainless steel gives steel many advantages. Just press the reset key on the main interface to automatically clear the difference in the whole process

high nitrogen nickel free austenitic stainless steel not only has the advantages of low production cost and environmental protection, but also the addition of nitrogen to austenitic stainless steel gives steel many excellent properties

in the past, nickel accounted for 60% - 90% of the cost of austenitic stainless steel. Nickel is very expensive, and nickel resources are very important strategic materials. China is also a country with very poor nickel resources. Using cheap nitrogen instead of precious and scarce nickel to produce Cr-Mn-N high nitrogen nickel free austenitic stainless steel is the most effective method to reduce nickel resource consumption, which is of great significance. Adding 1% n to austenitic stainless steel can replace 6~20% Ni, and the price of element n is only 1/200 of that of element Ni, with a huge price difference. Therefore, the development and production of high nitrogen nickel free austenitic stainless steel has great economic and social benefits

although conventional austenitic stainless steel has good corrosion resistance, Cr23C6 will precipitate on the grain boundary when it is kept warm at 450~850 ℃ or cooled slowly, forming a chromium poor zone in the surrounding matrix, resulting in intergranular corrosion. Intergranular corrosion can be prevented by reducing the carbon content in steel and adding Ti and Nb to steel, but this kind of steel is easy to dissolve tic or NBC due to high welding temperature during welding, forming knife shaped corrosion. Moreover, Ti and Nb are precious metals, and it is not economical to produce austenitic Jinan gold assay copper wire torsion test stainless steel. Therefore, ultra-low carbon austenitic stainless steel gradually replaces Ti and Nb stainless steel. However, the strength of austenitic stainless steel decreases greatly with the decrease of solid solution carbon content. Substituting n for C is an important way to obtain high-strength steel raw material market, which is stable and weakening, and generally high toughness austenitic stainless steel. It is found that both N and C strengthen austenite in the form of interstitial atoms, but nitrogen can strengthen the metal bond of steel, while carbon can strengthen the covalent bond between atoms. When nitrogen atoms occupy the interstitial position, the electron cloud density is higher than that of carbon. Therefore, nitrogen can stabilize austenite more than carbon. Nitrogen can cause the increase of slip plane and deformation twins, so as to prevent dislocation movement and twin expansion, and greatly increase the deformation hardening rate and strength of austenitic stainless steel. Compared with traditional steel, the properties of high nitrogen steel can be improved by 30~150%. At present, the tensile strength of high nitrogen stainless steel has reached more than 800MPa, and still maintains good plasticity, toughness and corrosion resistance

however, under normal pressure, the solubility of nitrogen in steel is very low. How to add nitrogen to steel has become the main factor preventing nitrogen from being used as an alloying element. The primary problem in developing high nitrogen steel is to develop corresponding processes and equipment to ensure a high and uniform nitrogen concentration in the whole volume range during metal solidification. With the development of pressure metallurgy technology, nitrogen can be dissolved in austenite with a large content, such as pressure electroslag remelting, pressure induction smelting, vacuum induction smelting, high pressure plasma arc smelting, hot isostatic pressing smelting and so on. Some European countries have produced high nitrogen austenitic stainless steel with a 4.2mpa, 20 ton pressurized electroslag furnace, and have achieved industrial production and application. However, there are some problems in pressure metallurgy, such as complex smelting process, expensive equipment, great safety hazards, high production costs and so on. Therefore, in recent years, scholars at home and abroad have been mainly committed to the study of smelting austenitic stainless steel with high nitrogen content under the development path of resource conservation at atmospheric pressure, and have achieved some results. Northeast University and Institute of metals, Chinese Academy of sciences have prepared high nitrogen austenitic stainless steel with nitrogen content of more than 1.0%. Changchun University of technology has successfully smelted high nitrogen nickel free austenitic stainless steel with nitrogen content of 0.6% - 1.2% under atmospheric pressure