With the rapid advancement of science and technology, more and more industries are placing higher demands on the performance of steel materials, especially those used at high temperatures. Heat-resistant steel is widely used in the manufacture of boilers, steam turbines, power machinery, industrial furnaces, and components operating at high temperatures in industries such as aviation and petrochemicals. The development of heat-resistant steel is closely linked to advances in energy and power machinery. The performance of heat-resistant steel is crucial to the success of new technologies in thermal power generation, atomic energy, aerospace, aviation, petroleum, and chemical industries, and its importance is increasing. Currently, the biggest bottleneck in improving energy efficiency in industries such as civilian nuclear power, thermal power generation, gas-fired power generation, and the petrochemical industry is the availability of metal materials, specifically the development of low-cost, high-performance heat-resistant stainless steel. Developing new heat-resistant stainless steel is not only an effective strategy for energy conservation and emission reduction, but also can alleviate the increasingly scarce nickel resources.
The earliest research on austenitic heat-resistant steel began in the 1930s. Krupp et al. developed stabilized austenitic steel based on 18-8 steel by reducing the C content and adding elements such as Ti, V, and Nb. They obtained fine-grained steel with dispersed carbides, which allowed the material to form Nb and Ti carbonitrides and M23C6 type compounds during long-term service. These are the predecessors of Type 321 and Type 347 steels. Type 316 austenitic steel was obtained by adding 3% Mo to 18-8 steel. The emergence of these steels increased the corrosion resistance of the steel on the basis of the original steel. In the 1970s, due to the impact of the energy crisis, many countries invested a lot of research work in the field of thermal power steel. By adjusting the stabilizing elements (Ti, V, Nb) on the basis of 18-8 austenitic steel, Tempaloy A-1[4] steel and TP347H heat-resistant steel with fine grain structure were developed.[5] In the 1980s and 1990s, the Cr mass fraction was increased to 25%. Over long-term service, Cr diffuses to the surface, combining with oxygen to form an oxide layer, providing excellent antioxidant properties. However, as the Cr content increases, the precipitation of the brittle σ phase becomes more pronounced. Therefore, the Ni content was also increased to stabilize the austenite structure while suppressing the precipitation of the σ phase. As a result, the 25-20 type austenitic heat-resistant steel exhibits significantly improved oxidation resistance, a stable austenite structure, and a long service life, making it suitable for harsher operating conditions. This series of steel exhibits high structural stability and oxidation resistance at temperatures between 800°C and 1200°C, making it a popular alternative to Cr20Ni25 and Alloy 800 grades for manufacturing heat-resistant industrial furnace components.
Judging from current research and production levels, Europe and the United States lead the way in the development, production, and user acceptance of heat-resistant steel. Representative companies include Outokumpu and Sandvik in Sweden and ATI in the United States. In Asia, Japan is the primary producer of heat-resistant stainless steel, but the service life of its steel grades lags behind Sweden.
Research and development of heat-resistant stainless steel in China began at the beginning of this century. Dongfang Special Steel was one of the first to undertake this research and is also one of the first domestic companies to supply commercial grade material.
The company’s greatest advantage lies in its use of Consteel electric furnaces for the primary refining of nickel-iron alloys, which consumes significantly less energy than traditional electric furnaces. This method eliminates the existing raw material structure of pure nickel and scrap steel, offering the advantages of a short smelting cycle, low raw material costs, and low process energy consumption. Combined with argon-oxygen refining, this method can produce high-value-added products at a low cost.
Cherry
Website: www.jinyoumetal.com
Email: Cherry@jinyoumetal.com
WhatsApp/WeChat: +86 13373795593
