“The difference between \"special steel\" and \"high-quality steel\"

Thread Content

Twenty years ago, the concept of \"high-quality steel\" was rarely mentioned; in other words, when \"special steel\" was referred to, it included high-quality steel. As for what constitutes \"special steel,\" it was often described as follows: steel produced by converters was generally called \"ordinary steel\"”； The steel grades produced by electric furnaces are generally referred to as \"special steel,\" and even in the 1990s, some people in our industry used this term. The rapid development of China’s steel industry over the past two decades has been astonishing. In the mid-1990s, ultra-high power arc furnaces combined with off-furnace refining, as well as continuous casting and rolling, represented the most advanced equipment technologies in the special steel industry. Back then, while working in companies, we even discussed whether it was feasible to use continuous casting and rolling technology for producing bearing steel. Today, however, such ultra-high power continuous casting and rolling technologies have almost become a basic requirement. A fact that we should not forget is that it was precisely in the mid-to-late 1990s, thanks to Xingcheng Special Steel’s promotion of the use of ultra-high power furnace-based secondary refining along with continuous casting and rolling technologies in the production of bearing steel, that the efficiency of bearing steel production was significantly improved. On this basis, further attempts were made to use converter-based furnace secondary refining technology for producing bearing steel, which helped the company establish itself as a leader in the production and sales of bearing steel. At the same time, more metallurgical enterprises began to employ converter-based furnace secondary refining technology to produce carbon and low-alloy special steel grades such as those specified by national standards 699 and 3077 – products that are commonly referred to as high-quality steel. As a result, the concept of \"high-quality steel\" gained widespread acceptance within the industry. Therefore, the high-quality steel I mention later mainly refers to the products specified in technical standards such as GB 699 and 3077. Of course, such a classification method is not intended to discuss the categorization of \"high-quality steel\" and \"special steel\"; it is merely a temporary explanation for exploring subsequent issues. As for their specific classification methods, industry leaders and experts will have more professional opinions... 1 Common types of \"high-quality steel\": High-quality steel (falling between special steel and ordinary carbon steel, generally without alloys) refers to steel that possesses good mechanical properties, including high tensile and compressive strengths as well as good toughness. It is easy to machine, and its mechanical properties improve significantly after heat treatment. In terms of composition, it features fewer impurities in the steel material and finer, more uniform grain structures. Common high-quality steels include carbon alloy steel, alloy structural steel, die steel, spring steel, high-quality round bars, high-performance tool steel, bearing steel, high-carbon steel, gear steel, carbon structural steel, alloy structural steel, tube billet steel, roll steel, and alloy structural steel, among others. Carbon structural steel: Simply put, it is high-quality carbon structural steel, also referred to as carbon structural steel ； Specifically, its carbon content is less than 0.08%. Low-carbon steel is used for rolling thin sheets and deep-drawn products ； Medium-carbon alloy steel is used to manufacture quenched and tempered parts with moderate dimensions, including tie rods, bushings, gears, piston pins, fasteners, etc ； High-carbon nodular steel is used for manufacturing springs and parts that require wear resistance. Alloy steel: Steel used for mechanical parts and various engineering components, containing one or several alloying elements in specified amounts. It can be divided into ordinary alloy structural steel and special-purpose alloy structural steel. Alloy structural steel is widely used in structures such as ships, vehicles, aircraft, missiles, weapons, railways, bridges, pressure vessels, and machine tools. Mold steel can be roughly divided into three categories: (cold-work mold steel), (hot-work mold steel), and (plastic mold steel), which are used in forging, stamping, cutting, die-casting, and other processes. Spring steel refers to steel that is specifically used for manufacturing springs and elastic components due to its elasticity in the quenched and tempered state. Bearing steel is the steel used to manufacture balls, rollers, and bearing rings. Bearings are subjected to great pressure and friction during operation; therefore, bearing steel is required to have high and uniform hardness and wear resistance, as well as a high elastic limit. Gear steel is a general term for steels that can be used to manufacture gears. Gear steel is one of the key materials among the special alloy steels used in automobiles, railways, ships, and construction machinery; it is the material used to manufacture components that are essential for ensuring safety. 2 Common Types of \"Special Steels\" Special steels: There is no unified definition or concept for special steels worldwide. Generally, special steels are considered to be those that have a specific chemical composition (with one or several alloying elements added to carbon steel), are produced using special manufacturing processes, possess unique microstructures and properties, and can meet particular requirements. Compared to ordinary steel, special steels possess higher strength and toughness, as well as improved physical, chemical properties, biocompatibility, and processability. It features high strength and hardness, good plasticity and toughness, wear resistance, corrosion resistance, and many other excellent properties. 1. Tungsten steel, manganese steel: extremely hard; used to manufacture metal cutting tools, tractor tracks, axles, etc. 2. Manganese silicon steel: It has exceptional toughness and is used to manufacture bullets, spring coils, etc. 3. Molybdenum steel: resistant to high temperatures; used for manufacturing aircraft crankshafts and particularly hard tools, etc. 4. Tungsten-chromium steel: high hardness and great toughness; used for machine tool cutters and molds, etc. 5. Nickel-chromium steel (stainless steel): It has excellent corrosion resistance and is resistant to oxidation. It is used in the manufacture of acid-resistant towers for chemical production, medical devices, and everyday items. Special steel is the primary type of steel used in most sectors of the national economy, including machinery, automotive industry, military sector, chemical industry, home appliances, shipbuilding, transportation, railways, and emerging industries. China’s special steel industry is responsible for producing the special steel grades required by defense and military industries, high-tech industries, as well as key sectors such as machinery and automotive manufacturing.