Special steel, that is, special steel, is the most important type of steel used in most industries of the national economy, such as machinery, automobiles, military industry, chemicals, household appliances, ships, transportation, railways and emerging industries. Special steel is an important symbol to measure whether a country can become a steel powerhouse.
Special-purpose steel refers to other components that work under special conditions and have special requirements for steel, such as physical, chemical, mechanical and other properties.
Special performance steels are also special quality alloy steels. These steels refer to steels with electromagnetic, optical, acoustic, thermal and electrochemical actions and functions. Commonly used are stainless steel, heat-resistant steel, electrical silicon steel, electronic pure iron and various precision alloys (soft magnetic alloys, such as magnetic alloys, elastic alloys, expansion alloys, thermal double alloys, resistance alloys, primary battery materials, etc.). .
Stainless steel is named for its good corrosion resistance, and its main alloying components are chromium and nickel. Chromium has high chemical stability and can form a dense and tough purification film in an oxidizing medium; in addition, when the chromium content exceeds 11.7%, the electrode potential of the alloy can be significantly increased, thereby effectively preventing further oxidation of the alloy. Nickel is also a facilitator. The addition of nickel to chromium steel can improve the corrosion resistance of the alloy in non-oxidizing media. When the content of chromium and nickel is constant, the lower the carbon content in the steel, the better the corrosion resistance.
The corrosion resistance of stainless steel is also related to the uniformity of the matrix structure. When a uniform alloy solid solution is formed, the corrosion rate of steel in the electrolyte can be effectively reduced.
Austenitic stainless steel is a chromium-nickel series stainless steel with a single austenitic structure. It has good corrosion resistance, low temperature toughness, pressure processing and welding processability, non-magnetic, and is widely used as low temperature steel and low temperature steel working in corrosive media. Non-magnetic steel; ferritic stainless steel mainly contains chromium, which undergoes phase transformation during heating and cooling, and is a commonly used wear-resistant material in the nitric acid and nitrogen fertilizer industries; martensitic stainless steel has high carbon content and good hardenability. A martensitic structure is obtained. This steel has good toughness and low carbon content, and can be used to make impact-resistant parts that work in corrosive media; high carbon is used to make springs, bearings, surgical blades, etc.; it has a two-phase mixed structure of austenite and ferrite. The stainless steel of the matrix is a duplex stainless steel, which has the advantages of high strength, good toughness, and resistance to intergranular corrosion. Among them, 00Cr18Ni5Mo3Si2 steel is mainly used in the manufacture of heat exchangers and condensers in oil refining, fertilizer, paper, petroleum, chemical and other industries, and 0Cr26Ni5Mo2 is used in the manufacture of seawater corrosion equipment; molybdenum, niobium, lead, copper and other elements in the hardened phase make them After quenching and aging treatment, it has high strength and toughness, and is mainly used to manufacture springs, washers, bellows, etc.
Electrical steel, also known as silicon steel, is an iron-silicon binary alloy with a carbon content of less than 0.05%. It has the characteristics of small iron loss, small coercive force, high magnetic permeability and magnetic induction intensity, and is one of the commonly used soft magnetic materials (for short-term or repeated magnetization). The main factors affecting the performance of electrical steel are chemical composition and structure. Silicon has the greatest influence on the magnetic properties of electrical steel. When 3.0% Si is added to pure iron, the magnetic permeability is increased by 1.6-2 times, the hysteresis loss is reduced by 40%, the resistivity is increased by 4 times (which can reduce the eddy current loss), and the total iron loss is reduced. Doubled, but the hardness and strength are also Significantly increased. Usually the silicon content does not exceed 4.5%, otherwise it is too hard and difficult to process. The presence of harmful impurities (N, C, S, O, etc.) will cause the lattice distortion of the steel, increase the stress, and hinder the magnetization process, so the content of impurities should be strictly controlled.
Silicon steel is mainly used in electric power industries such as motors, transformers, electrical appliances, and electrical instruments. Most are rolled into 0.3, 0.35, 0.5 sheets, including hot and cold rolling. cold rolled
Post time: Oct-31-2022