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The difference between grain-oriented silicon steel and non-grain-oriented silicon steel

Category: Industry News Publish Time：2018-09-25

Silicon steel sheets Silicon steel, commonly known as silicon steel sheets, is an indispensable low-carbon silicon-iron soft magnetic alloy in the electric power, electronics, and military industries. It is also the largest-produced metal functional material, accounting for about 1% of the world's steel production. It is a silicon-iron alloy containing 0.8%-4.8% silicon, which is hot and cold rolled into silicon steel sheets with a thickness of less than 1 mm. Adding silicon can improve the resistivity and maximum permeability of iron, reduce coercivity, core loss (iron loss), and magnetic aging. It is mainly used as the core of various motors, generators, and transformers. Classification of silicon steel sheets Silicon steel sheets can be divided into low-silicon and high-silicon types according to their silicon content

　　Silicon steel sheet

　　Silicon steel, also known as silicon steel sheet, is a low-carbon silicon-iron soft magnetic alloy indispensable to the electric power, electronics, and military industries. It is also the metal functional material with the largest output, accounting for about 1% of the world's steel output. It is a silicon-iron alloy containing 0.8%-4.8% silicon, which is hot and cold rolled into silicon steel sheets with a thickness of less than 1 mm. The addition of silicon improves the resistivity and maximum permeability of iron, reduces coercivity, core loss (iron loss), and magnetic aging, and is mainly used as the core of various motors, generators, and transformers.

　　Classification of silicon steel sheets

　　Silicon steel sheets can be divided into low-silicon and high-silicon types according to their silicon content.

　　1. Low-silicon sheet

　　Low-silicon sheets contain less than 2.8% silicon. They have a certain mechanical strength and are mainly used for manufacturing motors; they are commonly known as motor silicon steel sheets.

　　2. High-silicon sheet

　　High-silicon sheets contain 2.8%-4.8% silicon. They have good magnetic properties but are brittle. They are mainly used for manufacturing transformer cores and are commonly known as transformer silicon steel sheets. There is no strict boundary between the two in practical use, and high-silicon sheets are often used to manufacture large motors.

　　Classification by production process

　　They can be divided into hot-rolled and cold-rolled types.

　　Cold-rolled sheets can be further divided into grain-oriented and grain-non-oriented types: Cold-rolled sheets have uniform thickness, good surface quality, and high magnetic properties. Therefore, with the development of industry, hot-rolled sheets tend to be replaced by cold-rolled sheets.

　　Cold-rolled silicon steel sheet

　　Cold-rolled silicon steel sheets are divided into grain-oriented and grain-non-oriented steel strips.

　　Grain-non-oriented cold-rolled strips are usually used as cores for motors or welding transformers; grain-oriented cold-rolled strips are used as cores for power transformers, pulse transformers, and magnetic amplifiers. Cold-rolled oriented thin silicon steel strips are made by pickling, cold rolling, and annealing 0.30 or 0.35 mm thick oriented silicon steel strips.

　　Cold-rolled non-oriented silicon steel sheets are made by hot rolling steel billets or continuous casting billets into strips of about 2.3 mm thickness. Cold-rolled electrical steel strips have features such as a smooth surface, uniform thickness, high stacking factor, and good punching properties, and have higher magnetic induction and lower iron loss than hot-rolled electrical steel strips.

　　Using cold strips instead of hot-rolled strips to manufacture motors or transformers can reduce their weight and volume by 0%-25%. If oriented cold-rolled strips are used, the performance is even better. Replacing hot-rolled strips or low-grade cold-rolled strips with them can reduce the energy consumption of transformers by 45%-50%, and the transformer's operating performance is more reliable.

　　Definition of non-oriented silicon steel sheet

　　Non-oriented silicon steel sheet is a silicon steel sheet that forms a non-oriented deformation texture crystalline structure according to a certain production process.

　　Oriented silicon steel sheet

　　In the early 1920s, Williams studied single crystals in silicon iron and obtained um=1400000 in the easy magnetization axis {100} direction, believing that there should also be excellent performance in the {100} axial direction in polycrystalline plates.

　　In 1926, Honda and Kaya discovered that the crystal direction of iron is the easiest to magnetize, or the edge direction of the crystal cube is the easiest to magnetize.

　　In 1934, Goss (N.P.Goss) successfully developed oriented silicon steel sheets in the laboratory. He used a method combining cold rolling and high-temperature heat treatment to make the grains in the silicon steel sheets arranged orderly along the rolling direction, resulting in excellent magnetic properties.

　　In 1935, Goss published an article in TransAmer.Soc.Metals introducing his research results and applied for a British patent (No.442211).

　　In the same year, Armco in the United States began industrial production of cold-rolled oriented silicon steel sheets. In the 1940s, both Armco and Allegheny in the United States produced high-quality oriented silicon steel sheets for transformers. Armco's brand name was Tran-cor (Westinghouse called it Hipersil); Allegheny's brand name was Silectron (GE called it Corosil).

　　In 1953, Japan trial-produced cold-rolled oriented silicon steel sheets.

　　In 1958, Japan introduced Armco's patented technology and began the industrial production of cold-rolled oriented silicon steel sheets. Based on this, it continuously improved, making Japan's cold-rolled silicon steel sheets reach the world's highest level.

　　The magnetic conductivity of single-oriented silicon steel sheets is low in the direction perpendicular to the rolling direction. To overcome this shortcoming, the German vacuum melting company invented double-oriented silicon steel sheets in the 1940s.

　　In 1957, GE and Westinghouse in the United States also produced double-oriented silicon steel sheets almost simultaneously. In the 1960s, Kawasaki and Yawata factories in Japan also successfully developed double-oriented silicon steel sheets. Its magnetic properties in the rolling direction and the perpendicular direction are similar to the magnetic properties of single-oriented silicon steel sheets in the rolling direction. The grains of this silicon steel sheet have a cubic structure.

　　In 1968, Nippon Steel Corporation in Japan began industrial production of high-magnetic density oriented silicon steel sheets, whose commercial name is "OrientcoreHi-B", abbreviated as "Hi-B"; in 1972, large-grain high-magnetic oriented silicon steel sheets were developed; in 1981, small-grain high-magnetic oriented silicon steel sheets were further developed; in 1982, Japan began producing high-magnetic oriented silicon steel sheets with surface laser irradiation treatment (ZDKH), further reducing iron loss.

　　In 1988, Japan developed high-magnetic oriented silicon steel sheets using a mechanical method to form a micro-stress method (ADMH). The development of oriented silicon steel sheets by Nippon Steel Corporation can be seen. The performance of single-oriented silicon steel sheets in several countries in the 1950s. The quality changes of oriented and non-oriented silicon steel sheets in Japan between 1955 and 1975. The decline curve of core steel sheet iron loss between 1880 and 1970.

　　Relationship between non-oriented and oriented silicon steel sheets

　　1. Different silicon content

　　Both are cold-rolled silicon steel sheets, but with different silicon content. Cold-rolled non-oriented silicon steel sheets have a silicon content of 0.5%-3.0%, while cold-rolled oriented silicon steel sheets have a silicon content of more than 3.0%.

　　2. Different production processes

　　(1) Non-oriented silicon steel sheets have relatively lower process requirements than oriented silicon steel sheets. Non-oriented silicon steel sheets are hot-rolled from steel billets or continuously cast billets into strips of approximately 2.3mm thickness.

　　When producing low-silicon products, the hot-rolled strip is pickled and cold-rolled to a thickness of 0.5mm in one pass.

　　When producing high-silicon products, the hot-rolled strip is pickled after hot rolling (or normalized at 800-850℃ before pickling), cold-rolled to 0.55 or 0.37mm thick, annealed at 850℃ in a continuous furnace with a hydrogen-nitrogen mixed atmosphere, and then cold-rolled again with a small reduction rate of 6-10% to 0.50 or 0.35mm thick. This small reduction rate cold rolling allows grain growth during annealing, reducing iron loss.

　　(2) Both types of cold-rolled sheets are finally annealed at 850℃ in a continuous furnace under a 20% hydrogen-nitrogen mixed atmosphere, and then coated with a phosphate and chromate insulating film. After cold rolling to the finished thickness, the supplied state is mostly 0.35mm and 0.5mm thick steel strips.

　　The Bs of cold-rolled non-oriented silicon steel is higher than that of oriented silicon steel. Oriented silicon steel sheets require low oxide inclusion content in the steel and must contain 0.03-0.05% C and inhibitors (second-phase dispersed particles or grain boundary segregation elements). The role of inhibitors is to prevent the growth of primary recrystallization grains and promote the development of secondary recrystallization, thereby obtaining high [001] orientation.

　　Inhibitors themselves are detrimental to magnetism, so after completing their inhibitory function, high-temperature purification annealing is required. When using second-phase inhibitors, the billet heating temperature must be increased to dissolve the original coarse second-phase particles, and then precipitated as fine particles during hot rolling or normalization to enhance the inhibitory effect.

　　The cold-rolled finished thickness is 0.28, 0.30 or 0.35mm. Cold-rolled oriented thin silicon steel strip is made by pickling, cold rolling and annealing 0.30 or 0.35mm thick oriented silicon steel strip.

　　Compared with cold-rolled non-oriented silicon steel, oriented silicon steel has much lower iron loss and strong directional magnetic properties; it has superior high permeability and low loss characteristics in the easily magnetized rolling direction. The iron loss of oriented steel strip in the rolling direction is only 1/3 of that in the transverse direction, the permeability ratio is 6:1, its iron loss is about 1/2 of that of hot-rolled strip, and the permeability is 2.5 times that of the latter.

　　3. Different grain structures

　　The grains of oriented silicon steel are arranged in an orderly manner, while the grains of non-oriented silicon steel are arranged in a disorderly manner. Non-oriented silicon steel is mainly used in the stators and rotors of motors, compressors, and large hydroelectric generator sets. Oriented silicon steel is generally used in transformer cores and some motors.

　　Generators and transformers have the same requirements for silicon steel sheets: low iron loss, good magnetization characteristics, high stacking factor, etc., but transformers generally use oriented silicon steel sheets. Generators use non-oriented silicon steel sheets.

　　4. Different properties and uses

　　Due to the different performance characteristics of the two, there are differences in the direction of use: The main use of cold-rolled non-oriented silicon steel sheets is in generator manufacturing, so it is also called cold-rolled motor silicon steel. The main use of cold-rolled oriented silicon steel strips is in transformer manufacturing, so it is also called cold-rolled transformer silicon steel.

　　Silicon steel sheet performance indicators

　　1. Low iron loss. The most important indicator of quality, countries around the world use iron loss values to classify grades, the lower the iron loss, the higher the grade, and the higher the quality.

　　2. High magnetic induction intensity. Silicon steel sheets that can obtain higher magnetic induction under the same magnetic field have smaller volume and weight of motor or transformer cores made from them, and can relatively save silicon steel sheets, copper wires and insulating materials, etc.

　　3. High stacking factor. The silicon steel sheet surface is smooth, flat and uniform in thickness, which improves the stacking factor of the core.

　　4. Good punching performance. This is more important for manufacturing small and micro motors cores.

　　5. Good adhesion and weldability of the surface to the insulating film, which can prevent corrosion and improve punching performance.

　　6. Small magnetic aging phenomenon. Silicon steel sheets must be annealed and pickled before delivery.

　　1. Hot-rolled silicon steel thin sheets for electrical use (GB5212-85)

　　Hot-rolled silicon steel thin sheets for electrical use use low-carbon loss silicon iron soft magnetic alloy as the material, and are hot-rolled into thin sheets with a thickness of less than 1mm. Hot-rolled silicon steel thin sheets are also called hot-rolled silicon steel sheets. Hot-rolled silicon steel sheets can be divided into low-silicon (Si≤2.8%) and high-silicon (Si≤4.8%) steel sheets according to their silicon content.

　　 2. Cold-rolled silicon steel thin sheets for electrical use (GB2521-88)

　　Using electrical silicon steel with 0.8%-4.8% silicon content as the material, it is cold-rolled. Cold-rolled silicon steel sheets are divided into two types: non-oriented grain and oriented grain steel strips. Cold-rolled electrical steel strips have the characteristics of flat surface, uniform thickness, high stacking factor, and good punching performance, and have higher magnetic induction and lower iron loss than hot-rolled electrical steel strips.

　　Used in the manufacture of motors and transformers. Usually, non-oriented grain cold-rolled strips are used for motors or welding transformers; oriented grain cold-rolled strips are used for cores of power transformers, pulse transformers and magnetic amplifiers. Steel plate specifications: thickness is 0.35, 0.50, 0.65mm, width is 800-1000mm, length is ≤2.0m.

　　3. Hot-rolled silicon steel thin sheets for household appliances (GBH46002-90)

　　The grade of hot-rolled silicon steel sheet for home appliances is indicated by J (home appliance) D (electrical appliance) R (hot-rolled), i.e., JDR. The number after JDR is the iron loss value * 100, and the number after the hyphen is the steel plate thickness (mm) * 100. The electromagnetic performance requirements for hot-rolled silicon steel sheets for home appliances can be slightly lower, with the minimum iron loss value (P15/50) being 5.40 W/kg. Generally, it is not delivered after pickling and washing.

　　Used in various household appliances such as electric fans, washing machines, vacuum cleaners, range hoods, and micro-motors.

　　There are two methods to identify grain-oriented silicon steel sheets.

　　1. Visual inspection method

　　Grain-oriented silicon steel sheets are grayish-white;

　　2. Hand-bending method

　　Take a silicon steel sheet and bend it twice by hand. Grain-oriented sheets will shed grayish-white residue, and will break after bending two to three times. Non-grain-oriented silicon steel sheets are difficult to break even after ten bends.

Keywords: The difference between grain-oriented silicon steel and non-grain-oriented silicon steel

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