There is no uniform definition and concept of special steel for prefabricated warehouse. It is generally believed that special steel is steel which has special chemical composition, special craft production, special organization and performance, and can meet special needs. Compared with ordinary steel, special steel has a higher strength and toughness, physical properties, chemical properties, biocompatibility and process performance.
China and Japan, the European Union on the definition of special steel is relatively close to the special steel is divided into high-quality carbon steel, alloy steel, high alloy steel (alloying elements greater than 10%) three categories, including alloy steel and high alloy steel accounted for special steel production Of 70%. The main steel has special carbon structural steel, carbon tool steel, carbon spring steel, alloy spring steel, alloy structural steel, ball bearing steel, alloy tool steel, high alloy tool steel, high speed tool steel, stainless steel, , As well as high temperature alloys, precision alloys, electric alloys and so on. At present the world has nearly 2000 special steel grades, about 50,000 varieties specifications. In addition to a wide variety of special steel, the specifications also show different characteristics with ordinary steel. In addition to the board, tube, silk, belt, rod and profile, there are composite materials, surface alloying materials, surface treatment materials, precision forging materials, precision castings, powder metallurgy products.
Third, China's steel number that method
Steel grades referred to as steel, is the name of each specific steel products, is a common understanding of the common language of steel. China's steel number that method, according to the national standard "steel product grades that method" (GB221-79), the use of Chinese phonetic alphabet, chemical element symbols and Arabic numerals combined method. which is:
1) Chemical elements in steel are represented by international chemical symbols such as Si, Mn, Cr, etc. The mixed rare earth element is represented by "RE" (or "Xt").
2) product name, use, smelting and casting methods, generally use the abbreviation of Chinese phonetic alphabet.
3) The main chemical elements in steel (%) are expressed in Arabic numerals.
Classification of China 's Steel Numbering Method
1.carbon structural steel
1) consists of Q + digital + quality grade symbol + deoxidation method symbol. Its steel is numbered "Q", which represents the yield point of the steel, followed by the number of yield points, in units of MPa, for example, Q235 for carbon structural steel with a yield point (σs) of 235 MPa.
2) If necessary, the steel mark may be followed by a symbol indicating the quality level and deoxidation method. The quality grade symbols are A, B, C, D, respectively. Debona method symbol: F said boiling steel; b said semi-killed steel: Z said sedative steel; TZ said special sedative steel, sedimentary steel can not sign symbols, that is, Z and TZ can not be marked. For example, Q235-AF represents Class A boiling steel.
3) Special purpose carbon steel, such as bridge steel, marine steel, etc., basically the use of carbon structural steel representation, but in the steel to add the final use of the letter.
2.high-quality carbon structural steel
1) The two digits at the beginning of the steel number indicate the carbon content of the steel, expressed as a fraction of the average carbon content, for example, steel with an average carbon content of 0.45%, steel number "45", which is not a sequence number and therefore can not be read Into 45 steel.
2) high manganese content of high quality carbon structural steel, manganese should be marked, such as 50Mn.
3) High quality carbon structural steels for boiling steel, semi-killed steel and specialized applications should be specifically marked on steel grades, such as semi-killed steel with an average carbon content of 0.1%, with steel grades 10b.
3.carbon tool steel
1) steel crown "T", so as not to mix with other steel.
2) The figures in the steel number represent the carbon content, expressed as a fraction of the average carbon content. For example, "T8" means an average carbon content of 0.8%.
3) Where the manganese content is higher, "Mn" is indicated at the end of the steel, for example "T8Mn".
4) high-quality high-quality carbon tool steel phosphorus, sulfur content, lower than the general high-quality carbon tool steel, steel in the last filling the letter "A" to show the difference, such as "T8MnA".
4.easy to cut steel
1) steel crown "Y" to distinguish it from high quality carbon structural steel.
2) The number after the letter "Y" indicates the carbon content, expressed as a fraction of the average carbon content, for example
The average carbon content of 0.3% of the free cutting steel, the steel number "Y30".
3) Mn content is higher, also marked "Mn" after steel, such as "Y40Mn".
5.alloy structural steel
1) The two digits at the beginning of the steel number indicate the carbon content of the steel, expressed in terms of the average carbon content,
Such as 40Cr.
2) steel in the main alloying elements, in addition to individual micro-alloying elements, the general expressed as a few percent. When the average alloy content <1.5%, the steel is generally marked only element symbols, but not marked content, but in special circumstances easy to confuse those in the element symbol can also be marked with the number "1", such as steel "12CrMoV" and "12Cr1MoV", the former chromium content of 0.4-0.6%, the latter is 0.9-1.2%, the rest of the same components. When the average content of alloy elements ≥1.5%, ≥2.5%, ≥3.5% ..., the elements should be marked after the content of the symbol can be expressed as 2,3,4 ... ... and so on. Such as 18Cr2Ni4WA.
3) steel vanadium V, titanium Ti, aluminum AL, boron B, rare earth RE alloy elements, are micro-alloying elements, although the content is very low, should be marked in the steel. Such as 20MnVB steel. Vanadium is 0.07-0.12% and boron is 0.001-0.005%.
4) high quality steel should be added in the steel "A" to distinguish it from the general high quality steel.
5) Special purpose alloy structural steel, steel crown (or suffix) on behalf of the use of the symbol of the steel. Such as riveting screw dedicated 30CrMnSi steel, steel said ML30CrMnSi.
6.low-alloy high-strength steel
1) steel number of the representation, and alloy steel is basically the same.
2) for professional use of low-alloy high-strength steel, steel should be the last marked. For example, 16Mn steel, for the bridge of special steel for the "16Mnq", automotive girder for the special steel "16MnL", the pressure vessel for the special steel "16MnR".
Spring steel according to the chemical composition can be divided into two kinds of carbon spring steel and alloy spring steel, the steel means that the former is basically the same with the quality of carbon structural steel, which is basically the same with the alloy steel.
8. rolling bearing steel
1) The steel plate is marked with the letter "G", indicating the rolling bearing steel.
2) The carbon content of the high carbon chromium bearing steel is not indicated, and the chromium content is expressed in parts per thousand, for example, GCr15. Carbide bearing steel steel number that method, basically the same and alloy steel.
9.alloy tool steel and high speed tool steel
1) When the average carbon content of the alloy tool steel is ≥1.0%, the carbon content is not indicated; when the average carbon content is less than 1.0%, it is expressed in parts per thousand. Such as Cr12, CrWMn, 9SiCr, 3Cr2W8V.
2) steel alloy element content of the representation method, basically the same with the alloy structural steel. But the lower chromium content of the alloy tool steel, the chromium content is expressed in thousands of minutes, and in the content of the number before the "0", so that it and the general element content expressed by a few percent of the method Differentiated. Such as Cr06.
3) high-speed tool steel steel is generally not marked with carbon content, only marked a few percent of the average content of various alloying elements. For example, the steel number of the tungsten high speed steel is expressed as "W18Cr4V". Steel is the letter "C", indicating that its carbon content is higher than the crown "C" of the common steel.
10. stainless steel and heat-resistant steel
1) The carbon content in the steel is expressed in parts per thousand. For example, "2Cr13" steel average carbon content of 0.2%; if the carbon content of steel ≤0.03% or ≤0.08%, respectively, before the steel known as "00" and "0" said, such as 00Cr17Ni14Mo2,0Cr18 Ni9, etc. The
2) The main alloying elements in steel are expressed as a few percent, while titanium, niobium, zirconium, nitrogen, etc. are marked by the above-mentioned alloy structural steel for microalloying elements.
11. welding rod steel
Its steel number is preceded by the letter "H" to distinguish it from other steel. For example, stainless steel wire "H2Cr13", can be distinguished from stainless steel "2Cr13".
12.electrical silicon steel
1) The steel number consists of letters and numbers. Steel head head letter DR said electrician hot-rolled silicon steel, DW said electrician cold-rolled non-oriented silicon steel, DQ said electrician cold-rolled oriented silicon steel.
2) The number after the letter indicates 100 times the iron loss (W / kg).
3) steel tail plus "G", said at high frequency test; without "G", said the frequency of 50 weeks under the test. For example, DW470 indicates that the maximum weight per unit weight of the cold-rolled non-oriented silicon steel product at 50 Hz is 4.7 W / kg.
13. electrician with pure iron
1) Its grade consists of the letter "DT" and the number, "DT" means electrical iron, and numbers indicate the serial numbers of different grades, such as DT3.
2) The letters added after the numbers indicate electromagnetic performance: A - Advanced, E - Premium, C - Super, eg DT8A.