The subdivision description of Chinese steel number means

1. carbon structural steel and low alloy high strength structure grade representation method

The above used steel is usually divided into general purpose steel and special steel two categories. Brand representation method, by the steel yield point or yield strength of Chinese pinyin letters, yield point or yield strength value, steel quality grade and other parts, and steel deoxidation degree, is actually composed of 4 parts.

① General structural steel uses the pinyin letter "Q" on behalf of yield point. The numerical value of yield point (unit: MPa) and the symbols of quality class (A, B, C, D, E) and deoxidation method (F, b, Z, TZ) specified in Table 1 shall constitute the brand in order. For example, the brand of carbon structural steel is Q235AF, Q235BZ; The grade of low alloy high strength structural steel is Q345C, Q345D.

Q235BZ represents the calm carbon structural steel with yield point ≥235MPa and mass grade B.

Q235 and Q345 are the most typical grades of engineering steel, the largest production and usage, and the most widely used grades. These two brands are available in almost every country in the world.

In the grade composition of carbon structural steel, the calm steel symbol "Z" and the special calm steel symbol "TZ" can be omitted. For example, the grade of Q235 steel with grade C and grade D respectively should be Q235CZ and Q235DTZ, but can be omitted as Q235C and Q235D.

Low alloy high strength structural steels are composed of killed steel and special killed steel, but the end of the grade does not indicate the deoxidation method symbol.

(2) The special structural steel is generally represented by the symbol "Q" representing the yield point of steel, the yield point value and the symbol representing the product use specified in Table 1. For example, the steel grade of pressure vessel is represented by "Q345R"; The brand of weatherproof steel is Q340NH; Q295HP steel for welding gas cylinders; Q390g boiler steel grade; Q420q Steel grade for bridge.

(3) According to needs, the brand of general low-alloy high-strength structural steel can also use two Arabic numerals (representing the average carbon content, measured in a few thousand) and chemical element symbols, in order to express; The special grade of low-alloy high-strength structural steel may also be indicated in order by using two Arabic numerals (representing average carbon content in parts per million) and symbols of chemical elements, as well as some specified symbols representing the purpose of the product.

2. Grade expression method of high quality carbon structural steel and high quality carbon spring steel

High quality carbon structural steel uses two Arabic numerals (in a few thousand to indicate the average carbon content) or Arabic numerals and element symbols to form the grade.

① The symbols "F" and "b" are added at the end of the grades for boiling-off steel and semi-killed steel. For example, the average carbon content of the boiling steel is 0.08%, its grade is expressed as "08F"; A semi-killed steel with an average carbon content of 0.10% is marked "10b".

(2) Dead steel (S, P ≤0.035%) general non-standard symbols. For example, a calm steel with an average carbon content of 0.45% would have a grade of "45".

③ For high-quality carbon structural steel with higher manganese content, the manganese symbol is added after the Arabic numeral indicating the average carbon content. For example, a steel with an average carbon content of 0.50% and manganese content of 0.70%-1.00% would be labeled "50Mn".

④ High quality carbon structural steel (S, P ≤0.030%), add the symbol "A" after the grade. For example: the average carbon content of the high quality carbon structural steel is 0.45%, its brand is "45A".

⑤ Super high quality carbon structural steel (S≤0.020%, P≤0.025%), add the symbol "E" after the grade. For example: the average carbon content is 0.45% of the super high quality carbon structural steel, its brand is "45E".

The grade of high quality carbon spring steel is expressed in the same way as the grade of high quality carbon structural steel (65, 70, 85, 65Mn steels exist in both GB/T1222 and GB/T699 respectively).

3, alloy structural steel and alloy spring steel grade expression method

① The grade of alloy structural steel is indicated by Arabic numerals and standard symbols of chemical elements.

A two-digit Arabic numeral indicating the average carbon content (in parts per million) is placed at the head of the brand.

The expression method of alloying element content is: when the average content is less than 1.50%, only the element is indicated in the brand, and the content is generally not indicated. The average alloy content was 1.50% ~ 2.49%, 2.50% ~ 3.49%, 3.50% ~ 4.49%, 4.50% ~ 5.49%,... And write 2, 3, 4, 5 after the alloying element...... .

For example, if the average content of carbon, chromium, manganese and silicon is 0.30%, 0.95%, 0.85% and 1.05% respectively, the grade of alloy structural steel is "30CrMnSi" when the content of S and P is less than or equal to 0.035%.

High quality alloy structural steel (S and P content ≤0.025%, respectively), the symbol "A" at the end of the grade. For example, "30CrMnSiA".

For super high quality alloy structural steel (S≤0.015%, P≤0.025%), add the symbol "E" at the end of the grade, for example, "30CrM nSiE".

The symbol for the purpose of the product specified in Table 1 shall be added to the head (or tail) of the special alloy structural steel grade. For example, the 30CrMnSi steel specially used for riveting screws is expressed as ML30CrMnSi.

② The grade of alloy spring steel is expressed in the same way as that of alloy structural steel.

For example, the spring steel whose average content of carbon, silicon and manganese is 0.60%, 1.75% and 0.75%, respectively, is labeled "60Si2Mn". High quality spring steel, with the symbol "A" at the end of the grade, the grade is "60Si2MnA".

4, easy cutting steel grade expression method

Free cutting steel is represented by standard chemical element symbols, prescribed symbols and Arabic numerals. Arabic numerals indicate average carbon content (in parts per million).

(1) Sulfur and sulfur and phosphorus free cutting steel, in the symbol "Y" and Arabic numerals after the free cutting element symbol. For example, a free-cutting steel with an average carbon content of 0.15% would be represented as "Y15".

(2) The manganese element symbol is added after the symbol "Y" and Arabic numerals for sulfur or phosphorus free cutting steel with higher manganese content. For example, the brand of free-cutting steel with an average carbon content of 0.40% and manganese content of 1.20% ~ 1.55% is "Y40Mn".

③ For free-cutting steel containing calcium, lead and other free-cutting elements, add the symbol of free-cutting elements after the symbol "Y" and Arabic numerals. For example, Y15Pb or Y45Ca.

5, non-tempering mechanical structure steel grade expression method

For non-tempered mechanical structural steel, the symbols "YF" and "F" are added to the head of the grade respectively to indicate non-tempered mechanical structural steel for easy cutting and non-tempered mechanical structural steel for hot forging. The other contents of the grade representation method are the same as those of alloy structural steel. For example, YF35V or F45V.

6, the tool steel brand expression method

Tool steel is divided into carbon tool steel, alloy tool steel and high-speed tool steel.

① Carbon tool steel is represented by standard chemical element symbols, prescribed symbols and Arabic numerals. Arabic numerals indicate average carbon content (measured in thousands).

a. Common carbon tool steel with manganese content, Arabic numeral after tool steel symbol "T". For example, carbon tool steel with an average carbon content of 0.80% is represented by "T8".

b. For carbon tool steels with higher manganese content, add the manganese element symbol after the tool steel symbol "T" and the Arabic numeral. For example, T8Mn.

c. High quality carbon tool steel, add "A" to end of grade. For example, T8MnA.

② Alloy tool steel and high speed tool steel

The grade representation method of alloy tool steel and high speed tool steel is the same as that of alloy structural steel. The symbols of alloy elements and Arabic numerals stipulated in the standard are used to indicate, but the average carbon content is generally not indicated. For example, the average carbon content of alloy tool steel is 1.60%, and the content of chromium, molybdenum and vanadium is 11.75%, 0.50% and 0.22%, respectively. The brand is expressed as "Cr12MoV". The brand of high-speed tool steel with an average carbon content of 0.85% and tungsten, molybdenum, chromium and vanadium content of 6.00%, 5.00%, 4.00% and 2.00%, respectively, is "W6Mo5Cr4V2".

If the average carbon content is less than 1.00%, an Arabic numeral may be used to indicate the carbon content (measured in thousands). For example, an alloy tool steel with an average carbon content of 0.80%, manganese content of 0.95%, and silicon content of 0.45% is represented as "8MnSi".

Low chromium (mean chromium content < 1.00%) alloy tool steel with the number "0" in front of the chromium content (in the thousandths). For example, an alloy tool steel with an average chromium content of 0.60% would have the grade "Cr06".

7, plastic die steel brand expression method

The grade of plastic die steel is indicated in the same way as the grade of high-quality carbon structural steel and alloy tool steel, except that the symbol "SM" is added to the head. For example: carbon plastic die steel with an average carbon content of 0.45%, its brand is "SM45"; The average carbon content is 0.34%, chromium content is 1.70%, molybdenum content is 0.42% of alloy plastic die steel, its brand is expressed as "SM3Cr2Mo".

8, bearing steel grade expression method

Bearing steel is divided into four categories: high carbon chromium bearing steel, carburized bearing steel, high carbon chromium stainless bearing steel and high temperature bearing steel.

① High carbon chromium bearing steel, the symbol "G" is added to the head of the grade, but the carbon content is not indicated. Chromium content is measured in thousands, and other alloying elements are expressed by alloying content of alloying structural steel. For example, a bearing steel with an average chromium content of 1.50% would have a grade of "GCr15".

(2) Carburized bearing steel, the use of alloy structural steel brand method, and add a symbol "G" in the head of the brand. For example, G20CrNiMo. High quality carburized bearing steel, with "A" at the end of the grade. For example, G20CrNiMoA.

(3) High carbon chromium stainless bearing steel and high temperature bearing steel, the use of stainless steel and heat resistant steel brand representation method, brand head does not add the symbol "G". For example: high carbon chromium stainless bearing steel "9Cr18" and high temperature bearing steel "10Cr14Mo".

9, stainless steel and heat-resistant steel brand expression method

Stainless steel and heat-resistant steel grades are denoted by alloying element symbols and Arabic numerals as specified in the standard. "Y" is added to the head of the grade for cutting stainless steel and free-cutting heat-resistant steel.

An Arabic numeral is generally used to indicate the average carbon content (measured in thousands); When the average carbon content is greater than or equal to 1.00%, it is indicated by two Arabic numerals; When the upper limit of carbon content is less than 0.10%, "0" represents carbon content; When the upper limit of carbon content is less than 0.03% and > 0.01% (ultra-low carbon), "03" represents carbon content; When the upper limit of carbon content (very low carbon ≤0.01%), "01" represents the carbon content. When no lower limit of carbon content is specified, Arabic numerals are used to indicate the upper limit of carbon content.

Alloying element content is expressed in the same way as alloying structural steel. For example: stainless steel with an average carbon content of 0.20% and chromium content of 13%, its brand is "2Cr13"; Chrome-nickel stainless steel with an upper carbon content of 0.08%, an average chromium content of 18%, and a nickel content of 9%, whose brand is expressed as "0Cr18Ni9"; Sulfur free cutting chrome stainless steel with an upper carbon content of 0.12% and an average chromium content of 17%, whose brand is denoted as "Y1Cr17"; The average carbon content is 1.10%, chromium content is 17% of high carbon chromium stainless steel, its brand is "11Cr7"; For the ultra-low carbon stainless steel with the upper carbon content of 0.03%, the average chromium content of 19% and nickel content of 10%, its brand is "03Cr19Ni10"; The very low carbon stainless steel with an upper carbon content of 0.01%, an average chromium content of 19%, and a nickel content of 11%, is represented by the brand "01Cr19Ni11".

The current domestic standard of stainless steel is revised according to JIS standard, but the expression method of stainless steel is different from that of Japan and other countries. We use alloying elements and average C content, and Japan uses letters and Arabic numerals to indicate the purpose. For example, stainless steel grade SUS202, SUS316, SUS430, S-steel, U-use, S-stainless(stainless). For example, heat resistant steel brands SUH309, SUH330, SUH660, H-Heatresistins. Different numbers in the label indicate different types of stainless steel. In Japan, stainless steel is used for various types of products, with corresponding letters after the brand name, such as stainless steel rod SUS-B, hot rolled stainless steel plate SUS-HP; Heat resistant steel rod SUHB, heat resistant steel plate SUHP. Britain, the United States and other western countries, stainless heat-resistant steel brand expression method is basically consistent with Japan, mainly with Arabic numbers, and the number is the same, that is, the brand is the same. Because Japan's stainless steel is made of American steel.

10, welding with steel grade expression method

The welding steel includes carbon steel for welding, alloy steel for welding and stainless steel for welding, etc., and its brand is indicated by adding a symbol "H" to the head of all kinds of welding steel brands. For example, H08, H08Mn2Si, and H1Cr18Ni9.

High quality welding steel with the symbol "A" at the end of the grade. For example, H08A and 08Mn2SiA.

11. The grade of silicon steel for electrical engineering

The steel number consists of numbers, letters and numerals.

The letter symbols of unoriented and oriented silicon steel are "W" and "Q" respectively.

Thickness at the front, letters in the middle, iron loss at the back, for example, 30Q113. In oriented silicon steel, the highly magnetically sensitive letter symbol "G" is placed next to "Q", e.g. 30QG113

The number after the letter represents 100 times the iron loss (W/kg).

The letter "G" indicates the test at a high frequency; Where "G" is not added, it means that it is tested at a frequency of 50 cycles.

30Q113 represents the maximum iron loss per unit weight of cold-rolled oriented silicon steel products for electrical purposes at 50 H frequency of 1.13W/kg.

The expression method of cold-rolled silicon steel is consistent with the Japanese standard (JISC2552-86), only the letter symbols are different. For example, the oriented silicon steel is 27Q140, the corresponding JIS brand is 27G140, and the corresponding JIS brand is 30QG110 (G: common material, P: high oriented). Non-oriented silicon steel is rated 35W250, while JIS is rated 35A250.