The subdivision of the method of steel number representation in China

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

The above steel is usually divided into two categories: general steel and special steel. The grade representation method is composed of the Chinese pinyin letters of the yield point or yield strength of the steel, the yield point or yield strength value, the quality grade of the steel, and the degree of steel deoxidation, which is actually composed of four parts.

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

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

The two grades Q235 and Q345 are the most typical grades of engineering steel, the largest production and use, 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 sedative steel symbol "Z" and the special sedative steel symbol "TZ" can be omitted, for example: Q235 steel whose quality grade is C and D respectively, its grade should be Q235CZ and Q235DTZ, but can be omitted as Q235C and Q235D.

Low alloy high strength structural steel has killed steel and special killed steel, but the end of the grade does not write a symbol indicating the deoxidation method.

② 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, etc., for example, the pressure vessel is represented by the steel grade "Q345R"; The grade of weatherproof steel is Q340NH; Q295HP welding gas cylinder steel grade; Q390g boiler steel grade; Q420q Steel grade for bridge.

(3) According to needs, the grade of general low-alloy high-strength structural steel can also use two Arabic numerals (indicating the average carbon content, measured in a few tens of thousands) and chemical element symbols, expressed in order; The grade of special low-alloy high-strength structural steel can also use two Arabic numerals (representing the average carbon content, measured in a few tens of thousands) and chemical element symbols, as well as some specified symbols representing the use of the product, in order.

2. high-quality carbon structural steel and high-quality carbon spring steel grade expression method

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

① Boiling steel and semi-killed steel, add the symbol "F" and "b" at the end of the grade. For example, the average carbon content of boiling steel is 0.08%, and its grade is expressed as "08F"; For semi-killed steel with an average carbon content of 0.10%, the grade is denoted as "10b".

(2) Killed steel (S, P ≤0.035%, respectively) general non-standard symbols. For example: the average carbon content of 0.45% of the killed steel, its grade is expressed as "45".

③ For high-quality carbon structural steel with higher manganese content, add the manganese element symbol after the Arabic numeral indicating the average carbon content. For example, if the average carbon content is 0.50% and the manganese content is 0.70% ~ 1.00%, the steel grade is expressed as "50Mn".

④ High quality carbon structural steel (S, P ≤0.030%), add the symbol "A" after the grade. For example, high-grade high-quality carbon structural steel with an average carbon content of 0.45% is expressed as "45A".

⑤ Extra high quality carbon structural steel (S≤0.020%, P≤0.025%), add the symbol "E" after the grade. For example: the average carbon content of 0.45% of the extra high quality carbon structural steel, its grade is expressed as "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 steel exists simultaneously in the two standards 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 represented by Arabic numerals and standard chemical element symbols.

A two-digit Arabic numeral indicating the average carbon content (in tens of thousands of parts) is placed at the head of the label.

The expression method of alloying element content is: when the average content is less than 1.50%, only the element is indicated in the grade, 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%,... When the alloy element is written as 2, 3, 4, 5...... .

For example: the average content of carbon, chromium, manganese, silicon is 0.30%, 0.95%, 0.85%, 1.05% of alloy structural steel, when the content of S, P ≤0.035%, its brand is expressed as "30CrMnSi".

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

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 special alloy structural steel grade should be added at the head (or tail) of the grade to represent the use of the product as specified in Table 1. For example, the riveting screw special 30CrMnSi steel, steel number is expressed as ML30CrMnSi.

The grade of alloy spring steel is the same as that of alloy structural steel.

For example, the average content of carbon, silicon and manganese is 0.60%, 1.75% and 0.75% respectively, and the brand is expressed as "60Si2Mn". High quality spring steel, plus the symbol "A" at the end of the grade, its grade is expressed as "60Si2MnA".

4. free cutting steel grade expression method

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

(1) Sulfur free cutting steel and sulfur and phosphorus free cutting steel are not added after the symbol "Y" and Arabic numerals. For example, a free-cutting steel with an average carbon content of 0.15% is represented as "Y15".

2 Higher manganese content of sulfur or sulfur, phosphorus free cutting steel in the symbol "Y" and Arabic numerals after the manganese element symbol. For example: the average carbon content of 0.40%, manganese content of 1.20% to 1.55% of the free cutting steel, its brand is expressed as "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, set this parameter to Y15Pb or Y45Ca.

5. non-tempering mechanical structural steel grade expression method

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

6. tool steel grade expression method

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

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

a. Ordinary manganese content carbon tool steel, after the tool steel symbol "T" is an Arabic numeral. For example: carbon tool steel with an average carbon content of 0.80%, its grade is expressed as "T8".

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

c. High quality carbon tool steel, add "A" at the end of the 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 alloy element symbols and Arabic numerals specified in the standard are used, but the average carbon content is generally not indicated, for example: the average carbon content is 1.60%, the chromium, molybdenum, vanadium content is 11.75%, 0.50%, 0.22% of the alloy tool steel, its brand is expressed as "Cr12MoV"; The high speed tool steel with an average carbon content of 0.85%, tungsten, molybdenum, chromium and vanadium content of 6.00%, 5.00%, 4.00% and 2.00% respectively, its brand is expressed as "W6Mo5Cr4V2".

If the average carbon content is less than 1.00%, an Arabic numeral can be used to indicate the carbon content (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 expressed as "8MnSi".

Low chromium (average chromium content < 1.00%) alloy tool steel, adding the number "0" before the chromium content (in a few thousandths). For example, an alloy tool steel with an average chromium content of 0.60% is represented as "Cr06".

7. plastic die steel grade expression method

In addition to the symbol "SM" added to the head, the rest of the representation method is the same as that of high-quality carbon structural steel and alloy tool steel. For example: the average carbon content of 0.45% carbon plastic die steel, its brand is expressed as "SM45"; The average carbon content is 0.34%, the chromium content is 1.70%, the molybdenum content is 0.42% of the 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, plus the symbol "G" in the grade head, but does not indicate the carbon content. Chromium content is measured in a few thousand parts, and other alloying elements are expressed according to the alloy content of alloy structural steel. For example, bearing steel with an average chromium content of 1.50% is represented as "GCr15".

(2) Carburized bearing steel, using the grade of alloy structural steel, and the symbol "G" is added to the head of the grade. For example, G20CrNiMo. High quality carburized bearing steel, plus "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 grade representation method, grade head without 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 grade expression method

Stainless steel and heat-resistant steel grades are indicated by alloy element symbols and Arabic numerals specified in the standard, and "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 ≥1.00%, it is indicated by two Arabic numerals; When the upper limit of carbon content is less than 0.10%, "0" indicates the carbon content; When the upper limit of carbon content is ≤0.03%, > 0.01% (ultra-low carbon), "03" indicates the carbon content; When the upper limit of carbon content (extremely low carbon when ≤0.01%), "01" indicates the carbon content. When no lower limit of carbon content is specified, Arabic numerals are used to indicate the upper limit of carbon content.

The expression method of alloying element content is the same as that of alloying structural steel. For example: stainless steel with an average carbon content of 0.20% and a chromium content of 13%, its brand is expressed as "2Cr13"; Chromium nickel stainless steel with an upper carbon content of 0.08%, an average chromium content of 18% and a nickel content of 9%, and its grade is expressed as "0Cr18Ni9"; Sulfur free cutting chromium stainless steel with an upper carbon content of 0.12% and an average chromium content of 17%, and its brand is expressed as "Y1Cr17"; High-carbon chromium stainless steel with an average carbon content of 1.10% and a chromium content of 17%, and its grade is expressed as "11Cr7"; The upper limit of carbon content is 0.03%, the average chromium content is 19%, the nickel content is 10% of the ultra-low carbon stainless steel, its brand is expressed as "03Cr19Ni10"; The upper limit of carbon content is 0.01%, the average chromium content is 19%, the nickel content is 11% of the very low carbon stainless steel, its brand is expressed as "01Cr19Ni11".

The current domestic stainless steel standard is revised with reference to JIS standards, but the expression method of stainless steel grade is different from the standards of Japan and other countries. We are expressed by alloying elements and the average C content, and Japan is expressed by letters and Arabic numerals indicating the purpose. For example, stainless steel grades SUS202, SUS316, SUS430, S-steel, U-use, S-stainless. For example, heat resistant steel grades SUH309, SUH330, SUH660, H-Heatresistins. Different numbers in the grades indicate different types of stainless steel. Japan says different kinds of stainless steel products, add corresponding letters after the grade, such as stainless steel rod SUS-B, hot rolled stainless steel plate SUS-HP; Heat resistant steel rod SUHB, heat resistant steel plate SUHP. In Western countries such as the United Kingdom and the United States, the expression method of stainless steel grades is basically the same as that of Japan, mainly expressed in Arabic numerals, and the numbers expressed are the same, that is, the grades are the same. Because Japan's stainless steel is used in the United States.

10. welding steel grade expression method

Welding steel includes carbon steel for welding, alloy steel for welding and stainless steel for welding, etc., and its grade is expressed by adding a symbol "H" to the head of various welding steel grades. 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. electrical silicon steel grade expression method

The steel number consists of numbers, letters, and numerals.

The letter symbols of non-oriented and oriented silicon steels are "W" and "Q" respectively.

The thickness is in the front, the letter symbol is in the middle, and the iron loss value is in the back, such as 30Q113. In oriented silicon steel, the highly magnetic letter symbol "G" is placed together with "Q", for example, 30QG113

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

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

30Q113 indicates that the maximum iron loss per unit weight of cold-rolled oriented silicon steel products for electrical purposes at 50 Hz is 1.13W/kg.

The expression method of cold-rolled silicon steel is consistent with the Japanese standard (JISC2552-86), but the letter symbol is different, such as oriented silicon steel grade 27Q140, and the corresponding JIS grade is 27G140, 30QG110 and the corresponding JIS grade is 30P110 (G: indicates ordinary materials, P: indicates high orientation). Non-oriented silicon steel grade 35W250, the corresponding JIS grade 35A250.