Representation of common metal grades

Common Metal Material grade representation method (I)  
There are many kinds of metal materials used for machine parts. In order to make production and management convenient and orderly, the relevant standards stipulate the expression methods of their grades for different metal materials to show unity and facilitate adoption and use.  
Designation of iron and steel products (refer to GB/T221-2000)
-- Basic overview of the standard
The GB/T221-2000 standard was revised on April 1, 2000 with reference to the changes in the representation methods of foreign steel product grades and domestic steel product grades (such as Q345 replacing 16Mn), and was implemented on November 1, 2000.  
-- Changes in main technical contents
(1) Since some steel product grades have their own special standards, the original standard has cancelled the designation methods of ferroalloys, cast alloys, superalloys, precision alloys, corrosion resistant alloys and cast iron, cast steel, powder materials, etc.  
(2) The appearance of some new steel products has further improved the original standard. The new standard has added decarburized low phosphorus grain iron, vanadium bearing pig iron, cast wear-resistant pig iron, guaranteed hardenability steel, non quenched and tempered mechanical structural steel, plastic mold steel, oriented silicon steel (for telecommunications) and other brand representation methods.  
(3) Some steel grades that do not adapt to the development of science and technology and are incompatible with production have been completely changed or modified. For example, carbon structural steel A3 is changed to Q235, and low-alloy high-strength structural steel 16Mn is changed to Q345. The grades of stainless steel, heat-resistant steel and cold-rolled silicon steel have also been modified.  
(4) Table 3 of "Examples of steel product grade representation" in the original standard has been deleted because it is not applicable to the new standard.  
-- Basic principles of steel product grade representation
(1) All grades of iron and steel products in national standards and industrial standards shall be prepared according to the grade representation method specified in GB/T221-2000. The grades of steel products that do not conform to the regulations shall be changed when the standard is revised, and the grades of some new steel products shall also be prepared accordingly.  
(2) The product brand is generally represented by the combination of Chinese phonetic alphabet, chemical element symbols and Arabic numerals.  
(3) When the Chinese phonetic alphabet is used to represent the product name, purpose, characteristics and process method, the first letter is generally selected from the Chinese phonetic alphabet representing the product name. When it is repeated with the letter selected by another product, the second letter or the third letter can be used instead, or the first pinyin letter of two Chinese characters can be selected at the same time.  
(4) If there is no Chinese character or Chinese Pinyin available for the time being, the symbols shall be English letters.


Designation of common metal materials (II)
Example and description of steel product grade representation
-- Pig iron grade indication method Pig iron grade shall be indicated by symbols and Arabic numerals specified in Table 1.  
a. Arabic numerals indicate the average silicon content (in thousandths).  
For example, the grade of cast iron with silicon content of 2.75%~3.25% is "Z 30";  
The grade of pig iron for steelmaking with silicon content of 0.85%~1.25% is expressed as "L 10".  
b. For vanadium bearing pig iron and decarburized low phosphorus granular iron, Arabic numerals indicate the average content of vanadium and carbon (both in thousandths).  
For example, the grade of vanadium containing pig iron with vanadium content not less than 0.40% is "F 40"; Decarburized low phosphorus granular iron for steelmaking with carbon content of 1.20%~1.60% is represented by "TL 14".  
－ Carbon structural steel and low-alloy high-strength structural steel grades are generally divided into general steel and special steel.  
a. The pinyin letter "Q" representing the yield point is used for general structural steel. The yield point value (unit: MPa), quality grade, deoxidation method and other symbols constitute the brand in order. For example: carbon junction
Structural steel grades are expressed as Q235AF, Q235BZ; low-alloy high-strength structural steel grades are expressed as
Are: Q 345C, Q345D. In the grade composition of carbon structural steel, killed steel symbol "Z" and special killed steel symbol "TZ" can be omitted, for example, the quality grades of C and D
Q235 steel shall be Q235CZ and Q235DTZ, but can be omitted as Q235C and Q235DTZ
     Q235D 。 Low alloy high strength structural steel includes killed steel and special killed steel, but the symbol indicating deoxidation method is not added at the end of the grade.  
b. Special structural steel is generally represented by the symbol "Q" representing the steel yield point, the yield point value and the symbol representing the product use, for example, the steel grade used for pressure vessels is represented by "Q345R"; The grade of weathering steel is expressed as: Q340NH.  
c. As required, the grade of general low-alloy high-strength structural steel can also be composed of two Arabic numerals (average carbon content in ten thousandths) and standard element symbols; For the grades of special low-alloy high-strength structural steel, in addition to the general composition, the symbols specified in Table 1 to represent the product use shall also be added.
－ Indication method of grade of high-quality carbon structural steel and high-quality carbon spring steel
High quality carbon structural steel adopts two Arabic numerals (the average carbon content is expressed in ten thousandths) or the combination of Arabic numerals, element symbols and specified symbols to form the grade.  
a. For rimmed steel and semi killed steel, the symbols "F" and "b" shall be added at the end of the grade. For example, the grade of rimmed steel with an average carbon content of 0.08% is expressed as "08F"; The grade of semi killed steel with an average carbon content of 0.10% is expressed as "10b".  
b. Killed steel (S, P ≤ 0.035% respectively) is generally not marked with symbols. For example, for killed steel with an average carbon content of 0.45%, its grade is expressed as "45".  
c. For high-quality carbon structural steel with high manganese content, add the symbol of manganese element after the Arabic numeral representing the average carbon content. For example, the grade of steel with average carbon content of 0.50% and manganese content of 0.70%~1.00% is expressed as "50Mn".  
d. High quality carbon structural steel (S and P ≤ 0.030% respectively) shall be marked with "A" after the grade. Example
For example, the grade of high-grade high-quality carbon structural steel with an average carbon content of 0.45% is shown as "45A".  
－ Super quality carbon structural steel (S ≤ 0.020%, P ≤ 0.025%), with the symbol "E" added after the grade.  
For example, the grade of super quality carbon structural steel with an average carbon content of 0.45% is "45E".  

The indication method of high-quality carbon spring steel grades is the same as that of high-quality carbon structural steel grades (65, 70, 85 and 65Mn steels exist in both GB/T1222 and GB/T699 standards).

Designation of common metal materials (III)
Designation of alloy structural steel and alloy spring steel
－ The grades of alloy structural steel are represented by Arabic numerals and standard chemical element symbols
Use two Arabic numerals to express the average carbon content (in tens of thousands), and put it at the head of the brand. The expression method of alloy element content is: when the average content is less than 1.50%, only elements are indicated in the grade, and generally the content is not indicated; When the average alloy content is 1.50% ～ 2.49%, 2.50% ～ 3.49%, 3.50% ～ 4.49%, 4.50% ～ 5.49%,..., it is written as 2, 3, 4, 5... after the alloy element. For example, for alloy structural steel with average content of carbon, chromium, manganese and silicon of 0.30%, 0.95%, 0.85% and 1.05% respectively, when the content of S and P is ≤ 0.035%, its grade is expressed as "30CrMnSi". High quality alloy structural steel (S and P content ≤ 0.025% respectively) is indicated by the symbol "A" at the end of the grade. For example: "30 CrMnSiA". Special grade high-quality alloy structural steel (S ≤ 0.015%, P ≤ 0.025%) shall be marked with "E" at the end of the grade, such as "30CrM nSiE".  
The special alloy structural steel grade shall also be added with the specified symbol representing the product use at the head (or tail) of the grade.  
－ The expression method of alloy spring steel grade is the same as that of alloy structural steel
For example, the grade of spring steel with average contents of carbon, silicon and manganese of 0.60%, 1.75% and 0.75% is "60Si2Mn". High quality spring steel, with the symbol "A" at the end of the grade, is represented as "60Si2MnA".  
Designation of free cutting steel
Free cutting steel is represented by standard chemical element symbols, symbols specified in Table 1 and Arabic numerals. Arabic numerals indicate the average carbon content (in parts per ten thousand).  
a. For sulfurized free cutting steel and sulfurized and phosphorous free cutting steel, free cutting element symbol is not added after the symbol "Y" and Arabic numerals. For example, the grade of free cutting steel with an average carbon content of 0.15% is shown as "Y15".  
b. The symbol "Y" and Arabic numerals shall be followed by the symbol of manganese element for free cutting steels containing sulfur or sulfur and phosphorus with higher manganese content. For example, the grade of free cutting steel with an average carbon content of 0.40% and a manganese content of 1.20%~1.55% is expressed as "Y40Mn".  
c. For free cutting steel containing free cutting elements such as calcium and lead, the free cutting element symbol shall be added after the symbol "Y" and Arabic numerals. For example: "Y15Pb", "Y45Ca".  
－ The designation of non quenched and tempered mechanical structural steel is non quenched and tempered mechanical structural steel. The symbols "YF" and "F" are added at the head of the designation to indicate free cutting non quenched and tempered mechanical structural steel and non quenched and tempered mechanical structural steel for hot forging. Other contents of the designation are the same as those of alloy structural steel. For example: YF35V, F45V.


Designation of common metal materials (IV)  
Designation of tool steel
Tool steels are classified into carbon tool steels, alloy tool steels and high-speed tool steels.  
- Standard chemical element symbol is used for carbon tool steel
No., specified symbols and Arabic numerals. Arabic figures represent the average carbon content (in thousandths).  
a. For ordinary carbon tool steel with manganese content, the symbol "T" for tool steel is followed by Arabic numerals.  
For example, the grade of carbon tool steel with an average carbon content of 0.80% is "T 8".  
b. For carbon tool steel with higher manganese content, the symbol of manganese element is added after the symbol "T" and Arabic numerals of tool steel. For example: "T8Mn".  
c. High quality carbon tool steel, add "A" at the end of the grade. For example: "T8MnA".  
- Alloy tool steel and high-speed tool steel
The designation 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 grade of alloy tool steel with an average carbon content of 1.60%, chromium, molybdenum and vanadium content of 11.75%, 0.50% and 0.22% respectively is "Cr12MoV"; High speed tool steel with an average carbon content of 0.85% and tungsten, molybdenum, chromium and vanadium contents of 6.00%, 5.00%, 4.00% and 2.00% respectively is designated as "W6Mo5Cr4V 2".  
If the average carbon content is less than 1.00%, an Arabic numeral can be used to represent the carbon content (in thousandths). For example, the grade of alloy tool steel with average carbon content of 0.80%, manganese content of 0.95% and silicon content of 0.45% is expressed as "8MnSi". For low chromium (average chromium content<1.00%) alloy tool steel, add "0" before the chromium content (in thousandths). For example, the grade of alloy tool steel with an average chromium content of 0.60% is "Cr 06".  
Representation of steel grades for plastic moulds
Except for adding the symbol "SM" at the head of the plastic mold steel grade, the other representation methods are the same as those of high-quality carbon structural steel and alloy tool steel grades. For example, the grade of carbon plastic die steel with an average carbon content of 0.45% is "SM 45"; Alloy plastic die steel with an average carbon content of 0.34%, chromium content of 1.70% and molybdenum content of 0.42% is designated as "SM3Cr2Mo".  
Designation of bearing steel
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.  
－ For high carbon chromium bearing steel, the symbol "G" is added at the head of the grade, but the carbon content is not indicated. Chromium content is expressed in thousandths, and other alloy elements are expressed in accordance with the alloy content of alloy structural steel. For example, the grade of bearing steel with an average chromium content of 1 □ 50% is expressed as "GCr 15".  
-- Carburized bearing steel shall be represented by the grade of alloy structural steel, and the symbol "G" shall be added at the head of the grade. For example: "G20 CrNiMo". High quality carburized bearing steel, add "A" at the end of the grade. For example: "G20CrNiMoA".  
- High carbon chromium stainless bearing steel and high temperature bearing steel shall be represented by grades of stainless steel and heat-resistant steel, with no sign "G" added at the head of the grades. For example, high carbon chromium stainless bearing steel "9Cr 18" and high temperature bearing steel "10Cr14Mo". (Global Metal Network OMETAL. COM) (Do you want to see such a large amount of metal information for free every day? 1. Click here Set the Global Metal Network as your homepage 2. Click here Add the global metal net to your favorites.)