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Detailed Description of Steel Grade Representation in China



1. Designation of carbon structural steel and low alloy high strength structural grade

The above steel is usually divided into general steel and special steel. The indication method of steel grade is composed of Chinese phonetic alphabet of yield point or yield strength of steel, the value of yield point or yield strength, the quality grade of steel, and the deoxidation degree of steel, which is actually composed of four parts.

① The Pinyin letter "Q" representing the yield point is used for general structural steel. The yield point value (unit: MPa), quality grade (a, B, C, D, e) specified in Table 1, deoxidation method (F, B, Z, TZ) and other symbols are used to form the brand in sequence. For example, the grades of carbon structural steel are q235af and q235bz; the grades of low alloy high strength structural steel are Q345C and Q345D.

Q235bz refers to the killed carbon structural steel with yield point value ≥ 235mpa and quality grade B.

Q235 and Q345 are the most typical grades of engineering steel, with the largest production and use and the most extensive use. These two brands are available almost all over the world.

In the grade composition of carbon structural steel, the killed steel symbol "Z" and the special killed steel symbol "TZ" can be omitted. For example, for Q235 steel with quality grade of C and D, its grade should be q235cz and q235dtz, but Q235C and q235d can be omitted.

Low alloy high strength structural steel has killed steel and special killed steel, but the symbol of deoxidation method is not added at the end of the grade.

② The special structural steel is generally represented by the symbol "Q" which represents the steel yield point, the yield point value and the symbol for product use specified in Table 1. For example, the steel grade for pressure vessel is "Q345R"; the grade of weathering steel is q340nh; the steel grade for q295hp welding gas cylinder; q390g boiler steel; q420q bridge steel.

③ According to the need, the grade of general low alloy high strength structural steel can also be expressed in sequence by two Arabic numerals (representing the average carbon content, in tens of thousands) and chemical element symbols; the grade of special low alloy high strength structural steel can also be expressed by two Arabic numerals (representing the average carbon content in tens of thousands) and chemical element symbols, as well as some regulations The symbol representing the purpose of the product, expressed in order.

 

2. Designation of high quality carbon structural steel and high quality carbon spring steel

High quality carbon structural steel is made of two Arabic numerals (average carbon content expressed in tens of thousands) or Arabic numerals and element symbols.

① For rimming steel and semi killed steel, the symbols "F" and "B" shall be added respectively 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"; and that of semi killed steel with an average carbon content of 0.10% is expressed as "10B".

② Killed steel (s, P ≤ 0.035% respectively) is generally not marked. For example, the grade of killed steel with an average carbon content of 0.45% is expressed as "45".

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

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

⑤ For super grade high quality carbon structural steel (s ≤ 0.020%, P ≤ 0.025%), the symbol "e" shall be added after the grade. For example, the grade of super grade high quality carbon structural steel with an average carbon content of 0.45% is expressed as "45e".

The designation of high-quality carbon spring steel is the same as that of high-quality carbon structural steel (65, 70, 85 and 65Mn steels exist simultaneously in GB / t1222 and GB / t699 respectively).

 

3. Designation of alloy structural steel and alloy spring steel

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

Use two Arabic numerals to indicate the average carbon content (in tens of thousands), and put it on the head of the brand.

The expression method of alloy element content is as follows: 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 is 1.50% 2.49%, 2.50% 3.49%, 3.50% 4.49%, 4.50% 5.49% When the alloy element is added, it is written as 2, 3, 4, 5.

For example, if the average content of carbon, chromium, manganese and silicon are 0.30%, 0.95%, 0.85% and 1.05% respectively, when the content of S and P is ≤ 0.035%, the 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: "30CrMnSiA".

For super quality alloy structural steel (s ≤ 0.015%, P ≤ 0.025%), the symbol "e" is added at the end of the grade, for example: "30crm nsie".

The special alloy structural steel grade shall be added with the symbol of product use specified in Table 1 at the head (or tail) of the grade. For example, for 30CrMnSi steel for riveting, the steel grade is expressed as ml30crmnsi.

② The designation of alloy spring steel is the same as that of alloy structural steel.

For example, for spring steel with an average content of 0.60%, 1.75% and 0.75% of carbon, silicon and manganese respectively, the grade is expressed as "60Si2Mn". For high quality spring steel, the symbol "a" is added at the end of the grade, and the grade is expressed as "60Si2MnA".

 

4. Designation of free cutting steel

Free cutting steel is represented by standard chemical element symbols, specified symbols and Arabic numerals. The Arabic numbers indicate the average carbon content (in tens of thousands).

① Free cutting element symbols are not added after the symbol "Y" and Arabic numerals for sulfur added free cutting steel and sulfur and phosphorus free cutting steel. For example: average carbon content

 

5. Designation of non quenched and tempered mechanical structural steel

For non quenched and tempered mechanical structural steel, the symbols "YF" and "F" are added at the head of the grade 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".

 

6. Designation of tool steel grades

Tool steels can be divided into carbon tool steel, alloy tool steel and high speed tool steel.

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

a. Common carbon tool steel with manganese content is Arabic numerals after the symbol "t". For example, the grade of carbon tool steel with an average carbon content of 0.80% is expressed as "T8".

b. For carbon tool steel with high manganese content, manganese element symbol shall be added after 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 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 not indicated. For example, the alloy tool steel with an average carbon content of 1.60%, chromium, molybdenum and vanadium content of 11.75%, 0.50% and 0.22% is expressed as "Cr12MoV"; the average carbon content is 0.85%, and the contents of tungsten, molybdenum, chromium and vanadium are 6.00%, 5.00%, 4.00% and 2.00%, respectively Its grade is "W6Mo5Cr4V2".

If the average carbon content is less than 1.00%, one Arabic numeral can be used to indicate the carbon content (in thousands). For example, the grade of 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".

For low chromium (average chromium content < 1.00%) alloy tool steel, add "0" before chromium content (in thousandth). For example, the grade of alloy tool steel with an average chromium content of 0.60% is expressed as "cr06".

 

7. Steel grade indication of plastic mould

In addition to the symbol "SM" on the head, the designation of plastic mold steel is the same as that of high quality carbon structural steel and alloy tool steel. For example, the grade of carbon plastic die steel with an average carbon content of 0.45% is expressed as "sm45"; the grade of alloy plastic die steel with an average carbon content of 0.34%, chromium content of 1.70% and molybdenum content of 0.42% is expressed as "sm3cr2mo".

 

8. Representation of bearing steel grade

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

① For high carbon chromium bearing steel, the symbol "g" is added at the head of the brand, but the carbon content is not indicated. The chromium content is expressed in thousandth, and other alloying elements are expressed as alloy content of alloy structural steel. For example, the grade of bearing steel with an average chromium content of 1.50% is expressed as "GCr15".

② Carburized bearing steel is represented by the grade of alloy structural steel, and the symbol "g" is added at the head of the grade. For example, "g20crnimo.". High quality carburized bearing steel, add "a" at the end of the grade. For example, "g20crnimoa.".

③ High carbon chromium stainless bearing steel and high temperature bearing steel are indicated by stainless steel and heat-resistant steel, and the mark "g" is not added at the head of the brand. For example: high carbon chromium stainless bearing steel "9Cr18" and high temperature bearing steel "10cr14mo".

 

9. Designation of stainless steel and heat resistant steel

The grades of stainless steel and heat-resistant steel are represented by alloy element symbols and Arabic numerals specified in the standard. For cutting stainless steel and free cutting heat-resistant steel, "Y" is added at the head of the grade.

Generally, one Arabic numeral is used to indicate the average carbon content (in thousands); when the average carbon content is more than or equal to 1.00%, two digits are used Arabic numerals: when the upper limit of carbon content is less than 0.10%, the carbon content is represented by "0"; when the upper limit of carbon content is ≤ 0.03% and > 0.01% (ultra-low carbon), the carbon content is represented by "03"; when the upper limit of carbon content (≤ 0.01%, extremely low carbon), the carbon content is represented by "01". When there is no lower limit for carbon content, Arabic numerals are used to represent the upper limit of carbon content.

The expression method of alloy element content is the same as that of alloy structural steel. For example, the grade of stainless steel with an average carbon content of 0.20% and a chromium content of 13% is expressed as "2Cr13"; the grade of chromium nickel stainless steel with an upper carbon content of 0.08%, an average chromium content of 18% and a nickel content of 9% is "0Cr18Ni9"; the grade of sulfur free cutting chromium stainless steel with an upper limit of carbon content of 0.12% and an average chromium content of 17% is expressed as "y1cr17"; the average carbon content is 1 The grade of high carbon chromium stainless steel with 17% chromium content is expressed as "11cr7"; the grade of ultra-low carbon stainless steel with upper carbon content of 0.03%, average chromium content of 19% and nickel content of 10% is "03cr19ni10"; the grade of ultra-low carbon stainless steel with upper carbon content of 0.01%, average chromium content of 19% and nickel content of 11% is "01cr19ni11".

The current domestic standard of stainless and heat-resistant steel is revised according to JIS standard, but the designation method of stainless and heat-resistant steel is different from that of Japan and other countries. We use alloy element and average C content to express, Japan uses letter and Arabic numeral to indicate usage. For example, stainless steel grades SUS202, SUS316, SUS430, S-STEEL (steel), u-use (use), s-stainless steel (stainless steel). For example, heat-resistant steel grades suh309, suh330, suh660, h-heatresistins. Different numbers in the grade indicate different types of stainless and heat-resistant steels. Japan means that for different products of stainless and heat-resistant steel, the corresponding letters are added after the brand, such as stainless steel bar sus-b, hot-rolled stainless steel plate sus-hp, heat-resistant steel bar suhb, heat-resistant steel plate suhp. In western countries, such as Britain and the United States, the designation of stainless and heat-resistant steel grades is basically the same as that of Japan, mainly in Arabic numerals, and the numbers expressed are the same, that is, the grades are the same. Because Japan's stainless and heat-resistant steel is American.

 

10. Steel grades for welding

Steel for welding includes carbon steel for welding, alloy steel for welding and stainless steel for welding, etc. the mark indication method is to add the symbol "H" at the head of various welding steel grades. For example: "H08", "h08mn2si", "h1cr18ni9".

High quality welding steel with "a" at the end of the grade. For example: "H08A", "08mn2sia".

 

11. Designation of silicon steel for electrical purposes

The steel grade consists of numbers, letters and numbers.

The letter symbols of non oriented and oriented silicon steel are "W" and "Q", respectively

The thickness is placed at the front, the letter symbol is placed in the middle, and the iron loss value is placed at the back, such as 30q113. In oriented silicon steel, the letter symbols "g" and "Q" with high magnetic induction are put together, such as 30qg113

The number after the letter indicates 100 times the iron loss value (w / kg).

If the letter "g" is used, it means that the test is carried out at a high frequency; if no "g" is added, it means that the test is carried out at the frequency of 50 cycles.

30q113 indicates that the maximum core loss per unit weight of cold-rolled grain oriented silicon steel for electrical purposes at 50 Hz frequency is 1.13w/kg.

The indication method of cold-rolled silicon steel is consistent with Japanese standard (jisc2552-86), but the letter symbol is different. For example, the grade of oriented silicon steel is 27q140, and the corresponding JIS grade of 30qg110 is 30p110 (G: common material, P: high orientation). The grade of non oriented silicon steel is 35w250, and the corresponding JIS grade is 35a250.


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