■Numbering and Expression of Stainless Steel
① International elemental chemical symbols and domestic symbols are used to express chemical composition, and Arabic characters the content, for example, China, Russia 12CrNi3A.
② Certain digit of numbers expresses the serial of steel, for example, America, Japan serial 300, serial 400, and serial 200.
③ Latin alphabets and order form the reference number of usage only.
■Chinese nomenclature of stainless steel
＜Regulations of GB/T221-2000＞
According to GB/T221-2000, grades of stainless steel and heat resistant steel are expressed in regulated symbols of alloy and Arabic numbers, and grades of stainless steel and heat resistant steel starts with a “Y”.
Generally used single digit Arabic number to express carbon content (by the thousandth). If the average carbon content is no less than 1.00%, it is expressed in doubt-digit Arabic number.
If the upper limit of carbon content is lower than 0.1%, use “0” for the carbon content. If the upper limit is no more than 0.03% while over 0.01% (Ultra low carbon steel), use “03” for the carbon content.
If the upper limit of carbon content is no more than 0.01% (extreme low carbon), use “01” for carbon content. If there is no lower limit to the carbon content, use Arabic number for upper limit of the carbon content.
Alloying element content is express in the same form of structural alloy steel. For example, when the average carbon content is 0.20%, and chromium content is13%, the expression of stainless steel is “2Cr13”.
- When the upper limit of carbon content is 0.08%, average chromium content is 18%, and nickel content is 9%, the expression of chromium-nickel stainless steel is “0Cr18Ni9”.
- When the upper limit of carbon content is 0.12% and average chromium content is 17%, the expression of the sulfur-added free-cutting chromium stainless steel is “Y1Cr17”.
- When the average carbon content is 1.10% and chromium content is 17%, the grade of the high-carbon chromium stainless steel is “11Cr17”.
- When the upper limit of carbon content is 0.03%, average chromium content is 19%, and nickel content is 10% ,the expression of the low-carbon stainless steel is “03Cr19Ni10”.
- When the upper limit of carbon content is 0.01%, average chromium content is 19%, and nickel content is 11%, the expression of the extreme low carbon stainless steel is “01Cr19Ni11”.
＜Regulations of GB/T221-2008＞
According to GB/T221-2008, regulated chemical element symbols and Arabic numbers (which express element contents) should be used, to form grades of stainless steel and heat resistant steel.
１、Carbon content
- Double-digit or 3-digit number is used to express the best control value of carbon content (by ten thousandth or a hundred thousandth).
- If the upper limit of carbon content is only set, when the upper limit is no more than 0.10%, use 3/4 of the limit number to express the carbon content. When the upper limit is over 0.10%, use 4/5 of the limit number to express the carbon content.
- For example, if the upper limit is 0.08%, the carbon content is expressed as 06, if the upper limit is 0.20%, the carbon content is expressed as 16, if the upper limit is 0.15%, the carbon content is expressed as 12.
0.08→0.08×3/4＝0.06（％） →06
0.20→0.20×4/5＝0.16（％） →16
0.15→0.15×4/5＝0.12（％） →12
- For ultra-low carbon stainless steel (carbon content is no more than 0.030%), use 3-digit Arabic number to express the best control value (by a hundred thousandth).
- For example, when the upper limit of carbon content is 0.030%, it is expressed as 022. When the upper limit of carbon content is 0.020%, it is expressed as 015.
0.030→0.030×3/4＝0.0225 →022
0.020→0.030×3/4＝0.015 →015
- Products with upper or lower limits should be expressed in the form of carbon content ×100.
- For example, when the carbon content is 0.16%～0.25%, it is 20 in the grade expression.
（0.16+0.25）/2＝0.205 → 20
2,Alloying element content
- Alloying elements and their contents should be expressed by the chemical element symbols and Arabic numbers. Niobium, Titanium, Zirconium, Nitrogen and other alloying elements, which are intentionally added to the steel, even low in content, should be expressed in grades.
- For example, when the carbon content is no more than 0.08%, chromium content is between 18.00%～20.00%, and nickel content is between 8.00%～11.00%, the grade of stainless steel is 06Cr19Ni10.
0.08×3/4＝0.06 →06
- When the carbon content is between 0.15%～0.25%, chromium content is between 14.00%～16.00%, Manganese content is between 14.00%～16.00%, Nickel content is between 1.50%～3.00%, and Nitrogen content is between 0.15%～0.30%, the grade of stainless steel is 20Cr15,Mn15Ni2N.
（0.15＋0.25）/２＝0.20 → 20
- When the carbon content is no more than 0.25%, chromium content is between 24.00%～26.00%, and nickel content is between 19.00%～22.00%, the grade of the heat resistant steel is 20Cr25Ni20.
0.25×4/5＝0.20 →20
Regulations of GB/T17616-2013
China’s Unified Digital Code System (GB/T17616-2013) prescribed that Capital Latin letter be the prefix, and followed by 5 digits.
About stainless steel, there are:
S —— stainless, corrosion and heat resistant
S1—— ferritic type
S2—— austenite and ferritic type
S3—— austenite type
S4—— martensite type
S5—— precipitation hardening type.
Stainless steel for welding and cast, heat resistant steel for cast, metallurgy stainless steel and heat resistant steel, to name a few, are not included.
Source:中国特钢企业协会不锈钢分会
http://www.cssc.org.cn/page148?article_id=67
* Partially modified
