Representation method of steel grade in China (VI): Non quenched and tempered mechanical structural steel

For non quenched and tempered mechanical structural steel, the symbols “YF” and “F” are respectively added at the head of the brand to represent free cutting non quenched and tempered mechanical structural steel and non quenched and tempered mechanical structural steel for hot forging. Other contents of the brand representation method are the same as those of alloy structural steel. For example: “yf35v”, “f45v”.

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, symbols specified in Table 1 and Arabic numerals. Arabic numerals indicate the average carbon content (in thousands).

a. Ordinary carbon tool steel with manganese content is Arabic numerals after the symbol “t” of tool steel. 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, add manganese element symbol after tool steel symbol “t” and Arabic numerals. For example: “t8mn”.

c. High quality carbon tool steel with “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 generally not indicated. For example, the alloy tool steel with average carbon content of 1.60%, chromium, molybdenum and vanadium content of 11.75%, 0.50% and 0.22% respectively is indicated as “Cr12MoV”; The grade of high-speed tool steel with 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 “W6Mo5Cr4V2”.

If the average carbon content is less than 1.00%, an Arabic numeral can be used to represent the carbon content (in thousands). 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 the number “0” before the chromium content (in thousands). For example, the grade of alloy tool steel with an average chromium content of 0.60% is expressed as “cr06”.