① This standard has stipulated that brand No. with “A” can only be ordered as extremely high quality steel while other brand should be ordered as high quality steel.
② According to the requirements of the needer, goods can be ordered according to high quality steel (without “A”) or extremely high quality steel (all brand No.s). “A” or “E” should be added to the brand No (“A” should be crossed out as for those with “A” already). Once the needer raises any other requirements aimed at the chemical component of brand No., goods can be ordered according to special requirements.
③ The unified numeral code should be listed according to the GB/T 17616 stipulations. The last number of high quality steel should be “2”; senior high quality steel (“A” steel) should be “3”; extremely high quality steel (“E” steel) should be “6”.

① Permitted scope of hot processing temperature: quench ± 15℃; low temperature tempering ± 20℃; high temperature tempering ±50℃.
② The mechanical property listed in Chart is applicable to steel materials whose cross-section size is no more than 80mm. As for steel materials whose size is 80 to 100mm, it is permitted that the stretching rate after breaking, cross-section shrinkage and shock absorption power can be lowered 1% (absolute value), 5% (absolute value) and 5% respectively; as for steel materials whose size is 100 to 150mm, it is permitted that the stretching rate after breaking, cross-section shrinkage and shock absorption power can be lowered 2% (absolute value), 10% (absolute value) and 10% respectively; as for steel materials which size is 150 to 250mm, it is permitted that the stretching rate after breaking, cross-section shrinkage and shock absorption power can be lowered 3% (absolute value), 15% (absolute value) and 15% respectively.
③ Boron steel can undergo normalizing prior to quenching, with the normalizing temperature not exceeding the quenching temperature. For chromium-manganese-titanium steel, the first quenching may be substituted with normalizing.
④ There should be no yield in the sample steel during the stretching test. When it is impossible to test the yield point σs, residual extension stress στ0.2 can be tested.
⑤ The hardness values in the table represent the Brinell hardness (HB10/3000) of the steel in the annealed or high-temperature tempered supply condition.

Heat Treatment:
Quench Heat Temperature 850°C，Coolant oil；Tempering Heat Temperature 200°C Coolant water, air.