Special steel with its use pinyin prefix to indicate. Such as: ball bearing steel, steel standard to the "G". A GCr15 means carbon is about 1.0%, a chromium content of about 1.5% (which is a special case, the chromium content in the number of units expressed in thousandths) of ball bearing steel. Y40Mn, which means that the carbon content was 0.4%, the manganese content is less than 1.5% of free-cutting steel, and so on. For high quality steel, show that in the steel adding at the end of "A" word, e.g. 20Cr2Ni4 § 7-1 alloyed steel alloying elements in the steel, the basic group element iron and carbon steel with alloying elements added will occur interaction. Alloying of steel in the hope to improve the organization and performance of steel alloying elements and iron, the interaction of carbon and iron-carbon phase diagram and heat treatment of steel.