It is also named as wind steel or sharp steel, which means it can be hardened in air and sharp in quenching. A kind of complex alloy containing tungsten, molybdenum, chromium, vanadium, cobalt and carbide forming component .. which total elements content is 10~ 25% .. It may still maintain quite high hardness during high speed machining that caused high temperature (about 500 ° C) surrounding. The major benefit of high speed steel is its HRC above 60—Red Hardness.For carbon tool steel, after quenching and low temperature backfire , it remains high hardness under room temperature. However, the hardness will be reduced speedily when it is over 200 ° C and the hardness will be reduced into the same situation of backfire if the temperature up to 500° C, which already lost its ability of cutting metal. That is not suitable to produce cutting tool. High speed Steel is with good red hardness which may make up for the weakness of carbon tool steel so it can be used in manufacturing cutting tool.