Whether the improved machinability and toughness landscape with the river and its manufacturing method

摘要

The present invnetion provides a prehardened steel excellent in cutting performance, toughness and hardness, and used for metal molds for plastics forming, and a processing for pruducing same. Said prehardened steel is a tool steel, contains, based on weight %, the following components: C: 0.05-0.17%; Si: less than 0.6%; Mn: 0.5-2.0%; Ni: 2.5-3.5%; Cr: less than 2.0%; one or two of W and Mo(1/2W+Mo): less than 0.7%; Al: 0.5-1.5%; Cu: 0.7-2.5%; and has a mixing tissue of an upper bainite and a lower bainite, preferably a mixing tissue with 20-80% by area of the lower bainite; with a hardness of 34-45 HRC. It is allowable to replace the Fe part with less than 0.3% of S. The manufacturing method comprising the steps of heating the tool steel having the components mentioned above to austenitic area, executing upper/lower mixing bainite generating heating treatment for cooling the mixing area of the upper bainite and the lower bainite, after that, executing a tempering treatment for generating a hardness of 34-45 HRC.