Potenziale kaltgewalzter, verguteter Federbandstahle - Themenzuordnung 3: Federwerkstoffe und Halbzeuge

摘要

Cold rolled steel in his diversity is strongly required in the modern steel working industry as well as in the car manufacturing in the oncoming years. Cold rolled and tempered material with their high strength and application potential can be used to design new products or to substitute conventional applications by using a perfect mixture from cold forming and heat treatment technology. In order to improve the usage property of tools and parts it is useful to change the material condition by using a heat treatment in that way that for example hardness, strength, toughness or wear resistance is adapted in an optimal way to the particular application. Therefore one can optimize the relation between the demands of a part the part geometry and the dimensions. This means we get a higher security to early failures. On the other hand one can reduce the material thickness with equal reliability. In this paper the properties and the potentials of bainitic, martensitic and sorbitic hardened spring steel will be presented. Applications of bainitic hardened spring steel are mostly in the car manufacturing and electric industry. For example bainitic hardened PT-strip (PT -"pretempered") can by used for fine-blanking. Complicated geometries can be produced with a material having the final strength already in the steel. This means problems of the piece hardening like distortion, cracking and connected with this the scrap can be avoided. Highest demands like for example in the usage of power springs or constant force springs lead to the development of texture rolled spring steel. In the past these springs were made out of stainless steel wire. The technology for producing these springs out of wire was ported to the steel strip. Modified carbon steel grades with a high degree of purity are heat treated by an isothermal heat treatment line. Starting with a heat treated microstructure and a tensile strength of 1300 MPa the following cold rolling on special rolling mills leads to final tensile strength of approx. 2500 MPa. This means texture rolled strip has substituted many application in the filed of austenitic stainless steel. The technical advantages of the texture rolled carbon steel in comparison to the stainless steel grades is the save of material because of a higher youngs modulus, the higher viscosity and connected with this high durability. Intention of this presentation is to give the audience an overview of the application potential, the mechanical and technological properties and special characteristic of the heat treated steel strip.