Heat-treatable steel: No compromises in terms of properties – both hard and tough

The heat treatment of steel looks back on a long tradition. In many cases, the component properties can only be achieved as required outside of the steel mill and hot strip plant by further heat treatment in the actual component manufacturing process. For heat treatment processes, the focus should be placed accordingly on the setup of specific mechanical technological properties such as high yield strength and tensile strength, sustained strength and resistance to wear.

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Cogwheels and tilt levers made of case hardened steels

Salzgitter Flachstahl offers a large portfolio of heat-treated steel grades that comprises conventional case hardened and tempered steel, carbon alloy steel and press-hardened steel for special applications (e.g. structure parts in the car body).
This group, in turn, includes tempered boron alloy steels (22MnB5, 26MnB5) which develop ultimate strength in the hardened state and manganese/chromium alloyed air-hardening steel grades (such as the LH®800/900 that was developed by Salzgitter Flachstahl). As the name already indicates, when cooled in quiet air, these steel types can reach a high tensile strength of more than 900-1000 MPa, at a fracture elongation above 13% (at the component for LH®900). These steel grades offer key advantages and are characterized by their high yield point. They are also insensitive to stress and can be formed and tempered separately in different, autarkic workflows. The production process therefore benefits from higher flexibility, depending on the existing process environment. The air-hardening steel grades LH®800/900 were developed and qualified in the past three years in cooperation with a customer and haven been meanwhile released for series applications.

It is not only the alloying concept that has a strong influence on the properties of materials and components. In the manufacturing process, the influence on component geometries already starts in the cold rolling phases. One of the outstanding features of the hot strip produced in Salzgitter is its compliance with stringent geometrical tolerances to the benefit of customers.

Example: The limitation of the thickness tolerance from 50 to 20 percent of the standard increases the usable strip length. On a coil with strip of 3 mm thickness and 1200 width, this increase amounts to approx. 4 percent of the output strip length.