Different grades of steel are available in coil form at the start of the production sequence. The automobile industry uses these materials to produce chassis components in a multi-step process.
Blanking is the first step in the forming process at the customer’s plant. The steel material is still in the original condition in which it left the thyssenkrupp Steel mill.
With certain components, the supplier joins various steel grades with different properties to create blanks. These vary in thickness and may have different mechanical properties and coatings.
smartform®technology, patented and licensed by thyssenkrupp Steel, makes it easier to use ultra-high-strength cold formed steels with strengths up to 1,200 MPa. This technology allows manufacturers to produce more quickly, with greater dimensional accuracy, and at lower cost – and it can be adapted for existing press lines.
Deep-drawing the shaped blanks reduces the material’s thickness by five to ten percent. A high level of ironing and consequently the use of conventional blanks with a flange is necessary to compensate for springback of the component.
The sheet metal blanks must first be heated to between 880 °C and 950 °C to allow forming and subsequent hardening of the material at the customer’s plant.
The full strength range of a steel grade is exploited in this step. Different strengths can be achieved in one and the same component using different temperatures and cooling rates inside the die.
The heated shaped blanks are formed in the customer’s die and then rapidly cooled. The sudden change in temperature produces a targeted transformation of the microstructure which causes the material to harden.
In many cases, the component will need to be trimmed to the final geometry by the customer following forming. This can be done mechanically or by laser.