Method for producing a hot-formed and press-hardened metal component
The present invention relates to a method for producing a hot-formed and press-hardened metal component for an automobile having at least two regions of different hardness. A hardenable sheet-metal blank is heated to at least an austenizing temperature and a first region of the sheet-metal blank is intermediately cooled at a cooling speed greater than the lower critical cooling speed of the material of the sheet-metal blank. The sheet-metal blank is then hot-formed and press-hardened in a press-hardening tool by quenching the first region from a bainitic structure transformation stage, thereby adjusting a mixed structure of martensite and bainite in the first region.
1. A method for producing a hot-formed and press-hardened metal component for an automobile, said metal component having at least two regions of different hardness, the method comprising the steps of:
Heating a hardenable sheet-metal blank to at least an austenizing temperature,
Intermediately cooling a first region of the heated sheet-metal blank with a cooling speed selected to be greater than a lower critical cooling speed of a material of the sheet-metal blank to a cooling temperature,
Holding the first region at the cooling temperature isothermally for a predetermined time, thereby forming a bainitic-austenitic mixed structure in the first region,
Holding a second region of the metal component above the austenizing temperature until the metal component is conveyed to a press-hardening tool and
In the press-hardening tool, hot-forming and press-hardening the intermediately cooled sheet-metal blank to the metal component by quenching a first region of the metal component in the press-hardening tool from a bainitic structural transformation stage, thereby adjusting in the first region a mixed structure of martensite and bainite.
2. The method of claim 1 , wherein the first region is cooled to a cooling temperature between 600 and 400° C.
3. The method of claim 1 , wherein the first region is cooled to a cooling temperature of about 500° C.
4. The method of claim 1 , wherein the cooling speed of intermediate cooling is selected to be greater than an upper critical cooling speed of a material of the sheet-metal blank.
5. The method of claim 1 , wherein the intermediate cooling is performed using cooling plates.