Side rail and method for producing a hot-formed and press-hardened side rail

Abstract

A side rail and to a method for producing a side rail are disclosed. The side rail has a region of a first type and a region of a second type which have mutually different strengths. A transition region having a width of less than 50 mm is formed between the two regions. The side rail has in the region of the first type a bainitic structure and in the region of the second type a martensitic structure.

1 . A side rail comprising:
 at least two regions of different strength produced by hot-forming and press-hardening, wherein a region of a first type has after press-hardening a substantially bainitic structure and a region of a second type has after press-hardening a substantially martensitic structure, and   a transition region between the region of the first type and the region of second type being smaller than 80 mm.   
     
     
         2 . The side rail of  claim 1 , wherein the transition region is smaller than 50 mm. 
     
     
         3 . The side rail of  claim 1 , wherein the transition region is smaller than 30 mm. 
     
     
         4 . The side rail of  claim 1 , wherein the transition region is smaller than 20 mm. 
     
     
         5 . The side rail of  claim 1 , wherein the substantially martensitic structure of the region of the second type comprises additional structure components in a concentration of less than 50%. 
     
     
         6 . The side rail of  claim 1 , wherein the substantially martensitic structure of the region of the second type comprises additional structure components in a concentration of less than 30%. 
     
     
         7 . The side rail of  claim 1 , wherein the substantially martensitic structure of the region of the second type comprises additional structure components in a concentration of less than 15%. 
     
     
         8 . The side rail of  claim 5 , wherein the additional structure component comprises bainite. 
     
     
         9 . The side rail of  claim 1 , wherein the substantially bainitic structure of the region of the first type comprises additional structure components in a concentration of less than 50%. 
     
     
         10 . The side rail of  claim 1 , wherein the substantially bainitic structure of the region of the first type comprises additional structure components in a concentration of less than 30%. 
     
     
         11 . The side rail of  claim 1 , wherein the substantially bainitic structure of the region of the first type comprises additional structure components in a concentration of less than 15%. 
     
     
         12 . The side rail of  claim 1 , wherein the region of the first type is at least partially enclosed by the region of the second type. 
     
     
         13 . The side rail of  claim 12 , wherein the region of the first type is completely enclosed by the region of the second type. 
     
     
         14 . The side rail of  claim 1 , wherein the region of the first type is spot-shaped with a diameter of less than 40 mm. 
     
     
         15 . The side rail of  claim 1 , wherein the region of the first type is spot-shaped with a diameter of less than 20 mm. 
     
     
         16 . The side rail of  claim 1 , wherein the region of the first type is spot-shaped with a diameter of less than 10 mm. 
     
     
         17 . The side rail of  claim 1 , wherein the region of the first type is constructed as a coupling location for coupling additional components to the side rail. 
     
     
         18 . The side rail of  claim 1 , wherein the region of the first type is formed in regions of the side rail which are subject to strong deformations in a crash or which are configured to dissipate crash energy through deformations. 
     
     
         19 . The side rail of  claim 1 , wherein the region of the first type has an increased wall thickness in relation to the region of the second type. 
     
     
         20 . The side rail of  claim 1 , further comprising a passage or an edge, or both, in the region of the first type after hot-forming. 
     
     
         21 . The side rail of  claim 1 , wherein the region of the first type has a stretchability A50 between 10% and 30%. 
     
     
         22 . The side rail of  claim 1 , wherein the region of the first type has a stretchability A50 between 12% and 20%. 
     
     
         23 . The side rail of  claim 1 , wherein the region of the first type has a stretchability A50 between 12% and 16%. 
     
     
         24 . The side rail of  claim 1 , wherein the region of the first type has a stretchability A50 between 14% and 16%. 
     
     
         25 . The side rail of  claim 1 , wherein the region of the first type has a tensile strength between 500 and 1000 N/mm 2 . 
     
     
         26 . The side rail of  claim 1 , wherein the region of the first type has a tensile strength between 550 and 800 N/mm 2 . 
     
     
         27 . The side rail of  claim 1 , wherein a yield strength or a tensile strength decreases or increases in the transition region with a gradient of more than 100 N/mm 2  per 10 mm. 
     
     
         28 . The side rail of  claim 1 , wherein a yield strength or a tensile strength decreases or increases in the transition region with a gradient of more than 200 N/mm 2  per 10 mm. 
     
     
         29 . The side rail of  claim 1 , wherein a yield strength or a tensile strength decreases or increases in the transition region with a gradient of more than 400 N/mm 2  per 10 mm. 
     
     
         30 . The side rail of  claim 1 , wherein the region of the second type has a strength of more than 1000 N/mm 2 . 
     
     
         31 . The side rail of  claim 1 , wherein the region of the second type has a strength of more than 1200 N/mm 2 . 
     
     
         32 . The side rail of  claim 1 , wherein the region of the second type has a strength of more than 1400 N/mm 2 . 
     
     
         33 . The side rail of  claim 1 , wherein region of the first type has a yield strength between 200 and 800 N/mm 2 . 
     
     
         34 . The side rail of  claim 1 , wherein region of the first type has a yield strength between 250 and 600 N/mm 2 . 
     
     
         35 . The side rail of  claim 1 , wherein region of the first type has a yield strength between 250 and 500 N/mm 2 . 
     
     
         36 . The side rail of  claim 1 , wherein region of the first type has a yield strength between 300 and 500 N/mm 2 . 
     
     
         37 . The side rail of  claim 1 , wherein the side rail is manufactured from a Tailor Welded Blank or a Tailor Rolled Blank. 
     
     
         38 . A method for producing a hot-formed and press-hardened side rail having at least two regions of different hardness, the method comprising the steps of:
 providing a hardenable metal plate or semi-finished product and heating the hardenable metal plate or semi-finished product to at least an austenizing temperature,   intermediately cooling a region of a first type of the metal plate or semi-finished product with a cooldown speed selected to be greater than a lower critical cooldown speed of a material of the metal plate or semi-finished product, and   hot-forming and press-hardening the metal plate or semi-finished product in a press-hardening tool to form the side rail.   
     
     
         39 . The method of  claim 38 , wherein a region of a second type is held above the austenizing temperature until the region of a second type is transported into the press-hardening tool. 
     
     
         40 . The method of  claim 38 , wherein the cooldown speed during intermediate cooling of the region of the first type is selected such that a bainitic structure is obtained. 
     
     
         41 . The method of  claim 40 , wherein the region of the first type is cooled to a cooling temperature between 600 and 400° C. 
     
     
         42 . The method of  claim 41 , wherein the region of the first type is cooled to a cooling temperature of about 500° C. 
     
     
         43 . The method of  claim 40 , wherein the region of the first type is held at the cooling temperature for a predetermined time. 
     
     
         44 . The method of  claim 40 , wherein the region of the first type is held at the cooling temperature isothermally. 
     
     
         45 . The method of  claim 38 , further comprising the step of quenching the region of the first type in the press-hardening tool from a bainitic structure transformation stage, whereby a mixed structure of martensite and bainite, or a mixed structure of martensite, bainite and at least one of ferrite and perlite, is adjusted in the region of the first type. 
     
     
         46 . The method of  claim 38 , further comprising the step of holding the region of the first type isothermally so as to form a substantially pure bainitic structure by press-hardening. 
     
     
         47 . The method of  claim 38 , wherein the cooldown speed of the intermediate cooling is selected to be greater than an upper critical cooling-down speed. 
     
     
         48 . The method of  claim 38 , wherein the intermediate cooling of the region of the first type is performed in the press-hardening tool. 
     
     
         49 . The method of  claim 48 , wherein the intermediate cooling of the region of the first type is performed by using cooling plates arranged in the press-hardening tool. 
     
     
         50 . The method of  claim 38 , wherein the metal plate is pre-formed into a semi-finished product while cold before being heated to at least the austenizing temperature.