Method for producing a cold-rolled steel strip having trip-characteristics made of a high-strength mangan-containing steel

Abstract

The invention relates to a method for producing a cold-rolled steel strip made of a high-strength mangan-containing steel with TRIP-characteristics, containing (in wt. %) C: 0.0005 to 0.9, Mn: more than 3.0 to 12, with the remaining portion being iron including unavoidable steel-associated elements, with the optional addition of one or more of the following elements (in wt. %): Al: up to 10; Si: up to 6; Cr: up to 6; Nb: up to 1.5; V: up to 1.5; Ti: up to 1.5; Mo: up to 3; Cu: up to 3; Sn: up to 0.5; W: up to 5; Co: up to 8; Zr: up to 0.5; Ta: up to 0.5; Te: up to 0.5; B: up to 0.15; P: max. 0.1, in particular <0.04; S: max. 0.1, in particular <0.02; N: max. 0.1, in particular <0.05; Ca: up to 0.1. According to the invention, in order to improve a corresponding method, the cold-rolling to a required end thickness occurs at a temperature of over 50° C. to 400° C. before the first impact.

What is claimed is: 
     
         1 .- 25 . (canceled) 
     
     
         26 . A method, comprising:
 producing a steel strip from high-strength, manganese-containing steel with TRIP properties, said steel comprising (in wt. %):   C: 0.0005 to 0.9   Mn: more than 3.0 to 12,   with the remainder being iron including unavoidable steel-associated elements; and   cold-rolling the steel strip to a required end thickness at a temperature prior to a first rolling pass above 50° C. to 400° C.   
     
     
         27 . The method of  claim 26 , further comprising adding of one or more of the following alloying elements (in wt. %):
 Al: to 10   Si: to 6   Cr: to 6   Nb: to 1.5   V: to 1.5   Ti: to 1.5   Mo: to 3   Cu: to 3   Sn: to 0.5   W: to 5   Co: to 8   Zr: to 0.5   Ta: to 0.5   Te: to 0.5   B: to 0.15   P: max. 0.1, in particular <0.04   S: max. 0.1, in particular <0.02   N: max. 0.1, in particular <0.05   Ca: to 0.1.   
     
     
         28 . The method of  claim 26 , wherein the temperature is 70° C. to 250° C. 
     
     
         29 . The method of  claim 26 , wherein the steel strip is a hot strip or a pre-strip which is heated to a temperature above 50° C. to 400° C., preferably from 70° C. to 250° C., or a hot strip or a pre-strip at a temperature above 50° C. to 400° C., preferably from 70° C. to 250° C., before undergoing cold-rolling to the required end thickness. 
     
     
         30 . The method of  claim 26 , further comprising cooling the steel strip to a temperature of 50° C. to 400° C., in particular to a temperature of 70° C. to 250° C. between rolling passes of the cold-rolling. 
     
     
         31 . The method of  claim 26 , wherein the C content is 0.05 to 0.42. 
     
     
         32 . The method of  claim 26 , wherein the Mn content is >5 to <10. 
     
     
         33 . The method of  claim 27 , wherein the Al content is 0.1 to 5, in particular >0.5 to 3. 
     
     
         34 . The method of  claim 27 , wherein the Si content is 0.05 to 3, in particular >0.1 to 1.5. 
     
     
         35 . The method of  claim 27 , wherein the Cr content is 0.1 to 4, in particular >0.5 to 2.5. 
     
     
         36 . The method of  claim 27 , wherein a sum of Al+Si+Cr is >1.2. 
     
     
         37 . The method of  claim 27 , wherein the Nb content is 0.005 to 0.4, in particular 0.01 to 0.1. 
     
     
         38 . The method of  claim 27 , wherein the V content is 0.005 to 0.6, in particular 0.01 to 0.3. 
     
     
         39 . The method of  claim 27 , wherein the Ti content is 0.005 to 0.6, in particular 0.01 to 0.3. 
     
     
         40 . The method of  claim 27 , wherein the Mo content is 0.005 to 1.5, in particular 0.01 to 0.6. 
     
     
         41 . The method of  claim 27 , wherein the Sn content is <0.2, in particular <0.05. 
     
     
         42 . The method of  claim 27 , wherein the Cu content is <0.5, in particular <0.1. 
     
     
         43 . The method of  claim 27 , wherein the W content is 0.01 to 3, in particular 0.2 to 1.5. 
     
     
         44 . The method of  claim 27 , wherein the Co content is 0.01 to 5, in particular 0.3 to 2. 
     
     
         45 . The method of  claim 27 , wherein the Zr content is 0.005 to 0.3, in particular 0.01 to 0.2. 
     
     
         46 . The method of  claim 27 , wherein the Ta content is 0.005 to 0.3, in particular 0.01 to 0.1. 
     
     
         47 . The method of  claim 27 , wherein the Te content is 0.005 to 0.3, in particular 0.01 to 0.1. 
     
     
         48 . The method of  claim 27 , wherein the B content is 0.001 to 0.08, in particular 0.002 to 0.01. 
     
     
         49 . The method of  claim 27 , wherein the Ca content is 0.005 to 0.1. 
     
     
         50 . The method of  claim 26 , wherein the required end thickness is less than 10 mm, preferably less than 4 mm. 
     
     
         51 . The method of  claim 26 , wherein the steel strip is produced by:
 melting a melt of the high-strength, manganese-containing steel;   casting the melt to form a pre-strip through a horizontal or vertical strip casting process approximating a final dimension or casting the steel melt to form a slab or thin slab through a horizontal or vertical slab or thin slab casting process;   re-heating the slab or thin slab to a temperature in a range of 1050° C. to 1250° C. and then hot-rolling the slab or thin slab to form a hot strip, or re-heating the pre-strip to a temperature in a range of 1000° C. to 1200° C. and then hot-rolling the pre-strip to form a hot strip, or hot-rolling the pre-strip without re-heating by using heat generated during casting to form a hot strip with optional intermediate heating between individual rolling passes of the hot-rolling; and   reeling the hot strip at a reeling temperature between 820° C. and ambient temperature.   
     
     
         52 . The method of  claim 51 , further comprising annealing the hot strip at an annealing temperature of 580 to 820° C. and an annealing duration of 1 minute to 48 hours, after the hot strip has been reeled. 
     
     
         53 . The method of  claim 52 , further comprising cold-rolling the hot strip. 
     
     
         54 . The method of  claim 26 , further comprising annealing the steel strip at an annealing temperature of 580 to 820° C. and an annealing duration of 1 minute to 48 hours, after the steel strip has been cold-rolled. 
     
     
         55 . The method of  claim 26 , further comprising acid-cleaning and/or skin-pass rolling the steel strip, after the steel strip has been cold-rolled. 
     
     
         56 . The method of  claim 26 , further comprising coating the steel strip with a metallic, organic or inorganic corrosion protection coating, after the steel strip has been cold-rolled. 
     
     
         57 . The method of  claim 26 , further comprising using the steel strip to produce a component by hot-forming, cold-forming or warm-forming or to produce a pipe with longitudinal or spiral weld seam or to produce a component for automotive and utility vehicle industry and for engineering, white goods and construction, or using the steel strip in a low-temperature range below 0° C. to −273° C., or using the steel strip as a ballistic steel.