Heavy plate and thermomechanical treatment method for a starting material for the production of the heavy plate

Abstract

A heavy plate and a thermomechanical treatment method of a starting material, more particularly a slab ingot, for producing the heavy plate consisting of a steel alloy. An optimum of toughness values and the yield strength ratio R p0.2 /R m can be found in which a cooling from a second final rolling temperature, more particularly ≥Ar3, of the second rolling procedure to a first temperature between 250 and 500° C., more particularly 300 to 450° C., is carried out at a first cooling rate in a first stage after the second rolling procedure, and a cooling to room temperature is carried out at a second cooling rate in a subsequent second stage, wherein a straightening procedure, more particularly a hot straightening procedure, is carried out after the first stage, more particularly during the second stage, and wherein the first cooling rate is >the second cooling rate.

1 . A thermomechanical treatment method for a starting material for the production of a heavy plate consisting of a steel alloy, containing the following, each in wt %: 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   0.01 to 0.20 
                   carbon (C), 
                 
                     
                   0.5 to 2.50 
                   manganese (Mn), 
                 
                     
                   0.05 to 0.80 
                   silicon (Si), 
                 
                     
                   0.01 to 0.20 
                   aluminum (Al), 
                 
                     
                   <0.05 
                   phosphorus (P), 
                 
                     
                   <0.01 
                   sulfur (S), 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
               
            
           
         
         and optionally individual elements from the following group or combinations thereof: 
       
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   0 to 1.5 
                   chromium (Cr) 
                 
                     
                   0 to 1.0 
                   molybdenum (Mo) 
                 
                     
                   0 to 1.0 
                   copper (Cu) 
                 
                     
                   0 to 5.0 
                   nickel (Ni) 
                 
                     
                   0 to 0.30 
                   vanadium (V) 
                 
                     
                   0 to 0.20 
                   titanium (Ti) 
                 
                     
                   0 to 0.20 
                   niobium (Nb) 
                 
                     
                   0 to 0.005 
                   boron (B) 
                 
                     
                   0 to 0.015 
                   nitrogen (N) 
                 
                     
                   0 to 0.01 
                   calcium (Ca) 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
         and residual iron (Fe) and inevitable production-related impurities, which treatment method comprises the following steps:
 heating the starting material to above the Ac3 temperature and partial forming the starting material using a first rolling procedure, 
 accelerated cooling of the starting material after the first rolling procedure from a first final rolling temperature to below the Ar3 temperature 
 heating the starting material after the accelerated cooling to a second initial rolling temperature for a second rolling procedure above the Ac3 temperature and final forming of the starting material by the second rolling procedure to a thickness of the heavy plate and 
 multi-stage cooling optionally with at least one straightening procedure after the final forming in that
 a cooling from a second final rolling temperature of the second rolling procedure to a first temperature between 250 and 500° C., is carried out at a first cooling rate in a first stage after the second rolling procedure, and 
 a cooling of the starting material to room temperature is carried out at a second cooling rate in a subsequent second stage, 
 wherein a straightening procedure is carried out after the first stage, 
 and wherein the first cooling rate is >the second cooling rate. 
 
 
       
     
     
         2 . The thermomechanical treatment method according to  claim 1 , wherein a ratio of the first cooling rate to the second cooling rate is at least 2:1. 
     
     
         3 . The thermomechanical treatment method according to  claim 1 , wherein the second cooling rate is ≤5° C./s. 
     
     
         4 . The thermomechanical treatment method according to  claim 1 , wherein the straightening procedure is carried out with a degree of plasticization of 40 to 80%. 
     
     
         5 . The thermomechanical treatment method according to  claim 1 , wherein the final forming is carried out to a thickness of the heavy plate in a range of 8 to 150 mm. 
     
     
         6 . The thermomechanical treatment method according to  claim 1 , wherein the steel alloy contains the following, each in wt %: 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   0.02 to 0.1 
                   carbon (C), 
                 
                     
                   1.0 to 2.0 
                   manganese (Mn), 
                 
                     
                   0.1 to 0.80 
                   silicon (Si), 
                 
                     
                   0.010 to 0.15 
                   aluminum (Al), 
                 
                     
                   <0.050 
                   phosphorus (P), and 
                 
                     
                   <0.010 
                   sulfur (S). 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         7 . The thermomechanical treatment method according to  claim 1 , wherein the steel alloy optionally contains at least one element from the following group or combinations thereof, each in wt %: 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   0 to 0.75 
                   copper (Cu) 
                 
                     
                   0 to 3.0 
                   nickel (Ni) 
                 
                     
                   0 to 0.20 
                   vanadium (V) 
                 
                     
                   0 to 0.003 
                   boron (B). 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
               
            
           
         
       
     
     
         8 . The thermomechanical treatment method according to  claim 1 , wherein the straightening procedure is carried out at a straightening temperature within a temperature range from the first temperature to the first temperature (minus 100° C. 
     
     
         9 . A heavy plate produced by the thermomechanical treatment method according to  claim 1 , wherein the heavy plate has a yield strength ratio (R p0.2 /R m ) of <0.9. 
     
     
         10 . The heavy plate according to  claim 9 , wherein the heavy plate has a yield strength ratio (R p0.2 /R m ) of >0.70. 
     
     
         11 . The heavy plate according to  claim 10 , wherein the heavy plate has a yield strength ratio (R p0.2 /R m ) in a range from 0.75 to 0.85. 
     
     
         12 . The heavy plate according to  claim 9 , wherein the heavy plate has a thickness in a range from 8 to 150 mm. 
     
     
         13 . The thermomechanical treatment method according to  claim 1 , wherein the accelerated cooling of the starting material after the first rolling procedure from the first final rolling temperature is to below the Ar1 temperature. 
     
     
         14 . The thermomechanical treatment method according to  claim 1 , wherein the cooling from the second final rolling temperature of the second rolling procedure is from a temperature≥Ar3. 
     
     
         15 . The thermomechanical treatment method according to  claim 1 , wherein the first temperature is between 300 and 450° C. 
     
     
         16 . The thermomechanical treatment method according to  claim 1 , wherein the straightening procedure is a hot straightening procedure. 
     
     
         17 . The thermomechanical treatment method according to  claim 1 , wherein the straightening procedure is carried out during the second stage.