Method for processing a steel product produced using said method

Abstract

The invention relates to a method for processing a steel product, in which the steel product is passed between a set of rotating rolls of a rolling mill stand in order to roll the steel product. According to the invention, the rolls of the rolling mill stand have different peripheral velocities such that one roll is a faster moving roll and the other roll is a slower moving roll, and the peripheral velocity of the faster moving roll is at least 5% higher and at most 100% higher than that of the slower moving roll, and the thickness of the steel product is reduced by at most 15% per pass, and the rolling takes place at a maximum temperature of 1350° C. The invention also relates to a steel product produced using the method, and to the use of this steel product.

1 . A method for processing a steel product, in which the steel product is passed between a set of rotating rolls of a rolling mill stand in order to roll the steel product, wherein the rolls of the rolling mill stand have different peripheral velocities such that one roll is a faster moving roll and the other roll is a slower moving roll, the peripheral velocity of the faster moving roll is at least 5% higher and at most 100% higher than that of the slower moving roll, the thickness of the steel product is reduced by at most 15% per pass, and the rolling takes place at a maximum temperature of 1350° C.  
     
     
         2 . The method as claimed in  claim 1 , wherein the thickness of the steel product is reduced by at most 8% each pass,  
     
     
         3 . The method as claimed in  claim 1  wherein the peripheral velocity of the faster moving roll is at most 50% higher than that of the slower moving roll.  
     
     
         4 . The method as claimed in  claim 1 , wherein the rolling mill is designed in such a manner that the rolls have different diameters.  
     
     
         5 . The method as claimed in  claim 1 , wherein the rolls have different rotational speeds.  
     
     
         6 . The method as claimed in  claim 1 , wherein the steel product is introduced between the rolls at an angle of between 5 and 45° with respect to the perpendicular to the plane through the center axes of the rolls.  
     
     
         7 . The method as claimed in  claim 1 , wherein the rolling operation is repeated one or more times after the rolling has been carried out for the first time.  
     
     
         8 . The method as claimed in  claim 7 , wherein the steel product is passed through the rolling mill stand in opposite directions for each pass.  
     
     
         9 . The method as claimed in  claim 7 , wherein the steel product is successively passed through two or more rolling mill stands.  
     
     
         10 . The method as claimed in  claim 1 , wherein the passing of the steel product between the set of rotating rolls having different peripheral velocities is preceded or followed by a rolling operation which is carried out using a rolling mill in which the rolls have substantially identical peripheral velocities.  
     
     
         11 . The method as claimed in  claim 1 , wherein the rolling is carried out on a steel product of which at least a skin layer has a substantially austenitic structure.  
     
     
         12 . The method as claimed in  claim 1 , wherein the rolling is carried out on a steel product of which at least a skin layer has a substantially austenitic-ferritic two-phase structure.  
     
     
         13 . The method as claimed in  claim 1 , wherein the rolling is carried out on a steel product of which at least a skin layer has a substantially ferritic structure.  
     
     
         14 . The method as claimed in  claim 1 , wherein the rolling is carried out while the temperature of the steel product is higher than 0° C. and lower than 720° C.  
     
     
         15 . The method according to  claim 14 , wherein the rolling is carried out on a steel product having a substantially martensitic structure.  
     
     
         16 . A method for producing a steel product comprising the steps of: 
 continuous casting of a steel strand;    optionally heating and/or temperature homogenising the steel strand between a casting machine and a rolling device;    optionally rolling the steel product in one or more rolling mill stands of the rolling device with rolls having substantially identical peripheral velocities;    optionally accelerated cooling after the last rolling step;    optionally cutting the steel product into slabs or coils before or after rolling;    optionally coiling the steel product    cooling the steel product    wherein between casting the strand and accelerated cooling or coiling or cooling, or after cooling, the steel product is subjected to the method of  claim 1 .    
     
     
         17 . The method for producing a steel product according to  claim 16 , wherein the thickness of the cast strand is below 150 mm.  
     
     
         18 . The method for producing a steel product according to  claim 16 , wherein the thickness of the cast strand is below 20 mm.  
     
     
         19 . The method according to  claim 16 , wherein the steel product that is produced is a stainless steel product.  
     
     
         20 . The method for producing a steel product according to  claim 16 , wherein the rolling is carried out on a steel product having a substantially austenitic structure, the steel is acceleratedly cooled thereafter, and the steel product essentially comprises ferrite, bainite and/or martensite.  
     
     
         21 . The method for producing a steel product according to  claim 16 , wherein the average grainsize of the steel product is smaller than 5 μm.  
     
     
         22 . The method according to  claim 1 , wherein the steel product is subjected to a heat treatment before or after the rolling step.  
     
     
         23 . The method as claimed in  claim 1 , wherein a surface of the steel product which is to be rolled is covered by one or more layers prior to rolling.  
     
     
         24 . The method as claimed in  claim 23 , wherein the covering layer is a metal.  
     
     
         25 . A steel product produced according to the method of  claim 1  having a thickness of between 10 and 300 mm.  
     
     
         26 . A steel product produced according to the method of  claim 1 , wherein the steel product is a steel billet.  
     
     
         27 . A steel section, produced using a billet according to  claim 26 .  
     
     
         28 . A steel product produced according to the method of  claim 1 , wherein the starting point is a steel ingot.  
     
     
         29 . A steel plate, strip or billet produced by continuous casting, using the method as claimed in  claim 1 .  
     
     
         30 . A steel strip produced according to the method of  claim 16 .  
     
     
         31 . A clad steel product produced according to  claim 23  for use in a member of the group consisting of pipes, chemical plants, power plants, vessels, and pressure vessels.  
     
     
         32 . A steel strip produced according to  claim 16 , wherein the steel is a HSLA-steel comprising at least one of the elements niobium, titanium, vanadium or boron.  
     
     
         33 . The method as claimed in  claim 1 , wherein the thickness of the steel product is reduced by at most 5% each pass.  
     
     
         34 . The method as claimed in  claim 1 , wherein the peripheral velocity of the faster moving roll is at most 20% higher than that of the slower moving roll.  
     
     
         35 . The method as claimed in  claim 1 , wherein the steel product is introduced between the rolls at an angle of between 10 and 25° with respect to the perpendicular to the plane through the center axes of the rolls.  
     
     
         36 . The method as claimed in  claim 1 , wherein the steel product is introduced between the rolls at an angle of between 15 and 25° with respect to the perpendicular to the plane through the center axes of the rolls.  
     
     
         37 . The method as claimed in  claim 1 , wherein the rolling is carried out on a steel product having a substantially austenitic structure throughout.  
     
     
         38 . The method as claimed in  claim 1 , wherein the rolling is carried out on a steel product having a substantially austenitic-ferritic two-phase structure throughout.  
     
     
         39 . The method as claimed in  claim 1 , wherein the rolling is carried out on a steel product having a substantially ferritic structure throughout.  
     
     
         40 . The method for producing a steel product according to  claim 16 , wherein the thickness of the cast strand is below 100 mm.  
     
     
         41 . The method for producing a steel product according to  claim 16 , wherein the thickness of the cast strand is below 80 mm.  
     
     
         42 . The method for producing a steel product according to  claim 16 , wherein the thickness of the cast strand is below 10 mm.  
     
     
         43 . The method for producing a steel product according to  claim 16 , wherein the thickness of the cast strand is below 5 mm.  
     
     
         44 . The method for producing a steel product according to  claim 16 , wherein the rolling is carried out on a steel product having a substantially austenitic structure, the steel is acceleratedly cooled thereafter, the steel product essentially comprises ferrite, bainite and/or martensite, and the ferrite content after cooling is at least 60%.  
     
     
         45 . The method for producing a steel product according to  claim 16 , wherein the rolling is carried out on a steel product having a substantially austenitic structure, the steel is acceleratedly cooled thereafter, the steel product essentially comprises ferrite, bainite and/or martensite, and the ferrite content after cooling is 70%.  
     
     
         46 . The method for producing a steel product according to  claim 16 , wherein the rolling is carried out on a steel product having a substantially austenitic structure, the steel is acceleratedly cooled thereafter, the steel product essentially comprises ferrite, bainite and/or martensite, and the ferrite content after cooling is more than 80%.  
     
     
         47 . The method for producing a steel product according to  claim 16 , wherein the average grainsize of the steel product is smaller than 2 μm.  
     
     
         48 . The method for producing a steel product according to  claim 16 , wherein the average grainsize of the steel product is smaller than 1 μm.  
     
     
         49 . The method according to  claim 1 , wherein the steel product is subjected to a heat treatment before or after the rolling step selected from at least one member of the group consisting of a normalising treatment, a full anneal, a stress relief anneal or a speroidisation annealing treatment.  
     
     
         50 . The method as claimed in  claim 23 , wherein the covering layer is a steel with a different composition than that of the steel product.  
     
     
         51 . The method as claimed in  claim 23 , wherein the covering layer is a stainless steel.  
     
     
         52 . The method as claimed in  claim 23 , wherein the covering layer comprises a member of the group consisting of Titanium, Nickel, Copper, Aluminium and alloys thereof.  
     
     
         53 . A steel product produced according to the method of  claim 1 , having a thickness between 20 and 160 mm.  
     
     
         54 . A steel product produced according to the method of  claim 1 , having a thickness between 20 and 60 mm.  
     
     
         55 . A steel product produced according to the method of  claim 25 , for use in a member of the group consisting of buildings, bridges, earth moving equipment, pipe line, ship building, and off shore constructions.  
     
     
         56 . An H-section, produced using a billet according to  claim 26 .  
     
     
         57 . A steel product produced according to the method of  claim 1 , wherein the starting point is a steel ingot, wherein the steel product has a core and pores in the core of the product have a maximum dimension of less than 200 μm.  
     
     
         58 . A steel product produced according to the method of  claim 1 , wherein the starting point is a steel ingot, wherein the steel product has a core and pores in the core of the product have a maximum dimension of less than 100 μm.  
     
     
         59 . A steel product produced according to the method of  claim 1 , wherein the starting point is a steel ingot, wherein the steel product has a core and pores in the core of the product have a maximum dimension of less than 20 μm.  
     
     
         60 . A steel product produced according to the method of  claim 1 , wherein the starting point is a steel ingot, wherein the steel product has a core and pores in the core of the product have a maximum dimension of less than 10 μm.  
     
     
         61 . A steel plate, strip or billet produced by continuous casting, using the method as claimed in  claim 1 , wherein the steel product has a core and pores in the core of the plate, strip or billet have a maximum dimension of less than 200 μm.  
     
     
         62 . A steel plate, strip or billet produced by continuous casting, using the method as claimed in  claim 1 , wherein the steel product has a core and pores in the core of the plate, strip or billet have a maximum dimension of less than 100 μm.  
     
     
         63 . A steel plate, strip or billet produced by continuous casting, using the method as claimed in  claim 1 , wherein the steel product has a core and pores in the core of the plate, strip or billet have a maximum dimension of less than 20 μm.  
     
     
         64 . A steel plate, strip or billet produced by continuous casting, using the method as claimed in  claim 1 , wherein the steel product has a core and pores in the core of the plate, strip or billet have a maximum dimension of less than 10 μm.  
     
     
         65 . A steel strip produced according to the method of  claim 16 , for use in parts of automobiles, transport equipment, piling, buildings, construction.  
     
     
         66 . A steel strip produced according to  claim 16 , wherein the steel is an ultra low carbon steel.  
     
     
         67 . A steel strip produced according to  claim 16 , wherein the steel is an ultra low carbon steel at least partly stabilized with at least one of the elements titanium, niobium or boron.