Steel and process for production, and a method of processing the steel

Abstract

A steel, particularly as steel sheet, having the following composition: 0.02-0.1% by weight of carbon; 0.01-0.1% by weight of silicon; 0.60-2.00% by weight of manganese; >0 and ≤0.01% by weight of aluminum; 0.01-0.30% by weight of copper; 0.01-0.60% by weight of nickel; 0.01-0.30% by weight of chromium; 0.005-0.050% by weight of niobium; 0.005-0.050% by weight of titanium; 0.0005-0.0050% by weight of sulfur; 0.001-0.005% by weight of calcium; ≤ 0.0050% by weight of oxygen; ≤0.010% by weight of nitrogen; ≤0.02% by weight of phosphorus; 0-0.0050% by weight of magnesium; 0-0.0060% by weight of Vanadium; 0-0.15% by weight of molybdenum; and balance: iron and production-related impurities, and a process for production and a method of processing the steel.

We claim: 
     
         1 . A steel, comprising:
 0.02-0.1% by weight of carbon;   0.01-0.1% by weight of silicon;   0.60-2.00% by weight of manganese;   >0 and ≤0.01% by weight of aluminum;   0.01-0.30% by weight of copper;   0.01-0.60% by weight of nickel;   0.01-0.30% by weight of chromium;   0.005-0.050% by weight of niobium;   0.005-0.050% by weight of titanium;   0.0005-0.0050% by weight of sulfur;   0.0010-0.0050% by weight of calcium;   ≤0.0050% by weight of oxygen;   ≤0.010% by weight of nitrogen;   ≤0.02% by weight of phosphorus;   0-0.0050% by weight of magnesium;   0-0.0060% by weight of vanadium;   0-0.15% by weight of molybdenum; and   balance: iron and production-related impurities.   
     
     
         2 . The steel according to  claim 1 , comprising at least one of the following:
 <0.05% by weight of carbon;   1.00-1.70% by weight of manganese;   ≤0.1% by weight of copper;   ≤0.4% by weight of nickel;   ≤0.10% by weight of chromium;   >0.001% by weight of oxygen;   0.001-0.0040% by weight of sulfur.   
     
     
         3 . The steel according to  claim 2 , comprising ≤0.2% by weight of nickel. 
     
     
         4 . The steel according to  claim 1 , comprising a bainitic microstructure. 
     
     
         5 . The steel according to  claim 4 , comprising a fine-grain bainitic microstructure. 
     
     
         6 . The steel according to  claim 1 , comprising an average grain size of <15 μm. 
     
     
         7 . The steel according to  claim 6 , comprising an average grain size of <14 μm. 
     
     
         8 . The steel according to  claim 1 , comprising a proportion of high-angle grain boundaries of >50%. 
     
     
         9 . The steel according to  claim 8 , comprising a proportion of high-angle grain boundaries of >60%. 
     
     
         10 . The steel according to  claim 1 , comprising nonmetallic inclusions. 
     
     
         11 . The steel according to  claim 10 , comprising complex agglomerates that have a matrix of a CaTiOs compound, and Al 2 O 3 , MgO and MnS constituents intercalated therein. 
     
     
         12 . The steel according to  claim 10 , wherein a ratio of density of particles of nonmetallic inclusions in a size range from 0.5 to 2 μm to a density of particles of nonmetallic inclusions in a size range from 2 to 5 μm is less than 5. 
     
     
         13 . The steel according to  claim 12 , wherein the density ratio is less than 3. 
     
     
         14 . The steel according to  claim 1 , wherein the steel is a cast steel. 
     
     
         15 . The steel according to  claim 14 , wherein the steel is a cast and rolled semifinished product. 
     
     
         16 . The steel according to  claim 15 , wherein the steel is a slab or a sheet. 
     
     
         17 . The steel according to  claim 1 , wherein the steel, after treatment by physical welding simulation of a coarse grain zone with an energy input of 3.5 kJ/mm to 30 KJ/mm, has a notch impact energy of at least 75 J, where the notch impact energy is ascertained by a Charpy notch impact bending test at −40° C. or at −20° C. according to standard DIN EN ISO 148-1:2017. 
     
     
         18 . The steel according to  claim 17 , wherein the treatment by physical welding simulation of the coarse grain zone is with an energy input of >7 KJ/mm. 
     
     
         19 . The steel according to  claim 18 , wherein the treatment by physical welding simulation of the coarse grain zone is with an energy input of >15 KJ/mm. 
     
     
         20 . The steel according to  claim 18 , wherein the steel has a notch impact energy of at least 100 J. 
     
     
         21 . The steel according to  claim 20 , wherein the steel has a notch impact energy of at least 130 J. 
     
     
         22 . The steel according to  claim 17 , wherein the notch impact energy is ascertained by the Charpy notch impact bending test at −40° C. for a welding simulation with just a single cycle and at −20° C. for a welding simulation with two cycles. 
     
     
         23 . The steel according to  claim 1 , wherein the steel, after processing by welding in a region affected by heat of welding or with an energy input of 3.5 KJ/mm to 30 KJ/mm has a notch impact energy of at least 75 J, where the notch impact energy is ascertained at a fusion line of a weld seam formed by the welding by the Charpy notch impact bending test at −40° C., according to standard DIN EN ISO 148-1:2017. 
     
     
         24 . The steel according to  claim 23 , wherein the steel is processed with an energy input of >7 KJ/mm. 
     
     
         25 . The steel according to  claim 24 , wherein the steel is processed with an energy input of >15 KJ/mm. 
     
     
         26 . The steel according to  claim 25 , wherein the steel has a notch impact energy of at least 100 J. 
     
     
         27 . The steel according to  claim 26 , wherein the steel has a notch impact energy of at least 130 J. 
     
     
         28 . A process for producing steel, comprising the step of forming the steel with the following composition:
 0.02-0.1% by weight of carbon;   0.01-0.1% by weight of silicon;   0.60-2.00% by weight of manganese;   >0 and ≤0.01% by weight of aluminum;   0.01-0.30% by weight of copper;   0.01-0.60% by weight of nickel;   0.01-0.30% by weight of chromium;   0.005-0.050% by weight of niobium;   0.005-0.050% by weight of titanium;   0.0005-0.0050% by weight of sulfur;   0.0010-0.0050% by weight of calcium;   0.0005-0.0050% by weight of oxygen;   ≤0.010% by weight of nitrogen;   ≤0.02% by weight of phosphorus;   0-0.0050% by weight of magnesium;   0-0.0060% by weight of vanadium;   0-0.15% by weight of molybdenum; and   balance: iron and production-related impurities.   
     
     
         29 . The process according to  claim 28 , including casting the steel by continuous casting to form a semifinished product. 
     
     
         30 . The process according to  claim 29 , including casting the steel by continuous casting to form a slab. 
     
     
         31 . The process according to  claim 29 , including heating the semifinished product to a temperature between 110° and 1250° C. 
     
     
         32 . The process according to  claim 31 , including heating the semifinished product to a temperature between 1150 and 1200° C. 
     
     
         33 . The process according to  claim 29 , including thermomechanically rolling the semifinished product in at least two rolling phases, where a degree of forming after a first phase is >0.20. 
     
     
         34 . The process according to  claim 29 , including welding the semifinished product with an energy input of 3.5 KJ/mm to 30 KJ/mm. 
     
     
         35 . The process according to  claim 34 , including welding the semifinished product with an energy input of >7 KJ/mm. 
     
     
         36 . The process according to  claim 35 , including welding the semifinished product with an energy input of >15 KJ/mm.