High-toughness ultrahigh-strength steel and manufacturing method thereof

Abstract

The present application discloses a high-toughness ultrahigh-strength steel and a manufacturing method thereof, and belongs to the technical field of metal materials. The present application is intended to solve the problem that the existing low-alloy ultrahigh-strength steel has poor toughness and poor hardenability. The high-toughness ultrahigh-strength steel includes the following elements in mass percentages: C: 0.27% to 0.35%; Si: 1.10% to 1.70%; Mn: 0.70% to 1.10%; Cr: 1.00% to 1.40%; Ni: 0.10% to 0.50%; Mo: 0.05% to 0.50%; W: 0.05% to 0.10%; Nb: 0.01% to 0.04%; and iron and unavoidable impurities: the balance. The high-toughness ultrahigh-strength steel of the present application has excellent strength, toughness and hardenability.

1 .- 10 . (canceled) 
     
     
         11 . A high-toughness ultrahigh-strength steel, comprising the following elements in mass percentages: C: 0.27% to 0.35%; Si: 1.10% to 1.70%; Mn: 0.70% to 1.10%; Cr: 1.00% to 1.40%; Ni: 0.10% to 0.50%; Mo: 0.05% to 0.50%; W: 0.05% to 0.10%; Nb: 0.01% to 0.04%; and iron and unavoidable impurities: the balance. 
     
     
         12 . The high-toughness ultrahigh-strength steel according to  claim 11 , further comprising: V: 0% to 0.150%. 
     
     
         13 . The high-toughness ultrahigh-strength steel according to  claim 11 , comprising the following elements in mass percentages: C: 0.28% to 0.34%; Si: 1.20% to 1.60%; Mn: 0.80% to 1.10%; Cr: 1.20% to 1.35%; Ni: 0.15% to 0.30%; Mo: 0.05% to 0.30%; W: 0.05% to 0.10%; Nb: 0.015% to 0.038%; and iron and unavoidable impurities: the balance. 
     
     
         14 . The high-toughness ultrahigh-strength steel according to  claim 12 , further comprising: V: 0.03% to 0.1%. 
     
     
         15 . The high-toughness ultrahigh-strength steel according to  claim 11 , wherein a microstructure of the high-toughness ultrahigh-strength steel is lath martensite+film-like residual austenite+finely-diffused composite ε-carbide+nano-scale NbC. 
     
     
         16 . A manufacturing method of a high-toughness ultrahigh-strength steel, comprising:
 S1: smelting to obtain a steel ingot;   S2: subjecting the steel ingot to temperature equalization in a heating furnace;   S3: forging;   S4: conducting hot annealing to obtain a forged piece; and   S5: normalizing, oil-quenching, and tempering the forged piece successively to obtain the high-toughness ultrahigh-strength steel;   wherein the high-toughness ultrahigh-strength steel comprises the following elements in mass percentages: C: 0.27% to 0.35%; Si: 1.10% to 1.70%; Mn: 0.70% to 1.10%; Cr: 1.00% to 1.40%; Ni: 0.10% to 0.50%; Mo: 0.05% to 0.50%; W: 0.05% to 0.10%; Nb: 0.01% to 0.04%; and iron and unavoidable impurities: the balance.   
     
     
         17 . The manufacturing method according to  claim 16 , wherein
 in the S3, the forging comprises forming through three-upsetting and three-drawing with a forging deformation ratio of larger than or equal to 6.   
     
     
         18 . The manufacturing method according to  claim 16 , wherein
 in the S4, the hot annealing is conducted at 650° C. to 680° C. for more than or equal to 12 h.   
     
     
         19 . The manufacturing method according to  claim 16 , wherein
 in the S5, the normalizing is conducted at 920° C. to 970° C.   
     
     
         20 . The manufacturing method according to  claim 16 , wherein in the S5, the oil-quenching is conducted at 870° C. to 930° C. and the tempering is conducted at 220° C. to 260° C.