Steel for alloy structure and manufacturing method therefor

Abstract

Disclosed is a steel for an alloy structure, the chemical elements of the steel being, in percentage by mass: 0.35-0.45% of C, 0.27-0.35% of Si, 0.6-0.8% of Mn, 0.015-0.05% of Al, 0.06-0.1% of V, 0.2-1.0% of Zr, 0.001-0.005% of Mg, 0.025% or less of P, 0.015% or less of S, 0.005% or less of N, 0.001% or less of 0, the balance being Fe and other inevitable impurities. In addition, also disclosed is a manufacturing method for the steel for an alloy structure, the method comprising steps of: (1) smelting, refining, and casting; (2) blooming and cogging; (3) secondary hot rolling to form a product; and (4) heat treatment including quenching and tempering. The steel for an alloy structure is designed by adding trace alloy elements, the steel for an alloy structure is further strengthened and toughened, and the manufacturing cost is low.

1 . A steel for an alloy structure, comprising the following chemical elements in percentage by mass:
 0.35-0.45% of C, 0.27-0.35% of Si, 0.6-0.8% of Mn, 0.015-0.05% of Al, 0.06-0.1% of V, 0.2-1.0% of Zr, 0.001-0.005% of Mg, 0.025% or less of P, 0.015% or less of S, 0.005% or less of N, 0.001% or less of O, the balance being Fe and other inevitable impurities.   
     
     
         2 . The steel for the alloy structure according to  claim 1 , further comprising at least one selected from the following chemical elements: Ce, Hf, La, Re, Sc, and Y, wherein the total addition amount of these elements is 1% or less. 
     
     
         3 . The steel for the alloy structure according to  claim 1 , wherein the content by mass percentage of chemical elements satisfies at least one of the following:
 0.08-0.1% of V;   0.3-0.7% Zr; and   0.001-0.003% of Mg.   
     
     
         4 . The steel for the alloy structure according to  claim 1 , wherein a ratio of the content by mass of chemical elements further satisfies at least one of the following:
 Zr/N=40˜200;   Zr/V=2˜16.7; and   Zr/C=0.4˜2.8.   
     
     
         5 . The steel for the alloy structure according to  claim 1 , wherein a ratio of the content by mass of chemical elements further satisfies at least one of the following:
 Mg/O=0.5˜3; and   Mg/S=0.6˜5.0.   
     
     
         6 . The steel for the alloy structure according to  claim 1 , wherein a microstructure of the steel for the alloy structure is ferrite+pearlite, and the steel for the alloy structure contains ZrC, ZrN, MgO, and MgS particles. 
     
     
         7 . The steel for the alloy structure according to  claim 6 , wherein the sum of the number of the ZrC and ZrN particles is 3-15 pieces/mm 2 . 
     
     
         8 . The steel for the alloy structure according to  claim 6 , wherein the sum of the number of the MgO and MgS particles is 5-20 pieces/mm 2 . 
     
     
         9 . The steel for the alloy structure according to  claim 6 , wherein the ZrC, ZrN, MgO, and MgS particles have a diameter of 0.2-7 μm. 
     
     
         10 . The steel for the alloy structure according to  claim 1 , wherein the steel for alloy structure has a yield strength of 755 MPa or more, a tensile strength of 900 MPa or more, an elongation percentage of 12% or more, and an impact toughness of 100 J or more. 
     
     
         11 . A manufacturing method for the steel for the alloy structure according to  claim 1 , comprising steps of:
 (1) smelting, refining, and casting;   (2) blooming and cogging;   (3) secondary hot rolling to form a product; and   (4) heat treatment comprising quenching and tempering.   
     
     
         12 . The manufacturing method according to  claim 11 , wherein a heating temperature is 1,150-1,250° C. in the step of blooming and cogging; and a heating temperature is 1,150-1,250° C. in the step of secondary hot rolling to form the product. 
     
     
         13 . The manufacturing method according to  claim 11 , wherein in the step of heat treatment, a heating temperature is controlled within a range of 855-890° C. during quenching, and a cooling speed is controlled within a range of 50-90° C./s during quenching; and a heating temperature is controlled within a range of 645-670° C. during tempering, and a cooling speed is controlled within a range of 50-90° C./s during tempering.