Steel for mining chain and manufacturing method thereof

Abstract

A steel for mining chain and a manufacturing method thereof, wherein the steel has compositions by weight percentage: C: 0.20-0.28%, Si: 0.01-0.40%, Mn: 0.50-1.50%, P≤0.015%, S≤0.005%, Cr: 0.30-2.00%, Ni: 0.50-2.00%, Mo: 0.10-0.80%, Cu: 0.01-0.30%, Al: 0.01-0.05%, Nb: 0.001-0.10%, V: 0.001-0.10%, H≤0.00018%, N≤0.0150%, O≤0.0020%, and the balance is Fe and inevitable impurities. The manufacturing method comprises steps of smelting, refining and vacuum treatment, casting, heating, forging or rolling, and quenching and tempering heat treatment processes. The steel in the present invention has high strength and good impact toughness, good elongation and reduction of area. The steel can also resist stress corrosion cracking and have good weather resistance, wear resistance and fatigue resistance, which can be used in scenarios where the steel having high strength and toughness is required, such as construction machinery and marine engineering.

1 . A steel for mining chain, comprising by weight: C: 0.20-0.28%, Si: 0.01-0.40%, Mn: 0.50-1.50%, P≤0.015%, S≤0.005%, Cr: 0.30-2.00%, Ni: 0.50-2.00%, Mo: 0.10-0.80%, Cu: 0.01-0.30%, Al: 0.01-0.05%, Nb: 0.001-0.10%, V: 0.001-0.10%, H≤0.00018%, N≤0.0150%, O≤0.0020%, and the balance being Fe and inevitable impurities; and 
 having a coefficient r M/N  of microalloying elements ranging from 1.0 to 9.9, wherein 
           r       m   /   n         =           A   l       /   2       +           N   b       /   7       +     V     /   4       /     N           
 having trace elements as follows: As≤0.05%, Pb≤0.05%, Sn≤0.02%, Sb≤0.01%, Bi<0.01%, and having a coefficient J H  of harmful elements being ≤500, wherein 
           J   H     =         P     +       S   n       +       A   s       +       P   b       +       S   b       +       B   i           ∗           S   i       +       M   n           ∗       10000             .               
. 
     
     
         2 . The steel for mining chain of  claim 1 , having Ceq≤0.80, wherein 
       
         
           
             
               C 
               e 
               q 
               = 
               
                 C 
               
               + 
               
                 
                   M 
                   n 
                 
               
               / 
               6 
               + 
               
                 
                   
                     
                       C 
                       r 
                     
                   
                   + 
                   
                     
                       M 
                       o 
                     
                   
                   + 
                   
                     V 
                   
                 
               
               / 
               5 
               + 
               
                 
                   
                     
                       N 
                       i 
                     
                   
                   + 
                   
                     
                       C 
                       u 
                     
                   
                 
               
               / 
               
                 
                   15 
                 
                 
                   
                       
                     . 
                   
                 
               
             
           
         
       
       . 
     
     
         3 . The steel for mining chain of  claim 1 , having an index I of atmospheric corrosion resistance being≤7.0, wherein 
       
         
           
             
               I 
               = 
               26.0 
               
                 
                   C 
                   u 
                 
               
               + 
               3.9 
               
                 
                   N 
                   i 
                 
               
               + 
               1.2 
               
                 
                   C 
                   r 
                 
               
               + 
               1.5 
               
                 
                   S 
                   i 
                 
               
               + 
               17.3 
               
                 P 
               
               − 
               7.3 
               
                 
                   C 
                   u 
                 
               
               
                 
                   N 
                   i 
                 
               
               − 
               9.1 
               
                 
                   N 
                   i 
                 
               
               
                 P 
               
               − 
               33.4 
               
                 
                   
                     
                       C 
                       u 
                     
                   
                 
                 2 
               
               
                   
                 
                   
                       
                     . 
                   
                 
               
             
           
         
       
       . 
     
     
         4 . The steel for mining chain of  claim 1 , wherein in said inevitable impurities, 
       
         
           
             
               B 
               ≤ 
               0 
               .0010, 
                 
               Ti 
               ≤ 
               0 
               .003, 
                 
               Ca 
               ≤ 
               0 
               .005 
               . 
             
           
         
       
       . 
     
     
         5 . The steel for mining chain of any of  claim 1 , having microstructures of tempered martensite, bainite, and retained austenite. 
     
     
         6 . The steel for mining chain of  claim 1 , having a yield strength R p0 . 2 ≤1000 MPa, a tensile strength R m≤ 1200 MPa, a elongation A≥12%, a reduction of area Z≥50%, a Charpy impact work A kv≤ 60 J, and a coefficient of hydrogen embrittlement ƞ(Z)≤15%. 
     
     
         7 . A manufacturing method of the steel for mining chain of  claim 1 , comprising steps of smelting, casting, heating, forging or rolling, quenching heat treatment, and tempering heat treatment processes, wherein
 in said heating process, the heating temperature is 1050 ~ 1250° C., the holding time is 3-24 hr.;   in said forging or rolling process, the final forging temperature or the final rolling temperature is ≤800° C.;   in said quenching heat treatment, the heating temperature is 850-1000° C., the holding time is 60-240 min, and a water quenching is implemented after austenitization;   in said tempering heat treatment, the tempering temperature is 350~550° C., the holding time is 60-240 min, and an air cooling or water cooling is implemented after tempering.   
     
     
         8 . The manufacturing method of the steel for mining chain of  claim 7 , wherein said smelting comprises smelting in electric furnace or smelting in converter, and refining and vacuum treatment; said casting is die casting or continuous casting. 
     
     
         9 . The manufacturing method of the steel for mining chain of  claim 7 , wherein in said forging process, a steel billet is directly forged to size of final product; in said rolling process, a steel billet is directly rolled to size of final product; or a steel billet is rolled to a specified intermediate billet size, and then heated and rolled to size of final product, wherein the heating temperature of the intermediate billet is 1050~1250° C., and the holding time is 3-24 hr. 
     
     
         10 . The manufacturing method of the steel for mining chain of  claim 7 , wherein in said rolling process, a steel billet is subjected to descaling of high pressure water when out of the heating furnace and is then rolled, and after rolling, the steel billet is air cooled or slow cooled. 
     
     
         11 . The steel for mining chain of  claim 2 , having microstructures of tempered martensite, bainite, and retained austenite. 
     
     
         12 . The steel for mining chain of  claim 3 , having microstructures of tempered martensite, bainite, and retained austenite. 
     
     
         13 . The steel for mining chain of  claim 4 , having microstructures of tempered martensite, bainite, and retained austenite. 
     
     
         14 . The steel for mining chain of  claim 2 , having a yield strength R p0 . 2 ≤1000 MPa, a tensile strength R m≤ 1200 MPa, a elongation A≥12%, a reduction of area Z≥50%, a Charpy impact work A kv ≤60 J, and a coefficient of hydrogen embrittlement ƞ(Z)≤15%. 
     
     
         15 . The steel for mining chain of  claim 3 , having a yield strength R p0 . 2 ≤1000 MPa, a tensile strength R m≤ 1200 MPa, a elongation A≥12%, a reduction of area Z≥50%, a Charpy impact work A kv ≤60 J, and a coefficient of hydrogen embrittlement ƞ(Z)≤15%. 
     
     
         16 . The steel for mining chain of  claim 4 , having a yield strength R p0.2 ≤1000 MPa, a tensile strength R m≤ 1200 MPa, a elongation A≥12%, a reduction of area Z≥50%, a Charpy impact work A kv ≤60 J, and a coefficient of hydrogen embrittlement ƞ(Z)≤15%. 
     
     
         17 . The manufacturing method of the steel for mining chain of  claim 9 , wherein in said rolling process, a steel billet is subjected to descaling of high pressure water when out of the heating furnace and is then rolled, and after rolling, the steel billet is air cooled or slow cooled.