High-plasticity steel and manufacturing method therefor

Abstract

Provided in the present invention are a high-plasticity steel and a manufacturing method therefor. The steel comprises the following components in percentage by mass: C: 0.10-0.35%, Si: 0.8-2.0%, Mn: 1.0-3.0%, P: ≤0.02%, S ≤0.005%, Al: 0.1-2.0%, N: ≤0.005%, with the balance being Fe and other inevitable impurities. The steel of the present invention can achieve good matching among a low yield strength, a low yield ratio, a high tensile strength and an ultrahigh elongation rate, and can be widely applied to components with complex shape requirements, or other parts that require thinning while maintaining high strength, such as those in commercial or passenger vehicles.

1 . A steel comprising the following components in percentage by mass: C: 0.10-0.35%, Si: 0.8-2.0%, Mn: 1.0-3.0%, P: ≤0.02%, S ≤0.005%, Al: 0.1-2.0%, N: ≤0.005%, with the balance being Fe and other inevitable impurities. 
     
     
         2 . The steel according to  claim 1 , wherein the steel further comprises Ti; in percentage by mass, the content of Ti is less than or equal to 0.2%, preferably 0.05-0.2%, more preferably 0.05-0.1%. 
     
     
         3 . The steel according to  claim 1 , wherein the steel further comprises one or more selected from the group consisting of Mo, Nb, V, Cu, Ni, Cr and B,
 wherein, in percentage by mass,   the content of Mo is less than or equal to 0.5%, preferably less than or equal to 0.3%;   the content of Nb is less than or equal to 0.1%, preferably less than or equal to 0.06%;   the content of V is less than or equal to 0.1%, preferably less than or equal to 0.06%;   the content of Cu is less than or equal to 0.5%, preferably less than or equal to 0.3%;   the content of Ni is less than or equal to 0.5%, preferably less than or equal to 0.3%;   the content of Cr is less than or equal to 0.5%, preferably less than or equal to 0.3%;   the content of B is less than or equal to 0.001%, preferably less than or equal to 0.0005%.   
     
     
         4 . The steel according to  claim 1 , wherein the inevitable impurities includes, in percentage by mass, O ≤0.003%, preferably O ≤0.002%; S ≤0.003%; and/or N ≤0.004%. 
     
     
         5 . The steel according to  claim 1 , wherein the components of the steel satisfies one or more of the following: C: 0.15˜0.25%, Si: 1.0˜1.6%, Mn: 1.5˜2.5%, Al: 0.3˜1.0% in percentage by mass. 
     
     
         6 . The steel according to  claim 1 , wherein the steel has a microstructure of ferrite, bainite, and residual austenite with a content of ≥5%. 
     
     
         7 . The steel according to  claim 1 , wherein the steel has a yield strength of 500 MPa or more, preferably 600 MPa or more, more preferably 700 MPa or more; a tensile strength of 780 MPa or more, preferably 980 MPa or more;
 and an elongation rate of 25% or more, preferably 30% or more.   
     
     
         8 . The steel according to  claim 2 , wherein in percentage by mass, the content of C is 0.10-0.25%, the content of Ti is 0.05-0.2%, and wherein the steel has a yield strength of 600 MPa or more, a tensile strength of 780 MPa or more, an elongation rate of 30% or more, and a hole expansion rate of 50% or more; or,
 wherein in percentage by mass, the content of C is 0.25-0.35%, the content of Ti is 0.05-0.2%, and wherein the steel has a yield strength of 700 MPa or more, a tensile strength of 980 MPa or more, an elongation rate of 25% or more, and a hole expansion rate of 30% or more.   
     
     
         9 . The steel according to  claim 1 , any one of  claims 1 to 8 , wherein the hole expansion rate of the steel is  30 % or more, preferably  50 % or more. 
     
     
         10 . A method for manufacturing the steel according to  claim 1 , including the following steps:
 1) smelting and casting   smelting the components according to  claim 1  in a converter or an electric furnace, then secondary refining in a vacuum furnace, and then casting it into a casting blank or a casting ingot;   2) reheating the casting blank or the casting ingot   heating temperature ≥1100° C., holding time: 1-2 hours;   3) hot rolling and cooling the casting blank or the casting ingot   wherein the casting blank or the casting ingot is hot rolled at an initial rolling temperature of 1000° C. or higher, then subjected to 5-7 passes of rolling with a relatively large deformation rate of 50% or more at 1000° C. or higher, then subjected to 3-7 passes of final rolling with a cumulative deformation of 70% or more after an intermediate blank reaches ≥950° C., obtaining a steel strip; wherein the final rolling temperature is 800˜950° C.;   wherein the cooling is staged cooling, after the final rolling, the steel strip is water-cooled to a temperature between 600˜750° C. at a cooling rate of 30° C./s or more; after air cooling for 1˜10 seconds, the steel strip is then cooled to a temperature between 350˜550° C. at a cooling rate of 10° C./s or more and coiled, and then cooled to room temperature at a cooling rate of 50° C./h or less, obtaining a hot-rolled strip steel.   
     
     
         11 . The method according to  claim 10 , wherein the method further includes step 4) pickling, wherein the hot-rolled strip steel is pickled at a running speed of 30˜120 m/min, with a pickling temperature of 75˜85° C. and a straightening rate of 2% or less, and then rinsed at a temperature in the range of 35˜50° C., and the surface of the hot-rolled strip steel is dried at a temperature of 120˜140° C., and oiled. 
     
     
         12 . The steel according to  claim 2 , wherein the steel further comprises one or more selected from the group consisting of Mo, Nb, V, Cu, Ni, Cr and B,
 wherein, in percentage by mass,   the content of Mo is less than or equal to 0.5%, preferably less than or equal to 0.3%;   the content of Nb is less than or equal to 0.1%, preferably less than or equal to 0.06%;   the content of V is less than or equal to 0.1%, preferably less than or equal to 0.06%;   the content of Cu is less than or equal to 0.5%, preferably less than or equal to 0.3%;   the content of Ni is less than or equal to 0.5%, preferably less than or equal to 0.3%;   the content of Cr is less than or equal to 0.5%, preferably less than or equal to 0.3%; and   the content of B is less than or equal to 0.001%, preferably less than or equal to 0.0005%.   
     
     
         13 . The steel according to  claim 2 , wherein the inevitable impurities includes, in percentage by mass, O ≤0.003%, preferably O ≤0.002%; S ≤0.003%; and/or N ≤0.004%. 
     
     
         14 . The steel according to  claim 2 , wherein the components of the steel satisfies one or more of the following: C: 0.15˜0.25%, Si: 1.0˜1.6%, Mn: 1.5˜2.5%, Al: 0.3˜1.0% in percentage by mass. 
     
     
         15 . The steel according to  claim 2 , wherein the steel has a microstructure of ferrite, bainite, and residual austenite, with the content of the residual austenite being ≥5%. 
     
     
         16 . The steel according to  claim 2 , wherein the steel has a yield strength of 500 MPa or more, preferably 600 MPa or more, more preferably  700  MPa or more; a tensile strength of 780 MPa or more, preferably 980 MPa or more; and an elongation rate of 25% or more, preferably 30% or more. 
     
     
         17 . The steel according to  claim 3 , wherein the steel has a yield strength of 500 MPa or more, preferably 600 MPa or more, more preferably 700 MPa or more; a tensile strength of 780 MPa or more, preferably 980 MPa or more; and an elongation rate of 25% or more, preferably 30% or more. 
     
     
         18 . The steel according to  claim 4 , wherein the steel has a yield strength of 500 MPa or more, preferably 600 MPa or more, more preferably 700 MPa or more; a tensile strength of 780 MPa or more, preferably 980 MPa or more; and an elongation rate of 25% or more, preferably 30% or more. 
     
     
         19 . The steel according to  claim 5 , wherein the steel has a yield strength of 500 MPa or more, preferably 600 MPa or more, more preferably 700 MPa or more; a tensile strength of 780 MPa or more, preferably 980 MPa or more; and an elongation rate of 25% or more, preferably 30% or more. 
     
     
         20 . The steel according to  claim 2 , wherein the hole expansion rate of the steel is 30% or more, preferably 50% or more.