Hot press forming steel plate, formed member using same, and method for manufacturing the plate and member

Abstract

The present invention relates to a hot press forming steel plate made of a composition comprising: 0.3-1.0 wt % of C; 0.0-4.0 wt % of Mn; 1.0-2.0 wt % of Si; 0.01-2.0 wt % of Al; 0.015 wt % or less of S; 0.01 wt % or less of N; and the remainder being Fe and unavoidable impurities. Further, the present. invention relates to a method for manufacturing the hot press forming steel plate, characterized by comprising the steps of: heating, to between 1100 and 1300° C., a steel slab having the composition; performing hot rolling finishing between. an Ar3 transformation point and 950° C.; and performing winding between MS and 720° C. Further, the present invention. relates to a hot press formed member characterized by having the composition, and having a dual phase microstructure made of bainite and residual austenite. In addition, the present invention relates to a method for manufacturing the hot press formed member, characterized by comprising the steps of: heating the steel plate having the composition to a temperature of an Ac3 point or higher; hot press molding the heated steel plate; performing cooling at a cooling speed of 20° C./sec or higher to a temperature between MS and 350° C.; and performing a heat treatment in a heating furnace between MS and 550° C.

1 . A steel sheet for hot press forming, comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities. 
     
     
         2 . The steel sheet for hot press forming of  claim 1 , further comprising at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%. 
     
     
         3 . The steel sheet for hot press forming of  claim 1 , further comprising B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%). 
     
     
         4 . The steel sheet for hot press forming of  claim 1 , wherein the steel sheet is one of a hot-rolled steel sheet, a cold-rolled steel sheet, and a plated cold-rolled steel sheet coated with a plating layer. 
     
     
         5 . A method for manufacturing a steel sheet for hot press forming, the method comprising:
 heating a steel slab to a temperature range of 1100° C. to 1300° C., the steel slab comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities;   performing a finish hot-rolling process at a temperature within a range of Ar 3  transformation point to 950° C. to form a steel sheet; and   coiling the steel sheet at a temperature within a range of M s  to 720° C.   
     
     
         6 . The method of  claim 5 , wherein the steel slab further comprises at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%. 
     
     
         7 . The method of  claim 5 , wherein the steel slab further comprises B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%). 
     
     
         8 . A method for manufacturing a steel sheet for hot press forming, the method comprising:
 heating a steel slab to a temperature range of 1100° C. to 1300° C., the steel slab comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities;   performing a finish hot-rolling process at a temperature within a range of Ar 3  transformation point to 950° C. to form a steel sheet;   coiling the steel sheet at a temperature within a range of M s  to 720° C.;   pickling the steel sheet;   cold-rolling the steel sheet;   continuously annealing the steel sheet at a temperature within a range of 750° C. to 900° C.; and   overaging the steel sheet at a temperature within a range of M s  to 550° C.   
     
     
         9 . The method of  claim 8 , wherein the steel slab further comprises at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%. 
     
     
         10 . The method of  claim 8 , wherein the steel slab further comprises B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%). 
     
     
         11 . A method for manufacturing a steel sheet for hot press forming, the method comprising:
 heating a steel slab to a temperature range of 1100° C. to 1300° C., the steel slab comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities;   performing a finish hot-rolling process at a temperature within a range of Ar 3  transformation point to 950° C. to form a steel sheet;   coiling the steel sheet at a temperature within a range of M s  to 720° C.;   pickling the steel sheet;   cold-rolling the steel sheet;   continuously annealing the steel sheet at a temperature within a range of 750° C. to 900° C.;   overaging the steel sheet at a temperature within a range of M s  to 550° C.; and   plating the overaged steel sheet by any one of hot-dip galvanizing, galvannealing, electro galvanizing, and hot-dip aluminizing.   
     
     
         12 . The method of  claim 11 , wherein the steel slab further comprises at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%. 
     
     
         13 . The method of  claim 11 , wherein the steel slab further comprises B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%). 
     
     
         14 . A hot-press formed member comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities, wherein the hot-press formed member has a dual phase microstructure formed by bainite and retained austenite. 
     
     
         15 . The hot-press formed member of  claim 14 , further comprising at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%. 
     
     
         16 . The hot-press formed member of  claim 14 , further comprising B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%). 
     
     
         17 . The hot-press formed member of  claim 14 , wherein the hot-press formed member has a TS(MPa)*EI(%) value of 25,000 MPa % or greater. 
     
     
         18 . The hot-press formed member of  claim 16 , wherein the hot-press formed member has a TS(MPa)*EI(%) value of 25,000 MPa % or greater. 
     
     
         19 . A method for manufacturing a hot-press formed member, the method comprising:
 heating a steel sheet to a temperature equal to or higher than Ac 3 , the steel sheet comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities;   hot-press forming the heated steel sheet;   cooling the hot-press formed steel sheet to a temperature range of M s  to 550° C. at a rate of 20° C./sec or higher; and   heat-treating the cooled steel sheet at a temperature within a range of M s  to 550° C. in a heating furnace.   
     
     
         20 . The method of  claim 19 , wherein the steel sheet further comprises at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%. 
     
     
         21 . The method of  claim 19 , wherein the steel sheet further comprises B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%). 
     
     
         22 . The method of  claim 19 , wherein the steel sheet is one of a hot-rolled steel sheet, a cold-rolled steel sheet, and a plated cold-rolled steel sheet coated with a plating layer.