Plated steel sheet for hot press forming having excellent impact properties after hot press forming, hot press formed member, and manufacturing methods thereof

Abstract

The present invention provides: a plated steel sheet for hot press forming having excellent impact properties after hot press forming; a hot press formed member manufactured using the plated steel sheet for hot press forming; and manufacturing methods thereof. The plated steel sheet comprises: a base steel sheet containing, by weight, 0.15-0.4% of C, 0.1-1% of Si, 0.6-8% of Mn, 0.001-0.05% of P, 0.0001-0.02% of S, 0.01-0.1% of Al, 0.001-0.02% of N, and 0.01-0.5% of Cr, with the remainder comprising Fe and miscellaneous impurities; and a plating layer formed on the surface of the base steel sheet and composed of zinc, aluminum, or an alloy containing zinc and aluminum, wherein the ratio (C S/C B) of the content (C S) of C in a surface layer to the content (C B) of C in the base steel sheet is 0.6 or less, and the ratio ((Mn S+Cr S)/(Mn B+Cr B)) of the total content (Mn S+Cr S) of Mn and Cr in the surface layer to the total content (Mn B+Cr B) of Mn and Cr in the base steel sheet is 0.8 or more.

1 . A hot press formed member comprising:
 a base steel sheet; and   an alloy plating layer formed of an alloy comprising zinc or aluminum on the base steel sheet,   wherein a ratio (C PS /C B ) of a C content (C PS ) of a member surface layer portion to a C content (C B ) of the base steel sheet is 1.2 or less,   wherein a ratio ((Mn PS +Cr PS )/(Mn B +Cr B )) of the sum (Mn PS +Cr PS ) of contents of Mn and Cr of the member surface layer portion to the sum (Mn B +Cr B ) of contents of Mn and Cr of the base steel sheet is 0.8 or more, and   wherein the member surface layer portion refers to a region to a depth of 25 μm from the surface of the base steel sheet excluding the alloy plating layer.   
     
     
         2 . The hot press formed member of  claim 1 , wherein the base steel sheet comprises, by wt %, 0.15% to 0.4% of carbon (C), 0.1% to 1% of silicon (Si), 0.6% to 8% of manganese (Mn), 0.001% to 0.05% of phosphorus (P), 0.0001% to 0.02% of sulfur(S), 0.01% to 0.1% of aluminum (Al), 0.001% to 0.02% of nitrogen (N), 0.01% to 0.5% of chromium (Cr), a balance of Fe, and other impurities 
     
     
         3 . The hot press formed member of  claim 2 , wherein the base steel sheet comprises, by wt %, one or more of 0.0005% to 0.01% of boron (B) and 0.01% to 0.05% of titanium (Ti). 
     
     
         4 . The hot press formed member of  claim 1 , wherein a coverage rate of ferrite at a martensitic grain boundary of the member surface layer portion is 30% or less. 
     
     
         5 . The hot press formed member of  claim 1 , where the ratio (CPS/CB) of the C content (CPS) of the member surface layer portion to the C content (CB) of the base steel sheet is 1.1 or less. 
     
     
         6 . The hot press formed member of  claim 1 , where the ratio (CPS/CB) of the C content (CPS) of the member surface layer portion to the C content (CB) of the base steel sheet is 1.05 or less. 
     
     
         7 . The hot press formed member of  claim 1 , where the ratio (CPS/CB) of the C content (CPS) of the member surface layer portion to the C content (CB) of the base steel sheet is 0.95 or more. 
     
     
         8 . The hot press formed member of  claim 1 , wherein the ratio ((MnPS+CrPS)/(MnB+CrB)) of the sum (MnPS+CrPS) of contents of Mn and Cr of the member surface layer portion to the sum (MnB+CrB) of contents of Mn and Cr of the base steel sheet is 0.9 or more. 
     
     
         9 . The hot press formed member of  claim 1 , wherein the ratio ((MnPS+CrPS)/(MnB+CrB)) of the sum (MnPS+CrPS) of contents of Mn and Cr of the member surface layer portion to the sum (MnB+CrB) of contents of Mn and Cr of the base steel sheet is 0.93 or more. 
     
     
         10 . The hot press formed member of  claim 1 , wherein the ratio ((MnPS+CrPS)/(MnB+CrB)) of the sum (MnPS+CrPS) of contents of Mn and Cr of the member surface layer portion to the sum (MnB+CrB) of contents of Mn and Cr of the base steel sheet is 0.97 or more. 
     
     
         11 . The hot press formed member of  claim 1 , wherein the ratio ((MnPS+CrPS)/(MnB+CrB)) of the sum (MnPS+CrPS) of contents of Mn and Cr of the member surface layer portion to the sum (MnB+CrB) of contents of Mn and Cr of the base steel sheet is 2 or less. 
     
     
         12 . A hot press formed member comprising:
 a base steel sheet; and   an alloy plating layer formed of an alloy comprising zinc or aluminum on the base steel sheet,   wherein a ratio (C PS /C B ) of a C content (C PS ) of a member surface layer portion to a C content (C B ) of the base steel sheet is 1.2 or less,   wherein a ratio ((Mn PS +Cr PS )/(Mn B +Cr B )) of the sum (Mn PS +Cr PS ) of contents of Mn and Cr of the member surface layer portion to the sum (Mn B +Cr B ) of contents of Mn and Cr of the base steel sheet is 0.8 or more,   wherein the member surface layer portion refers to a region to a depth of 25 μm from an interface of the base steel sheet and the alloy plating layer, and   wherein the interface of the base steel sheet and the alloying plating layer is a point at which the aluminum content is 1% by GDS analysis,   
     
     
         13 . The hot press formed member of  claim 12 , wherein the base steel sheet comprises, by wt %, 0.15% to 0.4% of carbon (C), 0.1% to 1% of silicon (Si), 0.6% to 8% of manganese (Mn), 0.001% to 0.05% of phosphorus (P), 0.0001% to 0.02% of sulfur(S), 0.01% to 0.1% of aluminum (Al), 0.001% to 0.02% of nitrogen (N), 0.01% to 0.5% of chromium (Cr), a balance of Fe, and other impurities. 
     
     
         14 . The hot press formed member of  claim 13 , wherein the base steel sheet comprises, by wt %, one or more of 0.0005% to 0.01% of boron (B) and 0.01% to 0.05% of titanium (Ti). 
     
     
         15 . The hot press formed member of  claim 12 , wherein a coverage rate of ferrite at a martensitic grain boundary of the member surface layer portion is 30% or less. 
     
     
         16 . The hot press formed member of  claim 12 , where the ratio (CPS/CB) of the C content (CPS) of the member surface layer portion to the C content (CB) of the base steel sheet is 1.1 or less. 
     
     
         17 . The hot press formed member of  claim 12 , where the ratio (CPS/CB) of the C content (CPS) of the member surface layer portion to the C content (CB) of the base steel sheet is 1.05 or less. 
     
     
         18 . The hot press formed member of  claim 12 , where the ratio (CPS/CB) of the C content (CPS) of the member surface layer portion to the C content (CB) of the base steel sheet is 0.95 or more. 
     
     
         19 . The hot press formed member of  claim 12 , wherein the ratio ((MnPS+CrPS)/(MnB+CrB)) of the sum (MnPS+CrPS) of contents of Mn and Cr of the member surface layer portion to the sum (MnB+CrB) of contents of Mn and Cr of the base steel sheet is 0.9 or more. 
     
     
         20 . The hot press formed member of  claim 12 , wherein the ratio ((MnPS+CrPS)/(MnB+CrB)) of the sum (MnPS+CrPS) of contents of Mn and Cr of the member surface layer portion to the sum (MnB+CrB) of contents of Mn and Cr of the base steel sheet is 0.93 or more. 
     
     
         21 . The hot press formed member of  claim 12 , wherein the ratio ((MnPS+CrPS)/(MnB+CrB)) of the sum (MnPS+CrPS) of contents of Mn and Cr of the member surface layer portion to the sum (Mn B +Cr B ) of contents of Mn and Cr of the base steel sheet is 0.97 or more. 
     
     
         22 . The hot press formed member of  claim 12 , wherein the ratio ((MnPS+CrPS)/(MnB+CrB)) of the sum (MnPS+CrPS) of contents of Mn and Cr of the member surface layer portion to the sum (MnB+CrB) of contents of Mn and Cr of the base steel sheet is 2 or less.