Plated steel sheet having excellent plating adhesion and corrosion resistance after hot press forming, preparation method for plated steel sheet, and hot pressed forming member

Abstract

The present disclosure relates to a plated steel sheet for hot press forming, having excellent paint adhesion and corrosion resistance after hot press forming; a preparation method for the plated steel sheet; and a hot press formed member. The plated steel sheet according to an aspect of the present disclosure comprises a base steel sheet and a plating layer consisting of Al—Fe alloy formed on the base steel sheet, wherein the sum of contents of Al and Fe in the plating layer is 80% or more by weight, the average content of Fe in the plating layer is 20% or more by weight, and the product of Ra and RPC of the surface of the plating layer may be 60-150 μm/cm. Here, Ra represents arithmetic mean roughness and the unit thereof is μm, and RPc represents the number of peaks per unit length and the unit thereof is /cm.

1 . A plated steel sheet for hot press forming, comprising:
 a base steel sheet; and   a plating layer comprising an Al—Fe alloy formed on the base steel sheet,   wherein the sum of contents of Al and Fe in the plating layer is 80% or more by weight,   an average content of Fe in the plating layer is 20% or more by weight, and   a product of Ra and RPc on the surface of the plating layer is 60 to 150 μm/cm,   where Ra represents arithmetic mean roughness and a unit thereof is μm, and RPc represents the number of peaks per unit length and a unit thereof is /cm.   
     
     
         2 . A plated steel sheet for hot press forming, comprising:
 a base steel sheet; and   a plating layer comprising an Al—Fe alloy formed on the base steel sheet,   wherein the sum of contents of Al and Fe in the plating layer is 80% or more by weight,   the average content of Fe in the plating layer is 20% or more by weight, and   a number of cracks existing in each region obtained by dividing a field of view obtained when a surface of the plating layer is observed with a scanning electron microscope at a magnification of 100 times, into 10 horizontal and vertical sections, is 10 to 200 per 1 mm 2 , and   a ratio of an area occupied by an indentation portion on the surface of the plating layer is 5 to 50%,   wherein the indentation portion refers to a region having a brightness of 70% or more as compared to the highest brightness measured in a region observed with an optical microscope at a magnification of 100 times.   
     
     
         3 . The plated steel sheet for hot press forming of  claim 1 , wherein an content of Fe in a surface portion of the plating layer is 50% or more as compared to an average content of Fe in the plating layer,
 wherein the content of Fe of the surface portion is a value measured through an EDS surface analysis at a site enlarged 100 times by a scanning electron microscope (SEM), and the average content of Fe refers to a value obtained by integrating an content curve of Fe from a surface layer obtained through a GDS analysis to a depth at which Fe and Al contents intersect, and then dividing the integrated content curve of Fe by a distance from the surface layer to the depth at which the Fe and Al contents intersect.   
     
     
         4 . The plated steel sheet for hot press forming of  claim 3 , wherein a content of Fe on the surface portion of the plating layer is 15% or more by weight. 
     
     
         5 . The plated steel sheet for hot press forming of  claim 2 , wherein a content of Fe in the surface portion of the plating layer is 50% or more as compared to an average content of Fe in the plating layer,
 wherein the content of Fe of the surface portion is a value measured through an EDS surface analysis at a site enlarged 100 times by a scanning electron microscope (SEM), and the average content of Fe refers to a value obtained by integrating an content curve of Fe from a surface layer obtained through a GDS analysis to a depth at which Fe and Al contents intersect, and then dividing the integrated content curve of Fe by a distance from the surface layer to the depth at which the Fe and Al contents intersect.   
     
     
         6 . The plated steel sheet for hot press forming of  claim 5 , wherein the content of Fe on the surface portion of the plating layer is 15% or more by weight. 
     
     
         7 . The plated steel sheet for hot press forming of  claim 1 , wherein the average content of Fe in the plating layer is 90% or less. 
     
     
         8 . The plated steel sheet for hot press forming of  claim 1 , wherein the plating layer comprises 20 wt % or less in the sum of contents of one or two or more elements selected from Mg, Zn, Mn, Cr, Mo, Si and Ti. 
     
     
         9 . The plated steel sheet for hot press forming of  claim 1 , wherein the composition of the base steel sheet comprises, by weight, C: 0.01 to 0.5% Si: 2.0% or less (excluding 0%), Mn: 0.1 to 4.0%, P: 0.05% or less, S: 0.02% or less, Al: 0.001 to 1%, Cr: 5.0% (excluding 0%), N: 0.02% or less, Ti: 0.1% or less (excluding 0%), B: 0.0001 to 0.01%, and a balance of Fe, and inevitable impurity elements. 
     
     
         10 . The plated steel sheet for hot press forming of  claim 9 , wherein the composition of the base steel sheet further comprises one or more elements selected from Nb: 0.1% or less, Mo: 0.5% or less, Ni: 1% or less, Cu: 1% or less, and V: 0.5% or less. 
     
     
         11 . A manufacturing method for a plated steel sheet for hot press forming, comprising:
 obtaining an Al—Fe alloy plated steel sheet in which a plating layer comprising an Al—Fe alloy is formed on a base steel sheet; and   performing skin pass rolling on the Al—Fe alloy plated steel sheet under a condition that an SPMI expressed by the following relational equation 1 is 5000 to 8500,   
       
         
           
             
               
                 
                   
                     SPMI 
                     = 
                     
                       
                         P 
                       
                       × 
                       
                         Ra 
                         roll 
                       
                       × 
                       
                         RPc 
                         roll 
                       
                     
                   
                 
                 
                   
                     [ 
                     
                       Relational 
                       ⁢ 
                           
                       Expression 
                       ⁢ 
                           
                       1 
                     
                     ] 
                   
                 
               
             
           
         
         where the P refers to depression force (unit: ton) during the skin pass rolling, the Ra roll  refers to arithmetic average roughness (unit: μm) on a surface of a skin pass rolling roll, and the RPc roll  refers to the number of peaks (unit:/cm) per unit length of the skin pass rolling roll, and also, a unit of the SPMI is √ton·μm/cm. 
       
     
     
         12 . The manufacturing method for a plated steel sheet for hot press forming of  claim 11 , wherein the Al—Fe alloy plated steel sheet is obtained by a process comprising a step of obtaining an aluminum-plated steel sheet plated with aluminum or an aluminum alloy; and a step of heating and alloying the aluminum plated steel sheet. 
     
     
         13 . The manufacturing method for a plated steel sheet for hot press forming of  claim 12 , wherein the step of heating and alloying the aluminum plated steel sheet is performed by online heating in a state in which a steel sheet is directly connected to a line for plating aluminum or an aluminum alloy, and the plated steel sheet is running. 
     
     
         14 . The manufacturing method for a plated steel sheet for hot press forming of  claim 12 , wherein the step of heating and alloying the aluminum plated steel sheet is performed by batch annealing for heating a coiled plated steel sheet in a box-type annealing furnace. 
     
     
         15 . The manufacturing method for a plated steel sheet for hot press forming of  claim 11 , wherein the composition of the base steel sheet comprises, by weight, C: 0.01 to 0.5%, Si: 2.0% or less (excluding 0%), Mn: 0.1 to 4.0%, P: 0.05% or less, S: 0.02% or less, Al: 0.001 to 1%, Cr: 5.0% or less (excluding 0%), N: 0.02% or less, Ti: 0.1% or less (excluding 0%), B: 0.0001 to 0.01%, a balance of Fe, and inevitable impurity elements. 
     
     
         16 . The manufacturing method for a plated steel sheet for hot press forming of  claim 15 , wherein the composition of the base steel sheet further comprises one or more elements selected from Nb: 0.1% or less, Mo: 0.5% or less, Ni: 1% or less, Cu: 1% or less, and V: 0.5% or less. 
     
     
         17 - 23 . (canceled) 
     
     
         24 . The plated steel sheet for hot press forming of  claim 2 , wherein the average content of Fe in the plating layer is 90% or less. 
     
     
         25 . The plated steel sheet for hot press forming of  claim 2 , wherein the plating layer comprises 20 wt % or less in the sum of contents of one or two or more elements selected from Mg, Zn, Mn, Cr, Mo, Si and Ti. 
     
     
         26 . The plated steel sheet for hot press forming of  claim 2 , wherein the composition of the base steel sheet comprises, by weight, C: 0.01 to 0.5% Si: 2.0% or less (excluding 0%), Mn: 0.1 to 4.0%, P: 0.05% or less, S: 0.02% or less, Al: 0.001 to 1%, Cr: 5.0% (excluding 0%), N: 0.02% or less, Ti: 0.1% or less (excluding 0%), B: 0.0001 to 0.01%, and a balance of Fe, and inevitable impurity elements. 
     
     
         27 . The plated steel sheet for hot press forming of  claim 26 , wherein the composition of the base steel sheet further comprises one or more elements selected from Nb: 0.1% or less, Mo: 0.5% or less, Ni: 1% or less, Cu: 1% or less, and V: 0.5% or less.