Aluminum alloy-plated steel sheet, hot-formed member, and methods for manufacturing aluminum alloy-plated steel sheet and hot-formed member

Abstract

Embodiments of the present disclosure provides an aluminum alloy-plated steel sheet having high surface quality and weldability, a hot-formed member, and methods for manufacturing the aluminum alloy-plated steel sheet and the hot-formed member. The aluminum alloy-plated steel sheet includes: a base steel sheet; and an aluminum alloy plating layer formed on the base steel sheet, wherein the aluminum alloy plating layer includes, by weight %, Zn: 21% to 35%, Si: 1% to 6.9%, Fe: 2% to 12%, and the balance of Al and inevitable impurities.

1 . A hot-formed member obtained by hot forming an aluminum alloy-plated steel sheet, the aluminum alloy-plated steel sheet comprising a base steel sheet and an aluminum alloy plating layer formed on the base steel sheet,
 wherein the aluminum alloy plating layer comprises, by weight %, Zn: 21% to 35%, Si: 1% to 6.9%, Fe: 2% to 12%, Mg: 1.2% or less (including 0%), and a balance of Al and inevitable impurities, and   the hot-formed member has a microstructure comprising, in area %, 90% or more martensite and at least one of ferrite and bainite as a remainder.   
     
     
         2 . The hot-formed member of  claim 1 , wherein the hot-formed member has a tensile strength of 1200 MPa or more. 
     
     
         3 . A method for manufacturing an aluminum alloy-plated steel sheet, the method comprising:
 preparing a base steel sheet; and   forming an aluminum alloy plating layer on each surface of the base steel sheet by dipping the base steel sheet in a plating bath having a temperature of 560° C. to 680° C.,   wherein the plating bath comprises, by weight %, Zn: 23% to 40%, Si: 1% to 8%, and a balance of Al and inevitable impurities.   
     
     
         4 . The method of  claim 3 , wherein the base steel sheet comprises, by weight %, C: 
     
     
         0 . 15% to 0.39%, Mn: 0.5% to 3%, B: 0.01% or less (including 0%), Ti: 0.1% or less (including 0%), and a balance Fe and inevitable impurities. 
     
     
         5 . The method of  claim 3 , wherein the plating bath further comprises Mg: 1.4% or less. 
     
     
         6 . The method of  claim 3 , wherein the plating bath has a ratio of Al/(Zn+Si) within a range of 1.3 to 2.6, where Al, Zn, and Si respectively refer to Al, Zn, and Si contents in weight %. 
     
     
         7 . The method of  claim 3 , further comprising heat treating the base steel sheet at 650° C. to 850° C. prior to the forming of the aluminum alloy plating layer. 
     
     
         8 . The method of claim  37 , wherein the heat treating is performed in a reducing atmosphere comprising, by volume %, hydrogen gas in an amount of 25% or less (including 0%) and the balance of nitrogen gas. 
     
     
         9 . The method of  claim 3 , wherein the temperature of the plating bath is within a range of a plating liquid melting point +20° C. to a plating liquid melting point +80° C. 
     
     
         10 . The method of  claim 3 , wherein a temperature of the base steel sheet at an inlet of the plating bath is within a range of the temperature of the plating bath +5° C. to the temperature of the plating bath +50° C. 
     
     
         11 . The method of  claim 3 , further comprising controlling a plating amount of the aluminum alloy plating layer after the forming of the aluminum alloy plating layer. 
     
     
         12 . The method of  claim 11 , wherein the plating amount is within a range of 15 g/m 2  to 150 g/m 2  based on one side.