Hot dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement

Abstract

A hot-dip galvanized steel sheet having excellent resistance to cracking caused by liquid metal embrittlement is provided. The hot-dip galvanized steel sheet having excellent resistance to cracking caused by liquid metal embrittlement includes a base steel sheet having a microstructure in which an austenite fraction is 90 area % or more; and a hot-dip galvanizing layer formed on the base steel sheet, wherein the hot-dip galvanizing layer includes an Fe—Zn alloy layer; and a Zn layer formed on the Fe—Zn alloy layer, and the Fe—Zn alloy layer has a thickness of [( 3.4 ×t)/ 6 ] μm or more, where t is a thickness of the hot-dip galvanizing layer. In addition, provided is the hot-dip galvanized steel sheet in which plating layer delamination easily occurring in vehicle welding and molding conditions according to the related art, is prevented, and cracking caused by liquid metal embrittlement is suppressed.

1 . A hot-dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement, comprising:
 a base steel sheet having a microstructure in which an austenite fraction is 90 area % or more; and   a hot-dip galvanizing layer formed on the base steel sheet,   wherein the hot-dip galvanizing layer includes an Fe—Zn alloy layer, and a Zn layer formed on the Fe—Zn alloy layer, and the Fe—Zn alloy layer has a thickness of [(3.4×t)/6] μm or more, where t is a thickness of the hot-dip galvanizing layer.   
     
     
         2 . The hot-dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement of  claim 1 , wherein the Fe—Zn alloy layer includes 3 wt % to 15 wt % of iron (Fe). 
     
     
         3 . The hot-dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement of claim  1 , wherein the base steel sheet comprises, by wt %, carbon (C): 0.10% to 0.30%, manganese (Mn): 10% to 30%, silicon (Si): 0.01% to 0.03%, titanium (Ti): 0.05% to 0.2%, manganese (Mn): 10% to 30%, aluminum (Al): 0.5% to 3.0%, nickel (Ni): 0.001% to 10%, chromium (Cr): 0.001% to 10%, nitrogen (N): 0.001% to 0.05%, phosphorus (P): 0.020% or less, sulfur (S): 0.001% to 0.005%, and iron (Fe) as a residual component thereof, and inevitable impurities. 
     
     
         4 . The hot-dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement of  claim 1 , wherein the hot-dip galvanizing layer further includes an Fe—Al or Fe—Al—Zn alloy layer below the Fe—Zn alloy layer. 
     
     
         5 . The hot-dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement of  claim 4 , wherein the alloying suppression layer includes 0.6 wt % or less of aluminum (Al). 
     
     
         6 . The hot-dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement of  claim 1 , further comprising an Fe—Ni alloy layer disposed directly below a surface of the base steel sheet. 
     
     
         7 . The hot-dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement of  claim 1 , wherein the Fe—Ni alloy layer is provided by coating Ni having an adhesion amount of 300 mg/m 2  to 1000 mg/m 2 . 
     
     
         8 . The hot-dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement of  claim 1 , wherein the Fe—Ni alloy layer has a thickness of 0.05 μm to 5 μm. 
     
     
         9 . The hot-dip galvanized steel sheet having excellent resistance to cracking due to liquid metal embrittlement of  claim 1 , further comprising one or more selected from a group consisting of an Fe—X alloy layer, an Fe—Al—X alloy layer, an Fe—Al—Zn—X alloy layer, and an Fe—Zn—X alloy layer, disposed between the base steel sheet and the hot-dip galvanizing layer, where X is one of nickel (Ni) and chromium (Cr).