Method for manufacturing plated steel having excellent processability and corrosion resistance

Abstract

Provided is a method of manufacturing a plated steel material having excellent workability and corrosion resistance according to an exemplary embodiment of the present disclosure and the method includes steps of immersing a base steel in a hot-dip alloy plating bath; and forming a hot-dip alloy-plated layer on the base steel by drawing the immersed base steel from the hot-dip alloy plating bath and performing a cooling process. A first average cooling rate in the cooling process varies depending on a difference between a first temperature that is a temperature of the hot-dip alloy plating bath and a second temperature that is a solidification start temperature of a MgZn 2 phase constituting the hot-dip alloy-plated layer.

1 . A method of manufacturing a plated steel material having excellent workability and corrosion resistance, the method comprising:
 immersing a base steel in a hot-dip alloy plating bath; and   forming a hot-dip alloy-plated layer on the base steel by drawing the immersed base steel from the hot-dip alloy plating bath and performing a cooling process,   wherein a first average cooling rate in the cooling process varies depending on a difference between a first temperature that is a temperature of the hot-dip alloy plating bath and a second temperature that is a solidification start temperature of a MgZn 2  phase continuing the hot-dip alloy-plated layer.   
     
     
         2 . The method according to  claim 1 ,
 wherein when the difference between the first temperature and the second temperature is less than 50° C., the first average cooling rate is 10 to 20° C./s,   wherein when the difference between the first temperature and the second temperature is 50° C. or higher and less than 100° C., the first average cooling rate is 15 to 35° C./s, and   wherein when the difference between the first temperature and the second temperature is 100° C. or higher, the first average cooling rate is 20 to 50° C./s.   
     
     
         3 . The method according to  claim 1 , wherein the first average cooling rate is an average cooling rate from a time point at which the immersed base steel is drawn from the hot-dip alloy plating bath to a time point at which the MgZn 2  phase starts to solidify. 
     
     
         4 . The method according to  claim 1 , wherein a second average cooling rate in the cooling process from a time point at which the MgZn 2  phase starts to solidify to a time point at which the solidification is completed satisfies a relationship of Formula 1 below.
   0.0114 ×T− 0.2841≤second average cooling rate≤0.025× T+ 10 ( T : solidification start temperature of MgZn 2  phase).  <Formula 1>
   
     
     
         5 . The method according to  claim 1 , wherein the hot-dip alloy plating bath is a Zn plating bath comprising, by wt. %, 6 to 23% of Al, 3 to 7% of Mg, and inevitable impurities. 
     
     
         6 . The method according to  claim 1 , wherein an area fraction of a MgZn 2  phase here a ratio of an average minor axis length (a) to an average major axis length (b) is 0.5 or less in the entire MgZn 2  phase on a surface of the hot-dip alloy-plated layer formed on the base steel is 70% or less.