Hot-dip galvanized steel sheet and galvannealed steel sheet

Abstract

Disclosed is a hot-dip galvanized steel sheet, in which a steel sheet of the hot-dip galvanized steel sheet before galvanization contains, on the percent by mass basis, 0.06% to 0.15% carbon (C); 1% to 3% manganese (Mn); 0.01% to 0.05% phosphorus (P); 0.03% to 1% chromium (Cr); 0.03% to 1% molybdenum (Mo); and 0.02% to 0.15% aluminum (Al). The steel sheet before galvanization has a silicon (Si) content of 0.2% or less (inclusive of 0%) and a sulfur (S) content of 0.03% or less (inclusive of 0%) and has a K value of −2.0 or more, in which the K value is calculated according to following Equation (1): K value=3×[Mo]−5×[Cr]  (1) wherein “[Element]” represents the content (percent by mass) of the element.

1 . A hot-dip galvanized steel sheet, wherein a steel sheet of the hot-dip galvanized steel sheet before galvanization comprises, on the percent by mass basis:
 0.06% to 0.15% carbon (C);   1% to 3% manganese (Mn);   0.01% to 0.05% phosphorus (P);   0.03% to 1% chromium (Cr);   0.03% to 1% molybdenum (Mo); and   0.02% to 0.15% aluminum (Al), wherein the steel sheet before galvanization has a silicon (Si) content of 0.2% or less (inclusive of 0%) and a sulfur (S) content of 0.03% or less (inclusive of 0%), and   
       wherein the steel sheet before galvanization has a K value of −2.0 or more, the K value being calculated according to following Equation (1):
     K  value=3×[Mo]−5×[Cr]  (1) 
 
       wherein “[Element]” represents the content (percent by mass) of the element. 
     
     
         2 . The hot-dip galvanized steel sheet according to  claim 1 , wherein the steel sheet of the hot-dip galvanized steel sheet before galvanization further comprises, on the percent by mass basis, at least one selected from the group consisting of:
 0.15% or less (exclusive of 0%) titanium (Ti);   0.15% or less (exclusive of 0%) niobium (Nb); and   0.15% or less (exclusive of 0%) vanadium (V).   
     
     
         3 . The hot-dip galvanized steel sheet according to  claim 1 , wherein the steel sheet of the hot-dip galvanized steel sheet before galvanization further comprises, on the percent by mass basis:
 0.01% (exclusive of 0%) boron (B).   
     
     
         4 . The hot-dip galvanized steel sheet according to  claim 1 , wherein the steel sheet of the hot-dip galvanized steel sheet before galvanization further comprises, on the percent by mass basis:
 0.01% or less (exclusive of 0%) calcium (Ca).   
     
     
         5 . A galvannealed steel sheet, wherein a steel sheet of the galvannealed steel sheet before galvanization comprises, on the percent by mass basis:
 0.06% to 0.15% carbon (C);   1% to 3% manganese (Mn);   0.01% to 0.05% phosphorus (P);   0.03% to 1% chromium (Cr);   0.03% to 1% molybdenum (Mo); and   0.02% to 0.15% aluminum (Al), wherein the steel sheet before galvanization has a silicon (Si) content of 0.2% or less (inclusive of 0%) and a sulfur (S) content of 0.03% or less (inclusive of 0%),   
       wherein the steel sheet before galvanization has a K value of −2.0 or more, the K value being calculated according to following Equation (1):
     K  value=3×[Mo]−5×[Cr]  (1) 
 
       and wherein the steel sheet before galvanization has an F value of 0.7 to 3.0, the F value being calculated according to following Equation (2):
     F  value=[Mn]/(20×[P]+3×[Cr]+3×[Mo])  (2) 
 
       wherein “[Element]” in Equations (1) and (2) represents the content (percent by mass) of the element. 
     
     
         6 . An automotive member comprising the hot-dip galvanized steel sheet of  claim 1  as a material. 
     
     
         7 . An automotive member comprising the galvannealing of  claim 5  as a material.