| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To manufacture a hot-dip galvanized steel sheet and a hot-dip galvannealed steel sheet which use a high-strength steel sheet containing Si as its base metal and has no unplated part. <P>SOLUTION: A base steel sheet includes, by mass%, 0.05-0.30% C, 1.5-3.0% Si, 0.5-3.0% Mn, 0.01-3.0% Al, 0.001-0.01% S and 0.001-0.1% P. The manufacturing method includes: heating the base steel sheet in an atmosphere containing 0.01-20 vol.% O<SB>2</SB>and 1-50 vol.% H<SB>2</SB>O so as to keep a temperature in the range of 873-1,123 K; subsequently heating the steel sheet in an atmosphere containing 1-50 vol.% H<SB>2</SB>, and in such conditions that partial pressure of water vapor PH<SB>2</SB>O, partial pressure of carbon dioxide PCO<SB>2</SB>, the highest arrival temperature of the steel sheet T(K) and a Si content of the steel sheet [Si%] satisfy the relations of 0<PH<SB>2</SB>O/PCO<SB>2</SB><323.6-15.2logT<SP>2</SP>-71.5[Si%], 0<log(PH<SB>2</SB>O+15PCO<SB>2</SB>)<2.3 and 1,023≤T≤1,173; and then subjecting the steel sheet to hot-dip galvanizing treatment. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
