To provide a hot dip galvannealed steel sheet having excellent appearance quality by suppressing plating alloying unevenness caused by ruggedness on the surface of the steel sheet, unevenness of the crystal grain sizes on the surface of the steel sheet and unevenness in elements on the surface of the steel sheet.
When a steel having a composition comprising, by mass, 0.001 to 0.003% C, 0.005 to 0.1% Si, 0.01 to 0.4% Mn, 0.005 to 0.03% P and 0.005 to 0.02% S, and the balance Fe with inevitable impurities is hot-rolled, the pressure of descaling discharge water in primary descaling before the start of rough rolling is controlled to 980 to 3,000 KPa, also, a slab surface temperature T when starting the descaling is made to satisfy inequality (A); 1,000T3,330(S%)+1,200, further, water for descaling is jetted to the surface of the steel sheet at a water temperature of 20C, and hot rolling primary descaling is performed. Thereafter, the steel sheet is subjected to a rough rolling mill and finish rolling.
IGARASHI YASUO
SATO YOSHIHIRO
| JPH06262245A | 1994-09-20 | |||
| JP2002241897A | 2002-08-28 | |||
| JP2000054029A | 2000-02-22 | |||
| JP2000045027A | 2000-02-15 | |||
| JP2001172744A | 2001-06-26 | |||
| JP2006247714A | 2006-09-21 |
Fumio Yamamoto