To provide a method for producing a high strength hot dip Zn-Al-Mg alloy plated steel sheet in which pearlitic transformation in hot dip plating is suppressed, and which has a low yield ratio and excellent strength and corrosion resistance.
A hot rolled steel strip produced by subjecting a slab comprising 0.05 to 0.20% C, ≤1.5% Si, 1.0 to 2.5% Mn, ≤0.05% P and ≤0.01% S to hot rolling or a cold rolled steel strip produced by subjecting the same to pickling and cold rolling successively to the hot rolling is used as a plating original sheet. The plating original sheet is heated to the temperature range of Ac1 to Ac3 in a reduction annealing furnace, and thereafter cooled to 650°C at a cooling rate of 3 to 10°C/s, further cooled to 440°C at a cooling rate of ≥10°C/s, and then introduced into a hot dip Zn-Al-Mg alloy plating bath heated to a bath temperature of ≤440°C, and taken up so as to temper into a composite structure of ferrite with a mean crystal grain size of ≤15 μm and martensite with a volume ratio of 5 to 45%. Thus, the high strength hot dip Zn-Al-Mg alloy plated steel sheet having a low yield ratio can be produced.
YAMAMOTO TOMOO
MATSUMOTO TAKASHI
| JP2004323958A | 2004-11-18 | |||
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| JP2002302734A | 2002-10-18 | |||
| JP2001254144A | 2001-09-18 | |||
| JPH05331537A | 1993-12-14 | |||
| JPS55122821A | 1980-09-20 | |||
| JP2001140022A | 2001-05-22 |
Okada Manri