To produce a hot-dip Zn-Al base alloy plated steel sheet having 5 mass% Al level which can be used in the high temp. of 350°C.
This high heat resistant hot-dip Zn-Al base alloy plated steel sheet is the one, in which the alloy plating layer constituted with 3.0-7.0 mass% Al, 0.05-0.5 mass% Si, 0.01-0.5 mass% Mg and the balance Zn is formed on the steel sheet surface and Fe-Al-Si base alloy layer, and concentrating Si is formed between this alloy plating layer and the base steel sheet. Particularly, when the heating is executed under the atmosphere at 350°C for 100 hr, the alloying of the plating layer is not progressed. When the hot-dip metal plating is executed, the bath temp. for the hot dipping Zn-Al base alloy plating bath is held to a temp. of 'the m.p. of the Zn-Al base alloy+40°C' or higher, and further, the plate temp. of an original plating plate just before dipping into the plating bath is controlled to a temp. of the bath temp. or higher.
HATTORI YASUNORI
KIKKO TOSHIHARU
