Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Patent
1980-11-26
1982-12-14
Sheehan, John P.
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
75128A, 75128C, 75128D, 75128G, 75128W, 75128Z, 420585, C22C 3840
Patent
active
043636608
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an iron-base alloy having high resistance to molten zinc attack, and more particularly, to such an iron-base alloy that can be cast, worked or build-up welded as a structural member to be directly exposed to molten zinc, for example, a structural member of a continuous molten zinc plating apparatus.
The invention further relates to a structural member of a continuous molten zinc plating apparatus produced from such an iron-base alloy.
BACKGROUND ART
As schematically represented in FIG. 1, a continuous molten zinc plating apparatus comprises a plating bath (pot) 1, support roll 2, sink roll (pot roll) 3, sleeve 4, hanger (arm) 5 and a snout 6. In the apparatus shown in FIG. 1, a steel plate 7 supplied to the bath through the snout 6 is directed as shown by the arrow to the sink roll 3 supported by the hanger 5, and after being plated with a given amount of zinc, it is recovered from the bath 1 through the support roll 2. In the figure, the rolls rotate in the direction indicated by the arrow.
Conventionally, the structural members of the continuous molten zinc plating apparatus are produced by casting or plastic working of low-carbon steel or stainless steel (e.g. JIS SUS No. 304,309) or cast stainless steel (e.g. JIS HH). For example, cast stainless steel from which the support roll, sink roll, sleeve and bearing metal are produced is exposed to mechanical wear of fluid zinc and its resistance to molten zinc attack (hereunder referred to as erosion resistance) is so low that it must be replaced every one or two weeks. Therefore, researchers are making experiments on the build-up welding of Stellite alloy or plasma-spray coating of tungsten carbide (WC) on the surface of stainless steel.
Low-carbon steel of which the plating bath or snout is made has poor erosion resistance in molten zinc even when its degree of fluidity is relatively low. Therefore, the wall of the plating bath or snout is made of a thick plate or lined with a thin sheet of Hayne's alloy (e.g. HA-No. 25) generally considered to have relatively high erosion resistance in stationary zinc.
However, even the lined structural member does not present satisfactory erosion resistance when molten zinc is in a fluid state (e.g. the inside of the snout, or where the member is contacted by the topmost level of bath or in the vicinity thereof).
A support roll having good erosion resistance can be made of a structural member build-up welded with Stellite alloy since Stellite alloy has good mechnical wear resistance and exhibits relatively good erosion resistance in fluid zinc. On the other hand, Stellite alloy is so hard that the support roll may cause a steel plate being galvanized to develop a flaw and the support roll may develop a crack on the surface when it is being reground. Therefore, the structural member made by build-up welding with Stellite alloy cannot have a long useful life. Besides, as is typically found with Stellite No. 6 whose standard composition is Co: 61%, Cr: 28%, W: 5%, Ni: 1.5%, and others: 4.5% (by weight), Stellite alloys have a high content of expensive Co and this presents a high-cost problem.
DISCLOSURE OF INVENTION
Therefore, one object of this invention is to provide an iron-base alloy which is cheap, has good erosion resistance against fluid molten zinc, adequately withstands mechanical wear, has a hardness not great enough to damage a steel plate, and which can be used as a casting material, working material or a build-up welding material.
Another object is to provide a structural member made of such iron-base alloy which can be continuously used for a long period of time as the constituent material of a continuous molten zinc plating apparatus.
A further object of this invention is to provide a method of using such iron-base alloy to prevent the erosion of fluid molten zinc.
To achieve these objects, we have made various studies and experiments and have accomplished this invention.
According to our finding, Nb (and/or Ta), Mo (and/or W), Co and C are elements that reduce
REFERENCES:
patent: 2801916 (1957-08-01), Harris et al.
patent: 3282687 (1966-11-01), Cape
patent: 3488186 (1970-01-01), Decker et al.
patent: 3834901 (1974-09-01), Kamiya et al.
patent: 4272289 (1981-06-01), Herchenroeder et al.
Sakonooka Akihiko
Wakita Saburo
Mitsubishi Kinzoku Kabushiki Kaisha
Sheehan John P.
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