Stock material or miscellaneous articles – Composite – Of metal
Patent
1998-11-30
2000-07-11
Jones, Deborah
Stock material or miscellaneous articles
Composite
Of metal
428469, 4284721, B32B 900
Patent
active
060870192
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a plated steel sheet used as a can producing material, a building material, steel sheets for air conditioner and water heater, steel sheets for automobiles and the like which require a high corrosion resistance.
BACKGROUND ART
In general, the production of the plated steel sheet is carried out by subjecting a raw material for the plated steel sheet to hot rolling, removing an iron oxide layer covering the surface of the steel sheet in a pickling equipment, subjecting to cold rolling, if necessary, and then subjecting to plating in a continuous hot dipping apparatus, an electric plating apparatus or the like. The reason why the removal of the iron oxide layer is essential in this method is due to the fact that the iron oxide layer obstructs the plating and results in a start point of peeling a plated layer to degrade the adhesion property of the plated layer.
On the other hand, JP-A=6-279967 proposes that reduction treatment is carried out in a reducing gas atmosphere without removing the iron oxide layer and thereafter hot dip galvanizing is conducted in the production of hot dip galvanized hot rolled steel sheets. Concretely, the reduction treatment is carried out in a H.sub.2 atmosphere having a high concentration of 75%.
According to the above method, the hot dip galvanizing not forming non-plated portion is realized by sufficiently conducting the reduction in a heating furnace of a continuous hot dipping apparatus without removing the iron oxide layer. However, since the H.sub.2 concentration as a reducing atmosphere is high, the pickling cost is reduced, while the cost required for the heating furnace of the continuous hot dipping apparatus largely increases.
If it is intended to plate a cold rolled raw material not requiring the reduction of the iron oxide layer in the same continuous hot dipping apparatus as mentioned above, it is necessary to change the H.sub.2 concentration to about not more than 10% because if the iron oxide layer is not existent, hydrogen is absorbed in the inside of the steel sheet during the heating and then discharged from the steel when the steel sheet becomes low temperature after the plating and hence it is vaporized at an interface to the plated layer to cause local peeling of the plated layer. Therefore, the change of the H.sub.2 concentration brings about the lowering of the productivity and the increase of the cost.
DISCLOSURE OF THE INVENTION
It is a main object of the invention to provide a novel plated steel sheet solving the above problems by positively retaining an iron oxide layer in a steel sheet plated without removing the iron oxide layer and optimizing a structure of the iron oxide layer.
It is another object of the invention to provide means for providing a plated layer having an excellent adhesion property to an alloy steel being weak in the hot dipping such as high-strength steel sheet, stainless steel sheet, electromagnetic steel sheet or the like through the hot dipping.
That is, in the alloy steel sheet such as high-strength steel sheet, stainless steel sheet or the like, the alloying components such as Si, Mn and Cr are selectively oxidized at an annealing step before the hot dipping treatment to concentrate on the surface of the steel sheet as an oxide and hence the formation of non-plated portion and the lowering of the adhesion property of the plated layer are inevitably caused. In order to realize the hot dipping in these steel sheets, therefore, there are proposed a method wherein an electric plating is carried out prior to the hot dipping in the high-strength steel sheet (see JP-A-61-147865 and JP-A-2-194156) and a method wherein oxidation is carried out and reduction is carried out and then plating is conducted in a continuous hot dipping line (see JP-A-55-122865 and JP-A-6-41708). Similarly, in case of the stainless steel sheet, there are proposed a method wherein an electric plating is carried out prior to the hot dipping (see JP-A-63-47356 and JP-A-63-235485) and a method wherein the hot dippin
Isobe Makoto
Kato Chiaki
Kohno Masaaki
Seto Kazuhiro
Jones Deborah
Kawasaki Steel Corporation
Resnick Jason D
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