Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2000-11-09
2002-11-12
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S621000, C428S667000, C428S586000, C428S425800, C428S035900, C428S036910, C525S107000, C525S131000
Reexamination Certificate
active
06479152
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to stainless steel materials having excellent formability. Particularly, the invention relates to stainless steel sheets and pipes which are used for the production of household appliance products, building materials, motor vehicle parts and the like, and can be utilized, without removing a lubricating film thereon, after pressing or pipe expanding.
2. Description of the Related Art
Various types of materials are used for household appliance products, building materials, motor vehicle parts and the like and, among them, there are stainless steel materials such as stainless steel sheets or pipes. When stainless steel materials are used, they are frequently subjected to a forming process such as stamping or pipe expanding. In such a forming process, a stainless steel material is conventionally coated with a lubricant, typically a stamping oil and, after a forming process, the lubricant is removed in a degreasing process. On the other hand, as an increasingly growing tendency in late years, omitting stamping oil application and degreasing processes is demanded in terms of increased productivity, reduced production cost, and improved working environment.
For example, Japanese Patent No. 2719571 describes a water-base lubricant paint composition which is applied to a cold-rolled steel sheet or zinc-plated steel sheet, to enable the steel sheet to be formed without a stamping oil. The paint composition contains a urethane resin of an ether-ester type, a water-soluble or water-dispersible epoxy resin, a polyolefin wax, and silica powder.
In the field of plated steel sheets, lubricative plated steel sheets, which do not need application and removal of a stamping oil, have been already put to practical use. For example, Japanese Patent No. 2743237 describes a lubricative plated sheet which does not need application and removal of a stamping oil, the plated sheet having a chemical conversion film of chromate or phosphate provided on the surface of the plated sheet and a lubricative film obtained by baking a water-base lubricant coating containing a urethane resin of an ether-ester type, an epoxy resin, a polyolefin wax, and silica applied on the conversion film.
On the other hand, also in the field of stainless steel materials, there has been proposed a stainless steel sheet having a chromate layer formed on the surface of the stainless steel sheet and a lubricative coating layer, which is provided on the chromate layer, of an organic resin into which a wax or fluorine-containing resin as a lubricant component is incorporated (JP-A-6-264255, JP-A-8-41652, etc.). There has also been proposed a stainless steel pipe having a film containing an organic resin and an organic lubricant such as polyolefin wax or fluorine-containing resin particle provided on the surface of the pipe (JP-A-10-137864).
Also, in the field of stainless steel materials, a stainless steel sheet or pipe which can be efficiently formed without application and removal of a stamping oil after and before the forming process, has been proposed.
The inventors of this application have recognized, in the course of consideration of applying a lubricative film such as those described in the abovementioned Japanese Patent Nos. 2719571 and 2743237 to stainless steel materials, that there are problems with stainless steel materials, which have properties of being essentially hard and having a small elongation (low formability) compared to plated steel sheets and the like.
Generally speaking, it is thought that a dominant requirement in the forming process for a lubricative steel sheet or pipe is to prevent the metal substrate being exposed during the forming. For example, in the case of steel sheet, when a metal substrate is exposed during the forming, a metallic mold and a metal substrate of steel sheet come in contact with each other to cause a phenomena of “galling”, which is also called “pickup” or “fouling”, resulting in reduced lubricating effect and prevention of satisfactory forming. In the case where a steel pipe is expanded, as the expanding process progresses, portions of wall of the pipe on the expanding members of an expanding tool continue to be in contact with the expanding members, whereas portions of wall of the pipe between the expanding members are stretched in the circumferential direction by the portions on the expanding members, and tend to result in a smaller thickness compared to a thickness of the portions on the expanding members. Although this tendency can be reduced by enhancing lubricity of the inner surface of the steel pipe, which is in contact with the expanding members, galling can occur in such a case, depending on performance of a lubricant film on the surface of the steel pipe. For measures against these problems, the following have been contemplated: (1) lowering the coefficient of friction of the surface of the lubricative steel sheet or pipe, (2) controlling the hardness of the lubricant film, (3) improving the adhesion of the lubricant film to the metal substrate, and (4) providing the lubricate film with a thickness depending on a surface roughness of the metal substrate so that the metal substrate is not partially exposed at the surface of the lubricant film after the formation of the lubricant film. These measures are particularly important for stainless steel materials having lower formability compared to plated steel sheets and the like. Nevertheless, among these, the measures of (1), (3), and (4) have been already studied, whereas the hardness of (4) has not been studied to date. In other words, stainless steel materials having a lubricant film provided which have been proposed to date are not necessarily optimized in terms of a hardness of film.
SUMMARY OF THE INVENTION
The inventors have reached the present invention of stainless steel sheets and pipes, as really useful lubricative stainless steel materials, by optimizing the lubricant film, particularly in terms of its hardness, in the course of studying the application of lubricant films, as described in Japanese Patent Nos. 2719571 and 2743237, to stainless steel materials.
The lubricative stainless steel sheet of the invention is characterized by having a chromate film on at least one of the surfaces of a stainless steel sheet substrate, the chromate film having an amount of adhered Cr of 5 to 100 mg/m
2
, and, on the chromate film, a lubricant film obtained by applying, to the chromate film, a water-base coating containing (a) a urethane resin of an ether-ester type having a skeleton of bisphenol type, a skeleton of ester, and a carboxyl group, (b) an epoxy resin, and (c) a polyolefin wax, and baking the applied coating, the sum of the amounts of the urethane resin of (a) and the epoxy resin of (b) being 70 to 95% by weight of the total solids of the coating, the amount of the polyolefin wax of (c) being 5 to 30% by weight of the total solids of the coating, and the lubricant film having a thickness of 0.5 to 5 micrometers and a Vickers hardness of at least 15.
The lubricative stainless steel pipe of the invention is characterized by having a chromate film on at least one of the outer and inner surfaces of a stainless steel pipe substrate, the chromate film having an amount of adhered Cr of 5 to 100 mg/m
2
, and, on the chromate film, a lubricant film obtained by applying, to the chromate film, a water-base coating containing (a) a urethane resin of an ether-ester type having a skeleton of bisphenol type, a skeleton of ester, and a carboxyl group, (b) an epoxy resin, and (c) a polyolefin wax, and baking the applied coating, the sum of the amounts of the urethane resin of (a) and the epoxy resin of (b) being 70 to 95% by weight of the total solids of the coating, the amount of the polyolefin wax of (c) being 5 to 30% by weight of the total solids of the coating, and the lubricant film having a thickness of 0.5 to 5 micrometers and a Vickers Hardness of at least 15.
The lubricative stainless steel pipe of the invention can be produced by a method which com
Anai Isao
Hiroshige Itsuro
Kato Katsuhiko
Miyauchi Yujiro
Tanoue Toshio
Bissett Melanie
Nippon Steel Corporation
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