Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1999-03-17
2001-06-19
Lorin, Francis J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S634000
Reexamination Certificate
active
06248456
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a surface-treated steel sheet having a low contact resistance excellent in conductivity, unchanged or stable conductivity even after aging, corrosion resistance, and adhesion, and it also relates to a connection terminal member using said steel sheet.
BACKGROUND OF THE INVENTION
Conventionally, a carbon—carbon combination has been used as a chief material for electric connection terminal members from the viewpoint of conductivity and corrosion resistance. The carbon—carbon combination is, however, expensive and involves a problem in formability, so it has been investigated to provide a combination of carbon and metal sheet. But, the carbon-metal sheet combination has a problem that an oxide or hydroxide is formed on the surface of a metal sheet combined with carbon and therefore the carbon-metal sheet combination has its conductivity remarkably decreased as i4 ages.
In order to solve the problem mentioned above, there has been an increasing demand for a material for making an electric connection terminal cheaper than carbon and as well conductive as carbon.
An electric connection terminal member made of metal-only material is cheap but poor in corrosion resistance because oxide or hydroxide is formed on the surface of such metal-made member as time passes, resulting in deterioration of conductivity. Therefore, the metal-only material is inadequate to use for the connection terminal member.
In order to solve the problem as mentioned above, it is a technical object to provide a surface-treated steel sheet having a low contact resistance excellent in conductivity, unchanged or stable conductivity even after aging, corrosion resistance, and adhesion, and also to provide a connection terminal member using this steel sheet.
DISCLOSURE OF THE INVENTION
A surface-treated metal sheet of the present invention is characterized in that a coating film which contains carbon black or graphite, carboxy methylcellulose, and an aqueous organic resin is formed on a steel sheet and the steel sheet thus coated with the said coating film has a low contact resistance.
A surface-treated metal sheet of the present invention is also characterized in that a coating film which contains carbon black or graphite, carboxy methylcellulose, an aqueous organic resin, and a cross-linking agent of the aqueous organic resin is formed on a steel sheet and the steel sheet thus coated with the said coating film has a low contact resistance.
In such surface-treated steel sheets, the aqueous organic resin may preferably be acrylic resin, polyester resin, urethane resin of phenolic resin.
The steel sheet may preferably be plated with Zn, Ni, Sn, Co or any alloy of said metals. Further, the steel sheet may preferably be provided with a multilayer plating composed of a lower layer of Ni-plating and an upper layer of Zn-, Sn- or Co-plating and also the thus plated steel sheet may preferably be subjected to diffusion treatment.
Furthermore, the connection terminal member according to claim
7
is characterized in that a contacting portion of the electric connection terminal member with carbon is made of the surface-treated steel sheet according to the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
A steel sheet is provided with a mono layer plating such as Zn, Ni, Sn or Co, or an alloy plating with any alloy of said metals or a multilayer plating with any of said metals. Or, another steel sheet may be primarily plated Keith any type of plating among those mentioned above and then diffusion-treated. A coating film is formed on the thus treated steel sheet by using a water soluble after-treatment solution containing carbon or graphite, carboxy methylcellulose, and an aqueous organic resin composed of acrylic resin, polyester resin, urethane resin or phenolic resin. The thus formed coating film serves to isolate the surface of the plated steel sheet from oxygen in the atmosphere which would induce oxidation of the steel sheet. Therefore, the coating film prohibits the formation of an oxide film which would cause decrease in conductivity of the steel sheet, thus enabling to inhibit the deterioration of conductivity and the corrosion resistance of the steel sheet. Further, even though covered with a coating film, the steel sheet is almost free from deterioration of conductivity because the coating film contains carbon black or graphite excellent in conductivity.
The present invention is explained more in detail below with reference to preferred embodiments.
As the plated steel sheet, a cold rolled steel sheet which is provided with a mono layer plating of Zn, Ni, Sn or Co, or an alloy plating or a multilayer plating with any of said metals, or provided with any plating of said metals and thereafter diffusion-treated may be used. In the case of multilayer plating, it is preferred that the first plating is performed using Ni, Sn or Co in view of homogenization of the following plating. Particularly, a Sn—Ni alloy is excellent in acid resistance, so it is preferred that a steel sheet plated with Sn—Ni alloy composition is applied to a connection terminal for use in things liable to induce an acidic atmosphere such as lead storage battery or fuel cell. Suitable amount of the plating may be in the range of 2 to 50 g/m
2
. In the case of plating less than 2 g/m
2
, the resultant plated steel sheet is poor in corrosion resistance. More than 50 g/m
2
of plating leads to a increase in costs. The diffusion treatment may preferably be carried out in an atmosphere of oxygen-free nitrogen gas, hydrogen gas, mixed gas of nitrogen and hydrogen, or argon gas at a heating temperature ranging from 232° C. to 600° C. Heating time for the diffusion treatment may preferably be not so long as to diffuse Fe into the surface of the plated steel sheet in view of corrosion resistance.
The steel sheet that has been plated or first plated and then diffusion-treated is treated by using an aqueous water solution containing 10 to 3500 g/l of carbon black or graphite, 0.1 to 40 g/l of carboxy methylcellulose, and 1 to 200 g/l of aqueous organic resin as solid which composed of acrylic resin, polyester resin, urethane resin or phenolic resin.
The carbon black may be channel type black, furnace black, acetylene black or kettchen black. The graphite may be artificial graphite, vein graphite, flake graphite or amorphous graphite. In the case of graphite content less than 10 g/l by concentration, the resultant product is poor in conductivity. On the other hand, in the case of graphite concentration exceeding 350 g/l, dispersibility of such graphite becomes remarkably poor.
The aqueous organic resin may be a water-soluble type resin, water-dispersible type resin or emulsion type resin.
The aqueous acrylic resin includes a polymer and copolymer such as acrylic acid and ester thereof, acrylamide, acrylonitrile, and methacrylic acid and ester thereof. Functional groups for the esters may be carboxyl group, amino group, methyl group, ethyl group, butyl group, amyl group, ethylhexyl group or octyl group. Aqueous ethylene-acrylic resin may also be included in the above mentioned functional groups.
The aqueous polyester resin may include polyoxyethylene nonylphenol-ether, polyoxyethylene nonylphenol-ether sodium sulfate, lauryl sodium sulfate, and water-solubilized rosin soap. It also may include resins having a hydrophilic group such as carboxyl group, sulfone group, sulfate group, phosphate group, amino group, ammonia salt, hydroxide group, ether group or amide group, that is, alkyd resin, maleic acid resin, and unsaturated polyester.
The aqueous urethane resin includes resins having end groups of water-soluble COOH or amine.
The aqueous phenolic resin includes a resol type resin which is obtained by reacting phenol with formaldehyde in the presence of alkali catalyst.
If the aqueous organic resin concentration which composed of acrylic resin, polyester resin, urethane resin or phenolic resin is less than 1 g/l by concentration as solid contents, resultant product is poor in the corrosion resistance.
Ohmura Hideo
Ohmura Hitoshi
Tomomori Tatsuo
Yamane Keiji
Browdy & Neimark
Lorin Francis J.
Toyo Kohan Co. Ltd.
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