Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Coating moving substrate
Reexamination Certificate
1999-06-30
2001-05-22
Gorgos, Kathryn (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Coating moving substrate
C205S149000, C205S170000, C205S188000, C205S219000, C205S318000, C205S320000, C204S206000, C204S208000, C204S209000
Reexamination Certificate
active
06235180
ABSTRACT:
FIELD OF THE INVENTION
Hot rolled or heat treated steel rods and steel wires (hereafter abbreviated as steel wires) are often provided for a cold drawing process. Before cold drawing, usually a phosphate film is formed on a surface thereof. This Invention relates to a method and an apparatus for promptly forming phosphate film having an excellent performance.
BACKGROUND ART
In the cold drawing operation, the phosphate film is further covered by a lubricant such as metallic soap, and the phosphate film may carry the metallic soap forming a lubricative layer. In the cold drawing, a diameter of the steel wires become decreased by passing through several dies, and it is preferred that the phosphate film may keep its excellent performance until the steel wires passes through the last die.
The phosphate film is often formed by dipping the steel wires into a bath where a solution for making the phosphate film are contained and no electrolytic deviced are provided. In this case, a productivity of the processing bath is able to be enhanced by increasing the travelling speed of the steel wires if a prompt formation of the phosphate film become possible.
Accordingly, a method being possible to form the phosphate film promptly is preferable. In order to form the phosphate film promptly, a liquid containing chemicals of forming phosphate film in high concentration has been used. However, in this case, a great deal of sludge is produced in the liquid, and it must be frequently removed in order to obtain a phosphate film of excellent quality.
In the process of forming the phosphate film on the steel wires, the steel wires must be descaled previously by dipping it into the hydrochloric or sulfuric acid solution. And steel wires being removed its oxide film by this descalling process are dipped into the forming solution of phosphate film.
The present inventors had found a electrolytic process where phosphate film can be formed promptly by using the steel wires as electrolytic cathode in a solution of not containing a complexing agent, and filed it in JP4-36498A.
According to the electrolytic process of JP4-35498A, a productivity of the phosphate film formation had been much enhanced, however, it does not improved the quality of the phosphate film, and the quality of the phosphate film by this process had almost been in the same level as those produced by conventional process.
JP6-322592A disclosed a formation of phosphate film on the steel wires by electrolytic process. However, this is a process of using the steel wires as anode. Also, this is a process of using the pulse electrolytic current in the electrolytic operation.
DISCLOSURE OF THE INVENTION
As explained above, a productivity of the phosphate film formation had been much enhanced by the electrolytic process of JP4-36498A, however, it does not improve the quality of the phosphate film. The presen inventors further studies JP4-36498A process, and suceeded to improve the quality of the phosphate film.
According to a new findings of the inventors, the quality of the phosphate film has a close relation with the descaling process of steel wires. As explained before, in the process of forming the phosphate film on the steel wires, the steel wires are descaled previously by dipping it into the hydrochloric or sulfuric acid solution. In this descaling process, oxide film may be removed from the steel wires. However, it leaves smut on the surface of the steel wires.
The smut formed may usually be removed by rinsing the steel wires in a water. However, small amount of smut remained on the surface of the steel wires may form the phosphate film of insufficient quality. The smut may decrease a adhesive strength of the phosphate film to the surface of the steel wires, resulting an insufficient lubricative properties in cold drawing of the steel wires and an insufficient surface properties of the final product of the steel wires.
The purpose of the invention is, therefore, to provide a new method and an new apparatus, suitable for more promptly forming the phosphate film having more excellent quality than the conventional process on the steel wires of low carbon grades, a high-carbon grades and a low alloy containing grades without generating any smut and any sludge.
The present invention is (1): a method for forming phosphate film on steel wires comprising a descaling process and a phosphate film forming process characterized in that the descaling process is a an electrolytic pickling of steel wires using the steel wires as cathode and using as acid solution other than phosphoric acid as an electrolyte, and the phosphate film forming process is an electrolytic process using the steel wires as cathode and using a forming solution of phosphate film as an electrolyte.
Also, the present invention is (2): a method used for forming phosphate film on steel wires comprising a descaling process, an intermediate process and a phosphate film forming process characterized in that the descaling process is a electrolytic pickling of the steel wires using the steel wires as cathode and using acid other than a phosphoric acid as an electrolyte, and the intermediate process is a process of contacting the steel wires with a intermediate liquid containing colloidal titanium and alkali metal phosphate, and the phosphate film forming process is an electrolytic process using the steel wires as cathode and using forming solution of phosphate film as an electrolyte.
Also, the present invention is (3): a method used for forming phosphate film in steel wires according to (1) or (2) above, characterized in that the steel wires for the descaling process are the steel wires being mechanically descaled as a pretreatment therefor.
Also the present invention is (4): a method used for forming phosphate film on steel wires according to any of (1)~(3) above, characterized in that an electrolyte in the descaling process is selected from sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, hydrosilicofluoric acid and zircon hydrofluoric acid, and a temperature of the electrolyte is 90° C. or lower in the descaling process, and a current density of the steel wires is 1 A/dm
2
~100 A/dm
2
in D.C. and an electrolytic time is 1~60 seconds in the descaling process.
Also, the present invention is (5): a method used for forming phosphate film on steel wires according to any of (1)~(4) above, characterized in that an electrolyte in the phosphate film forming process contains 2~60 g/liter of zinc ion, 2~80 g/liter of phosphoric acid ion and 3~100 g/liter of nitric acid ion, and a molar ratio of zinc ion to phosphoric acid ion is 0.9~1.5 and a molar ratio of nitric acid ion to phosphoric acid ion is 0.7~2.5, temperature of the electrolyte is 90° C. or lower, and the current density of the steel wires is 1 A/dm
2
~100 A/dm
2
in D.C. and an electrolytic time is 1~13 seconds in the phosphate film forming process.
Also, the present invention is (6): an apparatus used for forming phosphate film on steel wires comprising a descaling bath and a phosphate film forming bath characterized in that the descaling bath is an electrolytic pickling bath of steel wires using steel wires as cathode and using acid other than phosphoric acid as an electrolyte, and the phosphate film forming bath is an electrolytic film forming bath using the steel wires as cathode and using a forming solution of phosphate film as an electrolyte.
Also, the present invention is (7): an apparatus used for forming phosphate film on steel wires comprising a descaling bath, an intermediate bath and a phosphate film forming bath characterized in that the descaling bath is an electrolytic pickling bath of steel wires using steel wires as cathode and using acid other than phosphoric acid as an electrolyte, and the intermediate bath is a bath of contacting the steel wires with a intermediate liquid containing colloidal titanium and alkali metal phosphate, and the phosphate film forming bath is an electrolytic film forming bath using steel wires as cathode and using a forming solution of phosphate film as an electrolyte.
Also
Katsumata Tomoaki
Kobayashi Naoyuki
Moriyama Atsushi
Takagi Shigemasa
Gorgos Kathryn
Keehan Christopher M.
Nihon Parkerizing Co. Ltd.
Pillsbury & Winthrop LLP
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