Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Metal or metal alloy
Reexamination Certificate
2000-08-21
2003-06-24
Kastler, Scott (Department: 1742)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Metal or metal alloy
C266S114000, C148S574000
Reexamination Certificate
active
06582586
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process and an apparatus for removing scales and preventing scale formation on hot rolled or heat-treated metallic materials or hot metallic materials, such as steel, iron alloys, copper, copper alloys, zinc, zinc alloys, aluminium, aluminium alloys on the like materials in such circumstances as to form oxide scales as in a hot rolling step and/or a cold rolling step or a heat-treating step following the continuous casting step, or a hot metallic material cooling step following these steps or in a pickling step as well, whereby suppression and removal of scales can be carried out efficiently at a low cost for a short time.
BACKGROUND ART
Prior Art
Metallic materials, particularly steel materials, react with atmospheric oxygen in a heating step and a rolling step or a hot steel material cooling step to form iron oxide called scales on the surfaces. The scales formed on the surfaces of steel materials are partly peeled off during the press working, etc. and pressed into products, sometimes thereby degrading the product quality, for example, flaw formation, etc. On the other hand, to prevent the quality degradation, a pickling step to wash off the scales with an aqueous hydrochloric acid solution, etc. has been additionally required.
Thus, processes for controlling oxidation on the steel material surfaces, thereby preventing scale formation have been so far proposed.
For example, a process for suppressing scale formation by applying an oxidation-suppressing agent to steel material surfaces to form a film is popular, but water, when contained in the oxidation-suppressing agent, boils at a temperature of 500° C. or higher on the steel material surfaces and a water vapor layer is formed on the steel material surfaces, causing a failure to form an oxidation-suppressing agent film on the steel material surfaces or a failure of even application of the oxidation-suppresing agent. That is, there is such a disadvantage or a failure of full control of scale formation.
To overcome such a disadvantage, for example, Japanese Patent Koaki (Laid-Open) No. 4-236714 publication proposes a process for preventing scale formation on the steel material surfaces by applying to or spraying onto hot steel materials a polymer solution comprising copolymers containing ethylene oxide and propylene oxide as monomer components, which can be separated into liquid polymers and water when the solution reaches a temperature of 100° C. or higher and can form an aqueous polymer solution at a temperature below 100° C. upon mixing with water, but the pickling treatment still needs a long time.
Problem to be solved by the Invention
The process for suppressing oxidation of steel materials disclosed in said Japanese Patent Kokai (Laid-Open) No. 4-236714 publication cannot remove such scales as formed before the application of the polymer solution. Even by applying the such a polymer solution thereto, scale formation is inevitable, though in a very small amount, ultimately requiring a pickling step to wash off such scales.
An object of the present invention is to overcome the problems of prior art and provide a process and an apparatus for removing scales and preventing scale formation on metallic materials in a hot rolling step and/or a heat treatment step, etc., which can conduct suppression and removal of scales efficiently and can largely shorten the treatment time in the successive pickling step.
DISCLOSURE OF THE INVENTION
Means for solving Problem
Gists of the present invention are as follows:
(1) A process for removing scales and preventing scale formation on a metallic material, characterized by contacting cooling water with a metallic material at a temperature of 100° to 1,200° C. in a water cooling step for the metallic material, while applying a direct current or an alternating current to the metallic material at a current density of 0.1 to 10
5
A/m
2
of unit surface area through the cooling water.
(2) A process for removing scales and preventing scale formation on a metallic material, characterized by contacting cooling water at a pH of −2 to 4 with a metallic material at a temperature of 100° to 1,200° C. in a water cooling step for the metallic material.
(3) A process for removing scales and preventing scale formation on a metallic material, characterized by contacting cooling water at a pH of −2 to 4 with a metallic material at a temperature of 100° to 1,200° C. in a water cooling step for the metallic material, while applying a direct current or an alternating current to the metallic material at a current density of 0.1 to 10
5
A/cm
2
of unit surface area through the cooling water.
(4) A process for removing scales and preventing scale formation on a metallic material according to the foregoing item (1) or (3), characterized by using the metallic material as one of a positive electrode or a negative electrode or providing the metallic material between a positive electrode and a negative electrode for the current application.
(5) A process for removing scales and preventing scale formation on a metallic material according to any one of the foregoing items (1), (3) and (4), characterized by providing at least two of pairs each consisting of a positive electrode and a negative electrode facing each other discretely in a water cooling tank filled with cooling water so that the positive electrodes and the negative electrodes can be alternately arranged in a parallel with one another at distances, passing the metallic material through between the positive electrodes and the negative electrodes in the pairs in the cooling water, thereby contacting the cooling water with the metallic material, and applying a direct current to the metallic material by passing the current between the positive electrodes and the negative electrodes in the pairs.
(6) A process for removing scales and preventing scale formation on a metallic material according to any one of the foregoing items (1) and (3) to (5), characterized in that the cooling water has an electric conductivity of 0.01 to 100 S/m.
(7) A process for removing scales and preventing scale formation on a metallic material according to any one of the foregoing items (1) to (6), characterized in that water deaerated to a dissolved oxygen gas concentration of not more than 4.46×10
−5
mol/m
3
(1 ppm) is used as the cooling water.
(8) A process for removing scales and preventing scale formation on a metallic material according to any one of the foregoing items (1) to (7), characterized in that high pressure water with the pressure of 0.2942 to 49.03 MPa is made to hit the metallic material during the water cooling.
(9) A process for removing scales and preventing scale formation on a metallic material according to any one of the foregoing items (1) to (8), characterized in that high pressure water with the pressure of 0.2942 to 49.03 MPa is made to hit the metallic material after the water cooling.
(10) A process for removing scales and preventing scale formation on a metallic material according to any one of the foregoing items (1) to (9), characterized in that water containing at least one of hydrogen, ammonia, nitrogen, carbon dioxide and inert gases at a total dissolved gas concentration of 4.46×10
−5
mol/m
3
to 2.23 mol/m
3
(1 to 5×10
4
ppm) is used as the cooling water.
(11) A process for removing scales and preventing scale formation on a metallic material according to any one of the foregoing items (2) to (10), characterized in that hydrochloric acid, sulfuric acid or nitric acid is added to the cooling water.
(12) A process for removing scales and preventing scale formation on a metallic material according to any one of the foregoing items (2) to (10), characterized in that an oxidizing agent is added to the cooling water, thereby adjusting the cooling water to an ORP (oxidation-reduction potential) value of 0.5 V in NHE (Normal Hydrogen Electrode) to 2.0 V in NHE, or a reducing agent is added to the cooling water, thereby adjusting the cooling water to an ORP v
Akashi Tooru
Hamausu Shuuichi
Kondou Yasumitsu
Sakashita Masao
Kastler Scott
Nippon Steel Corporation
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