Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/24—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds

Definitions

• a method for producing a steel sheet having resistance against rust formation comprising applying an oxidation treatment to a steel sheet containing not more than 0.15% of C, not more than 0.15% of Si, not more than 0.02% of S, 0.005 to 0.15% of P, 0.01 to 0.25% of Cu, and at least one from 0.3 to 2.0% of Mn, 0.05 to 2.0% of Cr, 0.05 to 2.0% of Al, 0.01 to 0.2% of Sb, 0.001 to 0.20% of As and 0.01 to 0.20% of Bi, with the balance being substantially iron and unavoidable impurities, whereby a non-visible oxide film composed of y-Fe O is formed on the steel sheet.
• the present invention relates to a method for producing steel sheets having resistance against rust formation.
• rusts which are formed in a very short time as formed during the steel sheet production or in the transportation of the steel sheets, or rusts which are formed in a relatively long period as formed on edge portions of food cans during their storage are problems.
• the rust problem in cans is increasing as tin free steels (TFS) are being more and more substituted for tin plates as can materials in recent days.
• TFS tin free steels
• seam or double seam portions of cans, cut edges of crown caps, and scored portions of recently developed easy-open cans are particularly problemsome because they are very susceptible to rust formation due to partial exposure of their non-coated surface, and rust flows therefrom to stain the whole appearance.
• the problem is less critical because the tin flows into the cut portion and serves to protect the exposed metal surface against rust formation.
• the present inventors have conducted extensive studies in order to develop a method for preventing rust which is formed in a very short time or rust which is formed in a relatively long time as mentioned above and to develop a method for producing steel sheets having resistance to rust formation without sacrifice of their workabilities at far less cost than conventional corrosion resistant steels.
• a steel sheet having resistance against rust formation can be obtained by applying an electrolytic oxidation treatment or a chemical oxidation treatment to a carbon steel sheet containing one or more of Mn, Sb, As, Bi, Cr and Al in a very small amount.
• the object of the present invention is to provide a method for producing steel sheets having resistance against rust formation by a simple treatment.
• the feature of the present invention is that an oxidation treatment such as an electrolytic oxidation treatment and a chemical oxidation is applied to a carbon steel comprising one or more of not more than 2.0% of Mn; 0.01 to 0.20% of Sb; 0.01 to 0.20% of As; 0.01 to 0.20% of Bi; not more than 2.0% of Cr, with the balance being substantially iron and unavoidable impurities.
• an oxide film is formed on the steel sheet by an oxidation treatment.
• oxide film is formed by nature in the air without the oxidation treatment.
• the natural oxide film is composed mainly of 'y-Fe O and its thickness ranges from 10 to 30 A., accompanied with many defects such as the presence of pores and irregular film thickness and thus poor resistance against rust formation.
• the film grows and the film construction is changed to form a two-layer film; a film of R 0, near the matrix surface and a film of u-Fe O outside the film of Fe O Through experiments it has been found that such a natural film does not improve resistance against rust formation.
• the rust preventive oxide film on the surface of the steel sheets is obtained not by the natural oxide film formation nor merely by the electrolytical or chemical oxidation treatment, but is obtained by the combination of the steel composition containing one or more of Mn, Sb, As and Bi in a certain.
• oxide film ('y-F6 O film) is stabilized and dense and thus a steel surface having remarkable resistance against rust formation can be obtained.
• the special elements composing the steel used in the present invention are one or more of Mn, Sb, As, Bi, Cr, and Al.
• Each of these elements give the steel surface a non-visible stabilized and dense oxide film having good resistance against rust formation.
• Particularly effective for densing and stabilizing a film having a thickness to 50 A. composed of spinnel type oxide mainly composed of -,-Fe,o and for assuring the above effect, Mn, Cr and Al each in an amount more than as usually contained in steels and Sb, As, Bi each in an amount more than 0.01% are required.
• excessive amounts of these elements do not improve substantially the resistance against rust formation, but cause embrittlement of the material, and particularly excessive contents of Mn, Cr and Al colours the steel surface (interference colour) and thus should be avoided from the viewpoint of appearance.
• the upper limits of Sb, As and Bi are set as 0.20% and the upper limits of Mn, Cr and Al are set as 2.0%. Namely, when Cr, Al or Mn is contained in a large amount, the film is an excessively oxidized state and thus film is coloured (becomes visible), wh'ich deteriorates the commercial value of the product.
• Mn which is usually contained in steels, similar results will be produced when it is contained in combination with Cr and Al, and thus the total amount of Mn+Cr+Al should be not more than 2.0%. However, less than 0.05% of Cr, less than 0.3% of Mn or less than 0.05% of Al is not effective for producing a desired film.
• Carbon is necessary only for assuring the required mechanical properties and it is desirable to restrict the carbon content to not more than 0.15% to assure resistance against rust formation.
• Si Silicon has adverse effects both on mechanical properties and resistance against rust formation, and it is necessary to limit the silicon content as low a value as possible, desirably less than 0.15
• Phosphorus is not particularly elfective in combination of the oxidation treatment, but is generally effective to give resistance against rust formation a certain range of content. However, a large content will embrittle the material and thus the phosphorus content is limited to the range of 0.005 to 0.15%.
• S Similarly as silicon, sulfur is usually contained in steels, but it has adverse effects both on the mechanical properties and resistance against rust formation. In order to prevent the adverse effects on the mechanical properties by sulfur it is well known to add manganese. But manganese must be present as a solid solution which does not combine with sulfur in order for the manganese to be effective for resisting rust formation in combination with the oxidation treatment. From the above point, it is desirable to limit the sulfur content as low as possible, desirably less than 0.020%
• Cu In the same Way as phosphorus, copper is not effective for resisting rust formation in combination with the oxidation treatment, but it is effective by itself when added in a ceratin amount. However, a large amount of copper has adverse effects and it is desirable to limit the copper content to the range of 0.05 to 0.25%
• the steel sheet containing the above elements in the above ranges are obtained by an ordinary method comprising steel making, cogging, hot rolling, cold rolling, annealing and, if necessary, temper rolling.
• anodic oxidation in an electrolyte electrolytic oxidation
• an immersion treatment in a solution of oxidizing agent chemical oxidation
• Other oxidation treatments such as an immersion treatment in canstic soda (alkali black colouring), a fused nitrate process,
• the super-heated water vapour process and oxidation by heating in the air are not used in the present invention.
• the immersion treatment in caustic soda, the fused nitrate process and the super-heated water vapour process are directed to formation of a thick magnetite layer of several microns on the steel sheet surface and blacken the sheet surface as they are commonly used as a blacking method. These treatments are undesirable for the present invention.
• the oxidation by heating in air is the most simple method for an oxide film formation, it does not improve, but rather deteriorates the resistance against rust formation, and particularly when heated above 250 C., the film is coloured by bluing, and thus this method is not desirable. It has been found that only the electrolytic oxidation or chemical oxidation is effective for the steel sheet containing the special elements such as Mn, As and Cr, in order to avoid the difficulties as mentioned above.
• the electrolytic oxidation treatment for improving the rust formation resistance in combination with the elements such as Mn, As, Bi, Cr and Al as mentioned above does not require any special consideration, and an ordinary oxidation method can be used.
• the electrolyte any electrolyte which gives electric conductivity to the liquid may be used, whether they are acidic, neutral or alkaline.
• an electrolyte containing halogen ions such as Clor SO;- which likely destroy the passivated film should be avoided.
• the most desirable electrolyte includes a low concentration solution of nitrate, sodium borate, sodium carbonate, sodium altho-silicate, caustic soda etc.
• the anodic treatment is conducted for several minutes to several ten of minutes using the steel sheet as the anode and a suitable material as the cathode.
• a constant potential method or a constant current method may be used.
• the constant potential method it is desirable to set the potential in the passivation range which depends on the type of the electrolyte solution, and in the constant current method it is necessary to select an appropriate current density depending on the type of the solution.
• Desirable treating conditions are: a concentration of the solution between 3 to 10%, a treating temperature between the ordinary temperatures and C., and a treating time between several seconds and several tens of seconds.
• a dense and stabilized thin non-visible oxide film is formed on the steel sheet surface by adding a very small amount of the special elements as contrasted to the conventional techniques.
• the oxide film is formed in a super oxidation state, the film is coloured and the appearance of the steel sheet is damaged.
• the period before rust formation can be remarkably prolonged and it is possible to keep the steel sheet from rust formation under certain service conditions and periods.
• Table 1 shows the rust formation ratios before and after the oxidation treatment of the steel sheets of the present invention in comparison with those of conventional comparative materials.
• the rust formation ratio of the present inventive steel sheets is remarkably low as compared with that of the comparative materials and thus the present inventive steel sheets has an excellent rust formation resistance.
• Comparativematerial..- 0.05 0.01 0.25 0.015 do 100 90 8 0.07 0.02 0.29 0.013 Chemical oxidation, in 10% 45 3 potassium permanganate solution for 30 seconds at 90 0. Comparative material... 0.07 0. 02 0.29 0.013 do 100 100 9 0. 05 0.01 0.25 0. 015 Sameasin Examplel 7.5 Comparative material..- 0.05 0. 01 0.25 0.015 100 90 10 0.05 0.01 1.0 0.015 0.015 0.08 do 100 10 Comparativematerial...
• a method for producing a steel sheet having resistance against rust formation comprising applying an oxidation treatment to a steel sheet having substantially the following composition:
• the rust formation of the comparative materials is one obtained when the specimens are kept in the same humid ity cell for 6 hours.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Chemical Treatment Of Metals (AREA)
• Electrochemical Coating By Surface Reaction (AREA)

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Cited By (4)

• 1970
  • 1970-08-10 JP JP45069848A patent/JPS4913143B1/ja active Pending
• 1971
  • 1971-08-06 US US00169845A patent/US3764398A/en not_active Expired - Lifetime
  • 1971-08-09 CA CA120,167A patent/CA964083A/en not_active Expired

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