US2455331A - Method of enameling - Google Patents
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- US2455331A US2455331A US560183A US56018344A US2455331A US 2455331 A US2455331 A US 2455331A US 560183 A US560183 A US 560183A US 56018344 A US56018344 A US 56018344A US 2455331 A US2455331 A US 2455331A
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- 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
- C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
- C23D3/00—Chemical treatment of the metal surfaces prior to coating
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- 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
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- 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
- C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
- C23D5/00—Coating with enamels or vitreous layers
Definitions
- This invention relates to the art of enameling and, in particular, to the coating of iron or steel' articleswith a finish layer of enamel, particularly white or light-colored vitreous. enamel, applied directly thereto without the application of a dark groundv coat as required by the previous enameling practice.
- Kautz Patent 2,099,340 granted more than half a century later thanthe Niedringhaus et al. patent, describes the production ofv a surface layer of substantially pure iron on the formed article by oxidizing it and then reducing the oxide. This process,l however, has not been successful. We believe that they defect of ⁇ the process is that it produces a coarse surface which traps the hydrates contained in the frit, preventing the elimination of the water of crystallization therefrom in thedrying, withthe result that water vapor is evolved on ring which is injurious to the' surface of the enamel.
- a sheet or' plate of low-carbon steel or iron enameling stock i. e., steel (either open-hearth, Bessemer or electric-furnace steel) containing from .010% to .25% carbon (although usually not over 0.10% carbon) into the shape of the desired nished article.
- steel either open-hearth, Bessemer or electric-furnace steel
- carbon although usually not over 0.10% carbon
- We then eliminate carbon from the surfaces of the formed ⁇ article by heating it to a temperature of 1100 degrees F. or above in a decarburizing atmosphere and maintaining it at such temperature for a substantial period, i. e. from five to thirty minutes.
- Figure 1 shows such a sheet designated 'I0, in the as-rolled condition.
- the sheet is 'of appropriate gauge, depending on the nature 'of the article to be formed therefrom.
- the 'sheet is formed into the shape of the desired in'ished 'article by known methods of drawing, bending, etc., together With such welding as may be required.
- Figure 2 illustrates an article II formed from the sheet Illa, speciflcally the food compartment of a mechanical refrigerator.
- the enamel to be applied contains a substantial quantity of a white or light-colored substitute for cobalt oxide, we believe the nickelsulphate dip may be eliminated.
- Compounds of the cerium group have been mentioned as a suitable substitute (German Patent 282,348).
- Other elements whose compounds are mentioned in the literature for use in promoting the adherence of white or light-colored enamels are antimony (Tetrick, Journal of the American Ceramic Society, p.,349, 1934), zirconium (Anon, Bureau of Standards, Technical News Bulletin No. 122, p. 10, 1927) and molybdenum (Kautz, Journal of the American Ceramic Society, p. 283, 1940).
- the nickel dip is necessary to improve the adherence of many white or colored enamel compositions (Andrews, Enamels book, p. 177, 1935). Cobalt solutions have been used in a similar manner (Anon, Journal of the American Ceramic Society, Abstracts, p. 519, 1928). Tetrick, in the article cited, also discusses the value of chemical etchingtreatments of the base metal in improving enamel adherence. Hot acid gases may be used to etch the metal surface in a manner to improve enamel adherence generally (Turin, Iron Age, p. 70, 1944). Etching should be done prior to the decarburizing operation.
- FIG. 3 shows one mode of performing this part of the process.
- a continuous or tunnel-type furnace I2 is provided with a conveyor I3 for moving formed articles progressively therethrough.
- the furnace is provided with appropriate heating means to maintain the temperature at around 1400 degrees F. and the speed of the'conveyor is so adjusted with reference to the length of the furnace that each article will be within the heating zone of the furnace for the period of time indicated, i. e., from i'lve to thirty minutes.
- a decarburizing atmosphere is supplied to the interior of the furnace, through a conduit I4, for
- the composition of the gas may vary widely but it should include free hydrogenA and free water vapor 'in such amounts as to inhibit oxidation of the metal of the articles being processed.
- Gas of the following composition has proved satisfactory: 5% CO2, 10% CO, 12% H2, water vapor corresponding to a dew point of about 85 degrees F., and the balance substantially nitrogen.
- This composition of gas for the atmosphere of the furnace I2 is similar to what is known as bright-annealing gas but has a somewhat higher water-vapor content.
- the furnace I2 may conveniently have a heating-up zone, a, soaking zone and a cooling zone.
- the above-mentioned atmosphere is preferably maintained in each zone.
- the cooling zone should be so constructed and arranged as to reduce the temperature of the articles gradually to a nal value not greatly in excess of that of the atmosphere, unless a certain amount of oxide scale is deliberately produced on the articles by removing them from the furnace at temperatures somewhat above atmospheric in order to provide the oxidation necessary when the articles are subsequently fired in a neutral atmosphere as is done in certain special enameling practices.
- the dipping of the article in nickel sulphate may follow the decarburlzing treatment just described instead of preceding it. It is important, however, that the pckling be done before the decarburizing operation.
- a frit appropriate for forming a nish layer of vitreous enamel usually white or light-colored containing an opacifler. This frit is applied directly to the surface of the processed articles.
- Figure 4 shows one of the articles at II a having.
- the frit-coated articles are next fired in thev known manner by placing them in a conventional enameling furnace such' as indicated at I5 in Figure 5.
- the ware is heated to a temperature of about 1500 degrees F., i. e.,
- FIG. 6 illustrates to enlarged scale the layer of nish enamel I 6 applied directly to th'e base metal I1 and bonded therewith.
- Warping of the ware is also reduced or eliminated. This; appears to result'from thelrelief of ⁇ warping stress;
- this frit is milled with about 6% clay, an opacier, such as zirconium oxide type, in amount to produce desired opacity (generally 6 to 8%) and the necessary amount of water. Frits of this type when fused not Wet and bond themselves properly to th'e base except in the presence of oxygen, free or combined.
- the milled frit is generally applied in a liquid vehicle over the surface of the article prior to heating and consequently is in the form of a dull porous coating when applied.
- the frit is a glass and has no ⁇ fixed melting point, but as the temperature is increased it does ultimately soften to the extent that the particles coalesce.
- the layer of frit is porous and the oxygen in th'e furnace atmosphere can penetrate through to the base. If this base is naked iron or steel, gases form. If these gases escape through the coalesced frit of finish enamel, they leave pits or other defects. If they do not escape, they form bubbles or blisters.
- ground-coat enamel is essentially a cobalt-oxide glass.
- a typical formula is the following:
- this frit is milled with about 6% clay.
- Such frit is relatively quite fluid and has a low surface tension when fused by heating to usual enameling temperatures. We believe that the gases escape readily through this fluid ground coat and that any pits thus formed disappear as the enamel thereafter levels itself off.
- finish enamels have a high viscosity because of the presence of the opacier, and if pits form therein, the enamel will not level itself off to the extent necessary to give a commercial iin- 'ish.
- the iron or steel principally used in the enameling industry varies in carbon content from .010% to 0.25%'.
- the lower figure is about the minimum obtainable by current steel-making processes in extensive use and producing metal in theform desired for fabrication.
- the particular carbon content specied will depend upon a number offactors'such as the complex-ityof the articles and the corresponding difliculties of forming it, the stiffness desired in the nal product, etc.
- the treatment of the articles in the furnace I2 removes gas-forming compounds such as iron carbide from the surfaces of the articles as well as inwardly of the surfaces to a predetermined depth, depending on the extent of the processing, the minimum objective being, in any case, to leave no carbides or other gas-forming constituents at or near the surface which would react with the furnace atmosphere penetrating through the porous frit during iiring.
- An important aspect of our invention is the surface treatment of the articles after they have been formed to shape. We have found that if the treatment is applied to the steel prior to fabrication, enameling defects are prone to occur in those parts of the article where the metal has been bent or die-shaped to a material extent or has been abraded as in metal finishing and even in zones where the metal has been heated to high temperature as in welding operations which may be employed in fabrication.
- van article is made from conventional ferrousy enameling stock having a carbon content of from ,010% to .25% and in which the article is approximate- 1y in its final shape, the steps including,:c1ean ing the article with a cleaning solution and drying it to prepare the ferrous surface thereof for enameling, then heating the article to a temperature between about 1100 degrees and about 1400 degrees F.
Description
Nov, 30, 1948.
METHOD J. C. ECKEL ETAL 0F ENAMELING Filed oct. 24, 1944 4 1, ff, l f
Jaya
uunranaluuuurnauaam vapnnunn/r INVENTORS Jos eph C. Ec/fe/ and Hugh E/Pom/'ne Patented Nov. 30, 1948 METHOD F ENABIELING Joseph C. Eckel, Ingram, and Hugh E. Romine, Grafton, Pa.
Application October 24, 1944, Serial No..560,183
4 Claims. l
`This invention relates to the art of enameling and, in particular, to the coating of iron or steel' articleswith a finish layer of enamel, particularly white or light-colored vitreous. enamel, applied directly thereto without the application of a dark groundv coat as required by the previous enameling practice.
It has proved impossible prior to our invention, to' enamel metal articlesv with a nish layer of enamel by applying a single coat of frit directly to the base metal and ring it, because of the clevelopment of bubbles,v pits or specks in the surface of the enamel. Although numerous attempts have been made to overcome the defects mentioned, none ofV them so far as We are aware has been successful. Niedringhaus Patent 200- 626, granted in 1878, discloses a method of expelling the carbon from the base metal before coating with frit, by heating` it to a white heat in the presence of lime, butr this method has notachieved any commercial acceptance, so far as We are aware, probably because the treatment described does notv eliminate the iron carbide in the surf ace of the metal. Kautz Patent 2,099,340, granted more than half a century later thanthe Niedringhaus et al. patent, describes the production ofv a surface layer of substantially pure iron on the formed article by oxidizing it and then reducing the oxide. This process,l however, has not been successful. We believe that they defect of` the process is that it produces a coarse surface which traps the hydrates contained in the frit, preventing the elimination of the water of crystallization therefrom in thedrying, withthe result that water vapor is evolved on ring which is injurious to the' surface of the enamel.
Badger et al. (Ceramic Industry, July, 1937, p. 41) observed that the removal of part of the surface carbon from a piece of high-carbon steel (drill rod, presumably about 1% carbon). permitted it to be successfully coated with ordinary ground coat' enamell after it was heated in a hydrogen atmosphere to a temperature from 800' degrees toy 856 degrees C., but they did. not vdeal at all. with the problem of. applying nish enamels such asthel whiteenamel usedf'or refrigerators, bathroom xtures and the like, and
their disclosure did not enable the industryl to adopt the direct applicationV of commercial. coats.
of' finish enamels.
The practice in the art has therefore been to apply a groundcoat of the cobalt-oxide type [the ordinary ground coat enamel of Badger et all, before applying the finishl coat of" enamel, usually a white or light-colored enamel. This practice involves greater processing time, laborV and material cost than would be required for applyinggaA single coatv of' finish enamel directly to the base. metal, but there has been no other process satis.- factory to the trade at large for achieving the desired results.
We have discovered a novel methodv of applying directly to the base metal a single coat of finish enamelv and fusing it thereon without the occurrence of pits or specks therein, and by which, despite the entire absence of a ground,v coat, a nished product may be made superior to that obtained by present practices,v with minimum rejections. The product exhibits an improved adherence ofthe enamel to the base metal and less likelihood of chipping of the enamel because of the reduced thickness thereof. It also has a higher gloss.' The absence of surface defects eliminates the loss involved in the downgradingV and rejection of ware made. by existing practice, which is necessaryA because of the. occurrence of such defects in a portion, at least, of the Ware.
Ina preferred practice, we form a sheet or' plate of low-carbon steel or iron enameling stock, i. e., steel (either open-hearth, Bessemer or electric-furnace steel) containing from .010% to .25% carbon (although usually not over 0.10% carbon) into the shape of the desired nished article. We then clean the article, and give it an acid pickle and a nickel-sulphate dip. We then eliminate carbon from the surfaces of the formed` article by heating it to a temperature of 1100 degrees F. or above in a decarburizing atmosphere and maintaining it at such temperature for a substantial period, i. e. from five to thirty minutes. After cooling the article substantially to atmospheric temperature, we apply directlls7 to the base metal` a layer of iinish coat vitreous enamel frit and heat. the article thusl coated `to a temperature sufficient to cause fusion of the frit yand formation of a smooth continuous enamel layer.
A complete understanding oi the preferred practice of our invention may be optained from the following. detailed description which refers` example.
out our method upon articles formed from any suitable enameling stock, e. g., low-carbon steel or iron sheets or plates having from .010% to .25% carbon. Figure 1 shows such a sheet designated 'I0, in the as-rolled condition. The sheet is 'of appropriate gauge, depending on the nature 'of the article to be formed therefrom. The 'sheet is formed into the shape of the desired in'ished 'article by known methods of drawing, bending, etc., together With such welding as may be required. Figure 2 illustrates an article II formed from the sheet Illa, speciflcally the food compartment of a mechanical refrigerator. We next clean the article to remove grease used as a lubricant in forming, and perspiration spots resulting from the necessary manual handling, and subject it to an acid pickle and Aa nickelsulphate dip, in the known manner, rinsing the article after each operation.
If the enamel to be applied contains a substantial quantity of a white or light-colored substitute for cobalt oxide, we believe the nickelsulphate dip may be eliminated. Compounds of the cerium group have been mentioned as a suitable substitute (German Patent 282,348). Other elements whose compounds are mentioned in the literature for use in promoting the adherence of white or light-colored enamels are antimony (Tetrick, Journal of the American Ceramic Society, p.,349, 1934), zirconium (Anon, Bureau of Standards, Technical News Bulletin No. 122, p. 10, 1927) and molybdenum (Kautz, Journal of the American Ceramic Society, p. 283, 1940). The nickel dip is necessary to improve the adherence of many white or colored enamel compositions (Andrews, Enamels book, p. 177, 1935). Cobalt solutions have been used in a similar manner (Anon, Journal of the American Ceramic Society, Abstracts, p. 519, 1928). Tetrick, in the article cited, also discusses the value of chemical etchingtreatments of the base metal in improving enamel adherence. Hot acid gases may be used to etch the metal surface in a manner to improve enamel adherence generally (Turin, Iron Age, p. 70, 1944). Etching should be done prior to the decarburizing operation. We believe that the most successful enamels for our process will be those which have good adherence due to the enamel composition and that complete reliance should not be placed on surface treatments such as nickel dipping and etching in order to obtain adherence as such surface treatments appear to give less satisfactory results in commercial practice.
We then heat the article to a temperature of about 1100 degrees F. or above, and preferably in the neighborhood of 1400 degrees F., in a decarburizing atmosphere, and hold it at such temperature for a substantial period, say from ve to thirty minutes. Figure 3 shows one mode of performing this part of the process. A continuous or tunnel-type furnace I2 is provided with a conveyor I3 for moving formed articles progressively therethrough. The furnace is provided with appropriate heating means to maintain the temperature at around 1400 degrees F. and the speed of the'conveyor is so adjusted with reference to the length of the furnace that each article will be within the heating zone of the furnace for the period of time indicated, i. e., from i'lve to thirty minutes.
A decarburizing atmosphere is supplied to the interior of the furnace, through a conduit I4, for The composition of the gas may vary widely but it should include free hydrogenA and free water vapor 'in such amounts as to inhibit oxidation of the metal of the articles being processed. Gas of the following composition has proved satisfactory: 5% CO2, 10% CO, 12% H2, water vapor corresponding to a dew point of about 85 degrees F., and the balance substantially nitrogen. This composition of gas for the atmosphere of the furnace I2 is similar to what is known as bright-annealing gas but has a somewhat higher water-vapor content.
The furnace I2 may conveniently have a heating-up zone, a, soaking zone and a cooling zone. The above-mentioned atmosphere is preferably maintained in each zone. Thus the articles are protected against atmospheric oxidation until they have been cooled. The cooling zone should be so constructed and arranged as to reduce the temperature of the articles gradually to a nal value not greatly in excess of that of the atmosphere, unless a certain amount of oxide scale is deliberately produced on the articles by removing them from the furnace at temperatures somewhat above atmospheric in order to provide the oxidation necessary when the articles are subsequently fired in a neutral atmosphere as is done in certain special enameling practices.
The dipping of the article in nickel sulphate may follow the decarburlzing treatment just described instead of preceding it. It is important, however, that the pckling be done before the decarburizing operation.
After the articles h'ave been processed as above,
described, they are sprayed or otherwise coated with a frit appropriate for forming a nish layer of vitreous enamel, usually white or light-colored containing an opacifler. This frit is applied directly to the surface of the processed articles.
Figure 4 shows one of the articles at II a having.
a coating of flrit thereon.
The frit-coated articles are next fired in thev known manner by placing them in a conventional enameling furnace such' as indicated at I5 in Figure 5. In this process, the ware is heated to a temperature of about 1500 degrees F., i. e.,
slightly above the fusion point of the frit. On removal from the furnace the ware is cooled in air, according to the usual practice in the enameling art. Theenamel layer thus formed on the ware is smooth and continuous, unmarred by defects, such as pits or specks. Figure 6 illustrates to enlarged scale the layer of nish enamel I 6 applied directly to th'e base metal I1 and bonded therewith.
It will be apparent from the foregoing that our invention is characterized by important advantages over the previous practice of enameling. The ability to apply a inish layer of enamel directly to the base metal without the formation of defects in the surface saves the substantial cost and processing time involved in applying the ground coat which has heretofore been necessary.
The preliminary processing of the formed articlesA Further advantagesV reside in the fact that the enamel layer` applied by our invention has excellent adherence to th'e base metal. In addition, the removal of surface carbides appears to improve the resistance of the ware to sagging under the,
temperature of the enameling furnace. Warping of the ware is also reduced or eliminated. This; appears to result'from thelrelief of `warping stress;
a'fordedby the heating of `the Ware for eli-mi- -natingfcarbides from the surface thereof. A. further advantage is that the total thickness of enamel applied by our method is less than that applied-in th'e prior practice. As a result, Ware enameled by our method is more resistant to chipping than that previously made. It also has a 'higher gloss. While the invention has been described with reference to the use of low-carbon steel as a base metal, it is also applicable to lowmetalloid steel and open-hearth iron.
'We believe that the superior results obtained by .practicing our method may be explained as follows, although we do not limit ourselvesto this particular theory: The frit for forming a finish enamel such .as the white or. light-colored enamels used in bathroom fixtures, refrigerators, stoves,
and the.. like, must *include` an opaciiier. A typical formula is the following:
Percent- Parts age Feldspar 3l. 5 33. 5 Borax 24. 4 25. 9 Quartz. 19.0 20.1 Soda ash. 4. l 4. 4 Soda nlitre.; 3. 5 3. 7 Fluorspar l1. 7 12.4
For use, this frit is milled with about 6% clay, an opacier, such as zirconium oxide type, in amount to produce desired opacity (generally 6 to 8%) and the necessary amount of water. Frits of this type when fused not Wet and bond themselves properly to th'e base except in the presence of oxygen, free or combined. The milled frit is generally applied in a liquid vehicle over the surface of the article prior to heating and consequently is in the form of a dull porous coating when applied. The frit is a glass and has no `fixed melting point, but as the temperature is increased it does ultimately soften to the extent that the particles coalesce. Until this coalescence occurs, the layer of frit is porous and the oxygen in th'e furnace atmosphere can penetrate through to the base. If this base is naked iron or steel, gases form. If these gases escape through the coalesced frit of finish enamel, they leave pits or other defects. If they do not escape, they form bubbles or blisters.
In the ordinary enameling processes now in vogue, the ground-coat enamel is essentially a cobalt-oxide glass. A typical formula is the following:
For use, this frit is milled with about 6% clay. Such frit is relatively quite fluid and has a low surface tension when fused by heating to usual enameling temperatures. We believe that the gases escape readily through this fluid ground coat and that any pits thus formed disappear as the enamel thereafter levels itself off. On the other hand, finish enamels have a high viscosity because of the presence of the opacier, and if pits form therein, the enamel will not level itself off to the extent necessary to give a commercial iin- 'ish. If the nish enamel is applied over a groundcoat enamel, there is no reaction as, for example, y'between the steel and the furnace atmosphere, which cause gases to evolve, since the steel base is walled on' by a continuous and unbroken llayer of ground-coat enamel. We believe that the reactions which result in gas formation in these circumstances are complex and that the composition of the gases may vary considerably under different conditions. We believe, however, that theyare always at least in part carbon monoxide.
The iron or steel principally used in the enameling industry varies in carbon content from .010% to 0.25%'. The lower figure is about the minimum obtainable by current steel-making processes in extensive use and producing metal in theform desired for fabrication. The particular carbon content specied will depend upon a number offactors'such as the complex-ityof the articles and the corresponding difliculties of forming it, the stiffness desired in the nal product, etc. We believe that even in the softest enameling iron or steel there is a substantial amount of carbon at or near the surface in the form ofiron carbide with which the oxygen from the furnace atmosphere will react to form carbon monoxide. In our process the treatment of the articles in the furnace I2 removes gas-forming compounds such as iron carbide from the surfaces of the articles as well as inwardly of the surfaces to a predetermined depth, depending on the extent of the processing, the minimum objective being, in any case, to leave no carbides or other gas-forming constituents at or near the surface which would react with the furnace atmosphere penetrating through the porous frit during iiring.
It should be pointed out that even in the Dresent practice of rst firing a ground-coat enamel and then placing and firing a finish coat thereover, difficulties are sometimes encountered with what is known as re-boiling. This defect, which is Well known in the art, manifests itself by the presence of pits or bubbles in the Ware, sometimes requiring down-grading or outright rejection. Re-boiling defects may occur from even minor changes, many of which are extremely difficult to locate. Re-boiling defects are entirely eliminated by our discovery because it permits the application directly to the base of a frit for a finish enamel, even though it contains substantial quantities of an opacier. Such enamels are so viscous at enameling-furnace that any gases which might be given olf by the base metal would form blisters or bubbles which, if they break, would show as pits remaining in the surface of the enamel after the gas escapes.
An important aspect of our invention is the surface treatment of the articles after they have been formed to shape. We have found that if the treatment is applied to the steel prior to fabrication, enameling defects are prone to occur in those parts of the article where the metal has been bent or die-shaped to a material extent or has been abraded as in metal finishing and even in zones where the metal has been heated to high temperature as in welding operations which may be employed in fabrication.
Although we have disclosed herein a preferred practice of our invention, it will be recognized that modifications thereof may be made within the scope of the appended claims.
We claim:
1. In a method of enameling in which an articlev is made `from conventional ferrous enameling stock having a carbon content of from .010% to .25% and in which the article is approximately in its final shape, the steps including, cleaning the article with a cleaning solution and drying it to prepare the ferrous surface thereof for enameling, then heating the articleto a temperature in the neighborhood of 1400 degrees F. in a decarburizing atmosphere containing free hydrogen and water vapor and effective to inhibit oxidation of and to decarburize the ferrous metal surface, maintaining the article at such temperature and in such atmosphere for a period of time between about and 30 minutes until its ferrous surface has been freed from gas-forming constituents such as iron carbide, gradually cool- Ving the article in a non-oxidizingatmosphere substantially to atmospheric temperature, applying directly to the surface of the article a layer of light-colored finish-coat vitreous enamel frit containing an opacier, and heatingthe article thus coated to a temperature sufficient to convert the frit into a coat of fused enamel.
2. The method as defined by claim 1 characterized by said first-mentioned atmosphere being composed substantially of 12% hydrogen, 10% carbon monoxide, 5% carbon dioxide, water vapor corresponding to a dew point of 85 degrees F. and the balance substantially nitrogen.
3. In a method of enameling in which an article is made from conventional ferrous enameling stock having a carbon content of from .010% to .25% and in which the article is approximately in its final shape, the steps including, cleaning the article with a cleaning solution and drying it to prepare the ferrous surface thereof for enameling, then heating the article to a temperature in the neighborhood of 1400 degrees F. in a decarburizing atmosphere containing free hydrogen and water vapor and effective to inhibit oxidation of and to decarburize the ferrous metal surface, maintaining the article at such temperature and in such atmosphere for a period of time between about 5 and 30 minutes until its ferrous surface has been freed from gasforming constituents such as iron carbide, gradually cooling the article in a non-oxidizing atmosphere substantially to atmospheric temperature, applying directly to the surface of the arthe article thus coated to a temperature sume.
cient to convert the frit into a ycoat of fused enamel.
4. In a method of enameling in which van article is made from conventional ferrousy enameling stock having a carbon content of from ,010% to .25% and in which the article is approximate- 1y in its final shape, the steps including,:c1ean ing the article with a cleaning solution and drying it to prepare the ferrous surface thereof for enameling, then heating the article to a temperature between about 1100 degrees and about 1400 degrees F. in a decarburizing atmosphere containing free hydrogen and water vapor and effective to inhibit oxidation of and toY decarburize the ferrous metal surface, maintaining the article at such temperature and in such atmosphere for a period of time between' about 5 and 30 minutes until its ferrous surface has been freed from gas-forming constituents such as iron carbide, gradually cooling the article in a non-oxidizing atmosphere substantially to atmospheric temperature, applying directly to the surface of the article a layer of light-colored nish-coat vitreous enamel frit containing an opacier, and heating the article thus coated to a temperature suicient to convert the frit into a coat of fused enamel.
JOSEPH C. ECKEL. HUGH E. ROMINE.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Badger et al.,
Aromic Industry, July 1937,
pagefll.
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Cited By (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2532640A (en) * | 1946-08-24 | 1950-12-05 | Gen Motors Corp | Process of enameling |
US2594129A (en) * | 1948-04-10 | 1952-04-22 | Air Reduction | Method of preparing surfaces for tinning |
US2656285A (en) * | 1948-06-03 | 1953-10-20 | Armco Steel Corp | Production of coated soft iron and steel sheets |
US2677625A (en) * | 1951-02-15 | 1954-05-04 | United States Steel Corp | Flat rolled ferrous metal for vitreous enameling |
US2755210A (en) * | 1949-06-25 | 1956-07-17 | Armco Steel Corp | Method of treating iron or mild steel to promote the adherence of porcelain enamel, and stock so produced |
US2886463A (en) * | 1956-07-31 | 1959-05-12 | Allis Chalmers Mfg Co | Method of enameling mild steel |
US2956906A (en) * | 1959-06-22 | 1960-10-18 | Bethlehem Steel Corp | Enameled sheet steel |
US3055779A (en) * | 1959-03-16 | 1962-09-25 | Pfaudler Permutit Inc | Method of making enameled ductile iron |
US3265541A (en) * | 1963-09-16 | 1966-08-09 | Armco Steel Corp | Elimination of enamel fishscaling in iron and steel sheets |
US3303064A (en) * | 1963-11-29 | 1967-02-07 | Inland Steel Co | Alloy steel article and method of producing |
US3333987A (en) * | 1964-12-02 | 1967-08-01 | Inland Steel Co | Carbon-stabilized steel products and method of making the same |
US3406047A (en) * | 1966-02-07 | 1968-10-15 | Wilson Eng Co Inc Lee | Vitreous enameling steel and method of making same |
US3421951A (en) * | 1966-04-08 | 1969-01-14 | Signode Corp | Steel strapping |
US4012239A (en) * | 1972-11-21 | 1977-03-15 | Union Siserurgique du Nord et de l'Est de la France, par abreviation "USINOR" | Process for treating steel sheets for the purpose of enamelling the sheets |
US4707385A (en) * | 1984-01-11 | 1987-11-17 | Miele & Cie. Gmbh & Co. | Method for directly enameling steel parts using a single enamel coating |
EP1052310A2 (en) * | 1999-05-14 | 2000-11-15 | MANNESMANN Aktiengesellschaft | Process and apparatus for enamelling the surface of a steel object |
US20170041656A1 (en) * | 2015-08-04 | 2017-02-09 | Pandora Media, Inc. | Media channel creation based on free-form media input seeds |
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US1817080A (en) * | 1929-04-10 | 1931-08-04 | George E Howard | Transmission mechanism |
US1822064A (en) * | 1930-06-23 | 1931-09-08 | Clarence S Sorensen | Compressor |
US2081477A (en) * | 1933-04-25 | 1937-05-25 | Egersdorfer Fritz | Pump |
US2241701A (en) * | 1937-05-26 | 1941-05-13 | Waterbury Tool Co | Power transmission |
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Publication number | Priority date | Publication date | Assignee | Title |
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US1020285A (en) * | 1910-05-07 | 1912-03-12 | Reynold Janney | Rotary pump or motor. |
US1817080A (en) * | 1929-04-10 | 1931-08-04 | George E Howard | Transmission mechanism |
US1822064A (en) * | 1930-06-23 | 1931-09-08 | Clarence S Sorensen | Compressor |
US2081477A (en) * | 1933-04-25 | 1937-05-25 | Egersdorfer Fritz | Pump |
US2241701A (en) * | 1937-05-26 | 1941-05-13 | Waterbury Tool Co | Power transmission |
Cited By (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2532640A (en) * | 1946-08-24 | 1950-12-05 | Gen Motors Corp | Process of enameling |
US2594129A (en) * | 1948-04-10 | 1952-04-22 | Air Reduction | Method of preparing surfaces for tinning |
US2656285A (en) * | 1948-06-03 | 1953-10-20 | Armco Steel Corp | Production of coated soft iron and steel sheets |
US2755210A (en) * | 1949-06-25 | 1956-07-17 | Armco Steel Corp | Method of treating iron or mild steel to promote the adherence of porcelain enamel, and stock so produced |
US2677625A (en) * | 1951-02-15 | 1954-05-04 | United States Steel Corp | Flat rolled ferrous metal for vitreous enameling |
US2886463A (en) * | 1956-07-31 | 1959-05-12 | Allis Chalmers Mfg Co | Method of enameling mild steel |
US3055779A (en) * | 1959-03-16 | 1962-09-25 | Pfaudler Permutit Inc | Method of making enameled ductile iron |
US2956906A (en) * | 1959-06-22 | 1960-10-18 | Bethlehem Steel Corp | Enameled sheet steel |
US3265541A (en) * | 1963-09-16 | 1966-08-09 | Armco Steel Corp | Elimination of enamel fishscaling in iron and steel sheets |
US3303064A (en) * | 1963-11-29 | 1967-02-07 | Inland Steel Co | Alloy steel article and method of producing |
US3333987A (en) * | 1964-12-02 | 1967-08-01 | Inland Steel Co | Carbon-stabilized steel products and method of making the same |
US3406047A (en) * | 1966-02-07 | 1968-10-15 | Wilson Eng Co Inc Lee | Vitreous enameling steel and method of making same |
US3421951A (en) * | 1966-04-08 | 1969-01-14 | Signode Corp | Steel strapping |
US4012239A (en) * | 1972-11-21 | 1977-03-15 | Union Siserurgique du Nord et de l'Est de la France, par abreviation "USINOR" | Process for treating steel sheets for the purpose of enamelling the sheets |
US4707385A (en) * | 1984-01-11 | 1987-11-17 | Miele & Cie. Gmbh & Co. | Method for directly enameling steel parts using a single enamel coating |
EP1052310A2 (en) * | 1999-05-14 | 2000-11-15 | MANNESMANN Aktiengesellschaft | Process and apparatus for enamelling the surface of a steel object |
EP1052310A3 (en) * | 1999-05-14 | 2004-08-11 | EHW Thale Email GmbH | Process and apparatus for enamelling the surface of a steel object |
US20170041656A1 (en) * | 2015-08-04 | 2017-02-09 | Pandora Media, Inc. | Media channel creation based on free-form media input seeds |
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