US3406047A - Vitreous enameling steel and method of making same - Google Patents

Vitreous enameling steel and method of making same Download PDF

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Publication number
US3406047A
US3406047A US525388A US52538866A US3406047A US 3406047 A US3406047 A US 3406047A US 525388 A US525388 A US 525388A US 52538866 A US52538866 A US 52538866A US 3406047 A US3406047 A US 3406047A
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United States
Prior art keywords
steel
sheet
carbon
enameling
iron
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Expired - Lifetime
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US525388A
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English (en)
Inventor
James K Magor
Donald S Gaydosh
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Lee Wilson Engineering Co Inc
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Lee Wilson Engineering Co Inc
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Publication date
Application filed by Lee Wilson Engineering Co Inc filed Critical Lee Wilson Engineering Co Inc
Priority to US525388A priority Critical patent/US3406047A/en
Priority to GB38607/66A priority patent/GB1146724A/en
Priority to NL6615179A priority patent/NL6615179A/xx
Priority to BE693109D priority patent/BE693109A/xx
Priority to FR92968A priority patent/FR1509636A/fr
Application granted granted Critical
Publication of US3406047A publication Critical patent/US3406047A/en
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
    • C21D3/02—Extraction of non-metals
    • C21D3/04—Decarburising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0257—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding
    • 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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2221/00—Treating localised areas of an article
    • C21D2221/10—Differential treatment of inner with respect to outer regions, e.g. core and periphery, respectively
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S148/00—Metal treatment
    • Y10S148/901—Surface depleted in an alloy component, e.g. decarburized

Definitions

  • This invention relates to a new and improved sheet steel for-vitreous enameling and method of making same, and more specifically to a sheet steel suitable for single coat or direct white vitreous enameling that does not exhibit the serious loss in strength after. forming and enameling that is exhibited by presently available direct white enameling sheet steels.
  • the suitability of a steel for one coat or direct white enameling is judged primarily by its ability to accept an enamel coat that is free of visible blemishes or defects and this suitability is known to be dependent upon such processing variables as chemical composition, hot rolling practice, cold rolling practice, and annealing practice. Correlations among these variables and freedom from observable defects in overlying enamel coats have long been sought.
  • the visible defectsin enamel coats that are caused by evolved gases may be classified into two categories, namely, (l) delayed or low-temperature defects, such as fish scales, shiners, pop-offs, and bloats, and (2) high-temperature defects, such as blisters, pinholes, pits, black specks, and copperheads.
  • the delayed defects appear after the enameled steel has been fired, occurring during the cooling after the glass has become rigid, or even long after the steel-enamel unit has been cooled to room temperature.
  • the source of this trouble is known to be hydrogen dissolved or trapped in the steel which is liberated in the steel-enamel elevated temperature reaction and subsequently precipitated at the steel-enamel interface with resulting rupturing of the enamel glass.
  • the high temperature defects are formed during the time of firing and result from a gas induced boiling of the enamel, the so called primary boiling phenomenon. It is generally agreed that the evolution of the carbon oxides, CO and CO during the first firing of the enamel causes primary boiling, and that these carbon oxides are formed by oxidation of the carbon in or adjacent to the sheet steel surfaces.
  • Sheet steels (the term sheet being used inclusively herein to refer to thin steel either in elongated strip or separate flat sheet form) in widespreaduse for many decades in the enameling trade for the two coat practice are principally low metalloid rimmed steel (commonly referred to as enameling iron, enameling steel, or ingot iron and specifically produced for vitreous enameling applications) and rimmed cold rolled steel, a general purpose-low carbon sheet with inclusion free surfaces produced for general usage in the stamping and forming trades and diverted to enameling usage because of its non- Durham, N.C., and Donald S. Gaydosh,
  • a 1948 describes the surface decarburization by wet hydrogent annealing of formed sheet steel articles preceding the application of a light colored finish coat of porcelain enamel.
  • the articles are in substantially their final shape at the time of annealing.
  • the superficial surface decarburizing treatment proposed by Eckel et al. has not yielded a satisfactory direct white enameling steel despite diligent, prolonged, and exhaustive testing programs, both laboratory and commercial; and the use of continuous annealing techniques in steel mill processing to ob tain superficial decarburization also proved to be unsuitable for the production of non-primary boiling direct white enameling sheet steels.
  • a rimmed steel of typical analysis as follows:
  • Carbon percent 0.050.10 Manganese do 0.12-0.45 Phosphorus percent maximum 0.010 Sulphur do 0.025 Silicon do 0.010 Copper do 0.10 Iron Balance is processed by producing a hot rolled strip or band on a continuous hot strip mill, pickling, cold reducing the hot band to the desired thickness, open-coil decarburizing at 1300 F. to reduce carbon uniformly throughout full sheet thickness to 0.005% max., and then temper rolling if desired.
  • the decarburizing atmosphere may be hydrogen, hydrogen-nitrogen or DEOX type gas moistened with water at the annealing temperature to obtain an environment oxidizing to carbon but non-oxidizing to iron.
  • Typical tensile properties and hardness of such a through decarburized open coil of steel strip annealed product are:
  • the desired product i.e., a direct white enameled sheet with a minimum yield strength in the range 22,000 to 25,000 pounds per square inch after enamel firing, regardless of the amount of prestraining, had not been developed prior to the present invention and accordingly it is an object of our invention to provide a sheet steel product, and method of making same, that will exhibit the desirable direct white enameling characteristics of through decarburized rimmed steel and that will, at the same time, exhibit after forming and enamel firing, a yield strength in the range common to normal non-decarburized low carbon rimmed steel.
  • FIGURE 1 is a partial iron-iron carbide equilibrium diagram illustrating the decarburization reaction which occurs in carrying out our process.
  • FIGURE 2 is a chart showing the carbon content of a cross section of a steel sheet, from the center to one outer surface thereof, that has been processed in accordance with our invention.
  • FIGURE 3 illustrates the micro-structure of the cross section of a steel sheet in accordance with our invention after two phase gamma-alpha decarburization has been completed.
  • FIGURE 4 is a cross sectional view similar to FIGURE 3 but illustrating the micro-structure of the sheet after it has been cold rolled to the final thickness.
  • FIGURE 5 is a cross sectional view similar to FIG- URES 3 and 4 but illustrating the micro-structure of the sheet illustrated in FIGURE 4 after it has been subjected to sub-critical annealing and temper rolling.
  • the sheet steel product of this invention is attained by the practice of a two phase decarburization (from the gamma-iron to the alpha-iron condition) as is illustrated in FIGURES l and 2.
  • a coil of strip steel suitably opened so that all surfaces thereof are exposed to the treating atmosphere, is heated in an enclosed furnace chamber or retort by a circulating gaseous atmosphere to the minimum temperature at which the structure of the steel is substantially entirely gamma-iron.
  • the particular temperature required is dictated by the chemical composition of the steel, and for the non-alloyed 4 plain carbon steels, is dependent on the carbon and manganese content.
  • a temperature of 1525 F. provides the required temperature environment wherein the structure of the steel is a solid solution of carbon in gamma-iron.
  • the alphairon crystals or grains grow inwardly from both outer surfaces of the sheet replacing the previously existing original gamma-iron crystals or grains.
  • the gamma-iron and the alpha-iron phases, or structures, or crystals coexist in equilibrium at the moving decarburization front which is illustrated by line a-b in FIGURE 2.
  • the right hand vertical dot and dash line 10 represents the center of the cross section of the sheet and the left hand vertical line 11 represents one outer surface of the sheet.
  • the line 12 charts the carbon content of the steel against the distance inwardly from the outer surface toward the center, and it will be seen that, under the conditions of FIGURE 2, decarburization from the original .24% carbon down to less than .005% carbon has proceeded from the outer surface 11 inwardly a little less than one-half of the distance 'to the center 10 of the cross section of the sheet, or a little less than one-fourth the thickness of the sheet.
  • the vertical portion of line 12 (FIGURE 2) between the essentially carbon free outer alpha-iron zone and the high carbon gamma-iron inner center zone or core, moves inwardly from the surface of the sheet during this decarburizing treatment at a calculable rate as the carbon is removed from the sheet by outward lattice diffusion and subsequent oxidation at the sheet surface. It will be understood that a similar and substantially equal decarburization will simultaneously occur from the other surface of the sheet inwardly toward the center to produce a similar substantially carbon free outer alpha-iron zone on the other side of the sheet.
  • This two phase gamma-alpha decarburization pro-' cedure is continued until a cross sectional micro structure of the sheet as illustrated in FIGURE 3 is obtained.
  • the sharp demarcation line or boundary between the decarburized outer zones and the high carbon inner ferrite-carbide zone or core is characteristic of our gammaalpha decarburizing practice which allows center core carbon to be retained at its original value while the surfaces, and the sub-surface zones for a predetermined degree inwardly, are rendered substantially carbon free.
  • the coil of steel is cold reduced to the required final thickness, the micro structure of the cross section of the so cold reduced sheet being shown in FIGURE 4.
  • Relief of the coid rolling stresses is then preferably effected by a sub-critical anneal in the temperature range of 1150 F. to 1275 F.
  • the resulting stress relieved product may then be temper rolled to meet specific forming requirements and the cross sectional micro structure of the fully processed sheet is illustrated in FIGURE 5.
  • demarcation lines a, b, between the outer zones and the center zone remain clearly defined in the sheet under the three conditions illustrated in FIGURES 3, 4 and 5
  • the following procedure has been used in the processing, according to this invention, of a hot rolled and pickled steel.
  • the two phase gamma-alpha decarburizing treatment described above was carried out according to the following schedule:
  • the coil was cold-reduced from the hot rolled thickness of 0.095" to 0.036" (20 gage) and then sub-critically annealed (as an open coil) for 3 hours at 1275 F. in dry 20% hydrogen- 80% nitrogen gas atmosphere.
  • the two phase alpha-gamma decarburizing step be carried on for a time sufficient to decarburize the sheet inwardly from each surface thereof for a distance at least 25% of the strip thickness. It is also preferred that the decarburization be terminated when the undecarburized center core portion has a thickness of not less than about 25 of the strip thickness.
  • our improved process may be utilized for the production of enameling steel from sheet of other carbon contents and that the specific times, temperatures, gas compositions, etc. referred to herein may be modified from those specifically mentioned. Accordingly we do not wish to be limited to the specific procedures and products herein illustrated and described but claim as our invention all embodiments coming within the scope of the appended claims.
  • the method of producing steel sheet for vitreous enameling which comprises subjecting a low carbon steel sheet having an initial carbon content of not less than of about .20% to a two-phase gamma-alpha decarburization step by heating the sheet to the minimum temperature at which the structure of the steel is substantially entirely gamma-iron, subject the sheet, while maintaining said temperature, to a decarburizing atmosphere, maintaining the sheet in said atmosphere at said temperature until outer zones of alpha-iron having a carbon content of not more than about 0.006% are produced extending inwardly on each side of the sheet for at least about 25 but not more than about 37% of the sheet thickness, and subsequently subjecting thhe sheet to cold reduction followed by sub-critical annealing.
  • a steel sheet for vitreous enameling produced by the process defined in claim 1.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
US525388A 1966-02-07 1966-02-07 Vitreous enameling steel and method of making same Expired - Lifetime US3406047A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US525388A US3406047A (en) 1966-02-07 1966-02-07 Vitreous enameling steel and method of making same
GB38607/66A GB1146724A (en) 1966-02-07 1966-08-30 Vitreous enameling steel and method of making same
NL6615179A NL6615179A (2) 1966-02-07 1966-10-27
BE693109D BE693109A (2) 1966-02-07 1967-01-24
FR92968A FR1509636A (fr) 1966-02-07 1967-01-30 Acier destiné à l'émaillage vitreux et son procédé de fabrication

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US525388A US3406047A (en) 1966-02-07 1966-02-07 Vitreous enameling steel and method of making same

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US (1) US3406047A (2)
BE (1) BE693109A (2)
FR (1) FR1509636A (2)
GB (1) GB1146724A (2)
NL (1) NL6615179A (2)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3850014A (en) * 1973-04-09 1974-11-26 Best Lock Corp Anti-shatter padlock shackle, and process
US3865638A (en) * 1973-11-23 1975-02-11 Gen Motors Corp Plastically deformed hardened steel parts and method of forming same
US3891820A (en) * 1971-08-25 1975-06-24 Siemens Ag Weld-plating of steel
US4069069A (en) * 1976-08-02 1978-01-17 United States Steel Corporation Method for improving the surface quality of annealed steel strip
US4326899A (en) * 1979-09-17 1982-04-27 United States Steel Corporation Method of continuous annealing low-carbon electrical sheet steel and duplex product produced thereby
US4677031A (en) * 1985-04-10 1987-06-30 Nippon Gakki Seizo Kabushiki Kaisha Conductive plate
EP1052310A3 (de) * 1999-05-14 2004-08-11 EHW Thale Email GmbH Verfahren und Vorrichtung zur Emaillierung der Oberfläche eines Stahlkörpers

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2835446A1 (de) * 1978-08-12 1980-02-14 Kloeckner Werke Ag Verfahren zur herstellung eines stahles fuer die direktweissemaillierung

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2455331A (en) * 1944-10-24 1948-11-30 Joseph C Eckel Method of enameling
US3152020A (en) * 1961-05-11 1964-10-06 United States Steel Corp Fracture tough ultra high strength steel sheets
US3323953A (en) * 1964-09-15 1967-06-06 United States Steel Corp Method of treating steel and novel product

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2455331A (en) * 1944-10-24 1948-11-30 Joseph C Eckel Method of enameling
US3152020A (en) * 1961-05-11 1964-10-06 United States Steel Corp Fracture tough ultra high strength steel sheets
US3323953A (en) * 1964-09-15 1967-06-06 United States Steel Corp Method of treating steel and novel product

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3891820A (en) * 1971-08-25 1975-06-24 Siemens Ag Weld-plating of steel
US3850014A (en) * 1973-04-09 1974-11-26 Best Lock Corp Anti-shatter padlock shackle, and process
US3865638A (en) * 1973-11-23 1975-02-11 Gen Motors Corp Plastically deformed hardened steel parts and method of forming same
US4069069A (en) * 1976-08-02 1978-01-17 United States Steel Corporation Method for improving the surface quality of annealed steel strip
US4326899A (en) * 1979-09-17 1982-04-27 United States Steel Corporation Method of continuous annealing low-carbon electrical sheet steel and duplex product produced thereby
US4677031A (en) * 1985-04-10 1987-06-30 Nippon Gakki Seizo Kabushiki Kaisha Conductive plate
EP1052310A3 (de) * 1999-05-14 2004-08-11 EHW Thale Email GmbH Verfahren und Vorrichtung zur Emaillierung der Oberfläche eines Stahlkörpers

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Publication number Publication date
FR1509636A (fr) 1968-01-12
BE693109A (2) 1967-07-24
NL6615179A (2) 1967-08-08
GB1146724A (en) 1969-03-26

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