US3827922A - Method of retarding metal scale formation with carbon-containing mgo-b2o3 coatings - Google Patents
Method of retarding metal scale formation with carbon-containing mgo-b2o3 coatings Download PDFInfo
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- US3827922A US3827922A US00291849A US29184972A US3827922A US 3827922 A US3827922 A US 3827922A US 00291849 A US00291849 A US 00291849A US 29184972 A US29184972 A US 29184972A US 3827922 A US3827922 A US 3827922A
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- 229910052799 carbon Inorganic materials 0.000 title abstract description 7
- 239000002184 metal Substances 0.000 title abstract description 7
- 229910052751 metal Inorganic materials 0.000 title abstract description 7
- 230000000979 retarding effect Effects 0.000 title abstract description 7
- 238000000576 coating method Methods 0.000 title description 32
- 238000000034 method Methods 0.000 title description 19
- 230000015572 biosynthetic process Effects 0.000 title description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title description 5
- 239000000203 mixture Substances 0.000 abstract description 12
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 abstract description 10
- 230000003647 oxidation Effects 0.000 abstract description 8
- 238000007254 oxidation reaction Methods 0.000 abstract description 8
- 239000008199 coating composition Substances 0.000 abstract description 5
- 239000000725 suspension Substances 0.000 abstract description 4
- 239000002002 slurry Substances 0.000 abstract description 3
- 239000006185 dispersion Substances 0.000 abstract description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 50
- 239000000395 magnesium oxide Substances 0.000 description 26
- 239000011248 coating agent Substances 0.000 description 24
- 235000012245 magnesium oxide Nutrition 0.000 description 24
- 239000007787 solid Substances 0.000 description 19
- 229910000831 Steel Inorganic materials 0.000 description 9
- 238000010438 heat treatment Methods 0.000 description 9
- 239000010959 steel Substances 0.000 description 9
- 239000003981 vehicle Substances 0.000 description 9
- 239000011230 binding agent Substances 0.000 description 8
- 239000002245 particle Substances 0.000 description 8
- 238000007792 addition Methods 0.000 description 7
- 239000010425 asbestos Substances 0.000 description 7
- 238000005755 formation reaction Methods 0.000 description 7
- 229910052895 riebeckite Inorganic materials 0.000 description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical group [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
- 239000000571 coke Substances 0.000 description 5
- 230000001681 protective effect Effects 0.000 description 5
- 238000005507 spraying Methods 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- 239000004615 ingredient Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 238000009472 formulation Methods 0.000 description 3
- 238000005098 hot rolling Methods 0.000 description 3
- 150000004760 silicates Chemical class 0.000 description 3
- 229920001800 Shellac Polymers 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000004208 shellac Substances 0.000 description 2
- ZLGIYFNHBLSMPS-ATJNOEHPSA-N shellac Chemical compound OCCCCCC(O)C(O)CCCCCCCC(O)=O.C1C23[C@H](C(O)=O)CCC2[C@](C)(CO)[C@@H]1C(C(O)=O)=C[C@@H]3O ZLGIYFNHBLSMPS-ATJNOEHPSA-N 0.000 description 2
- 229940113147 shellac Drugs 0.000 description 2
- 235000013874 shellac Nutrition 0.000 description 2
- 239000002562 thickening agent Substances 0.000 description 2
- 230000004580 weight loss Effects 0.000 description 2
- 229920000663 Hydroxyethyl cellulose Polymers 0.000 description 1
- 239000004354 Hydroxyethyl cellulose Substances 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000008135 aqueous vehicle Substances 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 150000001642 boronic acid derivatives Chemical class 0.000 description 1
- 229920003064 carboxyethyl cellulose Polymers 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004590 computer program Methods 0.000 description 1
- 239000013068 control sample Substances 0.000 description 1
- 238000004320 controlled atmosphere Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- -1 e.g. Substances 0.000 description 1
- QHZOMAXECYYXGP-UHFFFAOYSA-N ethene;prop-2-enoic acid Chemical compound C=C.OC(=O)C=C QHZOMAXECYYXGP-UHFFFAOYSA-N 0.000 description 1
- 229920006242 ethylene acrylic acid copolymer Polymers 0.000 description 1
- 229920006226 ethylene-acrylic acid Polymers 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000002529 flux (metallurgy) Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 235000019447 hydroxyethyl cellulose Nutrition 0.000 description 1
- 239000006233 lamp black Substances 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 235000014380 magnesium carbonate Nutrition 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
Images
Classifications
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/68—Temporary coatings or embedding materials applied before or during heat treatment
- C21D1/70—Temporary coatings or embedding materials applied before or during heat treatment while heating or quenching
-
- 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
- C23C24/00—Coating starting from inorganic powder
-
- 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
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/27—Web or sheet containing structurally defined element or component, the element or component having a specified weight per unit area [e.g., gms/sq cm, lbs/sq ft, etc.]
- Y10T428/273—Web or sheet containing structurally defined element or component, the element or component having a specified weight per unit area [e.g., gms/sq cm, lbs/sq ft, etc.] of coating
Definitions
- the composition is admixed with a suitable vehicle and is applied to the metal surface in the form of a dispersion, suspension or as a slurry.
- This invention is directed to a composition for reducing oxidation and scaling of ferrous articles during high temperature heat treatments.
- the oxida tion and growth of scale on the surface thereof, and its subsequent removal prior to hot rolling results in a loss of metal that can be quite substantial.
- the economic loss is even more significant if the article contains appreciable amounts of expensive alloying additions.
- additional problems are encountered.
- the nickel-bearing grades develop scales that are abnormally tenacious and extremely ditficult to remove. If such scale is rolled-in during the hot-rolling procedure, the removal of the resulting inclusions results in pits which must be subsequently removed by grinding. This results in even further material loss as Well as significantly increased processing cost.
- the figure is a graph depicting the protective value of a steel article utilizing the composition of this invention in comparison to that of bare steel and one covered with asbestos.
- compositions of this invention are admixed in a suitable vehicle and applied in any convenient manner.
- they may be admixed in the form of slurry or they may be suspended by the use of a suitable dispersant.
- a suitable dispersant A number of particularly e'ifective vehicles are reported in the examples below.
- a computer program was written to process the experimental data obtained from each coating tested, and to compare these data with that obtained from oxidation of bare and asbestos covered, 3 Ni steel, heated in air at 1300 C. for 1, 2, 4, and 6 hours.
- the weight loss for the asbestos covered specimens was divided by the weight loss in the particular test and multiplied by 100. This produced an empirical graduated system of protection values in which asbestos is rated at and bare steel at 67 (see the figure).
- the protection numbers for the 1, 2, 4 and 6 hour exposures of each coating formulation were added and divided by 4 to provide an average protection value.
- Such coatings are normally composed of refractory oxides, e.g. alumina, silica, magnesia and fluxes, e.g. silicates, borates, phosphates in combination with a variety of other ingredients.
- refractory oxides e.g. alumina, silica, magnesia and fluxes, e.g. silicates, borates, phosphates in combination with a variety of other ingredients.
- protective sheets of refractory materials e.g., asbestos, have been employed to retard oxidation during heating. These expedients have been useful in many instances.
- these refractory coat- The superiority of the B O -periclase coatings, especially at exposure periods greater than about two hours is clearly evident.
- the borate should be supplied either as (anhydrous) B 0 or as boric acid.
- C in any amount up to about 15% will provide enhanced protection, it is preferable to employ greater than about 6%.
- Any well known source of finely divided C e.g. lamp black, coke breeze, is acceptable.
- the C burns out of the coating. Therefore, to prevent undue porosity, C in excess of about 12 percent (solids fraction) or particle sizes in excess of 60 mesh should preferably be avoided. Maxiumum benefit is achieved if the particle size is finer than 200 mesh.
- TiO additions within the range of about 11 to about 17% TiO is especially marked for short (e.g. less than three hours) annealing times. For periods of four hours and greater the TiO;, containing coatings are about equal in protection value to those in which no TiO is employed.
- compositions of this invention may therefore be formulated in the following manner.
- the MgO content of the solids fraction may range from about 65 to 80 percent. Significantly lower values of TiO- e.g. 1 to 8 percent, may be detrimental to the basic (MgO-B O -C) coating. When TiO within the preferred range is not employed, the MgO content of the solids fraction should always be greater than about 75 percent, and preferably greater than about 82 percent (depending somewhat on the concentration of the other ingredients).
- MgO magnesite and precipitated magnesia
- the denser grained periclase has been found to provide significantly enhanced protection. Because of the above-mentioned detrimental effect of SiO' the periclase should be as pure as possible. In all cases, the SiO content should be below 2 percent and preferably less than 1 percent. It is desirable that the particles be finer than 60 mesh, especially if the coating is to be sprayed (as opposed to painting). For some unknown reason, if the periclase particle sizes are within the very narrow range of 120-140 mesh, the protection afforded is markedly increased.
- borate content is less than about 2 percent in the solids fraction, there is a loss of coating adherence at high temperatures and the protection afforded is inferior to that of asbestos.
- the vehicle itself, may be either organic or water base.
- a water-base vehicle may be preferable.
- solids content may vary from as low as 10% to as high as a more limited range, e.g. 40-70% is preferable, especially if spraying is employed.
- a solids content below about 40% excessive heating would be required to evaporate the vehicle, while a solids content in excess of 70% could be difficult to spray.
- the suspension of solids in water requires a thickener to increase the viscosity and a dispersant to keep the particles in suspension.
- a binder is required to provide green strength (low temperature cohesion) for the coating.
- the coating in some instances tended to pull away from the substrate, even though the binder provided excellent cohesion of the particles.
- the vehicle-binder system consisted of the following:
- the coating should be applied in a thickness ranging from at least about 0.04 gm./cm. to no greater than about 0.25 gm./cm. Below 0.04 gm./cm. protection is totally insufficient. To insure adequate protection for a period greater than about three hours, it is preferable to employ a coating of at least about 0.08 gm./cm. in thickness.
- the upper limit of 0.25 gm./ cm. is dictated by the tendency of thicker coatings to spell-off due to thermal shock. To further minimize this tendency, a more preferred upper limit is about 0.15 grn./cm. in thickness.
- a coating composition consisting essentially of from 40 to 70% solids in a suitable vehicle, wherein said solids consist'essential- 1y of (a) 75 to 95 percent MgO,
- a coating composition consisting essentially of from 40 to about percent solids in a suitable vehicle, wherein said solids consist essentially of (a) 65 to percent MgO,
- ferrous article is a steel containing Ni as a purposeful alloy addition and said heat-treatment is conducted at temperatures in excess of about 2300 F. for a period less than about 3 hours.
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- Engineering & Computer Science (AREA)
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- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
- Paints Or Removers (AREA)
- Chemical Treatment Of Metals (AREA)
- Fireproofing Substances (AREA)
Abstract
A COATING COMPOSITION CONTAINING 75-95% MGO, 210% B2O3 AND 0-15% C, WHICH IS EFFECTIVE IN RETARDING OXIDATION OF FERROUS METAL ARTICLES, ESPECIALLY AT TEMPERATURES IN EXCESS OF 2150* F. ADDITIONAL PROTECTION IS ACHIEVED WHEN ABOUT 11-17% TIO2 IS SUBSTITUTED FOR ABOUT THE SAME AMOUNT OF MGO. THE COMPOSITION IS ADMIXED WITH A SUITABLE VEHICLE AND IS APPLIED TO THE METAL SURFACE IN THE FORM OF A DISPERSION, SUSPENSION OR AS A SLURRY.
Description
w.,! sosss E AL 3,827,932 METHOD OF RETARDING METAL SCALE FORMATION WITH CA BON'CONTAINING m,0-a, o, COATINGS Filed Sept. 25, 1972 COATED WITH FORMULATION 0F lNl/E/VT/O/V BARE STEEL HOURS AT l3000 United States Patent METHOD OF RETARDING METAL SCALE FORMA- TION WITH CARBON-CONTAINING MgO-B O COATINGS William E. Boggs, Franklin Borough, William A. Underman, North Versailles Township, Allegheny County, and Roland B. Snow, Mount Lebanon, Pa., assignors to United States Steel Corporation Filed Sept. 25, 1972, Ser. No. 291,849 Int. Cl. B23k 35/24 US. Cl. 14827 Claims ABSTRACT OF THE DISCLOSURE A coating composition containing 75-95% MgO, 2- 10% B 0 and 015% C, which is effective in retarding oxidation of ferrous metal articles, especially at temperatures in excess of 2150 F. Additional protection is achieved when about 11-17% T10 is substituted for about the same amount of MgO. The composition is admixed with a suitable vehicle and is applied to the metal surface in the form of a dispersion, suspension or as a slurry.
This invention is directed to a composition for reducing oxidation and scaling of ferrous articles during high temperature heat treatments.
During the heat treating of ferrous articles, the oxida tion and growth of scale on the surface thereof, and its subsequent removal prior to hot rolling, results in a loss of metal that can be quite substantial. The economic loss is even more significant if the article contains appreciable amounts of expensive alloying additions. In certain of the alloy grades, additional problems are encountered. Thus, for example, the nickel-bearing grades develop scales that are abnormally tenacious and extremely ditficult to remove. If such scale is rolled-in during the hot-rolling procedure, the removal of the resulting inclusions results in pits which must be subsequently removed by grinding. This results in even further material loss as Well as significantly increased processing cost.
The art has employed several dilferent methods to decrease such scaling. The use of inert or reducing atmospheres, While effective in many cases, has not been widely employed for large slabs or billets, due to the marked increase in operating cost and the significant capital investment required. Equally important, it is often necessary (as in hot rolling) to remove the slab from the controlled atmosphere furnace while still at elevated temperature. Thus, during such a procedure, excessive oxidation will nevertheless occur on exposure to the atmosphere. To overcome the well known deficiencies of controlled atings, can in themselves, contribute to the formation of scale pits. It has been discovered that in many instances, such as when the temperature is in excess of about 2150 F that such pits form by reaction of the iron oxide with the silicates in the coating. In addition to such pitting, a more generalized and accelerated attack occurs in the presence of silicates, after about three hours at temperatures above 2300 F. Because of this discovered difiiculty, associated with conventional silicate containing coatings, a new coating was developed that contained essentially no siliceous materials. The basic coating, which contains from to MgO, 12-10% B 0 and 0 to 15% C (all percentages by weight) is not only more effective in providing oxidation resistance at elevated temperatures, but also enhances the formation of a scale which more easily removed. When about 11% to about 17% TiO is substituted for about an equivalent weight percent of MgO, corrosion protection is further enhanced; especially for short time (e.g. less than three hours) heat treatments.
Further objects and advantages of the invention will be more apparent from the following description, taken in conjunction with the appended claims and the drawing, in which:
The figure is a graph depicting the protective value of a steel article utilizing the composition of this invention in comparison to that of bare steel and one covered with asbestos.
The compositions of this invention are admixed in a suitable vehicle and applied in any convenient manner. Thus, they may be admixed in the form of slurry or they may be suspended by the use of a suitable dispersant. A number of particularly e'ifective vehicles are reported in the examples below.
A computer program was written to process the experimental data obtained from each coating tested, and to compare these data with that obtained from oxidation of bare and asbestos covered, 3 Ni steel, heated in air at 1300 C. for 1, 2, 4, and 6 hours. In order to obtain a normalized protection value, the weight loss for the asbestos covered specimens (taken as a standard) was divided by the weight loss in the particular test and multiplied by 100. This produced an empirical graduated system of protection values in which asbestos is rated at and bare steel at 67 (see the figure). To simplify comparison, the protection numbers for the 1, 2, 4 and 6 hour exposures of each coating formulation were added and divided by 4 to provide an average protection value.
The protection values of a series of B O -periclase formulations made with a vehicle-binder system consisting of 30 ml. shellac in 180 ml. ethanol are shown in Table I.
Specimen completely oxidized.
mospheres, a number of ceramic type coatings have been proposed. Such coatings are normally composed of refractory oxides, e.g. alumina, silica, magnesia and fluxes, e.g. silicates, borates, phosphates in combination with a variety of other ingredients. Similarly, protective sheets of refractory materials, e.g., asbestos, have been employed to retard oxidation during heating. These expedients have been useful in many instances. However, it has now been found that, under certain conditions, these refractory coat- The superiority of the B O -periclase coatings, especially at exposure periods greater than about two hours is clearly evident. Nevertheless, it was determined that further benefits could be achieved by the addition of up to about 15% finely divided carbon. Apparently, the slower burning carbon provides additional protection during the burn-out of the organic binder. The enhanced protection achieved by the addition of finely divided carbon (in this case, coke breeze) is shown in Table II, in which the same ethanol shellac, vehicle-binder system was employed.
tends to increase the scaling rate in a manner somewhat analogous to that of SiO A particularly desirable range TABLE II Composition of solids, Average percent Protection value (asbestos=100) coating Coating weight, number B203 MgO Coke 1 hr. 2 hr. 4 hr. 6 hr. Avg. g./em. I
The superiority of the instant coatings is believed to be due to the formation of magnesio-wiistite solid solutions, having more protective properties than normal scale. Further studies were undertaken to determine if the introduction of a third refractory oxide might further limit the solubility of FeO in MgO. Of a number of such oxides which were tried, Ti0 alone, produced an improvement in the scale retardation of the basic (MgO-B O -C) coating. In the experiments reported in Table III, 200 grams of solids mixture were suspended in an aqueous vehicle containing 100 ml. of water, 1 gram of hydroxyethyl cellulose, 13 ml. of concentrated NH OH and 10 ml. of 25% ethylene acrylic acid copolymer. The results reported for the control sample are the average of five utilizes from about 5.0 to about 7.5 percent B 0 Since it is preferable to avoid the addition of extraneous cations, the borate should be supplied either as (anhydrous) B 0 or as boric acid.
Although C in any amount up to about 15% will provide enhanced protection, it is preferable to employ greater than about 6%. Any well known source of finely divided C, e.g. lamp black, coke breeze, is acceptable. During the initial portion of the annealing treatment, the C burns out of the coating. Therefore, to prevent undue porosity, C in excess of about 12 percent (solids fraction) or particle sizes in excess of 60 mesh should preferably be avoided. Maxiumum benefit is achieved if the particle size is finer than 200 mesh.
Depending on the method of application and the heattreating parameters, a variety of vehicle-binder formula- TABLE III Composition of solids, percent 1 Protection value Average coa ng Coating number B203 Coke MgO T10 1 hr. 2 hr. 4 hr. 6 hr. Avg. weight 1 Total solids content, in all cases, equaled 200 grams.
The effectiveness of TiO additions within the range of about 11 to about 17% TiO is especially marked for short (e.g. less than three hours) annealing times. For periods of four hours and greater the TiO;, containing coatings are about equal in protection value to those in which no TiO is employed.
The compositions of this invention may therefore be formulated in the following manner.
When Ti0 within the preferred range of about 11 to about 17 percent is employed, the MgO content of the solids fraction may range from about 65 to 80 percent. Significantly lower values of TiO- e.g. 1 to 8 percent, may be detrimental to the basic (MgO-B O -C) coating. When TiO within the preferred range is not employed, the MgO content of the solids fraction should always be greater than about 75 percent, and preferably greater than about 82 percent (depending somewhat on the concentration of the other ingredients).
Various forms of MgO, such as magnesite and precipitated magnesia will provide some protection. However, the denser grained periclase has been found to provide significantly enhanced protection. Because of the above-mentioned detrimental effect of SiO' the periclase should be as pure as possible. In all cases, the SiO content should be below 2 percent and preferably less than 1 percent. It is desirable that the particles be finer than 60 mesh, especially if the coating is to be sprayed (as opposed to painting). For some unknown reason, if the periclase particle sizes are within the very narrow range of 120-140 mesh, the protection afforded is markedly increased.
If the borate content is less than about 2 percent in the solids fraction, there is a loss of coating adherence at high temperatures and the protection afforded is inferior to that of asbestos. However, no more than about 10 percent borate should be employed, since this ingredient tions may be employed. The vehicle, itself, may be either organic or water base. For safety purposes, a water-base vehicle may be preferable. While solids content may vary from as low as 10% to as high as a more limited range, e.g. 40-70% is preferable, especially if spraying is employed. Thus, with a solids content below about 40%, excessive heating would be required to evaporate the vehicle, while a solids content in excess of 70% could be difficult to spray. The suspension of solids in water requires a thickener to increase the viscosity and a dispersant to keep the particles in suspension. A binder is required to provide green strength (low temperature cohesion) for the coating. However, when the total organic mattter (thickener plus binder) exceeded about two percent of the total weight of the solids, the coating in some instances tended to pull away from the substrate, even though the binder provided excellent cohesion of the particles.
A specific example employing a preferred water base formulation (i.e., that described in the figure) is given below.
The vehicle-binder system consisted of the following:
(1) ml. H 0
(2) 1 gm. carboxy ethyl cellulose (3) 13 ml. NH OH (4) 10 ml.-24% ethylene acrylic acid polymer The ingredients are added and mixed in the order given, to maintain the effectiveness of the copolymer. The solids that actually form the coating are mixed and blended separately, in the following proportions 178 gm. periclase-60 mesh 10 gm. B 0 12 gm. Fine Coke Breeze (Petroleum) The solids fraction is then added to the water-base vehicle, with stirring, and is sprayed on the steel slab to be protected.
Regardless of the vehicle-system and the method of application, the coating should be applied in a thickness ranging from at least about 0.04 gm./cm. to no greater than about 0.25 gm./cm. Below 0.04 gm./cm. protection is totally insufficient. To insure adequate protection for a period greater than about three hours, it is preferable to employ a coating of at least about 0.08 gm./cm. in thickness. The upper limit of 0.25 gm./ cm. is dictated by the tendency of thicker coatings to spell-off due to thermal shock. To further minimize this tendency, a more preferred upper limit is about 0.15 grn./cm. in thickness.
We claim:
1. In the method for retarding the formation of scale during heat treatment of ferrous articles at temperatures in excess of about 2150 F., comprising the application of a protective refractory coating to at least one surface of said article, the improvement which comprises,
spraying on said ferrous articles a coating composition consisting essentially of from 40 to 70% solids in a suitable vehicle, wherein said solids consist'essential- 1y of (a) 75 to 95 percent MgO,
(b) 2 to 10 percent B (c) about 6 to about 12 percent C, and
(d) less than 2 percent SiO said spraying being conducted to provide a coating thickness of from about 0.04 to about 0.25 gm./ cm. of article surface.
2. The method of claim 1, in which said heat treatment is conducted for a period in excess of one hour in duration, and wherein said MgO is periclase and substantially all of said periclase and said C is of a particle size finer than 60 mesh.
3. The method of claim 2, wherein said periclase is greater than about 82 percent, said B 0 is from about to about 7.5 percent, and said SiO is less than about 1 percent.
4. The method of claim 3, wherein said coating is applied in thickness of from about 0.08 to about 0.15 gm./cm. of article surface.
5. The method of claim 4, wherein said ferrous article is a steel containing Ni as a purposeful alloy addition, and said heat-treatment is conducted at temperatures in excess of about 2300 F. for a period greater than about 3 hours.
6. In the method for retarding the formation of scale during heat treatment of ferrous articles at temperatures in excess of about 2150 F., comprising the application of a protective refractory coating to at least one surface of said article, the improvement which comprises,
spraying on said ferrous articles a coating composition consisting essentially of from 40 to about percent solids in a suitable vehicle, wherein said solids consist essentially of (a) 65 to percent MgO,
(b) 2 to 10 percent B 0 (c) 11 to 17 percent TiO (d) 6 to 12 percent C, and
(e) less than 2 percent SiO said spraying being conducted to provide a coating thickness of from about 0.04 to about 0.25 gm./
cm. of article surface.
7. The method of claim 6, wherein said MgO is periclase, and substantially all said periclase and said C is of a particle size finer than 60 mesh.
8. The method of claim 7, wherein said B 0 is within the range of about 5 to about 7.5 percent, and said SiO, is less than 1 percent.
9. The method of claim 8, wherein said coating is applied in a thickness of from about 0.08 to about 0.15 gm./cm. of article surface.
10. The method of claim 9, wherein said ferrous article is a steel containing Ni as a purposeful alloy addition and said heat-treatment is conducted at temperatures in excess of about 2300 F. for a period less than about 3 hours.
References Cited UNITED STATES PATENTS 3,583,887 6/19'71 Steger et al 148-27 3,700,506 10/1972 Tanaka et a1 148--113 3,484,306 12/1969 Mueller 14827 3,037,878 6/1962 Cowles et al 14813.1 3,178,321 4/1965 Satterfield 148l3.1
WALTER R. SAT'I'ERFIELD, Primary Examiner U.S. Cl. X.R.
, UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3827'922 Dated August 197a Inventor(s) William Bogg's et a1.
It is certified that error appears 'in the above-identified patent .and that said Letters Patentare hereby corrected as shown below:
, E- I, under't'he heading "Average coating I g./Cm line 2, "0.0167" I I should be 1.- 0.1 4;;
I Signed and sealed this 19th day of November 1974.
(SEAL) Attest:
McCOY M. GIBSON JR. C MARSHALL DANN- Arresting Officer Commissioner of Patents FORM (w'sg) uscoMM-oc eos'le-peo I i .5. GOVERNMENT PRINTING OFFICE 2 9'9 0-366-334,
Priority Applications (10)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US00291849A US3827922A (en) | 1972-09-25 | 1972-09-25 | Method of retarding metal scale formation with carbon-containing mgo-b2o3 coatings |
GB4355573A GB1451235A (en) | 1972-09-25 | 1973-09-17 | Temporary scale retardant coatings |
BE135730A BE804948A (en) | 1972-09-25 | 1973-09-17 | TEMPORARY COATINGS DELAYING OXIDATION |
DE19732347728 DE2347728A1 (en) | 1972-09-25 | 1973-09-21 | COATING DIMENSIONS FOR DELAYING SCALE FORMATION AT TEMPERATURES ABOVE 1177 DEGREES C. |
IT69810/73A IT999582B (en) | 1972-09-25 | 1973-09-24 | COMPOSITION AND PROCEDURE TO REDUCE THE OXIDATION OF FERROUS ARTICLES DURING HEAT TREATMENTS |
CA181,736A CA1006186A (en) | 1972-09-25 | 1973-09-24 | Temporary scale retardant coatings |
PL1973165419A PL86828B1 (en) | 1972-09-25 | 1973-09-25 | |
FR7334371A FR2200339B1 (en) | 1972-09-25 | 1973-09-25 | |
JP48107089A JPS503931A (en) | 1972-09-25 | 1973-09-25 | |
US05/473,543 US3956028A (en) | 1972-09-25 | 1974-05-28 | Temporary scale retardant coatings |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US00291849A US3827922A (en) | 1972-09-25 | 1972-09-25 | Method of retarding metal scale formation with carbon-containing mgo-b2o3 coatings |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US05/473,543 Division US3956028A (en) | 1972-09-25 | 1974-05-28 | Temporary scale retardant coatings |
Publications (1)
Publication Number | Publication Date |
---|---|
US3827922A true US3827922A (en) | 1974-08-06 |
Family
ID=23122118
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US00291849A Expired - Lifetime US3827922A (en) | 1972-09-25 | 1972-09-25 | Method of retarding metal scale formation with carbon-containing mgo-b2o3 coatings |
Country Status (9)
Country | Link |
---|---|
US (1) | US3827922A (en) |
JP (1) | JPS503931A (en) |
BE (1) | BE804948A (en) |
CA (1) | CA1006186A (en) |
DE (1) | DE2347728A1 (en) |
FR (1) | FR2200339B1 (en) |
GB (1) | GB1451235A (en) |
IT (1) | IT999582B (en) |
PL (1) | PL86828B1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3930905A (en) * | 1972-10-26 | 1976-01-06 | Allmanna Svenska Elektriska Aktiebolaget | Method of manufacturing an object of silicon steel |
US3956028A (en) * | 1972-09-25 | 1976-05-11 | United States Steel Corporation | Temporary scale retardant coatings |
US3959028A (en) * | 1972-11-20 | 1976-05-25 | The International Nickel Company, Inc. | Process of working metals coated with a protective coating |
US4096000A (en) * | 1973-04-11 | 1978-06-20 | Nippon Steel Corporation | Annealing separator for silicon steel sheets |
US4511124A (en) * | 1983-05-03 | 1985-04-16 | Lone Star Steel Company | Method and composition for fluidization of accumulated pit scrap in soaking pits |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2164665B (en) * | 1984-09-24 | 1988-06-08 | Honda Motor Co Ltd | Spacers for use in brazing |
-
1972
- 1972-09-25 US US00291849A patent/US3827922A/en not_active Expired - Lifetime
-
1973
- 1973-09-17 BE BE135730A patent/BE804948A/en unknown
- 1973-09-17 GB GB4355573A patent/GB1451235A/en not_active Expired
- 1973-09-21 DE DE19732347728 patent/DE2347728A1/en not_active Ceased
- 1973-09-24 IT IT69810/73A patent/IT999582B/en active
- 1973-09-24 CA CA181,736A patent/CA1006186A/en not_active Expired
- 1973-09-25 JP JP48107089A patent/JPS503931A/ja active Pending
- 1973-09-25 PL PL1973165419A patent/PL86828B1/pl unknown
- 1973-09-25 FR FR7334371A patent/FR2200339B1/fr not_active Expired
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3956028A (en) * | 1972-09-25 | 1976-05-11 | United States Steel Corporation | Temporary scale retardant coatings |
US3930905A (en) * | 1972-10-26 | 1976-01-06 | Allmanna Svenska Elektriska Aktiebolaget | Method of manufacturing an object of silicon steel |
US3959028A (en) * | 1972-11-20 | 1976-05-25 | The International Nickel Company, Inc. | Process of working metals coated with a protective coating |
US4096000A (en) * | 1973-04-11 | 1978-06-20 | Nippon Steel Corporation | Annealing separator for silicon steel sheets |
US4511124A (en) * | 1983-05-03 | 1985-04-16 | Lone Star Steel Company | Method and composition for fluidization of accumulated pit scrap in soaking pits |
Also Published As
Publication number | Publication date |
---|---|
JPS503931A (en) | 1975-01-16 |
GB1451235A (en) | 1976-09-29 |
BE804948A (en) | 1974-03-18 |
CA1006186A (en) | 1977-03-01 |
FR2200339B1 (en) | 1978-11-10 |
DE2347728A1 (en) | 1974-04-04 |
FR2200339A1 (en) | 1974-04-19 |
PL86828B1 (en) | 1976-06-30 |
IT999582B (en) | 1976-03-10 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: USX CORPORATION, A CORP. OF DE, STATELESS Free format text: MERGER;ASSIGNOR:UNITED STATES STEEL CORPORATION (MERGED INTO);REEL/FRAME:005060/0960 Effective date: 19880112 |