US3214820A

US3214820A - Steel foil and manufacture

Info

Publication number: US3214820A
Application number: US257310A
Authority: US
Inventors: Edwin J Smith; Edward P Spencer
Original assignee: National Steel Corp
Current assignee: National Steel Corp
Priority date: 1963-02-08
Filing date: 1963-02-08
Publication date: 1965-11-02
Anticipated expiration: 1982-11-02
Also published as: GB1056131A; BE643299A; LU45354A1; DE1527572A1; NL6400848A

Description

NOV- 2, 1965 E. J. SMITH ETAL 3,214,820

STEEL FOIL AND MANUFACTURE Filed Feb. 8, 1963 2 Sheets-Sheet 1 EDWARD P SPENCER 0 d' N O 0 8' N I 5 5 5 5 5 8 8 g g SHANLEY AND o NHL (sami) sanxoml ATTORNEYS Nov. 2, 1965 Filed Feb. 8, 1965 E. J. SMITH ETAL 3,214,820

STEEL FOIL AND MANUFAGTURE 2 Sheets-Sheet 2 MILD STEEL STRIP .003#I T0 .065" GAGE IRON ALLDY- LAYER FREE PLATING COLD REDUCING AT LEAST 70% STEEL FOIL .000I" T0 .002" GAGE FIG4 INVENTOR EDWIN J` SMITH EDWARD P. SPENCER United States Patent O Y, 3,214,820 p STEEL FOIL AND MANUFACTURE Edwin J. Smith and Edward P. Spencer, Steubenville,

Ohio, assignors to National Steel Corporation, a corporation of Delaware Enea Feb. s, i963, ser. No. 257,310 l1 Claims. (Cl. 29-18) The present invention is concerned with new flat rolled steel product and related strip steel finishing operations.

Production methods for flat rolled steel and the basic stri-p steel `finishing processes and products have lcng been well established and standardized in the steel industry. Hot rolled products are reduced in hot strip mills to ygages las thin as 0.0449 and then reduced in cold rolling mills to gages as thin as 0.006. In recent strip steel tinishing operations, further cold reduction has produced thin tinplate gages as low as .004".

The invention departs from practices of the prior art and includes teachings on products and processes of manufacture which realistically establish steel in the metallic foil art. One object of the invention is the manufacture of plated steel foil with many industrial and commercial uses which possesses high strength, abrasion resistance and which can be bent and crumpled without breaking. This product is produced by cold rolling plated steel having a starting gage between about .003 inch and .065 inch to reduce the plate steel 70% and higher to a finish gage between about .0001 inch and .002 inch.

By way of example, tinplated steel foil below a halfthousandt-h of an -inch has been produced in accordance with the teachings of the invention without any of the problems developed in thin tin practice. It is -springy and can be bent repeatedly through substantially 360 without cracking or breaking and can be crease folded and opened 4repeatedly without cracking or breaking. Coating adherence and coating protection .are excellent. It has high tensile strength, from live to ten times that of :aluminum foil of the same gage, is more abrasion-resistant than common foils, such as aluminum, yet can 'be torn and cut readily. It has a smooth, fully plated, bright surface. Tests indicate that its corrosion resistance exceeds that which would be expected from the thickness of it-s tinplating which can be about two-millionths of an inch.

An object of the invention is lmanufacture of steel base foil as hereinafter described. Part of the invention was the discovery that it was actually possible to make plated steel foil and, also, the conception of numerous lapplications for a plated steel foil in modified land combined forms for packaging, for consumer and engineer-ing uses, and for other industrial uses which have opened the door to many practical uses `of steel foil in all forms.

In the metallic foil industry, as previously constituted, foil was defined as thin metal membrane of less than .006 thickness and was distinguished from metal of greater thickness called sheet, strip, or plate. Steel does not remain a pliable membrane up to .006 thickness. Steel of less than .006, say .005, is not foil. For example, .005 tinplate and the lighter forty-pound per base box tinplate lare available in `the rigid can market for beer, oil, food, etc. Therefore, -in describing the present invention, it becomes necessary to set limits for steel foil gages other than those accepted for the common metals `of the foil industry. Steel foil, therefore, as referred to herein, is defined as thin metal membrane of not greater than about .002 thickness. Further, steel foil, especially in a plated condition, is distinguished from other ilat rolled finished steels, such as thin tinplate, by a cold redu-ction after plating of substantially in excess of 50%, e.g. 70% and higher, without an anneal.

Test standards for steel foil have not been established as yet. It has 'become -obvious that testing apparatus and methods, e.g. Rockwell and Brinell hardness, Pittsburgh lock-seam tests, and the like, customarily used in the steel indust-ry, are not applicable to steel foil. At present, comparative tests with other metal foils and steel products must lbe used. For example, steel 4foil has a tensile strength five to ten times greater than that of aluminum foil of the sa-me gage. The abrasion resistance of steel, again partially dependent upon the plating, far exceeds that of aluminum, making tinpla-ted steel foil, for example, far superior to aluminum foil for many industrial uses.

It has been found that the springiness and other rnechanical properties peculiar to steel in foil form can be varied by the rolling procedure. For example, tinplate sto-ck reducing in .a single pass to foil gage is not as springy as tinplate stock reduced a total of 90% by col-d rolling passes of from 20% to 30% reduction .per pass. -Bot'h products have a similar appearance and both, in the as rolled condition, would be considered full har but the springiness and -other special mechanical properties peculiar to steel foil would differ.

Full hard, as previously known in the steel industry, may require further definition when applied to steel foils. Undoubtedly, both of the above 90% cold reduced samples have the strength and other properties associated with full hard as known in the steel industry but neither exhibits the poor bending qualities or brittleness ordinarily associated with full-hard steel which has been cold reduced 90%. Even when reduced t-o foil gages in a single pass of greater than 90% reduction, steel foil does not exhibit any of the brittleness expected. It can be bent and folded repeatedly without cracking. Some of the mechanical properties of foil are influenced considerably by the method and speed `of reduction. It is believed that the heat produced during rolling has a greater effect, often instantaneously, at the thin gages involved than would be the case with -conventional steel strip.

Many desirable properties of plated steel foil materialize because of proper practice in the manufacture of plated steel foil. Again using tinplated steel foil by way of example only, it has been found very important in practice, for purposes of 'avoiding rolling and other problems, to metal coat the strip steel in an iron-alloy layer free manner. Ordinarily, this would involve either electroplating, gas plating, electrophoretic plating, or vapor plating, all herein embraced under the `term plating; however, some hot ydip experts maintain that steel can be hot dip coated without an iron-alloy layer, and to the extent that this is possible, such a product could be used, especially with the heavier gage steel foils.

The .present invention includes the discovery that a matte-finish tinplate is preferred as starting stock for tinplate foil. Practice with matte-finish tinplate substantiates the aforementioned teachings on avoidance of an alloy layer between the coating metal and the base metal. n flow brightening of electroplated tinplate, an alloy layer is for-med. It has been found with .011 tinplate having one pound per base box of coating that the ill eHects of an alloy layer begin to show up at thicknesses of approximately two to three-thousands of `an inch. Tin-iron alloy crystals protrude through the -coating and grey streaks show up on the surface of the product at about these thicknesses. Also, tin-iron alloy scale forms on the work rolls. The matte-finish of tin, zinc, and other coating metals is converted to a bright lfinish in rolling to the foil gage-s taught by the present invention.

In rolling plated strip steel to foil gages, work hardening properties of the coating metal can be critical.

With fini-shed strip steel currently available and that contemplated by the invention, reductions greater than 95% will take place without intermediate annea'l. It has been found in cold reducing to foil gages that the coating metal reduces in proportion to the base metal. While the lsteel Vitself can be cold reduced in the prescribed ranges without an anneal, many of the coating metals included in the invention cannot withstand such cold reduction without an anneal. Therefore, it is necessary, in some instances, to match the cold reducing properties and thickness of the coating metal to the starting thickness of the steel base metal. For example, coating metal which will only reduce 60% without an lanneal should be used only with a coated starting stock having a thickness gage calling for not more than 60% reduct-ion to the finished foil. Otherwise, as the maximum permissible reduction without anneal is reached, coating metal will come off during contact with the work rolls. On the other hand, with many coating metals, this problem can be solved by the roll-ing practice. For example, controlling rolling lubricant temperature can add the necesary malleabllity to zinc and solve many work-hardening `problems of low temperature anneal metals. `Other metal-s `such as tin are found to be self-annealing during cold rolling with or without control of lubricant temperature. Where an an* nealing problem does exist with a coating met-al, selected frequency induction heating can usually be readily matched to the needs of a particular problem because of the precisional control of temperature and heat penetration available. Induction and :other forms of heating, such as hot oil baths, can also be used for heat treating the steel itself since the various effects of heat treatment such as stabilizing, strain relief, and softening occur readily yand apparently at lower temperatures when dealing With toil gages.

The coating metal thickness, both starting and iinal, become more important when it is considered that plated steel foil will be reduced to gages as low as one ten-thousandth of an inch (0001"). The combinations of plating thickness and -steel base metal thickness gages available in foil form approach infinity when it is considered that the foil can vary between about .002 and about .0001 and Ialso that the initial coating weight can vary, with tin for example, from a ash coating up to several pounds per base box (2117.78 sq. ft.). The scope of these variations can be co-mprehended from graphical representations suc'h as those shown in the accompanying drawings, wherein:

FIGURE 1 is a graphical representation of the change in thickness of strip steel with percentage cold reductions falling within the scope of the present invention;

FIGUR-E 2 is a graphical representation of the change in thickness of certain tin coating Weights applied to strip steel with percentage cold reductions falling within the scope of the .present invention; and

FIGURE 3 is a graphical representation lof the change in thickness of certain zinc coating weights applied to strip `steel with percentage cold reductions falling within the scope of the present invention.

FIGURE 4 is a schematic representation of method steps included in the invention.

Several examples from the above graphical representations follow:

.010 'blackplate reduced 90% will have a thickness of about .001; if the b'lackplate had a coating of 1.5 lbs. of tin per base box, the coating thickness would be about nine-millionths of an inch (9X10`G); if initial coating had been a .25 lb. per base box, the coating thickness would have been one and six-tenths millionths of an inch (1.6 104i).

.005 blackplate, when reduced 80%, would have a thickness of .001; if the starting coating thickness was 1.5 lbs. of tin per base box, the iinal thickness would be about seventeen and one-half millionths inch (17.5 10 6); it the coating weight initially applied was .5 lb. per base box,

the iinal thickness would be about six-millionths inch (6 10-6).

The infinite number of variations available can be conceived by combining the graphical representations of FIGURES 1 and 2 for tin or FIGURES 1 and 3 ier zinc. Other coating metal combinations, dependent on practical initial coating thickness limits, can be obtained in like manner. In this regard, while examples from experience with tin, Zinc, `Zinc alloy, aluminum, aluminum alloy, stainless type steel, and titanium, will predominate in this disclosure, the invention is not so limited. Conventional strip steel inishing operations are concerned with various protective coatings for steel; similarly, with the present invention. Among the metallic coatings to be considered are the following metals and their alloys-tin, terne, zinc, aluminum, copper, nickel, chromium, cadmium, stainless steel, silver, gold, and titanium. Special consideration will be given to a steel foil plated with stainless type steel. As a practical matter, strip steel can be coated economically with most of the aforementioned metals, without an alloy layer, with coatings up to .001 thick and higher in continuous strip lines. For example, referring to FEG- URE 3, .6 ounce per square foot of Zinc has a thickness of labout .001.

As dened, plated steel foil includes gages up to about two one-thousandths of an inch (.002") made by a cold reduction of cold reduced and annealed strip stock substantially in excess of 50%, with cold reductions ot 97 and higher being contemplated. Therefore, starting muterial for the present invention can be conventional steel mill product. Plated strip steel having a thickness of about sixty-ve thousandths inch (.065), when reduced approximately 97%, will have a gage of about two thousanths of an inch (.002).

Cold reduction can be carried out by cold rolling passes of as low as 10% reduction per pass or up to 90% or higher reduction per pass. Certain plated stock, such as tinplate, can take large cold reductions readily without any visible effect on the coating or the strip; it is believed that the lubricity of tin aids in this respect. Similar experience has been had with Zinc, aluminum, aluminum alloy, stainless type steel coatings and titanium. At thin gages, tinplated steel foil and steel plated with any of the malleable metals included in this invention may be reduced two strands at a time by rolling the strands back to back through the cold reducing mill with conventional non-bonding materials such as rolling oils being used between strands.

The amount of cold reduction per pass is largely determined by the economics of the process and, to sonic extent, by the desired properties of the finished product and the cold reducing properties of the coatings. The following table will help illustrate why economics enters into this determination. This table shows the number of passes required at various percentages to reduce material having starting gages of .005, .0072, and .0011l to a foil of .0005.

T able I Number of cold rolling passes required to produca .0005 foil Percent Starting gage reduction per pass 2l 25 20 1U l2 l-t 7- 8- t) 4+ 5 u 3+ /1- 11+ 3- 3 L1- 2 2+ 3- 2- 2- M 1 1+ 2- tot :tl iront the standard gages of strip steel would require a reduction of substantially 70% or higher. If such cold reductions are carried out with less than 40% reduction per pass, the number of passes required is high for ordinary steel mill practice. Therefore, the aim is to have the reduction per pass exceed 40%; but, consideration must be given to the desired properties of the foil and the effect of large cold reductions on the coating. Reductions in the range of 40% to 60% per pass are preferable. Larger cold reductions per pass tend to reduce the springiness of the foil and special consideration must be given to the coating which should be either self-annealing or permit a cold reduction in the range -desired without an anneal and should exhibit high malleability. The large cold reductions and tine gages required to produce steel foil can be handled well with a cold rolling mill of the Sendzimir type. The properties and the pressure and tension controls available on this type of mill are well known in the art so that no further description of a Sendzimir mill is necessary to an understanding of the invention.

By making economically feasible reduction of plated steel strip to foil gages, the invention makes possible many new consumer and engineering use products. Also, many existing products can be fabricated more economically. Many of the new uses and new products of plated steel in foil gages result from the combination of high tensile strength steel with the special pr-operties of a coating metal such as copper, cadmium, silver, and the like. Copper plated steel strip, for example, reduced to foil gages, can be used to form reactance devices, coil windings, capacitors, etc., can be used in plural layers to make pliable short radius turn conductors, and can be used in other similar uses which take advantage of the high electrical conductivity of the surface layer copper and the high tensile strength and excellent handling properties of the steel. Silver-plated steel foil can qualify economically for many special electrical uses from which it had previously been barred and, similarly, for cadmium and cadmium alloy plated steel foil.

While aluminum plate-d steel foil also has many electrical applications because of its good electrical conductivity, it and some of its alloys such as aluminum-manganese will be considered with tin and zinc for making many products where corrosion protection is the most important function of the coating metal. Steel foil, plated with any of these coating metals, has numerous uses in packaging, building, decorating, making special textiles, and numerous other industrial applications. These uses are multiplied by the advantages of laminating steel foil which will be considered later.

ln packaging, for example, metal plated steel foil from about .0001" to about .0007 has many of the normal consumer foil uses especially in industrial wrapping. Metal plated steel foil up to about .001 or .0015" makes excellent foil pouches for freeze-dry products, and the like, where creating a light and Vapor barrier is important. While plated steel foil of various gages up to about .002 makes excellent semi-rigid packaging tray structures such as that used for precooked frozen foods, etc., the advantages of all these packaging and other uses over other metallic foils is the high tensile strength of the steel, its abrasion resistance, and the easy handling properties which permit fabricating with much less difiiculty than the other metallic foils. These properties are especially helpful in handling the ne foil gages used for label stock.

In the boiling industry, any of the lower cost coating metal foils can be used for water vapor barrier and insulation purposes more economically than metallic foils currently available. Special corrosion protection and strength characteristics for many products are available with titanium plated steel foil. Honeycomb core and expanded metal are typical applications for such foil, as well as for foils plated with the more common corrosionresistant metals such as tin, zinc, and aluminum.

Nickel and some of the nickel alloy plated steel foils find special uses, along with copper and copper alloy plated steel foils, in the decoration and novelty fields. These and some of the lower-priced metal plated steel foils of the lower thickness gages can also be readily slit into tine thread providing metallic textile materials of higher strength than any currently available.

In making products from steel foil, the fabrication may employ folding, die forming, scoring, embossing, and/or a variety of forms of printing. Other uses than those specifically enumerated above will be obvious from the present disclosure and are considered to be within the scope of the present invention.

Stainless steel plated steel foil can be produced by several methods in accordance with the teachings of the invention. In this context, stainless steel is used in its broad sense, including what is often referred to in the art as a stainless type steel or merely stainless As such, utilization of nickel and/or chromium, or alloys thereof, as an alloying agent(s) in sufficient quantities to make steel rust and corrosion resistant are included. One method is plating mild steel with stainless steel and reducing as previously describe-d. Other methods involve plating -mild steel strip with chromium and/or nickel, or their alloy; processes for plating nickel, chromium and/or iron are known, e.g. U.S. Patent 2,927,066 and Electroplating Engineering Handbook, Reinhold Publishing Corporation, 1955, pages 176, 177. Heat diffusion applied to the plated strip or after the plated strip has been reduced to foil gages produces stainless steel plated foil. Methods and apparatus for causing heat diffusion of plated metals are known in the art so that no further description is necessary to an understanding of this phase of the invention. However, cold reduction practice within the scope of the present invention has been found to produce stainless plated steel foil without heat diffusion; for example, mild steel simultaneously plated with chromium and nickel and then cold reduced to foil gages produces highly satisfactory stainless plated steel foil. rl`he savings involved in such a process are obvious. Various new industrial, commercial, and consumer uses of stainless plated steel `foil building structures, such as honeycomb panels, in the packaging industry for disposable containers, wrappings, laminated and otherwise, have been developed as a result of this new product.

The invention also includes the lamination of steel foil, plated or unplated, with one or more of the following materials: paper, paperboard, Mylar and other well known thermosetting lm materials, heat sealing films commonly referred to as thermoplastic lms, natural and synthetic textiles, felts, fibers, and filaments, plastic, fiber, and wood sheeting or other metals. The steel foil and lamina are normally joined by an adhesive which may be heat or pressure sealed in continuous-line operations. Steel foil has special advantages over other metallic foils for laminated products and in manufacture of laminated products because of the high tensile `strength and abrasion resistance of steel foil.

Through this invention, all the advantages of steel or all the advantages of steel and a plating metal can be added to the properties of other laminating materials making various new products economically feasible. The uses of laminated steel foil extend to all the uses in industries referred to earlier in relation to non-laminated steel and are expanded by properties and uses for the laminating material itself.

Many of the laminae set forth above may be joined by pressure or heat to the steel foil, may be spray coated, or may be joined by use of adhesives. In formulating an adhesive, the mate-rial to be laminated to the steel foil and the surface character of the foil should be considered. Most suitable adhesives can be formulated from basic latex and resin base adhesive inclding epoxy resin compounds, vinyl phenolics, and rubber-base adhesive such as neoprene. The proper formulation can take care of foil surface oil problems but, in the interest of uniform adherence, the toil surface may be cleaned by cathode cleaning, vapor cleaning, or solvent wipe or rinse. Often merely heating the foil will evaporate the oil and provide uniformity. For example, tinplated foil heated to about 300 F. provided uniform lamination using the adhesive referred to in the trade as Polybond, a vinyl type copolymer, which is available from Polymer Industries, Springdale, Connecticut.

ln disclosing the invention, specific descriptions of several products and processes were resorted to in the interest of clarity; the scope of the invention is not to be limited by such description but is to be determined by the appended claims.

What is claimed is:

1. Method for producing metal plated, non-embrittled, steel foil comprising applying an iron-alloy-layer `free metallic coating to strip steel, the strip steel having a thickness gage between about .003 and about .065 and a carbon content up to about .15%, and

cold reducing the metal coated strip steel at least 70%,

without annealing the steel during the cold reducing, by cold rolling to a thickness gage between about .0001 and about .002.

2. The method ot claim 1 in which the coating metal is selected from the group consisting of tin, terne, zinc, zinc alloy, aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy, chromium, chromium alloy, cadmium, stainless steel, silver, gold, and titanium.

3. The method of claim 1 in which the cold reduction includes a single cold rolling pass in which the reduction is about 50%.

4. The method of claim 1 in which the metallic coating applied is matte-finish tin and in which the cold reducing is carried out on the matte-finish tinplated strip.

5. Method for producing metal plated, non-embrittled, steel foil comprising applying an iron-alloy-layer free metallic coating to strip steel, the strip steel having a thickness gage between about .003" and about .065 and a carbon content up to about .15 the metallic coating having a thickness gage ranging up to about .001, and cold reducing the metal coated strip steel at least 70%, without annealing the steel during the cold reducing, by cold rolling to a thickness gage between about .0001 and about .002.

6. Method for producing tinplated, non-embrittled, steel foil comprising electrolytically applying a matte-finish tinplating to mild steel strip, the thickness gage `of the steel strip being between about .003 and about .065", the coating weight of the tin ranging up to about 2.0 lbs. per base box, and

cold reducing the matte-finish tinplated steel strip at least 70% without annealing the steel during the cold reducing, by cold rolling to a thickness gage between .0001 and .002.

7. Method for producing non-embrittled steel foil having a stainless type steel plating comprising the steps of coating steel strip with stainless type steel metal components including nickel and chromium, the steel strip having a thickness gage of between about .003 and about .065 and a carbon content ranging up to about 0.15%, and

cold reducing the metal coated steel strip at least 70%,

without annealing the steel during the cold reducing, by cold rolling to foil having a thickness gage between about .0001 and .002.

8. The method of claim 7 further including the step of heating the coated steel strip before cold reducing to cause diffusion of the stainless type steel metal cornponents into the steel strip.

9. Method for producing stainless type steel coated, non-embrittled, steel foil comprising coating steel strip with stainless type steel metal components including nickel and chromium, the steel strip having a thickness gage of between about .003 and about .065l and a carbon content ranging up to about 0.15%,

cold reducing the metal coated steel strip at least 70%, without annealing the steel during the cold reducing, by cold rolling to foil having a thickness gage bctween about .0001 and .002", and then heating the cold reduced coated steel strip to cause diffusion of the stainless type steel metal components into the steel of the foil.

10. Method for producing stainless type steel plated,

non-embrittled, steel foil comprising plating strip steel simultaneously with chromium and nickel, the strip steel having a thickness gage between about .003 and about .065" and a carbon content ranging up to about 0.15%, and

cold reducing the plated strip at least 70%, without annealing the steel during the cold reducing, by cold rolling to foil having a thickness gage between about .0001l and .002.

1l. Method for producing a metal plated, nonembrittled, steel foil comprising applying a plurality of metallic coatings to strip steel, the strip steel having a (thickness gage between about .003" and about .065 and a Carbon content up to about .15%, the coating metals being selected from the group consisting of tin, terne, zinc, aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy, chromium, chromium alloy, stainless steel, silver, gold, and titanium, and

cold reducing the metallic coated strip steel at least 70%, without annealing the steel during the cold reducing, by cold rolling to a thickness gage between .0001 and about .002.

References Cited by the Examiner UNITED STATES PATENTS 1,656,892 1/28 Shover 29-528 1,675,134 6/28 Roemer 80-60-7 2,018,522 10/35 Herrmann 29 25.3 2,116,107 5/38 Erb 29-18 X 2,316,296 4/43 Simonds 220-72 2,378,458 6/45 Avallone 29-528 X 2,384,086 9/45 Glock 204-36 2,573,524 10/51 Weisberg 220-72 X 2,576,922 12/51 Camin 29-528 X 2,594,012 4/52 Gritlin 220-72 2,731,403 1/56 Rubin 204 28 X 2,762,764 9/56 Owen Ztl-4h28 2,854,732 10/58 Hessenberg 29-528 2,858,235 10/58 Rex 29-528 2,961,365 11/60 Scroog 161-214 2,973,571 3/61 Meyering 29-194 2,998,642 9/61 McCawley 29-l94 3,007,854 11/61 Smith 204-*28 3,009,238 11/61 Wesley 204-40 3,044,156 7/62 Whitfield 9-194 3,050,825 8/62 Field .2Q-4.51 3,054,703 9/62 Brasure 161-214 3,057,050 10/62 Hodge 29-528 X 3,064,874 11/62 Kaufeld 229-37 X 3,088,624 5/63 Kinghorn 220`72 3,095,361 6/63 Stone 20436 3,105,022 9/63 Boggs 204-40 X FOREIGN PATENTS 486,219 6/38 Great Britain. 487,844 9/ 36 Great Britain.

New York, 1963, vol. 2, page 134.

RICHARD H. EANES, In., Primary Examiner.

Claims

1. METHOD FOR PRODUCING METAL PLATED, NON-EMBRITTLED, STEEL FOIL COMPRISING APPLYING AN IRON-ALLOY-LAYER FREE METALLIC COATING TO STRIP STEEL, THE STRIP STEEL HAVING A THICKNESS GAGE BETWEEN ABOUT .003" AND ABOUT .065" AND A CARBON CONTENT UP TO ABOUT .15%, AND COLD REDUCING THE METAL COATED STRIP STEEL AT LEAST 70%, WITHOUT ANNEALING THE STEEL DURING THE COLD REDUCING, BY COLD ROLLING TO A THICKNESS GAGE BETWEEN ABOUT .0001" AND ABOUT .002".