US2609594A - Method of producing vitreous enamelled metal articles - Google Patents

Description

Patented Sept. 9, 1952 METHOD OF PRODUCING VITREOUS I ENAMELLED METAL ARTICLES Roland Aiwhitbeck, Lorain, Ohio, assignor .to f

Gilron Products Company,

corporation of Qliio Cleveland, Ohio, a

No Drawing, Application October is, 1949, r

- Serial No. 122,147

This invention relates to a method'iof producing vitreous enamelled metal products. a

In the prior method .of vitreous enamelling in general use today, the steel enamelling stock used is of a type 1 having a rough surfacefand greater porosity-than steels of likecomposition produced for other uses, Thesurface generally is a series of substantial Jpeaks anddepressions, providing what is generally referred to as a coarse or heavy"tooth., 1 v

The prior method of forming vitreous enamelling stock has may disadvantages, one of the most important beihgfthatl in the rolling, 'forming and fabricating operations the tooth or the metal is levelled ofifand reducedand the pores become filled with the lubricating oils, greases and compounds'lso that thefjOVerall. pcrosity of the metal also is reduced. e a

As a result, the oils and greases must beremoved from the metal and the metal pickled to restore the tooth and the porosity.

Furthermore, in the prior processes, thelu bricants containingoils, greases, and fatty acids must besaponified and emulsified for removal. If not removed, they are detrimental to enamelling. In fact, if they remain long on the material, they etch and oxidize the surface to such an extent that the stock requires pickling and neutralizing to rec'ondition it for enamelling.

Furthermore, the 011s; greases and fatty acids the adhesion of the enameL' Most rejects in' "-14. Claims. (01. 29-148) prior enamelling processes are-due to these 1u-" bricants becomingentrapped in the metal prior to enamelling.

Vitreous enamel stock is received from the mill in clean condition. Starting vvith'such clean, relatively'porous and heavy toothed'stock, the prior method of vitreousenamelling, or orform ing articles for vitreous enamelling, comprises generally the following steps, in order: first, the clean stock is oiled-and blanked out cold; next, it is coated with lubricating'oil or greases and drawn or o rwise formed to shape and fabri-li' cated; then it is cleaned by boiling in a strong alkaline solution following which it is rinsed with water; after rinsing, it is subjected to a,

deep picklestep torestore the tooth of the metal.

which hasbeen badlysmashed down during the forming operations. After being deep pickled-it is water rinsed and passed through av neutralizing bath, dried and then enamelled, the enamelling steps following the conventional procedure. As an example of the time cycle required, a given piece. may be processed, beginning with the initial oiling for blanking and continuing through ,final drying preparatory to ,enamel l-ing, in thirty-five minutes. Of this time, about'thirty minutes is required for the deep pickling 'opera,-

tion to restore the tooth which was. damaged during forming. I v

In accordance with my invention the-original tooth and porosity ofv the stock are-preserved in substantially their original. condition. I My new process comprises coating clean vitreous enamel, stock with a water soluble, self-adherent, dry,.

homogeneous, protective, lubricating and reinforcing coating so thatithevalleys between the.

so-called teeth of the stock are well filledand the teeth themselves coated over, blanking the coated stock, if blanking is, required, in the absence of any additional lubricants, forming the stock in the condition in which it exists after blanking, or if blanking is not required, in the condition in which it exists after originally coating, washing off the stockwith water, and. then drying and vitreous enamelling the formed.

stock with the tooth thereof substantially in the shape in which it existed at the completion of the washing step. I

If desired, in order to assure the optimum results and eliminate any troubles due to possible extraneous circumstances, such as slight contamination of thebath or stock from greases upon. withdrawal therefrom.

The term aqueous bath as used'in the claims is meant to include water alone as well as alkaline cleaning solutions and other aqueous cleaning solutions.

Another optional step following the cleaning in water, or in the aqueous cleaning'bath, is to subject the sheet to a light pickle for superficially .roughening the surface of the stock without substantially affecting the shape of the tooth which latter, after the forming operation, is in substantially the condition it was in prior to forming. If the light pickle step is used, the stock is passed promptly thereafter through a neutralizing bath to eliminate from the stock any possible acids from the pickling bath. In fact, whether the light pickle step is used or not, the neutralizing step is desirable because it occasionally happens that there is some carryover of residual acids from the pickling steps performed at the steel mill in originally producing the vitreous enamelling stock.

As a comparative example of the time cycle required in my process, if it is assumed that the same piece heretofore mentioned in describing the time cycle of the prior process were processed in accordance with my invention, starting with the clean stock, coating, blanking, forming, washing with a mild aqueous alkaline cleaner, cold rinsing, light pickling, neutralizing and drying, the entire time required is about five minutes as compared to the thirty-five minutes required in the prior process, the light pickling step in my process requiring about one minute.

Thus I have found that by properly .filling the valleys between the teeth and coating the teeth of the stock with an easily removed lubricating and reinforcing material which is water soluble and, when dried on the stock, produces a dry, solid, permanent, self-adherent, homogeneous, lubricating and protective film which has substantial body resistance to compression, the tooth of the metal can be laterally supported to an extent that it effectively resists the reduction and leveling off effect occasioned by the'forming and fabricating'operations so that, upon removal of the material after formation, the tooth and surface of the formed and fabricated stock are so nearly in their original condition that the stock is. suitable without the heretofore required deep pickling step or other steps heretofore required for vitreous enamelling.

Further, I have found that by selecting such a material which also fills or seals the pores of the metal yet is easily removed without chemical action on the metal itself, the porosity of the metal, after forming and fabricating, can be maintained substantially inits original condition.

According to my present invention, the raw,

ars t p ous steel enamelli'ng stock is coated with a homogeneous, completely water soluble material. This coating may be applied to the raw metal while it is in the condition in which it issues from the steel mill. However, if any oils, greases, rust proofing materials and the like have been placed on the material, at the mill or in subsequent handling prior to the coating step of the present invention, the metal is thoroughly cleaned so as to restore its surface as near to the original milled condition as possible.

A suitable coating composition for this process comprises lubricating and protective organic binder and water soluble alkaline earth metal borates, such composition being free from any inorganic barrier material.

The proportions of the ingredients of the dry mix composition for use in my process are as follows, the percentage given being by weight:

The coating is applied by dissolving the composition in water in the ratio of about one pound of dry mix to one gallon of water and is applied to the stock by dipping or otherwise, followed by drying, and thereby forms on the stock a dry, homogeneous, self-adherent film which is both lubricating and protective.

One class of materials which may be used as the organic lubricating binders are water-soluble soaps, preferably having a melting point of at least about 3.6 C. upwardly and more particularly high titre soaps having a melting point of from between about 36 to 42 C. and up, specific examples being tallow soap, palm oil soap stearic acid soap, cocoa butter soap, Borneo tallow soap, hydrogenated tallow soap, coaceric soap, Japanic soap, palmitic acid soap, stearin flux soap, multiple pressed tallow soap, hydrogenated palm oil soap, and multiple-pressed palm oil soap. It should be noted that each of the above soaps may be used individually or in admixture with one or more of the other soaps in any desired proportions, in so long as the amount of soap-present is within the broad limits hereinbefore recited. 7

An additional class of materials are watersoluble aliphatic polyhydric alcohols having less than four hydroxy groups, fatty acid esters thereof or mixtures of either or both, and with a particular preference for those having a melting point of at least about 40 C., specific examples being polyethylene glycol, polyethylene glycol oleate, glyceryl stearate, propylene glycol sterate, di-glycol stearate, etc.

As herein'before indicated, mixtures of compounds in each class are contemplated for use in blending the ultimate compositoin; More over, it should be particularly stated thata mixture of the two aforementioned classes may be employed, such as, for example, a soap and a polyhydric alcohol, soap and an ester of the alcohol, a mixture of soaps and an alcohol or an ester or .a mixture of the two. When employing such a mixture the soap preferably should be in the same or greater amount as the polyhydric alcohol.

The alkali metal borates employed in combination with the organic lubricating binder include borax, lithium borate, and potassium borate. Borax is the preferred material due to its ready availability and low cost and also, in certain methods of application, the other borates tend to disburse the organic binder and if the coated metal stock stands for any considerable period of time it tends to become tacky.

In some instances, it will be found beneficial to combine with the aforesaid composition a minor amount of an organic hydrophillic colloidal material such as, for example, cornstarch, potato starch, wheat starch, etc. Under such circumstances, the colloidal material will be present in an amount from between about 1% to 8%, the lubricating binder about 15 to 25% and the borate about 67 to 84%.

After forming, the article is Washed in water in any conventional washing machine and then dried. It will be found that the water soluble coating is completely removed from the valleys between the projections or teeth of the metal and from the pores by the water cleaning operation, and that neither the tooth nor porosity has been adversely afiected substantially by the cold forming and fabrication operations. Accordingly, without any further steps, the dried article is then enamelled in the usual manner of enamelling flat raw enamel stock having its original heavily toothed and porous surface.

It must be understood, however, thatif there is to be an appreciable time delay between the step of water washing and enamelling, it is desirable to protect the surface of the article temporarily from rust and foreign matter. For this purpose, a protective film compatible with the enamel material or frits is used. -Such a film may be sodium carbonate, borax, lithium borate, or a combination thereof, or sodium cyanide, or nickel salts.

The borate, and particularly borax, whether from the original coating used during forming or from a subsequent step, such as rust proofing, is highly beneficial in limited quantity to'the subsequent enamelling operation as it acts as a flux for the enamelling material. Therefore, extreme care in washing after forming is not essential.

Thus, in accordance with the present process, the cavities or valleys between the teeth or pro-' jections of the material are filled with a substance having sufficient body to reinforce the teeth and prevent their reduction and distortion during rolling, drawing and the like; the pores are filled and prevented from clogging with material which is difiicult to remove; the material which operates in this manner is readily applied and-is as easily removed and any slight amount left on the article is beneficial in the enamelling operation.

It has been found that the present method, in addition to being applicable with various steels and alloy stocks of heavy tooth and high porosity such as commonly used for vitreous enamelled articles, is applicable to ordinary carbon steels. Its applicability to ordinary carbon steel results from two factors. First, the pickling steps. of prior methods, when applied to ordinary carbon steels, bring the carbon of the steel to the surface and render the surface unsuitable for enamelling. Furthermore, the tooth and porosity of the original ordinary carbon steel is limited. and is further reduced during drawing and fabricating in accordance with prior practices. Since the pickling step is eliminated and the mechanical reduction of the tooth is prevented by the present.

method, ordinary carbon steels can be enamelled in accordance herewith. This is particularly true of ordinary carbon steels which have been dull rolled.

Indirect advantages result from the practice of the above process, in that the number of rejects is reduced from a relatively high percentage of processed pieces to a negligible amount, the die life is increased indefinitely, and the down time for die touch-up, repair, jamming and the like is eliminated.

Having described the composition to be employed in my new process it therefore becomes convenient to list a few illustrative examples of such compositions, the percentages given being by weight:

Example 1 g Parts Tallow soap 15 Borax i 8 Example 2 Palm oil soap is Borax 82 I Example 3 Tallow soap 1 24 Borax 75 Borax 85 v Example 16 Tallow soap 5 Polyethylene glycol 10 Borax 85 Example 17 Palm oil soap 10 Polyethylene glycol 12 Borax 7'8 Example 18 Tallow soap Palm oil soap 10 Polyethylene glycol 0 Polyethylene glycol oleate 1 Lithium borate 80 Example 19 Cocoa butter soap 30 Polyethylene glycol oleate 5 6 l Example 4 Parts Tallow soap 10 Palm oil soap 6 Borax 84 Example 5 Palm oil soap 20 Borax Example 6 1 Polyethylene glycol 15 Borax Example 7 Polyethylene glycol 22 Borax l=- 78 Example 8 Polyethylene glycol 20 Polyethylene glycol oleate Borax 80 Example 9 I Polyethylene glycol oleate '7 Lithium borate 93.

Example 10 Polyethylene glycol 28 Potassium borate 72 Example 11 Glyceryl monostearate 12 Polyethylene glycol oleate f v Potassium borate 88 Example 12 Propylene glycol stearate; '30 Lithium borate 7O Example 13 Diglycol stearate 18 Borax 82 Example 14 Propylene glycol stearate 20 do Glycol stearate f- Lithium borate '80 Example 15 Polyethylene glycol stearate Propylene glycol stearate Lithium borate 65 V s. Example 20 Parts Stearie acid soap 5 Polyethylene glycol 30 Potassium borate Ewample zl Borneo tallow' soap LL; 20 Glyceryl monostearate' 5 Polyethylene glycol oleate f"? Potassium borate} i,

Borax Example 22 Hydrogenated tallow soap 'l Propylene glycol stearate 25 Lithium borate 70 Example 23 Coaceric Y '1 Japanic Diglycol stearate g r 8 Propylene glycol stearate f Lithium borate} Borax Example 24 Palmitic acid soap 15 Diglycol stearate 5 Borax Example 25 V Stearin flux soap 20 Borax 80 Example 26 Hydrogenated tallow soap 35 Borax 65 Example 27 Hydrogenated palm oil soap lo Lithium borate 90 Example 28 Triple-pressed tallow soap I 30 Hydrogenated palm oil soap Potassium borate 79 Example 29 7 Cocoa butter soap lS Potassium borate 82 Example 30 Stearin flux soap l5 Lithium borate Example 31 Coaceric soap 25 Borax '75 Example 32 V Japanic soap o 22 Potassium borate} 78 Borax Eazample 33 Borneo tallow soap 20 Borax 8o Lithium borate Example 34 I Stearate acid soap 428 Borax 72 A 8' Example35 V l v Parts Stearin flux soap :7 I V 15 Steario acid soap Borax 85 Lithium borate f" "*T'f Example 36 Borneo tallow soap 20 Triple-pressed palm oil soap Borax 80 Example 37 Stearin flux soap l7 Borax l v Sulphonated castor oil 3 7 Example 38 Hydrogenated tallow soap 22 Borax 73 Lithium borate Liquid glycol 5 Sodium 'lauryl sulphate ""7 Qther modes of applying the principle of the invention may be employed; change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

This application is a continuation-in-part of my copending application, Serial No. 690,833, filed August 15, 1946 and now abandoned.

I therefore particularly point out and distinctly claim as my invention:

1. The method of producing vitreous enamelled metal articles. comprising coating heavy tooth porous metal stockto a thickness sumcient to coat the peaks of the teeth of the stock and substantially fill the valleys between the teeth with a water-soluble, homogeneous, self-adherent'and tenacious dry lubricating and protective reinforcing coating having sufficient body resistance to compression to reinforce and prevent substantial deformation of the teeth of the stock during cold pressureforming thereof between two metallic dies, cold pressure forming the coated stock into the desiredshape between two metallic dies in the absence of any additional lubricants, Washing oil" in an aqueous bath at least a major portion of the coating material remaining after the shaping operation, drying the shaped stock, whereby the teeth and porosity of the stock are preserved, and subsequently, in the absence of any pickling operation suificient to cause substantial change in the shape of the teeth of the stock, vitreous enamelling the shaped stock directly on the formed surface while its tooth and porosity are substantially in the condi tion in which they existed at the completion of the washing step. i V V 2 The method according to claim 1 characterized inthat said composition comprises essentially organic lubricating and binding material and a larger portion of inorganic glass forming and water liberating material.

3; The method according to claim 2 characterized in that said organic lubricating and binding material is soap and the inorganic glass forming and water liberating material is borax.

4. The method of producing vitreous enamel metal stock articles comprising coating heavy tooth metal stock to a thickness sufficient to coat the peaks of the teeth of the stock and substantially fill the valleys between the teeth with a J water-soluble, homogeneous, dry, lubricating and protecting coating comprising the following ingredients by weight:

Per cent W ater-soluble organic lubricating binder about 10-33 Water-soluble alkali metal borate do 90-67 cold pressure shaping the coated stock to theform desired between two metallic dies in the absence of any additional lubricant, washing 011 in an aqueous bath at least a substantial portion of the coating material remaining after the shaping operation, drying the shaped stock, whereby the teeth and porosity of the stock are preserved, and subsequently, in the absence of any pickling operation suflicient to cause substantial change in the shape of the teeth of the stock, vitreous enamelling the shaped stock while its surface is in substantially the condition in which it existed at the completion of the washing step.

5. A method in accordance with claim 4 wherein in the washing operation after the coated stock has been shaped, a portion of the lubricating and protective coating is permitted to remain on the shaped article to function as a flux during the vitreous enamelling operation.

6. A method in accordance with claim 4 wherein the lubricating and protective coating comprises the following ingredients by weight:

Per cent Water-soluble soaps about 10-33 Water-soluble borate do 90-67 Per cent Water-soluble soap about 10-33 Borax do 90-67 11. A method in accordance with claim 4 wherein the lubricating and protecting coating comprises:

Per cent Starch 1-8 Water-soluble soap 15-25 Borax 67-84 12. The method of producing vitreous enamelled articles comprising coating heavy tooth porous vitreous enamel metal stock to a thickness sufilcient to coat the peaks of the teeth of the stock and substantially fill the valleys between the teeth with a water-soluble, homogeneous,

self-adherent and tenacious dry lubricating and protective reinforcing coating of organic lubricant and binder comprising essentially at least one from the group consisting of water-soluble soap, water-soluble aliphatic polyhydric alcohols having less than four hydroxy groups, fatty acid esters of said alcohols, and any mixtures of any of the foregoing, and a larger portion of inorganic water-soluble glass forming and water liberating material, cold pressure forming the stock into the desired shape between two metallic dies in the absence of any additional lubricants, washing oif in an aqueous bath at least a major portion of the coating material remaining after the shaping operation, drying the shaped stock, whereby the teeth and porosity of the stock are preserved in condition for vitreous enamelling, and subsequently, in the absence of any pickling operation sufiicient to cause substantial change in the shape of the teeth of the stock, vitreous enamelling the shaped stock directly on the formed surface while its teeth and porosity are substantially in the condition in which they existed at the completion of the washing operation.

13. The method according toclaim 12 characterized in that the stock is subjected to a' light pickling operation operative to superficially roughen the surface of the stock without substantially afiecting the shape of the teeth, as they existed after the forming operation, prior to vitreous enamelling.

14. The method of producing articles to be vitreous enamelled from heavy toothed porous vitreous enamel stock comprising coating heavy toothed porous vitreous enamel stock to a thickness sufficient to coat the peaks of the teeth of the stock and substantially fill the valleys between the teeth with a water soluble, homogeneous, self-adherent and tenacious dry lubricating and protective coating having sufiicient body resistance to compression to reinforce and prevent substantial deformation of the teeth of the stock during cold pressure forming thereof between two metallic dies, cold pressure forming the coated stock into the desired shape between two metallic dies in the absence of any additional lubricants, washing off in an aqueous bath at leasta major portion of the coating material remaining after the shaping operation and then drying the stock, whereby the tooth and porosity of the stock are preserved and subsequent pickling for restoring the teeth is unnecessary.

ROLAND A. WHIT'BECK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 23,184 Whitbeck Dec. 20, 1949 1,769,577 Hopkins July 1, 1930 2,126,128 Montgomery Aug. 9, 1938 2,133,445 Guerin Oct. 18, 1938 2,145,252 Engle Jan. 31, 1939 2,206,597 C-anfield July 2, 1940' I 2,321,656 Chester June 15, 1943 2,323,071 Montogomery June 29, 1943 2,399,775 Whistler May 7, 1946 2,422,883 Bruderlin June 24, 1947 2,469,123 Martin May 3, 1949 2,469,473 Orozco May 10, 1949 2,510,071 Chester June 6, 1950 2,512,161 Ledel June 20, 1950 2,578,585 Orozco Dec. 11, 1951 2,578,586 Orozco Dec. 11, 1951 2,581,310 Sweo Jan. 1, 1952 2,588,234 Henricks Mar. 4, 1952 2,602,034 Eckel July 1, 1952