US3380859A - Metal cold forming - Google Patents

Description

United States Patent 3,380,859 METAL COLD FORMING Gaillard W. Dell, Detroit, and Edwin W. Goodspeed,

Royal Oak, Mich, assignors to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing. Filed Aug. 10, 1964, Ser. No. 388,698 20 Claims. (Cl. 148-615) ABSTRACT OF THE DISCLOSURE A process for deforming ferrous metal surfaces wherein the metal surface is coated with a phosphate or oxalate coating and is then rinsed With an aqueous solution of an amine, which solution has a pH Within the range of about 9 to 12, prior to the application of a soap type lubricant. The preferred amine rinse solutions used are aqueous solutions of triethanolamine and ethylene diamine.

This invention relates to improvements in the cold forming of metals and, more particularly, relates to an improved neutralizing rinse for use in such metal cold forming processes.

In the cold forming of metals, it has become the practice to form a chemical coating, such as a phosphate coating or an oxalate coating, on the surface of the metal article which is to 'be deformed. Generally, this is done by contacting the metal surface with an aqueous acid phosphate or oxalate solution for a period of time sufficient to effect the formation of the desired coating. This contact between the chemical coating solution and the metal surface may be effected in various ways, such as by immersion, spraying, flooding, roll coating, and the like. Thereafter, and prior to subjecting the metal to deformation, it is commonly the practice to apply to the chemically coated metal surface a soap-type lubricant. This lubricant material may be of the so-called reactive type which reacts with the previously applied chemical coating or it may be of the so-called nonreactive type which is principally absorbed by the chemical coating, with little or no reaction between the lubricant material and the chemical coating taking place. In either instance, there is formed on the metal surface a substantially smooth, unctuous film which forms an excellent parting layer during the metal deforming operations. Generally, the fatty acid or soap lubricant material is applied to the chemically coated metal surface by roll coating or by immersion.

In effecting the formation of the chemical and lubricant coating on metal surfaces to be deformed in a commercial operation, the metal workpieces coming from the phosphate or oxalate coating bath are still wet with the acidic coating solution. Accordingly, it is desirable to remove or neutralize the acidity on the surface of the chemically coated metal surfaces prior to the time they are contacted with the lubricant material.

While it is known that a water rinse will remove the acidic solution adhering to the workpiece after it has been contacted with an acid phosphate or oxalate solution, in a continuous operation utilizing an immersion water rinse, the water very quickly becomes acidic. Even 3,38%,859 Patented Apr. 30, 1968 "ice when a constantly overflowing water rinse is used, it too soon becomes acidic and the surface of the work remains acidic. Heretofore, it has also been proposed to utilize solutions of an alkali metal hydroxide, such as sodium hydroxide, as a rinse. Although they are effective in neutralizing the acidic solution remaining on the metal surface after contact with the chemical coating solution, it is difiicult to control the pH of such solutions. As these sodium hydroxide rinse solutions are replenished so as to maintain the desired alkalinity in the solution, it has been found that even a small excess of sodium hydroxide added to the solution will raise the pH sufficiently high so that the neutralizing rinse may attack and partially remove the chemical coating.

It is, therefore, an object of the present invention to provide an improved neutralizing rinse for treating chemically coated metal surfaces prior to the application of a lubricant material.

A further object of the present invention is to provide an improved process for treating metal surfaces prior to a metal deforming operation.

Another object of the present invention is to provide an improved process for the cold forming of metal articles.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

Pursuant to the above objects, the present invention includes an improvement in the process for preparing metal surfaces for deformation wherein the surface to be deformed is contacted with a chemical coating material and a lubricant material, which improvement comprises rinsing the chemically coated metal surface, prior to the application of the lubricant material, with an aqueous solution of an amine, which solution has a pH within the range of about 9 to about 12. By rinsing the chemically coated metal surfaces with such aqueous amine solutions, the acidity on the surface is neutralized and there is obtained a better penetration of the subsequently applied lubricant material into the chemical coating so that better results are obtained in the subsequent metal deforming operations. In this regard it has been found that when the chemically coated metal surfaces are rinsed with the amine solution in accordance with the present process, prior to the application of a fatty acid soap lubricant of the reactive type, precipitation of the lubricant on the surface of the chemical coating is substantially prevented, so that the lubricant material penetrates the coating and reacts with the interior thereof. Additionally, even where lubricants of the non-reactive type are used, it is found that they are absorbed into the chemical coating and excellent results are obtained when the treated metal is subjected to drawing or cold forming.

More specifically, in the method of the present invention, the metal surface to be deformed is subjected to an aqueous acidic solution which functions to form an integrally bound chemically induced coating on the metal surface. Such solutions are conventional and known in the art and include aqueous solutions of phosphoric acid and oxalic acid, as well as aqueous solutions of zinc phosphate, manganese phosphate, one or more alkaline earth metal phosphates, alkali metal phosphates, including ammonium phosphate and zinc phosphate or manganese phosphate modified with an alkaline earth metal phosphate or alkali metal phosphate including ammonium phosphate.

Additionally, such chemical coating solutions include similar aqueous acidic solutions of oxalates, including ferric oxalate and the like. After the desired chemical coating has been formed on the metal surface, the surface is rinsed with an aqueous amine solution having a pH within the range of about 9 to about 12, which solution will be described in more detail hereinafter.

Thereafter, the rinsed metal surface is contacted with a lubricant composition. Typically, the lubricating compositions used comprise a soap of a fatty acid as the principal lubricating material. In these compositions the fatty acid soap may be added as such or it may be formed in situ in the composition by the reaction of an alkali metal hydroxide and a fatty acid. Additionally, such lubricant compositions may also contain either a rosin acid or a rosin soap in addition to or in place of at least a portion of the fatty acid soap. Typically, the fatty acids or fatty acid soaps used contain about 8 to about 22 carbon atoms and preferably about 12 to about 18 carbon atoms. These lubricant materials, like the chemical coating materials, are conventional and are known in the art, so that further description of them is not deemed to be necessary.

Considering now the rinsing solution, this is an aqueous solution of an amine and has a pH within the range from about 9 to about 12. In general, the amines used must be soluble in water at least to the extent that they can form an aqueous solution having a pH within the range indicated. Additionally, they should not have an adverse effect on the chemical coating, the lubricant coating or the metal itself. The amines which may be used are exemplified by the lower alkyl and alkoxy amines, including mono-, di-, and triamines, as well s primary, secondary and tertiary amines, wherein the lower alkyl or alkoxy group contains about 1 to about 8 carbon atoms, and also by the cycloaliphatic amines and heterocyclic amines. Typical of specific amines which may be used to form the rinsing solutions are ammonia, monoethanolamine, diethanolamine, triethanolamine, morpholine, diethanolamine, triethanolamine, cyclohexylamine, ethylenediamine, piperidine, diethanoltriamine, and the like. Of these, triethanolamine and ethylenediamine are preferred. Typically, these and other amines are utilized in the aqueous rinsing solution in amounts within the range of about 0.5 to about 15 grams per liter, with amounts within the range of about 0.6 to 3 grams per liter of water being preferred.

In addition to the amines, the rinse solution of the present invention may also contain a material capable of inhibiting the corrosion of the rinsed metal surfaces. Exemplary of the corrosion inhibitors which may be used are the alkali metal nitrites, such as sodium nitrite. Where such corrosion inhibitors are used, they are typically included in the composition in amounts up to about 4 grams per liter with amounts within the range from about 1 to about 3 grams per liter being preferred.

In applying the alkaline rinse solution of the present invention, various suitable application techniques may be used. For example, the solution may be applied to the coated metal surface by spraying onto the surface, by flooding the surface with the solution, by immersing the surface in the solution, and the like. In many instances, excellent results have been obtained by immersing the chemically coated metal surfaces in the alkaline rinse solution and accordingly, this method is generally preferred.

Typically, during application the temperature of the rinse solution may vary over a wide range, for exampl from room temperature, e.g., 20 degrees Centigrade, up to and approaching the boiling point of the solution. Generally, it is preferred that the rinse solution be maintained below the boiling point to avoid excessive evaporation losses of the solution and volatilization of the amine component thereof. Preferably, the solutions are used at a temperature within the range of about 60 to about degrees centigrade.

In carrying out the metal deforming process of the present invention, the metal articles to be deformed ar first coated with the chemical coating composition as has been described hereinabove. Typically, the chemical coating material may be applied by immersion, roller coating, spray coating or flooding. Thereafter, the chemically coated surface is rinsed with the aqueous amine solution of the present invention having a pH within the range of about 9 to about 12. This solution is preferably applied to the chemically coated surface by immersion technique, although spraying or flooding techniques may also be used. After the chemically coated surface has been rinsed, it is coated with the lubricant material as has been described hereinabove. Typically, these lubricants are applied by roller coating or immersion. After the application of the lubricant material to the coated metal surface, the surfaces are then subjected to the deformation or cold forming operations, such as cold extrusion, drawing, or the like. It is believed that the details of such cold forming operations are sufficiently well known to those in the art that further description thereof is not necessary. It has been found that wh n these various deformation or cold forming operations are carried out on metal surfaces which have been treated in accordance with the process of the present invention excellent results are obtained and no difficulties are encountered by virtue of the lubricant composition being unable to penetrate into the interior of the previously applied chemical coating.

It has further been found that the alkaline rinsing solutions of the present invention do not adversely affect either the subsequently applied lubricant material or the previously applied chemical coating. This is an important feature of the present invention, particularly since some quantities of the rinse material may be carried over into the lubricant composition. The fact that excellent results are obtained in terms of the drawa'bility or formability of the coated parts after treatment in the process of the present invention is further evidence of the lack of adverse effects of the present alkaline rinse solution on either the lubricant or chemical coating material.

It is to be appreciated that in the process of the present invention, as has been described hereinabove, reference has been made to the use of the subject aqueous solutions of amines to rinse the acidic chemical coatings obtained on the metal surface prior to applying the lubricant c at ing material. This is not intended to imply that this aqueous amine solution is the only rinse solution used. In many instances at least a double rinse is used between the application of the chemical coating and the lubricant coating, the first being a water rinse and preferably an overflowing water rinse, and the second being the present neutralizing rinse. Accordingly, when reference is made herein to rinsing the chemically coated metal surface prior to the application of the lubricant material, with the subject amine solutions, this is to be understood as including those processes where another rinse or rinses are used before the amine rinse as well as those processes wherein the amine rinse is the only rinse used.

In order that those skilled in the art may better understand the present invention and the manner in which it may be practiced, the following specific examples are given. It is to be appreciated that these examples are only exemplary of the preferred embodiments of the present invention and are not to be taken as limitations thereof. In these examples, mild steel panels measuring 4 inches by 6 inches were immersed in a conventional zinc phosphate coating solution to deposit a zinc phosphate coating on the surface of the panels. Thereafter, the chemicallycoated panels were rinsed in an overflowing water rinse. The panels were then immersed in various alkaline rinse solutions for about one minute at about 50 degrees centigrade. The panels were then removed from the rinse solution and immersed in a conventional sodium stearate lubricant composition until the desired lubricant film was formed on the surface of the panels. Using the above procedure, the following results were obtained:

Upon removing the panels from the lubricant material, it was found that in each of the above instances there was formed on the panel a film of lubricant material suitable for protecting the surface of the panel during a cold forming operation. Moreover, it was noted that in no instance was there any evidence of any adverse effects on the lubricant film from the alkaline rinse solution.

Example 17 The procedure of the preceding examples was repeated with the exception that the chemical coating applied to the steel sheets was an acid oxalate coating rather than a phosphate coating. The amine rinse solution used was an aqueous solution of triethanolamine containing 3.26 grams of triethanolamine per liter of solution. The rinsed panels were then immersed in a conventional fatty acid lubricant composition which contained 160 grams per liter of the fatty acid soa in a water solution and was at a temperature of about 65 degrees centigrade. Upon removing the panels from the lubricant material, it was found that there was formed on the surface of each a substantially smooth, uniform, coating which was suitable for protecting the panels during a cold forming operation.

Example 18 The procedure of Example 17 was repeated using a number of oxalate coated steel panels measuring 4 inches by 6 inches. One-half of the number of the coated steel r panels was rinsed in an aqueous solution of triethanol- 0 Example 19 An aqueous fatty acid soap lubricant composition containing 160 grams per liter of solution was made up and to this was added triethanolamine in an amount of 7.6 grams per liter. A steel panel measuring 4 x 6 inches which had previously :been coated with a conventional zinc phosphate coating rinsed in an overflowing water rinse and rinsed in a triethanolamine solution was then immersed in the lubricant composition to effect the coating of the panel with the lubricant. Upon removing the panel from the lubricant material, the lubricant film on the panel appeared normal and there was not seen to be any evidence of deterioration of the film clue to the presence of the relatively large quantity of triethanolamine in the lubricant composition.

From the results obtained in the preceding Examples 18 and 19, it is seen that the alkaline aqueous rinses of the present invention do not adversely affect the chemical coating On the panel or the lubricant material which is deposited on the rinsed surfaces.

While there have been described various embodiments of the invention, the compositions and methods described are not intended to be understood as limiting the scope of the invention as it is to be understood that changes therewithin are possible, and it is intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. In the process for preparing a ferrous metal surface for a deforming operation, wherein the metal surface is coated with an acidic chemical coating selected from the group consisting of phosphate and oxalate coatings and a coating of a soap-type lubricant material, the improvement which comprises rinsing the chemically coated metal surface prior to the application of the lubricant material with an aqueous solution of an amine, which solution has a pH within the range of about 9 to about 12.

2. The method as claimed in claim 1 wherein the aqueous amine solution contains the amine in an amount within the range of about 0.5 to about 15 grams per liter of solution.

3. The method as claimed in claim 2 wherein the amine solution is an aqueous solution of triethanolamine.

4. The method as claimed in claim 2 wherein the amine solution is an aqueous solution of ethylenediamine.

5. The method as claimed in claim 2 wherein the chemically coated surface is rinsed in water prior to being rinsed with the amine solution.

6. A method for preparing a ferrous metal surface for a metal deforming operation which comprises forming on the metal surface an acidic chemical coating selected from the group consisting of phosphate and oxalate coatings, rinsing the thus-formed chemical coating with an aqueous solution of an amine, which solution has a pH within the range of about 9 to about 12, and thereafter, fOlll'Il ing on the thus-rinsed surface a coating of a soap-type lubricant material.

7. The method as claimed in claim 6 wherein the aqueous amine solution contains the amine in an amount within the range of about 0.5 to about 15 grams per liter of solution.

8. The method as claimed in claim 7 wherein the amine solution is an aqueous solution of triethanolamine.

9. The method as claimed in claim 7 wherein the amine solution is an aqueous solution of ethylenediamine.

10. The method as claimed in claim 7 wherein the chemically coated surface is rinsed in water prior to being rinsed with the amine solution.

11. A method of deforming ferrous metal which comprises forming on the surface of the metal to be deformed an acidic chemical coating selected from the group consisting of phosphate and oxalate coatings, rinsing the thus-formed chemical coating with an aqueous solution of an amine which solution has a pH within the range of about 9 to about 12, applying to the thus-rinsed surface a coating of a soap-type lubricant material, and thereafter subjecting the metal to a cold forming operation.

12. The method as claimed in claim 11 wherein the aqueous amine solution contains the amine in the amount within the range of about 0.5 to about 15 grams per liter.

13. The method as claimed in claim 12 wherein the amine solution is an aqueous solution of triethanolamine.

14. The method as claimed in claim 12 wherein the amine solution is an aqueous solution of ethylenediamine.

15. The method as claimed in claim 12 wherein the chemically coated surface is rinsed in Water prior to being rinsed with the amine solution.

16. A ferrous metal surface having a soap-type lubricant coating thereon formed in accordance With the process of claim 6.

17. A ferrous metal surface having a soap-type lubricant coating thereon formed in accordance with the process of claim 7.

18. A ferrous metal surface having a soap-type lubricant coating thereon formed in accordance With the process of claim 8.

8 19. A ferrous metal surface having a soap-type lubricant coating thereon formed in accordance with the process of claim 9.

20. A ferrous metal surface having a soap-type lubricant coating thereon formed in accordance with the process of claim 10.

References Cited UNITED STATES PATENTS 2,662,836 12/1953 Montgomery ct a1. 148-615 3,154,436 10/1964 Keller et al l486.16 X- RALPH S. KENDALL, Primary Examiner.