US2717221A

US2717221A - Metal working method

Info

Publication number: US2717221A
Application number: US138274A
Authority: US
Inventors: Robert M Christner
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-01-12
Filing date: 1950-01-12
Publication date: 1955-09-06
Anticipated expiration: 1972-09-06

Description

United States Patent 0 METAL WORKING METHOD Robert M. Christner, Beaver Falls, Pa.

No Drawing. Application January 12, 1950, Serial No. 138,274

2 Claims. (Cl. 117-127) This invention pertains to the working of metals and a composition of matter for use in metal-working, and relates especially to the working of ferrous metals. the present time the invention has particular utility in forming operations in which the metal is worked in or over dies. It is especially useful in the cold drawing of stainless steel, and will be particularly described in this connection. This application constitutes a continuationin-part of my application Serial No. 536,847, filed May 22, 1944, and now abandoned.

In the cold drawing of ordinary low carbon steel, the steel is pickled, and upon removal from the pickling vat, is allowed to dry. The drying of the pickling solution on the surface of the steel leaves a light, deposit of rust which is very beneficial as a lubricant in the subsequent drawing of the steel through a die.

In the drawing of stainless steel, however, the steel is resistant to the action of pickling solutions, and a coating may not therefore be formed on the surface of stainless steel by pickling. When attempts are made to draw the stainless steel, it merely sticks or galls in the die. This is especially true in the drawing of tubing over a mandrel where the metal is being worked on both the inner surface of the tube and the outer surface. Many attempts have been made to find a satisfactory drawing lubricant, but materials developed for this purpose have been generally unsatisfactory. Consequently the present method of cold drawing stainless steel involves the coating of the steel with a film of lead. The lead coated stainless steel rod or tube is then drawn and after completion of the drawing operation, as well as for each intermediate annealing operation, the lead is removed by nitric acid, which acid reacts with the lead, but does not attack the stainless steel. This is quite an expensive operation, as well as a relatively slow one. Moreover, it is diflicult to apply the lead to secure a uniform thickness of coating, and any variation in the thickness of the lead film reflects itself in the surface of the stainless steel tube. Variations in the thickness of the lead leave waves or irregularities which are sometimes referred to as lead dents which, in highly finished stainless steel, have to be removed or rendered less conspicuous by polishing.

Additionally, the amount of reduction in each drawing pass must be substantially less than the reduction which can be taken in each pass in the cold drawing of low carbon steel. Not only must the reduction be less, but the cold working using a lead film seems to rapidly produce work hardening of the metal, requiring that it be annealed one or more times in between the initial and final drafts. It is unusual, for example, in drawing stainless steel tubing over a mandrel to get more than one or at most two drafts before annealing is necessary. As previously stated annealing requires complete removal 2,717,221 Patented Sept. 6, 1955 2 cium oxide in water, and I also prepared separate solutions of iron sulphate andsodium hydroxide. These solutions were then mixed, and a reaction followedfiesultingin a solution of sodium sulphate being formed of the lead film, as any residuum of lead will damage the stainless steel when it is heated to annealing temperature.

According to my application hereinbefore referred to, I disclose a process wherein I prepared a mixture of calalong with a precipitate which was ferrous oxide. The precipitate so formed was mixed with the calcium hydroxide mixture first prepared, and this was applied to the surface of the metal to be drawn. I have since discovered in working with my invention as there disclosed, that I had not completely removed the sodium sulphate from the ferrous hydroxide, and when the ferrous oxide so contaminated with sodium sulphate was mixed with the calcium hydroxide or lime water preparation, calcium sulphate was formed in a limited amount, and the calcium sulphate was the important factor with the iron compound that resulted in the exceptional lubricating properties of the material which I used. This developed from experiments wherein I tried to remove completely, by thorough washing, all sodium sulphate from the iron hydroxide. I then discovered that the compound was less effective than where the precipitate was not free of the sodium sulphate. Thus, while my original practice of having a mixture comprised predominately of iron hydroxide and lime gave a successful drawing operation, I have found that substantially better results are obtained where the iron hydroxide is associated principally with calcium sulphate. Of special importance therefor is the ferrous hydroxide which is converted upon application to the surface of the iron which upon drying in the air changes from the ferrous to ferric compound, while the calcium sulphate or the lime have a complementary action, the sulphate, .for reasons unknown to me, give a much better body and adhesion than the lime, making a greater number of draws possible with one coating.

According to the preferred practice of the present invention, I preparelime water by introducing lime into water. I separately dissolve iron sulphate in water. I then bring the two mixtures together and agitate them. This results in the precipitation of hydroxide of iron and calcium sulphate as a single compound, or with the calcium sulphate and iron hydroxide in intimate physical association. 1

Enough lime is used in the water so as to form a rather heavy suspension. The solution of iron sulphate is a highly concentrated solution, it being desirable that the calcium sulphate and iron hydroxide be in a rather creamlike slurry. Enough lime is used to completely convert all of the iron sulphate, but the proportions are not critical, and there may be in the finished product unreacted lime.

After the reaction resulting from the mixture of the lime water and the solution of iron sulphate, the material is then ready to-use. The calcium sulphate and iron hydroxide which tend to precipitate canbe kept in suspensionby agitation of the mixture, and the articles to be drawn can be dipped into this liquid slurry.

As an alternative, after the reaction has been effected, excess water may be removed by evaporation, reducing the mass to a thick, paste-like condition, which can be put into drums and shipped and sold as a commercialmaterial soap, soap powder or other lubricant being mixed with the reaction product. Roughly about 50% of the mix is soap, but these proportions are not critical, .but without soap the product will not cold work satisfactorily or'remain on the surface of the metal. Soap of a type commonly used in the art has a base consisting of the sodium salt or oleic, stearic or palmitic acid or mixtures thereof, and such soap may or may not be mixed with sodium or potassium carbonate. The purchaser remixes the paste with two or three parts of water to convert it back into a slurry. This is the preferred way of distributing the product commercially.

I may state that the paste which is so formed has a green color, but if it is allowed to dry in contact with the air, it turns brown. Likewise, when tubes or other products to be drawn are dipped into the slurry and then dried in the open air, the deposit on the surface of the tubes will likewise turn brown.

Instead of partially evaporating the water, the precipitate may be separated entirely from the water and dried. It can be dried to a brown powder. This powder will have no quality of adhering to the surface of stainless steel, but the powder can be advantageously mixed with dry soap powder lubricant of the type used in drawing stainless steel wire, and the lubricant, when so mixed with the dried compound above referred to, will perform much more satisfactorily, especially in the drawing of stainless steel wire which has previously also been coated with the slurry and then dried in the air.

Acccording to my invention, therefore, the reaction product obtained by the mixing of calcium hydroxide and iron sulphate, and preferably carrying some free lime, is used as a lubricant either by being first dried and then put into the lubricant box of a drawing bench, or by being applied to the surface of the stainless steel as a slurry which is then air dried, Being applied in this fashion, it intimately clings to the surface of the stainless steel and provides a drawing or lubricating compound which is highly efiective, and which enables stainless steel to be drawn with drastic reductions, without lead coating the stainless steel, and with less intermediate annealing than is presently required.

I prefer to use iron sulphate and lime for the preparation of the drawing compound, because these are readily available, cheap, and highly satisfactory. However, I

have reason to believe that the hydroxides or other alkaline earth metals such as magnesium, barium and strontium could be used in place of calcium oxide or hydroxide, and that the sulphate of other neutral or substantially neutral or non-basic metal could be used in place of iron sulphate, as for example cadmium sulphate, nickel sulphate, or cobalt sulphate.

Also, the process disclosed in my original patent application may be used wherein iron sulfate is reacted with sodium hydroxide to precipitate ferrous hydroxide, or other base such as ammonium or potassium hydroxide. The ferrous hydroxide so produced may then be mixed in waterwith lime to form a slurry, or the ferrous hydroxide may be mixed with a generally but not necessarily equal part of soap. The iron hydroxide and soap can be used as such, but as stated above, it is less satisfactory than when lime is also added, and particularly less satisfactory than where calcium sulphate is also present.

In the foregoing description I have referred especially to the drawing of stainless steels, and for this purpose I know of no comparable method or material. My invention, however, is not limited to true stainless steels, but is applicable also to the drawing of other steels, including low carbon steel and steels having a high-content of nickel and chromium or other alloy ingredients, so long as the steels are of the type which may be drawn.

As hereinbefore indicated, the use of a drawing composition as herein described enables stainless steel to be drawn with about the same facility as ordinary steels are now drawn; the reduction in each draft may be substantially heavier than where a film of lead is used, and complete reduction may frequently be made without intervening annealing or normalizing and where annealing is necessary the coacting substance need not be removed. Why the material retards the Work hardening properties of the stainless steel when being drawn is not known to me, but is an observed fact. As many as six drawing passes in the formation of stainless steel tubes, and with substantial reductions in several of the passes, have been effected without intervening heat treatment. I have referred especially to the drawing of tubes, because this is the most diflicult, but the invention applies likewise to drawing stainless steel rods and wire.

While the composition has application primarily to the drawing of steels and particularly stainless steels, I believe that the composition may also have utility in the piercing of stainless steel billets, the lubrication of dies in which metals are shaped, and may be usefully employed in the coating of molds in which metals are cast, and believe that the composition may be advantageously used with non-ferrous metals.

While 5 have illustrated and described certain embodiments of my invention and have specifically mentioned certain materials it will be understood that this is not by way of limitation, but by way of illustration, and that various substitutions and modifications may be made within the contemplation of my invention. Once the surface condition which is created by the use of my invention has been observed, one skilled in the art may readily select equivalent materials and properties to give like satisfactory results.

it should be noted that by forming the calcium sul phate and the ferrous hydroxide together in one reaction, the precipitate has a high bulk factor; higher than would be obtained by merely mixing together separately formed calcium sulphate and ferrous hydroxide, and that there is a more intimate physical association and union of these components where this reaction is used to ob.-

tain the compound. The reaction is indicated .as follows:

CalUH)sFeSOs=CaSO4+Fe(OH)z Both the calcium sulphate and the ferrous hydroxide are relatively insoluble in the aqueous environment, and precipitate as a single mass. As above indicated, suflicient lime is used so that there may .be some calcium oxide in the resulting mix, but this would be only a small and unimportant percentage. Also it may be pointed out that the compound may be mixed with soap or other lubricant either in the dry form above described, or as a paste.

I claim:

in the process of drawing stainless steel the steps which comprise coating the steel with a slurry formed of water and the reaction product of ferrous sulphate and lime in water in substantially stoichiometric amounts, drying the slurry on the stainless steel to form a coating thereover and during which drying the iron compound present is oxidized by contact with air.

2. In the process of drawing stainless steel, the steps which comprise mixing a solution of ferrous sulphate and sufficient lime to completely react the ferrous sulphate and produce a slurry which is predominantly the reaction products of the ferrous sulphate and lime, but in which there may be an unimportant amount of unreacted lime, applying the slurry so formed to the surface of the stainless steel and drying the same in air before drawing the steel and thereby effecting the oxidation in situ of the ferrous compound in the coating so formed to the ferric compound.

References Cited in the file of this patent UNITED STATES PATENTS 1,801,542 Harth Oct. 11, 1932 1,902,493 Dantsizen Mar. 21, 1933 1,916,677 Lloyd July 4, 1933 2,238,738 Hurd Apr. 15, 1941 2,394,620 Leonard Feb. 12, 1946 FOREIGN PATENTS 42,944 France Oct. 16, 1933

Claims

1. IN THE PROCESS OF DRAWING STAINLESS STEEL THE STEPS WHICH COMPRISE COATING THE STEEL WITH A SLURRY FORMED OF WATER AND THE REACTION PRODUCT OF FERROUS SULPHATE AND LIME IN WATER IN SUBSTANTIALLY STOICHIOMETRIC AMOUNTS, DRYING THE SLURRY ON THE STAINLESS STEEL TO FORM A COATING THEREOVER AND DURING WHICH DRYING THE IRON COMPOUND PRESENT IS OXIDIZED BY CONTACT WITH AIR.