US2067530A - Drawing metal - Google Patents

Description

Patented Jan. 12, 1937 UNETEE STATES mews PATENT QFFEQE No Drawing. Application December 28, 1935,

Serial No. 56.535

8 Claims.

This invention relates to the cold working of metals, and more particularly to cold drawing tubes and other sections, to which the invention is especially applicable and for which reason it will be described with special reference thereto.

alloy steels normally dificult to draw; and which possesses other advantages which will appear hereinafter.

Another objectis to provide a lubricant for use in cold working metals, particularly cold drawing ferrous metal tubing, which is easily anplied to the stock and is easily removed after the working operations have been finished; which is cheap; and which is particularly adapted for the practice of the method embodied in the inven tion.

Having reference'particularly to cold drawing operations, in the practice of which the invention is especially beneficial, it is customary to use a lubricant to assist the drawing and in an attempt to minimize the formation of surface'de-- fects. customarily the drawing stock, such for example as tubing, is annealed and pickled,.following which a lubricant is applied to the inside and outside surfaces and the tube is drawn through a die and over a mandrel to reduce the diameter and wall thickness, with reduction in cross sectional area.

Tallow materials, such as tallow, emulsions, are used commonly to lubricate ordinary steels. Various other lubricants are used or have been proposed, particularly for alloy steels of certain types. For instance, special oils are used in particular cases, and some types of solid lubricants have been: proposed. None of these prior lubricants is wholly satisfactory from all standpoints or for general use. Thus, the tallow lubricants are satisfactory for some steels or some purposes, but they are not generally applicable to all steels with completely satisfactory results. For example, tallow lubricants are unsuited for the.production of small diameter thin-walled tubes which when drawn with such a lubricant must be annealed, pickled and relubricated after each pass, 55 they are not suitable for drawing stainless which is applicable to stainless steel and other steel tubing. Where oils are used it is common practice to burn off the residual oil; this is objectionable because fumes of obnoxious character or detrimental to health may be formed, thus necessitating the installation of ventilating apparatus.

Particularly serious difiiculties are encountered in the drawing'of alloy steels, especially the socalled stainless steels, in the drawing of which with previously used lubricants seizure occurs between the tube and the dies and mandrels. This is objectionable because such seizure causes surface defects which are objectionable from the standpoint of appearance and may render the product not acceptable to the purchaser, or because of damage to the tools. To overcome this a practice has been to lead-dip the tubing prior to drawing but such a practice is not desirable because the use of the lead bath increases the drawing costs, which are further increased through the necessity and difficulty of removing residual lead when the drawing has been completed.

I have discovered, and it is upon this that my invention is predicated, that a dry coating of a mixture of lamp black'and a suitable adhesive satisfactorily prevents seizing, gives improved lubrication as compared with other lubricating materials known to me, and at least with ordinary steels makes it possible to draw them to any size that the strength of the steel in the point will stand, without scratching or pick-up on the tools. These and other advantages have been amply demonstrated both by extensive experimental workand by large scale commercial operations.

In accordance with the present invention, therefore, the difliculties outlined hereinabove are overcome or minimized by the use of a lubri cant comprising lamp black and an adhesive. In the practice of the invention, a mixture of lamp black and adhesive, most suitably a liquid adhesive, is applied to the article to be worked, for instance a tube, the coating is dried, and the thus-coated article is then drawn in customary manner. The adhesive element of the lubricant used in my invention acts apparently to hold the lamp black particles in position until they have entered the die, thus retaining all or substantially all of the lubricating material in position to af- 5o ford maximum lubricating eflect.

Various adhesives may be used in the practice of this invention. I now prefer to use silicate solutions, especially aqueous sodium silicate solutions. These possess the advantages that they 5| perform satisfactorily, are cheap, and present no fire hazard because of the lack of flammability of both the silicate and the solvent. and important advantage is that residues remaining after drawing can be removed quickly and cheaply.

The proportions of the lamp black and adhesive will vary according to the steel and the severity of the drawing, and also according to the ad.- hesive used. Stated generally, there must be enough lamp black to satisfactorily lubricate, and enough adhesive to hold it in place. One lubricant which I have found to be satisfactory for many purposes is composed of 110 gallons of 50 B. sodium silicate (water glass) solution, 150 pounds of lamp black, and water to bring the mixture to 330 gallons. In the use of this and other compositions embodied within the invention the tube or other article is treated with the composition to provide a continuous coating over the surfaces which are to be exposed to the working tools. This may be accomplished most readily by dipping the tube or other article into a tank containing the mixture. The coating is then dried, either by permitting the solvent to evaporate, or by the use of drying ovens or the like, thus producing a solid continuous coating of lubricant over the treated portion. The tube is then drawn.

As indicating the benefits to be derived from the invention, the lubricant mixture just described was used in the drawing of an order of tubing formed from S. A. E. 4615 steel. This tubing after application and drying of the lubricant was given a double cold pass, with a total of 45 per cent reduction in area, with no intermediate annealing. No trouble was encountered in the drawing operations, the surface of the tubing was satisfactory, and the tools were not damaged.

The same composition has also been applied to other commercial operations with entire success. For example, it was used in the drawing of an order of tubing made from steel containing about 28 per cent of chromium, about 5 per cent of nickel, and about 1.5 per cent of molybdenum. Before drawing the tubing had an outside diameter of 1.72 inch and a wall thickness of 0.135 inch. The tubing was coated with the composition described, and was drawn in two passes, the first reducing it to 1.5 inch outside diameter and a wall thickness of 0.127 inch, and the second reducing it to 1.25 inch outside diameter and a wall thickness of 0.125 inch. The total reduction in area was 34 per cent. No annealing or relubrieating was done between the passes, but no pickup or chattering occurred. The residue left on the tubing after drawing was washed off in ordinary soda and acid tubs and the tubing was then annealed, and subsequently pickled, no difficulty being encountered in pickling. It then presented a very clean surface inside and out.

This particular type of steel had been very hard to draw with prior lubricating practice, and it had been almost impossible to pickle it. Thus, tubes from the lot just referred to were lubricated by application of a special sulfurized drawing oil,

containing about 3 per cent of sulfur, which had been found by experience to be the best lubricant for this steel, but as thus lubricated they could not be drawn. The tube is dipped in the oil, then burned off in a furnace, and then redipped and drawn. After each pass it is annealed and put through the cycle again. The

drawing diificulties have been so severe that sometimes two burning-oi steps have been neces- A further sary in each cycle thus increasing drawing costs and aggravating pickling troubles. The pickling difficulties probably arise from the residue left on the tubing as a result "of the burning-off step, the residue being baked into the surface when the tube is annealed. That residue burnt into the tube not only interferes with but is not removed by pickling, and this causes trouble in the succeeding pass. As previously drawn, i. e., prior to my invention, it has been necessary to sandblast this tubing in order to obtain satisfactory final finishes.

Adhesives other than silicates may also be used, such as glue and varnish, and other materials adapted to act as adhesives in the production of dry coatings containing lamp black. Likewise, solid substances in addition to lamp black may be added to the lubricants. For instance, I have found that lithopone may be used in addition to lamp black without detrimentally affecting the drawing characteristics or surface finish. As exemplifying such compositions reference may be-made to one that has been used for commercial drawing operations. 480 pounds of Armours bone glue, 100 pounds of lamp black, 900 pounds of lithopone, and water to bring it to approximately 500 gallons. To preserve the composition there may be added about 5 pounds of carbolic acid. In the use of this lubricant it is desirable to dry the dipped tubes in a hot air drier to expedite drying the coating to sufficient film strength to permit drawing. With that solution there have been satisfactorily drawn over 90,000 feet of tubing weighing in excess of tons and comprising tubes made from S. A. E. 2315, S. A. E. 3140 and S. A. E. 1045 steels, and the well-known 188 chrome-nickel stainless steel. Of this steel 25,000 feet were made from S. A. E. 2315, being 1.125 inch outside diameter and 0.188 inch wall thickness. This material was given an anneal at 2050 F., coated with the foregoing composition, dried, and then drawn twice, without annealing or pickling, to finish, each pass effecting about 20 per cent reduction in area. The yield of salable tubing was exceptionally high on this order, and it was estimated that the tool life was at least treble that obtained with prior lubricants. There was no tool pick-up, and die and mandrel marks were not found in the inspection of the finished tubing. Similar results were obtained with the remainder of the tubing referred to. In contrast, the same tubing when drawn in single passes with tallow caused large mandrel breakage.

Likewise, tubes of common steels, such as S. A.

E. 1015 and 1020 and having an outside diameter.

of 2 inches and a wall thickness of 0.12 inch were drawn with the lamp black-glue-lithopone lubricant in two passes to 1.25 inch outside diameter and 0.083 inch wall thickness, effecting a total of 57 per cent reduction in area, without pickling, annealing or redoping between passes.

It thus appears that the invention makes it possible to cut down on the number of pickling and annealing cycles now used, especially in the smaller sizes where a large number of passes have been necessary.

In the use of these lubricants it is desirable to avoid the formation of tears or other accumulations of the lubricating mixture prior to or during drying. Thus, using glue solutions, the mixture may tend to accumulate, or form tears, unless the tube has been carefully drained, and this excess accumulation may tend to cause formation of slight dents. This difficulty is overcome,-

It comprised however, by using rather thin draining the tubes, for example,-at an angle of about 45 aiter dipping. The ability to use solutions thin enough to avoid tears is another advantage of the silicate adhesive compositions.

My work has shown that in using the lubricant provided by this invention it is unnecessary to use also a lubricating oil, at least for many purbeen applied.

poses. I now prefer, however, to use such an oil after the coating has been dried because it tends to improve thesuriace finish. However, the rather expensive drawing compound oils are unnecessary, and cheap materials, such as fuel oil, afiord satisfactory results owing to the improved lubrication aflforded by the invention.

My work has shown that the adhesive is necessary to obtain the full benefits of the invention.

For instance, suspensions of lamp black in drawing oil have been applied to tubing which has then been drawn in the same manner as tubing to which my adhesive-lamp black lubricants have The oil-lamp black compositions, however. did not permit satisfactory drawing of the tubing.

According to the provisions of the patent statutes, I have explained theprinciple and mode practicing my invention and have described what I now consider to represent However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as speciilcally described.

I claim:

1. That method of cold working metal which comprises the steps of providing the metal with a solutions and its best embodiment.

coating ot-a mixture comprising lamp black and thus coated.

2. That method of colddrawing metal which.

3. That method of cold drawing metal which comprises the steps of coating the metal with a mixture comprising lamp black; lithopone, and a liquid adhesive, drying the coating on the metal, and cold drawing the metal while thus coated. I 4. That method of cold drawing ferrous metal tubing which comprises the steps of cleaning the tubing, providing its with a coating of a mixture comprising lamp black and a liquid adhesive, and cold drawin the tubing while thus coated.

5. That method of cold drawing ferrous metal tubing which comprises the the surfaces of the tubing prising lamp black and an aqueous sodium silicate' solution, drying the coating, and cold drawing the tubing while thus coated.

6. That method 01 cold drawing tubing which comprises the'steps of cleaning the tubing, providing the surfaces with a coating of a mixture comprising lamp black, lithopone, and an adhesive, and cold drawing the tubing while thus coated.

'7. A lubricant for cold drawing ferrous tubing comprising a mixture of lamp blackand a sodium silicate solution.

8. A lubricant for cold with a mixture comdrawing ferrous metal outer and inner surfaces steps of providing ferrous metal tubing comprising a mixture of lamp black, lithopone, and an adhesive. I

HARRY K. IHRIG.

CERTlFI-QAIE OF CORRECTION.

Patent No. 2,067 ,530.

January- 12, 193" HARRY H. IHRIG.

It 'is hereby certified that error appears in the printed specifica ion 0 the above numbered patent requiring correction as follows: Page 3, second column, line 1, claim 1, after the word "and" insert sodium Silicate, and

1 cold working the metal while; and that the said Letters Patent should be 5 read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 9th day of March, A. D. 1937.

Henry Nan Arsdale (Seal) Acting Commissioner of Patents.