DE2052977A1 - Method for producing a lubricant coating on an object with an electrically conductive surface - Google Patents

Description

DIPL.-ING. HANS W. GROENING

FATE N ADVERTISER

Ϊ DÜSSELDORF

STEIITSTRASSE

iA.3 / r

(MIl) 187β! .

October 27, 1970 II / H

American Metal Climax Inc. New York, N.Y. 10020, USA

A 17 - 1st

Method for producing a lubricant coating on an object with electrically conductive surface

The invention relates to a method for producing a lubricant coating on an object with electrically conductive surface, in particular, but not exclusively, on a metallic object such as wire to provide lubrication during wire drawing, rolling or pressing achieve.

As is known, it is desirable and in certain cases essential during metalworking operations such as for example in wire and pipe drawing, belt rolling,

-2-IU3O * \ ι ecm ORIGINAL INSPECTED

Forging and deep drawing provide lubrication. The use of a lubricant makes it possible to achieve higher levels Working speeds and a greater degree of metal deformation can be obtained than it would be without a lubricant is possible. Naturally, the more effective the lubricant, the higher the working speed and the greater the achievable extent of the deformation.

An extremely effective group of lubricants in the metalworking field is commonly used referred to in the art as "high pressure" lubricants. These lubricants can be reactive Cleavage pieces such as Cl or S "provide what is believed to be a chemical reaction with of the metal surface during metalworking, for example metal chloride or sulfide to form that is effective as a lubricant. The reactive split piece in high pressure lubricants will Obtained from an organic compound, which at room temperature does not even contact the metallic object reacted. From the point of view of lubrication alone, the reactive split piece could also

109821/2224

obtained from compounds that are reactive at room temperature, such as HCl, but such reactive compounds have obvious disadvantages because of having hydrogen chloride itself react with the metal of the wire and corrode the surface of the metallic counter-surface.

If you now ensure that the reactive split piece comes from a non-reactive organic compound, no such corrosive attack is caused on the metallic object and the split piece reacts with the metal only after it is removed from the organic compound by thermal, during the Metalworking generated energy has been released.

High-pressure lubricants have been found to be more effective than simple organic ones in metalworking Lubricants, especially when high temperatures and pressures are generated during metalworking. High pressure lubricants are particularly useful for drawing stainless steel, titanium and nickel alloys used, which otherwise tend to strong metal transfer from the workpiece to the metalworking tool.

-4-

109821/2224

_ it-

The one to release the reactive split piece from the organic compound to react the split piece thermal energy required with the metal surface to form the lubricant is caused by plastic deformation of the metal during machining, in particular by friction and recovered plastic deformation of local bumps on the metal object. Usually he delivers Increase in temperature of the whole object does not lead to the release of the split piece and to react with it the metal surface has sufficient thermal energy; therefore the reaction of the split piece with the Metal surface limited to the area where local friction and deformation of the workpiece takes place. This was proven with the help of the radioactive marking technique.

It is therefore a characteristic feature of conventional high pressure lubrication that between the The metal object and the metalworking tools have very close contact, perhaps even a local one Welding must be produced in order to generate the necessary thermal energy for the above-mentioned reactions to release. In addition, the object moves

- 5 -

109821/2224

in many metalworking operations, such as

in wire or pipe drawing, past the processing tool at high speed, in wire drawing for example at about 304.8 m / min through a tool whose contact length is 1.27 mm, so that the

Contact time of the wire with the drawing die to 250 ^ usec ^

amounts to.

Hence, the release of the reactive cleavage and its reaction with the metal surface must be within this very short period of time if it is to be effective as a lubricant. Requires the response longer, the wire has already left the drawing die before the reactive split piece has a lubricant can deliver. This can damage the surface of the metal object to be processed and / or of the processing tools come, on the one hand because of the necessary, very close contact, on the other hand also possibly because of the required welding, both to generate enough thermal energy so that the reactive split piece acts as a lubricant. Another possibility of damage in metalworking operations that run at such a high speed, lies in the fact that the metal object is already

- R -

109821/2224

moved out of the contact zone with the drawing die before the necessary reactions can occur.

It is therefore an object of the invention to provide a new, improved method for producing a lubricant film to create on an object with an electrically conductive surface in which the above Disadvantages can be overcome or reduced.

This object is achieved according to the invention by a method for producing a lubricant coating on a Object with an electrically conductive surface, in which the object is placed in an electrolytic cell is solved, which is characterized in that the electrolyte of the cell is a soluble organic Containing sulfur compound, the object made the anode of the cell and an electric current is sent through the cell, as a result of which a sulfur-containing component is formed in the electrolyte, from which the lubricant coating is created on the surface of the object.

The lubricant coating can be electrochemical

- 7-

109821/2224

Reaction of the sulfur-containing component can be generated with the surface of the object.

The lubricant coating can, however, also by reaction of the sulfur-containing constituent with another Component of the electrolyte can be obtained.

The object can be a metal object.

At least the surface of the object can - in order to act as an anode in the electrolytic cell be connected to an electrical circuit; another electrode is in contact with the electrolyte of the cell and is connected to the circuit as a cell cathode.

The organic sulfur compound can be thioacetamide or thiourea. The organic sulfur compound can be present in an aqueous-sulfuric acid solution with a concentration in the range from about 0.02N and 0.2 η H ₀ SO.

Preferably no more than 5% by weight of the organic sulfur compound should be present in the electrolyte be.

Thioacetamide is used as the organic sulfur compound

109821/2224 -ß-

preferred.

A molybdenum compound can be an additional component of the electrolyte. In this case it forms Molybdenum disulfide as a lubricant coating on the object.

If no additional component is contained in the liquid, the surface of the object can look off Mild steel, tin or molybdenum be made.

When the electrolyte contains the additional component, the surface of the object can look off Mild steel, tin, stainless steel, titanium, molybdenum or a nickel alloy exist.

If desired, after applying a lubricant coating to the metal article The method described above is followed by a deformation of the object.

If desired, the object can be treated with an electrolyte immediately after the deformation process Brought in touch and a relatively high one

- O -

109821 1211k

Alternating current can be passed through the liquid associated with the object in order to coat the lubricant to remove.

The deformation can be done by drawing, pressing, rolling or forging.

If the deformation is a continuous process, such as wire drawing or rolling, the electrolyte is called Bath provided through which the object is continuously passed.

If the deformation takes place discontinuously, such as in forging, the electrolyte is provided as a bath into which the object is placed and from which it is removed before deformation; if the lubricant coating j is to be removed after the metalworking process, the object is immersed in a suitable bath and then removed therefrom immediately after the metalworking process.

The method according to the invention makes it possible to provide an object with a lubricant coating,

-10-

1 fl Φ 8

without relying on thermal energy released during the metalworking process is used to create the lubricant coating. In addition, it is used to produce the lubricant coating time spent relatively short, so that the process according to the invention is based on continuous manufacturing processes can be applied without reducing the rate of production to an inefficient level to have to lower.

Therefore, the method according to the invention also has the considerable advantage that the formation of the lubricant coating by the applied voltage and the current density regardless of the speed of the Metalworking process or after close contact or the welding process between the metal object and the metalworking tool is precisely controlled can be, thereby eliminating the aforementioned problem of possible damage to the metal object or the Metalworking tool as a result of such close contact and possible welding process is avoided, before the high-pressure lubricants used for this purpose are able to produce a lubricating effect.

-11-

In addition, the amount of lubricant present can be controlled simply and easily just by adjusting the voltage and current density and / or the contact time between the liquid and the metal object. For example, in continuous metalworking operations such as wire drawing, the length of the bath that the wire immediately prior to drawing g

be selected so that it is suitable for the intended Pulling speed has the appropriate length. In the case of a discontinuous process, as in forging or deep drawing, the immersion time of the object in the "id is measured in such a way that that the desired amount of lubricant coating is obtained.

In addition, in processes such as deep drawing, it is sometimes desirable to apply lubricant films to certain, To create specified locations to promote the formation of different metal flow during drawing. This can be done with the method according to the invention, for example, by arranging a further electrode in relatively close proximity to the metal object in the areas where a local

-12-

109821/2224

Lubricant film. Is to be generated so that the predominant part of the lubricant coating on these Places and relatively little or no lubricant coating is formed in other places.

With some high-pressure lubricants used up to now, the organic compound that makes the reactive Contains cracks, especially in the presence of moisture. This leads to corrosion of the metal object, the removal of high-pressure lubricants and their decomposition products after the metalworking process made necessary. This has usually been done using two separate operations organic solvents and inorganic fluxes made. According to the method according to the invention can the coating can be removed immediately after the metalworking operation in that the metal object with a liquid of the same composition as that of the carrier liquid with that of the metal object brought into contact with the metal working process, and brought into contact with the metal object associated fluid, an alternating voltage difference is created in order to destroy the lubricant film and so restore the metal to its original state.

-13-

109821/2224

The apparatus for removing the coating is similar to that for applying the lubricant coating is used.

In cases where the procedure is carried out with the electrolyte without an additional component, the lubricant coating produced is a compound of the metal from which the object is made. Is this Metal, for example mild steel, the lubricant coating is iron sulfide.

However, when the other component is included in the liquid, the lubricant formed is independent from the metal of the object. For example, if the other component is a molybdenum compound, will Molybdenum disulfide is formed in the electrolyte and a surface layer is formed on the surface of the object deposited from molybdenum disulfide, regardless of what metal the object is made of. One has recognized that molybdenum disulfide was a better lubricant forms as, for example, iron sulfide.

The exact mechanism by which the molybdenum disulfide is deposited on the metal wire and the type the bond between the molybdenum disulfide and the

109821/2224

Metal wire is not yet fully recognized, but the molybdenum disulfide is relatively strong bound the metal object, although apparently not as strongly as that as a result of reaction with the metal the lubricant film formed by the wire.

With the aid of the method according to the invention, it is therefore possible to apply a relative to the metal object tightly bound lubricant such as molybdenum disulfide (which is well known as an excellent lubricant) regardless of the nature of the metal from which the object is made, while-doing this with conventional high-pressure lubricants do not, and was only possible with compounds of the metal from which the object is made.

Example 1 . > \

Annealed molybdenum wire with a diameter of 1.2mm was made by a tungsten carbide die with a Cold drawn speed of 2.74 m / min to 8% reduction in cross section. Without lubrication, the The surface of the wire was considerably damaged and the tensile load was over 6 8 kg.

-15-

109821/2224

With generous use of a graphite-containing oil commonly used for drawing molybdenum, the tensile load was reduced to about 40.8 to 49.9 kg, this time the wire exhibiting a satisfactory appearance on its surface. A piece of the wire was 5 sulfuric acid, log / 1 thioacetamide and log / 1 of ammonium molybdate in a container, the ⁿ / ä

contained, connected as an anode, and for 10 seconds

2
a current of 100 mA / cm from a 6 volt battery passed through. When this wire was pulled down, a tensile load of about 40.8 to 54.4 kg was measured, and electron microscopy showed that the surface quality of this wire was slightly superior to that of the drawn wire.

Example 2

Tempered mild steel wire 1.0 mm in diameter was through a tungsten carbide drawing die at 1.83 m / min Cold pulled down to 12% cross-section ± reduction. Without lubricant, the wire surface was heavily grooved and the tensile load was 47.6 kg. Hit a conventional,

-16-

109821/2224

chlorinated high pressure lubricant, the tensile load was approximately 42.2 kg and the wire possessed one satisfactory surface quality. When a metal soap lubricant was used, the surface was too satisfactory, but the tensile load dropped to about 34.0 kg, with an electrolytically produced as in Example 1 Lubricant, a tensile load of 31.75 kg was determined and again a good surface finish was achieved.

Example 3

Tempered stainless steel wire 18/8 1.0 mm in diameter was passed through a hoist carbide drawing die at 1.83 m / min Cold drawn down to 2 5% reduction in cross-section. In the absence of lubricant, there was considerable metal abrasion and the tensile load was about 89.4 kg. A metal soap lubricant made the surface greatly improved, the tensile load was 66.7 kg. With an electrolytically produced according to Example 1 Lubricant, the surface quality was again satisfactory, and the tensile load was 65.8 kg.

Example 4

Tempered mild steel wire was left with no lubricant 5% reduction in cross section pulled down. It kicked

-17- 10982 1/2 2 2 A

significant abrasion and a pulling force of 31.75 kg was required. Another piece of the wire was made the anode in a cell containing n / 10 H ₂ SO ₁₊ and 10 g / l thioacetamide, and was held for 10 sec. a current of 300 mA / cm passed through. The force required to pull this wire was 28.6 kg and the surface finish was satisfactory.

Example 5

Tempered mild steel wire was pulled down to 5% reduction in area without lubricant. The abrasion was considerable, the required pulling force was 31.75 kg. Another sample of the wire was placed in a container which contained n / 10 H ₂ SO ₁₁ and 10 g / 1 thiourea, connected as an anode and 10 sec. long

2
a current of 300 mA / cm passed through. The force required to pull this wire was 28.6 kg and the surface finish was again satisfactory.

The equipment used in the above examples is shown schematically in a drawing.

-18-

109821/2224

The drawing shows the device, which has a wire drawing die 10 made of tungsten carbide can. The metalworking drawing die 10 is mounted in a drawing block 11 which has a load cell 12 is provided in order to be able to measure the tensile load. The drawing block 11 is on a conventional one, not shown, draw bench attached, and a wire to be tested 14 is by means of a conventional coil 15, which is on the draw bench, pulled by the die 10.

On the input side of the drawing die 10, the wire is passed through an electrolytic bath 16 which has suitable seals 17 made of neoprene and which contains the solution described in the examples. Furthermore, in the bath 16 counter electrodes 18 are attached above and at some distance from the wire 14 and connected to a battery 20 via an ammeter 19, while the wire 14 is connected in an electrical circuit to the positive pole of the battery 20 via a variable resistor 21 is. The connection to the continuous wire 14 is made via contacts with which the pulling element 10 is provided.

-19-

109821/2224

If the lubricant is to be removed immediately after drawing, a bath 22 similar to bath 16 is provided on the exit side of die 10 so that wire 14 is drawn through both baths by means of spool 15 of the draw bench. In this second bath 22, the wire 14 is connected to a circuit with an alternating current source 2 3. Ä

If the process is carried out in the case of strip or sheet rolling, a bath of suitable size with suitable Seals are used to prevent a loss of solution when the sheet metal or the end is in or out will.

If the inventive method is discontinuous Operations, such as forging or deep drawing, is used, an open-top bath of suitable dimensions is used and the object to be processed is lowered into the bath for a time sufficient to form or remove a coat of suitable thickness.

Should a lubricant coating only be applied to certain areas

-20-

109821/2224

of the workpiece arise, the counter electrode is designed accordingly, so that the upper run only on the points near the counter electrode is deposited.

109821/2224

Claims (21)

DIPL.-IPTG. HANS W. GROENING PATE NTANWAIiT 4 DÜSSELDORF STEIKTSTRASSE 17 (AW SSB. ΪδΚΙΟβΑΙΙΙΙΙ KASSX ,: RSBIIfPATJtKT ΤΒΙΪΓΟΪ (0 * 11) 15781 October 27, 1970 U / H American Metal Climax Inc.
A 17 - 1st Patent claims: (ι. ^ A method for producing a lubricant coating on an object with an electrically conductive surface, in which the object is introduced into an electrolytic cell, thereby
characterized in that the electrolyte of the cell (16) contains a soluble organic sulfur compound, the object (14) is made the anode of the cell (16) and an electric current is passed through the cell (16), whereby the
Electrolyte, a sulfur-containing component is formed from which the lubricant coating
generated on the surface of the object (14)
will. 2. The method according to claim 1, characterized in that -2- 1 09821 / 222A that the sulfur-containing component under formation
of the lubricant coating reacts electrochemically with the surface of the object (I ¹ I). 3. The method according to claim 1, characterized in that the sulfur-containing component is formed
of the lubricant coating reacts with another component of the electrolyte. 4. The method according to any one of the preceding claims, characterized in that the object (14) is a metallic object. 5. The method according to any one of the preceding claims, characterized in that at least the surface of the object is connected to an electrical circuit and acts as an anode in the electrolytic cell (16), wherein a further electrode (18) with the electrolyte of the cell (16 ) in touch
and is connected to the circuit as the cathode of the cell (16). 6. The method according to any one of the preceding claims, characterized in that the organic sulfur -3- 109821/2224 compound is thioacetamide. 7. The method according to any one of claims 1 to 6, characterized in that the organic sulfur compound Is thiourea. 8. The method according to any one of the preceding claims, characterized in that the organic sulfur compound is an aqueous sulfuric acid solution with a concentration in the range from about 0.02 to 0.2 η H ₂ SO ₁₁ . 9. The method according to any one of the preceding claims, characterized in that the electrolyte is not more than 5 wt. the organic sulfur compound contains. 10. The method according to any one of claims 3 to 9, characterized in that the additional component of the electrolyte is a molybdenum compound. 11. The method according to claim 10, characterized in that the molybdenum compound is ammonium molybdate. -4- 109821/2224 12. The method according to any one of the preceding claims, characterized in that the application of the Lubricant coating a deformation of the object (1 * 0 follows. 13. Method according to claim 12, characterized in that the object (I ¹ O consists of metal and deformed by drawing, pressing, rolling or forging will. 14. The method according to claim 12 or 13, characterized in that that the deformation immediately follows the application of the lubricant coating. 15 · method according to one of claims 11 to lh, characterized in that after deformation Ψ the metal object with another electrolyte brought into contact and a voltage is applied to the liquid near the object in order to generate the Remove the lubricant coating. 16. The method according to claim 15, characterized in that that the electrical voltage passes through -5- 09821 / 222ύ a relatively strong alternating current is applied through the further electrolyte. 17. Method according to one of Claims 12 to 16, characterized in that the deformation is continuous runs out and the electrolyte is provided as a bath (22) through which the metal object (14) is continuous is carried out. 18. The method according to any one of claims 12 to 16, characterized characterized in that the deformation takes place discontinuously and the electrolyte is provided as a bath into which the object is introduced and from which it is removed before deformation. 19. The method according to claim 17, characterized in that that the further electrolyte with which the object is brought into contact after the deformation, is provided as a bath that the object passes through continuously. 20. The method according to claim 18, characterized in that the further electrolyte with which the object is brought into contact after deformation, 109821/2224 is contained in a bath into which the object is introduced and from which it is removed after deformation will. 21. The method according to claim 18 or 20, characterized in that the further electrode is in the working position to the metallic object is only held in the areas> where a lubricant film is to be created so that a local lubricant film is generated on the object, or a lubricant film of increased strength at certain Places the object can be provided. 109821/2224