DE3880084T2 - METHOD FOR LUBRICATING THE SURFACE OF METALLIC MATERIALS MADE OF COPPER OR IRON AND COPPER ALLOYS DURING COLD OR HOT FORMING AND MEANS TO CARRY OUT THIS LUBRICATION. - Google Patents

Abstract

Process for lubricating the surface of metal pieces made of copper or of iron- or copper-based alloys, intended to be deformed when cold or with heating, which process comprises a traditional surface preparation and the application of at least one lanthanide halide.

Description

The invention relates to a method for lubricating the surface of metallic workpieces made of copper or iron or copper alloys before they are hot or cold formed.

It also relates, as new industrial products, to lubricating agents used in the above-mentioned process, said agents essentially comprising a lubricant and compositions containing said agent.

The alloys in question are those in which copper or iron is the main component and which in particular contain brass, bronze, copper-nickel alloys, nickel-copper-zinc alloys, steels, cast iron and stainless steels.

When a metal or alloy is to be cold worked, in particular when it is at room temperature before the forming operation, which may be extrusion, cold heading, stretching or wire drawing, or when the elastic limit of the metal is modified by increasing the temperature before the forming operation, which may be die forming, Forging or pressing, it would be advisable to reduce the frictional forces beforehand in order to reduce the deformation pressures to a level compatible with the resistance of the materials making up the tool used.

It is known that in order to achieve this goal, lubrication is used which allows a very low coefficient of friction to be obtained, which must be maintained throughout the entire duration of the deformation process in order to ensure that the piece formed has a good surface condition and thus to avoid excessively rapid wear of the tool.

The means used to date to reduce the friction coefficient consist of carrying out a surface preparation on the workpiece to be deformed, followed by lubrication.

Surface preparation may consist of degreasing, pickling, blasting, fine shearing, phosphating, oxalating, galvanizing or copper plating or a combination of several of these treatments.

The metal prepared in this way is then provided with a lubricating layer which can be composed

* from a lubricating oil based on mineral, animal, vegetable or synthetic oils containing extreme pressure additives, natural or synthetic fat esters and antioxidants

* from a soap resulting from the reaction between a natural or synthetic fatty acid containing a carbon chain C₁₀ to C₂₂ and an alkali hydroxide, an amine or an alkanolamine, said soap also containing dispersants, the formation insoluble soap avoid complexing agents, bactericides, fungicides or

* from a solid lubricant used alone or as a dispersion in one of the two products described above, the solid lubricants most commonly used are molybdenum disulphide for cold working and graphite for hot working.

Molybdenum disulphide and graphite are satisfactory in terms of reducing the coefficient of friction, but they have a number of significant disadvantages, since when applied in the form of powders or black dispersions they are very sticky and difficult to remove, they cause contamination of the workplace and workshop and contamination of the treated workpieces and work equipment.

Furthermore, the difficulties encountered in removing molybdenum disulphide and graphite from the treated surface cause problems in operations following deformation, such as before the application of paint, machining, a new deformation cycle and other thermal treatments which may be hampered by the presence of sulphur in the case of molybdenum disulphide.

Finally, the clogging of the distribution circuits (circuits de distribution) often occurs due to the same difficulties in removing the products in question.

The overall disadvantages of using molybdenum disulfide and graphite have led the expert over the last twenty years to develop new lubricant compositions based on mineral salts or synthetic products whose lack of performance made it impossible to find significant industrial applications.

And it is to the applicant's credit, after completing its fundamental research, that it has provided a solution to this difficult problem by discovering that it is possible to give metal workpieces, before cold or hot forming, a friction coefficient at least as low as that obtained with molybdenum disulphide or graphite, without the disadvantages associated with the use of these products, by treating the said metal workpieces after the conventional surface pretreatment (including degreasing, shot blasting, fine shearing, phosphating, oxalation or several of these treatments) with at least one of the lanthanide halides from the group comprising lanthanum fluoride and cerium fluoride, preferably applied in the form of an aqueous or oily dispersion or coated with a wax or mixed with a powdered dry soap, the products in question having the are easily eliminated, neither black nor sticky.

This means that the method according to the invention for lubricating the surface of metallic workpieces made of copper or iron or copper alloys intended for cold or hot forming is characterized in that after the conventional surface treatment, at least one of the lanthanide halides of the group comprising lanthanum fluoride and cerium fluoride is applied to the surface of the workpieces, preferably in the form of an aqueous or oily dispersion or a mixture of a wax or a powdered dry soap.

Likewise, an object of the invention is the use of a lubricant which consists essentially of at least one of the lanthanide halides of the group comprising lanthanum fluoride and cerium fluoride, for lubricating the surface of metallic workpieces made of copper or iron or copper alloys before cold or hot working.

The above-mentioned lubricant is preferably used in the form of an aqueous dispersion or in the form of a mixture with a powdered dry soap.

The above-mentioned dispersions or mixtures, as well as the concentrates from which the dispersions are made, represent new industrial products or mixtures.

It is noted that cerium fluoride has already been added to lubricants intended for use under extreme temperature or pressure conditions (U.S. Patent No. 4,507,214) and that the cerium and lanthanum fluorides have been used in hot-pressure metal melting processes (U.S. Patent No. 3,380,280).

But not only do these earlier documents not refer to the cold or hot working of copper or iron-based metals, but no indication is given that would lead the skilled person to apply the compositions in question to that field of technology.

As stated above, lanthanide halides can be used in the form of aqueous or oily dispersions or coated in a wax or mixed with a powdered dry soap.

Insofar as they are primarily aqueous lanthanide halides, they contain surface-active agents that act as wetting agents or dispersants, which can be selected from

- anionic derivatives and in particular the salts formed between, on the one hand, an alkali metal hydroxide, an amine or an alkanolamine and a natural or synthetic fatty acid comprising a carbon chain of C₁₀ to C₂₂ and, on the other hand, the salts of an alkali metal hydroxide, an amine or an alkanolamine, a sulphonated or sulphated fatty substance, a sulphated fatty alcohol, a sulphated fatty amine, a sulphated nonionic substance, a sulphonated hydrocarbon and a sulphonated alkylaryl.

- From non-ionic derivatives and in particular from esters of polyethylene glycol, oxyethylenated and oxypropylenated derivatives of alcohols with higher molecular weight, amides, substituted amides, fatty acids, esters or amines.

These aqueous dispersions may also contain one or more complexing agents, one or more anti-corrosive agents, one or more preservatives or, moreover, several of these different products at the same time.

The complexing agents can be selected from the group comprising EDTA, NTA, phosphonates of the salts of alkali metals or of alkanolamine and polyphosphates.

The anti-corrosive agents can be chosen from the salts of alkali metals or alkanolamines with sulfonic acids, carboxylic acids, oleic sarcosines (oleylsarcosines) and alkylarylsulfonamidocarboxylic acid.

The preservatives can be selected from formaldehyde solution, triazine derivatives, orthophenylformaldehyde solution or its sodium salt.

The oily dispersions can contain mineral oils from petroleum, which can be paraffin oils, naphthenic oils, aromatic oils. The oil can also be a synthetic oil such as a poly-α-olefin or an alkylate, a vegetable oil such as rapeseed oil, castor oil, soya oil or animal oil such as lard oil, cow's foot oil (l'huile de pied de boeuf). These oily dispersions can also contain synthetic fatty esters such as polyethylene glycol esters and viscosity additives such as aluminosilicates and the modified carboxyl derivatives.

They may also contain one or more dispersants, one or more preservatives or even several of these products at the same time.

The dispersants can be calcium or aluminum alkylarylsulfonates.

The preservatives can be selected from triazine derivatives.

The waxes used to coat the lanthanide halides can be mineral waxes such as microcrystalline waxes or paraffins, as well as animal or vegetable waxes.

They may also contain texturing agents such as fatty acid esters, in particular polyglycol carboxylates such as polyethylene glycol oleate, which allow the appearance of the final product to be modified.

The powdered dry soaps can be formed from the reaction products of alkali and/or alkaline earth hydroxides with at least one natural or synthetic fatty acid containing a carbon chain of C₁₀ to C₂₂.

Finally, it is possible to provide inert fillers in the above-mentioned lubricant products, which can be carbonates, sulphates or water.

The application of the lubricant and dispersant and mixtures for its use according to the invention on the surface of the workpiece to be deformed can be carried out

- by spraying with a compressed air gun

- in the immersion bath in the cold or heat

- manually by coating with a brush, a brush, a roller or

- by rubbing a wax stick

- by coating by passing through a box with powdered soap for wire drawing.

When the lubricant is applied in the form of an aqueous or oily dispersion or in the form of a mixture with a wax, its concentration in the application medium is from 0.05 to 60% by weight; it is preferably from 0.05 to 5% by weight in the case of an aqueous dispersion, from 0.1 to 15% by weight in the case of an oily dispersion and from 5 to 60% by weight in the case of a mixture with a wax and from 0.05 to 5% by weight in the case of a mixture with a powdered soap.

To prepare the aqueous or oily dispersions, powders or liquids can be used which, in addition to at least one of the lanthanide halides of the group containing lanthanum fluoride and cerium fluoride, contain the other dispersion components in the concentrate.

These concentrated products may have a content of at least one of the above-mentioned lanthanide halides, which may be 5 to 30% by weight in the case of aqueous dispersions and 1 to 50 % in the case of those intended to produce oily dispersions, respectively.

If dilution is necessary at the time of application, it is carried out using water for aqueous dispersions and using oil or a petroleum-based solvent in the case of an oily dispersion.

Moreover, the lubricants can be introduced into the application environment simultaneously with a conventional lubricant and advantageously the user can be left to use independently a set of products that allow the process according to the invention to be carried out, namely:

- a first essential product containing a lanthanide halide, in particular a cerium and/or a lanthanum fluoride with a concentration of 1 to 99.9% and

- in the case of carrying out the process by application of an aqueous dispersion, a second product leading to the precipitation of a soap, or

- in the case of carrying out the process by application of an oily dispersion, a third product containing an oil which may comprise the additives provided for in this case,

- in the case of implementation of the process by mixture with a powdered dry soap, a fourth product containing this powdered dry soap the first and the second, third or fourth product may be marketed in the form of "kits" on a case-by-case basis.

Before explaining the invention by means of the following comparative examples, in which some advantageous embodiments are shown without limiting the scope of the invention, a special advantage is emphasized which resides in the possibility of realising the deformation of different workpieces using the same manufacturing process and a single operation sequence for surface pre-treatment and lubrication, insofar as the application of the state of the art processes required different surface pre-treatments.

example 1

A comparative test is carried out using successive oil dispersions of cerium fluoride, graphite and molybdenum disulfide in the so-called ring test (test de l'anneau). The graphites and molybdenum disulfides used are of the usual quality for this type of application, namely

- a graphite powder with a grain size classification such that 50% of the grains are smaller than 8 µm and 100% are smaller than 32 µm, the specific surface area BET is 16 m²/g, this graphite can be that of LONZA grade T10,

- a powdered molybdenum disulphide with 99% purity and a grain classification so that 50% of the grains have a size of less than 8 µm, e.g. those of quality No. 4 from the company KS PAUL.

The cerium fluoride used is in white powder form with 98% purity, a grain classification such that 74% of the grains have a size of less than 100 µm.

The ring test used to measure the friction coefficients obtained using the various oily dispersions is described in the publication "Metal deformation process: friction and lubrication" by J.A. SCHEY, pages 270 to 271, edited by Marcel Dekker, 1970.

This test allows to determine the coefficient of friction existing between a tool and a material subjected to plastic deformation under specific surface and lubrication conditions.

When a metal ring is squeezed between two flat hand anvils (tas plats), it is found that the diameter of the hole for a given compression deformation depends on the friction conditions; the weaker the frictions, the larger the hole.

The rings used for the test are made of steel of quality XC 10 and have the following dimensions:

- outer diameter 42 mm

- inner diameter 21 mm

- Height 7mm.

The tool used for the test consists of two flat hand anvils made of steel of quality Z 20 OC 12. The reduction in the height of the metal ring during the tests varies between 20 and 40%.

The results from the measurements of the change in height and the change in inner diameter made it possible to derive the value of the contact friction coefficient using prefabricated nomograms.

In the present example, the rings were lubricated by immersion at ambient temperature in dispersions containing 5% by weight of graphite, molybdenum sulphide or cerium fluoride in naphthenic oil of uniform viscosity of 75 centistokes at 40ºC.

The results obtained are summarized in Table 1. Table 1 Test Friction coefficient Appearance of the ring after deformation Mineral oil shiny and clean Mineral oil black and sticky

This example demonstrates the fact that the lubricant according to the invention allows to obtain friction coefficients sufficient to obtain favorable visual results without contaminating the treated part.

Example 2

A comparative test is carried out under industrial conditions and consisting of a "pre-extrusion" process ("filage avant") carried out on a workpiece of the hollow steel forging type.

Traditionally, the forging blanks to be subjected to pre-extrusion are prepared by successively carries out a phosphating which can be carried out in the usual way using a phosphating bath of the type sold by the applicant under the trade name THERMOGRANODINE 701. This phosphating is followed by a dip coating in an aqueous dispersion of MoS₂ containing 5% by weight of this product.

It is impossible to carry out the above-mentioned pre-extrusion by phosphating followed by a simple lubrication by soap deposit: it leads in fact to rapid contamination of the tools and the pieces obtained are unacceptable.

In the present comparative test, two series of 600 forging blanks (lopins) of the same type as above are successively subjected to phosphating using THERMOGRANODINE 701 and to immersion lubrication, using in the first case a conventional aqueous dispersion of 5% by weight of MoS₂ and in the second case a mixture of an aqueous dispersion of 0.5% by weight of CeF₃ and a solution of 5% by weight of an anionic surfactant consisting of a soap, in this case sodium stearate, for example sold by the applicant under the trade name PROLUB TS 438 and which leads to the deposition of a lubricating soap.

The conditions for carrying out the lubrication are summarized in Table II. Table II According to the prior art According to the invention Composition of the bath MoS₂ dispersion 5 % in water PROLUB TS 438:5 % CeF₃: 0.5 % water in qsp 100 Temperature Duration of immersion minute

The dimensional control of the 600 pieces deformed after treatment according to the method of the invention gave identical results to those recorded after treatment according to the prior art method; the results show that the deformed pieces comply with the tolerances given in Table III: Table III Tolerance in mm around the standard outer diameter inner diameter

The outer diameters φ 1, φ 2, φ 3 and the inner diameter φ in. are specified for the shape of the workpiece and can be seen in the only drawing showing this workpiece in axial section, respectively in a, b, c and d.

The deformation angle control by profile projection shows similar results for both methods.

The deformed workpieces obtained by the process according to the invention are easier to machine and appear cleaner than with the conventional process.

This example therefore shows that, thanks to the invention, it is possible to carry out industrial cold working of pieces which, in the prior art, required the use of molybdenum disulphide; the advantage obtained by the invention lies in the clean appearance of the pieces obtained, which is not the case for pieces treated according to the prior art, which must be cleaned before the subsequent operations.

Example 3

A comparative test is carried out under industrial conditions and consisting of a pre-extrusion operation followed by a post-extrusion operation (filage arriere) of steel forging blanks (lopins en acier) using a hydraulic press with a force of 600 T (ram feed speed = 40 min/s).

Two series of 2100 forging blanks of the above-mentioned type are subjected to successive pre-extrusion and post-extrusion operations after a lubrication treatment according to the prior art processes for the first series and according to the process according to the invention for the second series, each of these treatments being carried out after phosphating with the product THERMOGRANODINE 701, which is a phosphating bath sold by the Applicant and used in a conventional manner. The characteristics of the two lubrication treatments are summarised in Table IV. Table IV According to the prior art According to the invention Composition of the lubricating bath Treatment time Bath temperature Lubricating soap PROLUB TS 438: 5 wt.% in water 5 wt.% of the lubricating soap PROLUB TS 438 and 0.5 wt.% CeF₃ in water Minutes

The pre-extrusion and post-extrusion operations were carried out, 50 pieces were taken from each series and subjected to the classic dimensional control and the comparative measurement of the standard deviation. The results obtained are summarized in Table V. Table V According to the state of the art According to the invention Standard deviation post-extrusion Standard deviation pre-extrusion

When assessing these results, it is found that the lubrication process according to the invention allows the cold forming operations to be carried out industrially with greater functional reliability than the process according to the state of the art.

Example 4

A comparative test is carried out under industrial conditions and consists of a post-extrusion operation of steel workpieces; two series of 500 steel forging blanks are involved; the operation is carried out using a hydraulic press with a force of 1600 T (ram speed = 50 mm/s).

The steel forging blanks were previously phosphated using a THERMOGRANODINE 701 bath and then lubricated:

- as regards the first series, successively with the help of an anionic soap, e.g. PROLUB TS 438 5 wt.% in water (for 5 minutes at 80ºC), then with the help of powdered MoS₂ applied with a brush,

- as regards the second series, by immersion in an aqueous dispersion containing 5% by weight of an anionic soap, which may consist of that sold under the trade name PROLUB TS 438, and 0.5% by weight of CeF₃, the immersion time being 5 minutes and the temperature of the dispersion being 80°C.

After the post-extrusion operation, the dimensional control carried out on both series of 500 pieces was found to be compliant with the standards and identical in both cases. It is worth highlighting the advantage of the clean appearance and non-polluting nature of the pieces lubricated using the method according to the invention, which also allows lubrication to be carried out in a single step, whereas the prior art method requires two.

From a more general point of view and in connection with Examples 2, 3 and 4, which were carried out using the same production route, it should be stressed that in the case of lubrication according to the prior art, it is usual to recourse to different processes depending on the deformation difficulties, whereas the process according to the invention makes it possible to use a single sequence of operations for surface preparation in the three cases.

Example 5

A comparative test is carried out under industrial conditions when carrying out cold deformation of forged blanks made of stainless steel of the Z6 C13 type, whereby the deformation was carried out by means of a mechanical press with a force of 600 T.

Two series of forging blanks were prepared with regard to deformation by applying the methods of the prior art for the first series and the method according to the invention for the second.

The two lubricating treatments were carried out by a surface pre-treatment which was identical in both cases and consisted of an oxalation based on the oxalic acid salts applied using the Applicant's commercial product under the trade name THERMOGRANODINE SS1 and SS5.

The lubricant treatment according to the prior art comprises successively a treatment with 5% by weight of an anionic lubricant soap PROLUB TS 438 in water, the duration being 5 minutes and the temperature 80°C, then a coating by immersion in a dispersion containing 5% by weight of MoS₂ in water, the duration being 1 minute and the bath temperature 60°C.

The lubricant treatment according to the invention comprises a single treatment step using an aqueous dispersion containing 0.5% by weight of CeF3 which also contains 5% by weight of PROLUB TS 438, the duration being 5 minutes and the temperature of the dispersion being 80°C.

The results obtained after the deformation process are summarized in Table VI: Table VI Workpieces treated according to the state of the art Workpieces treated according to the invention Press force (in tons) Dimensional control Appearance of the workpieces black, sticky clean, shiny

It should be emphasized again that in this example the lubricant treatment according to the invention was carried out in a single step, while in the treatment according to the prior art two steps had to be carried out.

Example 6

A comparative test of hot extrusion of brass under industrial conditions is carried out, consisting of heating brass blocks to 750ºC, then hot extrusion to obtain a wire of diameter varying between 5 and 11 mm, the drawing dies (filière) having been previously lubricated.

This lubrication was carried out according to the state of the art with a solid lubricant, ie graphite, coated with 50 wt.% of a paraffin wax with a dropping point of 80ºC, while the lubrication according to the invention was carried out by means of a mixture of 50 wt.% CeF₃ in the same paraffin wax.

Extrusion carried out after lubrication according to the invention resulted in a wire with a cleaner appearance than that resulting from the use of the lubricant according to the prior art. No abnormal wear of the dies was observed.

Example 7

An industrial test of dry drawing of galvanized steel wire is carried out. Lubrication is carried out using "soap containers" ("boites savon") into which the lubricating soap is placed dry. The drawing of the wire through the "soap container" makes it possible to obtain a lubricant coating by liquefying the dry soap on the hot wire, which allows it to pass through the drawing iron.

The test was carried out on a wire drawing machine with eight drawing irons, which allowed a total taper starting from 2.4 mm diameter at the inlet up to 0.69 mm diameter at the outlet.

The wire to be drawn is made of steel with 0.45% carbon content and is galvanized. Its resistance is 180 kg/cm².

The addition of 1% CeF₃ in the product PROLUB TN 110, distributed by the Compagnie Francaise de Produits Industriels, and consisting of sodium stearate, allows wire drawing to be carried out at a speed of 540 m/min, whereas PROLUB TN 110 alone does not allow this. In This last case causes rapid wear of the drawing dies and breakage of the wire.

Example 8

A test to evaluate lubricity was carried out in accordance with the automotive standard CNOMO D 55 1136 on a Shell Royal Dutch four-ball machine ("Machine 4 Billes Shell Royal Dutch"). This is a comparative test carried out by adding various lubricants described in Table VII to a paraffin oil with a viscosity of 620 centistokes at 40ºC, such as ENERPAR 27, sold by Societe Française BP.

The average diameter of the wear indentation is measured using a 100 kg batch. A small diameter indicates good lubrication. The test was carried out at ambient temperature. Table VII Prepared lubricants Impression diameter Paraffin oil

The lanthanum fluoride used occurs as a white powder with a purity of over 99% and a grain size classification in which at least 74% of the grains have a size of up to 100 µm.

From the study of the results summarized in Table VII, it can be concluded that cerium fluoride and lanthanum fluoride can be considered as additives that allow a satisfactory lubrication to be obtained, comparable to that of molybdenum disulphide, while giving a much better appearance to the treated parts.

Claims (10)

1. Process for lubricating the surface of metallic workpieces made of copper or of iron and copper alloys, which are intended for cold or hot forming, characterized in that after the production of the conventional surface, at least one of the lanthanide halides of the group containing lanthanum fluoride and cerium fluoride is applied to the surface of the workpieces. 2. Process according to claim 1, characterized in that the lanthanide halide is applied in the form of an aqueous or oily dispersion, a mixture with a wax or a mixture with a powdered dry soap. 3. Process according to one of claims 1 and 2, characterized in that the application of the lanthanide halide is in the form of an aqueous dispersion, an oily dispersion, a mixture with a wax or a mixture with a powdery dry soap on the surface of the workpieces to be deformed - by spraying with a compressed air gun - in the immersion bath in the cold or heat - manually by coating with a brush, a brush, a roller - by rubbing a wax stick or - by rubbing with a powdered dry soap. 4. Process according to one of claims 1 to 3, characterized in that the aqueous dispersion by means of which the lanthanide halide is used contains at least one surfactant which acts as a wetting agent or dispersant. 5. Use of a lubricant which essentially contains at least one of the lanthanide halides of the group comprising lanthanum fluoride and cerium fluoride for lubricating the surface of metallic workpieces made of copper or iron and copper alloys which are intended for cold or hot forming. 6. An aqueous dispersion containing a surface-active agent acting as a wetting agent or dispersant and 0.05 to 5% by weight of at least one of the lanthanide halides of the group comprising lanthanum fluoride and cerium fluoride. 7. A wax-based mixture containing 5 to 60 wt.% of at least one of the lanthanide halides of the group comprising lanthanum fluoride and cerium fluoride. 8. Concentrate for preparing the aqueous dispersion according to claim 6, comprising a surfactant, which acts as a wetting agent or dispersant and contains 5 to 30 wt.% of at least one of the lanthanide halides of the group comprising lanthanum fluoride and cerium fluoride and optionally a powdered dry soap. 9. Mixture based on a powdered dry soap, comprising 0.05 to 5% by weight of at least one of the lanthanide halides of the group containing lanthanum fluoride and cerium fluoride. 10. Use of an oily dispersion comprising 0.1 to 15% by weight of at least one of the lanthanide halides of the group containing lanthanum fluoride and cerium fluoride for lubricating the surface of metallic workpieces made of copper or iron and copper alloys which are intended for cold or hot forming.