FR2773817A1 - A new lubricating composition for the pretreatment of steel components before cold forming - Google Patents

Abstract

A water-based alkaline soap/polyamide composition for reducing friction between the surface of a steel component and the forming tool in cold forming operations such as extruding, wire drawing etc. A new lubricating composition for the pretreatment of steel components before cold forming operations which comprises an alkaline soap and a non-modified or modified water-soluble polyamide (or mixture of both types of polyamide). Independent claims are also included for: (1) the lubricant bath containing the composition and process of application; and (2) a two-compartment kit with separation of the soap from the polyamide.

Description

COMPOSITION, BATH AND LUBRICATION METHOD
OF THE SURFACE OF METAL PARTS IN STEEL
MUST BE COLD CHALLENGES
The subject of the invention is a composition for the lubrication of the surface of metallic steel parts to be cold deformed.

 It also relates to the bath comprising the above-mentioned composition and with the aid of which the surface of the metallic steel parts to be cold-deformed is treated.

 Finally, it relates to the process for implementing the above composition and bath as well as the use of these for the lubrication of the surface of metallic steel parts to be deformed when cold.

 Cold deformation operations of metal parts, including those of steel, include extrusions, cold stamping, drawing and drawing.

 I1 is known to reduce, during cold deformation operations, the frictional forces appearing between the part to be deformed and the tool, to subject, before the deformation operation, the part to be deformed to a lubrication treatment. .

 In fact, excessively high friction forces result, on the one hand, in appearance defects in the surface of the deformed parts and, on the other hand, accelerated wear of the tool used during the operation deformation.

 The lubrication treatment successively comprises a step of preparing the surface of the parts to be deformed and a lubrication step proper.

 The surface preparation step can include degreasing, pickling, shot blasting, refining, phosphating, boraxing, oxalation or a combination of these treatments.

 The actual lubrication step consists in coating the prepared part as indicated above with an oily or dry lubricating layer.

 The oily lubricating layer can consist of mineral, animal, vegetable or synthetic oils, reactive or not, possibly containing so-called extreme pressure and lubricity additives; it has the drawback of leaving an annoying fatty liquid deposit for the subsequent handling and storage of the parts.

 The dry lubricating layer consists of a soap which can be reactive or not.

 Reactive soaps are used in the case of significant cold deformation.

 Such a reactive soap often consists of zinc stearate obtained in situ by an application of sodium stearate on a deposit of zinc phosphate and, where appropriate, of manganese, this deposit coating the steel part.

 This operation can be carried out, for example, by dipping the part to be lubricated in an aqueous conversion bath based on zinc phosphate, heated between about 600C and 700C, then in an aqueous bath of alkaline soap based on sodium stearate ( for example, that marketed by the Applicant Company under the brand PROLUB TS 438 ET, at 5% in water) heated to 70-800C.

The main reaction involved is described by
N. Bay in the "Journal of Materials Processing Technology", page 26, 46 (1994) and results in the following chemical equation:
Zn3 (P04) 2 + 6 CH3 (CH2) x COONa <3 (CH3 (CH2) CO) 2Zn + 2 Na3PO4
So-called non-reactive soaps are used in the case of minor deformations (wire drawing for example); these include metallic soaps in powder form, such as the sodium stearates previously mentioned.

 To improve the efficiency of the lubricating layer, it has been proposed to add mineral pigments such as graphite, molybdenum disulfide, borax, sodium pyrophosphate, talc, mica, or kaolin; thus, in patent EP 0 315 532 B1, the improvement of lubrication performance is described by the addition of halides of solid lanthanides.

 The elimination of these mineral pigments after the deformation operations poses problems; in fact, during subsequent heat treatments such as annealing, the layers containing these mineral pigments leave deposits on the parts which eventually foul the annealing furnace.

 Another drawback lies in the fact that, in the case of black materials such as molybdenum disulphide or graphite, there is a deterioration in working conditions due to the presence of black dirty dust in the workshop, on the operators, the work station, the tools and the treated parts.

 In the case of difficult cold deformations, the deposit of the usual quantity of soap is not enough and the formed parts may have defects in the form of grooves; however, such grooves cause deterioration of the tool matrix and, to remedy this, the amount of soap is increased by increasing its concentration in the bath.

 However, by increasing the quantity of soap, it is no longer possible to ensure the homogeneity of the coating and, moreover, the adhesion of the soaped layer to its support is made insufficient; moreover, an excess of lubricant is entrained in the forming die.

 Those skilled in the art therefore wish to reduce the weight of the lubrication layer. Such a reduction has the advantage of making the layer more regular, of avoiding problems of adhesion and of facilitating the adjustment of the layer weights on the parts to be deformed. Furthermore, the treatment of the part after deformation becomes much easier. Indeed, the deposit being weaker, one can hope for a reduced fouling in the subsequent annealing furnace or a shorter cleaning time in the aqueous alkaline and / or degreasing acid baths. Finally, two other advantages inherent in a reduced deposit reside, on the one hand, in the savings made thanks to a lower consumption of soap and, on the other hand, in lesser environmental problems due to the reduction in discharges aqueous.

 The object of the invention is, above all, to remedy the drawbacks of the prior art and in particular to provide a composition of the kind in question which responds better than those which already exist to the various requirements of practice.

 And the Applicant Company had the merit of having found, after in-depth research, that this object was achieved as soon as a lubricating composition based on soap is made to contain an effective amount of a polyamide possibly amended.

 It follows that the composition according to the invention for the lubrication of the surface of metallic steel parts to be cold deformed is characterized in that it comprises at least one alkaline soap and at least one polyamide chosen from the group comprising unmodified polyamides and modified water-soluble polyamides, as well as mixtures of these unmodified polyamides and these modified polyamides.

 According to an advantageous embodiment, the composition in accordance with the invention comprises one or more adjuvants chosen from the group comprising sequestering, anticorrosion, preserving, surfactants, dyes, perfumers, texture or filler agents.

 According to another advantageous embodiment, the composition according to the invention comprises from 30 to 99.9%, preferably from 60 to 98% by weight of alkaline soap and from 0.1 to 70%, preferably from 2 to 40% by weight of unmodified polyamide and / or modified polyamide.

 According to another advantageous embodiment of the composition according to the invention, the alkaline soap entering into its constitution is chosen from the group comprising sodium soaps, potassium soaps and mixtures of these soaps.

According to another advantageous embodiment of the composition according to the invention, the unmodified polyamide is chosen from the group comprising those represented by the formulas
r
tNH (CH2) xCO
and
Ê NH (CH2) x NH CO (CH2) y CO;
where the value of x and y is a number
whole from 4 to 12, as well as mixtures of these products.

 According to another advantageous embodiment of the composition according to the invention, the unmodified polyamide entering into its constitution is chosen from the group comprising polyamides 6, 6.6 and 11 as well as their mixtures.

 According to another advantageous embodiment of the composition according to the invention, the modified water-soluble polyamide is chosen from the group comprising those obtained by at least partial incorporation of ether bridges in the polymer chain and those obtained by incorporation into less partial nitrogen in amine form, in ion form or in nitrile form.

 According to another advantageous embodiment of the composition according to the invention, the polyamide entering into its constitution is in granular form, the average diameter of the constituent particles being less than 100 μm and, preferably, close to 20 μm.

 According to another advantageous embodiment of the composition according to the invention, the modified polyamide entering into its constitution is used in the form of pellets whose diameter is advantageously close to 5 mm, these pellets being soluble in water, the alcohol and polar solvents in general.

 The solubility of the modified polyamides is such that by mixing, optionally in an acid medium, an amount less than 100 g and preferably more than 5 g of modified polyamide with 100 ml of the solvent (s) at 800C (or at the point d 'boiling if it is below 800C) for three hours then cooling to 250C, the final mixture obtained is perfectly homogeneous and clear.

 With regard to the adjuvants possibly comprising the composition in accordance with the invention, the following will be noted.

 The sequestering agents can be chosen from the group comprising the alkali metal or alkanolamine salts of EDTA, NTA, phosphonic, gluconic, glucoheptonic and polyphosphoric acids, as well as the polyacrylic acid derivatives known as sequestering agents.

 The anticorrosion agents can be chosen from the group comprising the alkali metal or alkanolamine salts of benzoic, sulfonic or nitrogen acids, carboxylic, oleylsarcosinic acids and alkylaryl-sulfoamidocarboxylic acids.

 The preservatives can be chosen from the group comprising formaldehyde, triazine derivatives, orthophenylphenol or its sodium salt, sodium omadine derivatives, isothiazolone derivatives and diodocarbamate derivatives.

Surfactants whose action can be wetting and / or dispersing can be chosen from the group comprising:
- the anionic derivatives and in particular the salts formed between an alkali hydroxide, an amine or an alkanolamine and a carboxylic acid having a carbon chain from C10 to
C22, as well as the salts of an alkali hydroxide, an amine or an alkanolamine of a sulfonated or sulfated fatty substance, sulfated fatty alcohols, sulfated fatty amides, sulfonated hydrocarbons, alkylaryl sulfonates and
- non-ionic derivatives and in particular polyalkylene glycol esters of high molecular weight alcohols, amides, substituted amides, fatty acids, esters or amines.

 The dyes can be constituted by fluorescein and the perfuming agents by pine essence.

 The texturing agents making it possible to modify the appearance of the product can be chosen from the group comprising fatty acid esters, in particular polyglycol carboxylates such as polyglycol oleate.

 The fillers can be chosen from the group comprising alkali carbonates or phosphates, mineral or synthetic hydrocarbons such as paraffins or isoparaffinic waxes as well as waxes of animal or vegetable origin, carboxylic, phosphoric or sulfonic acids, their oxides, their salts, their esters, higher alcohols, amines, polyalkylene glycols or their derivatives containing one or more chemical functions on the same chain, water-soluble resins such as cellulose, methylcellulose, styrene-acrylic copolymers and styrene-maleic anhydride copolymers.

 The bath according to the invention for the lubrication of the surface of metallic steel parts to be cold deformed is characterized in that it is water-based and that it has a proportion of 0.1 to 50 %, preferably from 1 to 20% by weight of the composition according to I, invention.

 The process according to the invention for the lubrication of the surface of metallic steel parts to be cold deformed is characterized in that the composition or the bath conforming to the application to the parts to be cold deformed invention, this application can be done, when it is the bath which is implemented, by soaking for a period of 15 seconds to 15 minutes, the temperature of the bath preferably being from 40 to 900C.

 For the convenience of use, it is advantageous to present the composition in accordance with the invention in the form of a "kit".

 Such a "kit" can advantageously include two compartments, one of which contains the soap or soaps and any adjuvants and the other of which contains the polyamide alone.

 The contents of the two compartments are then mixed when the composition or the bath is made up.

 The advantage of such a "kit" is that, in the case where the cold deformation to which a metal piece of steel must be subjected is not very significant, the lubrication provided by the soap alone may be sufficient and it it then becomes possible to save the polyamide for large deformation operations where only the composition according to the invention can make it possible to achieve advantageous results.

 The invention can be understood even better with the aid of the examples which follow, these examples being in no way limiting but relating to advantageous embodiments of the invention.

EXAMPLE 1
32.9 g of water are poured into a heatable mixer and then, with stirring, 10.9 g of sodium hydroxide. 3 g of benzoic acid and 0.2 g of pentasodium salt of aminotrimethylenephosphonic acid are then loaded. 5 g of oleic acid, 66 g of stearic acid are then introduced, then slowly 10 g of polyamide 6, the average diameter of the constituent particles of which is 20 μm. After 2 hours of mixing at 900C, 100 g of a lubrication composition according to the invention called "lubricant (1)" are obtained, which is in the form of a powder of homogeneous ivory color.

 Seamless steel tubes are immersed in an aqueous solution of a composition based on zinc acid phosphate marketed by the Applicant Company under the trademark THERMOGRANODINE 67 M. They are then dried and then immersed for 3 minutes in an aqueous bath of 20,000 liters maintained at 680C, comprising 2.5% by weight of lubricant (1). The total weight of soap deposited is approximately 8 g / m2. The tubes can then be drawn at maximum speed, with an elongation rate of 20%, without scratching or damaging the tool.

 An entirely identical operation is carried out on steel tubes identical to the previous ones, but using a composition called "lubricant (2) fi; the lubricant (2) is identical in all respects to the lubricant (1), with the difference it does not contain polyamide. We are obliged to deposit 15 g / m2 of soap, that is to say to maintain the immersion for 6 minutes to achieve lubrication of the same efficiency as with the lubricant (1) .

 The lubrication composition in accordance with the invention therefore makes it possible to work with a quantity of soap half as large as in the case of the lubricant (2), which leads to a lower cost of soap, in cleaning the tubes and in fouling the furnace. annealing.

EXAMPLE 2
A press is used allowing the deformation by cold striking of blanks full of steel in five successive work stations in each of which each piece is struck once.

 We record the appearance after striking the plot.

A first batch of 500 pieces is immersed in an aqueous bath of a composition based on zinc acid phosphates and manganese marketed by the Company
Applicant under the brand THERMOGRANODINE 780 CF.

 These pieces are then dried and then immersed in an aqueous bath maintained at 700C and containing the lubrication composition constituted by the lubricant (1) at a concentration of 3% for 5 minutes.

 They are again dried at 900C and subjected to the above deformation by striking.

 The treatment therefore comprises a lubrication step and five deformation steps without any additional intermediate lubrication.

 The appearance after striking of the plots is considered satisfactory, the plots showing no scratches.

 An identical operation is carried out on a second batch of 500 plots identical to the preceding ones by using an aqueous bath containing a lubricant (3), which is identical to the lubricant (1), except that it does not contain polyamide , the latter having been replaced by teflon at the same concentration, the temperature being 700C and the immersion time being the same.

 The appearance of the plots of this second batch is not satisfactory because we note the presence of numerous scratches.

EXAMPLE 3
A press is used allowing the cold deformation of a piece of solid raw steel in a single operation.

 The appearance after striking the plot is noted and it is checked whether the tool matrix has been dirty or not.

A first batch of 2,200 plots is immersed in an aqueous bath comprising a composition based on zinc acid and manganese phosphates sold by the Company
Applicant under the brand THERMOGRANODINE 780 CF.

 These pieces are then dried and then immersed in an aqueous bath maintained at 700C and containing the lubrication composition constituted by the lubricant (1) at a concentration of 3%; the immersion is 5 minutes.

 The pieces are then dried at 900C.

 The appearance after striking of the pieces is considered satisfactory and the tool matrix is clean.

 An identical operation is carried out on a second batch of 2200 plots identical to the previous ones, with the difference that in place of the lubricant (1) a reactive soap based on sodium stearate sold by the Applicant Company under the brand PROLUB is used. TS 438 always at 3% concentration.

 To obtain a satisfactory appearance of the deformed pieces and to avoid fouling of the matrix, it is necessary to add to the surface of the pieces and in addition to the reactive soap, molybdenum disulphide powder applied with a brush before the deformation.

 The major drawbacks noted reside in a deterioration of working conditions with the significant presence of black dust in the workshop, on the work station, the tools and the treated parts.

EXAMPLE 4
65.4 g of stearic acid are poured into a heatable mixer and then, with stirring at 850 ° C., 20.4 g of polyamide 6.6, the average diameter of the constituent particles of which is 10 μm
9.2 g of sodium hydroxide and 9.2 g of water are then loaded and the mixture is brought to 1200C for 2 hours.

 Then 9.2 g of sodium carbonate are added and, after homogenization, the whole is passed through a grinder to obtain 100 g of a lubrication composition in accordance with the invention called "lubricant (4) including grain size at 52% between 0.3 and 1 mm.

 Steel wires with a diameter of 5.5 mm coated with a layer of lubricant (4) applied by entrainment during the passage of the wires in boxes filled with said composition, were subjected to a drawing operation during from which their diameter was brought in 10 passes to 1.5 mm; the son thus obtained have no irregularity in diameter and, moreover, their surface condition is satisfactory.

Claims (10)

RBVENDICATIONS  1. Composition for the lubrication of the surface of metallic steel parts to be cold deformed, characterized in that it comprises at least one alkaline soap and at least one polyamide chosen from the group comprising unmodified polyamides and polyamides water-soluble modified polymers and mixtures of these unmodified polyamides and modified polyamides.  2. Composition according to claim 1, characterized in that it comprises one or more adjuvants chosen from the group comprising sequestering agents, anticorrosion, preservation, surfactants, colorants, perfumers, texture or filler.  3. Composition according to one of claims 1 and 2, characterized in that it comprises from 30 to 99.9%, preferably from 60 to 98% by weight of alkaline soap and from 0.1 to 70%, preferably from 2 to 40% by weight of unmodified polyamide and / or of modified polyamide.  4. Composition according to one of claims 1 to 3, characterized in that the alkaline soap entering into its constitution is chosen from the group comprising sodium soaps, potassium soaps and mixtures of these soaps.  5. Composition according to one of claims 1 to 4, characterized in that the unmodified polyamide is chosen from the group comprising those represented by the formulas ÉNH (CH2) XCO $  and  4 NH (CH2) xNH CO (C H2) y C 0  where the value of x and y is a number  whole from 4 to 12, as well as mixtures of these products.  6. Composition according to one of claims 1 to 5, characterized in that the modified water-soluble polyamide is chosen from the group comprising those obtained by at least partial incorporation of ether bridges in the polymer chain and those obtained by at least partial incorporation of nitrogen in amine form, in ion form or in nitrile form.  7 Composition according to one of claims 1 to 6, characterized in that the unmodified polyamide entering into its constitution is in granular form, the average diameter of the constituent particles being less than 100 µm and, preferably, around 20 pine.  8. Bath for the lubrication of the surface of metallic steel parts to be cold deformed, characterized in that it is water-based and that it has a proportion of 0.1 to 50%, preferably from 1 to 20% by weight of the composition according to one of claims 1 to 4.  9. Method for lubricating the surface of metallic steel parts to be cold deformed, characterized in that the composition according to one of claims 1 to 7 or the composition is applied to the parts to be cold deformed bath according to claim 8, this application being able to be made, when it is the bath which is implemented, by soaking for a duration of 15 seconds to 15 minutes, the temperature of the bath preferably being from 40 to 900C.  10. Kit for presenting the composition according to one of claims 1 to 7, characterized in that it comprises two compartments, one of which contains the soap or soaps and any adjuvants and the other of which contains the polyamide alone .