EP2449068A1

EP2449068A1 - Rolling fluids

Info

Publication number: EP2449068A1
Application number: EP10740326A
Authority: EP
Inventors: Nicole Genet; Frédéric JARNIAS
Original assignee: Total Raffinage Marketing SA
Current assignee: TotalEnergies Marketing Services SA
Priority date: 2009-07-03
Filing date: 2010-07-02
Publication date: 2012-05-09
Also published as: FR2947559A1; US20120111079A1; US8413475B2; WO2011001414A1; KR20120107906A; RU2536468C2; FR2947559B1; CN102471716A; RU2011152232A

Abstract

The invention relates to a cold rolling fluid, including: (a) a hydrocarbon base including at least 50 wt % of isoparaffins; (b) one or more frictional modifiers selected from among fatty alcohols, fatty acids, fatty amines, fatty acid esters, or polymer esters resulting from the esterification of alpha-olefin copolymers and dicarboxylic acids using alcohols; and (c) one or more phosphorous anti-wear and/or extreme pressure additives. The invention also relates to an emulsion containing the rolling fluid and to the use of said rolling fluid for cold-rolling steel.

Description

i

ROLLING FLUIDS

FIELD

The present invention relates to oils for the cold rolling of steel, in particular of austenitic and ferritic steel.

BACKGROUND TECHNOLOGY

Rolling is an operation of shaping metal material by plastic deformation. It is intended to reduce the thickness of a sheet by passing between two or more pairs of axisymmetric tools rotating about their axis (typically cylinders). Their rotation causes friction product in the right-of-way consisting of entry, work and exit areas. Longitudinal pulling (exit) and countertrain (input) forces applied simultaneously make it possible to reduce the normal force imposed by the cylinders (clamping force).

Cold rolling makes it possible, after hot rolling, to give the product precise geometry, mechanical and metallurgical control characteristics and a well-controlled surface condition. The roughness obtained results from the transfer of the roughness of the tool on the sheet. It depends heavily on lubrication. Some bands must be delivered bright, so smooth (with a roughness close to 0.2μm). To manufacture a smooth sheet, polished or even polished cylinders are used as well as a low viscosity lubricant.

The surface states of the rolled strips may have irregularities, for example streaks which reflect the local rupture of the lubricating film resulting in the tearing of metal particles and their adhesion to the rolls.

From a chemical point of view, corrosion phenomena can appear. The presence of reaction films or the pollution of the strips by lubricants from previous operations are also difficulties to be avoided. During the annealing of the rolled strips, residues may stain the surface.

Figure 1 shows a metal strip in the right of way of a rolling mill. In the input zone, the initial thickness band ei is driven at a speed V ₁ by two rolls. It is plastically deformed in the work area and leaves the right-of-way with a thickness e ₂ . Due to the conservation of the quantity of material, the band is accelerated in the right-of-way as it is reduced and elongated. Thus, the output speed V ₂ of the band is greater than the input speed V ₁ . The reduction rate is defined by r = (ei - e ₂ ) / ei. In a usual rolling pass, there is a "neutral point" in the right-of-way, for which the peripheral speed of the rolls is equal to the local speed of the band. Its position depends on both the longitudinal stresses applied to the belt, the friction conditions, the reduction and the rolling speed.

Thus, except for a small area surrounding the neutral point, there exists in the right-of-way a relative sliding plate-cylinder, and thus a friction and shear stresses at the interface. Upstream of the neutral point, the cylinders tend to drive the belt into the right-of-way, the friction is motor.

The friction must be sufficient to allow the effective conduct of the sheet in the right-of-way but not excessive in order to avoid seizing or surface condition problems. The presence of a lubricant is essential to control the friction and consequently the regularity of thickness and the surface condition of the bands. It is therefore important to control the lubricant behavior at the level of the contact between the rolls and the strip to better control the friction in cold rolling.

Upstream of the neutral point, the cylinders tend to drive the belt into the right-of-way, the friction is motor. In this upstream zone, a mixed elastohydrodynamic (EHD) friction regime is encountered: in the most upstream zone, the lubricant film is continuous, the wear is low, there is no contact between the asperities of the two surfaces antagonists, but the pressures generated in the film are high enough to cause significant elastic deformations of the surfaces. The type of friction generated in this area can be reproduced on a ball - disk EHD tribometer.

Downstream of the neutral point, the sliding is opposed to the advance of the band: the friction is resistant. In this zone, there is a limit friction regime. In contrast to EHD lubrication, limiting lubrication is a regime in which the friction and wear of the two surfaces in relative motion are jointly determined by the properties of the solid surfaces and those of the lubricant. Thus, the thickness and nature of the oxide layers, the creation of fresh surface and its reactivity vis-à-vis the constituents of lubricants, including additives, greatly influence the friction. This type of friction can be reproduced on a plan Cameron cylinder plane tribometer.

The behavior of the rolling fluids upstream and downstream of the neutral point (of the right-of-way) is mainly governed respectively by the bases and fatty substances for the upstream part, where one is in EHD and mixed friction mode. Additivation, especially extreme pressure additives, contributes significantly in combination with the bases and the greasy substances, the performance of said fluids for the downstream part, where one is in the limit lubrication regime.

The work on rolling oils essentially concerns the nature of the fatty substances or synthetic esters introduced into the compositions. The fluids of the prior art are not optimized from the point of view of bases and additives.

The application EP 1 123965 thus describes a fluid for the cold rolling of steel comprising a hydrocracked or non-hydrocracked naphthenic or paraffinic base oil, optionally deflavored with solvent or by hydrotreating, the viscosity of which can be adjusted by kerosene cuts, from 1 to 80% of di (2 ethylhexyl) adipate as fat. The composition may further contain phosphorus, sulfur or phosphosulfur antiwear and extreme pressure additives.

EP 0242 925 discloses rolling fluids containing esters of amino alcohols and fatty acids having at least 6 carbon atoms. No extreme pressure additivation is disclosed in this document, and no indication is given on the nature of the mineral bases employed in said fluids.

No specific choice of base or additives is made in the rolling fluids of the prior art to ensure optimal friction properties in the EHD regime and / or limit regime. As a result, a given reduction ratio of the sheet thickness requires a number of rolling passes with these fluids. The use of these fluids of the prior art can also lead to seizures that no longer make it possible to laminate, or to microgrippings that are harmful to the surface state.

There is therefore a need for oils that make it possible to improve the productivity of the rolling mills, for example by reducing the number of passes necessary to obtain a given reduction ratio, without seizing or micro-sinking detrimental to the surface condition and in particular to the shine of the sheets.

The rolling fluids according to the invention have, on steel surfaces, coefficients of friction in the elastohydrodynamic regime Significantly lower than the lubricants commonly used in cold rolling. Thus, the neutral point is moved downstream, which leads to higher reduction rates per pass and reduces the total number of passes to achieve a given reduction rate. This improves the efficiency of the rolling mill.

In particular, when they contain phosphorescent extreme pressure additives, and / or phospho sulfur and / or sulfur, the fluids according to the invention also have, on steel surfaces, boundary friction properties superior to the fluids of the invention. prior art. In fact, the coefficients of friction obtained on a Cameron Plint tribometer with such fluids according to the invention show that, on ferritic and austenitic steel surfaces, friction coefficients that are significantly lower are obtained, up to more high and under higher load (thus in more severe friction regime), than with commercial lubricants for cold rolling of steel.

Under heavy load, commercial lubricants lead to an immediate seizure, while friction is observed up to temperatures of the order of 100 ⁰ C under heavy load with the lubricants according to the invention. Thus, the risk of seizure are considerably reduced and we can apply stronger loads on the cylinders and obtain significant thickness reduction rates with a reduced number of passes. This further contributes to improving the yield of the rolling mills, and also improves the surface finish of the rolled sheets.

This is all the more advantageous as these very good properties can be obtained with rolling fluids according to the invention having a low level of sulfur, or even free of sulfur.

The additives containing sulfur have a very effective action on the friction properties, especially in the limit regime, but tend to form iron sulphide on the fresh surfaces created by rolling, which leads to staining of the sheets. These tasks can be eliminated, in the case of austenitic steel, by annealing at 1200 ^° C., but H2S is formed, causing corrosion of the refractories of the furnaces. In the case of ferritic steel, annealing at 900 ^° C. does not eliminate the stains.

The rolling fluids according to the invention containing certain phosphorus additives, in combination optionally with phospho sulfur and / or sulfur additives, have very good friction properties with a low level of sulfur, or even in the absence of sulfur.

Thus, according to one embodiment, the rolling fluids according to the invention make it possible to increase the yield of the rolling mills, to improve the surface condition and therefore the gloss of the rolled sheets, avoiding the risks of staining of the sheets.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a cold rolling fluid comprising:

(a) a hydrocarbon base comprising at least 50% by weight of iso paraffins,

(b) one or more fatty substances, preferably chosen from fatty acid esters, or the polymer esters obtained by esterification of copolymers of alpha olefins and of dicarboxylic acids with alcohols. Preferably, in the rolling fluid according to the invention the hydrocarbon base (a) comprises at least 60% by weight of iso paraffins.

Preferably in said fluid, the hydrocarbon base (a) consists of petroleum fractions having an initial and final distillation point, measured according to the ASTM D86 standard, between 200 and 400, and consisting of hydrocarbon molecules having between 13 and 25 carbon atoms.

Preferably, the hydrocarbon bases (a) have an aromatic content of at most 100 ppm, and a sulfur content of at most 1 ppm measured according to ASTM D2622.

According to one embodiment, the fluid according to the invention further comprises:

(c) one or more additives antiwear and / or extreme pressure phosphorus and / or phospho sulfur and / or sulfur.

Preferably, the rolling fluid according to the invention has a sulfur content, measured according to ASTM D2622, is less than 1100 ppm, preferably less than 1000 ppm, preferably less than 500 ppm.

According to a preferred embodiment, the rolling fluid according to the invention comprises as compound (c) one or more organophosphorus compounds derived from phosphoric and / or phosphorous acid, said fluid having a phosphorus content measured according to the standard NFT 60-106 at least 500 ppm, with the proviso that, when said fluid contains exclusively phosphoric acid derivatives as compound (s) (c), it contains at least one sulfur or phospho-sulfur compound, and its sulfur content, measured according to ASTM D2622, is at least 300 ppm.

According to a preferred variant, the rolling fluid according to the invention comprises at least one phosphorous acid derivative as compound (c), and has a sulfur content measured according to ASTM D2622 of less than 300 ppm.

Preferably, the VI (viscosity index) of the rolling fluid according to the invention, measured according to the ASTM D2270 standard, is greater than 110, preferably greater than 120, and preferably greater than 130.

Its kinematic viscosity at 100 ^° C., measured according to ASTM D445, is preferably between 2 and 3, preferably between 2.5 and 2.65 cSt.

Its kinematic viscosity at 40 ^° C., measured according to ASTM D445, is preferably between 7.5 and 9, preferably between 7.6 and 8.8 cSt.

According to one embodiment, the rolling fluid according to the invention comprises:

from 50 to 90% by weight of a hydrocarbon base (a)

from 5 to 20% by weight of one or more fatty substances (b) from 0.5 to 7% by weight of one or more organophosphorus compounds derived from phosphoric and / or phosphorous acid (c).

According to one embodiment, the rolling fluid according to the invention may further comprise from 1 to 20% by weight of one or more surfactants, preferably chosen from nonionic or anionic surfactants.

The present invention also relates to an aqueous emulsion comprising the latter rolling fluid.

The present invention also relates to the use of a rolling fluid or an aqueous emulsion according to the invention for the cold rolling of steel, preferably austenitic or ferritic steel.

DETAILED DESCRIPTION

Hydrocarbon bases

The hydrocarbon bases for rolling fluids confer on the said fluid, in combination with the fatty substances, most of their friction properties in the zone of entry of the rolling mill, where one is in the EHD regime. These properties can be enhanced by the action of additives.

These bases also give the fluid the fluidity and volatility properties required for cold rolling applications. Indeed, the rolling fluid must be easily removed in temperature in the annealing operations, and also, previously, can be removed to a large extent during the winding of the sheets in coils.

The hydrocarbon bases commonly used in rolling fluids are lubricating bases of mineral origin (from petroleum cuts), which can be paraffinic or naphthenic, hydrocracked or not.

The paraffinic bases used in the prior art rolling fluids are derived from solvent-reduced distillates to remove the aromatics and some of the paraffins. Some paraffinic bases may be hydrotreated to lower their aromatics content (which will be converted to naphthenes). These bases have not undergone any specific process for the conversion of n paraffins (hydrodewaxing type, or hydroisomerization or hydrodewaxing), and their isoparaffin content is substantially that of the starting crudes. They are most often referred to as "neutral solvent" or "hydrotreated" paraffinic bases, and typically contain about 55% paraffins, about half of which are isoparaffins.

The naphthenic bases used in the rolling fluids of the prior art are most often derived from hydrocracked gasoil cuts. Typically by diesel cuts the initial and final distillation point petroleum fractions, measured according to ASTM D86, between 200 and 400, and consist of hydrocarbon molecules having between 13 and 25 carbon atoms. These naphthenic bases have a high content of naphthenes (of the order of 45%, or 60%, or 70% by weight and more) and a paraffin content of the order of 20 to 55% by weight, of which 15 to 30% isoparaffins. Such bases are for example described in applications WO 03/074634 and WO 03/074635.

The rolling fluids according to the invention comprise, as constituent (a), a hydrocarbon base comprising at least 50% by weight of iso-paraffins, preferably at least 60% by weight, and even more preferably at least 65% by weight. . This component (a) can be obtained with a single base or with several bases leading to a mixture comprising at least 50% by weight of iso-paraffins, preferably at least 60% by weight, even more preferably at least 65% by weight. The constituent (a) of the fluids according to the invention thus has, in contrast to the mineral bases commonly used in cold rolling fluids, a high content of iso paraffins.

Preferentially, said hydrocarbon bases (a) comprise less than 10% by weight of n paraffins, or even less than 7% by weight of n-paraffins. A low n paraffin content has a favorable effect on the pour point. Said bases preferably have a pour point of less than -15 ° C. according to ASTM D97, preferentially less than -20 ^° C. This gives the rolling fluids according to the invention a very good storage stability.

The kinematic viscosity at 40 ^° C. of these bases is preferably between 6.5 and 8 cSt, preferably between 7 and 7.8 cSt and their kinematic viscosity at 100 ^° C. is preferably between 2 and 3 cSt, preferentially between 2 and 3 cSt, preferably between 2 and 3 cSt, preferably between 2 and 3 cSt, preferably between 2 and 3 cSt. 2.5 cSt. Their VI (for bases of KV100 greater than 2), is generally greater than 100, preferably of the order of 105, 108 or beyond.

Preferentially, the hydrocarbon base (a) consists of petroleum fractions of initial and final distillation point, measured according to ASTM D86, between 200 and 400, and consisting of hydrocarbon molecules having between 13 and 25 carbon atoms (gas cuts). ).

Preferably, these are hydro-dewaxed gas oil sections, where the n paraffins have been converted to iso paraffins, said gas oil section having optionally been purified for the removal of sulfur or aromatic hydrocarbons, and optionally redistilled. The content of total paraffins (iso paraffins and normal paraffins) of the hydrocarbon bases used in the compositions according to the invention is measured by mass spectrometry according to ASTM D2786. This method makes it possible to distinguish, for petroleum cuts having an average number of carbon atoms between 16 and 32, 7 families of hydrocarbons: paraffins, naphthenes at 1, 2, 3, 4, 5, 6 cycles.

The n-paraffin content of these bases is measured by gas-phase chromato graphy, on apolar column, with a column-type injector, an FID detector.

The samples are previously diluted in carbon disulphide.

The aromatic content is measured by UV absorption spectrometry.

The iso-paraffin content of the bases is then calculated by difference with the total paraffin content according to ASTM D2786.

For environmental and safety reasons, it is desirable that these hydrocarbon bases have a low aromatic content (typically less than 100 ppm) and a low sulfur content (less than 10 ppm, typically less than 1 ppm). For this purpose, they may undergo purification steps that typically consist of hydrodesulphurization or hydrogenation steps to reduce the sulfur content and remove the unsaturated aromatic or cyclic products by converting them to naphthenes. The hydrocarbon bases used in the compositions according to the invention preferably have an aromatic content of less than 100 ppm and a sulfur content, measured by ASTM D2622, of less than 1 ppm.

The hydrocarbon bases used in the compositions according to the invention contribute, in combination with the fatty substances, to their very favorable properties (very low coefficients of friction) in the EHD regime.

Furthermore, the use of hydrocarbon bases with a high content of iso paraffins contributes to maintaining a sufficient film thickness of oil irrespective of the rolling temperature. In cold rolling, the average temperature is of the order of 100 ^° C., but can reach a temperature peak of the order of 170 ^° C. for the austenitic steels and of the order of 130 ^° C. for the steels. ferritic. It can be considered that the rolling temperature is between 50 and 180 ^° C.

A minimal thickness of oil film helps prevent seizures and micro seizures. Thus, when the rolling fluids according to the invention are used, there is no seizure under heavy load at much higher temperatures than with the fluids of the prior art. The glossy appearance of the rolled sheets with the fluids according to the invention can also be explained by a reduction of microgrips, without this binding the applicant. Fat body

The fatty substances or friction modifiers used in the rolling fluids according to the invention have the function of protecting the friction surfaces by forming a surface adsorbed film. They contribute to the friction properties of rolling fluids in the EHD regime.

These fatty substances may be fatty alcohols, fatty acids, natural or synthetic fatty esters and fatty amines, preferably esters.

By way of example, mention may be made of fatty substances of vegetable and animal origin, fatty alcohols comprising between 10 and 22, or between 12 and 18 carbon atoms, and in particular lauryl alcohol, fatty acids such as capric, lauric, myristic, stearic or linolenic acids, esters of fatty acids and monoalcohols or polyols, for example trimethylolpropane, pentaerythritol, 2-ethylhexyl alcohol, glycerol, for example glycerol monoleate, trimethylolpropane trioleate pentaerythritol tetraoleate.

It is also possible to use various synthetic compounds, in particular synthetic esters, such as the esters of amino alcohols and of fatty acids described in patent EP 0242925, di (2-ethylhexyl) adipate, etc.

The polar nature of these fatty substances (esters, alcohols) also makes it possible to solubilize the additives included in the formulas of rolling fluids.

They also make it possible to adjust the viscosity of the rolling fluids to the required level. The rolling fluids according to the invention thus preferably have a kinematic viscosity at 40 ^° C. of between 7.5 and 9 cSt, preferably between 7.6 and 8.9, or between 8.3 and 8.8 cSt, where between 8 and 8.8 cSt.

Their kinematic viscosity at 100 ^° C. is preferably between 2 and 3 cSt, preferably between 2.3 and 2.65 cSt or between 2.5 and 2.6 cSt.

The kinematic viscosities at 40 and 100 ^° C. are measured according to ASTM D445.

The fatty substances that are preferentially selected for the rolling fluids according to the invention are esters which provide additional VI (viscosity index) to the strongly isoparaffinic bases described above. Fatty acid esters, for example mono, di or tri esters of polyols, preferentially of neopolyols, preferentially trimethylolpropane or pentaerythritol, and of fatty acids comprising between 10 and 22 atoms, are preferably used in the present invention. of carbon, or synthetic esters also called polymeric esters, obtained by esterification of copolymers of alpha olefins and dicarboxylic acids with alcohols. The use of these esters, and particularly the polymer esters, makes it possible to increase the residual viscosity of the rolling fluid according to the invention under strong mechanical or thermal stresses: these fatty substances remain on the sheet under these extreme conditions while the Hydrocarbon base is more volatile and have the additional role of vector additives.

A high VI indicates the tendency of the fluid to remain stable in viscosity during temperature variations. VI is measured according to ASTM D2270, from the kinematic viscosities measured at 40 and 100 ^° C. according to ASTM D445. Thus the iso-paraffinic bases alone have an IV of the order of 100 to 110, whereas the VI of the rolling fluids according to the invention is greater than 110, preferably greater than 120, 125, or 130, or 140 and beyond. The known commercial fluids have, when they are, VI much lower, of the order of 70 to 80.

A high VI helps to ensure a minimum film thickness regardless of the rolling temperature.

The preferred fatty substances of the rolling fluids according to the invention provide, in combination with the isoparaffinic bases, very good friction properties in the EHD regime, and a high VI, guaranteeing a sufficient film thickness of oil whatever the temperature. rolling.

This contributes, in combination with the anti wear and extreme pressure additives, to the supply of fluids which make it possible to improve the yield of the rolling mills, to roll without risk of jamming or micro galling, and thus to improve the surface condition. rolled sheets.

These fats preferably represent about 5 to 25% by weight, preferably 7 to 20% or 10 to 18% by weight of the rolling fluids according to the invention. Too low a content does not, in general, a significant effect, a higher content generally leads to too high viscosities, and / or a difficulty of removal of fluids after rolling operations. However, other amounts may be determined by those skilled in the art.

Extreme pressure and anti wear additives

Extreme pressure properties are the ability of lubricants to protect surfaces against galling under very severe tribological operating conditions: very high contact temperatures due to high loads associated with high sliding speeds and / or to load shocks.

Extreme pressure (EP) and anti-wear additives act under these severe conditions (high load, limit regime). They form a protective tribochemical film at the metallic surface by reaction of the additive or its decomposition products with the metal. Under the effect of the contact temperature, EP additives are chemically decomposed to release active elements such as sulfur or chlorine. These will attack the metal at the level of the asperities in contact to form in situ protective self-lubricating films consisting of sulphides, chlorides, metal phosphides, characterized by low shear strengths.

Extreme pressure additives (EP) are mainly sulfur, chlorinated, phosphorus or phospho sulfur derivatives. Some chlorine additives, for example medium chain chlorinated paraffins (between 14 and 17 carbon atoms) are also extreme pressure additives. Their use will be avoided in the fluids according to the invention, because of their toxicity.

The anti-wear and / or extreme pressure additives used in the fluids according to the invention are preferably phosphorus and / or sulfur and / or phosphosulfur-containing additives, for example such as those described below.

Examples of phosphorus EP additives are, for example, alkyl phosphates or alkyl phosphonates, phosphoric acid, phosphorous acid, mono-, di- and triesters of phosphorous acid and phosphoric acid, and their salts, for example amine salts or zinc salts. Examples that may be mentioned include alkyl or aryl phosphites or hydrogen phosphites, didodecyl phosphite, dilauryl hydrogen phosphite, di or tri trialkyl phosphate, such as dilauryl phosphate, tri (2-ethylhexyl) phosphate, tricresyl phosphate or dialkyl (or diaryl) phosphate. and their salts, for example amine or zinc salts.

Examples of anti-wear and extreme pressure phospho sulfur additives are for example and not limited to thiophosphoric acid, thiophosphorous acid, esters of these acids, their salts, dithiophosphates, particularly zinc dithiophosphates. Examples of salts of thiophosphoric acid esters and thiophosphorous acid are those obtained by reaction with a nitrogen compound such as ammonia or an amine or zinc oxide or zinc chloride.

Examples of sulfur-containing anti-wear and extreme pressure additives include dithiocarbamates, especially zinc dithiocarbamates, dimercaptothiadiazoles and benzothiazoles, mercaptobenzothiazole, sulfur-containing olefins (for example, di, tri, pentasulfides), fatty substances and the like. sulfur, for example esters, triglycerides, methyl esters, or fatty acids, for example oleic acid sulfur.

Sulfur-containing additives have a very effective effect on friction properties but tend to form iron sulphide on fresh surfaces created by rolling, which leads to staining of the sheets, especially during the storage before annealing of the sheet metal coils, which have a core temperature of up to 140 ^° C. These tasks can be eliminated, in the case of steel austenitic, annealing at 1200 ⁰ C, but H2S is formed causing corrosion refractory furnaces. In the case of ferritic steel, annealing at 900 ^° C. does not eliminate the stains.

It is therefore preferable, while maintaining good friction performance, particularly in limit regime, to limit the sulfur content of the cold rolling fluids.

According to a preferred embodiment, the anti-wear and extreme pressure additives of the fluids according to the invention are organophosphorus compounds, optionally in combination with phosphorus-containing sulfur compounds and / or sulfur compounds.

These organophosphorus compounds preferably used in the fluids according to the invention are derivatives of phosphorous acid, namely phosphates or hydrogenophosphates or dihydrogenphosphates, generally denoted below as "phosphates", or derivatives of phosphorous acid, namely phosphites or hydrogenophosphites or dihydrogenophosphites, hereinafter referred to as "phosphites". These are typically alkyl or aryl phosphates, hydrogenophosphates, dihydrogen phosphates, phosphites, hydrogen phosphites, dihydrogen phosphites.

Typically, the alkyl chains contain from 10 to 22, preferably from 12 to 18 carbon atoms.

These compounds are preferably present in the fluids according to the invention in quantities leading to a content of phosphorus element, measured according to NFT 60-106, at least equal to 500 ppm, preferably between 800 and 3000, preferably between 1000 and 2000 ppm. and guarantee excellent friction performance for very low sulfur levels in said fluid.

The Applicant has found that organophosphorus compounds derived from phosphorous acid ("phosphites"), more reactive than those derived from phosphoric acid (phosphates) as an EP agent, make it possible to obtain, in combination with the bases and fats according to the invention, excellent friction performance with a very low sulfur content, less than 300 ppm, or even 200 or 150 ppm, or 50 or 10 ppm of sulfur, and even when are free of sulfur.

When only phosphates are used, however, the sulfur content in the rolling fluid must be at least 300 ppm, preferably between 500 and 1000 ppm, or between 850 and 950 ppm. Typically, the sulfur content of the rolling fluids according to the invention, measured according to ASTM D2622, is less than 1100 ppm, preferably less than 1000 ppm, preferentially less than 500 ppm, that is to say sulfur contents for which we do not observe staining of the sheets.

In a preferred embodiment of the invention, the rolling fluids contain phosphorous acid derivatives, and optionally sulfur-containing or phospho-sulfur-containing EP additives, and have a phosphorus content measured according to NFT 60-106 of at least 500 ppm. and a sulfur content measured according to ASTM D2622 of less than 300 ppm, preferably less than 200, 100, 50 ppm, even more preferably less than 10, or 1 ppm of sulfur, or are even more preferably free of sulfur.

Other additives

The rolling fluids according to the invention may also contain any type of additives suitable for their use, for example antioxidants, for example amines or phenolics, corrosion inhibitors, anti-foaming agents, etc.

The rolling fluids according to the invention may for example comprise between 0.05 and 1% by weight of an antioxidant, preferably phenolic.

The rolling fluids according to the invention may for example comprise between 0.01 and 0.1 percent by weight of one or more anticorrosive additives, preferably a phosphoric acid salt, preferably an amine phosphate.

use

The rolling fluids according to the invention are particularly suitable for cold rolling of steel sheets, in particular austenitic and ferritic steel.

Cold rolling is an additional thinning experienced by flat products (typically sheets). It is preceded by hot rolling, which takes place at temperatures of the order of 800 to 1200 ^° C. The cold rolling, which is itself carried out at temperatures of the order of 40 to 180 ^° C. Its objective is to give flat products a specific geometry (thickness, flatness), a microstructural state and a surface state suitable for subsequent annealing treatments.

For these cold rolling operations, the fluids according to the invention can be used in the form of an entire oil, or in the form of an oil-in-water emulsion.

The use of rolling fluids in the form of emulsions has the advantage of better caloric evacuation (better control of temperature) in the rolling process. Rolling fluids can also be found in the form of an emulsion when the entire lubricant is used for the temporary protection of the plates against corrosion. In this case, the sheets are rinsed with water before rolling and the resulting effluent is recycled as a rolling fluid. This presents an economic advantage as well as a lower environmental impact.

The use in emulsion form requires the incorporation of surfactants. These surfactants may be any type of surfactant, preferably nonionic surfactants such as fatty alcohols, fatty acids, fatty amines or fatty acid methyl esters, ethoxylated, or anionic surfactants such as soaps, sulphonates, alcohol sulphates. fat.

The rolling fluids according to the invention intended to be emulsified contain between 1 and 20%, preferably between 1.5 and 5% of such surfactants.

These rolling fluids may have a relatively high content of antioxidant, for example of the order of 0.2 to 1%, against of the order of 0.05% for fluids intended to be used in the form of whole oil .

The present invention also relates to aqueous emulsions comprising these rolling fluids, preferably at a level of 3 to 10% relative to the total weight of emulsion.

Example 1 Preparation of rolling fluids

Several rolling fluids were prepared from hydrocarbon bases derived from petroleum fractions, initial and final distillation points of between 270 and 380 ^° C., fatty substances and extreme pressure additives.

The base (a) of the fluids A and B contains 67.8% by weight of isoparaffins, 5.5% by weight of n paraffins, 26.7% by weight of naphthenes.

The base (a) of fluids C and D contains 64.6% by weight of isoparaffins, 5.7% by weight of n paraffins, 29.7% by weight of naphthenes.

The base (a) of fluids E and F contains 62.5% by weight of isoparaffins, 5.7% by weight of n paraffins, 31.8% by weight of naphthenes.

The mass compositions of these fluids are grouped in Table 1 below.

Table 1: Composition of rolling fluids (% by mass)

These fluids were compared to a commercial rolling fluid containing as base a naphthenic hydrocarbon fluid comprising less than 45% by weight of isoparaffins, fatty substances and sulfur-containing EP additives (sulfurized triglycerides) and phosphorus (triaryl phosphates). Their characteristics and those of the commercial fluid G are grouped in table 2 below.

The commercial fluid has an isoparaffin content and a VI lower than the fluids according to the invention.

Table 2: Characteristics of Prepared Fluids and Commercial Fluids for Rolling Steel Example 2 Study of Elastohydrodynamic (EHD) Friction Properties

The friction properties of the fluids described above were studied on a ball / disk EHD tribometer. This tribometer makes it possible to measure the coefficient of friction as a function of the applied rolling / sliding ratio SRR, at a constant driving speed Ve.

The coefficient of friction, defined as the ratio between the tangential force or friction force and the normal stress, is measured by a strain gauge force sensor in a ball / steel disc contact in the presence of the lubricant to be tested. . Figure 2 shows the device and the position of the sensors.

The test conditions are as follows:

Steel disk, threaded steel ball 100 C6 diameter 19.05 mm.

Test product: approximately 100 ml of fluid to be tested.

Measuring points at 40 ⁰ C and 100 ⁰ C under normal stress 25 N

Ratio increment Speed Slip / Roll Speed (SRR%): 5 - 10 - 20 - 40 - 60 - 80 - 100% for Ve = 1m / s.

The results of these measurements are summarized in Table 3 below:

Table 3: coefficients of friction measured on tribometer EHD ball disk

The coefficients of friction obtained with the fluids according to the invention B and D and F are significantly lower than those obtained with the commercial reference denoted G in Table 2.

The friction conditions are representative of the mill entrance zone, where the slip ratio SRR varies between about 1 to 5% and about 40%. The low coefficients of friction obtained with the fluids according to the invention will, in use, move the neutral point inwardly of the right-of-way, which makes it possible to increase the reduction in sheet thickness per pass, or else to reduce the number of passes to achieve a given reduction.

Example 3: Study of Friction Properties under Limit Regime, Cameron Plint

The friction properties of the fluids described in Example 1 were also studied on Cameron Plint Cylinder / Plan Tribometer, representative of conditions in limit regime. This tribometer makes it possible to measure coefficients of friction under severe conditions, in pure slip.

The test conditions here are as follows:

Mobile Cylinder: Diameter 6mm, Length 14mm (Steel Kors)

Fixed plate sheet: ferritic or austenitic stainless steel

Stroke: 15 mm

Frequency: 20 Hz + 1/20 gearbox = 1 Hz

Charge: 100 N and 200 N

Duration: greater than 2400 s

Temperature: 7 steps of 4500 seconds at increasing temperatures: ambient, 50 - 80 - 110 - 140 - 170 - 200 ⁰ C

Volume of oil required: 7 ml

At the beginning of each temperature step, acquisition of an instantaneous coefficient and on the last minute of the bearing, an average coefficient of friction.

These conditions are representative of the friction conditions in the working zone of the rolling mill.

The results of these tests under a load of 100 N and 200 N are presented respectively in tables 4 and 5. The absence of results beyond a certain temperature indicates that a seizure occurred.

Table 4: coefficients of friction under load of 100 N, on ferritic sheet.

The fluids A, B, C, D and E according to the invention all have lower coefficients of friction than the commercial reference products. The behavior is particularly favorable for temperatures below 100 ^° C., the most probable correlation range with operating temperatures. The surface conditions observed are bright, without staining or staining.

Table 5: coefficients of friction under load of 200 N, on ferritic sheet.

The fluids according to the invention make it possible to roll without seizing under heavy load while the commercial reference product (G) leads to an immediate seizure. On austenitic steel, the fluids according to the invention lead to even lower friction coefficients, albeit with a slightly earlier seizure (see Table 6):

Table 6: friction coefficients under load of 200 N, on austenitic sheet

These excellent results make it possible to predict an absence of seizure in service under severe friction conditions representative of the working area of the rolling mill. We can therefore obtain significant reductions in thickness with a reduced number of passes.

The low friction coefficients observed also lead to a very bright surface state (few microgrippings), and the low sulfur contents (for fluids A to D) make it possible to avoid staining of the sheets by formed iron sulphide products. on cool surfaces.

Claims

1. Cold rolling fluid comprising:

(a) a hydrocarbon base comprising at least 50% by weight of iso paraffins,

(b) one or more friction modifiers selected from fatty alcohols, fatty acids, fatty amines, fatty acid esters, or polymeric esters obtained by esterifying copolymers of alpha olefins and dicarboxylic acids with alcohols,

(c) one or more anti-wear and / or extreme pressure phosphorus additives chosen from organophosphorus compounds derived from phosphoric and / or phosphorous acid, said fluid having a phosphorus content measured according to the NFT 60-106 standard of at least 500; ppm

with the proviso that, when said fluid contains exclusively phosphoric acid derivatives as compound (s) (c), it contains at least one sulfur-containing or phospho-sulfur compound, and its sulfur content, measured according to ASTM standard D2622 is at least 300 ppm.

2. The rolling fluid according to claim 1, wherein the hydrocarbon base (a) comprises at least 60% by weight of iso paraffins.

3. Fluid according to claims 1 to 2 wherein the hydrocarbon base (a) consists of petroleum fractions having an initial and final distillation point, measured according to ASTM D86, between 200 and 400, and consist of hydrocarbon molecules. having between 13 and 25 carbon atoms.

4. The rolling fluid according to one of claims 1 to 3 wherein the hydrocarbon bases (a) have an aromatic content of at most 100 ppm, and a sulfur content of at most 1 ppm measured according to ASTM D2622.

5. Fluid according to claims 1 to 4, further comprising:

6. The rolling fluid according to claims 1 to 5, the sulfur content, measured according to ASTM D2622, is less than 1100 ppm, preferably less than 1000 ppm, preferably less than 500 ppm.

7. Fluid according to claims 5 to 6 comprising as compound (c) one or more organophosphorus compounds derived from phosphoric acid and / or phosphorous, said fluid having a phosphorus content measured according to the standard NFT 60-106 at least equal to 500 ppm, with the proviso that, when said fluid contains exclusively phosphoric acid derivatives as compound (s) (c), it contains at least one sulfur-containing or phospho-sulfur compound, and its sulfur content, measured according to ASTM D2622, is at least 300 ppm.

8. The rolling fluid of claim 7 comprising at least one phosphorous acid derivative as the compound (c), said rolling fluid having a sulfur content measured according to ASTM D2622 of less than 300 ppm.

9. The rolling fluid according to one of claims 1 to 8, the VI measured according to ASTM D2270 is greater than 110, preferably greater than 120, preferably greater than 130.

10. The rolling fluid according to one of claims 1 to 9, the kinematic viscosity at 100 ⁰ C, measured according to ASTM D445, is between 2 and 3, preferably between 2.5 and 2.65 cSt.

11. The rolling fluid according to one of claims 1 to 10, the kinematic viscosity at 40 ^° C., measured according to ASTM D445, is between 7.5 and 9, preferably between 7.6 and 8.8 cSt.

12. The rolling fluid according to one of claims 1 to 10 comprising:

from 50 to 90% by weight of a hydrocarbon base (a)

from 5 to 20% by weight of one or more fatty substances (b)

from 0.5 to 7% by weight of one or more organophosphorus compounds derived from phosphoric and / or phosphorous acid (c).

13. The rolling fluid according to one of claims 1 to 11 comprising 1 to 20% by weight of one or more surfactants, preferably selected from nonionic or anionic surfactants.

14. Aqueous emulsion comprising a rolling fluid according to one of claims 1 to 13.

15. Use of a rolling fluid according to one of claims 1 to 13, or an emulsion according to claim 14 for the cold rolling of steel, preferably austenitic or ferritic steel.