DE102008016348B4 - High temperature lubricants and their use in a process for hot working metals - Google Patents

Abstract

High-temperature lubricant, preferably die lubricant, based on graphite dispersed in water, comprises 5-40 wt.% of graphite, 0.1-5 wt.% of surfactant as a wetting agent, 0.1-0.5 wt.% of bactericide and/or fungicide, 0.5-20 wt.% of salts and 29.5-94.29 wt.% of water as carrier medium and auxiliary material, 0.01-5 wt.% of an inorganic cerium compound and/or an organic cerium(III)- or cerium(IV)-compound as an oxidation catalyst and titanium dioxide, manganese dioxide, ferrocene, iron tallate and/or iron hydroxide complex as oxidant. High-temperature lubricant, preferably die lubricant, based on graphite dispersed in water, comprises 5-40 wt.% of graphite, 0.1-5 wt.% of surfactant as a wetting agent, 0.1-0.5 wt.% of bactericide and/or fungicide, 0.5-20 wt.% of salts and 29.5-94.29 wt.% of water as carrier medium and auxiliary material, 0.01-5 wt.% of an inorganic cerium compound and/or an organic cerium(III)- or cerium(IV)-compound as an oxidation catalyst and titanium dioxide, manganese dioxide, ferrocene, iron tallate and/or iron hydroxide complex of formula (Fe(OH) x) (where x is not defined) as oxidant. An independent claim is included for a method for hot forming of metals, comprising spraying a die form, prior to the forming of a workpiece, with a high temperature lubricant based on graphite dispersed in water or based on graphite in mineral oil, where the carbonization residuals are avoided.

Description

The The present invention relates to a high temperature lubricant, in particular die lubricants, based on water-dispersed graphite or based on graphite in mineral oil, according to claims 1 or 2 and a method for hot forming metals using the high temperature lubricant of the invention.

at The machining of metals requires lubricants that at high processing temperatures an optimal sliding of the metal between the processing tools. It can in particular when processing hard or difficult to deform metals a quick wear of the Processing tools come. The lubricants should be the friction resistance between metal and tool to reduce the wear of the tools to reduce. The lubricants must be high temperatures withstand.

For quite some time, corresponding formulations based on graphite have been known. Since graphite itself lubricates only poorly (0.2, in a high vacuum 0.5), additives such as phosphates, borates or halides of Na, K, etc. are proposed. This is how the German Auslegeschrift works DE 2 154 232 B for a high-temperature lubricant for the hot deformation of metals, a mixture of graphite and alkali phosphates or borates is described.

Around lubrication over a wide range of approx. 200 ° C (die) up to 1150 ° C (Metal workpiece, to ensure iron here) Organic components such as polymers or mineral oils are also used.

organic additions are only up to 600 ° C lubricating, then burn or coke, salts or Salt mixtures are effective only from the onset of melting (usually above 300 ° C).

adversely when using organic additives First, the relatively limited temperature range and second, the risk of coking. These coking residues can become build in the form (engraving) and influence the dimensional accuracy of the workpiece.

By the increase of the inorganic portion, such as phosphates, etc., although the lubrication partial improved, but there is also the danger of caking here by residues.

salts or salt mixtures in conjunction with graphite are used since they contribute to lubrication in the melt flow and between the graphite particles or layers reduce the relatively strong Van der Waals forces.

The German DE 2 108 738 A1 describes a high-temperature lubricant for chipless metal forming containing an alkali metal sulfate, borax, potassium chloride, Natriumacetattrihydrat and graphite in powder form having a particle size which does not exceed 10 microns. Furthermore, this agent may additionally contain ammonium sulfate and a stabilizer from the class of polysaccharides and / or alkylcelluloses and / or alginates.

Also the DE 2 048 537 A1 describes a phosphate-based high-temperature lubricant for thermoforming metals in the form of a firmly adhering layer in combination with a binder and a solvent, this lubricant consisting of a dispersion of a mixture or a melt of phosphates with sodium and / or potassium and / or zinc and / or aluminum and / or boron, optionally with the addition of calcium fluoride, sodium fluoride, zinc sulfide, graphite and / or sodium-zinc polyphosphate in a highly polymeric binder and an organic solvent. This high temperature lubricant can be used in forging, rolling, pressing, drawing or cleats.

Also the layout DE 2 046 727 B discloses a high-temperature lubricant for chipless metal forming, consisting of an alkali metal sulfate, borax, potassium chloride, sodium acetate trihydrate and graphite in powder form having a particle size not greater than 10 microns, optionally further ammonium sulfate, a mixture of magnesium hydroxide, thiatriazole derivatives, azoisobutyrodinitrile and / or azodicarbonamide, a dispersant from the class of sulfonated aliphatic polyesters and / or sulfated alcohols and / or sodium alkylsulfonates and a stabilizer from the class of polysaccharides and / or alkylcelluloses and / or alginates and water.

For editing of metals at high temperatures are especially graphitic lubricants, as mentioned above were enforced. Graphite is particularly heat resistant and indicates in combination with mineral oils and inorganic salts particularly good lubricating properties.

EP 0 442 661 A1 discloses a method of thermoforming metal wherein a lubricant is applied to the surface of a metallic workpiece which is subsequently reshaped. The lubricant contains a rare earth metal halide. In particular, an aqueous-based high temperature lubricant containing up to 10% graphite, 2-30% trifluoride, wetting agents, antimicrobials, salt and carriers is taught. A similar lubricant composition is disclosed in U.S. Pat WO 00/66667 A1 disclosed.

A disadvantage of these graphite-containing lubricants, however, is that due to the high carbon content leads to carburizing of the metal surface of the workpiece. This in turn can lead to defective end products with poor processing or material properties. Many of the above-mentioned lubricants contain borax, which, however, can lead to sticking of the tool and the workpiece so that damage to the tools occurs or the machines come to a standstill. Furthermore, borax-containing lubricants adversely affect the metal surface of the tool or workpiece. To circumvent the problem of coking the tool describes the DE 197 40 109 A1 a graphite-free lubricant that contains little or no carbon.

The EP 0164637 A1 however, describes a high-temperature lubricant for non-cutting hot forming of metals containing a solid lubricant, in particular graphite and an organic in the heat residue-decomposing organic product, for example. Alkylene polymers, a polyphosphate, a boron compound, an alkali metal silicate and an organic stabilizer.

The invention is primarily not an improvement in the lubricating effect, since these can only be achieved by a very high technical effort successes. So, for example with the US 2005/0130851 A1 or US Pat. No. 6,231,980 B1 , proposed for special applications mixtures with so-called fullerenes or nanotubes. However, these "high-tech" lubricants are not acceptable for the practice due to the high price. Also, additives from very fine carbides and / or nitrides have been discussed. For example, a lubricant is known, consisting of nanoscale titanium nitride, which is used in space travel.

The Rather, the object of the present invention is a graphite-containing To provide lubricant of the above type which despite undiminished lubricating effect minimizes the coking effect in the mold, the tool protects and significantly increased tool life.

• – 5 bis 40 Gew.-% Graphit,
• – 0,1 bis 5 Gew.-% Tensid als Netzmittel,
• – 0,1 bis 0,5 Gew.-% Bakterizid und/oder Fungizid,
• – 0,5 bis 20 Gew.-% Salze und
• – 29,5 bis 94,29 Gew.-% Trägermedium und Hilfsstoffe enthält, wobei das Hochtemperaturschmiermittel weiterhin 0,01 bis 5 Gew.-% einer anorganischen Cer-Verbindung und/oder einer organischen Cer-III- oder Cer-IV-Verbindung als Oxidationskatalysator enthält und als zusätzlicher Oxidationskatalysator TiO₂, MnO₂, Ferrocen, Eisentallat und/oder Fe(OH)_x enthalten ist/sind.

This object has been achieved by a high-temperature lubricant, in particular die lubricant, based on water-dispersed graphite, which

• From 5 to 40% by weight of graphite,
• 0.1 to 5% by weight of surfactant as wetting agent,
• From 0.1 to 0.5% by weight of bactericide and / or fungicide,
• - 0.5 to 20 wt .-% salts and
• - 29.5 to 94.29 wt .-% carrier medium and auxiliaries, wherein the high-temperature lubricant further comprises 0.01 to 5 wt .-% of an inorganic cerium compound and / or an organic cerium-III or cerium-IV compound contains as oxidation catalyst and as an additional oxidation catalyst TiO ₂ , MnO ₂ , ferrocene, ferrous ion and / or Fe (OH) _x is / are included.

• – 5 bis 40 Gew.-% Graphit,
• – 0,5 bis 20 Gew.-% Salze und
• – 35 bis 94,49 Gew.-% Trägermedium und Hilfsstoffe enthält, wobei das Hochtemperaturschmiermittel weiterhin 0,01 bis 5 Gew.-% einer anorganischen Cer-Verbindung und/oder einer organischen Cer-III- oder Cer-IV-Verbindung als Oxidationskatalysator enthält und als zusätzlicher Oxidationskatalysator TiO₂, MnO₂, Ferrocen, Eisentallat und/oder Fe(OH)_x enthalten ist/sind.

Furthermore, the object has been achieved by a high-temperature lubricant, in particular die lubricant, based on graphite in mineral oil, which

• From 5 to 40% by weight of graphite,
• - 0.5 to 20 wt .-% salts and
• - Contains 35 to 94.49 wt .-% of carrier medium and auxiliaries, wherein the high-temperature lubricant further 0.01 to 5 wt .-% of an inorganic cerium compound and / or an organic cerium-III or cerium-IV compound as the oxidation catalyst contains and as additional oxidation catalyst TiO ₂ , MnO ₂ , ferrocene, Eisentallat and / or Fe (OH) _x is / are included.

It This is a novel lubricant as it is for example used in the hot forming of metals.

• – anorganischen Cer-Verbindungen, vorzugsweise Cer(III)-oxid Ce₂O₃, Cer(IV)-oxid CeO₂, Cer(III)-chlorid CeCl₃, Cer(IV)-sulfat Ce(SO₄)₂, Cer(III)-nitrat Ce(NO₃)₃·6 H₂O, Cer(III)-fluorid CeF₃, Cer(III)-oxalat Ce₂(C₂O₄)₃ und/oder Cer(IV)-ammoniumnitrat (NH₄)₂Ce(NO₃)₆; und/oder
• – der organischen Cer-III- oder Cer-IV-Verbindungen, vorzugsweise der Cer-Alkoholate als Ethylate, n-Propylate, iso-Propylate, n-Butylate oder tert.-Butylate und/oder der Cer-Carboxylate der Essigsäure, Propionsäure, Butansäure, Hexansäure, Oxalsäure, Malonsäure, Bernsteinsäure, Glutarsäure, Adipinsäure, Octansäure, 2-Ethyl-Hexansäure, Valeriansäure, Caprinsäure, Naphtensäure und/oder Laurinsäure, enthalten.

In a preferred embodiment of the high-temperature lubricant according to the invention are cerium compound / s from the group of

• - inorganic cerium compounds, preferably cerium (III) oxide Ce ₂ O ₃ , cerium (IV) oxide CeO ₂ , cerium (III) chloride CeCl ₃ , cerium (IV) sulfate Ce (SO ₄ ) ₂ , cerium (III) nitrate Ce (NO ₃ ) ₃ .6H ₂ O, cerium (III) fluoride CeF ₃ , cerium (III) oxalate Ce ₂ (C ₂ O ₄ ) ₃ and / or cerium (IV) ammonium nitrate (NH ₄ ) ₂ Ce (NO ₃ ) ₆ ; and or
• The organic cerium-III or cerium-IV compounds, preferably the cerium alcoholates, as the ethylates, n-propylates, isopropyls, n-butylates or tert-butylates and / or the cerium carboxylates of acetic acid, propionic acid, Butanoic, hexanoic, oxalic, malonic, succinic, glutaric, adipic, octanoic, 2-ethylhexanoic, valeric, capric, naphthenic and / or lauric acids.

The high-temperature lubricant according to the invention contains TiO ₂ , MnO ₂ , ferrocene, ferrous ion and / or Fe (OH) _x as additional oxidation catalysts. It has now been found that additives such as TiO ₂ , MnO ₂ , ferrocene (di (cyclopentadienyl) iron), iron compounds with a complex salt of an organic acid (for example Eisentallat) and / or Fe (OH) _x o Be converted in part to the corresponding carbides or carbides / nitirides. It is particularly advantageous if these catalysts are oxides available. Since these hard metal particles form in place, can be dispensed with the use of expensive carbide particles. In the case of the high temperatures, which occur, for example, during drop forging, the corresponding hard metals are produced in this way. These fine particles, which are ideally nano-scale, embed themselves in the micro-cracks in the tools and harden them. In practice, tool life could be increased up to 25%. It has proved to be particularly advantageous if oxidation catalysts are added to the mixture. On the one hand, they facilitate the conversion into the abovementioned carbides or carbides / nitrides, on the other hand, the oxidation of the graphite is accelerated, which contributes to gas lubrication.

In the past, lubricants with good lubricating properties could be produced again and again, but especially during die-forging lubricant residues accumulated in the tools (dies). By adding cerium compounds, possibly in conjunction with additional oxidation catalysts TiO ₂ , MnO ₂ and / or Fe (OH) _x , the graphite is oxidized and the dies remain clean. It is particularly advantageous, for example, when cerium compounds are combined with iron or else the combination Cer-Fe-Ti.

Since conventional die lubricants contain in part phosphates or similar salts (see above), mixtures of ammonium and alkali phosphates (borates) or other nitrogen bases are suitable as additionally contained salts. Preferably, an alkali phosphate, sulfate, borate, halide, nitrate, chlorate and / or perchlorate are included. These salts change during the lubrication process, in which the temperature usually rises from about 200 ° C to over 1000 ° C, with release of nitrogen into pyrophosphates, which has a positive effect on the melt flow. The nitrogen is reacted, for example, with TiO ₂ to TiN / TiC.

When Wetting agent is used in the high-temperature lubricant according to the invention preferably naphthalene sulfonate or lignin sulfonate used.

at a high-temperature lubricant according to the invention based on water-dispersed graphite is the carrier medium Water and the auxiliaries are preferably alginates, polyacrylates, Stabilizers of the suspension and / or nitrogen compounds.

at a high-temperature lubricant according to the invention based on graphite in mineral oil the carrier medium a mineral oil and the auxiliaries are preferably nitrogen compounds, for example Urea.

in the This invention further provides a method of hot working of metals, wherein a die before forming a workpiece with a high-temperature lubricant based on water-dispersed Graphite or based on graphite in mineral oil is sprayed or brushed, whereby coking residues in the mold, preferably by their regeneration, be avoided by a High-temperature lubricant according to claim 1 or 2 is used.

It could be found that oxidizing agents, which only at higher Temperature become effective, reduce coking residues. The oxidizing agents allowed to do not decompose quickly, so they end up reshaping are still effective. Particularly advantageous has been shown, when so-called oxidation catalysts are added. Oxidation catalysts, such as organic cerium compounds are used, for example, in motor oils for marine diesel used (reduction of the carbon).

According to the invention has shown that a conventional Lubricants based on graphite and inorganic salts through additives of titanium dioxide or iron hydroxide in conjunction with cerium compounds Not only a very good lubrication, but above all, a significant improved tool life shows. In addition, the forms (dies or engravings) cleaner. The increase Tool life is (presumably) due to the fact that at the high temperature, as for example when die forging occurs, a conversion of titanium dioxide into titanium carbide, also possibly in titanium nitride, which penetrates into the tool surface and she cures.

Examples:

• – 5 bis 40% Grafit
• – 0,1 bis 5% Netzmittel
• – 0,1 bis 0,5% Bakterizid/Fungizid
• – 0,5 bis 20% „Salze” (Alkali-Phosphate, -Sulfate, -Borate oder -Halogenide, auch ggf Nitrate, Chlorate oder Perchlorate)
• – 0,01 bis 5% Oxidationskatalysator (Cer-, Ti-, Fe-, Mn-Verbindungen)
• – Rest Trägermedium und Hilfsstoffe

• 1.) Ein herkömmliches Schmiermittel auf der Basis von in Wasser dispergiertem Grafit wurde mit 0,1% Cersulfat versetzt und beim Schmieden von Achszapfen 1:10 mit Leitungswasser verdünnt bei der Sprühschmierung eingesetzt. Es konnte eine durchschnittliche Erhöhung der Werkzeugstandzeit von 16% erzielt werden.
• 2.) Das gleiche Schmiermittel wie unter 1), jedoch mit 1% Titandioxid, ergab eine Erhöhung der Werkzeugstandzeit von 13%.
• 3.) Ein Schmiermittel, wie unter 1.), mit 0,1% Cersulfat und 1% Titandioxid ergab eine Verbesserung der Werkzeugstandzeit von 25%.
• 4.) Ein Schmiermittel auf Basis Grafit in Mineralöl mit 0,1% Cer-Octoat ergab eine Standzeiterhöhung von 12%, mit zusätzlich 1% Fe-Tallat, wurden durchschnittlich 18% Werkzeugstandzeit-Erhöhung erzielt (Hammerschmieden).

An improved high temperature lubricant based on water dispersed graphite may be composed as follows:

• - 5 to 40% graphite
• - 0.1 to 5% wetting agent
• - 0.1 to 0.5% bactericide / fungicide
• - 0.5 to 20% "salts" (alkali phosphates, sulphates, borates or halides, also nitrates, chlorates or perchlorates, if desired)
• 0.01 to 5% oxidation catalyst (cerium, Ti, Fe, Mn compounds)
• - Rest carrier medium and excipients

• 1.) A conventional lubricant on the basis of water-dispersed graphite was mixed with 0.1% cerium sulfate and used in the forging of journals 1:10 diluted with tap water in the spray lubrication. An average increase in tool life of 16% was achieved.
• 2.) The same lubricant as under 1), but with 1% titanium dioxide, resulted in an increase in tool life of 13%.
• 3.) A lubricant, as under 1.), with 0.1% cerium sulfate and 1% titanium dioxide resulted in an improvement of the tool life of 25%.
• 4.) A lubricant based on graphite in mineral oil with 0.1% cerium octoate resulted in a service life increase of 12%, with an additional 1% Fe tallate, an average 18% tool life increase was achieved (hammer forging).

It has been shown that Fe and Mn oxidation catalysts are not so effective in aqueous formulations containing phosphates or borates (Fe / Mn phosphates or borates), the better TiO ₂ .

Claims (10)

High-temperature lubricant based on water-dispersed graphite, containing - 5 to 40 wt .-% graphite, - 0.1 to 5 wt .-% surfactant as wetting agent, - 0.1 to 0.5 wt .-% bactericide and / or Fungicide, - 0.5 to 20% by weight of salts and - 29.5 to 94.29% by weight of carrier medium and auxiliaries, characterized in that the high-temperature lubricant further contains 0.01 to 5% by weight of an inorganic cerium Contains compound and / or an organic cerium-III or cerium-IV compound as the oxidation catalyst and as an additional oxidation catalyst TiO ₂ , MnO ₂ , ferrocene, ferrous ion and / or Fe (OH) _x is / are included. High-temperature lubricant based on graphite in mineral oil, containing - 5 to 40 wt .-% graphite, - 0.5 to 20 wt .-% salts and - 35 to 94.49 wt .-% carrier medium and excipients, characterized in that High-temperature lubricant further contains 0.01 to 5 wt .-% of an inorganic cerium compound and / or an organic cerium-III or cerium-IV compound as the oxidation catalyst and as an additional oxidation catalyst TiO ₂ , MnO ₂ , ferrocene, iron tetallate and / or Fe (OH) _x is / are included. High-temperature lubricant according to claim 1 or 2, characterized in that the high-temperature lubricant a die lubricant is. High-temperature lubricant according to claim 1 or 2, characterized in that the inorganic cerium compounds cerium (III) oxide Ce ₂ O ₃ , cerium (IV) oxide CeO ₂ , cerium (III) chloride CeCl ₃ , cerium (IV) - sulfate Ce (SO ₄ ) ₂ , cerium (III) nitrate Ce (NO ₃ ) ₃ .6H ₂ O, cerium (III) fluoride CeF ₃ , cerium (III) oxalate Ce ₂ (C ₂ O ₄ ) ₃ and / or cerium (IV) ammonium nitrate (NH ₄ ) ₂ Ce (NO ₃ ) ₆ is / are. High-temperature lubricant according to claim 1 or 2, characterized in that the organic cerium-III or cerium-IV compounds Cerium alcoholates as Ethylates, n-propylates, iso-propylates, n-butylates or tert-butylates and / or cerium carboxylates of acetic acid, propionic acid, Butyric acid, hexanoic, oxalic acid, malonic, Succinic acid, glutaric acid, adipic acid, octanoic acid, 2-ethylhexanoic acid, valeric acid, capric acid, naphthenic acid and / or lauric acid is / are. High-temperature lubricant according to claim 1, characterized in that the wetting agent is naphthalene sulfonate or lignin sulfonate is. High-temperature lubricant according to claims 1 or 2, characterized in that the salt is an alkali phosphate, sulfate, borate, halide, nitrate, chlorate and / or perchlorate. High-temperature lubricant according to claim 1, characterized characterized in that the carrier medium is water and the auxiliaries, preferably alginates, polyacrylates, stabilizers the suspension and / or nitrogen compounds. High-temperature lubricant according to claim 2, characterized characterized in that the carrier medium a mineral oil and the auxiliaries are nitrogen compounds. Method for hot forming metals, wherein a Die-forming before forming a workpiece with a high-temperature lubricant based on of water-dispersed graphite or graphite-based graphite mineral oil sprayed or brushed, characterized in that coking residues avoided be made by a high-temperature lubricant according to claim 1 or 2 is used.