Process for preparing a workpiece prior metal forming

Abstract

The present invention relates to a process for preparing a metallic workpiece for cold forming by contacting at least one metallic surface thereof with an aqueous acidic phosphating solution to form at least one phosphate coating, comprising step 1 to step 6, wherein 1) a roughness value of the metallic workpiece is determined, 2) a surface A of the metallic workpiece is determined, 3) a current density is determined from a surface A of the metallic workpiece, 4) a factor FS is determined, using the current density determined in step 3, 5) phosphating is carried out electrolytically, whereby FS ≤ 200 A s / dm2 and 6) coating weight and optionally coating adhesion are determined, to a metallic workpiece, which has been coated with at least one phosphate coating according to the aforementioned process or to a metallic workpiece, which has been coated with at least one phosphate coating according to the aforementioned process and additionally with at least one lubricant layer, to a use of the metallic workpiece, which has been coated with at least one phosphate coating or with at least one such phosphate coating and additionally with at least one lubricant layer for cold forming or in sliding friction and to a metallic workpiece, which has been formed or forged by using the aforementioned metallic workpiece.

Description

[0001] 231668WO01 Chemetall GmbHProcess for preparing a workpiece prior metal formingThe present invention relates to a process for preparing a metallic workpiece for coldforming by contacting at least one metallic surface thereof with an aqueous acidicphosphating solution to form at least one phosphate coating, to a metallic workpiece, which has been coated with at least one phosphate coating, to a metallic workpiece, which has been coated with at least one phosphate coating and additionally with at least one lubricant layer, to a metallic workpiece, which has been coated with at leastone phosphate coating, additionally a salt carrier coating and additionally with at leastone lubricant layer, to a use of the metallic workpiece which has been coated with atleast one phosphate coating or with at least one such phosphate coating and additionally with at least one lubricant layer for cold forming or in sliding friction, and to a metallic workpiece, which has been formed or forged by using the metallic workpiece. Background of the invention Phosphating processes have been in use for decades for corrosion protection, to increase the adhesion of subsequent coatings, such as e.g. a paint film, or / and to improve the cold forming process. Aqueous zinc-rich phosphating solutions are conventionally used for this purpose. In automotive construction, for example, car bodies are pretreated with very high-quality zinc-manganese-nickel phosphating treatments, which ensure very high corrosion protection and very good paint adhesion, before the paint system is applied. Cold forming with substantially two-layer parting layer systems such as those based e.g. on phosphate and soap can be used in particular for the cold forming of strips,sheets, bosses - mainly in the form of cylindrical discs, approximately isometric bodiesand short rods, wires, pipes, rods or / and complex formed component parts. It is used in particular for iron and steel materials including high-alloy steels such as e.g. special steels, but to a certain extent also for aluminium, aluminium alloys, magnesium alloys, titanium, titanium alloys, zinc and zinc alloys. These processes are also suitable in principle for other metallic materials. 231668WO01 Chemetall GmbHCold forming can in principle be a) slide drawing such as e.g. wire drawing, tubedrawing or profile drawing, b) cold massive forming such as e.g. cold extrusion, cold-heading or ironing, or c) deep drawing.Wire drawing is carried out on wires, profiles or / and rods, made in particular from ironand steel materials, occasionally from aluminium- or titanium-rich materials. Wiredrawing is used for example to draw low-carbon wires such as e.g. cold-heading wiresor high-carbon wires such as spring wires to substantially smaller diameters and correspondingly longer lengths. Tube drawing is used to draw tubes longitudinally, thereby reducing their diameters and wall thicknesses. In cold extrusion, solid bodies are pressed into solid bodies having an altered geometry, wherein the lengths, wall thicknesses or diameters of the metallic components to be formed are substantially changed. Bosses can be formed into hollow bodies which can optionally be further extended lengthways and reduced in diameter by subsequent ironing. Cold extrusion is used in particular to produce small parts for gears, steering mechanisms, engines and pumps. In cold-heading, wires, profiles or rods are cut off to a certain length and largely or entirely given their commercial shape by upsetting. They are formed in particular into nuts, rivets or screws. In ironing, oblong hollow bodies can be extended by a factor of commonly about 4 and reduced correspondingly in cross-section or in diameter and wall thickness. Corresponding hollow bodies can be used as cans, sleeves or pipes. In deep drawing, the wall thickness of the metallic component to be formed remains unchanged or substantially unchanged. In deep drawing, strips are cut and the metal sections or sheets formed into cooking pans, oil trays or sinks, for example. Cold-upsetting wire generally has carbon contents in the range from 0.05 to 0.45 wt.% and is used among other things to produce nuts, rivets or screws. It is conventionally pre-drawn and annealed. A coating based on zinc phosphate, lubricant carrier salt or 231668WO01 Chemetall GmbH calcium hydroxide is then usually applied, followed by a coating based on a metal soap. The cold-upsetting wire coated in this way is then drawn in the calibrating drawing die,bent (cut) and cold upset. Coating is generally carried out by dipping or in a continuousprocess through a bath. After upsetting, threads can be incorporated into the screws to be manufactured by cutting or rolling.In the state-of-the-art electrolytic deposition processes are known, especially theelectrolytic deposition of ZnPhos in an inline process. An example here isEP1 574 601A1, which describes an electrolytic deposition method of ZnPhos.According to the process a current density of between 5 A / dm2 and 50 A / dm2 is usedfor the deposition of zinc phosphate or zinc-calcium phosphate. In WO 2017 / 118716A2, which relates to a self-lubricating, electrolytically deposited phosphate coating onmetal workpieces, comprising stabilized solid lubricants incorporated into thephosphate coating and to a method for the production thereof, a current intensity of 12 A / dm2is disclosed.The process described in WO2006 / 122651 A1 reports from a CaPhos agent which cancontain Mg and / or Mn. The application parameters here are roughly given as current density from 1 A / dm2to 200 A / dm2and a resulting coating weight from 2 to 40 g / m2. From the state of the art, only little information is known about the adjusting of variousparameter needed for electrolytic deposition processes. It isn´t described well, whatthe actual working window of the application technique is. This means that only validdata according to the current density are available. Applying these data to realexperiments results always in an empiric approach what could be the best parametersaccording to time, current density and surface preparation, which isn’t considered intotal. EP 1574601 A1 itself even does not describe any limits. There is a point whenelementary Zn is deposited instead of the desired ZnPhos-coating. To summarize this:All what is described is, that one has a treatment bath, one uses current for depositionand in order to find out the best working window, the user must conduct a trial-errormethod. Also, until now, it hasn’t been considered, how different surface topographiesinfluence the deposition window. It could be estimated that the deposited coatingweight equals somehow the electric energy which flows. Besides this, the prior art does 231668WO01 Chemetall GmbHnot describe at all if the coating shows an overall good adhesion or if one works in anapplication window where one has an access amount of loose coating on top of thesurface, by meaning that coating can be wiped off even by using a sponge.Thus, there is a need to provide a process suitable for preparing a metallic workpiecefor cold forming with which adjusting of various parameter needed for electrolyticdeposition processes can be carried out and whereby the individual process steps canbe optimized for each other making use of easily accessible parameter, and further toenable an optimized deposition and to find better application windows then described in the prior art. ProblemIt has been therefore an objective underlying the present invention to provide a processsuitable for preparing a metallic workpiece for cold forming with which adjusting of various parameter needed for electrolytic deposition processes can be carried out and whereby the individual process steps can be optimized for each other making use of easily accessible parameter, and further to enable an optimized deposition and to find better application windows than described in the prior art. Solution This objective has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e., by the subject matter described herein. A first subject-matter of the present invention is a process for preparing a metallicworkpiece for cold forming by contacting at least one metallic surface thereof with anaqueous acidic phosphating solution to form at least one phosphate coating, comprising step 1 to step 6, wherein 231668WO01 Chemetall GmbH1) a roughness value Ra of the metallic workpiece is determined,2) a surface A of the metallic workpiece is determined,3) a current density is determined from the surface A of the metallic workpiece,4) a factor FS is determined, using the current density determined in step 3:FS = IDensity* t t = treatment time in [s], ,5) phosphating is carried out electrolytically,whereby the following applies: FS ≤ 200 A s / dm2,6) coating weight CW and optionally coating adhesion are determined.A further subject-matter of the present invention is a metallic workpiece, which has been coated with at least one phosphate coating or with at least one such phosphate coating and additionally with at least one lubricant layer, a metallic workpiece, which has been coated with at least one phosphate coating, additionally a salt carrier coating and additionally with at least one lubricant layer according to the inventive process as defined hereinbefore and hereinafter. A further subject-matter of the present invention is the use of the metallic workpiece which has been coated with at least one phosphate coating or with at least one such phosphate coating and additionally with at least one lubricant layer according to the inventive process as defined hereinbefore and hereinafter for cold forming or in sliding friction. 231668WO01 Chemetall GmbHA further subject-matter of the present invention is a metallic workpiece, which hasbeen formed or forged by using the metallic workpiece as defined hereinbefore andhereinafter. The process described here enables answering the following questionsconcerning the kind of surface topography and the kind of application window, thatare required in order to obtain a coating suitable for cold forming operations like e.g.,wire drawing and further enables an optimized deposition and the determination ofbetter application windows then described in the prior art.It has been in particular surprisingly found that taken into account the correlation ofsurface topography parameters with the application parameters needed for a resultingcoating, the coating weight as well as the expected adhesion of the coating areindividually adjustable.Furthermore, it has been in particular surprisingly found, that by correlation of FS tothe resulting coating weight during application, all application parameters look quitesimilar. Therefore, a coating weight window can be created taken into account differentroughness values of the metallic surfaces of the metallic workpiece. This coating weight window will be described in detail hereinafter.Moreover, it has been in particular surprisingly found that by correlation of FS withadequate adhesion values an adhesion window can be created for a coating with anadequate adhesion useful for forming operations taking Ra, t, and IDensity inconsideration, while FS ≤ 200 A s / dm2. This adhesion window will be described in detailhereinafter. The calculation of the factor FS is described by taking the current density in mind. The determination of the current density IDensityis well known to the expert, especially in thefield of galvanizing. The current density is an important parameter in electroplating,which indicates the amount of electric current per unit area that flows through an electrode surface. In electroplating processes, such as electrolytic coating or electrochemical cleaning, the current density plays a decisive role in controlling andoptimising the process. The current density is usually measured in amperes per squarecentimetre (A / cm²) or milliamperes per square centimetre (mA / cm²). By controlling the 231668WO01 Chemetall GmbH current density, various aspects of the electroplating process can be controlled, including the thickness and uniformity of the deposited layer, the adhesion strength tothe substrate and the quality of the surface. Too high a current density can lead toundesirable effects such as pores, unevenness or uneven plating, while too low a current density can lead to slow process times and inefficient use of energy. Precise control of the current density is therefore crucial for achieving high-quality and uniformelectroplated coatings. Optimising the current density is a complex task that requiresthe consideration of various factors such as electrolyte composition, temperature, electrode materials and process parameters. By precisely controlling the current density, electroplating processes can be made more efficient and high-quality coatings with the desired properties can be produced. The measurement of the IMeasuredWireSurface can be done by using an Amp-Meter, normally this value can be directly taken from the rectifier producing the direct current, or an AMP-Meter must be installed in the wiring. The surface A is defined as the surface within the electrical field between the anodes. In respect of a wire surface A is calculated through the lateral area of a cylinder with the height of the anode length and the circumference of the wire. By meaningA=Circumference Wire * Anode Length.Detailed description of the invention The term “comprising” in the sense of the present invention, in connection for examplewith the inventive process, preferably has the meaning of “consisting of”. With regard,e.g., to said inventive process referred to hereinbefore, it is possible – in addition to allmandatory steps present therein that one or more further optional steps identifiedhereinafter to be also included therein.The proportions and amounts in wt.-% (% by weight) of any of the constituents given hereinafter, which are present in each of the compositions add up to 100 wt.-%, based in each case on the total weight of the respective composition. 231668WO01 Chemetall GmbH Especially the deposition of a CaPhos-coating has been investigated in order to find better application windows then described. Those application windows are needed for application line construction. The present invention describes the correlation of the surface topography as well as application parameters for phosphating to the resulting coating weight as well as to the expected adhesion of the coating. The surface topography is described by the Ra roughness value. The definition for Ra (arithmetic mean roughness value) is: The treatment of metallic surfaces using pickling or blasting technology, majorly wet- blasting but also using shot-blasting for example, leads to the creation of unstructured surfaces in a range from 0,1-10 µm. The surface area is normally calculated through e.g. flat surface width * length = A. Different surface topographies will deliver here different real surface areas since the above-described formula does not consider this. If it is required to consider the real surface area, this can be expressed by a surface factor in a way that: AReal= A * SurfaceFactor The present invention describes a new process for preparing a metallic workpiece for cold forming that takes the real surface into account. In the process for preparing a metallic workpiece for cold forming at least one metallic surface is contacted with an aqueous acidic phosphating solution to form at least one phosphate coating. The process comprises at least step 1 to step 6. Further steps can be inserted between the individual steps, placed in front of step 1 or added after step 6. Further steps can further include rinsing or drying steps. 231668WO01 Chemetall GmbH In a first step a roughness value Raof the metallic workpiece is determined using a confocal microscope, the handling of which is known to the skilled man. In a second step a surface A of the metallic workpiece is determined. In a third step a current density is determined from a surface A of the metallic workpiece as explained hereinbefore. In a fourth step a factor FS is determined, using the current density determined in step 3: FS = IDensity * t t = treatment time in [s], , and in a fifth step phosphating is carried out electrolytically, whereby the following applies:FS ≤ 200 A s / dm2. In the last step coating weight and optionally coating adhesion are determined which is explained in detail hereinafter. It can be estimated that the surface topography will lower FS in the following way: If FSReal is correlated to the resulting coating weight during application, it has been established that all application parameters look quite similar and a working window with + / - 1.7 g / sqm width can be defined. Before being phosphated, the metallic workpiece is commonly pickled, degreased, cleaned, rinsed, mechanically descaled, ground, peeled, brushed, subjected to abrasive blasting or / and wet blasting or / and heat treated. In the above-described process the phosphating is carried out with a phosphating solution which comprises at least 5 g / l of compounds of calcium, magnesium or / and 231668WO01 Chemetall GmbH manganese including the ions thereof, calculated as calcium, magnesium and manganese, and also phosphate and comprises a) from 5 to 65 g / l of Ca and from 0 to 20 g / l of Mg or / and Mn or b) from 5 to 50 g / l of Mg and from 0 to 20 g / l of Ca or / and Mn or c) from 5 to 80 g / l of Mn and from 0 to 20 g / l of Ca or / and Mg, whereby the total content of all other cations selected from among cations of the 2nd main group and of the 1st, 2nd and 5th to 8th transition group of the periodic table of the chemical elements apart from calcium, magnesium or / and manganese is less than0.5 g / l, an alkaline earth metal-comprising phosphating solution is free of fluoride andof complex fluoride and phosphating is carried out electrolytically at a current densityin the range from 2 to 200 A / dm2, with a phosphate layer having a coating weight perunit area in the range from 2 to 20 g / m2being formed. Phosphating solutions according to the invention for the electrolytic deposition of calcium, magnesium or / and manganese phosphate can preferably have the following composition:Phosphating solutions preferably contain at least 5 g / l calcium, magnesium or / andmanganese ions, phosphoric acid and optionally also at least one further inorganic or / and organic acid such as e.g. nitric acid, acetic acid or / and citric acid. The phosphating solution is conventionally an aqueous solution. In individual embodiments it can be a suspension, if for example it has a content of precipitated product or / and a very fine-particle additive. The cation can in principle be incorporated with any acid forming a water-soluble salt or / and with any complexing agent. In addition to the cited inorganic acids, at least one organic monocarboxylic, dicarboxylic or / and tricarboxylic acid, at least one phosphonic acid or / and at least one of the salts and esters thereof can also be used in particular. This / these acid(s) advantageously form(s) at least one water-soluble compound with calcium, magnesium or / and manganese ions. The amount of nitric acid can be reduced as far as zero by the addition of e.g. at least one suitable carboxylic acid, since the 231668WO01 Chemetall GmbH content of calcium, magnesium or / and manganese can be coordinated in this way and dissolved in water. The phosphating solution contains phosphate and a) 5 to 65 g / l of Ca and 0 to 20 g / l of Mg or / and Mn or b) 5 to 50 g / l of Mg and 0 to 20 g / l of Ca or / and Mn or c) 5 to 80 g / l of Mn and 0 to 20 g / l of Ca or / and Mg. In a), b) or c) the content of the first cation can be in the range from 12 to 40 g / l in particular. The content of the second and third cation in a), b) or c) can in particular display a content of 1 to 12 g / l for the second cation and a content of 0 or 0.1 to 8 g / l for the third cation. If the content of calcium, magnesium and manganese is too low, a phosphate coating or even no phosphate coating can be formed. If the content of calcium, magnesium and manganese is too high, the film quality of the phosphate coating can deteriorate. This can lead in particular to precipitations in the bath. The phosphating solution can additionally also contain other alkaline-earth metals such as e.g. strontium or / and barium, but in particular ions of alkali metals, such as e.g. sodium, potassium or / and ammonium, above all to adjust the S value, to raise the pH and to improve the low-temperature stability. The content in the phosphating solution of alkali metals including ammonium, in particular in the form of ions, selected above all from the group comprising sodium, potassium and ammonium, is preferably in the range from 0.01 to 100 g / l, particularly preferably in the range from 0.05 to 75 g / l, most particularly preferably in the range from 0.08 to 50 g / l, in particular in the range from 0.1 to 30 g / l, above all in the range from 0.2 to 20 g / l, calculated proportionally as the particular alkali metal or as ammonium. In a preferred embodiment the Ra roughness value of the metallic workpiece is in a range between 0,3-10 µm. By using cleaning methods resulting in unstructured surfaces, it has been established that the SurfaceFactor can be expressed by: and . 231668WO01 Chemetall GmbH In a further preferred embodiment, the surface factor is correlated to the resulting coating weight CW, whereby the following applies: . For the determination of the coating weight CW of the coated metallic workpiece the coated metallic workpiece has been weighed, and the coating was then rubbed off in a standardized manner. The metallic workpiece was then weighed again, the coating was completely removed, and the metallic workpiece was weighed for the last time. The coating is rubbed off by pressing a sponge onto the bar material with a defined force and rubbing it once over the entire coating. With the measured weights and the known real surface of the bar, the total layer weight and the proportion of abraded and adhesive layer can be calculated. For the correlation of the surface factor and the adhesion of the coating, the following adhesion window can be applied: The resulting expression above expresses the coating loss in %. A boarder at maximum 65% loss was set on the basis of empirical values. In the process for preparing a metallic workpiece for cold forming the metallic workpiece is connected as cathode in the phosphating solution and is treated with direct current or with a superimposition of direct current and alternating current. 231668WO01 Chemetall GmbH A direct current or an alternating current or a superposition of a direct current and an alternating current can be used as the current for electrolytic phosphating. Direct current or a superposition of direct current and alternating current is preferably used for electrolytic phosphating. The direct current can preferably have an amplitude inthe range from 2 to 200 A / dm2, particularly preferably in the range from 1 to 10A / dm2, in particular in the range from 10 to 60 A / dm2. The alternating current canpreferably have a frequency in the range from 0.1 to 100 Hz, particularly preferably in the range from 0.5 to 10 Hz. The alternating current can preferably have an amplitude in the range from 0.5 to 30 A / dm2, particularly preferably in the range from 1 to 20 A / dm2, most particularly preferably in the range from 1.5 to 15 A / dm2, in particular in the range from 2 to 8 A / dm2. With a superposition of direct current and alternating current, the abovementioned electrical conditions can be combined. With a superposition of direct current and alternating current, the ratio of the direct current component to the alternating current component as with the aforementioned electrical conditions can be varied within broad limits. The ratio of direct current component to alternating current component is preferably kept in the range from 20 : 1 to 1 : 10, particularly preferably in the range from 12 : 1 to 1 : 4, most particularly preferably in the range from 8 : 1 to 1 : 2, above all in the range from 6 : 1 to 1 : 1, relative to the components measured in A / dm2.The contactable or contacted holder for the metallic workpiece to be coated, such ase.g. for a wire, which is often used above the bath, can be made from any metallic electrically conductive material, preferably from an iron or copper material. It servesas a cathode and connects the metallic workpiece as the cathode. The flow of currentbetween the cathode and the anode passes through the phosphating solution, which has good electrical conductivity. The contactable or contacted anode is largely or entirely placed in the phosphating solution in the bath and is preferably made from a metallic, electrically conductivematerial which - in the event that it dissolves in the phosphating solution andaccumulates, in some circumstances also as sludge - does not adversely affect thephosphating solution and the electrolytic phosphating process. Iron materials, whichdissolve slowly in the bath and form an iron phosphate-rich sludge, are therefore also 231668WO01 Chemetall GmbH suitable in principle. The anode preferably consists of a material which is not dissolvable or only slightly dissolvable in the bath solution, based on titanium for example, which in particular because of its conductivity and possible slight dissolvability in the bath solution can also be coated with a noble metal from the 8th subgroup of the periodic table. If the metallic object to be coated is connected as the cathode and is coated electrolytically, there is little or no pickling attack in the acid phosphating solution - unlike the case with the currentless method. When iron anodes were used, iron nevertheless accumulated in the bath. In some circumstances this accumulation was up to around 10 g / l Fe2+. These quantities did not cause any problems. Largeramounts of Fe2+ can be precipitated out by the addition of at least one oxidizingagent such as e.g. hydrogen peroxide, sodium chlorate or / and ambient oxygen. When platinum-plated titanium anodes, for example, were used, no iron accumulatedin the bath. The use of a suitable oxidizing agent is often advantageous because itallows the treatment time to be reduced, since the hydrogen produced in the electrochemical reaction is immediately oxidized to H+ions and so the hydrogen gas, which often accumulates at the surface in bubbles, can no longer block the coating of the surface. Brushite, but not an apatite, was detected radiographically as the main constituent of the calcium-rich electrolytically deposited phosphate coatings. By the currentless method calcium-rich phosphating solutions produced no coating at all. The main constituent of the magnesium-rich or / and manganese-rich electrolytically produced phosphate coatings could not be detected radiographically even on thick coatings; instead, unlike the case with phosphate coatings deposited without current, it appears to be X-amorphous. In order to deposit the phosphate coating according to the invention, the metallic workpiece such as e.g. a wire or several wires isolated from one another and contacted separately, is connected as the cathode, introduced into the bath with the phosphating solution and coated electrolytically using a current. Once the current has been switched off, the coated metallic workpiece can be removed from the bath.Alternatively, in continuous processes the coated metallic workpiece can be 231668WO01 Chemetall GmbH transported to bath sections in which there is no significant current flow or no current flow at all, and in which no significant electrolytic coating or no electrolytic coating atall is thus applied in the bath and removed there.The content of phosphate in the phosphating solution, calculated as PO4, is preferably in the range from 2 to 500 g / l as PO4, in particular as phosphate ions, particularly preferably in the range from 4 to 320 g / l, most particularly preferably in the range from 8 to 200 g / l, in particular in the range from 12 to 120 g / l, above all in the range from 20 to 80 g / l. If the content of phosphate is too low, too slight a phosphate coating or even no phosphate coating can be formed. If the content ofphosphate is too high, this has no adverse effect or can reduce the film quality of thephosphate coating. Under some conditions and with too high a phosphate content the phosphate coating can then become spongily porous and precipitations in the bath can occur. The phosphate content is preferably somewhat hyperstoichiometric in comparison to the cation content. The content of nitrate in the phosphating solution is preferably 0 or close to 0 g / l or in the range from 1 to 600 g / l, particularly as nitrate ions, particularly preferably in the range from 4 to 450 g / l, most particularly preferably in the range from 8 to 300 g / l, in particular in the range from 16 to 200 g / l, above all in the range from 30 to 120 g / l. If the phosphating solution contains little or no nitrate, it is more favourable for the waste water. A low or moderate content of nitrate can have an accelerating effect on electrolytic phosphating and can therefore be advantageous. Too low or too high a nitrate content in the phosphating solution has no substantial influence on the electrolytic phosphating process and on the quality of the phosphate coating. The content in the phosphating solution of at least one substance selected from organicacids, the salts and esters thereof - selected in particular from monocarboxylic,dicarboxylic and tricarboxylic acids and the salts and esters thereof, such as e.g. basedon citric acid, gluconic acid or / and lactic acid - and from phosphonic acids, the saltsand esters thereof, selected in particular from organic phosphonic and diphosphonic acids, the salts and esters thereof, including the anions thereof, is preferably zero or close to zero or in the range from 0.1 to 200 g / l, particularly preferably in the range 231668WO01 Chemetall GmbH from 1 to 150 g / l, most particularly preferably in the range from 3 to 100 g / l, in particular in the range from 6 to 70 g / l, above all in the range from 10 to 40 g / l. They act in particular as complexing agents. Complexing agents mostly have no effect if all cations are already dissolved in water. They are necessary if a cation content in a particular composition cannot be converted by any other means into a water-soluble form. Too low or too high a complexing agent content in the phosphating solution has no substantial influence on the phosphating process and on the quality of the phosphate coating. The entire cation content is preferably added in the form of nitrate(s) or / and other, water-soluble salts, so that an addition of complexing agent(s) is not necessary. The phosphating solution comprises preferably as accelerator, at least one substance, selected from among substances based on chlorate, guanidine, hydroxylamine, nitrite, nitrobenzenesulfonate, perborate, peroxide, peroxosulfuric acid and further accelerators comprising nitro groups, wherein the phosphating solution has a contentof accelerators apart from nitrate in the range from 0.1 to 100 g / l. The content in thephosphating solution of accelerators other than nitrate such as e.g. based on nitrobenzene sulfonate (e.g. SNBS = sodium nibrobenzene sulfonate), chlorate, hydroxylamine, nitrite, guanidine such as e.g. nitroguanidine, perborate, peroxide, peroxysulfuric acid and other nitrogen-containing accelerators is preferably zero, close to zero or in the range from 0.1 to 100 g / l, as compounds or / and ions, calculated as the corresponding anion. The content of accelerators other than nitrate in the phosphating solution is particularly preferably in the range from 0.01 to 150 g / l, most particularly preferably in the range from 0.1 to 100 g / l, in particular in the range from 0.3 to 70 g / l, above all in the range from 0.5 to 35 g / l. The experiments showed that an addition of at least one accelerator is helpful and advantageous in many embodiments, in particular an addition of at least one nitrogen-containing accelerator. It was originally expected that the accelerators would substantially only increase the rate of film formation and would therefore have a weaker effect than in conventional currentless phosphating. It was found, however, that the accelerating effect of the accelerators including nitrate on the phosphating process in electrolytic phosphating is not usually 231668WO01 Chemetall GmbH less than in conventional currentless phosphating and that the various accelerators differ markedly in their effects on the film properties in particular. The content of chlorate in the phosphating solution is preferably zero, close to zero or in the range from 1 to 100 g / l ClO3-ions, particularly preferably 2 to 80 g / l, most particularly preferably in the range from 3 to 60 g / l, above all in the range from 5 to 35 g / l. Chlorate can have a particularly strong accelerating effect in comparison to other accelerators and can help to form markedly finer-grain phosphate coatings. The content of compounds based on guanidine, such as e.g. nitroguanidine, in the phosphating solution is preferably zero, close to zero or in the range from 0.1 to 10 g / l calculated as nitroguanidine, particularly preferably 0.2 to 8 g / l, most particularly preferably in the range from 0.3 to 6 g / l, above all in the range from 0.5 to 3 g / l. Relative to its content, a guanidine compound such as nitroguanidine can have a strongly accelerating effect in comparison to other accelerators and nitrate, but it gives off no oxygen and often leads to fine-grain phosphate coatings having particularly good adhesive strength. The content of nitrobenzene sulfonate in the phosphating solution is preferably zero, close to zero or in the range from 0.1 to 10 g / l calculated as the corresponding anion, particularly preferably 0.2 to 8 g / l, most particularly preferably in the range from 0.3 to 6 g / l, above all in the range from 0.5 to 3 g / l. Relative to its content, nitrobenzene sulfonate can have a strong accelerating effect in comparison to other accelerators and often leads to fine-grain phosphate coatings having good adhesive strength. Under a scanning electron microscope, the phosphate coatings produced accordingto the invention often do not display the typical crystal shapes - unlike the chemicallycomparable phosphate coatings deposited without current - but instead on the onehand have particle-like formations which are often open in the middle like short sections of tubing and look as if they had been formed around a fine hydrogen bubble. These entities often have an average particle size in the range from 1 to 8 µm. The hydrogen bubbles could successfully be made finer by the addition of a particular accelerator such as e.g. nitroguanidine or alternatively avoided altogetherby the addition of a reducing agent such as e.g. based on an inorganic or organic 231668WO01 Chemetall GmbH acid, the salts or / and esters thereof, so that the phosphate coatings do not have too much of a particulate appearance. On the other hand, there are some phosphate films, which can also be recognised by the particle-like entities, which in some cases appear to have burst open. It is therefore particularly preferable to add a reducing agent, preferably in the range from 0.1 to 15 g / l, which in the pH range between 1 and 3 forms no poorly soluble compounds with calcium, magnesium or / and manganese, to the phosphating solution in order to influence and in particular to homogenise the morphology of the phosphate coating. In phosphate coatings with inadequate homogeneity, which are inadequately closed, clear differences are sometimes discernible in the formation of the phosphate coating in different areas ofthe sample. For that reason, all phosphate coatings according to the invention differsignificantly from phosphate coatings deposited without current.It is preferable that to the phosphated surfaces of the metallic surfaces of the metallicworkpiece further at least one lubricant or at least one lubricant compositioncomprising at least one lubricant is applied, because it was found, that on a metallicworkpiece in coating weights of more than 18 g / m2the phosphate coatings according to the invention often have less adhesive strength before being coated with at least one lubricant or with at least one lubricant composition. Coatings of less than 2.5g / m2 on the metallic workpiece often has a limited release effect on the coatingsystem between the metallic workpiece and die because the coating is too thin, so that in cold forming the metallic workpiece and die can easily be cold welded, causing striation, wire breakage, mechanical separation of the welded remainder of the wire from the die or / and damage to the die. At least one lubricant or at least one lubricant composition having at least one substance selected from soaps, oils, organic polymers and waxes is preferably applied to this phosphate coating in at least one layer. The following are mostly used as lubricants or lubricant compositions, each of which displays at least one of the substances cited below, optionally also in combination with one another: 231668WO01 Chemetall GmbH1. Metal soaps based on alkali metal, which are water-soluble and are able to bereacted chemically at least partly with the phosphates in the phosphate coating and which are preferably applied in liquid form, mainly as sodium soap,2. Metal soaps based on alkaline-earth metal, in particular as aluminium, calciumor / and zinc soap, which are water-insoluble and which are unable or scarcely able to be reacted chemically with the phosphates in the phosphate coating and for that reason are preferably used as a powder or in the form of a paste,3. Oils,4. Flexible or / and reactive organic polymers, which like certain organic polymersbased on (meth)acrylate or / and polyethylene, for example, display lubricating properties, and5. Waxes such as e.g. crystalline waxes, which can optionally be mixed with atleast one each of a metal soap, layered silicate, additive and agent to increase the viscosity of the solution or suspension, such as e.g. starch. These lubricants or lubricant compositions can be used in the process according to the invention following phosphating. Liquid lubricants or lubricant compositions can be applied to the workpieces by dipping in a bath, for example. Powdered or paste-like lubricants or lubricant compositions are preferably placed in a die box, through which a wire, for example, can be drawn and coated.The metallic workpiece which has been coated in this way described hereinbefore iscold formed and optionally subsequently heat treated, ground, lapped, polished, cleaned, rinsed, coated with at least one metal, coated with at least one pretreatment composition and / or passivating composition, coated with at least one organic composition or / and processed to give a composite component. A further subject of the invention is the metallic workpiece, which has been coated with at least one phosphate coating or with at least one such phosphate coating and additionally with at least one lubricant layer produced in the way described above. 231668WO01 Chemetall GmbHA further subject is the use of the metallic workpiece which has been coated with atleast one phosphate coating produced as described hereinbefore or with at least onesuch phosphate coating produced as described hereinbefore and additionally with at least one lubricant layer for cold forming or in sliding friction.Finally, a further subject of the invention is a metallic workpiece, which has beenformed or forged by using the metallic workpiece described hereinbefore. The phosphating solution particularly preferably displays the following contents: 5to 60 g / l of Ca, Mg or / and Mn,0 to 25 g / l of alkali metal(s) or / and NH4,8 to 100 g / l of PO4,5 to 240 g / l of nitrate or / and accelerator(s) and0 to 50 g / l of complexing agent(s).The phosphating solution most particularly preferably displays the following contents: 8to 50 g / l of Ca, Mg or / and Mn,0 to 20 g / l of alkali metal(s) or / and NH4,12 to 80 g / l of PO4,12 to 210 g / l of nitrate or / and accelerator(s) and0 to 40 g / l of complexing agent(s).In particular the phosphating solution displays the following contents: 10 to 40 g / l of Ca, Mg or / and Mn,0 to 15 g / l of alkali metal(s) or / and NH4,16 to 65 g / l of PO4,18 to 180 g / l of nitrate or / and accelerator(s) and0 to 32 g / l of complexing agent(s).The invention is further described with reference to the accompanying figures, in whichFig.1 depicts metallic surfaces, untreated and treated by using pickling or blastingtechnology. Especially described are surfaces, which are untreated with Ra = 3.23 231668WO01 Chemetall GmbHµm, Rz = 17,5 µm, pickled with Ra = 1.68 µm, Rz = 10.4 µm, shot blasted with Ra =3.06 µm, Rz = 16.6 µm, standard with Ra = 2.20 µm, Rz = 14.4 µm, rougher with Ra =2.67 µm, Rz = 17,9 µm and smoother with Ra = 1.56 µm, Rz = 10.2 µm; andFig.2 depicts the correlation of FS to the resulting coating weight CW duringapplication.Fig.3 depicts abrasion tests.The abrasion test has been conducted according to the following scheme: 1.Coating the wire samples2.Weighing each wire with an analytical scale (→weight after coating)3.Wipe the wire with standardized pressure4.Weigh again (→weight after wiping)5.Remove coat completely 6. Weigh again (→weight without coat) The following formulas have been used:Overall coating weight = (weight of coated wire – weight of uncoated wire) [g] / coated surface of wire [m²]Wiped away coating weight= (weight of coated wire – weight of wiped wire) [g] / coated surface of wire [m²] Abrasion loss = wiped away coating weight / Overall coating weight * 100 [%]Fig. 3 reflects the conducted test. That data which could be correlated have beencollected. The resulting expression expresses the coating loss in %. According to ourexpert knowledge a boarder has been set at maximum 65% loss.Examples The following examples further illustrate the invention, but are not to be construed as limiting its scope. 231668WO01 Chemetall GmbH Description of the experiments and their implementation To investigate the influence of the surface quality, in particular of wet-blastedsurfaces, on the adhesive strength of an electrolytically applied CaHPO4-coating ina first step, the surfaces of the differently pre-treated substrates were analysed usingconfocal microscopy. Fine, standard and coarse wet-blasted metallic surfaces, especially metallic barsurfaces, were analysed, as well as a metallic surface, especially a metallic barsurface, that had only been cleaned. Roughness characteristics of the different pretreatments pretreatment Ra [µm] Rz [µm] Sa [µm] Sz [µm] Sdr [%]wet blasted1,59 13,35 1,80 16,92 36,1fine wet blasted2,29 19,08 2,37 23,27 50,4standard wet blasted3,02 23,48 3,06 27,07 58,0coarse cleaned 0,59 4,98 0,47 7,40 3,67The Sdr-value, which describes the increase in surface area in % compared to an ideally planar surface, is particularly important. The pretreated bar material was then coated in a Gardobond Z 3200 bath with the following bath parameters.concentration: 280 g / lphosphate points: 50pH-value: 1,85bath-temperature: room temperatureSeveral bars of the respective pretreatment type were coated with the following current parameters. 231668WO01 Chemetall GmbHcoating time: 3s and 6sfactor: 50, 80, 110 As / dm² (current density in A / dm² x time in s)The current to be set for coating was calculated using the real surface of the bar material. Test overview with planned factor and coating time, current intensity and calculatedcurrent density and factor is described below. The current intensity is the valueactually applied to the rectifier during the test. This value is used to calculate the actual factor. Table 1: current current intensity density planned coa^ng (A) (A / dm²) actual No. pretreatmentfactor^me (s)IMeasuredWireSurface IDensity factor 1wet-blasted fine 50 3 15,2 17,0 512 wet-blasted fine 50 6 7,7 8,6 523 wet-blasted fine 80 3 22,7 25,4 764 wet-blasted fine 80 6 12,2 13,7 825 wet-blasted fine 110 3 32,6 36,5 1096 wet-blasted fine 110 6 16,5 18,5 1117 wet-blasted standard 50 3 16,3 16,5 508 wet-blasted standard 50 6 9,5 9,6 589 wet-blasted standard 80 3 27,3 27,6 8310 wet-blasted standard 80 6 13,5 13,7 8211 wet-blasted standard 110 3 33,2 33,6 10112 wet-blasted standard 110 6 18,1 18,3 11013 wet-blasted coarse 50 3 17,9 17,3 5214 wet-blasted coarse 50 6 8,3 8,0 4815 wet-blasted coarse 80 3 32,5 31,3 9416 wet-blasted coarse 80 6 14,4 13,9 8317 wet-blasted coarse 110 3 33 31,8 9518 wet-blasted coarse 110 6 19,4 18,7 11219 cleaned only 50 3 10,3 16,8 5020 cleaned only 50 6 4,9 8,0 4821 cleaned only 80 3 17,3 28,1 8422 cleaned only 80 6 8,3 13,5 8123 cleaned only 110 3 23,8 38,7 11624 cleaned only 110 6 11,3 18,4 110 231668WO01 Chemetall GmbH Coating weight and coating adhesion To determine the coating weight, the coated rods were weighed on an analytical balance and then the coating was rubbed off in a standardised manner. The rods were then weighed again, the coating completely removed and the rods weighed for the last time. The coating is rubbed off by pressing a sponge onto the bar material with a defined force and rubbing it once over the entire coating. With the measured weights and the known real surface of the bar, the total coating weight CW and the proportion of abraded and adhesive layer can be calculated. Refer is further made to Fig.3 and related text thereto.

[0002] 231668WO01 Chemetall GmbH Table 2 proportion coating coating coating of coating actual coating weight wiped off adhesive wiped off No. pretreatmentfactor time (s) (g / m²) (g / m²) (g / m²) (%) 1wet-blasted fine 51 3 3,9 1,6 2,3 402 wet-blasted fine 52 6 3,8 0,6 3,2 163 wet-blasted fine 76 3 5,4 2,9 2,5 534 wet-blasted fine 82 6 5,9 2,3 3,6 385 wet-blasted fine 109 3 7,1 4,8 2,3 686 wet-blasted fine 111 6 7,3 4,0 3,2 55wet-blasted 7standard 50 3 3,6 1,2 2,4 34wet-blasted 8standard 58 6 4,2 1,0 3,2 24wet-blasted 9standard 83 3 5,8 3,3 2,5 57wet-blasted 10standard 82 6 5,9 2,2 3,7 38wet-blasted 11standard 101 3 6,9 4,2 2,7 61wet-blasted 12standard 110 6 7,9 3,8 4,1 48wet-blasted 13coarse 52 3 4,1 1,0 3,1 24wet-blasted 14coarse 48 6 3,5 0,3 3,2 9wet-blasted 15coarse 94 3 6,1 3,5 2,6 58wet-blasted 16coarse 80 6 5,6 1,8 3,7 33wet-blasted 17coarse 110 3 6,3 3,5 2,7 56wet-blasted 18coarse 110 6 7,6 3,6 4,1 4719 cleaned only 50 3 4,0 2,0 2,0 5020 cleaned only 50 6 3,0 1,2 1,7 4221 cleaned only 80 3 5,7 4,0 1,7 7022 cleaned only 80 6 5,3 3,0 2,3 5723 cleaned only 110 3 7,3 5,4 1,9 7424 cleaned only 110 6 6,9 4,1 2,7 60

Claims

231668WO01 Chemetall GmbH CLAIMS 1. Process for preparing a metallic workpiece for cold forming by contacting atleast one metallic surface thereof with an aqueous acidic phosphating solution to form at least one phosphate coating, comprising step 1 to step 6, wherein 1) a roughness value Raof the metallic workpiece is determined, 2) a surface A of the metallic workpiece is determined, 3) a current density is determined from the surface A of the metallic workpiece, 4) a factor FS is determined, using the current density determined in step 3: FS = IDensity* t t = treatment time in [s],, 5) phosphating is carried out electrolytically, whereby the following applies: FS ≤ 200 A s / dm2,6) coating weight CW and optionally coating adhesion are determined.

2. Process according to claim 1, characterized in that the phosphating is carriedout with a phosphating solution comprises at least 5 g / l of compounds of calcium, magnesium or / and manganese including the ions thereof, calculated as calcium, magnesium and manganese, and also phosphate and comprises231668WO01 Chemetall GmbH a) from 5 to 65 g / l of Ca and from 0 to 20 g / l of Mg or / and Mn or b) from 5 to 50 g / l of Mg and from 0 to 20 g / l of Ca or / and Mn or c) from 5 to 80 g / l of Mn and from 0 to 20 g / l of Ca or / and Mg, the total content of all other cations selected from among cations of the 2nd main group and of the 1st, 2nd and 5th to 8th transition group of the periodic table of the chemical elements apart from calcium, magnesium or / and manganese is less than 0.5 g / l, an alkaline earth metal-comprising phosphating solution is free of fluoride and of complex fluoride and phosphating is carried out electrolytically at a current density in the range from 2 to 200 A / dm2, with a phosphate layer having a coating weight per unit area in the range from 2 to 20 g / m2being formed.

3. Process according to claims 1-2, characterized in that the Ra roughness valueof the metallic workpiece is in a range between 0,3-10 µm and that a surface factor is .

4. Process according to claims 1-3, characterized in that the surface factor iscorrelated to the resulting coating weight CW, whereby the following applies:.

5. Process according to claims 1-4, characterized in that the surface factor iscorrelated to the adhesion of the coating, whereby the following adhesion window applies:231668WO01 Chemetall GmbH.

6. Process according to claims 1-5, wherein the metallic workpiece is connectedas cathode in the phosphating solution and is treated with direct current or with a superimposition of direct current and alternating current.

7. Process according to any of the preceding claims, wherein the metallicworkpiece is pickled, degreased, cleaned, rinsed, mechanically descaled, ground, peeled, brushed, subjected to abrasive blasting or / and wet blasting or / and heat treated before phosphating.

8. Process according to any of the preceding claims, wherein the phosphatingsolution has a content of phosphate in the range from 2 to 500 g / l, calculated as PO4.

9. Process according to any of the preceding claims, wherein the phosphatingsolution comprises, as accelerator, at least one substance, selected from among substances based on chlorate, guanidine, hydroxylamine, nitrite, nitrobenzenesulfonate, perborate, peroxide, peroxosulfuric acid and further accelerators comprising nitro groups, wherein the phosphating solution has a content of accelerators apart from nitrate in the range from 0.1 to 100 g / l.

10. Process according to any of the preceding claims, wherein a reducing agentwhich does not form any sparingly soluble compounds with calcium, magnesium or / and manganese in the pH range from 1 to 3 is added to the phosphating solution in order to influence the morphology of the phosphate coating.

11. Process according to any of the preceding claims, wherein at least one lubricantor at least one lubricant composition comprising at least one lubricant is applied to the phosphated surfaces.231668WO01 Chemetall GmbH12. Process according to claim 11, wherein the metallic workpiece, which has beencoated in this way is cold formed and optionally subsequently heat treated,ground, lapped, polished, cleaned, rinsed, coated with at least one metal, coated with at least one pretreatment composition and / or passivating composition, coated with at least one organic composition or / and processed to give a composite component.

13. Metallic workpiece, which has been coated with at least one phosphate coatingproduced according to any of claims 1 to 10 or with at least one such phosphatecoating and additionally with at least one lubricant layer according to claim 11.

14. Use of the metallic workpiece, which has been coated with at least onephosphate coating produced according to any of claims 1 to 10 or with at leastone such phosphate coating and additionally with at least one lubricant layer according to claim 11 for cold forming or in sliding friction.

15. Metallic workpiece, which has been formed or forged by using the metallicworkpiece according to claim 13.

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