TW201732045A - Iridium-platinum alloy and machined article made thereof - Google Patents

Abstract

The present invention relates to an iridium-platinum alloy which contains platinum in an amount of 70 wt% or less, the remainder being iridium and unavoidable impurities, and has an average grain width to height ratio of at least 5.

Description

铱Platinum alloy and processed articles thereof

The present invention relates to a ruthenium platinum alloy and a processed article thereof.

铱 is a platinum group metal. Its hardness and melting point are extremely high. In addition, niobium is one of the second most dense elements (after niobium) and one of the most corrosion resistant metals. Due to these attributes, tantalum and niobium containing alloys are materials that are of interest to several applications, such as spinnerets, spark plugs, balance wheels and jewelry.

WO 2011/034566 describes a jewellery article made of a metal containing at least 75 wt% bismuth.

US 2005/0129960 A1 describes an alloy composition comprising from 1 to 10 at% Zr and/or Hf, the balance being ruthenium; and articles coated from the alloy composition.

EP 2 281 905 A1 describes a ruthenium-based metal composition which does not contain Zr and Hf and which comprises 0.5 to 30 wt-ppm boron and 0.5 to 20 wt-ppm calcium.

CN 101483319 A describes a ruthenium platinum alloy and its use as a spark plug electrode material.

US 2006/0270924 A1 describes an electrode for medical applications comprising a substrate coated with a porous Pt-Ir alloy.

However, due to the hardness, brittleness and high melting point of the crucible, the crucible is difficult to process and form. Or forged.

The platinum ruthenium alloy can be obtained by adding platinum to lower the melting point. However, in particular, where the alloys are bismuth (Ir content is more than 50% by weight), they are still extremely brittle and hard materials and are therefore still extremely difficult to process.

If a shaped article is prepared by processing (such as milling) a molded body made of a material that is extremely rigid and brittle, the article typically exhibits surface defects. In particular, the material may break along the edges created during the machining process. However, for many applications, processed objects having such surface defects (eg, edge defects) are unacceptable.

It is an object of the present invention to provide a niobium containing alloy which has improved forgeability and which is suitable for the preparation of shaped articles by processing. If the structure of the shaped article contains edges, the number and size of the defects along the edges (e.g., due to the broken material) should be kept as low as possible.

The target is solved by a ruthenium platinum alloy containing platinum in an amount of 70% by weight or less, the balance being ruthenium and unavoidable impurities, and an average particle width to height ratio of at least 5.

Figure 1 shows an optical image of an etched microsection.

Figure 2 shows an optical image of an etched microsection.

The shape of the particles can be indicated by the width to height ratio of the particles. If the width is compared with the height Nearly 1, the particles have a relatively "circular" shape, while a width to height ratio well above 1 indicates an elongated particle shape. In other words, the higher the aspect ratio, the slender the particles. Typically, if the material has been subjected to recrystallization treatment, it contains a large amount of equiaxed particles or even particles (i.e., particles having a width to height ratio close to 1).

In the present invention, it has surprisingly been realized that a molded body (made of a platinum alloy having elongated particles such that an average particle width to height ratio of at least 5) can be processed into articles having a reduced number of surface defects. In detail, the number and size of edge defects can be significantly reduced.

Preferably, the average particle width to height ratio is at least 8, more preferably at least 10. In a preferred embodiment, the average particle width to height ratio is in the range of from 5 to 25, more preferably from 8 to 20, and even more preferably from 10 to 16.

Preferably, the iridium platinum alloy contains platinum in an amount of 50% by weight or less, more preferably 45% by weight or less. In a preferred embodiment, the iridium platinum alloy contains platinum in an amount of from 70 wt% to 25 wt%, more preferably from 50 wt% to 25 wt%, even more preferably from 45 wt% to 25 wt%.

As indicated above, the alloy consists of rhodium, platinum and unavoidable impurities. By using platinum having high purity (for example, purity of at least 99.9%, more preferably at least 99.99%) and platinum having high purity (for example, purity of at least 99.9%, more preferably at least 99.99%) The starting material maintains the amount of unavoidable impurities in the final Ir-Pt alloy at an extremely low level. Preferably, the rhodium platinum alloy contains less than 200 wt-ppm of rhodium. More preferably, the iridium platinum alloy contains less than 200 wt-ppm bismuth, less than 150 wt-ppm copper, less than 100 wt-ppm calcium, less than 50 wt-ppm boron, and less than 100 wt-ppm iron.

Preferably, the average number of pores per mm ² of the iridium platinum alloy is less than 0.04, more preferably less than 0.03.

Preferably, the iridium platinum alloy has a hardness of 500 HV1 or less, more preferably 480 HV1 or less.

As will be discussed in further detail below, the rhodium platinum alloy of the present invention is preferably prepared by subjecting the Ir-Pt cast body to one or more forming steps such as rolling or forging. Therefore, it is preferred that the iridium platinum alloy is a formed iridium platinum alloy, in particular, a rolled or forged iridium platinum alloy. The shaped iridium platinum alloy can be a disc or a plate. However, other shapes are also possible.

Furthermore, the present invention relates to a method for preparing a ruthenium platinum alloy, the method comprising (i) a platinum melt prepared from free bismuth, platinum and unavoidable impurities to prepare a cast body, (ii) preheating the cast body and subjecting the preheated cast body to one or more forming steps such that the recrystallized degree of the formed iridium platinum alloy is less than 30%.

Typically, the casting step (i) involves melting the ruthenium and platinum metal in a boiler (e.g., an induction boiler) to prepare a ruthenium platinum melt and then casting the melt into a mold. The melt consists of rhodium and platinum as well as unavoidable impurities. Preferably, the iridium platinum melt contains platinum in an amount of 70% by weight or less, more preferably 50% by weight or less, even more preferably 45% by weight or less. In a preferred embodiment, the iridium platinum melt contains platinum in an amount from 70 wt% to 25 wt%, more preferably from 50 wt% to 25 wt%, even more preferably from 45 wt% to 25 wt%.

Cool (eg, water cooled) the mold as appropriate. It may be preferred that the mold be composed of a material having a high thermal conductivity (for example, at least 200 W/(m*K) or at least 300 W/(m*K) at 20 ° C), such as copper. The preferred mold is, for example, a water-cooled copper mold.

As is known to those skilled in the art, heat can be performed above the recrystallization temperature. Recrystallization is achieved by rational (static recrystallization), optionally in combination with shaping (eg, rolling) treatment (dynamic recrystallization). Generally, those skilled in the art are aware of parameters that affect the recrystallization temperature. The degree of recrystallization depends inter alia on the processing temperature (i.e., above or below the recrystallization temperature) and the duration of the treatment.

In the method of the present invention, the preheating and subsequent forming (e.g., rolling) steps are carried out under conditions such that the finally obtained shaped (e.g., rolled) ruthenium platinum alloy has a degree of recrystallisation of less than 30%. As explained further below, the degree of recrystallization indicates the relative area (in %) of the microsections covered by the recrystallized equiaxed particles.

Based on common general knowledge, those skilled in the art will be able to identify suitable processing conditions for step (ii) that ensure that the final obtained shaped (e.g., rolled) ruthenium platinum alloy has a recrystallisation of less than 30%. As just one example, the forming of the cast body (e.g., rolling) can be carried out at a temperature low enough to maintain recrystallization to a very low extent or even below the recrystallization temperature. In principle, it is also possible that one or more shaping steps are carried out at least partially at a forming temperature above the recrystallization temperature, but the duration of such forming steps at a temperature above the recrystallization temperature is maintained Short enough to avoid any substantial recrystallization.

In a preferred embodiment, the formed iridium platinum alloy has a degree of recrystallisation of less than 20%, more preferably less than 10%, and even more preferably less than 5%.

Preferably, at least the final forming step is carried out at a forming temperature _Tf lower than the recrystallization temperature _Trc of the iridium platinum alloy. More preferably, each forming step is carried out at a forming temperature lower than the recrystallization temperature of the iridium platinum alloy. Alternatively, it is also possible that one or more forming steps other than the final forming step are carried out at a forming temperature above the recrystallization temperature, but the duration of such forming steps is kept short enough to avoid any Substantial recrystallization. As is known to those skilled in the art, the recrystallization temperature is the temperature (typically 1 hour) at which recrystallization can be accomplished in a commercially achievable time.

In a preferred embodiment, _Tf is at least 300 ° C, more preferably at least 400 ° C, even more preferably at least 500 ° C, but less than the recrystallization temperature T _{rc of the} iridium platinum alloy.

Preferably, the cast body is preheated at a temperature T _ph below the recrystallization temperature T _rc of the iridium platinum alloy. In a preferred embodiment, _Tph is at least 300 ° C, more preferably at least 400 ° C, even more preferably at least 500 ° C, but less than the recrystallization temperature T _{rc of the} iridium platinum alloy. The heating time at T _ph can vary over a wide range. _Preheating the cast body at Tph can be, for example, 5 to 120 minutes or 10 to 90 minutes.

Suitable forming methods are known to those skilled in the art. Preferably, step (ii) is formed by rolling, forging or a combination of the two.

Preferably, step (ii) comprises two or more forming steps, for example, 6 to 30 forming steps, more preferably 10 to 26 forming steps.

Preferably, each forming step is carried out at a forming rate of less than 4.0 s ^-1 , more preferably less than 3.0 s ^-1 and/or a forming degree of less than 10.0%, more preferably less than 8.0%.

As is known to those skilled in the art, the forming rate can be determined by the following formula

Where n is the rotational speed of the reel, H ₀ is the thickness of the sample prior to the rolling step, r' = r / 100; r: the decrease in the thickness of the sample during the rolling step, and R is the radius of the reel.

The degree of formation corresponds to a decrease in the thickness (in %) of the sample caused by the forming process.

The total formability can be at least, for example, 50%, more preferably at least 65%.

If step (ii) comprises two or more forming steps, it may be preferred to reheat the casting body after at least one of the forming steps to avoid forming the iridium-platinum alloy (eg, rolling) ) too much cooling during processing. Typically, in order to reheat between the two forming steps, the iridium-platinum alloy is transferred from the forming (eg, rolling) apparatus to the oven and reheated in an oven to preferably be lower than the iridium platinum alloy as explained above. The temperature of the recrystallization temperature is then transferred to the forming apparatus to continue the forming process. The reheating time can vary over a wide range. Reheating of the cast body can be carried out, for example, from 0.5 minutes to 20 minutes or from 1 minute to 10 minutes. Depending on the size of the cast body, reheating can be carried out after at least 50% of the forming step, more preferably after each forming step except the final forming step.

In a preferred embodiment, the ruthenium platinum melt consisting of rhodium, platinum and unavoidable impurities comprises from 70 wt% to 25 wt%, more preferably from 50 wt% to 25 wt%, even more preferably from 45 wt% to 25 wt%. a quantity of platinum; preheating the cast body to a temperature T _ph from 500 ° C to less than 1350 ° C, more preferably from 800 ° C to less than 1300 ° C, even more preferably from 1000 ° C to less than 1250 ° C; The plurality of forming steps are carried out at a temperature _Tf from 500 ° C to less than 1350 ° C, more preferably from 800 ° C to less than 1300 ° C, even more preferably from 1000 ° C to less than 1250 ° C.

Preferably, the iridium platinum alloy prepared by the method of the present invention corresponds to the iridium platinum alloy described above (i.e., the average particle width to height ratio is at least 5). Therefore, it is preferred that the iridium platinum alloy contains platinum in an amount of 70% by weight or less, and the balance is ruthenium and unavoidable impurities. The average particle width to height ratio is at least 5. For other preferred properties of the iridium platinum alloy, reference may be made to the statements provided above.

Furthermore, the invention relates to a processed article comprising a iridium platinum alloy and having a density of at least 21.4 g/cm ³ .

Preferably, the article of manufacture is any other component or component of a balance or clock mechanism. It can also be a jewelry part.

The balance wheel is used in the clock and is sometimes referred to as the rotor. Typically, the balance or rotor is a freely rotating semi-circular disc in which each movement of the pointer of the clock automatically winds the main spring. Its own weight returns it to the upright position.

Preferably, the iridium platinum alloy of the processed article consists of ruthenium, platinum and unavoidable impurities.

Preferably, the processed article (in particular, the balance wheel) has a density of at least 21.6 g/cm ³ , more preferably at least 21.8 g/cm ³ .

Preferably, at least 70% by weight, more preferably at least 80% by weight, even more preferably at least 90% by weight of the balance wheel consists of a ruthenium platinum alloy. Optimally, the balance wheel consists of a ruthenium platinum alloy.

Preferably, the iridium platinum alloy consists of ruthenium, platinum and unavoidable impurities and contains no more than 50% by weight of platinum, more preferably no more than 45% by weight of platinum. In a preferred embodiment, the iridium platinum alloy of the balance comprises from 50 wt% to 0,01 wt%, more preferably from 45 wt% to 5 wt%, even more preferably from 45 wt% to 15 wt% or from 45 wt% to 25 wt%. Amount of platinum in %.

Preferably, the iridium platinum alloy of the balance corresponds to the iridium platinum alloy described above (i.e., the average particle width to height ratio is at least 5). Therefore, it is preferred that the iridium platinum alloy contains platinum in an amount of 70% by weight or less, the balance being ruthenium and unavoidable impurities, and the average particle width The ratio of degrees to height is at least 5. For other preferred properties of the iridium platinum alloy, reference may be made to the statements provided above.

Furthermore, the present invention relates to a method for preparing a processed article, the method comprising - preparing a ruthenium platinum alloy by the method described above, - Processing bismuth platinum alloy.

Preferably, the workpiece is a balance. Typically, processing includes milling. Additionally or alternatively, the machining may include drilling, turning, or other generally known processing steps.

Furthermore, the invention relates to a clock comprising a balance wheel as described above.

Furthermore, the invention relates to the use of the above-described iridium platinum alloy for the preparation of processed articles (in particular, balance wheels).

Measurement method

The parameters referred to in the present invention are determined as follows:

Microsection preparation for microstructure analysis

The microsections are taken perpendicular to the rolled surface and in the (ie parallel to) direction of the roll. The material is embedded in the epoxy under vacuum. The surface to be analyzed is ground and polished. For grinding, a wet grinder Labo-Pol-25 from Struers was used at 200 rpm in eight grinding steps (120, 320, 500, 800, 1200, 1500, 2400 and 4000). Polishing was carried out using a Struers apparatus LakoPol-5 (250 rpm) having a fineness of up to 1 μm (diamond polishing paste). Subsequently, the sample was electrolytically etched with 20% KCN.

Average particle width to height ratio

The average ratio of particle width to particle height of the sample is determined as follows: As already mentioned above, if the sample is rolled, the microsection is taken perpendicular to the surface of the rolled sample and parallel to the direction of the roll. If the rolling step is performed on the surface of the sample and the rolling direction is changed, microsections are prepared in the direction of the roll of the final rolling step. At least two subsections are selected on the microsection, each subsection containing at least 40 particles. For each particle, a light microscope (Olympus PMG3) with a scale was used to determine its width (i.e., its maximum dimension in the roll direction) and its height (i.e., its maximum dimension perpendicular to the roll direction). . For each particle, the ratio of the particle width to the particle height was determined. Finally, the average particle width to height ratio is determined as an arithmetic mean based on the ratio of individual particles.

Average recrystallization

Microsections were prepared as described above, i.e., perpendicular to the surface of the rolled sample and in the direction of rolling. At least two subsections are selected on the microsection, each subsection containing at least 40 particles. For each subsection, the relative area (in %) covered by the recrystallized (i.e., equiaxed) particles is determined. The relative area covered by the recrystallized particles can be determined via the image analysis software. The particles having a particle width to height ratio of 0.75 to 1.25 are regarded as recrystallized particles. Finally, the average recrystallization degree is determined as an arithmetic mean value based on the value of the subsection.

Number of ² holes per μm

In the case of using a light microscope (magnification: 500x), the number of holes on the area of 50 x 50 μm ² was counted and then converted into the number of holes per 1 μm ² . Overall, this was done for 10 different regions on the microsection and the average number of wells was calculated as the arithmetic mean.

density

The density is determined by buoyancy according to the Archimedes principle. The sample weight was measured using a Mettler Toledo balance SB23001 DeltaRange. Next, the weight of the sample in water is determined. The amount of water absorbed is determined by weighing the wet sample. To calculate the sample density, the density of water at 22.5 ° C is assumed to be 0.99791 g/cm ³ . The density is calculated as follows: density (g/cm ³ ) = 0.99791 (g/cm ³ ) x (SW _dry / (SW _{wet -} SW _water ))

Where SW _dry is the weight of the dry sample (in g), SW _wet is the weight of the wet sample (in g), and SW _water is the weight of the sample in water.

hardness

The hardness of the ground sample was determined using the device Zwick Roell ZHμ under the load of HV1.

Amount of impurities

The amount of impurities was determined by using a glow discharge lamp (GDL) of a device of Horiba-Jobin-Yvon GD Profiler HR. Sample excitation was achieved by sputtering and an emission spectrum was obtained. The amount of impurities in the ppm range is determined by comparing the intensity of the emission line with the calibrated standard.

Example

In the following examples, a ruthenium platinum alloy having a different average particle width to height ratio was prepared. From such Ir-Pt alloys, the balance wheel is prepared by milling and the defects of the workpieces are detected at the edges thereof.

Inventive Example 1 (IE1): Ir-Pt alloy, Pt content: 40% by weight

An appropriate amount of ruthenium (3N purity) and platinum (3N purity) for obtaining an Ir-Pt alloy having a Pt content of 40% by weight were melted at 2,200 ° C under an argon atmosphere using an ZrO ₂感应 induction boiler. The ruthenium platinum melt was cast into a water-cooled copper mold. After solidification, a platinum-plated cast body was obtained. The cast body is removed from the mold and the cast wrinkles on its surface are removed by milling.

The cast body was preheated in an oven at 1200 ° C for 30 minutes under an air atmosphere. Next, the preheated cast body was subjected to 19 rolling steps. After each rolling step, in addition to the final rolling step, the casting body was transferred from the roll press to the oven, heated again at a temperature of 1200 ° C for about 5 minutes, and then transferred to a roll press for processing. The next rolling step.

The thickness and thickness reduction (in mm and in %) of the cast body prior to the rolling process and after each rolling step are listed below in Table 1, and the forming rate of each rolling step.

As is known to those skilled in the art, the forming rate can be determined by the following formula

Where n is the rotational speed of the reel, H ₀ is the thickness of the sample prior to the rolling step, r'=r/100; r: the decrease in the thickness of the sample during the rolling step, and R is the radius of the reel.

The reel has a rotational speed of 22 rpm and a reel radius of 155 mm.

After the final rolling step, a 220 x 50 x 3 mm plate was obtained. The etched microsections were prepared perpendicular to the surface of the rolled sample. An optical image of the etched microsection is shown in FIG.

The average particle width to height ratio of the Ir/Pt40 alloy was 12.5. The number of holes is 0.01 per μm ² . The pore size value is much lower than 5 μm. The degree of recrystallization is extremely low (well below 30%).

Impurities are present in low amounts: Rh < 200 wt-ppm, Cu < 150 wt-ppm, Ca < 100 wt-ppm, B < 50 wt-ppm, Fe < 100 ppm.

The sample hardness was 475 HV1 and the density was 22.0 g/cm ³ .

The cast body composed of the Ir/Pt40 alloy is processed into a balance wheel by milling. The edge of the milled article is detected for defects > 10 μm in size. However, no defects were detected.

Comparative Example 1 (CE1): Ir-Pt alloy, Pt content: 40% by weight

An appropriate amount of ruthenium (3N purity) and platinum (3N purity) for obtaining an Ir-Pt alloy having a Pt content of 40% by weight were melted at 2,200 ° C under an argon atmosphere using an ZrO ₂感应 induction boiler. The ruthenium platinum melt was cast into a water-cooled copper mold. After solidification, a platinum-plated body is obtained. The cast body is removed from the mold and the cast wrinkles on its surface are removed by milling.

The cast body was heated in an oven at 1400 ° C for 30 minutes under an air atmosphere. Next, the heated cast body was subjected to 19 rolling steps. After each rolling step, the cast body was heated for a further 4 minutes at a temperature of 1400 ° C in addition to the final rolling step. The rolling conditions were the same as those of Inventive Example 1 except for the higher temperature. Therefore, casting The thickness and thickness reduction (in mm and in %) of the body prior to the rolling process and after each rolling step and the forming rate of each rolling step correspond to those listed above in Table 1. Those who are.

After the final rolling step, a 220 x 50 x 3 mm plate was obtained. The etched microsections were prepared perpendicular to the surface of the rolled sample. An optical image of the etched microsection is shown in FIG.

The Ir/Pt40 alloy of CE1 is a mixture of particles having a width to height ratio close to 1 and slightly elongated particles having a width to height ratio of up to 5. Therefore, the average particle width to height ratio is much lower than 5. The number of pores per μm ² 0.05. A considerable degree of recrystallization greater than 30% was detected.

Similar to Inventive Example 1, impurities were present in low amounts: Rh < 200 wt-ppm, Cu < 150 wt-ppm, Ca < 100 wt-ppm, B < 50 wt-ppm, Fe < 100 ppm.

The sample hardness of CE1 was 485 HV1 and the density was 22.0 g/cm ³ .

The casting body made of the Ir/Pt40 alloy of CE1 was processed into a balance wheel by milling under the same processing conditions as those used in Inventive Example 1. A defect of >10 μm in the edge of the milled article is detected. A relatively large number of such large-sized edges at the edge are detected.

The results of Inventive Example 1 and Comparative Example 1 are summarized in Table 2.

As exemplified in the examples, a molded body made of a ruthenium platinum alloy having elongated particles can be processed into articles having a reduced number of surface defects. In detail, the number and size of edge defects can be significantly reduced.

Claims (15)

A ruthenium platinum alloy containing platinum in an amount of 70% by weight or less, the balance being ruthenium and unavoidable impurities, and an average particle width to height ratio of at least 5. a platinum alloy according to claim 1 wherein the average particle width to height ratio is in the range of from 5 to 25, more preferably from 8 to 20, even more preferably from 10 to 16; and/or The iridium platinum alloy contains platinum in an amount of from 70 wt% to 25 wt%, more preferably from 50 wt% to 25 wt%, even more preferably from 45 wt% to 25 wt%. For example, in the platinum alloy of claim 1 or 2, the average number of pores per μm ² is less than 0.04; and/or the hardness is 500 HV1 or less, more preferably 480 HV1 or less. A platinum alloy as claimed in claim 1 or 2, which contains less than 200 wt-ppm of bismuth, less than 150 wt-ppm of copper, less than 100 wt-ppm of calcium, less than 50 wt-ppm of boron and less than 100 wt-ppm. Iron. The platinum alloy of the first or second aspect of the patent application is a roll-pressed or forged iridium-platinum alloy, preferably having the shape of a disk or a plate. A method for preparing a ruthenium-platinum alloy, comprising: (i) a ruthenium platinum melt composed of free ruthenium, platinum, and unavoidable impurities to prepare a cast body, (ii) preheating the cast body and pre-heating the cast body The one or more forming steps are subjected to a recrystallization degree of the shaped iridium platinum alloy of less than 30%. The method of claim 6, wherein at least the final forming step is performed at a forming temperature T _f lower than a recrystallization temperature; and/or wherein the preheating of the casting body is at a temperature lower than the recrystallization temperature _Performed under T _ph . The method of claim 6 or 7, wherein the casting body is preheated from 500 ° C to less than 1350 ° C, more preferably from 800 ° C to less than 1300 ° C, even more preferably from 1000 ° C to less than a temperature T _{ph of} 1250 ° C; and the one or more forming steps are at a temperature T from 500 ° C to less than 1350 ° C, more preferably from 800 ° C to less than 1300 ° C, even more preferably from 1000 ° C to less than 1250 ° C Under _f . The method of claim 6 or 7, wherein the forming of the step (ii) is roll pressing or forging or a combination thereof; and/or the step (ii) comprises two or more forming steps, more preferably 6 to 30 forming steps. The method of claim 6 or 7, wherein each forming step is at a forming rate of less than 4.0 s ^-1 , more preferably less than 3.0 s ^-1 and/or less than 10.0%, more preferably less than The forming degree was 8.0%. A processed article comprising a ruthenium platinum alloy and having a density of at least 21.4 g/cm ³ . For example, the processed article of claim 11 is a balance wheel. The processed article of claim 11 or 12, wherein at least 80% by weight, more preferably at least 90% by weight of the processed article is made of the iridium platinum alloy; and/or the iridium platinum alloy is made of ruthenium or platinum And an unavoidable impurity composition and containing not more than 50% by weight of platinum, more preferably not more than 45% by weight of platinum. The processed article of claim 11 or 12, wherein the iridium platinum alloy is a ruthenium platinum alloy according to any one of claims 1 to 5. A method for preparing a processed article, comprising preparing a ruthenium platinum alloy by subjecting the ruthenium platinum alloy to a process, in particular, milling, by a method according to any one of claims 6 to 10. .