CH699084B1 - Process die forming of metal parts. - Google Patents

Abstract

Process of stamping of a metal or metal alloy component using matrix of a press, comprises: (a)preparing a lubricating composition comprising at least one anionic surfactant compound and at least one amphoteric or non-ionic surfactant compound, in an aqueous solution; (b) bubbling a gas in the composition; applying the obtained composition on the component; and (c) stamping the component by applying a pressure on a patch, volume and dimensions for obtaining the component, through the matrix.

Description

Technical area

The present invention relates to a method of stamping metal parts.

State of the art

The implementation of stamping processes, cold or hot, is common to achieve high quality metal parts, including having precise dimensions and a good surface finish. In these processes, a piece of metal or metal alloy is subjected to high pressure exerted by counter-matrices, possibly after having been preheated. The dies are machined with great precision to guarantee the reliability of the result of stamping.

Given the harsh conditions of implementation of these methods, the surfaces of forgings or dies can suffer damage. In the case of parts, the damage may be a change in the surface condition and a change in appearance of the parts, which are no longer usable. In the case of dies, damage requires at least a correction that takes time and can lead to high costs due to the cessation of production.

[0004] Various technical solutions have been proposed in the prior art to limit, or even avoid, such complications.

For example, US Patent 5,743,121, issued April 28, 1998 in the name of General Electric Company, proposes a stamping process in which a billet, on the one hand, is covered with a layer glass-based protection, and dies, on the other hand, are lubricated with graphite.

More specifically, the graphite generally used in stamping processes is in the form of a colloidal suspension of very fine graphite particles in the aqueous phase or in concentrated ammonia. The solution is sprayed onto the dies of the press before the stamping operation to avoid the aforementioned damage.

In addition, the use of a lubricant on the dies facilitates the extraction of the forged part out of the dies. Indeed, if a piece remains stuck in one of the matrices, the damage can be much larger and require, for example, the completion of a new matrix, or both.

However, graphite suspensions available on the market all contain traces of crystalline silica, found in natural graphite and which has the major disadvantage of being carcinogenic. In addition, the stamped pieces tend to integrate iron, present in the graphite in the form of traces, during the application of the pressure, because of the crystalline phase changes involved in this operation, which gives them a depreciated aspect related to the appearance of a black coloring. This last disadvantage is particularly noticeable when the stamped parts are made of a metal or light metal alloy, such as for example titanium.

It may be noted that, in an attempt to solve the above problem, boron nitride, sometimes called "white graphite", has been used as a lubricant to replace graphite. However, the very high price of this product, which is also toxic, makes it unsuitable for regular use.

Disclosure of the invention

The present invention is intended to provide an alternative to stamping processes currently used, providing a method that does not present a danger to the health of its users, and is environmentally friendly.

Another object of the present invention is to provide a stamping process ensuring an immaculate appearance on the surface of the metal or metal alloy stamped.

For this purpose, the present invention relates more particularly to a method of stamping a piece of metal or metal alloy by means of dies of a press comprising the following steps: <tb> a) <sep> preparing a lubricating composition comprising, in aqueous solution, at least one anionic surfactant compound and at least one surfactant compound of amphoteric or nonionic type; <tb> b) <sep> bubbling a gas into said composition; <tb> c) <sep> apply on said piece the composition resulting from step b); <tb> d) <sep> stamp said workpiece by applying a pressure on a billet, of volume and dimensions adapted to obtain said workpiece, by means of said dies

Thanks to these particular characteristics, the application of the lubricant composition obtained according to the invention on the parts before proceeding to a stamping operation ensures a good quality of the part obtained and its extraction out of the dies.

Indeed, while anionic surfactants are commonly used in the field of soaps and nonionic surfactants in the fields of cosmetics and pharmaceuticals, the Applicant has found, unexpectedly, that injection of a gas into the lubricating composition in which the parts before stamping are quenched, provides a lubrication quality superior to that obtained with the methods of the state of the art. In addition, the process according to the invention is distinguished by its absence of toxicity.

It has even emerged from these experiments, that in particular in the case of stainless steels, the surface of the stamped parts is better than the methods of the state of the art.

Other features and advantages of the present invention will become more apparent upon reading the detailed description of a preferred embodiment which follows.

Mode (s) of realization of the invention

According to the present invention, the method of stamping a piece of metal or metal alloy by means of dies of a press comprises the following steps: <tb> a) <sep> preparing a lubricating composition comprising, in aqueous solution, at least one anionic surfactant compound and at least one surfactant compound of amphoteric or nonionic type; <tb> b) <sep> bubbling a gas into said composition; <tb> c) <sep> apply on said piece the composition resulting from step b); <tb> d) <sep> stamp said workpiece by applying pressure to a billet, of volume and dimensions adapted to obtain said workpiece, through said dies.

Preferably, the lubricating composition comprises between 1 and 20%, preferably between 2 and 15%, and more preferably between 4 and 9%, by weight, of an anionic surfactant compound relative to its total mass. and less than 10%, preferably less than 5% and more preferably less than 2%, by weight, of an amphoteric or nonionic surfactant compound, based on its total mass.

As regards the surfactants, any known surfactant meeting the criteria required for the implementation of the present invention may be used. Those skilled in the art will not encounter any particular difficulty in selecting surfactants that meet their specific needs. Preferably, the surfactants retained will not be toxic to the users of the lubricant composition used according to the present invention and will have a high biodegradability.

By way of nonlimiting example, one or more of the following compounds may be used as surfactant anionic type: alkylsulfates, alkylarylsulfates, soaps (R-CH2-COO-Na, with R = C10-C16) or alternatively alkylbenzenesulfonates (or ABS, R-C6H4-SO3-Na, with R = C10-C13). Such compounds are 90% biodegradable.

Similarly, by way of non-limiting example, one or more of the following compounds may be used as surfactant nonionic type: polyethylene glycol ethers (R-CH2-O- (CH2-CH2) -O) nH, with R = C10-C18) or alkylphenol ethoxylates (R-C6H4-O- (CH2-CH2-O) nH, where R = C8-C12). These compounds are also 90% biodegradable.

It is important to note that the composition just described is clean, from an environmental point of view, odorless and nontoxic.

It may advantageously use mainly deionized water to produce the lubricant composition to optimize the qualities of the latter.

The gas bubbling into the lubricant composition may be injected into the lubricant composition at a pressure of between 2 and 15 bar, preferably between 5 and 10 bar.

The gas used may preferably be carbon dioxide, but any other suitable gas may be used.

Advantageously, the lubricant composition may be prepared according to step a) in a bath, wherein said gas is injected according to step b), the workpiece to be stamped then being dipped in said bath according to the invention. step c).

Thus, for example, one can make a bath containing demineralized water, about 6% by weight of an anionic surfactant soap, and less than 2% by weight of a nonionic surfactant. . Carbon dioxide is injected into the bath with a pressure of 5 bar. The pieces placed in a basket are soaked in the bath and then stamped.

The parts obtained according to the method of the invention have a beautiful appearance and the stamping process does not present a danger to the health of its users.

For comparison, the parts were dipped in an identical bath but in which no gas is injected. Stamping could not be done due to jamming of the press.

The method according to the invention is particularly applicable, by way of non-limiting indicative, the stamping of precious metal parts, steel, of any type, stainless steel, brass, titanium or alloy titanium, zirconium or zirconium alloy, tantalum or tantalum alloy, these components are commonly used for example in the manufacture of timepiece boxes. Of course, the skilled person can adapt the teaching of the present invention to the stamping of metals or alloys other than those mentioned without departing from the scope of the invention.

In addition, the process according to the invention mainly concerns cold-formed processes.

However, the method according to the invention can also be advantageously used in a hot stamping process without departing from the scope of the present invention. In this case, the part can be heated between 700 ° C and 1000 ° C. By way of non-limiting example, the stamping of titanium alloy parts is usually carried out at a temperature between about 800 ° C and 920 ° C.

Moreover, thanks to its particular characteristics giving it a high efficiency, the first steps of the stamping method according to the present invention can be implemented in a simple manner, before stamping a part by application. pressure on a piece, of volume and dimensions adapted to obtain this piece, through antagonistic matrices of a press.

The Applicant has found that the application of a lubricant composition on the dies, in combination with the application of the lubricant composition on the billet before proceeding to the stamping, as described in the art previous, was not necessary to ensure a good quality surface finish.

Advantageously, the original color of the stamped part, which is a function of its composition, is not affected by the stamping process in which the lubricant composition according to the present invention is applied to the parts. In addition, as already mentioned, it should be emphasized that parts stamped in this way have a better surface condition than those obtained by the processes of the prior art, insofar as the microcracks visible on the latter do not appear.

The foregoing description corresponds to a preferred embodiment of the invention described in a non-limiting manner. In particular, the nature of the reagents described to achieve the composition that have been described are not limiting.

Claims (6)

A method of stamping a piece of metal or metal alloy by means of dies of a press comprising the steps of: a) preparing a lubricating composition comprising, in aqueous solution, at least one anionic surfactant compound and at least one amphoteric or nonionic surfactant compound; b) bubbling a gas in said composition; c) applying to said part the composition resulting from step b); d) stamping said workpiece by applying a pressure on a billet, of volume and dimensions adapted to obtain said workpiece, by means of said dies. 2. Method according to claim 1, characterized in that the lubricating composition comprises between 1 and 20%, preferably between 2 and 15%, and more preferably between 4 and 9%, by weight, of an anionic surfactant compound. relative to its total mass, and less than 10%, preferably less than 5% and more preferably less than 2%, by weight, of an amphoteric or nonionic surfactant compound, relative to its total mass. 3. Method according to any one of claims 1 and 2, characterized in that the lubricant composition contains at least a majority of demineralised water. 4. Method according to any one of claims 1 to 3, characterized in that the gas bubbling into the lubricant composition is injected into said composition at a pressure between 2 and 15 bar, preferably between 5 and 10 bar. 5. Method according to any one of the preceding claims, characterized in that said gas is carbon dioxide. 6. Method according to any one of the preceding claims, characterized in that said lubricating composition is prepared according to step a) in a bath in which said gas is injected according to step b), the workpiece to be stamped being soaked in said bath according to step c).