EP0143964A2 - Cold-deformation facilitation process - Google Patents

Abstract

A process for providing metals with a lubricant coating before cold processing comprises the steps of applying an aqueous solution of a thermoplastic water soluble resin containing dispersed melamine-(iso)cyanuric acid adduct to the surface of the metal, drying the solution to form a film and applying a lubricant, for example a soap or an oil.

Description

The invention relates to a method for facilitating the cold forming of metals by applying a lubricant film based on resin.

Lubricants are applied in order to avoid the cold forming of metals, e.g. by pressing, rolling, wire or tube drawing and forging, friction and wear of metal and tools. At relatively low _V erformungsgrad find lubricant application, where high-pressure additives or viscosity settings are set added. With a high degree of deformation, the formation of a coating is common, for example in the case of normal steel by means of phosphating and soaping, in the case of stainless steel by means of oxalate treatment and soaping. The pretreatment by Uberzugsbildung requires heating the _B ehandlungslösung and generally cleaning the resulting rinsing water, possibly also a costly removal of processed treatment baths. The removal of the coating remaining after the deformation often causes additional difficulties.

More recently, simplification and shortening of the pretreatment process has been demanded for energy saving, environmental protection, increasing productivity, etc. In this context, pretreatment to facilitate cold working of metals is achieved by applying a lubricant medium films based on resins have a certain meaning. Thus, for example, from DE-OS 29 34 138, inter alia, for metal machining as appropriate designated _S chmier- medium known, containing an adduct of melamine and cyanuric acid or _I socyanursäure. The liquid phase of the lubricant can contain water, organic solvent, mineral oil or synthetic oil. The melamine / cyanuric acid or isocyanuric acid adduct, an aqueous polymer dispersion in a film-forming _H arzzusam- mensetzung, for example, be incorporated in a synthetic or natural resin paint or a paint of a thermosetting liquid resin.

Although resin-based coatings have advantages for certain areas of application, they are particularly flawed when preparing metals for cold forming. For example, take the _D rahtzug chatter marks, and there is often a tear of the wire.

The object of the invention is to provide a method for facilitating the cold working of metals, which does not have the disadvantages of the known, in particular the above-mentioned, processes, allows a perfect cold working, enables easy removal of the remaining residues and is simple to carry out.

The object is solved by the method of the aforementioned _A rt is designed according to the invention is such that first applying to the metal surface an aqueous solution or dispersion of a water-soluble thermoplastic resin having a content of melamine / cyanuric acid or isocyanuric acid adduct, and dries up and then applies a metal soap and / or a lubricating oil.

As thermoplastic water-soluble resins are recommended polyacrylic acid, _C opolymerysate of acrylic acid and other Vinyl compounds, polyacrylamide, polyvinylpyrrolidone, copolymers of maleic acid and of vinyl compounds, saponification products of polyvinyl acetate, etc. Examples of vinyl compounds with copolymerized acrylic acids or maleic acids are vinyl acetate, styrene, methyl vinyl ether, acrylamide, vinyl pyrrolidone. In the properties of _E ntfern- bility of remaining after cold forming residue are superior to acrylic resins.

A preferred embodiment of the invention provides that an aqueous solution or dispersion is first applied which contains resin to adduct in a weight ratio of 1: 0.3 to 1: 2. At a ratio of more than 1: 0.3, the _S drops chmiereigenschaft, in such less than 1: 2, the bonding effect decreases the resin, so that the adhesion properties of the coating deteriorate. If necessary, the coating can also come off during cold forming and chatter marks can occur.

The aqueous solution or dispersion of melamine / cyanuric acid adduct and resin should not contain any surfactants. Surfactants deteriorate the properties of the adhesion of the thermoplastic water-soluble resin to the metal. They can also lead to softening of the resin coating, so that the good lubrication results are lost.

The weight of the dried coating should preferably be 0.3 to 30 g / m ² . Below the layer weight of 0.3 g / m ^2, the _S can chmiereigenschaft to, that is, on the metal surface can chatter marks or marks and occur on the tool wear. With a layer weight of more than 30 g / m ² , adhesions can occur, so that the work performance ultimately deteriorates. A layer weight of 0.5 to 2 g / m ^{2 is} recommended for cold forming by pressing, and a layer weight of 5 to 15 g / m ² for cold forming by wire or tube drawing.

Melamine / cyanuric acid adducts - the term cyanuric acid is also understood to mean isocyanuric acid - can be prepared by mixing an aqueous melamine solution and an aqueous cyanuric acid or isocyanuric acid solution and removing the precipitated adduct. It can also be obtained by dispersing melamine or cyanuric acid or isocyanuric acid or both in water in the solid phase and reacting with one another. In the latter case, the particle diameter of the starting materials should be in the range of 0.5 to 5 _/ um.

In the second stage of the process, metal soap and / or lubricating oil are applied. Suitable metal soaps are, for example, soaps based on calcium stearate, barium stearate, zinc stearate, sodium stearate and lithium stearate. They can have an addition of calcium carbonate, talc, graphite and / or molybdenum disulfide. Suitable lubricating oils are, for example, commercially available oils and fats or mineral oils.

The aqueous solution or dispersion of resin and melamine / cyanuric acid adduct is applied to the metal surface in a conventional manner, e.g. by immersion, spraying, brushing, pouring over and rolling up. Thereafter, they are generally left to dry at ambient temperature, which can take about 30 minutes and more. Then drying is continued under the action of heat. Then you apply metal soap and / or lubricating oil.

The implementation of the process in the aforementioned two-stage form is necessary because the simultaneous application of the solution or dispersion of the thermoplastic water-soluble resin and the melamine / cyanuric acid adduct together with metal soap and / or lubricating oil does not achieve the aim pursued by the invention. A one step process would result in the adhesion of the thermoplastic water soluble resin deteriorate on the metal surface and lead to detachment of the coating during the deformation and thus to chatter marks.

When the forming process is carried out, the coating does not come off in any phase of cold working. There is no contact between the metal surface and the tool, although the temperature of the metal surface rises to about 100 to 150 ° C. due to the heat of deformation and friction of the metal. Nevertheless, the stretchability of the cover is so high that it adapts well to the shape change of the workpiece and does not tear.

Since the melamine / cyanuric acid or isocyanuric acid adduct does not decompose up to 300 ° C and has good lubricating properties, it acts as a lubricant in cold machining. The coating of water-soluble resin and melamine / cyanuric acid adduct is separated into two stages. The lower layer near the metal surface with increased components of thermoplastic water-soluble resin in particular improves the adhesive properties, while the upper layer in particular improves the lubricating properties of the coating.

With the invention it is possible to save energy, to simplify the pretreatment process and to contain environmental damage compared to the conventional formation of a coating by applying lubricant when cold-forming metals. At the same time, it was possible to achieve a coating with a good lubricating effect.

The invention is illustrated by the following examples, for example and in more detail.

Examples 1 to 5

Steel wire made of 304 stainless steel was pickled with acid, washed with water and immersed in a treatment solution of water-soluble resin and melamine / cyanuric acid adduct according to TABLE 1 for 1 minute at 30 ° C. After draining and drying naturally for 1 hour, it was dried with hot air at 120 ° C for 30 minutes and a solid coating was formed. Calcium stearate powder was then applied and drawn in the wire drawing bench. The drawing conditions were:

Pulling speed 50 m / min.

The tensile force was measured, the appearance of the wire was examined and the properties of the removability of the coating remaining on the metal surface were examined. The results are shown in TABLE 2.

Examples 6 to 10

In the same way as described in Examples 1 to 5, pipes made of SUS 304 stainless steel were provided with a solid coating. Then was pulled iehbank after application of lubricating oil (rapeseed oil) on the _Z. The drawing conditions were:

The pulling forces and the plug forces were measured. Furthermore, the external appearance after pulling was examined and the removability of the smear layer was examined. The results are shown in TABLE 3.

Examples 11 to 15

Sheets of stainless steel SUS 304 were coated using the same processing solutions as in Examples 6 to 10 on one side in such a way that after drying a coating of 3 _/ um yielded. It was then dried in hot air from 100 to 120 ° C. Then lubricating oil (machine oil) was applied to the same side and deep-drawn in the deep-drawing test press.

• - Versuchsmaterial: 90 ß x 0,8 mm
• - Tiefziehversuch: Flachbodenzylinder-Ziehen Kraft der Faltenunterdrückung: 20.000 Newton

Thermoforming conditions:

• - Test material: 90 ß x 0.8 mm
• - Deep-drawing test: flat-bottomed cylinder pulling force of wrinkle suppression: 20,000 Newtons

The results of the appearance after deep drawing and the removability of the remaining coating are shown in TABLE 4.

Comparative experiment 1:

Stainless steel wire of the quality mentioned in Examples 1 to 5 was pickled with acid, washed with water and provided with an oxalate coating of 10 g / m ² layer weight. It was then washed with water and metal soap in one Amount of 4 g / m applied. After drying, the pulling was carried out under the same conditions as given in Examples 1 to 5. The results are shown in Table 2.

Comparative experiment 2:

Stainless steel wire of the quality mentioned in Examples 1 to 5 was pickled with acid, washed with water and, after drying for 1 minute at room temperature, immersed in a resin diluted with solvent. The mixture was then naturally dried for 1 day and pulled under the same conditions as given in Examples 1 to 5. The amount of resin applied was 10 g / m ² . The results are shown in Table 2.

Comparative experiment 3:

The pulling test according to Example 2 was repeated, only the treatment solution applied in the first stage did not contain any melamine / cyanuric acid adduct. The amount of resin applied was 10 g / m ² . The result of the test is shown in Table 2.

Comparative experiment 4:

The procedure was as in Example 1. However, no calcium stearate was applied. The result of the test is shown in Table 2.

Comparative experiment 5:

Stainless steel tubes of the same quality as used in Examples 6 to 10 were pickled with acid, washed with water, provided with an oxalate coating of 12 g / m ² and washed again with water. After drying, metal soap was applied in an amount of 4 g / m ² and under the the same conditions as in Examples 6 to 10. The results are shown in Table 3.

Comparative experiment 6:

Stainless steel tubes of the quality mentioned in Examples 6 to 10 were pickled with acid, washed with water and, after drying, immersed in a resin diluted with solvent at room temperature for 1 minute. Then it was naturally dried and lubricating oil applied for 1 day. Finally, pulling was carried out under the same conditions as in Examples 6 to 10. The amount of resin applied was 10 g / m ² . The results are shown in Table 3.

Comparative experiment 7:

The pulling test according to Example 7 was repeated, except that the treatment solution applied in the first stage was free from melamine / cyanuric acid adduct. The amount of Earz applied was 10 g / m ² . The _V ersuchsergebnis contains Table 3 below.

Comparative experiment 8:

The experiment according to Example 6 was repeated, but no lubricating oil was applied. The result of the experiment is shown in Table 3.

Comparative experiment 9:

Analogously to Examples 11 to 15 was applied to stainless steel plates, an acrylic resin film of 3 _/ um and then applied to provided with lubricating oil from 3 _/. It was deep drawn under the conditions of Examples 11-15. The results are shown in Table 4.

To determine the removability after cold working Remaining residues (Tables 2 to 4) were worked with an alkaline degreasing solution in which the deformed metal objects were immersed at 80 ° C for 1 hour. The removal of the lubricant residue was assessed with the naked eye.

Claims (3)

1. A process for facilitating the cold working of metals by applying that first applying a lubricant film on _H arzbasis, gekennzeichet characterized on the metal surfaces, an aqueous solution or dispersion of a water-soluble thermoplastic resin having a content of melamine / cyanuric acid or isocyanuric acid adduct, and dries up and then applies a metal soap and / or a lubricating oil. 2. The method according to claim 1, characterized in that first an aqueous solution or dispersion containing resin to adduct in a weight ratio of 1: 0.3 to 1: 2 is applied. 3. The method according to claim 1 or 2, characterized in that an aqueous solution or dispersion is applied such that a layer weight of 0.3 to 30 g / m ² results after drying.