DE102008042219A1 - Chemical deburring of workpieces, e.g. zinc pressure castings, by treatment in aqueous acid containing oxidizing agent then in solution containing surfactant and builder - Google Patents

Abstract

A chemical method for deburring workpieces involves (a) treating the workpieces with first aqueous acid solution(s) (I)containing oxidizing agent(s) and (b) further treating the workpieces with second solution(s) (II) containing surfactant(s) and builder(s). Independent claims are included for: (1) workpieces obtained by the process; (2) the use of the solutions (I) for chemical deburring of workpieces; and (3) the use of the solutions (II) for cleaning chemically deburred workpieces (specifically workpieces deburred using (I)).

Description

The The present invention relates to a method for chemical deburring of workpieces, wherein the parts to be machined sequentially various process solutions are exposed as well Workpieces which by the inventive Procedures are obtained. The present invention further relates the use of special solutions for chemical deburring or treating workpieces.

Light metal components are often produced by die casting. such Components made of zinc, magnesium and / or aluminum alloys used in many areas. There is hardly an area of daily Life in which you do not encounter components made of die-cast zinc. Most of these are inconspicuous and not at first glance such recognizable. Zinc diecasting is mainly used when high strength, dimensional stability and corrosion resistance are in demand. Because of the long service life of die casting molds (500 000 to 2 000 000 press-fit processes are involved in zinc die-casting quite common), the short cycle times, the high Ensure productivity, and the low necessary finishing is zinc die casting especially for Large series economically interesting. The cost price of a die-cast part therefore has a particular effect on the material zinc for large series of 50,000 casts positive, d. H. Reducing costs, from - even in comparison with others Production processes such as stamping, forming or forging. components made of die-cast zinc are used, among other things, in the automotive industry, in mechanical and apparatus engineering, in electrical engineering and electronics as well as in construction.

adversely on the die casting process of zinc and magnesium alloy components However, that is because of the manufacturing process in general Pressing and cutting burrs and chips on the workpieces remain and remove the corresponding defects by deburring Need to become.

conventional Procedures for removing these burrs are largely mechanical processes such as grinding, polishing, sandblasting and Electrochemical removal (ECM). The quality of this obtained workpieces is often not satisfied stellend and further are in particular the mechanical methods to the disadvantage of the fact that they have a large workforce require. Furthermore, workpieces with internal Burrs with conventional methods practically not satisfactory to work.

One Method, which requires only a small amount of personnel and At the same time it can process internal burrs so-called chemical deburring.

A method for deburring is from the US 2,955,027 in which a combination of chromic acid and hydrofluoric acid or fluorosilicic acids and / or fluoroboric acid is used. However, according to current knowledge, the use of chromic acid and hydrofluoric acid as well as chromates or fluorides in acidic solutions is associated with high ecological risks and high health risks, so that there is still a need for alternative methods.

The The present invention is based on the one shown The object of the prior art is a method for chemical deburring which is economical and highly flexible for deburring of (pressure) cast and injection molded parts can be used.

About that In addition, the inventive method is the Disadvantages of the prior art over come. Especially should the inventive method without the use of environmentally hazardous substances and / or hazardous to health Get along.

• (1) in einem ersten Verfahrensschritt die zu behandelnden Werkstücke mit mindestens einer ersten wässrigen sauren Lösung mindestens einer oxidierenden Verbindung behandelt werden; und
• (2) in einem zweiten Verfahrensschritt die aus Verfahrensschritt (1) resultierenden Werkstücke mit mindestens einer zweiten Lösung, umfassend mindestens ein oberflächenaktives Mittel und mindestens eine Builderverbindung, behandelt werden.

The solution to this problem is based on a method for the chemical deburring of workpieces. The inventive method is then characterized in that

• (1) in a first process step, the workpieces to be treated are treated with at least one first aqueous acidic solution of at least one oxidizing compound; and
• (2) in a second process step, the workpieces resulting from process step (1) are treated with at least one second solution comprising at least one surface-active agent and at least one builder compound.

According to the invention, it has been found that by means of the two-stage treatment, which first takes place with at least one first aqueous acidic solution of at least one oxidizing compound and then with a second solution comprising at least one surface-active agent and at least one builder compound, metallic workpieces can be efficiently chemically deburred , The invention In addition, modern methods offer advantages in that they do not use environmentally hazardous substances or substances hazardous to health.

The inventive method is for chemical Deburring of metal workpieces suitable. Under Metallic workpieces are under the present Invention understood three-dimensional objects, which have a metallic content, but not complete must consist of metallic materials, and for example be prepared by pressing and cutting operations and in particular Have burrs (defects). In the context of the present invention However, it is preferred if the metallic workpiece consists of one, two or more metals or alloys.

Under The chemical deburring is understood in the context of the present Invention targeted removal of material on a workpiece surface for removing roughness or roughness by means of a chemical Solution.

The Chemical deburring is a chemical process in which the to be machined workpieces in a first, as above dipped defined chemical solution in which a removal of the material takes place.

The advantageous effect of this method is, in particular, that as soon as the workpiece to be machined immersed in the bath is, the processing on all wetted surfaces largely regardless of the size and shape of the Component takes place. This material is by chemical dissolution abraded on the surface, which leveled and is smoothed. Unlike mechanical deburring methods begins the leveling in the micro range and recorded only with increasing Treatment duration also larger structures, the rounded and smoothed on the surface.

at Corners and edges, the material removal is amplified many times, which causes these areas to be degraded preferentially. there be ridges up to a few tenths of a millimeter in size reliably eliminated. The material removal takes place without any load on the workpiece. Due to the freedom of loading of the Procedures can be soft and bend sensitive parts safely to be edited.

The inventive method works in a wide Concentration range very uniform, causes a long Life of the bath and allows reliable reproducible compliance with tight tolerances.

• (1) Entgraten von Kanten und Flächen im gesamten Oberflächenbereich, also auch an nur schwer zugänglichen Stellen wie im Inneren von Bohrungen und Durchbrüchen;
• (2) Beseitigung von Schuppen, Flittern, Überlappungen und Partikeln von Oberflächen zur Schaffung partikelarmer Systeme und um die Verunreinigung von Betriebsmedien zu vermeiden;
• (3) Herstellung technisch reiner Oberflächen;
• (4) Glättung der Oberflächen zur Verminderung von Reibung und Verschleiß;
• (5) Erhöhung der Dauerfestigkeit durch Beseitigung von lokalen Zugspannungen und Risskeimen;
• (6) Vorbehandlung vor dem Beschichten, Galvanisieren und Emaillieren zur Verbesserung von Schichthaftung und -aufbau sowie der Kantenüberdeckung;
• (7) Vorbehandlung vor PVD-, CVD- und Diffusionsverfahren;
• (8) Verbesserung der Löt- und Schweißbarkeit; und
• (9) Verbesserung der Reinigungsfähigkeit.

The method according to the invention can be used in a wide range and is particularly suitable for the following tasks:

• (1) deburring of edges and surfaces in the entire surface area, so also in hard to reach places such as inside holes and breakthroughs;
• (2) removal of scales, flakes, overlaps and particles from surfaces to create low particulate systems and to avoid contamination of operating media;
• (3) production of technically pure surfaces;
• (4) smoothing surfaces to reduce friction and wear;
• (5) increasing fatigue strength by eliminating local tensile stresses and cracking germs;
• (6) pretreatment before coating, plating and enameling to improve layer adhesion and buildup and edge coverage;
• (7) pretreatment before PVD, CVD and diffusion processes;
• (8) improvement of solderability and weldability; and
• (9) Improvement of cleanability.

The inventive method is suitable from the three-dimensional design of the individual workpieces for any configurations. Larger workpieces can thus in correspondingly large bathrooms treated for the first and second process steps become. Furthermore, it is possible in a bath of the first or second process step, several workpieces simultaneously to treat. For this it is possible the individual To hang workpieces on a rack and then the Frame together with the workpieces to be treated in to give the bath. This is also an automation of the invention Process easily possible.

The inventive method is suitable for the chemical deburring of workpieces made of any metal or any metal mixtures (alloys). In particular, workpieces can be processed with the method according to the invention, which as the main components aluminum, zinc and / or magnesium. In addition, minor amounts of other alloy constituents known in the relevant literature, such as, for example, copper, rare earths, calcium, silicon and / or further metals from the group of transition elements, may be present in minor amounts. In particular, it is possible with the method according to the invention to deburr workpieces containing zinc, aluminum and magnesium and their alloys. Furthermore, it is possible by the inventive method, deburring workpieces comprising zinc, aluminum, copper and their alloys.

These Workpieces are preferably as die-cast workpieces generated.

In particular, within the scope of the present invention, it is possible to chemically deburr workpieces made of die-cast zinc alloys. These alloys usually contain small amounts of aluminum (generally up to 10% by weight) and / or copper (up to 5% by weight). These zinc die-cast work pieces include, in particular workpieces, which are obtained starting from the alloys ^® Zamak 3 and Zamak ^®. 5 The fact that the method according to the invention is particularly suitable for the chemical deburring of workpieces which are suitable starting from these copper-containing zinc alloys is particularly surprising, since the copper content of these alloys usually causes problems in the case of chemical deburring, since a firmly adhering black copper coating or copper oxide coating on the Surface of the work remains, which can not be easily removed from the workpiece.

As well Advantageously, the deburring of workpieces made of magnesium casting alloys within the scope of the present invention possible. such Alloys are well known in the literature. Exemplary Alloys with the designation AZ 41 with approx. 4% aluminum and approx. 1% zinc and AZ 91 with about 9% aluminum and 1% zinc besides magnesium to be named. Another commonly used magnesium casting alloy, ZE 41, is mainly used in workpieces for the Used aviation technology. It contains besides magnesium about 4% zinc and about 1% rare earths.

Before the workpieces the first treatment step of the invention Can be subjected to the usual procedure Pretreatment steps performed on the workpieces become. These include, in particular, the cleaning of the surfaces the workpieces of dirt and / or oil residues. Between these individual pretreatment steps and in particular before the first method step according to the invention can each rinsing provided be. Through these rinses can be achieved that no carryover of the respective process media in the next Treatment level, which otherwise leads to injury the bathrooms to the uselessness of the bathrooms can lead.

The If necessary pretreated workpieces are then the first process step of the invention Process supplied.

Process step (1)

The inventive method comprises as a first Process step (1) the treatment of a workpiece with at least a first aqueous acidic solution at least one oxidizing compound.

The at least one oxidizing compound is preferably selected from the group consisting of nitric acid, salts of Nitric acid, chloric acid, salts of chloric acids, Ferric chloride and any mixtures thereof.

The Concentration of this at least one oxidizing compound is preferably 1 to 30% by weight, particularly preferably 2 to 20% by weight, in each case based on the treatment bath used in process step (1).

in the The scope of the present invention is the use of nitric acid particularly preferred.

The Use of dilute nitric acid in one Concentration range of in particular 1.00 to 30.00 wt .-%, preferably 2.00 to 20.00 wt .-%, each based on the treatment bath, is in terms of chemical deburring of die-cast particles comprising zinc, especially prefers.

The Treatment bath, which in process step (1) of the invention In addition, the method used may have more Supplements included.

One possible addition here are surface-active Substances which are preferably in an amount of 0.01 to 5 g / L, especially preferably 0.02 to 3.5 g / L, in particular 0.02 to 3.00 g / L, especially 0.02 to 2.00 g / L, in each case based on that in the process step (1) used treatment bath.

Especially in this case, preference is given as surface-active substances Surfactants from the group of polyoxyethylene ethers with 2 to 10 ethylene oxide units be used.

When Another possible addition to the treatment of the Process step (1) can use at least one complexing agent become. Without wishing to be bound by theory, according to the invention thereof assumed that the complexing agent complexed the copper and thus it does not cause the reaction of in solution gone copper with the surface of the workpiece comes. This will re-deposit on the surface avoided the treated workpiece. The complexing agent becomes for example, selected from the group consisting of the tartrates and citrates. In particular, ammonium tartrate can be used become.

The Working temperature of the bath in process step (1) can in wide Ranges vary. Usually, the process step (1) the process of the invention at room temperature carried out. In the context of the present invention can the process step (1) but also at temperatures in one Range of 10 to 40 ° C are performed.

The Duration of treatment of the workpieces with the first treatment solution can vary widely and depends essentially from the amount of material coming from the workpiece should be removed. For economic reasons However, it is preferred, the process step (1) for a Period of 15 seconds to 10 minutes, more preferred 15 seconds to 5 minutes to perform.

in the The workpieces are connected to the first process step transferred to a second bath for the second process step.

Process step (2)

In the second process step, the process step (1) obtained, machined workpieces with at least one second solution, comprising at least one surface-active Agent and at least one builder compound, treated.

at the at least one buider compound is preferably to select a connection that is selected from the group of Silicates, the polyphosphates, the phosphonocarboxylic acids, Iminodisuccinat, polyaspartic acid, salts the polyaspartic acid and mixtures of these compounds. Among these builder compounds is 2-phosphonobutane-1,2,4-tricarboxylic acid and iminodisuccinate particularly preferred. More preferred is iminodisuccinate.

The Concentration of this at least one builder compound in the treatment bath of the second process step of the invention Method is preferably 1 to 30 wt .-%, especially preferably 2 to 20 wt .-%, each based on the treatment bath of the second process step.

About that In addition, the second treatment bath may comprise further additives. To mention here are, for example, pickling inhibitors. These pickling inhibitors can generally be selected from the group consisting of 2-propyn-1-ol, 2-butyne-1,4-diol and Mixtures thereof.

The Concentration of this pickling inhibitor compound in the treatment bath of the second process step of the invention Method is preferably 0.01 to 2 wt .-%, especially preferably 0.05 to 1 wt .-%, each based on the treatment bath of the second process step.

About that In addition, it is preferable that the one used in the second process step Treatment bath comprises surface-active substances. Especially in this case, preference is given as surface-active substances Surfactants from the group of polyoxyethylene ethers with 2 to 10 ethylene oxide units be used.

The Concentration of these compounds in the treatment bath of the second Process step of the method according to the invention is preferably 0.001 to 1 wt .-%, more preferably 0.01 to 0.5 wt .-%, each based on the treatment of the second process step.

The Treatment in the second process step is preferably carried out in the presence of ultrasound, so it is within the present Invention is preferred, the second treatment bath with ultrasound apply.

Of the thereby exerted on the workpieces to be treated Energy input by the ultrasound is preferably 2 to 60 W / L, more preferably 5 to 30 W / L.

The Working temperature of the bath in process step (2) can in wide Ranges vary. Usually, the process step (2) the process of the invention at room temperature carried out. In the context of the present invention can the process step (2) but also at temperatures in one Range of 10 to 60 ° C are performed.

The Duration of treatment of the workpieces with the second treatment solution can vary widely and depends essentially from the amount of material that went after deburring in the process (1) remains as residue on the workpiece and must be washed down by this. Usually However, it is preferred that the process step (2) for a period of 30 seconds to 60 minutes, more preferably 30 seconds to 30 minutes, especially 1 minute to 30 minutes to perform.

in the Following the process step (2), the workpieces be subjected to any refining steps.

The Processing of the workpieces by means of the invention The method can thus be divided into several stages, which can be divided into Pretreatment, deburring by the invention Divide process steps (1) and (2) and finishing. If necessary, you can choose between the individual processing steps each careful rinsing, the a carry-over of the respective process media to the next treatment stage help prevent lying, which otherwise leads to injury the bathrooms can lead to uselessness. One or more further rinses can also be provided between method steps (1) and (2), but are not mandatory. In particular, on a Rinsing step between process steps (1) and (2) omitted the process of the invention.

The Treatment in the individual process steps, in particular the process steps (1) and (2), is conveniently carried out in separate Dipping baths, whereby small parts as bulk goods in Drums can be edited unless they are to Sealing or mutual damage tend. sensitive and larger parts can be in baskets or edited on individual holding means edited. Through long holes, the bath liquid can be pumped through be while wires, straps and chains be appropriately treated in the drafting procedure can. Very large parts can through Sprinkling be edited.

About that In addition, it is possible the individual process steps of the method according to the invention, but in particular the process steps (1) and (2) of the invention Procedure to perform in a container, in which the workpieces first with the first Treatment solution for a certain time applied be removed, then the first treatment solution is removed, the workpieces are optionally rinsed and finally with the second treatment solution be charged. After removing the second treatment solution from the chamber can then the deburred workpieces optionally be subjected to a further rinsing process and, where appropriate, further processed.

in the However, it is not absolutely necessary within the scope of the present invention that the workpieces further treatment steps than the Process steps (1) and (2) are subjected. That exists the inventive method in particular only from the process steps (1) and (2), in particular without further Rinsing, pretreatment and / or refining steps.

The proposed method differs in an inventive way of the known from the prior art method in particular in that the use of chromium-containing and / or fluoride-containing baths can be dispensed with.

In a first embodiment of the present invention is therefore the first process step in the absence of a chromium-containing Treatment bath performed.

In a second embodiment of the present invention becomes the first process step in the absence of a fluoride-containing Treatment bath performed.

In a third embodiment of the present invention is the first step in the absence of a chromium-containing and a fluoride-containing treatment bath.

In A fourth embodiment of the present invention becomes the second process step in the absence of a chromium-containing Treatment bath performed.

In a fifth embodiment of the present invention Invention is the second process step in the absence of fluoride-containing treatment bath performed.

In a sixth embodiment of the present invention becomes the second process step in the absence of a chromium-containing and a fluoride-containing treatment bath.

The Treatment time depends on the required result and the initial state of the surface. Appropriate treatment times for the process steps (1) and (2) were already above are defined and usually between 15 seconds to 60 Minutes. Should have processing times well under a minute be necessary, it is better in terms of controllability, to dilute the bath more and the ablation speed to lower. For longer treatment times because of necessary high removal rates, it is sometimes advantageous to in between do the washing up. This particular, to be on the surfaces to remove forming deposits and a uniform Save processing result.

Another The present invention relates to the inventive Procedure available workpieces.

Another The present invention is the use of an aqueous acidic solution as defined above for the chemical deburring of workpieces.

Another The subject of the present invention is the use of a solution comprising at least one surfactant and at least one builder compound, according to above standing definition for cleaning workpieces, which previously subjected to a chemical deburring. The chemical Deburring is preferably carried out according to the procedure in Process step (1) of the invention described above Process.

The The present invention will become more apparent from the following examples explained without restricting it.

EXAMPLES

Example 1:

Die castings for automobile locks are treated with the following alloy composition:
Al: 4% by weight;
Cu: 1% by weight; and
Zn: remainder (Zamak ^® 5).

• (1) in ca. 7-%iger HNO₃ bei Raumtemperatur 2 Minuten behandelt.

The die castings will be

• (1) treated in about 7% HNO ₃ at room temperature for 2 minutes.

• (2) Nach Entnahme aus dieser Ätzlösung werden im zweiten Verfahrensschritt die Werkstücke direkt in ein Ultraschallbad überführt.

The bathroom was made up of: 30% by weight a 20% nitric acid solution; 1.0% by weight ammonium tartrate; 2.5% by weight Propynolethoxylat; 1.5% by weight ethyl diglycol; 0.05% by weight Polyoxyethylene monoundecyl ether (8 EO); and Ad 100 water

• (2) After removal from this etching solution, the workpieces are transferred directly into an ultrasonic bath in the second process step.

The bath contains: 7.5% by weight iminodisuccinate: 5% by weight 2-phosphonobutane-1,2,4; 3.7% by weight a solution of 3% 2-propynol-1 in ethylene glycol propargyl ether; 0.03% by weight Polyoxyethylene monoundecyl ether (8 EO); and Ad 100 Water.

By the alkalinity of the iminodisuccinate solution becomes the acid adhering to the workpiece to a pH buffered between 3 and 7. The ultrasound treatment takes place with an energy input of 10 W / L in 2 minutes. Die castings showed after treatment also in the internal cavities no visible or tactile burrs and were free from annoying dark buildup.

Example 2:

Die castings as in Example 1 are treated in step (1) at room temperature for 2 minutes in the following bath: 30% by weight FeCl3 · 6H2O; 1.0% by weight ammonium tartrate; 1.5% by weight ethylene diglycol; 0.05% by weight Polyoxyethylene monoundecyl ether (8 EO); and Ad 100 water

Of the Step (2) was carried out as in Example 1.

The Die castings showed no visible or after treatment palpable ridges more and were blank.

Example 3:

specimens magnesium alloy AZ-91 are used in step 1 with the deburring liquid such as treated in Example 1 for two minutes. After removal from this etching solution The workpieces are in the second procedural step in the ultrasonic bath with the wheel composition as in Step 2 of Example 1 two minutes treated with 10 W / L.

The Specimens have no visible burrs were shiny and bright.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 2955027 [0006]

Claims (21)

Process for the chemical deburring of workpieces, which is characterized by the method steps that (1) in a first process step, the workpieces to be treated with at least a first aqueous acidic solution at least one oxidizing compound are treated; and (2) in a second process step which consists of process step (1) resulting workpieces with at least a second Solution comprising at least one surfactant Agent and at least one builder compound to be treated. Method according to claim 1, characterized in that in that the method processes workpieces which at least one ingredient selected from the group consisting of magnesium, zinc, aluminum, copper and their alloys, include. Method according to claim 1 or 2, characterized that the process zinc alloy workpieces are processed. Method according to claim 1 or 2, characterized that with the process magnesium alloy castings to be edited. Method according to one of claims 1 to 4, characterized in that the at least one oxidizing Compound is selected from the group consisting of Nitric acid, salts of nitric acid, chloric acid, Salts of chloric acids, ferric chloride and any Mixtures thereof. Method according to one of claims 1 to 5, characterized in that the concentration of at least an oxidizing compound 1 to 30 wt .-%, based on the treatment bath of the first process step. Method according to one of claims 1 to 6, characterized in that the treatment of the process step (1) comprises at least one complexing agent. Method according to claim 7, characterized in that that the complexing agent is selected from the group, consisting of tartrates and citrates. Method according to one of claims 1 to 8, characterized in that the method step (1) additionally in the presence of at least one surfactant is carried out. Method according to claim 9, characterized in that that the at least one surfactant in a Amount of 0.01 to 5 g / L, based on the treatment bath of the first Process step, is used. Method according to claim 9 or 10, characterized that the surfactant from the group of polyoxyethylene ethers with 2 to 10 ethylene oxide units is selected. Method according to one of claims 1 to 11, characterized in that the builder compound, which is used in process step (2) to form a compound is selected from the group of silicates, polyphosphates, phosphonocarboxylic acids, iminodisuccinate, Polyaspartic acid, salts of polyaspartic acid and mixtures of these compounds. Method according to claim 12, characterized in that that the builder compound is 2-phosphonobutane tricarboxylic acid-1,2,4 or iminodisuccinate. Method according to one of claims 1 to 13, characterized in that the concentration of at least a builder compound in the treatment bath of the second process step 1 to 30 wt .-%, based on the treatment bath, is. Method according to one of claims 1 to 14, characterized in that as at least one surface-active Substance at least one surfactant from the group of polyoxyethylene ethers with 2 to 10 ethylene oxide units is used. Method according to one of claims 1 to 15, characterized in that the second treatment bath pickling inhibitors which are selected from the group consisting from 2-propyn-1-ol, 2-butyne-1,4-diol and mixtures thereof. Method according to one of claims 1 to 16, characterized in that in the second method step Energy input by ultrasound of 2 to 60 W / L exercised becomes. Workpieces, available through the Method according to one of claims 1 to 17. Use of an aqueous acidic solution as defined in any of the claims 1 to 17 for the chemical deburring of workpieces. Use of a solution comprising at least a surfactant and at least one builder compound, as defined in any of the claims 1 to 17 for cleaning workpieces which a chemical Deburring were subjected. Use according to claim 20, characterized that for chemical deburring an aqueous acidic solution as defined in any of the claims 1 to 17 is used.