DE2034261A1 - Process for dip copper plating of parts, in particular wires - Google Patents

Description

B 1418 '

Gebr _e Böhler & Go. Aktiengesellschaft, Vienna

A process for T _a uchverkupferung of parts, in particular

Wires

The invention relates to a method for T _a uchverkupferung of parts, in particular wires, made of stainless or acid-resistant chromium or chromium-nickel steels and titanium and its alloys ·

3? For various purposes, for example in the Screw production as a lubricant in hot upsetting, thin copper coatings are applied to parts, especially wires made of rustproof or acid-resistant chrome or chrome-nickel steels as well as from Titan and its alloys are required, but the galvanic copper plating prevents adhesion because of the formation of a the passive layer causing great difficulties. A solution to this * ben was by adding hydrofluoric acid to the copper bath in Combination with the use of chopped current before the start of the electrolysis attempts to dip copper plating of such parts or However, wires have so far been considered impossible.

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The invention now creates the possibility of the opposite the electrolytic deposition in various respects much more economical process of dip copper plating in Electroless copper baths can also be used for parts or wires made of the metals or alloys mentioned above.

The characteristic of the method according to the invention is that the parts or wires, before being introduced into the copper bath, are wrapped in a spiral covering their surface, made of a contact metal that is electrochemically less noble than copper and does not tend to passivate. The selection made for the contact metal in the context of the electrochemical series is therefore limited by the fact that metals whose dissolution in the copper plating bath is inhibited as a result of the formation of a protective layer, such as lead, for example, precipitate. Aluminum and iron are preferred as contact metals, but magnesium and zinc, for example, are also suitable. The reactivation is carried out in the inventive process simultaneously with the copper plating and remains, since the contact metal covers only a very porous w copper layer, until the dissolution of the contact metal effectively.

The winding typical for the characteristic of the invention is preferred carried out with an iron wire, optionally coated on the surface with Zn or Cd, or with an aluminum wire.

It has proven to be advantageous if, according to a further Feature of the invention the wrapped parts or wires before being introduced into the copper bath in an acidic, preferably hydrochloric acid pickling solution. Should the inventive

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Proper methods for dip copper plating of wires are used, see above these can be wound into rings in a particularly advantageous manner after they have been wrapped and the wire rings in an acidic, preferably copper-plated sulfuric acid immersion copper bath *

According to a preferred further embodiment of the invention. According to the method, the wire diameter and winding pitch are determined. of the contact metal used for wrapping selected so that the treatment time with the complete dissolution of the Contact metal is terminated in the acidic immersion copper bath.

The invention will in the following with reference to embodiments, etc. relating to the Tauchverkupferung of wires as the most important application, explained in more detail.

Example 1:

For the production of copper-plated chrome-nickel steel wire for screw production with a desired final diameter of 8.ο mm, a wire rod (material no.4501) pretreated in the usual way was pulled forward to the preferred dimension of 8.3 mm, then to approx. 1040 ° C for relaxation heated and quenched in water. After an approximately I5 minutes continuous immersion treatment of wärmebehan- g punched wire in a molten salt bath (8O% sodium hydroxide, 15% sodium nitrate and 5% borax) and subsequent treatment in sulfuric acid for neutralization of adhering residual alkali from the molten salt bath the wire was in a mixed acid, Consisting of approx. 10 % HN (U + 2 % HF brightly pickled. A soft iron wire 0.5 mm thick with a winding pitch of approx. 25 mm was then wound onto the washed wire using a wire winding machine and the wire rings formed therefrom after a short pre-activation (5 min in 15% hydrochloric acid) and an intermediate wash in a sulfuric acid (containing _{2 vol. # HgSOi 1)}

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Immersion copper bath (4 <fo CuSO ^) introduced. After a treatment time of about 5 minutes at a bath temperature of 50 ° C, the copper-plated wire rings were washed, dried and then finished with a smooth draw to the final dimension of 8.0 mm with powder soap as a lubricant on a drawing block, with the Cover wire serving as contact metal was removed again. The copper layer after smoothing was 5 my.

Example 2;

Analogously to Example 1, the same chrome-nickel wire was used, but with a wrapping of 0.6 mm thick aluminum wire as the contact metal (winding pitch about 30 mm) in an acidic copper immersion bath. After the wire rings had been treated for about 5 minutes, the contact metal had practically completely dissolved in the acidic copper bath, so that the bending process before drawing to the final dimension of 8.0 mm was unnecessary. The copper layer was then 6 my.

Example 3?

Instead of the chromium-nickel steel wire, a wire made of titanium metal was processed in a manner analogous to that in Example 2. The aluminum wire used as the contact metal was 0.5 mm thick (winding pitch: 25 mm) dimensioned so that the dip coating was complete after approx. 5 minutes with its complete dissolution W revealed.

Basically it can be said that the winding pitch of the Contact metal wire on the one hand after that for the copper plating desired thickness and, on the other hand, as economical as possible Bathroom use oriented. With tight turns it will

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due to the higher contact metal supply in the time unit more copper excreted. However, because of the less favorable surface ratio of base and contact metal, the Copper losses due to deposition on the contact metal wire greater. A winding pitch of 10-70 mm, preferably 20-60 mm, has proven to be useful in manufacturing practice, especially for wires Proven to be useful. In order to ensure the smallest possible contact area with good contact with the base metal, especially thin round wires of 0.5 to 1.2 mm, preferably 0.4 to 0.8 mm thick, are used for the wrapping " costume. The preactivation in an acidic pickling solution is recommended above all to avoid irregularities in the contact copper plating to be excluded with certainty due to any impurities or oxide residues that may arise during the wrapping process.

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Claims (7)

- / ■ Patent claims: Ii. Process for dip copper plating of parts, in particular Wires made of rust- or acid-resistant chrome or chrome-nickel steels as well as made of titanium and its alloys, characterized in that the parts or wires are inserted before the into the copper bath with a spiral covering its surface made of an electrochemical compared to copper less noble contact metal that does not tend to passivate, 2. The method according to claim 1, characterized in that the wrapping with a round wire of 0.3 - 1 * 2 mm, preferably 0.4-0.8 mm thick and with a winding pitch of 10-70 mm, preferably 20-66 mm. 3. The method according to claims 1 and 2, characterized in that that the wrapping is carried out with an iron wire optionally coated on the surface with Zn or Cd will. 4. The method according to claims 1 and 2, characterized in that the wrapping is carried out with an aluminum wire will. 5. The method according to claims 1 to 4, characterized in that the wrapped parts or wires before introduction preactivated in the copper bath in an acidic, preferably hydrochloric acid pickling solution. 109883/154? B 1418 6. The method according to any one of the preceding claims for Dip copper plating of wires, characterized in that the wires are wound into rings after they have been wrapped and the wire rings in an acidic, preferably sulfuric acid Copper immersion bath can be copper-plated. 7. The method according to any one of the preceding claims, characterized in that the wire diameter and winding pitch of the contact metal wire used for wrapping can be selected so that the treatment time with the complete Dissolution of the contact metal in the acidic immersion copper 'bath is ended. Gebr. Bohl er & C ο ι Aktiengesellschaft, " Patent Office 109883/1547