DE2119086A1 - Process for the electrolytic removal of lubricants used in drawing or rolling on metal rods - Google Patents

Description

USS ENGINEERS AND CONSULTANTS, INC. PITTSBURGH, PENNSYLVANIA,
525 William Penn Place
V. St. A.

Process for the electrolytic removal of lubricants used in drawing or rolling on metal strands

Choosing a method of cleaning metal strands is largely determined by the type of dirt, to be removed and the type of finishing operation that will be applied thereafter. To the Creation of a clean, active surface as a basis for the coating or sheathing of metal strands, So for example wires, rods, tapes, the processes in which acid is removed or have become electrolytically stripped with acid has proven to be unsuitable because acid alone is neither water-soluble nor removes water-insoluble lubricants that usually be used when pulling or rolling. An effective method of removing lubricant has been to to burn away lubricants on the metal strand at high temperatures and then in an acid

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Patent attorneys Dipl.-Ing. Martin Licht, Dipl.-Wirtsch.-Ing. Axel Hansmann, Dipl.-Phys. Sebastian Herrmann Oppenmier office: PATENT ADVOCATE DR. REINHOLD SCHMIDT

to pickle · In many cases, however, this procedure has proven impractical because of the high cost and the adverse effect of heating on the resulting mechanical properties of the Basic metal object

Alkaline cleaning has already been used to remove such contaminants before further treatment was carried out. In this connection, reference is made, for example, to US Pat. No. 1,041 _{. The alkaline 9} electrolytic process generally works with a current density in the range of 0 _{9 0465}

up to 0.465 A / cm · Due to the low current densities used this procedure requires relatively long electrical cleaning cells, for example 18 m long, as well as long immersion times of, for example, 30 to 60 seconds · This latter method still suffers from one additional disadvantage, which is that the quality of cleaning is often poor, with difficulties resulted in subsequent coating processes. Therefore, if a complete purification was requested, therefore generally had to work with an intermediate cleaning step or an additional cleaning stage to achieve the desired results. Thus, typical manufacturing practice for the Electro-galvanizing of cold-rolled steel strips an electro-alkaline cleaning for 15 seconds at 0.109 A / cm, A commercially available alkaline cleaner is used, followed by pickling with hydrochloric acid and blank plating over 10 seconds in a zinc cyanide bath (cyanide precipitate) followed by rinsing before electroplating takes place

The object of the invention is therefore to provide a one-step process for the effective purification of

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Metal strands do create · This includes creation a cleansing treatment that su an improved Adhesion of the later coatings leads. Furthermore, the cleaning method according to the invention should all additional Eliminate the need for cleaning steps to compensate the known unsuitable, electro-alkaline cleaning are necessary «

According to the invention, this object is now achieved with the aid of a Process solved in which the metal strands with an oM Direct current at a current density of 4.65 to 9.3 A / om with an immersion time of at least 0.4 seconds in a « aqueous, alkaline electrolytes are electrolyzed, the electrolyte being a solution of alkali metal hydroxides, Phosphates and carbonates are used in a ratio and concentration that creates conductivity which enables the passage of the electrolysis current

An oloctroalkallic purification process is preferred, in which the metal strands are electrelysized at a current density of 4.65 to 9.3 A / c · ² in an electrolyte containing a mixture of 6 to 16 % HaOH, 0.5 to 6 pounds Ma ₄ P ₂ O ₇ and 0.5 to .5 % Na ₂ CO ₃ , the duration of which is at least 0.4 seconds. • tofftragor. The critical setting of the above parameters and other aspects of the method described here are explained in more detail with reference to the following Eimselhelten:

To determine the optimal current density, which is necessary for the effective removal of the substances mentioned, A series of tests was carried out at a constant voltage of to V (exceptions are indicated),

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SAD ORIGINAL.

in which different currents> were obtained due to the differences in the conductivity of the electrolyte used. In each experiment the wire was electrolyzed as the cathode for one second and then as the anode for one second. The wire samples used were drawn onto press fabric using borax as the soaking agent carrier and sodium stearate as the lubricant. The effectiveness of the cleaning process was determined by the extent of the adhesion) which resulted from a subsequent electrolytic plating with CuSO ₄ . After the copper plating, the amount of copper that could be rubbed off the test sample was determined and was rated on a scale of 1 to k , with 4 representing complete adhesion and i representing only slight adhesion (i.e. a small fraction of the plating was rubbed off).

TABLE I. Electrolyte limiting current density evaluation of the

Clinging

6 % NaOH, 3 % Na ₂ CO- 7.0 A / cm ² 3 % Na ₁₁ P ₂ O ₇₁ O ₁ IOH ₂ O (18 V) 5 % NaOH, 3.5 % Na ₂ CO ₃ 5.27 A / cm ² 3.5 Na ₄ P ₂ O ₇ , 0.10H ₂ O

% £ NaOH, 4 % Na ₂ CO. 4.03 A / cm ^2%% Na ₄ P ₂ O O _71, 10H ₂ O

2 % NaOH, 5% Na ₂ CO ₅ 3.10 A / cm ² 5 * Na ₄ P ₂ O ₇₄ O, 10H ₂ O

i% NaOH, 5.5% Na ₂ CO ₅ 2.17 A / cm ² 5.5 N ^{a% F} 2 ^O 7 _f o, Ioho

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From the above it follows that for a satisfactory and quick removal of lubricant films, high current density electrical cleaning is significant Represents improvement as evidenced by the increased adhesion of the copper plating. High current densities but are not only advantageous for achieving a more complete removal of lubricants, but also of essential importance in two other respects: 1. They enable higher working speeds and shorter cleaning cells due to the much faster lubricant removal that they allow and 2. they are more effective than low current densities, i.e. they provide equivalent cleaning to one lower energy consumption. To illustrate this latter benefit, it is pointed out that the degree of Disease removal, which is 6.2 A / cm in 0.4 sec. (2.47 coulombs / cm) is at least as good as that which can be achieved with the known process

/ 2 wise, i.e. at a current density of 0.155 A / oe over 60 seconds (9.3 coulombs / cm), or that the ratio of energy consumption is almost 1: 4.

From Table I it can also be seen that in order to achieve the required high current densities, which are required for absolutely effective cleaning, the conductivity of the electrolyte must be considerably higher than that of the electrolyte usually used in electro-alkaline cleaning mixture containing 60 to 80 fo NaOH or an equivalent amount of highly conductive alkali metal hydroxide, further 5 his 30% Na ^ P ₂ O and 5 to 25% Na ₂ CO contains · This mixture, which a non-foaming surface active agent are added can, in order to improve the wetting of the strand material, is dissolved in water up to a concentration of 10 to 20% by weight and on during use

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a temperature in the range between 66 and 99 ° C. Instead of the above components, other known Stepping building blocks, i.e. sesquicarbonate for the carbonate and trisodium phosphate or the tripolyphosphate for the Tetrasodium pyrophosphate It is of course necessary that the solution has sufficient conductivity to to enable electrolysis at a current density of at least 4.65 A / cm.

In order to avoid arcing at the high current densities used, the electrical current is the Metal strand fed through the electrolyte. A preferred device for this process is described in US Pat. No. 3,338,809, in which the electrodes are used Surrounding a metal strand without actually touching it. When using the above device »that of another suitable one. Cell construction should consider some factors · Suitable for alkaline electrolytes an electrode that is insoluble at the pH values used, for example iron, better than lead, to one too to avoid excessive heating of the wire should be in the

There is no strong voltage drop in the wire, otherwise

2 / the energy loss E / R becomes too great. Therefore must Cell length should be kept as small as possible. It has been found that for effective cleaning one minimum contact time of about 0.4 seconds is required, with slightly longer times being preferred while a contact time of over 2.5 seconds from economic Reasons is less desirable and does not seem to have a stronger cleaning effect · Around this minimal Therefore, to obtain immersion time when the operating speed is increased must necessarily also include the number the cell chewers are enlarged. The polarity is chosen so that the metal strand in the laston canter is anodic, which avoids the risk of itself

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Electrolyte impurities settle on the treated metal strand

It has been found that when the method described here is used, it operates at the high current density the cyanide low level of the known processes can be maintained and a coating is still obtained in which the adhesion and cohesion are at least as good as with the usual treatment methods

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Claims (5)

CHALLENGE PATENI ¹ Process for cleaning ferrous metal strands, whereby lubricants are removed from the metal strands, characterized in that the metal strand with direct current at a current density of 4.65 to 9.3 A / cm and one Immersion time of at least 0.4 seconds in an aqueous, alkaline electrolyte is electrolyzed from. one Solution containing alkali metal hydroxides, phosphates and carbonates, the mentioned constituents with respect to their proportion and their concentration are chosen so that they generate a conductivity that allows the passage of the "Electrolyzing electricity enables. 2. The method according to claim 1, characterized in that the electrolyte is kept at a temperature of 71 to 99 ° C and essentially from 10 to 20 wt .-% of a mixture of 60 to 80 % NaOH, 5 to 30 % Na ^ P ₃ O ₇ and 5 to 25 # Na CO. 3. The method according to claim 1 or 2, characterized in that that the current is introduced into the metal strand via the electrolyte, and that the current density is at least 7.0 A / cm. _4e method according to claim 3 »characterized in that the polarity of the metal strand is reversed as it passes through a series of treatment zones, the polarity of the strand in the last treatment zone being anodic« 5. The method according to claim 3 »characterized in that that the lubricants are selected from the group consisting of oils, fats and water-soluble soaps as well composed of the carrier. 109845/1690