LU82951A1 - METHOD FOR MANUFACTURING METAL WIRES FOR REINFORCING RUBBER OBJECTS - Google Patents

Description

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The present invention relates to a method of manufacturing metallic wires for reinforcing rubber articles such as tires. More particularly, it relates to the manufacture of coated steel wires.

i S For the reinforcement of rubber articles, steel wires covered with a layer of brass are used. The main function of brass is to ensure adequate adhesion between rubber and steel and it also plays an important role during wire drawing. Generally, a com-10 brass carrying 60% to 75 1 of copper is used.

Studies have shown that in order to have good adhesion, with certain types of erasers, in particular in aging, a brass with a more ricae layer is needed on the surface.

This zinc gradient can be obtained in different ways.

For example, by alternating deposition on the steel wire of copper and zinc layers, the last layer of zinc, then heat-diffusion. If the thermodiffusion is not total, a layer richer in zinc is obtained on the surface. Another process, which is the subject of French patent 2,393,856, consists in depositing on the wire covered with a brass of current composition, a thin layer of zinc.

'' After drawing, a brass with a non-homogeneous composition is obtained, rich in zinc on the surface.

With such a treatment, a good 25 ‘behavior of adhesion to aging is effectively obtained. However, this method has drawbacks. The presence of a layer rich in zinc on the surface causes disturbances in wire drawing. The cited document states that the optimum deposition of zinc is about 0.06 g per kilo of wire and that problems occur in the spinning from 0.1 g of zinc per kilo. However, the document reports a zinc deposition rate of up to 50 × 10 -5 mg per mm 2 of application surface which, for the wire / i

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2 t '1 of smaller diameter mentioned in the patent, corresponds to an amount of 0.3 g per kilo.

However, additional tests have shown that the best adhesion results are obtained only for quantities of zinc greater than 0.1 g / kg and preferably between 0.3 and 0.7 g / kg. But in this case, the wire drawing problems become very acute and make this operation quite impossible industrially.

On the other hand, it has been observed, in particular, for quantities of zinc omitted between 0.1 and 0.3 g / kg and greater than these values, that the problems of wire drawing increase with the duration of storage. wire before drawing. Thus, the difficulties are greater when the wire is drawn for example two months after zinc plating than when it is drawn for example on the same day. The explanation that we give to this phenomenon is that it forms at the brass-zinc interface, by diffusion under ambient conditions, layers of intermediate phases, fragile, undeformable and which even under very small thickness make the wire that cannot be threaded under industrial conditions.

20 (Numerous breaks, significant wear on the sector). This phenomenon is all the more marked as the layer of zinc is important.

The present invention proposes to provide a new process making it possible to reconcile both good resistance to aging adhesion and wire drawing under good industrial conditions.

It relates to a method of manufacturing a steel wire for the reinforcement of rubber articles such as tires according to which a layer of zinc is deposited on a brass-plated steel wire suitable for drawing and the wire is drawn for bring to the desired diameter, characterized in that an amount of zinc of between 0.1 g and 1 g is deposited per kilo of steel wire and that the wire drawing is carried out continuously with the zincing operation.

Preferably, the quantity of zinc deposited is between 0.1 and 0.6 g / kg of steel. ff "f» "

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Λ 3 The application of zinc is preferably carried out by electrolytic deposition, when the wire passes through an appropriate electrolytic bath. All types of bath known in zinc plating can be used: cyanide-based bath, basic non-cyanide bath, acid bath, pyrophosphate bath, etc. Non-toxic baths are preferably used.

Brass plating is carried out according to the usual methods: electrolytic codeposition, or plating by thermodiffusion.

Standard brass containing 60% at 75% copper is used, the quantity deposited being between 2 g / kg and 7 g / kg of steel.

Optionally, a light stripping can be carried out before galvanizing. Steel is a patented hard steel commonly used for this type of application. The diameter of the treated wires is preferably between 0.80 and 1.90 mm, but can also be outside these limits. The drawing, which takes place continuously with the zinc plating, is carried out under normal conditions with regard to all the parameters (speed, number of passes, number of dies, nature and shape of the dies, lubricant, etc.) ..). The speed is preferably between 10 and 25 m / s.

The method can be implemented by a device according to the invention comprising an electrolytic galvanizing cell associated with a drawing machine. Preferably, according to the invention, the device comprises a galvanizing cell slaved to the running of the drawing machine. According to the servo system, the electric current is established, at start-up, only when the wire drawing machine has reached its normal running speed; the circuit is cut off automatically when the drawing machine stops.

Advantageously, according to the invention, the DC supply takes place, from the AC network, by means of a regulated intensity rectifier. This system is advantageous compared to the constant voltage system. Indeed, by the phenomenon of polarization, a deposit is formed at the anode, which increases the resistance of the circuit. If the voltage is kept constant, the intensity decreases at the same time as the resistance increases and the quantity deposited, which is proportional to the intensity, also decreases. We have an irregular deposit. According to the invention, the enslavement and the constant-intensity feeding result in regular deposition, therefore a regular product.

But the invention will be better understood with the aid of the examples 5 and pies below, given by way of illustration but not limitation: - Figure 1 schematically shows a device for the> ease of implementation of the method according to invention.

Figure 2 is a graph showing the advantages of the invention.

- Figure 3 is a graph of the variation in the composition of brass, as a function of depth, for wires treated according to the invention.

The device according to FIG. 1 mainly comprises an electrolytic galvanizing cell 1, and a wire drawing machine 2 placed downstream, partially shown. The galvanizing cell 2 comprises a tank 3 containing the bath which is crossed by the brass-plated wire F. The brass-coated wire is supplied from a furnace-netting coil 4. The bath circulates in a closed circuit by means of a pump 5 to 20. from a tank 6. It is fed into the tank 3 by the inlet duct 7 and it is evacuated at the two ends of the tank 3 by the conduits 8 and 9 which bring it back to the tank 6. The anode is consisting of a basket 10 in which zinc pellets have been deposited, the wire F is connected to the cathode via the 25 axes of the guide wheels 11 and / or 12 located at the inlet and at the outlet of the tank 3. The wire is pulled through the tank, by the drawing machine 2. At the exit of the bath, the galvanized wire is rinsed in a, box 14. The wire then enters continuously in the drawing machine 2 of which only two dies have been shown 15 and two capstans 30 for drawing 16. The wire drawn under the usual conditions is received on any suitable support not shown. The device also comprises means (not shown) for controlling the operation of the galvanizing cell to the operation of the drawing machine.

According to these means, the galvanizing cell only starts up when the drawing machine has reached its normal operating speed ^ / ’l 5

The operation of the galvanizing cell stops at the same time as the wire drawing. The dlspoaitif also coaports means *, not shown, of known type of current supply 1 regulated intensity.

5 In order to highlight the advantages of the invention, a series of tests has been carried out, they are the subject of the following examples:

Example 1 -

This example relates to adhesion resistance tests at aging.

The adhesion test is carried out on strand and takes place as follows:

An eraser A is used to make calendered sheets with the strand to be tested and these sheets are aged for 5 weeks at 21 ° C. and at 65% relative humidity, in a strictly controlled atmosphere. At time "zero" and each week, a sample of rubber-coated strand is taken and placed in a test of adhesion standardized according to the American standard ASTM D 2229-73 itself produced in gum A. adherence by the method according to the above standard.

The results are reported in Table 1 below and on the graph according to Figure 2, on which the aging time T is plotted in abdsses and the adhesion expressed in decanewtons, on the ordinate.

25 1 a Witness - The witness is made up of a strand with the name 4 x 0.25 S 12.5, that is to say made up of 4 wires of 0.25 mm diameter twisted in S in steps of 12.5 m. The 0.25 mm diameter wire is obtained by drawing a 1.25 mm diameter wire of patented hard steel. Before drawing, the 1.25 mm diameter wire was coated with a layer of brass, at a rate of 5.8 g of brass per kilo of steel wire, brass comprising 66 Z copper and 34 Z Zinc. After drawing, a brass-plated wire of 0.25 diameter is obtained comprising 5 g / kg of brass with 65.8 Z of copper and 34.2 Z of zinc. The loss of 0.8% by weight of brass is a normal loss which is often observed in wire drawing. From / / '- · - - --—----- l «6 of this wire, we therefore make a strand 4 x 0.25 S 12.5 and we practice the adhesion test on this strand.

The results are reported in Table 1 below and on the graph according to Figure 2: curve A.

5 1 b - The above adhesion test is carried out on a strand produced from a 1st wire treated according to the invention. The starting wire is identical to that of Example 1 a, that is to say wire with a diameter of 1.25 mm coated with a brass with 66 X of Copper and 34 X of Zinc at a rate of 5.8 g of brass per kilo of steel wire.

Then, according to the invention, a zinc coating is applied to the brass, at a rate of 0.15 g of groin per kilo of steel wire. A wire is obtained before entering the wire drawing machine comprising 5.95 g of coating per kilo of steel wire and the average composition of which is: 64.5 X copper and 35.5 X Zinc. The wire is drawn continuously with zinc plating, under the conditions of the invention. A thin wire with a diameter of 0.25 mm is obtained coated with 4.8 g / kg of a brass of overall composition 65 X of copper and 35 X of zinc. From this wire, a 4 x 0.25 S 1.25 strand is made as in Example 1 and the same adhesion test is applied to this strand.

2. The results are shown in Table 1 and on the graph according to FIG. 2: curve B. There is already a marked improvement in the resistance to aging.

the- The above adhesion test is carried out on a strand produced from a second wire according to the invention.

^ 5 The starting thread is identical to that of examples 1 a and 1 b. Then, according to the invention, zinc plating is carried out, the quantity of zinc being 0.5 g / kg of steel wire. Before entering the drawing machine, a wire is obtained comprising an amount of coating of 6.3 g / kg, the overall composition of which is 60.5 X of Copper and 39.5 X of Zinc. The wire is drawn continuously with zinc plating, under the conditions of the invention. After drawing, a thin wire 0.25 mm in diameter is obtained, coated with 5.6 g / kg of a brass of overall composition 62 X Copper. From this fine wire, a strand 4 x 0.25 S 12.5 is made as in Examples 1a and 1b and the adhesion test is applied.

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The results are reported in Table 1 and on the graph according to Figure 2: curve C.

There is a significant improvement in the resistance to aging adhesion.

5 Table 1 -

adhesion in 'décaneirtons- daH

Examples Time 0 1 week 2 wk. 3 s in, 4 sea. 5 weeks

10 rfaoî. 38 2M 18 · Ζ 17.3 17_ 1 b__37__28.3 26.8 24.2 23.8 21.2 le 1 36 | 32.8 1 31 30.8 30.4 30.6

The above examples correspond to the storage times of the calendered plies before making the tires.

It is found that the improvement in the tenor of the adhesion to aging increases with the quantity of zinc applied on the surface.

The quantity of zinc applied to the surface, before drawing, partially mixes with the brass during drawing, by mechanical phenomena and partial thermodiffusion.

A finished wire is obtained covered with a brass of non-homogeneous composition, richer in zinc on the surface, as shown by the surface analyzes made by photoelectron spectroscopy ESCA (Electron Spectroscopy for Chemical Analysis).

The graph according to FIG. 3 gives, as a function of the depth: "peel depth", the value of the atomic percentage of copper measured from intensity peaks corresponding to the electronic energy levels 2 p 3 / Z. The analysis relates to three wires: control wire according to example 1 a. and son according to examples 1 b and 1 c.

It can be seen: 30 - generally for the three wires, the composition of the brass changes with the depth: the copper content increases with the depth and then practically stabilizes from around 500 X, - for the wires treated according to the invention , the brass is poorer in Copper on the surface: by comparing it with the adhesion results above, this confirms that the degree of adhesion to aging increases with the zinc content on the surface. . Example 2 -

The purpose of this example is to demonstrate that the wire drawing is not affected by the zinc coating when, in accordance with the invention, wire drawing is carried out continuously with zinc plating.

. 2a- The control wire is the brass wire with a diameter of 1.25 mm, according to Example 1 a. subjected to drawing in the usual conditions to obtain a wire with a final diameter of 0.25 mm. The test consists in measuring the mileage of drawn wire before having to change the dies, taking into account the usual tolerances in the diameter of the finished wire. The mileage, for the witness thread, is expressed by the base number 100.

2b- The wire treated is the wire according to Example 1b.

that is to say the wire according to 1 has coated with 0.15 g / kg of zinc. It is drawn continuously with zinc plating under conditions identical to the control wire 2 a. The drawn wire length before changing the dies, brought back to the base 100 is 120.

20 -2c- The treated wire is the wire according to Example 1 c.

that is to say the wire according to 1 has coated with 0.5 g / kg of zinc. It is drawn continuously with zinc plating under conditions identical to the witness wire 2 a. The drawn wire length before changing the dies, brought back to the base 100 is 95.

2 d - A wire is used which has undergone a treatment of the type known according to French patent 2,393,856. The starting wire is the brass-plated wire according to example l_a, coated with 0.35 g / kg of zinc.

After zinc-coating, the wire is stored for 15 days, then drawn under the same conditions as the control wire 2 a. The drawn wire length 30 before changing the dies, brought back to the base 100, is from 5 to 10. In addition, it can be seen that the wire is very irregular and that breaks are frequent. Wire drawing under industrial conditions cannot be carried out.

Example 2 shows that, unlike the known methods, there are no particular difficulties in wire drawing or increasing the difficulties with the quantity of zinc deposited on the surface if, in accordance with the invention , continuous wire drawing is carried out with zinc plating. On the other hand, if we draw, discontinuously, in accordance with the prior art, we meet with gran-5 difficulties in drawing which increase with the level of zinc deposited and the duration of intermediate storage.

Examples 1 and 2 taken together clearly demonstrate the advantages of the invention: - no difficulty in drawing for zinc deposits ranging from 10 to 1 g / kg of steel, - resistance to aging adhesion , significantly improved compared to the known art, thanks to larger zinc deposits: up to 1 g / kg of steel.

Example 3 - 15 The purpose of this example is to demonstrate the improvement in the resistance of adhesion to aging.

The test takes place as follows:

With the test thread, a calendered sheet is made with a rubber B. A test piece is made, each one being produced by cutting two pieces of said sheet, which are placed one on the other, crossed at 90 °. Aging is carried out in a climatic oven at 35 ° C. and 98% relative humidity, aimed at reproducing storage conditions in a tropical climate. The test pieces are allowed to age respectively zero, 3, 6, 9, 15 days after which they are vulcanized. After vulcanization, the two pieces of ply are separated by tearing off and there are zero to five depending on the rubber covering adhering to the wires: five corresponding to maximum covering and zero corresponding to zero covering.

The control wire is obtained from a steel wire 1.25 om in diameter, coated with brass with 65% copper at the rate of 4.7 g / kg. This wire is drawn under the usual conditions up to a diameter of 0.25 om. A 0.25 mm diameter wire is obtained coated with a brass with 64.5 Z of copper at a rate of 4 g / kg. A strand 35 4 x 0.25 S 12.5 is produced from this wire as in the examples / 1 ° above and is subjected to the test above; the following results are obtained:

Table 2 -

Days 0 3 6 9 15

Kote 53 1 0 0 5 The test is then subjected to a wire produced by the process according to the invention.

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The starting wire is a brass-plated steel wire with a diameter of 1.25 mm, the quantity of brass is 4.5 g / kg and its composition: 69.5 X of copper and 31.5 X of zinc. On this brass-plated wire, zinc plating is applied at the rate of 0.4 g of zinc per kilo of steel. The 0. wire after zincing and before entering the drawing machine is coated with a quantity of brass of 4.9 g / kg comprising overall 63.8 X of copper. The galvanized wire is drawn continuously according to the invention. After drawing, a brass-plated wire with a final diameter of 0.25 mm is obtained, the quantity of brass being 4.1 g / kg and its overall composition: 65 X of copper and 35 X of zinc. This wire is committed in strand 4 x 0.25 S 12.5, which is subjected to the test described above; the following results are obtained;

Table 3 - 2Q Days 0 3 6 9 15

Note 5 5 5 5 4

There is a very significant increase in the resistance * of the adhesion to aging with the wire produced by the process according to the invention.

Example 4 - 25. It also aims to highlight, the holding of adhesion to aging. This is an autoclave aging test, in the presence of humidity, at 120 ° C for 8 hours under a pressure of about 2 bars. The adhesion is measured according to standard ASTM - D 2229-73 on test specimens produced with a rubber c.

The indicators consist of two strands 4 x 0.25 S 12.5 and 5 x 0.25 S 9.5, the wires of which were obtained by drawing a • · · χ /. ... ". Jöi **" * - · "" - 11 £ 11 of 1.25 in. The tests are carried out on strands of identical construction to the controls constituted by wires obtained by the same process as the control wires with, as a difference, the application of zinc plating according to the invention.

The results are reported in the following table: (Table 4):

In this table: - the "construction" column gives the shape of the strands, 10 - the "brass: AZ wire" column concerns the brass plated wire Before

Zinc plating and gives the quantity of brass deposited in g / kg compared to steel, and the percentage of copper in this brass, - the "addition Zn" column gives the quantity of zinc deposited, in g / kg compared to l steel, in the case of wires according to demand, 15 - the "brass: AT wire" column gives the quantity of brass after zinc plating and before wire drawing and the overall percentage of copper in this brass, - the "brass: strand" column gives the quantity of brass remaining after drawing and the overall percentage of copper in this brass, 20 - in the "Adhesion" column measured according to standard ASTM D 2229-73,

Aq designates the initial adhesion, before autoclaving and A the adhesion after 8 h of autoclave, expressed in daN. / 1/3/1 / • # * 12 - »---------- Η-- • · Ο« η m

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On the first control strand 41, there is a significant drop in adhesion between the initial adhesion and after passage through the autoclave.

5 On the strand 42, produced from wires treated according to the invention, it can be seen that if the adhesion to time zero is of the same order as for the strand 41, on the other hand the fall in adhesion to aging is much weaker.

The same remarks can be made for strand 45 compared to witness 44.

There is also a small drop in grip for the strand 43.

The above examples clearly demonstrate the advantages of the invention which makes it possible to have improved adhesion resistance to aging compared to known methods, combined with good wire drawing.

The invention is applicable to steel wires for the reinforcement of rubber articles in particular for the reinforcement “™ é

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Claims (1)

14 * <* 1 / - Method of manufacturing a steel wire for the reinforcement of rubber articles such as tires, according to which a · layer of zinc is deposited on a lai tonné wire suitable for drawing * 5, then the wire is drawn to bring it to the desired diameter, characterized in that an amount of zinc between 0.1 and 1 gram per kilo of steel is deposited and that the wire drawing is carried out continuously with the zinc plating operation. 2 / - Method according to claim 1, characterized in that the quantity of zinc deposited is between 0.1 and 0.6 grams per kilo of steel. 3 / - Method according to one of claims 1 and 2, characterized in that the application of zinc is carried out by electrolytic deposition. 15 4 / - Method according to one of claims 1 to 3, charac terized by the fact that the zinc coating is applied to a brass wire whose amount of brass is between 2 grams and 7 grams per kilo of steel. 5 / - Device for the implementation of the method according to one of claims 1 to 4, characterized in that it comprises an electrolytic galvanizing cell disposed upstream of a wire drawing. * 6 / - Device according to claim 5, characterized in that the market for the zinc plating cell is controlled by the operation of the drawing machine. 7 / - Device according to claim 6, characterized in that the supply of electric current to the galvanizing cell, is regulated intensity. Drawings: —3— page plates of which - * - Pa9e par ·. - ..... pages de otscn ^ n __A__pages de revenoica-t- For short description Luxembourg, te 2 A. AJ- A a 80 The representative: /) /