WO2006128745A1

WO2006128745A1 - Card clothing wire with oxide-free surface

Info

Publication number: WO2006128745A1
Application number: PCT/EP2006/060631
Authority: WO
Inventors: Aloïs LOOVERIE; Christiaan Scheerens
Original assignee: Nv Bekaert Sa
Priority date: 2005-05-30
Filing date: 2006-03-10
Publication date: 2006-12-07
Also published as: CN101189374A; CN101189374B; EP1885924A1

Abstract

A card clothing wire (10) has a foot portion (12) and has teeth (14). The teeth (14) each having a front surface (16) that is substantially free from oxides. The front surface (16) is preferably coated with a diamond-like carbon coating (20).

Description

CARD CLOTHING WIRE WITH OXIDE-FREE SURFACE Field of the invention.

The present invention relates to a card clothing wire having a foot portion and having teeth. The teeth each have a front surface and other surfaces.

Background of the invention.

Carding is a process of opening and cleaning fibers. The carding process separates fibers from each other, lays them parallel and condenses them into singular untwisted bunches or strands. The carding process can be done by hand or by machines. If done by means of machines, the working components are formed either by needles or by saw toothed steel wires. The present invention relates to such a saw toothed steel wire or card clothing wire.

Card clothing wires are present in various types of geometry depending upon the eventual application. The tolerances on particularly the teeth of the card clothing wire are limited in order to guarantee a qualitative carding process. During the carding process, however, the card clothing wire is subject to severe abrasion.

Abrasion of small particles, even the smallest, from the teeth of the card clothing wire must be avoided not only because of the proper functioning of the carding process but also because a number of critical applications, such as cotton yarns for the medical industry do not tolerate particles present between the cotton fibers.

Summary of the invention.

It is an object of the present invention to avoid the drawbacks of the prior art. It is a further object of the present invention to preserve the integrity of the teeth of the card clothing wire. It is another object of the present invention to increase the resistance against abrasion of the card clothing wire.

According to a first aspect of the present invention, there is provided a card clothing wire having a foot portion and having teeth. The teeth each have a front surface. At least the front surface of the teeth is substantially free from oxides.

Within the context of the present invention, the terms 'substantially free from oxides' refer to a surface where oxides are only present in amount not exceeding 5% of the total surface, e.g. not exceeding 3

% of the total surface. Oxides, if present, can be visually or at least optically detected. A picture can be taken of the surface and enlarged in order to quantify the amount of oxide free surface.

The front surface of the teeth is the most active surface during carding and is most subject to abrasion. So it is important that the front surface is substantially free of oxides. Preferably, however, the all the other surfaces of the teeth are also substantially free of oxides. The absence of oxides facilitates meeting the narrow tolerances.

In a preferable embodiment of the invention, at least the front surface of the teeth of the card clothing wire has a coating of a diamond-like carbon DLC having an amorphous network of carbon and hydrogen. Preferably the other surfaces of the teeth, and possibly other parts of the card clothing wire, also have a coating of a diamond-like carbon DLC having an amorphous network of carbon and hydrogen. DLC coatings (a-C: H) are a mixture of sp2 and sp3 bonded carbon atoms with a hydrogen concentration between 0 - 80%, e.g. between 10% and 75%.

The thickness of this DLC coating ranges from 0.5 μm to 10 μm, e.g. from 1 μm to 5 μm. This DLC coating combines the advantages of having a high degree of surface hardness with hardness values above 10 GPa (nano indentation) and a low coefficient of friction with values ranging from 0.10 to 0.20 (dry steel ball on disc test, 10

Newton, 0.17 m/s, 25 ⁰C, 50 % relative humidity, 100.000 cycles). The high hardness increases the resistance against abrasion. The low coefficient of friction may increase the speed of the carding process without harming its quality. The fact that the substrate under the DLC coating is substantially free of oxides is advantageous for the adhesion of the DLC coating to the steel substrate of the teeth.

According to a second aspect of the present invention, there is provided a method of manufacturing a card clothing wire. The method comprises the following steps: a) providing a saw-toothed profiled steel wire having a front surface; b) providing this front surface oxide free.

As will be explained hereafter in greater detail, providing the front surface oxide free can be done basically in three different ways: a) removing in a mechanical way; b) removing in a chemical way; c) avoiding the oxides during processing.

In a preferable embodiment of the second aspect of the present invention, at least the the front surface of the teeth is coated by a diamond-like carbon having an amorphous network of carbon and hydrogen.

Brief description of the drawings.

The invention will now be described into more detail with reference to the accompanying drawings wherein - FIGURE 1 is perspective and enlarged view of part of a card clothing wire;

FIGURE 2 is cross-section of part of a tooth of card clothing wire.

Description of the preferred embodiments of the invention.

A card clothing wire can be made as follows.

Starting product is a wire rod (usual diameters 5.5 mm or 6.5 mm) with a steel composition along the following lines: a carbon content ranging from 0.30 % to 2.0 %, e.g. from 0.5 to 1.2 %; e.g. from 0.6 to 1.1 %; -A-

a silicon content ranging from 0.10 % to 2.5 %, e.g. from

0.15 to 1.60 %; a manganese content ranging from 0.10 % to 2.0 %, e.g. from 0.50 to 0.90 %; - a chromium content ranging from 0.0 % to 2.0 %, e.g. from

0.10 % to 1.50 %; e.g. from 0.10 % to 0.90 %; a vanadium content ranging from 0.0 % to 2.0 %, e.g. from

0.05 % to 0.60 %, e.g. from 0.10 % to 0.50 %; a tungsten content ranging from 0.0 % to 1.5 %, e.g. from 0.1 % to 0.70 %.

In some compositions either chromium or vanadium is present. In some other compositions both chromium and vanadium are present. The amounts of sulfur and phosphorous are preferably kept as low as possible, e.g. both below 0.05 %, e.g. below 0.025 %.

The wire rod is cold and dry drawn until the desired non-round profile is reached. Rolling can be carried out by means of Turks heads or by means of rolls. Drawing can be done by means of profile drawing dies. The profile depends upon the application can be square, rectangular, or take an L-form. The basis leg of the L forms the foot and the top leg of the L will house the eventual teeth. After this profiling, the teeth are formed in the profile wire by means of a laser operation, a cutting operation or a punching operation. The teeth may take various forms and have varying pitches, depending upon the application. The forming of the teeth may be followed by a deburring operation.

Thereafter the formed saw toothed wire is subjected to some heat treatments, which aim at stress-relieving the foot of the saw-toothed wire and at hardening the teeth. Therefore, the entire saw toothed wire is heated until a temperature in the neighborhood of 600 ⁰C and the teeth get an additional heating until they reach a temperature of about 900 ⁰C. Thereafter the entire wire is quenched so that the foot is stress relieved and the teeth are hardened since the teeth are subjected to a much greater jump in temperature. The global heating until 600 ⁰C can be done by means of induction heating or by means of a gas burner. The heating of the teeth until 900 ⁰C can be done by means of an additional gas burner, or by passing the teeth through a plasma arc or torch. The quenching operation can be done in an oil bath or in a bath of polymers.

The result of this manufacturing process is a card clothing wire 10, an example of which is shown in perspective on FIGURE 1. Following parts can be distinguished on a card clothing wire 10: - the foot 12;

- the teeth 14; the front surface 16 of the teeth 14; other surfaces 18 of the teeth.

Following alternatives exist to make the teeth 14 and possibly also other parts of the card clothing wire 10 oxide free.

As a first alternative, the surfaces are made oxide free in a mechanical way. This can be done e.g. by post-treatments such as sand blasting, glass blasting, or brushing.

As a second alternative, the surfaces are made oxide free in a chemical way. This can be done by etching the card clothing wire in HCI or in H₂SO₄ and carefully rinsing and drying the card clothing wire afterwards.

A third alternative is just to avoid the creation and presence of oxides. This can be achieved, e.g. by carrying out the most critical steps of the processing in an oxide free environment, e.g. under a protective gas atmosphere.

FIGURE 2 shows schematically a cross-section of a part of a tooth 14 of a card clothing wire 10. The steel front surface 16 is covered by a DLC coating 20. The card clothing wire 10, or at least part of the teeth 14 of the card clothing wire 10, can be covered with a DLC coating by means of a chemical vapor deposition process (CVD) or by means of a plasma assisted chemical vapor deposition process (PACVD).

A PACVD process for deposition of DLC mainly occurs as follows. The card clothing wire 10 with the oxide free surfaces is placed in a vacuum chamber. A liquid organic precursor containing the elements C and H in suitable proportions is introduced in the vacuum chamber. A plasma is formed from the introduced precursor by an electron assisted DC- discharge using a filament with a filament current of 50-150 A, a negative filament bias DC voltage of 50-300 V and with a plasma current between 0.1 and 20 A and a composition is deposited on the card clothing wire, to which a negative DC- bias or negative RF self- bias voltage of 200 to 1200 V is applied, in order to attract ions formed in the plasma.

The base pressure in the vacuum chamber is 3xlO^"7 mbar and the typical working pressure is maintained at IxIO^"4 to IxIO^"3 mbar by diffusions pumps. The card clothing wire 10 can be cleaned by an in-situ (Ar-) plasma etching process prior to deposition. This plasma etching may last for 3 to 30 minutes. The card clothing wire 10 temperature does generally not exceed 200 °C during the deposition process.

In some alternative embodiments, the DLC coated may comprise several doping elements such as N or one or another metal (W, V, ...)■ In still some other alternative embodiments, an additional intermediate coating between the steel substrate and the DLC coating may be provided. Such an intermediate coating may be a diamond-like nanocomposite coating such as disclosed in US-A-6 228 471.

Claims

1. A card clothing wire having a foot portion and having teeth, said teeth each having a front surface, characterized in that at least said front surface of said teeth is substantially free from oxides.

2. A card clothing wire as claimed in claim 1, wherein said teeth further comprise other surfaces different from said front surface, said other surfaces being substantially free from oxides.

3. A card clothing wire as claimed in any one of the preceding claims, wherein at least said front surface has a coating of diamond-like carbon having an amorphous network of carbon and hydrogen.

4. A card clothing wire as claimed in any one of the preceding claims, wherein said other surfaces have a coating of diamond- like carbon having an amorphous network of carbon and hydrogen.

5. A method of manufacturing a card clothing wire, said method comprising the following steps: a) providing a saw-toothed profiled steel wire having a front surface; b) providing said front surface oxide free.

6. A method as claimed in claim 5, wherein said front surface is provided oxide free in a mechanical way.

7. A method as claimed in claim 5, wherein said front surface is provided oxide free in a chemical way.

8. A method as claimed in claim 5, wherein said front surface is provide oxide free by surface treatments in an oxide free environment.

9. A method as claimed in any one of claims 5 to 8, said method comprising the following step: c) coating at least said front surface by a diamond-like carbon having an amorphous network of carbon and hydrogen.