EP0707104A2 - Process for increasing the durability of loom reed blades - Google Patents

Abstract

The method according to the invention consists in that reed lamellae, which consist in particular of cold-rolled steel strip of the types X 12 CrNi 177, X 5 CrNiMo 1810 and X 7 CrNiAl 177, in their entirety at a temperature T> 480 ° C and a time period t> 2 Simply exposed to heat for hours and at the same time a thermochemical treatment of the abrasively stressed surface areas is carried out and then the reed lamellae are cooled to room temperature.

Description

The invention relates to a method for increasing the service life, in particular of reed lamellae by heat and thermochemical treatment.

Weaves, for example for air jet weaving machines, consist of a large number of profiled weave lamellae arranged next to one another in an upper and a lower frame rail, hereinafter called lamellae.
The individual slats have on their one longitudinal edge two spaced apart projections which delimit a U-shaped recess. In the finished reed, the recesses form a channel which extends over its width and is open towards the fabric stop edge for guiding the weft thread. The channel base furthest away from the fabric stop edge strikes the weft thread against the fabric edge.
In the case of reeds for air jet weaving machines, the area of the weft insertion channel is exposed to special requirements with regard to wear behavior.
The reeds of rapier weaving machines, in which the rapiers are guided by the reed, among other things, are subject to the same requirements.

Reeds, whose lamellae are made of high-quality steel, have a service life of around 1000 operating hours, depending on which weft material is used as a weft thread. Then the reeds have to be exchanged for a new reed due to the wear of the slats.

The frequent weaving of the reed is costly and not only in relation to the reed itself, but also with regard to the downtime of the weaving machine associated with the change.

The basic material used for the slats is decisive for the long service life of the reed.
It is known that cold rolled strip steel of the grades X 12 CrNi 177, X 5 CrNiMo 1810 or X 7 CrNiAl 177 is used for lamellas and the lamellas are produced from them by punching.
Slats made of such a material can be used for all types of weft threads, but due to the relatively low strength of about 1200 N / mm², they only have a short service life, approx. 1000 operating hours.

From DE-OS 22 20 859 a reed rod with a locally limited hardening zone is known, in which the front surface has such a hardened zone. The hardening zone is to be achieved by either locally hardening the outer surfaces of the reed rod or by using a cheaper material with a thin layer of particularly hard material.
The cited DE-OS does not disclose how and how a locally wear-resistant surface is achieved on the reed bars.
In the invention published in 1973 according to The aforementioned DE-OS is a method for increasing the service life of reed lamellas, which did not meet the requirements placed on the reed lamellas, particularly with regard to the hardness values on the abrasively stressed surface areas.

To increase the service life of the reeds, it is known to subject the lamellae to a galvanic treatment, such as hard chrome plating.

With hard chrome plating, a hard chrome layer of approximately 10 μm is applied to the fins, which can have a thickness of approximately 0.15 mm to 0.8 mm. This layer has a hardness of around 700 HV.
When processing abrasive wefts, such as jute, glass yarn, glass rowing, it is shown that, compared to non-hard-chrome-plated fins, a service life increase of about double could be achieved.

Fins that are hard chrome-plated must be treated after the chrome plating in order to smooth out the roughnesses that arise during the chrome plating process on the surfaces of the U-shaped recess of the fin. The aftertreatments are also expensive.

From CH-PS 671 034 it is known to apply a layer of chromium oxide (Cr₂O₃) constituents to the surface of machine parts of a weaving machine, for example strands, relay nozzles and leaf lamellae of reeds, which are made of stainless steel.
The method for coating consists in that the parts in question are immersed in a solution of a chromium-containing composition, for example in an aqueous solution of CrO₃, or are coated by this. Subsequently, these parts are heated at a temperature of 500 to 600 ° C in a reaction treatment, so that a layer is formed on the surface of the parts, which contains Cr₂O₃ as the main component.
The CH-PS 671 034 also discloses that a porous ceramic layer can be formed on the surface of the machine parts by applying a coating of a chromium-containing composition containing abrasion-resistant particles, such as Al₂O₃ or SiO₂ particles.
The CH-PS process is intended to achieve hardness values of 500 HV or more on the surface.

However, it is generally known that chromium-containing layers can achieve a hardness of approximately 700 HV on the surface and such layers require post-treatment.

Finally, it is known from EP 0 550 752 to provide a part of the surface of reed lamella of a reed with a diamond-like carbon layer, referred to as DLC (diamond-like carbon film).
The basic material of the reed slats is made of stainless steel.
To improve the adhesion of the wear layer, an intermediate layer, for example a titanium carbide alloy, is first applied to the lamella surface in question.
The DLC layer is applied by chemical vapor deposition, in which the parts to be coated are brought into contact with a hydrocarbon gas in a reaction space under a certain pressure and at a certain temperature.
It has been shown in practice that even the layer applied to the surface of the lamellae does not have the expected wear resistance, fatigue strength and flexural fatigue strength.

It is known from the literature, see also DIN Taschenbuch 155, Stahl und Eisen Güteorm 2, (1985) pp. 188-120, Beuth Verlag GmbH Berlin-Cologne, 2nd edition, to increase the strength of the aforementioned types of steel, a heat treatment in the form of a single or double heat aging.
The simple hot aging of the punched lamellae, which have a thickness of up to about 0.75 mm and which consist, for example, of the steel grade x 7 CrNiAl 177, at a temperature T of 480 ° C to 550 ° C and a hot aging time t of A strength of 1400 N / mm² can be achieved for 1 to 2 hours. This means an increase in strength of 15% to 25% compared to the steel types of the same chemical composition that have not been subjected to hot aging.

It is also known from the tool industry to vacuum a thin layer of high hardness, e.g. to produce a titanium nitride layer on the surface of the machining tools. The physical separation from the gas phase used for this e.g. sputtering or ion plating is very expensive. The layers obtained are relatively thin. For these reasons, the use for slats is not likely and is not recommended.

The object of the invention is therefore to provide a method for increasing the service life of reed lamellae, which are preferably produced from the steel grades x 12 CrNi 177, X 5 CrNiMo 1810 or X 7 CrNiAl 177, by means of which the service life of the reed lamellae is a multiple compared to known methods can be increased and in which the hardness on the abrasively stressed surface areas is not achieved by surface coating.
In particular, the methods are intended to achieve a high degree of hardness in the areas of the lamella that are subject to wear, that is to say the edge areas, while the much larger area of the lamella remains unhardened.
Furthermore, it is an object of the invention to provide a method according to which both the service life of reed disks and that of brake disks of the weft brakes, the surfaces of which already have a hard chrome layer, are increased.

According to the invention the object is solved by the features of patent claims 1, 2 and 4.
It is essential to the invention according to claims 1 and 2 that the reed lamellae are simultaneously subjected to two treatment processes in a reaction space within a certain period of time in order to achieve high wear resistance at the edge area of the reed lamella exposed to wear.
It proves to be particularly advantageous if the edge regions of the lamellae exposed to the abrasive stress are subjected to treatment for the duration of the simple hot aging Ionization of the nitrogen by glow discharge (plasma nitriding) are exposed.
With the combined treatment process, nitrided lamella edge areas are obtained that have a hardness of up to 1200 HV.
The rest of the surface area of the slats is not provided with this hardening layer, which means that there is no risk of the slats breaking when used in the weaving reed of the loom.
The inventive method according to claims 1 and 2 now avoid the application of wear-resistant layers on the base material. Instead, these methods are based on the use of a base material for the reed lamellae, with which a certain strength can be achieved by simple warm aging and, in combination with the heat aging process, with a known thermochemical treatment, preferably by gas nitriding or plasma nitriding, a further increase in the Wear resistance is achieved on the relevant surface areas.

With the. Furthermore, compared to surface coating, methods result in reed lamellae with a diffusion layer, which have a higher wear resistance, a higher fatigue strength and a higher bending fatigue strength than coated lamellae. Due to the heat treatment and the plasma coating of the lamellae in packaged form, it is also possible for the individual lamellae to remain absolutely straight and for the hard diffusion layer to be formed only on the exposed surface area of the lamellae, e.g. on the area provided with the weft insertion channel.

A further improvement in the wear resistance in the relevant edge areas of the lamellae can be achieved if the according to the procedure. Claims 1 and 2 treated lamellae by ion implantation, preferably of N atoms, are further treated.

The final hardness that can be achieved in the edge area of the lamella is around 1800 HV.

Surprisingly, it has been shown that the reed and brake discs of weft brakes, which preferably consist of cold-rolled steel strip of the aforementioned types and have a hard chrome layer, by ion implantation, e.g. of N atoms in the hard chrome layer, achieve a service life that is up to 5 times longer than that of the lamellae which only carry a hard chrome layer.

The invention will be explained in more detail below using an exemplary embodiment.

Fig. 1 :

eine Webblattlamelle in der Seitenansicht mit dem angedeuteten abrasiv beanspruchten Randbereich,

Fig. 2 :

einen Schnitt durch die Webblattlamelle nach der Linie A - A in vergrößertem Maßstab,

Fig. 3 :

die Bremslamellen einer Schußfadenbremse in der Draufsicht.

Show it:

Fig. 1:

a reed lamella in the side view with the indicated abrasively stressed edge area,

Fig. 2:

a section through the reed lamella along the line A - A in an enlarged scale,

Fig. 3:

the brake discs of a weft brake in top view.

The illustrated reed lamella 1 forms the reed of an air jet loom with a plurality of such lamellae.
The outer contour of each of the two longitudinal legs 1a and 1b merges into a projection 2 and 3. The two projections 2 and 3 delimit a recess 4, for example a U-shaped recess.
The recess 4 of the plurality of reed lamellae 1 forms the weft insertion channel in the reed.
When processing particularly abrasive weft threads, such as glass sliver, the contour 4a of the recess 4 is exposed to high wear.

For the purpose of achieving an efficient thermal and thermochemical treatment, it is proposed to first line up the large number of reed lamellae 1, which consist of cold-rolled steel strip of the X 12 CrNi 177 type and are produced by punching, and to hold them together in a package 5.
The plate pack thus formed is gem in the manner shown. Fig. 1 a reaction chamber, which is under a certain pressure (partial vacuum) supplied.
The plate pack is simply aged in the reaction chamber at a temperature> 480 ° C and for a period of about 8 hours.
According to the invention, the exposed surface contour 6 of the slats 1 is now exposed to the ionization of the nitrogen by glow discharge (plasma nitriding) while supplying a nitriding gas (nitrogen) parallel to the heat aging. The nitrogen atoms diffuse into the exposed surface contour 6 and form a first hard edge layer 7 of approximately 0.1 mm.
The plate pack is then cooled to room temperature.
After cooling, the lamellae 1 are subjected according to the invention to a treatment by ion implantation in an evacuated reaction space. Here, only the plasma nitrided contour 4a of the recess 4 is preferably implanted inons.
The duration of the ion implantation is about 4 hours. During this process step, a second and comparatively harder edge layer 8 of approximately 10 μm is formed.

In FIG. 2 the hard edge layers 7 and 8 of the exposed surface contour 6 of the lamellae 1 are shown in the form of a micrograph.

The brake disks 9, 10 of a weft brake 11 shown in FIG. 3 have mutually opposite surfaces 9a, 10a between which the weft 12 is pulled. The surfaces 9a and 10a are preferably provided with a hard chrome layer.
In the case of weft brakes, it is particularly advantageous if the braking surfaces have high wear resistance. The individual brake disks 9, 10 are made, for example, from a cold-rolled steel strip of the X 12 CrNi 177 type and hard-chromed on the inside after the manufacturing process.
The service life of these brake discs with a hardness of around 700 HV is approx. 1000 operating hours.
It has surprisingly been found that ion implantation of the hard chromium-plated surfaces can achieve a service life that is up to 5 times longer than that of the hard chromium layer not treated by ion implantation.

DRAWING LEGEND

1

Reed lamella

1a

Longitudinal leg

1b

Longitudinal leg

2nd

head Start

3rd

head Start

4th

Recess

4a

contour

5

contraption

6

free surface contour

7

Boundary layer

8th

Boundary layer

9

Brake disc

9a

surface

10th

Brake disc

10a

surface

11

Weft brake

12th

Weft

Claims (4)

Process for increasing the service life of abrasively stressed surface areas of reed lamellae, which consist of hot-aging, in particular cold-rolled, steel strips of the types X 12 CrNi 177, X 5 CrNiMo 1810 and X 7 CrNiAl 177 or tempered, tempered nitriding steels and the lamellae are packaged in an evacuable reaction chamber undergo an abrasion-reducing treatment, characterized in that the treatment consists of the following steps a) simple aging of the reed lamella at a temperature T between 480 and 550 ° C and a time t of about 8 hours, b) parallel to simple hot aging, thermochemical treatment of the abrasively stressed surface areas, by exposing the surface areas to a nitriding gas stream, preferably an ammonia gas stream, during the hot aging period, and subsequently c) cooling the reed lamella to room temperature. Process for increasing the service life of abrasively stressed surface areas of reed lamellae, which consist of hot-aging, in particular cold-rolled, steel strips of the grades X 12 CrNi 177, X 5 CrNiMo 1810 and X 7 CrNiAl 177 or tempered, tempered nitriding steels, and the lamellae are packaged in an evacuable reaction chamber undergo an abrasion-reducing treatment, characterized in that the treatment consists of the following steps a) simple aging of the reed lamella at a temperature T between 480 and 550 ° C and a time t of about 8 hours, b) parallel to the simple hot aging, thermochemical treatment of the abrasively stressed surface areas by plasma nitriding, by partially evacuating the reaction space in a manner known per se, then introducing a nitrogen-containing gas into the treatment space and setting a treatment pressure of 1 to 10 mb, and subsequently c) cooling the reed lamella to room temperature. Method according to claim 1 or 2, characterized in that after the heat and thermochemical treatment, the hard reaction layers of the abrasively stressed surface areas are exposed at room temperature to a known ion implantation of preferably N atoms. Method for increasing the service life of abrasively stressed surface areas, in particular of reed disks and brake disks of weft brakes by treatment in a reaction space, the disks preferably being cold rolled strip steel of the grades X 12 CrNi 177, X 5 CrNiMo 1810 and X 7 CrNiAl 177 and have a hard chrome-plated surface, characterized in that the abrasively stressed surface areas are exposed to a known ion implantation of preferably N atoms.

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