DESC:FIELD
The present disclosure relates to a surface coated card-clothing and a process of manufacturing the same.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.
Carding refers to a mechanical process that disentangles, cleans and individualizes fibers to produce a continuous web or sliver suitable for subsequent processing.
Card-clothing refers to strips of wire-toothed card used for covering cylinders of carding machines. Card clothing is made from a sturdy flexible backing in which closely spaced wire pins are embedded.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Carding is a common technique in spinning mills, used for removal of impurities in textile fibres as well as enabling the parallel alignment of the fibres. The carding machine mainly comprises rollers with saw toothed wires through which the fibres are passed. Typically, the card-clothing component of a carding machine comprises saw toothed wire tips on a metal base or a wire teeth embedded in a foundation of multiple fabric layers with rubber toppings. The component is used to cover rollers i.e. cylinder, doffer or flat bars, stationary flats and the like, on a carding machine. The saw toothed wire of the card-clothing is in continuous contact with the fibres and are therefore susceptible to wear and abrasion.
In order to improve the properties and wear resistance of the card clothing, the processes in the art disclose the application of a coating material on the components such as the wires. However, the conventional coating is performed at high temperatures that changes the microstructure of the components particularly hardened wire tips, thereby affecting the abrasion resistance of the components and also their performance. Further, after the coating process, the sharpness of the components particularly the hardened wire tips need to be retained. In practice, this is not so because the coating process, by its very nature, applies an uneven coat on the components, particularly at the wire tips.
There is, therefore, felt a need for an effective process for manufacturing surface coated card-clothing that overcomes the above mentioned limitations.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a surface coated card-clothing having good abrasion resistance, corrosion resistance and wear resistance.
Still another object of the present disclosure is to provide a simple and economical process for manufacturing a surface coated card-clothing without affecting its metallurgical properties.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a surface coated card-clothing comprising a plurality of teeth structures, provided with at least a partial coating of chromium nitride having a thickness in the range of 1 µm to 10 µm.
The present disclosure further provides a process for manufacturing a surface coated card-clothing. The process comprises obtaining a card-clothing comprising a plurality of teeth structures. The card-clothing is cleaned to obtain a cleaned card-clothing. The cleaned card-clothing is heated at a temperature in the range of 80 °C to 180 °C for a time period in the range of 1 hour to 2 hours to obtain a heated card-clothing. At least a portion of the heated card-clothing is coated with chromium nitride to obtain a surface-coated card-clothing, having a coating thickness in the range of 1 µm to 10 µm. The coating is carried out by cathodic arc physical vapour deposition (CAPVD) method.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a card-clothing device 100, in accordance with the present disclosure;
Figure 2 illustrates a cross section of card-clothing device 100 of Figure 1;
Figure 3 illustrates plurality of teeth structures 102 of a card-clothing 200;
Figure 4 illustrates cross section of teeth structure 102 of Figure 3;
Figure 5 illustrates Scanning electron microscopic (SEM) image of surface treated card clothing of Experiment 1, in accordance with the present disclosure;
Figure 6 illustrates magnified view of Scanning electron microscopic (SEM) image of Figure 5.
Figure 7a illustrates surface morphology (optical microscopic image) of teeth structure before micro blasting; and
Figure 7b illustrates surface morphology (optical microscopic image) of teeth structure after micro blasting.
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The textile fibres in mills are subjected to card-clothing treatment, prior to subsequent processing, wherein saw-toothed wires in card-clothing device are used for disentangling, cleaning and aligning the fibres. The portion of the card-clothing device which is most exposed to the fibres is mainly the surface and the tip of the wire that get prone to abrasion and wear due to frequent contact. Further, the wire being of metal is also likely to get corroded.
To overcome these limitations, a coating material is applied to the card-clothing. A commonly used process includes high temperature deposition of metal on the surface and the tip of the card-clothing teeth. However, the use of high temperature coating process causes change in the microstructure of the hardened tips of card-clothing teeth thereby leading to the deterioration in abrasion resistance of the card-clothing teeth.
The present disclosure provides a surface coated card-clothing and an economical process for manufacturing the same without affecting the microstructure of the card-clothing teeth material. The surface coated card-clothing obtained by the process of the present disclosure has improved abrasion resistance and corrosion resistance, which leads to extended life of the card-clothing teeth and improved carding action.
In one aspect, the present disclosure provides a surface coated card-clothing. The surface coated card-clothing comprises a plurality of teeth structures provided with at least a partial coating of chromium nitride having a thickness in the range of 1 µm to 10 µm.
In accordance with Figures 1 and 2, the surface treated card-clothing comprises a plurality of teeth structures 102, wherein at least a portion of the plurality of teeth structures 102 comprises a coating, wherein the thickness of the coating is 2 µm.
In accordance with the present disclosure, the plurality of teeth structures 102 are supported on a metal base 104 as shown in Figures 1 and 2. Typically, the plurality of teeth structures 102 are configured to perform the carding action. The metal base 104 provides a support for the plurality of teeth structures 102. The metal base 104 is supported by side plates 106A and 106B
As shown in Figure 2, the metal base 104 is supported on a metal beam 206, the metal base 104 is supported through channel structures fitted with screws.
In an embodiment, the metal base 104 is made of aluminium, the side plates 106A and 106B are made of steel and the metal beam 206 is made of aluminium.
In one embodiment, the plurality of teeth are steel structures.
As shown in Figure 3, the coated card-clothing comprises a rib portion 108 and plurality of teeth structures 102.
In one embodiment, the base portion 108 as well as the plurality of teeth structures 102 are coated. In another embodiment, only the plurality of teeth structures 102 are coated.
As shown in Figure 4, each of the plurality of teeth structures 102 comprises a tip portion 102A and a surface portion 102B.
In one embodiment, the tip portion 102A as well as the surface portion 102B are coated. In another embodiment, only the tip portion 102A is coated.
Each of the plurality of teeth structures 102 are flame-hardened having martensitic microstructure with high hardness. Typically, the rib 108 has relatively lower hardness than the teeth structures 102.
In an embodiment of the present disclosure, the coated card-clothing has a hardness value in the range of 2200 HV to 2500 HV.
In an exemplified embodiment, the coated card-clothing has a hardness value of 2240 HV.
The coated card-clothing of the present disclosure has a resistance to oxidation of at least upto 700 °C.
The coated card-clothing has a co-efficient of friction in the range of 0.4 to 0.7. In an embodiment, the co-efficient of friction is 0.5.
In another aspect, the present disclosure provides a process for manufacturing a surface coated card-clothing. The process comprises the following steps:
Initially, a card-clothing comprising a plurality of teeth structures is obtained by passing round steel wire through a set of rollers to obtain a profiled strip. Wire teeth are then punched on the profiled strip to obtain a wire having plurality of teeth structures.
In an embodiment, the wire teeth are treated by heat so that the tip portion have relatively more hardness. These hardened wire is cut into pieces and stacked on an aluminium base to obtain the card-clothing comprising a plurality of teeth structures.
The card-clothing with a plurality of teeth structures is cleaned using at least one process selected from ultrasonic cleaning and micro blasting to obtain a cleaned card-clothing.
In an embodiment, the cleaning is done by micro blasting which is carried out using fine alumina powder.
In another embodiment, the cleaning is done by using ultrasonic cleaning procedures. Typically, ultrasonic cleaning is done by using commercial cleaning agents having pH in the range of 10-12. These agents are capable of creating cavitation when ultrasonic waves pass through it. The step of cleaning ensures removal of oxides and scales formed during hardening process of the card-clothing.
The cleaned card-clothing is heated at a temperature in the range of 80 °C to 180 °C for a time period in the range of 1 hour to 2 hours to obtain a heated card-clothing.
In an exemplary embodiment, the card-clothing is cleaned and heated to 120°C for 1.5 hrs.
At least a portion of the heated card-clothing is coated with chromium nitride to obtain a surface-coated card-clothing, having a coating thickness in the range of 1 µm to 10 µm. The coating is carried out by cathodic arc physical vapour deposition (CAPVD) method.
The CAPVD technique enables the deposition of relatively hard but ductile coating layer on the card-clothing.
In an embodiment, the Cathodic Arc Physical Vapour Deposition (CAPVD) method is performed in a stepwise manner. The heated card-clothing is mounted on a holder and subjected to coating of chromium nitride by CAPVD technique to obtain a coated card-clothing with the coating thickness of 2 µm.
Typically, the metal cathode in CAPVD method is selected as per the composition of the desired coating material. In an embodiment, when the coating material is chromium nitride, the metal cathode is a chromium electrode.
Typically, the CAPVD coating is conducted in a vacuum chamber, evacuated to a pressure below 8 x10-3 Pa.
The CAPVD coating step includes application of DC Arc current supply to metal cathodes in the range of 60 Amp to 100 Amp, preferably 75 Amp to 85 Amp, to generate metal ions.
The metal ions are accelerated in the CAPVD coating by using negative bias voltage generated using DC power supply in the range of 450 V to 800 V. The accelerated metal ions bombard on substrate surface and knocks out contaminants which improve adhesion between the coating and card-clothing substrate interface.
The coating deposition is initiated by introducing pure N2 gas at a pressure in the range of 0.1 Pa to 0.8 Pa, preferably 0.3 Pa to 0.6 Pa.
The nitrogen gas flow is selected depending upon the system characteristics, including the cathode size and pumping speed, to obtain coating of desired stoichiometry. Typically, for chromium nitride coating, the nitrogen gas flow rate is in the range of 0.0002 to 0.0006 m3/min.
The coating deposition is carried out by applying negative voltage to the vacuum chamber walls in the range of 100 V to 200 V. In an embodiment, the voltage is 160 V.
The coating step is carried out for a time period in the range of 1 hour to 2 hours. In an embodiment, the coating step is carried out for 1.5 hours.
Chromium nitride provides relatively a harder coating in comparison to conventional hard chrome plating. The coating thickness being in the range of 1 µm to 10 µm, ensures that the sharpness of the edges of the card-clothing teeth is retained. The process of the present disclosure enables better temperature control than the conventional processes, thereby unaffecting martensitic structure of the card-clothing teeth. The coated card-clothing obtained has improved properties and relatively better carding action.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS
Experiment 1: Preparation of coated card-clothing
A card-clothing was cleaned by micro blasting with fine alumina powder to obtain a cleaned card-clothing. The cleaned card-clothing was mounted on a holder operable to rotate and was heated to 120°C for 1.5 hrs to obtain a heated card-clothing. The heated card-clothing was subjected to deposition of a coating of chromium nitride (CrN) by Cathode Arc Physical Vapour Deposition (CAPVD) technique to obtain the surface coated card-clothing having thickness of 2 µm.
The CAPVD coating was carried out as follows:
Chromium cathode having 99.98 % purity was used in the process. The distance between the holder and the cathode was 10 cm. The holder was electrically connected to a DC bias power Supply. The deposition was carried out in a vacuum chamber, which was initially evacuated by a high vacuum pump to a pressure below 1x10-3 Pa. A constant gas flow of Argon was introduced into the chamber through a valve to render a chamber pressure lower than 1 Pa. Upon application of DC (80 Amp) to the chromium cathodes, chromium ions were generated from the cathode surface. The chromium ions were accelerated for 5 minutes in pure argon gas inside vacuum chamber using negative bias voltage generated using DC power supply at 600 V. The accelerated Cr ions were bombarded on the heated card-clothing. Pure N2 gas was introduced inside the chamber through a valve at a pressure of 0.4 Pa. The coating deposition was carried out by applying negative voltage at 160 V to the vacuum chamber walls. The coating step was carried out for 1.5 hours to obtain the surface treated card clothing coated with chromium nitride having thickness of 2 µm.
The surface coated card-clothing was analyzed by Scanning electron microscopy (SEM) as shown in Figures 5 and 6.
Effect of micro blasting:
Micro blasting was carried out at 6 kg/cm with alumina powder of mesh size 1000 for 30 seconds. The tip images were taken using surface profile meter and optical microscope at 100X magnification before and after micro-blasting. The surface morphology of the teeth of card-clothing before and after micro-blasting are shown in Figures 7a and 7b.
From Figures 7a and 7b, it is clear that the oxide patches which are observed before microblasting are completely removed after microblasting. Thus, the teeth structure of card-clothing becomes oxide free after micro-blasting.
The average surface roughness (Ra) values of the teeth of card-clothing before and after micro blasting are 0.55 µm and 0.52 µm respectively. Thus, after micro blasting, the surface roughness (Ra) value reduces marginally from 0.55 µm to 0.52 µm.
Hardness of surface coated card-clothing:
The hardness was measured at 20 mN load using Berkovich indentor. The average hardness value measured is 2240 HV.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a coated card-clothing, wherein the card-clothing:
? has improved properties such as improved wear resistance, abrasion resistance, corrosion resistance and high surface hardness; and
? is prepared by using a simple and economical process having better control of temperature, thereby unaffecting the metallurgical properties of the card-clothing.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:We claim:
1. A surface coated card-clothing comprising a plurality of teeth structures, provided with at least partial coating of chromium nitride having thickness in the range of 1 µm to 10 µm.
2. The card-clothing as claimed in claim 1, wherein said plurality of teeth are steel structures.
3. The card-clothing as claimed in claim 1, wherein said plurality of teeth structures are supported with a metal base support.
4. The card-clothing as claimed in claim 1, wherein hardness of said surface coated card-clothing is in the range of 2200 HV to 2500 HV.
5. A process for manufacturing a surface coated card-clothing, said process comprises the following steps:
(i) obtaining a card-clothing comprising a plurality of teeth structures;
(ii) cleaning the card-clothing to obtain a cleaned card-clothing;
(iii) heating the cleaned card-clothing to a temperature in the range of 80 °C to 180 °C for a time period in the range of 1 hour to 2 hours to obtain a heated card-clothing; and
(iv) coating at least a portion of the heated card-clothing with chromium nitride to obtain a surface-coated card-clothing, having a coating thickness in the range of 1 µm to 10 µm, wherein said coating is carried out by cathodic arc physical vapour deposition (CAPVD) method.
6. The process as claimed in claim 5, wherein said cleaning is done by using at least one process selected from ultrasonic cleaning and micro blasting, wherein said ultrasonic cleaning is carried out by using ultrasound in the presence of a cleaning agent having pH in the range of 10-12 and wherein said micro blasting is carried out by using fine alumina powder.
7. The process as claimed in claim 5, wherein said CAPVD method is conducted in a vacuum chamber at a pressure below 8 x10-3 Pa.
8. The process as claimed in claim 5, wherein said CAPVD method is carried out by applying a direct current in the range of 60 amp to 100 amp.
9. The process as claimed in claim 5, wherein said CAPVD method is carried out by introducing nitrogen gas at a pressure in the range of 0.1 Pa to 0.8 Pa and at a rate in the range of 0.0002 to 0.0006 m3/min.
10. The process as claimed in claim 5, wherein said CAPVD method is carried out by using chromium electrode as a cathode.