WO2015136550A2

WO2015136550A2 - A method for manufacturing a filtration cum distribution device for molten aluminium casting

Info

Publication number: WO2015136550A2
Application number: PCT/IN2015/000116
Authority: WO
Inventors: Anshul Janak NANAVATY; Shreyas Sumanbhai SHAH; Dixit Rameshbhai SHAH
Original assignee: Urja Products Pvt. Ltd.
Priority date: 2014-03-08
Filing date: 2015-03-05
Publication date: 2015-09-17
Also published as: WO2015136550A4; WO2015136550A3

Abstract

The present invention discloses a method for manufacturing a filtration-cum-distribution device (1) for molten aluminium casting. The said process is for manufacturing a substantially rigid filter basket for even distribution and proportionate filtration of molten metal. The said process includes weaving glass yarns into fabric, then coating the said fabric with thermosetting resins and immediately treating the fabric thermally to make the said fabric semi-rigid. Then, cutting the fabric in the form of sheets of predetermined dimensions. After that, positioning the fabric sheets between male and female moulds to impart particular shape to the fabrics. Further, heat treating the said moulds to achieve stiffened rigid fabrics and thereby stitching the fabric pieces to form rigidized filter basket.

Description

A METHOD FOR MANUFACTURING A FILTRATION CUM DISTRIBUTION DEVICE FOR MOLTEN ALUMINIUM CASTING

Field of the invention

The present invention relates to a method for manufacturing a filtration-cum-distribution device for molten aluminium casting. More particularly, to a method for manufacturing a substantially rigid device of a combination of fibreglass fabrics in form of a filter basket for even distribution and proportionate filtration of molten metal during casting. Back ground and prior art of the invention

During casting operation, especially aluminium casting, molten aluminium is transferred from a holding furnace into a casting pit, where it solidifies to form an aluminium ingot or any desired shape. During such aluminium transferring process, impurities that being present in molten aluminium can be introduced into the aluminium casting. The flow of metal can also be turbulent which needs to be channelized and controlled. Also, most importantly oxides are being formed when molten aluminium comes in contact with oxygen present in the atmosphere. Introduction of oxides and the said impurities can cause serious problems during subsequent manufacturing processes of aluminium. Hence, it is important that the flow of aluminium into the mould is smooth, non-turbulent and the casting should be devoid of oxides and other impurities. To mitigate these problems and to optimize distribution, molten aluminium is usually poured into the mould through a filtration- cum-distribution device which is in the form of funnels, spout socks, launder socks or in the form of stitched flexible bag of coated woven glass fibres known as a filter basket. Such conventional filtration-cum-distribution devices are quite flexible and loose in shape. During casting operation, such conventional filters loose its inherent shape in which they are stitched. For instance, U.S. patent 5,207,974, discloses a distributor device having "bag-in-bag" design, comprising an inner bag of impermeable fabric and an outer bag having outlet openings. The device is suspended above the mould and liquid metal is poured into the inner bag. When the metal reached the top of the inner bag, it overflows into the outer bag, and then flows through the openings into the mould. The bag is flexible and is susceptible to the disadvantages mentioned above.

Also, U.S. patent 5,871,660 describes two different distributor devices. One of these is a flexible bag type, which is susceptible to the disadvantages mentioned above. The other device comprises a rigid nozzle having four outlet openings that are angled to direct the molten metal towards the sides of the mould. The nozzle is geometrically complex and is difficult and expensive to produce. During the conventional manufacturing process, such devices are being coated with polyvinyl acetate or other resins and they are not usually subjected to moulds and subsequently passed into furnace oven for heat treatment, i.e. they are being processed only once to have semi-rigid characteristic and then immediately stitched to give the desired shape to form the filter basket. Hence, they loose their shape during the filtration process due to its low grade of stiffness and rigidity as a result of old manufacturing process being adapted. Hence, need arose to develop a manufacturing process that would help in stiffening the glass fiber fabrics to ensure a substantially rigid filtration- cum-distribution device in the form of a rigid filter basket that would maintain its shape during casting.

Object of the invention

The main object of the present invention is to provide an effective manufacturing process to enhance the stiffness of the fibreglass fabrics and use these rigid fabrics to ensure a rigid filtration-cum-distribution device in the form of a filter basket for even filtration and proportionate distribution of molten aluminium during casting.

Another object of the invention is to provide the simplified manufacturing process and steps carried out in manufacturing a rigid filtration-cum-distribution device for filtration and proportionate distribution of molten aluminium during casting.

Summary of the Invention

The present invention relates to a process for manufacturing a filtration-cum-distribution device for aluminium casting is disclosed. According to the present invention, glass yarns are primarily woven to make a fabric. Thermo setting resins are then applied on said fabric for surface coating and are thermally treated at various temperature zones through vertical or horizontal coating equipment to make the fabric in a semi-rigid form. Then, this fabric is manually cut into pieces of various shapes and sizes of pre-determined dimensions. After that, fabric pieces are positioned in male and female moulds to give particular shape and stiffness. Said moulds are subjected to heat treatment to achieve stiffened rigid fabrics using either an industrial oven or conveyor belt furnace or a batch furnace. These fabrics get rigidized after the heat treatment process. After that, fabric pieces are subjected to different kinds of stitching to form a rigidized filter basket of desired form.

Detailed description of the drawings

Fig. 1 shows perspective view of a filtration-cum-distribution device in the form of a rigidized filter basket used for molten aluminium casting according to the present invention.

Fig. 2 shows flowchart for different steps involved in the method for manufacturing a filtration-cum-distribution device as illustrated in Fig. 1.

Hereinafter, exemplary steps of the present invention will be described with reference to the accompanying flow chart. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make thfef subject matter of the present invention rather unclear. Detailed description of the invention

As directed in Fig. 1, a filtration-cum-distribution device (1) in the form of a rigid filter basket, to be manufactured in accordance with the present invention consists of an outer casing (2), an inner main body (4), a base (3), an inner pouch (5) and side tabs (6).

The outer casing (2) is made up of solid or outer closed weave fabric which is sewn around the inner main body (4). Its function is to control the direction of the metal outflows, to hold back oxides and to reduce casting turbulence.

The inner main body (4) of a device (1) is made up of an inner mesh open weave fabric. In conjunction with the outer casing (2), it controls the molten metal distribution, the spread and speed of metal in the mould.

The side tabs (6) are made u of a solid weave material. They work together to keep oxides within the device and check the height of molten metal within the basket.

The base (3) is made up of additional base fabric which acts together to direct the metal flow sideways and to protect the fabric of the main body from burn- through and stop vertical diffusion caused due to initial pressure during molten metal pour.

The outer casing (2) extends up to the base (3) to have bottom holes or side holes (7) through which the molten aluminium flows. The bottom holes or side holes (7) helps draining the device (1) at the end of the cast. In use, the molten aluminium flows through the small pores of the inner pouch (5) and then through the openings in the inner mesh fabric of inner main body (4), which helps to prevent turbulence in the flow of aluminium. As directed in Fig. 2, in the said method of manufacturing the filtration- cum-distribution device (1), primarily glass yarns are woven to make fabric. The said fabric is of two types: 1) Fabric having open weave areas and 2) Solid fabric with closely woven areas. Said yarn is commonly known as Έ' Glass or 'C' Glass yarn, composing of 50-55% silicon dioxide and remaining 45-50% inorganic salts like calcium, boron, etc. The process of weaving these yarns involves doubling, twisting, warping and finally weaving into fabrics. Depending upon intensity of filtration required, the open area of the fabric is selected from 25 Mesh to 400 Mesh. Solid fabrics are closely woven fabrics 5 that support the open weave fabrics.

However, said woven fabrics are loose in structure and can not withstand molten aluminium temperature which is generally in the range of 720°C to 750°C. To counter these issues, loom state fabrics have to be coated with thermosetting resins to enhance temperature withstand ability and }(} chemical resistance by either spray coating or dip coating the fabric. This thermosetting resin is coated on both the side and both the surfaces of the solid fabric with closely woven areas as well as open mesh fabric.

In the coating step, thermosetting resin is diluted with a solvent and a 15 concentration of 5-35% is achieved. This resin is applied on said fabric.

Subsequently, after applying said resin, the fabric is immediately passed into various temperature zones for curing at different thermal stages through a vertical coating tower or horizontal furnace at a speed of 0.5 to 4.0 meters per minute. Said thermal stages include a drying stage, a baking 20 stage and a curing stage. Drying occurs at a temperature zone ranging from 30°C to 60°C to dry the coated substances on the said fabric, baking occurs at temperature zone ranging from 60°C to 100°C to remove vola tiles from the coated fabric and then curing occurs at a temperature zone ranging from 100°C to 150°C to remove remaining volatile substances from the coated 5 said fabric that being left in the previous stage. At the end of such coating and subsequent heat treatment the fabric is still semi-rigid in nature and can be easily re-wound or wrapped on any shape.

Then after, the fabric is manually cut into sheets of predetermined dimensions. The fabric sheets are then placed in between male and female moulds to impart a certain shape to the fabric. Then, the said moulds are subjected to further heat treatment for achieving higher stiffness on the fabrics. This required stiffness is achieved by using equipment like industrial oven, conveyor belt furnace or batch oven. Said moulds are placed on a trolley or conveyor belt which is subjected to passing through 250°C - 450°C temperature with dwell time of 5 - 35 minutes. This process is carried out in either a stationary oven or furnace which is electrically heated or in a furnace working on a timed conveyor belt and fired by gas.

After the completion of heat treatment, said moulds are taken out from the oven containing fabric pieces which are now quite stiff.

Subsequently, said fabric pieces are subject to stitching process to form a rigid filter basket of desired form. Various kinds of stitches are given to fabric ranging from continuous stitch to chain stitch to interlock stitch to intermit stitching. The outermost fabric of the device which is made from solid fabric gives support to the inner open mesh fabric. Inner open mesh fabric is stitched to the solid fabric extending support during the process of distribution and filtration. The invention is illustrated more in detail in the following example. The example describes and demonstrates embodiments within the scope of the present invention. This example is given solely for the purpose of illustration and is not to be construed as limitations of the present invention, as many variations thereof are possible without departing from the spirit and scope.

5 Example:

1) Primarily glass yarns were woven to make solid as well as open mesh fabric.

2) Then, a thermosetting resin, having a concentration of 30% diluted with acetone was coated chemically on the fabric.

10 3) After that, the fabric was immediately passed into various temperature zones for treating the fabrics at different thermal stages through vertical tower coating equipment at a speed of 3.0 meter per minute to make the fabric in a semi-rigid form.

Said thermal stages include drying, baking and curing.

15 i. Drying occurred at a temperature zone of 60°C,

ii. Baking occurred at a temperature zone of 100°C, and

iii. Curing occurred at a temperature zone of 150°C.

4) Then, the fabric is cut in the form of sheets of predetermined dimensions.

¾j 5) The fabric sheets were positioned in male and female moulds and subsequently the said moulds were placed on a trolley or conveyor belt at 400°C temperature for dwell time of 10_minutes to make the fabric sheets rigid.

6) Then, fabric pieces are subjected to stitching process to form a rigid 25 filter basket. Observation:

The present invention filter basket has ideal characteristics of high temperature withstanding, chemical resistance and rigidity.

While, the invention has been described with respect to the given embodiment/it will be appreciated that many variations, modifications and other applications of the invention may be made. However, it is to be expressly understood that such modifications and adaptations are within the scope of the present invention, as set forth in the following claim.

Claims

We Claim:

1. A Method for Manufacturing a Filtration cum Distribution Device (1) for Molten Aluminium Casting comprising following steps:

5 a) weaving the glass yarns to make into fabric;

b) chemically coating thermosetting resin by applying said resin on the fabric and by thermally treating the fabric to make the fabric in a semi-rigid form;

c) cutting this fabrics in pieces of pre-determined shapes;

10 d) rigidifying the fabric by positioning the fabric pieces between a male and female mould and by subsequently treating the moulds thermally to achieve a resultant rigidized fabric;

e) stitching the molded fabrics to form a rigid filter basket.

1 3

2. The Method for Manufacturing a Filtration cum Distribution Device (1) for Molten Aluminium Casting as claimed in claim 1, wherein the glass yarns are composed of 50-55% silicon dioxide and 45-50% inorganic salts of calcium and boron.

20

3. The Method for Manufacturing a Filtration cum Distribution Device (1) for Molten Aluminium Casting as claimed in claim 1, wherein in step b), the chemical coating is carried out with thermosetting resin

^■$$ diluted with a solvent and having concentration of 5-35%.

4. The Method for Manufacturing a Filtration cum Distribution Device (1) for Molten Aluminium Casting as claimed in claim 1, and 3, wherein in step b), the resin is applied by means of spray coating or dip coating.

5. The Method for Manufacturing a Filtration cum Distribution Device (1) for Molten Aluminium Casting as claimed in claim 1, wherein at step b), the thermal treatment is carried out at 40°C to 150°C temperature; with a speed of 0.5 to 4.0 meters per minute.

6. The Method for Manufacturing a Filtration cum Distribution Device (1) for Molten Aluminium Casting as claimed in claim \, wherein step d) is carried out by means of industrial oven, conveyor belt furnace or a batch oven.

7. The Method for Manufacturing a Filtration cum Distribution Device (1) for Molten Aluminium Casting as claimed in claim 1, wherein at step d), the thermal treatment is carried out at 250°C to 450°C temperature with a dwell time of 5 to 35 minutes.

8. The Method for Manufacturing a Filtration cum Distribution Device (1) for Molten Aluminium Casting as claimed in claim 1, wherein step e) is carried out with continuous stitch to chain stitch to interlock stitch to intermit stitching.