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Product Description
This digital document is an article from Modern Casting, published by American Foundrymen’s Society, Inc. on January 1, 1995. The length of the article is 1873 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.

Citation Details
Title: Changing industry requires careful recruiting. (metal castings industry)(includes related article) (Industry Overview)
Author: Michael J. Lessiter
Publication: Modern Casting (Magazine/Journal)
Date: January 1, 1995
Publisher: American Foundrymen’s Society, Inc.
Volume: v85 Issue: n1 Page: p46(2)

Article Type: Industry Overview

Distributed by Thomson Gale

Changing industry requires careful recruiting. : An article from: Modern Casting

Product Description
You may know what your environmental compliance obligations are, but do you know how EPA sees them? Created by the EPA, this industry-specific handbook includes a comprehensive environmental profile, industrial process information, pollution prevention techniques, pollutant release data, and regulatory requirements unique to the metal casting industry. Use the information presented in this book to build a foundation for developing holistic solutions to environmental problems, research the metal casting industry and its environmental regulations, understand compliance issues, develop industry-specific training sessions/programs, or create and improve innovative pollution-prevention programs that would make any EPA inspector smile.

Profile of the Metal Casting Industry

THE BELL METAL INDUSTRY

 Any of several chemical elements that are usually shiny solids that conduct heat and can be formed into sheets are known as metals. The Metal Industry is primarily concerned with metallurgy and metalworking. At first the metals are extracted from the metal-ores found in their natural state deep within the earth and then these ores are purified through a detailed procedure to obtain the metals in their pure form, these processes comprise metallurgy. Then the pure form of the metal so obtained is used to manufacture structures as well as different      machines and parts of machines. The procedures which involve the manufacturing of machines and other useful items from the metals so obtained through the metallurgical processes constitute metalworking.

This article tries to reveal the functioning of a cottage industry called Bell metal industry. This will help the people who are interested to know about the cottage industries.

Alloy

Alloys are formed by the mixturing of two or more metals. Alloys consist of tiny crystals called grains. In every grain the atoms are packed together in a particular geometric arrangement. Grain size determines particular characteristics in alloys. Eg: smaller grains make stronger alloys. The first alloy made by people was bronze. The oldest bronzes consisted of copper and arsenic it was in about 3500 BC.The manufacturing of alloys is also carried out in the Metal Industry through the proportionate homogeneous mixing of two or more metallic elements (metals in the pure state). The alloys so formed are mainly manufactured in order to enhance the natural properties of the metals by combining them together. Here we are going to describe one of the most popular as well as useful alloy of Tin and Copper; Bronze. The oldest alloy known to human beings is bronze mixture of copper and arsenic. The existence of Bronze dates back to 3500 BC. Gradually people replaced the arsenic with tin. The period in history between the Stone Age and the Iron Age became known as the Bronze Age. Bronze was commonly used to cast containers such as cups and urns. People made battle axes, shields, swords, ornaments and some times primitive stoves with Bronze.

 It was the period when people used bronze for tools and weapons. It followed the Stone Age, when stone was the prime material. When iron tools became wide spread, the Bronze Age ended and the Iron Age began.

 The Bronze Age is not a particular period of time. Some areas had their bronze age early, others had it late. In some places it lasted for a long time, and in others it was short or skipped altogether.

The earliest known use of bronze was in Sumer in Mesopotamia (now Southern Iraq), about 3500 BC. The Chinese began to use bronze during the Shang Dynasty (about 1766 BC to 1122 BC). During this period, the use of bronze became wide spread in Northern China. People continued to use bronze until some time between 1500 and 1000 BC. Then iron, which first appeared in Asia Minor, became common. The Bronze Age in most regions overlapped an earlier Stone Age and a later iron stage .because people did not stop using one material all at once. Some South American Indians had began to use bronze before white explores came. In short the oldest bronzes consisted of copper and arsenic. It was about 3500 BC. Over the next few hundred years, people discovered that mixing tin with copper produced a more useful bronze.

People began to make tools, ornaments and weapons out of this metal. This metal is much harder than pure copper and it is easier to melt and cast into useful shapes.

For special purposes Phosphorous, Lead, Zinc and other metals may be added in Bronze. For eg: Phosphorous hardens and strengthens Bronze. Because of reputation of Bronze for hardness and durability, the name has been adopted commercially for many Copper alloys that contain little or no tin but are similar in colour to Bronze. Eg: Brass (55% Cu + 45 % Zn), Zn is corrosive.

 The Tin, which is used to make Bronze, is a costly metal. It has 600 per Kg. so the bell metal is also costly. Therefore except bells and cooking vessels. All other items are manufactured by Brass. Brass is an alloy of Copper and Zinc. In short some excellent Brass alloys have been in correctly called Bronze. Nowadays Brass is imported to India from Moradabad of UP. However it is usually understood that when the word Bronze is used by itself, the alloy will contain a considerable amount of Tin.

Bell Metal Industry

 This is a traditional cottage industry. Bell metal workers belong to Moosari community. Moosari, Blacksmith, Goldsmith, Carpenter and Mason are the five groups called Viswakarma. Moosari is doing bell metal and brass casting. The main difference between these two works is that, bell metal products have no permanent moulds but in brass casting permanent moulds are present. In bell metal works 100 % hand made workers are involved. No need of any kind of machinery. They make the tools themselves. (But nowadays very rarely it is imported from Andrapradesh).so this industry is under the department of handicrafts and khadi and village industry. The main raw materials for this industry are clay, wax, castor oil, fire wood, coconut shells, and coconut husk, cow dung and metals. The main metal used in this industry is bell metal.

There is a famous definition for handicraft i.e.: “TWO PIECE NEVER BE SAME”. In the hands of skilled artisans or “moosaris” of kerala, the process of casting bell metal has evolved to its ultimate, to produce single piece casting weighing u to a tone. The perfection of casting technology and alloy composition through an unbroken tradition of many countries has resulted in diverse product forms varying from bells to cooling vessels. The stand proof to a rich visual language and style, a strength shared by all craft traditions of India.

Bell Metal

 Bell metal is an alloy of copper and tin in the ratio of 78: 22. This alloy in a particular fixed ratio of 78% of 99.9 pure copper and 22 % of tin was first invented by the Germans. They used this metal to make church bells. Because, this alloy has special sound damping characteristics that give these bells a rich tone. Thus this alloy got the name BELL METAL .Nowadays bell ghams are used for the production of bells. But a musical effect is not present in these types of bells.

Production Process

 The process of casting is known as “varku” in Malayalam makes use of natural bees wax in a unique way. A layer of wax is wrapped around a rigid clay core. All the intricate details ands designs of the final product are worked in to the wax by hand. The wax model is covered again in clay and allowed to dry. This three layered mould is heated in a furnace to remove the wax, leaving a cavity between the clay core and the outer clay mould. Melted bell metal is poured into the mould and takes the shapes of the wax model. After cooling minimum 24 hours, the clay core and outer mould are broken open. The cast form is then finished and polished by chiseling and filing. This is done for the shining of the vessel.

 The entire operation is skill intensive and performed with the simplest tools. For the alloy, tin and copper are recovered from scrap. All the in gradients including the clay and wax are recycled leaving no wastage. The most important part of this work is the preparation of mould. This mould is not readily available and not a machine made one. This is fully made manually. Only clay and wax is used for the preparation of mould.

 The temperature of the mould and the metal fluid should be equal. This is generally 900c to 950 c[1] .the same temperature of both the mould and the melted fluid ensure the smooth flow of the liquid to the hollow portion without any hindrance. This is a highly skilled job. Only the practical knowledge of the workers is used here. In short it is a 100% handy craft phenomena. That is there are any instruments for the measurement of temperature.100% success is not expected in this type of moulding process. Generally 20% damage or defect is expected. That is about 20% of manufacturing loss are occurs.

Properties and Uses

The strongest bronze contains a high percentage of tin and little lead. Alloys with a high tin content also have a low melting point. They are preferred for intricate ornamental castings such as statues. When bronze is to be used for this purpose, lead is often added to the alloy. The result is a cheaper alloy that is easier to cut. Lead is also added to bronze when the manufactured article will need to be lubricated. For e.g.: bearings are made from leaded bronze. Bronze that contains only phosphorous and tin wears best against steel when no lubricating agent is used. Because it is easily cast in large shapes. It is used for making bells.

Most alloys resist corrosion. Statues and bells made of bronze will wealthier to a beautiful brown colour or develop a green patina (film) characteristic of copper. After such films form, bronze corrodes very slowly. Because of these bronze articles frequently last hundred of years. This metal generally will not react with acids. So it is very healthy to prepare food in the vessels made out of bell metal. This metal cannot be welded. This is a heavy and brittle one. If fallen down it m ay develop cracks, even break into pieces.

Examples for Bell Metal Products

 Bell metal is mainly used for making bells and non corrosive cooking vessels. Brass is used for different types of lamps and so many other utilities and decorative items. The tin is a costly metal. So the bell metal is also costly. Therefore except bells and cooking vessels all other items are manufactured by brass. Another problem of pure bell metal is that it is highly brittle metal just like glass. Nowadays use of cooking vessels in bell metal reduced. More than 80% use modern kitchen and modern techniques of cooking. So the moosari community also changed from their traditional job and is doing some other craft like goldsmith, tailoring etc. At the same time the existing moories are getting orders from temples and churches. All workers are busy now for making deepasthambham, different types of huge and small lamps, idols, prabhamandalam, poojabells, arathy and so many pooja vessels. These products are selling mainly through show rooms and against orders from customers. In the good olden days of Kerala the vessels made out of this metal was considered as dowry. It was like an asset

Mirror of Aranmula is one of the famous bell metal products. Manufacturing of this mirror is a skilled work. Firstly bell metal is arranged as a level surface or plane. Then a leveled polishing is done over it without any holes. Then it shines like a mirror. If this mirror falls down, it breaks into very minute particles just like dust particles. Mainly the bell metal industry is found in kerala and west Bengal. In traditional cultures many similarities are present between kerala and the Bengal.  This particular cottage industry that is bell metal industry is a monopoly of Keralites, especially the moosaries of Payyanore of North Malabar, Mannar of Alappey and Nadavaramba of Trichur.

The other example for bell metal product is “lakshmi vilakku” .The secrets behind the manufacturing of this lamp are in the hands of the moosaries of Payyanore.These lamps are considered as the symbol of prosperity. This lamp reminds us the golden bell metal days. The manufacturing of “lakshmi vilakku” was done by pouring the bell mertal to the mould. Nowadays it is very popular in northern Kerala.Now the bell metal industry cannot be considered as the monopoly of moosaries. Because many people out of this community are doing bell metal jobs and so many moosaries were changed from their traditional job and is doing some other craft works.

Conclusion

Here we are talking about the Bell Metal. Its an alloy with high proportion of tin to copper was the material used for making utensils for ritual and household use. Bell Metal did not tarnish easily and suitable for serving dishes. Traditionally the plate’s tumblers or bowls were forged out of lump of on anvils and steel shapers by a team, heating and beating the metal simultaneously. Bigger pots are shaped and forged in parts and joined or brazed with soldering paste finished and polished. In this article we saw the cottage industry of bell metals and their production as a whole.

[1] Personnel interview with Mr.Krishnappa Swamy, Director, Bellwics Ltd, Nadavaramba.

High pressure die casting enables economical quantity production of castings at a fast rate. These castings can comprise of varied holes, screw threads, recesses, and are identified by a high dimensional accuracy and good surface finish. They enable good economy of metal and need very little surface finishing. The principal on which pressure die casting is based, includes forcing molten metal into a mold or the die, under considerable pressure. The machines which are used for this reason operate on one or two systems :

* Hot Chamber Machines ( for metals with a low softening point )
* Cold Chamber Machines ( for metals with a high softening point )

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In the hot chamber machines the metal is kept liquid in a crucible within the machine, and the pressure chamber that delivers the metal into the die is located in the metal bath. This machinery can be pneumatically operated, or more sometimes develop the pressure by the action of a ram. The casting metal for a cold chamber machine, is kept liquid in a holding furnace, from which it is moved to the pressure chamber, by means of a scoop or a special automatic device and is forced into the die by the way of a ram. Some straightforward machines are hand operated, but fully automatic machines are far more frequently employed for high rates of production.

In pressure die casting, precision made dies of complex multipart design and so extraordinarily dear are used, and exposed to severe conditions of work, by high pressures and high successive variations in temperature. For the production of zinc and zinc alloy castings the dies may be made of unalloyed steel, however for magnesium, aluminum, copper and the alloys of these metals, the dies are often made from hot-work steel, that has much greater sturdiness.

Another development in high pressure die casting is vacuum die casting. It produces castings which have an even better finish than standard high pressure castings. There are two systems, the die is either enclosed in a hood which abandons the air, or the holding furnace is installed under the casting machine, so that on the evacuation of the air from the die, the metal is sucked into the die and is compacted in it, and a process for making iron castings based on this principle has been developed..

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Casting process started about 6000 years ago. The oldest surviving casting figure is of a copper frog from 3200 BC. Casting may be used to form most intricate of shapes, both internal and external. With the use of casting, we can minimize or eliminate several operations like machining, forging and welding.

With the advancement in technology, casting is now playing a greater role in our lives than before. Even in construction, objects are now casted in a single piece which would otherwise require assembly of several pieces if made by other methods. The example is flyover construction, where material like cement, concrete, iron are casted In a required shape and then fixed.

There are several other advantages of metal casting process including meeting the requirements of mass production. In automobile industry, thousands of cast engine blocks and transmission cases are produced every year. Through casting, heavy metal objects can be casted which would otherwise be difficult to produce. Hydroelectric plant parts, pump housing, valves are examples of the advantages of metal casting.

The casting process is further divided into expendable casting and non-expendable mold casting. Expendable casting includes Sand Casting, Plaster Casting, Shell Molding and Investment Casting This type of casting involves the use of temporary and non-reusable molds.

Non-expendable mold casting includes at least four different methods including permanent mold casting, die casting, centrifugal casting and continuous casting.

I will give you definitions of major casting processes that are used to make metals for different industries.

Die Casting

Die casting is a process for producing engineered metal parts by forcing molten metal under high pressure into reusable molds often called as dies. These dies can be designed to produce complex shapes with a high degree of accuracy and repeatability. Most die castings are made from nonferrous metals, specifically zinc, copper, and aluminum based alloys, but ferrous metal die castings are possible.

Aluminum Casting Process

Aluminum is one of the few metals that can be cast by all of the processes used in casting metals. There are factors like cost, quality and feasibility that affects production of aluminum parts. If you are interested in contacting suppliers of aluminum, ferrous and non-ferrous casting.

Investment Casting

Investment Casting is one of the oldest methods for metal forming. It is also called as lost-wax casting. Investment casting process is generally used for small castings but the process has also produced aircraft doors, heavy steel casting and aluminum casting. This process is more expensive than die casting or sand casting. Investment casting process is generally used for aerospace and power industries.

In the end, I would like to say that casting are helping the industries grow. They are shaping the future. They play an important role in our lives and made life much easier for us.