Casting Ch 1

7/31/2019 Casting Ch 1

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CASTING & WORKING OF METALS

Met E 301

DR. M. YOUSAF ANWAR


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Course Outline

Introduction to casting processes. Patterns and pattern-allowances, molding methods andmechanization, storage, handling, preparation, andreclamation of molding sands.

Study of processes other than sand casting e.g. plastercasting, investment casting, die and permanent moldcasting, centrifugal casting, slush casting.

Introduction to melting in crucible furnace, cupola,electric arc furnace, cored and coreless induction furnace,

converters etc. Common metals and alloys used infoundry.

Cleaning, inspection and repair of castings.

Introduction to metal working ,i.e. Rolling, Forging,

Extrusion and Drawing etc.


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Recommended Books:

1. Principles of Metal Casting

By

Richard W. Heine and Philip C. Rosenthal

2. Foundry Engineering

By

Howard F. Taylor, Merton C. Flemings and John Wulff


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INTRODUCTION

A casting may be defined as a metal object obtained byallowing molten metal to solidify in a mold the shape of the

object being determined by the shape of the mold cavity.

Founding or casting is the process of forming metal objects

by melting metal and pouring it into mold.

A foundry is a commercial establishment for founding or

producing castings.

Wrought metal products differ from cast metal products inthat the metal has received mechanical working treatment

such as forging, rolling or extrusion.

Wrought objects are cast as ingots and then plastically

worked to approximately the desired shape.


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Advantages of Casting Process

The most intricate of shapes, both external andinternal, may be cast. As a result, many otheroperations such as machining, forging and weldingmay be minimized or eliminated.

Because of their metallurgical nature, some metalscan only be cast to shape since they cannot be hot-worked into bars, rods, plates, or other shapes from

ingot form as a preliminary to other processing. Construction may be simplified. (single piece)

Metal casting is a process highly adaptable to the

requirements of mass production.


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Extremely large, heavy metalobjects may be cast whenthey would be difficult or economically impossible to

produce otherwise.

Some engineering properties are obtained morefavorably in cast metals. A number of examples are give

below;

i) Machinability and vibration damping capacity in cast irons.

ii) More uniform properties from a directional standpoint; i.e.,

properly cast metals exhibit the same properties regardless of

which direction the test piece is selected relative to the original

casting. This is not true for wrought metals.

iii) Strength and lightness in certain light metals alloys which can be

produced only as castings.

iv) Good bearing qualities are obtained in cast bearing metals.


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In general, a wide range of alloy composition and

properties is produced in cast form.

A decided economic advantage may exist as a result of

any one or a combination of the points listed above.


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The Foundry Industry

Casting enter into every field in which metals serve

men.

Castings are used in transportation, communication,

construction, agriculture, power generators and in

limitless other activities too numerous to describe.Because of their wide spread use, castings are

produced almost anywhere that manufacturing occurs.

Types of Foundries:

Foundries may be classified as ferrous ornon-

ferrous, grey iron, steel, malleable, brass and

bronze orlight metal (Al, Mg) shops.


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Foundries are further classified according to thenature of their work and their organizationalframework.

i) Jobbing Foundry: A jobbing foundry is one having aphysical plant such that it usually contracts to producea casting or a small number of castings of a givenkind.

ii)Production Foundry: A production foundry is ahighly mechanized shop which requires that largenumbers of a given kind of casting be made in orderto produce them at a low cost.

iii) Semi-production Foundry: Semi-production

foundries are those in which a portion of the work isof a jobbing nature while the balance is productioncasting.

.


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iv) Captive Foundry: A captive foundry is onewhich is an integral part of some manufacturingcompany and whose castings are consumedmainly in the products of the parent organization

v) Independent Foundry:An independent foundryis usually a separate company that produces

castings for any number of customers.


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BASIC STEPS IN MAKING SAND CASTINGS

Five fundamental steps of the sand casting process are as

follows;

1. Patternmaking (including core boxes)

2. Coremaking

3. Molding

4. Melting and pouring

5. Cleaning

Patternmaking:

Patterns are required to make molds.

A pattern may be simply visualized as an approximate

replica of the exterior of the casting.


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If the casting is to be hollow, as in case of a pipe fitting,additional patterns, referred to as core boxes, are used toform the sand that is used to create these cavities.

Coremaking:

Cores are forms, usually made of sand, which are placedinto a mold cavity to form the interior surfaces of

castings. Thus the void space between the core andmold-cavity surface is what eventually becomes thecasting.

*Core room

.

i


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Molding:

Molding consists of all operations necessary to prepare a moldfor receiving molten metal

Molding usually implies;

Ramming molding sand around a pattern placed in a supportingframe;

Withdrawing the pattern to leave the mold cavity;

Setting of cores in the mold cavity (if required);

Finishing and closing of the mold.

The mold is then ready for pouring.

Melting and Pouring:

The preparation of molten metal for casting is referred to simplyas melting.

Melting is usually done in a specifically designated area of thefoundry, and the molten metal transferred to the molding area

where the molds are poured.


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Cleaning:

Cleaning refers to all operations necessary to theremoval of sand, scale, and excess metal from the

casting.

* Defective castings may be salvaged by welding or

other repair.


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THE ENGINEER AND THE FOUNDRY INDUSTRY

* Knowledge of foundry processes and casting problems.

* Design of castings.* Specifications.

* Intelligent use of the properties of cast metals.

* Purchasing of castings.

* Processing of castings.

Casting Ch 1

Documents

Transcript of Casting Ch 1