Engineering Materials and Processes - PowerPoint Presentation

Slide1

Engineering

Materials and ProcessesLecture 5 – Casting Process

Casting iron in a sand mould:WikipediaSlide2

Casting

Engineering Materials and ProcessesReference Text

Section

Higgins RA & Bolton, 2010.

Materials for Engineers and Technicians,

5th

ed, Butterworth HeinemannCh 5

This lecture follows exactly with Higgins Chapter 5.Slide3

Cooling a thick casting causes poor grain structure. Large ingots are a problem.Grains in cast aluminiumwww.spaceflight.esa.int

Engineering Materials and Processes

Ingot casting

(Higgins 5.2)Slide4

Low Pressure Metal Casting (Higgins 5.3 Sand-casting) Engineering Materials and Processes

VIDEOMetal casting: Sand MouldsScutt, Don. [Chadstone, Vic.] : Double D Technical Productions, c2004. DVD (29 min.)This program covers jobbing moulding, cold box moulding, pit moulding, rapid prototyping, investment casting, medium volume green sand moulding, automated cold box moulding, hot box moulding, high volume lost foam moulding, hunter process, disamatic.

Mt Druitt College Library: DVD 671.252/METARecommended Viewing: All sections.

5.6 Investment-casting

5.7 Full-mould process (Lost foam)Slide5

Porosity in Low PressurePorosity occurs because the casting shrinks on solidification. High pressure can fix this, but it makes the mould very expensive. Another way is to use a reservoir of molten metal that feeds more liquid as it solidifies.

In this low pressure casting, aluminium alloy was poured down the runner into the mould. The hollow in the top of the runner caused by liquid flowing from the runner into the mould as the casting solidified. As well as the hollow at the top, you can see some holes in the runner and one hole within the casting itself. The runners and risers will later be cut off and discarded.http://openlearn.open.ac.ukEngineering Materials and ProcessesSlide6

High Pressure Metal Die Casting(Higgins: 5.4 Die-casting)Engineering Materials and Processes

VIDEOMetal casting: Die Casting Scutt, Don. [Chadstone, Vic.] : Double D Technical Productions, c2004. DVD (29 min.) This video shows six casting processes and outlines the advantages, limitations and areas of application of each process. Included are gravity casting high pressure hot chamber die casting, high pressure cold chamber die casting and squeeze casting. Mt Druitt College Library: DVD 671.253/META

Recommended Viewing: All sections.

5.4.1 Pressure die-casting

5.4.2 Gravity die-casting

5.5 Centrifugal castingSlide7

(Higgins: 5.9 The choice of casting process)Engineering Materials and Processes

In order of precision:1. Investment-casting2. Die-casting3. Sand-casting4. Full-mould processIn order of melting point:1. Investment-casting2. Sand-casting3. Die-castingSlide8

Metal Casting ProcessesEngineering Materials and Processes

Wikipedia: CastingSlide9

(Higgins: 5.9 The choice of casting process)Engineering Materials and Processes

The initial costs of mould and equipment are higher in the case of die-casting (B) than for sand-casting (A). Labour costs are higher for sand casting. The break-even value, i.e. the number of castings which must be made before the use of die-casting is justified, may be of the order of several thousands. Once the break-even value has been reached, the cost per die-casting becomes less than the cost per sand-casting.Higgins Fig 5.8Slide10

Shrinkage AllowanceAtoms in a solid fit closer together than in a liquid, so shrinkage occurs. A few substances expand when they solidify because they have a very loose packing arrangement. E.g. Water (ice), and Silicon.

Based on;http://www.calculatoredge.comMetal

Contraction (%) Grey cast iron

0.7 to 1.05

White cast iron

2.1

Malleable iron 1.5Steel2.0Brass1.4Alluminium1.8Aluminium alloys 1.3 to 1.6Bronze1.05 to 2.1Magnesium1.8Zinc2.5Manganese steel 2.6Engineering Materials and ProcessesSlide11

Design Study http://openlearn.open.ac.uk/mod/oucontent/view.php?id=399740&section=2.1

Engineering Materials and ProcessesLearning Space > All Units > Engineering and Technology > T173_2> Manufacturing > PART 2. Casting:

2 Casting2.1 Introduction2.2 Properties for processing – casting

2.3 Types of casting

2.3.1 Permanent pattern

2.3.2 Permanent mould

2.3.3 Expendable mould and pattern2.4 Casting processes2.5 Casting metals2.6 Casting plastics2.7 Casting microstructure and defects2.8 Casting our gearwheelSlide12

Engineering Materials and Processes

Graphical comparison of materials properties. Online Properties Resources.Metal Grains and processing

DoITPoMS:

Dissemination of IT for the Promotion of Materials Science

Wikipedia: CastingSlide13

GLOSSARYBinders Break EvenCharge Cope Core Draft Drag FeederFettlingFlash Gas Porosity GateGreen Sand

Impurity Engineering Materials and Processes

Castings Glossary

Inclusion

Investment Casting

Ladle

Lost Foam Parting LinePattern RiserSand Casting Shrinkage Shrink Hole Sink MarksSlag Sprue Vacuum Casting Slide14

QUESTIONSMoodle XML: Some questions in 10107 ProcessingDefine all the glossary terms.

List 2 advantages that casting offers over other manufacturing processes.List in a table the advantages/disadvantages of casting processes: Sand, investment, gravity die and high pressure die. Include melting point, accuracy, setup costs, production costs, design limitations.Sand casting pattern and sand mould costs $1900 and each part costs $50 in labour. Die casting mould (die) costs $25000 and per part is $10. Calculate the break-even quantity where die-casting becomes cheaper than sand casting.Explain the following casting terms: Flash, porosity, feeder, runner, draft, ejectors, cores. Engineering Materials and Processes