Casting notes wk2

Page 1: Introduction

• Welcome to Manufacturing Technology

• ENME607 Week 2 Session 1

• Institution: AUT

Page 2: Session Overview

• Week 2 Focus: Casting Fundamentals

• Required Readings: Kalpakjian, Chapter 10, pages 237-255, 7th Edition

Page 3: Parts Made by Casting

• Big Components:

  • Engine blocks and heads for automobiles

  • Wood burning stoves

  • Machine frames

  • Railway wheels

  • Pipes

  • Church bells

  • Large statues

  • Pump housings

• Small Components:

  • Dental crowns

  • Jewelry

  • Small statues

• Materials:

  • All metals can be cast, both ferrous (iron-containing) and nonferrous (non-iron).

Page 4: Examples of Typical Cast Parts

• Automotive Applications:

  • Gray-iron castings, including:

    • Transmission valve body

    • Hub rotor with disk-brake cylinder

    • Source: Central Foundry Division of General Motors Corporation

• Other Applications:

  • Cast transmission housing

  • Polaroid PDC-2000 digital camera case (die-cast high-purity magnesium)

  • Aluminum piston

Page 5: Advantages of Casting

• Capability to create complex geometries

• Allows for both external and internal shapes to be cast

• Ability to produce very large parts

• Effective for mass production processes

Page 6: Disadvantages of Casting

• Various mechanical property limitations

• Potential for poor dimensional accuracy and surface finish

• Safety hazards due to handling hot molten metal

• Environmental concerns associated with casting processes

Page 7: Fundamentals of Casting

• Key methods discussed include:

  • Melting: Cupola Furnaces, crucible methods, and cupola processes

Page 8: Iron-Carbon Phase Diagram

• Diagram shows solidification temperatures:

  • Liquid phase melts up to 1600°C, solid phase variations depend on carbon content

  • Key points include:

    • 1148°C: Austenite

    • 727°C: Eutectoid reaction

    • Cementite formation

• Carbon Content:

  • Ranges from 0% to approximately 6.67%

Page 9: Aluminum-Magnesium Phase Diagram

• Illustrates melting and solidifying points of aluminum and magnesium:

  • Key temperatures include 660°C, 437°C for various alloy compositions

  • Composition range from 0% to 100% magnesium in aluminum

Page 10: Solidification of Pure Metals

• Graph of temperature vs. time for pure metal solidification:

  • Solidification occurs at a constant temperature

Page 11: Density and Solidification

• Density changes during solidification illustrated as a function of time:

  • Solid and liquid phases demonstrate shrinkage patterns

Page 12: Solidification of Alloyed Metals

• Overview of alloy solidification process:

  • Shows temperature distribution and formation of dendrites in the mushy zone

  • The freezing range is critical to the solidification process

Page 13: Solidification at the Mold Wall

• Description of grain development at the mold wall:

  • Grains favorably oriented grow away from the cooling surface

Page 14: Grain Structures in Cast Metals

• Types of cast structures:

  • Pure metals: Columnar and equiaxed grain structures

  • Solid-solution alloys: Altered structure from pollutants/nucleating agents

• Key terms:

  • Chill Zone: Site of equiaxed grain formation

  • Columnar Grains: Formed with controlled heat flow

Page 15: Dendritic Structures

• Overview of dendritic growth in solidified metals:

  • Illustrated effects of temperature gradients on structure

Page 16: Visualization of Dendritic Structures

• Animation demonstrating the influence of temperature on dendritic structures when solidifying pure metals.

Page 17: Types of Dendritic Structures

• Three basic types:

  • Columnar dendritic

  • Equiaxed dendritic

  • Equiaxed nondendritic

• Source: D. Apelian

Page 18: Solidification of Iron and Carbon Steels

• Solidification patterns for gray cast iron:

  • 11 minutes into cooling, dendrites touch but casting remains mushy

  • Complete solidification takes about two hours

  • Variations observed with increasing carbon content

Page 19: Key Points on Alloy Solidification

• Solidification begins below the liquidus temperature (TL) and continues to solidus temperature (Ts).

• Alloys in the mushy state consist of columnar dendrites

• Dendritic formation risks:

  • Poor material properties (strength/ductility)

  • Potential for defects (cracking/voids)

Page 20: Impact of Cooling Rates on Grain Structure

• The rate of cooling affects grain size, with rapid cooling producing finer grains versus slower cooling yielding larger grains in terms of structure.

Page 21: Quiz Preparation

• Quiz Focus:

  • Identify columnar zones

  • Differentiate equiaxed zones

  • Recognize chill zones and last solidification areas

Page 22: Analysis of Cast Structures

• Discussion on the relative strength of different cast structures:

  • Comparison required for structures (a), (b), and (c) under tensile stress.

Page 23: References

• Recommended textbook:

  • Manufacturing, Engineering & Technology, Fifth Edition by Serope Kalpakjian and Steven R. Schmid, ISBN: 0-13-148965-8.

  • © 2006 Pearson Education, NJ.

  • Practical applications of cast structures discussed.

Page 24: Application in Turbine Blade Manufacturing

• Case study on practical applications related to casting processes and design.

Page 25: Overview of Casting Process

• Key steps in casting:

  • Melting metal, pouring into molds, solidification, removal of final part

Page 26: Gating Systems in Casting

• Explain the role of gating systems:

  • Reservoirs (risers) for molten metal to prevent porosity and allow for excess metal escape

• Design considerations:

  • Optimize fluid dynamics for effective metal flow without premature solidification

Page 27: Next Session Overview

• Upcoming focus on temperature distribution during metal solidification

• Reference figure detailing thermal relationships in solidification for casting

Page 28: Learning Objectives

• Be able to explain columnar, equiaxed, and dendritic cast structures

• Analyze cast cross-sections and identify zones within cast structures.