Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 12-1 CHAPTER 12 Metal Casting: Design, Materials, and Economics

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 12-2 Design Considerations in Castings  Corners, angles, and section thickness  Sharp corners, angles and fillets should be avoided, since they cause cracking and tearing during solidification. Fillet radii affects stress concentration and proper liquid-metal flow.  Section changes in casting should smoothly blend into each other. Hot spots can develop shrinkage cavities and porosity (happen at the largest inscribed circles within the casting cross section) This can be eliminated with small cores.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 12-3 Casting Design Modifications Figure 12.1 Suggested design modifications to avoid defects in castings. Note that sharp corners are avoided to reduce stress concentrations.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 12-4 Casting Cross-Sections Figure 12.2 Examples of designs showing the importance of maintaining uniform cross- sections in castings to avoid hot spots and shrinkage cavities.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 12-5 Design Considerations in Castings  Shrinkage: allowances for shrinkage during solidification should be provided for, so as to avoid cracking of the casting.  Parting Line: in general, it is desirable for the parting line to be along a flat plane, rather than contoured.  Machining Allowances  Residual Stress: stress relieve may be necessary.  Draft  Tolerances  Flat Areas: large flat areas should be avoided since they may warp because of temperature gradients during cooling, or may develop poor surface finish because of uneven flow of metal during pouring. Flat surfaces can be broken up with ribs and serrations.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 12-6 Avoiding Shrinkage Cavities Figure 12.3 Examples of design modifications to avoid shrinkage cavities in castings. Source: Steel Castings Handbook, 5th ed. Steel Founders' Society of America, Used with permission.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 12-7 Chills Figure 12.4 The use of metal padding (chills) to increase the rate of cooling in thick regions in a casting to avoid shrinkage cavities. Source: Steel Castings Handbook, 5th ed. Steel Founders' Society of America, Used with permission.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 12-8 Normal Shrinkage Allowance for Some Metals Cast in Sand Molds

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page 12-9 Parting Line Figure 12.5 Redesign of a casting by making the parting line straight to avoid defects. Source: Steel Casting Handbook, 5th ed. Steel Founders' Society of America, Used with permission.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page Casting Design Modifications Figure 12.6 Examples of casting design modifications. Source: Steel Casting Handbook, 5th ed. Steel Founders' Society of America, Used with permission.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page Desirable and Undesirable Die-Casting Practices Figure 12.7 Examples of undesirable and desirable design practices for die-cast parts. Note that section-thickness uniformity is maintained throughout the part. Source: American Die Casting Institute.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page Mechanical Properties for Various Groups of Cast Alloys Figure 12.8 Mechanical properties for various groups of cast alloys. Note that gray iron has very little ductility and toughness, compared with most other cast alloys, some of which undergo considerable elongation and reduction of area in tension. Note also that even within the same group, the properties of cast alloys vary over a wide range, particularly for cast steels. Source: Steel Founders' Society of America.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page Mechanical Properties for Various Groups of Cast Alloys (cont.) Figure 12.8 Mechanical properties for various groups of cast alloys. Note that gray iron has very little ductility and toughness, compared with most other cast alloys, some of which undergo considerable elongation and reduction of area in tension. Note also that even within the same group, the properties of cast alloys vary over a wide range, particularly for cast steels. Source: Steel Founders' Society of America.

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page Typical Applications for Casting and Casting Characteristics

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page Properties and Typical Applications of Cast Irons

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page Mechanical Properties of Gray Cast Irons

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page Properties and Typical Applications of Cast Nonferrous Alloys

Kalpakjian Schmid Manufacturing Engineering and Technology © 2001 Prentice-Hall Page General Cost Characteristics of Casting Processes