2-13 Cold working process

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Slide 1: Introduction to Cold-Working
Cold working: Forming metal at a low temperature, typically room temperature.
Compared to hot working:
Produces brighter finishes.
Results in higher accuracy with minimal machining.
Examples of cold-working methods:
Cold rolling: Used for sheets and flats.
Cold drawing: Used to reduce bar size.
Advantages: Improved surface finish, better dimensional control.
Example: Cold-rolled steel sheets used in automotive body panels due to their smooth finish and high precision.
Slide 2: Cold Rolling and Cold Drawing
Cold rolling: Primarily used for wide flats and sheets.
Cold drawing:
Hot-rolled bars are cleaned, then pulled through a die, reducing their size without material loss.
Used for creating precise bars and shafts.
Mechanical properties:
Both cold rolling and cold drawing increase yield and ultimate strength, along with hardness.
Example: Precision shafts used in mechanical assemblies are commonly cold drawn to ensure tight tolerances.
Slide 3: Effects on Material Properties
Cold working distorts grain structure without changing grain size.
Key effects:
Increased yield strength and hardness.
Decreased ductility (less ability to deform without breaking).
Fig. 2-12: Comparison of cold-drawn vs. hot-rolled bar properties.
Example: Cold-worked steel is often used in structural applications where high strength and rigidity are needed.
Slide 4: Specialized Cold-Working Processes
Heading: Upsetting or gathering metal, often used for making screw and rivet heads.
Roll threading: Forming threads by squeezing a blank between dies.
Spinning: Working sheet metal into circular shapes on a rotating form.
Stamping: Includes blanking, coining, forming, and shallow drawing, commonly used in mass production.
Example: Threaded bolts and fasteners are made using roll threading, ensuring strong and precise threads without cutting.