Learn with steem || Tutorial class || Mechanical Engineering|| Topic- Mechanical working of metals

MANUFACTURING PROCESS

• Metal forming
• Metal Removing
• Metal joining

• higher productivity suitable for mass production
• high standard quality of fabricated products
• higher strength better corrosion and wear resistance
• minimum waste of metal
• higher dimensional accuracy and surface finish
• strength can be increased
• As grain of materials get elongated in the direction of metal flow better mechanical strength can be achieved.
• Extra thin foil wire steel sheet etc can be found by mechanical working only.

No oxidation and scaling material loss reduced.

• surface defects removed
• excellent surface finish
• higher dimensional accuracy
• good for mass production and automation
• material become work hardened, therefore strength increases
• physical property of metals which do not respond to heat treatment can be improved.

• Large forces are required for deformation.
• ductility or formability of metal is low at low temperatures, inter stage annealing is required, increases the cost of production
• difficult to produce complex shapes
• sensitive controls are required
• only ductile metal can be cold worked.

material commonly used for cold working

• Low medium carbon steels (0.25 to 0.45%)
• low alloy steels
• copper and its alloys
• Aluminium, magnesium, titanium, beryllium etc.

• The strength of metals is low at high temperature hence low tonnage equipment are sufficient.
• Very large workpieces can be deformed.
• Because of high ductility at high temperatures and absence of work hardening, large deformation can be undertaken.
• Interstage annealing & stress relieving are not to much required.
• Blowholes and porosities are eliminated.
• Grain size can be controlled to be minimum. Metal become tougher.
• Segregation may be reduced or eliminated, since hot working promoted diffusion of constituents.

TYPICAL HOT WORKING TEMPERATURES

• Due to oxidation and scaling, heavy material loss. Results in poor dimensional accuracy and surface finish are also not so good.
• Automation is difficult due to high working temperatures.
• Thin parts (sheets, wires etc.) Cannot be produced due to loss of ductility at high temperature.
• High energy cost to heat the metals to high temperature.
• Surface decarbonization in steels reduce strength and hardness on the surface.
• Due to high working temperatures, surface reactions between the metal and the furnace atmosphere occurs. Reactive metal like Ti, required inert atmosphere.

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