Skema Answer Manufacturing Proces 2
FACULTI OF MECHANICAL ENGINEERING
UNIVERSITI MALAYSIA PAHANG
BMM3643 (Sem II 2012/13)
Assignment #2
1.
a) Define the various regimes of cold working,warm working,and hot working in terms of the melting point of the material being formed. b) Indicate some of the advantages of cold working relative to warm and hot working. c) What are some of the negative aspects of hot working? (8 marks)
Answer
a) The temperatures required for hot working generally exceed 0.6 times the melting point of the material on an absolute temperature scale. Cold working generally requires temperatures below 0.3 times the melting point, and warm working is the transition region, between 0.3 and 0.6 times the melting point. b) Advantages of cold working are; i) better accuracy, ii) better surface finish, iii) increased strength due to work hardening, iv) possible directional properties due to grain flow, and v) no heating of work required. c) Disadvantages associated with hot working involve the reactions which may be promoted by elevated temperature, such as rapid oxidation. Tolerances are poorer and the metallurgical structure will be nonuniform if the amount of deformation or thermal history varies throughout the product.
2. a) What is the difference between open-die and impression-die forging? b) Explain the reasons why the flash assists in die filling, especially in hot forging. c) Why are heated dies generally employed in hot-press forging operations? (8 marks)
Answer
a) Open-die forging does not confine the flow of metal in all directions, so the final shape is dependent upon the manipulation and skill of the equipment operator. Impression-die forging operations confine metal flow in all directions to provide good repeatable control of size and shape. b) The flash is excess metal which is squeezed out from the die cavity into the outer space between the two
UNIVERSITI MALAYSIA PAHANG
BMM3643 (Sem II 2012/13)
Assignment #2
1.
a) Define the various regimes of cold working,warm working,and hot working in terms of the melting point of the material being formed. b) Indicate some of the advantages of cold working relative to warm and hot working. c) What are some of the negative aspects of hot working? (8 marks)
Answer
a) The temperatures required for hot working generally exceed 0.6 times the melting point of the material on an absolute temperature scale. Cold working generally requires temperatures below 0.3 times the melting point, and warm working is the transition region, between 0.3 and 0.6 times the melting point. b) Advantages of cold working are; i) better accuracy, ii) better surface finish, iii) increased strength due to work hardening, iv) possible directional properties due to grain flow, and v) no heating of work required. c) Disadvantages associated with hot working involve the reactions which may be promoted by elevated temperature, such as rapid oxidation. Tolerances are poorer and the metallurgical structure will be nonuniform if the amount of deformation or thermal history varies throughout the product.
2. a) What is the difference between open-die and impression-die forging? b) Explain the reasons why the flash assists in die filling, especially in hot forging. c) Why are heated dies generally employed in hot-press forging operations? (8 marks)
Answer
a) Open-die forging does not confine the flow of metal in all directions, so the final shape is dependent upon the manipulation and skill of the equipment operator. Impression-die forging operations confine metal flow in all directions to provide good repeatable control of size and shape. b) The flash is excess metal which is squeezed out from the die cavity into the outer space between the two