extrusion

Question 1

advantages of cold working

Answer 1

greater accuracy, surface finish, higher strength and hardness, no heating required

Question 2

disadvantages of cold working

Answer 2

higher forces and power required, limits on the amount of forming that can be done

Question 3

advantages of warm working

Answer 3

(below recrystallisation temp)
lower forces and power
more intricate work geometries possible.
need for annealing may be reduced or eliminated.

Question 4

advantages of hot working

Answer 4

shape can be significantly altered.
lower forces and power.
metals that fracture in cold working can be hot formed.
strength properties isotropic.
no strengthening of part occurs from work hardening

Question 5

disadvantages of hot working

Answer 5

lower dimensional accuracy.
higher total energy required.
surface oxidation (scale).

Question 6

what is recrystallisation in metal forming

Answer 6

at high enough temperatures, new grains will form during deformation, so metal will not become harder.

Question 7

what is extrusion

Answer 7

compression process in which work metal is forced to flow through die opening, produce desired cross sectional shape

Question 8

what is direct extrusion

Answer 8

stationary die, billet moves. high billet/chamber friction force. hollow sections like tubes are produced

Question 9

what is indirect extrusion

Answer 9

stationary billet, die moves. metal flows through ram. low billet/chamber friction

Question 10

what products made with extrusion

Answer 10

tubes and pipes, profiles with constant cross section.
usually hot working - use Al allots, Cu alloys, Mg alloys, Ti alloys, Pb alloys

Question 11

advantages/disadvantages of extrusion

Answer 11

pros: continuous, high production volumes, low cost per pound.
cons: limited complexity - uniform CSA shape only

Question 12

extrusion/drawing

Answer 12

cross section of bar/rod/wire reduced by pulling through die opening. bar drawing for large diameter bar, wire drawing for small diameter bar