question_answer

Which one of the following statements in extrusion processes in not correct?

A) In forward extrusion, the problem of friction is prevalent because of relative motion between heated metal billet and cylinder wall

B) In backward extrusion, the problem of friction is completely eliminated

C) Forward cold extrusion is similar to forward hot extrusion forces except extrusion ratios are higher and extrusion pressures are less

D) Cold extrusion forging is similar to impact extrusion except that side walk are much thicker and their height is smaller.