Mumbai University > Mechanical Engineering > Sem 3 > Production Process 1

Marks: 5M

Year: May 2015

Planetary Rolling Mills:

• The Planetary Mill is a medium output mill for rolling of steel strip.
• Its output is less than continuous mills of many stands but more than the reversing two-high or the three-high mill.
• This mill can be used to roll all metals but it is especially useful for those which have low ductility.
• All forces in the mill are compressive so there are no discontinuities such as sometimes occur in normal rolling practise when the mill.rolls pull the metal into the roll throat.
• The deformation of metal in the Planetary Mill is very rapid and so the temperature of the incoming metal can be raised as much as 300°F while in the mill throat.
• Because of this increase metals can be introduced into the mill at less than critical temperature and raised to proper rolling temperature in the mill itself.
• The advantage of lower than critical entry temperature is reduced scale formation on the slab.
• This results in material saving, lower heating costs, and more importantly, less chance of rolled in scale on the strip surface.
• In operating the Planetary Mill some care must be taken in preparing the slabs for rolling.
• A convex edge is required on the slab so that when spread occurs the strip has a square finished edge. The slab surface must be carefully prepared to remove imperfections. Any marks on the slab surface will be magnified on the strip.
• As a medium producer the Planetary Mill is a good investment. It can produce continuous heavy weight coils • at a rate of approximately one ton, per inch of width, per hour.
• Due to ease of 11 change over" of mill guides and screw down gear the mill can be used to do small orders. Strip produced can be maintained to a tolerance of ± ~ 002 in. on all thicknesses between 060 and 250 in.
• One Planetary Mill can affect the same per cent reduction as a continuous mill of eight stands each of which produced a thirty per cent reduction.

Cluster Rolling Mill

• By using cluster mill, very thin sheets can be rolled to very close on a mill with small diameter work rolls.
• Here each of the work rolls is supported by two backing rolls.
• It is very typical mill.
• The sendzimir mill is a modification of the cluster mill with 20 rolls. which is very well adapted to rolling thin sheets or foil from high-strength alloys.
• Hard materials, including stainless steels, titanium alloys and nickel alloys may be rolled in these mills.