Roll-compacting, impregnation and infiltration, Other Engineering

Q. Describe the continuous production of metal strip by roll compacting of powder. Differentiate between impregnation and infiltration.

Ans. Roll-compacting : It is the process of converting loose powder into a green compact of accurate shape and size.

        During operation, the powder is compressed to nearly one-third of its original volume. A large number of presses generally used for this purpose are either mechanical or hydraulic or a combination of both. Mechanical presses are suitable for low pressures. But their production rate is high. Hydraulic presses are best suited where higher pressures are employed. They also facilitate production of parts of uniform density, which is not possible with mechanical presses.

        The metal powder compacted into the form of metal strips by passing a discrete stream of powder through a pair of rolls rotating in opposite directions. It is known as roll-compacting or roll-pressing as shown in fig.

        Impregnation : It is a process of introducing oil, grease wax or other lubricating materials when self lubricating properties are desired. The process consist of immersing the parts in a both of lubricant which is heated to a temperature of about 95ºC. The porous parts are kept for a period of about 10 to 20 minutes in the bath. The impregnation can also be carried out by drawing oil through the part by vacuum. The finish bearing may be saturated by a considerable quantity of lubricant 20% by volume. The lubricant is retained in the part by capillary action and is withdrawn by heat or pressure as required in service.

       The impregnation is also done by low melting metals or preferably by plastic for the purpose of eliminating surface pores for plasting the pm/parts.

       Infiltration : It is a process in which molten metal of a lower melting point than the major constitutent is forced under pressure to fill the pores. A proper size piece of copper brass is placed either on the top or bottom of the part and when this secondary metal melts, during sintering of iron, due to capillary action the infiltrate soaks through the porous part.

       The effect of infiltration is to give the p/m parts higher tensile strength, fatigue strength and hardness.

       The density is increased from 70% to 100%. In addition to these it seals the surface porosity so that secondary operations. Such as plating can be carried out if required. 

Posted Date: 8/3/2012 4:53:37 AM | Location : United States







Related Discussions:- Roll-compacting, impregnation and infiltration, Assignment Help, Ask Question on Roll-compacting, impregnation and infiltration, Get Answer, Expert's Help, Roll-compacting, impregnation and infiltration Discussions

Write discussion on Roll-compacting, impregnation and infiltration
Your posts are moderated
Related Questions
HELP IN ELECTRONIC...I AM DOING ELECTRONIC ENG. ... GUIDE ME THE WAY...

Question: (a) Describe the spreading and dispreading processes of a CDMA system. (b) Autocorrelation properties are used to recover the signals correctly at the receiver. Ex

in the circuit what is the voltage at point with respect to ground

Auxiliary power unit oil System: A sump at the bottom of the gearbox collects the returning oil, in some APU's the rear face of the sump is finned and let into the intake plenu

what is clampers and how many types

Explain derivatives in terms of capital markets The term mixture indicates that it has no separate value that is its value is entirely resulting from the of the actual resources


Flifla sells tomatoes every day in Suk al Marqazi, the downtown fruit and vegetable market. He finds that he can order tomatoes in crates of 25 kg and he is able to stock a maximum

hardness of bore well water is less than sea water