CRYOGENICS Grinding

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BY:

ADITYA AGGARWALME-1(3RDYEAR)

ROLL NO. 29

CRYOGENIC GRINDING

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1. INTRODUCTION2. CRYOGENS AND ITS APPLICATIONS3. CRYOGENIC GRINDING PROCESS

4. ADVANTAGES OF CRYOGENICGRINDING5. APPLICATIONS OF CRYOGENICGRINDING6. DISADVANTAGES OF CRYOGENIC

GRINDING7. EXPERIMENTAL STUDY8. CONCLUSION

LEARNING OBJECTIVES

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The word cryogenics originates from Greek

word cryo, which means cold.

Temperatures as low as -180C are attained in

cryogenic systems.

The extremely low temperature are produced

by using substances called cryogens 'such as

liquid nitrogen and liquid helium.

Cryogens are stored in vessels called as Dewar

flask which provides good insulation.

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The branch of physics andengineering that involve the

study of very low temperatures,

how to produce them, and howmaterials behave at those

temperatures.

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CONT.

4. Cryogens are used in food industry for foodhandling and processing.

5. Cryogens are used in various machining

operations such as cryogenic deburring, cryogenicdeflashing, cryogenic tempering and cryogenicgrinding.

6. Cryogens like liquid nitrogen are used in specialchilling andfreezing applications.

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CRYOGENIC GRINDING PROCESS

1. Cryogenic grinding , also known as freezer milling/freezer grinding/ cryomilling is the act of cooling or

chilling a material and then reducing it to smallerparticle size.

2. Almost all materials embrittle when exposed to lowtemperature. Cryogenic size reduction utilizes the

cooling effect of liquid nitrogen to embrittle materialsprior to and or during the grinding process.

cont.

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CONT.

3. Materials which are elastic in nature, which have lowmelting points, which have low combustiontemperatures and which are sensitive to oxygen canbe ideally machined by cryogenic grinding process.

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EXPRIMENTAL SET-UP

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TYPES OF CRYOGENICGRINDING/MILLING

Freezer millingCryomilling

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Freezer milling is a type ofcryogenic milling that uses asolenoid to mill samples. Thesolenoid moves the grindingmedia back and forth insidethe vial, grinding the sampledown to analytical fineness.

FREEZER MILLING

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Cryomilling is a variation of mechanical milling, inwhich metallic powders or other samples (e.g.

temperature sensitive samples and samples withvolatile components) are milled ina cryogen (usually liquid nitrogen or liquidargon) slurry or at a cryogenics temperature under

processing parameters, so a nanostructuredmicrostructure is attained.

CRYOMILLING

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Cryogrinding of steel :-The large amount of heat generatedduring grinding at high speed raises the temperatures atcutting zones excessively. Cryogens such as liquid nitrogenwill help in reducing the effect of heat on tool and workpiece, thereby increasing the life of the tool.

Thermoplastics :-Nylon, PVC, Polyethylene, Polypropyleneare usually machined using cryogenic grinding to form finepowders.

Thermo sets :-Synthetic and natural vulcanized rubber andmaterials such as bakelite can be economically machinedwith cryogenic grinding and recycled.

APPLICATIONS

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Higher material removal rate can be achieved.

Tool wear and tear is minimized to a great extent.

Grinding forces are reduced. Cryogens act as coolant and hence the effects of

overheating of the tool and work piece are reduced.

Materials which are soft and elastic in nature such as

rubber can be easily machined with this process. Smaller particle size can be achieved.

Better surface finish and dimensional accuracy can beachieved.

ADVANTAGES

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Cryo-grinding do have distinctive advantages over theconventional cooling processes, but

The application of cryogen in moist atmosphere may

cause formation of ice around the delivery nozzle andthe piping system carrying the cryogen. This maycause a possible blockage in the delivery system ofliquid nitrogen.

Economic considerations should be solved.

DISADVANTAGES

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Cryogenic grinding improves product quality bycontrolling thermal effects.

Oxidation and surface burning are eliminated.

Surface damage is eliminated.

Finer particle size is achieved.

Material removal rate is high.

The process is economical in the long run.

CONCLUSION

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THANK YOU ALL