| 1. Introduction:Mechanical properties
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| | set-up Cryogenic treatment of the tool
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| like hardness, wear resistant, tensile
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| | was done by indirect cooling and with no
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| strength are very important for cutting
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| | direct contact with liquid nitrogen. The
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| tool. The Cryogenic treatment on metal
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| | Cryo-treatment is a doubled walled
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| has been extensively employed since many
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| | stainless steel container with
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| years for various application like
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| | inter-spaced filled with Polyurethane
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| stabilizing dimension of precision
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| | foam. The top cover made of stainless
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| machined part and gauges with change in
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| | steel has a double end shaft fan motor
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| temperature, removal of internal
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| | assembly mounted centrally. The liquid
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| stresses, improving wear resistant and
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| | nitrogen, connecting valve, pressure
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| hardness.Cryogenic treatment of metal
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| | gauzes, feed through and outlet
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| parts means cooling these parts at a
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| | connections are all mounted on the top
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| predetermined rate, up to a given
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| | flange.Below the top cover a cylindrical
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| Cryogenic temperature (-80C),
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| | buffer tank is mounted where the liquid
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| maintaining these parts at that lowest
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| | nitrogen get collected and evaporated
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| temperature for a given duration of time
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| | vapour are vented through a vent pipe.
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| and then allowing these parts to warm-up
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| | The shaft of the fan motor assembly
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| at a given warming-up rate to room
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| | passes through this buffer tank and has
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| temperature.So the main variable of the
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| | fan blades mounted on both sides. A
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| Cryogenic treatment are:a. Rate of
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| | copper disk has been fixed to the bottom
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| cooling.b. The lowest maintained
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| | of the buffer tank to ensure better heat
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| temperature for a given duration.c. The
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| | transfer. Aluminium fans are fixed at the
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| duration for which the specimen are
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| | bottom to ensure forced convection
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| maintained at the lowest temperature.d.
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| | cooling of the space inside the
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| The rate of warming up(Chillar, Agarwal.
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| | Cryo-treatment chamber. The specimen kept
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| 1995)Cryogenic treatment has been
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| | in the stainless steel tray can be cooled
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| successfully applied on steel to improve
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| | by two ways:i. A circulating fan housed
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| its mechanical properties. This occurs
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| | below the buffer tank, induce forced
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| because of transformation of almost all
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| | convection currents picking up cold from
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| the retained Austenite in steel to
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| | stored liquid nitrogen in the buffer tank
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| Martensite thereby making the steel more
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| | downward over the specimen. The cold gas
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| Wear resistant.2. Literature
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| | moving down to the bottom of the chamber
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| Survey:Evidence of Cryogenic treatment
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| | gets cooled and moves radially sideways.
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| was found during 1937 in Soviet Union
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| | These gases re-enter on the fan region
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| (Carry and Robert 1980). Metals are
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| | through the opening of the slots in the
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| gradually cooled to cryogenic temperature
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| | aluminium fins. Thus forced convection
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| (-80C), soaked for a prolonged
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| | current loop is established within the
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| period and warmed to room temperature at
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| | chamber.ii. Part of the liquid nitrogen
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| a predetermined rate, the lattice
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| | stored in the buffer tank is made to
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| structure of the atoms change due to
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| | circulate over the shroud by
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| stress being relived during Cryogenic
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| | thermo-syphon effect. To facilitate this
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| treatment. In case of ferrous metal, the
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| | a copper tube is connected to the buffer
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| soft ductile FCC structure Austenite gets
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| | tank and is brazed on the outer wall of
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| converted into strong and harder BCC
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| | the shroud over its entire length. A
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| structured Martensite. Apart from this, a
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| | solenoid valve is operated by a PID
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| wide precipitate of newly formed
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| | controller with predetermined set points,
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| Eta-Carbides (responsible for increased
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| | is used to regulate the liquid nitrogen
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| wear resistance) into the hard Martenside
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| | supply to the chamber. The temperature of
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| structure induces a dense lattice
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| | the specimen is measured using
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| structure.Some theories by Zhmud (1980)
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| | temperature sensors.Another method can be
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| are:a. Cryogenic treatment was effective
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| | by using refrigerator with ethyl alcohol
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| for intemperate and adequate tempered
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| | and dry ice as refrigerant for Cryogenic
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| tool.b. The soaked time (5min to 10 hrs)
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| | treatment. The specimen to be treated was
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| had no effect on the tool life.c. A
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| | placed in a clean and dry thermocol box.
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| decrease in tool life within 5-7 days
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| | The specimen with the thermocol box were
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| after treatment and increases again with
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| | then kept in a refrigerator for duration
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| repeated treatment.Cryogenic treatment
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| | of 12hrs to bring down the temperature of
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| can be performed by different methods.One
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| | the specimen to 0C. After a
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| of such methods consists of a
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| | period of 12 hrs, dry ice was added into
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| Cryo-treatment chamber and an auxiliary
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| | the thermocol box using a spatula.
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| liquid nitrogen supply system. In this
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