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Controlling the hardness of workpieces during immersion cooling


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f controlling the hardness of workpieces is during emotion cooling this many metal workpieces must be subjected to a heat treatment in order to obtain certain material characteristics
the desired characteristics of the workpiece depend to a great extent on the specific cooling process as well as the type of alloys these was pieces are heated to a
temperature of 850 degrees celsius and the alloy components
mainly become dissolved in older facilities each part is quenched in an oil bath without any protective measures as a result of a change in the high-temperature phase the desired metal a graphic structures produced the formation of martensite begin
suddenly in the parts after the temperature falls below the martensite start temperature the cubic plane centered austenite lattice is transformed into a tetragonal plane centered martensite lattice during this transformation the volume increases as does the tension of the atom letters as a result the material attains a higher degree of hotness
the degree of hotness can for instance be
determined by diamond penetration testing once the penetration depth and
the diameter have been calculated this provides a measure for the degree of hotness with increasing distance from the surface of the workpiece the indentations become larger and the surrounding area becomes malleable in soft on hardened workpieces the diamond indentation is at its largest and the degree of hotness at its lowest In the
following the process for the cooling down of heated metal parts in water or oil and polymers will be examined in the laboratory tests the progression of temperature and the weighting process on the sampling surface are recorded and mapped 1st water the steel cylinder heated at 850 degrees celsius is immersed in the liquid
characteristic values of the quenching medium can be obtained during the course of the surface waiting in the water the cooling is
characterized by 3 phases the film boiling the nucleate boiling phase and convective heat transfer the rising of the nuclear boiling front shown here slowed down by a factor of 20 and the part
which has just been immersed is enclosed by a film of vapor and if the surface temperature falls at any part along the workpiece for instance on its lower age is below the light and frost temperature and a permanent wetting of the surface nucleate boiling takes place the the weighting can also begin at various
defects for example on the lower and upper age of the cylinder if the light and frost temperature is 1st reached here uh the
conductivity changes between the sampling surface and the counter electrode also must at the same time are measured the Reds temperature curve indicates the calling process the yellow conductivity curve indicates the wetting process if the vapor film collapses liquid wets the sample and conductance increases the weighting
process is also dependent on the geometry of the workpiece In the case of the ball the film boiling is followed instantly by the partial film evaporation and at the same time the surface temperature of the whole surface area falls below the light and frost temperature on the left and the lower side of the ball the partial film boiling changes to a nuclear boiling varies with the regular front in
a propeller is used to generate a current in the water bath at the small flashes indicate the direction of the current as a result of the current the weighting process changes at the length
of each face becomes shorter at the respective curve showing the change in
temperature or conductivity indicates the process the yellow curve shows a shortened film boiling and a quicker nucleate boiling phase once more a comparison of the 2 curves without conviction fissuring can be caused in the workpiece by very sudden quenching
same color penetrant testing red liquid is applied 1st it penetrates into the fishes it remains there even after rinsing the surface it if a white contrast agent is now applied the red color is
absolved due to the hygroscopic properties and the fishes are clearly visible a further fall detecting method is based on the fact that
fissures in the workpiece disturb the magnetic field these magnetic disturbances can be made visible by a fluorescent oil we a moderate quenching is achieved by the medium
oil the Orioles quenching capacity is also primarily determined by the weighting process and the viscosity of the the slow-motion shots show the film boiling sampling surface and with the help of the stray ation round the would is a relatively wide hot cell of oil which reduces the cooling capacity In the case of non-conducting electrical quenching media the weighting process
is determined by 4 temperature probes the red curve indicates the progression of temperature in the center of the workpiece the other 3 curves represent constrains surface cooling measured at different levels the transition from film boiling to nucleate boiling phase can be red at the points of discontinuity on each curve
and with surface hardening by induction the area near the surface of the workpieces heated selectively a quiz polymer is
mainly used as a cooling medium during surface hardening it is non-combustible there is relatively little dense smoke and it generally contains no toxic fumes this during emotion cooling in the quiz polymer solution the desired effect is
that the vapor film on the whole surface collapses explosively car air this results in an even cooling i the explosive nature of this phenomenon can easily be seen in slow motions so in the in the beginning of the weighting is caused by large bubbles being released from the upper edge what do think overheated polymer layer forms around the workpiece which ensures a relatively slow cooling of the remaining temperature we we the temperature curves measured in the center of the
test piece decrease slightly the temperature progression of the area near to the surface and the wedding process is not given again the yellow connection curve changes dramatically in accordance to the wetting and jumps to its maximum value we the time-dependent temperature distribution in the cross section of the sample during quenching 1st in polymer is visualized by simulation calculations the whole sample surface cools here practically simultaneously this leads to an even hardness on the surface and minimal distortion during quenching for example in water a
different cooling process occurs corresponding to the beginning of the wetting the cooling starts at the bottom of the workpiece if there is a gradual waiting a large temperature difference results excellent because the characteristics of the parts change during cooling the temperature difference cannot be represented by 1 single temperature curve the the process once
again in order to get a three-dimensional impression of the inhomogeneous temperature progression the sequence stopped after approximately 7 seconds the temperature distribution which is predominant at this point is presented here three-dimensionally TL different hardness values are obtained on the sample surface during this cooling process the hardness falls from the lower end of the sample to its upper end the results obtained in these laboratory experiments I used in the industrial
hardening of workpieces for process controlling in chamber furnaces here
a hardening is being used with clearly visible path currents because of fast awaiting the workpiece at the surface
attains an approximately homogeneous surface hardness the oxidation by
means of combustion prevents the oxidize ation of workpiece during the hardening process
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Formal Metadata

Title Controlling the hardness of workpieces during immersion cooling
Alternative Title Steuerung der Härte beim Tauchkühlen von Werkstücken
Author Tensi, Hans
Stitzelberger-Jakob, Peter
Contributors Schledding, Thomas (Redaktion, Ton)
Thienel, Joseph (Kamera)
Lechner, Kuno (Kamera)
Wittmann, Horst (Kamera)
Frixe, Erwin (Assistenz)
Kemner, Klaus (Ton)
Walter, Jörg (Tonmischung)
Prudlik, Christina (Schnitt)
Fanelli, Franz-Uwe (Schnitt)
License No Open Access License:
German copyright law applies. This film may be used for your own use but it may not be distributed via the internet or passed on to external parties.
DOI 10.3203/IWF/C-1892eng
IWF Signature C 1892
Publisher IWF (Göttingen)
Release Date 1995
Language English
Producer IWF (Göttingen)

Technical Metadata

IWF Technical Data Film, 16 mm, LT, 141 m ; F, 13 min

Content Metadata

Subject Area Engineering
Abstract The quenching of heated components in water, oil and polymer solutions is examined. The wetting process is defined by the type of quenchant used. The cooling behaviour is shown in real time and in slow-motion and elucidated by diagrams. The spatial temperature distribution is visualized by simulations and animation. The measurement of hardness, techniques of crack detection as well as various methods used by hardening companies are presented.
Keywords quenching / components
hardness / components
crack / components
heat treatment
heat transition
Leidenfrost temperature
film boiling
nucleate boiling


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