ASM Cryogenic Treatment Definition

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Cold and Cryogenic Treatment of SteelRevised by F. Diekman, Controlled Thermal Processing

COLD TREATNG OF STEEL is widelyaccepted within the metallurgical profession asa supplemental treatment that can be used toenhance the transformation of austenite to mar-tensite and to improve stress relief of castingsand machined parts. Common practice identi-fies 84 C (120 F) as the optimal tempera-ture for cold treatment. There is evidence,

however, that cryogenic treatment of steel (alsoreferred to as deep cryogenic treatment, orDCT), in which material is brought to a temper-ature on the order of 184 C (300 F),improves certain properties beyond theimprovement attained at cold treatment tem-peratures. This discussion explains the practicesemployed in the cold treatment of steel and pre-sents some of the results of using cryogenictreatment to enhance steel properties.

Cold Treatment of Steel

Cold treatment of steel consists of exposing

the ferrous material to subzero temperatures toeither impart or enhance specific conditions orproperties of the material. Increased strength,greater dimensional or microstructural stability,improved wear resistance, and relief of residualstress are among the benefits of the cold treat-ment of steel. Generally, one hour of cold treat-ment for each 2.54 cm (1 in.) of cross section isadequate to achieve the desired results.

All hardened steels are improved by a propersubzero treatment to the extent that there willbe less tendency to develop grinding cracksand therefore they will grind much more easilyafter the elimination of the retained austeniteand the untempered martensite.

Hardening and Retained Austenite

Whenever hardening is to be done duringheat treating, complete transformation fromaustenite to martensite generally is desired priorto tempering. From a practical standpoint, how-ever, conditions vary widely, and 100% trans-formation rarely, if ever, occurs. Cold treatingmay be useful in many instances for improvingthe percentage of transformation and thus forenhancing properties.

During hardening, martensite develops as acontinuous process from start (Ms) to finish(Mf) through the martensite formation range.Except in a few highly alloyed steels, martens-ite starts to form at well above room tem-perature. In many instances, transformationessentially is complete at room temperature.Retained austenite tends to be present in vary-

ing amounts, however, and when consideredexcessive for a particular application, must betransformed to martensite and then tempered.

Cold Treating versus Tempering. Immedi-ate cold treating without delays at room temper-ature or at other temperatures during quenchingoffers the best opportunity for maximum trans-formation to martensite. In some instances,however, there is a risk that this will causecracking of parts. Therefore, it is important toensure that the grade of steel and the productdesign will tolerate immediate cold treatingrather than immediate tempering. Some steelsmust be transferred to a tempering furnacewhen still warm to the touch to minimize thelikelihood of cracking. Design features such assharp corners and abrupt changes in section cre-ate stress concentrations and promote cracking.

In most instances, cold treating is not donebefore tempering. In several types of industrialapplications, tempering is followed by deepfreezing and retempering without delay. Forexample, such parts as gages, machineways,arbors, mandrils, cylinders, pistons, and balland roller bearings are treated in this mannerfor dimensional stability. Multiple freeze-drawcycles are used for critical applications.

Cold treating also is used to improve wearresistance in such materials as tool steels,high-carbon martensitic stainless steels, andcarburized alloy steels for applications in which

the presence of retained austenite may result inexcessive wear. Transformation in service maycause cracking and/or dimensional changes thatcan promote failure. In some instances, morethan 50% retained austenite has been observed.In such cases, no delay in tempering after coldtreatment is permitted, or cracking can developreadily.

Process Limitations.In some applications inwhich explicit amounts of retained austenite areconsidered beneficial, cold treating might bedetrimental. Moreover, multiple tempering,

rather than alternate freeze-temper cyclingenerally is more practical for transformiretained austenite in high-speed and high-cbon/high-chromium steels.

Hardness Testing. Lower-than-expectRockwell C hardness (HRC) readings may indcate excessive retained austenite. Significaincreases in these readings as a result of co

treatment indicate conversion of austenite martensite. Superficial hardness readings, suas HR15N, can show even more significachanges.

Precipitation-Hardening Steels. Specifictions for precipitation-hardening steels minclude a mandatory deep freeze after solutitreatment and prior to aging.

Shrink Fits. Cooling the inner member ofcomplex part to below ambient temperatucan be a useful way of providing an interfeence fit. Care must be taken, however, to avothe brittle cracking that may develop when tinner member is made of heat treated steel whigh amounts of retained austenite, which coverts to martensite on subzero cooling.

Stress Relief

Residual stresses often contribute to part faure and frequently are the result of temperatuchanges that produce thermal expansion aphase changes, and consequently, volumchanges.

Under normal conditions, temperature gradents produce nonuniform dimensional and vume changes. In castings, for exampcompressive stresses develop in lower-voluareas, which cool first, and tensile stresdevelop in areas of greater volume, which colast. Shear stresses develop between the t

areas. Even in large castings and machinparts of relatively uniform thickness, the suface cools first and the core last. In such casstresses develop as a result of the phase (vume) change between those layers that tranform first and the center portion, whitransforms last.

When both volume and phase changes occin pieces of uneven cross section, normal cotractions due to cooling are opposed by tranformation expansion. The resulting residustresses will remain until a means of relief

ASM Handbook, Volume 4A, Steel Heat Treating Fundamentals and ProcessesJ. Dossett and G.E. Totten, editors

Copyright # 2013 ASM InternationaAll rights reserv

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applied. This type of stress develops most fre-quently in steels during quenching. The surfacebecomes martensitic before the interior does.Although the inner austenite can be strained tomatch this surface change, subsequent interiorexpansions place the surface martensite undertension when the inner austenite transforms.Cracks in high-carbon steels arise from suchstresses.

The use of cold treating has proved beneficialin stress relief of castings and machined parts ofeven or nonuniform cross section. Features ofthe treatment include:

Transformation of all layers is accomplishedwhen the material reaches 84 C (120 F).

The increase in volume of the outer martens-ite is counteracted somewhat by the initialcontraction due to chilling.

Rewarm time is controlled more easily thancooling time, allowing equipment flexibility.

The expansion of the inner core due to trans-formation is balanced somewhat by theexpansion of the outer shell.

The chilled parts are handled more easily. The surface is unaffected by low

temperature. Parts that contain various alloying elements

and that are of different sizes and weightscan be chilled simultaneously.

Advantages of Cold Treating

Unlike heat treating, which requires that tem-perature be controlled precisely to avoid rever-sal, successful transformation through coldtreating depends only on the attainment of theminimum low temperature and is not affectedby lower temperatures. As long as the materialis chilled to 84 C (120 F), transformationwill occur; additional chilling will not causereversal.

Time at Temperature. After thorough chill-ing, additional exposure has no adverse effect.In heat treating, holding time and temperatureare critical. In cold treatment, materials of dif-ferent compositions and of different configurationsmay be chilled at the same time, even thougheach may have a different high-temperature trans-formation point. Moreover, the warm-up rate ofa chilled material is not critical as long asuniformity is maintained and large temperaturegradient variations are avoided.

The cooling rate of a heated piece, however,

has a definite influence on the end product. For-mation of martensite during solution heat treat-ing assumes immediate quenching to ensurethat austenitic decomposition will not result inthe formation of bainite and cementite. In largepieces comprising both thick and thin sections,not all areas will cool at the same rate. As aresult, surface areas and thin sections may behighly martensitic, and the slower-cooling coremay contain as much as 30 to 50% retainedaustenite. In addition to incomplete transforma-tion, subsequent natural aging induces stress

and also results in additional growth aftermachining. Aside from transformation, no othermetallurgical change takes place as a result ofchilling. The surface of the material needs noadditional treatment. The use of heat frequentlycauses scale and other surface deformations thatmust be removed.

Equipment for Cold Treating

A simple home-type deep freezer can be usedfor transformation of austenite to martensite.Temperature will be approximately 18 C(0 F). In some instances, hardness tests canbe used to determine if this type of cold treatingwill be helpful. Dry ice placed on top of thework in a closed, insulated container also iscommonly used for cold treating. The dry icesurface temperature is 78 C (109 F), butthe chamber temperature normally is approxi-mately 60 C (75 F).

Mechanical refrigeration units with circulat-ing air at approximately 87 C (125 F) arecommercially available. A typical unit has thesedimensions and operational features:

Chamber volume, up to 2.7 m3 (95 ft3) Temperature range, 5 to 95 C (40 to

140 F) Load capacity, 11.3 to 163 kg/h (25 to

360 lb/h) Thermal capacity, up to 8870 kJ /h

(8400 Btu/h)

Although liquid nitrogen at 195 C (320 F)may be employed, it is used less frequentlythan any of the previous methods because ofits cost.

Cryogenic Treatment of Steels

Cryogenic treatment, also referred to as cryo-genic processing, deep cryogenic processing,deep cryogenic treatment (DCT), cryogenictempering, and deep cryogenic tempering, is adistinct process that uses extreme cold to mod-ify the performance of materials. (The use ofthe word tempering is a misnomer, because thisis not a tempering process.)

The process is differentiated from cold treat-ment by the use of lower temperatures, thepresence of distinct time/temperature profiles,and its application to materials other than steel

(Ref 1). Cryogenic treatment has been in exis-tence only since the late 1930s, making it a rel-atively new and emerging process. The latedevelopment of the process is mainly due tothe fact that cryogenic temperatures have beenavailable in useful commercial quantities onlysince the early 1900s.

Cryogenic treatment can provide wear-resis-tance increases several times those created bycold treatment with hardened steels (Ref 2).The process is not confined to hardened steels,but also shows results with most metals,

cemented carbides, and some plastics (Ref5). Use of the process on metals other than sproduces similar affects as with steel. Resultthe process include relief of residual stre(Ref 6); reduced retained austenite (in hardesteel); the precipitation of fine carbides in rous metals (Ref 7, 8); and increased wresistance, fatigue life, hardness, dimensiostability, thermal and electrical conductiv

and corrosion resistance (Ref 9).What are cryogenic temperatures? The sci

tific community generally defines cryogetemperatures as temperatures below 150(238 F, or 123 K) (Ref 10). This, admittedis an artificial upper limit. Temperatures upresently in cryogenic treatment are gener185 C (300 F, or 89 K). These are tempetures easily reached with liquid nitrogen. Sowork is being done with liquid helium at teperatures down to 268 C (450 F, or apprimately 6 K).

Cryogenic treatment was made easierachieve and more successful by the develment of microprocessor-based temperature c

trols in the 1960s and 1970s and by pioneering research by Randall BarronLouisiana Tech University. Research into process has been accelerating. The CryogeSociety of America maintains a databasepeer reviewed research papers (Ref 11).

Cryogenic Treatment Cycles

One distinct difference from cold treatmis that cryogenic processing requires a sdrop in temperature in order to reap all beneof the process. The ramp down in temperatusually is on the order of 0.25 to 0.5 C/m(32.5 to 32.9 F/min). The object of this sramp down is to avoid high-temperature graents in the material that can create harmstresses, and to allow time for the crystal latstructure to accommodate the changes thatoccurring.

Typical cryogenic treatment consists oslow cool-down from ambient temperatureapproximately 193 C (315 F), where iheld for an appropriate time. Hold perirange from 4 to 48 h depending on the materAt the end of the hold period, the materiabrought back to ambient temperature at a rof approximately 2.5 C/min (36.5 F/mThe temperature-time plot for this cryogetreatment cycle is shown in Fig. 1. By condu

ing the cool-down cycle in gaseous nitrogtemperature can be controlled accuratand thermal shock to the material is avoidSingle-cycle tempering usually is performafter cryogenic treatment to improve impresistance, although double or triple tempercycles sometimes are used.

It is worthy of note that most time-tempeture profiles have been empirically developSome research is being done to optimize profiles for individual steels. For instance, soresearch indicates the holding time for A

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T42 steel should not be longer than 8 h(Ref 12). In contrast, research indicates thatthe hold time should be 36 h for AISI D2 (Ref13). This indicates there is much research tobe done to optimize the process for all materi-als. Research into the optimal ramp downtimes, hold times, and ramp up times wouldmaximize the effect of the process and mini-mize the time needed to accomplish its results.

There are several theories behind the effectsof cryogenic treatment. One theory involvesthe more nearly complete transformation ofretained austenite into martensite. Thistheory has been verified by x-ray diffractionmeasurements. Another theory is based onthe strengthening of the material broughtabout by precipitation of submicroscopic car-bides as a result of the cryogenic treatment(Ref 7, 8). Allied with this is the reductionin internal stresses in the martensite that hap-pens when the submicroscopic carbide precip-itation occurs. A reduction in microcrackingtendencies resulting from reduced internal

stresses also is suggested as a reason forimproved properties. Studies also show reduc-tion in residual stresses. Another theory postu-lates that the extreme cold reduces thefree energy of the crystal structure and createsa more orderly structure. Another area to con-sider is the basic effect of cold on the crystalstructure of metals. Point defects in the crystalstructure are temperature dependent. Lower-ing the temperature of the crystal structurewill cause the number of point defects in thecrystal structure to change according to:

Nd Nexp Ed=kT

whereNd is the number of defects present,Nisthe total number of atomic sites, Ed is the acti-vation energy needed to form the defect, k isthe Boltzmann constant, and T is the absolutetemperature. Reducing the temperature at asuitably slow rate drives the point defects

out of the structure to the grain boundaries. Inother words, the solubility of vacancies andother point defects in the matrix drops. Thiscould account for some of the effects seenin DCT.

In the past, the absence of a clear-cut under-standing of the mechanism by which cryogenictreatment improves performance had hamperedits widespread acceptance by metallurgists.Some confusion has arisen from the fact thatthere are a number of different effects onmetals, many of which cannot be seen in simplemicrostructural examination of the materialwith a light microscope. The lack of easilydetected microstructural changes led many to

discount the process. Another reason was thegenerally accepted belief that nothing happensto solid objects as the temperature drops.Extreme cold has been available on earth onlyfor about 100 years. Understanding of materialsscience developed with the observation thatheat changes properties. Much of the earlyresearch was centered around determiningwhether or not cryogenic treatment actuallyprovided the advantages claimed. Because theearly research and actual industry usage haveproven the validity of the process, research

now is turning to determine why the resuare seen and how to maximize those results.

Uses of Deep Cryogenic Treatment

Deep cryogenic treatment is used in maways to reduce wear. It is in common use control distortion of metal objects, modify tvibrational characteristics of metals, increa

fatigue life, reduce abrasive wear, and reduelectrical resistance. It is safe to say the appcations for this process are extremely broad.

The process is in commercial use for higspeed steel (HSS) and carbide cutting tooknives, blanking tools, forming tools, and moResearch as far back as 1973 indicates that decryogenic processing results in over three timlife increase in end mills, 82 times life improvment in punches, over two times the life thread dies, six times the life in copper resistanelectrodes, six times the life in progressive diand over four to five times the life in broach(Ref 2). Research estimates a 50% reductiin tooling costs with H13 and M2 steels th

have been deep cryogenically treated (Ref 14Other studies have shown that DCT increas

abrasion resistance of cast iron. Cast iron brarotors consistently show a three to five timlife increase when tested to SAE2707 bradynamometers (Ref 15). This has been validatagainst real-world experience in passenger caracing cars, trucks, and mining vehicles.

Deep cryogenic treatment also has beproven to create a phase change in cementcarbide (Ref 5). A study by the National Aernautics and Space Administration (NASproved the release of residual stresses in weldaluminum (Ref 6), and other studies proincreases in fatigue life in steel springs (R

16) and in load capacity of gears (Ref 17).Deep cryogenic treatment is used in the autmotive racing industry to increase life in virtuaevery engine component. Drive line componesuch as transmission and differential gears, supension springs, torsion bars, axles, suspensimembers, and, of course, brakes are treated.

Deep cryogenic treatment also is in commcial use by musical instrument makers. YamaWind Instruments has done extensive testingDCT and offers the process on its wind instrments (Ref 18). There is much activity in thigh-performance stereo industry in treativacuum tubes, wire, power cords, vacuutubes, transformers, connectors, and more.

Equipment for Cryogenic Treatment

All cryogenic treatment equipment is coprised of a thermally insulated container asome means of extracting the latent heat the payload to reach the desired low temperture. In most cases the insulation is a somaterial that contains small closed cells trapped still air. The thermal conductivity such insulation essentially is that of still, noconvecting air, assuming that the solid mater

Fig. 1 Plot of temperature vs. time for the cryogenic treatment cycle. Tempering may or may not be necessary,depending on the material treated. Some materials require multiple tempering cycles. Some companies arenow treating materials down to 268 C (450 F, or 6 K)

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that encloses the air pockets is of thin cross sec-tion and low conductivity. \Examples are poly-urethane foam, aerogel, and expanded glassfoam. Fifteen centimeters (6 in.) of any of thesewill conduct approximately (15 Btu/h.ft2)across a temperature differential of 204 C(400 F), which exists between the interior ofa refrigerator at 195 C (320 F) and ambienttemperature of 26 C (80 F).

These solid insulating materials are relativelyinexpensive and, in the case of foamed-in-placepolyurethane, can readily fill irregularly shapedcavities. They all suffer from one importantdrawback: temperature cycling establishes atemperature gradient across the insulating slabthat results in differential contraction in thematerial. Repeated temperature cycles ulti-mately result in fatigue cracking of the insula-tion. Energy expenditure to sustain thetemperature difference goes up, and tempera-ture uniformity within the refrigerator maydeteriorate.

The use of vacuum insulation in cryoproces-sor design avoids these problems. A vacuum

insulated container consists of two concentricshells, usually cylindrical, separated by a smalldistance relative to their diameters, which arejoined around the perimeter of one end of theshells. The space between the shells containsreflective insulation and is evacuated to a pres-sure of approximately 533 Pa (106 torr). Thisessentially eliminates heat flow by conductionand convection because most of the conductingor convecting gas has been removed. Heat gainvia infrared radiation is minimized by multiplereflective layers placed in the vacuum space.Heat flow across a vacuum-insulated space,given a temperature difference across the wallsof 204 C (400 F), is (0.008 Btu/h.ft2), a factorof 1900 better than solid insulation of 15 cm(6 in.) thickness (Ref 19). The principle modeof heat transmission into the interior of a vac-uum-insulated container is metallic conductionthrough the perimeter that joins the inner andouter shells.

In addition to providing a barrier to heatflow relative to solid insulation, the vacuum-insulated vessel is immune to thermal cyclingfatigue. Additionally, the vacuum-insulatedvessel can sustain elevated operating tempera-tures far in excess of that permissible with theuse of polyurethane. This permits the post-refrigeration tempering of components in onedevice, eliminating the need for a separate tem-pering oven.

Heat extraction from the payload is effectedby the phase change of a low-boiling-pointfluid. If mechanical refrigeration is used, ahigh-pressure fluid is allowed to expand andbecome a gas within an evaporator coil insidethe insulated space. The evaporator coil is aheat exchanger that absorbs heat from the pay-load via convection, natural or forced, withinthe chamber. This ensures the relatively slowcooling of the payload and avoids thermalshock resulting from too rapid cooling. Rapidcooling can cause shrinkage of the outside of

the cooled component while the relativelywarm interior does not shrink. Tensile stressinduced this way can lead to cracking or the ini-tiation of residual stress, especially at sharpedges. Reaching cryogenic temperatures bymechanical refrigeration for industrial size pay-loads requires multistage refrigeration. Theseare very expensive machines to build andmaintain.

Fortunately, liquid nitrogen is abundant,readily available, and relatively inexpensive. Ithas a boiling point of 196 C (321 F) anda heat of vaporization of approximately150 Btu/liter. It is produced in huge industrialgas production facilities and delivered to thefacility where the expansion and phase changeoccurs, free of the capital and maintenanceexpense demanded by in-house mechanicalrefrigerators.

Two other approaches have been tried buthave difficulties: a hybrid of mechanicalrefrigeration and LN2 (liquid nitrogen) cooling,and a controlled immersion of components intoLN2.

The hybrid approach uses mechanical refrig-eration to do an initial cooling of the payload tosome sub-atmospheric temperature that is wellabove the desired cryogenic range. At that pointa spray of LN2 droplets is showered onto thepayload to bring the temperature down to thedesired point. Unless the mechanical refrigera-tion has sufficient Btu removal rate, the payloadwill be substantially warmer than indicated bythe thermocouple that monitors chamber tem-perature. This causes the LN2 spray to comeon prematurely, with the resultant rapid coolingof parts and the increased possibility ofcracking.

The controlled immersion of componentsinto LN2 has been tried in two versions: thepayload is lowered slowly into a pool of LN2,or a chamber is slowly flooded with LN2 sothe liquid level rises to and eventually coversthe payload.

Both versions suffer from a serious weaknessarising from the effects of fundamental physics.First, the temperature gradient above a pool ofLN2 is very steep. Second, the rate of heattransport between warm solid and a cold gasat 195 C (320 F) is much slower than therate between the same warm solid and a liquidat 195 C. Therefore, in either of the aboveversions, a slow decrease in the distance separ-ating the part and the liquid does not ensure aslow rate of cooling of the part. The risk of

thermal shock is increased by the steep temper-ature gradient above the liquid and the suddenincrease in the heat transfer rate when liquidcontact is made.

Cryogenic treatment is a process that holdsgreat promise to modify and improve productsin many markets, including reducing wear andextending the service life of many components.Continuing research efforts are being underta-ken to understand the underlying science ofDCT so process improvements can be madeand the technology advanced.

ACKNOWLEDGMENT

Article revised and updated from E.A. Cson, Cold Treating and Cryogenic Treatmof Steel,Heat Treating, Vol 4, ASM HandboASM International, 1991, p 203206.

REFERENCES

1. R.F. Barron, A Study of the EffectsCryogenic Treatment on Tool SProperties,

2. R.F. Barron, Yes, Cryogenic TreatmeCan Save You Money!, Fall CorrugaContainers Conference (Denver, CTechnical Association of the Pulp Paper Industry, 1973, p 3540

3. S. Kalia, Cryogenic Processing: A StudMaterials at Low Temperatures, J. LTemp. Phys., Vol 158 (No. 56), Ma2010, p 934945

4. H.A. Stewart, A Study of the EffectsCryogenic Treatment of Tool Steel Prop

ties,Forest Prod. J., Feb 2004, p 53565. A. Yong, Cryogenic Treatment of CuttTools, doctoral thesis, National Univerof Singapore, 2006

6. P. Chen, T. Malone, R. Bond, P. Torres, Effects of Cryogenic Treatmon the Residual Stress and MechanProperties of an Aerospace AluminAlloy, NASA, Huntsville, AL, 2002

7. D.N. Collins, Cryogenic Treatment of TSteels,Adv. Mater. Process., 1998

8. F. Meng, K. Tagashira, R. Azuma, H. Sohma, Role of Eta-Carbide Preciptions in the Wear Resistance Improvemeof Fe-12Cr-MO-V-1.4C Steel, ISIJ Innational, 1994

9. S. Sendooran and P. Raja, MetallurgInvestigation on Cryogenic Treated HTool

10. R. Radebaugh, About Cryogenics, MacMillan Encyclopedia Of ChemisNew York, 2002, http://cryogenics.ngov/AboutCryogenics/about%20cryogenics.htm (accessed July 17, 2013)

11. Cryogenic Treatment Database, CryogeSociety of America, Inc., Oak Park, www.cryogenictreatmentdatabase.org(accessed July 17, 2013)

12. C.L. Gogte, D.R. Peshwe, and R.K. Pakar, Influence of Cobalt on the Cryogecally Treated W-Mo-V High Speed St

Cryogenic Treatment Database, N2010, www.cryogenictreatmentdataborg/article/influence_of_cobalt_on_the_cryogenically_treated_w-mo-v_high_speed_steel/ (accessed July 17, 2013)

13. D. Das, A.K. Dutta, and K.K. Ray, Inence of Varied Cryotreatment on the WBehavior of AISI D2 Steel, Wear, Vol (No. 12), Jan 2009, p 297309

14. A. Molinari et al., Effect of Deep Crgenic Treatment on the Mechanical Propties of Tool Steels, J. Mater. Proc

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Tech., Vol 118 (No. 13), Dec 2001,p 350355

15. SAE2707 Method B, Society of Automo-tive Engineers, July 2004

16. D.L. Smith, The Effect of CryogenicTreatment on the Fatigue Life of ChromeSilicon Steel Compression Springs, Ph.D.thesis, Marquette University, 2001

17. A. Swiglo, Deep Cryogenic Treatment to

Increase Service Life, The InstrumentedFactory for Gears, Chicago, INFACIndustry Briefing, 2000

18. Cryogenic Treated YTR-8335RGS Trum-pets, Yamaha Bell and Barrel, Aug 2010,http://yamahawinds.wordpress.com/tag/cryogenic-treatment/ (accessed July 18,2013)

19. J. Levine, Cryogenic Equipment, HeatTreat. Prog., 2001, p 4244

SELECTED REFERENCES

R.F. Barron, Effect of Cryogenic Treatmenton Lathe Tool Wear, in Proceedings of the8th International Congress of Refrigeration,Vol 1, 1971

R.F. Barron, Cryogenic Treatment ProducesCost Savings for Slitter Knives, TAPPI J.,Vol 57 (No. 5), May 1974

R.F. Barron, Cryogenics CRYOTECH, HeatTreat. Mag., June 1974

R.F. Barron, Cryogenic Treatment of Metalsto Improve Wear Resistance, Cryogenics,Vol 22 (No.5), Aug 1982

R.F. Barron, How Cryogenic TreatmeControls Wear, presented at 21st Inter-PlaTool and Gage Conference (Shreveport, LAWestern Electric Company, 1982

R.F. Barron and C.R. Mulhern, CryogenTreatment of AISI-T8 and C1045 Steels, Advances in Cryogenic Engineering Mateals, Vol 26, Plenum Press, 1980

R.F. Barron and R.H. Thompson, Effect

Cryogenic Treatment on Corrosion Restance, Advances in Cryogenic EngineerinVol 36, Plenum Press, 1990, p 13751379

V.E. Gilmore, FrozenTools,Pop. Sci.,June 19 M. Kosmowski, The Promise of Cryogeni

Carbide Tool J., Nov/Dec 1981 T.P. Sweeney, Jr., Deep Cryogenics: T

Great Cold Debate, Heat Treat., Feb 1986

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ASM Cryogenic Treatment Definition