For the heat-treatment of steel, cast iron and aluminium alloys PetroFer Chemie H. R. Fischer GmbH + Co. KG P. O. Box 10 06 45 31106 Hildesheim Germany Telephone: +49 51 21 / 76 27- 0 Fax: +49 51 21 / 5 44 38 www.petrofer.com | [email protected]
Quenchants For the heat-treatment of steel, cast iron and aluminium alloys
PetroFer ChemieH. R. Fischer GmbH + Co. KGP. O. Box 10 06 4531106 HildesheimGermanyTelephone: +49 51 21 / 76 27- 0 Fax: +49 51 21 / 5 44 38www.petrofer.com | [email protected]
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Table of contents
1.1.1
1.21.3
1.3.11.3.2
1.3.31.4
1.51.6
1.71.8
1.9
2.2.1
2.1.1
2.1.2
2.2 2.3
2.4 2.5
2.6
2.7
3.3.1
3.1.13.1.2
3.23.2.1
3.2.2
4.4.1
4.2
GENERAL INFORMATION ON QUENCHANTS PETROFER and quenching
Physical and chemical data The quenching process
Vapour blanket phase Boiling phase
Convection phase The effect of bath temperature
on the quenching process Resistance to vaporization
Ageing resistance, service life and consumption Safety precautions
Maintenance and monitoring Cleaning heat-treated components
QUENCHING OILS
Accelerated quenching oilsLow viscosity accelerated quenching oils
ISOMAX / FASTQUENCH Accelerated quenching oils with high vaporization
stability ISORAPID / FASTQUENCH Hot quenching oils MARQUENCH
Quenching oils for vacuum furnaces VACUQUENCHNormal speed quenching oils ISODUR
Water-washable E-type quenching oilsBiodegradable (mineral oil free) quenching fluids
SYNTHERMTempering oils and synthetic tempering fluids
ISOTEMP / SYNTHERM
WATER-MISCIBLE QUENCHING MEDIAPolymer quenchants
AQUATENSID/AQUACOOLFEROQUENCH
Other water-miscible quenchantsEmulsions AQUANOL / BLACKYNOL WL
Water additive salts AQUARAPID / AQUASAL
QUENCHING SALTSAlkali salts AS 135 / AS 200
Chloride salts GS 405 / 406
Dedicated to quality
Founded in Germany over 50 years ago, PETROFER has attained market leadership in many areas through its dedication to cus-
tomer service and product development.
Today, PETROFER’S commitment to its customers is stronger than ever and continuous investment in personnel and resources
will ensure that the company is more than capable of meeting the needs of its customers in the forseeable future.
PETROFER products play a vital role in a wide variety of industri-al applications such as heat-treatment, metalworking, cleaning,
wire drawing, corrosion prevention, lubrication, hydraulics and in paper-manufacturing processes. In addition, PETROFER has
developed products for a wide range of other speciality appli-cations.
The excellence of today’s product range is the result of the company’s philosophy of continuous improvement and the de-
dication of PETROFER personnel at the development centre in Hildesheim, Germany.
Environmental compatibility and health and safety have been key factors in developing today’s range of PETROFER products and,
in keeping with its position as a market leader, the company’s goal has always been to provide customers with the most ad-
vanced technology possible.
From its origins in central Europe PETROFER has developed a worldwide network of associates and distributors to ensure that
the needs of its international customers can be met completely. Wherever you are located, PETROFER chemists and engineers
will work with you to find the optimum solution for your process.
PETROFER’S commitment to quality assurance and the envi-ronment is reflected in the company’s accreditation to ISO/TS
16949, ISO 9001 and DIN EN ISO 14001.
Wherever you are, you can count on PETROFER’S expertise, qua-lity, and dedication to meet your needs.
2 3
By having our own extensive development facilities and a complete range of pro-ducts we can ensure that the best solution for your needs is achieved. Many factors
are important in choosing the most suitable quenchant:
– hardenability of the steel – component details (size, shape etc.)
– metallurgical properties required – furnace equipment
– operator safety – post-treatment
– environmental issues
As many variables often have to be considered, it is important that a comprehensive knowledge of the quenchant is available i.e.
– physical and chemical data – quenching properties
– resistance to evaporation – thermal and ageing stability
– physiological and ecological properties
This brochure provides a general overview of quenching and details of various quen-chants in our range and their potential applications.
1. General information on quenchants
1.1 PETROFER and quenchingThe metallurgical properties of heat-treated steel components are primarily depen-
dent upon the austenitizing conditions, the hardenability of the steel and the quen-ching process used.
Modern heat-treatment processes are forever making new demands on quenching fluids and PETROFER’s extensive development programmes ensure that our pro-
duct technology is more than capable of meeting these new requirements. These programmes are designed not only to improve the technical properties of our quen-
chants but also to provide economic and environmental benefits.
We are constantly screening new raw materials for their suitability of use in quen-chants and our existing product range is reviewed continually to ensure that the best
available technology is used.
By using this approach, and testing new products not only in our own laboratory heattreatment facility but also in collaboration with equipment manufacturers, we
can offer you the most comprehensive range of quenchants available today:
ACCELERATED QUENCHING OILS HOT QUENCHING OILS
BIODEGRADABLE QUENCHING OILS VACUUM QUENCHING OILS
WATER-BASED POLYMER QUENCHANTS, NON-FLAMMABLE MOLTEN SALT BATHS
4 5
Figure 1: Application temperature range as a function of oil viscosity, for various types of quenching oils.
1. 2 Physical and chemical data
Important data used for identifying petroleum products are typically: viscosity, flashpoint and specific gravity. Unfortunately, however, these properties do not determine the suitabilty of an oil for use in quenching.
Consumption of a quenching oil depends not only on viscosity but also on the resistance of the oil to evaporation. Figure 1 shows that the recommended application temperature range of various quenching oils ensures that their viscosity at the
working temperature is similar and, with regard to the question of consumption, relatively low.
Flash-point is, however, especially important in that it limits the application temperature range of an oil. Typically the upper temperature limit should be approximately 60 °C below the oil’s flash point.
Specific gravity of a pure mineral oil can give an indication of its origin. However, it can be significantly modified by additives and therefore the quality of a quenching oil cannot be determined on the basis of its specific gravity.
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Figure 2:Various ways of showing the cooling characteristics of a quenchant.
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1. 3 The quenching process
A quenchant is characterized primarily by its quenching properties and these are difficult to describe in words. Descrip-tions such as ”harsh” or ”mild” are of little use in this technological era. The quenching process can however be studied
using test probes such as:
– nickel and nickel alloy probes: cylinders 12,5 mm Ø (ISO 9950) or a ball (GM-test)
– steel probes, 3-80 mm Ø (Meinhardt-method)
– a silver ball, 20 mm Ø (MPI-silver ball method)
– silver cylinders 8or16mm (Cetim method AFNOR NFT 60178)
Usually the cooling effect of the quenchant is shown either by plotting temperature vs. time or by plotting rate of cooling vs. temperature. Figure 2 shows the connection between the two methods of representation.
For every quenchant, whose boiling range is below the temperature of the component to be treated, the cooling process occurs in three phases (Figure 3).
The three phases and their importance to the quenching process are described on the following pages.
OIL BATH TEMPERATURES
correct temperature range optimum working viscosityt
temperature too lowhigh viscosity,
reduced agitation, increased drag-out loss
temperature too highunnecessary smoke formation,
increased fire hazard
6 7
1. 3.1 Vapour blanket phase
A vapour “blanket” forms on the component immediately after immersion in the quenchant. This vapour layer acts as an insulator because of its low thermal conductivity and therefore the cooling rate in this phase is low.
The duration of this phase depends essentially upon the quenchant’s composition. Our accelerated quenching oils have a very short vapour blanket phase and, in this respect, are superior to most other quenching oils.
A short vapour blanket phase is not only necessary to avoid undesirable pretransformation microstructures but it also ensures a steady lowering of temperature on the total surface of the component thus minimizing thermal stress and distortion.
INFLUENCEOFTHECOOLINGPHASES
short vapour phasefast, homogeneous cooling of the
entire workpiece surface
wide boiling phasegood heat extraction
from larger diameters
cooling properties in the
convection phase
can be influenced strongly by agitation
1. 3. 2 Boiling phase
After a period of time, depending primarily upon the quenchant and component geometry, the vapour blanket starts to break down and the boiling phase begins.
Heat is conducted away at an increasing rate by evaporation of the quenchant at the component’s surface. The rate of cooling reaches its maximum and as the surface temperature falls boiling becomes weaker and finally ceases.
Figure 3:The phases of the cooling process of quenchants having a boiling temperature below the quenching temperature.
vapour blanket phase boilingphase convectionphase
8 9
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Figure 4:Effect of various cooling characteristics on achievable hardness. (TTT-diagram C45, unalloyed steel 0,45 % C).
58 HRC 27 HRC
1. 3. 3 Convection phase
In the last phase of cooling heat is conducted away only by convection. Consequently cooling in this phase can be significantly affected by circulation of the quenchant.
A high degree of cooling in the convection phase will result in deeper hardening of the component.
For evaluation of the cooling curves shown in Figure 2 (page 7) the following points are therefore important:
– duration of the vapour blanket phase – temperature range of the boiling phase
– the cooling rate during the convection phase and the temperature at which it begins.
The maximum cooling rate cannot be used to compare quenchants as it only shows the steepest slope of the tempera-ture/time curve and not the position of the curve in relation to the TTT diagram.
The TTT diagram in Figure 4 shows that the duration of the vapour blanket phase is of considerable importance in the selection of a quenchant. A short vapour blanket phase is necessary when quenching low alloy or plain carbon steels as
only a few seconds (or, in extreme cases, fractions of a second) are available for the temperature to fall below the critical temperature range of approx. 600-500 °C. If this requirement is not met, undesirable soft structures such as bainite,
pearlite, troostite and possibly ferrite occur.
For the hardening of alloy steels, where the TTT curve lies further to the right, the duration of the vapour phase is less critical, but the comments made in section 1.3.1 regarding uniform cooling of the surface to reduce thermal stress and
distortion, should be borne in mind.
10 11
1. 4The effect of bath temperature on the quenching process
Quenching oils do not, for all practical purposes, change their cooling characteristics when their bath temperature remains within the recommended working range.
Only extremely low or greatly elevated temperatures lead to lengthening of the vapour phase and thus a change in the performance of the oil.
However, aqueous quenchants are considerably more affected by bath temperature. This is caused by the much smaller dif-ference between the working temperature range and the boiling range of aqueous solutions in comparison with oils (water
boils at about 100 °C whereas oils boil from about 300 °C upwards). Consequently, when aqueous media are being used, bath temperatures must be kept constant within relatively narrow limits. Figure 5 shows the influence of bath temperature
on the quenching performance of several fluids.
1. 5Resistance to vaporization
The description of the cooling process given in the preceding sections refers to quenching of individual components. If components are quenched in baskets, or batches, then the quenchant’s resistance to vaporization is vital to the achieve-
ment of optimum and consistent hardness.
In batches of components a vapour ”cushion” forms at the start of quenching and this cushion envelopes the whole batch.
Consequently, by using a quenchant which is resistant to vaporization, this vapour cushion within the batch rapidly decays and all the pieces in the batch are cooled evenly.
The use of water-miscible quenchants, which are inevitably less resistant to evaporation, therefore requires special consi-deration for batch processes and, in most cases, quench oils are preferred due to their increased resistance to vaporization.
Good resistance to evaporation is also necessary for the successful use of a quenchant in sealed furnaces (integral quench furnaces) i.e. where the quenching bath is operated under a protective atmosphere.
Figure 5: Change in quenching speed in relation to bath tempera-ture (shownschemati-cally).
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INFLUENCE OF THE BATH TEMPERATURE ON THE QUENCHING PROPERTIES
quenching oilsinsignificant when the oil is within
its working viscosity range
polymer solutionsconsiderable, depending on the type of polymer, may be used
advantageously to adjust special quenching properties
water very distinctive
Figure 6: Test-equipment for vaporization-stability.
12 13
1. 6Ageing resistance, service life and consumption
Resistance to evaporation has a considerable effect on consumption and thus on oil bath economics. Experi-ence has shown that, on batch quenching, probably more oil is lost through evaporation than through “drag-
out” by the components.
Ageing resistance is, however, of the greatest importance in determining the economics of any oil bath. Oils having poor oxidation resistance will form a sludge, after a short period in use, and this normally results in
deposits on the cooler; the coldest place in the quenching bath.
Ultimately, discoloration appears on the surface of the treated components which is either difficult, or impos-sible, to remove. At this stage replacement of the oil is unavoidable.
During the development of our quenching oils we have placed great emphasis on their resistance to oxidation (ageing) by using highly stable base oils and, in many cases, sophisticated proprietary additive packages.
Several important points need to be observed, when using an oil bath, in order to achieve the optimum ope-rating conditions.
In order to keep the thermal loading within limits, and also to avoid severe variations
in the working temperature of the bath, a relationship between the weight of the
batch (or hourly throughput of the furna-ce) and the volume of quenchant must be
maintained.
This relationship depends upon the con-ditions of use of the oil and upon the size
of the components. Large components which take longer to cool cause a lower
thermal loading to the oil bath than tight-ly packed batches of small components
which give off their heat rapidly.
Consequently the following values are only intended as a guide to the relation-
ship between the weight of quenching oil and the gross weight of the batch to be
quenched:
– open oil baths: 10:1
– sealed furnaces: 10:1 to 7:1
– hot quenching oils used at their highest temperatures 10:1 to 15:1
These values can also be used where quenching of small batches at short inter-
vals takes place and the hourly throughput of steel is then used in the calculation.
The following points must also be obser-ved, in particular when operating open hot
oil baths:
STABILITY OF QUENCHANTS
high evaporation stability of oils
avoids trouble some smoke formation, reduces consumption
good oxidation stabilitylong servic elife, avoids formation
of oil sludge
thermal stabilityinsignificant smoke formation–
no change in the basic properties
Figure 7b: Quenching oil with poor ageing resistance after an oxidation test.
Figure 7a: Quenching oil with good ageing resistance after an oxidation ageing test.
– the cooler and heating elements should not be made of copper as this acts as a
catalyst in the oxidation of all mineral oil products.
– the level of agitation in the system must not be excessive such that air is drawn
into the oil. This condition will result in foaming and increased oxidation of the
oil.
– the heating area loading of the heating elements should be limited to about 1
W/cm². If a higher loading is used good movement of oil in the area of the ele-
ments must be maintained to avoid overheating.
The life of water-miscible quenchants is usually limited by several factors. In the
case of surface hardening operations the solution often has to be replaced because
of the effects of contamination from previ-ous processes.
The thermal loading can also take its toll in the long term. In view of this, and the
need to control the concentration of water miscible quenchants, more intensive mo-
nitoring is required for these products.
14 15
1. 7Safety precautions
Quenching oils are combustible liquids and in the quenching process the temperature of the components being treated is usually well above the flash point of the oil. However, providing simple precautions are taken, there are no fire hazards
in practice.
Ingress of water into quenching oil baths (typically through a leaking cooler or as condensate) does, however, create a special hazard. As little as 0,1-0,3 % water-contamination can considerably increase the fire hazard as well as changing
the quenching characteristics of the oil significantly. Our own publications
“Water in Quenching Oil?” and “Oil Fires in Heat Treatment Shops and their Avoidance”
provide detailed information about these subjects.
The pamphlet “For your own Safety” also contains important guidelines for commissioning and operating oil baths. If water-miscible quenchants are used, these are incombustible and therefore no fire hazard exists.
NEGATIVE FACTORS WHEN WORKING WITH QUENCHING OILS
contamination with water change of the quenching properties,
high fire hazard
bath temperature too close to the flash point
increased fire hazard
immersion speed of the batch is too low
strong flame formation, increased fire hazard,
trouble some smoke- and soot-formation
contamination with fire extinguishing medium
certain extinguishing powders as well as all foams change the quenching
characteristic and other properties
drag-in of soot into E-oils may lead to stains on the work pieces
1. 8Maintenance and monitoring
Aqueous quenchants must be carefully monitored with respect to both operating temperature and the concentration of the solution. Our instructions should be carefully followed to ensure successful results.
Under normal operating conditions quenching oils do not require regular monitoring. Attention should, however, be paid to ensuring the working temperature of the oil is maintained and that the temperature never exceeds one which is at least
60 °C below the oil’s flashpoint before quenching a batch. The oil should also be regularly checked for water contamination.
We recommend checking oil baths at least annually and water-miscible quenchants at shorter intervals depending upon the operating conditions.
16 17
NEGATIVE INFLUENCES ON THE CLEANING PROCESS
insufficient agitation in the cleaning bath
remaining oil residues, especially in tightly packed batches
insufficient oil separation from the washing bath, insufficient
washing properties of the cleaner
oil residues remain on the parts, trouble some smoke formation
during tempering
insufficient skimming, oil floating on top
of the washing bath
washed batch may pick up oil when being withdrawn
1. 9Cleaning heat-treated components
When water-miscible quenchants are used, post cleaning of the heat-treated components is often unnecessary, even before tempering. However when high
concentrations are being used rinsing of the components is recommended.
PETROFER’s quenching oils will produce hardened components with a bright fi-nish, providing of course there was no prior surface oxidation, suitable for further
treatment, such as electroplating, without problems. Oil residues do not burn into the surface of the metal and therefore can be easily removed.
Removal of quenching oil generally requires the use of hot cleaners, added to the rinse water, or an emulsifiable oil (E type oils, see 2.6.) should be used. Degrea-
sing with solvents in a soak tank or in vapour is also possible.
The hot cleaner chosen should be formulated to provide rapid release of the quen-ching oil so that it can be easily removed from the rinse tank.
PETROFER has developed “FEROCLEAN” for this purpose, thus enabling rinse water to be used for longer periods with savings in disposal costs. For removal of
separated oil the use of weir systems, or oil skimmers, is practical.
Even emulsions from E-type quenching oils are destabilized when small quanti-ties (0,5-2 %) of FEROCLEAN are added to the rinsing water.
Centrifuges also enable very good oil separation from rinse water and can be used for both conventional and E-type oils.
In the following pages our range of quenchants, subdivided into groups, is described. Individual product information is available for all of the products listed.
18 19
Designat ion
viscosity at 40 °C (mm2/s)
application temperature range (°C)
ISOMAX 160 12,2 40 –70
ISOMAX 166 12,5 40 –70
ISOMAX 169 14,0 40 –70
FASTQUENCH 180 14,5 40 –70
2. Quenching oils
2.1Accelerated quenching oils
Accelerated oils are those quenching oils which are treated to enhance quen-ching performance. Until recently such treatment was only effective in low vis-
cosity oils but our continuing development work has also made it possible to provide higher viscosity, hot quench oils with enhanced cooling properties.
2.1. 1Low viscosity accelerated quenching oils
Low viscosity accelerated quenching oils are used mainly in hardening plain carbon and alloyed quenching and tempering steels. Good penetration and/or
through-hardening can be achieved even with large components.
ISOMAX FASTQUENCH
These oils are generally used in open baths. For sealed furnaces the more vapori-zation resistant ISORAPID oils are preferred.
Some typical applications are: (depending on the heat-treatment equipment
sometimes ISORAPID oils may be preferable) – hardening of high tensile bolts, screws, nuts, washers etc.
– heat-treating of die-forged parts – hardening of hand tools
– hardening direct from hot forging temperatures – heat-treatment of bar and sections
– hardening of leaf and coil springs
20 21
2.1. 2
Accelerated quenching oils with high vaporization stability These oils have been specially designed for use in sealed integral quench-furna-
ces. Their high resistance to vaporization prevents the furnace atmosphere from being affected by oil vapours and also ensures rapid decay of the vapour blanket
on quenching. In this way, all the parts in the batch are uniformly, and rapidly, cooled.
ISORA PIDAs a result of their high resistance to vaporization these oils are also particular-
ly useful in continuous furnaces, where large quantities of components (usually small parts) reach the oil-bath simultaneously and it is therefore important to
avoid the formation of a long lasting vapour cushion.
Additionally it should be noted that using high vaporization stability oils in open quench tanks will also reduce smoke and flame formation. This can be extremly
beneficial when direct quenching from forging temperatures or quenching in pit furnaces.
These oils are also used successfully for low distortion hardening of transmis-sion parts. The low level of distortion is achieved by the short vapour blanket
phase of these oils, which effects a fast and uniform cooling of the whole of the component’s surface.
FASTQUENCHFASTQUENCH accelerated quench oils are formulated from specially refined oils
and semi-synthetic and synthetic additives. Their vapour phase is even shorter than that obtained with standard accelerated oils which enables a more uniform
transfer of heat from the component and thus minimizes distortion.
In addition, the evaporation resistance is also higher than that of accelerated oils in the standard line.
The data for a typical product – FASTQUENCH 293 – are shown in the table. This oil technology is also available for hot quenching oils (e.g. MARQUENCH 844 HY).
*) The use of MARQUENCH hot quenching oils is recommended for continuous operation in this temperature range.
Designat ionviscosity at 40 °C
(mm2/s)application
temperature range (°C)
ISORAPID 221 21 50 – 80
ISORAPID 229 FQ 17 50 – 80
ISORAPID 277 24 50 – 80 (max. 130)*
ISORAPID 277 HM 25 50 – 80 (max. 130)*
ISORAPID 455 50 50 – 100 (max. 150)*
ISORAPID 459 49 50 – 100 (max. 150)*
FASTQUENCH 293 31 50 – 100 (max. 140)*
23
Designat ionviscosity
at 40 ° C (mm2/s)
viscosity at 150 ° C (mm2/s)
application temperature range* (°C)
MARQUENCH 325 42 2,6 50 – 150
MARQUENCH 722 78 3,5 60 – 150 (max. 180)
MARQUENCH 729 75 3,4 60 – 150 (max. 180)
MARQUENCH 722 S 4 94 3,7 60 – 120
MARQUENCH 849 156 5,1 70 – 150 (max. 180)
MARQUENCH 875 110 4,3 70 – 160 (max. 200)
2. 2Hot quenching oils MARQUENCH
First generation hot quenching oils provided slow cooling properties, and poor oxidation resistance, and were therefore very restricted in their range of application. The manu-
facture of MARQUENCH accelerated hot oils was only possible following our develop-ment of new additives and new standards have now been set for the operation
of hot oils with respect to:
– quenching speed – distortion control
– service life
The optimum hardness and lowest distortion is achieved with MARQUENCH 722 or MARQUENCH 729 and the more MARQUENCH 849 because of the extremely short va-
pour blanket phase and the cooling rate being kept low during martensite formation. In view of these properties the oils are used throughout the automotive industry for harde-
ning transmission parts which are especially susceptible to distortion.
MARQUENCH 722 or 729 can be successfully used to harden thinwalled components (such as deep drawn parts) which are usually unalloyed and fine grained and therefore
difficult to harden even when in a carburized condition.
In hardening of steel strip (carbon steels and alloyed grades) the minimum of distortion is achieved with MARQUENCH 722 or 729.
*) The use of MARQUENCH hot quenching oils is recommended for continuous operation in this temperature range.
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MARQUENCH 722 and 729 have also proved to be excellent for hardening small compo-nents even when used at low bath temperatures (70-90 °C).
The cooling characteristics of MARQUENCH 875 and 325 are designed to give the gre-atest possible hardness penetration. These oils are therefore preferred for hardening of
larger parts e.g. large gear wheels, pinion gears etc.
When MARQUENCH accelerated hot quenching oils are applied at high temperatures, MARQUENCH 722 is prefered for sealed furnaces, MARQUENCH 729 can be used in
sealed furnaces as well as in open tanks, 875 and 325 are used predominantly in open tanks.
If there are no special requirements with regard to high quenching speeds, MARQUENCH 600, 800 and 1400 can be considered. They are, for instance, also used for hardening
steel strip.
MARQUENCH 3500 has proved itself especially useful for high temperature applications.
This applies to both bainite hardening e.g. of rear-axle gears of nodular grey iron (S.G. iron) and to its use as the sealer cup oil in rotary hearth furnaces and vertical furnaces
with a floating “base”.
Our special brochure “Hardening in Hot Quenching Oils” contains further information on the applications and properties of hot quenching oils.
*) The use of MARQUENCH hot quenching oils is recommended for continuous operation in this temperature range.
Designat ion
viscosity at 40 ° C (mm2/s)
viscosity at 150 ° C (mm2/s)
application temperature range* (°C)
MARQUENCH 600 58 3,2 60 – 150
MARQUENCH 800 113 4,3 80 – 160 (max. 180)
MARQUENCH 1400 260 6,3 100 – 180 (max. 200)
MARQUENCH 3500 480 9,1 150 – 250 (max. 265)
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Designat ionviscosity
at 40 °C (mm2/s)
application temperature range (°C)
VACUQUENCH B 244 28 30 – 70
VACUQUENCH 305 30 40 – 80
VACUQUENCH 605 55 50 – 150
2. 3Quenching oils for vacuum furnaces
VACUQUENCHVacuum heat-treatment with oil quenching creates extremely severe require-
ments for the oils used. VACUQUENCH vacuum quenching oils must display the following special properties in order to achieve suitable vacuum conditions and
spotlessly clean surfaces:
– extremely high resistance to vaporization – low gas absorption capacity
– rapid degassing capability – extremely high degree of purity
VACUQUENCH quenching oils were developed in close collaboration with manu-facturers of vacuum furnace equipment and have proved their suitability over
many years of practical use.
They work in furnaces designed both with and without a gastight intermediate door, even when quenching is performed under high vacuum.
VACUQUENCH B 244 produces a very high degree of cooling. It is suitable for quenching carburized parts, for hardening quench and tempering steels to achie-
ve a deep case-or through hardening, and also for cooling stainless steels after solution annealing to give a precipitatefree matrix.
VACUQUENCH 605 provides a particularly low stress, low distortion cooling re-gime. It is used for hardening bearing steel, tool steel and high-speed steels (if
necessary after precooling in the gas stream) where these are not suitable for pressure gas quenching because of the cross-section of the material.
VACUQUENCH 305 lies between the two oils previously described in terms of its cooling action. It is, therefore, used in commercial heat-treatment shops or plants
with a wide variety of heat-treatment requirements.
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2. 4Normal quenching oils
ISODURThese oils, also known as bright-quenching oils, are those which rely on viscosity
to determine quenching speed. ISODUR normal quenching oils shows lower cooling characteristics as their viscosity increases.
The term ”bright quenchin goils” hase volved historically and can easily lead to the mistaken view that other oils do not give bright surfaces after quenching.
All of the quenching oils in our range produce clean, bright surfaces when compo-nents are quenched without prior oxidation.
ISODUR normal quenching oils are used, for example, for hardening and tempering large forgings of alloy steels, bar and section quenching and for hardening tool steel.
CONTROLLING THE SURFACE APPEARANCE OF COMPONENTS
For special requirements with regard to obtaining extremely bright, shining sur-faces or for homogeneous darkening of surfaces during the quenching process,
PETROFER can provide special quenchoils (details upon request).
ISODUR 220 is the standard grade in this series with the widest application spec-trum i.e. the best possible compromise for quenching case-hardening, hardening
quench and tempering steels and tool steels in the same bath.
2. 5
Water-washable E-type quenching oilsAll PETROFER’s heat-treatment oils, except MARQUENCH
1400 and 3500, can be supplied in water-washable ver-sions. These oils contain specially designed surfactants
to enable the oil film after quenching to either be rinsed off with water or, in the case of certain components e.g.
ball bearings, to help the subsequent cleaning process remove oil residues.
The water-washable grades are identified by the letter ”E” which is placed after their name (e.g. ISOMAX 166E).
Type E oils do not differ in their physical data, cooling characteristics and oxidation resistance from the stan-
dard grades previously described.
Conversion of existing quenching oil baths, both of our own range and those of other suppliers, to ”water-was-
hable” types is usually possible at anytime. However, prior checking of a sample from the bath by our labora-
tory is recommended before any such action is taken.
Designat ionviscosity at 40 °C
(mm2/s)application
temperature range (°C)
ISODUR 160 10 30 – 70
ISODUR 220 19 50 – 80
ISODUR 350 38 60 – 90
ISODUR 450 58 60 – 90
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2. 6Biodegradable (mineral oil free)
quenching fluids SYNTHERM
Additional to the line of mineral oil based quenching oils PETROFER has developed a line of biodegradable quenchants based on synthetic and/or natural raw materials.
In addition to the advantage of environmental acceptability these products also have other outstanding properties.
Some of these products have extremely high flash points and a vaporization stability superior to mineral oil based quenchants, despite their low viscosities.
Consequently not only is consumption low but also the environmental input is reduced.SYNTHERM “oils” are available with a very high quench rate-faster than mineral oils –
so that steels with very low hardenability, which previously had to be quenched in aqueous media, can be “oil” quenched to obtain the necessary hardness.
The SYNTHERM oil range con tains products which are easily cleaned with water and also grades which can be removed with a hot cleaner such as FEROCLEAN.
The application of SYNTHERM oils should be discussed with PETROFER’s Technical Service Department in advance due to their special properties.
Designat ion
viscosity at 40 °C (mm2/s)
application temperature range (°C)
SYNTHERM LO 180 10,5 40 – 80 (max. 150)
SYNTHERM 354 38,0 80 – 120 (max. 180)
SYNTHERM LO 460 50,0 60 – 100 (max. 150)
2. 7Tempering oils and synthetic tempering fluids
ISOTEMP SYNTHERM
Tempering oils and synthetic tempering fluids are used mainly for:
– stress-relieving and tempering of hardened steel parts – heating parts for shrink fitting
– eliminating hydrogen from steel that has been pickled – ageing of plastics for stabilizing
ISOTEMP tempering oils are derived from mineral base oils and they are categorized by their application temperature range.
SYNTHERM synthetic tempering fluids are significantly superior to tempering oils in oxi-dation resistance.
Even at high working temperatures damp parts can be treated and they are therefore used in baths in continuous manufacturing lines for tempering wet parts e.g. after induction
hardening or a washing process. SYNTHERM 354 OA was especially designed for cooling saltbath nitrided components.
Tempering oils
Designat ionviscosity at 40 °C
(mm2/s)
viscosity at 150 °C
(mm2/s)
application temperature max. (°C)
ISOTEMP 200 108 4,3 200
ISOTEMP 230 225 6,3 230
ISOTEMP 280 480 9,0 280
Synthetic tempering fluids
Designat ionviscosity at 40 °C
(mm2/s)
viscosity at 150 °C
(mm2/s)
application temperature range (°C)
SYNTHERM 354 38 2,7 100 – 200 (max. 220)
SYNTHERM 354 OA 37 2,7 30 – 80 (max. 200)
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3. Watermiscible quenching media
3.1Polymer Quenchants
As has been shown quenching oils cover a wide range of cooling performance yet there is still a significant gap between the maximum achievable cooling rate of a low viscosity accelerated oil and that achievable with ordinary cold water.
Water-miscible quenchants which fill this gap are thus an ideal complement to the quenching oil range. Heat-treatment ope-rations can be carried out with these water-based quenchants which would either be impossible or extremely difficult with an
oil. This particularly relates to spray-quenching in induction and flame-hardening processes where a high degree of fire risk exists when using an oil.
Emulsions have been employed in these applications instead of oil but unfortunately they do not give the low cooling rates in the temperature range for martensite transformation necessary to reduce, or eliminate, the danger of cracking. These cooling
characteristics can only be achieved with polymer quenchants.
As a result of our continuous development programmes we are today able to offer users a complete range of watermiscible quenchants which successfully covers the whole spectrum from oil-to water-quenching.
Accelerated quenching oils can already be replaced in a wide range of applications as polymer solutions (FEROQUENCH) are available which give comparable cooling characteristics. These solutions are therefore suitable for hardening alloyed quench
and tempering steels and some tool steels as well as for quenching components directly from forging.
However, general substitution of quenching oils by watermiscible quenchants is – at present – not possible. It must be realised that these products contain from 60 to 98 % of water in the ready-to-use condition, the level depending on the concentration
for a given application.
The physical properties of the water phase (in particular its tendency to evaporate) are not modified to the extent that identical conditions are achieved to those found in quenching oil applications.
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All water-miscible quenchants are of course incombustible, and, in contrast to oil quenching, the risk from fume and fire is avoided.
This is particularly useful when hardening forged parts directly from forging temperatures and for interrupted quenching (time quenching) of components.
Our range of water-miscible quenchants is distinguished by high thermal stability. The products are low foaming, provide excellent corrosion protection and are not susceptible to attack by micro-organisms.
The use of water-miscible products can often be a new venture for customers and therefore it is sensible to discuss applications thoroughly. This is obviously not so important with induction and flame-hardening operations where the use of water-miscible quen-
chants has been established for many years.
However, for other applications, we recommend consultation with PETROFER’s Technical Service Department to make use of our extensive experience in this field. This is particularly important if a quenching oil is being replaced.
In the following section our range of water-miscible quenchants is described, including emulsions and salt solutions.
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3.1.1AQUATENSID
AQUATENSID solutions reduce the quenching effect of water by virtue of the poly-mer in solution becoming insoluble during the quenching process and platingout
onto the hot surface of the component. The thickness of the insulating film for-med varies with the concentration of the polymer in the original solution.
When the component cools to the temperature of the quenching fluid, the film dissolves completely thus ensuring that drag-out of polymer remains low. For this
reason AQUATENSID quenching solutions are very economical in use.
AQUATENSID products are used in quench baths mainly for hardening low alloy, and quench and tempering steels, which are difficult to harden with oil quenching
but which are prone to cracking with water quenching. The AQUATENSID products are also used extensively in induction and flame-hardening processes.
The examples used in the following section are taken from the wide range of applications suitable for AQUATENSID quenchants:
– quenching forgings and bar and sections of low alloy and plain carbon steels as well as steel castings
– quenching and surface hardening components for chain drives – hardening bolts and nuts, screws and self-tapping screws
– hardening tongs, wrenches and other tools – partial quenching of tools without fire risk and smoke
– hardening carburized or carbonitrided small parts in continuous furnaces (typical of chain and bicycle industries)
– hardening of spring elements – induction and flame-hardening of crankshafts, camshafts and pinion shafts, gears, splines, spindles, rollers, constant velocity joints, saw blades, bedways, etc.
Our own publication “Aqueous Quenchants in Hardening” contains the results of our research and experience in the practical application of AQUATENSID products.
Attention is also drawn to the application of AQUATENSID products for aluminium heat-treatment. Aluminium alloy components, after homogenization annealing,
are quenched with extremely low distortion when using AQUATENSID solutions instead of water. Successful applications are quenching of
– sheet and sections in the aerospace industry – castings and forgings used for example in the automotive industry.
In these cases the high cost of reworking is avoided by the use of AQUATENSID.
AQUACOOL AQUACOOL is an highly effective polymer quenchant. It is mainly applied in cases
when a very high concentration of AQUATENSID would be necessary to avoid cracks – especially in induction hardening processes. AQUACOOL can be used in
these cases more effectively.
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3.1.2FEROQUENCH
The FEROQUENCH group of products provide an even more significant reduc-tion (compared with AQUATENSID) in quenching speed when added to water at
various concentrations. Solutions in the range 8-20 % (depending on the FERO-QUENCH-type) give cooling curves practically equal to those of quenching oils.
Reduction of the quenching rate, compared to that of water, is achieved by the formation of a polymer film on the part’s surface during cooling. In the beginning
of the cooling process a thin polymer film ensures uniform collapse of the vapour blanket and the start of the boiling phase.
With further cooling, an insulating film develops and the thickness of the film varies with concentration. Its insulating effect ensures a controlled heat flow from
the component into the quenchant.
Products from the FEROQUENCH group are used to treat steels of higher har-denability e.g. for quenching alloyed tempering and case-hardening steels and
for hardening tool steels. Interrupted quenching of components is possible at any surface temperature desired.
Individual brochures are available for the various products in the range as well as publications covering research results and practical applications:
“New polymer quenchants open up new fields of application”
“Practical experience with water-miscible quenchants in the heat-treatment of carburized components using an example from the bearing industry”
Product properties are described in detail in these publications which contain suggestions for interesting applications.
40 41
3. 2Other water-miscible quenchants
In addition to the polymer based quenchants, already described, the range of water-miscible products has for many years contained emulsion and salt based
products.
3. 2.1Emulsions
BLACKYNOL WLAlso in immersion tanks emulsions are used only for special applications in view
of their uncontrolled vapour phase. A relatively stable cooling action is only achie-ved by using high bath temperatures which results in a very long vapour blanket
phase.
BLACKYNOL WL is, however, normally used in immersion tanks for the cooling of tempered parts. By quenching parts in BLACKYNOL WL after tempering in an oxi-
dising atmosphere above approx. 500 C, the dark film of oxide on the component takes on a deep shiny black appearance. This film not only gives components a
good appearance but also provides good corrosion protection.
A typical application is in the quenching of bolts and nuts after tempering.
3. 2. 2Water additive salts
AQUARAPIDAQUASAL
Certain water soluble salt combinations are unique in their ability to shorten the vapour blanket phase. Consequently they can be used at temperatures of about
50 °C while the quenching action of plain water decreases significantly above temperatures of 20 °C.
Water quenching salts are practically only used for hardening plain carbon or free machining steels to attain maximum hardness.
The product range varies in chemistry from the harmless AQUARAPID F to the nitrite containing AQUARAPID and the cyanide containing AQUASAL.
They will, depending on their chemical composition, provide various surfaces on hardened components:
– silvery bright (AQUASAL) – uniform light grey (AQUARAPID F)
– dark (AQUARAPID)
The corrosion protection of the equipment and components also depends on the product’s composition.
Also fully organic polymer quenchants allow an extremely high quenching speed like the before mentioned salt-based products. An example is FEROQUENCH HQ.
42 43
4. Quenching saltsA range of quenchants is not complete without a selection of molten salts. These
are used for both quenching and tempering of steel and also for heat-treating (homogenizing and precipitation hardening) of light metal alloys.
4.1Alkali salts
AS 135AS 200
The various types of alkali based products differ in application by their melting point and, therefore, their lowest application temperature. The maximum possible
bath temperature for these products is 550 C (or 600 C when pots of oxidation-resistant steels are used). At higher temperatures thermal decomposition of the
salt increases rapidly.
The properties of the salts will depend on whether or not they contain nitrite. The nitrite-free alkali salt (AS 200, with its lowest application temperature of only
240 °C) has been found to be particularly suitable in the heat-treatment process known as conversion in the bainite stage (bainitic hardening or austempering).
This is usually carried out in continuous furnaces such as shaker-hearth or belt-furnaces. AS 135 can be used for the same application but it is mostly applied
to quench components which have been carburized or austenitized in salt baths (marquenching).
Residues from salt baths containing cyanides become almost totally degraded by thermal decomposition during quenching in AS baths. Also the non water soluble
residues from these baths are “rinsed off” by the AS 135 salt bath. Consequently cleaning of components is significantly easier.
The quenching rate of AS-baths is reduced by carry-over from hardening or car-burizing saltbaths. However, the quenching action can either be enhanced or res-
tored by adding water in quantities up to 2 %.
4. 2Chloride salts
GS 405 / 406Tool and high speed steels are quenched in the temperature range 460-560 °C in
GS 405 salt-baths.
In application in high speed steel salt bath lines the minimum application tempe-rature for GS 405 increases continuously due to carry over from high temperature
salt baths and as the salt “thickens”. This effect can be counteracted by additions of GS 406 to the GS 405 bath.
Designation
melting point (°C)
application temperature range (°C) application
AS 135 140 160 – 550marquenching;
transformation to bainite, tempering
AS 200 230 240 – 550 transformation to bainite, tempering
GS 405 430 440 – 700quenching HSS
and tool steels, tempering
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