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Quenchants
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]
Dedicated to
quality
Table of contents
Founded in Germany over 50 years ago, PETROFER has attained
market leadership in many areas through its dedication to customer service and product development.
GENERAL INFORMATION ON QUENCHANTS
1.
PETROFER and quenching
1.1
Physical and chemical data
1.2
The quenching process
1.3
Vapour blanket phase
1.3.1
Boiling phase
1.3.2
Convection phase
1.3.3
The effect of bath temperature
1.4
on the quenching process
Resistance to vaporization
1.5
Ageing resistance, service life and consumption
1.6
Safety precautions
1.7
Maintenance and monitoring
1.8
Cleaning heat-treated components
1.9
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 industriВ­
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 applications.
QUENCHING OILS
Accelerated quenching oils
Low viscosity accelerated quenching oils
ISOMAX / FASTQUENCH
Accelerated quenching oils with high vaporization
2.1.2
stability ISORAPID / FASTQUENCH
Hot quenching oils MARQUENCH
2.2
Quenching oils for vacuum furnaces VACUQUENCH
2.3
Normal speed quenching oils ISODUR
2.4
Water-washable E-type quenching oils
2.5
Biodegradable (mineral oil free) quenching fluids
2.6
SYNTHERM
Tempering oils and synthetic tempering fluids
2.7
ISOTEMP / SYNTHERM
2.
2.1
2.1.1
The excellence of today’s product range is the result of the
company’s philosophy of continuous improvement and the dedication 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 advanced 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 environment 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, quality, and dedication to meet your needs.
2
WATER-MISCIBLE QUENCHING MEDIA
3.
Polymer quenchants
3.1
AQUATENSID/AQUACOOL
3.1.1
FEROQUENCH
3.1.2
Other water-miscible quenchants
3.2
Emulsions AQUANOL / BLACKYNOL WL
3.2.1
Water additive salts AQUARAPID / AQUASAL
3.2.2
4.
4.1
4.2
QUENCHING SALTS
Alkali salts AS 135 / AS 200
Chloride salts GS 405 / 406
3
1. General information
on quenchants
1.1 PETROFER and quenching
The metallurgical properties of heat-treated steel components are primarily dependent upon the austenitizing conditions, the hardenability of the steel and the quenching process used.
Modern heat-treatment processes are forever making new demands on quenching
fluids and PETROFER’s extensive development programmes ensure that our product technology is more than capable of meeting these new requirements. These
programmes are designed not only to improve the technical properties of our quenchants but also to provide economic and environmental benefits.
We are constantly screening new raw materials for their suitability of use in quenchants 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
By having our own extensive development facilities and a complete range of products 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 quenchants in our range and their potential applications.
5
OIL BATH TEMPERATURES
correct temperature range
optimum working viscosityt
1. 3
The quenching process
high viscosity,
reduced agitation,
increased drag-out loss
temperature too low
A quenchant is characterized primarily by its quenching properties and these are difficult to describe in words. Descriptions 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:
unnecessary smoke formation,
increased fire hazard
temperature too high
– nickel and nickel alloy probes: cylinders 12,5 mm � (ISO 9950) or a ball (GM-test)
– steel probes, 3-80 mm � (Meinhardt-method)
1. 2
Physical and chemical data
– a silver ball, 20 mm � (MPI-silver ball method)
– silver cylinders 8or16mm (Cetim method AFNOR NFT 60178)
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.
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.
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.
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.
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.
100
100
100
80
80
80
60
60
60
50
50
50
40
40
40
100
80
60
50
30
25
55
5
4,5
4,5
4,5
4,0
4,0
4,0
20
16
14
3,5
3,5
3,5
12
3,0
3,0
3,0
aplication range
kinematic viskosity in mm2/s
40
10
9
8
7
6
00
0
10
10
10
20
20
20
30
30
30
40
40
40
50
50
50
60
60
60
70
70
70
80
80
80
90
90
90
100
100
100
110
110
110
120
120
120
Low viscosity accelerated quenching oil
accelerated quenching oil, high vaporization stability
hot quenching oil
130
130
130
140
140
140
temperature in В°C
30
30
30
25
25
25
20
20
20
16
16
16
14
14
14
12
12
12
10
10
109
99
88
8
77
7
66
6
900
900
800
800
700
700
600
600
500
500
400
400
300
300
200
200
100
100
5
4,5
Figure 1:
Application temperature range as a function of oil
viscosity, for various types of quenching oils.
4,0
3,5
0
10
20
30
40
50
60
70
80
temperature in В°C
6
0
0
0
3,0
90
100
110
120
130
140
Figure 2:
Various ways of showing the cooling
characteristics of a quenchant.
5
10
15
cooling time in sec.
20
0
25
50
75
100
125
rate of cooling in В°C/s
7
1. 3.1
Vapour blanket phase
1. 3. 2
Boiling 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.
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.
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 phase
wide boiling phase
cooling properties in the
convection phase
fast, homogeneous cooling of the
entire workpiece surface
good heat extraction
from larger diameters
can be influenced strongly
by agitation
vapour blanket phase
boilingphase
convectionphase
Figure 3:
The phases of the cooling process of quenchants having a boiling temperature below the quenching temperature.
8
9
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.
900
800
700
The maximum cooling rate cannot be used to compare quenchants as it only shows the steepest slope of the temperature/time curve and not the position of the curve in relation to the TTT diagram.
temperature in В°C
600
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.
500
400
Ms
300
200
100
58 HRc
27 HRc
0
0,1
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
10 2
10 3
10 4
10 5
time in sec.
Figure 4:
Effect of various cooling characteristics
on achievable hardness. (TTT-diagram C45,
unalloyed steel 0,45 % C).
58 HRC
10
1
27 HRC
11
1. 4
The 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 difference 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.
I N F L U E N C E O F T H E B AT H T E M P E R AT U R E
O N T H E Q U E N C H I N G P R O P E RT I E S
insignificant when the oil is within
its working viscosity range
quenching oils
polymer solutions
water
considerable, depending on the type of polymer, may be used
advantageously to adjust special quenching properties
very distinctive
1. 5
Resistance 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 achievement of optimum and consistent hardness.
mittlere Abkühlgeschwindigkeit von 800-300 °C in °C/s
150
In batches of components a vapour ”cushion” forms at the start of quenching and this cushion envelopes the whole batch.
125
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.
100
150
150
150
150
150
The use of water-miscible quenchants, which are inevitably less resistant to evaporation, therefore requires special consideration for batch processes and, in most cases, quench oils are preferred due to their increased resistance to vaporization.
75
125
125
125
125
125
100
50
100
100
100
100
75
75
75
75
75
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.
25
50
50
50
50
50
0
25
25
25
0
00
25
25
0
50
25
00
0
00
75
100
125
150
temperaturt in В°C
00
25
25
25
50
25
50
25 50
water additive salt
water
low viscosity acceleradted
quentching oil
50
50
75
75
75
75
100
75 100
100
100
125
100 125
125
125
150
125 150
150
150
150
hot quenching oil
polymer-quenchant
Figure 5:
Change in quenching speed in relation to bath temperature (shownschemati-cally).
Figure 6:
Test-equipment for vaporization-stability.
12
13
STABILITY OF QUENCHANTS
high evaporation
stability of oils
good oxidation stability
thermal stability
avoids trouble some smoke formation,
reduces consumption
long servic elife, avoids formation
of oil sludge
insignificant smoke formation–
no change in the basic properties
Figure 7b: Quenching oil with poor ageing resistance after an oxidation test.
1. 6
Ageing resistance, service life and consumption
Resistance to evaporation has a considerable effect on consumption and thus on oil bath economics. Experience has shown that, on batch quenching, probably more oil is lost through evaporation than through “dragout” 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 impossible, 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 operating conditions.
Figure 7a: Quenching oil with good ageing resistance after an oxidation ageing test.
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 furnace) and the volume of quenchant must be
maintained.
This relationship depends upon the conditions 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 tightly packed batches of small components
which give off their heat rapidly.
Consequently the following values are
only intended as a guide to the relationship between the weight of quenching oil
and the gross weight of the batch to be
quenched:
– open oil baths: 10:1
– 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/cmВІ. If a higher loading is used good
movement of oil in the area of the elements 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 previous processes.
– 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 intervals takes place and the hourly throughput
of steel is then used in the calculation.
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 monitoring is required for these products.
The following points must also be observed, in particular when operating open hot
oil baths:
14
15
NEGATIVE FACTORS WHEN WORKING WITH QUENCHING OILS
1. 7
Safety 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”
contamination with water
bath temperature too close
to the flash point
immersion speed
of the batch is too low
contamination with fire
extinguishing medium
change of the quenching properties,
high fire hazard
increased fire hazard
strong flame formation,
increased fire hazard,
trouble some smoke- and soot-formation
certain extinguishing powders as well
as all foams change the quenching
characteristic and other properties
provide detailed information about these subjects.
drag-in of soot into E-oils
may lead to stains on the work pieces
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.
1. 8
Maintenance 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
1. 9
Cleaning 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 finish, 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. Degreasing 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 quenching 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 quantities (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.
N E G AT IVE INFLUENCES ON THE CLEANING PROCESS
insufficient agitation
in the cleaning bath
insufficient oil separation from
the washing bath, insufficient
washing properties of the cleaner
insufficient skimming,
oil floating on top
of the washing bath
18
remaining oil residues, especially
in tightly packed batches
oil residues remain on the parts,
trouble some smoke formation
during tempering
washed batch may pick up oil
when being withdrawn
19
2. Quenching oils
2.1
Accelerated quenching oils
Accelerated oils are those quenching oils which are treated to enhance quenching performance. Until recently such treatment was only effective in low viscosity oils but our continuing development work has also made it possible to
provide higher viscosity, hot quench oils with enhanced cooling properties.
2.1. 1
Low 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 vaporization 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
Designation
viscosity at 40 °C
(mm 2/s)
ISOMAX 160
ISOMAX 166
ISOMAX 169
Fastquench 180
20
12,2
12,5
14,0
14,5
application
temperature range (В°C)
40 –70
40 –70
40 –70
40 –70
21
2.1. 2
Accelerated quenching oils with high vaporization stability
These oils have been specially designed for use in sealed integral quench-furnaces. 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 PID
As a result of their high resistance to vaporization these oils are also particularly 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 transmission 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.
FASTQUENCH
FASTQUENCH 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).
viscosity at 40 °C
(mm 2/s)
Designation
ISORAPID 221
21
ISORAPID 229 FQ
50 – 80
50 – 80
24
ISORAPID 277 HM
25
ISORAPID 455
FASTQUENCH 293
50 – 80
17
ISORAPID 277
ISORAPID 459
application
temperature range (В°C)
50
49
31
(max. 130)*
50 – 80
(max. 130)*
50 – 100
(max. 150)*
50 – 100
(max. 150)*
50 – 100
(max. 140)*
*) The use of MARQUENCH hot quenching oils is recommended for continuous operation in this temperature range.
23
2. 2
Hot 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 manufacture of MARQUENCH accelerated hot oils was only possible following our development 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 vapour 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 hardening 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.
viscosity
at 40 ° C
(mm 2/s)
Designation
MARQUENCH 325
42
MARQUENCH 722
78
MARQUENCH 729
MARQUENCH 849
MARQUENCH 875
3,4
94
156
110
application
temperature
range* (В°C)
2,6
50 – 150
60 – 150
3,5
75
MARQUENCH 722 S 4
viscosity
at 150 ° C
(mm 2/s)
3,7
5,1
4,3
(max. 180)
60 –  150
(max. 180)
60 – 120
70 –  150
(max. 180)
70 –  160
(max. 200)
*) The use of MARQUENCH hot quenching oils is recommended for continuous operation in this temperature range.
24
25
MARQUENCH 722 and 729 have also proved to be excellent for hardening small components even when used at low bath temperatures (70-90 °C).
The cooling characteristics of MARQUENCH 875 and 325 are designed to give the greatest 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.
viscosity
at 40 ° C
(mm 2/s)
Designation
MARQUENCH 600
58
MARQUENCH 800
MARQUENCH 1400
MARQUENCH 3500
113
260
480
viscosity
at 150 ° C
(mm 2/s)
application
temperature
range* (В°C)
3,2
60 – 150
4,3
6,3
9,1
80 – 160
(max. 180)
100 –  180
(max. 200)
150 –  250
(max. 265)
*) The use of MARQUENCH hot quenching oils is recommended for continuous operation in this temperature range.
26
27
2. 3
Quenching oils for vacuum furnaces
VACUQUENCH
Vacuum heat-treatment with oil quenching creates extremely severe requirements 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 manufacturers 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 achieve 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 regime. 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.
Designation
VACUQUENCH B 244
VACUQUENCH 305
VACUQUENCH 605
28
viscosity
at 40 °C
(mm 2/s)
application
temperature
range (В°C)
28
30 – 70
30
55
40 – 80
50 – 150
29
2. 4
Normal quenching oils
ISODUR
These 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 components 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 surfaces 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 spectrum i.e. the best possible compromise for quenching case-hardening, hardening
quench and tempering steels and tool steels in the same bath.
Designation
viscosity at 40 °C
(mm 2/s)
ISODUR 160
10
ISODUR 220
ISODUR 350
ISODUR 450
30
19
38
58
application
temperature range (В°C)
30 – 70
50 – 80
60 – 90
60 – 90
2. 5
Water-washable E-type quenching oils
All PETROFER’s heat-treatment oils, except MARQUENCH
1400 and 3500, can be supplied in water-washable versions. 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 standard grades previously described.
Conversion of existing quenching oil baths, both of our
own range and those of other suppliers, to ”water-washable” types is usually possible at anytime. However,
prior checking of a sample from the bath by our laboratory is recommended before any such action is taken.
31
2. 7
Tempering oils and synthetic tempering fluids
ISOTEMP
SYNTHERM
Tempering oils and synthetic tempering fluids are used mainly for:
2. 6
Biodegradable (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.
– 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 oxidation 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.
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.
Tempering oils
Designation
Designation
SYNTHERM LO 180
SYNTHERM 354
SYNTHERM LO 460
viscosity at 40 °C
(mm 2/s)
10,5
38,0
50,0
application
temperature range (В°C)
40 –  80
(max. 150)
ISOTEMP 200
ISOTEMP 230
viscosity
at 150 °C
(mm 2/s)
108
4,3
225
ISOTEMP 280
200
230
6,3
480
application
temperature
max. (В°C)
9,0
280
80 –  120
(max. 180)
60 –  100
(max. 150)
Synthetic tempering fluids
Designation
SYNTHERM 354
SYNTHERM 354 OA
32
viscosity
at 40 °C
(mm 2/s)
viscosity
at 40 °C
(mm 2/s)
viscosity
at 150 °C
(mm 2/s)
38
2,7
37
2,7
application
temperature
range (В°C)
100 –  200
(max. 220)
30 –  80
(max. 200)
33
3. Watermiscible quenching media
3.1
Polymer 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 operations 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.
34
35
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.
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.
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 quenchants has been established for many years.
36
37
3.1.1
AQUATENSID
AQUATENSID solutions reduce the quenching effect of water by virtue of the polymer in solution becoming insoluble during the quenching process and platingout
onto the hot surface of the component. The thickness of the insulating film formed 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.
38
39
3.1.2
FEROQUENCH
The FEROQUENCH group of products provide an even more significant reduction (compared with AQUATENSID) in quenching speed when added to water at
various concentrations. Solutions in the range 8-20 % (depending on the FEROQUENCH-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 hardenability 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. 2
Other 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. 2.1
Emulsions
BLACKYNOL WL
Also in immersion tanks emulsions are used only for special applications in view
of their uncontrolled vapour phase. A relatively stable cooling action is only achieved 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 oxidising 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. 2
Water additive salts
AQUARAPID
AQUASAL
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 salts
A 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.
4.1
Alkali salts
AS 135
AS 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 oxidationresistant 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 beltfurnaces. 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 carburizing saltbaths. However, the quenching action can either be enhanced or restored by adding water in quantities up to 2 %.
4. 2
Chloride salts
GS 405 / 406
Tool 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 temperature 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
AS 135
AS 200
GS 405
44
melting point
(В°C)
140
230
430
application
temperature range (В°C)
160 – 550
240 – 550
440 – 700
application
marquenching;
transformation to
bainite, tempering
transformation to
bainite, tempering
quenching HSS
and tool steels,
tempering
45
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