Transcript Elementary Heat Treatments

THE SEALED QUENCH FURNACE
Module 1
APPRECIATION OF THE SEALED
QUENCH FURNACE
Brian J. Birch, Brian Ellis & Leanie Mackenzie
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Glossary
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Introduction
This Module is an introduction to the sealed quench furnace
and includes the following topics:
1.
Background
 What iron and steel are
 Why steel is heat treated and surface engineered
2.
Heat Treatment
 When it began
 How it is carried out
3.
Sealed Quench Furnaces
 What they are
 How they work
4.
Summary of the Module
5.
Self-Test & Test Results
Objectives
Upon completion of this Module, the learner will be able to:

Understand the need for heat treatment of steel

Appreciate what surface engineering does and why it is
carried out

Comprehend the role of controlled atmosphere furnaces,
specifically
the
sealed
quench
furnace,
in
surface
engineering

Visualise the sealed quench furnace and its underlying
principles

Understand, in simple terms, how the sealed quench
furnace works
Section 1 - Background
Iron has been the most important metal
in use in the World for the past two and
a half thousand years and continues to
be so today
In the Middle ages, the alchemists
(early
chemists)
adopted
the
astrological symbol for Mars (right) as
their symbol for iron
Mars was of course, the Roman God of
war and iron was the most important
metal used for making weapons
Significantly, or perhaps ironically, this
symbol is used nowadays to symbolise
man
Background - Iron
With the emergence of chemistry as a
science, the first essential was to
classify and categorise the chemical
elements
This involved determining which
chemicals were elements and giving
each one a simple alphabetical symbol
to replace the earlier picture symbols
or glyphs used by the alchemists
The modern chemical symbol for iron
is Fe which comes from the Latin
name for iron - Ferrum
Background - Steel
Unfortunately, pure iron is relatively soft and would not last very long if
used as a tool
Luckily, when a small amount of carbon (up to about 1.5%) is added to
the iron it is called steel and can be made much harder by a heat
treatment called quite simply, hardening
If some other metals, such as chromium, nickel and manganese are
added to the steel it can be made much stronger and tougher and is
called alloy steel
In simple terms:
The amount of carbon in the steel determines how hard it will be
after hardening
The various metals with which it is alloyed determine how strong
or tough it will be, after hardening
Background - Steel
Probably the best-known alloy steel is stainless steel, which is simply
steel to which at least 13% chromium has been added to make it rustproof (or stainless)
For the best corrosion resistance, the stainless steel should have at
least 18% chromium plus additional nickel
The spoon shown below carries the numbers 18 – 8 on the back which
means that it is made of a stainless steel containing 18% chromium
and 8% nickel
Background – Hardening Steel
A 2.7 tonne component being
lowered into an oil quench tank
(Bodycote Melrose Park, USA)
Another advantage of steel is
that when it is produced, it is
quite
soft
and
can
be
machined easily into complex
shapes
However, it can then be
hardened by heating it to a
high
temperature
(above
o
850 C) and cooling it rapidly in
oil or water – a process called
quenching
After hardening, a reduced
hardness but an increased
toughness can be obtained by
heating the components at a
chosen temperature, usually
between 150oC and 600oC – a
process called tempering
Background – Surface Engineering
This view of the crosssection of a component,
magnified 100 times using a
microscope, shows the steel
surface (at the right) after
case hardening
Sometimes, even hardened
steel is not good enough for a
particular application or use
Therefore, another of the
major roles of heat treatment
is to modify the surface of
steel components, so that they
are suitable for the purpose
for which they were designed
or, that they last longer when
carrying out a particular job
This
is
called
surface
engineering
Surface engineering produces
a different structure on the
surface of steel, which can be
seen when a component is cut
and prepared in a laboratory
Background – Surface Engineering
Surface engineering by heat treatment requires the use of a hightemperature furnace to heat the parts up, a controlled atmosphere to
modify their surface carbon content and a tank of oil (or water) in
which they can be quenched
The majority of components subject to surface engineering by heat
treatment are processed in special controlled atmosphere furnaces
Sealed quench furnaces constitute the most common type of
controlled atmosphere furnaces in use in modern industrial
enterprises
A sealed quench furnace is a furnace in which the heating chamber is
attached to the cooling or quenching chamber, both being enclosed
so that the workload is always under the controlled atmosphere and
is never exposed to the air whilst at temperature
This means that components are clean and bright and not oxidised
when they are removed from the furnace
Background - What is Surface Engineering?
Surface Engineering involves the
use of heat treatments, such as
case hardening, to create a
surface structure and core or
central structure which together
possess properties unachievable
in either the core or surface
materials alone
Put simply, the engine, gearbox
and many other parts in this
excavator would soon wear out if
they were not surface engineered
by carburising and hardening
Background - How Bodycote
Engineers Surfaces
Bodycote employs a number of techniques by means of which the
surface of metal components can be modified, including:
 Heat treatments:
- Carburising
- Carbonitriding
- Nitrocarburising
- Nitriding
 Surface alloying treatments
- Boriding
- Siliconising
 Coatings:
- PVD (Physical Vapour Deposition)
- Ceramic coating
Section 1 - Summary

In Section 1, you have been introduced to iron but
found that it was too soft for everyday use

You have come to appreciate how important iron
became, owing to its ability to be easily converted to
steel, which could be hardened by heat treatment

The other important characteristic of steel is the ease
with which it can be surface engineered by relatively
simple and cheap heat treatments such as case
hardening

These surface engineering heat treatments are mostly
carried out in controlled atmosphere furnaces,
particularly sealed quench furnaces
Section 1 – Self-Test (1)
What is steel?
Tick all that are correct





Iron with chromium added
Iron with carbon added
Hardened iron
Stainless steel
Metal tools
Section 1 – Self-Test (1)
What is steel?
Tick all that are correct





Iron with chromium added
Iron with carbon added
Hardened iron
Stainless steel
Metal tools
Section 1 – Self-Test (1)
What is steel?
Tick all that are correct





Iron with chromium added
Iron with carbon added
Hardened iron
Stainless steel
Metal tools
Section 1 – Self-Test (1)
What is steel?
Tick all that are correct
 CORRECT
•
•





Iron with chromium added
Iron with carbon added
Hardened iron
Stainless steel
Metal tools
Hardened iron
• Iron must be made into steel by adding carbon
before it can be hardened
Metal tools
• Steel must be mainly made of iron, not simply any
metal
Section 1 – Self-Test (2)
How is steel hardened?
Tick the one that is correct





By
By
By
By
By
surface engineering
quenching
tempering
adding other metals
carburising
Section 1 – Self-Test (2)
How is steel hardened?
Tick the one that is correct
 CORRECT





By
By
By
By
By
surface engineering
quenching
tempering
adding other metals
carburising
• Surface engineering only modifies the surface and may not
cause hardening
• Tempering is carried out after hardening to control the
hardness and improve the toughness
• Adding other metals to iron is just alloying
• Carburising only increases the surface carbon content, it still
needs quenching to harden it
Section 1 – Self-Test (3)
What is surface engineering?
Tick the one that is correct





Heat treatment in a sealed
quench furnace
Making components that work
Hardening
and
tempering
steel surfaces
Creating a surface and core
with better properties than
they have alone
Changing the shape of the
surface
Section 1 – Self-Test (3)
What is surface engineering?
Tick the one that is correct





 CORRECT
Heat treatment in a sealed
quench furnace
Making components that work
Hardening
and
tempering
steel surfaces
Creating a surface and core
with better properties than
they have alone
Changing the shape of the
surface
Section 2 - Heat Treatment
Heat treatment is the oldest technique of
surface engineering and has been carried
out almost since man’s first use of iron
The earliest published text books on case
hardening (i.e. hardening only the
surface of a component) being used to
improve the quality of iron date back
almost a thousand years
These early techniques involved heating
iron objects in a container, surrounded
by a mixture of carbon-bearing materials
such as animal skins, hooves, horn and
fat, then removing them and cooling
them rapidly by plunging them into a
nearby stream
The picture shows a blacksmith’s
shop from the Middle Ages
Heat Treatment – Early Methods
With this case hardening treatment, the early blacksmiths produced a
hard steel surface on the iron, with a soft but tough centre – an ideal
combination for weapons or farming tools
It took nearly 900 years before these primitive methods began to be
replaced by more controllable, industrialised processing in salt baths
and gaseous atmospheres
Remarkably, the traditional case hardening method, which became
known as pack carburising, was still being carried out widely in the UK
in the 1960s
Even today, pre-packaged pack carburising compound is still available
to small engineering companies and hobbyists who wish to carry out
their own case hardening
#18
PACK CARBURIZER
Heat Treatment - Surface Engineering
Surface engineering by heat treatment can be divided into two
groups based on the processing temperatures:
Nitriding and nitrocarburising, which are generally carried out at
temperatures between 450°C & 590°C
Carburising and carbonitriding which are generally carried out at
temperatures between 800°C & 1000°C
In practice, this difference in processing temperature leads to the
treatments being carried out in different types of equipment
We are concerned here with high-temperature equipment capable of
carrying out carburising and carbonitriding
In fact, these high-temperature processes require the same
temperature range as many other heat treatment processes, such as
hardening and normalising, so they tend to be carried out in general
purpose equipment such as sealed quench furnaces
Heat Treatment - Controlled Gas
Atmospheres
Controlled gas atmospheres, or simply controlled atmospheres, have
now largely superseded solid (box or pack) and salt bath (liquid)
atmospheres for heat treatment
This is due to:a) Better control of the surface carbon content of the component
b) Higher productivity of the equipment
c) Less possibility of oxidation of the component’s surface
d) Less labour required to run the equipment
e) Easier to automate and control the process
f) Better working conditions for the operators
g) More environmentally friendly - without the serious problems of
handling toxic salts or the difficulties of disposing of waste salts
and spent pack carburising powders
Heat Treatment - What are Controlled
Atmospheres?
A controlled atmosphere is one that not only protects the surface of
steel components from oxidation during processing but can also
control the carbon content in the surface of the component
Put more simply, the atmosphere within the furnace chamber is a
vital factor in achieving the chemical reactions that need to occur
during heat treatment
The active ingredients of controlled atmospheres are carbon
monoxide and hydrogen
This composition means that the gas mixture is highly flammable,
toxic and potentially explosive
Heat Treatment – Using Controlled
Atmospheres
Properly applied and controlled, gas atmospheres provide a source of
the elements essential to surface engineering heat treatment
processes
Controlled atmospheres are produced with a composition that
provides a protective gas for the most common heat treatable steels
containing about 0.40% carbon
In addition, enriching gases such as methane can be added to
develop a high-carbon atmosphere for increasing the surface carbon
content of steels - a process called carburising
If ammonia is added to the atmosphere at the same time as
methane, it provides a high nitrogen and carbon atmosphere for
increasing both the surface carbon and nitrogen content of steels - a
process called carbonitriding
Heat Treatment - Controlled Atmosphere
Furnaces
IPSEN T11 Sealed
Quench Furnace
Special furnaces are used for
processing steels using controlled
atmospheres
They must be gas tight and have
certain safety features which allow
them to be used with the toxic and
flammable gases involved
Controlled atmosphere furnaces fall
into two major categories:
a) Batch furnaces – where the
work is charged and discharged
as a single unit or batch
b) Continuous furnaces – where
the work enters and leaves the
furnace in a continuous stream
Sealed quench furnaces are a type
of batch furnace
Heat Treatment - What is a Batch
Furnace?
A batch furnace heat treats components in discrete lots (batches),
each of which is finished before the next batch is started
Batch furnaces generally consist of an insulated heating chamber
with an external reinforced steel shell and one or more access doors
to the heating chamber
After the heating period is over, the load must be transferred from
the furnace for quenching in an external tank of oil or water
The addition of a second chamber containing a quench tank and a
powered load transfer system converts the basic furnace into a
sealed quench furnace (known as an integral quench furnace in North
America)
When provided with a fully automatic control system, including a
loader and unloader, the sealed quench furnace becomes a highly
efficient unit requiring minimum labour to operate and is sometimes
referred to as a semi-continuous furnace
Section 2 - Summary

In Section 2 you have been shown the early origins of
heat treatment and the primitive methods then used

It
has
also
been
demonstrated
that
such
early
techniques still have a place in industry today

You
have
been
introduced
to
modern
industrial
processes using controlled atmospheres, which have
largely replaced the old methods

Some of the methods and equipment used in modernday processing, particularly the sealed quench furnace,
have been briefly explained
Section 2 – Self-Test (1)
What was used in early
case hardening?
Tick all that are correct





Hooves
Animal skins
Oil quenching
Pack Carburizer #18
Urine
Section 2 – Self-Test (1)
What was used in early
case hardening?
Tick all that are correct





Hooves
Animal skins
Oil quenching
Pack Carburizer #18
Urine
Section 2 – Self-Test (1)
What was used in early
case hardening?
Tick all that are correct
 CORRECT





Hooves
Animal skins
Oil quenching
Pack Carburizer #18
Urine
• Oil quenching is a modern technique developed for alloy steels
• Pack Carburizer #18 is the modern version of the old
blacksmith’s mixtures
• Urine was actually used in medieval times to quench the parts.
A practice echoed today by the use of brine (salt water) as a
quenchant
Section 2 – Self-Test (2)
Which of these processes
are carried out at high
temperatures?
Tick all that are correct





Nitriding
Carburising
Carbonitriding
Nitrocarburising
Tempering
Section 2 – Self-Test (2)
Which of these processes
are carried out at high
temperatures?
Tick all that are correct





Nitriding
Carburising
Carbonitriding
Nitrocarburising
Tempering
Section 2 – Self-Test (2)
Which of these processes
are carried out at high
temperatures?
Tick all that are correct





Nitriding
Carburising
Carbonitriding
Nitrocarburising
Tempering
 CORRECT
Carburising and Carbonitriding are generally carried
out at between 800°C & 1000°C
• Nitriding and nitrocarburising are low temperature
treatments, being carried out at between 450°C & 590°C
• Tempering is also a low temperature treatment, being
carried out at between 150ºC & 650ºC
Section 2 – Self-Test (3)
The gases used in
controlled atmospheres
are?
Tick all that are correct





Toxic
Corrosive
Alloyed
Explosive
Flammable
Section 2 – Self-Test (3)
The gases used in
controlled atmospheres
are?
Tick all that are correct





Toxic
Corrosive
Alloyed
Explosive
Flammable
Section 2 – Self-Test (3)
The gases used in
controlled atmospheres
are?
Tick all that are correct





Toxic
Corrosive
Alloyed
Explosive
Flammable
Section 2 – Self-Test (3)
The gases used in
controlled atmospheres
are?
Tick all that are correct
 CORRECT





Toxic
Corrosive
Alloyed
Explosive
Flammable
• Gases are generally not corrosive except in the presence
of water
• Only metals can be alloyed
Section 3 - Sealed Quench Furnaces
Anyone who sees a sealed
quench furnace for the first time
remarks on the flames & noise
In addition, they often comment
on the general smell of hot oil
and a background roar, which
sometimes increases for a few
minutes as the burners change to
high-fire to heat the furnaces up
These
are
perfectly
normal
reactions of those new to sealed
quench operations, and not an
indication of problems
However, believe it or not,
modern sealed quench furnaces
are clean, quiet and very safe in
operation - a far cry from the
earliest units of fifty years ago
[Play video]
Section 3 - Sealed Quench Furnaces
IPSEN TQ10 furnace front door being opened using
the manual override switch. As the furnace is at
about 900oC, the atmosphere burns off as soon as
it comes into contact with the air.
(Bodycote Macclesfield, UK.)
[Return to previous slide]
[Continue]
Sealed Quench Furnaces - Introduction
The sealed quench is a batch furnace in which the heating and
quenching chambers are combined in a single unit
The two chambers are separated by a refractory-lined door which can
be opened to allow the hot charge to be transferred from the heating
chamber to the cooling chamber
In the UK, most of the furnaces are loaded at the front and unloaded
at the rear (straight-through design)
Sealed Quench Furnaces - Introduction
An alternative design, which is
also widely available in North
America, is loaded and unloaded
through the same door (in-out
design)
In this design, the quench rack
has two sets of rollers, one
above the other so that the
furnace can still be loaded
whilst the load just treated is
still in the quench oil on the
lower set of rollers
In a similar way, the furnace
can still be loaded whilst the
load just treated is being
atmosphere cooled on the upper
rollers
Sealed Quench Furnaces - Introduction
Sealed quench furnaces usually
operate over the temperature range
750°C to 1000°C but can operate
from 570oC to 1100°C with suitable
modifications
They are usually fairly small in size
owing to the limitations of the
internal mechanical transfer system
and the quenching capacity
The picture shows the largest
European sealed quench unit, an
Ipsen TQ37 – it is about half of the
capacity of the largest American
unit (which is about 4m3 in working
volume
and with a 3,000kg
maximum load weight)
Sealed Quench Furnace - Description
The hot zone consists of a
steel outer shell, which is
lined on the inside with
refractory bricks
The load stands on a hearth
which consists of a thick
ceramic plate with holes in,
supported
by
refractory
brick pillars which permit
free
circulation
of
the
controlled atmosphere
The charge is surrounded by
the controlled atmosphere
which
protects
the
components from oxidation
and provides the ideal
environment for carrying out
treatments
such
as
hardening, carburising and
carbonitriding
Schematic view of the
front chamber of a
sealed quench furnace
Sealed Quench Furnace – Heating Chamber
Schematic view of the
front chamber of a
sealed quench furnace
The furnaces are heated by
four to six radiant tubes per
side, depending upon the size
of the furnace
These are fired by natural gas
and air, which are pre-mixed
before reaching the burners at
the base of the tubes
The radiant tubes are situated
between
the
refractory
brickwork and an inner silicon
carbide refractory muffle
This muffle is the hot wall
observed when the furnace is
loaded and it prevents direct
radiation from the radiant
tubes which could cause hot
spots on the work load
Sealed Quench Furnace – Heating Chamber
The muffle and the holes in
the hearth provide a flow path
for the controlled atmosphere
during processing
The gas is circulated through
the charge and over the
radiant tube heaters by a fan
in the roof
Two transfer chains, located in
grooves on either side of the
hearth, move the load from
the heating chamber into the
quench chamber
Schematic view of the
front chamber of a
sealed quench furnace
Sealed Quench Furnace - Quench Chamber
Schematic view of the
cooling chamber of a
sealed quench furnace
The rear chamber of the furnace
consists of a water-cooled steel
shell above an oil filled quench
tank
A quench rack is fitted in the
chamber to move the work load
into and out of the oil as required
The oil is circulated around the
components by motor driven
propellers situated at each side of
the tank
The temperature of the oil can be
raised
by
means
of
the
immersion heaters at each side of
the tank
An external oil cooler is also
provided in case the oil gets too
hot
Sealed Quench Furnace - Quenching
If the load does not require
quenching, it is held above
the oil and fans fitted in the
roof can cool it fairly quickly
The spent atmosphere gas
which flows through from
the heating chamber leaves
through a vent in the roof
near the rear door and is
burned-off there
Above the furnace are large
ducts to draw away the used
gases
and
vent
them
outside the factory
Schematic view of the
cooling chamber of a
sealed quench furnace
Sealed Quench Furnaces - Preparing
Work for Processing
All parts should be thoroughly cleaned before they are charged in the
furnace to avoid unwanted reactions with the oils, etc. on the components or
the atmosphere
Cleaning is normally carried out in a hot alkaline solution and then the
components are washed in clean water
Even small amounts of water carried into the furnace will disturb the
atmosphere and so, parts entering the furnace must be completely dry
Trials are underway involving the use of enzymes which are biodegradable
and much more environmentally friendly than the alkaline solutions currently
used
After cleaning, those components that
only need selected areas casehardening
require stopping-off before they are
assembled into loads
A transmission shaft being
stopped-off by an automatic
machine prior to carburising
(Bodycote Birmingham, UK)
Sealed Quench Furnaces - Preparing
Work for Processing
Proper jigging and fixtures
are essential to ensure that
components are correctly
supported and spaced to
minimise
distortion
and
ensure correct treatment
For example, long, thin
components must be stood
vertically so that they don’t
bend, whilst gears can be
suspended from a bar
through their centre hole so
the oil cools both sides
evenly
A load of shafts, stood vertically,
with a layer of gears on top,
about to be loaded into a furnace
(Bodycote Macclesfield, UK)
Sealed Quench Furnaces - Preparing
Work for Processing
With critical parts, such as
gears for case hardening, the
individual parts within the
work load must be well
spaced
to
allow
the
atmosphere to penetrate the
load during processing and
also for the oil to circulate
throughout the load during
quenching
Both the gas and oil will flow
better through the gears
when they are jigged end on
to the flow, as in the
photograph, rather than flat
Sealed Quench Furnaces - How they Work
[Animation]
The front door is opened by two hydraulic cylinders, one at either
side of the door
The load is charged into the hot furnace by an automatic loader
designed to place the load in the correct position on the hearth for
the internal transfer chains
Once the front door is shut, the operating temperature (set point)
and atmosphere are re-established quickly
The load is held at temperature for the required time, either for the
process to be complete (hardening) or for the required case depth to
be achieved (carburising or carbonitriding)
The load is then automatically transferred on to the quench rack in
the rear chamber above the oil tank for quenching or atmosphere
cooling
Sealed Quench Furnaces - How they Work
You will notice that, prior to quenching, the two transfer chains move
half a revolution so that the chain dogs contact the workload basket
This ensures that the cold chain (at less than a hundred oC), which
normally resides in the chain case, is ready to push the load from the
furnace hearth on to the quench rack
This avoids putting a heavy load on the hot chain (at the working
temperature of the furnace – up to 1000oC) which could result in it
stretching
At this point, the electric chain drive motor stops so that the middle
door, which separates the furnace hot zone from the quench vestibule,
can open to allow the load to be transferred
[Animation]
Sealed Quench Furnaces - How they Work
Once the load has transferred to the quench rack, the middle door
closes and the load can either be held where it is and atmosphere
cooled or lowered into the oil and quenched
Oil immersion times are accurately controlled and when the allotted
quench time is complete, the load will be raised out of the oil and
stood for a few minutes to allow oil retained on the charge to drip
back into the quench tank
The load is then ready to be removed from the furnace by the
automatic unloader
After treatment in the sealed quench furnace, some other processes
must be carried out, such as washing and tempering
[Animation]
Sealed Quench Furnaces - Quality Control
A typical laboratory in a heat
treatment facility
Before the components are
ready for use, they must be
checked by the inspection staff
to ensure that they meet the
drawing requirements
Representative samples or actual
components are sent to the
laboratory to be cut up and used
for hardness and structural
analysis, to make sure that their
quality is in accordance with the
specification
At the same time, the paperwork
is checked to see that all
processing details are correct
Only when all of these quality
checks have been passed can
the components be certified as
fit for use
Summary of the Module

In this Module, you have come to appreciate the background
to steel and understand why and how it is heat treated

The role of surface engineering heat treatments has been
briefly outlined, from the earliest primitive techniques to
modern controlled atmosphere processing

A sealed quench furnace, the most important of the modern
surface engineering plant, has been illustrated and its
underlying principles have been explained

The preparation of components and the assembly of loads in
preparation for processing were described in some detail

The operation of a modern, straight-through sealed quench
furnace has been demonstrated using an animated schematic
diagram
Section 3 - Self-Test (1)
What is a sealed quench
furnace?
Tick all that are correct





A batch furnace
An in-out furnace
A modern heat treating unit
A continuous furnace
An integral quench furnace
Section 3 - Self-Test (1)
What is a sealed quench
furnace?
Tick all that are correct





A batch furnace
An in-out furnace
A modern heat treating unit
A continuous furnace
An integral quench furnace
Section 3 - Self-Test (1)
What is a sealed quench
furnace?
Tick all that are correct





A batch furnace
An in-out furnace
A modern heat treating unit
A continuous furnace
An integral quench furnace
Section 3 - Self-Test (1)
What is a sealed quench
furnace?
Tick all that are correct
 CORRECT





A batch furnace
An in-out furnace
A modern heat treating unit
A continuous furnace
An integral quench furnace
• An in-out furnace is only one design of sealed quench
furnace, some are of a straight-through design
• A continuous furnace is the opposite of a batch furnace
Section 3 - Self-Test (2)
A sealed quench furnace
consists of?
Tick all that are correct





A
A
A
A
A
straight-through design
heating chamber
load transfer system
quench chamber
tempering furnace
Section 3 - Self-Test (2)
A sealed quench furnace
consists of?
Tick all that are correct





A
A
A
A
A
straight-through design
heating chamber
load transfer system
quench chamber
tempering furnace
Section 3 - Self-Test (2)
A sealed quench furnace
consists of?
Tick all that are correct





A
A
A
A
A
straight-through design
heating chamber
load transfer system
quench chamber
tempering furnace
Section 3 - Self-Test (2)
A sealed quench furnace
consists of?
Tick all that are correct
 CORRECT





A
A
A
A
A
straight-through design
heating chamber
load transfer system
quench chamber
tempering furnace
• Sealed quench furnaces can be either straight-through or inout design
• They are a high-temperature furnace, not suitable for lowtemperature tempering
Section 3 - Self-Test (3)
Why must Long thin shafts
be jigged vertically?

Tick the one that is correct




To get as many as possible
in a load
To prevent distortion
To allow oil quenching
To give even heating
To fit gears on top
Section 3 - Self-Test (3)
Why must Long thin shafts
be jigged vertically?

Tick the one that is correct




 CORRECT
To get as many as possible
in a load
To prevent distortion
To allow oil quenching
To give even heating
To fit gears on top
Section 3 - Self-Test (4)
Why are components
stopped-off?
Tick the one that is correct





To allow them to be welded
To improve their appearance
To
keep
part
of
the
component soft
To keep them straight
To make them easier to
harden
Section 3 - Self-Test (4)
Why are components
stopped-off?
Tick the one that is correct





 CORRECT
To allow them to be welded
To improve their appearance
To
keep
part
of
the
component soft
To keep them straight
To make them easier to
harden
Test Results – Section 1
Q1





Q2





Q3





What is steel?
Iron with Chromium added
Iron with carbon added
Hardened iron
Stainless steel
Metal tools
You scored 15 out of 15
How is steel hardened?
By
By
By
By
By
surface engineering
quenching
tempering
adding other metals
carburising
What is surface engineering?
Heat treatment in a sealed quench furnace
Making components that work
Hardening and tempering steel surfaces
Creating a surface and core with better properties than they have alone
Changing the shape of the surface
Test Results – Section 2
Q1 What was used in early case hardening?





Q2





Q3





Hooves
Animal skins
Oil quenching
Pack Carburizer #18
Urine
You scored 15 out of 15
Which of these processes are carried out at high temperatures?
Nitriding
Carburising
Carbonitriding
Nitrocarburising
Tempering
The gases used in controlled atmospheres are?
Toxic
Corrosive
Alloyed
Explosive
Flammable
Test Results – Section 3
Q1 What is a sealed quench furnace?





A batch furnace
An in-out furnace
A modern heat treating unit
A continuous furnace
An integral quench furnace
Q2 A sealed quench furnace consists of?





Q3





A
A
A
A
A
straight-through design
heating chamber
load transfer system
quench chamber
tempering furnace
Why must Long thin shafts be jigged vertically?
To
To
To
To
To
get as many as possible in a load
prevent distortion
allow oil quenching
give even heating
put gears on top
Test Results – Section 3 (continued)
Q4 Why are components stopped-off?
 To allow them to be welded
 To improve their appearance
 To keep part of the component soft
 To keep them straight
 To make them easier to harden
You scored 20 out of 20
Test Results – Summary
The pass mark for this Module is 80%
You scored 50 out of 50, giving a result of 100%
Congratulations, you have passed the Module.
automatically receive a Pass Certificate shortly
You
will
Unfortunately, you have failed the Module. You need to pass the
Module before you progress. Please contact your training
manager to arrange to re-sit it.
Unfortunately, you have failed the Module. However, you will
automatically receive a Certificate of Attendance shortly
END
Background – Hardening Steel
A 2.7 tonne forging (at 990ºC) being lowered into an oil
quench tank. The flames are from the first oil touched by the
component and are rapidly extinguished as the part cools
[close window]
Background – Surface Engineering
The vertical line on the right is the surface of the
component, which has been cut through at right angles to
produce this photograph. The light brown colour just below
the surface has a high carbon content which reduces, the
further away you are from the surface. The left hand half of
the photograph shows the original low carbon steel –
unaffected by the case hardening.
[close window]
Section 2 - Heat Treatment
The picture shows
a blacksmith’s
shop from the
Middle Ages with a
rectangular water
trough for
quenching, on top
of the hearth.
Scattered around
the picture are the
various tools of his
trade – most of
which are virtually
the same as those
used by modern
blacksmiths.
[close window]
Controlled Atmosphere Furnaces
IPSEN T11 Sealed
Quench FurnaceIPSEN T11 Sealed Quench Furnace
[close window]
Sealed Quench Furnaces - Introduction
The sealed quench is a batch furnace in which the heating and
quenching chambers are combined in a single unit
The two chambers are separated by a refractory-lined door which can
be opened to allow the hot charge to be transferred from the heating
chamber to the cooling chamber
In the UK, the furnaces are loaded at the front and unloaded at the
other end (straight-through design)
A straight-through sealed quench furnace, based on a design by Ipsen
[close window]
Sealed Quench Furnaces-Introduction
An in-out
sealed quench
furnace, based
on a design by
Surface
Combustion
[close window]
Sealed Quench Furnaces-Introduction
This was the largest, straight-through sealed quench unit - an
Ipsen TQ37 – originally installed at Bodycote, Corby, UK. It
has a working size of about 1.2m x 0.9m x 1.8m long and
could take a load of 2,200kg.
[close window]
Sealed Quench Furnace - Description
[close window]
Heating Chamber
[close window]
Heating Chamber
[close window]
Quench Chamber
[close window]
Sealed Quench Furnace - Quenching
[close window]
Sealed Quench Furnaces - Preparing
Work for Processing
A load of shafts stood
vertically with a layer of
gears on top, prepared
for medium case
hardening. It is about to
be loaded into an Ipsen
TQ10 sealed quench
furnace.
(Bodycote Macclesfield, UK)
This photograph shows a mixed load of
shafts stood vertically with a layer of
gears on top
[close window]
Sealed Quench Furnaces - Preparing
Work for Processing
A batch of gears
assembled into a
load, ready for
carburising. The
components are
made up using
modular jigging,
designed to
support the
component for
distortion-free
case hardening
and quenching.
(Bodycote Macclesfield, UK)
[close window]
Quality Control
A laboratory technician carrying out hardness testing. Visible
on the back bench are, from left to right, a Rockwell hardness
tester, a mounting press (for encapsulating samples in plastic
to make them easier to hold) and a lab muffle furnace. Two
sets of polishing wheels can be seen on the right hand bench.
[close window]
Background - Steel
The number 18-8 means that the spoon is made of
stainless steel containing 18% chromium and 8%
nickel. Sometimes you can find items that are marked
18:10. These contain 18% chromium but have 10%
nickel, which improves their corrosion resistance.
Look in your kitchen draw to see what your stainless
steel cutlery is made from.
[close window]
Hazard signs
HAZARD
IDENTIFICATION
SIGNS
Do not ignore them
From a distance,
these signs warn
you about the
hazards in the
area you are about
to enter
Close to, these
signs remind you
about the hazards
found in the area
in which you are
working
[close window]
What is Surface Engineering?
This is a backhoe
earth moving
machine, made in
the UK by JCB. The
gears in its
transmission are
carburised and
hardened, as is
the rack and
pinion steering
mechanism. Many
other parts only
survive this heavy
duty application
by being hardened
and tempered.
[close window]
What is Surface Engineering?
This Roman statue
shows Mars, the Roman
God of War. He was the
son of Jupiter (King of
the Gods) and Juno
(Goddess of heaven &
the moon). According to
legend, Mars was the
father of Romulus and
Remus, the founders of
Rome.
The month of March
(Martius) is named after
him, as is the red planet,
Mars, seen in the
background.
[close window]
What is Surface Engineering?
Name: Iron
Symbol: Fe
Colour: Silvery
Atomic Number: 26
Melting Point: 1,535°C
Boiling Point: 2,750°C
Atomic Mass: 55.845 amu
Number of Protons/Electrons: 26
Number of Neutrons: 30
Classification: Transition metal
Crystal Structure: Cubic
Density at 20°C: 7.86 g/cm3
Iron does not occur
naturally on Earth as it
oxidises too easily.
However, it can be found
in meteorites like the
one above from
Argentina
[close window]
What is Surface Engineering?
Pack carburising is still used
because it requires relatively
simple
and
inexpensive
equipment and can be used in
either
batch
or
continuous
furnaces to produce a deep case,
which it does efficiently and
economically.
Parts are placed in a steel
container surrounded by the
pack carburising compound. The
container is sealed then heated
in an air furnace to the
operating temperature.
After processing, the container
is removed from the furnace,
broken open and the parts are
removed by hand and quenched
in water.
Logo of an American
company currently
selling pack
carburising compound
[close window]
What is Surface Engineering?
View of the rear of a sealed quench furnace as soon as the
rear door has been opened.
Before the rear door can open, a flame curtain must ignite
in front of the door. As the door opens, the flame curtain
ignites the atmosphere gases and they burn spectacularly,
but harmlessly.
[close window]
What is Surface Engineering?
The centre of the shaft is stopped off prior to carburising.
This area of the shaft must not be carburised because a gear
is welded to it at our electron beam welding facility at
Skelmersdale, UK. Carburised steel is very difficult to weld.
The photograph shows a similar shaft with the gear
attached, ready for assembly into a gearbox.
[close window]