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					THE SEALED QUENCH FURNACE

         Module 1
APPRECIATION OF THE SEALED
     QUENCH FURNACE
 Brian J. Birch, Brian Ellis & Leanie Mackenzie
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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 rust-
proof (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

                                  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
                                  850  oC) 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
 A 2.7 tonne component being      chosen temperature, usually
lowered into an oil quench tank   between 150oC and 600oC – a
  (Bodycote Melrose Park, USA)    process called tempering
    Background – Surface Engineering
                               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
  This view of the cross-      Surface engineering produces
 section of a component,       a different structure on the
magnified 100 times using a    surface of steel, which can be
microscope, shows the steel    seen when a component is cut
surface (at the right) after   and prepared in a laboratory
      case hardening
 Background – Surface Engineering

Surface engineering by heat treatment requires the use of a high-
temperature 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)


                                 Iron with chromium added
What is steel?
                                 Iron with carbon added
  Tick all that are correct
                                 Hardened iron
                                 Stainless steel
                                 Metal tools
           Section 1 – Self-Test (1)


                                 Iron with chromium added
What is steel?
                                 Iron with carbon added
  Tick all that are correct
                                 Hardened iron
                                 Stainless steel
                                 Metal tools
           Section 1 – Self-Test (1)


                                 Iron with chromium added
What is steel?
                                 Iron with carbon added
  Tick all that are correct
                                 Hardened iron
                                 Stainless steel
                                 Metal tools
           Section 1 – Self-Test (1)


                                     Iron with chromium added
What is steel?
                                     Iron with carbon added
  Tick all that are correct
                                     Hardened iron
                                     Stainless steel
                                     Metal tools


    CORRECT
           •   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?             By   surface engineering
 Tick the one that is correct      By   quenching
                                   By   tempering
                                   By   adding other metals
                                   By   carburising
              Section 1 – Self-Test (2)


  How is steel hardened?                By   surface engineering
    Tick the one that is correct        By   quenching
                                        By   tempering
                                        By   adding other metals
                                        By   carburising

 CORRECT
        • 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?       Heat treatment in a sealed
 Tick the one that is correct       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?       Heat treatment in a sealed
  Tick the one that is correct       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



 CORRECT
          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
                     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
  IPSEN T11 Sealed   Sealed quench furnaces are a type
   Quench Furnace    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 modern-
    day processing, particularly the sealed quench furnace,
    have been briefly explained
          Section 2 – Self-Test (1)


What was used in early          Hooves
case hardening?                 Animal skins
 Tick all that are correct      Oil quenching
                                Pack Carburizer #18
                                Urine
          Section 2 – Self-Test (1)


What was used in early          Hooves
case hardening?                 Animal skins
 Tick all that are correct      Oil quenching
                                Pack Carburizer #18
                                Urine
             Section 2 – Self-Test (1)


  What was used in early               Hooves
  case hardening?                      Animal skins
    Tick all that are correct          Oil quenching
                                       Pack Carburizer #18
                                       Urine


 CORRECT
         • 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        Nitriding
are carried out at high         Carburising
temperatures?                   Carbonitriding
 Tick all that are correct
                                Nitrocarburising
                                Tempering
          Section 2 – Self-Test (2)


Which of these processes        Nitriding
are carried out at high         Carburising
temperatures?                   Carbonitriding
 Tick all that are correct
                                Nitrocarburising
                                Tempering
           Section 2 – Self-Test (2)


 Which of these processes           Nitriding
 are carried out at high            Carburising
 temperatures?                      Carbonitriding
  Tick all that are correct
                                    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               Toxic
controlled atmospheres          Corrosive
are?                            Alloyed
 Tick all that are correct
                                Explosive
                                Flammable
          Section 2 – Self-Test (3)


The gases used in               Toxic
controlled atmospheres          Corrosive
are?                            Alloyed
 Tick all that are correct
                                Explosive
                                Flammable
          Section 2 – Self-Test (3)


The gases used in               Toxic
controlled atmospheres          Corrosive
are?                            Alloyed
 Tick all that are correct
                                Explosive
                                Flammable
           Section 2 – Self-Test (3)


The gases used in                     Toxic
controlled atmospheres                Corrosive
are?                                  Alloyed
  Tick all that are correct
                                      Explosive
                                      Flammable


 CORRECT
          • 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      [Play video]
operation - a far cry from the
earliest units of fifty years ago
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     Schematic view of the
treatments        such      as     front chamber of a
hardening, carburising and       sealed quench furnace
carbonitriding
Sealed Quench Furnace – Heating Chamber

                           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
   Schematic view of the   radiation from the radiant
                           tubes which could cause hot
     front chamber of a
                           spots on the work load
   sealed quench furnace
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      Schematic view of the
   quench chamber                      front chamber of a
                                     sealed quench furnace
Sealed Quench Furnace - Quench Chamber

                           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
   Schematic view of the   immersion heaters at each side of
    cooling chamber of a   the tank
   sealed quench furnace   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       Schematic view of the
gases    and    vent  them         cooling chamber of a
outside the factory               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

                                 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
A typical laboratory in a heat   checks have been passed can
      treatment facility         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         A batch furnace
furnace?                        An in-out furnace
 Tick all that are correct      A modern heat treating unit
                                A continuous furnace
                                An integral quench furnace
          Section 3 - Self-Test (1)


What is a sealed quench         A batch furnace
furnace?                        An in-out furnace
 Tick all that are correct      A modern heat treating unit
                                A continuous furnace
                                An integral quench furnace
          Section 3 - Self-Test (1)


What is a sealed quench         A batch furnace
furnace?                        An in-out furnace
 Tick all that are correct      A modern heat treating unit
                                A continuous furnace
                                An integral quench furnace
             Section 3 - Self-Test (1)


  What is a sealed quench               A batch furnace
  furnace?                              An in-out furnace
    Tick all that are correct           A modern heat treating unit
                                        A continuous furnace
                                        An integral quench furnace


 CORRECT
         • 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         A   straight-through design
consists of?                    A   heating chamber
 Tick all that are correct      A   load transfer system
                                A   quench chamber
                                A   tempering furnace
          Section 3 - Self-Test (2)


A sealed quench furnace         A   straight-through design
consists of?                    A   heating chamber
 Tick all that are correct      A   load transfer system
                                A   quench chamber
                                A   tempering furnace
          Section 3 - Self-Test (2)


A sealed quench furnace         A   straight-through design
consists of?                    A   heating chamber
 Tick all that are correct      A   load transfer system
                                A   quench chamber
                                A   tempering furnace
            Section 3 - Self-Test (2)


  A sealed quench furnace            A   straight-through design
  consists of?                       A   heating chamber
   Tick all that are correct         A   load transfer system
                                     A   quench chamber
                                     A   tempering furnace



 CORRECT
        • Sealed quench furnaces can be either straight-through or in-
          out design
        • They are a high-temperature furnace, not suitable for low-
          temperature tempering
          Section 3 - Self-Test (3)


Why must Long thin shafts          To get as many as possible
be jigged vertically?               in a load
 Tick the one that is correct      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           To get as many as possible
  be jigged vertically?                in a load
    Tick the one that is correct      To prevent distortion
                                      To allow oil quenching
                                      To give even heating
                                      To fit gears on top



 CORRECT
          Section 3 - Self-Test (4)


Why are components                 To allow them to be welded
stopped-off?                       To improve their appearance
 Tick the one that is correct      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                  To allow them to be welded
  stopped-off?                        To improve their appearance
    Tick the one that is correct      To    keep   part    of  the
                                       component soft
                                      To keep them straight
                                      To make them easier to
                                       harden


 CORRECT
                      Test Results – Section 1
Q1   What is steel?
    Iron with Chromium added                   You scored 15 out of 15
    Iron with carbon added
    Hardened iron
    Stainless steel
    Metal tools

Q2   How is steel hardened?
    By   surface engineering
    By   quenching
    By   tempering
    By   adding other metals
    By   carburising

Q3   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?
    Hooves                               You scored 15 out of 15
    Animal skins
    Oil quenching
    Pack Carburizer #18
    Urine

Q2   Which of these processes are carried out at high temperatures?
    Nitriding
    Carburising
    Carbonitriding
    Nitrocarburising
    Tempering

Q3   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?
    A   straight-through design
    A   heating chamber
    A   load transfer system
    A   quench chamber
    A   tempering furnace

Q3   Why must Long thin shafts be jigged vertically?
    To   get as many as possible in a load
    To   prevent distortion
    To   allow oil quenching
    To   give even heating
    To   put gears on top
      Test Results – Section 3 (continued)

Q4 Why are components stopped-off?     You scored 20 out of 20
 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 – 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.         You   will
automatically receive a Pass Certificate shortly
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,                           Close to, these
 these signs warn                         signs remind you
   you about the                          about the hazards
  hazards in the                          found in the area
area you are about                         in which you are
     to enter                                  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               Iron does not occur
Number of Protons/Electrons: 26     naturally on Earth as it
Number of Neutrons: 30                oxidises too easily.
Classification: Transition metal   However, it can be found
Crystal Structure: Cubic             in meteorites like the
Density at 20°C: 7.86 g/cm3             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
                                     Logo of an American
container is sealed then heated
                                      company currently
in an air furnace to the
                                         selling pack
operating temperature.
                                    carburising compound
After processing, the container
is removed from the furnace,
broken open and the parts are
removed by hand and quenched
in water.
                        [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]

				
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