the sealed quench furnace

THE SEALED QUENCH FURNACETHE SEALED QUENCH FURNACE

Module 1

APPRECIATION OF THE SEALED APPRECIATION OF THE SEALED QUENCH FURNACEQUENCH FURNACE

Brian J. Birch, Brian Ellis & Leanie Mackenzie

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IntroductionIntroduction

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

This Module is an introduction to the sealed quench furnace and includes the following topics:

ObjectivesObjectives

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

Upon completion of this Module, the learner will be able to:

Section 1 - BackgroundSection 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 - IronBackground - 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 - SteelBackground - 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


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 nickelThe 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 SteelBackground – Hardening Steel

Another advantage of steel is that when it is produced, it is quite soft and can be machined easily into complex shapesHowever, it can then be hardened by heating it to a high temperature (above 850oC) and cooling it rapidly in oil or water – a process called quenchingAfter 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

A 2.7 tonne component being lowered into an oil quench tank

(Bodycote Melrose Park, USA)

Background – Surface EngineeringBackground – Surface Engineering

Sometimes, even hardened steel is not good enough for a particular application or useTherefore, 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 jobThis is called surface engineeringSurface engineering produces a different structure on the surface of steel, which can be seen when a component is cut and prepared in a laboratory

This view of the cross-section of a component,

magnified 100 times using a microscope, shows the steel surface (at the right) after

case hardening


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 Background - What is Surface Engineering?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 alonePut 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 BodycoteBackground - How BodycoteEngineers SurfacesEngineers 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 - SummarySection 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)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


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

What is steel?Tick all that are correct

Iron with chromium added Iron with carbon added Hardened iron Stainless steel Metal tools


By surface engineering By quenching By tempering By adding other metals By carburising

How is steel hardened?Tick the one that is correct


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

How is steel hardened?Tick the one that is correct

By surface engineering By quenching By tempering By adding other metals By carburising


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

What is surface engineering?

Tick the one that is correct


CORRECT

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

Section 2 - Heat TreatmentSection 2 - Heat Treatment

Heat treatment is the oldest technique of surface engineering and has been carried out almost since man’s first use of ironThe 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 yearsThese 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 MethodsHeat 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 atmospheresRemarkably, the traditional case hardening method, which became known as pack carburising, was still being carried out widely in the UK in the 1960sEven 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 EngineeringHeat 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 Heat Treatment - Controlled Gas AtmospheresAtmospheres

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 Heat Treatment - What are Controlled Atmospheres?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 componentPut more simply, the atmosphere within the furnace chamber is a vital factor in achieving the chemical reactions that need to occur during heat treatmentThe active ingredients of controlled atmospheres are carbon monoxide and hydrogenThis composition means that the gas mixture is highly flammable, toxic and potentially explosive

Heat Treatment – Using Controlled Heat Treatment – Using Controlled AtmospheresAtmospheres

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 Heat Treatment - Controlled Atmosphere FurnacesAtmosphere Furnaces

Special furnaces are used for processing steels using controlled atmospheresThey must be gas tight and have certain safety features which allow them to be used with the toxic and flammable gases involvedControlled 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

IPSEN T11 Sealed Quench Furnace

Heat Treatment - What is a Batch Heat Treatment - What is a Batch Furnace?Furnace?

A batch furnace heat treats components in discrete lots (batches), each of which is finished before the next batch is startedBatch furnaces generally consist of an insulated heating chamber with an external reinforced steel shell and one or more access doors to the heating chamberAfter the heating period is over, the load must be transferred from the furnace for quenching in an external tank of oil or waterThe 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 - SummarySection 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


What was used in early case hardening?

Tick all that are correct

Hooves Animal skins 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

What was used in early case hardening?


Hooves Animal skins Oil quenching Pack Carburizer #18 Urine


Nitriding Carburising Carbonitriding Nitrocarburising Tempering

Which of these processes are carried out at high temperatures?



CORRECTCarburising 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





The gases used in controlled atmospheres are?


Toxic Corrosive Alloyed Explosive Flammable


CORRECT• Gases are generally not corrosive except in the

presence of water• Only metals can be alloyed

Toxic Corrosive Alloyed Explosive Flammable

The gases used in controlled atmospheres are?


Section 3 - Sealed Quench FurnacesSection 3 - Sealed Quench Furnaces

Anyone who sees a sealed quench furnace for the first time remarks on the flames & noiseIn 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 upThese are perfectly normal reactions of those new to sealed quench operations, and not an indication of problemsHowever, 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

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Section 3 - Sealed Quench FurnacesSection 3 - Sealed Quench Furnaces

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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.)

Sealed Quench Furnaces - IntroductionSealed 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 chamberIn the UK, most of the furnaces are loaded at the front and unloaded at the rear (straight-through design)


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 rollersIn 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 usually operate over the temperature range 750°C to 1000°C but can operate from 570oC to 1100°C with suitable modificationsThey are usually fairly small in size owing to the limitations of the internal mechanical transfer system and the quenching capacityThe 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 - DescriptionSealed Quench Furnace - Description

The hot zone consists of a steel outer shell, which is lined on the inside with refractory bricksThe 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 atmosphereThe 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 ChamberSealed Quench Furnace – Heating Chamber

The furnaces are heated by four to six radiant tubes per side, depending upon the size of the furnaceThese 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 muffleThis 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 ChamberSealed 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



Sealed Quench Furnace - Quench ChamberSealed Quench Furnace - Quench Chamber

The rear chamber of the furnace consists of a water-cooled steel shell above an oil filled quench tankA quench rack is fitted in the chamber to move the work load into and out of the oil as requiredThe oil is circulated around the components by motor driven propellers situated at each side of the tankThe temperature of the oil can be raised by means of the immersion heaters at each side of the tankAn external oil cooler is also provided in case the oil gets too hot

Schematic view of the cooling chamber of a


Sealed Quench Furnace - QuenchingSealed 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 Furnaces - Preparing Sealed Quench Furnaces - Preparing Work for ProcessingWork 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)


Proper jigging and fixtures are essential to ensure that components are correctly supported and spaced to minimise distortion and ensure correct treatmentFor 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)


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 quenchingBoth 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 WorkSealed Quench Furnaces - How they Work

The front door is opened by two hydraulic cylinders, one at either side of the doorThe 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 chainsOnce the front door is shut, the operating temperature (set point) and atmosphere are re-established quicklyThe 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

[Animation]


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]


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 ControlSealed 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 requirementsRepresentative 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 specificationAt the same time, the paperwork is checked to see that all processing details are correctOnly when all of these quality checks have been passed can the components be certified as fit for use

A typical laboratory in a heat treatment facility

Summary of the ModuleSummary 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)Section 3 - Self-Test (1)

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


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

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


A sealed quench furnace consists of?


A straight-through design A heating chamber 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

A sealed quench furnace consists of?


A straight-through design A heating chamber A load transfer system A quench chamber A tempering furnace


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 fit gears on top


CORRECT

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 fit gears on top


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


CORRECT

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

Test Results – Section 1Test Results – Section 1Q1 What is steel? Iron with Chromium added 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

You scored 15 out of 15

Test Results – Section 2Test Results – Section 2

Q1 What was used in early case hardening? Hooves 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

You scored 15 out of 15

Test Results – Section 3Test Results – Section 3Q1 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)Test Results – Section 3 (continued)

You scored 20 out of 20Q4 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

Test Results – SummaryTest 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

ENDEND

Background – Hardening SteelBackground – 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]


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 TreatmentSection 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.

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Controlled Atmosphere FurnacesControlled Atmosphere Furnaces

IPSEN T11 Sealed Quench FurnaceIPSEN T11 Sealed Quench Furnace

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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 chamberIn the UK, the furnaces are loaded at the front and unloaded at the other end (straight-through design)

[close window]

A straight-through sealed quench furnace, based on a design by Ipsen

Sealed Quench Furnaces-IntroductionSealed Quench Furnaces-Introduction

[close window]

An in-out sealed quench furnace, based on a design by Surface Combustion

Sealed Quench Furnaces-IntroductionSealed Quench Furnaces-Introduction

[close window]

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.

Sealed Quench Furnace - DescriptionSealed Quench Furnace - Description

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Heating ChamberHeating Chamber

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Quench ChamberQuench Chamber

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Sealed Quench Furnace - QuenchingSealed Quench Furnace - Quenching

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This photograph shows a mixed load of shafts stood vertically with a layer of gears on top

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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)


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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)

Quality ControlQuality Control

[close window]

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]

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.

Hazard signsHazard signs

[close window]

From a distance, these signs warn

you about the hazards in the

area you are about to enter

HAZARD IDENTIFICATION

SIGNS

Do not ignore them

Close to, these signs remind you about the hazards found in the area in which you are

working

What is Surface Engineering?What is Surface Engineering?

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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]

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.


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Name: Iron Symbol: Fe Colour: Silvery

Atomic Number: 26 Melting Point: 1,535°C Boiling Point: 2,750°C Atomic Mass: 55.845 amuNumber of Protons/Electrons: 26Number 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


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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


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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.


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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.

the sealed quench furnace

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