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THE SEALED QUENCH FURNACE. Module 1. APPRECIATION OF THE SEALED QUENCH FURNACE. Brian J. Birch, Brian Ellis & Leanie Mackenzie. How to use this training module. To navigate through the training module use the Previous and Next buttons located at the bottom of the screen

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The sealed quench furnace

THE SEALED QUENCH FURNACE

Module 1


Appreciation of the sealed quench furnace

APPRECIATION OF THE SEALED QUENCH FURNACE

Brian J. Birch, Brian Ellis & Leanie Mackenzie


How to use this training module

How to use this training module

  • To navigate through the training module use the Previous and Next buttons located at the bottom of the screen

  • You can click on any of the images or diagrams with the mouse, to enlarge them and see additional information

  • Any words in this training module in blue and underlined, can be clicked on for a detailed explanation from the Glossary

  • The complete list of technical words associated with the whole of this Course and concise explanations of them, can be viewed using the Glossary button located at the bottom of the screen


Introduction

Introduction

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

  • Background

    • What iron and steel are

    • Why steel is heat treated and surface engineered

  • Heat Treatment

    • When it began

    • How it is carried out

  • Sealed Quench Furnaces

    • What they are

    • How they work

  • Summary of the Module

  • Self-Test & Test Results


Objectives

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

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

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

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 alloysteel

  • 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 steel1

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

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 850oC) 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

A 2.7 tonne component being lowered into an oil quench tank (Bodycote Melrose Park, USA)


Background surface engineering

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

  • Surface engineeringproduces 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


Background surface engineering1

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 engineeringby heat treatment are processed in special controlled atmospherefurnaces

  • 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 - What is Surface Engineering?


Background how bodycote engineers surfaces

Background - How BodycoteEngineers 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

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)


Section 1 self test 11

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)


Section 1 self test 12

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)


Section 1 self test 13

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)

  • 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

By surface engineering

By quenching

By tempering

By adding other metals

By carburising

How is steel hardened?

Tick the one that is correct

Section 1 – Self-Test (2)


Section 1 self test 21

How is steel hardened?

Tick the one that is correct

By surface engineering

By quenching

By tempering

By adding other metals

By carburising

Section 1 – Self-Test (2)

  • 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

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


Section 1 self test 31

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)

  • CORRECT


Section 2 heat treatment

Section 2 - Heat Treatment

  • Heat treatment is the oldest technique of surface engineeringand 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

Heat Treatment – Early Methods

  • With this casehardening 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

    #18PACK CARBURIZER


Heat treatment surface engineering

Heat Treatment - Surface Engineering

  • Surface engineering by heat treatment can be divided into two groups based on the processing temperatures:

    • Nitridingand nitrocarburising, which are generally carried out at temperatures between 450°C & 590°C

    • Carburisingand carbonitridingwhich 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 quenchfurnaces


Heat treatment controlled gas atmospheres

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:-

    • Better control of the surface carbon content of the component

    • Higher productivity of the equipment

    • Less possibility of oxidationof the component’s surface

    • Less labour required to run the equipment

    • Easier to automate and control the process

    • Better working conditions for the operators

    • 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

Heat Treatment - What are Controlled Atmospheres?

  • A controlled atmosphereis 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 monoxideand hydrogen

  • This composition means that the gas mixture is highly flammable, toxic and potentially explosive


Heat treatment using controlled atmospheres

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

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:

    • Batch furnaces – where the work is charged and discharged as a single unit or batch

    • 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 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

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 case hardening?

Tick all that are correct

Hooves

Animal skins

Oil quenching

Pack Carburizer #18

Urine

Section 2 – Self-Test (1)


Section 2 self test 11

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)


Section 2 self test 12

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)

  • 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

Nitriding

Carburising

Carbonitriding

Nitrocarburising

Tempering

Which of these processes are carried out at high temperatures?

Tick all that are correct

Section 2 – Self-Test (2)


Section 2 self test 21

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)


Section 2 self test 22

Nitriding

Carburising

Carbonitriding

Nitrocarburising

Tempering

Which of these processes are carried out at high temperatures?

Tick all that are correct

Section 2 – Self-Test (2)

  • 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)


Section 2 self test 31

The gases used in controlled atmospheres are?

Tick all that are correct

Toxic

Corrosive

Alloyed

Explosive

Flammable

Section 2 – Self-Test (3)


Section 2 self test 32

The gases used in controlled atmospheres are?

Tick all that are correct

Toxic

Corrosive

Alloyed

Explosive

Flammable

Section 2 – Self-Test (3)


Section 2 self test 33

Toxic

Corrosive

Alloyed

Explosive

Flammable

The gases used in controlled atmospheres are?

Tick all that are correct

Section 2 – Self-Test (3)

  • CORRECT

    • Gases are generally not corrosive except in the presence of water

    • Only metals can be alloyed


Section 3 sealed quench furnaces

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 quenchfurnaces 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 furnaces1

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

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 introduction1

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 introduction2

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

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 atmospherewhich protects the components from oxidationand 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

Sealed Quench Furnace – Heating Chamber

  • The furnaces are heated by four to six radiant tubesper 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 tubeswhich could cause hot spots on the work load

Schematic view of the front chamber of a sealed quench furnace


Sealed quench furnace heating chamber1

Sealed Quench Furnace – Heating Chamber

  • The muffle and the holes in the hearth provide a flow path for the controlled atmosphereduring 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

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 immersion heaters at each side of the tank

  • An external oil cooler is also provided in case the oil gets too hot

Schematic view of the cooling chamber of a sealed quench furnace


Sealed quench furnace quenching

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

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 processing1

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 processing2

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

Sealed Quench Furnaces - How they Work

  • 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

[Animation]


Sealed quench furnaces how they work1

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 dogscontact 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 work2

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

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 checks have been passed can the components be certified as fit for use

A typical laboratory in a heat treatment facility


Summary of the module

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)


Section 3 self test 11

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)


Section 3 self test 12

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)


Section 3 self test 13

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)

  • 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 consists of?

Tick all that are correct

A straight-through design

A heating chamber

A load transfer system

A quench chamber

A tempering furnace

Section 3 - Self-Test (2)


Section 3 self test 21

A sealed quench furnace consists of?

Tick all that are correct

A straight-through design

A heating chamber

A load transfer system

A quench chamber

A tempering furnace

Section 3 - Self-Test (2)


Section 3 self test 22

A sealed quench furnace consists of?

Tick all that are correct

A straight-through design

A heating chamber

A load transfer system

A quench chamber

A tempering furnace

Section 3 - Self-Test (2)


Section 3 self test 23

A sealed quench furnace consists of?

Tick all that are correct

A straight-through design

A heating chamber

A load transfer system

A quench chamber

A tempering furnace

Section 3 - Self-Test (2)

  • 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 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)


Section 3 self test 31

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)

  • CORRECT


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)


Section 3 self test 41

Why are components stopped-off?

Tick the one that is correct

Section 3 - Self-Test (4)

  • 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


Test results section 1

Test Results – Section 1

You scored 15 out of 15

Q1 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


Test results section 2

Test Results – Section 2

You scored 15 out of 15

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


Test results section 3

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

Test Results – Section 3 (continued)

You scored 20 out of 20

  • 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


The sealed quench furnace

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


The sealed quench furnace

END


Background hardening steel1

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

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Background surface engineering2

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.

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Section 2 heat treatment1

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.

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Controlled atmosphere furnaces

Controlled Atmosphere Furnaces

IPSEN T11 Sealed Quench Furnace

IPSEN T11 Sealed Quench Furnace

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Sealed quench furnaces introduction3

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

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Sealed quench furnaces introduction4

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Sealed Quench Furnaces-Introduction

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


Sealed quench furnaces introduction5

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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.


Sealed quench furnace description1

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Sealed Quench Furnace - Description


Heating chamber

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Heating Chamber


Heating chamber1

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Heating Chamber


Quench chamber

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Quench Chamber


Sealed quench furnace quenching1

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Sealed Quench Furnace - Quenching


Sealed quench furnaces preparing work for processing3

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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


Sealed quench furnaces preparing work for processing4

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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)


Quality control

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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.


Background steel2

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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.


Hazard signs

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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


What is surface engineering

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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.


What is surface engineering1

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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.


What is surface engineering2

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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: 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


What is surface engineering3

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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


What is surface engineering4

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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.


What is surface engineering5

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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 weldingfacility 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.


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