Heat treat process

Heat treating process

Learning target: I can identify all the steps to
complete the heat treat process.

What is it?

Heat treatment is a controlled process used to alter the microstructure of metals and alloys such as steel and aluminium to impart properties which benefit the working life of a component, for example increased surface hardness, temperature resistance,
ductility and strength.

Open Ended

Metal becomes what after its been heat treated?

When would I use it
and why?

​Heat treating material makes the
material stronger! It will not bend but it
could break. Commonly used in knife
blades and different tools to hold up,
without it knives would just bend.

Terms to know!

●

Annealing

●

Tempering

●

Quenching

●

Surface hardening

Annealing

Annealing is a specific process of heat treatment that alters the properties of metal.

While there are many different types of heat treatment, annealing is popular because it increases ductility and reduces hardness.

When would I
use it and why?

Annealing is used to reverse the effects of work hardening.

If I need to do a lot of machining on a hardened block because an engineer forgot to put it on the print and it was
already heat treated. I would anneal it back to soft properties for easy machining.

Tempering

The maximum hardness of a steel grade, which is obtained by hardening, gives the material a low toughness.

Tempering reduces the hardness in the material and increases the toughness .

Through tempering you can adapt materials properties (hardness/toughness
ratio) to a specified application.

When would I
use it and why?

It is mandatory to temper the steel after it has been hardened.

Also known as drawing back.

Once hardened the steel must be tempered to lower the hardness so the steel becomes tough and not so brittle.

Each steel has different temp specs.

Tempering temp is lower than the heat treating temp.

Without this step it could be as hard and as brittle as glass.

Drag and Drop

Tempering has a ​

Placeholder

temp. Heat treating has a ​

Placeholder

temp.

Drag these tiles and drop them in the correct blank above

lower

higher

same

different

Quenching

Quenching improves a metal's performance by rapidly cooling the heated metal, thereby altering its molecular structure and increasing its hardness.

The rate of quenching may be adjusted to achieve the desired properties.

When would I
use it and why?

Some steels require a fast cooling after heat treating that would be called quenching just like you will see on the famous Forged In Fire.

On the show you see them put their knife in the oil quench and pull it out almost immediately, WRONG!

It needs to be left in the quench long enough to almost completely cool off!

Multiple Choice

When oil quenching you pull the metal out of the oil immediately after submerging it.

• True

• False

Surface
Hardening

Case-hardening or surface hardening is the process of
hardening the surface of a metal object while allowing the metal deeper underneath to remain soft, thus forming a thin layer of harder metal at the surface.

The term face hardening is also used to describe this technique, when discussing modern armour.

When would I
use it and why?

The middle of the material not
being hardened and only the
outside edges are hardened.

That will keep the material
from breaking into 2 pieces
and the outside will be strong and sturdy.

Multiple Choice

Surface hardening hardens the entire block all the way through to the middle.

• True

• False

How to
check!

Use a rockwell tester to check the hardness of material.

B scale for mild steel.

C scale for hardened steel.

↑

This is a

diamond tip
used only for
checking “C”

scale