Module 2 - Heat treatment & metals Flashcards
Why do we heat treat ferrous metals
Generally alters the properties of Metals
-For stress relief
-Achieve final strength and harness
-To release the effects of strain hardening and to -prepare the material for further deformation
Describe the process of Annealing, and what is does to the material
Heating to red heat then cooled slowly in furnace.
Relieves any stress from distorted grains. Large uniform grains.
Not really wanted due to poor toughness.
Increases ductility
Lowers strength + hardness
Describe the process of Normalizing, and what is does to the material
Heating the steel to above the critical temperature range, holding it long enough to transform the grain structure, then air cooling it.
Normalizing produces a more uniform grain size leading to improved hardness, strength and Ductility.
Describe the process of Hardening, and what is does to the material
Heating the steel to temperature above the critical point, holding it at this temperature, then quenching it in water oil.
Hardening increases the hardness (go figure, like obviously am i right?!) and improves wear resistance but makes it more brittle.
Describe the process of Tempering, and what is does to the material
Heating already hardened steel to a temperature below the critical point, holding it for some time, then cooling it in air.
Tempering is done to remove brittleness that’s induced through hardening, to achieve a good combo of hardness and toughness.
What an example of when something may be annealed?
(note 1 material may undergo many heat treatment)
Tools made from high carbon steel; like knives screwdrivers and hammers.
Metal Construction materials - like beams and plates
Cables and wires - annealed to improved ductility in copper cables.
What an example of when something may be normalizing?
(note 1 material may undergo many heat treatment)
Automotive parts - like crankshafts, pistons & axles.
Railway components
machinery parts like gears, spindles and springs.
What an example of when something may be Hardened?
(note 1 material may undergo many heat treatment)
Fasteners - bolts, nuts & screws
Cutting tools - screw bits, scissors and knives.
Moving parts - bearings & gears
What an example of when something may be Tempering ?
(note 1 material may undergo many heat treatment)
Fasteners - bolts, nuts & screws
Automotive parts - transmission parts, crankshafts, and engine blocks
Hand Tools: Hammers, chisels, and screwdrivers
What is surface hardening?
Surface hardening is the process or hardening a metals surface t make it resistant to abrasion and wear.
What are surface hardening methods?
Carburising
Nitriding
Flame Hardening
Induction Hardening
how does grain size effect a metals properties?
Generally, smaller grains lead to higher strength and hardness but may reduce ductility. Larger grains can enhance ductility but may compromise strength.
What is surface hardening?
Surface hardening is the process or hardening a metals surface t make it resistant to abbrasion and wear.
What are surface hardening methods?
Carburising
Nitriding
Flame Hardening
Induction Hardening
What factors influence the grain structure of a material?
Factors influencing grain structure include the cooling rate during solidification, alloy composition, heat treatment processes, and mechanical deformation.
Why is there different grain sizes?
The different sizes of the grain structure due to the amount heat treatment that is done.
define pearlite
Pearlite is a microstructure found in some steels and cast irons. It’s composed of alternating layers of ferrite (a solid solution of carbon in iron) and cementite (iron carbide, Fe3C).
How is this picture showing us the way the grain structures changes?
It shows us one of the way the grain change during hot rolling.
what does normalizing do the grain structure of a material
Normalizing refines and homogenizes (make more uniform) the grain structure of ferrous materials.
what does hardening do the grain structure of a material
alters the grain structure by transforming softer phases (like austenite) into harder phases (like martensite).
What does annealing do to the grain structure of metals?
refines the grain structure of metals by promoting recrystallization, which replaces deformed grains with a more uniform and isotropic grain structure
What does tempering do to the grain structure of metals?
Tempering doesn’t really change the grain structure instead it alters the size and distribution of carbides in the martensite, forming a microstructure called “tempered martensite”.
