Slide 1
Heating and cooling change steel’s internal structure
Heat treatment deliberately heats and cools metal to alter its properties. Steel can become harder, softer or tougher depending on composition and treatment.
More to Read
The chemical recipe alone does not fully specify performance. Two pieces of the same steel can have different microstructures and mechanical behaviour after different thermal histories.
Slide 2
Heating and holding prepare the transformation
Suitable heating can change the phases present in steel. Holding time helps the interior reach the intended condition before cooling.
More to Read
A thick part heats less uniformly than a thin one. The schedule must account for temperature gradients and diffusion, rather than assuming the furnace reading instantly describes the whole component.
Slide 3
Rapid cooling can produce a hard structure
Rapid cooling, called quenching, can produce martensite, a hard structure, in suitable steels. The cooling rate must suit the alloy and section size.
More to Read
The transformation and uneven cooling can introduce residual stresses or distortion. Greater cooling severity is therefore not automatically better; it may increase cracking risk without adding useful performance.
Slide 4
Tempering trades some hardness for less brittleness
Tempering reheats quenched steel to adjust its structure. It commonly reduces excessive brittleness while sacrificing some hardness.
More to Read
The chosen temperature and time target a balance of strength, toughness and dimensional stability. A cutting edge and a spring may therefore need different treatments even when both benefit from hardening.
Slide 5
Tests must confirm the finished condition
Hardness tests and microstructural checks help confirm treatment results. A nominal recipe does not guarantee uniform properties throughout every part.
More to Read
Surface decarburization, atmosphere and prior processing can alter the outcome. Verification should match the critical location and property, because one surface hardness reading cannot reveal every internal defect.
Sources
- Heat Treatment Services
TWI
- Introduction to Fracture Mechanics
MIT / David Roylance