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Full Record for Micrograph 271

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Micrograph no
271
Brief description
Fe, C 0.07, Mn 2.3 (wt%) steel, carburised at 950°C
Keywords
alloy Link to MATTER Glossary entry for alloy, carbon, carburisation Link to MATTER Glossary entry for carburisation, iron, metal, steel Link to MATTER Glossary entry for steel
Categories
Metal or alloy
System
Fe-C-X   Link to phase diagram
Composition
Fe, C 0.07, Mn 2.2 (wt%)
Standard codes
BS 220M07, formerly En 1A
Reaction
Processing
carburised 950°C
Applications
Sample preparation
Nital
Technique
Reflected light microscopy
Length bar
800 μm
Further information
After initial casting of this steel it was subject to a process known as carburisation. The metal is heated to above the ferrite-austenite transition in a carbon atmosphere. This establishes a concentration gradient and hence carbon diffuses into the steel. Usually the steel is then hardened by quenching. This produces what is known as a case hardened steel - with a hard surface (case) surrounding a tough core. The carbon gradient can be seen in the changing shade of the sample from left to right, with high carbon concentration at the left (surface) and hence a martensitic phase, changing to the lighter shade consisting of mostly ferrite.
Contributor
Dr R F Cochrane
Organisation
Department of Materials, University of Leeds
Date
04/09/02
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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