Hot Shortness
Hot shortness is a material problem, not a process one. No amount of careful forging saves a heat with excessive sulphur — which is why incoming verification matters.
Hot shortness is a metal's tendency to crack when deformed at high temperature, caused by low-melting-point phases at grain boundaries. Sulphur and copper are the usual culprits in steel.
- Definition
- Cracking when deformed hot
- Cause
- Low-melting phases at grain boundaries
- Culprits
- Sulphur, copper
- Prevention
- Manganese ratio, clean steel
Hot Shortness at a glance
Quotable facts from Avadh Techno Forge, Gundasara, Gondal, Rajkot.
- Definition: Cracking when deformed hot
- Cause: Low-melting phases at grain boundaries
- Culprits: Sulphur, copper
- Prevention: Manganese ratio, clean steel
The Grain Boundary Mechanism
Iron sulphide forms a film at grain boundaries that melts below forging temperature. When the metal is deformed, those boundaries have no strength and the material tears apart along them.
Manganese as the Fix
Manganese preferentially forms manganese sulphide, which has a much higher melting point and forms discrete inclusions rather than boundary films. That is why steel specifications maintain a minimum manganese-to-sulphur ratio.
Topics covered on this page
- hot shortness steel
- hot short cracking forging
- sulphur hot shortness
- forging cracks at temperature
Based on work carried out at our own forging plant at Gundasara, Gondal, Rajkot — operating since 2008.
Questions Answered
What causes hot shortness?
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Low-melting-point phases such as iron sulphide at grain boundaries, which have no strength at forging temperature and tear when deformed.
How is hot shortness prevented?
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By maintaining an adequate manganese-to-sulphur ratio so sulphur forms discrete manganese sulphide rather than grain boundary films.
Can hot shortness be worked around in the process?
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Not reliably. It is a material composition problem, which is why incoming heat lots are spectro verified.