18.. heat treatment
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Copyright 2004, TWI Ltd World Centre for Materials Joining Technology
TWICSWIP 3.1
WIS 5WELDING INSPECTION
HEAT TREATMENT
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Copyright 2004, TWI Ltd World Centre for Materials Joining Technology
Many metals must be given heat treatment before andafter welding.
The inspectors function is to ensure that the treatment isgiven correctly in accordance with the specification or asper the details supplied.
Below are the types of heat treatment available.
Annealing
Normalising
Quench Hardening
Temper
Stress Relief
Preheat
HEAT TREATMENT
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Copyright 2004, TWI Ltd World Centre for Materials Joining Technology
The temperatures mentioned are for steels.
Process Annealing
Temp 9200C
Cooling Hold, furnace coolResult Improves ductility, Decreases
toughness, Makes bending etc easier,Lowers yield stress
HEAT TREATMENT
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Copyright 2004, TWI Ltd World Centre for Materials Joining Technology
The temperatures mentioned are for steels.
Process Normalising
Temp 9200C
Cooling Hold, air coolResult Relieves internal stress, improves
mechanical properties, Increasestoughness
HEAT TREATMENT
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Copyright 2004, TWI Ltd World Centre for Materials Joining Technology
The temperatures mentioned are for steels.
Process Quench, Harden
Temp 9200C
Cooling Hold, quench coolResult Hardens carbon steels, prevents
carbide precipitation in austeniticsteels, prevents temper brittleness
when cooling after tempering,prepares metal for tempering
HEAT TREATMENT
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Copyright 2004, TWI Ltd World Centre for Materials Joining Technology
The temperatures mentioned are for steels.
Process Temper
Temp 550-7000C
Cooling Hold, air coolResult Increases toughness of quenched steel
HEAT TREATMENT
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The temperatures mentioned are for steels.
Process Stress relief
Temp 550-7000C
Cooling Hold, furnace or controlled coolingResult Relieves residual stresses, improves
stability during machining, reduceshydrogen levels, prevents stress
corrosion cracking
HEAT TREATMENT
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The temperatures mentioned are for steels.
Process Pre-heat for welding
Temp 50-2500C. higher by exception
Cooling Hold during welding.Result Prevents cracking and hard zones
HEAT TREATMENT
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The inspector, in general, should ensure that:
Equipment is as specified
Temperature control equipment is in goodcondition
Procedures as specified, is being used e.g. Method of application
Rate of heating and cooling
Maximum temperature
Soak time Temperature measurement (and calibration)
DOCUMENTATION AND RECORDS
HEAT TREATMENT