HEAT TREATMENT

HEAT TREATMENT:

Normalizing:

• It is heated to 900°c then allowed to cool in air to ambient temperature.
• Increases strength & toughness.

Quenching & Tempering:

• It is heated to 900°c then cooled as quickly as possible by quenching in water [or] oil.
• It increases hardness.
• Quenching should be followed by tempering.
• Tempering will improve ductility.

Solution Annealing:

• It is heated to 1100°c then rapidly cooled in water to prevent any carbides [or] other phases forming.
• It is applied to ASS such as 304 &316 grades to minimize weld decay.
• It is done to minimize weld decay.
• It may cause angular distortion.
• It is only for stainless steel.

Annealing:

• It is heated to 900°c & cooled in furnace it self.
• It reduces strength and toughness but improves ductility.

PWHT:

• The main reason for PWHT is reduce residual stress.
• It is also called as stress-relief.
• Temperature for carbon and C-Mn is 600°c.
• Temperature for cerium molybdenum steel [CR-Mo] is 700-760°c.
• Maximum heating rate 60-200°c/hr.
• Soaking time 1hr for 25mm thickness[1inch]
• Cutting torch & flame torch can’t be used for PWHT & Pre Heat.
• Flame torch is used for Pre Heat.