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De-Embrittlement of 1¼Cr–½Mo Steels
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Abstract
It is known that the toughness reduction of Cr-Mo steels owing to temper embrittlement can be alleviated by heat treatment above a certain temperature. This phenomenon (i.e., de-embrittlement) is, therefore, worth considering when there is a concern regarding brittle fracture in aging pressure equipment. In this study, vintage 1¼Cr-½Mo steels were taken from fluid catalytic cracking (FCC) reactors / orifice chambers and catalytic reforming reactors which started operation in 1970s. The steels were then heat-treated at various temperatures ranging between 530 °C and 720 °C (986 °F and 1,328 °F). Charpy impact toughness of as-received and heat-treated samples was investigated. The results showed that de-embrittlement could be achieved regardless of the impurity levels and operation periods. The result further indicated that the heat treatment at 570 °C (1,058 °F) was still effective as a de-embrittlement heat treatment for aging 1¼Cr-½Mo steels. This temperature is lower than the temperature noted in API RP571.
American Society of Mechanical Engineers
Title: De-Embrittlement of 1¼Cr–½Mo Steels
Description:
Abstract
It is known that the toughness reduction of Cr-Mo steels owing to temper embrittlement can be alleviated by heat treatment above a certain temperature.
This phenomenon (i.
e.
, de-embrittlement) is, therefore, worth considering when there is a concern regarding brittle fracture in aging pressure equipment.
In this study, vintage 1¼Cr-½Mo steels were taken from fluid catalytic cracking (FCC) reactors / orifice chambers and catalytic reforming reactors which started operation in 1970s.
The steels were then heat-treated at various temperatures ranging between 530 °C and 720 °C (986 °F and 1,328 °F).
Charpy impact toughness of as-received and heat-treated samples was investigated.
The results showed that de-embrittlement could be achieved regardless of the impurity levels and operation periods.
The result further indicated that the heat treatment at 570 °C (1,058 °F) was still effective as a de-embrittlement heat treatment for aging 1¼Cr-½Mo steels.
This temperature is lower than the temperature noted in API RP571.
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