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11292 Effect of Post Weld Heat Treatment on the Hydrogen Trapping Behavior of Pressue Vessel Steel

The effect of post weld heat treatment (PWHT) was studied on a variety of microstructures of the pressure vessel steel (ASTM A516) ranging from the ferrite/pearlite to the tempered bainite obtained by different cooling processes.

Product Number: 51300-11292-SG
ISBN: 2011 11292 CP
Author: Sung Jin Kim, Hwan Gyo Jung and Kyoo Young Kim
Publication Date: 2011
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The effect of post weld heat treatment (PWHT) was studied on a variety of microstructures of the pressure vessel steel (ASTM A516) ranging from the ferrite/pearlite to the tempered bainite obtained by different cooling processes. The hydrogen trapping behavior in sour environment was investigated by means of the electrochemical permeation technique and the modified JIS Z3113 method. The ISO17081 standard was used to evaluate the hydrogen trapping in the electrochemical permeation experiment by measuring several hydrogen permeation parameters such as the apparent hydrogen diffusivity (Dapp), the permeability (JssL) and the apparent hydrogen solubility (Capp). As the microstructure changed from bainite to ferrite/pearlite and also after tempering and PWHT, the value of Dapp showed a continuous increase while the value of Capp showed a continuous decrease. The value of Dapp was maximum whereas the value of Capp was minimum for all the specimens after PWHT. It suggests that proper PWHT is essential to control the number of reversible trapping site of hydrogen by obtaining the microstructure and low interfacial area of the spheroidized carbide caused by the agglomeration and growth of the fine carbide particles.

Keywords: pressure vessel steel, sour environment, hydrogen trapping, electrochemical, hydrogen permeation method, post weld heat treatment, diffusible hydrogen

The effect of post weld heat treatment (PWHT) was studied on a variety of microstructures of the pressure vessel steel (ASTM A516) ranging from the ferrite/pearlite to the tempered bainite obtained by different cooling processes. The hydrogen trapping behavior in sour environment was investigated by means of the electrochemical permeation technique and the modified JIS Z3113 method. The ISO17081 standard was used to evaluate the hydrogen trapping in the electrochemical permeation experiment by measuring several hydrogen permeation parameters such as the apparent hydrogen diffusivity (Dapp), the permeability (JssL) and the apparent hydrogen solubility (Capp). As the microstructure changed from bainite to ferrite/pearlite and also after tempering and PWHT, the value of Dapp showed a continuous increase while the value of Capp showed a continuous decrease. The value of Dapp was maximum whereas the value of Capp was minimum for all the specimens after PWHT. It suggests that proper PWHT is essential to control the number of reversible trapping site of hydrogen by obtaining the microstructure and low interfacial area of the spheroidized carbide caused by the agglomeration and growth of the fine carbide particles.

Keywords: pressure vessel steel, sour environment, hydrogen trapping, electrochemical, hydrogen permeation method, post weld heat treatment, diffusible hydrogen

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