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Polythionic Acid Stress Corrosion Cracking Of UNS S34751 Containing Higher Cu For Improvement Of Creep Strength

Picture for Polythionic Acid Stress Corrosion Cracking Of UNS S34751 Containing Higher Cu For Improvement Of Creep Strength
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Product Number: 51321-16636-SG
Author: Yuhei Suzuki / Takahiro Osuki/ Masaki Ueyama/ Etsuo Dan/ Nao Otaki/ Hirokazu Okada
Publication Date: 2021
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$20.00
$20.00

It has been known that application of distinctive version UNS S34751 with extra low Carbon and Higher Nb/C ratio was effective to prevent Polythionic Acid Stress Corrosion Cracking (PTA-SCC) without Post Welding Heat Treatment (PWHT) and neutralization treatment in several plants of petroleum refineries. On the other hand, due to lower creep strength, it is difficult to apply UNS S34751 to high temperature application such as Delayed Coker operated over 700 oC (1,292 oF). In order to suppress possibility of PTA-SCC occurrence, improvement of creep property for UNS S34751 is required for high temperature application. In addition, stress relaxation cracking susceptibility should be considered at such high temperature. It was found that Copper addition contributes to strengthen creep property of UNS S34751, and the allowable tensile stress is higher than that of S34709. In this study, PTA-SCC tests and stress relaxation tests were conducted to clarify the effects of Copper content on both resistances. New developed material UNS S34752 shows excellent resistance of PTA-SCC and stress relaxation cracking.

Key words: Polythionic acid stress corrosion cracking, Sensitization, Austenitic stainless steel, Delayed coker, UNS S34709, UNS S34752, Creep property, Stress relaxation cracking

It has been known that application of distinctive version UNS S34751 with extra low Carbon and Higher Nb/C ratio was effective to prevent Polythionic Acid Stress Corrosion Cracking (PTA-SCC) without Post Welding Heat Treatment (PWHT) and neutralization treatment in several plants of petroleum refineries. On the other hand, due to lower creep strength, it is difficult to apply UNS S34751 to high temperature application such as Delayed Coker operated over 700 oC (1,292 oF). In order to suppress possibility of PTA-SCC occurrence, improvement of creep property for UNS S34751 is required for high temperature application. In addition, stress relaxation cracking susceptibility should be considered at such high temperature. It was found that Copper addition contributes to strengthen creep property of UNS S34751, and the allowable tensile stress is higher than that of S34709. In this study, PTA-SCC tests and stress relaxation tests were conducted to clarify the effects of Copper content on both resistances. New developed material UNS S34752 shows excellent resistance of PTA-SCC and stress relaxation cracking.

Key words: Polythionic acid stress corrosion cracking, Sensitization, Austenitic stainless steel, Delayed coker, UNS S34709, UNS S34752, Creep property, Stress relaxation cracking

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Picture for Effect of Carbon Content on Polythionic Acid Stress Corrosion Cracking Resistance for UNS S34751 with Extra Low Carbon Content
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Effect of Carbon Content on Polythionic Acid Stress Corrosion Cracking Resistance for UNS S34751 with Extra Low Carbon Content

Product Number: 51319-12783-SG
Author: Takahiro Osuki
Publication Date: 2019
$20.00

Polythionic Acid Stress Corrosion Cracking (PASCC) of conventional austenitic stainless steel is serious problem at desulfurization units in petroleum refinery.Post Weld Heat Treatment after welding and/or neutralization treatment using alkaline solution are required during each turn around to prevent PASCC according to NACE SP0170-2012.It has been known that proprietary version Type 347LN has superior PASCC resistance even if without Post Weld Heat Treatment (PWHT) compared with Type 347(H) or Type 321(H). Although the proprietary version Type 347LN is lower C content compare with standardized C content range (0.02%) to suppress precipitation of M23C6 carbide it is not reported that the effect of the slight variation of C content to PASCC resistance.Therefore the relationship between C content and PASCC resistance was investigated by using long term aged samples with simulated welding Heat Affected Zone.　As the result it was clarified that the strict control of C content less than 0.015% was effective to keep superior PASCC resistance under extra low C content range less than 0.02%.Key words:  Polythionic acid stress corrosion cracking Sensitization Proprietary version Type 347LN Hydroprocessing C content matching filler weld metalBest regardsTakahiro Osuki from NSSMC
Picture for 98592 EFFECTS OF SENSITIZATION AND
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98592 EFFECTS OF SENSITIZATION AND SERVICE FLUID CHEMISTRY ON POLYTHIONIC ACID STRESS CORROSION CRACKING OF 18-8 STAINLESS STEELS

Product Number: 51300-98592-SG
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Picture for Effects of Alloying Elements for Resistance to Naphthenic Acid Corrosion of 18Cr Austenitic Stainles
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Effects of Alloying Elements for Resistance to Naphthenic Acid Corrosion of 18Cr Austenitic Stainless Steels

Product Number: 51317--9057-SG
ISBN: 9057 2017 CP
Author: Masahiro Seto
Publication Date: 2017
$20.00

In this study, the effect of Mo, Cu and W contents in stainless steels on both NAC and PTA SCC resistance are investigated. The purpose was to optimize a proprietary version of UNS S34751 (TP347LN) with excellent PTA SCC resistance.
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