Conditions leading to stress corrosion cracking of A516 Grade 70 and A285 Type C pressure vessel steels and E7018, E6010 and EM12K weld filler-metals in kraft continuous digesters were determined using electrochemical, slow strain rate and fracture mechanics techniques. The influence on stress corrosion cracking of organic constituents found in kraft pulping liquors was also investigated.

Stress corrosion cracking was observed in solutions containing less than 30 g/L NaOH at a temperature of 140°C. The potential range for cracking was determined in two typical digester environments. Crack propagation rates were found to be strongly dependent on applied stress intensity, but relatively independent of metallurgy. Organic-containing liquors were found to be more oxidizing than liquors containing only inorganic species and, in one case, organic components of kraft liquors were found to act as crack inhibitors. The mechanism of cracking in digesters was identified as caustic stress corrosion cracking.

Subject
Digesters, Impregnation, Cooking, Liquor, Weldments, Crack propagation, Corrosion cracking, Stress cracking, Black liquors, Steel, Caustic stress corrosion cracking, Weld metal, Stress corrosion cracking
© 1985 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1985
Association for Materials Protection and Performance (AMPP)
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