Zirconium 705 (Zr + 2-3% niobium) is finding its way into more acetic acid plants as a replacement for Zirconium 702 (unalloyed Zr). The alloy was first proposed for the Chemical Process Industry(CPI) use in the early 1970s, but has not found wide spread use because of a few problems early in its history. Research revealed that the problems encountered were related to delayed hydride cracking (DHC). However, proper processing of the alloy after welding produces components free of DHC. The main advantage of Zirconium 705 (Zr 705) as compared to Zirconium 702 (Zr 702) is higher tensile and yield strengths. This allows pressure containing components to be rated at higher pressures which can increase plant efficiencies or they can be fabricated with thinner wall sections, thus reducing equipment cost. These advantages of Zr 705 will be reviewed as well as actual plant history of the alloy in acetic acid services.

Subject
Costs, Materials, Corrosion resistant alloys, Valves, Welding, Stress cracking, Thermal stress, Stress, Hydrides, Acetic acid, Zirconium alloys, Wrought metals, Hydrogen
Keywords:
Zirconium 705, Zirconium 702, delayed hydride cracking, acetic acid
© 1995 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).
1995
Association for Materials Protection and Performance (AMPP)
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