1、AWS D18.2:2009An American National StandardAbstractThis standard addresses factors that affect weld discoloration on the inside of austenitic stainless steel tube. The documentcontains a color illustration relating the discoloration to the oxygen content of the backing shielding gas.Guide to Weld Di
2、scoloration Levels onInside of Austenitic Stainless Steel Tube1. This standard provides a visual comparison guide that can be used to specify surface discoloration criteria for sanitary(hygienic) welds in austenitic stainless steel tube.This figure has been extracted from AWS D18.1/D18.1M:2009.2. Th
3、e Tube Sample. The tube sample was prepared using an automatic orbital “bead-on-plate” weld on the outsidediameter of a 2 in 50.8 mm stainless steel tube. The weld penetrated through the tube wall. The concentration of oxygenin ppm added to the pure argon backing gas for each weld was as follows:No.
4、 110 ppm No. 350 ppm No. 5200 ppm No. 71000 ppm No. 912 500 ppmNo. 225 ppm No. 4100 ppm No. 6500 ppm No. 85000 ppm No. 1025 000 ppm3. The illustration is most useful as a reference to identify the degree of discoloration rather than to specify oxygenlimits in the backing gas. The amount of discolora
5、tion and its appearance can be influenced by factors other than oxygensuch as:High levels of moisture in the backing gas will increase the degree of discoloration.Contaminants such as hydrocarbons, moisture, and some types of particulate on the surface prior to welding caninfluence discoloration lev
6、els.Hydrogen gas in the argon backing gas can significantly reduce the amount of discoloration.The metals surface finish can affect the appearance of discoloration.No portion of this standard may be reproduced, stored in a retrieval system, or transmitted in any form, including mechanical, photo-cop
7、ying, recording, or otherwise, without the prior written permission of the copyright owner.Weld Discoloration Levels on Inside of Austenitic Stainless Steel Tube550 N.W. LeJeune Road, Miami, FL 33126Statement on the Use of AWS American National Standard StandardsAll standards (codes, specifications,
8、 recommended practices, methods, classifications, and guides) of the American Welding Society (AWS)are voluntary consensus standards that have been developed in accordance with the rules of the American National Standards Institute(ANSI). When AWS American National Standards are either incorporated
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11、an AWS standard must be byagreement between the contracting parties.International Standard Book Number: 978-0-87171-756-6American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126 2009 by American Welding Society. All rights reserved.Printed in the United States of AmericaAWS American National
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22、e for an official interpretation.This standard is subject to revision at any time by the AWS D18 Committee on Welding in Sanitary Applications. It must be reviewed everyfive years, and if not revised, it must be either reaffirmed or withdrawn. Comments (recommendations, additions, or deletions) and
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24、onse to the comments. Guests are invited to attend all meetings of the AWS D18 Committee on Welding in SanitaryApplications to express their comments verbally. Procedures for appeal of an adverse decision concerning all such comments are provided inthe Rules of Operation of the Technical Activities
25、Committee. A copy of these Rules can be obtained from the American Welding Society,550 N.W. LeJeune Road, Miami, FL 33126.AWS D18 Committee on Welding in Sanitary ApplicationsJ. E. Campbell, Chair WeldTech Solutions CorporationW. L. Roth, 1st Vice Chair Procter & Gamble, IncorporatedR. Howard, 2nd V
26、ice Chair Vogt Power InternationalR. Starks, Secretary American Welding SocietyR. E. Avery Nickel InstituteR. D. Campbell Bechtel National, IncorporatedL. Hanson Johnsonville Sausage, LLCB. K. Henon Arc Machines IncorporatedE. K. Johnson SWECO Division of M-I LLCJ. McSwiggin Rodem, IncorporatedJ. Williams James Williams, PC Advisors to the AWS D18 Committee on Welding in Sanitary ApplicationsL. P. Connor ConsultantJ. R. Hannahs ProfessorM. P. Lang United Association Local 501G. B. Melton TWIJ. R. Miller RetiredR. K. Smith Richard K. Smith
