The Welding of Stainless Steels - edelstahl-rostfrei.de

1 The Welding of Stainless Steelsby Pierre-Jean CunatMaterials and Applications Series, Volume 3 THE Welding OF Stainless STEELSEuro InoxEuro Inox is the European market development associ-ation for Stainless of Euro Inox include: European Stainless steel producers National Stainless steel development associations Development associations of the alloying prime objectives of Euro Inox are to createawareness of the unique properties of Stainless steelsand to further its use in both existing applications andnew markets.

2 To achieve these objectives, Euro Inoxorganises conferences and seminars, and issuesguidance in printed and electronic form, to enabledesigners, specifiers, manufacturers and end users tobecome more familiar with the material. Euro Inox alsosupports technical and market 978-2-87997-180-32-87997-087-3 Polish version978-2-87997-177-3 Czech version978-2-87997-178-0 Dutch version978-2-87997-179-7 Turkish versionFull Acciai Speciali & ALZ BelgiumUGINE & ALZ FranceArcelor Mittal Stainless Steel Association (BSSA) Edelstahl de D veloppement de l Inox ( ) Chromium Development Association (ICDA) Molybdenum Association (IMOA) Unia Dystrybutor w Stali (PUDS)

3 Welding OF Stainless STEELSThe Welding of Stainless SteelsSecond Edition, 2007(Materials and Applications Series, Volume 3) Euro Inox 2001, 2007 PublisherEuro InoxRegistered office: 241 route d Arlon1150 Luxembourg, Grand Duchy of LuxembourgPhone +352 261 03 050, Fax +352 261 03 051 Executive office: Diamant Building, Bd. A. Reyers 801030 Brussels, BelgiumPhone +32 2 706 82 67, Fax +32 2 706 82 69E-mail: Cunat, Joinville-le-Pont, FranceAcknowledgementThe paragraphs marked (*) in the text are extracted from Working with Stainless Steels ,Paris (SIRPE) 1998 Cover PhotographESAB AB, G teborg (S)

4 Contents1 General information on Stainless steels22 Stainless steel Welding processes 33 Weldability of Stainless steels234 Selecting shielding gases for Welding of Stainless steels245 Selecting Welding consumables for Welding of Stainless steels256 Joint preparation in arc welding267 Finishing treatments for welds288 Safe practices309 Glossary: terms and definitions32 DisclaimerEuro Inox has made every effort to ensure that theinformation presented here is technically , the reader is advised that the material contained herein is for general information purposesonly.

5 Euro Inox, its members, staff, and consultants,specifically disclaim any liability or responsibility forloss, damage, or injury, resulting from the use of theinformation contained in this noticeThis work is subject to copyright. Euro Inox reserves allrights of translation in any language, reprinting, re-useof illustrations, recitations and broadcasting. No partof this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by anymeans, electronic, mechanical, photocopying, recordingor otherwise, without the prior written permission ofthe copyright owner, Euro-Inox, Luxembourg.

6 Violationsmay be subject to legal proceeding and liable for monetary damages per infringement as well as costand legal fees and fall under prosecution act of theLuxembourg copyright law and regulations within theEuropean Welding OF Stainless STEELS21 General Information on Stainless Austenitic - Ferritic DuplexStainless Steels : Fe-Cr-Ni (Mo)-NThe microstructure of duplex stainlesssteels consists of a mixture of austeniteand ferrite. They exhibit characteristics of both phases with higher strength andductility.

7 Nitrogen is added to providestrength and also aids in weldability. Theyare magnetic and non-hardenable by heattreatment. Range of compositions: C - 21% Cr 26% - Ni 8% - (Mo ) -N Martensitic Stainless Steels : Fe-Cr-(Mo-Ni-V)These alloys can be heat treated to a widerange of useful hardness martensic structure obtained is of compositions: C - Cr 17% - (Mo - Ni 6% - V ) Austenitic Stainless Steels : Fe-Cr-Ni (Mo)These alloys are the most popular gradesof Stainless Steels because of their excel-lent formability, corrosion resistance, andweldability.

8 All are non-magnetic in theannealed of compositions: C - 16% Cr 28% - Ni 32% - (Mo 7%) Ferritic Stainless Steels : Fe-Cr-(Mo)Ferritic Stainless Steels have a low carboncontent, with chromium (and molybdenum)as major alloying are non-hardenable by heat treatmentand are always of compositions: C - Cr 30% - (Mo )THE Welding OF Stainless STEELS32 Stainless Steel Welding Arc Processes with a RefractoryMetal Gas Tungsten Arc Welding :GTAW (*)The GTAW process, also known as the TIG(Tungsten Inert Gas) or WIG (Wolfram InertGas) process, is illustrated in the above fig-ure.

9 The energy necessary for melting themetal is supplied by an electric arc struckand maintained between a tungsten ortungsten alloy electrode and the work-piece, under an inert or slightly reducingatmosphere. Stainless Steels are alwayswelded in the DCEN (Direct CurrentElectrode Negative) or DCSP (Direct CurrentStraight Polarity) mode. In these condi-tions, it is the workpiece that is struck bythe electrons, enhancing penetration, whilethe electrode, which is generally madefrom thoriated tungsten (2% ThO2), under-goes very little wear.

10 If a filler metal isemployed, it is in the form of either barerods or coiled wire for automatic inert gas flow which protects the arczone from the ambient air, enables a verystable arc to be maintained. Depending onthe base material, shielding gases consistmainly of mixtures of argon (Ar), helium(He) and hydrogen (H2) (see section 4 Selection of shielding gases for weldingstainless steel ).70 90 20 Direction of travelShieldinggas inletCopper support+Backing gasFiller metalArcShielding gasWeldingpower supplyTorchCeramic nozzleRefractory metal electrodePrinciple of manual gas tungsten-arc weldingWeldingpowersupplyShielding gasShielding gasWaterWaterPlasma-forming gasPlasma-forming gasCathode (thoria-ted W)Direction of travelWeld poolPlasma streamSolidified weldWorkpieceH.