Welding Guide. Stainless Steels

WELDING GUIDE STAINLESS STEELS properties • how to weld them • where to use them STAINLESS STEELS PROPERTIES – HOW TO WELD THEM WHERE TO USE THEM A description of the physical and mechanical properties of a variety of commercial stainless steels. Recommendations on the applications of each type and how to arc weld each including filler materials. By Damian Kotecki, PhD Technical Director, Stainless and High Alloy Product Development and Frank Armao Senior Application Engineer TABLE OF CONTENTS 1.0 Introduction ........................ 2 2.0 Types of Stainless Steels... 2 2.1 Ferrite Promoters 2.2 Austenite Promoters 2.3 Neutral Effect 3.0 Weldability of Stainless Steels ....................................2 3.1 Ferritic Stainless Steels 3.2 Martensitic Stainless Steels 3.3 Austenitic Stainless Steels 3.3.1 Sensitization 3.3.2 Hot Cracking 3.4 Precipitation Hardening Stainless Steels 3.5 Duplex Stainless Steels 4.0 Physical Properties .......... 10 5.0 Mechanical Properties ..... 10 6.0 Selection of a Stainless Steel ....................................12 7.0 Design for Welding Stainless Steels ..................14 8.0 Selection of Filler Metals ...14 9.0 Selection of a Welding Process ...............................18 9.1 Shielded Metal Arc Welding 9.2 Submerged Arc Welding 9.3 Gas Metal Arc Welding 9.4 Flux Cored Arc Welding 9.5 Gas Tungsten Arc Welding 10.0 Procedures for Welding Stainless Steels ..................21 10.1 Welding with the Shielded Metal Arc Process 10.2 Welding with the Submerged Arc Process 10.3 Welding with the Gas Metal Arc Process 10.4 Welding with the Gas Tungsten Arc Process Sources of Additional Information Copyright © 2003 by The Lincoln Electric Company All Rights Reserved Safety in Welding WELDING OF STAINLESS STEELS 1.0 INTRODUCTION Stainless steels are defined as iron base alloys which contain at least 10.5% chromium. The thin but dense chromium oxide film which forms on the surface of a stainless steel provides corrosion resistance and prevents further oxidation. There are five types of stainless steels depending on the other alloying additions present, and they range from fully austenitic to fully ferritic. and austenitic precipitation hardening stainless steels. They are identified as the 600-series of stainless steels (e.g., 630, 631, 660). The alloying elements which appear in stainless steels are classed as ferrite promoters and austenite promoters and are listed below. 2.1 FERRITE PROMOTERS Chromium – provides basic corrosion resistance. 2.0 TYPES OF STAINLESS STEELS Molybdenum – provides high temperature strength and increases corrosion resistance. Austenitic stainless steels include the 200 and 300 series of which type 304 is the most common. The primary alloying additions are chromium and nickel. Ferritic stainless steels are non-hardenable Fe-Cr alloys. Types 405, 409, 430, 422 and 446 are representative of this group. Martensitic stainless steels are similar in composition to the ferritic group but contain higher carbon and lower chromium to permit hardening by heat treatment. Types 403, 410, 416 and 420 are representative of this group. Duplex stainless steels are supplied with a microstructure of approximately equal amounts of ferrite and austenite. They contain roughly 24% chromium and 5% nickel. Their numbering system is not included in the 200, 300 or 400 groups. Precipitation hardening stainless steels contain alloying additions such as aluminum which allow them to be hardened by a s