E-Book Overview
Praxair Technology, Inc. 1999. 50р. This training program was written to give you a better understanding of the MIG welding process. MIG is an acronym for Metal Inert Gas, which is not technically correct for stainless steels because shielding gases for these materials contain an active gas such as oxygen or carbon dioxide.
E-Book Content
GAS METAL ARC WELDING OF STAINLESS STEEL TABLE OF CONTENTS Section Topic 1 Introduction Page 1 Section Topic Page 6 Metal Transfer 23 A. Short-Arc 2 Base Metals 2 B. Globular Transfer A. Alloying Elements C. Spray Transfer B. Stainless Steels D. Pulsed Spray Transfer 1. Ferritic Alloys 2. Austenitic Alloys 7 Welding Stainless Steels 29 8 Technique and 33 3. Martensitic Alloys 4. Precipitation Hardening Alloys 5. Duplex Stainless Steels Equipment Set-Up A. Torch Angle 3 Electrical Characteristics 7 B. Feed Roll Tension C. Burnback A. Constant Voltage Power D. Arc and Puddle Position Supply Basics B. Constant Voltage Power E. Vertical Down Welding Supply Settings F. Gaps C. Electrical Stick-Out G. Crater Filling D. Constant Voltage Power H. Arc Starting Supply Characteristics 1. Slope 9 Weld Discontinuities 2. Inductance and Problems 3. Heat Input A. Lack of Fusion 38 B. Porosity 4 Shielding Gases 13 C. Burn-Through A. Shielding Gas Functions D. Undercut B. Flow Rates E. Spatter C. Gas Losses F. Cracking G. Sensitization of 5 Electrodes 19 Alloying Elements A. Filler Metal Alloying Additions B. Wire Designations 10 Precautions and Safe Practices 43 11 Conclusion and Chemistries C. Solidification of the Weld Puddle 47 SECTION 1 1 Introduction ▲ This training program was written to give As you learn more about GMAW, it will you a better understanding of the MIG become apparent that this is a sophisti- welding process. MIG is an acronym for cated process. Welders who have used Metal Inert Gas, which is not technically “stick” welding (Shielded Metal Arc correct for stainless steels because shield- Welding or SMAW) are sometimes of the ing gases for these materials contain opinion that the GMAW process is sim- an active gas such as oxygen or carbon pler; but to deposit a high quality bead dioxide. The correct term according to the requires as much knowledge as, or more American Welding Society (AWS) is Gas than, with the SMAW process. The reason Metal Arc Welding (GMAW). We will use for this is the number of variables that the correct terminology as defined by the affect the arc and the degree of control AWS and also explain the slang used so the operator has over those variables. that you will be familiar with all the terms applicable to this process. The purpose of this manual is to make you a better welder by increasing your knowledge of how the GMAW process works. A more knowledgeable welder can be Power 2% more productive by working smarter, not Equipment 4% harder. Figure 1 shows why your company Wire and Gas 14% is interested in educ