Elimination of Backing Gas in Austenitic and Duplex Stainless Steel Welds Using Semiautomatic Gas Tungsten-Arc Hot Wire Welding

By Charles Patrick, Director of Technical Services/Consultant at Republic Testing Laboratories, LLC, Juvenal Calvo, President at Republic Testing Laboratories, LLC, Scott Witkowski, Vice-President at Republic Testing Laboratories, LLC, and William F. Newell, Jr., PE, Co-Founder/Vice President – Engineering at Euroweld, Ltd. This article appears in the May/June 2022 issue of Inspectioneering Journal.

12 Likes

1 Comment

Topics

The Effect of High Pressure High Temperature and Sour Service Environment on Subsea Dissimilar Joints

January/February 2020 Inspectioneering Journal

The author will discuss the failure of a dissimilar joint while examining the root causes of the failure along with potential solutions and preventive actions that would not compromise the welding production rate.
Effect of High Temperature Hydrogen Attack in Dissimilar Materials

May/June 2018 Inspectioneering Journal

HTHA of hydrogen-containing equipment can be prevented with appropriate material selection and fabrication, appropriate welding procedures, regular inspection of equipment using proven, effective technologies and equipment operated by qualified...
Hamstrung by Hydrogen Damage Mechanisms

November/December 2017 Inspectioneering Journal

Hydrogen is a common culprit of equipment damage in the process industries. As hydrogen-induced damage can occur in multiple forms, it’s critical to identify the specific damage mechanism you’re dealing with before undertaking measures to...
Electroless Nickel Surface Coatings

May/June 2012 Inspectioneering Journal

Electroless nickel (ENC) is a family of coatings based on nickel-phosphorous metallic compounds. ENC was developed in 1943 by Abner Brenner, an electrochemist at the U.S. Bureau of Standards. While working on the electroplating of nickel onto...
Impact of Welding Defects on Integrity of Equipment & Piping

January/February 2019 Inspectioneering Journal

Welding imperfections vary in impact from being acceptable to requiring repair. It is important to ensure the quality of welds using NDT and to ensure the strength of the entire piping system with hydrotesting.

Introduction

Open root welding of austenitic and duplex stainless steel with gas tungsten-arc welding (GTAW) plays a critical role in fabricating pressure components serving various industries. While several improvements in welding processes and equipment have been introduced, the basic welding practices have remained unchanged. For example, the only reliable method of welding austenitic and duplex stainless steel piping while preventing oxidation of the root bead was through either back purging with inert gas or using one of the following: flux agents, flux coated/flux-cored rods, and gas metal-arc welding using the waveform controlled short-circuiting transfer mode (GMAW-S) [1-4]. This article aims to focus on the elimination of backing gas for open root welding of austenitic duplex stainless steel welds using a flux-cored wire for the root pass.

To fully evaluate and provide validation of the resulting weldment, the weld test coupons were fabricated and subjected to a testing protocol consisting of radiographic examination, mechanical tests, ferrite tests, hardness tests, corrosion tests, and chemical tests, which verified that the weldments were not compromised by elimination of the backing gas.

Materials, Welding Equipment, and Monitoring

Materials Austenitic Stainless Steel

The base material for the austenitic stainless steel was SA-312 Type 304/304L, nominal pipe size (NPS) of 8-inch (203 mm), 0.500-inch (13 mm) wall thickness (schedule 80) pipe [5].

Table 1 lists the chemical composition per the Material Test Report (MTR).

Table 1. Chemical Composition of SA-312 Type 304/304L Pipe, Wt. %.
C	Si	Mn	P
0.02	0.33	1.18	0.033
S	Ni	Cr	N
0.011	8.07	18.26	0.065

Welding consumables were: SFA-5.22/SFA-5.22M (AWS A5.22/A5.22.M:2012), E308LT1/E308T1-4, 0.045 inch (1.14 mm) diameter flux-cored wire for the root pass SFA-5.9/SFA-5.9M (AWS A5.9/A5.9.M:2012), ER308/308L, 0.045 inch (1.14 mm) diameter bare wire for the balance of welding [6-9]. Chemical composition per Certified Material Test Report (CMTR) for each welding consumable is listed in Tables 2 and 3, respectively.

This content is available to registered users and subscribers

Create your free account and get access to:

Unlock one premium article of your choosing per month
Exclusive online content, videos, and downloads
Insightful and actionable webinars

GET STARTED

Interested in unlimited access? VIEW OUR SUBSCRIPTION OPTIONS

Current subscribers and registered users can log in now.

About the Authors

Charles Patrick, Director of Technical Services/Consultant at Republic Testing Laboratories, LLC

Charles W. “Pat” Patrick is currently contracted to Republic Testing Laboratories, LLC as Director of Technical Services and the President/CEO of Howling Lobo Consultants, LLC. His diverse professional experience spans 50+ years of welding engineering and consulting both domestically and internationally, providing services related to welding, materials, and nondestructive testing... Read more »

Juvenal Calvo, President at Republic Testing Laboratories, LLC

Juvenal Calvo is currently President of Republic Testing Laboratories, LLC and Vice President of TIPTIG USA. He is a Mechanical Engineer with 15 years of diverse engineering and hands-on welding, including experience with multi-national and regional manufactures in the Aerospace, Steel, Power, Nuclear, Pharmaceutical, and Oil & Gas industries. Mr. Calvo has demonstrated the ability to... Read more »

Scott Witkowski, Vice-President at Republic Testing Laboratories, LLC

Scott Witkowski is currently Vice-President of Republic Testing Laboratories, LLC and former President/Founder of Maverick Testing Laboratories, Inc. Scott’s experience includes piping, structural, pressure vessels, valves, and associated components as they relate to welding, materials, and testing. Scott’s diversified expert Scott Witkowski is currently Vice-President of Republic... Read more »

William F. Newell, Jr., PE, Co-Founder/Vice President – Engineering at Euroweld, Ltd.

William is President of W. F. Newell & Associates, Inc., and Co-Founder/Vice President – Engineering of Euroweld, Ltd. He is involved in welding engineering applications and consulting in the nuclear & fossil electric power and heavy industrial arenas for nearly 50 years, both domestic and internationally. Bill is a member on national and international code bodies, a Life Member... Read more »