STP-PT-058 TEMPER BEAD QUALIFICATION HARDNESS ACCEPTANCE CRITERIA STP-PT-058 TEMPER BEAD QUALIFICATION HARDNESS ACCEPTANCE CRITERIA Prepared by: David Abson, Adrienne Barnes and Sayee Raghunathan TWI Ltd Steve Jones Rolls-Royce plc Date of Issuance: June 28, 2013 This document was prepared as an account of work supported by ASME Pressure Technology Codes and Standards (PTCS) through the ASME Standards Technology, LLC (ASME ST-LLC) Neither ASME, ASME ST-LLC, the authors, nor others involved in the preparation or review of this report, nor any of their respective employees, members or persons acting on their behalf, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe upon privately owned rights Reference herein to any specific commercial product, process or service by trade name, trademark, manufacturer or otherwise does not necessarily constitute or imply its endorsement, recommendation or favoring by ASME ST-LLC or others involved in the preparation or review of this report, or any agency thereof The views and opinions of the authors, contributors and reviewers of the report expressed herein not necessarily reflect those of ASME ST-LLC or others involved in the preparation or review of this report, or any agency thereof ASME ST-LLC does not take any position with respect to the validity of any patent rights asserted in connection with any items mentioned in this document, and does not undertake to insure anyone utilizing a publication against liability for infringement of any applicable Letters Patent, nor assumes any such liability Users of a publication are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, is entirely their own responsibility Participation by federal agency representative(s) or person(s) affiliated with industry is not to be interpreted as government or industry endorsement of this publication ASME is the registered trademark of the American Society of Mechanical Engineers No part of this document may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher ASME Standards Technology, LLC Two Park Avenue, New York, NY 10016-5990 ISBN No 978-0-7918-6908-6 Copyright © 2013 by ASME Standards Technology, LLC All Rights Reserved Temper Bead Qualification Hardness Acceptance Criteria STP-PT-058 TABLE OF CONTENTS Foreword vi Executive Summary vii PART I 1 INTRODUCTION 2 OVERVIEW OF CONTROLLED DEPOSITION REPAIR STRATEGIES REPAIR USING NEAR-MATCHING WELD METAL REPAIR USING NI-BASE WELD METAL 10 HAZ HARDNESS 11 RESIDUAL STRESSES 18 REPAIR OF SERVICE AND AGED MATERIAL 19 CODES AND STANDARDS 20 8.1 Fabrication Specifications, Codes and Standards 20 8.1.1 American Codes and Standards 20 8.1.2 European Codes and Standards 21 VARIABLES AFFECTING TEMPER BEAD 22 10 SUMMARY AND CONCLUSIONS 23 References – Part I 24 PART II 29 INTRODUCTION 30 EXPERIMENTAL DETAILS 31 2.1 Parent Steels 31 2.2 Welding Consumables 31 2.3 Welding Details 31 2.4 Metallographic Preparation and Examination 33 2.5 Hardness Testing 33 2.6 Charpy Impact Testing 34 RESULTS 36 3.1 Parent Steels 36 3.2 Welding 38 3.3 Weld Metal Chemical Composition 38 3.4 Metallographic Observations 39 3.5 Hardness Data 49 3.6 Charpy Impact Data 54 3.7 Investigation of the relationship between HAZ hardness and HAZ Charpy Toughness 58 DISCUSSION 62 CONCLUSIONS 64 iii STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria RECOMMENDATIONS 65 References – Part II 66 Appendix A – “Poor” and “Optimum” welding procedures 67 Appendix B – Hardness Test Records 73 Appendix C – Charpy Test Data 89 Acknowledgments 97 Abbreviations and Acronyms 98 LIST OF TABLES Table 1—HAZ Hardness Values Reported in the Literature for Controlled Deposition Repairs – C-Mn steel 12 Table 2—HAZ Hardness Values Reported in the Literature for Controlled Deposition Repairs in C-Mn-Ni-Cr-Mo and C-Mn-Ni-Cr-Mo Steels 13 Table 3—HAZ Hardness Values Reported in the Literature for Controlled Deposition Repairs – 0.5%Cr-0.5%Mo-0.25%V Steel 14 Table 4—HAZ Hardness Values Reported in the Literature for Controlled Deposition Repairs – 1.25%Cr-0.5%Mo Steel 14 Table 5—HAZ Hardness Values Reported in the Literature for Controlled Deposition Repairs – 2.25%Cr-1%Mo Steel 16 Table 6—HAZ Hardness Values Reported in the Literature for Controlled Deposition Repairs – 9%Cr-1%Mo Steel 17 Table 7—Initial Welded Panels for Procedure Development 32 Table 8—Chemical Composition of Parent Steels (determined by TWI) 37 Table 9—Welded Panels for Subsequent Study 38 Table 10—Chemical Composition of Weld Metals 38 Table 11—Hardness Data for Weldments in P4 Parent Steels 50 Table 12—Hardness Data for Weldments in P5A Parent Steels 52 Table 13—Parent Steel Charpy Toughness Data 56 Table 14—HAZ Charpy Toughness Data Compared with the HAZ Charpy Toughness Data for P5 (Lower CE) Parent Steel Supplied by Rolls-Royce 57 Table 15—HAZ Charpy Toughness and Hardness Data – 1-Layer 60 Table 16—HAZ Charpy Toughness and Hardness Data – 4-Layer 61 LIST OF FIGURES Figure 1—Schematic Diagram Illustrating the Relationship between the Fe-C Phase Diagram and the Different Regions of the HAZ [1] Figure 2—Schematic Representation of Two-Layer Refinement Parameters Figure 3—Illustration of the Use of Shims, Tack Welded from the Inside of the Repair Cavity, to Avoid a Large Untempered HAZ at the Surface iv Temper Bead Qualification Hardness Acceptance Criteria STP-PT-058 Figure 4—Illustration of the Early Stages of a Small Patch Repair – the Weld Beads Stop and Start on the Initial Peripheral Bead Figure 5—Weld Metal and Parent Steel Hardness for Grade 91 Steel, as a Function of LarsenMiller Parameter [24] Figure 6—Schematic Representation of the Bead Arrangement for the Cascade Weld 32 Figure 7—Diagram Showing the Intended Positions of Hardness Indentations in the 1-Layer and 4-Layer Sections 34 Figure 8—Completed Panels Showing the Cascade Weld and the Additional Weld Pad Added within the 4-Layer Region to Allow Charpy Specimens to be Machined with the Notch Lying in the HAZ 35 Figure 9—Photomicrographs of Weld Transverse Sections from Weld TW1 Reflecting the "Optimum" Procedure in P5 Steel 39 Figure 10—Photomicrographs of Weld Transverse Sections from Weld TW6 Reflecting the "Poor" Procedure in a P4 Steel 40 Figure 11—Photomicrographs Showing a Coarse-Grain Region in the 4-Layer Region of TW 41 Figure 12—Photomicrographs Showing a Fine-Grain Region in the 4-Layer Region of TW 42 Figure 13—Photomicrographs Showing a Fusion Boundary Region in 1-Layer Region of TW 44 Figure 14—Grain Size Measurements for Weldments in the Lower IIW CE P4 Steel 45 Figure 15—Grain Size Measurements for Weldments in the Higher IIW CE P4 Steel 46 Figure 16—Grain Size Measurements for Weldments in the Lower IIW CE P5 Steel 47 Figure 17—Grain Size Measurements for Weldments in the Higher IIW CE P5 Steel 48 Figure 18—Parent Steel Charpy Toughness P4 54 Figure 19—Parent Steel Charpy Toughness P5 55 Figure 20—Mean Vickers Hardness vs Absorbed Energy at -12 °C – 1-Layer 58 Figure 21—Maximum Vickers Hardness vs Absorbed Energy at -12 °C – 1-Layer 58 Figure 22—Mean Vickers Hardness vs Absorbed Energy at -12 °C – 4-Layer 59 Figure 23—Maximum Vickers Hardness vs Absorbed Energy at -12 °C – 4-Layer 59 Figure 24—Hardness versus Charpy 30 5J Temperature for Course-Grained HAZ Regions, for 5KJ/mm Submerged Arc Welds 63 v STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria FOREWORD Part I – Review of Controlled Deposition Repair Literature Where repairs to steel fabrications are required, but where a subsequent Post-Weld Heat Treatment (PWHT), although desirable, is impractical, as a result of constraints of cost, time or feasibility, it may be appropriate to carry out a controlled deposition repair, which generates a fine-grained HeatAffected Zone (HAZ), by judicious choice of welding parameters and welding procedure For some applications, the resulting maximum HAZ hardness is of interest and potential concern Published literature on controlled deposition repair welding in C-Mn and low alloy steels by different welding processes has been reviewed, and the resulting maximum HAZ hardness values have been tabulated Part II – Experimental Program Repair welding without a subsequent PWHT is allowed in various ASME fabrication codes, but is not currently allowed for P4 and P5A steels The present project was undertaken to determine reasonable upper limits for the HAZ hardness produced during controlled deposition Shielded Metal Arc Welding (SMAW) repairs in these two steels, and also to investigate whether there is any correlation between HAZ hardness and HAZ impact toughness The project was supported by ASME Pressure Technology Codes and Standards (PTCS) and was carried out by TWI Ltd, in collaboration with Rolls-Royce plc, who supplied the parent steels and welding consumables, and performed all of the welding on the project About ASME Established in 1880, the American Society of Mechanical Engineers (ASME) is a professional notfor-profit organization with more than 135,000 members and volunteers promoting the art, science and practice of mechanical and multidisciplinary engineering and allied sciences ASME develops codes and standards that enhance public safety, and provides lifelong learning and technical exchange opportunities benefiting the engineering and technology community Visit www.asme.org for more information The ASME Standards Technology, LLC (ASME ST-LLC) is a not-for-profit Limited Liability Company, with ASME as the sole member, formed in 2004 to carry out work related to newly commercialized technology The ASME ST-LLC mission includes meeting the needs of industry and government by providing new standards-related products and services, which advance the application of emerging and newly commercialized science and technology and providing the research and technology development needed to establish and maintain the technical relevance of codes and standards Visit www.stllc.asme.org for more information vi Temper Bead Qualification Hardness Acceptance Criteria STP-PT-058 EXECUTIVE SUMMARY Part I – Review of Controlled Deposition Repair Literature Background For fabrications where the need for a welded repair has been identified, but for which a Post-Weld Heat Treatment (PWHT) would be impractical or expensive, it is possible to affect a repair by using a procedure which is intended to give rise to significant refinement and tempering of the Heat-Affected Zone (HAZ) microstructure Various approaches to such repair, in terms of selection of welding parameters, welding process and consumables, have been explored by numerous organizations over several decades Published investigations and the provision for controlled deposition repair in various standards are considered in this review Objective To compile a review of the literature relating to controlled deposition and temper bead repair welding Work Carried Out Publications from a wide range of sources have been reviewed, and relevant information, including values of maximum HAZ hardness, has been extracted, and incorporated into this review The current requirements of key codes and standards have also been addressed TWI’s Weldasearch database has been used to assist in locating relevant sources of information Part II – Experimental Program Background In appropriate circumstances, a controlled deposition repair may be carried out without a subsequent PWHT The approach is well established, and such repairs are allowed in various ASME fabrication codes, generally employing SMAW The present project was carried out on 1.25%Cr-0.5%Mo (P-No Gr-No 1) and 2.25%Cr-1%Mo (P-No 5A Gr-No 1) steels It is intended to establish, for controlled deposition repair welds in these steels, the likely maximum HAZ hardness values, and to investigate whether there is a correlation between HAZ microstructure, hardness and Charpy toughness To this end, panels have been welded in the 3G position, and the HAZ ASTM grain size, the hardness, and also the HAZ Charpy toughness, have been determined The project was carried out in collaboration with Rolls-Royce plc, who supplied the parent steels and welding consumables, and performed all of the welding on the project Objectives To determine maximum HAZ Vickers hardness values for controlled deposition (“temper bead”) repair welds in 1.25%Cr-0.5%Mo and 2.25%Cr-1%Mo steels for incorporation into ASME codes To investigate any possible correlation between HAZ grain size, hardness and Charpy toughness Work Carried Out 1.25%Cr-0.5%Mo (P-No Gr-No 1) and 2.25%Cr-1%Mo (P-No 5A Gr-No 1) parent steels were selected with the aim of obtaining a steel of each group with an IIW CE towards the top of the likely range, and also a steel with a lower value of IIW CE Controlled deposition welds were deposited in the 3G position as “cascade” welds, so that sections could be taken through 1, 2, and 4-layer deposits for subsequent study The thickness of the 4-layer region was extended locally so that vii STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria Charpy specimens could be extracted with the notch located in the HAZ below the controlled deposition deposit A procedure with 50% bead overlap, and also one with 25% overlap (intended to reflect incorrect application of a controlled deposition procedure), were employed The metallographic sections were polished and etched, and were examined under an optical microscope at a range of magnifications, so that ASTM grain sizes of the HAZ could be determined in selected locations The Vickers hardness was also determined in approximately the same locations Charpy specimens were machined from each of the parent materials, and were tested to give transition curves HAZ Charpy toughness was subsequently measured in triplicate at specific temperatures Conclusions (a) The grain size in the coarse-grain regions was generally in the range ASTM to ASTM 7, while that in the fine-grain regions generally ranged from ASTM to ASTM 14 (b) For both the “optimum” and “poor” procedures the grain size in the fine grain regions was finer for the 4-layer section than for the 1-layer section, indicating that the deposition of the later layers affected some HAZ grain refinement (c) For the P-No 5A deposits and also for the 1-layer P-No transverse sections, the HAZ hardness was marginally higher for the “poor” procedure For the P-No panels, the HAZ hardness was marginally higher for the “optimum” procedure in the 4-layer transverse sections (d) Suggested upper limits for the mean value of the HAZ hardness are 300HV5 for P-No deposits and 380HV5 for P-No 5A deposits These were estimated by rounding the absolute maximum hardness values obtained from satisfactory controlled deposition repairs (e) Given the relative size of a Vickers hardness indentation and the width of the transformed HAZ in a controlled deposition procedure, it is necessary to use an indenter load less than 10 kg, in order to avoid a misleading measurement of HAZ hardness (f) The HAZ Charpy toughness data show greater scatter for the “poor” procedure than for the “optimum” procedure, with the minimum value generally being lower for the former A low mean value of Charpy toughness was generally associated with the procedure that gave the higher HAZ hardness Whilst only a limited range of HAZ hardness values was obtained, a trend of decreasing Charpy toughness with increasing HAZ hardness was generally observed viii Temper Bead Qualification Hardness Acceptance Criteria STP-PT-058 PART I Review of Controlled Deposition Repair Literature Temper Bead Qualification Hardness Acceptance Criteria 85 STP-PT-058 STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria 86 Temper Bead Qualification Hardness Acceptance Criteria 87 STP-PT-058 STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria 88 Temper Bead Qualification Hardness Acceptance Criteria APPENDIX C – CHARPY TEST DATA 89 STP-PT-058 STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria 90 Temper Bead Qualification Hardness Acceptance Criteria 91 STP-PT-058 STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria 92 Temper Bead Qualification Hardness Acceptance Criteria 93 STP-PT-058 STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria 94 Temper Bead Qualification Hardness Acceptance Criteria 95 STP-PT-058 STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria 96 Temper Bead Qualification Hardness Acceptance Criteria STP-PT-058 ACKNOWLEDGMENTS The supply of the parent steels and welding consumables, and the welding program was arranged at Rolls-Royce, by Professor S Jones, of Rolls-Royce The welding was carried out by M Baker, of Rolls-Royce, with assistance from S Sleep, of TWI The assistance of colleagues at TWI with the experimental work is gratefully acknowledged Assistance with the welding procedure was provided by M Consonni of TWI Hardness testing was carried out by R Taheri, who also carried out metallographic preparation, with contributions also from A Spencer and D Shaw Charpy testing was carried out by The Test House The authors further acknowledges, with deep appreciation, the activities of ASME ST-LLC and ASME staff and volunteers who have provided valuable technical input, advice and assistance with review of, commenting on, and editing of, this document 97 STP-PT-058 Temper Bead Qualification Hardness Acceptance Criteria ABBREVIATIONS AND ACRONYMS ASME American Society of Mechanical Engineers FCAW Flux-Cored Arc Welding GMAW Gas Metal Arc Welding GTAW Gas Tungsten Arc Welding HAZ Heat-Affected Zone P-GMAW Pulsed Gas Metal Arc Welding PWHT Post-Weld Heat Treatment SAW Submerged Arc Welding SMAW Shielded Metal Arc Welding 98 STP-PT-058 A2501Q