Welding of steam turbine components

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Study report of the COST 505 welding group
Industrial research and development

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Commission of the European Communities
physical sciences
Welding of steam turbine components
Study report
of the
COST 505 Welding Group
EUR 14296 EN F Commission of the European Communities
physical sciences
Welding of steam turbine components
Study report
of the
COST 505 Welding Group
H. H. Cerjak
Professor for Material Science and Welding Technology
University of Technology
A-Graz
Contract No COST-0023-A (CH)
Directorate-General
J$|jL EUROP. Biblioth.
Science, Research and Develop
1992 N.C. EUR 14304 El
C1. Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Telecommunications, Information Industries and Innovation
L-2920 Luxembourg
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting
on behalf of then is responsible for the use which might be made of
the following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1992
ISBN 92-826-4377-8
© ECSC-EEC-EAEC, Brussels • Luxembourg, 1992
Printed in Belgium PREFACE
Welding of Steam Turbine Components
Research on high temperature materials which are critical for
the safe and efficient operation of power engineering
equipment has been an important feature of COST concerted
action programmes for the last twenty years; starting with
COST 50; "Materials for Gas Turbines".
In recent years specific attention has been devoted to
"Materials for Steam Turbines" - COST 505. The countries
represented in this work have been Austria, Belgium, Denmark,
Finland, Germany, Italy, Sweden, Switzerland, United Kingdom,
together with the Institute for Advanced Materials, JRC of the
Commission of the European Communities. Jointly, organisations
from these countries have tackled a range of problems
concerned with the improvement and reliability of steam
turbines. The findings from some of the working groups are
being published as a series of Monographs.
One of the coordination groups examined the influence of
different welding procedures, parameters, consumables and t heat treatment parameters on the microstructure and,
hence, on the mechanical properties of forged and cast high
temperature steels used in steam turbine plant. Both similar
and dissimilar metal joints were investigated and conditions
determined in which high efficiency automatic and semi­
automatic processes could be effectively used.
The members of this group are listed on page 7 in Table 2.1.
Their work is examined in the light of present day literature
and experiance in this critical review which was conducted
with financial assistance from the Commission of the European
Communities. The interests of the Management Committee for
COST 505 and the wider European industrial scene were
represented by a "Steering Group" comprising Dr. J. Ewald,
Siemens, D, and Prof. R. Stickler, University of Vienna, A.
Their guidance, support and comments are duly acknowledged.
J. B. Marriott,
Secretariat, COST 505.
JBM/5/1238
Petten, 18th October 1991 CONTENTS
Abstract
Acknowledgement
1. Introduction 1
2. Description of COST 505 Action-Welding Group activities 5
3. The influence of welding on material and component behaviour 9
4. Weldability of 1 % CrMoV casting steel - HAZ behaviour 15
4.1. Materials investigated 1
4.2. Heat-affected-zone-(HAZ)-simulation 20
4.2.1. Principles of HAZ simulation technique
4.2.2. Applied simulation procedures2
4.3. Microstructure of simulated HAZ9
4.3.1. Welding TTT-diagrams
4.3.2. Grain size in the HAZ 35
4.3.3. HAZ-microstructural development during welding
and annealing7
4.33.1. Initial Microstructure
4.3.3.2. Microstructural changes caused by a weld thermal
cycle and annealing9
4.33.3. Carbide precipitation sequence during annealing 42
4.4. Mechanical Properties, Tensile Tests 43
4.4.1. Mechanical properties of simulated HAZ-microstructures 4
4.4.2.ls of real welded materials 50
-v 4.5. Hardness of HAZ 51
4.5.1. Hardness of simulated HAZ-microstructures 5
4.5.2.s of real welded joints5
4.6. Toughness behaviour of HAZ8
4.6.1. Toughness of simulated HAZ-microstructures
4.6.2. Influence of PWHT on the toughness of
simulated HAZ-microstructures 66
4.6.3. Toughness of HAZ in real welded joints, comparison to
simulated HAZ 71
4.7. Creep behaviour of HAZ 80
4.7.1. Creep behaviour of simulated HAZ-microstructures 8
4.7.2. Creepr of real welded joints 87
4.8. Low cycle fatigue behaviour of HAZ 9
4.8.1. Low cycle fatigue and creep fatigue behaviour of
simulated HAZ- microstructures
4.8.2. Low cycle fatigue behaviour of real weldments 102
4.9. Tendency to stress relief cracking of simulated HAZ-microstructures 104
4.10. Relaxation behaviour of simulated HAZ-microstructures 113
5. Improvement of the weld material for 1 % CrMoV casting steel9
5.1. Materials and welding procedures investigated 11
5.2. Mechanical properties of weld materials at RT and elevated temperaturesl25
5.3. Toughness behaviour of welds 129
5.3.1. Influence of PWHT condition on the toughness
5.3.2. Susceptability to temper embrittlement 131
5.4. Creep behaviour of weld materials4
5.4.1. 1 % CrMoV welds
5.4.2. 2 1/4 Cr-1 Mo weld materials6
6. Dissimilar welds; 1 % CrMoV cast steel to 12 % CrMoV forged pipe 137
6.1. Materials and welding procedures investigated 138
6.2. Hardness behaviour of dissimilar welds 141
6.3. Metallurgical investigation of the fusion line area of dissimilar welds 147
6.3.1. Metallographic investigation7
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