Surface Phenomena in Fusion Welding Processes

395 Pages·2005·19.776 MB·English

by  G.F. Deyev

Surface Phenomena in Fusion Welding Processes
© 2006 by Taylor & Francis Group, LLC
Surface Phenomena in

Fusion Welding

Processes
German Deyev
Dmitriy Deyev
© 2006 by Taylor & Francis Group, LLC
9883_Discl.fm Page 1 Tuesday, October 11, 2005 10:06 AM
Published in 2006 by
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Library of Congress Cataloging-in-Publication Data
Deyev, German F.
Surface phenomena in fusion welding processes / by German F. Deyev and Dmitriy G. Deyev
p. cm.
Includes bibliographical refrences and index.
ISBN 0-8493-9883-5 (alk. paper)
1. Welding. 2. Surfaces (Technology) I. Deyev, Dmitriy G. II. Title.
TS227.D49 2005
671.5'2--dc22 2005052851
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Preface
Theindustryiscurrentlyapplying highly diverse welding processes.However,the
maintechnologicalprocessappliedinmanufactureofweldmentsisfusionwelding.
Fusion welding is used to join practically all metals and alloys of similar and
dissimilar materials of any thickness. In the application of fusion welding, the
partsarejoined eitherbymeltingoftheparts’edges orasaresultofsimultaneous
melting of the base and additional (electrode) metal. A weld pool forms from the
metalmelt,itssubsequentsolidification,proceedingwithoutapplicationofexternal
pressure, leads to the formation ofthe weld.
Dependingonthekindoftheappliedheatsource,adistinctionismadebetween
the following fusion welding processes: electric arc, electron beam, electroslag,
laser, and gas welding. Irrespective of the actual welding process applied, the
main aim of any process is producing a sound welded joint. This is only possible
if a sufficiently comprehensive allowance is made for the main physicochemical
processes proceedingin the welding zone.
Heating, melting, evaporation, solidification, and subsequent cooling of solid
metal, the transition of a substance from one phase into another, initiation of new
phases, substance distribution inside a phase, interaction of the contacting
phases — all these and many other processes are characteristic of fusion welding.
Since all or part of the above processes proceed simultaneously in different
regions of the weld pool and welded joint, and their occurrence and progress is
determined by a large number of factors, studying the process as a whole is a real
challenge. On the other hand, there is no doubt that many of the above processes
are related, to varying degrees, to the surface phenomena and surface properties
ofthe applied materials.
Forinstance,formationofvariousdefects(pores,non-metallicinclusions,lack-
of-penetration,solidificationcracks,etc.),hydrodynamicprocessesintheweldpool,
formationofdepositedmetalandweldroot,electrode-metaltransfer,interactionof
moltenmetalwiththegasandslag,andanumberofotherprocessesare,toacertain
extent, related to surface phenomena. Surface phenomena largely determine the
strengthofthebondsjoiningthedissimilarmetals.Theroleofsurfacephenomena
is particularly high in welding in space, when the influence of gravity forces
becomes minor.
Therefore, in the development of welding technologies, as well as welding
consumables, it is necessary to know and take into account both the surface
properties (surface and interphase tension) of the applied materials, and surface
phenomena (wettability, electrocapillary phenomena, adsorption, etc.), that affect
the boundaries ofcontacting phases.
© 2006 by Taylor & Francis Group, LLC
Authors
German Deyev earned a B.S. degree in civil engineering from Cheljabinsk State
Polytechnical Institute (Cheljabinsk, Russia, 1963), an M.S. degree in engineering
of welding technology and production from the Cheljabinsk State Polytechnical
Institute (Cheljabinsk, Russia, 1965), and a Ph.D. degree in civil engineering with
specialization in ‘the role of surface properties and phenomena in the formation
of welds and deposited metal’ from Cheljabinsk State Polytechnical Institute
(Cheljabinsk, Russia,1971).
Professor Deyev served as the chairman of the Department of Welding at the
University of Lipetsk from 1976 until 1999. In December 1993, he was appointed
dean of the Metallurgical Faculty of the University of the Lipetsk. During his
academic career, Professor Deyev has received 24 awards. He is a member of the
American Welding Society. Professor Deyev has to his credit 6 books and over
120 publicationsand articlesin professionaljournals.
Dmitriy Deyev earned a B.S. degree in civil engineering in 1994, an M.S.
degree in engineering of welding technology and production from the Lipetsk
State Polytechnical Institute (Lipetsk, Russia, 1995), and a Ph.D. degree in Civil
Engineering from Voronezh State University (Voronezh, Russia, 1998). He
served as the leading specialist at the Department of Transportation of the Lipetsk
State Government from 1995 until 1999. Dmitriy Deyev has written many publi-
cations and articlesin professionaljournals.
© 2006 by Taylor & Francis Group, LLC
Contents
Chapter1 Characterizationofthe Fusion Welding Process .............. 1
1.1 Some Features ofFusion Welding ............................. 1
1.1.1 The Basics ofWeldFormation .......................... 1
1.1.2 The Influenceof Gases ................................ 2
1.1.3 The Influenceof Slag ................................. 3
1.2 Welding Heat Sources ...................................... 4
1.2.1 The D.C.vs. A.C. Welding ............................ 4
1.2.2 ElectronBeam Welding ............................... 7
1.2.3 Laser Welding ....................................... 8
1.3 FusionWelding Processes ................................... 9
1.3.1 Electric Arc Welding ................................. 9
1.3.1.1 Gas Shielding ................................ 10
1.3.2 Electroslag Welding .................................. 11
1.3.3 ElectronBeam andLaser Welding ....................... 12
1.4 Physicochemical Processes of Welded JointFormation ............ 13
1.4.1 Direct Interaction ofTheMetal andTheGas .............. 14
1.4.1.1 Theoretical Models ............................ 14
1.4.1.2 TheDrawback of the Theoretical Models .......... 16
1.4.2 Influenceof Surfactants ............................... 17
1.4.3 The Gas-Adsorption Ability ............................ 18
1.4.4 The Influenceof Vacuum .............................. 19
1.4.5 The Influenceof Fluxes ............................... 20
1.4.6 The Role of the Slag .................................. 21
1.4.7 The Physiochemical Processes at the Solid–Molten
Metal Boundary ...................................... 23
1.4.7.1 TheNucleation Process ........................ 23
1.4.7.2 MeltOvercooling ............................. 24
1.4.7.3 Presence of RefractoryImpurities ................ 24
1.4.7.4 Shape ofthe Interface ......................... 25
1.4.7.5 Effect ofMetal Stirring ........................ 25
1.4.8 Calculation ofs Values ........................... 26
sol21
1.4.9 The Crystallization Phenomena ......................... 28
1.4.9.1 Electromagnetic Stirring and Ultrasonic
Oscillations .................................. 29
1.4.9.2 Segregation Processes ......................... 30
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Chapter2 Surface Properties and Phenomena ........................... 35
2.1 SurfaceProperties and Phenomena on the Boundaries of
Contacting Phases .......................................... 35
2.1.1 The Concept ofSurface Energy ......................... 35
2.1.2 SurfaceEnergy vs.Surface Tension ...................... 37
2.1.3 Interphase Tension .................................... 37
2.1.4 The Adsorption Process ................................ 40
2.1.5 The Electrochemical Phenomena ........................ 42
2.2 Determination ofSurface Properties ofMelts .................... 44
2.2.1 Pendant Drop Method ................................. 44
2.2.2 Drop WeightMethod .................................. 44
2.2.3 Sessile Drop Method .................................. 45
2.2.4 Methodof MaximumPressure inthe Bubble ............... 46
2.2.5 Large Drop Method ................................... 48
2.2.6 Methodof Metal Melting in the Pendant State ............. 49
2.2.7 Methodto Determine the Surface Tension of aMetal in
the Zoneof the Arc Active Spot ......................... 49
2.3 Methodsof Measurementof the Surface Tension of SolidsMetals ... 51
2.3.1 Methodof Multiphase Equilibrium ....................... 51
2.3.2 Methodof “Zero Creep” ............................... 52
2.3.3 Methodof Groove Smoothing .......................... 53
2.3.4 Methodof AutoelectronicEmission ...................... 54
2.3.5 Methodof Thermal Etching of Grain Boundaries ........... 54
2.4 MethodstoDetermine the Surface Energy of the Interphases ....... 56
2.4.1 The Sessile DropMethod .............................. 56
2.4.2 The Drop Weighing Method ............................ 57
2.4.3 Turned CapillaryMethod .............................. 57
2.4.4 DropsContact Method ................................ 58
2.4.5 X-ray Photography ofa Sessile Drop ..................... 58
2.5 Wettability, Spreading, andElectrocapillary Phenomena ........... 59
2.5.1 General Considerations ................................ 59
2.5.2 AModern Unit for Studyingthe Welding Phenomena ....... 59
2.5.3 Studyingthe Electrocapillary Phenomena ................. 61
2.5.4 AComparison of the DifferentMethods .................. 64
Chapter3 Results of Studying the Surface Properties
and Phenomena ............................................. 65
3.1 SurfaceTensionof Molten and Solid Metals .................... 65
3.1.1 Influence ofAlloy Composition ......................... 65
3.1.2 The Influenceof Gases ................................ 67
3.1.2.1 Hydrogen, Nitrogen, andOxygen ................ 67
3.1.2.2 TheBehavior ofCO ........................... 69
3.1.2.3 TheBehavior ofCO /Air ...................... 70
2
3.1.2.4 TheBehavior ofBinary Gas Mixtures ............. 76
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3.1.2.4.1 Armco-Ironand Steels ................ 76
3.1.2.4.2 Aluminumand its Alloys .............. 76
3.1.2.4.3 Copper andits Alloys ................ 77
3.1.2.4.4 Titaniumand itsAlloys ............... 79
3.1.2.4.5 Nickel and itsAlloys ................. 80
3.1.2.4.6 The Role of Metal Temperature ........ 81
3.2 Interphase SurfaceEnergies inMetal–Slag and
Solid Metal–Melt Systems .................................. 82
3.2.1 Composition of the System ............................. 83
3.2.1.1 Carbon ..................................... 84
3.2.1.2 Sulfur ...................................... 84
3.2.1.3 Phosphorus .................................. 84
3.2.1.4 Oxygen ..................................... 84
3.2.1.5 Cr, Mo, W,and Si ............................ 85
3.2.1.6 Individual Slag Components .................... 85
3.2.2 Temperature ofthe System ............................. 86
3.2.3 Experimental Determination ofInterphase Tension ......... 86
3.2.3.1 TheAvailable Informationon Welding
Processes .................................... 87
3.2.3.2 Solidification Processes ........................ 88
3.3 Wettabilityand Spreading of Metal Melts over the
Surface ofSolids .......................................... 88
3.3.1 Influenceof Material Composition ....................... 90
3.3.2 Influenceof Surface Roughness ......................... 92
3.3.3 Influenceof External Fields ............................ 92
3.3.4 IsothermalConditions ................................. 95
3.3.4.1 Steel/Copper and Copper-Based alloys ........... 95
3.3.4.2 SteelAluminum .............................. 96
3.3.4.3 Copper/Aluminum ............................ 98
3.3.4.4 Titanium and TitaniumAlloys/Aluminum ......... 99
3.3.5 Behaviorunder Non-IsothermalProcess .................. 100
3.3.5.1 Influence ofArc Parameters .................... 101
3.3.5.2 Gas-Shielded Welding ......................... 102
3.3.5.3 TheFluoc Effect .............................. 102
3.3.5.4 TheRole ofPreheading ........................ 103
3.4 Influenceof WeldingHeatSourceson Wettability
and Spreading ............................................. 105
3.4.1 Influenceof Arc Discharge ............................. 105
3.4.1.1 DirectArc ................................... 107
3.4.1.2 Indirect Arc ................................. 107
3.4.1.3 TheRole ofSubstrate Composition .............. 109
3.4.1.4 Composite Materials .......................... 110
3.4.2 GeneralMechanistic Considerations ..................... 113
3.4.2.1 Experimental DeterminationofD ............... 117
m
3.4.2.2 TheNatureof the Gas Flame ................... 118
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3.5 Wettability ofthe SolidMetal by Nonmetal Melts .............. 119
3.5.1 The Influenceof Sulfur/Sulfides ........................ 119
3.5.2 Influence ofChlorides/Fluoridesof Fluxes ................ 122
3.5.2.1 TheExperimental Procedure .................... 123
3.6 Electrocapillary Phenomena ina Metal–Slag System ........... 123
3.6.1 Electrochemical Nature ofInteractions ................... 124
3.6.2 The Approach ....................................... 124
3.6.3 Experimental Methods ................................. 125
3.6.4 The Influenceof Cell Dimensions ....................... 128
3.6.5 Influence ofan External Electric Field .................... 131
Chapter4 Electrode-Metal Transfer andSurface Phenomena ............ 135
4.1 ForcesInfluencing Electrode-Metal Transfer ..................... 135
4.1.1 The Natureof Electrode-Metal Transfer .................. 135
4.1.2 The Processof Drop Formation ......................... 136
4.1.3 The Electromagnetic Force ............................. 137
4.1.4 The Reactive Forces .................................. 138
4.1.5 Other Forces ........................................ 138
4.2 Transfer andSpatter ofElectrode Metal inWelding ina
Gaseous Medium ........................................... 138
4.2.1 Stagesin Drop Transfer ............................... 138
4.2.2 Drop Detachment ..................................... 140
4.2.3 Formationof Metal Spatter ............................. 141
4.2.4 The Role ofPart Preheating ............................ 142
4.2.5 Wettability andWelding Current ........................ 145
4.2.6 The Role ofOxidizing Gases ........................... 146
4.2.7 Influence ofElectrodeWire Composition ................. 148
4.2.8 Flux-Cored Wiresand Filler Metal ....................... 149
4.3 Transfer ofthe Electrode Metal Contacting the Slag .............. 150
4.3.1 The Underlying Factors ................................ 150
4.3.2 The Impact of Interphase Tension ....................... 150
4.3.2.1 Basic-Type Coating ........................... 150
4.3.2.2 Acidic Coating ............................... 152
4.3.3 The Influenceof WeldingPolarity ....................... 153
4.3.3.1 Polarity andSingle-ComponentCoatings .......... 153
4.3.3.2 Polarity Effect with Flux ....................... 155
4.3.3.2.1 Submerged-ArcWelding with a Flux .... 155
4.3.3.2.2 Electroslag Welding .................. 155
Chapter5 Formation ofWeld and Deposited Metal ..................... 157
5.1 Weldand Serviceability ofa Welded Structure .................. 157
5.1.1 Causes ofStrength Deterioration ........................ 157
5.1.1.1 Cracks and Crack-LikeDefects .................. 160
5.1.1.2 Undercuts ................................... 161
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5.1.1.3 Craters ...................................... 162
5.1.1.4 Rolls ....................................... 163
5.2 Formationof the Penetration Zone ............................ 164
5.2.1 Shape andDimensions ofthe Penetration Zone ............ 164
5.2.1.1 Penetration Depth ............................. 165
5.2.2 The Influenceof Base-Metal Surface Properties ............ 166
5.2.3 The Action ofSurfactants .............................. 168
5.2.4 ThermocapillaryPhenomena ........................... 169
5.2.4.1 Evidence from Laser Welding and ArcWelding .... 171
5.2.4.2 ConsumableElectrode Welding ................. 172
5.2.5 Effect ofCurrentPolarity .............................. 173
5.2.6 Experimental Findings ................................ 177
5.2.6.1 Influence ofWelding Current ................... 178
5.2.6.2 Durationof Arc Discharge Action ............... 178
5.2.6.3 Dimensions andSpacing ofthe SteelPlates ........ 179
5.2.6.4 Calculations ................................. 181
5.3 Formationof the Weld Bead andRoot ......................... 182
5.3.1 Issues inthe Formationof Butt Welds .................... 182
5.3.2 The Graphical Method ................................ 182
5.3.3 The Role of Temperature Fields and InclinationAngles ..... 184
5.3.3.1 Angle ofInclination ........................... 185
5.3.4 Surface Tension vs. Gravitational Force .................. 187
5.3.4.1 Angle ofTransition ........................... 188
5.4 Formationof the Deposited Metal ............................. 189
5.4.1 Wetting Angle ....................................... 189
5.4.2 Experiments with Electron Beam Surfacing ............... 191
5.4.2.1 TheCritical Rate ofDeposition .................. 191
5.4.2.2 Electron Beam Oscillations ..................... 194
5.4.3 Temperature Gradient andthe Speed of Displacement ....... 194
5.5 Defects ofWeldShape and Surface Phenomena ................. 198
5.5.1 Groove Filling and Unfilling ........................... 198
5.5.1.1 Extending the Timeof Weld-PoolExistence ....... 199
5.5.1.2 Surface Roughness ............................ 199
5.5.2 Multilayer Welding ................................... 200
5.5.2.1 Formation of Burns-Through .................... 201
5.5.2.2 Formation of Craters .......................... 201
5.5.2.3 Formation of Rolls ............................ 202
Chapter6 Non-Metallic Inclusions ..................................... 205
6.1 Non-Metallic Inclusions inthe Welds .......................... 205
6.1.1 Types ofNon-Metallic Inclusions ....................... 205
6.1.2 The Influenceof Non-Metallic Inclusions ................. 208
6.1.2.1 Thermal–Structural Factors ..................... 208
6.1.2.2 Strength ofWeldedJoints ...................... 208
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