Welding Metallurgy & Weld Ability of Metals

8/3/2019 Welding Metallurgy & Weld Ability of Metals

1/131

WELDING METALLURGY

AND

WELDABILITY OF METALS


2/131

IT IS ESTIMATED THAT THERE ARE MORE THAN

40,000 METALLIC ALLOYS CURRENTLYIN USE.

THIS LARGE NUMBER OF METALLIC ALLOYS

OFTEN MAKE IT DIFFICULT:

- TO IDENTIFY THE PARTICULAR TYPE ON HAND,

AND,

- TO IDENTIFY THE WELDING TASKS THAT ARE

FIT FOR PURPOSE IN ALL KINDS OF SERVICE.


3/131

CRITERIA IN INITIAL SCREENING OF METALLIC

ALLOYS AND THEIR WELDABILITY:

PERFORMANCE REQUIREMENTS:

- WHAT IS IT?

- WHAT DOES IT DO?- HOW DOES IT DO IT?

WELDABILITY REQUIREMENTS

RELIABILITY REQUIREMENTS

RESISTANCE TO SERVICE CONDITIONS


4/131

GENERAL CLASSIFICATION OF METALLIC

ALLOYS:

FERROUS IRON-BASED

NON-FERROUS NON-IRON-BASED


5/131

FERROUS METALLIC ALLOYS:

STEELS ACCOUNT FOR OVER 60%OF THE METALLIC ALLOYS USED

IN THE INDUSTRY

CAST IRONS


6/131

NON-FERROUS METALLIC ALLOYS FOR

MAJOR INDUSTRIAL APPLICATIONS:

NICKEL ALLOYS

TITANIUM ALLOYS

COPPER ALLOYS

ALUMINUM ALLOYS


7/131

3 BASIC TYPES OF PLAIN CARBON STEELS:

LOW-CARBON STEELS ( MILD STEELS )

< 0.2% C

MEDIUM-CARBON STEELS

~ 0.5% C

HIGH-CARBON STEELS

~ 0.8% C


8/131

PREPARING AMETALLOGRAPHIC SPECIMEN

FOR MICROSTRUCTURE ANALYSIS

CUT A SECTION OF THE METALLIC ALLOYS FORMICROSTRUCTURE ANALYSIS.

GRIND THE SPECIMEN IN SUCCESSIVELY FINERSILICON CARBIDE ABRASIVE GRITS OF 120 / 320 /600 / 1200.

POLISH THE FINELY GROUND SPECIMEN ONNAPPED POLISHING CLOTHS IN, FIRST,COLLOIDAL CHROMIUM OXIDE SUSPENSION,THEN, IN COLLOIDAL ALUMINUM OXIDESUSPENSION.

DIP THE BUFFED SPECIMEN IN A 3% NITRICACID SOLUTION.

THE SPECIMEN IS NOW READY TO BE VIEWEDUNDER A METALLOGRAPHIC MICROSCOPE.


9/131

THE ETCHED SPECIMEN CAN NOW BE VIEWEDUNDER AN OPTICAL METALLOGRAPHIC MICROSCOPE

CAPABLE OF UP TO 1000X MAGNIFICATION.


10/131

A MORE SOPHISTICATEDSCANNING ELECTRON METALLOGRAPHIC MICROSCOPE

CAPABLE OF UP TO 10,000X MAGNIFICATION.


11/131

A TYPICAL MICROSTRUCTURE OF A LOW-PLAIN-CARBON

STEEL SHOWING GRANULAR FERRITES ( ).BECAUSE OF THE VERY LOW CARBON CONTENT, ALL THE

CARBON IS DISSOLVED AND FINELY DISPERSED IN THEIRON MATRIX.

THE GRANULAR FERRITES STRUCTURES ARE

VERY SOFT, LOW-STRENGTH AND DUCTILE.THE GRANULAR FERRITES IN A LOW-PLAIN-CARBON

STEEL DO NOT TRANSFORM TO A DIFFERENT STRUCTUREEVEN AFTER CYCLIC HEATING AND COOLING -

TRANSLATING TO VERY GOOD WELDABILITY OF THE LOW-PLAIN-CARBON STEEL STRUCTURE


12/131

IMPACT STRESSES

IMPACT STRESSES

TENSILE /COMPRESSIVESTRESSES

THE GRANULAR FERRITES, WHEN SUBJECTEDTO IMPACT STRESSES, JUST FLATTEN,

AND WHEN SUBJECTED TO TENSILE AND

COMPRESSIVE STRESSES, JUST ELONGATE.

THE FERRITE GRAINS ACT AS SLIP PLANES, GIVING THEMICROSTRUCTURE A CERTAIN AMOUNT OF DUCTILITY.


13/131

ANY EXCESS CARBON IN A MEDIUM-PLAIN-CARBON STEEL,

WHICH CAN NOT BE DISSOLVED IN THE IRON MATRIX,COMBINES WITH IRON TO FORM HARD AND BRITTLE IRONCARBIDES ( CEMENTITES ) WHICH APPEAR AS PEARLITES.

THE MICROSTRUCTURE CONTAINS FREE GRANULARFERRITES AND LAMELLAR PEARLITES.

PEARLITES CONTAIN PARALLEL LAYERS OF FERRITEGRAINS AND CEMENTITE. THE PARALLEL LAYERS ACT ASSLIP PLANES, GIVING THESE METALLIC ALLOYS A CERTAIN

AMOUNT OF DUCTILITY.

ON THE OTHER HAND, THESE METALLIC ALLOYS START

BECOMING HARD AND BRITTLE BECAUSE CARBIDESBEGIN TO FORM.


14/131

THE PLAIN-HIGH-CARBON STEEL CONSISTS OFFULLY PEARLITE MICROSTRUCTURES.

THE MICROSTRUCTURE IS CALLED PEARLITE

BECAUSE IT LOOKS LIKE MOTHER OF PEARLS

AS SEEN UNDER THE MICROSCOPE.

PEARLITES ARE LAMELLAR OR LAYERED ALTERNATEPLATELETS STRUCTURES OF FERRITE ( WHITE STREAKS )

AND CEMENTITE ( DARK STREAKS )

THE PLATELETS STRUCTURES ACT AS SLIP PLANES,INDUCING A CERTAIN AMOUNT OF DUCTILITY. THE

PRESENCE OF CARBIDES, OF AROUND 35% IN THE OVER-ALL STRUCTURE, PROMOTES HARDENABILITY, STRENGTH

AND RIGIDITY.


15/131

IN ORDER TO FULLY APPRECIATE THE EFFECTS OFWELDING HEAT TO PLAIN CARBON STEELS,

WE WILL ATTEMPT TO EXPLAIN THE BASICS OFHEAT TREATMENT.

HEAT TREATMENT IS THE CONTROLLED HEATING ANDCOOLING OF METALS TO ALTER THEIR PROPERTIES

SUCH AS HARDNESS AND STRENGTH WITHOUTCHANGING THE PRODUCT SHAPE.

WHEN A HIGH-PLAIN-CARBON STEEL IS HEATED TOAROUND 1,000C, ALL THE STRUCTURES FERRITES,

CEMENTITES, PEARLITESTRANSFORM TO THE AUSTENITE PHASE ( ).

IT IS IN THE DIFFERENT COOLING RATES, FROM THEAUSTENITE PHASE, THAT THE HIGH-PLAIN-CARBON STEELWILL TRANSFORM BACK TO DIFFERENT STRUCTURES TO

ROOM TEMPERATURE, AND ALTER ITS PROPERTIES.

THE DIFFERENT COOLING RATES ARE AS FOLLOWS:


16/131

FULL ANNEALING ( FURNACE-COOLING ) SOFTENINGVERY SLOW-COOLING RATES, ALLOWING ALL THECARBON TO GET DISSOLVED AND FINELY DIFFUSED INTHE IRON MATRIX. A FULLY FERRITIC MICROSTRUCTUREIS FORMED, WHICH IS VERY SOFT, LOW-STRENGTH AND

DUCTILE.

NORMALIZING ( AIR-COOLING ) TOUGHENINGQUICKER COOLING RATES THAN ANNEALING, FREEFERRITES AND PEARLITES ARE FORMED. START OFHARDENING OF THE MICROSTRUCTURE DUE TO

FORMATION OF CARBIDES, BUT SOME DUCTILITY ISRETAINED DUE TO THE FREE FERRITES AND THEPLATELET STRUCTURES OF PEARLITE.

OIL QUENCHING ( RAPID-COOLING ) HARDENINGMICROSTRUCTURE BECOMES VERY HARD AND BRITTLETHROUGH THE FORMATION OF MARTENSITES.

WATER QUENCIHING ( DRASTIC RAPID COOLING )

HARDENING

COARSE, JAGGED, ROUGH AND DISORIENTEDMARTENSITES ARE FORMED, WHICH ARE EXTREMELYHARDER AND MORE BRITTLE, COMPARED TO

MARTENSITES FORMED BY OIL QUENCHING.


17/131

MARTENSITES ARE FORMED BY RAPID COOLING,WHICH TRAPS THE CARBON ATOMS THAT DO NOTHAVE TIME TO DIFFUSE OUT OF THE IRON MATRIX,

AND CHEMICALLY COMBINE WITH THE IRONTO FORM IRON CARBIDES. A TYPICALMICROSTRUCTURE OF MARTENSITES HAS

ACICULAR, SHARP, NEEDLE-LIKE APPEARANCE.MARTENSITES ARE VERY HARD AND BRITTLE

AND ARE USUALLY NOT WELDABLE.


18/131

UNTEMPERED MARTENSITES, WHILE VERY HARDAND STRONG, ARE TOO BRITTLE TO BE USEFUL

FOR MOST INDUSTRIAL APPLICATIONS.

AFTER WATER OR OIL QUENCING, THE STEELSARE TEMPERED, TO AROUND150C ~ 550C, TO IMPART

TOUGNESS.

AT THESE TEMPERATURES, THERE IS NO CHANGEIN THE MICROSTRUCTURES OF THE STEELS. WHAT

HAPPENS IS THAT THE MARTENSITES ARE REFINED ANDRE-ORIENTED.

AFTER WELDING, THE TERMS USED FOR

THIS HEAT TREATMENT PROCESS ARESTRESS-RELIEVING, OR PWHT.


19/131

IN WELDING, THE EFFECT OF HEAT TREATMENT

IS SOMETIMES INADVERTENTLY DONE.THE WELDING HEAT INPUT MAY RAISE THE

TEMPERATURE OF THE PLAIN CARBON STEELSIN EXCESS OF 800C.

THE HIGHER THE CARBON CONTENT,

AND, THE FASTER THE COOLING RATE,RESULT IN THE FORMATION OF

MORE CARBIDES. THIS WILL MAKETHE PLAIN CARBON STEELS

MORE SUSCEPTIBLE TO CRACKINGDURING WELDING.

IN WELDING, NECESSARY PRECAUTIONSSHOULD ALREADY BE TAKEN TO AVOID THESE

FORMATION OF CARBIDES IN MEDIUM-AND HIGH-PLAIN-CARBON STEELS .


20/131

FROM THE VIEWPOINT OF WELDING, CARBIDES IN PLAIN-CARBON-STEELS ARE HARMFUL, BECAUSE OF THEIR

CRACKING TENDENCIES.

HOWEVER, THERE ARE ATTRIBUTES OF THESE CARBIDESWHICH ARE VERY BENEFICIAL TO MANY INDUSTRIAL

APPLICATIONS.


21/131

LONG-SPAN BEAMS, SUPPORTING HEAVY LOADS ALONGTHEIR AXIS, MUST HAVE RIGIDITY, OTHERWISE THE

BEAMS WILL SAG.

CARBIDES IN PLAIN-CARBON STEELS GIVERIGIDITY TO THE BEAMS.


22/131

MANY INDUSTRIAL PARTS ARE MANUFACTUREDFROM HEAT-TREATED, HIGH-HARDNESS STEELS

FOR METAL-TO-METAL WEAR RESISTANCE.


23/131

REALIZING THE STRONG INFLUENCE OF CARBON

ON THE HARDNESS AND STRENGTH OFPLAIN-CARBON STEELS, AND THE CONSEQUENT

BENEFICIAL EFFECTS, THE TENDENCY IS TO ADDMORE CARBON TO THE PLAIN-CARBON STEELS.

HOWEVER, THERE IS A MAXIMUM LIMITON THE SOLUBILITY OF CARBON IN STEELS,

BEYOND WHICH ANOTHER DIFFERENT

MICROSTRUCTURES WILL BE FORMEDWHICH ARE CAST IRONS,

TO INDUCE THE SAME EFFECT AS CARBON,ALLOYING ELEMENTS ARE ADDED INSTEAD, WITH EACH

HAVING THEIR INDIVIDUAL CARBON EQUIVALENT.

THESE ALLOYED CARBON STEELS LOW-ALLOYEDOR HIGH-ALLOYED OR TOOL STEELS

VARY IN TERMS OF ALLOYING ELEMENTS,STRENGTH AND DURABILITY.


24/131

THE CARBON EQUIVALENT SCALES THE CONCENTRATIONOF EACH ALLOYING ELEMENT BY ITS ABILITY TO

PROMOTE CARBIDE FORMATION.

C.E. = %C + %Mn + %Ni + %Cr + %Cu + %Mo

6 15 5 13 4

THE ALLOYING ELEMENTS INTERACT WITHCARBON TO PRODUCE DESIRED COMBINATIONS

OF HARDENABILITY, STRENGTH AND TOUGHNESS

CARBON STRONG CARBIDE FORMERS.

CHROMIUM NEXT TO CARBON AS STRONG CARBIDEFORMERS.

MANGANESE / NICKEL / MOLYBDENUM / VANADIUMMILD CARBIDE FORMERS; IMPROVES TOUGHNESS ANDSTRENGTH.


25/131

STAINLESS STEELS THE BASE METAL COMPOSITIONSARE TYPICALLY THAT OF CARBON STEELS, WITH THEADDITION OF AT LEAST 11% CHROMIUM. THIS IS THEMINIMUM AMOUNT OF CHROMIUM NECESSARY TOFORM A STABLE, PASSIVE CHROMIUM OXIDE FILM. ITIS THIS FILM THAT IS THE BASIS FOR THE CORROSIONRESISTANCE OF ALL STAINLESS STEELS, THAT GIVESSTAINLESS STEELS THAT UNIQUE STAINLESS STEELLUSTER.

THE BASIC CLASSIFICATIONS OF STAINLESS STEELS ARE:


26/131

THE BASIC CLASSIFICATIONS OF STAINLESS STEELS ARE:

AUSTENITIC STAINLESS STEELS ( 300 SERIES ) WITH AMINIMUM OF 11% CHROMIUM AND 8% NICKEL, THE HIGHCHROMIUM AND NICKEL FREEZE THE AUSTENITE PHASEDOWN TO ROOM TEMPERATURE. THE NICKEL FURTHER

ACTS AS AUSTENITE STABILIZER DURING THERMALCYCLIC CONDITIONS.

THERMAL CYCLE CAUSED BY WELDING HAVE LITTLEINFLUENCE ON MECHANICAL PROPERTIES. THEADJACENT BASE MATERIAL TEMPERATURE, THOUGH,

HAS TO BE CONTROLLED DOWN TO A MAXIMUNM OF250C TO PREVENT CARBIDE PRECIPITATION ALONGTHE GRAIN BOUNDARIES.

PRE-HEAT AND PWHT ARE SELDOM REQUIRED.

AUSTENITIC STAINLESS STEELS ARE TOUGH AND NON-

MAGNETIC.

THE TWO TYPES OF AUSTENITIC STAINLESS STEELSMOST COMMONLY USED ARE:

304FOR GENERAL CORROSION RESISTANCE.

316

WITH THE ADDITION OF A MINIMUM OF 2.5%MOLYBDENUM; FOR SEVERE CORROSION RESISTANCE.


27/131

A TYPICAL MICROSTRUCTURE OF AN AUSTENITIC

STAINLESS STEEL APPEARING AS AUSTENITE GRAINS, ( ) WHICH ARE SOFT, HIGHLY-DUCTILE, TOUGH

AND NON-MAGNETIC.


28/131

THREE KINDS OF CRYSTAL STRUCTURE IN STEELS

GRANULAR FERRITES ARE BODY-CENTERED CUBIC.

GRANULAR AUSTENITES ARE FACE-CENTERED CUBIC,BEING MORE COMPACT, ARE TOUGHER.

CEMENTITES AND MARTENSITES ARE HEXAGONAL

CLOSE-PACKED, THOUGH MORE COMPACT, ARE LESSSTABLE.


29/131

DURING WELDING AUSTENITIC STAINLESS STEELS, WHENTHE TEMPERATURE REACHES 500C ON THE BASE

METAL, CHROMIUM CARBIDES PRECIPITATEPREFERENTIALLY ALONG THE GRAIN BOUNDARIES

OF THE AUSTENITE MICROCTRUCTURES, ALSO CALLEDSENSITIZATION. THIS DETERIORATION MAKES THE

AUSTENITIC STAINLESS STEELS MORE SUSCEPTIBLE TOCORROSION ATTACKS, AND IS THE MOST COMMON

REASON IN WELD FAILURES OF AUSTENITIC STAINLESSSTEELS


30/131

THE HEAT-TINT VISUAL APPEARANCE OF THE

WELD AREA IS DUE TO CARBIDES PRECIPITATION,OR SENSITIZATION.


31/131

THE 400 SERIES STAINLESS STEELSTHESE ARE THESTRAIGHT-CHROMIUM, WITHOUT THE ADDITION OF A

MINIMUM OF 8% NICKEL.THE TWO TYPES OF 400-SERIES STAINLESS STEELSARE:

FERRITIC GRADES STAINLESS STEELSTHESESTAINLESS STEELS ARE FERRITIC AT ALL TEMPERATURES,

WITH THE ADDITION TO BASIC 400-SERIES STAINLESSSTEELS OF FERRITE STABILIZERS HIGHER CHROMIUM,SILICON, MOLYBDENUM, COBALT, TITANIUM.

FERRITIC STAINLESS STEELS ARE SOFT, DUCTILE ANDHIGHLY MAGNETIC.

A TYPICAL APPLICATION FOR FERRITIC STAINLESSSTEELS ARE IN MAGNETIC TRAPS IN PIPELINES, WHICHFACILITATE TRAMP METAL SEPARATION FROM CORROSIVEFLUIDS.


32/131

MAGNETIC TRAPS MADE FROM WIRE MESHOF FERRITIC STAINLESS STEELS FACILTATE

TRAMP METAL SEPARATION FROMCORROSIVE LIQUIDS.


33/131

MARTENSITIC GRADES STAINLESS STEELSTHESE ARE

ESSENTIALLY 400-SERIES STAINLESS STEEL ALLOYS OFA HIGHER CHROMIUM AND CARBON CONTENTS THATPOSSESS A FULLY MARTENSITIC MICROSTRUCTURE INTHE HARDENED CONDITION.

THE MARTENSITIC GRADES STAINLESS STEELS ARE

HIGHLY MAGNETIC AND ARE HARDENABLE BY HEATTREATMENTS.

A TYPICAL APPLICATION OF MARTENSITIC GRADESSTAINLESS STEELS ARE INDUSTRIAL KNIFE BLADES. THEMARTENSITE MICROSTRUCTURES AND EXCESS

CARBIDES MAINTAIN CUTTING EDGES AND CORROSIONRESISTANCE.


34/131

KNIFE BLADES USED IN THE FOOD INDUSTRYARE SOME OF THE TYPICAL APPLICATIONS

FOR MARTENSITIC GRADE STAINLESS STEELSREQUIRING HARDNESS ON CUTTING EDGES

BE MAINTAINED AND SUPERIORCORROSION RESISTANCE IN SERVICE.


35/131

DUPLEX GRADES STAINLESS STEELS THEY GETTHEIR NAME BECAUSE THEY CONTAIN BOTH FERRITICAND AUSTENITIC MICROSTRUCTURE IN EQUAL AMOUNT.

IN FULLY AUSTENITIC STAINLESS STEELS REQUIRINGEXTENSIVE AND HEAVY WELDING, PRECIPITATEDCARBIDES FORM ALONG THE GRAIN BOUNDARIES OF THEAUSTENITE MICROSTRUCTURES, THESE PRECIPITATEDCARBIDES ARE VERY PRONE TO CORROSIVE ATTACK,WHICH MAY RENDER THE PART IMPRACTICAL, SPECIALLY

IN APPLICATIONS REQUIRING RESISTANCE TO VERYAGGRESSIVE MEDIA.

DUPLEX GRADES STAINLESS STEELS WERE FORMULATEDFOR FABRICATIONS OF STAINLESS STEELS REQUIRINGEXTENSIVE AND HEAVY WELDING WORK. THE FERRITIC

STRUCTURES IN THE MATRIX REDUCE CARBIDESPRECIPITATION.

TYPICAL USES OF DUPLEX GRADES STAINLESS STEELSARE FOR HEAT EXCHANGERS, CHEMICAL TANKS,REFINERIES, PRESURE VESSELS AND OFFSHOREAPPLICATIONS.


36/131

TYPICAL MICROSTRUCTURES OF DUPLEX GRADESSTAINLESS STEELS, WHICH ARE A MIX OF 50 / 50

FERRITES AND AUSTENITES MICROSTRUCTURES.THE DARK AREAS ARE FERRITE MICROSTRUCTURES

AND THE WHITE AREAS ARE AUSTENITESMICROSTRUCTURES.


37/131

FABRICATION OF A FRACTIONATION TOWER OF DUPLEX

GRADES STAINLESS STEELS. EVEN IN VERY EXTENSIVEAND HEAVY WELDING, THE PART IS NOT PRONE TO

CARBIDES PRECIPITATION BECAUSE OF THE PRESENCEOF THE FERRITIC MICROSTRUCTURES IN THE MATRIX.


38/131

BECAUSE OF THE HEAT INPUT DURING WELDING OFDUPLEX GRADES STAINLESS STEELS, THE

BALANCE OF THE FERRITES AND AUSTENITESMICROSTRUCTURES MAY BE ALTERED.

IF THE FERRITES ARE TOO LOW BECAUSE OFTRANSFORMATION, CARBIDES PRECIPITATIONMAY TAKE PLACE.

ALTERNATIVELY, IF THE FERRITES BECOME HIGH,THE STAINLESS STEELS ARE PRONE TO CORROSIONBECAUSE OF THE DEPLETION OF THE AUSTENITICMICROSTRUCTURES.

THE FERRITE DETECTOR IS USED TO DETERMINETHE FERRITE NUMBER ( FN ) OF DUPLEX GRADESSTAINLESS STEELS. THE VOLUME PERCENTAGEOF FERRITES CAN BE ESTIMATED AS ABOUT 70%OF THE FN.


39/131

THE FERRITE DETECTOR IS A NON-DESTRUCTIVEINSPECTION INSTRUMENT BASED ON THE MUTUAL

ATTRACTION OF A PERMANENT BAR MAGNET TO A KNOWNSTANDARD AND AN UNKNOWN MATERIAL.


40/131

IRON-IRON CARBIDE

PHASE DIAGRAM


41/131

THE IRON-IRON CARBIDE PHASE DIAGRAM ISESSENTIALLY A MAP OF THE PHASES THAT EXISTIN IRON AT VARIOUS CARBON CONTENTS ANDTEMPERATURES UNDER EQUILIBRIUM CONDITIONS.


42/131


43/131

AUSTENITIC MANGANESE STEELS THESE TYPICALLYCONTAIN 1.2% C AND A MINIMUM OF 12% MANGANESE.

A UNIQUE COMBINATION OF PROPERTIES IS ACHIEVEDIN THAT IT IMPARTS HIGH TOUGHNESS AND DUCTILITY

WITH HIGH WORK-HARDENING CAPACITY AND, GOODRESISTANCE TO WEAR.

TOOL STEELS MAY HAVE HIGH-WEAR AND ABRASIONRESISTANCE, BUT IN SOME INDUSTRIAL APPLICATIONS,MAY NOT BE ABLE TO WITHSTAND THE HIGH-IMPACT

LOADS BECAUSE OF THEIR CRACKING TENDENCIES.AUSTENITIC MANGANESE STEELS ARE PRIMARILY USEDIN EARTHMOVING, MINING, CEMENT PLANTS, QUARRYING,OIL WEL DRILLING, RAILROADING, DREDGING.

IN THE AS-CAST CONDITION, AUSTENITIC MANGANESE

STEELS ARE RELATIVELY SOFT. THEY CAN BE MACHINEDTO SHAPES IN THIS CONDITION. ONCE THESE ARE USEDAND SUBJECTED TO CONSTANT IMPACT LOADS, THEYWORK-HARDENED ( OR, COLD-HARDENED ), ACHIEVINGHIGH-HARDNESS TOGETHER WITH THEIR HIGH-IMPACTPROPERTIES.


44/131

THE RAIL WHEELS AND THE RAIL TRACKSARE MANUFACTURED FROM AUSTENITIC

MANGANESE STEELS, REQUIRING METAL-TO-METAL WEARRESISTANCE AND HIGH-IMPACT LOADS..


45/131

AUSTENITIC MANGANESE STEELS ARE USEDEXTENSIVELY IN EARTH-MOVING EQUIPMENT FOR

BUCKETS, SHOVELS, TEETH, WHEREVERY SEVERE WEAR AND IMPACT LOADS

ARE ENCOUNTERED.


46/131

IN ROCK-CRUSHING MACHINERIES FOR MINING ANDCEMENT PLANTS, AUSTENITIC MANGANESE STEELS AREEXTENSIVELY USED FOR HANDLING AND PROCESSINGEARTHEN MATERIALS SUCH AS CRUSHERS, GRINDING

MILLS. MANGANESE STEELS PROVIDE TOUGH, RUGGED,HIGH-WEAR RESISTANCE AND HARSH IMPACT

PROPERTIES FOR THE RUGGED APPLICATIONS.

THERMIT RAILROAD WELDING THIS IS A PROCESS OFIGNITING A FORMULATED PYROTECHNIC POWDER MIX OF


47/131

IGNITING A FORMULATED PYROTECHNIC POWDER MIX OFEXOTHERMIC, HIGH-ENERGY ALUMINO-THERMIC METALALLOYS, PRODUCING A SUPER-HEATED LIQUID METALTHAT IS POURED BETWEEN THE RAILTRACKS END-JOINTS,TO FORM A WELDED JOINT.

THE CHEMICAL REACTION IS AS FOLLOWS:

8Al + 3Fe3O4 + FeMn ( Mn Alloys ) + Mg ( IGNITER )

= 9Fe + 4Al2O3 + HEAT

TYPICALLY THE ENDS OF THE RAILS ARE CLEANED,ALIGNED FLAT, AND SPACED APART, AROUND 2 INCHES. AGRAPHITE MOLD IS CLAMPED AROUND THE RAIL ENDS.THE RAILS ENDS ARE PREHEATED TO AROUND 500C.THE POWDER MIX IS IGNITED IN THE REFRACTORYCRUCIBLE AND ALLOWED TO REACT TO COMPLETION.

THE REACTION CRUCIBLE IS THEN TAPPED AT THEBOTTOM ( LEAVING THE ALUMINUM OXIDE IN THECRUCIBLE ), THE MOLTEN STEEL FLOWS INTO THE MOLD,FUSING WITH THE RAIL ENDS, AND FORMING THE WELD.AFTER COOLING, THE MOLD IS REMOVED AND THE WELDIS CLEANED AND GRINDED TO PRODUCE A SMOOTHJOINT.


48/131

THERMIT RAIL WELDING CRUCIBLE AND MOLD.


49/131

A GRAPHITE MOLD IS CLAMPED AROUND THE RAIL ENDS.

THE RAILS ENDS ARE PREHEATED TO AROUND 500C.


50/131

THE POWDER MIX IS IGNITED IN THE REFRACTORYCRUCIBLE AND ALLOWED TO REACT TO COMPLETION. THE

REACTION CRUCIBLE IS THEN TAPPED AT THE BOTTOM (LEAVING THE ALUMINUM OXIDE IN THE CRUCIBLE ), THE

MOLTEN STEEL FLOWS INTO THE MOLD, FUSING WITH THE

RAIL ENDS, AND FORMING THE WELD.


51/131

IN WELDING MANGANESE STEELS, THE BASE METALSHOULD NOT REACH MORE THAN 250C. TO DO THIS,SKIP / INTERMITTENT WELDING IS DONE. THE WELD

AREA ITSELF IS SHOWERED WITH WATER AFTER PAUSINGEVERY AFTER LAYER.


52/131

IN HARDFACING STEELS, BUFFER LAYERSSHOULD NOT BE MORE THAN 45RC. THE 45RCHARDFACING ELECTRODES CAN BE WELDED

MULTI-PASS. THE 60RC HARDFACING ELECTRODESCAN BE WELDED ONLY AT SINGLE-PASS LAYER.

WELDING THE 60RC HARDFACING ELECTRODE MULTI-PASS WILL CAUSE CRACKING AND / OR SPALLING OF THE

WELDS.


53/131

IN HARDFACING STEEL PARTS SUBJECTED TO METAL-TO-METAL CONTACT WEAR, ONE PART

SHOULD HAVE A 10RC LOWER HARDNESS THANTHE OTHER PART.


54/131

IN THE TRANSITION FROM STEELS TO CAST IRONS,AT AROUND 2% CARBON, WHITE CAST IRONS

ARE FORMED, IN WHICH THE CARBON IS PRESENTFULLY AS CARBIDES, OR CEMENTITES.

THE WHITE CAST IRONS MICROSTRUCTURESARE VERY HARD, SUITABLE FOR APPLICATIONS

REQUIRING METAL-TO-METAL CONTACT

HIGH-WEAR, RESISTANCE. THEY CAN ONLYBE CASTED, THEY CAN NOT BE MACHINED,WROUGHT ( FORGED, ROLLED, EXTRUDED ),HEAT-TREATED NOR SUBJECTED TO IMPACT.

THEY ARE USED IN SERVICE FROM THEIRAS-CAST CONDITION AS THEY CAN NOT BE

SUBJECTED TO ANY FURTHER PROCESSING

WHITE CAST IRONS ARE NAMED AFTERTHEIR WHITE FRACTURED SURFACE DUE

TO THE CARBIDES.


55/131

WHITE CAST IRONS MICROSTRUCTURES SHOWINGNEARLY COMPLETE CARBON SOLUTION IN A MATRIX

OF MASSIVE, ACICULAR, NEEDLE-LIKE CEMENTITES,WHICH ARE VERY HARD AND BRITTLE..


56/131

A TYPICAL EXAMPLE OF THE INDUSTRIAL APPLICATIONOF WHITE CAST IRON IS IN THE MIXER BLADES

OF SAND MULLERS.


57/131

GRAY CAST IRONS AT 3.0-4.0% CARBON CONTENTS, THE

CARBON REACHES A SUPERSATURATED CONDITIONWHERE THE EXCESS CARBON CAN NO LONGER DIFFUSE

INTO THE IRON MATRIX, NOR COMBINE WITH THE IRON.THE SUPERSATURATED EXCESS CARBON WILL JUSTFLOAT AS FREE CARBON, IN THE FORM OF GRAPHITEFLAKES IN A MATRIX OF FERRITES AND PEARLITES.

THE GRAPHITE FLAKES ACT AS STRESS RAISERS

WHICH MAY INITIATE FRACTURE WHEN THEGRAY CAST IRONS ARE SUBJECTED TO MODERATE

IMPACT. WHEN SLIGHTLY HEATED, DURINGEXPANSION AND CONTRACTION, THE

GRAPHITE FLAKES ACT AS CRACK-PROPAGATORS.

WITHOUT THE GRAPHITE FLAKES, THE MATRIX ISJUST LIKE PLAIN-CARBON STEELS, WHICH CAN HAVEA TENSILE STRENGTH OF UP TO 70,000 PSI. THE

GRAPHITE FLAKES IN GRAY CAST IRONS FORM VOIDS ANDARE POROUS, REDUCING THE STRENGTH

DOWN TO AROUND 25,000 PSI.


58/131

MOST COMMERCIAL GRADES OF GRAY CAST IRONSCONTAIN 3.0-4.0% CARBON. THE SUPERSATURATEDCARBON WHICH CAN NOT DIFFUSE NOR REACT WITH

THE IRON ANYMORE, APPEARS AS FREE GRAPHITESIN A TYPICALLY STEEL MATRIX OF FERRITES ANDPEARLITES.

IN MANY ENGINEERING MATERIALS WITH


59/131

IN MANY ENGINEERING MATERIALS, WITHINTRICATE DESIGNS OF COMPLICATED SHAPES ANDSIZES OF THICK AND THIN SECTIONS, WHERE THETENSILE STRENGTH OF 25,000 PSI IS SUFFICIENT

ENOUGH FOR THE APPLICATION,GRAY CAST IRONS ARE HIGHLY BENEFICIAL.

THE MICROSTRUCTURE OF GRAY CAST IRONSALLOW MASSIVE CASTINGS TO BE FORMED, FOR

EXAMPLE A 10-TON OPEN GEAR.

THE GRAPHITE FLAKES ACTS AS CHIP BREAKERS,

MAKING THE GRAY CAST IRONS HIGHLY MACHINABLE.THEY TEND TO DAMPEN MECHANICAL VIBRATIONS,

HELPING THE MACHINERIES RUN SMOOTHLY.GRAY CAST IRONS ALSO HAVE

GOOD CORROSION RESISTANCE.

TYPICAL EXAMPLES OF PARTS MANUFACTUREDFROM CAST IRONS ARE CYLINDER BLOCKS, HEADS

AND GEARBOXES.

GRAY CAST IRONS ARE NAMED AFTER THEIR GRAYFRACTURED SURFACE DUE TO THE GRAPHITE FLAKES.


60/131

A SPIRAL MOLD TESTS THE MEASURE OF FLUIDITY OF AMELT. THE HIGH CARBON CONTENT OF GRAY CAST IRON

MAKES THE MELT HIGHLY FLUID TO FORM INTRICATETHICK AND THIN SECTIONS.

PLAIN-CARBON STEELS EASILY SOLIDIFY IN THESPIRAL PASSAGE. HENCE, CAST STEELS ARE LIMITED

TO MASSIVE, SIMPLE, UNCORED DESIGNS.


61/131

THE CYLINDER BLOCKS, HEADS, ETC., OF GENERATOR

SETS ARE MADE OF GRAY CAST IRONS


62/131

TURBINE HOUSINGS ARE MADE OF GRAY CAST IRONS.


63/131

THE CYLINDER BLOCKS, HEADS,TRANSMISSION HOUSINGS, GEARBOX CASES,

EXHAUST MANIFOLDS, ETC., OF MOTOR ENGINESARE MADE OF GRAY CAST IRONS.


64/131

IN WELDING GRAY CAST IRONS, THERE IS A TEARINGEFFECT ON THE BASE METAL AS IT EXPANDS ANDCONTRACTS, SINCE THE STRENGTH OF THE BASE

METAL IS LOWER THAN THE WELD METAL. THIS CANBE COUNTER-ACTED BY PEENING THE BASE METAL,

TO PUSH BACK THE TEARING FORCE.


65/131

WHEN WELDING GRAY CAST IRONS, THE HEATGENERATES GASES FROM THE MOISTURE, OILS,

CHEMICALS ABSORBED BY THE GRAPHITE FLAKES.THE GRAPHITE FLAKES THEMSELVES OXIDIZE TO

FORM GASES. THESE GASES RISE AND FLOAT AT THESURFACE, FORMING A GAS FILM WHICH CAN NOT BEPENETRATED BY THE WELDING ARC.

THE SURFACE IS SEARED BY RUNNING AN

OXY-ACETYLENE FLAME AT THE SURFACEAND BRUSHING THE CARBON SOOT FORMED

BY THE GAS FILM.


66/131

IF THE GRAPHITE FLAKES IN GRAY CAST IRONS WEREROUNDED INSTEAD FLAKE-LIKE SHAPES, THEY ACT AS

CRACK-STOPPERS AND INCREASE THE STRENGTHSIMILAR TO CARBON STEELS OF 70,000 PSI.

ROUNDED EXCESS CARBON IS PRODUCED EITHER

BY MALLEABILIZING HEAT TREATMENTS ORINOCULATION OF THE WHITE CAST IRON MELT

WITH EITHER MAGNESIUM OR CESIUM,


67/131

MALLEABLE CAST IRONS ARE MADE BY HIGH-TEMPERATURE HEAT TREAMENTS OF WHITE

CAST IRON CASTINGS. AT THE MALLEABILZINGTEMPERATURE OF 950C, THE CEMENTITESDECOMPOSE AND THE CARBON LIBERATED

FORMS ROUNDED GRAPHITES.


68/131

THE INOCULANTS MAGNESIUM OR CESIUM ARE HIGHLY

VOLATILE. THEY GO FROM SOLID TO GAS IN CONTACTWITH THE MELT. THIS PHENOMENA NODULARIZES THE

EXCESS CARBON, FORMING NODULAR, OR SPHEROIDAL,OR DUCTILE CAST IRONS.


69/131

A TYPICAL MICROSTRUCTURE OF MALLEABLECAST IRONS FORMED BY MALLEABILIZING HEAT

TREATMENTS OF WHITE CAST IRONS ORDUCTILE CAST IRONS ( ALSO CALLED NODULAR

OR SPHEROIDAL CAST IRONS ) FORMED BYINOCULATION OF GRAY CAT IRONS WITHMAGNESIUM OR CESIUM. THE EXCESS CARBONIS ROUNDED, INCREASUING THE STRENGTH UPTO 70,000 PSI AND IMPROVING WELDABILITY OF

THE MICROSTRUCTURE.


70/131

PIPE FITTINGS ARE MADE OF MALLEABLE CAST IRONS.


71/131

CRANKSHAFTS ARE MADE OF DUCTILE CAST IRONS.


72/131

THERMAL SPRAY WELDINGIS WIDELY USED, WHEREMELTED MATERIALS ARE SPRAYED ONTO THE SURFACEOF PARTS, THE COATINGS PROVIDING WEAR, IMPACT,

TEMPERATURE OR CORROSION RESISTANCE.

THERMAL SPRAYING CAN PROVIDETHIN ( AROUND I MM ) TO THICK EVEN COATINGS( OF SEVERAL MM ), OVER LARGE AREAS AT HIGH

DEPOSITION RATES.


73/131

REBUILDING THE WORN-OUT SURFACE OF A NOZZLESEGMENT COMBUSTOR COMPONENT IN A GAS TURBINE

USING THE HOT METAL SRAY FUSION PROCESS WITHCOBALT-BASED VACUUM-BRAZED METAL ALLOYS.


74/131

SPRAYING MAGNESIUM-ZIRCONATE THERMAL BARRIERCOATING ON THE INSIDE SURFACE OF A TRANSITIONPIECE COMBUSTOR COMPONENT IN A GAS TURBINE

USING THE POWDER FLAME SPRAY PROCESS.


75/131

REBUILDING THE WORN-OUT SHAFTING OF THEHELICAL PINION GEAR OF THE ROLLING MILLS

GEAR BOX USING THE COLD EXOTHERMIC METAL SPRAYPROCESS WITH NICKEL-CHROMIUM NICKEL ALLOYS.


76/131

REBUILDING THE SHAFTING BUSHING SURFACEOF THE SCREW CONVEYOR USING THE COLDEXOTHERMIC METAL SPRAY PROCESS WITH

ALUMINUM-BRONZE METAL ALLOYS.


77/131

COATING A SINK ROLL USED IN A STEEL MILL PLANT WITH

ZIRCONIA OR TUNGSTEN CARBIDE POWDERSON A HIGH-VELOCITY-OXYGEN-FUEL SPRAY GUN.


78/131

SPRAY COATING FOR EROSION AND CORROSIONPROTECTION OF BOILER TUBES IN POWER GENERATION

PLANTS.


79/131

HIGH-VELOCITY-AIR-FUEL SPRAY COATING PROCESSON A TURBINE BLADE.


80/131

WE HAVE A HYPOTHETICAL SITUATION

JOINING 2MM PLATES OF ALUMINUM ALLOYS

AND STAINLESS STEEL.

ARE THESE WELDABLE ?

YES USING THE FRICTION STIR WELDING TECHNIQUE.


81/131


82/131


83/131


84/131


85/131


86/131


87/131


88/131


89/131


90/131


91/131


92/131


93/131

WE HAVE A HYPOTHETICAL SITUATION

CLAD-WELDING BOTH SURFACES OF TWO DIFFERENTPLATES THICKNESSES OF ALUMINUM ALLOYS

AND STAINLESS STEEL.

ARE THESE WELDABLE ?

YES USING THE EXPLOSION WELDING TECHNIQUE.


94/131

EXPLOSION WELDING USES THE ENERGYOF A CONTROLLED EXPLOSIVE DETONATION

TO CREATE A METALLURGICAL WELDBETWEEN METALS.


95/131

EXPLOSION WELDING PROCESS IS USED FOR THEMETALLURGICAL JOINING OF DISSIMILAR METALS.

THIS PROCESS IS USED MOST COMMONLY TO CLAD

A THICKER PLATE ( BACKER ) WITH A THINNERLAYER OF CORROSION RESISTANT MATERIAL

( ALLOY CLADDER STAINLESS STEEL,NICKEL ALLOY, TITANIUM OR ZIRCONIUM ).


96/131

IN PREPARATION, THE BACKER AND THE

ALLOY CLADDER MATING SURFACES ARE GROUND.


97/131

THE PREPARED BACKER AND THE ALLOY CLADDER

ARE THEN FIXTURED PARALLEL AT A PRECISE SPACING.

A MEASURED QUANTITY OF A SPECIFICALLYFORMULATED EXPLOSIVE IS PLACED ON THECLADDING METAL SURFACE.


98/131

THE EXPLOSIVE IS THEN DETONATED AND THEDETONATION FRONT TRAVELS UNIFORMLY ACROSS

THE SURFACE FROM INITIATION. THE CLADDING METALBENEATH THE DETONATING EXPLOSIVE IS PROPELLED TO

COLLIDE WITH THE BASE METAL AT A SPECIFIC IMPACTVELOCITY AND ANGLE. THE MATING SURFACES COLLIDE

UNDER PRESSURE. THE EXTREME PRESSUREPRODUCES A CONTINUOUS METALLURGICAL WELD.

ALTHOUGH THE EXPLOSION CLADDING GENERATESINTENSE HEAT, THERE IS INSUFFICIENT TIME FOR

THE HEAT TO CONDUCT INTO THE METALS AND

NO BULK HEATING OCCURS.


99/131

THE EXPLOSION WELDING CLADDED-PLATESARE THEN FLATTENED AND CUT.


100/131

TESTING AND INSPECTION

ULTRASONIC

EXAMINATION OF BOND

PHISICAL MEASUREMENT

CERTIFICATIONS


101/131

A TYPICAL MICROSTRUCTURE OF THE ZONEOF AN EXPLOSION WELDED JOINT BETWEEN

PLAIN-LOW-CARBON STEEL AND STAINLESS STEEL.


102/131

AS-EXPLOSION CLAD FLAT PLATE CONSISTINGOF 20MM THICK STAINLESS STELL CLAD ON

200MM THICK CARBON STEEL.


103/131

EXPLOSION-CLAD 6MM THICK TITANIUM PLATETO 45MM THICK CARBON STEEL PLATE

FOR BOILER TUBE SHEET BLANKS,AFTER POST EXPLOSION WELDING FLATTENING.


104/131

FINISHED VESSEL FABRICATED FROMEXPLOSION CLAD PLATE.


105/131

A 5 METER DIAMETER DOME OF 5MM THICK TYPE 410STAINLESS STEEL ON 80MM THICK TYPE A387 STAINLESS

STEEL FORMED FROM EXPLOSION CLAD PLATE.

GALVANIC CORROSION SERIESCORRODED END (ANODIC OR LEAST NOBLE)

MAGNESIUMMAGNESIUM ALLOYS

ZINC ALUMINUM


106/131

ZINC ALUMINUM

ALUMINUM 28CADMIUM ALUMINUM 17ST

STEEL OR IRONCAST IRON

CHROMIUM-IRON (ACTIVE STAINLESS TYPE 410)NICKEL-RESIST CAST IRON

18-8 CHROMIUM-NICKEL IRON (ACTIVE STAINLESS TYPE 304)18-8-3 CHROMIUM-NICKEL-MOLYBDENUM IRON (ACTIVE STAINLESS TYPE 316)

LEAD-TIN SOLDERSLEADTIN

NICKEL (ACTIVE)INCONEL-NICKEL-CHROMIUM ALLOY (ACTIVE)

HASTELLOY ALLOY C (ACTIVE)BRASSESCOPPER

BRONZESCOPPER-NICKEL ALLOYSMONEL-COPPER ALLOYS

SILVER SOLDERSNICKEL (PASSIVE)

INCONEL-NICKEL-CHROMIUM ALLOYS (PASSIVE)CHROMIUM-IRON (PASSIVE STAINLESS TYPE 410)TITANIUM

18-8 CHROMIUM-NICKEL-IRON (PASSIVE STAINLESS TYPE 304)18-8 CHROMIUM-NICKEL-MOLYBDENUM-IRON (PASSIVE STAINLESS TYPE 316)

HASTELLOY C (PASSIVE)SILVER

GRAPHITEGOLD PLATINUM

PROTECTED END (CATHODIC OR MOST NOBLE)

GALVANIC CORROSION AN ELECTRICAL POTENTIAL,OR VOLTAGE, DIFFERENCE WILL EXIST BETWEEN

TWO DIFFERENT METALS THAT ARE IN ELECTRICAL


107/131

CONTACT AND IMMERSED IN A CORROSIVE SOLUTION.THIS POTENTIAL DIFFERENCE CAUSES CURRENT TO

FLOW AND THE LESS NOBLE, OR MORE ANODIC. METALSUFFERS INCREASED CORROSION RATE. THE SEVERITY

OF ATTACK DEPENDS UPON THE RELATIVE VOLTAGEDIFFERENCE BETWEEN THE METALS, THE RELATIVEEXPOSED AREAS OF EACH, AND THE PARTICULAR

CORROSIVE ENVIRONMENT.

IN WELDING, THE SELECTION OF THE DISSIMILARMETALS TO BE JOINED, AND THE FILLER METALSTO BE USED, MUST TAKE INTO CONSIDERATION

THE PHENOMENA OF GALVANIC CORROSION.

A CLEAR EXAMPLE WHERE GALVANIC CORROSION

FINDS USEFUL APPLICATION IS IN CATHODICPROTECTION. A SACRIFICIAL METAL IS ATTACHEDTO THE METAL TO BE PROTECTED.

CATHODIC PROTECTION SYSTEMS ARE MOST COMMONLYUSED TO PROTECT STEEL, FUEL PIPELINES, OFFSHORE

OIL PLATFORMS AND ONSHORE OIL WELL CASINGS.


108/131

THE SACRIFICIAL ALUMINUM ANODE IS USEDTO PROTECT THE STEEL STRUCTURE AT AN

OFFSHORE OIL PLATFORM.


109/131

THE CHEAPEST, MOST ECONOMICAL, FASTEST,RELIABLE AND NON-DESTRUCTIVE METAL IDENTIFICATION

IS BY CHEMICAL REAGENT REACTION TEST,

WHICH ARE SHOWN ON THE FOLLOWING DIAGRAMS.


110/131


111/131


112/131


113/131


114/131


115/131


116/131

THE ATOMIC ABSORPTION SPECTROMETER TECHNIQUETYPICALLY USES A FLAME TO ATOMIZE THE METAL

SAMPLE. A BEAM OF LIGHT PASSES THROUGH THISFLAME, ABSORBING A SET OF QUANTITY OF ENERGY

( LIGHT OF A GIVEN WAVELENGTH ). EACH WAVELENGTHIN THE SERIES IS SPECIFIC TO ONLY ONE

PARTICULAR ELEMENT.


117/131

A PORTABLE NON-DESTRUCTIVE FIELDATOMIC ABSORPTION SPECTROMETER.

NICKEL AND ITS ALLOYS THESE ARE NON-FERROUSMETALS WITH HIGH-STRENGTH AND TOUGHNESS,EXCELLENT CORROSION RESISTANCE, AND SUPERIOR


118/131

ELEVATED TEMPERATURE PROPERTIES.

NICKEL ALLOYS ARE USED FOR A WIDE VARIETY OF

APPLICATIONS, THE MAJORITY OF WHICH INVOLVECORROSION RESISTANCE AND / OR HEAT RESISTANCE:

- AIRCRAFT GAS TURBINES- STEAM TURBINE POWER GENERATION PLANTS- NUCLEAR POWER SYSTEMS

- CHEMICAL AND PETROCHEMICAL INDUSTRIESAMONG THE MOST COMMON NICKEL ALLOYS USED IN THEHEAVY INDUSTRIES ARE:

- INCOLLOY- INCONEL

- HASTELOY- HAYNES- NIMONIC- MONEL

NICKEL ALLOYS ARE HIGHLY WELDABLE AND NO SPECIALPRECAUTION IS REQUIRED.


119/131

NICKEL ALLOYS ARE PRIMARILY USED INTURBINE POWER GENERATION PLANTS.


120/131

TITANIUM AND ITS ALLOYSTHE COMBINATION OFHIGH STRENGTH-TO-WEIGHT RATIO, EXCELLENT

MECHANICAL PROPERTIES,AND CORROSIONRESISTANCE MAKES TITANIUM AND ITS ALLOYS

THE BEST MATERIAL CHOICE FOR MANY CRITICAL

APPLICATIONS SUCH AS STATIC AND ROTATINGGAS TURBINE ENGINE COMPONENTS, AIRPLANES,MISSILES AND ROCKET.

TITANIUM AND ITS ALLOYS ARE HIGHLY OXIDIZABLE WHENWELDED. CARE MUST BE TAKEN TO CONTROL THE HEAT

OF THE BASE METAL DOWN TO 250C. OTHERWISE,TARNISHING WILL DEVELOP.


121/131


122/131

MAIN ENGINE LE7A

H2A ROCKET

TITANIUM AND ITS ALLOYS AREUSED VERY EXTENSIVELY INTHE AEROSPACE INDUSTRY.


123/131

COPPER AND ITS ALLOYS THERE ARE AS MANYAS 400 DIFFERENT COPPER AND COPPER-ALLOY

COMPOSITIONS. THE FOLLOWING ARE THE PRINCIPALALLOYING ELEMENTS OF THE MORE COMMON TYPES:

PURE COPPER FOR ELECTRICAL APPLICATION

BRASS ZINC

PHOSPHOR BRONZES TIN

ALUMINUM BRONZES ALUMINUM

SILICON BRONZES SILICON

COPPER NICKEL, NICKEL SILVERS NICKEL

COPPER AND ITS ALLOYS HAVE VERY FAST HEATDISSIPATION RATE. THE WELD AREA REMAINSALWAYS COLD DURING WELDING, MAKINGEXCESSIVE PREHEAT NECESSARY.


124/131

ELECTRICAL ENERGY IS WASTED IN ANY SYSTEMBECAUSE A PORTION OF THE ELECTRICITY FLOWINGTHROUGH THE CONDUCTOR IS CONVERTED TO HEAT

RATHER THAN BEING DELIVERED AS USABLE ELECTRICALENERGY.

ELECTROLYTIC COPPER ( PURE COPPER ) EXHIBITSHIGH ELECTRICAL CONDUCTIVITY AND HIGH HEAT

DISSPATION RATE, MAKING IT VERY IDEAL FORELECTRICAL COMPONENT PARTS, LIKE BUS BARS.


125/131

BECAUSE OF THEIR UNIQUE LUBRICITY PROPERTIES,ESPECIALLY WHERE HIGH TEMPERATURES ARE

INVOLVED, IN REDUCING FRICTION AND PROLONGINGSERVICE LIFE, COPPER ALLOYS FIND VERY GOOD

APPLICATION IN BUSHINGS, BEARINGS AND SLEEVES.

THEY FIND EXTENSIVE USES IN OFFSHORE, STEEL MILLAND CONSTRUCTION EQUUIPMENT.


126/131

AN ECCENTRIC BUSHING MADE OF COPPER ALLOYS USEDIN STEEL MILLS.

ALUMINUM AND ITS ALLOYS THEY HAVE A STRONGRESISTANCE TO CORROSION, AND IS RATHER


127/131

MALLEABLE. THEY ARE RELATIVELY LIGHT METAL.THEY ARE EASILY MACHINABLEAND CAN HAVE A WIDE

VARIETY OF SURFACE FINISHES. THEY ALSO HAVE GOODELECTRICAL AND THERMAL CONDUCTIVITIES AND ISHIGHLY REFLECTIVE TO HEAT AND LIGHT.

PURE ALUMINUM HAS VERY LOW STRENGTH. HOWEVER,WHEN ALLOYED, MAINLY, WITH SILICON, CAN ATTAINSTRENGTH COMPARABLE TO CARBON STEELS, WHICH

GIVE THE ALUMINUM ALLOYS A VERY WIDE APPLICATION,ESPECIALLY IN THE AUTOMOTIVE INDUSTRY.

ALUMINUM AND ITS ALLOYS ARE HIGHLY HYGROSCOPIC.THEY ABSORB MOISTURE VERY RAPIDLY. AS A RESULT,THEIR SURFACES ARE OXIDIZED, FORMING ALUMINUM

OXIDES. ALUMINUM OXIDES ARE VERY HARD AND HAVE AVERY HIGH MELTING POINT. THIS CAUSES WELDABILITYPROBLEMS. THE BEST REMEDY IS TO GRIND THE OXIDESKIN BEFORE ATTEMPTING TO WELD ALUMINUM AND ITSALLOYS.


128/131

THE H.M.S. LAURIER LAPIERRE IS THE WORLDS FIRST

ALUMINUM WARSHIP. THE CONCEPT OF AN ALUMINUM

WARSHIP IS ECONOMICALLY SOUND. THEY WILL ONLYWEIGH 1/12 OF TRADITIONAL IRON AND STEEL WARSHIPS.THE COST OF FUEL IS ONLY 1/4 OF THE TRADITIONALSTEEL-HULLED SHIPS. THE LIGHTER ALUMINUMWARSHIPS WILL TRAVEL FASTER AND WITH GREATMANEUVERABILITY, MAKING THEM LESS SUSCEPTIBLE TO

TARGET AND CAN EASILY INTERCEPT ENEMY VESSELS.


129/131

ALUMINUM WHEELS GIVE THE AUTOMOBILESA SPORTY DESIGN. ALUMNUM WHEELS ALSO

IMPROVE AUTOMOBILE PERFORMANCE

BECAUSE OF THEIR LIGHTWEIGHT ANDVERY GOOD HEAT DISSIPATION.


130/131

TYPICAL APPLICATIONS OF ALUMINUM ALLOYSIN THE AUTOMOTIVE INDUSTRY.


131/131

Welding Metallurgy & Weld Ability of Metals

Documents