WELDING METALLURGY

AND

WELDABILITY OF METALS

• IT IS ESTIMATED THAT THERE ARE MORE THAN

40,000 METALLIC ALLOYS CURRENTLY

IN 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.

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

GENERAL CLASSIFICATION OF METALLIC

ALLOYS:

• FERROUS – IRON-BASED

• NON-FERROUS – NON-IRON-BASED

FERROUS METALLIC ALLOYS:

• STEELS – ACCOUNT FOR OVER 60%

OF THE METALLIC ALLOYS USED

IN THE INDUSTRY

• CAST IRONS

NON-FERROUS METALLIC ALLOYS FOR

MAJOR INDUSTRIAL APPLICATIONS:

• NICKEL ALLOYS

• TITANIUM ALLOYS

• COPPER ALLOYS

• ALUMINUM ALLOYS

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

PREPARING A

METALLOGRAPHIC SPECIMEN

FOR MICROSTRUCTURE ANALYSIS

• CUT A SECTION OF THE METALLIC ALLOYS FOR

MICROSTRUCTURE ANALYSIS.

• GRIND THE SPECIMEN IN SUCCESSIVELY FINER

SILICON CARBIDE ABRASIVE GRITS OF 120 / 320 /

600 / 1200.

• POLISH THE FINELY GROUND SPECIMEN ON

NAPPED POLISHING CLOTHS IN, FIRST,

COLLOIDAL CHROMIUM OXIDE SUSPENSION,

THEN, IN COLLOIDAL ALUMINUM OXIDE

SUSPENSION.

• DIP THE BUFFED SPECIMEN IN A 3% NITRIC

ACID SOLUTION.

• THE SPECIMEN IS NOW READY TO BE VIEWED

UNDER A METALLOGRAPHIC MICROSCOPE.

THE ETCHED SPECIMEN CAN NOW BE VIEWED

UNDER AN OPTICAL METALLOGRAPHIC MICROSCOPE

CAPABLE OF UP TO 1000X MAGNIFICATION.

A MORE SOPHISTICATED

SCANNING ELECTRON METALLOGRAPHIC MICROSCOPE

CAPABLE OF UP TO 10,000X MAGNIFICATION.

A TYPICAL MICROSTRUCTURE OF A LOW-PLAIN-CARBON

STEEL SHOWING GRANULAR FERRITES ( α ).

BECAUSE OF THE VERY LOW CARBON CONTENT, ALL THE

CARBON IS DISSOLVED AND FINELY DISPERSED IN THE

IRON 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 STRUCTURE

EVEN AFTER CYCLIC HEATING AND COOLING -

TRANSLATING TO VERY GOOD WELDABILITY OF THE LOW-

PLAIN-CARBON STEEL STRUCTURE

IMPACT STRESSES

IMPACT STRESSES

TENSILE /

COMPRESSIVE

STRESSES

THE GRANULAR FERRITES, WHEN SUBJECTED

TO IMPACT STRESSES, JUST FLATTEN,

AND WHEN SUBJECTED TO TENSILE AND

COMPRESSIVE STRESSES, JUST ELONGATE.

THE FERRITE GRAINS ACT AS SLIP PLANES, GIVING THE

MICROSTRUCTURE A CERTAIN AMOUNT OF DUCTILITY.

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 IRON

CARBIDES ( CEMENTITES ) WHICH APPEAR AS PEARLITES.

THE MICROSTRUCTURE CONTAINS FREE GRANULAR

FERRITES AND LAMELLAR PEARLITES.

PEARLITES CONTAIN PARALLEL LAYERS OF FERRITE

GRAINS AND CEMENTITE. THE PARALLEL LAYERS ACT AS

SLIP PLANES, GIVING THESE METALLIC ALLOYS A CERTAIN

AMOUNT OF DUCTILITY.

ON THE OTHER HAND, THESE METALLIC ALLOYS START

BECOMING HARD AND BRITTLE BECAUSE CARBIDES

BEGIN TO FORM.

THE PLAIN-HIGH-CARBON STEEL CONSISTS OF

FULLY PEARLITE MICROSTRUCTURES.

THE MICROSTRUCTURE IS CALLED “PEARLITE”

BECAUSE IT LOOKS LIKE “MOTHER OF PEARLS”

AS SEEN UNDER THE MICROSCOPE.

PEARLITES ARE LAMELLAR OR LAYERED ALTERNATE

PLATELETS 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.

IN ORDER TO FULLY APPRECIATE THE EFFECTS OF

WELDING HEAT TO PLAIN CARBON STEELS,

WE WILL ATTEMPT TO EXPLAIN THE BASICS OF

HEAT TREATMENT.

HEAT TREATMENT IS THE CONTROLLED HEATING AND

COOLING OF METALS TO ALTER THEIR PROPERTIES –

SUCH AS HARDNESS AND STRENGTH – WITHOUT

CHANGING THE PRODUCT SHAPE.

WHEN A HIGH-PLAIN-CARBON STEEL IS HEATED TO

AROUND 1,000°C, ALL THE STRUCTURES – FERRITES,

CEMENTITES, PEARLITES –

TRANSFORM TO THE AUSTENITE PHASE ( γ ).

IT IS IN THE DIFFERENT COOLING RATES, FROM THE

AUSTENITE PHASE, THAT THE HIGH-PLAIN-CARBON STEEL

WILL TRANSFORM BACK TO DIFFERENT STRUCTURES TO

ROOM TEMPERATURE, AND ALTER ITS PROPERTIES.

THE DIFFERENT COOLING RATES ARE AS FOLLOWS:

FULL ANNEALING ( FURNACE-COOLING ) – SOFTENING

VERY SLOW-COOLING RATES, ALLOWING ALL THE

CARBON TO GET DISSOLVED AND FINELY DIFFUSED IN

THE IRON MATRIX. A FULLY FERRITIC MICROSTRUCTURE

IS FORMED, WHICH IS VERY SOFT, LOW-STRENGTH AND

DUCTILE.

NORMALIZING ( AIR-COOLING ) – TOUGHENING

QUICKER COOLING RATES THAN ANNEALING, FREE

FERRITES AND PEARLITES ARE FORMED. START OF

HARDENING OF THE MICROSTRUCTURE DUE TO

FORMATION OF CARBIDES, BUT SOME DUCTILITY IS

RETAINED DUE TO THE FREE FERRITES AND THE

PLATELET STRUCTURES OF PEARLITE.

OIL QUENCHING ( RAPID-COOLING ) – HARDENING

MICROSTRUCTURE BECOMES VERY HARD AND BRITTLE

THROUGH THE FORMATION OF MARTENSITES.

WATER QUENCIHING ( DRASTIC RAPID COOLING ) –

HARDENING

COARSE, JAGGED, ROUGH AND DISORIENTED

MARTENSITES ARE FORMED, WHICH ARE EXTREMELY

HARDER AND MORE BRITTLE, COMPARED TO

MARTENSITES FORMED BY OIL QUENCHING.

MARTENSITES ARE FORMED BY RAPID COOLING,

WHICH TRAPS THE CARBON ATOMS THAT DO NOT

HAVE TIME TO DIFFUSE OUT OF THE IRON MATRIX,

AND CHEMICALLY COMBINE WITH THE IRON

TO FORM IRON CARBIDES. A TYPICAL

MICROSTRUCTURE OF MARTENSITES HAS

ACICULAR, SHARP, NEEDLE-LIKE APPEARANCE.

MARTENSITES ARE VERY HARD AND BRITTLE

AND ARE USUALLY NOT WELDABLE.

UNTEMPERED MARTENSITES, WHILE VERY HARD

AND STRONG, ARE TOO BRITTLE TO BE USEFUL

FOR MOST INDUSTRIAL APPLICATIONS.

AFTER WATER OR OIL QUENCING, THE STEELS

ARE TEMPERED, TO AROUND150°C ~ 550°C, TO IMPART

TOUGNESS.

AT THESE TEMPERATURES, THERE IS NO CHANGE

IN THE MICROSTRUCTURES OF THE STEELS. WHAT

HAPPENS IS THAT THE MARTENSITES ARE REFINED AND

RE-ORIENTED.

AFTER WELDING, THE TERMS USED FOR

THIS HEAT TREATMENT PROCESS ARE

STRESS-RELIEVING, OR PWHT.

IN WELDING, THE EFFECT OF HEAT TREATMENT

IS SOMETIMES INADVERTENTLY DONE.

THE WELDING HEAT INPUT MAY RAISE THE

TEMPERATURE OF THE PLAIN CARBON STEELS

IN EXCESS OF 800°C.

THE HIGHER THE CARBON CONTENT,

AND, THE FASTER THE COOLING RATE,

RESULT IN THE FORMATION OF

MORE CARBIDES. THIS WILL MAKE

THE PLAIN CARBON STEELS

MORE SUSCEPTIBLE TO CRACKING

DURING WELDING.

IN WELDING, NECESSARY PRECAUTIONS

SHOULD ALREADY BE TAKEN TO AVOID THESE

FORMATION OF CARBIDES IN MEDIUM-

AND HIGH-PLAIN-CARBON STEELS .

FROM THE VIEWPOINT OF WELDING, CARBIDES IN PLAIN-

CARBON-STEELS ARE HARMFUL, BECAUSE OF THEIR

CRACKING TENDENCIES.

HOWEVER, THERE ARE ATTRIBUTES OF THESE CARBIDES

WHICH ARE VERY BENEFICIAL TO MANY INDUSTRIAL

APPLICATIONS.

LONG-SPAN BEAMS, SUPPORTING HEAVY LOADS ALONG

THEIR AXIS, MUST HAVE RIGIDITY, OTHERWISE THE

BEAMS WILL SAG.

CARBIDES IN PLAIN-CARBON STEELS GIVE

RIGIDITY TO THE BEAMS.

MANY INDUSTRIAL PARTS ARE MANUFACTURED

FROM HEAT-TREATED, HIGH-HARDNESS STEELS

FOR METAL-TO-METAL WEAR RESISTANCE.

REALIZING THE STRONG INFLUENCE OF CARBON

ON THE HARDNESS AND STRENGTH OF

PLAIN-CARBON STEELS, AND THE CONSEQUENT

BENEFICIAL EFFECTS, THE TENDENCY IS TO ADD

MORE CARBON TO THE PLAIN-CARBON STEELS.

HOWEVER, THERE IS A MAXIMUM LIMIT

ON THE SOLUBILITY OF CARBON IN STEELS,

BEYOND WHICH ANOTHER DIFFERENT

MICROSTRUCTURES WILL BE FORMED –

WHICH 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-ALLOYED

OR HIGH-ALLOYED OR TOOL STEELS –

VARY IN TERMS OF ALLOYING ELEMENTS,

STRENGTH AND DURABILITY.

THE CARBON EQUIVALENT SCALES THE CONCENTRATION

OF 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 WITH

CARBON TO PRODUCE DESIRED COMBINATIONS

OF HARDENABILITY, STRENGTH AND TOUGHNESS

CARBON – STRONG CARBIDE FORMERS.

CHROMIUM – NEXT TO CARBON AS STRONG CARBIDE

FORMERS.

MANGANESE / NICKEL / MOLYBDENUM / VANADIUM –

MILD CARBIDE FORMERS; IMPROVES TOUGHNESS AND

STRENGTH.

STAINLESS STEELS – THE BASE METAL COMPOSITIONS

ARE TYPICALLY THAT OF CARBON STEELS, WITH THE

ADDITION OF AT LEAST 11% CHROMIUM. THIS IS THE

MINIMUM AMOUNT OF CHROMIUM NECESSARY TO

FORM A STABLE, PASSIVE CHROMIUM OXIDE FILM. IT

IS THIS FILM THAT IS THE BASIS FOR THE CORROSION

RESISTANCE OF ALL STAINLESS STEELS, THAT GIVES

STAINLESS STEELS THAT UNIQUE STAINLESS STEEL

LUSTER.

THE BASIC CLASSIFICATIONS OF STAINLESS STEELS ARE:

AUSTENITIC STAINLESS STEELS ( 300 SERIES ) – WITH A

MINIMUM OF 11% CHROMIUM AND 8% NICKEL, THE HIGH

CHROMIUM AND NICKEL FREEZE THE AUSTENITE PHASE

DOWN TO ROOM TEMPERATURE. THE NICKEL FURTHER

ACTS AS AUSTENITE STABILIZER DURING THERMAL

CYCLIC CONDITIONS.

THERMAL CYCLE CAUSED BY WELDING HAVE LITTLE

INFLUENCE ON MECHANICAL PROPERTIES. THE

ADJACENT BASE MATERIAL TEMPERATURE, THOUGH,

HAS TO BE CONTROLLED DOWN TO A MAXIMUNM OF

250°C TO PREVENT CARBIDE PRECIPITATION ALONG

THE GRAIN BOUNDARIES.

PRE-HEAT AND PWHT ARE SELDOM REQUIRED.

AUSTENITIC STAINLESS STEELS ARE TOUGH AND NON-

MAGNETIC.

THE TWO TYPES OF AUSTENITIC STAINLESS STEELS

MOST COMMONLY USED ARE:

304 – FOR GENERAL CORROSION RESISTANCE.

316 – WITH THE ADDITION OF A MINIMUM OF 2.5%

MOLYBDENUM; FOR SEVERE CORROSION RESISTANCE.

A TYPICAL MICROSTRUCTURE OF AN AUSTENITIC

STAINLESS STEEL APPEARING AS AUSTENITE GRAINS, (

γ ) WHICH ARE SOFT, HIGHLY-DUCTILE, TOUGH

AND NON-MAGNETIC.

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 LESS

STABLE.

DURING WELDING AUSTENITIC STAINLESS STEELS, WHEN

THE TEMPERATURE REACHES 500°C ON THE BASE

METAL, CHROMIUM CARBIDES PRECIPITATE

PREFERENTIALLY ALONG THE GRAIN BOUNDARIES

OF THE AUSTENITE MICROCTRUCTURES, ALSO CALLED

“SENSITIZATION”. THIS DETERIORATION MAKES THE

AUSTENITIC STAINLESS STEELS MORE SUSCEPTIBLE TO

CORROSION ATTACKS, AND IS THE MOST COMMON

REASON IN WELD FAILURES OF AUSTENITIC STAINLESS

STEELS

THE HEAT-TINT VISUAL APPEARANCE OF THE

WELD AREA IS DUE TO CARBIDES PRECIPITATION,

OR SENSITIZATION.

THE 400 SERIES STAINLESS STEELS – THESE ARE THE

STRAIGHT-CHROMIUM, WITHOUT THE ADDITION OF A

MINIMUM OF 8% NICKEL.

THE TWO TYPES OF 400-SERIES STAINLESS STEELS

ARE:

FERRITIC GRADES STAINLESS STEELS – THESE

STAINLESS STEELS ARE FERRITIC AT ALL TEMPERATURES,

WITH THE ADDITION TO BASIC 400-SERIES STAINLESS

STEELS OF FERRITE STABILIZERS – HIGHER CHROMIUM,

SILICON, MOLYBDENUM, COBALT, TITANIUM.

FERRITIC STAINLESS STEELS ARE SOFT, DUCTILE AND

HIGHLY MAGNETIC.

A TYPICAL APPLICATION FOR FERRITIC STAINLESS

STEELS ARE IN MAGNETIC TRAPS IN PIPELINES, WHICH

FACILITATE TRAMP METAL SEPARATION FROM CORROSIVE

FLUIDS.

MAGNETIC TRAPS MADE FROM WIRE MESH

OF FERRITIC STAINLESS STEELS FACILTATE

TRAMP METAL SEPARATION FROM

CORROSIVE LIQUIDS.

MARTENSITIC GRADES STAINLESS STEELS – THESE ARE

ESSENTIALLY 400-SERIES STAINLESS STEEL ALLOYS OF

A HIGHER CHROMIUM AND CARBON CONTENTS THAT

POSSESS A FULLY MARTENSITIC MICROSTRUCTURE IN

THE HARDENED CONDITION.

THE MARTENSITIC GRADES STAINLESS STEELS ARE

HIGHLY MAGNETIC AND ARE HARDENABLE BY HEAT

TREATMENTS.

A TYPICAL APPLICATION OF MARTENSITIC GRADES

STAINLESS STEELS ARE INDUSTRIAL KNIFE BLADES. THE

MARTENSITE MICROSTRUCTURES AND EXCESS

CARBIDES MAINTAIN CUTTING EDGES AND CORROSION

RESISTANCE.

KNIFE BLADES USED IN THE FOOD INDUSTRY

ARE SOME OF THE TYPICAL APPLICATIONS

FOR MARTENSITIC GRADE STAINLESS STEELS

REQUIRING HARDNESS ON CUTTING EDGES

BE MAINTAINED AND SUPERIOR

CORROSION RESISTANCE IN SERVICE.

DUPLEX GRADES STAINLESS STEELS – THEY GET

THEIR NAME BECAUSE THEY CONTAIN BOTH FERRITIC

AND AUSTENITIC MICROSTRUCTURE IN EQUAL AMOUNT.

IN FULLY AUSTENITIC STAINLESS STEELS REQUIRING

EXTENSIVE AND HEAVY WELDING, PRECIPITATED

CARBIDES FORM ALONG THE GRAIN BOUNDARIES OF THE

AUSTENITE MICROSTRUCTURES, THESE PRECIPITATED

CARBIDES ARE VERY PRONE TO CORROSIVE ATTACK,

WHICH MAY RENDER THE PART IMPRACTICAL, SPECIALLY

IN APPLICATIONS REQUIRING RESISTANCE TO VERY

AGGRESSIVE MEDIA.

DUPLEX GRADES STAINLESS STEELS WERE FORMULATED

FOR FABRICATIONS OF STAINLESS STEELS REQUIRING

EXTENSIVE AND HEAVY WELDING WORK. THE FERRITIC

STRUCTURES IN THE MATRIX REDUCE CARBIDES

PRECIPITATION.

TYPICAL USES OF DUPLEX GRADES STAINLESS STEELS

ARE FOR HEAT EXCHANGERS, CHEMICAL TANKS,

REFINERIES, PRESURE VESSELS AND OFFSHORE

APPLICATIONS.

TYPICAL MICROSTRUCTURES OF DUPLEX GRADES

STAINLESS STEELS, WHICH ARE A MIX OF 50 / 50

FERRITES AND AUSTENITES MICROSTRUCTURES.

THE DARK AREAS ARE FERRITE MICROSTRUCTURES

AND THE WHITE AREAS ARE AUSTENITES

MICROSTRUCTURES.

FABRICATION OF A FRACTIONATION TOWER OF DUPLEX

GRADES STAINLESS STEELS. EVEN IN VERY EXTENSIVE

AND HEAVY WELDING, THE PART IS NOT PRONE TO

CARBIDES PRECIPITATION BECAUSE OF THE PRESENCE

OF THE FERRITIC MICROSTRUCTURES IN THE MATRIX.

BECAUSE OF THE HEAT INPUT DURING WELDING OF

DUPLEX GRADES STAINLESS STEELS, THE

BALANCE OF THE FERRITES AND AUSTENITES

MICROSTRUCTURES MAY BE ALTERED.

IF THE FERRITES ARE TOO LOW BECAUSE OF

TRANSFORMATION, CARBIDES PRECIPITATION

MAY TAKE PLACE.

ALTERNATIVELY, IF THE FERRITES BECOME HIGH,

THE STAINLESS STEELS ARE PRONE TO CORROSION

BECAUSE OF THE DEPLETION OF THE AUSTENITIC

MICROSTRUCTURES.

THE FERRITE DETECTOR IS USED TO DETERMINE

THE FERRITE NUMBER ( FN ) OF DUPLEX GRADES

STAINLESS STEELS. THE VOLUME PERCENTAGE

OF FERRITES CAN BE ESTIMATED AS ABOUT 70%

OF THE FN.

THE FERRITE DETECTOR IS A NON-DESTRUCTIVE

INSPECTION INSTRUMENT BASED ON THE MUTUAL

ATTRACTION OF A PERMANENT BAR MAGNET TO A KNOWN

STANDARD AND AN UNKNOWN MATERIAL.

IRON-IRON CARBIDE

PHASE DIAGRAM

THE IRON-IRON CARBIDE PHASE DIAGRAM IS

ESSENTIALLY A MAP OF THE PHASES THAT EXIST

IN IRON AT VARIOUS CARBON CONTENTS AND

TEMPERATURES UNDER EQUILIBRIUM CONDITIONS.

AUSTENITIC MANGANESE STEELS – THESE TYPICALLY

CONTAIN 1.2% C AND A MINIMUM OF 12% MANGANESE.

A UNIQUE COMBINATION OF PROPERTIES IS ACHIEVED

IN THAT IT IMPARTS HIGH TOUGHNESS AND DUCTILITY

WITH HIGH WORK-HARDENING CAPACITY AND, GOOD

RESISTANCE TO WEAR.

TOOL STEELS MAY HAVE HIGH-WEAR AND ABRASION

RESISTANCE, 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 USED

IN EARTHMOVING, MINING, CEMENT PLANTS, QUARRYING,

OIL WEL DRILLING, RAILROADING, DREDGING.

IN THE AS-CAST CONDITION, AUSTENITIC MANGANESE

STEELS ARE RELATIVELY SOFT. THEY CAN BE MACHINED

TO SHAPES IN THIS CONDITION. ONCE THESE ARE USED

AND SUBJECTED TO CONSTANT IMPACT LOADS, THEY

WORK-HARDENED ( OR, COLD-HARDENED ), ACHIEVING

HIGH-HARDNESS TOGETHER WITH THEIR HIGH-IMPACT

PROPERTIES.

THE RAIL WHEELS AND THE RAIL TRACKS

ARE MANUFACTURED FROM AUSTENITIC

MANGANESE STEELS, REQUIRING METAL-TO-METAL WEAR

RESISTANCE AND HIGH-IMPACT LOADS..

AUSTENITIC MANGANESE STEELS ARE USED

EXTENSIVELY IN EARTH-MOVING EQUIPMENT – FOR

BUCKETS, SHOVELS, TEETH, WHERE

VERY SEVERE WEAR AND IMPACT LOADS

ARE ENCOUNTERED.

IN ROCK-CRUSHING MACHINERIES FOR MINING AND

CEMENT PLANTS, AUSTENITIC MANGANESE STEELS ARE

EXTENSIVELY USED FOR HANDLING AND PROCESSING

EARTHEN 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 OF

IGNITING A FORMULATED PYROTECHNIC POWDER MIX OF

EXOTHERMIC, HIGH-ENERGY ALUMINO-THERMIC METAL

ALLOYS, PRODUCING A SUPER-HEATED LIQUID METAL

THAT 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. A

GRAPHITE MOLD IS CLAMPED AROUND THE RAIL ENDS.

THE RAILS ENDS ARE PREHEATED TO AROUND 500°C.

THE POWDER MIX IS IGNITED IN THE REFRACTORY

CRUCIBLE 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.

AFTER COOLING, THE MOLD IS REMOVED AND THE WELD

IS CLEANED AND GRINDED TO PRODUCE A SMOOTH

JOINT.

THERMIT RAIL WELDING CRUCIBLE AND MOLD.

A GRAPHITE MOLD IS CLAMPED AROUND THE RAIL ENDS.

THE RAILS ENDS ARE PREHEATED TO AROUND 500°C.

THE POWDER MIX IS IGNITED IN THE REFRACTORY

CRUCIBLE 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.

IN WELDING MANGANESE STEELS, THE BASE METAL

SHOULD NOT REACH MORE THAN 250°C. TO DO THIS,

SKIP / INTERMITTENT WELDING IS DONE. THE WELD

AREA ITSELF IS SHOWERED WITH WATER AFTER PAUSING

EVERY AFTER LAYER.

IN HARDFACING STEELS, BUFFER LAYERS

SHOULD NOT BE MORE THAN 45RC. THE 45RC

HARDFACING ELECTRODES CAN BE WELDED

MULTI-PASS. THE 60RC HARDFACING ELECTRODES

CAN BE WELDED ONLY AT SINGLE-PASS LAYER.

WELDING THE 60RC HARDFACING ELECTRODE MULTI-

PASS WILL CAUSE CRACKING AND / OR SPALLING OF THE

WELDS.

IN HARDFACING STEEL PARTS SUBJECTED TO METAL-TO-

METAL CONTACT WEAR, ONE PART

SHOULD HAVE A 10RC LOWER HARDNESS THAN

THE OTHER PART.

IN THE TRANSITION FROM STEELS TO CAST IRONS,

AT AROUND 2% CARBON, WHITE CAST IRONS

ARE FORMED, IN WHICH THE CARBON IS PRESENT

FULLY AS CARBIDES, OR CEMENTITES.

THE WHITE CAST IRONS MICROSTRUCTURES

ARE VERY HARD, SUITABLE FOR APPLICATIONS

REQUIRING METAL-TO-METAL CONTACT

HIGH-WEAR, RESISTANCE. THEY CAN ONLY

BE CASTED, THEY CAN NOT BE MACHINED,

WROUGHT ( FORGED, ROLLED, EXTRUDED ),

HEAT-TREATED NOR SUBJECTED TO IMPACT.

THEY ARE USED IN SERVICE FROM THEIR

AS-CAST CONDITION AS THEY CAN NOT BE

SUBJECTED TO ANY FURTHER PROCESSING

WHITE CAST IRONS ARE NAMED AFTER

THEIR WHITE FRACTURED SURFACE DUE

TO THE CARBIDES.

WHITE CAST IRONS MICROSTRUCTURES SHOWING

NEARLY COMPLETE CARBON SOLUTION IN A MATRIX

OF MASSIVE, ACICULAR, NEEDLE-LIKE CEMENTITES,

WHICH ARE VERY HARD AND BRITTLE..

A TYPICAL EXAMPLE OF THE INDUSTRIAL APPLICATION

OF WHITE CAST IRON IS IN THE MIXER BLADES

OF SAND MULLERS.

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

CARBON REACHES A SUPERSATURATED CONDITION

WHERE THE EXCESS CARBON CAN NO LONGER DIFFUSE

INTO THE IRON MATRIX, NOR COMBINE WITH THE IRON.

THE SUPERSATURATED EXCESS CARBON WILL JUST

FLOAT AS FREE CARBON, IN THE FORM OF GRAPHITE

FLAKES IN A MATRIX OF FERRITES AND PEARLITES.

THE GRAPHITE FLAKES ACT AS STRESS RAISERS

WHICH MAY INITIATE FRACTURE WHEN THE

GRAY CAST IRONS ARE SUBJECTED TO MODERATE

IMPACT. WHEN SLIGHTLY HEATED, DURING

EXPANSION AND CONTRACTION, THE

GRAPHITE FLAKES ACT AS CRACK-PROPAGATORS.

WITHOUT THE GRAPHITE FLAKES, THE MATRIX IS

JUST LIKE PLAIN-CARBON STEELS, WHICH CAN HAVE

A TENSILE STRENGTH OF UP TO 70,000 PSI. THE

GRAPHITE FLAKES IN GRAY CAST IRONS FORM VOIDS AND

ARE POROUS, REDUCING THE STRENGTH

DOWN TO AROUND 25,000 PSI.

MOST COMMERCIAL GRADES OF GRAY CAST IRONS

CONTAIN 3.0-4.0% CARBON. THE SUPERSATURATED

CARBON WHICH CAN NOT DIFFUSE NOR REACT WITH

THE IRON ANYMORE, APPEARS AS “FREE” GRAPHITES

IN A TYPICALLY STEEL MATRIX OF FERRITES AND

PEARLITES.

IN MANY ENGINEERING MATERIALS, WITH

INTRICATE DESIGNS OF COMPLICATED SHAPES AND

SIZES OF THICK AND THIN SECTIONS, WHERE THE

TENSILE STRENGTH OF 25,000 PSI IS SUFFICIENT

ENOUGH FOR THE APPLICATION,

GRAY CAST IRONS ARE HIGHLY BENEFICIAL.

THE MICROSTRUCTURE OF GRAY CAST IRONS

ALLOW 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 MANUFACTURED

FROM CAST IRONS ARE CYLINDER BLOCKS, HEADS

AND GEARBOXES.

GRAY CAST IRONS ARE NAMED AFTER THEIR GRAY

FRACTURED SURFACE DUE TO THE GRAPHITE FLAKES.

A SPIRAL MOLD TESTS THE MEASURE OF FLUIDITY OF A

MELT. THE HIGH CARBON CONTENT OF GRAY CAST IRON

MAKES THE MELT HIGHLY FLUID TO FORM INTRICATE

THICK AND THIN SECTIONS.

PLAIN-CARBON STEELS EASILY SOLIDIFY IN THE

SPIRAL PASSAGE. HENCE, CAST STEELS ARE LIMITED

TO MASSIVE, SIMPLE, UNCORED DESIGNS.

THE CYLINDER BLOCKS, HEADS, ETC., OF GENERATOR

SETS ARE MADE OF GRAY CAST IRONS

TURBINE HOUSINGS ARE MADE OF GRAY CAST IRONS.

THE CYLINDER BLOCKS, HEADS,

TRANSMISSION HOUSINGS, GEARBOX CASES,

EXHAUST MANIFOLDS, ETC., OF MOTOR ENGINES

ARE MADE OF GRAY CAST IRONS.

IN WELDING GRAY CAST IRONS, THERE IS A TEARING

EFFECT ON THE BASE METAL AS IT EXPANDS AND

CONTRACTS, SINCE THE STRENGTH OF THE BASE

METAL IS LOWER THAN THE WELD METAL. THIS CAN

BE COUNTER-ACTED BY “PEENING” THE BASE METAL,

TO PUSH BACK THE TEARING FORCE.

WHEN WELDING GRAY CAST IRONS, THE HEAT

GENERATES 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 THE

SURFACE, FORMING A GAS FILM WHICH CAN NOT BE

PENETRATED BY THE WELDING ARC.

THE SURFACE IS “SEARED” BY RUNNING AN

OXY-ACETYLENE FLAME AT THE SURFACE

AND BRUSHING THE CARBON SOOT FORMED

BY THE GAS FILM.

IF THE GRAPHITE FLAKES IN GRAY CAST IRONS WERE

“ROUNDED” INSTEAD FLAKE-LIKE SHAPES, THEY ACT AS

“CRACK-STOPPERS” AND INCREASE THE STRENGTH

SIMILAR TO CARBON STEELS OF 70,000 PSI.

“ROUNDED” EXCESS CARBON IS PRODUCED EITHER

BY MALLEABILIZING HEAT TREATMENTS OR

INOCULATION OF THE WHITE CAST IRON MELT

WITH EITHER MAGNESIUM OR CESIUM,

MALLEABLE CAST IRONS ARE MADE BY HIGH-

TEMPERATURE HEAT TREAMENTS OF WHITE

CAST IRON CASTINGS. AT THE MALLEABILZING

TEMPERATURE OF 950°C, THE CEMENTITES

DECOMPOSE AND THE CARBON LIBERATED

FORMS “ROUNDED” GRAPHITES.

THE INOCULANTS MAGNESIUM OR CESIUM ARE HIGHLY

VOLATILE. THEY GO FROM SOLID TO GAS IN CONTACT

WITH THE MELT. THIS PHENOMENA “NODULARIZES” THE

EXCESS CARBON, FORMING NODULAR, OR SPHEROIDAL,

OR DUCTILE CAST IRONS.

A TYPICAL MICROSTRUCTURE OF MALLEABLE

CAST IRONS – FORMED BY MALLEABILIZING HEAT

TREATMENTS OF WHITE CAST IRONS – OR

DUCTILE CAST IRONS ( ALSO CALLED NODULAR

OR SPHEROIDAL CAST IRONS ) – FORMED BY

INOCULATION OF GRAY CAT IRONS WITH

MAGNESIUM OR CESIUM. THE EXCESS CARBON

IS ROUNDED, INCREASUING THE STRENGTH UP

TO 70,000 PSI AND IMPROVING WELDABILITY OF

THE MICROSTRUCTURE.

PIPE FITTINGS ARE MADE OF MALLEABLE CAST IRONS.

CRANKSHAFTS ARE MADE OF DUCTILE CAST IRONS.

THERMAL SPRAY WELDING – IS WIDELY USED, WHERE

MELTED MATERIALS ARE SPRAYED ONTO THE SURFACE

OF PARTS, THE COATINGS PROVIDING WEAR, IMPACT,

TEMPERATURE OR CORROSION RESISTANCE.

THERMAL SPRAYING CAN PROVIDE

THIN ( AROUND I MM ) TO THICK EVEN COATINGS

( OF SEVERAL MM ), OVER LARGE AREAS AT HIGH

DEPOSITION RATES.

REBUILDING THE WORN-OUT SURFACE OF A NOZZLE

SEGMENT COMBUSTOR COMPONENT IN A GAS TURBINE

USING THE HOT METAL SRAY FUSION PROCESS WITH

COBALT-BASED VACUUM-BRAZED METAL ALLOYS.

SPRAYING MAGNESIUM-ZIRCONATE THERMAL BARRIER

COATING ON THE INSIDE SURFACE OF A TRANSITION

PIECE COMBUSTOR COMPONENT IN A GAS TURBINE

USING THE POWDER FLAME SPRAY PROCESS.

REBUILDING THE WORN-OUT SHAFTING OF THE

HELICAL PINION GEAR OF THE ROLLING MILLS

GEAR BOX USING THE COLD EXOTHERMIC METAL SPRAY

PROCESS WITH NICKEL-CHROMIUM NICKEL ALLOYS.

REBUILDING THE SHAFTING BUSHING SURFACE

OF THE SCREW CONVEYOR USING THE COLD

EXOTHERMIC METAL SPRAY PROCESS WITH

ALUMINUM-BRONZE METAL ALLOYS.

COATING A SINK ROLL USED IN A STEEL MILL PLANT WITH

ZIRCONIA OR TUNGSTEN CARBIDE POWDERS

ON A HIGH-VELOCITY-OXYGEN-FUEL SPRAY GUN.

SPRAY COATING FOR EROSION AND CORROSION

PROTECTION OF BOILER TUBES IN POWER GENERATION

PLANTS.

HIGH-VELOCITY-AIR-FUEL SPRAY COATING PROCESS

ON A TURBINE BLADE.

WE HAVE A HYPOTHETICAL SITUATION –

JOINING 2MM PLATES OF ALUMINUM ALLOYS

AND STAINLESS STEEL.

ARE THESE WELDABLE ?

YES – USING THE FRICTION STIR WELDING TECHNIQUE.

WE HAVE A HYPOTHETICAL SITUATION –

CLAD-WELDING BOTH SURFACES OF TWO DIFFERENT

PLATES THICKNESSES OF ALUMINUM ALLOYS

AND STAINLESS STEEL.

ARE THESE WELDABLE ?

YES – USING THE EXPLOSION WELDING TECHNIQUE.

EXPLOSION WELDING USES THE ENERGY

OF A CONTROLLED EXPLOSIVE DETONATION

TO CREATE A METALLURGICAL WELD

BETWEEN METALS.

EXPLOSION WELDING PROCESS IS USED FOR THE

METALLURGICAL JOINING OF DISSIMILAR METALS.

THIS PROCESS IS USED MOST COMMONLY TO CLAD

A THICKER PLATE ( “BACKER” ) WITH A THINNER

LAYER OF CORROSION RESISTANT MATERIAL

( “ALLOY CLADDER” – STAINLESS STEEL,

NICKEL ALLOY, TITANIUM OR ZIRCONIUM ).

IN PREPARATION, THE “BACKER” AND THE

“ALLOY CLADDER” MATING SURFACES ARE GROUND.

THE PREPARED “BACKER” AND THE “ALLOY CLADDER”

ARE THEN FIXTURED PARALLEL AT A PRECISE SPACING.

A MEASURED QUANTITY OF A SPECIFICALLY

FORMULATED EXPLOSIVE IS PLACED ON THE

CLADDING METAL SURFACE.

THE EXPLOSIVE IS THEN DETONATED AND THE

DETONATION FRONT TRAVELS UNIFORMLY ACROSS

THE SURFACE FROM INITIATION. THE CLADDING METAL

BENEATH THE DETONATING EXPLOSIVE IS PROPELLED TO

COLLIDE WITH THE BASE METAL AT A SPECIFIC IMPACT

VELOCITY AND ANGLE. THE MATING SURFACES COLLIDE

UNDER PRESSURE. THE EXTREME PRESSURE

PRODUCES A CONTINUOUS METALLURGICAL WELD.

ALTHOUGH THE EXPLOSION CLADDING GENERATES

INTENSE HEAT, THERE IS INSUFFICIENT TIME FOR

THE HEAT TO CONDUCT INTO THE METALS AND

NO BULK HEATING OCCURS.

THE EXPLOSION WELDING CLADDED-PLATES

ARE THEN FLATTENED AND CUT.

TESTING AND INSPECTION

• ULTRASONIC

• EXAMINATION OF BOND

• PHISICAL MEASUREMENT

• CERTIFICATIONS

A TYPICAL MICROSTRUCTURE OF THE ZONE

OF AN EXPLOSION WELDED JOINT BETWEEN

PLAIN-LOW-CARBON STEEL AND STAINLESS STEEL.

AS-EXPLOSION CLAD FLAT PLATE CONSISTING

OF 20MM THICK STAINLESS STELL CLAD ON

200MM THICK CARBON STEEL.

EXPLOSION-CLAD 6MM THICK TITANIUM PLATE

TO 45MM THICK CARBON STEEL PLATE

FOR BOILER TUBE SHEET BLANKS,

AFTER POST EXPLOSION WELDING FLATTENING.

FINISHED VESSEL FABRICATED FROM

EXPLOSION CLAD PLATE.

A 5 METER DIAMETER DOME OF 5MM THICK TYPE 410

STAINLESS STEEL ON 80MM THICK TYPE A387 STAINLESS

STEEL FORMED FROM EXPLOSION CLAD PLATE.

GALVANIC CORROSION SERIES

CORRODED END (ANODIC OR LEAST NOBLE)

MAGNESIUM

MAGNESIUM ALLOYS

ZINC ALUMINUM

ALUMINUM 28

CADMIUM ALUMINUM 17ST

STEEL OR IRON

CAST 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 SOLDERS

LEAD

TIN

NICKEL (ACTIVE)

INCONEL-NICKEL-CHROMIUM ALLOY (ACTIVE)

HASTELLOY ALLOY C (ACTIVE)

BRASSES

COPPER

BRONZES

COPPER-NICKEL ALLOYS

MONEL-COPPER ALLOYS

SILVER SOLDERS

NICKEL (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

GRAPHITE

GOLD 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

CONTACT AND IMMERSED IN A CORROSIVE SOLUTION.

THIS POTENTIAL DIFFERENCE CAUSES CURRENT TO

FLOW AND THE LESS NOBLE, OR MORE ANODIC. METAL

SUFFERS INCREASED CORROSION RATE. THE SEVERITY

OF ATTACK DEPENDS UPON THE RELATIVE VOLTAGE

DIFFERENCE BETWEEN THE METALS, THE RELATIVE

EXPOSED AREAS OF EACH, AND THE PARTICULAR

CORROSIVE ENVIRONMENT.

IN WELDING, THE SELECTION OF THE DISSIMILAR

METALS TO BE JOINED, AND THE FILLER METALS

TO BE USED, MUST TAKE INTO CONSIDERATION

THE PHENOMENA OF GALVANIC CORROSION.

A CLEAR EXAMPLE WHERE GALVANIC CORROSION

FINDS USEFUL APPLICATION IS IN CATHODIC

PROTECTION. A SACRIFICIAL METAL IS ATTACHED

TO THE METAL TO BE PROTECTED.

CATHODIC PROTECTION SYSTEMS ARE MOST COMMONLY

USED TO PROTECT STEEL, FUEL PIPELINES, OFFSHORE

OIL PLATFORMS AND ONSHORE OIL WELL CASINGS.

THE SACRIFICIAL ALUMINUM ANODE IS USED

TO PROTECT THE STEEL STRUCTURE AT AN

OFFSHORE OIL PLATFORM.

THE CHEAPEST, MOST ECONOMICAL, FASTEST,

RELIABLE AND NON-DESTRUCTIVE METAL IDENTIFICATION

IS BY CHEMICAL REAGENT REACTION TEST,

WHICH ARE SHOWN ON THE FOLLOWING DIAGRAMS.

THE ATOMIC ABSORPTION SPECTROMETER TECHNIQUE

TYPICALLY USES A FLAME TO ATOMIZE THE METAL

SAMPLE. A BEAM OF LIGHT PASSES THROUGH THIS

FLAME, ABSORBING A SET OF QUANTITY OF ENERGY

( LIGHT OF A GIVEN WAVELENGTH ). EACH WAVELENGTH

IN THE SERIES IS SPECIFIC TO ONLY ONE

PARTICULAR ELEMENT.

A PORTABLE NON-DESTRUCTIVE FIELD

ATOMIC ABSORPTION SPECTROMETER.

POSITIVE MATERIAL IDENTIFICATION USING A HAND-HELD

ENERGY DISPERSIVE X-RAY FLUORESCENCE ANALYZER

TO VERIFY ALLOYS OF COMPONENT PARTS

NICKEL AND ITS ALLOYS – THESE ARE NON-FERROUS

METALS WITH HIGH-STRENGTH AND TOUGHNESS,

EXCELLENT CORROSION RESISTANCE, AND SUPERIOR

ELEVATED TEMPERATURE PROPERTIES.

NICKEL ALLOYS ARE USED FOR A WIDE VARIETY OF

APPLICATIONS, THE MAJORITY OF WHICH INVOLVE

CORROSION RESISTANCE AND / OR HEAT RESISTANCE:

- AIRCRAFT GAS TURBINES

- STEAM TURBINE POWER GENERATION PLANTS

- NUCLEAR POWER SYSTEMS

- CHEMICAL AND PETROCHEMICAL INDUSTRIES

AMONG THE MOST COMMON NICKEL ALLOYS USED IN THE

HEAVY INDUSTRIES ARE:

- INCOLLOY

- INCONEL

- HASTELOY

- HAYNES

- NIMONIC

- MONEL

NICKEL ALLOYS ARE HIGHLY WELDABLE AND NO SPECIAL

PRECAUTION IS REQUIRED.

NICKEL ALLOYS ARE PRIMARILY USED IN

TURBINE POWER GENERATION PLANTS.

TITANIUM AND ITS ALLOYS – THE COMBINATION OF

HIGH STRENGTH-TO-WEIGHT RATIO, EXCELLENT

MECHANICAL PROPERTIES,AND CORROSION

RESISTANCE MAKES TITANIUM AND ITS ALLOYS

THE BEST MATERIAL CHOICE FOR MANY CRITICAL

APPLICATIONS SUCH AS STATIC AND ROTATING

GAS TURBINE ENGINE COMPONENTS, AIRPLANES,

MISSILES AND ROCKET.

TITANIUM AND ITS ALLOYS ARE HIGHLY OXIDIZABLE WHEN

WELDED. CARE MUST BE TAKEN TO CONTROL THE HEAT

OF THE BASE METAL DOWN TO 250°C. OTHERWISE,

TARNISHING WILL DEVELOP.

MAIN ENGINE LE7A

H2A ROCKET

TITANIUM AND ITS ALLOYS ARE

USED VERY EXTENSIVELY IN

THE AEROSPACE INDUSTRY.

COPPER AND ITS ALLOYS – THERE ARE AS MANY

AS 400 DIFFERENT COPPER AND COPPER-ALLOY

COMPOSITIONS. THE FOLLOWING ARE THE PRINCIPAL

ALLOYING 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 HEAT

DISSIPATION RATE. THE WELD AREA REMAINS

ALWAYS COLD DURING WELDING, MAKING

EXCESSIVE PREHEAT NECESSARY.

ELECTRICAL ENERGY IS WASTED IN ANY SYSTEM

BECAUSE A PORTION OF THE ELECTRICITY FLOWING

THROUGH THE CONDUCTOR IS CONVERTED TO HEAT

RATHER THAN BEING DELIVERED AS USABLE ELECTRICAL

ENERGY.

ELECTROLYTIC COPPER ( PURE COPPER ) EXHIBITS

HIGH ELECTRICAL CONDUCTIVITY AND HIGH HEAT

DISSPATION RATE, MAKING IT VERY IDEAL FOR

ELECTRICAL COMPONENT PARTS, LIKE BUS BARS.

BECAUSE OF THEIR UNIQUE LUBRICITY PROPERTIES,

ESPECIALLY WHERE HIGH TEMPERATURES ARE

INVOLVED, IN REDUCING FRICTION AND PROLONGING

SERVICE LIFE, COPPER ALLOYS FIND VERY GOOD

APPLICATION IN BUSHINGS, BEARINGS AND SLEEVES.

THEY FIND EXTENSIVE USES IN OFFSHORE, STEEL MILL

AND CONSTRUCTION EQUUIPMENT.

AN ECCENTRIC BUSHING MADE OF COPPER ALLOYS USED

IN STEEL MILLS.

ALUMINUM AND ITS ALLOYS – THEY HAVE A STRONG

RESISTANCE TO CORROSION, AND IS RATHER

MALLEABLE. THEY ARE RELATIVELY LIGHT METAL.

THEY ARE EASILY MACHINABLEAND CAN HAVE A WIDE

VARIETY OF SURFACE FINISHES. THEY ALSO HAVE GOOD

ELECTRICAL AND THERMAL CONDUCTIVITIES AND IS

HIGHLY REFLECTIVE TO HEAT AND LIGHT.

PURE ALUMINUM HAS VERY LOW STRENGTH. HOWEVER,

WHEN ALLOYED, MAINLY, WITH SILICON, CAN ATTAIN

STRENGTH 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 A

VERY HIGH MELTING POINT. THIS CAUSES WELDABILITY

PROBLEMS. THE BEST REMEDY IS TO GRIND THE OXIDE

SKIN BEFORE ATTEMPTING TO WELD ALUMINUM AND ITS

ALLOYS.

THE H.M.S. LAURIER LAPIERRE IS THE WORLD’S FIRST

ALUMINUM WARSHIP. THE CONCEPT OF AN ALUMINUM

WARSHIP IS ECONOMICALLY SOUND. THEY WILL ONLY

WEIGH 1/12 OF TRADITIONAL IRON AND STEEL WARSHIPS.

THE COST OF FUEL IS ONLY 1/4 OF THE TRADITIONAL

STEEL-HULLED SHIPS. THE LIGHTER ALUMINUM

WARSHIPS WILL TRAVEL FASTER AND WITH GREAT

MANEUVERABILITY, MAKING THEM LESS SUSCEPTIBLE TO

TARGET AND CAN EASILY INTERCEPT ENEMY VESSELS.

ALUMINUM WHEELS GIVE THE AUTOMOBILES

A SPORTY DESIGN. ALUMNUM WHEELS ALSO

IMPROVE AUTOMOBILE PERFORMANCE

BECAUSE OF THEIR LIGHTWEIGHT AND

VERY GOOD HEAT DISSIPATION.

TYPICAL APPLICATIONS OF ALUMINUM ALLOYS

IN THE AUTOMOTIVE INDUSTRY.

TYPICAL APPLICATIONS OF ALUMINUM ALLOYS

IN THE AUTOMOTIVE INDUSTRY.

That’s All Folks