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Steel Make-Upteel Make-UpDr. Eng. Hamed A. NagyDr. Eng. Hamed A. Nagy
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAIntroductoryntroductory Mechanical properties of a metal can beMechanical properties of a metal can be
altered by the application of variousaltered by the application of various
mechanical and thermal treatments.mechanical and thermal treatments. Drastic changes will also occur if theDrastic changes will also occur if the
chemical composition is changed.chemical composition is changed.
Also, chemical composition will also haveAlso, chemical composition will also havean effect on its corrosion resistance andan effect on its corrosion resistance and
weldability.weldability.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTABasic MetalBasic Metal
StructuresStructures
Atoms are so small that they cannot be seen,Atoms are so small that they cannot be seen,
even with the most powerful microscopes.even with the most powerful microscopes.
At certain temperature ranges, they tend toAt certain temperature ranges, they tend toform substances having specific shapes.form substances having specific shapes.
This is because there are definite forces actingThis is because there are definite forces acting
between these individual atoms These forcesbetween these individual atoms These forces
are in equilibrium.are in equilibrium.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTABasic MetalBasic Metal
StructuresStructures 'Home' positions.'Home' positions.
Interatomic Spacing.Interatomic Spacing.
Below a metal's yield point, Elastic,Below a metal's yield point, Elastic,WHY?WHY?
It was noted before that the metal atomsIt was noted before that the metal atoms
exhibit a very specific spacing at a givenexhibit a very specific spacing at a giventemperature, or internal energy.temperature, or internal energy.
Expansion?Expansion?
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTABasic MetalBasic Metal
StructuresStructures Liquid metal has a higher internal energyLiquid metal has a higher internal energy
with greater interatomic spacing, and iswith greater interatomic spacing, and is
considered to be amorphous.considered to be amorphous. There are several ways of reducing orThere are several ways of reducing or
eliminating residual stresses.eliminating residual stresses.
Stress relief.Stress relief. Vibration.Vibration.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTACrystal StructuresCry
stal Structures
In a solid metal, the atoms tend to alignIn a solid metal, the atoms tend to align
themselves into orderly lines, rows, and layersthemselves into orderly lines, rows, and layers
to form three dimensional crystalline structures.to form three dimensional crystalline structures. "Unit cell"."Unit cell".
Body-centered cubic (BCC),Body-centered cubic (BCC),
Face-centered cubic (FCC),Face-centered cubic (FCC),
Body centered tetragonal (BCT), andBody centered tetragonal (BCT), and
Hexagonal close-packed, (HCP).Hexagonal close-packed, (HCP).
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTASolidification of MetalsSolidification of Metals
Nuclei.Nuclei.
Then Grain.Then Grain.
Mechanical properties can be dependentMechanical properties can be dependent
upon the grain size of the metal.upon the grain size of the metal.
Effect varies with temperature.Effect varies with temperature.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAAlloyingAlloying
The properties of metallic elements can beThe properties of metallic elements can be
altered by the addition of other elements, whichaltered by the addition of other elements, which
may or may not be metallic.may or may not be metallic. Alloying elements are included in the baseAlloying elements are included in the base
metal lattice (the general arrangement ofmetal lattice (the general arrangement of
individual atoms) in various ways dependingindividual atoms) in various ways depending
upon the relative sizes of the atoms.upon the relative sizes of the atoms. Smaller atoms, such as carbon, nitrogen andSmaller atoms, such as carbon, nitrogen and
hydrogen, tend to occupy sites be interstitial.hydrogen, tend to occupy sites be interstitial.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAAlloyingAlloying
Alloying elements with atoms close to the sizeAlloying elements with atoms close to the sizeof those of the base metal tend to occupyof those of the base metal tend to occupysubstitutional sites.substitutional sites.
Nearly all engineering metals are alloysNearly all engineering metals are alloysconsisting of one major element and variableconsisting of one major element and variableamounts of one or more additional elements.amounts of one or more additional elements.Alloys usually consist of many randomlyAlloys usually consist of many randomly
oriented grains with each grain arranged in aoriented grains with each grain arranged in aspecific way and containing one or more of thespecific way and containing one or more of thecharacteristic phases that exist for the alloy.characteristic phases that exist for the alloy.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAMicrostructuralMicrostructural
Constituents ofConstituents of
Carbon SteelCarbon Steel The overall arrangement of grains, grainThe overall arrangement of grains, grain
boundaries, and phases present in a metallicboundaries, and phases present in a metallicalloy is called its microstructure.alloy is called its microstructure.
This microstructure is affected by theThis microstructure is affected by thecomposition or alloy content, and by othercomposition or alloy content, and by otherfactors such as forming and heat treatingfactors such as forming and heat treatingoperationsoperations
Iron and steels undergo changes in theirIron and steels undergo changes in theircrystallographic arrangement as a result ofcrystallographic arrangement as a result oftemperature changes.temperature changes.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAMicrostructuralMicrostructural
Constituents ofConstituents of
Carbon SteelCarbon Steel This allows us to change the mechanicalThis allows us to change the mechanical
properties of a specific alloy through heproperties of a specific alloy through he
application of various heat treatments.application of various heat treatments. "Iron-Carbon Phase Diagram""Iron-Carbon Phase Diagram"
Ferrite,Ferrite,
Austenite,Austenite,
CementiteCementite
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAMicrostructuralMicrostructural
Constituents ofConstituents of
Carbon SteelCarbon Steel Hypoeutectoid, eutectoid and hypereutectoidHypoeutectoid, eutectoid and hypereutectoid
typestypes
At 723 C, the horizontal line representingAt 723 C, the horizontal line representingtransformation temperature is referred to as thetransformation temperature is referred to as the
AC1AC1
Transformation will occur over a range ofTransformation will occur over a range of
temperatures with complete transformationtemperatures with complete transformationoccurring only when the temperature is raisedoccurring only when the temperature is raised
above the sloping line designated as the A3.above the sloping line designated as the A3.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAMicrostructuralMicrostructural
Constituents ofConstituents of
Carbon SteelCarbon Steel Pearlite can only occur when sufficient time isPearlite can only occur when sufficient time is
allowed for the atoms to diffuse into thatallowed for the atoms to diffuse into that
arrangement.arrangement. Diffusion is simply the migration of the atomsDiffusion is simply the migration of the atoms
within the solid metal structure.within the solid metal structure.
When the cooling from the austenitic rangeWhen the cooling from the austenitic range
occurs more rapidly, there are significantoccurs more rapidly, there are significantchanges in this transformation for a given steelchanges in this transformation for a given steel
alloy.alloy.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAMicrostructuralMicrostructural
Constituents ofConstituents of
Carbon SteelCarbon Steel Upon rapid cooling, principal microstructuresUpon rapid cooling, principal microstructures
produced include fine pearlite, bainite andproduced include fine pearlite, bainite and
martensite.martensite. However, martensite has characteristically theHowever, martensite has characteristically the
low ductility and toughness.low ductility and toughness.
To improve the ductility and toughness withoutTo improve the ductility and toughness without
significantly decreasing the hardness andsignificantly decreasing the hardness andtensile strength of the martensite, a processtensile strength of the martensite, a process
referred to as tempering is employed.referred to as tempering is employed.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAHeat TreatmentsHeat Treatments
The basic heat treatments include annealing,The basic heat treatments include annealing,
normalizing, quenching, tempering, preheat,normalizing, quenching, tempering, preheat,
post heat and thermal stress relief.post heat and thermal stress relief.
Annealing is a softening treatment used toAnnealing is a softening treatment used to
increase the metal's ductility at the expense ofincrease the metal's ductility at the expense of
its strength.its strength.
Metal is raised just into the austenitic range,Metal is raised just into the austenitic range,
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAHeat TreatmentsHeat Treatments
held for one our per inch of thickness orheld for one our per inch of thickness or
a minimum of one hour,a minimum of one hour,
and then cooled very slowly.and then cooled very slowly. Normalizing also softens the metal, butNormalizing also softens the metal, but
not as significantly as annealing.not as significantly as annealing.
The only difference is cooling in still air.The only difference is cooling in still air.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAHeat TreatmentsHeat Treatments
Quenching differs from annealing andQuenching differs from annealing andnormalizing in that the resulting mechanicalnormalizing in that the resulting mechanicalproperties show significantly increasedproperties show significantly increased
hardness and strength and decreased ductility.hardness and strength and decreased ductility. By immersing the part in a quenching medium,By immersing the part in a quenching medium,
such as water, oil or brine (salt water).such as water, oil or brine (salt water).
To improve the ductility without significantTo improve the ductility without significantdegradation of the metal's strengthdegradation of the metal's strengthcharacteristics, a tempering treatment ischaracteristics, a tempering treatment isusually performed.usually performed.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAHeat TreatmentsHeat Treatments
Reheated to a temperature below theReheated to a temperature below the
lower transformation temperature,lower transformation temperature,
held for a short time to allow the highlyheld for a short time to allow the highlystressed martensitic structure to relaxstressed martensitic structure to relax
somewhat, and then cooled.somewhat, and then cooled.
Preheat treatments.Preheat treatments. Thermal stress relief,Thermal stress relief,
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTADiffusionDiffusion
Atoms in the liquid state can move aboutAtoms in the liquid state can move about
easily with respect to each other;easily with respect to each other;
Increases with temperature.Increases with temperature. Major examples, HydrogenMajor examples, Hydrogen
Embrittlement and Sensitization.Embrittlement and Sensitization.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAAlloy GroupsAlloy Groups
Steels can be divided into three subcategories: plainSteels can be divided into three subcategories: plaincarbon steels, low-alloy steels, and high alloy steels.carbon steels, low-alloy steels, and high alloy steels.
Based on tonnage, plain carbon steels are the mostBased on tonnage, plain carbon steels are the most
widely used.widely used. They contain primarily iron but also small additions ofThey contain primarily iron but also small additions of
carbon, manganese, phosphorus, sulfur and silicon.carbon, manganese, phosphorus, sulfur and silicon.
Compositions of some of stainless steel types, whichCompositions of some of stainless steel types, whichare divided into five groups, austenitic, martensitic,are divided into five groups, austenitic, martensitic,ferrite, precipitation hardening, and the duplex grades.ferrite, precipitation hardening, and the duplex grades.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAAlloying Elements-Alloying Elements-
CarbonCarbon
is generally considered to be the mostis generally considered to be the most
important alloying element in steel (up toimportant alloying element in steel (up to
2%)2%) Most welded steels have less than 0.5%.Most welded steels have less than 0.5%.
Carbon can exist either dissolved in theCarbon can exist either dissolved in the
iron, or in a combined form such as ironiron, or in a combined form such as ironcarbide (Fe3C).carbide (Fe3C).
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTACarbonCarbon
Increased amounts of carbon increaseIncreased amounts of carbon increase
hardness and tensile strength, as well ashardness and tensile strength, as well as
response to heat treatment (hardenresponse to heat treatment (hardenability).ability).
On the other hand increased amounts ofOn the other hand increased amounts of
carbon reduce weldability.carbon reduce weldability.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTASulfurSulfur
Is usually an undesirable impurity in steelIs usually an undesirable impurity in steel
rather than an alloying element. In amountsrather than an alloying element. In amounts
exceeding 0.05% it tends to cause brittlenessexceeding 0.05% it tends to cause brittleness
and reduce weldability. Alloying additions ofand reduce weldability. Alloying additions of
sulfur in amounts from 0.10 to 0.30% will tendsulfur in amounts from 0.10 to 0.30% will tend
to improve the machinability of a steel.to improve the machinability of a steel.
Such types may be referred to as "resulfurized"Such types may be referred to as "resulfurized"or "free-machining". (not intended for useor "free-machining". (not intended for use
where welding is required).where welding is required).
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTASiliconSilicon
Usually only small amounts (0.20%) areUsually only small amounts (0.20%) arepresent in rolled steel when it is used as apresent in rolled steel when it is used as adeoxidizer.deoxidizer.
In steel castings, 0.35 to 1.00% is commonlyIn steel castings, 0.35 to 1.00% is commonlypresent.present.
Silicon dissolves in iron and tends toSilicon dissolves in iron and tends tostrengthen it.strengthen it.
Weld metal usually contains approximatelyWeld metal usually contains approximately0.50% silicon as a deoxidizer.0.50% silicon as a deoxidizer.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTASiliconSilicon
Some filler metals may contain up to 1% toSome filler metals may contain up to 1% to
provide enhanced cleaning the deoxidation forprovide enhanced cleaning the deoxidation for
welding on contaminated surfaces.welding on contaminated surfaces.
When these filler metals are used for weldingWhen these filler metals are used for welding
of clean surfaces, the resulting weld metalof clean surfaces, the resulting weld metal
strength will be markedly increased:strength will be markedly increased:
The resulting decrease in ductility couldThe resulting decrease in ductility couldpresent cracking problems in some situations.present cracking problems in some situations.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAChromiumChromium
is a powerful alloying element in steel.is a powerful alloying element in steel.
It is added for two principle reasons; first, itIt is added for two principle reasons; first, itstrongly increase the hardenability of steel, andstrongly increase the hardenability of steel, andsecond, it markedly improves the corrosionsecond, it markedly improves the corrosionresistance of alloys in oxidizing media.resistance of alloys in oxidizing media.
But could cause excessive hardness andBut could cause excessive hardness andcracking in, and adjacent to the weld.cracking in, and adjacent to the weld.
Stainless steels contain chromium in amountsStainless steels contain chromium in amountsexceeding 12%.exceeding 12%.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAMolybdenumMolybdenum
This element is a strong carbide former and isThis element is a strong carbide former and is
usually present in alloy steels in amounts lessusually present in alloy steels in amounts lessthan 1.0%.than 1.0%.
it is added to increase hardenability andit is added to increase hardenability and
elevated temperature strength.elevated temperature strength.
It is added to the austenitic stainless steels toIt is added to the austenitic stainless steels to
improve pitting corrosion resistance.improve pitting corrosion resistance.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTANickelNickel
GreatGreat
is added to steels to increase theiris added to steels to increase theirhardenability.hardenability.
It performs well in this function because it oftenIt performs well in this function because it oftenimproves the toughness and ductility of theimproves the toughness and ductility of thesteel, even with the increased strength andsteel, even with the increased strength andhardness.hardness.
Nickel is frequently used to improve a steel'sNickel is frequently used to improve a steel'stoughness at low temperatures.toughness at low temperatures.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAAluminumAluminum
Is added to steel in very small amountsIs added to steel in very small amounts
as a deoxidizer.as a deoxidizer.
It is also a grain refiner for improvedIt is also a grain refiner for improvedtoughness; steels with moderatetoughness; steels with moderate
aluminum additions are referred to asaluminum additions are referred to as
having been made to a 'fine grainhaving been made to a 'fine grainpractice'.practice'.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAVanadiumVanadium
Increases the hardenability of a steel.Increases the hardenability of a steel.
In amounts greater than 0.05%, thereIn amounts greater than 0.05%, there
may be a tendency for the steel tomay be a tendency for the steel tobecome embitter during thermal stressbecome embitter during thermal stress
relief treatments.relief treatments.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTANiobium (ColumbiumNiobium (Columbium((
like vanadium, is generally considered tolike vanadium, is generally considered to
increase the hardenability of a steel. However,increase the hardenability of a steel. However,due to its strong affinity for carbon, it maydue to its strong affinity for carbon, it may
combine with carbon in the steel to result in ancombine with carbon in the steel to result in an
overall decrease in hardenability.overall decrease in hardenability.
It is added to austenitic stainless steels as aIt is added to austenitic stainless steels as astabilizer to improve as-welded properties.stabilizer to improve as-welded properties.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTADissolved GasesDissolved Gases
Hydrogen, oxygen, and nitrogenHydrogen, oxygen, and nitrogen
All dissolve in molten steel and can embrittleAll dissolve in molten steel and can embrittle
steel if not removed.steel if not removed. Steel refining processes are designed toSteel refining processes are designed to
eliminate as much of these gases as possible.eliminate as much of these gases as possible.
Special fluxes or shielding gases are used toSpecial fluxes or shielding gases are used to
prevent their solution in the molten weld metal.prevent their solution in the molten weld metal.
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Dr. Eng. Hamed A. NagyWeld- Inspecta Co.
INSPECTAIron-Carbon Diagramron-Carbon Diagram
%C
Tempe
ratu
re
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INSPECTATTT DiagramTT Diagram
Time
Tempe
ratu
re
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