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Hsla steels

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High strength low alloy steels

High strength low alloy steels

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  • 1. HIGH STRENGTHHIGH STRENGTHLOW ALLOY STEELSLOW ALLOY STEELSN. PRAKASANME METALLURGY
  • 2. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSINTRODUCTION High-strength low-alloy (HSLA) steels, or microalloyedsteels, are designed to provide better mechanicalproperties and greater resistance to atmosphericcorrosion than conventional carbon steels. They are not considered to be alloy steels in thenormal sense because they are designed to meetspecific mechanical properties rather than a chemicalcomposition. HSLA steels are Low carbon, formable steelspossessing high strength than conventional steels.
  • 3. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSINTRODUCTION The HSLA steels in sheet or plate form have low carboncontent of 0.05 to 0.25% in order to produce adequateformability and weldability. And they have Manganese content up to 2.0%. Small quantities of chromium, nickel, molybdenum, copper,nitrogen, vanadium, niobium, titanium, and zirconium areused in various combinations for improving properties.
  • 4. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSINTRODUCTIONHigh-strength low-alloy (HSLA) steels possess,• High strength to weight ratio• Improved low temperature toughness• Fatigue resistance• High temperature creep resistance• Atmospheric corrosion resistance• Improved notch toughness• Weldability• Formability
  • 5. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSHSLA Steels Categories:HSLA steels can be divided into six categories:Weathering steels:• They contain small amounts of alloying elementssuch as Nickel, copper and phosphorus for improvedatmospheric corrosion resistance and solid-solutionstrengthening. Microalloyed ferrite-pearlite steels:• They contain very small (less than 0.10%) additionsof strong carbide or carbonitride forming elementssuch as niobium, vanadium, and titanium forprecipitation strengthening, grain refinement, andpossibly transformation temperature control
  • 6. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSHSLA Steels Categories:As-rolled pearlitic steels,• They may include carbon-manganese steels butwhich may also have small additions of other alloyingelements to enhance strength, toughness,formability, and weldability.Acicular ferrite (low-carbon bainite) steels,• They are low-carbon (less than 0.05% C) steels withan excellent combination of high yield strengths, (ashigh as 690 MPa) weldability, formability and goodtoughness
  • 7. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSHSLA Steels Categories:Dual-phase steels:• They have a microstructure of martensite dispersedin a ferritic matrix and provide a good combination ofductility and high tensile strengthInclusion-shape-controlled steels:• They provide improved ductility and toughness bythe small additions of calcium, zirconium, or titanium,or perhaps rare earth elements so that the shape ofthe sulfide inclusions is changed from elongatedstringers to small, dispersed, almost sphericalglobules.
  • 8. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSStrengthening mechanisms in HSLA• Refining the ferrite grain size (Grainsize effect)• Solid solution strengthening• Precipitation strengthening• Dislocation strengthening/Workhardening• Transformation strengthening
  • 9. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSStrengthening mechanisms in HSLA
  • 10. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSStrengthening mechanisms in HSLA
  • 11. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSStrengthening mechanisms in HSLA
  • 12. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSEFFECT OF ALLOYING ELEMENTS: Higher yield strength is achieved by the combinedeffects of fine grain size developed during controlledhot rolling and precipitation strengthening that is due tothe presence of vanadium, niobium, and titanium.
  • 13. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSEFFECT OF ALLOYING ELEMENTS:Vanadium Microalloyed Steels.
  • 14. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSVanadium Microalloyed Steels.Introduction• Vanadium containing steels up to 0.10% V arewidely used in the hot-rolled condition. Vanadium-containing steels are also used in the controlled-rolled, normalized, or quenched and temperedcondition.Strengthening mechanism• Vanadium contributes to strengthening by formingfine precipitate particles (5 to 100 nm in diameter) ofV(CN) in ferrite during cooling after hot rolling.• The strengthening from vanadium averages between5 and 15 MPa per 0.01 wt% V, depending on carboncontent and rate of cooling.
  • 15. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSVanadium Microalloyed Steels.Factors affecting strengthening mechanism• Cooling rate : is determined by the hot-rollingtemperature and the section thickness. Cooling rateaffects the level of precipitation strengthening in a0.15% V.• For a given section thickness and cooling medium,cooling rates can be increased or decreased• Increasing the temperature results in larger austenitegrain sizes, while decreasing the temperature makesrolling more difficult.
  • 16. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSVanadium Microalloyed Steels.Factors affecting strengthening mechanism• Cooling rate : An optimum level of precipitationstrengthening occurs at a cooling rate of about170°C/min
  • 17. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSVanadium Microalloyed Steels.Factors affecting strengthening mechanism Manganese Content:• A 0.9% increase in manganese contentincreases the strength of the matrix by 34Mpa because of solid-solution strengthening.• The precipitation strengthening by vanadiumwas also enhanced because manganeselowered the austenite-to-ferritetransformation temperature, thereby resultingin a finer precipitate dispersion.
  • 18. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSVanadium Microalloyed Steels.Factors affecting strengthening mechanism
  • 19. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSVanadium Microalloyed Steels.Factors affecting strengthening mechanism Ferrite Grain size:• Finer ferrite grain sizes can be produced by eitherlower austenite-to-ferrite transformationtemperatures or by the formation of finer austenitegrain sizes prior to transformation.• Vanadium steels subjected to recrystallizationcontrolled rolling require a titanium addition so that afine precipitate of TiN is formed that restrictsaustenite grain growth after recrystallization.
  • 20. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSVanadium Microalloyed Steels.Grade ASTM A 588 Grades A,B,C,• Composition : C: 0.10-0.20%; Mn: 0.75-1.35%;P:0.04%; S: 0.05%; Si:0.15-0.30%; Cr:0.30-0.70%;Ni: 0.25-0.50%; V: 0.01-0.10%• Properties: Atmospheric corrosion resistance fourtimes that of carbon Steels. Yield Strength Minimum345 Mpa.• Applications: Structural use – Welded, boltedstructures in buildings and bridges for Weightsavings and Durability.
  • 21. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSVanadium Microalloyed Steels.Grade ASTM A 633 Grade E,• Composition : C: 0.22%; Mn: 1.15-1.50%; P:0.04%;S: 0.05%; Si:0.15-0.30%; V: 0.04-0.11%;N: 0.01-0.03%• Properties (Normalized) : Enhanced Notchtoughness. Yield Strength Minimum 290-415 Mpa.• Applications: Structural use – Welded, boltedstructures for service at temperature about -40oC.
  • 22. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSNiobium Microalloyed Steels.Introduction• Niobium increases yield strength byprecipitation hardening.• The usual niobium addition is 0.02 to 0.04%.• Niobium steels are produced by controlledrolling, recrystallization controlled rolling,accelerating cooling and direct quenching.
  • 23. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSNiobium Microalloyed Steels.Strengthening mechanism• Niobium is more effective grain refiner thanvanadium.• Thus, the combined effect of precipitationstrengthening and ferrite grain refinementmakes niobium a more effectivestrengthening agent than vanadium.• Strengthening by niobium is 35 to 40 Mpaper 0.01% addition.
  • 24. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSNiobium Microalloyed Steels.• The magnitude of the increase in Yield strength isdepends on the size and amount of precipitatedniobium carbides.
  • 25. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSNiobium Microalloyed Steels.Grade ASTM A 808• Composition : C: 0.12%; Mn: 1.65%;P:0.04%; S: 0.05%; Si: 0.15-0.50%;Nb: 0.02-0.10%;• Properties : Improved Notch toughness.Charpy V - Notch Impact energy 40–60J.• Applications: Railway Tank Cars.
  • 26. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSNiobium Microalloyed Steels.Grade ASTM A 841• Composition : C: 0.20%; Mn: 0.70-1.35%; P:0.03%;S: 0.03%; Si: 0.15-0.50%;Cr: 0.25%; Ni: 0.25%; Cu: 0.35%; V: 0.06%;Nb: 0.03%; Al:0.02%• Properties (produced by Thermo-mechanicalcontrolled processes) : Yield strength 310-345 Mpa.• Applications: Welded pressure vessels
  • 27. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELS Some commonly used HSLA steel grades andapplications: ASTM A533 Grade B• C:0.22%, Mn:1.25%, Ni:0.50%, Mo: 0.50%• Yield Strength: 415 Mpa, Tensile strength: 620 Mpa• Quenched and tempered (620oC) – Ferrite andtempered bainite.• High strength and toughness• Applications:• Nuclear vessels,• Steam generation equipments
  • 28. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELS Some commonly used HSLA steel grades andapplications: ASTM A517 Grade F• C:0.15%, Mn:0.80%, Ni:0.85%, Mo:0.50%, Cr:0.50%• Yield Strength: 760 Mpa, Tensile strength: 860 Mpa• Quenched and tempered (650oC) – TemperedMartensite• High strength and toughness• Applications:• Bridge constructions,• Building constructions
  • 29. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELS Some commonly used HSLA steel grades andapplications: ASTM A543 Class 1• C:0.15%, Mn:0.35%, Ni:3.25%, Mo:0.50%, Cr:1.75%V: 0.02%• Yield Strength: 655 Mpa, Tensile strength: 760 Mpa• Quenched and tempered (650oC) – TemperedBainite and Martensite• High strength and toughness• Applications:• Nuclear pressure vessel,• Plates and forgings
  • 30. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELS Some commonly used HSLA steel grades andapplications: ASTM A203 Grade D• C:0.12%, Mn:0.45%, Ni: 3.50%• Yield Strength: 285 Mpa, Tensile strength: 520 Mpa• Good low temperature toughness• Impact Transition temperature : -60oC• Applications:• Low temperature service applications
  • 31. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELS Some commonly used HSLA steel grades andapplications: ASTM A553 Type I• C:0.10%, Mn:0.65%, Ni: 9.00%• Yield Strength: 655 Mpa, Tensile strength: 760 Mpa• Good low temperature toughness• Impact Transition temperature : -200oC• Applications:• Cryogenic tanks and equipments• Low temperature service applications
  • 32. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELS General Applications: Oil and gas pipelines, Heavy-duty highway and off-road vehicles, Aerospace applications, Construction and farm machinery, Industrial equipment, storage tanks, Mine and railroad cars, Passenger car components. Bridges, offshore structures, Power transmission towers, Building beams and panels etc,.
  • 33. HIGH STRENGTH LOW ALLOY STEELSHIGH STRENGTH LOW ALLOY STEELSReferences:Alloying: Understanding the basics by ASMInternationalStructure and properties of EngineeringMaterials by Henkel & Pense