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Presentation Industrial Material.pptx
- 1. Chapter 07: Ferrous Metals and Alloys DeGarmo’s Materials and Processing in Manufacturing
- 2. Classification of Common Ferrous Metals and Alloys Note: Figure 6-1 Classification of common ferrous metals andalloys. %Carbon > 2.11 - cast irons; %Carbon < 2.11 - steels
- 3. Advanced High-Strength Steels (AHSS) AHSS replaces low carbon and HSLA steels in automotive applications AHSS is primarily ferrite-phase, soft steels with varying amount of martensite, bainite or retained austenite – which offer high strength with enhanced ductility Improved formability Enable the stamping or hydroforming of complex parts Higher strength provides improved fatigue resistance Possibility of weight reduction
- 4. Types of Advanced High-Strength Steels (AHSS) Dual-phase (DP) steels microstructure of Ferrite and martensite Improved forming characteristics and no loss in weldability (compared with HSLA) High strain-rate sensitivity The faster the steel is crushed, the more energy it absorbs A feature to enhance crash resistance in automotive applications Transformation-induced plasticity (TRIP) steels Microstructure of Ferrite , hard martensite or bainite and at least 5 vol% of retained austenite At higher strains, the retain austenite transforms progressively to martensite, enabling high work-hardening to persist to greater levels of deformation Excellent energy absorption during crash deformation
- 5. Types of Advanced High-Strength Steels (AHSS) Complex-phase (CP) steels and martensitic (Mart) steels high strength with capacity for deformation and energy absorption CP steels – microstructure of ferrite and bainite with small amount of martensite, retained austenite and pearlite Strengthened by grain refinement created by a fine precipitate of Niobium, titanium or vanadium carbides or nitrides Mart steels – almost entirely martensite Other types Ferritic-bainite (FB) steels Twinning-induced plasticity (TWIP) steels - (17-24% Mn) Nano steels - (replace hard phase with nano-size precipitates)
- 7. Free-Machining Steels Steels machine readily and form small chips when cut The smaller the chips reduce friction on the cutting tool which reduces the amount of energy required Reduces tool wear Free-machining steels carry a cost of 15-20% over conventional steels Carbon steel with addition of S, Pb, Bi, Se, Te or P Enhance machinability Additions provide built-in lubrications sulfur combines with manganese to form soft manganese sulfide inclusions Lead – as insoluble particle Bismuth - more environmentally friendly than lead Ductility and impact properties are reduced
- 8. Precoated Steel Sheet Typical sheet metal processes shape bare steel followed by finishing (or coating) Expensive and time-consuming stages of manufacture Precoated steel sheets can also be formed Eliminates the post processing finishing operations Dipped, plated, vinyls, paints, primers and polymer coatings can be used These coating are specially formulated to endure the subsequent forming and bending
- 9. Steels for Electrical and Magnetic Applications Soft magnetic materials can be magnetized by low- strength magnetic fields Lose almost all of their magnetism when the field is removed Products such as solenoids, transformers, generators, and motors Materials such as high-purity iron, low-carbon steel, iron-silicon electrical steels, amorphous ferromagnetic alloys, iron-nickel alloys and soft ferrite (ceramic material) Amorphous metals No crystal structure, grains, or grain boundaries Magnetic domains can move freely Properties are the same in all directions Corrosion resistance is improved
- 10. Special Steels Maraging Steels • The term maraging is derived from the strengthening mechanism, which is transforming the alloy to martensite with subsequent age hardening. • Carbon free iron-nickel alloys with additions of cobalt, molybdenum, titanium and aluminium. • The common, non-stainless grades contain 17–19 wt.% nickel, 8–12 wt.% cobalt, 3–5 wt.% molybdenum, and 0.2–1.6 wt.% titanium.
- 11. • Air cooling the alloy to room temperature from 820 °C creates a soft iron nickel martensite, which contains molybdenum and cobalt in supersaturated solid solution. • Tempering at 480 to 500 °C results in strong hardening due to the precipitation of a number of intermetallic phases, including, nickel-molybdenum, iron- molybdenum and iron-nickel varieties. • With yield strength between 1400 and 2400 MPa maraging steels belong to the category of ultra-high- strength materials. • The high strength is combined with excellent toughness properties and weldability.
- 12. Applications • Maraging steel's strength and malleability in the pre-aged stage allows it to be formed into thinner rocket and missile skins than other steels, reducing weight for a given strength. • Aerospace, e.g. undercarriage parts and wing fittings. • Tooling & machinery, e.g. extrusion press rams and mandrels in tube production, gears. • Ordnance components and fasteners.
- 13. Long products for the aircraft industry (Courtesy of Boehler AG, Austria)
- 14. • Maraging steel production, import, and export by certain states, such as the United States, is monitored. • It is particularly suited for use in gas centrifuges for uranium enrichment • Lack of maraging steel significantly hampers this process. Older centrifuges used aluminum tubes; modern ones, carbon fiber composite.
- 15. Special Steels Maraging steels Used when extremely high strength is required Typically also have high toughness Very-low-carbon steel with 15-20% Nickel and significant amount of Co, Mo, Ti Steels for High-Temperature Service Plain-carbon steels should not be used for temperatures in excess of 250°C Tend to be low-carbon materials (< 0.1% carbon)
- 16. Summary The processing of steels determines the final material properties Steel’s typically have high strength, rigidity, and durability Steel is recyclable Different alloying elements may be added to produce known effects to the material