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Ferrous & Non Ferrous Metals

• Alloy steel is a mixture of steel and other metals
• It has desirable properties
• Contains around 1-5% of alloying elements
• It has precise chemical compositions for better mechanical properties, preventing corrosion

Alloy Steel

• Other elements (besides carbon) can be added to iron to improve mechanical property, manufacturing, or environmental protection
• Examples: Sulfur, Phosphorous, lead improve machine ability for parts with high production rates

Alloy Steel Types

• Low-alloy steel (HSLA): High-strength low alloy steel
• High-alloy steel: Stainless steel
• Tool steel: Made into tools
• Microalloyed steel: Refine the grain microstructure
• Maraging steel: High strength, high temperature alloy (super alloys)

Alloying Elements

• Manganese (Mn): Combines with sulfur to prevent brittleness. Increases hardenability, hardness, ductility, and wear resistance. Ideal for impact resisting tools.
• Sulfur (S): Imparts brittleness but improves machinability. Okay if combined with manganese. Some free-machining steels contain 0.08% to 0.15% S.
• Nickel (Ni): Provides strength, stability, and toughness.
• Molybdenum (Mo): Increases hardenability and strength, increases creep resistance at elevated temps.
• Chromium (Cr): Increases hardenability and strength, offers corrosion resistance.
• Vanadium (V): Increases strength without loss of ductility.
• Tungsten (W): Forms stable carbides, increases hot hardness. Used in tool steels.
• Silicon (Si): Increases strength without loss of ductility, enhances magnetic properties.
• Copper (Cu): Increases corrosion resistance, reduces surface quality and hot-working ability.
• Boron (B): For low carbon steels, drastically increases hardenability, improves machinability, and cold forming.
• Aluminum (Al): Acts as a deoxidizer, produces Al-nitrides during nitriding.

Steel Types

• Low Carbon Steel: Basic steel with low carbon % and is easy to work with.
• Medium Carbon Steel: Higher carbon content than low carbon steel, making it stronger but harder to work with.
•  High Carbon Steel: The highest carbon content of the three, making it the strongest steel type, but also the most brittle.

Selecting Steels (Applications)

• High-strength low-alloy structural steel
• Microalloyed steel
• Free-machining steel
• Bake-hardenable steel sheet
• Precoated steel sheet
• Electrical and magnetic applications
• Maraging steel
• High-temperature steel
• Stainless steel
• Tool steel

Types of High Alloy Steel

• Stainless Steels (Corrosion-Resistant Steels): Contain at least 10.5% chromium. AISI assigns a 3-digit number.
  • 200 and 300: Austenitic stainless steel
  • 400: Ferritic or Martensitic stainless steel
  • 500: Martensitic stainless steel

Stainless Steel

• Steel alloyed with chromium (18%), nickel (8%), magnesium (8%)
• Hard and tough
• Corrosion resistance
• Comes in different grades (e.g., sinks, cooking utensils, surgical instruments)

Stainless Steel Grades

• Ferritic chromium: Very formable, relatively weak, used in architectural trim, kitchen range hoods, jewelry, decorations, utensils.
• Austenitic nickel-chromium: Non-magnetic, machinable, weldable, relatively weak. Used in architectural products (fascias, curtain walls, store fronts), railings, chemical processing, food utensils.
• Martensitic chromium: High strength, high hardness, resistance to abrasion; used in turbine parts, bearings, knives.

Tool Steel

• Refers to a variety of carbon and alloy steels suitable for tools.
• High hardness, resistance to abrasion, excellent wear, ability to hold a cutting edge, resistance to deformation.
• Used in a heat-treated state
• High carbon content = very brittle

Water-hardening Group

• W-group tool steel gets its name from needing water quenching for hardening
• This type is essentially high carbon plain-carbon steel
• These steels perform well in low temperature operations, but are brittle
• Used in parts / applications where high temperatures are not encountered.

Cold-work Group

• Steels used in low-temperature cutting and forming
• High hardenability and wear resistance
• Used in production of larger parts needing less distortion during hardening

Shock-resistant Group

• Designed to resist shock at both low and high temperatures
• Low carbon content for toughness (approx. 0.5% carbon)
• Carbide-forming alloys for abrasion resistance and characteristics needed for hot work.

High Speed Steel (HSS)

• Medium carbon steel alloyed with tungsten, chromium, and vanadium
• Very hard, resist frictional heat even at high temperatures
• Used in machine cutting tools (lathe and milling) (drills)

Molybdenum High Speed Steels (HSS)

• Combining molybdenum, tungsten, and chromium creates alloys called "HSS"
• Measuring 63-65 Rockwell "C" Hardness

Cobalt High Speed Steels (HSS)

• Adding cobalt increases heat resistance
• Can give a Rockwell hardness up to 70 HRC

Hot-working Group

• Steel for cutting or shaping materials at high temps
• H-group tool steels developed for strength and hardness during prolonged exposure to high temp.
• Low carbon and moderate to high alloy tool steels provide good hot hardness and toughness.

Special-purpose Group

• P-type ("Plastic Mold"): Steel for plastic mold requirements, zinc die casting and plastic injection molding.
• L-type ("Low Alloy Special"): Type L6 is extremely tough, used for low alloy special purpose tools.
• F-type: Water hardened and more wear resistant than W-type tool steel.

Microalloyed Steel

• Alloy steel containing small amounts of specific elements (e.g., niobium, vanadium, titanium)
• Refine the grain microstructure or facilitates precipitation hardening
• Between carbon and low alloy steel
• Yield strength between 275 and 750 MPa (40 and 110 ksi).
• Weldability is good, can be improved by reducing carbon content

Maraging Steel

• High-strength, high-temperature alloys (super alloys)
• Used in structural applications and aircraft components
• Generally magnetic
• Alloys contain around 18% nickel

Other Alloy Steel Types

• Those steel types in which the residual elements (carbon, manganese, sulphur, silicon) are controlled, but no alloying elements are added. Used in many construction applications. A good example is A36 carbon structural steel.

• Wide-flanged beams (W shapes) replaced the previous steel of choice A36 with the high-strength, low-alloy steel known as A992. The remaining non-wide-flange beam shapes, A36 still remain the predominating steel.

Pipe & Square Tubing

• Examples of pipes: A53 (black & hot-dipped, galvanized) pipe
• Examples of tubing: A500 Cold-Formed Welded and Seamless Structural Tubing, A501 Hot-Formed Welded and Seamless Carbon Steel Structural Tubing