What is Steel? Prepared By: John Cawley

What is Steel? Prepared By: John Cawley

Presentation Objectives Describe the composition of steel. Identify the differences between steel and iron. Use the steel numbering system to identify various types of steel. Identify the effects of different alloying elements on steel. Describe various kinds of carbon steel and alloy steel. Compare the different types of cast iron.

Steel Composition Steel is one of the most widely used materials in the world. Composed primarily of iron. Most steel contains 90% iron. Many carbon steels contain more than 99% iron. The percentage of carbon in steel ranges from just above 0% to 2%

Carbon Content Steel with less carbon is more flexible but also then weaker. As carbon content increases, so does strength, hardness, and brittleness. Too much carbon and the material becomes relatively useless

Comparing Steel and Iron The relationship of steel to cast iron or wrought iron is primarily based on the carbon content Wrought iron contains essentially no carbon. Steel ranges from just above 0% to 2% carbon. Cast Iron typically contains 2% to 4% carbon. Anything above 6% carbon will make the material so brittle that it is relatively useless.

Steel Numbering System A numbering system is used to identify the many types of steels. A steel s numerical name usually consists of four numbers or digits. The first digit refers to the major alloy element. The second digit indicates the approximate percentage of the major alloying element. (hundredths of 1%) The last two or three digits refer to the percentage of carbon in the steel. Also stated as points of carbon. Example: A 2517 steel indicates a Nickel based steel with.17% carbon content

First Digit Identifies Major Alloy 1 - Plain Carbon (not an alloy steel) 2 - Nickel 3 - Chromium and Nickel 4 - Molybdenum 5 - Chromium 6 - Chromium and Vanadium 7 - Tungsten 8 - Nickel, Chromium and Molybdenum 9 - Silicon and Manganese

Type of Steel and Average Chemical Content in Percent Carbon steels 10XX 11XX 12XX Plain carbon, Mn 1.00% max Resulfurized free machining Resulfurized/rephosphorized free machining 15XX Plain carbon, Mn 1.00-1.65% Manganese steel 13XX Mn 1.75% Nickel steels 23XX Ni 3.50% 25XX Ni 5.00% 31XX Ni 1.25%, Cr.65-.80% Nickel-chromium steels 32XX Ni 1.75%, Cr 1.07% 33XX Ni 3.50%, Cr 1.50-1.57% 34XX Ni 3.00%, Cr.77% Molybdenum steels 40XX Mo.20-.25% 44XX Mo.40-.52% Chromium-molybdenum steels 41XX Cr.50-.95%, Mo.12-.30%

Type of Steel and Average Chemical Content in Percent Nickel-chromium-molybdenum steels 43XX Ni 1.82%, Cr.50-.80%, Mo.25% 47XX Ni 1.05%, Cr.45%, Mo.20-.35% Nickel-molybdenum steels 46XX Ni.85-1.82%, Mo.20-.25% 48XX Ni 3.50%, Mo.25% 50XX Cr.27-.65% 51XX Cr.80-1.05% Chromium steels 50XXX Cr.50%, C 1.00% min 51XXX Cr 1.02%, C 1.00% min 52XXX Cr 1.45%, C 1.00% min Chromium-vanadium steels 61XX Cr.60-.95%, V.10-.15% Tungsten-chromium steels 72XX W 1.75%, Cr.75%

Type of Steel and Average Chemical Content in Percent 81XX Ni.30%, Cr.40%, Mo.12% Nickel-chromium-molybdenum steels 86XX Ni.55%, Cr.50%, Mo.20% 87XX Ni.55%, Cr.50%, Mo.25% 88XX Ni.55%, Cr.50%, Mo.35% Silicon-manganese steels 92XX Si 1.40-2.00%, Mn.65-.85%, Cr 0-.65% 93XX Ni 3.25%, Cr 1.20%, Mo.12% Nickel-chromium-molybdenum steels 94XX Ni.45%, Cr.40%, Mo.12% 97XX Ni.55%, Cr.20%, Mo.20% 98XX Ni 1.00%, Cr.80%, Mo.25% Boron Intensified Steels designated by B Example: xxbxx Leaded Steels designated by L Example: xxlxx

AISI and SAE Numerical Steel Designations AISI steels also have a prefix which indicates the steel making process used. A denotes basic open-hearth alloy steel B denotes acid-bessemer carbon steel C denotes basic open-hearth carbon steel D denotes acid open-hearth carbon steel E denotes electric furnace steel Thus, an AISI A2340 steel indicates a nickel alloy steel made in the basic open-hearth. The Society of Automotive Engineers also has there own steel classification system.

Alloying Elements

Effects of Alloying Elements on Steel Machinability Strength Toughness Grain Refiner Wear Hardness Corrosion Resistance Red Hardness Facilitates Casting Process

Types of Steel Steel Carbon Steel Alloy Steel Tool Steel Stainless Steel Other Steel Low Carbon Medium Carbon Low Alloy Structural High Carbon High Alloy Maraging Spring Steel Electrical Specials Quench & Temper Structural Corrosion Resistant Specials

Carbon Steel Low-Carbon Steel 0.05-0.30% Carbon Comparatively less strength Comparatively less hardness Easy machining and forming Least expensive Largest quantity produced Medium-Carbon Steel 0.30-0.60% Carbon Hard and strong after heat treating More expensive than low-carbon steel High-Carbon Steel 0.60-1.00+% Carbon Hard and strong after heat treating More expensive than low and medium carbon steel

Low Carbon Steel Applications Fence Wire Nails/Rivets Chains Auto Bodies Storage Tanks Large Pipe Buildings Bridges Ships

Medium Carbon Steel Applications Wheels Axles Crankshafts Crane Hooks Connecting Rods Gears

High Carbon Steel Applications Tools Dies Knives Chisels Razor Blade Saws Files Railroad Wheels

Changing Properties Increased Carbon Content Tensile Strength is increased Hardness is increased Response to heat treating processes increased Ductility decreases Malleability decreases Weldability decreases

Alloy Steel Is more expensive than carbon steel Used only when a special property is needed Properties such as corrosion resistance, high temperature capability, electromagnetic behavior, high strength, and wear resistance

Maraging Alloy Steel Strong, low-carbon martensitic steel which contains a high percentage of nickel and in which hardening precipitates are formed by aging. 18-25% Nickel Low Carbon Content Very High Strength Good Ductility Good Toughness

Tool Steel Categories Category Description Materials Designation A Air Hardening A2, A3, A4, A5, A6 D Oil or Air Hardening (High Carbon, High Chromium) D1, D2, D3, D4, D5, & D7 H Hot Working (Chromium, Tungsten, Molybdenum) H10, H11, H12, H13, H14, H16, H19, H20, H21, H22, H23, H24, H25, H26, H27, H41, H42, & H43 L Special Purpose (Low Alloy) L2, L3, L6, & L7 M High Speed (Molybdenum) M1, M2, M3(I), M3(II), M4, M6, M7, M10, M15, M30, M33, M34, M36, M41, M42, M43, M44, M46, M47, & M50 O Oil Hardening O1, O2, O6, & O7 P Mold Making P2, P3, P4, P5, P6, P20, & P21 S Shock Resisting S1, S2, S5, & S7 T High Speed (Tungsten) T1, T2, T3, T4, T5, T6, T7, T8, T9, T15 W Water Hardening W1, W2, & W5

Tool Steel Companies List of companies brand names of tool steel Tool Steel Company.doc

Stainless Steel Extremely resistant to corrosion Costs more than carbon steel Harder to machine than other steels Used in all corrosive atmospheres

Cast Iron Good material when vibration is present Withstands compressive forces Poor strength when stretched More brittle than steel

Types of Cast Iron Gray (Most common) White (Most brittle) Malleable (Higher quality) Ductile (Higher quality) Special Alloy (Special properties)