STEEL ALLOY STEEL C 0 008 TO 2

STEEL & ALLOY STEEL- %C 0. 008 TO 2. 0 % AS PER I-C DIAG. ALLOY STEEL – ALLOYING ELEMENTS ADDED Cr, Ni, Ti, W, V, Mo ETC.

FLOW DIAGRAM FOR STEEL PIG IRON IN MOLTEN OR SOLID STATE BESSEMER PROCESS OPEN HEARTH PROCESS L. D. PROCESS LINZ & DONAWITZ PROCESS STEELS ELECTRIC PROCESS INDUCTION FURNACE

SYLLABUS: STEEL: • BROAD CLASSIFICATION OF STEEL, PLAIN CARBON STEEL DEFINITION , TYPES & PROPERTIES • COMPOSITIONS AND APPLICATIONS OF LOW, MEDIUM AND HIGH CARBON STEELS. ALLOY STEEL: DEFINITION AND EFFECTS OF ALLOYING ELEMENTS ON PROPERTIES OF ALLOY STEELS.

STEEL: OR PLAIN CARBON STEEL IT IS AN ALLOY OF IRON AND CARBON. % C RANGE 0. 008 TO 2%. OTHER RESIDUAL ELEMENTS SUCH AS Mn, Si, P, & S. BRODLY CLASSIFIED AS q UNALLOYED STEEL OR PLAIN CARBON STEELS q ALLOY STEELS

ROLE OF CARBON IN STEEL: C HAS STRENGTHING AND HARDENING EFFECT. IT LOWERS DUCTILITY i. e. DECRESE IN ELONGATION & REDUCTION OF AREA. • RISE IN % C CONTENT LOWERS MACHINABILITY AND WELDABILITY. • THERMAL & ELECTRICAL CONDUCTIVITY DECLINES. • MAGNETIC PERMEABILITY DECRESES DRASTICALLY. • LOWERS CORROSION RESISTANCE.

CLASSIFICATION OF STEEL Ø ACCORDING TO DEOXYDATION PRACTICE. 1. KILLED STEEL 2. SEMI KILLED 3. RIMMEED STEEL KILLED STEEL: STRONGLY DEOXYDIZED AND CHARACTERISED BY HIGH COMPOSITION AND PROPERTY UNIFORMITY. ALL FORGING STEELS AND STEELS CONTAINING 0. 25 % C ARE KILLED. THESE ARE HAVING FREEDOM FROM BLOW HOLES AND SEGREGATION. THERE IS NO EVOLUTION OF GAS AND THE TOP SURFACE OF THE INGOT SOLIDIFIES ALMOST IMMEDIATELY.

SEMI KILLED STEEL: STRUCTURAL STEELS CONTAIMIMG 0. 25 % C ARE GENERALLY SEMI KILLED. THE SURFACE HAS A SOUND SKIN OF COSIDERABLE THICKNESS. PLATES AND STRUCTURAL PRODUCTS ARE NORMALLY MADE OF SEMI KILLED STEELS. RIMMED STEEL: THE STEEL IS PARTIALLY DEOXYDIZED. A WIDE VARIATY OF STEELS FOR DEEP DRAWING IS MADE BY RIMMING PROCESS. i. e. EASE OF FORMING AND SURFACE FINISH ARE MAJOR CONSIDARATIONS. IDEAL FOR ROLLING. SHEETS AND STRIPS MADE FROM RIMMED STEEL HAVE EXCELLENT SURFACE QUALITY & COLD FORMING CHARACTERISTICS.

FREE CUTTING STEEL: HAVE HIGHER SULPHUR, PHOSPHROUS & LEAD. SULPHUR EXISTS IN THE FORM OF Mn. S ( MANGNESE SULPHIDE) , WHICH FORMS INCLUSIONS STRETCHED IN THE DIRECTION OF ROLLING. THESE INCLUSIONS PROMOTE THE FORMATION OF SHORT BRITTLE CHIPS AND REDUCE THE FRICTION BETWEEN THE SURFACE BEING MACHINED. GIVES GOOD SURFACE FINISH AT HIGHER CUTTING SPEEDS. P DISSOLVES IN THE FERRITE ( PURE IRON) INCRESES ITS BRITTLENESS.

FREE CUTTING STEEL… 0. 15 – 0. 35 % P CONSIDERABLY IMPROVES THE MACHINABILITY, WITHOUT REDUCING PHISICAL AND MECH. PROPERTIES TOOL LIFE INCREASED. THESE ARE SUPPLIED IN COLD DRAWN (WORK HARDENED) FORM. WHICH HAVE HIGH TS AND HARDNESS BUT LESS DUCTILE THAN ORDINARY C STEELS. LIMITATIOSHAVE LOWER DYNAMIC STRENGTH AND MORE SUSCEPTIBLE TO CORROSION.

Carbon and Alloy Steels • All of these steels are alloys of Fe and C – Plain carbon steels (less than 2% carbon and negligible amounts of other residual elements) • Low Carbon • Med Carbon • High Carbon (less than 0. 3% carbon) (0. 3% to 0. 6%) (0. 6% to 0. 95%) – Low Alloy Steel – High Alloy Steel – Stainless Steels (Corrosion-Resistant Steels) – contain at least 10. 5% Chromium

Plain Carbon Steel • Lowest cost • Should be considered first in most application • 3 Classifications AS PER C % • Low Carbon (less than 0. 3% carbon) • Med Carbon (0. 3% to 0. 6%) • High Carbon (0. 6% to 0. 95%)

Plain Carbon Steel • Again, alloy of iron and carbon with carbon the major strengthening element via solid solution strengthening. • If carbon level high enough (greater than 0. 6%) can be quench hardened (aka: dispersion hardening, through hardened, heat treated, austenized and quenched, etc. . ). • Can come in HRS and CRS options • HRS – HOT ROLLED STEEL • CRS- COLD ROLLED STEEL • The most common CRS are 1006 through 1050 and 1112, 1117 and other free machining steels

Plain Carbon Steel Low Carbon (less than 0. 3% carbon) 1. Low strength, good formability • If wear is a potential problem, can be carburized (diffusion hardening) • Most stampings made from these stee 2. Med Carbon (0. 3% to 0. 6%) • Have moderate to high strength with fairly good ductility • Can be used in most machine element 3. High Carbon (0. 6% to 0. 95%) • Have high strength, lower elongation • Can be quench hardened • Used in applications where surface subject to abrasion – tools, knives, chisels, agri implements.

LOW C STEEL: (0. 008 -0. 3% C) PROP: o SOFT, DUCTILE, MALLEABLE , TOUGH, MACHINABLE , WELDABLE o NON HARDENABLE BY HEAT TREATMENT. o GOOD FOR COLD WORK. o CAN BE DRAWN INTO WIRES AND SHEETS APP: WIRES, NAILS, RIVETS, SCREWS, WELDING RODS, SHIP PLATES, TUBES, FAN BLADES, GEARS, VALVES, CAM SHAFTS ETC.

Mild steel products Low carbon steel wire Low carbon steel bars

MEDIUM C STEEL: ( % C 0. 30 TO 0. 60) PROP: MEDIUM HARD, DUCTILE AND TOUGH. SLIGHTLY DIFFICULT TO MACHINE AND WELD. DIFFICULT TO COLD WORK HENCE HOT WORKED. CAN BE HARDEN BY HEAT TREATMENT. APP: BOLTS, AXLES, LOCK WASHERS, LARGE FORGING DIES, SPRINGS, SPROKETS, HAMMER, RODS, CRANK PINS ETC.

Seamless tube – medium c steel Circular saw blademedium to high c steel

HIGH C STEEL: 0. 6 - 1. 2 %C PROP: HARD, WEAR RESISTANT, BRITTLE AND DIFFICULT TO MACHINE AND WELD. CAN BE HARDENED BY HEAT TREATMENT. CAN NOT COLD WORK AND HENCE HOT WORKED. APP: FORGING DIES, PUNCHES, HAMMERS, SPRINGS, CLUTCH DISCS, CAR BUMPERS, CHISELS, VICE JAWS, SHEAR BLADES, DRILLS, LEAF SPRINGS, KNIVES, RAZOR BLADES, BALLS AND RACES OF BALL BEARINGS, MANDRELS , CUTTERS, FILES, REAMERS, WIRE DRAWING DIES, METAL CUTTING SAWS.

Neck Knife – High Carbon Steel Hunting knifehigh c steel Wire rope – high carbon steel

HRS vs. CRS • HRS – ingots or continuous cast shapes rolled in the “HOT” condition to a smaller shape. – Since hot, grains recrystallize without material getting harder! • HRS Characterized by: – Extremely ductile (i. e. % elongation 20 to 30%) – Moderate – Rough surface finish – black scale left on surface.

HRS vs. CRS • CRS – coil of HRS rolled through a series of rolling mills AT ROOM TEMPERATURE. – Since rolled at room temperature, get crystal defects called dislocations which impede motion via slip! – Work hardening – Limit to how much you can work harden before too brittle. – How reverse? Can recrystallize by annealing. • CRS Characterized by: – Less ductlie – almost brittle (i. e. % elongation 5 to 10%) – High strength

Alloy Steel IT IS ADDITION OF TWO OR MORE ELEMENTS . • Other elements (besides carbon) can be added to iron to improve mechanical property, manufacturing, or environmental property. • Elements such as Cr, Ni, W, V, Mo, Ti, Co, Mn, etc. • Example: sulfur, phosphorous, or lead can be added to improve machine ability. – Generally want to use for screw machine parts or parts with high production rates!

Alloy Steel • Again, elements added to steel can dissolve in iron (solid solution strengthening): – Increase strength, hardenability, toughness, creep, high temp resistance. • Alloy steels grouped into low, med and high-alloy steels. – High-alloy steels would be the stainless steel groups. – Most alloy steels you’ll use fall under the category of low alloy.

Alloy Steel • > 1. 65%Mn, > 0. 60% Si, or >0. 60% Cu • Most common alloy elements: – Chromium, nickel, molybdenum, vanadium, tungsten, cobalt, boron, and copper. • Low alloy: Added in small percents (<5%) – increase strength and hardenability • High alloy: Added in large percents (>20%) – i. e. > 10. 5% Cr = stainless steel where Cr improves corrosion resistance and stability at high or low temps

Alloying Elements used in Steel Manganese (Mn) • combines with sulfur to prevent brittleness • >1% – increases hardenability • 11% to 14% – – increases hardness good ductility high strain hardening capacity excellent wear resistance • Ideal for impact resisting tools

Alloying Elements used in Steel Sulfur (S) • • Imparts brittleness Improves machineability Okay if combined with Mn Some free-machining steels contain 0. 08% to 0. 15% S • Examples of S alloys: – 11 xx – sulfurized (free-cutting)

Alloying Elements used in Steel Nickel (Ni) • Provides strength, stability and toughness, Examples of Ni alloys: – – 30 xx – Nickel (0. 70%), chromium (0. 70%) 31 xx – Nickel (1. 25%), chromium (0. 60%) 32 xx – Nickel (1. 75%), chromium (1. 00%) 33 XX – Nickel (3. 50%), chromium (1. 50%)

Alloying Elements used in Steel Chromium (Cr) • Usually < 2% • increase hardenability and strength • Offers corrosion resistance by forming stable oxide surface • typically used in combination with Ni and Mo Molybdenum (Mo) • Usually < 0. 3% • increase hardenability and strength • Mo-carbides help increase creep resistance at elevated temps – typical application is hot working tools

Alloying Elements used in Steel Vanadium (V) • Usually 0. 03% to 0. 25% • increase strength – without loss of ductility Tungsten (W) • helps to form stable carbides • increases hot hardness – used in tool steels

Alloying Elements used in Steel Copper (Cu) • • 0. 10% to 0. 50% increase corrosion resistance Reduced surface quality and hot-working ability used in low carbon sheet steel and structural steels Silicon (Si) • About 2% • increase strength without loss of ductility • enhances magnetic properties

Alloying Elements used in Steel • • • Boron (B) for low carbon steels, can drastically increase hardenability improves machinablity and cold forming capacity Aluminum (Al) deoxidizer 0. 95% to 1. 30% produce Al-nitrides during nitriding

Selecting Steels • • • 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

Corrosion Resistant Steel • Stainless Steels (Corrosion-Resistant Steels) – contain at least 10. 5% Chromium – trade name • AISI assigns a 3 digit number – 200 and 300 … Austenitic Stainless Steel – 400 … Ferritic or Martensitic Stainless Steel – 500 … Martensitic Stainless Steel

Tool Steel • Refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. • Characteristics include high hardness, resistance to abrasion (excellent wear), an ability to hold a cutting edge, resistance to deformation at elevated temperatures (redhardness). • Tool steel are generally used in a heattreated state. • High carbon content – very brittle

Tool Steel AISI-SAE tool steel grades[1] Defining property AISI-SAE grade Significant characteristics Water-hardening W O Oil-hardening A Air-hardening; medium alloy D High carbon; high chromium S T Tungsten base M Molybdenum base Hot-working H H 1 -H 19: chromium base H 20 -H 39: tungsten base H 40 -H 59: molybdenum base Plastic mold P L F Cold-working Shock resisting High speed Special purpose Low alloy Carbon tungsten

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