UNIT 3 ALLOY STEELS TYPES OF ALLOY STEELS

UNIT 3 ALLOY STEELS

TYPES OF ALLOY STEELS • • • AISI HSLA AISI STEELS USED IN M/C CONSTRUCTION TOTAL 5% OF Cr, Ni, Cu, Mn, Mo, V ETC HARDENABILITY

HIGH STRENTH LOW ALLOY STEEL ALSO KNOWN AS MICRO ALLOYED STEEL ALLOY- Al. UMINIUM, NIOBIUM, VANADIUM REDUCED WEIGHT AND INCREASED STRENGTH USED AS STRUCTURAL & CONSTRUCTIONAL ALLOY STEEELS. • HIGH YEILD STRENGTH, WELDABILTY, CORROSION RESISTANCE • LOW ALLOY STRUCTURAL STEEL TWICE THE STRENGTH OF PLAIN CARBON STRUCTURAL STEEL • TO INCREASE STRENGTH DURING WELD TO MARTENSITE FORAMATION Mn, V, Si, NIOBIUM ADDED WITH LOW % & 02% Cu ADDED. • •

CHARACTERISTICS OF HSLA • • WEIGHT SAVINGS UPTO 20 – 30% DUCTILE, FORMATION AND MACHINABLE. APPLICATION BRIDGES, TOWERS, PR. VESSELS, AUTOMOBILES, TRAINS, WIDELY USED AS STRUCTURAL MATERIALS.

IMPORTANT ALLOY STEELS • STAINLESS STEEL, HSLA, MARAGING STEEL • 1. STAINLESS STEEL • ALLOYS ARE IRON, CHROMIUM AND CORROSION RESIST ELEMENTS. • 12% Cr ADDED TO FORM CHROMIUM OXIDE PROTECTIVE LAYER TO PROTECT STEEL EXPOSED TO OXYGEN. • LAYER ACT AS BARRIER TO AVOID OXIDATION, RUST OR CORROSION. • TO ENHANCE CORROSION RESISTANCE Cu, Al, Si, Ni, Mn ADDED

TYPES OF SS AUSTENITIC SS MARTENSITIC SS FERRITIC SS 1. AUSTENITIC SS HAVE AUSTENITIC STRUCTURE RETAINED AT ROOM TEMPERATURE. • USED IN GREAT TONNAGE • CARBON BELOW -0. 15% TO AVOID CHROMIUM CARBIDE FORMATION WHICH LEADS TO CORROSION RESISTANCE. • • •

CONTD… • IT CONTAINS Cr & Ni. NICKEL AVIODS THE EFFECT OF CHROMIUM AND RETAINS AUSTENITIC • CARBIDES ARE FORM WHEN THESE STEEELS ALLOWED TO COOL SLOWLY DURING WELDING • CARBIDES PARTICLES FORM CORROSION CALLED WELD DECAY. • TO PREVENT , STABILIZERS TITANIUM OR NIOBIUM ADDED IN SMALL OMUNTS. • NON-MAGNETIC, SCALE RESISTANCE, TOUGH, FORGED, ROLLED, DUCTILITY • AIRCRAFT, MILK CANSHEAT EXCHANGER ETC

• • FERRITIC SS FERRITIC STRUCTURE UPTO MELTING TEMP 12 -25% OF Cr & LESS THAN 0. 1% CARBON MAY BE STRENGTHENED BY WORK HARDENING MAGNETIC, TOUGHNESSWELDE, FORGED, ROLLED CON’T BE HEAT TREATED C-0. 08% TO 0. 1%, Si – 1% Mn – 1 TO 1. 5% HEATING ELEMENTS FOR FURNACE, INTERIOR DECORATIVE WORK, OIL BURNER PARTS

MARTENSITIC SS • 12 -25% OF Cr & LESS THAN 0. 1 TO 1. 5% CARBON • COMPOSITIONS HEATED TO AUSTENITIC RANG AND TRANSFORMS TO MARTENSITE BY SUITABLE COOLING RATES. • HARDNESS, DUCTILITY, THERMAL CONDUCTIVITY • PUMPS, VALVE PARTS, TUBINE BUCKETS SURGICAL INDUSTRIES.

TOOL STEELS • SHAPING A MTRL INTO COMPONENT • PROPERTIES • TOUGHNES, WEAR RESISTANCE, GOOD MACHINABILTY, RESIST SOFTENING OF STEEL ON HEATING, SLIGHT CHANGE OF FORM DURING HARDENING • WIDELY USED HSS 18 -4 -1 HSS • 18% TUNGSTEN, 4% -Cr, 1% V • Mo –CHEAPER ALLOY AND TWICE EFFECT AS TUNGSTEN • COBALT HSS- SUPER HSS 20% TUNGSTEN, 12% COBALT, 4% Cr, 2% V

MARAGING STEELS • LOW CARBON, HIGH ALLOY STEELS • VERY HIGH STRENGTH MATERIALS , HARDENED UPTO 1900 Mp. A TENSILE STRENGTH • 18 % Ni, 7% Co, LESS THAN 0. 05% TITANIUM • MARTENSITE FORMED UPON COOLING(AIR) FROM AUSTENITIC • COLD WORKED, HARDENED BY PRECIPITATION TEMP • HIGH TENSILE STRENGTH, IMPACT STRENGTH, SURFACE HARDENING BY NITRIDING • DRIVE SHAFTS, BARRELS, DIES, SPACE –VEHICLES CASES.

CAST IRONS • CARBON- 3 -4%, SULPHUR – 0. 1%, SILICON 01 -3%, PHOSPOROUS – 1. 0%, Mn-0. 5 – 1. 0% • CHEAP METULLURGICAL METAL • GOOD MECHANICAL RIGIDITY, CASTABILITY, MACHINABILITY • EFFECT OF ALLOY IN CI • CARBON • PRESENT AS FLAKES OF GRAPHITE, NETWORK OF HARD • CEMENTITE IS SILVERY WHITE COMPOUND , IF BROKEN WHITE IN COLOUR[WHIT IRON] • IF CI CONTAINS MORE GRAPHITE BROKEN, GREY IN COLOUR[GREY IRON]

NON FERROUS METALS LIGHT WEIGHT HIGH ELECTRICAL & THERMAL CONDUCTIVITY CORROSION RESISTANCE CASTING, ROLLING, FORGING, WELDING AND MACHINING ARE EASY • COLOUR • IMPORTANT METAL ARE CU, AL, LEADF, TIN, NI, TI, ZINC, MG ETC • •

IMPORTANT CU ALLOYS • BRASSES, BRONZES, GUN METAL, CUPRONICKEL 1. BRASS CU + ZINC SMALL AMOUNT OF TIN , LEAD, ALUMINIUM, MN ADDED MELTING POINT 800 TO 1000’C, NON MAGNETIC, POOR CONDUCTOR OF ELECTRICITY SOFT, DUCTILE, GOOD SURFACE FINISH , HIGH TENSILE STRENGTH WITH FUSABILITY 36% ZINC , BRASS IS SINGLE PHASE SOLID SOLUTION- ALPHA BRASSES BRASS STRONGER THAN CU EXPENSIVE TYPES – DEPENDS ON ZINC AND CU GLIDING, STD, MUNTZ, ADMIRALTY, HIGH TENSILE BRASS, FREE CUTTING BRASS

2. BRONZE • 75 -95%CU+5 -25%TIN • INCLUDES AL, SI, NICKEL • BRONZE STRENGTH INCREASES BY ADDING TIN • MORE THAN 12% TIN LEADS TO BRITTLE • HIGH STRENGTH ALLOYS WITH A GOOD CORROSION RESISTANCE THAN BRASS • TYPES 1. PHOSPHOR BRONZE CU-87 -90%, TIN-9 -10%, PHOSPHORUS 0. 1 -0. 8% PHOSPHORUS IMPROVES STRENGTH, DUCTILITY, SOUNDNESS OF CASTINGS RESISTANT TO SALT WATER, GOOD WEARING QUALITY, BEARING, WORM WHEEL GEARS, SPRINGS, PUMP PARTS

SILICON BRONZE • 96% CU, 3% SI, 1% MN • CORROSION RESISTANCE WITH HIGH STRENGTH • CASTROLLED, STAMPED, FORGED PRESSED • BOILERS, TANKS BERYLLIUM BRONZE • 97. 75% CU, 2. 25% BERYLLIUM • HGH YEILD POINT, FATIGUE LIMIT • EXCELLENT COLD & HOT CORROSION RESISTANCE • WEAR RESISTANCE 5 TIME THAN PHOSPHOR BRONZE • ELECTRICAL SWITCHES, CAMS, BUSHES

MANGANESE BRONZE 60% CU, ZINC – 35% , 5% - MANGANESE HARDER & STRONGER THAN PHOSPHOR BRONZE WORM GEARS, PLUNGERS, BUSHES ALUMINIUM BRONZE 6 -8% AL, DUCTILITY IMPROVED GEAR, PROPELLERS, AIR PUMPS, SLIDED VALVES ETC GUN METAL • CU+TIN+ZINC • ZINC – DEOXIDISER , CASTABILITY & MACHINABILITY • TYPES • ADMIRALTY, LEADED GUN METAL

CUPRONICKELS STRENGTHENING IMPURITIES LIKE IRON, MANGANESE DUCTILE AND MALLEABLE MORE CORROSION RESISTANCE THAN COPPER ALLOYS IN SEA WATER SILVER COLOURED MODERN CIRCULATION COINS -75% CU, 25% NI AND TRACE AMOUNT OF MANGANESE USED IN THERMOCOUPLES -55% CU, 45% NI BOATS, COINS, PROPELLERS, CRANKSHAFTS ALUMINIUM ALLOYS HEAT TREATABLE ALLOYS Al-cu, al-cu-ni, al-mg-si, al-zn-cu, al-li NON HEAT TREATABLE ALLOYS AL-MN. AL-MG, AL-SI

AL-CU ALLOYS 1. DURALUMIN 3. 5 -4. 5% CU, 0. 4 -0. 7 % MN, 0. 4 -0. 7 % MG AL REMAINING BARS, SHEETS, TUBES, RIVETS ETC AGE HARDENING PROPRTY 2. Y-ALLOY 3. 5 -4. 5% CU, 1. 8 -2. 3 % MN, 1. 2 -1. 7%MG GOOD STRENGTH AT HIGH TEMPERATURE PISTON, COMPONENTS IN AERO ENGINES MIN TENSILE STRENGTH OF 350 N/MM 2

BEARING MATERIALS • USED FOR MAKING BEARINGS • LOW COEFFICIENT OF FRICTION, TOUGHNESS, HIGH THERMAL CONDUCTIVITY, CORROSION RESISTANCE, CASTING QUALITIES ETC • WIDELY USED MATERIALS • 1. WHITE METAL • COPPERBASE METALS • AL BASE MEATLS • PLASTICS • CERAMICS

WHITE METALS • TIN BASED OR LEAD BASED ALLOYS • 10% OF ANTIMONY , THIS METAL COMBINES WITH TIN TO INTER METALLIC COMPOUND WITH SMALL HARD CUBIC CRYSTAL CALLED CUBIODS – HARD AND LOW FRICTION TIN BASE ALLOYS • ALSO NAMED AS BABBIT METALS • Sb 10% SN 82% Cu 4% Pb 4% • USED IN AUTOMOBILE INDUSTRIES LEAD BASED ALLOYS • CHEAPER THAN TIN BASED METALS • LOW PRESSURE LOW SPEED APPLICATION.

COPPER-BASE ALLOYS • PLAIN TIN ALLOYS, PHOSPOR ALLOYS, LEAD ALLOYS, SINTERED ALLOYS • PHOSPHOR ALLOYS USED AS LOAD BEARING CAPACITY • LEADED ALLOYS SUSTAIN HIGHER LOADS AT HIGHER SPEEDS THAN WHITE METALS • SINTERED BRONZE MADE BY COMPACTING AND SINTERING Cu- Sn POWDER. • AERO ENGINES, CRANKSHAFT BEARINGS, VACUUM CLEANERS, WASHING MACHINE ETC

AL BASED METAL • TIN, COPPER, NICKEL ALLOYS ARE MOSTLY USED • EXPENSIVE TIN BASE BEARING ALLOYS REPLACED BY THIS ALLOYS • BIG END BEARINGS IN AUTOMOBILE. PLASTIC BEARING • NYLONS AND POLY TETRA FLURO ETHYLENE • LOW LOAD APPLICATION CERAMIC BEARING METALS • USED AS SMALL PRECISION INSTRUMENTS, WATCHES • ALUMINA USED IN LARGE SPEED PRECISION INSTRUMENTS

PRECIPITATION HARDENING OR AGE HARDEING IMPROVING PHYSICAL PROPERTIES OF NON FERROUS METALS APPLICABLE TO AL, MG, NI ALLOYS OF AL-CU, CU-BERYLIUM, CU-TIN, MG-AL FINE PRECIPITATE PARTICLES OF NEW PHASE THREE STEPS STEP 1 -SOLUTION TREATMENT HEATED ABOVE SOLVUS TEMP TO OBTAIN SOLID SOLUTION HELD AT THIS TEMP TO GET UNIFORM HOMOGENEOUS SOLID SOLN.

STEP 2 QUENCHING PROCESS QUENCHED RAPIDLY COOLED