Metal Alloys ( 금속 합금 )

Metal Alloys (금속합금) Associate Professor Su-Jin Kim School of Mechanical Engineering Gyeongsang National University

Metal Alloys(금속) Metal Alloy (금속합금) Nonferrous (비철금속) Ferrous (철) … alloy Aluminum alloy Copper alloy Cast Irons (주철) Steels (강) 3.0~4.5% C<1.4%

Ferrous Alloys (철) • Ferrous alloys are useful metals in terms of mechanical, physical and chemical properties. • Alloys contain ironFe (density 7.9 g/cm3) as their base metal. • Carbon steels (700W/kg) are least expensive of all metals while stainless steels (7,000W/kg) is costly.

Steels (강) Composition and processing are controlled in a manner that is suitable for different applications. Several elements are added to steels for Strength(강도), Hardness(경도), Toughness(인성) Hardenability(경화성), Wear resistance(내마모성) Workability(가공성), Weldability(용접성), Machinability(절삭성)

Steels Carbon steel (탄소강) High alloy steel (고합급강) Low carbon (저탄소강) C < .25 % Med carbon (중탄소강) .25-.60% High carbon (고탄소강) .60-1.40% Heat Treatable (열처리) Stainless (스테인리스) Tool (공구) Plain Plain HSLA (고강도) Plain 304, 409 SUS304 1010 S10C 4310 SNCM10 1040 S40C 4340 SNCM40 4190 KD11 1095 high T pistons auto bridges crank wear drills turbines gears struc. towers shafts applic. saws furnaces wear sheet press. bolts dies corrosion applic. vessels hammers resistant ductility strength, hardenability, cost

Steels AISI/SAE JIS/KS Nomenclature(조성) for steels 10xx SxxC Plain Carbon Steels (탄소강) 40xx SMoxx Mo (.2 ~ .3%) 41xx SCMxx Cr (.80~1.1), Mo (.15~.25) 43xx SNCMxx Ni (1.65 ~ 2.0), Cr (.4 ~ .9), Mo (.2~.3) where xx is % C x 100 Ex) 1045 S45C – Plain Carbon Steel with 0.45 % C Stainless Steel 304 SUS304 Cr (11%~)

Carbon steels (탄소강) • Classified as low, medium and high: • Low-carbon steel or mild steel,C< 0.25%, bolts, nuts and sheet plates. • Medium-carbon steel, 0.25% ~ 0.60%, machinery, automotive and agricultural equipment. • High-carbon steel, C > 0.60%, springs, cutlery, cable. • Ex) S10C S45C

Alloy steels (합금강) • Steels containing significant amounts of alloying elements. • Structural-grade alloy steels used for construction industries due to high strength. • Other alloy steels are used for its strength, hardness, resistance to creep and fatigue, and toughness. • It may heat treated to obtain the desired properties.

HSLA High-strength low-alloy steels (고강도 저합금강) • Improved strength-to-weight ratio. • Used in automobile bodies to reduce weight and in structural plate.

Tool & Die steels (공구강 금형강) • Designed for high strength, impact toughness, and wear resistance at a range of temperatures. Ex) SKD11 SKD61 NAK80

Stainless steels • Characterized by their corrosion resistance, high strength and ductility, and high chromium content( Cr >11%). • Stainless as a film of chromium oxide protects the metal from corrosion. • It resist oxidization and maintain mechanical integrity at high temperature (1000°C).

Posco • Hot rolled steel, Steel plate, Wire rod, Cold rolled steel, Electric steel, Stainless steel, Galvanized steel, Titanium Posco http://www.posco.co.kr

Cast Irons (주철) Ferrous alloys with 3.0 ~4.5% C Low melting point  relatively easy to cast Generally brittle Cementite decomposes to ferrite + graphite Fe3C  3 Fe () + C (graphite) : slow process

Cast Irons Gray iron(회주철) graphite flakes weak & brittle in tension stronger in compression excellent vibrational dampening wear resistant Ductile iron(연주철) add Mg and/or Ce graphite as nodules not flakes matrix often pearlite – stronger but less ductile

Cast Irons White iron(백주철) < 1 wt% Si pearlite + cementite very hard and brittle Malleable iron(가단주철) heat treat white iron at 800-900ºC graphite in rosettes reasonably strong and ductile

Cast Irons 가열 급랭 서랭 연주철 회주철 백주철 가단주철

Metal Alloys ( 금속 합금 )