2. Ferrous/Non-Ferrous

List the four classifications of steels. For each classification, briefly describe the properties and typical applications.
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List the four classifications of steels. For each classification, briefly describe the properties and typical applications.
• Low-carbon, medium-carbon, high-carbon and high alloy steels.
• Low-C steel (<0.25 wt.% C), medium-C (0.25 - 0.6 wt.% C), high-C 0.6- 1.4wt.%C)
• Properties vary from soft-low-generic for low-C to hard-high-specialised for highC steels; high alloy steels (stainless) are 0.6-1.4 wt.%C + 11.0 wt.%C +other
Cite three reasons why ferrous alloys are used so extensively.
(1) Fe-compounds are abundant; (2) economical extraction, refining, and fabrication techniques are available; (3) Fe-alloy properties may be tailored to have a wide variety of mechanical and physical properties.
Cite three characteristics of ferrous alloys that limit their use.
(1)Relatively high densities;
(2) Comparatively low electrical conductivities;
(3) Susceptibility to corrosion in common environments
Which steels are used to make tools. Why?
High-carbon steels; contain perlitic structure, hard and strong, can be alloyed and effectively heat treated;
What is the function of alloying elements in tool steels?
High-C steels contain alloying ceramic compounds forming an exceptionally hard and wear resistant alloy (e.g., Cr23C6, V4C3, WC, BN, SiC); these dissipate heat, hold a sharp edge, provide resistance to oxidation, etc.
What are the most common alloying elements in cast iron alloys?
Cast irons contain 2.14 - 4.5 wt.% C and other alloying elements, such as 1.0 - 3.0 wt.% Si (most common), Mo, S, and others.
List five types of cast irons and briefly describe their characteristics and properties.
Grey, ductile (nodular), white, malleable and compacted graphite;
• Grey: (2.5-4.0 wt.% C, 1.0-3.0 wt.% Si), cheap, weak and brittle;
• Ductile: (C and Si same as in grey + Mg, Ce -> perlite is sphere-like), properties better than of grey, properties closer to low-C steel;
• White: (C same as grey; 1.0 wt.% Si only -> cementite), white, hard, wear resistant;
• Malleable: (C and Si same as in white; cementite converted to graphite at high T and under Ar); properties similar to medium-C steel; malleable and cheap;
• Compacted graphite iron (CGI) (3.1-4.0 wt.% C, 1.0-3.0wt.% Si, wormlike microstructure), EL~3% (low), high T conductivity, excellent resistance to T shock, low oxidation
What types of properties do non-ferrous metals possess that may not be available in the ferrous metals?
Non-Fe metals often possess certain properties not usually associated with ferrous metals, among them are: • corrosion resistance,
• ease of fabrication,
• high electrical and thermal conductivity,
• light weight,
• strength at elevated temperatures and
• colour
In what respects are the nonferrous metals generally inferior to steel?
The non-Fe alloys are generally inferior to steel in terms of:
• strength (yield and UTS)
• elastic modulus
• weldability
In what ways might the non-ferrous metals offer attractive ease of fabrication?
• Alloys with low melting points are often easy to cast, using sand moulds, permanent moulds, or dies;
• Many non-Fe alloys have high ductility coupled with low yield points, the ideal conditions for cold working;
• Good machinability is also a common characteristic;
What are the three properties of Copper and Copper Alloys that account for many of their uses and applications?• high electrical and thermal conductivity; • high ductility • corrosion resistanceWhat properties make Copper attractive for cold-working processes?• relatively low strength • high ductility In addition, by cold-working, the tensile strength can be raised from about 200 MPa to over 300 MPa, with a concurrent drop in EL from 60% to about 5%. The low recrystallisation T is attractive when additional cold working is desired.What are limiting properties of Copper that might restrict its area of application?• high density - heavier than Fe; • strength-to-weight comparisons place it below most engineering metals. In addition, some significant problems can occur when the metal is used at elevated T.What properties of Copper make it attractive for low-temperature applications?• strength of Cu increases as T drops; • material does not embrittle at low T; • %EL is retained, even under cryogenic T conditions; • electrical conductivity increases as T dropsWhat are some potential applications that would make use of Copper's antimicrobial properties?• door knobs; • sink handles; • HVAC components; Cu alloys are widely uses in public places, like hospitals, schools, public buildings, exercise facilities, nursing homes, shopping malls, mass transit facilities, airports, etc.Why might cold-worked brass require a stress relief prior to being placed in service?Brasses are susceptible to stress corrosion cracking. Stress corrosion requires a • hostile environment, and • stress To reduce the net stress acting in service, residual stress can be removed or reduced by a stress relief processDescribe the somewhat unique properties available with heat treated Copper-Beryllium (Cu-Be or BeCu) alloys.BeCu alloys can be age hardened to produce the highest strengths of the copper-based metals. In addition to having strengths similar to steel, the alloys are • non-sparking, • nonmagnetic, and • have high electrical and thermal conductivity.What are some of the attractive engineering properties of Aluminium and Aluminium Alloys?Al and Al-alloys have achieved popularity due to their • light weight, • high electrical and thermal conductivity, • good corrosion resistance, • workability, • variety of available finishes, and • recyclability.How does Al compare to steel in terms of weight? Discuss the merits of comparing cost per unit weight vs. cost per unit volume.A given volume of Al is about 1/3 the weight of the same volume of steel. The density of Al is about 2.7 g/cm3 while for steel density is about 7.9 g/cm3 . In manufacturing operations both cost per unit weight and cost per unit volume are useful quantities. If the volume of a particular part will be the same whether it is made of Al or steel, the relevant material cost for the part is cost per unit volume of material. Cost per unit weight is the more commonly cited value.What is primary benefit of Aluminium recycling compared to making new Aluminium from ore?The recycling of Al saves 95% of the energy required to process Al from ore.How does Al compare to Cu in terms of electrical conductivity?The electrical conductivity of pure Al is approximately • 62% that of Cu for the same size wire, and • 200% that of Cu on an equal weight basis;What features might limit the mechanical uses and applications of Aluminium and Aluminium alloys?Al alloys are • inferior to steel in the area of elastic modulus. In addition, the • wear, • creep, and • fatigue properties are generally rather poor. In addition, Al loses a significant portion of its strength when heated to T much above 175 °C.How are the wrought alloys distinguished from the cast alloys in the Aluminium designation system? Why would these two group of metals have distinctly different properties?Wrought means "worked" and the wrought Al alloys are designed to have properties that are desirable for making worked or formed parts. Mechanical properties that are desirable for making formed parts include • low yield strength, high ductility, high toughness, and high strain hardening rate if high strength is desired in the finished part. Cast or casting alloys are designed to have properties desirable for making cast parts. For example, casting alloys have • low melting temperature, high fluidity when molten and desirable assolidified structures and properties. In the aluminum system, wrought alloys are identified by a four-digit number, while cast alloys have a three-digit designation.What are some possible applications of Aluminium foams?Aluminium foam has been used in a number of applications relating to automotive, aerospace, military, architecture and design. Race cars have used the material for its excellent • energy absorption. It also offers excellent • thermal insulation and • sound and • vibration damping, and can be used inside tubes to impart • crush resistance.What are some attractive and restrictive properties of Magnesium and Magnesium Alloys?The most attractive property of magnesium is its • light weight and • companion good strength-to-weight ratio. Unfortunately, magnesium and magnesium alloys can also be characterised by poor • wear, • creep, • fatigue, and • corrosion resistance properties when in galvanic couples. The modulus of elasticity is low and the alloys possess limited ductility.Describe the designation system applied to magnesium alloys.The magnesium alloys classification utilises: • one or two prefix letters to specify the two largest alloying additions, • two or three numerals that specify the percentages of the two main alloying metals, • sometimes an appended letter to denote a base alloy variation, • sometimes a suffix to designate material temper.What is the most popular fabrication process applied to Magnesium alloys?Die casting is the most popular fabrication process for magnesium and magnesium alloys, accounting for 70% of all magnesium castings.Under what conditions should Magnesium be considered to be a flammable or explosive material?Magnesium is flammable or explosive when it is in a finely-divided form, such as powder or chips. A critical feature here is the ratio of surface area to volume. In addition, magnesium is flammable when heated above 425 °C in the presence of oxygen.What are the primary application of pure zinc? Of zinc-based engineering alloys?The primary application of pure zinc is the galvanising of iron and steel. The principal use of the zinc-based alloys is in die-casting operations. Zn-based alloys are low in cost, have low melting points, do not affect steel dies adversely, and can possess good strength and dimensional stability.What are some of attractive engineering properties of Titanium and Titanium alloys?Titanium and its alloys are • strong, • lightweight, • corrosion resistant, and • offer strengths similar to steel at temperatures up to 480 °CUnder what conditions might Titanium replace steel? or replace Aluminium?Titanium alloys are often used in place of steel when weight saving is desired, and in place of aluminium where high-temperature performance is required.