Chapter Questions
(a) List the four classifications of steels. (b) For each, briefly describe the properties and typical applications.
(a) Cite three reasons why ferrous alloys are used so extensively. (b) Cite three characteristics of ferrous alloys that limit their utilization.
What is the function of alloying elements in tool steels?
Compute the volume percent of graphite $V_{\text {Gi }}$ in a $2.5 \mathrm{wt} \% \mathrm{C}$ cast iron, assuming that all the carbon exists as the graphite phase. Assume densities of 7.9 and $2.3 \mathrm{~g} / \mathrm{cm}^3$ for ferrite and graphite, respectively.
On the basis of microstructure, briefly explain why gray iron is brittle and weak in tension.
Compare gray and malleable cast irons with respect to (a) composition and heat treatment, (b) microstructure, and (c) mechanical characteristics.
Compare white and nodular cast irons with respect to (a) composition and heat treatment, (b) microstructure, and (c) mechanical characteristics.
Is it possible to produce malleable cast iron in pieces having large cross-sectional dimensions? Why or why not?ferrous Alloys
What is the principal difference between wrought and cast alloys?
Why must rivets of a 2017 aluminum alloy be refrigerated before they are used?
What is the chief difference between heattreatable and non-heat-treatable alloys?
Give the distinctive features, limitations, and applications of the following alloy groups: titanium alloys, refractory metals, superalloys, and noble metals.
Cite advantages and disadvantages of hot working and cold working.
(a) Cite advantages of forming metals by extrusion as opposed to rolling. (b) Cite some disadvantages.
List four situations in which casting is the preferred fabrication technique.
Compare sand, die, investment, lost foam, and continuous casting techniques.
If it is assumed that, for steel alloys, the average cooling rate of the heat-affected zone in the vicinity of a weld is $10^{\circ} \mathrm{C} / \mathrm{s}$, compare the microstructures and associated properties that will result for 1080 (eutectoid) and 4340 alloys in their HAZs.
Describe one problem that might exist with a steel weld that was cooled very rapidly.
In your own words describe the following heat treatment procedures for steels and, for each, the intended final microstructure: full annealing, normalizing, quenching, and tempering.
Cite three sources of internal residual stresses in metal components. What are two possible adverse consequences of these stresses?
Give the approximate minimum temperature at which it is possible to austenitize each of the following iron-carbon alloys during a normalizing heat treatment: (a) $0.15 \mathrm{wt} \% \mathrm{C}$, (b) $0.50 \mathrm{wt} \% \mathrm{C}$, and (c) $1.10 \mathrm{wt} \% \mathrm{C}$.
Give the approximate temperature at which it is desirable to heat each of the following iron-carbon alloys during a full anneal heat treatment: (a) $0.20 \mathrm{wt} \% \mathrm{C}$, (b) $0.60 \mathrm{wt} \% \mathrm{C}$, (c) $0.76 \mathrm{wt} \% \mathrm{C}$, and (d) $0.95 \mathrm{wt} \% \mathrm{C}$.
What is the purpose of a spheroidizing heat treatment? On what classes of alloys is it normally used?
Briefly explain the difference between hardness and hardenability.
What influence does the presence of alloying elements (other than carbon) have on the shape of a hardenability curve?
How would you expect a decrease in the austenite grain size to affect the hardenability of a steel alloy? Why?
Name two thermal properties of a liquid medium that will influence its quenching effectiveness.
Construct radial hardness profiles for the following:(a) A $75-\mathrm{mm}$ (3-in.) diameter cylindrical specimen of an 8640 steel alloy that has been quenched in moderately agitated oil(b) A $50-\mathrm{mm}(2-\mathrm{in}$.$) diameter cylindrical$ specimen of a 5140 steel alloy that has been quenched in moderately agitated oil(c) A $90-\mathrm{mm}\left(3 \frac{1}{2}-\mathrm{in}\right.$.) diameter cylindrical specimen of an 8630 steel alloy that has been quenched in moderately agitated water(d) A $100-\mathrm{mm}$ (4-in.) diameter cylindrical specimen of an 8660 steel alloy that has been quenched in moderately agitated water
Compare the effectiveness of quenching in moderately agitated water and oil, by graphing on a single plot radial hardness profiles for $75-\mathrm{mm}(3-\mathrm{in}$.) diameter cylindrical specimens of an 8640 steel that have been quenched in both media.ecipitation Hardening
Compare precipitation hardening (Section 11.9 ) and the hardening of steel by quenching and tempering (Sections 10.5, 10.6, and 10.8 ) with regard to(a) The total heat treatment procedure(b) The microstructures that develop(c) How the mechanical properties change during the several heat treatment stages
What is the principal difference between natural and artificial aging processes?