Hot-rolled steels contain an oxide scale over their surface. It is formed during the heating process. Accordingly dimensional tolerances are not tight. In cold-rolled steels, the scale is removed before cold rolling process and thus the surface finish is very good in this case. Thus its dimensions are held within closer tolerances. Low-carbon cold rolled steels are easier to machine.
Describe the following alloy steels : (a) Case-hardening steels (b) Nitriding steels (c) High-tensile steels (d) Wear-resisting steels (e) Corrosion-resisting steels (f ) Heat-resisting steels.
(a) Case hardening steels-These usually contain less than 0.15% carbon. As carbon content is low, the core does not respond to hardening. By adding about 3% nickel and 0.45% manganese, these do not require further refining after carburising. Such a steel can be water-quenched and is used for
(a) What do you understand by killed steel? (b) What is 'piping' in steel and how it can be minimised ?
(a) Steels in which no gas evolution occurs on solidification are called killed steels.
(b) When the steel cools in the mould, shrinkage of the steel on solidifying causes 'piping usually in the upper portion of the ingot. This can be minimised by using a large-end-up mould with a refractory 'hot top' which supplies molten steel to the main body of the ingot while solidificati
(a) Distinguish between plain carbon steel and alloy steel.
(b) How the mechanical properties of an untreated plain carbon steel are influenced by increase in the carbon content ?
(a) Plain carbon steel is one which owes its distinctive properties chiefly to the carbon it contains.
An alloy steel is one which owes its distinctive properties chiefly to some element or elements other than carbon, or jointly to such other elements and carbon. The other elements are deliberatel
(a) What do you understand by steel? (b) What is the difference between hypo-eutectoid and hyper-eutectoid steels ? (c) How the plain carbon steels are classified depending upon carbon content ?
(a) Steel is a malleable alloy of iron and carbon, usually containing substantial quantities of manganese.
b) Hypo-eutectoid steels are those which contain less than approximately 0.9% carbon whereas hyper-eutectoid steels contain more than 0.9% carbon.
(c) The plain carbon steels a
(a) Give the ages of carbon in (i) low carbon steels, (ii) medium carbon steels, (iii) high carbon steels.
(b) Give the %age of the alloying elements in (i) low alloy steels and (ii) high alloy steels.
(c) All cast irons contain at least six elements. Name these elements.
(d) When will you recommend carburising of steel ? Give salient features of the process. (e) Give the composition and use of (i) Bronze, (ii) Duralumin.
(a) Carbon in low carbon steel : < 0.25%, me
Defects in a lattice structure of a crystalline material are :
(i) Point Defect. It occurs when an imperfection is restricted to the neighbourhood of a lattice point. Fig. 1.16 illustrates the three different types of point defects. In Fig. 1.16 (a) one lattice atom is missing, creating a vacancy. Since an atom vibrates about its lattice position,
the tendency of the atom to jump out of its regular position creating a vacancy increases rapidly with temperature. It is possible to i
The crystal structure of Iron is bcc (body centered cubic)
Chromium is bcc (body centered cubic)
Tungsten is bcc (body centered cubic)
Nickel is foc (face-centered cubic)
Zinc is cph (close packed hexagonal)
A Journal of Applied Mechanics and Mathematics by DrD, #48-B
Mass On Multiple Spring Supports
The previous post, #48 titled Mass on Multiple Spring Supports had several typographical errors. Strangely, they are all in the brief introductory example regarding the loads on the four legs
What is Gear Ratio and What is Torque Ratio definition.
गीयर रेशों क्या होती है और टार्क रेशो क्या होती है वर्णन कीजिए।
गीयर अनुपात ( Gear Ratio ) जब दो गीयर जिनके दाँते बराबर हो एक - दूसरे को चलाये तो एक के चलाने पर दूसरा भी उसी स्पीड में चलेगा जिसमें उसकी गियर रेशो 1 : 1 होगी। अगर एक छोटा गियर जिसके छ: दांते हैं एक बड़े 18 दाँतों वाले के गीयर को चलाता है। अगर छो
A Journal of Applied Mechanics and Mathematics by DrD, #48
Mass On Multiple Spring Supports
One of the classic problems of elementary mechanics is to determine the load on each leg of a four-legged table. The table top is assumed to be a uniform rectangle, the legs are of equal length, the center of mass is the centroid of the table top, and the floor is level. What is the load in ea
A Journal of Applied Mechanics and Mathematics by DrD, #47
What Makes a Ship Move?
One of the problems that often confronts engineers is the description of large, interconnected systems. Engineers tend to specialize, so that one is very knowledgeable on gears, another knows bearings, a third knows pumps, but none of them are comfortable with the whole system. In the automotive context, this is often exp