Metallurgy Engineering Interview Questions and Answers
Question - 41 : - How Much Gold Is In A Troy Ounce?
Answer - 41 : -
Troy ounce defined by the troy system of mass. In troy weight, there are 12 ounces in a pound, and a troy pound is 5760 grains (about 373.24 g), rather than 7000 (about 453.59 g). Note: at roughly 31.10 g, the troy ounce is about 10 per cent more than the morecommon avoirdupois ounce. These troy ounces are now used only when weighing precious metals like gold and silver. One ounce of gold is always 31.1 g.
Question - 42 : - What Is A Silver And Deming Drill Bit?
Answer - 42 : -
Silver and Denim is the name of a manufacturing company. This company could trace its history back to 1854, although the "Silver & Deming" name does not date back that far. The titular heads were Albert R. Silver and John Deming. Silver & Deming made a variety of machines that were primarily aimed at wheelwrights: hobboxing machines, spoketenoning machines, etc.
Silver & Deming apparently invented the largesize twist drill bit with a turneddown shaft so they can be used in a chuck smaller than the bit's cutting diameter. They did not patent this idea, so the idea was quickly copied by others, but these bits are still called "Silver & Deming drills".
Question - 43 : - Which Is Stronger, Tungsten Or Titanium?
Answer - 43 : -
Tungsten has high tensile strength and good creep resistance. At temperatures above 2205 OC (4000 OF), tungsten has twice the tensile strength of the strongest tantalum alloys and is only 10% denser. However, its high density, poor lowtemperature ductility, and strong reactivity in air limit its usefulness. Maximum service temperatures for tungsten range from 1925 to 2480 "C (3500 to 4500 OF), but surface protection is required for use in air at these temperatures.
Wrought tungsten (as cold worked) has high strength, directional mechanical properties, and some roomtemperature toughness. However, re crystallization occurs rapidly above 1370 "C (2500 OF) and produces a grain structure that is crack sensitive at all temperatures.
Question - 44 : - When Austenitized, Carbon Steel Is Quenched, Why Is The Bcc Crystal Elongated Into A Bodycentered Tetragonal Crystal Structure?
Answer - 44 : -
Martensite crystals ideally have planar interfaces with the parent austenite. The preferred crystal planes of the austenite on which the martensite crystals form are designated habit planes, which vary according to alloy composition. In steels, the parent phase is usually austenite with a facecentered cubic (fcc) crystal structure, but the crystal structure of the product phase may be bodycentered cubic (bcc). Under special conditions, steels undergo martensitic transformations in which the crystal structure of the product phase reverts to that of the parent. Most mediumcarbon and highcarbon steels form martensite with a bct crystal structure, because carbon atoms occupy only one of the three possible sets of octahedral interstitial positions.
Allotropy means the property by which certain elements (like Fe) may exist in more than one crystal structure. Iron exists in two allotropic forms: BCC and FCC. In other words at 700°C (1290°F) it undergoes an allotropic transformation from FCC to BCC (in quenching, i.e. iron has FCC structure above this temperature and BCC structure below that).
Question - 45 : - What Are Ceramics?
Answer - 45 : -
The word ceramic is derived from the Greek word keramikos, "having to do with pottery". The term covers inorganic nonmetallic materials whose formation is due to the action of heat. Up until the 1950s or so, the most important of these were the traditional clays, made into pottery, bricks, tiles and the like, along with cements and glass.
Historically, ceramic products have been hard, porous, and brittle. Technical Ceramics can also be classified into three distinct material categories:
- Oxides: Alumina, zirconia
- Nonoxides: Carbides, borides, nitrides, silicides
- Composites: Particulate reinforced combinations of oxides and nonoxides.
Ceramic materials can be crystalline or amorphous. They tend to fracture before any plastic deformation takes place, which results in poor toughness in these materials. Additionally, because these materials tend to be porous, the pores and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the tensile strength. These combine to give catastrophic failures, as opposed to the normally much more gentle failure modes of metals.
Question - 46 : - What Medal Conducts Heat Best?
Answer - 46 : -
In physics, thermal conductivity, (showed by the Latin capital of land), is the intensive property of a material which relates its ability to conduct heat.
Thermal conductivity is the quantity of heat, Q, transmitted through a thickness L, in a direction normal to a surface of area A, due to a temperature gradient (delta T), under steady state conditions and when the heat transfer is dependent only on the temperature gradient. In general, thermal conductivity tracks electrical conductivity metals being good thermal conductors.
There are exceptions: the most outstanding is that of diamond, which has a high thermal conductivity, between 1000, and 2600 W/mk, while its electrical conductivity is low.
Question - 47 : - What Affect Would Increasing The Charpy Impact Toughness On An Object Have On The Surface Of An Object It Strikes If All Else Remains The Same? Would It Cause More Damage To The Object It Strikes?
Answer - 47 : -
Charpy toughness is a measure of the metals ability to resist tearing or to absorb energy during an impact. Generally, we achieve that by altering the microstructure to be more ductile.
In the quenched and tempered alloys (steels) for example, that involves tempering to convert the hard brittle martensite to softer more ductile bainite or a ferrite carbide mixture.
Therefore, we are making a softer metal; therefore, if it affects another object it would tend to deform more.
There would be less damage to the object being struck because the striking object would deform more and distribute its load across more of the surface of the object being struck.
Question - 48 : - What Is The Difference Between Stainless Steel And Alloy Steel?
Answer - 48 : -
Stainless steels have at least 11 to 12% chromium in the alloy. Why 11 to 12% minimum you might ask? That much is required to provide a continuous layer of protective chromium oxide on the surface. Alloy steel just means that there are additional elements added to the ironcarbon.
Question - 49 : - What Kind Of Cleaning Substance Or Treatments Keep Or Help Prevent Cast Iron From Rusting?
Answer - 49 : -
Cast iron is a mixture of graphite (carbon) flakes in a matrix of steel (iron with carbon in solution). The graphite, which has the shape of corn flakes, does not contribute much to strength. If anything, it makes the cast iron somewhat porous or sponge like. The graphite does makes it easy to machine and has a dampening effect on the cast iron. However, it also makes for a lot of surface area, which allows plenty of air (oxygen) to get to the iron and form rust.
Question - 50 : - Is Nickel Considered A Non-sparking Metal?
Answer - 50 : -
Monel and nickel form almost identical spark streams. The sparks are small in volume and orange in color. The sparks form wavy streaks with no sparklers.
So is not as bright as sparks of ferrous alloys. Therefore, that is a way to identify nickel and monel.