Metallurgy Engineering Interview Questions and Answers
Question - 21 : - We Make Aluminum Moulds By Press Casting, Can U Suggest Any Thing So That The Moulds Should Shine After Casting?
Answer - 21 : -
Shininess of castings depends on the surface quality of cast parts. Casting surface finish is always a function of mold surface and characteristics. The selection of mold materials and the accuracy of mold finish maintained in premium casting operations ensure that specified requirements are met.
Sometimes there is the possibility of increasing surface finish of castings by increasing their surface tension. This is done for aluminum alloys by allowing formation of oxide inclusions, the most important of which is Al2O3, in the molten metal. The increase in surface tension prevents molten metal from penetrating into the mold depressions since as you know surface finish improves when the melt solidifies in contact with air. However, such a resolution is accompanied by decrease in mechanical properties of castings, as oxides will act as stress concentration sites.
By the way, I have not heard about usage of grain refiners as shine promoters for aluminum castings, though their application in such cases may rely on the same mechanism.
Question - 22 : - What Is The Difference Between Plaster Used In Gold Investment Casting And Ceramic Used In The Process Of Investment Casting Of Automobile Engine Parts And Turbine Blades Etc. When Both Are Used In The Lost-wax Method?
Answer - 22 : -
In general, the plaster used in gold investment casting is standard "plaster of Paris" or other such material it has a fine but inconsistent grain size and, for the most part, water based. The other parts you mentioned are generally a higher precision, the casting material is of a fine but consistent grain, high temperature, hard, and not always water based. This is especially important for turbine blades as the material from which they are cast is more difficult to fine finish than other metals and the precision is extremely important due to the speed of rotation. It would be safe to say that the latter could be used in place of the former but not the former in place of the latter. Hope this is helpful.
Question - 23 : - Does The Extrusion Process For A355 And A356 Alloy Effect On The Amount Of Impact Energy?
Answer - 23 : -
Yes, it does. I am not an expert in these things, but I do know that the parameters of the extrusion process directly affect the crystalline matrix of the alloy, which in turn governs the physical characteristics of the alloy. As the differences can be quite significant, I would recommend checking with qualified references for pertinent details. I know that quenching and max temperatures are big issues. Good luck, sorry I could not be of greater assistance.
Question - 24 : - Does Case Harden Steel Properties Detoriates Over Time? Especially For Guns, Parts Like Bolt Carrier, The Brand New Parts Has Been Kept For 10 Year And Properly Oiled. I Am Worried About Its Surface Hardness To Take The Blow During Firing?
Answer - 24 : -
Hardened steel does not generally deteriorate over moderate periods, especially not as short as ten years, providing it have been protected from corrosion. Strong magnetic fields and electric fields generated through or around the steel can have an effect, but this is highly unlikely. If your bolt carrier has been kept protected and oiled it should be fine. I have a shotgun that was made in 1740 which has lost none of its hardness as well as steel swords dating back to the 1600's that are still hard and sharp. You should not have a problem.
Question - 25 : - How Is Metal Heavy?
Answer - 25 : -
Not all metals are heavy. Hydrogen is a metal, and is the lightest element known. Lithium, also a metal is the third lightest element there are many heavy elements that are not metals. If you "Google" the definition of "metal" you will note the properties that qualify a substance as a metal. Mass (weight) is not the important factor. Common metals are heavy because they have a dense electron structure.
Question - 26 : - What Is The Melting Point Of E70 Steel, 304,308,316 Stainless Steels? In Addition, What Is The Hottest Part Of The Flame In A &re?
Answer - 26 : -
You may find the melting range of some frequently used stainless steels below. Steel is an alloy and instead of a unique melting point, has a melting range, which is the range in which under equilibrium conditions, liquid, and solid phases coexist.
304: 14001450 (oC)
308: 14001420 (oC)
316: 13751400 (oC)
Question - 27 : - How One Can Differentiate Between 304 & 316 Grades Of Steel (physically)?
Answer - 27 : -
There is no physical distinction between these two grades of stainless steels since there are very similar compositionally. However, it might be possible to differentiate them rapidly by comparing their electrical resistance (measurable via an ohmmeter), indeed with some considerations in order to minimize the errors. I assume you already know that the most reliable method of telling them from each other would be to perform a chemical analysis of them using EDS and other spectroscopy methods.
Question - 28 : - Which Of Different Types Of Cast Irons Is Stronger? Is Their Strength Superior To Steels?
Answer - 28 : -
Generally, steels are considered to have better mechanical properties and ductility. However, there are some types of cast irons like ductile iron, which, in contrast to other types of cast irons, are not brittle. The strength of these ductile irons can be enhanced by controlling their matrix via an austempering heat treatment. This Austempered Ductile Irons (ADI) has very good mechanical properties comparable to those of some grades of steel. However, keep in mind that in spite of lower mechanical properties and being brittle, cast irons have good fluidities and are cheaper than steels.
By the way, there are some special purpose gray and white irons, which are frequently used for special applications like where resistance to corrosion, wear, and heat is required.
Question - 29 : - What Is The Chemical Composition Of Ceramic And What Is Its Atomic Density?
Answer - 29 : -
There are literally thousands of different ceramic products. They have widely varying atomic structures and characteristics.
Question - 30 : - Can 1026 Steel Be Welded?
Answer - 30 : -
Weldability of IronCarbon alloys is a function of their carbon content and decreases as their carbon increases. Plain carbon steels can be roughly categorized into 3 main groups: 1low carbon plain steels which have less than 0.2wt% carbon and are the most wieldable and heat treatable carbon steels, 2medium carbon plain steels with a carbon content of 0.20.5wt% C, and 3high carbon plain steels with more than 0.5wt%C. The 1026 steel is a medium carbon steel (10 at the beginning implies its being a plain carbon steel and 26 at the ending denotes that it has 0.26wt%C). Thus, 1026 steel falls into the second category which although are not as wieldable as those of the first group, still are quite wieldable? Post heating (in order to establish controlled cooling) can reduce the risk of its becoming hard and brittle after welding operation.