77 + Interview Questions in Pouring – Gating Design in Casting-Forming-Welding I Page 1 InterviewSolution

1.	Which of the following is not desirable in casting design for minimum stress concentration?(a) Roundness of external corners(b) Local metal accumulations(c) No abrupt changes in casting walls(d) Uniform thickness of casting wallsI got this question during an interview.My question is from Product Design for Sand Castings topic in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct option is (b) LOCAL METAL accumulations Easiest explanation: In casting design for minimum stress concentration and good casting consistency, local metal accumulations and massive elements should be avoided as MUCH as possible to restrict the generations of shrinkage DEFECTS in the CASTINGS, which can also be caused by having of low strength of casting at a higher temperature.

Discussion

2.	What should be the ratio of rib thickness to wall thickness in castings for proper avoiding of concentration of metal at joints?(a) 1 to 2(b) >2(c) >1(d) 0.6 to 0.8I have been asked this question in final exam.Query is from Product Design for Sand Castings topic in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The CORRECT option is (d) 0.6 to 0.8 To elaborate: Rib thickness/Wall thickness = 0.6 to 0.8, When the CONCENTRATION is reduced, one of the WALLS is made THINNER as SHOWN in below figure. That is why for castings, ribs are always made thinner than the wall in the ratio, to avoid the concentration of metal at joints.

Discussion

3.	In the solidification process, external angles have a lower cooling rate than re-entrant angles of the casting.(a) True(b) FalseThis question was posed to me during an interview.Enquiry is from Product Design for Sand Castings in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct answer is (b) False Easy EXPLANATION: Solidification progresses from thin to thick sections and external angles have a greater cooling rate than re-entrant angles; the reason being that sand around a re-entrant angle is surrounded on TWO sides by the heat sources. And re-entrant angle should be MADE proper to avoid cracks which often BEGIN at the shrinkage CAVITIES.

Discussion

4.	Why is inoculation done certain times during melting of cast iron?(a) To enhance its mechanical properties(b) To reduce the liquid shrinkage of metal(c) To enhance the surface finishing(d) All of the mentionedThis question was addressed to me in semester exam.My question is based upon Furnaces for Melting in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer»

Discussion

5.	Which of the following gases can be beneficial in imparting certain desirable qualities to the castings?(a) Oxygen(b) Nitrogen(c) Hydrogen(d) Carbon monoxideI had been asked this question during an online exam.This intriguing question originated from Gases in Metals in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right option is (b) Nitrogen The BEST I can explain: Nitrogen can be ADDED in CASTINGS to impart desirable qualities. For example, when this gas is added to steels, it improves strength, FATIGUE life, CORROSION resistance and many other properties. Nitrogen would affect these properties only if it remains very fine nitrides in solid solutions.

Discussion

6.	Breaking of the sand mould is done after sufficient cooling of castings, to have_____(a) proper surface finish of castings(b) no any distortion to castings(c) high casting yield(d) less casting yieldThis question was addressed to me in homework.My question is from Casting Cleaning topic in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct answer is (b) no any distortion to castings The best explanation: The sand mould is to be broken to extract the casting. But the breaking of the sand mould is to be done only when the castings are sufficiently cooled, since the metal at high TEMPERATURE has very little strength, due to this it may CAUSE distortion to the casting if breaking of mould is done before proper COOLING of the mould.

Discussion

7.	Analysis of variations in the foundry procedures has no affect on the economy of production.(a) True(b) FalseI got this question in a national level competition.My query is from Product Design for Sand Castings topic in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct choice is (b) False To explain: ECONOMY of production is a very important factor. Variations in the foundry procedures, in the form of patterns and core boxes, are thoroughly investigated to ensure the most economical PLAN for PRODUCING castings of SPECIFIC QUALITY. Furthermore, operations apart from those of pattern shop and foundry are also considered to have economical plan.

Discussion

8.	Positive temperature gradient which gradually increases towards the feed head, avoid shrinkage defects.(a) True(b) FalseI got this question by my college professor while I was bunking the class.My doubt is from Product Design for Sand Castings topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT OPTION is (a) True Easiest explanation: Redesign is the most effective way to avoid SHRINKAGE defects. The designer tries to PLACE and proportion members and their intersections in such a way as to establish a positive temperature gradient which is lowest at points farthest away from the feed head and which gradually increases towards the feed head.

Discussion

9.	Which of the following methods is best for preventing the solutions of gases in metals?(a) Bubbling of gas(b) Vacuum melting(c) Venting arrangement(d) Elements inclusionThe question was posed to me during an interview.This intriguing question originated from Gases in Metals in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The CORRECT answer is (b) Vacuum melting Best explanation: Vacuum melting is increasingly being used for preventing the SOLUTIONS of GASES in metals and the combinations of reactive elements in the melt. Additions in the LADLE, RATHER than in the melt, have been found to be more effective for controlling the gases and chemical compositions.

Discussion

10.	Non-uniform cross-sectional areas of the high temperature casting lead to having hot spots in the casting.(a) True(b) FalseThis question was posed to me by my college professor while I was bunking the class.My question is based upon Product Design for Sand Castings topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct choice is (a) True For explanation I would say: In a casting of uniform WIDTH and THICKNESS, no temperature variations would exist throughout the length of the casting. However, if the casting has non-uniform cross-sectional areas, the temperature would vary CONSIDERABLY. And a HIGH temperature position is called as the hot spot, as shown in below figure.

Discussion

11.	Faster and uneven cooling of hot casting affects the castings badly or may cause several defects in the castings.(a) True(b) FalseThe question was asked in quiz.The above asked question is from Casting Cleaning topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct answer is (a) True To elaborate: When the HOT casting is exposed to the air, there is likely to be faster and uneven cooling because of which the casting may WRAP, crack or induce thermal stresses beneath the SKIN. The moulding sand provides a uniform cooling medium for the casting while producing least AMOUNT of internal stresses.

Discussion

12.	A reduced metal section at the casting joint makes easy removal of gates and risers from the castings.(a) True(b) FalseI had been asked this question in an internship interview.Question is from Casting Cleaning in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct option is (a) True The explanation is: Removal of GATES and risers can be simplified by providing a reduced METAL section at the casting joint, so for brittle materials such as grey cast iron, the gates can easily be broken by hitting with a hammer. The gates and risers can be REMOVED by hammering, chipping, hack sawing, ABRASIVE cutoff ETC.

Discussion

13.	Improper venting arrangement causes mechanical trapping of gases in metal castings.(a) True(b) FalseI have been asked this question during a job interview.This is a very interesting question from Gases in Metals topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct CHOICE is (a) True To explain I would say: The gases in metals lead to faulty castings. In metal castings, the gases may be trapped mechanically by having IMPROPER venting arrangements, in such SITUATIONS trapping of gases can be PREVENTED by making proper venting arrangements in the mould.

Discussion

14.	Which of the following metal has a melting point of about 660oC and latent heat of fusion 92.7 cal/g?(a) Aluminium(b) Lead(c) Magnesium(d) TinThe question was posed to me in a job interview.Origin of the question is Furnaces for Melting topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right option is (a) Aluminium Easy explanation: Iron is the metal having a melting point of about 660oC and LATENT heat of fusion of 92.7 cal/g. It has a mean SPECIFIC heat of 0.237 cal/g^oC and heat REQUIRED for melting 1 Kg of iron is 1022 KJ.

Discussion

15.	Which of the following formulas show the Sievert’s law of percent of hydrogen (H) present in a melt?(a) H = K(pHa)^2(b) H = K*pHa(c) H = K/pHa(d) H = K√pHaI had been asked this question in a national level competition.This interesting question is from Gases in Metals in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right answer is (d) H = K√pHa The BEST explanation: SIEVERT’s law states that the amount of hydrogen DISSOLVED in a melt varies as % hydrogen present (H) = K√pHa, where pHa is the partial pressure of hydrogen in the atmosphere over the melt, and K is a CONSTANT.

Discussion

16.	Presence of hydrogen in endothermic metals causes lattice distortion.(a) True(b) FalseThe question was asked during a job interview.My question is taken from Gases in Metals topic in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct OPTION is (b) False The best I can explain: Hydrogen dissolves in lattice defects of endothermic metals, HENCE PRODUCES no distortion. In exothermic metals, hydrogen is believed to dissolve interstitially so it produces the lattice distortion in exothermic metals. (titanium, zirconium, ETC.)

Discussion

17.	The formation of hot tears in the hand wheels or big gear wheels can be reduced by_____(a) making the hub of greater strength(b) reducing the thickness of the spokes(c) increasing the ductility of the spokes(d) increasing the thickness of the spokesThis question was posed to me by my college director while I was bunking the class.Question is taken from Product Design for Sand Castings in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct answer is (c) INCREASING the ductility of the spokes Best explanation: By increasing the ductility of the spokes, it is possible to reduce the formation of HOT TEARS in the hand wheels or BIG gear wheels. The ductility can be increased by making the spokes curved and having them in odd numbers. The odd number of spokes ensures that the restraining force acts in only one direction making the wheel more ductile.

Discussion

18.	In designing for economical moulding, it is not advisable to have complexities in the parting line.(a) True(b) FalseI got this question in an international level competition.This key question is from Product Design for Sand Castings topic in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct answer is (a) True The explanation is: Parting line is DETERMINED by the shape of the casting. The simplest parting line is that running through the centre line of the casting as SHOWN in the below figure. UNNECESSARY complexities in the parting line increase the cost. So the designer strives to design CASTINGS with parting planes that are straight or as NEARLY straight as possible.

Discussion

19.	What is inoculation of cast iron?(a) Addition of sulphur alloys(b) Addition of silicon alloys(c) Addition of oxides(d) Addition of parent metal’s oreI have been asked this question at a job interview.The doubt is from Furnaces for Melting topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct option is (b) ADDITION of silicon ALLOYS The best I can explain: INOCULATION of cast IRON is the addition of certain silicon alloys to molten iron to produce changes in graphite DISTRIBUTION.

Discussion

20.	Which of the following is/are not used to melt material in casting(foundry) industries?(a) Cupola furnace(b) Induction furnace(c) Ladle furnace(d) Crucible furnaceI got this question during an online interview.This is a very interesting question from Furnaces for Melting in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct answer is (c) Ladle FURNACE The best explanation: All of listed are the FURNACES used by metal foundry industries to melt down metal for CASTING purposes, except Ladle furnace.

Discussion

21.	Nitrogen cannot be used for ferrous and nickel based alloys in hydrogen removal technique because_____(a) it leads to form high dross in metal castings(b) it gives rise to porosity in metal castings(c) it affects the grain size(d) it generates blow holes in metal castingsThe question was asked during an interview.This interesting question is from Gases in Metals topic in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct choice is (c) it affects the grain size For explanation: For ferrous and NICKEL based alloys, nitrogen cannot be USED because it is soluble in these and ALSO it MAY form nitrides which affect the grain size; therefore, in ferrous alloys in particular, accurate control of the nitrogen is necessary. In such situations, carbon monoxide BUBBLES are used.

Discussion

22.	Pressure change of a melt is responsible for the cooling rate of the castings in the mould.(a) True(b) FalseI had been asked this question in an online quiz.The question is from Casting Cleaning topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT answer is (B) False For explanation: Pressure has no effects on cooling rate of castings; the cooling rate depends upon the casting thickness, the total mass as well as the type of MOULD. More the mass or DENSITY of the castings will show less cooling rate and more the surface area of castings will have fast cooling rate of the castings in the mould.

Discussion

23.	In the hydrogen removal process, carbon monoxide for ferrous alloys removes not only hydrogen but also nitrogen.(a) True(b) FalseThis question was addressed to me in quiz.Question is taken from Gases in Metals in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right answer is (a) True For explanation I would say: Carbon monoxide for FERROUS alloys removes not only hydrogen but also nitrogen. So, for ferrous metals, a MARKED DECREASE in the solubility of nitrogen during the phase change may give rise to porosity in the CASTINGS. And the re-entry of nitrogen from the AIR is also prevented by the impermeable slag at the top of the melt.

Discussion

24.	Which of the following types of mould will have the longest period of cooling time for the same castings?(a) Green sand mould of simple shape and size(b) Dry sand mould of simple shape and size(c) Dry sand mould of complex shape and size(d) Green sand mould of complex shape and sizeI have been asked this question in semester exam.My query is from Casting Cleaning in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right CHOICE is (c) Dry sand mould of complex shape and size Best explanation: Dry sand mould of complex shape and size will have the longest PERIOD of cooling TIME, it is around 18-30 hours for 3000-5000 kg of mass of castings. The cooling time also DEPENDS upon the mass of the castings, for the same sand mould the cooling time can be reduced up to 50% if the mass of castings COMES in the range of 1000-3000 kg.

Discussion

25.	In sand castings, modification of bosses is done to_____(a) have good surface finish(b) to reduce the chances of porosity(c) to eliminate the use of core(d) to reduce casting yieldThis question was addressed to me during an online exam.Origin of the question is Product Design for Sand Castings topic in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct ANSWER is (c) to eliminate the use of core The best explanation: Bosses are mainly used to increase the SECTIONAL thickness of the housing in order to improve the strength of certain parts of casting. The modified boss or the extension of a boss to the flange ELIMINATES the need of a core and also the undercut, which forms a LESS COMPLICATED design.

Discussion

26.	Cooling of casting walls of non uniform thickness results into formation of tears or warping in the metal casting.(a) True(b) FalseThis question was posed to me in an internship interview.This key question is from Product Design for Sand Castings in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct option is (a) True The best I can explain: If the CASTING walls have non-uniform THICKNESSES, then the thinner walls would have cooled down very quickly leaving the THICKER wall still in the PLASTIC STATE. When the thinner walls contract due to solid shrinkage, because of the plasticity, the thicker rib would warp.

Discussion

27.	Which of the following methods is used to detect a concentration of the metal?(a) Check triangle method(b) Euler’s method(c) Finn’s method(d) Check circle methodI have been asked this question in semester exam.Question is from Product Design for Sand Castings in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct choice is (d) Check circle METHOD The best I can explain: The check circle method is normally used for detecting the concentration of the metal to avoid the shrinkage problems which particularly severe in junctions by reducing the concentration of metal at joints. A concentration of metal always occurs at the point where TWO WALLS of equal thickness COME together.

Discussion

28.	Contours, cavities and passages in the casting can be possible without placing of any cores in the casting.(a) True(b) FalseI have been asked this question by my college professor while I was bunking the class.This interesting question is from Product Design for Sand Castings in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct option is (a) True For explanation I would SAY: In the normal moulding, it is not possible to have any contours, CAVITIES and PASSAGES in the casting. Cores are placed in the mould to achieve the required passages in the casting. But, a minor CHANGE in the design of casting can achieve this and also ECONOMIZE production cost, by eliminating cores.

Discussion

29.	The axis of the cylindrical boss should be in the parting plane to have satisfactorily use of boss in casting.(a) True(b) FalseI got this question during an interview.Origin of the question is Product Design for Sand Castings in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct option is (a) True For explanation I would say: Bosses are frequently used in order to provide longer bolt or tap HOLES in certain parts of the casting, this may be CAST satisfactorily if the axis of the cylindrical boss is parallel to the direction in which the pattern is DRAWN out from the mould or if the centerline of the boss is in the parting PLANE.

Discussion

30.	Which of the following methods is best for cleaning of sand particles sticking to the casting surface?(a) Chipping(b) Sand blasting(c) Grinding(d) HammeringThe question was posed to me by my college professor while I was bunking the class.My question is taken from Casting Cleaning in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT option is (b) Sand blasting The best I can EXPLAIN: For cleaning the sand PARTICLES sticking to the casting surface, sand blasting is used. The casting is kept in a closed box and a jet of compressed air with a blast of sand GRAINS or steel grit is directed against the casting surface, which thoroughly cleans the casting surface.

Discussion

31.	Which of the following processes is known as fettling?(a) Cleaning of castings(b) Pouring of melt into mould(c) Releasing of gases from the melt(d) Inclusion of slag in the castingsI had been asked this question in an online interview.The question is from Casting Cleaning in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer»

Discussion

32.	Variation in solubility of gases can cause the generation of gases in metal castings.(a) True(b) FalseI had been asked this question during an internship interview.Origin of the question is Gases in Metals in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct choice is (a) True Explanation: At different temperatures and PHASES, the gases may be generated due to the variation in their solubility. And chemical REACTIONS also lead to a generation of gases in metal castings. The gases most GENERALLY present are HYDROGEN and nitrogen, in which removal of hydrogen from the melt is very necessary for better castings.

Discussion

33.	Maintaining of hydrogen level to a minimum in a melt is very important because there is no simple dehydrogenating technique.(a) True(b) FalseThis question was posed to me during a job interview.My doubt is from Gases in Metals in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct answer is (a) True To explain: There is no SIMPLE dehydrogenating addition to eliminating hydrogen in the form of slag. So, care should be taken to maintain the hydrogen level to a minimum. The method USED for REMOVAL of hydrogen in which partial pressure of hydrogen is reduced by bubbling some other DRY insoluble gas through the melt; this method is not easy and also causes many other problems.

Discussion

34.	Which of the following methods is more convenient for the removal of very large size gates and risers from the steel castings?(a) Hammering(b) Chipping(c) Flame or arc cutting(d) Hack sawingThis question was addressed to me at a job interview.My doubt stems from Casting Cleaning topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer»

Discussion

35.	Flame or arc cutting method is used for the removal of dry sand cores from the castings.(a) True(b) FalseI had been asked this question by my school teacher while I was bunking the class.I want to ask this question from Casting Cleaning in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer»

Discussion

36.	Gas-Fired burner is used in which of the following furnace?(a) Induction Furnace(b) Reverberatory Furnace(c) Cupola Furnace(d) Crucible FurnaceThe question was posed to me in an online interview.I want to ask this question from Furnaces for Melting in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer»

Discussion

37.	Which of the following equations represent the solubility (S) of the hydrogen in the metals?(a) S = C exp[-Es/(kθ)](b) S = C exp[-Es(kθ)](c) S = C log[-Es/(kθ)](d) S = C log[-Es(kθ)]This question was addressed to me during an interview for a job.Asked question is from Gases in Metals in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
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Discussion

38.	Which of the following techniques is used for smoothening of the rough cut gate edges on the castings?(a) Hack sawing(b) Flame cutting(c) Sand blasting(d) Pedestal or swing frame grindingThe question was asked in an interview for job.My question is based upon Casting Cleaning in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT option is (d) Pedestal or SWING FRAME grinding For explanation I would say: The casting surface after removal of gates contain some rough surfaces left at the time of removal of gates, or some fins and other projections on the surface NEAR the parting line. These rough cut gate edges can be smoothened by using either the pedestal or swing frame GRINDER depending on the size of the casting.

Discussion

39.	Which of the following metals has the lowest liquid solubility (cc/kg) of hydrogen at atmospheric pressure?(a) Iron(b) Copper(c) Magnesium(d) AluminiumThe question was posed to me in an online quiz.My doubt is from Gases in Metals topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct CHOICE is (d) Aluminium To EXPLAIN: Hydrogen solubility is an acute problem in ferrous casting. Liquid solubility of hydrogen in aluminium is 7cc/kg, which is lowest COMPARATIVELY to other metals. So, it is not very difficult to handle aluminium and chances of INCLUSION of gas are also very less due to less liquid solubility.

Discussion

40.	Tumbling method, for cleaning of sand and unwanted fins from the castings, can be used for thin castings with fragile or overhung segments.(a) True(b) FalseI got this question in my homework.The question is from Casting Cleaning in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT choice is (B) False The explanation is: In the tumbling method, the CASTINGS are kept in a barrel which is completely closed and then rotated on a horizontal axis at 30-40 rpm. Movement of casting removes the sand and unwanted fins. However, one precaution to be taken for tumbling is that the castings should be rigid with no frail or OVERHUNG segments, which may get knocked off during the tumbling operation.

Discussion

41.	Which of the following metal has a melting point of about 420oC and latent heat of fusion 26.3 cal/g?(a) Nickel(b) Copper(c) Zinc(d) IronThe question was asked during a job interview.I'd like to ask this question from Furnaces for Melting topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer»

Discussion

42.	Which of the following metals comes in an exothermic group of metals when the solubility of hydrogen is concerned?(a) Iron(b) Titanium(c) Magnesium(d) NickelThe question was posed to me at a job interview.The above asked question is from Gases in Metals in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct option is (b) TITANIUM To explain: When the solubility of HYDROGEN is concerned, titanium comes in an exothermic group of METALS which absorb more hydrogen than ENDOTHERMIC metals (iron, magnesium, nickel ETC). Further, in exothermic metals, the solubility of hydrogen decreases with temperature. The reverse is true for endothermic metals.

Discussion

43.	For ferrous alloys, the breaking of mould should be done at a temperature_____(a) 780 ⁰C(b) 850 ⁰C(c) above 700 ⁰C(d) below 700 ⁰CThis question was addressed to me in an interview.My doubt is from Casting Cleaning in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» CORRECT ANSWER is (d) below 700 ⁰C Explanation: IDEALLY, the moulds should be broken at a temperature when no transformation occurs. For ferrous alloys, the breaking should be done at a temperature below 700 ⁰C. If the castings are fragile and THIN, they should be removed at a temperature as low as 400 ⁰C to avoid any deformation to the metal castings at the TIME of breaking of mould.

Discussion

44.	Which of the following is/are the advantage(s) of an Induction Furnace?(a) Higher yield(b) Cleaner melting(c) Compact Installation(d) All of the mentionedI had been asked this question by my college director while I was bunking the class.My query is from Furnaces for Melting topic in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct OPTION is (d) All of the mentioned For EXPLANATION I would SAY: Advantages offered by Induction Furnace are higher yield, FASTER startup, cleaner melting, NATURAL stirring and compact installation.

Discussion

45.	Which of the following reasons is the incorrect reason for frictional losses in the conduit?(a) Gradual change in flow direction(b) Sudden contraction of the flow cross-sections(c) Sudden enlargement of the flow cross-sections(d) Due to irrotational flow of molten metalThis question was posed to me during an interview.The above asked question is from Effects of Friction and Velocity Distribution in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT answer is (d) Due to irrotational FLOW of molten metal Best explanation: In REAL fluids, the frictional losses are always present, especially when there is a sudden contraction or ENLARGEMENT of the flow cross-sections and also due to a gradual change in the flow direction, e.g., in a 90° bend and similar other FITTINGS.

Discussion

46.	There is no direct contact of flame and metal in which of the following type of furnace?(a) Cupola(b) Crucible(c) Electric arc(d) InductionThe question was asked in examination.This question is from Furnaces for Melting in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct OPTION is (b) Crucible Easy explanation: In Crucible furnace, metal is placed in a crucible of REFRACTORY material. The crucible is HEATED with ELECTRIC resistance.

Discussion

47.	Which of the following ways can use for stopping the rapid solidification of the molten metal in the mould?(a) By having the mould of high permeability(b) By making a uniform flow of molten metal(c) By creating high pressure on the molten metal(d) By using too much superheatThis question was addressed to me in class test.The above asked question is from Effects of Friction and Velocity Distribution topic in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct option is (d) By using too much superheat The explanation: When the liquid metal is poured very SLOWLY, then the time taken to FILL up the mould is rather long and the SOLIDIFICATION may start even before the mould has been completely filled up. This can be AVOIDED by using too much superheat, but this creates the gas solubility problem which is not good for castings.

Discussion

48.	What is hearth in a furnace?(a) The electrodes are often called hearth(b) The walls of the furnace(c) The bowl shaped bottom of the furnace(d) The dome shaped roof of the furnaceThe question was asked in quiz.The above asked question is from Furnaces for Melting in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct option is (c) The bowl SHAPED bottom of the FURNACE The best explanation: The hearth is that bowl shaped bottom of the furnace. It is MADE up of a high REFRACTORY material (bricked and granular).

Discussion

49.	Which of the following chemical compound, is the most common flux added to the charge in a cupola furnace?(a) Coke(b) Methane(c) Carbon dioxide(d) LimestoneThe question was asked in examination.This intriguing question originated from Furnaces for Melting in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right choice is (d) LIMESTONE The explanation: Limestone (CACO3) is used as Flux in CUPOLA FURNACE in a proportion of about 2-4% of the metal CHARGE.

Discussion

50.	Which of the following metal has a melting point of about 1537^oC and latent heat of fusion 65.0 cal/g?(a) Nickel(b) Copper(c) Zinc(d) IronThis question was posed to me during an interview.Origin of the question is Furnaces for Melting topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct choice is (d) Iron To elaborate: Iron is the metal having a MELTING point of about 1537^oC and latent heat of FUSION of 65.0 cal/g. It has a mean specific heat of 0.141 cal/g-^oC and heat required for melting 1 Kg of iron is 1168 KJ.

Discussion

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Presence of hydrogen in endothermic metals causes lattice distortion.(a) True(b) FalseThe question was asked during a job interview.My question is taken from Gases in Metals topic in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I