77 + Interview Questions in Pouring – Gating Design in Casting-Forming-Welding I Page 2 InterviewSolution

51.	Incoming air pressure and quantity in cupola furnace are controlled by which of the following element?(a) Tuyeres(b) Tapping spout(c) Wind box(d) Blast pipeThe question was posed to me in an interview.Enquiry is from Furnaces for Melting topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct option is (c) WIND BOX To explain I would SAY: The air ENTERS the cupola through the tuyers. But the air blowers in the wind box controls the requisite pressure and quantity of air COMING inside.

Discussion

52.	Why is Velocity of a fluid in contact with any solid surface is zero?(a) Due to cohesive forces in the fluid particles(b) Due to low velocity of fluid(c) Due to no slip condition(d) Due to high intermolecular forces between the fluid particlesThis question was posed to me in homework.This key 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» Correct answer is (C) Due to no slip condition The explanation is: Velocity of a liquid METAL in the sprue and the gate is not uniform across the cross-sections. It is maximum at the axis of the conduit and zero at the solid surface due to high ADHESIVE bonding between the surface and the fluid PARTICLES, which is RESPONSIBLE for viscosity and results in no slip condition.

Discussion

53.	The primary purpose of sprue in casting mould is to _____(a) act as a reservoir for molten metal(b) feed the casting at rate consistent with the rate of solidification(c) feed molten metal from the pouring basin to the gate(d) help feed the casting until all solidification takes placeThe question was posed to me during an interview.The question is from Aspiration Effect topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct option is (c) feed molten metal from the pouring basin to the gate The EXPLANATION: Sprue is a CONNECTING PASSAGE between pouring basin and runner for molten metal in the tapered form to avoid the aspiration effect so that PRESSURE EQUALLY maintained in the column of liquid metal streaming to the mould.

Discussion

54.	What is the purpose of strainer in the gating system?(a) To make uniform flow(b) To make smooth surface finish of the casting(c) To remove dross from the molten metal(d) To create positive pressure throughout to avoid aspiration effectI got this question during a job interview.My enquiry is from Aspiration Effect topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right answer is (c) To remove DROSS from the molten metal The explanation: Ceramic strainer in the sprue removes dross and prevent SLAG from entering to the castings. Strainer additionally useful to laminize the flow.A typical strainer MIGHT be a cylinder of 30-50 mm diameter, 10-20 mm LONG, containing ten or more holes, of diameter APPROXIMATELY 3-5 mm.

Discussion

55.	Why are flux added to the charge ( parent metal to be melted) during melting of a metal?(a) To increase carbon content(b) To increase refractoriness(c) To add specific oxides(d) To remove specific oxidesThis question was posed to me during a job interview.This question is from Furnaces for Melting topic in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The CORRECT answer is (d) To remove SPECIFIC oxides Easy explanation: The flux is a chemical substance, added to the metal while MELTING it to remove oxides PRESENT in the metal.

Discussion

56.	Which of the following gating designs is used to avoid the splashing of the molten metal in the mould?(a) Vertical gating(b) Horizontal gating(c) Inclined gating(d) Bottom gatingI got this question during an interview.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) Bottom gating To ELABORATE: In the case of bottom gating design the liquid metal is filled in the mould from bottom to top, thus it avoids the splashing of the MOLTEN metal in the mould that can CAUSE erosion. And this design also prevents the oxidation which is associated with the vertical gating.

Discussion

57.	Which of the following gases is responsible for the Pin hole porosity in the molten metal?(a) Hydrogen(b) Nitrogen(c) Oxygen(d) Carbon-dioxideI had been asked this question in quiz.My question is taken from Aspiration Effect in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right answer is (a) Hydrogen The explanation: This is CAUSED by the dissociation of water inside the mould cavity. As the molten metal gets solidified, it loses TEMPERATURE which decreases the solubility of GASES by expelling the dissolved gases. The hydrogen while leaving the solidifying metal would cause LONG pin holes showing the path of escape.

Discussion

58.	The velocity distribution within the conduit depends on _____(a) shape of the conduit and nature of flow(b) temperature of the molten metal(c) impurities present in the molten metal(d) type of the molten metalI got this question in an online interview.This key question is from Effects of Friction and Velocity Distribution topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right answer is (a) shape of the CONDUIT and NATURE of flow Explanation: The velocity distribution within the conduit depends on the shape of the conduit and the nature of flow (i.e. TURBULENT or laminar). The velocity profile is parabolic in laminar flow and is logarithmic in turbulent flow. Shape of the conduit means cross-sectional area which VARIES in INVERSE proportion to the velocity.

Discussion

59.	Sprue design is made tapered instead of straight ___________(a) To easy flow of molten metal(b) To have smoothness in the metal flow(c) To maintain the pressure balance(d) To avoid the erosion of mould sandThe question was posed to me in an internship interview.My enquiry is from Aspiration Effect topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The correct option is (C) To maintain the pressure balance The EXPLANATION: Pressure balance is maintained, to AVOID the negative pressure (to ensure positive pressure anywhere in the liquid COLUMN), the SPRUE should be tapered. The ideal shape of the sprue is parabola but to reduce the manufacturing difficulty shape of the sprue is considered as tapered cylinder.

Discussion

60.	Electric arc furnaces are most suitable for which of the following type of material?(a) Ferrous(b) Non-Ferrous(c) Both ferrous and nonferrous(d) Neither ferrous nor nonferrousThis question was posed to me in an interview.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» Right CHOICE is (a) Ferrous Easy EXPLANATION: Electric furnaces are more SUITABLE for ferrous material in a LARGER capacity.

Discussion

61.	Which of the following can be the reason for the aspiration effect?(a) High pressure of molten metal(b) High pouring temperature of molten metal(c) Low viscosity of molten metal(d) High viscosity of molten metalThe question was asked during an interview.My question is taken from Aspiration Effect in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT choice is (B) High pouring temperature of molten metal Explanation: High pouring temperature which increases the amount of gas absorbed (leads to aspiration effect) by the molten metal in the furnace, in the LADLE and during the flow in the mould. When gases not allowed to ESCAPE, would be trapped inside the casting and weaken it.

Discussion

62.	For a smooth conduit, which of the following is the value of friction factor (f) for laminar and turbulent flow respectively?(a) 10/Re, 0.0791(Re)^-0.25(b) 16/Re, 0.0791(Re)^-0.25(c) 10/Re, 0.0771(Re)^-0.25(d) 16/Re, 0.0171(Re)^-0.25I have been asked this question by my college director while I was bunking the class.This key question is from Effects of Friction and Velocity Distribution in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct choice is (b) 16/Re, 0.0791(Re)^-0.25 The explanation: For a smooth CONDUIT, the VALUE of f is given by the equations f = 16/Re for laminar flow (Re < 2000), f = 0.0791(Re)^-0.25 for TURBULENT flow (Re > 2000), Where, Re is Reynolds NUMBER.

Discussion

63.	In the given below figure of Mechanism of vacuum generation, point ‘2’ is the indication of _____(a) Poynting point(b) Vena contracta(c) Stack point(d) Steric pointThe question was asked in unit test.Question is from Aspiration Effect topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct answer is (b) Vena contracta For explanation I WOULD say: The constricted region at point 2 in the figure is known as vena contracta. A sudden CHANGE in the flow direction cause the aspiration effect and thus VACUUM as the liquid METAL stream contracts around a sharp CORNER due to the momentum effect. To avoid vacuum, the mould is made to fit the vena contracta.

Discussion

64.	In an induction furnace, mixing and melting rates are altered by?(a) Controlling the temperature ranges only(b) Controlling the number of electrodes used only(c) Controlling power and frequency of current only(d) All of the mentioned factorsThis question was addressed to me in unit test.I would like to ask this question from Furnaces for Melting in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct ANSWER is (c) Controlling power and frequency of CURRENT only Best explanation: Due to the PRINCIPLE of induction used, the ELECTROMAGNETIC fields are produced. These EMF’s are used to stir the metal. Hence, controlling the power and frequency, Mixing and melting rates can be ALTERED.

Discussion

65.	In the given figure of Entry with rounded corner type of changes in flow geometry, the value of friction loss factor (eғ) is_____(a) 0.33eғs(b) 0.5eғs(c) 2eғs(d) eғsI have been asked this question during an interview.The origin of the question is Effects of Friction and Velocity Distribution topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT ANSWER is (a) 0.33eғs The best explanation: eғ = 0.33 eғs, where eғ is the friction loss factor. The value of eғ depends on whether the flow is enlarging or contracting in the DIRECTION of flow. And eғs REFERS to the value corresponding to a sharp change of geometry with identical INITIAL and final dimensions.

Discussion

66.	In the given below figure of outlet dimensions to prevent vacuum generation, what should be the relation between d’ and d?(a) d’/d = 1.3(b) d’/d > 2(c) d’/d = 2(d) d’/d > 2.2I got this question in class test.This question is from Aspiration Effect topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer»

Discussion

67.	For melting of cast iron, which of the following furnace is used?(a) Rotary furnace(b) Cupola furnace(c) Pit furnace(d) Electric furnaceI got this question during an internship 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» The correct option is (b) Cupola furnace Explanation: Cupola is a heavy furnace and has the capability to MELT down heavy METALS LIKE cast IRON. Hence, the Cupola furnace is mostly USED to melt cast iron for casting purposes.

Discussion

68.	Why is sand bed prepared for melting of metal in Cupola furnace?(a) It provides a refractory bottom(b) It soaks the moisture from the metal(c) It conducts the heat faster and uniformly(d) None of the mentionedThis question was addressed to me in an online quiz.This intriguing question comes from Furnaces for Melting topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT choice is (a) It PROVIDES a REFRACTORY bottom Easy explanation: A sand bed needs to be prepared because it provides a necessary refractory bottom for MOLTEN METAL and coke.

Discussion

69.	Which of the following effects can produce porous castings?(a) Aspiration effect(b) Viscous effect(c) Shapiro effect(d) Turbulent effectI have been asked this question during an internship interview.I want to ask this question from Aspiration Effect topic in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right answer is (a) ASPIRATION effect Easy explanation: When the mould is made, care should be taken to ensure that the pressure anywhere in the liquid metal stream does not fall below the atmospheric pressure. Otherwise, the gases originating from baking of the ORGANIC compounds in the mould will enter the MOLTEN metal stream, PRODUCING POROUS castings. This is known as Aspiration effect.

Discussion

70.	Gating design for a mould of 50cm25cm15cm is shown in below figure. The cross-sectional area of the gate is 5 cm^2. Neglecting friction and velocity distribution effects, what is the filling time (t) for the design (in second)?(a) 19.25(b) 21.86(c) 34.21(d) 10.39This question was addressed to me in an international level competition.Enquiry is from Effects of Friction and Velocity Distribution topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct choice is (b) 21.86 Easy EXPLANATION: H (Total height) = 15 cm, from the figure. v (Velocity of molten metal) = √2gH = √298115 cm/sec = 171.6 cm/sec. V (Volume of the mould) = 502515 cm³ and A (Cross-sectional area of the gate) = 5 cm^2. As we KNOW, t = V/Av So, t (Filling time) = 502515/5*171.6 sec = 21.86 sec.

Discussion

71.	Friction loss factor (eғ) in the conduit of liquid metal depends on _____(a) temperature of the molten metal(b) presence of dross in the molten metal(c) ratio of the flow area and Reynolds no. of the flow(d) whirling of the molten metalI had been asked this question by my school principal while I was bunking the class.I'd like to ask this question from Effects of Friction and Velocity Distribution in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» CORRECT choice is (C) ratio of the flow AREA and Reynolds no. of the flow Easiest explanation: eғ is the friction loss FACTOR and it depends on the ratio of the flow area and Reynolds number of the flow. For a laminar flow, the length and diameter of the smaller flow cross-section have to be taken into account. The value of eғ depends on whether the flow area is enlarging or contracting in the direction of flow.

Discussion

72.	Which of the following terms is modified in the integrated energy balance equation for non-uniform velocity distribution?(a) Potential energy(b) Kinetic energy(c) Pressure energy(d) Thermal energyThe question was asked in an interview for job.I want to ask this question 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» RIGHT answer is (b) Kinetic energy Easiest explanation: The non-uniform velocity DISTRIBUTION can be accounted for by modifying the kinetic energy term in the integrated energy balance equation by replacing the (velocity)² term by v̅²/β, where v̅ is the AVERAGE velocity and β is a constant. β is equal to 0.5 for laminar flow and 1 for turbulent flow in a circular conduit.

Discussion

73.	Which of the following reasons is the incorrect reason for the blow holes inside the castings?(a) Presence of moisture in the mould(b) Lower venting(c) Lower permeability of the mould(d) High pressure of the molten metalI have been asked this question in a job interview.Enquiry is from Aspiration Effect topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Correct choice is (d) HIGH pressure of the MOLTEN metal The best I can explain: Moisture left in the MOULD and core converted into steam because of the presence of heat in the molten metal. The parts of steam entrapped in the castings end up as blow holes, same as the ASPIRATION effect. Lower venting and lower permeability of the mould is also responsible for the blow holes inside the castings.

Discussion

74.	What is the function of slag hole in a cupola furnace?(a) To tap the slag generated(b) To generate the slag(c) To allow outflow of gases(d) All of the mentionedI had been asked this question in an international level competition.The doubt is from Furnaces for Melting in chapter Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» RIGHT option is (a) To tap the SLAG generated Explanation: Slag hole is a tapping hole in a cupola FURNACE. Through which slag generated during the MELTING process is tapped.

Discussion

75.	Splash core is used _____(a) to reduce the eroding force of the liquid metal(b) to make the flow smooth and slow(c) to remove dross from the molten metal(d) to prevent heavier impurities from entering the mouldThis question was posed to me in homework.My question comes from Aspiration Effect topic in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» Right option is (a) to reduce the eroding FORCE of the liquid METAL Explanation: A ceramic splash core is placed at the end of the sprue REDUCES the eroding force of the liquid metal stream. It acts the same as pouring basin that also reduces the eroding force of the liquid metal coming directly from the FURNACE as well as maintains a constant pouring head.

Discussion

76.	Which of the following items is used for trapping impurities from entering the mould?(a) Facing sand(b) Core(c) Skim bob(d) Pouring basinThis question was posed to me in class test.The above asked question is from Aspiration Effect in portion Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I
Answer» The CORRECT option is (c) Skim BOB For explanation: Skim bob is a trap placed in a horizontal gate to prevent HEAVIER and lighter impurities from entering the mould. It removes the dross if not strained by strainer and the sand also. Skim bob appears like as shown in the below figure.

Discussion

77.	The energy loss due to friction (Ef) in a circular conduit (on the basis of per unit mass) is given by_____(a) Ef = 4fLv̅²/2D(b) Ef = 8fLv̅²/2D(c) Ef = 4fLv̅³/2D(d) Ef = 4fLv̅²/DI had been asked this question by my college professor while I was bunking the class.The query 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» The correct ANSWER is (a) Ef = 4fLv̅²/2D For explanation I would say: Ef = 4fLv̅²/2D is the energy loss DUE to friction in a circular conduit. The frictional losses are PRESENT due to SUDDEN contraction or enlargement of the flow cross-sections. Where, v̅ = Average velocity, D = Diameter of the conduit, L = Length of the conduit and f = friction FACTOR.

Discussion

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