FACT aptitude questions for practice
1) In an examination Joshita scores a total of 738 marks out of 1175. What is her approximate percentage in the annual examination ?
Percentage of marks
= (738 / 1175) * 100 = 62.8 = 63
Ans : 63
2) Ms. Muskaan Daanish deposites an amount of Rs. 45800 to obtain p.c.p.a for 5 years. What total amount will Ms. Muskaan Daanish gets at the end of 5 years ?
= (Principal * Time * Rate) / 100
= (45800 * 5 * 12 ) / 100 = Rs. 27480
= Rs. (45800 + 27480)
= Rs. 73280
Ans : Rs. 73280
3) There are 6650 employees in an organisation, out of which 32% branches of the organisation How many such employees are there who got tranferred ?
Number of employees transferred
= 32% of 6650
= 6650 * 32 / 100 = 2128
Ans : 2128
4) Prateek invests Rs. 5730, which is 30% of the monthly income, in life insurance policy. What is his monthly income :
Let Prateek’s monthly income be x
x * 30 / 100 = 5730
x = 5730 * 100 / 30 = Rs. 19100
Ans : Rs. 19100
5) If the cost of 16 kgs of wheat is Rs. 384. What is the cost of 92 kilograms of wheat ?
CP of 16 kg of wheat
= Rs. 384
CP of 92 kg of wheat
= Rs. (384 * 92) / 16 = Rs. 2208
Ans : Rs. 2208
6) 15 * 35 / 25 + 12 = ?
? = (15 * 35) / 25 + 12
= 21 + 12 = 33
Ans : 33
7) (0.5)² = ?
? = 0.5 * 0.5 = 0.25
Ans : 0.25
8) (85)² – 85 = ?
? = (85)² – 85
= 85 (85 – 1) = 85 * 84 = 7140
Ans : 7140
9) 372 / 56 * 7 = ?
? = 372 / 56 * 7
Ans : 46.5
10) 6767 + 4892 = ? – 3285
? – 3285 = 6767 + 4892
? – 3285 = 11659
? = 11659 + 3285
Ans : 74944
FACT Chemical Engineering Question Paper
FACT Chemical Engineering Heat Transfer Model Questions
1. Loss of heat from unlagged steam pipe to the ambient air is by
(d) all (a), (b) & (c) (Ans)
2. Fourier’s law applies to the heat transfer by
(c) conduction (Ans)
(d) all (a), (b) & (c)
3. Fourier’s law of heat conduction applies to ………. surfaces.
(c) both (a) and (b) (Ans)
(d) neither (a) and (b)
4. Unsteady state heat conduction occurs, when
(a) temperature distribution is independent of time
(b) temperature distribution is dependent on time (Ans)
(c) heat flows in one direction only
(d) three dimensional heat flow is concerned
5. What is the unit of thermal conductivity ?
(a) Kcal/hr.m2 0C
(b) Kcal/hr.m. 0C (Ans)
6. The unit of heat transfer co-efficient is
(a) BTU/hr.ft2 0F (Ans)
7. Which of the following is correct ?
(a) Rate = Driving force * Resistance
(b) Driving force = Rate * Resistance (Ans)
(c) Resistance = Driving force * Rate
(d) Rate = Resistance/Driving force
8. An insulator should have
(a) low thermal conductivity (Ans)
(b) high thermal conductivity
(c) less resistance to heat flow
(d) a porous structure
9. Heat flux through several resistance in series in analogous to the current flowing through several
(a) resistances in parallel
(b) capacitors in series
(c) resistances in series (Ans)
(d) none of these
10. The overall resistance for heat transfer through a series of flat resistance, is the ….. of the resistances.
(b) geometric mean
(d) sum (Ans)
11. Which of the following has the highest thermal conductivity ?
(d) Silver (Ans)
12. Which area is used in case of heat flow by conduction through a cylinder ?
(a) Logarithmic mean area (Ans)
(b) Arithmetic mean area
(c) Geometric mean area
(d) None of these
13. For heat flow through very thick walled cylinder, use ………… mean radius.
(b) logarithmic (Ans)
(d) either (a) or (c)
14. What is the logarithmic mean of r1 and r2 ?
(a) r1 – r2/ln r1/r2 (Ans)
(b) r1 – r2/ln r2/r1
(c) r2 – r1/ln r1/r2
(d) r1 – r2/ – ln r1/r2
15. What is Nusselt number ?
(b) hD/k (Ans)
16. Prandtl number is given by
(c) Cp.µ/k (Ans)
FACT Placement Papers
Electronics and Electrical Engg Questions with answers
1. Two 100-W, 200-V lamps are connected in series across a 200-V supply. The total power consumed by each lam will be _____ watts.
(d) 25 (Ans)
2. Kirchhoff’s voltage law is nt valid for a non-linear network.
(b) False (Ans)
FACT engineering Mechanics Questions
FACT Mechanical Engineering Objective Type Questions Engineering Mechanics Multiple choice objective Type Questions with answers for practice, FACT model questions and answers for all competitive examinations,Fully solved previous years question papers with detailed explanations for all Bank IBPS PO CWE, Clerical Specialists officers,IT PSU HOCL,FACT,HAL GATE CAT solved questions of previous years
1. The unit of force in S.I. unit is
(b) newton (Ans)
2. The unit of work or energy in S.I. unit is
(c) kilogram metre
(d) joule (Ans)
3. The unit of power in S.I. unit is
(a) newton metre
(b) watt (Ans)
(d) pascal per sec
4. Forces are called concurrent when their line
(a) one point (Ans)
(b) two point
(c) one plane
(d) different planes
5. A force is completely defined when we specify
(c) point of application
(d) all the above (Ans)
6. Which of the following is not the unit of distance ?
(b) light year
(d) milestone (Ans)
7. Which of the following is not the unit of power ?
(a) kw (kilo watt)
(b) hp (horse power)
(c) k cal/sec
(d) k cal/kg sec (Ans)
8. Which of the following is not the unit of work, energy and heat ?
(a) k cal
(b) kg m (Ans)
9. Which of the following is not the unit of pressure ?
(d) newton (Ans)
10. When trying to turn a key into lock, following is applied
(a) coplanar force
(b) non-coplanar force
(d) couple (Ans)
11. Which of the following is not a scalar quantity ?
12. Which of the following is a vector quantities ?
(c) momentum (Ans)
13. Which of the following is not vector quantities ?
(a) weight (Ans)
14. The unit of moment of inertia of an area are
(a) kg m2
(b) m4 (Ans)
15. The unit of moment of inertia of mass are
(a) kg m2 (Ans)
16. Which of the following is not the unit of energy ?
(b) watt (Ans)
(c) K cal
(d) kgm x (m/sec2)
17. Which of the following is the example of lever of first order ?
(a) arm of man
(b) pair of scissors
(c) pair of the clinical tongs
(d) all of the above (Ans)
18. A pair of Smith’s Tong’s is an example of the lever of
(a) zeroth order
(b) first order
(c) second order (Ans)
(d) third order
19. Tension in a string is maximum at
(a) left support
(b) right support
(c) midway (Ans)
(d) quarter span
20. Which of the following is the unit of energy ?
(d) all the above (Ans)
FACT English Questions
FACT model questions and answers for all competitive examinations, Fully solved previous years question papers with detailed explanations for all Bank IBPS PO CWE, Clerical Specialists officers, IT PSU HOCL,FACT,HAL GATE CAT solved questions of previous years General English, aptitude and reasoning questions for practice,FACT Mechanical Engineering Objective Type Questions Engineering Mechanics Multiple choice objective Type Questions with answers for practice,
Directions (Qns. 1 to 10): (i) In this Section, 10 sentences are given. Each sentence has three parts, indicated by (a), (b) and (c). Read each sentence to find out whether there is an error. If you find an error in any one of the parts (a), (b) and (c), indicate that part as your answer. If a sentence has no error, indicate this by the letter (d), which stands for “no error”
(ii) Errors may belong to grammar, usage or idiom.
1. The Prime Minister’s good looks won him (a)/ The election but he has still to prove (b)/ That he’s not a just pretty face (c)/ No error (d).
Ans.c: ‘just a pretty face ‘ in place of ‘a just pretty face’.
2. The two books are the same (a)/ Except for the fact that this (b)/ Has an answer in the back (c)/ No error (d).
Ans.c: ‘on the back’ in place of ‘in the back’.
3. He estimated his income tax bill (a)/ by extrapolation over figures (b)/ submitted in previous years (c)/ No error (d).
Ans.b: ‘extrapolation of figures’ in place of ‘extrapolation over figures’.
4. The modern office block (a)/ sticks out like a sore thumb (b)/ among the old buildings in the area (c)/ No error (d).
5. I will try to put over (a)/ some feelers to gauge (b)/ people’s reactions to our proposal (c)/ No error (d).
Ans.a: ‘put out’ in place of ‘put over’.
6. A major contribution of Mathura Sculptors (a)/ of that period were the creation and popularisation (b)/ of the Buddha’s image in human form (c)/ No error (d).
Ans.b: ‘was’ in place of ‘were’.
7. Amit has been deceiving Mona (a)/ for many years but she (b)/ has not still tumbled to it (c)/ No error (d).
Ans.c: ‘yet’ in place of ‘still’.
8. Mahavira was an advocate of non – violence and vegetarianism (a)/ who revived and reorganized the jain doctrine (b)/ and established rules for their monastic order (c)/ No error (d).
Ans.c: ‘its’ in place of ‘their’.
9. Microwaves are the principle carriers (a)/ of television, telephone and data transmissions (b)/ between stations on earth and between the earth and satellites (c)/ No error (d).
Ans.a: ‘principal’ in place of ‘principle’.
10. An unit is an abstract idea (a)/ defined either by reference to (b)/ a randomly chosen material standard or to a natural phenomenon (c)/ No error (d).
Ans.a: ‘a unit’ in place of ‘an unit’.
General Awareness Questions answers
General Awareness Questions with answers
1. Who has taken over as the Director of Operations at the Bangalore based National Cricket Academy in place of his predecessor Dave What more who joined IPL team Kolkata Knight Raiders recently?
(a) Kapil Dev
(b) Madan Lal
(c) Sanjay Manjrekar
(d) Sandeep Patil
(e) Karsan Ghavri
2. Of which two sports have actors Mohanlal and Mammootty become goodwill ambassadors in Kerala recently?
(a) Football & Boat racing
(b) Judo & Table Tennis
(c) Basketball & Cricket
(d) Athletics & Volleyball
(e) Wrestling & Weightlifting
Athletics & Volleyball
3. Olympic gold medallist Abhinav Bindra will be the new face to promote guns made by which company?
(e) Smith & Wesson
4. Mahela Jayawardene hit his sixth Test double century in the first Test of the series between India and Sri Lanka at Ahmedabad recently. Who holds the record of exceeding the score of 200 runs in an inning for the highest number of times in Test Cricket till date?
(a) Don Bradman
(b) Brian Lara
(c) Wally Hammond
(d) Marvan Atapattu
(e) Javed Miandad
5. Who won the Shanghai Masters Tennis tournament organised recently?
(a) Andy Murray
(b) Nikolay Davydenko
(c) Rafael Nadal
(d) Roger Federer
(e) Novak Djokovic
6. Sachin Tendulkar has the second longest One Day International (ODI) career currently. Who holds the record for the longest ODI career spanning 20 years and 272 days?
(a) Allan Border
(b) Kapil Dev
(c) Javed Miandad
(d) Brian Lara
(e) Andrew Flintoff
7. China beat India in the final to win the Asia Cup Hockey Championship for Women in Bangkok recently. Which Indian player was declared the player of the tournament?
(a) Suraj Lata Devi
(b) Subhadra Pradhan
(c) Mamta Kharab
(d) Madhu Yadav
(e) S. Omana Kumari
8. Who won the 2009 FIFA Under-17 World Cup in Abuja, Nigeria recently?
9. Which of the following statements about the Federation Cup Women’s Tennis Team tournament organised recently is incorrect?
(a) The final was played at Reggio Calabria
(b) Russia was the losing finalist
(c) The final was played on clay court
(d) The losing finalist was unable to win a single match in the final
(e) Flavia Pennetta, Francesca Schiavone, Sara Errani and Roberta Vinci were members of the winning team
Russia was the losing finalist
10. Which of the following statements about the schedule of the 2011 World Cup announced recently are correct?
I. India and Pakistan are in the same group
II. Bangladesh will host two quarter-finals while India and Sri Lanka will host one quarter-final each
III. Opening ceremony of the World Cup will be organised in Dhaka
(a) I only
(b) I and II only
(c) I and III only
(d) II and III only
(e) I, II and III
II and III only
11. Which of the following was selected as the official broadcaster of 2010 Commonwealth Games recently?
(a) Satellite Information Service Live
(b) International Games Broadcast Services
(c) Nimbus Sports International
(d) Canadian Broadcasting Corporation
(e) Big Productions
Satellite Information Service Live
12. Which well-known former Olympic gold medallist is Chairman of the London Organising Committee for the Olympic Games?
(a) Daley Thompson
(b) Sebastian Coe
(c) Steve Overt
(d) Robin Cousins
(e) Eric Heiden
13. Virender Sehwag was in news recently for missing his triple century in the India-Sri Lanka series by less than 10 runs. Who is the only batsman to have scored three triple centuries in Test Cricket?
(a) Allan Border
(b) Donald Bradman
(c) Brian Lara
(d) Both (2) & (3)
(e) None of the above
None of the above
14. Virender Sehwag was in news recently for his score of 293 runs in the first inning of the third test match between India and Sri Lanka in Mumbai. Who has scored the highest number of double centuries in tests for India?
(a) Virender Sehwag
(b) Rahul Dravid
(c) Sachin Tendulkar
(d) Sunil Gavaskar
(e) Both (1) and (3)
15. Which former Test Cricketer of Australia is the Chief Executive Officer of the Federation of International Cricketers’ Association (FICA) that looks after the interest of cricketers of Test playing countries?
(a) Allan Border
(b) Tim May
(c) Kim Hughes
(d) Tom Moody
(e) David Boon
16. Which of the following statements about India’s performance in Test Cricket are correct in light of recent developments?
I. The victory against Sri Lanka in third test of the 2009 series at Brabourne Stadium in Mumbai was India’s 100th test victory
II. India is the only country to have not lost a single Test in 2009
III. India’s score of 726 for nine declared in the first innings of the third test of India-Sri Lanka series at Brabourne Stadium, Mumbai is its highest total in Test cricket
(a) I only
(b) I and II only
(c) II and III only
(d) III and I only
(e) I, II and III
II and III only
17. Who was appointed as the new captain of the 21-member Indian Hockey team for the FIH Men’s Champions Challenge tournament in Salta, Argentina from December 6 to 13?
(a) Tushar Khandekar
(b) Dilip Tirkey
(c) Arjun Halappa
(d) Rajpal Singh
(e) Dhanraj Pillai
18. World Professional Billiards Champion Pankaj Advani accepted the Eklavya award, the highest recognition for a sportsperson in which state recently?
(c) Tamil Nadu
(e) Andhra Pradesh
19. Suresh Kalmadi was elected unopposed as the President of the Asian ______ Association for a third term at Guangzhou, China recently.
20. Which of the following has acquired the theatrical telecast rights for cricket matches of the Indian Premier League (IPL) 2010 and 2019 for Rs 330 crore recently?
(a) Entertainment and Sports Direct (ESD)
(b) Satellite Information Services (SIS)
(c) Triplecom Media
(d) Fox Sports International (FSI)
(e) Big Entertainment
FACT Mechanical Engineering Questions
Mechanical Engineering Questions For Practice All PSU-Non-IT companies Examination
1. Which is the common element between brass and bronze ?
2. What does following alloy designation indicate FG 250 ?
Ans. Grey cast iron with tensile strength of 250 MPa.
3. How is ceramic defined ?
Ans. It is a solid formed by combination of metallic and non-metallic elements.
4. Give one example of metal classified as per structure as BCC, FCC, HCP and CCP.
Ans. BCC (body centred cubic) structure — Molybdenum
FCC (face centred cubic) structure — Aluminium
HCP (hexagonal closed packed) structure — Zinc
CCP (cubic closed packed) structure — Copper.
5. What is the name of solid solution of carbon in alpha iron and delta iron ?
Ans. Ferrite and austenite respectively.
6. Explain the difference between pearlite and cementile ?
Ans. Pearlite is eutectoid mixture of ferrite and cementile. Cementite is chemical compound of iron and carbon.
7. Give one example each of the following proportion of materials-dimensional, physical, technological and mechanical.
Ans. Roughness, enthalpy, toughness, and hardness respectively.
8. For which parts the Wahl factor and Lewis form factor used ?
Ans. For springs and gears respectively.
9. How oxygen can be removed from steel during melting ? What are fully killed steels ?
Ans. Oxygen can be removed by adding elements such as manganese, silicon or aluminium which, because of their high affinity for oxygen, react with it to form non-metallic oxides which rise into the slag. Steels which have had most of their dissolved oxygen removed are called “fully killed steels”.
10. Hydrogen cannot be removed easily from molten steel. What harm hydrogen has on property of steel ?
Ans. Execessive hydrogen results in the formation of small fissures often described as hairline cracks or flakes in the steel. Large forgings in alloy steel are particularly sensitive to this phenomenon.
11. What is allotrope ? In what forms of cubic pattern, iron exists ?
Ans. Some elements exist in more than one crystalline form. Each form is known as “allotrope”. Iron exists in two forms of cubic pattern, namely body centered cubic (bcc) and face-centered cubic (fcc).
12. What is the difference between alpha iron, delta iron and gamma iron ?
Ans. The bcc form of iron exists between room temperature and 9100 C, and between 14000 C and the melting point at 15390 C. The lower temperature form is know as “alpha”-iron and the higher temperature form as “delta”-iron. The face-centered cubic form existing between 910 C and 1400 C is referred to as “gamma-iron”.
13. Metals, in general are of low strength and do not possess required physio-chemical and technological properties for a definite purpose. Alloys are therefore more than metals alone. Discuss the arrangement of atoms and structures of alloys.
Ans. Alloys are produced by melting or sintering two ore more metals, or metals and a non metal, together. Alloys possess typical properties inherent in the metallic state. The chemical elements that make up an alloy are called its components. An alloy can consist of two or more components. The phase and structures of alloys describe the constitution, transformations and properties of metals and alloys. A combination of phases in a state of equilibrium is called a system. A phase is a homogeneous portion of a system having the same composition and the same state of aggregation throughout its volume, and separated from the other portions of the system by interfaces. For instance, a homogeneous pure metal or alloy is a single-phase system. A state in which a liquid alloy (or metal) coexists with its crystals is a two-phase system. Structure refers to the shape, size or the mutual arrangement of the corresponding phases in metals or alloys. The structural components of an alloy are its individual portions, each having a single structure with its characteristic features.
14. What is the difference between isotropic material and homogeneous material ?
Ans. In homogeneous material the composition is same throughout and in isotropic material the elastic constants are same in all directions.
15. Explain the difference between the points of inflexion and contra flexure.
Ans. At points of inflexion in a loaded beam the bending moment is zero and at points of contra flexure in loaded beam the bending moment changes sign from increasing to decreasing.
16. What is the difference between proof resilience and modulus of resilience ?
Ans. Proof resilience is the maximum strain energy that can be stored in a material without permanent deformation. Modulus of resilience is the maximum strain energy stored in a material per unit volume.
17. What is the difference between column and strut ?
Ans. Both column and strut carry compressive load. Column is always vertical but strut as member of structure could carry axial compressive load in any direction.
18. Explain the difference between ferrite, austenite and graphite ?
Ans. Ferrite is the solid solution of carbon and other constituents in alpha-iron. It is soft, ductile and relatively weak.
Austenite is the solid solution of carbon and other constituents in gamma-iron. It exists in ordinary steels at elevated temperatures, but it is also found at ordinary temperatures in some stainless steels.
Graphite has a hexagonal layer lattice.
19. Explain the terms-solid solution, eutectic, eutectoid and peritectic.
Ans. Solid Solution. When a homogeneous mixture of two (or more) atomic forms exists in solid state, it is known as solid solution.
Eutectic. A mixture of two (or more) phases which solidify simultaneously from the liquid alloy is called an eutectic. Alloys in which the components solidify simultaneously at a constant temperature the lowest for the given system, are called eutectic alloys.
Eutectoid. Eutectoid alloys are the alloys for which two solid phases which are completely soluble become completely insoluble on cooling before a certain temperature called eutectoid temperature.
Peritectic. A periectic transformation involves a reaction between a solid and liquid that form a different and new solid phase. This three phase transformation occurs at a point called peritectic point.
20. What do you understand by critical points in iron, iron-carbide diagram ?
Ans. The temperatures at which the phase changes occur are called critical points (or temperatures).
FACT Mechanical Engineering Questions
Mechnical Engineering Solved Papers
1. What do you understand by points Ac1, Ac3, Ac4, Ar1, Ar3 and Ar4.
Ans. Ac1 represents the beginning of transformation of ferrite to austenite on heating. Ac3 the end of transformation of ferrite to austenite on heating and Ac4 the change from austenite to delta iron on heating. On cooling the critical points are referred to as Ar4, Ar3 and Ar1 respectively.
2. What is the percentage of chromium in 18 : 4 : 1 HSS ?
3. What is stellite ?
Ans. It is a non-ferrous cast alloy containing cobalt, chromium and tungsten.
4. Which rays are produced by cobalt-60 in industrial radiography ?
Ans. Gamma rays.
5. What are killed steels and what for these are used ?
Ans. Killed steels are deoxidized in the ladle with silicon and aluminium. On solidification no gas evolution occurs in these steels because they are free from oxygen.
6. What is critical temperature in metals ?
Ans. It is the temperature at which the phase change occurs in metals.
7. Car tyres are usually made of ________?
Ans. Styrene-butadine rubber.
8. What is the structure of pure iron and whether it is soft or hard ?
Ans. Ferrite and it is soft.
9. Which elements increase the corrosion resistance of steel ?
Ans. Chromium and nickel.
10. What causes hardness in steel ? How heat treatment alters properties of steel ?
Ans. The shape and distribution of the carbides in the iron determines the hardness of the steel. Carbides can be dissolved in austenite is the basis of the heat treatment of steel. If steel is heated above the A1 critical temperature to dissolve all the carbides, and then cooled, suitable cooling thought the cooling range will produce the desired size and distribution of carbides in the ferrite, imparting different properties.
11. Explain the formation of microstructures of pearlite, bainite and martensite in steel.
Ans. If austenite containing about 0.80 percent carbon is slowly cooled through the critical temperature, ferrite and cementite are rejected simultaneously, forming alternate plates or lamellae. This microstructure is called pearlite. At temperatures just belot the A1 the transformation from austenite to pearlite may take an appreciable time to initiate and complete, but the product will be lameller pearlite. As the transformation temperature is lowered, the time to initiate transformation shortens but the product is pearlite of increasing fineness, and at temperatures approaching 5500 C it cannot be resolved into its lamellar constituents. Further decrease in transformation temperature causes a lengthening of the incubation period and a change in structure of the product to a form known as “bainite”.
If the temperature is lowered sufficiently, the diffusion controlled nucleation and growth modes of transformation are suppressed completely and the austenite transforms by a diffusionless process in which the crystal lattice effectively shears to a new crystallographic configuration known as “martensite”. This phase has a tetragonal crystal structure and contains carbon in supersaturated solid solution.
12. How with alloying of steel it is possible to a achieve properties which can not be achieved with heat treatment ?
Ans. A prerequisite to the hardening of steels is that martensite should be formed on cooling, but this can only be achieved if the rate of cooling is great enough to suppress the formation of pearlite or bainite and in plain carbon steels this can be achieved by quenching relatively small specimens in water. Larger specimens, however, cannot be cooled sufficiently rapidly though the whole section because of the limited rate at which heat can be extracted through the surface of the piece. However, this difficulty can be overcome by alloying the steels to modify their transformation characteristics. For example, some alloying additions such as nickel and molybdenum reduce the rate of diffusion so that pearlite formation is suppressed in favour of the martensitic transformation.
13. What are the major effects of alloying elements ?
Ans. (1) To alter the transformation temperatures and times
(2) To modify the room temperature and elevated temperature strengths of given structures by (a) stiffening the crystals and (b) introducing complex precipitates which tend to harden the steel.
(3) To modify the type of oxide film formed on the surface of the steel and thereby affect its corrosion resistance.
14. What is the difference between austenite stabilisers and ferrite stabilisers ?
Ans. Austenite stabilisers have the effect of extending the temperature range over which austenite is formed. Such elements are carbon, manganese, nickel, copper and cobalt.
Ferrite stabilisers have the effect of extending the temperature range over which alpha and delta ferrite are formed, which consequently reduces temperature range over which austenite is formed. Such elements are silicon, chromium, molybdenum, tungsten, titanium and niobium.
15. What are the effects of carbon on the properties of steel.
Ans. In general, an increase in carbon content produces higher ultimate strength and hardness but lowers ductility and toughness of steel alloys. Carbon also increases air-hardening tendencies and weld hardness, especially in the presence of chromium. In low-alloy steel for high-temperature applications, the carbon content is usually restricted to a maximum of about 0.15% in order to assure optimum ductility for welding, expanding, and bending operations. To minimize intergranular corrosion caused by carbide precipitation, the carbon content of austenitic (18-8 type) alloys is limited in commercial specifications to a maximum of 0.08%, or even less, i.e. 0.03% in the extremely low – carbon grades used in certain corrosion-resistant applications.
In plain carbon steels in the normalised condition, the resistance to creep at temperatures be low 4400 C appears to increase with carbon content up to 0.4% carbon, at higher temperatures there is but little variation of creep properties with carbon content.
An increase in carbon content lessens the thermal and electrical conductivities of steel and increases its hardness on quenching.
16. What is the role of silicon as alloying element in steels ?
Ans. Silicon contributes greatly to the production of sound steel because of its deoxidizing and degasifying properties. When added in amounts up to 2.5%, the ultimate strength of the steel is increased without loss in ductility. Silicon in excess of 2.5% causes brittleness, and amounts higher than 5% make the steel non-malleable.
Resistance to oxidation and surface stability of steel are increased by the addition of silicon. These desirable effects partially compensate for the tendency of silicon to lower the creep properties of steel. Silicon increases the electrical resistivity of steel and decrease hysteresis losses.