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UPMSP Intermediate Metal Craft: Moulding in Ferrous Metals study materials
UPMSP Intermediate Metal Craft: Moulding in Ferrous Metals study resources

UPMSP Intermediate Metal Craft: Moulding in Ferrous Metals practice questions

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Question 1Foundry safety, health and environment

When pouring molten iron from a hand ladle, which footwear practice protects the caster from molten metal entering the boots?

  1. Rubber gum boots with the trousers tucked inside
  2. Trousers worn outside leather spats that cover the boot tops Correct answer.
  3. Leather sandals fastened with buckles at the side
  4. Canvas shoes with short socks and open tops

Explanation

Molten metal splashes and runs down the body; if it enters the boot top it is held against the skin and causes deep burns. Trousers worn outside leather spats that cover the boot tops let metal run off, and the footwear should be easy to remove if metal gets inside.

Question 2Foundry safety, health and environment

Respirable dust from silica sand is the main chronic health hazard in a ferrous foundry. Repeated overexposure to this dust causes which disease?

  1. Metal fume fever
  2. Asbestosis
  3. Lead poisoning
  4. Silicosis Correct answer.

Explanation

Fine crystalline silica from moulding and core sand reaches the alveoli and causes progressive fibrosis of the lung known as silicosis. It develops after years of overexposure and is irreversible, so dust must be controlled by extraction, wet methods and suitable respiratory protection.

Question 3Foundry safety, health and environment

Why must ladles, skimmers and moulding tools be thoroughly dried and preheated before they contact molten iron?

  1. To increase the carbon content of the molten iron
  2. To prevent steam from moisture flashing and ejecting molten metal Correct answer.
  3. To reduce the sulphur picked up from the sand mould
  4. To make the metal flow more slowly into the mould

Explanation

Moisture on a ladle or tool flashes to steam on contact with molten iron and expands enormously, throwing metal out of the vessel. Drying and preheating drive off the water and also stop the metal chilling too quickly, so both safety and casting quality improve.

Question 4Foundry safety, health and environment

A cupola operator is warned that carbon monoxide may be present in the charging area. Which property makes carbon monoxide particularly dangerous to foundry workers?

  1. It has a sharp smell that warns of its presence
  2. It forms a visible brown haze in the workplace
  3. It is odourless and binds strongly to haemoglobin Correct answer.
  4. It is heavier than air and collects in floor pits

Explanation

Carbon monoxide has no colour or smell, so workers get no warning before exposure. It binds to haemoglobin far more strongly than oxygen, reducing oxygen delivery and causing headache, dizziness and collapse; gas detectors and good ventilation are therefore essential.

Question 5Foundry safety, health and environment

Which control is most effective in reducing a moulder's exposure to respirable silica dust while mixing and riddling sand?

  1. Working faster so the dust is released for less time
  2. Wet sweeping of the floor only at the end of the shift
  3. A dust mask carried in the pocket for use after work
  4. Local exhaust ventilation hooded over the mixing point Correct answer.

Explanation

Local exhaust ventilation captures dust at the point where sand is mixed or riddled, before it reaches the breathing zone. It protects everyone nearby and does not depend on the worker remembering to wear a mask; respirators are only the last line of defence.

Question 6Foundry safety, health and environment

Furnace workers on a hot shift should follow which practice to reduce the risk of heat stress?

  1. Avoid salt in food and drink strong coffee
  2. Drink water frequently and take scheduled cool rest breaks Correct answer.
  3. Wear extra clothing to promote sweating
  4. Drink water only after the shift ends

Explanation

Sweating in a hot foundry loses water and salts, so workers must drink small amounts frequently and rest in a cool area. Acclimatisation, cooling and scheduled breaks prevent heat exhaustion and heat stroke; waiting until thirst or the end of the shift is too late.

Question 7Foundry safety, health and environment

After shakeout, used green sand containing binder residues must be handled in which way?

  1. Spread on the factory yard as a cheap soil conditioner
  2. Dumped in the nearest drain so it washes away in the rain
  3. Burned in the open to destroy the organic binder
  4. Sent for reclamation or to an approved landfill with records kept Correct answer.

Explanation

Used foundry sand with binder residues is a regulated waste; it should be reclaimed for reuse or sent to an approved landfill, with disposal records kept. Open dumping, drain disposal and burning pollute soil, water and air and are not permitted routes.

Question 8Foundry safety, health and environment

The shakeout floor shows noise levels above 90 dB(A). Under the hierarchy of control, which action should come first?

  1. Enclose the shakeout unit to reduce noise at source Correct answer.
  2. Issue earplugs and stop measuring the noise
  3. Rotate workers every 30 minutes
  4. Put a warning sign at the door

Explanation

The hierarchy of control requires elimination and engineering measures before administrative controls and PPE. Enclosing or damping the shakeout reduces noise at source and protects every worker, whereas earplugs and rotation only reduce individual exposure after the hazard exists.

Question 9Foundry safety, health and environment

What is the purpose of an afterburner in the cupola off-gas cleaning system?

  1. To cool the cupola shell so the refractory lining lasts longer
  2. To remove sulphur from the molten iron before it is tapped
  3. To add oxygen to the blast so the coke burns more quickly
  4. To burn carbon monoxide and hydrocarbons so the exhaust gas is less toxic Correct answer.

Explanation

Cupola waste gas contains carbon monoxide and tarry hydrocarbons from incomplete combustion. An afterburner adds secondary air and burns these gases, cutting carbon monoxide and smoke before the gas reaches the bag filter or stack, so the final emission is less toxic.

Question 10Foundry safety, health and environment

A moulder working with a no-bake urethane binder system develops wheezing and chest tightness that improve at weekends. Which binder component should be suspected as the cause?

  1. The isocyanate in the resin Correct answer.
  2. The bentonite used for green sand
  3. Coke breeze added to the sand
  4. Silica flour used as a filler

Explanation

Two-part urethane no-bake binders contain an isocyanate component that is a known respiratory sensitiser. Repeated exposure can cause occupational asthma, with wheezing and chest tightness that ease away from work; exposure needs local extraction, respirators and health surveillance.

Question 11Foundry safety, health and environment

During fettling of a ferrous casting, a worker uses a pedestal grinder to remove gates and fins. Which eye and face protection is appropriate for this task?

  1. A single pair of dark sunglasses to reduce glare from the sparks
  2. Close-fitting impact goggles worn together with a full face shield Correct answer.
  3. A face shield worn alone with no eye covering beneath it
  4. Ordinary prescription spectacles without side shields

Explanation

Grinding and fettling throw high-speed metal particles and abrasive fragments in unpredictable directions. Impact goggles seal against the face and stop small particles and dust, while a face shield over them absorbs larger fragments that could injure the face and neck. The two together give the required protection; neither alone is sufficient for this task.

Question 12Foundry safety, health and environment

A moulder is choosing clothing for work beside a ladle of molten iron. Which garment is the most dangerous choice if metal splashes?

  1. Flame-retardant cotton coverall worn with a leather apron
  2. Leather spats worn over leather safety boots
  3. Polyester tracksuit worn under a leather apron Correct answer.
  4. Wool jacket with fastenings at the neck and cuffs

Explanation

Synthetic fabrics such as polyester melt at low temperature and stick to the skin, so a splash produces a deeper and more extensive burn than the metal alone would cause. Work near molten ferrous metal requires outer clothing that chars rather than melts, such as treated cotton or wool, with leather over-garments at the front.

Question 13Foundry safety, health and environment

A small splash of molten iron burns a moulder's forearm. The metal has solidified and the skin is reddened but unbroken. What is the correct immediate first aid?

  1. Apply butter or oil to the burn and bandage it tightly
  2. Burst any blisters and cover the area with cotton waste
  3. Cool under clean running water for at least 20 minutes, then cover with a sterile non-stick dressing Correct answer.
  4. Rub the area with a dry cloth and return the worker to the moulding floor

Explanation

Prompt cooling with clean running water limits the depth of tissue damage and relieves pain, and a sterile non-stick dressing protects the burned area from infection. Traditional remedies such as oils or butter retain heat and contaminate the wound, and blisters should never be opened on the shop floor. The worker should also be referred for medical assessment.

Question 14Foundry safety, health and environment

Oxygen and acetylene cylinders used for cutting gates and sprue are kept in the foundry yard. Which storage arrangement follows safe practice?

  1. Oxygen and acetylene cylinders chained together in a single rack to save space
  2. Acetylene cylinders kept in a below-ground pit so that they stay cool in summer
  3. Cylinders laid flat inside a closed wooden store beside the cupola charging door
  4. Cylinders upright, secured, segregated by gas type and kept away from ignition sources Correct answer.

Explanation

Gas cylinders must stand upright and be restrained so they cannot fall, and fuel gas must be separated from oxygen by distance or a fire-resistant partition. Storage must be away from ignition sources and from hot plant such as the cupola, and cylinders must never be laid flat or confined in pits where a leak can accumulate.

Question 15Foundry safety, health and environment

A moulder is issued a tight-fitting half-mask respirator for dusty work around the sand mixer. Which practice is needed for the mask to give the expected protection?

  1. Wearing the mask over a beard provided the straps are pulled tight
  2. Face-fit testing, daily fit checks and a clean-shaven seal area Correct answer.
  3. Wearing the mask only in winter when the dust can be seen
  4. Sharing the same mask between workers without cleaning it

Explanation

A tight-fitting respirator only protects if its face seal is intact, so the wearer must be fit-tested and must check the seal each time it is worn. Facial hair, a poor seal or a damaged valve lets contaminated air bypass the filter. Masks are personal items and must be cleaned and stored correctly between uses.

Question 16Foundry safety, health and environment

Moulding boxes of about 40 kg must be moved repeatedly across the floor. Which approach best controls the risk of back injury?

  1. Carry the box at arm's length so that it cannot strike the legs
  2. Lift quickly with straight legs and a twisted trunk so the load is held for less time
  3. Reserve all box movement for the youngest worker on the shift
  4. Use a roller conveyor or crane, and where manual lifting is unavoidable use team lifting with bent knees and the load close to the body Correct answer.

Explanation

The hierarchy of control favours removing the manual lift altogether through mechanical aids such as cranes, conveyors or trolleys. Where a lift cannot be avoided, team lifting with the load close to the trunk, bent knees and a straight back reduces spinal loading, and twisting under load must be avoided.

Question 17Foundry safety, health and environment

Before a worker enters the cupola wind belt or a sand silo to clear a blockage, which requirement applies?

  1. A colleague stands at the access door and calls in every 30 minutes to check the entrant
  2. The worker holds his breath and works quickly so that no toxic gas can be inhaled
  3. A written permit, isolation with lockout, atmosphere testing and a standby person outside Correct answer.
  4. Leaving the access door open for five minutes before entry makes the space safe for a short job

Explanation

These spaces are confined spaces where oxygen deficiency or carbon monoxide can overcome a worker within seconds, so entry requires a permit, isolation of moving plant and energy, and testing of the atmosphere before and during entry. A trained standby person must remain outside with means of raising the alarm and rescuing the entrant without entering unprotected.

Question 18Foundry safety, health and environment

Slag tapped from a cupola is run into a slag pit. Why must the pit be kept dry and free from standing water?

  1. Trapped moisture flashes to steam and can eject molten slag explosively Correct answer.
  2. Wet slag solidifies too quickly and blocks the tapping hole
  3. Water raises the sulphur content of the slag and spoils its reuse
  4. A dry pit makes the slag easier to load and sell as aggregate

Explanation

Molten slag at well over 1,000 degrees Celsius turns trapped water instantly into a large volume of steam, and the expansion can throw slag and metal out of the pit onto nearby workers. The pit, the ladle and the slag pot must therefore be dry before hot slag is run in, and no water should be allowed to collect around them.

Question 19Foundry safety, health and environment

A local exhaust hood is fitted at a core-making bench, but workers report odour and headaches. A smoke test shows the hood captures little because the worker stands between the hood and the work. Which analysis is correct?

  1. Odour from core binders is only a comfort issue and needs no control
  2. The hood is badly positioned; the source must be captured between the worker and the hood, not across the worker's body Correct answer.
  3. The hood is oversized, so the duct diameter should be reduced to increase capture
  4. Moving the worker further from the bench will improve capture

Explanation

A local exhaust hood must be placed so that the contaminant is drawn away from the breathing zone, with the source between the worker and the hood and as close to the source as possible. If the worker stands in the path of the airflow, the contaminated air is drawn across the face and body before it reaches the hood, so the exposure remains. Re-positioning the hood is the first correction to make.

Question 20Foundry safety, health and environment

A fettler uses a pneumatic chipping hammer for six hours each shift and reports tingling and blanching of the fingers. Which action best follows the hierarchy of control for hand-arm vibration?

  1. Issue ear defenders so that the vibration is less noticeable
  2. Substitute with a low-vibration or automated tool, limit trigger time, maintain the tools and provide health surveillance Correct answer.
  3. Issue thicker anti-vibration gloves and keep the same exposure time, since gloves are the first control
  4. Raise the air pressure so that the job is completed more quickly

Explanation

Hand-arm vibration syndrome is prevented first by eliminating or substituting the vibrating process, for example with automated fettling or low-vibration tools. Remaining exposure is controlled by limiting trigger time, keeping tools and inserts maintained, and providing health surveillance so that early symptoms are detected. Gloves are a last-stage measure and give little attenuation of vibration.

Question 21Moulding sands: composition, properties, testing and preparation

In a typical green moulding sand used for ferrous castings, which constituent forms the bulk of the mixture and supplies most of its refractoriness?

  1. Sea coal
  2. Silica sand Correct answer.
  3. Bentonite clay
  4. Water

Explanation

Silica (SiO2) sand usually makes up the greater part of a green moulding sand by mass and is the constituent that withstands the heat of the molten iron. Clay acts only as the binder and water tempers it, so both are present in much smaller proportions, while sea coal is a minor additive.

Question 22Moulding sands: composition, properties, testing and preparation

Which property of a rammed moulding sand allows steam and evolved gases to pass out through the mould wall instead of being trapped in the casting?

  1. Adhesiveness
  2. Permeability Correct answer.
  3. Collapsibility
  4. Refractoriness

Explanation

Permeability is the ability of the rammed sand mass to transmit gases through the pores between its grains. If permeability is too low, gases from the metal and from the mould cannot escape and appear as blows and pinholes in the casting.

Question 23Moulding sands: composition, properties, testing and preparation

What is the usual moisture content of a tempered green sand moulding mixture for ferrous castings?

  1. About 4 to 8 percent Correct answer.
  2. About 0.5 to 1 percent
  3. About 15 to 20 percent
  4. About 25 to 30 percent

Explanation

Green sand is tempered with roughly 4 to 8 percent water by mass, which is just enough to plasticise the clay film around the grains. Much less water leaves the clay stiff and weak, while much more creates free water that blocks the pores and destroys permeability.

Question 24Moulding sands: composition, properties, testing and preparation

A sieve analysis of a moulding sand gives a high AFS grain fineness number. What does this indicate about the sand?

  1. The clay content is above the specified limit
  2. The grains are coarser and permeability is higher
  3. The moisture content is above the optimum value
  4. The grains are finer and permeability is lower Correct answer.

Explanation

The grain fineness number increases as the average grain size decreases, because a finer sand has more grains per unit mass and leaves more residue on the finer sieves. Finer grains give a smoother casting surface but the smaller pores reduce the rate at which gas can escape, so permeability falls.

Question 25Moulding sands: composition, properties, testing and preparation

How is the clay content of a moulding sand determined in the standard laboratory test?

  1. A rammed specimen is compressed until it breaks
  2. The sample is heated to a high temperature and the loss in mass is measured
  3. Air is passed through a rammed specimen under pressure
  4. The sample is washed with water, and the dried sand residue is weighed Correct answer.

Explanation

In the clay content test a weighed sample is washed with water, often with a deflocculating agent, so that the clay fraction is carried away in suspension. The remaining sand is dried and weighed again, and the loss in mass is reported as the percentage of clay.

Question 26Moulding sands: composition, properties, testing and preparation

What is the main purpose of mulling a moulding sand mixture?

  1. To dry the sand thoroughly so that no moisture at all remains in the mixture
  2. To break down hard lumps and screen out oversize particles before the prepared sand is stored
  3. To burn off sea coal and other additives so that the sand can be reused
  4. To coat each grain with a film of clay and water so the binder develops full strength Correct answer.

Explanation

Mulling kneads and smears the mixture so that the clay and water are worked into a thin film around every sand grain. Plain stirring cannot produce this film, so properly mulled sand develops noticeably higher green strength at the same clay and moisture content.

Question 27Moulding sands: composition, properties, testing and preparation

The strength measured on a rammed moulding sand specimen that still contains its tempering water is known as what kind of strength?

  1. Hot strength
  2. Green strength Correct answer.
  3. Flowability
  4. Dry strength

Explanation

Green strength is measured on a specimen in the moist, as-rammed condition, so it represents the mould as it is actually rammed and poured. Dry strength is measured after drying, and hot strength is measured at elevated temperature during pouring.

Question 28Moulding sands: composition, properties, testing and preparation

In the standard permeability test, the sand specimen is rammed in a tube to which set of dimensions?

  1. 25.4 mm diameter and 25.4 mm height
  2. 50.8 mm diameter and 50.8 mm height Correct answer.
  3. 100 mm diameter and 150 mm height
  4. 50.8 mm diameter and 100 mm height

Explanation

The standard permeability specimen is a rammed cylinder 50.8 mm in diameter and 50.8 mm high, prepared with a specified rammer and number of blows. Keeping the specimen size and ramming energy constant allows permeability figures from different tests and laboratories to be compared directly.

Question 29Moulding sands: composition, properties, testing and preparation

Water is added to a green sand mixture beyond its optimum tempering level. What effect does this have on the mould?

  1. Green strength falls and permeability falls, raising the risk of gas defects Correct answer.
  2. Permeability falls while green strength continues to rise steadily
  3. Green strength rises and permeability rises, so venting improves
  4. Green strength stays unchanged while refractoriness increases noticeably

Explanation

Green compressive strength reaches a peak at the optimum moisture content and then drops as excess water pushes the clay films apart and weakens the bond. At the same time the free water fills the pores, so permeability falls sharply and gas evolved during pouring is more likely to be trapped as blows or pinholes.

Question 30Moulding sands: composition, properties, testing and preparation

A foundry compares bentonite with ordinary fireclay as a binder for green sand. What behaviour should be expected?

  1. Bentonite requires a much larger addition than fireclay before the same green strength can be reached
  2. Bentonite develops the same strength at a much lower addition because of its higher bonding power Correct answer.
  3. The two clays behave identically, so the choice depends only on the delivered cost
  4. Fireclay gives much higher hot strength, so bentonite is used only in core sand mixtures

Explanation

Bentonite is a strongly swelling montmorillonite clay with far greater bonding power than kaolinitic fireclay, so it develops the required green strength at an addition of only a few percent. Fireclay must be added in much larger amounts and is preferred where higher hot strength or dry sand practice is needed.

Question 31Moulding sands: composition, properties, testing and preparation

In a green moulding sand for ferrous castings, which constituent acts as the principal binder that develops plasticity when tempered with water?

  1. Silica sand grains
  2. Sea coal dust
  3. Clay minerals Correct answer.
  4. Iron oxide fines

Explanation

Clay minerals are the active binder in green sand. When tempered with water they form a plastic film around the silica grains, and ramming packs these coated grains into a strong mould. Silica supplies the bulk refractory skeleton, while sea coal and iron oxide are not the principal binders.

Question 32Moulding sands: composition, properties, testing and preparation

Which grain shape of silica sand gives the lowest surface area for a given grain size, so that less clay binder is needed to coat the grains?

  1. Sub-angular grains
  2. Angular grains
  3. Rounded grains Correct answer.
  4. Splintery grains

Explanation

Rounded grains have the smallest surface area for a given volume, so a thinner clay film can coat them and still develop adequate strength. This also improves flowability during ramming. Angular or splintery grains expose more surface and require more binder for the same strength.

Question 33Moulding sands: composition, properties, testing and preparation

What is the principal function of adding coal dust (sea coal) to a green sand moulding mixture?

  1. To harden the mould rapidly after ramming
  2. To raise the fusion point of the silica sand grains
  3. To form a reducing atmosphere at the mould face Correct answer.
  4. To raise the tempering water requirement of the sand

Explanation

Sea coal is a carbonaceous additive. When molten metal contacts the mould, the coal dust volatilizes and forms a reducing gas film at the interface, which helps prevent oxidation and improves surface finish. It does not raise the fusion point of silica or harden the mould.

Question 34Moulding sands: composition, properties, testing and preparation

The shatter index of a moulding sand is determined by dropping a standard rammed specimen and measuring the percentage retained on a sieve. What property does this test chiefly assess?

  1. Green sand toughness under impact Correct answer.
  2. Dry compression strength after baking
  3. Permeability of the rammed mould wall
  4. Active clay content of the mixture

Explanation

The shatter index is found by dropping a standard rammed green sand specimen and measuring how much material remains on a sieve. A high retained percentage indicates a tough sand that resists impact and handling damage. It is not a measure of dry strength, permeability, or clay content.

Question 35Moulding sands: composition, properties, testing and preparation

A rammed moulding sand specimen is dried at about 105–110 °C and then tested in compression. The strength obtained is known as which property?

  1. Hot strength
  2. Wet tensile strength
  3. Dry strength Correct answer.
  4. Green strength

Explanation

Dry strength is measured on a specimen that has been dried at about 105–110 °C to remove free moisture. Green strength is measured while the tempering water is still present, and hot strength is measured at elevated temperature. Wet tensile strength is a different test used for certain bonded sands.

Question 36Moulding sands: composition, properties, testing and preparation

What effect does a broad grain size distribution, containing both coarse and fine silica grains, usually have on a green sand mould?

  1. It removes the need for a clay binder
  2. It increases permeability while reducing surface finish
  3. It raises the fusion point of the silica grains
  4. It decreases permeability and improves surface finish Correct answer.

Explanation

A broad grain size distribution lets fine grains fill the voids between coarse grains, making the sand denser. This lowers permeability because fewer connected pores remain, but the finer grains produce a smoother mould surface. A narrow, uniformly coarse sand would give higher permeability but a rougher finish.

Question 37Moulding sands: composition, properties, testing and preparation

In a foundry sand preparation plant, what is the purpose of passing the prepared sand through an aerator?

  1. To break up lumps and fluff the sand Correct answer.
  2. To measure the moisture content of the sand
  3. To coat the sand grains with clay binder
  4. To remove metallic particles from the sand

Explanation

An aerator is a sand preparation machine that breaks up lumps and fluffs the mixed sand. This improves flowability so the sand can be rammed uniformly around the pattern. Metal removal is done by a magnetic separator, and clay coating is done by mulling.

Question 38Moulding sands: composition, properties, testing and preparation

After many cycles of use, a green sand contains a large amount of dead clay. What is the most likely effect on the moulding sand?

  1. Reduced green strength and increased water demand Correct answer.
  2. Increased active binder and lower water demand
  3. Higher permeability with no change in strength
  4. Complete elimination of the need for tempering water

Explanation

Dead clay is clay that has been heated enough to lose its binding ability. As it accumulates, the active binder content falls, so green strength drops and more water is needed to temper the sand. Permeability may also suffer because the fine dead clay increases the fines content.

Question 39Moulding sands: composition, properties, testing and preparation

A heavy steel casting is to be poured and metal penetration at the mould face is a serious risk. Which sand change is most effective for increasing refractoriness at the mould face?

  1. Substitute zircon sand for some silica Correct answer.
  2. Use a finer silica sand with more clay
  3. Increase the moisture content of the green sand
  4. Increase the sea coal addition considerably

Explanation

Zircon sand has a higher refractoriness and greater chilling capacity than silica, so it resists metal penetration at the mould face. Replacing part of the silica with zircon is therefore effective for heavy steel castings. Extra moisture and finer silica with more clay tend to increase penetration risk rather than reduce it.

Question 40Moulding sands: composition, properties, testing and preparation

Why is adequate collapsibility important in a moulding sand used for ferrous castings?

  1. It increases the green compression strength of the mould
  2. It allows gases to escape through the mould wall
  3. It prevents the sand from sticking to the pattern
  4. It lets the mould yield as the casting contracts Correct answer.

Explanation

Collapsibility is the ability of the mould to give way when the solidifying casting contracts. If the sand remains rigid, contraction is restrained and hot tearing can occur. Permeability concerns gas escape, not contraction allowance.

Question 41Moulding sands: composition, properties, testing and preparation

In moulding-sand terminology, which property describes the ability of the sand mixture to cling to the surface of a pattern or moulding box?

  1. Cohesiveness
  2. Refractoriness
  3. Collapsibility
  4. Adhesiveness Correct answer.

Explanation

Adhesiveness is the sand's ability to stick to foreign surfaces such as a pattern or moulding box, whereas cohesiveness is internal bonding between grains. A sand with good adhesiveness draws cleanly around pattern surfaces and helps the mould retain its shape at the box walls.

Question 42Moulding sands: composition, properties, testing and preparation

Which property of a green moulding sand allows it to deform and fill the recesses and corners of a pattern during ramming?

  1. Permeability
  2. Dry strength
  3. Green strength
  4. Flowability Correct answer.

Explanation

Flowability is the ability of the sand mix to deform and flow around the pattern under ramming, filling recesses and corners. Green strength and dry strength describe resistance to failure, while permeability describes gas passage.

Question 43Moulding sands: composition, properties, testing and preparation

In the standard laboratory green compressive strength test for foundry moulding sand, what size is the rammed cylindrical specimen?

  1. 50.8 mm diameter × 50.8 mm high Correct answer.
  2. 25.4 mm diameter × 25.4 mm high
  3. 50.8 mm diameter × 101.6 mm high
  4. 101.6 mm diameter × 50.8 mm high

Explanation

The standard green compression specimen is rammed in a tube to 50.8 mm diameter and 50.8 mm height, equivalent to 2 in by 2 in. The compression strength is then calculated from the failure load divided by the specimen cross-sectional area.

Question 44Moulding sands: composition, properties, testing and preparation

A used green moulding sand shows a rising loss-on-ignition value. Which material does this test most directly indicate is accumulating?

  1. Accumulated silica fines from the sand system
  2. Organic binders and sea coal Correct answer.
  3. Iron oxide dust from castings and shot
  4. Residual tempering water in the sand

Explanation

Loss on ignition measures the mass lost when a dried sand sample is ignited, chiefly from burning organic binders, sea coal and other carbonaceous additives. A rising value therefore points to accumulation of combustible matter, which can increase gas evolution; water is measured separately by moisture determination.

Question 45Moulding sands: composition, properties, testing and preparation

What is the usual effect of adding clay to a green sand beyond the optimum amount needed to coat the grains?

  1. Lower permeability and more gas defects Correct answer.
  2. Higher permeability and lower green strength
  3. No further need for tempering water
  4. Markedly higher refractoriness of the mould

Explanation

Clay beyond the optimum fills pore spaces and consumes extra temper water, so permeability falls and gas escape becomes harder. Strength may rise somewhat, but the added gas-defect risk usually outweighs that benefit.

Question 46Moulding sands: composition, properties, testing and preparation

In a foundry sand-preparation line, why is hot return sand passed through a cooler before mulling?

  1. To stabilize moisture and bond behaviour Correct answer.
  2. To remove every silica fine from the sand
  3. To harden the bentonite permanently
  4. To raise the clay content of the mixture

Explanation

Hot return sand causes moisture to evaporate unevenly and makes compactability and strength fluctuate. Cooling before mulling brings the sand to a stable temperature so water and binder additions can be controlled consistently.

Question 47Moulding sands: composition, properties, testing and preparation

A foundry uses calcium bentonite in its green sand and adds a small amount of sodium carbonate during preparation. What is the purpose of this addition?

  1. To reduce the refractoriness of the sand grains
  2. To increase the carbon content of the sand
  3. To precipitate silica fines as slag
  4. To sodium-activate the bentonite Correct answer.

Explanation

Sodium carbonate supplies sodium ions that exchange with calcium ions on calcium bentonite, converting it toward sodium bentonite. The activated clay swells and disperses better, giving improved plasticity and green bond strength.

Question 48Moulding sands: composition, properties, testing and preparation

A ferrous green sand mould repeatedly shows expansion scabs on flat surfaces. Which sand-preparation change is most directly aimed at making the sand more deformable at high temperature?

  1. Increasing temper water beyond the optimum
  2. Ramming the mould harder to raise density
  3. Adding wood flour for hot deformability Correct answer.
  4. Adding extra clay beyond the optimum

Explanation

Wood flour burns out in the mould, leaving additional void space and making the sand more deformable at high temperature. That helps relieve expansion stresses that cause scabs; harder ramming, excess clay, or excess water tend to worsen the problem.

Question 49Patterns, pattern making and core boxes

According to the standard pattern colour coding followed in Indian foundries, which colour is applied on those pattern surfaces that will be machined after casting?

  1. Yellow
  2. Black
  3. Red Correct answer.
  4. Blue

Explanation

Indian foundry practice uses a standard colour code on patterns so that the moulder can identify each surface at a glance. Red marks surfaces that will be machined after casting, warning that machining stock has already been allowed on them. Yellow is reserved for core prints and black for surfaces left unmachined.

Question 50Patterns, pattern making and core boxes

A pattern is to be made for a grey cast iron casting. Which contraction allowance is most commonly provided per metre of pattern length?

  1. 20 mm
  2. 2 mm
  3. 30 mm
  4. 10 mm Correct answer.

Explanation

Grey cast iron contracts by about 1% on solidification and cooling, which corresponds to roughly 10 mm per metre of pattern length. Steel contracts about twice as much, close to 20 mm/m, so a steel pattern would need a larger allowance than a cast iron one.