Testing Procedure

IS Standards

Foreword

  • 0.1 This Indian Standard was adopted by the Indian Standards Institution on 8 August 1966, after the draft finalized by the Foundry Sectional Committee had been approved by the Structural and Metals Division Council.
  • 0.2 This standard outlines basic principles of physical tests for foundry sands. Any standard sand testing equipment shall be used for testing foundry sands. ‘The detailed precautions supplied by the manufacturer with the testing equipment shall be followed along with the procedures specified in this standard. The test specimen to be used shall be one of the two recommended in this standard as applicable to the equipment.
  • 0.3 This standard keeps in view the manufacturing and trade practices followed in the country in this field. While prepare this standard assistance has been derived from the following:
    • DIN 52401 Examination of clay free and clay bonded moulding sand in the loose and in the compressed moist and green state. Deutscher Normenausschuss.
    • Foundry sand handbook. 1963. Ed 7. American Foundry men’s Society, Illinois, USA.
  • 0.4 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS : 2-1960*. The number of significant places retained- in the rounded off value should be the same as that of the specified value in this standard.

1. Scope

  • 1.1 This standard prescribes the methods of tests for foundry sand to evaluate their properties under standard conditions.

2. Terminology

  • 2.1 For the purpose of this standard, the term 'Foundry Moulding Sand' shall include high-silica sand, natural moulding sand, synthetic moulding, sand mixtures, and reclaimed sand placed in heaps on the foundry floor for reuse.
  • 2.2 The term 'Core Sand' shall cover sand that is suitable for making cores, usually low in clay substance.

Rules for rounding off numerical values.

3. Sampling

  • 3.1 Representative samples shall be drawn according to the scheme of sampling given in IS: 1811-1984*.

4. Preparation of Foundry Sand for Testing

  • 4.1 Preparation of High-Silica Sand - The samples in accordance with 3.1 shall be used without any processing.
  • 4.2 Preparation of Natural Moulding Sand
  • 4.2.1Tempering by Hand- Dry about 2-kg sample of sand for one hour at 1050 to 110°C. Spread the sand over a large area in a thin layer so that all moisture is expelled in the given time. After allowing the sand to cool down to room temperature, measure the quantity of water needed to give the desired moisture content ( in terms of percent weight of tempered mix ), adding little extra water (usually from O.25 to 1.O percent) to allow for evaporation. Spread the sand on a smooth, flat, dry, non-absorbent surface in a layer about 25 mm thick. Sprinkle a small quantity of the water from the measured quantity evenly over the sand and work the sand gradually. Spread again the sand into a thin layer and repeat the above operations, adding more water. Repeat the process until all the water has been thoroughly distributed in the sand. There should be no dry lumps or other evidence of uneven tempering.
  • 4.2.2Alternate Method of Tempering by Hand- In case sand has lower moisture content than desired, it need not be dried before tempering. Add sufficient water to bring the sand to the desired moisture content. In case the sand has higher moisture content than desired, the sand shall be partially dried, allowed to cool and then tempered with sufficient water to bring the moisture to the desired value.
  • 4.2.3Tempering by Mechanical Mixing - Dry about 2-kg sample of sand as given in 4.2.1. Place the dried sand in the laboratory mixer and add sufficient water to produce the desired moisture content plus an additional amount to allow for evaporation during mixing. Water should be added gradually within 30 seconds while the mixer is operating. Total mixing time should be 5 minutes.
  • Note: Any one method of tempering shall be followed throughout to prepare sand mixture of same or different moisture contents during the course of an investigation for evaluating a sand sample.
  • *Methods of sampling foundry sands

  • 4.3Preparation of Synthetically Bonded Sand Mixture - Test samples of synthetically bonded sand mixture shall be prepared in a mechanical mixer. Dry about 2 kg of sand for one hour at 105° to 110°C. Spread the sand over a large area in a thin layer so that all moisture is expelled in the given time. After drying and cooling to room temperature, weigh the correct amounts of sand or sands, and bond or bonds, as used in the foundry mixtures. Place the dried sand and then the dried bonding materials, in the mixer. Place the cover on the mixer, start the mixer and mix for two minutes. Following the two-minute mixing period, allow two minutes for dust to settle before removing the mixer cover. Add the required amount of water gradually within 30 seconds to give the required moisture percentage plus sufficient additional water to allow for evaporation during mixing. Mix for a period of 5 minutes. Remove the sand from the mixer as quickly as possible. Allow samples to stand in an air-tight container for two hours before testing.
  • Note: - Variation in physical properties with moisture content shall be determined by giving small increments to water content (say 0.5 to 1.0 percent).

5. PREPARATION OF STANDARD TEST SPECIMEN

  • 5.1 Apparatus - Standard sand rammer with accessories.
  • 5.2 Apparatus - Cylindrical test specimen of 50.8±0.03 mm height and 50.8 mm diameter (or of 50 ± 0.3 mm height and 50 mm diameter) shall be used.
  • 5.3 Procedure - Weigh sufficient quantity of tempered sand mixture to make, when rammed, a specimen of required height. Place the sand carefully in the specimen container. After levelling the sand in the container, gently lower the ramming head into the specimen container, until it is supported by the sand. Slowly raise the rammer weight by hand or by cam to the full height of the specimen and let it fall. Repeat twice, making a total of 3 rams to get the standard test specimen.
  • 5.3.1 - For sands which do not possess sufficient bond strength to permit handling, a circular drier plate shall be placed on top of a stripping post. After the specimen is stripped from the container, it shall be handled by lifting the drier plate.
  • 5.3.2 - For preparing specimens of low bond straight, ramming is done in a split specimen tube. The specimen, after it is rammed, is removed from the split specimen tube by opening the tube and allowing the specimen to rest on a drier plate.

SECTION 2 METHOD OF PHYSICAL TESTS FOR FOUNDRY MOULDING SANDS

6.DETERMINATION OF MOISTURE CONTENT

  • 6.1 Direct Weight Method*
  • 6.1.1 Procedure - Weigh accurately about 100 g of sample of sand in a tared covered porcelain dish. Dry it in a uniformly heated oven between 1050 and 1100 C for about one hour. Cool to room temperature and weigh. Repeat the process of drying and cooling till constant weight is attained.
  • 6.1.2Calculate the percentage moisture by the following formula: Moisture, percent = A/B x100
    Where
    A = loss of weight of the sand sample in g on heating, and
    B = weight in g of the sand sample taken
  • 6.1.3 Make the determination on three separate samples and take the average of three test results as the moisture content of the sand.
  • 6.2 Calcium Carbide Method
  • 6.2.1Apparatus - Speedy moisture tester.
  • 6.2.2Procedure - Weigh accurately about 6g of sample of sand and place it in the cap of the instrument. Take a measure of calcium carbide and place in the shaker. Place the cap and the shaker in the horizontal position, adjust stirrup, fasten cap to shaker with set screw on stirrup and finally shake the contents. Read moisture content on dial gauge keeping the apparatus in a horizontal position. Make determinations on three separate samples and take the average of three results as the moisture content of the sand mixture.
  • Note: The sand mixture and calcium carbide should not come in contact with each other until the cap of the moisture tester is securely in place.
  • 6.3 Control Methods For control tests, moisture in foundry sands may be determined by direct weight method, calcium carbide method or by any other method ( such as dielectric type moisture meters ) which will duplicate the accuracy of results obtained by the direct weight method.
    * This method is applicable for all sand mixtures except those containing volatile material (Other than water) or oxidisable materials such as core oils or both. For such sand mixture, calcium carbide method (see 6.2) shall be used.

7. DETERMINATION OF CLAY CONTENT

  • 7.1 ApparatusAn electric rapid agitator equipped with vertical baffles or a rotating sand washer shall be used
  • 7.2 Reagent
  • 7.2.1Sodium Hydroxide Solution (IS Standard) - Dissolve 30 g of sodium hydroxide in distilled water and dilute to a total volume of one litre. Or Sodium Pyrophosphate – Dissolve 20 g of tetra sodium pyro-phosphate in distilled water and dilute to total volume of one litre.
  • 7.3 Procedure
  • 7.3.1General-Take a 50 g representative sand sample. Spread it over a large area in thin layer and dry it for one hour at 1050 to 110°C so that all moisture is expelled. Weigh the dried sample and place it in an electric rapid agitator equipped with vertical baffles or a rotating sand washer. Add 475 ml of distilled water (pH 7.0 deionized or demineralized water) and 25 ml of sodium hydroxide/sodium pyrophosphate solution at room temperature. Stir for five minutes. (If a rotating washer is used, place the cover on the jar, and the jar in a machine making about 60 rev/ min in such a manner as to allow the jar to be opened at each revolution. Operate the machine for one hour. Then remove the jar from the machine, unseal the cover and wash the adhering sand into the jar) Wash sand from the stirrer into the jar and fill the jar with distilled water to a height of 150 mm above the bottom of the jar and in such a manner that the contents are well stirred. Allow to settle for 10 minutes and then syphon off the water to a depth of exactly 125 mm below the level to which it had been filled, leaving a minimum depth of 25 mm of water in the bottom of the jar. Add distilled water, again filling the jar to the 150 mm height, stirring the sediment at the bottom. After settling for the second time for 10 minutes, again siphon off 125 mm of the water. Add water again filling to 150 mm height, stirring the sediment at the bottom. After settling exactly for 5 minutes, siphon off 125 mm of the water. Repeat the process of five minutes standing and siphoning until the water is clear to a depth of 125 mm at the end of five-minute period. By this method, the material which fails to settle at a rate of 25mm per minute is removed. This is standard clay grade matter and includes all grains of 20 microns or less in diameter. Dry and weigh the remaining grains. The difference between the weight of the dried grains and that of the original 50 g sample represents clay content.
  • note Certain varieties of sand may rewire longer agitation to liberate properly the clay from the sand grains. Incomplete clay removal may be checked microscopically
  • 7.3.1.1 Calculate clay content and sand portion by the following formulae:-
    Clay content, percent = (W1-W2)/W1 x 100
    Sand portion, percent = W2/W1 x 100
    where
    W1 = weight in g of the dried sand sample taken for the test, &
    W2 = weight in g of the dried sand portion (free from clay).
  • 7.3.2.1Synthetic Sand MixtureThe procedure in accordance with 7.3.1 shall be slightly changed for sand mixtures containing coal dust, coal residues, and binder residues. As given in 7.3.1, 50g of foundry sand is washed after drying. In the course of washing operation a part of the coal dust and similar substances is removed, the remainder being part of the sand portion. The washed sand portion is heated in a porcelain crucible to 750°C for burning the coal and the coalfree sand is weighed. The heating loss, equal to the total coal content, is determined by heating to 750°C and weighing a separate sample of unwashed, dried foundry sand. The heating time should be sufficient for complete combustion of the coal contained in the sand. The clay substance shall be the difference between the true sand portion (washed and heated sample) plus coal portion (of unwashed and heated sample), and the total quantity of unwashed dried sand.
  • 7.3.2.1 If cereal binders (especially dextrin) are present in the sand, a preliminary wash shall be made without adding sodium hydroxide/sodium pyrophosphate to the distilled water. After stirring and allowing the sand to settle for 10 minutes, siphon off the water. Then proceed as under 7.3.1
  • 7.3.2.2 A sand mixture containing cement cannot be washed free of cement by the method given under 7.3.1. The cement shall be removed from the sand grains by adding 25 ml of dilute hydrochloric acid (1:1 by volume) instead of sodium hydroxide/sodium pyrophosphate, taking suitable precautions against acid attacking the agitating apparatus.

8. DETERMINATION OF GRAIN FINENESS

  • 8.1 General-The percentage of grain sizes shall be determined by sieving the dried clay-free sand. Sifting time shall be at least 15 minutes and the test sieves used shall be 3.35-mm, l.70mm, 850-micron, 600-micron, 425-micron, 300-micron, 212-micron, 150-micron, 106-micron, 75-micron and 53-micron IS Sieves.
  • Find the conversion table for IS Sieve designations, BSS and ASTM below:

    Sl No.
    Indian Standard Sieve Designation
    Sieve series width of Aperture (mm)
    Casting WtBSS Mesh No
    ASTM No.
    01
    3.35 mm
    3.35
    5
    6
    02
    1.70 mm
    1.70
    10
    12
    03
    850 micron
    0.850
    18
    20
    04
    600 micron
    0.600
    25
    30
    05
    425 micron
    0.425
    36
    40
    06
    300 micron
    0.300
    52
    50
    07
    212 micron
    0.212
    72
    70
    08
    150 micron
    0.150
    100
    100
    09
    106 micron
    0.106
    150
    140
    10
    75 micron
    0.075
    200
    200
    11
    53 micron
    0.053
    300
    270
  • 8.2 ApparatusA set of Indian Standards Sieves.
  • 8.3 ProcedureSieve 50 g of representative sample through 11 sieves indicated under 8.1 starting with the coarse sieve. Weigh out the sand retained on each sieve and the pan material individually and put down as percent of the dried unwashed sand.
  • 8.4 Evaluation of Fineness of Sand
  • 8.4.1 Size-Frequency Curve - The size-frequency curve shall be obtained by plotting the percent of sand retained on each sieve (see Fig. 1)
  • graph
  • 8.4.2 Cumulative Curve -The cumulative curve points shall indicate the percentage of particles larger than the sieve size represented by that point (See Fig.1). The cumulative curve is always smooth, whereas size frequency curve may not always be a broken line connecting the different sieve points. If sand is taken on specification, two cumulative curves may be drawn showing the limiting values for each sieve. Then, if the curve of the sand being tested falls between these two curves it shall be satisfactory. Finally, data for slit and clay may be plotted as a part of the same graph. Sieves that retain little material may be eliminated or additional ones may be added without distorting the curve. If there are faulty sieves these shall be indicated by a break at the same point in the curve when different samples of the same sand arc sieved
  • 8.4.3Sorting Coefficient -An index to the sorting or distribution of the grains in a sand sample shall be obtained from the sorting coefficient, So defined by the following formula:
    So = Q1/Q3
    where
    Q1 is the size in microns where the cumulative curve for sand crosses the 25 percent retained line and Q3 is the size in microns where the curve crosses 75 percent retained. Sorting coefficient is a rapid method of indicating the slope of the curve. This is also a measure of the distribution. The range of distribution numbers shall be from 1.0 for particles of uniform size, such as ball bearings to a maximum of about 10.0. Washed and graded sands shall range from l.14 to l.40 while naturally bonded sands are usually between I.40 and 2.50.
  • 8.4.4Grain Fineness Number - It is approximately 2.54 times the number of meshes per centimetre of that sieve which would allow to pass the sample if its grains were of a uniform size, that is, the average of the sizes of grain in the sample. It is approximately proportional to the surface area per unit weight of sand, exclusive of clay.
  • 8.4.4.1Calculation of fineness number - Express the weight in grams of various sizes according to the procedure given under 8.3 as percentage of the original 50 g sample. Multiply them by the multipliers as given in Table 1. Add the products and divide the total by the sum of the percentages of sand grains. The result shall be the grain fineness number.
  • TABLE 1 MULTIPLIER FOR GRAIN FINENESS NUMBER

    IS SIEVE
    MULTIPLIER
    3.35-mm
    3
    1.70-mm
    5
    850-micron
    10
    600-micron
    20
    425-micron
    30
    300-micron
    40
    212-micron
    50
    150-micron
    70
    106-micron
    100
    75-micron
    140
    53-micron
    200
    Pan
    300

9. DETERMINATION OF GRAIN SHAPE

  • 9.1 Apparatus -A low power stereoscopic microscope working with reflected light and giving magnifications of 30 x to 60 x.
  • 9.2 Procedure-The grain shape shall be determined by the microscopic examination of small portions of the grain size fractions from all the sieves and the pan at magnifications of 30 x to 60 x.
  • 9.2.1- The grain shapes to be distinguished are rounded, sub angular, angular and splintered as shown in Fig. 2. Identification for grain shape shall be based on the predominant grain shape of the largest fraction (by weight) of sand.

10. DETERMINATION OF PERMEABILITY

  • 10.0Permeability is defined as that physical property of the moulded mass of sand mixture which allows gas to pass through it. It is numerically equal to the volume of air in millilitres that will pass per minute under a pressure of 1 gf/cms through a specimen of 1 cms in crosssectional area and 1 cm high
  • 10.1 Determination of Base Permeability Base permeability is the permeability of packed dry sand grains containing no clay or other bonding substance.
  • 10.1.1Apparatus
  • 10.1.1.1 Standard permeability meter
  • 10.1.1.2Stop-watch
  • 10.1.1.3 Standard sand rammer along with the standard specimen container and special screens to be kept at each end of the specimen to hold the bond free sand in position in the specimen tube. The screen shall be saucer shaped, one pressed within the other, the saucer being of such diameter as to just fit into the standard specimen container. The outer screen shall be of metal and perforated with at least 100 holes at the rate of 16 holes of 1.6 mm diameter per square centimetre.
  • 10.1.2 Procedure -Wash the sample for its clay content in accordance with the method given under 7.3 and dry the sand grains thoroughly at 1050 to 1100. Place a base permeability screen, with sides of the cup upward, in the bottom of the standard specimen container. Place sufficient quantity of dried sand in the specimen container to produce the standard sand test specimen. Place the second base permeability screen, with sides of the cup downward, on top of the sand in the specimen container. Run the specimen in accordance with the method given in 5.3 but do not remove the specimen from the container. Place the specimen container with the specimen in the mercury seal of the permeability apparatus. Find out the time required for exactly 2000 ml of air to pass through the specimen. After the pressure has become steady, read the pressure on the pressure indicator and record in gf/cms.
  • Calculate the base permeability number (P) of the sand from the following formula:
    p=(vxh)/(pxaxt)
    where,
  • v = volume of air in ml passed through the specimen,
  • h = height of the test specimen in cm,
  • p = pressure of the air in gf/ cm2,
  • a = cross-sectional area of the test specimen in cm2, and
  • t = time in minutes.
  • 10.1.2.2 Test three specimens individually. The base permeability shall be the average of three tests. If the test result of one of the test specimens varies more than 10 percent from the average of three, this result shall be discarded and another specimen tested.
  • 10.2 Determination of Green PermeabilityThe green permeability of foundry moulding sand is the permeability of a moulded mass of sand in its moist or tempered condition. In other words, it is the permeability of a naturally or synthetically-bonded foundry moulding sand mixture which (a) has been mixed and tempered experimentally in the laboratory or (b) has been mixed and tempered for use in the foundry.
  • 10.2.1Apparatus- Same as described in 10.1.1
  • 10.2.2Test Specimen Ram the standard test specimen in a specimen container and follow the procedure as given in 10.1.2.
  • 10.3 Determination of Dry Permeability
  • 10.3.1Apparatus - Same as described in 10.1.1.
  • 10.3.1.1Special type of split specimen container used for ramming test specimens (see 5.3.2).
  • 10.3.1.2Standard drier
  • 10.3.1.3 Special permeability machine attachment for the determination of dry permeability.
  • 10.3.2Test specimen - The standard test specimen specified under 5 shall be used after drying at 1050 to 110°C in the drier for a period of 2 hours and cooling to room temperature in a desiccator.
  • 10.3.3Procedure Using the split specimen container to hold the dried specimen, determine the dry permeability as in 10.1.2.

11. DETERMINATION OF TENSILE STRENGTH

  • 11.0 The tensile strength of a moulding sand mixture is the maximum tensile stress which the sand mixture is capable of sustaining when prepared, rammed and tested according to standard procedures.
  • 11.1 Determination of Green Tensile Strength - Green tensile strength is the tensile strength of a foundry sand mixture in the moist or tempered condition.
  • 11.1.1 Apparatus - Dead weight type of universal sand strength testing machine or spring type of sand strength testing machine.
  • 11.1.2 Test Specimen -A specially designed specimen tube shall be used for making the standard test specimen (see 5.2). It shall be a two part tube designed so that the specimen may remain in the tube during testing and the two halves of the tube readily separate approximately at the middle of the specimen when it fails (see Fig. 3).
  • 11.1.2.1In preparing the test specimen the specimen tube is placed on its pedestal cap and the tube carefully filled with the correct weight of sand to be tested. The specimen tube and pedestal cap are then placed directly beneath the rammer and rammed according to the procedure given under 5.3.
  • 11.1.3 Procedure Place the rammed specimen contained in the specimen tube in the specimen tube holder and hold firmly by means of two clamp screws. Apply a uniform load along the axis of standard test specimen at the rate not exceeding 1.5 ± 0.5 gf/ mm2 per minute until the specimen breaks. Record the breaking load in grams and calculate the tensile strength in kgf/ cm& by dividing the breaking load with area of rupture section.
  • specimen-tube
  • 11.1.3.1An average of three tensile tests shall be taken. If the test result of one of the three varies more than 10 percent from the average of three, this result shall be discarded and another specimen tested.
  • 11.2 Determination of Dry Tensile Strength - Dry tensile strength is the tensile strength of a foundry sand mixture which has been dried at 1050 to 110°C and cooled to room temperature in a desiccator.
  • 11.2.1 Apparatus- Same is described in 11.1.1 together with a standard drier.
  • 112.2 Test SpecimenThe standard test specimen contained in the specimen tube (see 11.1.2 and 11.1.2.1) shall be used after drying at 1050 to 1100 C in a drier for a period of 2 hours or until dry, and cooling to room temperature.
  • 11.2.3 ProcedureTest the dried specimen in the specimen tube as under 11.1.3. In this test the rate of loading shall not exceed 10.0 ± 1.5 gf/ mm2 per minute.

12. DETERMINATION OF COMPRESSION STRENGTH

  • 12.1 Determination of Green Compression Strength - The green compression strength of a foundry moulding sand is the maximum compressive stress in gf/ mm2 which the sand in unbaked condition is capable of withstanding.
  • 12.1.1 Apparatus- Dead weight type of universal sand strength testing machine or spring type of sand strength testing machine.
  • 12.1.2 Test Specimen- The standard test specimen specified in 5 shall be used.
  • 12.1.3 Procedure Ram a standard test specimen and strip it from the specimen container. Place the test specimen in the compression machine in such a manner that the top of the specimen as rammed in the specimen container rests against the upper head of the machine. Apply a uniform load against the plane faces of the specimen so that the force is axial at a rate of 21 ± 4 gf/ mm2 per minute until the specimen breaks. Record the load at rupture
  • 12.1.3.1 Calculate the green compression strength from the following formula:-
  • Green compression strength, gf/ mm2 = F/A
  • where,
  • F = load at rupture in gf, and
  • A = cross-sectional area of the test specimen in mm2.
  • 12.1.3.2 Test three specimens individually. The compressive strength shall be the average of three tests. If the test result of one of the specimens varies by more than 10 percent, from the average of the three this result shall be discarded and another specimen tested.
  • 12.2 Determination of Dry and Baked Compression StrengthDry compression strength is the maximum compressive stress in gf/ mm2 which a dry sand mixture is capable of developing. In case the test specimen has been baked at a specified temperature above 1100 C, the maximum compressive stress in gf/ mm2 developed is known as ‘baked compression strength’.
  • 12.2.1 Apparatus12.1.1
  • 12.2.2Test Specimen- The standard test specimen specified in 5 shall be used.
  • 12.2.2.1 Drying - When the test is applied to sands for use in green sand moulds, the specimen shall be dried on a flat, rigid plate in a ventilated oven and allowed to cool to room temperature in a desiccator. Test the specimen after it has reached the room temperature.
  • 12.2.2.2 Baking- When the test is applied to sands used for dry sand moulding or to other mixtures which would normally be baked at a temperature higher than 1100C, a baking temperature and time which is suitable for that particular mixture should be used.
  • 12.2.3 Procedure -The standard test specimen after removal from the specimen container shall be dried or baked and cooled as specified in 12.2.2. The specimen should be placed in the apparatus with the same side against the compression head which was uppermost in the specimen container during ramming. Apply a uniform load against the plain surfaces of the specimen so that the force is axial at a rate of 100±15 gf/ mm2 per minute, until the specimen breaks. Record the load at rupture. Calculate the dry or baked compression strength as under 12.1.3.1.

13. DETERMINATION OF SHEAR STRENGTH

  • 13.1 Determination of Green Shear Strength- The green shear strength of sand is the maximum shear stress which a tempered sand mixture is capable of developing.
  • 13.1.1 Test Specimen - The standard test specimen specified in 5 shall be used.
  • 13.1.3Procedure Ram a standard test specimen and strip from the specimen container. Place the specimen between the shear heads of the machine in such a way that the load is applied along a line through its axis. Apply a uniform load to the diametrically opposite halves of the two plain surfaces of the specimen at the rate of 17 ± 4 gf/ mm2 per minute. Record the breaking load in kg and calculate the shear strength in gf/ mm2 by dividing the breaking load by area of rupture section.
  • 13.1.3.1 Test three specimens individually. The sheer strength shall be the average of three tests. If the test result of one of the specimens varied more than 10 percent, from the average of the three, this result shall be carded and another specimen tested.
  • 13.2 Determination of Dry Shear Strength - The method given in 13.1 shall be employed for the determination of dry shear strength, except that the test specimen shall be dried at 1050 to 110°C for 2 hours or until dried, and allowed to cool in a desiccator to room temperature before testing.

14. DETERMINATION OF BULK DENSITY

  • 14.1 Determination of Bulk Density before Compression
  • 14.1.1Procedure -Take 500 g of tempered sand mixture as prepared under 4 and allow it to fall in a one-litre measuring cylinder through a perforated disc rotating slowly at the 1 000 ml mark. After the whole sand has dropped into the measuring flask, even out the sand surface by slightly pressing with the perforated disc. The ratio of the mass of the sand to the volume occupied by it will represent the bulk density before compression in grams per millilitre (g/ ml).
  • 14.2 Determination of Bulk Density after Compression
  • 14.2.1Apparatus- Standard rammer and physical balance
  • 14.2.2 Test Specimen The standard test specimen specified in 5 shall be used.
  • 14.2.3 Procedure - Ram a standard test specimen as given in 5.3. Weigh it in a balance and also calculate its volume from its dimensions. The ratio of the weight of the specimen to the volume will give the bulk density after compression in g/ ml.

15. DETERMINATION OF GREEN MOULD SURFACE HARDNESS

  • 15.0Green mould surface hardness is the resistance offered by the surface of a green sand mould to penetration by a loaded plunger.
  • 15.1Apparatus- Standard mould surface hardness tester.
  • 15.1.1Procedure - Bring the unloaded plunger of the tester in contact with the mould surface. Apply the load to the plunger and read the hardness number on the graduated dial of the testing apparatus.
  • note -The test is performed on standard test specimen prepared as given in 5 or on the mould itself. The test should be performed immediately after the specimen is stripped from the tube or the pattern is withdrawn from the mould.

16. DETERMINATION OF FLOWABILITY

  • 16.0In general the term ‘Flowability’ refers to the movement of sand grains when they are subjected to moulding forces.
  • 16.1Apparatus -Standard sand rammer together with the standard flowability meter.
  • 16.2Test Specimen- - The standard test specimen specified in 5 shall be used.
  • 16.3Procedure - Read the percent flowability on the dial of the flowability meter after the fifth drop of the ramming weight. The stem of the flowability meter rests against the top of the plunger of the rammer and registers the movement of the rammer plunger between the fourth and fifth drops as percentage flowability.
  • 16.3.1Test three specimens individually. The flowability number shall be the average of three tests. If the test result of one of the specimens varies more than 10 percent from the average of three, this result shall be discarded and another specimen tested.

17. DETERMINATION OF SHATTER INDEX

  • 17.1 Test Specimen- The standard test specimen specified in 5 shall be used.
  • 17.2 Procedure - Ram a standard test specimen by 10 blows in accordance with the method given in 5.3 and allow it to fall from a height of 1 830 mm. Collect the portion of the sand retained on 12-mm IS Sieve. The percent weight retained shall be the shatter index.

18. DETERMINATION OF SINTERING POINT

  • 18.1 Determination of Sintering Point of High-Silica Sand – Sintering point of high-silica sand shall be determined in accordance with the method given under 3 of IS:1528-1962*. * Methods of sampling and physical tests for refractory materials.
  • 18.2 Determination of Sintering Point of Foundry Sand Mixtures
  • 18.2.1 Apparatus
  • 18.2.1.1Porcelain combustion boats - of 75 to 90 mm length and 10 to 15 mm width.
  • 18.2.1.2Electric furnace - with a testing temperature of at least 1 500°C.
  • 18.2.2.2 Procedure - Loosely fill the sand sample in the combustion boat and place the boat in the hot zone of the electric furnace. When temperature has reached 1000°C keep the temperature constant for at least 3 minutes. Take out the boat from the furnace, cool and observe whether the sintering of the sand grain has started. If not sintered, replace the combustion boat in the furnace and continue the test with temperature increments of 50°C till sintering occurs. Keep the combustion boat at each particular temperature for at least 3 minutes. After cooling, examine the sand sample for sintering by scraping or visual examination with a magnifier or microscope.
  • 18.2.3 Determination of ‘A’ Sintering Point of Foundry Sand Mixtures - ‘A’ sintering point is the lowest temperature at which the ribbon used in the sintering test makes a ‘V’ when lifted off the sand specimen.
  • NOTE -The ‘V’ determination is applicable to practically all types of sands except sands with very low dry strength.
  • 18.2.3.1Apparatus-Standard equipment for the determination of ‘A’ sintering point.
  • 18.2.3.2Test specimen -The standard test specimen as specified in 5 and dried for at least one hour at 1050 to 1100 C.
  • 18.2.3.3 Procedure - Place the sand specimen in position in the sintering apparatus under the platinum ribbon heater. Centre the specimen between the platinum ribbon holder terminals and place the platinum ribbon in contact with the rounded surface of the sand specimen, allowing 170-g load to be applied to the ribbon. Sight the optical pyrometer on the central part of the platinum ribbon and adjust it to read the desired temperature. Allow for the emissivity of platinum as given in Table 2. Pass an electric current through the platinum ribbon and adjust the variable resistance so that the brightness of the platinum ribbon matches the brightness of the filament or dot in the optical pyrometer, which has been set at the desired temperature. Heat to required temperature in about 30 seconds and start a stop-watch and allow the heated ribbon to remain in contact with the specimen to cool for exactly 15 seconds. Lift up the ribbon holder and ribbon and observe whether the ribbon adheres to the sand specimen and makes a ‘V’ when it is lifted. Rotate the specimen about 50 mm to a fresh surface and again place the platinum ribbon in contact with the specimen. All adhering material should be removed from the ribbon by scraping or dissolving in hydrofluoric acid after each individual determination. If the ribbon did not make a ‘V’ repeat the above procedure, this time increasing the true temperature by 23 deg. This corresponds to an increase in the observed temperature of about 22 deg. The actual values should be taken from Table.2. Repeat the above procedure either by increasing or decreasing the true temperature by increments or decrements of 25 deg , until ribbon does not make a definite ‘ V ’ at one temperature, but does at the next higher temperature. The lowest true temperature at which the platinum ribbon makes a definite ‘V’ when lifted off the sand specimen 15 seconds after the 4 minute heating period is the ‘A’ sintering point.
  • TABLE 2 TEMPERATURE CORRECTION FOR EMMISSIVITY OF PLATINUM

    (Clause 18.2.3.3)

    Observed Temperature 0C
    True Temperature
    917
    1000
    939
    1025
    961
    1050
    1005
    1075
    1027
    1125
    1048
    1150
    1070
    1175
    1091
    1200
    1113
    1225
    1134
    1250
    1156
    1275
    1177
    1300
    1199
    1325
    1220
    1350
    1242
    1375
    1263
    1400
    1284
    1425
    1305
    1450
    1326
    1475
    1348
    1500
    1369
    1525
    1390
    1550
    1411
    1575
    1432
    1600
    1452
    1625
    1473
    1650
    1494
    1675
    1515
    1700
    1536
    1725
  • 18.2.4Determination of ‘B’ Sintering Point of Foundry Sand Mixtures - ‘B’ sintering point is the lowest temperature at which the smaller sand grains show signs of fusion.
  • 18.2.4.1 Apparatus -Same as specified in 18.2.3.1.
  • 18.2.4.2Test specimen -The standard test specimen specified in 5 shall be used.
  • 18.2.4.3Procedure -The method to be adopted shall be the same as for the ‘A’ sintering point test, except that the platinum ribbon shall be lifted from the sand specimen immediately after the electric current is shut off, so as to preserve the surface in contact with the ribbon. The ‘B’ sintering point is the lowest temperature which causes traces of fusion to be seen at 20 to 25 diameter magnification. In the scraper method 2 minute interval shall be allowed after turning off the electric current before lifting the platinum ribbon from the sand specimen. The ribbon is removed from the holder, placed on a flat plate and scraped. The ‘B’ sintering point by this method shall be the lowest temperature which necessitates 50 passes of a mechanical scraper to remove the sand from the ribbon. The scraper shall be of such design as to apply 113 g load to a knife-edge in contact with the ribbon during scraping. The knife-edge shall be at 1400 angle with the plane of the ribbon.