GB/T 2684-1981 Test methods for raw sand and mixed materials for foundry
Some standard content:
National Standard of the People's Republic of China
Test Methods for Raw Sand and Mixtures for Foundry
GB 2684 — 81
This standard is applicable to the determination of the moisture content, mud content, particle size, compactness, permeability and strength of raw sand and mixtures for foundry. 1 Selection of Raw Sand and Mixture Samples
1.1 In order to test the quality of raw sand for foundry, an average sample can be selected from the same batch of raw sand. The average sample of bulk raw sand is selected from the corners and the center of the sand pile 200 to 300 mm away from the edge and surface in the train compartment, cabin, car, sand warehouse and sand pile with a sampler; the average sample of bagged raw sand is selected from 10% of the same batch of bags, but not less than 1 bag, and the total weight shall not exceed 5 kg. If the quality of a part of the raw sand is in doubt based on appearance observation, it should be sampled and tested separately. 1.2 The name, origin and sampling date of the sample must be indicated when selecting the sample. 1.3 The samples required for the test are selected from the samples. The number of samples can be determined according to the test items and shall not be less than 1 kg. 1.4 The method for selecting samples is the "four-point method" or a sample divider. 1.5 Except for the samples used for determining the moisture content, the samples used for other tests must be dried for ten minutes at a temperature of 140-160°C. The dried samples should be stored in a dryer for future inspection. 1.6 For the test samples in question, the remaining samples should be kept for three months after the test for review. 1.7 The mixed material samples are selected regularly according to the characteristics of the mixing equipment and the process regulations. If the mixed material is transported by a belt conveyor, three samples are taken from the conveyor regularly and mixed evenly, and the number is determined according to the test items. 2 Test method
2.1 Determination of moisture content
Moisture content is the white fraction of moisture contained in the raw sand and mixed materials for casting. The determination of individual moisture content is carried out by a rapid or arbitration method.
2.1.1 Rapid method
During the test, weigh 20 ± 0.05 g of the sample, put it into a sand tray, evenly spread it, place the sand tray in an infrared dryer, dry it for 6 to 10 minutes, and weigh it again after cooling. Calculate the moisture content according to the following formula: Gf-G2× 100%
Where: X—moisture content of the sample (%);
G—weight of the sample before drying (g);
G2—weight of the sample after drying (g). 2.1.2 Arbitration method:
During the test, weigh 50 ± 0.01 grams of the sample, place it in glass III, and bake it in an electric oven at a temperature of 105-110℃ for 7 minutes until it is heavy (after baking for 30 minutes, weigh it, and then weigh it every 15 minutes until the difference between two consecutive weighings does not exceed 0.02 grams, which is considered constant weight), place it in a desiccator, and weigh and calculate the water content when it cools to room temperature. 2.2 Determination of mud content
Mud content refers to the percentage of particles with a diameter of less than 0.020 mm contained in the original sand and old sand used for casting. During the test, weigh 50±0.1g of the dried sample (when measuring the mud content of old sand, if the particle size measurement is not required, weigh 20±0.1g of the sample), put it into a special sand washing cup with a capacity of 600ml, add 390ml of water and 10ml of 5% sodium pyrophosphate solution, boil for 3-5 minutes, then place the sand washing cup on the vortex sand washing machine, stir for 15 minutes, remove the sand washing cup, add clean water to the standard height of 125mm, stir with a glass rod for about 30 seconds, let it stand for 10 minutes, and use a siphon to remove the turbid water (as shown in Figure 1). For the second time, add clean water to the standard height of 125 mm, stir with a glass rod for about 30 seconds, let it stand for 10 minutes, and use a siphon to remove the muddy water. Figure 1
The operation after the third time is the same as the second time, but each time it is only left to stand for 5 minutes (if the test results require very accurate results, the corresponding standing time can be selected according to the different water temperatures listed in the table below). Repeat this process many times until the water in the sand washing cup has become transparent and no longer contains mud.
Water temperature ℃
Standing time
5°40″
5°30\
5'15″
4°30*
After the clean water in the sand selection cup is removed for the last time, pour the sample and the remaining water into a glass funnel with a diameter of about 100 mm for filtration, then place the sample and the filter paper in a glass dish and dry it in an electric oven to constant weight (temperature is 140-160℃). After drying, place it in a dryer and weigh it when it cools to room temperature. Calculate the mud content according to the following formula: G-G2×100%
Where: X-mud content of the sample (%) s
G weight of the sample before the test (g):
Gz weight of the sample after the test (g).
2.3 Determination of particle size
Particle size refers to the sand grain composition of the original sand or old sand used for casting. For the determination of particle size, unless otherwise specified, the dried sample whose mud content has been determined in the previous test should be selected. During the test, first turn the timer knob of the vibration-swing or electromagnetic micro-vibration sand screening machine to the time position required for screening (if the electromagnetic micro-vibration sand screening machine is used for screening, the vibration frequency and amplitude knobs should be turned at the same time to make the amplitude indicator point to 3 mm). At this time, put the sample on the top sieve (June) of the full set of standard sieves for casting, and then fasten the full set of sieves with the sample to the sand screening machine for screening. The screening time is 12 to 15 minutes. When the sand screening machine stops automatically, loosen the fastening handle, remove the standard sieve, and pour the sand left on each sieve and the chassis on smooth paper 1 respectively, and use a soft brush to carefully brush off the sand sandwiched in the mesh from the back of the sieve, and weigh the weight of the sand on each sieve. Finally, calculate the percentage of sand on each sieve to the total weight of the sample. GB 2684-- 81
After the test, add the weight of sand and mud content (g) on each sieve and chassis. The weight should not exceed 50±1g, otherwise the test should be repeated.
When using a sample whose mud content has not been measured, the sample is weighed 50±0.1g. 2.4 Determination of compaction rate
Compaction rate refers to the volume change ratio of wet mixture under a certain compaction force, which is used to judge the degree of proper mixing of molding sand.
The compaction rate is determined by passing the sample through a funnel with a 6-day sieve and dropping it into a cylindrical standard sample tube with an effective height of 120 mm (the distance from the sieve bottom to the upper end of the standard sample tube should be 140 mm), scraping off the excess sample on the sample tube with a scraper, and then impacting the sample tube with the sample on the hammer type sample making machine three times. The degree of sample volume compression is the compaction rate, expressed as a percentage, and its value can be read directly from the sample preparation machine. It can also be calculated according to the following formula: Ho-Hi×100%
Where: V-compaction rate of the sample (%); Hg---height of the sample before compaction (120 mm); H-height of the sample after compaction (mm). 2.5 Determination of air permeability
The ability of raw sand or mixed materials to allow gas to pass through is called air permeability. According to the nature and purpose of the sample to be tested, it can be divided into wet, dry and raw sand air permeability. The air permeability is determined by rapid or cutting methods.
2.5.1 Rapid method:
a When determining wet air permeability, weigh a certain amount of sample and put it into a cylindrical standard sample tube, and impact it three times on the hammer-type sample preparation machine. The height of the standard sample is 50±1 mm. Lift the bell of the direct-reading air permeability tester, place the sample tube with the sample inside on the sample holder of the direct-reading air permeability tester, and make the two fit tightly. Then turn the knob to the "working" position, so that the air permeability value can be directly read from the micro-pressure gauge.
When the air permeability of the sample is greater than or equal to 50, a 1.5 mm flow resistance hole should be used, and when the air permeability of the sample is less than 50, a 0.5 mm flow resistance hole should be used.
b. When measuring air permeability, prepare the standard sample according to the wet air permeability measurement method. Then push the punched sample out of the sample towel, dry or harden under the specified conditions, and then place the standard sample at room temperature in the sample tube for measuring dry air permeability, and use an air pump to inflate and seal the rubber ring in the sample tube. Then put it on the sample holder of the direct-reading air permeability tester for measurement. The measurement process is the same as the wet permeability measurement method.
c. When measuring the air permeability of raw sand, a mesh metal standard sheet that fits tightly with the inner wall of the sample tube is placed at the bottom and top of the sample tube, and then the standard sample is impacted on a hammer-type sample making machine. The rest of the process is the same as the wet air permeability measurement method. The air permeability of each sample must be measured three times, and the results should be averaged. However, if any test result differs from the average value by more than 10%, the test should be repeated.
2.5.2 Arbitration method:
During the test, first remove the flow-blocking hole component on the sample seat of the direct-reading air permeability tester, then lift the air bell to the elevation where the air volume inside the bell is 2000 cubic centimeters, and then put the punched sample tube containing the sample into the sample seat 7 of the air permeability tester to make the two fit tightly. Then turn the knob to the "working" position, and use a stopwatch to measure the time it takes for 2000 cubic meters of air to pass through the sample in the air clock, and read the pressure in front of the sample from the micromanometer, and calculate its air permeability according to the following formula: FPt
K= FPr=Pt
Where: V—the volume of air passing through the sample, cubic centimeters, V=2000 cubic centimeters; H—the height of the sample, centimeters;
F—the cross-sectional area of the sample, square centimeters, the pressure in front of the sample, centimeters of water column;
GB 2684--81
—the time it takes for 2000 cubic centimeters of air to pass through the sample, minutes; K-air permeability.
2.6 Determination of strength
Strength refers to the force per unit area when a standard sample made of a mixture is destroyed under the action of an external force. Its unit is kgf/cm2.
The strength of the specimen can be in wet state or in low state according to the different properties of the mixture, and can be in compression, shear, tension, bending and other conditions according to the different stress conditions.
Except for special provisions, the standard specimens used to measure various strengths are made by impacting three times on a hammer-type sample making machine. The specimens used to test compressive strength and shear strength are cylindrical standard specimens (as shown in Figure 2); the tensile strength is the "8"-shaped standard specimen (as shown in Figure 3), and the bending strength is the long strip standard specimen (as shown in Figure 4). @50±1
After the punched specimen is removed from the core box, the wet strength test can be carried out. If a static strength test is required, the specimen should be dried or hardened under the specified conditions before the test is carried out. 2.6.1 When measuring the compressive strength, place the prepared compressive specimen on the compression fire tool pre-installed on the strength testing machine (such as GB 2684-81
Figure 5). Then turn the hand wheel and gradually load the sample until the sample breaks. The strength value can be directly read from the pressure gauge. If a low pressure gauge is used, multiply by 1.
2.6.2 When measuring shear strength (as shown in Figure 6), place the shear fixture on the instrument. The operation method is the same as the compressive strength test method.
2.6.3 When measuring tensile strength (as shown in Figure 7), place the tensile fixture on the instrument, then place the punched tensile specimen into the fixture, and make the flat surfaces of the four rollers in the fixture stick to the waist of the specimen. Turn the hand wheel and gradually load until the specimen breaks. The tensile strength value can be directly read from the pressure gauge.
2.6.4 When measuring bending strength (as shown in Figure 8), place the bending fixture on the instrument, then place the punched bending specimen on the fixture, and make the triangular blade head align with the center of the specimen. Turn the hand wheel and gradually load until the specimen breaks. The number read from the tensile scale in the pressure gauge multiplied by 10 is the bending strength value. GB2684-81
2.6.5 When measuring the low wet pressure strength (as shown in Figure 9), place the low wet pressure fixture on the instrument and use the adjusting screw 2 to level the bent rod 1. The standard sample is made of a cylindrical opening and closing sample tube (a metal gasket is placed at the bottom of the sample tube). Then place the sample on the low wet pressure fixture, turn the hand wheel, and gradually load it until the sample breaks. The low wet pressure strength value is read from the pressure gauge. Figure 9
2.6.6 Calculation of strength value: During the wet strength test, the strength value of the three samples is calculated by averaging. If the strength value of any of the three samples differs from the average value by more than 10%, the test should be repeated. During the dry strength test, measure the strength values of five samples, then remove the maximum and minimum values, and take the average of the remaining three values as the dry strength value. If any of the three values differ from the average value by more than 10%, the test needs to be repeated. GB 2684-- 81
The relevant technical parameters in this standard are obtained by testing on domestic molding sand testing instruments. The models and names of the instruments are listed in the following table:
Double-disk infrared dryer
Vortex sand washing machine
Standard sieve for casting
Vibration-swing sand screening machine
Electromagnetic micro-vibration sand screening machine
Roller sand mixer
Hammer sample making machine
Direct-reading air permeability tester
Hydraulic strength testing machine
Measurement of water content of raw sand and mixed materials
Determine the mud content of raw sand and old sand
Determine the composition of raw sand particles
Determine the composition of raw sand particles
Determine the composition of raw sand particles
Prepare mixture
Prepare permeability, compression, shear, tension and bending test specimens and determine the compactness of mixtures, etc. Determine the permeability of raw sand and dry and wet permeability of mixtures Determine the compression, shear, tension and bending strength of mixtures If other types of molding sand testing instruments are used, the relevant technical parameters in the test should be adjusted under the conditions of comparison. Note: From the date of implementation of this standard, the original standard JB437-63 will be invalid.6 Calculation of strength value: In wet strength test, the strength value of three samples is calculated by averaging. If the strength value of any sample among the three samples differs from the average value by more than 10%, the test should be repeated. In dry strength test, the strength values of five samples are measured, and then the maximum and minimum values are removed, and the average value of the remaining three values is taken as the dry strength value. If any of the three values differ from the average value by more than 10%, the test needs to be repeated. GB 2684-- 81
The relevant technical parameters in this standard are obtained by testing on domestic molding sand testing instruments. The models and names of the instruments are listed in the following table:
Double-disk infrared dryer
Vortex sand washing machine
Standard sieve for casting
Vibration-swing sand screening machine
Electromagnetic micro-vibration sand screening machine
Roller sand mixer
Hammer sample making machine
Direct-reading air permeability tester
Hydraulic strength testing machine
Measurement of water content of raw sand and mixed materials bzxz.net
Determine the mud content of raw sand and old sand
Determine the composition of raw sand particles
Determine the composition of raw sand particles
Determine the composition of raw sand particles
Prepare mixture
Prepare permeability, compression, shear, tension and bending test specimens and determine the compactness of mixtures, etc. Determine the permeability of raw sand and dry and wet permeability of mixtures Determine the compression, shear, tension and bending strength of mixtures If other types of molding sand testing instruments are used, the relevant technical parameters in the test should be adjusted under the conditions of comparison. Note: From the date of implementation of this standard, the original standard JB437-63 will be invalid.6 Calculation of strength value: In wet strength test, the strength value of three samples is calculated by averaging. If the strength value of any sample among the three samples differs from the average value by more than 10%, the test should be repeated. In dry strength test, the strength values of five samples are measured, and then the maximum and minimum values are removed, and the average value of the remaining three values is taken as the dry strength value. If any of the three values differ from the average value by more than 10%, the test needs to be repeated. GB 2684-- 81
The relevant technical parameters in this standard are obtained by testing on domestic molding sand testing instruments. The models and names of the instruments are listed in the following table:
Double-disk infrared dryer
Vortex sand washing machine
Standard sieve for casting
Vibration-swing sand screening machine
Electromagnetic micro-vibration sand screening machine
Roller sand mixer
Hammer sample making machine
Direct-reading air permeability tester
Hydraulic strength testing machine
Measurement of water content of raw sand and mixed materials
Determine the mud content of raw sand and old sand
Determine the composition of raw sand particles
Determine the composition of raw sand particles
Determine the composition of raw sand particles
Prepare mixture
Prepare permeability, compression, shear, tension and bending test specimens and determine the compactness of mixtures, etc. Determine the permeability of raw sand and dry and wet permeability of mixtures Determine the compression, shear, tension and bending strength of mixtures If other types of molding sand testing instruments are used, the relevant technical parameters in the test should be adjusted under the conditions of comparison. Note: From the date of implementation of this standard, the original standard JB437-63 will be invalid.
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