A key component of our
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The Acid Demand Value is the amount of acid required to bring high pH and total alkalinity down to their proper levels. This gives insight to carbonates and salts in silica sand. A high acid demand value can lead to pinhole defects in castings due to the production of CO2 gas and lower the life of foundry sands in cold box systems. This value can also be used to determine the amount of catalyst that will need to be used for some binder systems.
Green Compression Strength
Green compression strength is the maximum compressive stress that a green sand is capable of sustaining when prepared, rammed, and broken under standard conditions. It is a widely used control tool to measure the rate of clay addition and moisture to a sand molding system.
The purpose of this test is to measure the levels of calcium in a bentonite sample. Bentonite is a primary component of a bond, it is important to know what kind of bentonite is going into it. Bentonite is generally characterized as either a calcium or sodium bentonite. Each type can have different properties when used in a molding sand.
AFS clay content is the portion of a foundry sand with a particle size of
Green shear measures green sand’s ability to resist forces that can cause internal structure to slide against each other. It is generally caused by the uneven application of force to a mold during transport to the pouring line. During pouring, the localized pouring pressure and gas pressure can create shearing stress in the mold.
Stepped Volatile Content Matter
Stepped volatile content matter is the measurement of the amount of matter that volatilizes at varying temperatures. Typically, temperatures used for this test are 450°F, 650°F, 950°F, 1200°F, and 1800°F. This test can be useful in determining the amount of organic material in a green sand sample.
AFS Grain Fineness Number
The AFS Grain Fineness Number is a way of measuring the average size of the particles in a sand sample. The fineness of a sand system can have an effect on casting finish and permeability of the sand.
Loss on Ignition
LOI determines the total amount of combustible and organic material in the sand. The quantity of gas-forming material in the sand will affect casting results. For example, high LOI may produce gas defects such as pinholes and blow outs as well as scabbing defects.
The sulfur test measures the percent of sulfur in a sample after combustion, using infrared detection cells. Sulfur contamination in green sand can come from several sources but the most common source is from chemicals used to bind cores. Sulfur build up in green sand can lead to some casting defects and can have a negative impact on emissions for a foundry. This is performed using a LECO Sulfur Detector.
When core binders and other organic materials break down in molding sands ammoniacal nitrogen can accumulate. Monitoring the level of ammoniacal nitrogen is important to help prevent nitrogen fissures and pinholes in molds and castings.
The methylene blue clay test determines the amount of active bentonite in a molding sand. Active bentonite contributes to the bonding of sand grains. This test can be used to determine the amount of new bond that may need to be added to a molding sand.
Thermal durability is a foundry property test of bentonite that has been exposed to a temperature of 1110°F for one hour; a process called calcining. Durability is determined by measuring the decrease seen in the foundry properties of a bentonite after calcining. This test can be used to select bentonites that may work well in a foundry.
Bulk density is the mass of many particles of a material divided by the total volume they occupy. This can be used to determine the amount of material that can be placed into a silo, truck, or railcar.
Moisture content is the amount of free water that is present a molding sand. This free water allows the sand to retain
Total hardness measures the combined amount of calcium and magnesium ions present in a bentonite sample. Measuring the total hardness is one way to characterize a bentonite.
The carbon test measures the percent of carbon in a sample after combustion, using infrared detection cells. Carbon content is important for green sands as it can help reduce casting defects. This is performed using a LECO Carbon Detector.
Mold Hardness (B-Scale)
Mold hardness measures the hardness of a green sand surface. The B-Scale hardness tester has a convex plunger. Hardness is determined by how deep the plunger goes into the mold. If a molding sand surface is too soft, it may cause buckling in the mold when the metal is being poured in. If a molding sand surface is too hard, it may cause cracking when metal is being poured.
Volatile Content Matter (VCM)
Volatile content matter is the measurement of material that volatilizes at 1200°F. The VCM can affect casting finish and shakeout properties. A low VCM can lead to poor casting peel, poor finish, and poor shakeout. A high VCM can lead to pinholes and other gas defects, as well as high smoke and brittle sand.
Permeability measures the amount of air is allowed to pass through a compressed 2x2 molding sand sample. Gases and steam are created when molten metal is poured into a sand mold. A low permeability value can lead to gas defects and blow outs.
Wet tensile is the measurement of the strength of a wet layer of sand that occurs near the mold/metal interface. This wet layer is a weak point that forms when heat from the molten metal pushes moisture into the mold where it then condenses as it cools. Strength in this wet layer is necessary to prevent distortion of the mold cavity.
Density measures the amount of sample needed to make a 2x2 specimen.
pH measures the alkalinity or the acidity of a sand. Monitoring a sands pH value can be used to determine if core butts or other impurities are building up in the sand system.
Other Specialized Tests
- Weight loss determination as a function of temperature using thermogravimetric analyzers
- Mineralogical composition determination using x-ray diffraction machines
- Elemental composition determination utilizing x-ray fluorescence spectrometers
Dry Compression Strength
Dry compression strength is the maximum load a dry 2x2 specimen can sustain before fracturing. Dry compression indicates the resistance of the mold to stresses during pouring and cooling of a casting and how well a sand will shakeout.
Sieve analysis is a method for determining the grain size distribution of particles in a sand. This is done using ASTM sieve sizes 6, 12, 20, 30, 40, 50, 70, 100, 140, 200, 270, and Pan. This measurement can determine the amount of fine material in