Method for measuring the performance of mold materials used in investment precision casting

author: kevin

2024-06-10

Method for measuring the performance of mold materials used in investment precision casting

Most technicians engaged in investment casting have limited knowledge of the performance parameters of the mold material. Today, precision casting manufacturer Tianyao Metal will talk to you about the method for measuring the performance of mold materials used in investment casting.

Firstly, we must understand the parameters of the mold material? There are a total of 12 performance parameters for investment casting materials in China, including melting point, bending strength, ash content, linear shrinkage rate, surface hardness, acid value, fluidity, viscosity, thermal stability, drop point, softening point, contact angle, etc. Below, we will introduce their respective measurement methods and standards.

1. Melting point: The temperature at which the first stagnation period appears on the cooling curve of a sample cooled and melted under specified conditions is the melting point of the mold material. Method for determining the melting point of mold materials GB/T14235.1-1993.

2. Bending strength: The room temperature bending strength of the mold material is represented by the strength obtained from the load of the mold sample when it is statically bent to brittle fracture at a certain loading speed. Method for determining the bending strength of mold materials GB/T14235.2-1993.

3. Ash content: Use ash free filter paper as the ignition core to ignite the sample, and then burn the solid residue to a constant weight to obtain its ash content. Method for determination of ash content in mold materials GB/T14235.3-1993.

4. Linear shrinkage rate: Inject the mold material into a circular cake sample at a certain temperature under a certain pressure, take out the sample, and leave it at a certain temperature for 24 hours. Measure the diameter size of the circular cake sample with a thickness of 4mm and a diameter of 100mm. Divide the difference in diameter size between the mold and the sample by the percentage of the direct reduction size of the mold. Method for determining the shrinkage rate of mold materials GB/T14235.4-1993.

5. Surface hardness: Melt the mold material and raise the temperature to 20 ℃ above the melting point, pour it into the sample forming machine, then cool it to room temperature at 20 ℃± 1 ℃, and then place the sample in a water bath and keep it at the test temperature for 24 hours. Insert the standard needle of the "penetrometer" into the sample under a load of 0.98N for 5 seconds, and measure the depth of the standard needle inserted into the sample as the surface hardness value of the mold material. Method for determining the surface hardness value of mold materials GB/T14235.5-1993.

6. Acid value: Dissolve the sample in neutral ethanol with a mass fraction of 95%, and then titrate with potassium hydroxide ethanol standard solution. Method for determination of acid value of mold materials GB/T14235.6-1993.

7. Liquidity: Place the mold sample in a capillary rheometer sample chamber at a certain temperature and keep it warm for a period of time. Press it out of the capillary under a certain load, measure its shear stress and shear rate as it flows through the capillary, and establish the relationship between shear stress and shear rate. Method for determining the flowability of mold materials GB/T14235.7-1993.

8. Viscosity: Using a dual cylinder rotary viscometer, the viscosity of the liquid mold material is measured at a specified temperature by changing the shear rate of the viscometer rotor. Method for determining the viscosity of mold materials GB/T14235.8-1993.

9. Thermal stability: Fix one end of the mold sample on the bracket of the thermal stability tester, hold it for 2 hours at the given temperature, and measure the sag of the cantilever extension end. The highest temperature value when the sag is less than or equal to 2mm is the thermal stability temperature of the mold. Method for determining the thermal stability of mold materials GB/T14235.9-1993.

10. Dropping point: Load the mold material into the grease cup of the dropper meter, and under the specified heating conditions, the temperature at which the sample in the cup drips out the first drop of liquid or flows out of the liquid column by 25mm is called the drop point. Method for determining the drop point of mold materials CICBA/D 01.10-1999.

11. Softening point: Using the global method, the temperature at which the steel ball wrapped in the mold material falls onto the metal plate is determined as the softening point. Method for determining the softening point of mold materials CICBA/D 01.10-1999.

12. Contact angle: Wash the 2mm x 25mm x 60mm investment mold sample, adjust the level under the microscope, place the sample on the loading stage, suck the tested adhesive into the syringe, and then drip it onto the surface of the sample. Adjust the focal length to measure the droplet height h, diameter D, and contact angle θ. Calculate using the following formula, θ=2artan (2h/D). Method for determining the softening point of mold materials CICBA/D 01.12-1999.

HB5350.7-2004 is also a standard for testing the performance of investment casting materials.