Quality control is the final stage of manufacturing to ensure that the products produced meet the needs of both consumers and manufacturers. To determine the quality of this material in the metal casting industry, two tests are performed: Destructive Test (DT) and Non-Destructive Test (NDT).
Destructive Test
A destructive test is one in which the test object is damaged. The goal of this test is to determine a material’s durability so that it can later produce high-quality material. The most important aspect of this test is the creation of test samples because it is directly related to the value of the test result. DT testing includes several tests, including impact tests, tensile tests, hardness tests, and spectrometer tests.
Impact Test
The impact test is used to determine the shock strength of a material or the notch value of a metal alloy.
The first step in conducting an impact test is to create a test sample of the appropriate size.
The testing stage begins after the sample is prepared and entered into the test equipment. Wait until the sample breaks at this stage of testing. Tensile strength, yield strength, and elongation values can be seen on the monitor screen.
Tensile Test
The tensile test is used to determine a material’s tensile strength, yield strength, and elongation.
The first step in the tensile test is to create samples that adhere to predetermined standards; samples are created on a lathe.
After the sample is prepared, it is placed in the testing equipment and tested. Wait until the sample breaks at this stage of testing. The monitor screen displays tensile strength, yield strength, and elongation values.
Hardness Test
The hardness test is used to determine the material’s resistance or surface strength. Hardness testing is classified into several types:
- Rockwell Hardness Guide (HRB and HRC)
- Rockwell Hardness Digital (HRB and HRC)
- Portable Hardness (Brinnel)
- Micro Vickers Hardness
The indentor differs between HRB and HRC; HRB uses a spherical indentor, whereas HRC uses a diamond-shaped indentor.
The hardness test begins with the creation of a test sample with a thickness of 10 mm.
The surface of the test sample should be flat to facilitate the test and provide more specific test value results. The value of the test results can be seen on the monitor screen during the testing stage.
Spectrometer Test (Composition Test)
The spectrometer test is used to determine the content of elements contained in metals. The spectrometer testing process seeks to determine how much the value of the constituent elements of the material, such as Fe, C, Mn, Si, Ni, V, Mo, and so on.
Because the elemental content of the metal affects its strength, spectrometer testing is the main reference in the above tests.
It is necessary to pay attention to the manufacture of test samples that are in accordance with standards when performing Destructive Test testing or testing by damaging the test object because it affects the results of the test value.
Non-Destructive Test
Non Destructive Testing (NDT) is a method of testing materials that do not cause damage to the object being tested. This test is performed to ensure that the material is still safe to use and not damaged. NDT testing is typically performed at least twice, once at the end of the fabrication process and once after the component has been used for a period of time, to detect system errors or failures in the components.
It is classified into two types based on damage or defects in the material: surface crack and inside crack.
The Non-Destructive Test involves several processes, including:
Visual Testing
Visual testing is a fairly common and straightforward technique. After the cast object has been disassembled, the visual testing process can begin. This is the quickest method because it only examines the physical state of the object (surface, dimensions, etc.). However, as technology advanced and the demand for accuracy in testing increased, it began to be developed using a camera, also known as a microscope.
Visual testing can be performed using only the senses of the eye and a microscope to detect invisible defects.
Dye Penetrant Testing
Dye penetrant testing is a technique used to locate casting defects on the surface of objects. This test uses specialized liquids, such as cleaners, penetrants, and developers, each of which serves a specific purpose. Here’s how it works.
- The purpose of liquid cleaner is to clean the object to be tested so that it is free of dirt.
- The penetrant fluid is used to determine the location and type of defect.
- The developer fluid is used to lift the penetrant fluid and determine the location and type of defect.