Quenching Crack and Non-quenching Crack Identification
Quenching crack (also known as quench crack or quenched fracture) is a form of plastic deformation that occurs in steel parts during heat treatment. Quenching cracks happen during the quick cooling after austenitizing. When the cooling is too rapid, an oversized residual stress can form in the material. If this stress becomes too large, this can cause the material to crack along its surface.
Quenching cracks can easily be identified by their “zigzag” shape. These cracks will have a cross-sectional area that appears much larger than what is seen on most other cracks that are found in steel parts. The size of quenching cracks can vary, but they normally range from just a few millimeters to over one centimeter in length.
These cracks can also be identified by their color. Quenching cracks will usually have a light gray color on the outside of the steel part. There may also be some small red spots on the outside of the part due to the heated areas that can form when the cracks occur.
Non-quenching cracks (also known as non-quenched fractures) are small and almost invisible fractures that form in steel parts during heat treatment. Non-quenching cracks most frequently occur in the crystal structure of steels after impact or due to hardening from other methods. These cracks are often very small and will not normally be visible to the naked eye.
Non-quenching cracks are difficult to identify and may require the use of a microscope to properly detect them. The best method of identifying these small fractures is to use an optical microscope to look for them. This analytical tool can provide a much higher level of detail than the naked eye, allowing you to better spot the small fractures.
Another way to identify non-quenching cracks is to use X-ray diffraction. This method works by sending an X-ray beam at a steel part, which will cause the diffraction of the electrons within the crystal structure of the material. In doing this, the technician can analyse the structure and better detect the non-quenching cracks.
Overall, quenching cracks and non-quenching cracks can both present some serious safety issues in terms of the strength and reliability of the steel parts. Although each of these two types of fractures can be identified with different techniques, it is important to ensure that only experienced technicians and engineers are performing these analyses. With the proper expertise and equipment, these types of fractures can be safely identified and rectified.
