There are several different surface defects that can be found in tool steel billets. These defects can occur during the manufacturing process or can be the result of handling, transportation, or storage. Some of the common surface defects found in tool steel billets include:
1. Decarburization: This defect occurs when the surface of the steel billet loses its carbon content due to exposure to high temperatures during heat treatment or improper cooling. Decarburization can lead to reduced hardness and wear resistance in the tool steel.
2. Scale: Scale refers to the formation of oxide layers on the surface of the steel billet. It can occur during the hot rolling process or due to exposure to high temperatures. Scale can negatively impact the surface finish and can also affect the mechanical properties of the tool steel.
3. Cracks: Cracks can occur on the surface of tool steel billets due to various reasons such as improper cooling, excessive stress during hot rolling, or quenching. These cracks can be either surface cracks (which are visible) or internal cracks (which may not be immediately visible).
4. Inclusions: Inclusions are non-metallic particles or impurities that are trapped within the steel billet during the manufacturing process. These inclusions can cause weak spots or discontinuities in the material, leading to reduced toughness and fatigue resistance.
5. Pitting: Pitting refers to the formation of small holes or cavities on the surface of the steel billet. It can be caused by localized corrosion, exposure to aggressive environments, or improper handling.
6. Roll marks: Roll marks are surface imperfections that occur due to the contact between the steel billet and the rolls during the hot rolling process. These marks can appear as grooves, scratches, or indentations on the surface of the tool steel.
7. Surface contamination: Tool steel billets can get contaminated with foreign substances such as dirt, oil, grease, or other particles during handling, transportation, or storage. These contaminants can negatively affect the surface finish and can also lead to corrosion or other defects.
It is important to detect and address these surface defects in tool steel billets to ensure the desired performance and reliability of the final tooling products. Various inspection techniques and quality control measures are employed to identify and mitigate these defects, such as visual inspection, ultrasonic testing, magnetic particle inspection, and surface cleaning processes.
Some common surface defects found in tool steel billets include scale, cracks, pits, and surface decarburization. Scale refers to the formation of oxidation layers on the surface of the billet, often caused by exposure to high temperatures during processing. Cracks can occur due to improper cooling or excessive stress during forging. Pits are small depressions or cavities on the surface, which can be caused by impurities or improper handling. Surface decarburization is the loss of carbon at the surface, resulting in reduced hardness and wear resistance.
