In die casting, blisters are defects that can occur on the surface of the finished product. Blisters are caused by pockets of gas or air trapped in the molten metal during the casting process. When the metal solidifies, the trapped gas expands, forming rounded or irregular bumps on the surface of the part.
There are several factors that can contribute to blistering, including:
1. High moisture content in the lubricants or other materials used in the process.
2. Inadequate venting of the mold cavity, which can trap pockets of air in the molten metal.
3. Excessive metal temperature, which can cause the release of gas from the lubricants or other materials used in the process.
4. Overheating of the metal in the mold, which can cause gas to be released and trapped in the molten metal.
How to identify Blisters on die casting parts
Blisters on die casting parts can usually be identified visually by their characteristic appearance. Here are some ways to identify blisters on die casting parts:
1. Raised bumps or rounded areas: Blisters usually appear as raised bumps or rounded areas on the surface of the part. They are often irregular in shape and may vary in size.
2. Uneven surface texture: Blisters can also cause an uneven surface texture on the part, with an irregular or rough surface in the affected area.
3. Cracks or breaks: In severe cases, blisters may cause cracks or breaks in the surface of the part. This can be more difficult to detect and may require closer inspection.
4. Hollow or thin-walled areas: Blisters can also cause hollow or thin-walled areas in the part, as the gas or air expands during the casting process and creates voids or thin spots.
5. Sound or tap test: A sound or tap test can be done to detect if there is blistering or porosity in the part. This involves tapping or bumping the part and listening for changes in sound, which can indicate areas of weakness or defects in the part.