Foundry stress
Foundry stress is a type of stress that affects certain alloys when they are manufactured in a foundry. Foundries are specialized industrial establishments dedicated to the production of molded or cast metal products, such as engine and machine components, tools, pipes and fittings. This type of stress, also known as internal stress, is caused by the thermal and structural properties of the alloy, which can cause distortions, warping and other imperfections in the finished product.
Foundry stress can be caused by a variety of factors, including cooling rate, casting temperature, casting technique, mould design, and material composition. The cooling rate of the manufactured item can have a profound effect on the amount of stress generated, as slower cooling rates can result in greater levels of residual stress. The temperature of the casting also affects the stresses, with lower temperatures creating higher levels of stress. Casting techniques such as sand castings, die castings, and investment castings can also create different degrees of stress.
Mould design has a major effect on levels of foundry stress, particularly in the case of die castings. If the die is not designed properly, excessive levels of stress can be generated during the casting process. This can lead to the formation of ‘cold shuts’ or other imperfections. On the other hand, a well-designed die can reduce residual stresses significantly.
Foundry stress can also vary depending on the alloy being used in the casting process. Steel alloys, for example, tend to display higher levels of foundry stress than other alloys. This is due to the different thermal expansion rates of steel and other alloys, which causes differential contraction and expansion rates. As each alloy behaves differently, it is important to consider which alloy will be best suited for a particular application.
Foundry stress has serious implications for the industry, as it can cause significant distortion and warping of the finished product. High levels of stress can also reduce the overall strength of the product, which can lead to unsafe working conditions. Proper consideration and testing of the finished product is therefore essential to ensure quality and safety.
In order to reduce the levels of foundry stress, various stress relief techniques can be utilised. Temperature treatments, such as annealing, can be used to reduce the effects of stress, as can shot peening and vibrating with metallic media. Care should always be taken when selecting any stress relief technique, as the wrong technique or technique applied incorrectly can do more harm than good.
Foundry stress is an important factor to consider when manufacturing metal products in a foundry. By understanding the factors which affect stress levels, and implementing suitable stress relief techniques, the quality and safety of foundry products can be greatly improved.
