9.1 What is residual stress? Residual stresses are stresses that exist in a metal after cooling / welding - NSC Mechanical Technology Welding and Metalwork - Question 9 - 2018 - Paper 1

1. The amount of cold work applied to the metal, as increased deformation typically leads to smaller grain sizes.
2. The temperature and time of annealing process, since higher temperatures and longer times allow grain growth.

1. Oil, which provides a slower cooling rate compared to water, reducing the risk of cracking.
2. Water, which is a fast quenching medium that can harden steel effectively but might induce more internal stresses.

Distortion in a weld results from the uneven expansion and contraction (warping) of the weld metal and adjacent base metal during the heating and cooling cycle of the welding process. This can lead to misalignment and other issues in the final welded assembly.

1. If the expansion that occurs when metal is heated is resisted, then deformation will occur during the welding process.
2. If contraction that happens on cooling is resisted, then stresses will be introduced, potentially leading to distortion.

Rapid cooling of metals creates significant temperature differences between the internal and external areas. This can induce high stresses within the metal, potentially resulting in cracking or other structural failures. Additionally, rapid cooling can refine the grain structure, leading to changes in mechanical properties.