welding-alloys.com 8 Process control to prevent porosity and cracking Preventing porosity and cracking starts with proper surface preparation and process control. Thoroughly cleaning the base metal removes contaminants such as oil, rust and grease, which can introduce gases into the weld pool and lead to porosity. It is also important to inspect the base metal for existing cracks, as these can propagate during welding. Additionally, managing arc length is crucial – a shorter arc length reduces the exposure of the molten weld pool to atmospheric gases, minimising the risk of porosity. Preheating and material selection to reduce cracking To reduce cracking, it is important to manage thermal stresses through preheating and select appropriate materials. Adequate preheating helps reduce thermal gradients, minimising residual stresses that could lead to cracking. Uniform, global preheating is preferable to localised methods, as it ensures even temperature distribution across the workpiece. Controlling weld deposit thickness is also important, as excessive thickness in hardfacing layers can induce high residual stresses, increasing the likelihood of cracking. Adjusting the deposit thickness as needed or selecting a material with more suitable properties can help mitigate this risk. Material selection also plays a crucial role – choosing a filler material with the right mechanical properties can improve crack resistance. For example, a grade with lower hardness may be beneficial in applications where impact loading is a concern.
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