Forging defects
Forging is a common metalworking process in which metal is hammered or highly pressured to increase its strength and hardness. The process relies on the heat and pressure created by hammering together two pieces of metal and this often leads to structural flaws and other types of defects. The occurrence of forging defects can be minimised with careful design, craftsmanship and attention to detail throughout the entire forging process, from pre-forging to post-forging operations.
Common forging defects include structural flaws, size imperfections, and surface cracks and indentations. Structural flaws can occur because of a number of reasons, including overheating or overpressing of the metal. This can lead to grain growth and the creation of air pockets which can weaken the structure of the metal. Size imperfections often occur if the forging equipment is not properly set, leading to a forged piece which is too large or too small. Surface cracks and indentations are typically caused by insufficient pressure during forging and can lead to potential stress fractures.
Apart from structural flaws, other types of forging defects include porosity, shrinkage, flow marks, and porosity defects. Porosity is a form of incomplete filling in the forged pieces, which can lead to internal leaks and weaknesses. Shrinkage is a form of deformation which occurs when the solidified metal is not completely filled during forging and it can create the possibility of stress cracking. Flow marks occur when hardened metal is bent excessively, leaving visible indentations and an uneven surface. Porosity defects are caused when gases become trapped during forging, and this can lead to premature fatigue or even failure of the forged piece.
Forging defects can be very costly and time consuming to repair or replace and so prevention is much better than a cure. Forging operations should be held to high quality standards and should be thoroughly monitored and inspected throughout the entire process. It is important to ensure that the design and materials used are appropriate for the job and that the forge is well maintained and regularly calibrated. In addition, temperature and pressure levels should be well controlled and experienced personnel should be used to monitor the process and identify any potential flaws.
Finally, it is important to remember that some degree of post-forging machining is often necessary in order to complete the piece and to eliminate any defects. By understanding the process and potential pitfalls, forging defects can be avoided and high quality products produced.
