Answer the following questions about a weld failure for the

Answer the following questions about a weld failure for the design shown below. Lab Failure analysis Report: The lab has attached the following initial failure evaluation information for your use. These data show a macro image of the weld cross-section and the micro-hardness survey taken across the HAZ (Starting in the base metal and moving out towards the weld bead) as shown in the macro-photo above. What type of weld is specified in this design? (Type, size, location, GDT tolerance, etc.) What can be concluded from the lab data? What is the most probable cause for the crack? How would you change the weld process to reduce the chance for cracks in future welds of this design?

Solution

a)

b) as seen from the lab data (graph), hardness of the weld HAZ is greater compared to both weld zone and base metal. weldability is poor when the material is too hard. so crack may initiate between hard and soft part of the weld.

c) due to non uniformity of cooling thermal stresses are developed in the weld zone and if stresses are more than the strength of the material cracks will be formed

d) pre heating and post heating of the material reduces the chances of crack.