Compared with a single-pass weld, multi-pass welds generally produce which grain outcome?

Compared with a single-pass weld, multi-pass welds generally produce which grain outcome?

• A. Finer grain with successive passes
• B. More brittle grain structure
• C. Wider grain boundaries
• D. No grain refinement

Answer: (A)

Grain size in welded joints is shaped by the heating and cooling cycles a weld undergoes. When you use multiple passes, the region experiences several heating events and quick cooling each time. Each pass can create new sites for grain formation and interrupt the growth of grains from previous passes. This sequence of repeated thermal cycles tends to break up growing grains and promote more numerous, smaller grains in the weld metal and heat-affected zone. That refinement generally improves toughness and strength compared with a single-pass weld. So the outcome with successive passes is a finer grain structure. The other ideas describe coarser or unchanged grains, which isn’t the typical result of multi-pass welding due to the added nucleation opportunities from the repeated thermal cycles.

Grain size in welded joints is shaped by the heating and cooling cycles a weld undergoes. When you use multiple passes, the region experiences several heating events and quick cooling each time. Each pass can create new sites for grain formation and interrupt the growth of grains from previous passes. This sequence of repeated thermal cycles tends to break up growing grains and promote more numerous, smaller grains in the weld metal and heat-affected zone. That refinement generally improves toughness and strength compared with a single-pass weld.

So the outcome with successive passes is a finer grain structure. The other ideas describe coarser or unchanged grains, which isn’t the typical result of multi-pass welding due to the added nucleation opportunities from the repeated thermal cycles.