Failure of steel in tensile test but weld remains intact

[maleck2010]

Does anyone know how to theoretically explain why sometimes we have steel that fails in tensile testing but its welded joint remains intact? The welded structure should be more brittle and we should expect that the fracture would likely occur in the welded area and, not, in other parts of the steel. Suppose that the structure was visually solid and had no apparent cracks. Any article or online reference on this specific issue also ? Thanks !

 

[unclesyd]

You need to comeback with a little more information about under what materials and conditions you making the welds in question.

The welded structure should be more brittle and we should expect that the fracture would likely occur in the welded area and, not, in other parts of the steel.

Under normal conditions this statement is wrong as you want the base metal to fail first. Unless you have some special circumstances the weld metal should be stronger than the base metal.
A weldproper is the last thing you want to fail.

 

[metengr]

Your statement;

Does anyone know how to theoretically explain why sometimes we have steel that fails in tensile testing but its welded joint remains intact?

Because by design this is exactly what is supposed to happen. Typically, you want the weld metal to be as strong or stronger than the base metal. The tensile test failure typically occurs in base metal near the weld region called the base metal heat affected zone. Why do you want the weld metal to be as strong or stronger than the base metal being joined? Because the weld is treated like a cast structure and contains a higher chance of having defects.

The welded structure should be more brittle and we should expect that the fracture would likely occur in the welded area and, not, in other parts of the steel.

Incorrect. Why would it be more brittle? For most metals, this statement is incorrect if proper selection of filler metal and welding parameters are followed.