re-welding on a plate - implications?

[Lepista]

Are there any implications for multiple welding different items in the same location on a piece of plate (i.e. attach something by welding, burning/cutting it off, welding something else on, and repeating)?

This is attaching large transportation items onto a structural deck.

Many thanks,
Lepista

 

[metengr]

For low carbon structural steels (not high strength low alloy) welding can be performed numerous times with no changes to bulk mechanical properties. I would expect that after a weld is removed, the area should be cleaned of any foreign deposits and checked using a surface nondestructive test (like Liquid Penetrant or magnetic particle) to ensure sound base metal before re-welding.

 

[sdz]

Lepista, a similar? situation I have seen is a jig for fabricating steel compoments where locating plates were continually welded on and then cut off. Over time this caused the jig to distort, concave towards the side with the welding. I suspect the same could happen in this case. Whether that's a problem probably depends on how critical flatness is and how often you want to use it.

 

[gtaw]

You may want to consider ultrasonic testing the area once it has been ground flush to check for lamellar tears just beyond the area of the HAZ. A straight beam interrogation will quickly detect laminations or lamellar tears should there be a problem as a result of the repeated thermal cycles and residual stress.

The thicker the deck, the greater the potential for lamellar tears.

If no problems are detected, weld away!

Best regards - Al

 

[chicopee]

gtaw, can you expound more on the phrase "straight beam interrogation?"

 

[gtaw]

The short version is:

It is a test method that employs longitudinal (ultrasonic) waves to examine the thickness of the test piece to detect planar discontinuities that lie parallel to the test surface.

It is a method used to check the thickness of a plate, check for or determine the extent of corrosion, or locate planar defects such as laminations or lamellar tears in "plate type" materials where the test surface and the opposite surface or the discontinuity of interest are parallel to each other.

I hope this is the description you are looking for.


Best regards - Al