weld question

huangyhg

weld question
i have a problem at a weld connection (gravity column to cap plate). the cap plate was 1" thick. the hss column had a 1/2" thickness. the weld specified was 5/16" (code minimum). the contractor used a 1/4" weld. is that fine or should i ask him to redo the weld.
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the 13th edition steel specification revised the minimum, to match aws.  under this code, the 1/4" weld does not violate this requirement, as it would be based on the thinner plate.
if 1/4" works for strength, i'd be inclined to leave it be.
i'm looking at the 13th edition and for a 1/2" piece, the min fillet weld is 3/16.  i don't see a problem (unless you're not using low hydrogen rods - then you need to base it on the thicker part joined).
a 1/4" weld can be added to with ease, (another pass), not necessary if strength is sufficient using 1/4" weld.
the connection does work w/ a 1/4" weld.
this maybe a theoretical question, why is there a minimum size of weld for a particular thickness. does a smaller weld fail when connecting two thicker parts?

read the commentary in the manual.
it is a requirement based on the quenching effect of a thick piece of metal (even though the requirement is based on the thinner piece being joined).
a thick piece of metal rapidly conducts heat away from the weld, leading to rapid cooling which results in a loss of ductility.
since you are dealing with a minimum weld size, be sure to get the ones you have inspected by a certified welding inspector.  a 1/4 inch fillet weld on thicker material is, as frv pointed out, subject to relatively fast cooling.  depending on the welding process used, this can result in porosity, edge lap, lack of penetration, convexity, and lack of fusion.