If you are preparing bend samples, i.e., cutting them from welded coupon, the edges must be ground to remove any base metal affected by the cutting process. So, it doesn't matter if the samples are cut with an oxy-fuel torch or plasma, the HAZ must be removed for the reasons noted by Brent. There is the possibility the HAZ can contain hard brittle microstructure that would cause the sample to fail (corner tears). The resulting corner tears would have little to do with weld soundness. The appropriate figures have already been listed.

The artificial aging is intended for reduced section tensile testing, to eliminate fish eyes caused by diffusible hydrogen, when it is permitted by the applicable A5.XX filler metal specification. It is an advantage when welding higher strength steels that are more susceptible to hydrogen cracking. If the samples are allowed to sit for a few days the bulk of the diffusible hydrogen will effuse into the atmosphere naturally, but there may be some retained in the typical hydrogen traps such as inclusions, atomic vacancies, grain boundaries, etc. Aging by heating the welded coupon for a period of time hastens the effusion process.

I recently did my little hydrogen experiment as described in my other posts, but instead of using baby oil at room temperature, I heated it to about 200 to 250 degrees F. The hydrogen formed a cloud of very tiny bubbles in the first several seconds. The “cloud” remained suspended in the oil for 10 or 15 minutes. The oil cooled quickly when the cold weld sample was immersed, but the hydrogen continued to produce little bubbles for an hour or two that were relatively large (compared to those in the “cloud”). The larger bubbles would rise to the oil surface while the “cloud” remained intact.

I tried to demonstrate the hydrogen trick in a classroom recently with Lincoln P5 (the reddish covered electrode) and was sorely disappointed by the results. I guess the lesson learned was to use 6010 electrodes with the “white” flux covering and, by the way, make the weld beads as long as possible. The welder helping me only made small “tack” welds about ¾ inch in length and they didn’t work worth a darn. Also, if you want to demonstrate the effects of extended atmospheric exposure, do not use E7018-H4R because the moisture resistant flux covering is really moisture resistant.

Best regards - Al