Hello Levi, there are code provisions for pre-heating of materials 1" and over in thickness in many production scenarios and under various codes. Likely, in the scenario you have spoken of here the instructor/WABO examiner has it up to his/her discression to elect to allow or disallow for pre-heating for the WABO test. I do plenty of WABO testing at our facility and if I were asked to be allowed to pre-heat I wouldn't have a problem with it, but, that's just my personal view and it's also not discussed specifically in the WABO 27-13 document, thus I believe it becomes discressionary. Hope this helps in your understanding a bit. Best regards, Allan

Levi,
According to D1.1 Table 3.2, for A36 1" thick plate, the preheat is 50°F (if welded with a low hydrogen process), so unless you were outside where the temp was below 50°F, you mostlikey didn't need any preheat...preheat won't hurt anything unless you go to some extreme, but if it isn't required, it would be just adding cost to the project.

I'm not as experienced as these guys but from a business owners point of view I have to agree that if it's not called out or required then it's just a waste of time and money. If I was paying you by the hour to weld 100 joints that did not need preheating and each joint takes 30 minutes to weld and you take an extra 15 minutes to preheat everyone, that's roughly 25 hours extra your gonna cost me in labor not to mention acet/oxy blowing out a rosebud big enough to heat. Why do you want to preheat it if you don't mind me asking? Knowing it's not required, I mean, me personally I've tested 1" before and didn't even think about asking if I could preheat it to 200 degrees so I'm just curious as to your reason.

Why would you want to preheat?

This might be a little late but I'll chime in anyway.
If it were me I would not let you preheat eiher.  If you have to run preheat on a test plate to make it pass, then that tells me that you will need to preheat every weld you make in production.  Because if you don't then I can't count on your weld being sound.  We can't afford to let you do that.

You may be looking at the weld test as being important to your future earning potential - so naturally you want to use any trick you can to assure that you will pass.
I have to look at a weld test as a basic test, under controlled conditions, as a measure of your skills.  If you pass, you would be making welds that my company will sell to a customer, and those welds have to be right or it will cost the company - and every employee of the company - lost revenue and lost reputation.

Too many welders have to have that "extra tenth of a volt", or different gas, or different rod sizes, or whatever. Some will whine very loudly until they either get it or are made to shut up.   But the most successful welders that I know of can make good welds under almost any conditions.

Bottom line is that there are people who can do the job if you can't. 
That's not meant as an insult to you - that's life and that applies to you, me, and every other person in the world.

So instead of wondering about preheating a test plate, think about how other people have passed the test and how they did it.

You asked for reasons and you got many opinions... What were you expecting? One answer only???
You got the answers you need  for your query... No need to get upset about it unless I'm reading you incorrectly???

Btw, "WELDCOME TO THE WORLD'S GREATEST WELDING FORUM!!! :) :) :)" Levi. ;)

Respectfully,
Henry

Levi.

The simple reason is that it is their test. They wish to see if the applicate can pass the test they set up, to their standards.
Now the AWS, ASME, and API can have someone come on here and give very specific reasons why their welding test are done the way they are.
I do not even come close to speaking for them. But again it is their test and their certifications.
And if you really want to preheat on a welding test just have some patience and wait till August and go to Las Vegas tack your plates up and set them in the direct sun for 3 hours when it is 105+, They will preheat real good.
Hope this helps
Thank you for your time and consideration.
Sincerely,
Kent

I was thinking that might be the reason("simlpy to aid in the wet-in and penetration on the root"). The inspector may have thought you needed to preheat to pass when asked that question. If I was testing you in my shop for a job, I'd wonder why as well, raises some doubt in your abilities.....not saying you can't, don't get all fired up but you see the point I'm trying to make? When I weld them out with no preheat, why does this guy want to preheat when it's not needed. See what I mean? When you go to test, I, the inspector or whoever don't know you from adam, so it makes a persons mind spiral when that is asked into things like, "is this guy gonna want to preheat everything?". When you asked and he said no, I suppose he would have been the best person to ask. But then again, questioning the inspector's probably not a good idea! LoL!! Unless you were extremely tactful about how you asked it to where it didn't sound like you were questioning his authority or whatever but just being curious. I think I talked to one guy that said that you were allowed so many degrees tilt on your 3g, not making it a true straight up weld. They would lean it back because you were allowed so many degrees, which means it's legal can be done no questions asked. I set mine all straight up, figured I can't go out and tilt a building when I get out on a job so I better learn to do it the right way.

I guess some don't want to see "allowable techniques to assist" because they want to see you weld it out like it's laid out to see if you can actually do it. I've been around a bunch of students and have them ask questions about ways they can use "techniques to assist" and have told them like I was told/taught, learn it the right way first, then the tricks of the trade will come to you when you get the piece of paper and get out in the field. I think one trick was walking the cup in tig. Some don't want you to do it to see if you can weld it without the "technique", see what I mean? This is what I learned from welders who have been doing it for over 40 years, another at 35 years and another at about 20 years. Basically it was don't cheat yourself while your learning. Sounds like your putting in the effort though, getting there early to class. I've seen guys waste day after day sitting in the classroom talking, outside smoking and joking and not burn 1 rod all day long. Good luck and keep at it Levi.

It would be my opinion that considering the central part of a GTAW arc plasma is upwards of 10,000 deg, and that the puddle is, I don't know, maybe 2500 deg, If a 200deg preheat makes a difference I doubt you could even notice.

The preheat requirements listed by the codes are minimum preheat requirements. There is nothing in the code that prohibits the use of higher preheats than those listed unless you are working with one of the quenched and tempered steels that has maximum interpass restrictions.

As far as preheat driving out hydrogen or moisture, my response would be to wear a pair of rubber boots because the BS is getting too deep to be wearing sandals.

Maintaining a reasonable interpass temperature will aid the diffusion of hydrogen, but it does not prevent or minimize how much diffusible hydrogen enters the weld puddle via the electrode or surface contamination.

I have welded on plenty of jobs where the foreman or supervisor ragged my butt for preheating the joint when it was not required by the applicable code. What they failed to recognize was that condensation that collects overnight (when working in the field or some of the fab shops I have been in) can wick between the members that form lap joints for example. The purpose of the preheat was to evaporate the surface condensation. Rather than arguing the point with them, I would simply ask them to witness what happens when I started the next joint. Like magic, the weld would perform as if on cue, the weld would look like shotgun pellets had hit it. Porosity everywhere. Their usual response was, "Do it right." and then they would walk away without further interference.

In your situation, it is highly improbable surface moisture would be an issue. As a matter of course, simply cleaning up the groove face and surfaces of the test plates, followed by tacking the members together would be sufficient to introduce some preheat into the plates to ensure there is no surface moisture present. As such, additional preheating is not necessary unless you were using a non-low hydrogen type electrode such as E6010, E6011, or E7010 for example.

Good luck, you seem to have your act together.

Best regards - Al