Your problem is twofold. First, you use the word 'strong' and the word 'ductile' without actually determining from an engineering standpoint what those are.
Second, and related, is that there is simply NO empirical evidence that wide amp or volt ranges, those within the capability of current electrodes for example, deteriorate mechanical properties below acceptable minimums. For example 60 ksi for carbon steel. Try as you might you will not reduce said mechanical properties to say 50 ksi, 55 ksi, etc, by running hot or cold, if the weld is sound. Won't happen. And the soundness of the weld, i.e., slag if you are running cold, is a characteristics of a welders ability, not the metal. This is the logic behind ASME's wide range allowances.
When concerned with 'mechanical' properties, as defined by tensiles and bends, the actual engineering functional definitions, the metal is the metal.
Also, historically the parameters established for prequals were arbitrary. There is no empirical evidence to suggest that the parameters as limited are somehow a magic threshold to 'strong' 'ductile' welds. The gentlemen involved simply swept all of the WPS's at hand into the round file and made the parameters up. Based upon vast years of experience to be sure.
Now, if we are talking low alloys such as X70 or Q and T's it is a different story. But then prequals don't apply to them. And it is also a different story when considering toughness properties.
And you make the point of heat input, cooling rates, grain size, etc. So, I would ask, why is it NONE of these things are a concern for carbon steels in tensile and bend regimes in either AWS, ASME, or API? Its because they will not reduce strength or ductility, and this is the important part, to below the specified minimums. But, as I mentioned, these things are essential for toughness, which is why those very things you mention are considered important in those regimes. AND empirically based.
One other point I might add.
If, under ASME, you qualified a procedure well within those limited ranges as established by prequalified procedures, say, centered the amps and volts in the range and using a single value, for example 135 amps and 22 volts for SMAW, and then took the liberties of broad ranges of parameters, as ASME allows, for example, 80 to 160 amps and 19 to 25 volts, well beyond the percentages allowed, where are the failures that would demonstrate this is a problem.
The answer is simple. There are none.
Oh, and one other point.
Prequals don't actually limit the parameters totally. All they do is make you write another piece of paper. Or multiple pieces of paper to do as you please. So, to address your argument about welders using wide ranges you could simply have one welder running at the lowest end, one welder running at the highest end, and another running high here and low there, anyway. You just have to have the piece of paper to say its OK. And we all know how paper is the best remedy for mechanical viability. That file of mine will go a long way towards making my shops welds stronger and more ductile.
We've had similar discussions in the past. We're diametrically opposed on the subject of the necessity of having welding controls in place to ensure predictable outcomes.
With my limited comprehension of ASME and past experience with WPSs written to meet Section IX that are completely useless, I can appreciate your position. For the most part, many of the WPSs I've reviewed to verify the requirements of Section IX are met are in fact written by individuals that were clueless about welding. They did however meet Section IX requirements. With that in mind the WPS listing voltage as 0 to 220V and amperage 0 to 400A were correct. They were unusable, but correct. As was the WPS listing the groove angle as 0 to 90 degrees and the root opening as 0 to 3 inches without backing. So, my friend, I see your point from an ASME perspective.
With regards to prequalified WPSs written in accordance with the New Farm Code, I again agree. At least earlier editions required the welding parameters to be in accordance with the manufacturer's recommendations. The New Farm Code is definitely wanting in several areas. All the more reasons for Engineers to think twice about adopting the 2015 edition of the New Farm Code. There is little I can say in defense of "pulp fiction".
Best regards - Al
I would rebut that control comes from the shop culture and welder training, not the WPS.
Take D1.1 for example: Table 3.7.
I don't see any voltage. I don't see any amperage minimums. Nothing at all about travel speed or gas flow. All things that are controlled rather tightly 'by percentage' in the prequals. Which means that all one has to do is generate another piece of paper and you can use in essence the exact same parameters as those liberal ASME WPS's.
So, where's the control?