D1.1 Preheat as Essential Variable vs. Thickness

Date 02-07-2018 15:45

Working with D1.1 2015, I need a FCAW WPS to weld ASTM A514 (Table 4.9 steel requiring PQR) to itself for all thicknesses.

Table 4.9 gives the minimum preheat and interpass temperatures for this material as:
50F: Up to 3/4
125F: Over 3/4 thru 1-1/2
175F: Over 1-1/2 thru 2-1/2
225F: Over 2-1/2

I plan to run a 1" PQR @ 125F. This will qualify all thickness, but I'm confused about the preheat requirements.
Can I simply list the min. preheat/interpass vs. thickness as above and as shown in table 4.9? Or do I need to run more than one PQR because preheat and interpass temperature are essential variables per Table 4.5 items 35 and 36? I don't understand note "d" or 4.8.3.

An example of the problem would be welding 1/2" material for production using a preheat temp. of 50F (which is a decrease in preheat temperature more than the 25F allowed by Table 4.5).

By Maggs47 (**)

Date 02-07-2018 17:46

Without knowing too much about the code, if those are all minimum temperatures, then you could write your WPS at 225F minimum and that will satisfy all thicknesses. Whether or not that's a good idea for successful welding, I'll leave to others to answer.

By 803056

Date 02-07-2018 20:32

The preheats listed by AWS D1.1 are the minimum prequalified preheat temperatures based on chemistry and thickness of the carbon or low alloy steel.

You can use the preheat listed or you can qualify the WPS with a lower preheat if you choose to do so. Most people use the preheat recommended for the base metal when they qualify the WPS. The table in clause 4 limits the lower preheat temperature as a function of the preheat recorded when the WPS was qualified.

Al

By Matt F

Date 02-07-2018 21:34

So I'll follow the recommended preheat for the thickness of my test plate when performing the PQR.

I'm free(qualified) to use completely different preheats for my different thicknesses, as long as I follow the recommendations on the chart?

By 803056

Date 02-08-2018 04:24

You can increase preheat, but not reduce the preheat below the limits of the table in clause 4. However, it is prudent to use the preheats listed in clause 3 as minimum preheat temperatures.

Al