Hi Jim!

This one is pretty straight forward:

http://www.nyemanufacturing.com/pdf/general_welding_procedures.pdf

Quenched and Tempered Steel

Steel such as the common T-1 or AR plate all fall into the family of quenched and tempered steel

After the steel is rolled it is quenched (water) to increase the hardness and strength...
In this state the material tends to be too brittle for practical use so it is then tempered (in a furnace) to regain the lost ductility and toughness...

First of all, "T-1 & AR" is like saying "Xerox Oreo or Kleenex," They are trade names...

T-1 Steels (trade names such as: "Algoma 100, N-A-Xtra 100, HY-80, etc.") - these steels are generally 100ksi yield strength... Although you can strength match these materials when welding (E11018 electrodes for example) it is actually often less problematic to "undermatch " with say a 80ksi YS consumable... You will find these materials used in trailer frames, truck parts, structural members, surface & submersible vessels, etc...

AR Plate (trade names such as:"Algoma 500 , AR500, Hardox, etc.) are all quenched and tempered but through a higher alloy content, the plate can achieve a much higher hardness and strength. These Q&T plates are generally used for abrasion & wear resistance...

Generally speaking, steel mills name their AR plate as follows:

AR400 = 400 brinell harness . A good rule to know is brinell hardness divided by 2 is the approximate tensile strength... For example, your AR400 is approximately 200ksi TS... Needless to say, you don't have any possibility to strength match this plate, nor does it matter since these AR type plates are used for their abrasion & wear resistant properties not strength...

Because of this, the best filler material to weld AR plate (since you can't strength match anyways) is any low hydrogen filler such as E7018 / E8018... Often in the heavy equipment industry they use a 80ksi filler that has 1% nickel (such as E8018-C1) for the low temperature impact properties if the plate will see lots of pounding...

Need for Low Hydrogen and Preheat

No need to get into specifics but, it is because of the higher alloy content that increases the need for preheat and a low hydrogen process... Generally speaking these high strength plates are more crack sensitive... This problem is increased by excessive hydrogen content (from the welding consumable) and excessive quench (lack of preheat)...

It has little to do with these plates having higher hydrogen content than their mild steel counterparts but rather they are just more susceptible to cracking if the hydrogen content is not controlled originating from the consumable filler metal... Just be careful with the preheat because it is real easy to get carried away...

Need to Avoid Excessive Preheat and Inter-pass Temperature

The steel makers will all give you a maximum inter-pass temp. and /or heat input... The reason that you must watch these two is that you can put too much heat into the steel therefore, softening it... In essence you will destroy the hardness and abrasion properties of the material if both are not controlled before, during even after welding as well...

Low Hydrogen Processes

Welding processes that are considered low hydrogen are all GMAW (MIG), all submerged arc, most gas shielded flux cores, some self shielded flux cores and obviously low hydrogen SMAW (stick) electrodes... Where it gets tricky is when using self shielded flux cores... A good rule is most self shielded flux cores that are qualified for seismic welding will be low hydrogen...

If you are ever in doubt, you can always look on the certificate of conformance (legal document that all welding consumable manufacturers must have on all their filler material) where it states the "diffusible hydrogen"suffix/number... The letter "H" and the corresponding number indicates milliliters of diffusible hydrogen per 100 grams of weld metal...
They are designated as H16, H8 and H4... For example, a designation of H4 indicates that there is 4mL of diffusible hydrogen per 100 grams of weld deposit... In other words, the lower the number, the lower the hydrogen content will result in the weld metal deposit.

Well, that's about it for now... Hope this helps.

Respectfully,
Henry

One other thing to keep under consideration is cracking due to joint restraint. Tightly fitting tee or corner joints may be prone to craxking due to the higher yield if the matetial. If you experience that problem, consider fitting joints in a manner/sequence that facilitates the joint to move while welding. Crush wires at tees/corners, butt joints that allow movement into correct angular alignment as opposed to holding them in place, and as mentioned above, preheat.

Gerald Austin

Jim,
As a contractor, we did a large car crushing structural steel job a few years ago that had lots of AR plate in it and the owner had us use E309 and E309T1 but offered little in technical details as to why...

As an inspector, repairing MRAP's battle damage (Mine Resistant Ambush Protected) combat vehicles in Afghanistan, SS 309 was the filler material of choice for company 'A' due to it's toughness, ductility and elongation properties. Armox, Weldox, ASTM A-517 and HSLA (High Strength Low Alloy) are common materials in our application.

Obvious differences between Abrasion Resistant and Ballistic Armor but there are similarities as well.

I have seen Company 'A' use 70K wire and company 'D' use 110K wire and company 'B' & 'C' use everything in between, all with acceptable PQR's. SS filler materials have all but been banned but not due to poor performance.
Scratching head.

Just some general suggestions if you want a good starting place for the 90K FCAW WPS/PQR;
75/25 Ar/CO2 @ 30cfh
E91T1 H4M Dual Shield
Preheat 150F
Interpass 400F
***** The 200F-300F range mentioned in the OP is a tight range that might be a problem in the field IMO*****
.045 Diameter
DCEP
170-190 Amps
25-30 Volts
7-8 Travel Speed
Vertical Progression-Uphill
Transfer-Globular

Hope this helps.

Pretty sure D1.1 only goes up to 100 KSI yield steels.

Hey Jim,
If the client is directing you to use a specific process, get it in writing.

The key is preheat and interpass temp.  I would consider 300F preheat and 500F max interpass.  It all depends on your plate thickness and level of restraint. 
Different fillers can be used.  Europeans and South Africans (MRAP), use 309 because of its affinity to hydrogen.  They've been doing that for years, so they stick with what they know.  70, 80, 90K wires are all good, but I personally prefer the lower end because of ductility.

Hope this helped.

Tyrone