now that you brought that up we might help out the op with a few tips on WPQR. I don't know about the OP but I passed my first 6G back in 1967. and most recently before I retired in 2013 I spent 10 years in the middle east as the senior engineer for a company among my many duties I was over the QAQC,
For my elevators and freight lifts that I designed i was probably a little strict when it came to fabrication procedures but some of them had to lift 30 to 40 tons as high as 60 feet others were just human meat boxes with no more requirement than to carry 10 to 15 passengers up 15 to 30 floors. No real challenge there after all OTIS had been doing it for over 100 years.
7018 has its place and has been the gold standard in the industry for years but it is hardly the only filler for all applications.
about everything I've spec to be welded out structurally for the past 30 years has been FCGMAW for those who are not aware of the acrnym that is fluxcored gas-shielded metal arc welding. OR AWS D1-1 FCAW for short.
My filler of choice (mostly just a personal preference) because I can use it in a very wide variety of applications, has been Hobart Excell 550 E71T1-1 with either 100% Co2 or 75/25 Argon Co2.
Here again this is not the absolute last in fillers particularly when dealing with building up the bearing race of a small er truck spindle, larger ones OK' anything thicker than 3/8" wall, unless the welder is well versed in being able to use very low amperages and voltages. ER 70S6 with 75/25 set just high enough to have a stable arc will do just fine even beter than a much stronger filler due to not wanting to induce more heat than needed.
Prior to welding on a truck spindle it needs to be cleaned any work hardened bilby layer needs to be ground off using iether a small belt sander or a rt angle grinder whit a soft 36 grit floppy disc. then the spindle should be slowly and evenly heated to not more than 300°f a few inches to both sides of the proposed weld area.
if using a mig as I said try to obtain the smallest possible stable arc. weld in a cross stringer pattern never starting or stopping at either end if using stick electrode NEVER EVER EVER USE 6011 filler material. the arc pattern is too random and deep penetrating. the same goes for the all favorite pipe welders root rod 6010 or 5P as we know it.
7018 as stated will work just fine but use the smallest diameter filler you can buy. the idea here is to build up not to fill a crack.
years ago before the filler material manufacturs gobble up Murex (spelling) products made a 1/16" diameter rod that welded like 7018 will overhead but had the buttering flow characteristic of an iron powder 7024 in the flat position.
make only a few side to side stringers at a time then wait until the temp. is below 250°f in the weld area before makeing a few more passes. start the process at 6o'clock weld to 7oclock then start at 1 o'clock and weld to 12o'clock then 6 o'clock to 5 o'clock then 11 o'clock to 12 o'clock then 7 to then 8 to 11 then 2 to 1 then 5 to 4 then 10 to 11 then 4 to 3 then 8 to 9 then 3 to 2 then 9 to 10. the pattern is not absolute but maintains a reasonably even flow of heat . after welding is complete a low post heat of around 300°f gradually reducing over 10 minutes or so. you will be ready to start dressing the weld to round. and the finished size but the final grinding should not be done until the spindle has returned to ambient temp. for a 3to 4" diameter bearing surface you will want +0000'-.0005" max.
Another way to weld up the spindle would be with an Exothermic metalizing spray like that of Ram Airco or Study they use ox/act flame and powdered metal dust. the torch is held several inches away for the preheated part and the powder is sprayed through the flame. the part never receives the electrical shock treatment that mig or wire can do and stays at around 300 to 400°f throughout the whole build up process. I've used them to weld up everything from crankshafts to the leading edges of gas turbine blades in the past.