6013 or 7018 rods for root runs?

[Bill Edwards]

I've always happily used 6013 for all welding jobs, but lately I've got some 7018 rods as I can use them on the oil cooled welder and keep them in an airtight container, and it seems a good idea to use them where a stronger weld is desirable.

I seem to find conflicting views on which rod should be used for a root run. Some seem to say a 6013 then fill with a 7018, I've also heard it done the other way round.
What is best, and why not just do the whole thing with the same rod as I normally would with a 6013?
Is there any benefit from using different rods for the root runs?

 

[wheresmejumper]

Is it a fillet or open root?
7018 is normally better in every aspect, for every pass, but open root is tricky

 

[TechnicAl]

If you root with 6013 and fill with 7018 the 7018 weld wont be low hydrogen as the hydrogen will diffuse from the 6013 weld. 6013 will have over 30 ppm where the low hys should be less than 5 if baked or perhaps less than 10 if from the box.
Having said all that 7018s produce a stronger weld which will still be stronger even if it has higher hydrogen
Given time the hydrogen all disappears

 

[Bill Edwards]

Both, depending on the job.
Am I best just using 7018's for the entire weld where I'd like more strength than a 6013? That does seem logical to me, but when other people use both it makes me think there must be a reason for it.

 

[BrokenBiker]

my rule of thumb, its its not structural, use 6013, if it has to be as strong as possible use 7018 for root and cap

 

[Liquid Metal]

my rule of thumb, its its not structural, use 6013, if it has to be as strong as possible use 7018 for root and cap

Get some 7016 rods. Much easier to root with if you ask me, especially out of position, and is a lo-hy rod, basically a 7018 without the iron powder additive in the flux (might have my wires crossed though re the iron powder lol)

If you root with 6013 and fill with 7018 the 7018 weld wont be low hydrogen as the hydrogen will diffuse from the 6013 weld. 6013 will have over 30 ppm where the low hys should be less than 5 if baked or perhaps less than 10 if from the box.
Having said all that 7018s produce a stronger weld which will still be stronger even if it has higher hydrogen
Given time the hydrogen all disappears

I do understand what you are saying about the Hydrogen content in a root deposited using 6013 diffusing into the covering passes when deposited with 7018.
Makes perfect sense.
My question is,
Being as it is not the best idea to root with 6013 and then fill and cap with 7018 due to the hydrogen diffusing into fill passes, how come so many companies use procedures stating a 6010/6011 cap and then Lo hy fill and cap for quite critical welds, ie process pipework and storage vessels for oil refineries?? With the hydrogen content of these rods would the problem not be a lot worse than a 6013 root
The company I work for myself, uses this procedure (6010 fleetweld 5p+ root and hot pass, Philips/Esab 7018 fill and cap, or vodex fill and cap for less strength critical work) aswell as procedures requiring a 7016 root and 7018 fill and cap.

Also, does the same apply if welding a root pass with Argon/co2 MIG, then using FCAW fill and cap with lo-hy wire Murex B55??

 

[Bill Edwards]

Thanks for all the replies.
It looks like I should just stick with the lo-hi rods. I'm happy to do this as they're only about £15 per 5kg pack and are in some ways better to weld with once you get used to them (I'm stuck with AC ). They seem to stick to the metal where I want them to, sometimes with 6013's I find it hard to get fusion to one of the parts, it doesn't seem to be an issue with the 70's, I've used a box of them and struggled to do any wrong. They even seem less affected by any bits of slag that aren't cleaned out of the way.

Thanks for the tip on using 7016's, but I'm limited to what's available from the agricultural stockist that work has an account with! Plus I've limited storage space to keep a few different types of rod dry.

 

[TechnicAl]

Get some 7016 rods. Much easier to root with if you ask me, especially out of position, and is a lo-hy rod, basically a 7018 without the iron powder additive in the flux (might have my wires crossed though re the iron powder lol)




I do understand what you are saying about the Hydrogen content in a root deposited using 6013 diffusing into the covering passes when deposited with 7018.
Makes perfect sense.
My question is,
Being as it is not the best idea to root with 6013 and then fill and cap with 7018 due to the hydrogen diffusing into fill passes, how come so many companies use procedures stating a 6010/6011 cap and then Lo hy fill and cap for quite critical welds, ie process pipework and storage vessels for oil refineries?? With the hydrogen content of these rods would the problem not be a lot worse than a 6013 root
The company I work for myself, uses this procedure (6010 fleetweld 5p+ root and hot pass, Philips/Esab 7018 fill and cap, or vodex fill and cap for less strength critical work) aswell as procedures requiring a 7016 root and 7018 fill and cap.

Also, does the same apply if welding a root pass with Argon/co2 MIG, then using FCAW fill and cap with lo-hy wire Murex B55??

The 6010s are good for rooting. They burn in well and dont suffer from lack of fusion so the joint fit up can be less than perfect but still produce a good sound weld. The trick is to put the hot pass in quickly so that the heat releases the hydrogen from the root weld as soon as possible. If you allowed it to cool the risk of cracking would increase significantly.

Mild Steel MIG wire welding is (usually) a low hydrogen process. However, some cheap foreign imports are not as low as more reputable brands. WE did a trial with Supramig and the H2 was 1ppm and after 24 hours there was nothing but I have seen numbers as high as 13ppm

 

[Bill Edwards]

6010's? I'm stuck with AC.

The MIG wire at 13 ppm may not be good compared to some, but it's still better than 6013's by quite a long way?

 

[BrokenBiker]

use 6011, they are ac rods iirc

 

[Bill Edwards]

True. But then I still have the problem of getting them. My boss isn't a welding man and really wouldn't understand the need, and as long as the things I weld don't fall apart why change...
7018's seem like a good rod for the general farm use, it could be over-complicating matters to use something unusual for the roots. At the end of the day, 6013's are strong stuff, 7018's even more so - I have to stop somewhere!

 

[BrokenBiker]

I have used both on farm equipment with no problems, i use 6013 much more often for normal fab work but use 7018 for heavy stuff and things that i really don't want to break

 

[TechnicAl]

6010's? I'm stuck with AC.

The MIG wire at 13 ppm may not be good compared to some, but it's still better than 6013's by quite a long way?

not necessarily........the structure of the steel also influences and the MIG wire weld is harder and more prone