[taylorkh]

A couple of years ago Jody did a video in which he described the virtues of 312, as a substitute for Hastaloy, when welding tool steel and other high carbon steels, stainless to mild steel, UFO metal to unobtainium etc. Following my usual monkey see monkey buy routine I sought out and purchased a couple of pounds of the stuff so I would have it handy just in case. I did a little weld and break testing with some old lawnmower blade material - sort of inconclusive - and put the rest away until I needed it.

This afternoon I needed it. I used up the half a rod left over from my earlier testing and then started on another rod. When I was done I decided to highlight the 312 with a sharpy marker before I put the partial rod in my pcv tube of "used so use these first" pieces of filler so as not to use it by accident instead of 308L or such. I noticed that the filler was marked 312H - for high carbon I believe.

I examined the rest of the 312 filler I have. All the rest of the 3/32" are 312 and all of the 1/16" are 312H. Both tubes are labeled ER312. The "manufactured" is listed as Welder's Choice." I purchased the filler from use-enco.com. I am wondering if it is worth raising H about the H in my filler (sorry about the pun Is there a big difference in 312 and 312H when it comes to welding steel with a high carbon content to start with?

TIA,

Ken

[Braehill]

Ken,
I believe that the H when dealing with stainless rod refers to high temp and not high Carbon. I'm sure I read that somewhere, but I'm not above being corrected if I'm wrong. I know we have 347H rod at work and I don't think we would ever add any more Carbon to a weld. This is used on 321 stainless at elevated temps in the 1200-1400* F range and I believe the carbides start forming around 885*F.

Len

[taylorkh]

Thanks Len,

I believe you are on to the answer. I "found" a copy of AWS standard A5.9-93 on-line. I suspect it might be a little out of date but it does indicate that fillers ER308H and ER316H have their carbon content limited to the upper end of the carbon content range of their non-H specification. 0.04 - 0.08% carbon as opposed to a maximum of 0.08% carbon for the non-H specification. I interpret this me mean that ER308 (non-H) could have as low as 0.00% carbon(?) The standard also indicates that the carbon in the H alloys "provides higher strength at elevated temperatures."

I do not find ER347H in the standard but I have found it in other on-line documents. It has the same carbon range ( 0.04 - 0.08%) as compared to 0.08% in the non-H ER347. Again, the description describes high temperature performance.

On the other hand there does not seem to be any such thing as ER312H on the Internet.

Thanks for your reply.

Ken