Max bead with using flat 1/16" & 3/32" Flux core????

By nitrorocket1 Date 05-22-2008 13:56

I am trying to put together some procedures and guidlines for the welding department. Right now we weld with both 1/16" and 3/32" flux core wires using 75/25 mix. The welding is done on die steels for on large forging dies. Wire consists of Cormet F25 and F35 die repair wires. The dies are preheated to 500 for welding and stress relieved after weld at 1100 degrees.
Right now some use a weave method to fill up large cavitys when welding a crack repair or impression solid. The weaves are generally in the 3/4" to 2.5" wide range. I would like to limit this stringers to eliminate excessive heat and stresses being that this material is very crack prone in the first place. We also occasionally have problems with slag inclusions, I believe this may be partially due to excessive weaving.
Is there a standard somewhere I can follow? Is there any data to back that stringers are superior to weaves as far as metallurgical weld quality is concerned? Is there industry standard overall bead widths based on wire size? I am having a hard time convincing the welders otherwise.

Thanks!

By jwright650 (*****)

Date 05-22-2008 14:21

We don't weld on the same materials(mild steel) or use the same gas(100% CO2), but we do use those diameters and about a 5/16" stringer is about as wide as I like to see because you loose pen at the root if you run any larger...particulary fillet welds. Wider passes with groove welds looses pen at the side walls or groove faces....slag is also a concern with carrying those large puddles.....man, I can't imagine that the puddle is staying fluid on those really wide weaves that you are speaking of...2.5" is pretty wide....I could see where the 3/4" weaves would stay fluid because of the size of the puddle when running a stringer is pretty large anyway with those dia wires.

By hogan

Date 05-22-2008 14:36

nitro, that seems like a very large weave. the AWS D1.1 code limits prequalified bead width for fcaw at 5/8" for flat, horiz, overhead, and 1" for vert. As john mentioned, we typlically weld mild steel. With your material heat is more of a concern.

http://www.welding-advisers.com/Welding-Tool-Steel.html

By GRoberts (***)

Date 05-22-2008 19:18

I'm not supporting it, or condemning it, but high heat input welding does seem to be a common practice in the forging die repair industry.

http://www.mpdwelding.com/floodwelding.htm

look up "flood welding" on google and you can find a lot of information.

The bottom line is whether the welding technique provides a satisfactory product, and if it meets applicable codes. (not sure if there are any for die repair). In your case, if it causing slag inclusions, that could be a reason the practice is unsatisfactory. However, you can get welders entrapping plenty of slag with stringers as well if their technique is not correct.

By flash77 Date 05-22-2008 23:50

Hi i would say 1\2 inch to 5\16 max and make sure your guys are wire brushing after each pass. It will take longer but you wont have repairs after stress relief and machining.

By DaveBoyer (*****)

Date 05-23-2008 02:49

I agree with Your preference to limit to stringer beads due to the reduced stress & cracking potential when compaired to a wide weave. What material are the dies made from?

By js55

Date 05-23-2008 13:22

Greg hit upon a good thought. You should limit the beads to that which is practical for your welders to achieve with good fusion and lack of slag and cracking, but keep in mind you are talking about forging dies. A material operating at high temps in which large grain size can be an advantage. Hence, the high heat input.
IMO I wouldn't get too carried away with limiting the beads. Limit it by what your welders are capable of achieveing as far as viable welds are concerned.

By nitrorocket1 Date 05-23-2008 19:23

Well, most all of the dies we repair are due to cracking and I am hoping and figuring that by limiting known causes of additional stress, that will help prolong time before recrack. I have also noticed that most "recrack" repairs, have the crack running along the old heat affected zone from the past crack repair.

By js55

Date 05-23-2008 19:52

Just as a devils advocate here, If your stress relief is doing what it should your service cracking is most likely not related to weld stresses. Isn't that why you stress relief?
If your HAZ's are cracking, maybe they are already cracked, if its weld related. In which case preheat increase may be the way to go.
Also, you heat something up to forging temp, there won't be any more weld related stresses.
Isn't your hot working temp even higher than your stress relief?
And keep in mind too that if you reduce your beads and run stringers now you have multiplied the number of HAZ 's you have. Not to mention your HAZ's are now in the weld deposit and not just the original base metal.
It's difficult for me to see how the cracks can be weld stress related when there won't be any weld stresses that survive the stress relief and the hot forging.
It seems to me either the cracks are already there or they are caused by something else.

By js55

Date 05-23-2008 19:54

By the way, what material are the dies?