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Did this weld cause the failure?
Posted: Fri Jun 15, 2018 12:16 pm
by nelson
- 20180615_114851.jpg (30.38 KiB) Viewed 749 times
This is a hot runner manifold for injection molding. 5 inch long, 1 inch square.
It's of A-2 steel tempered at 1000 F
The central gallery hole is plugged 1/8-27 with stainless plugs.
Plugs were welded over with 309 rod. In quick and out.
The piece was hardened After the welding.
After 2 days running higher pressure than I like due to not enough watts in the heaters it leaked, I pulled it out and saw this...wow.
Has anyone seen failure like this?
Can you say for sure that the weld caused this?
Thanks!
Re: Opinions appreciated on this one
Posted: Fri Jun 15, 2018 12:38 pm
by smithdoor
No but A-2 will crack with heating and cooling
Dave
nelson wrote:20180615_114851.jpg
This is a hot runner manifold for injection molding. 5 inch long, 1 inch square.
It's of A-2 steel tempered at 1000 F
The central gallery hole is plugged 1/8-27 with stainless plugs.
Plugs were welded over with 309 rod. In quick and out.
The piece was hardened After the welding.
After 2 days running higher pressure than I like due to not enough watts in the heaters it leaked, I pulled it out and saw this...wow.
Has anyone seen failure like this?
Can you say for sure that the weld caused this?
Thanks!
Sent from my SAMSUNG-SM-J320A using Tapatalk
Re: Opinions appreciated on this one
Posted: Fri Jun 15, 2018 6:28 pm
by Demented
Never seen a crack like that before, but I have seen A-2 fail on presses due to heat treating errors. It's always just chipped on me.
Re: Opinions appreciated on this one
Posted: Fri Jun 15, 2018 8:21 pm
by nelson
309 filler is more, I'm sure, ductile and springy than A-2 drawn to 1000F...just before the bottom drops out and it kinda annealed.
The central gallery hole is .394 or whatever a 1/8-27 pipe tap calls for. There are several holes right down the center weakening it along that line.
I'm trying S-7 now. I don't think the hammering from the pressure is what S-7 is made for, but hardness is critical because of the way this block goes in the mold. It is pressed in with 5/16 setsets crews jamming it against the backside of the A side of the mold.
I DO hug trees and dogs, but this, if it works, keeps 1700 lb./year out of the dumpster, increasing our profits as an added benefit.
Gotta go.
Re: Opinions appreciated on this one
Posted: Fri Jun 15, 2018 8:44 pm
by Demented
Give it a pretty decent pre-heat before welding, somewhere around 800*F. May be a good idea to raise it up to hardening temperature after too and letting it cool slowly. It will likely fail again if it doesn't go through the heat treating process again, but S7 is air quenching so that is relatively easy.