P91 Impacts

By 3.2 Inspector (***)

Date 03-11-2009 13:20

Jim,

What was the thickness of the test coupon?

3.2

By Jim Hughes (***)

Date 03-11-2009 13:24

1.1/2 inches thick P91 material.

By js55

Date 03-11-2009 14:21 Edited 03-11-2009 14:23

It will be very unusual to see high 20's low 30's from B9 flux core. We are starting to see more and more customer specs requiring impacts on B9. The usual requirement is as you state 70-72F, and usually around 20ft/lbs min. GTAW and SAW will usually pass with a margin. SMAW will generally be OK but somewhat lower. FCAW has trouble. What you are seeing is not unusual. What I've seen happen (though not with Supercore) is that you are given typicals that say high 20's or so, with Ni content saying ~0.4 because they know that everyone wants the Ni+Mn low to keep transformation up a little higher. But 20ft/lbs is not easy with FCAW and 0.4 Ni. When they quote typicals with impacts it usually bumps the Ni up. When they are forced to do actuals with impacts they bust it. The primary problem is that they can only fit so much stuff inside those little wires.
The thing is, you won't find a requirement in the code for B9 filler since it is almost exclusively for high temp service. It will be imposed by the customer who has concerns about time lapse from welding to HT and handling. The stuff is a rock before HT.

By Jim Hughes (***)

Date 03-11-2009 17:22

js55,
you must know our client. :) They are wanting to see 30 Ft-Lbs or above. Not an average. Our original PQR we had 24 29 and 30. So we tried to run another PQR to see if we could get our numbers up. I just recieved the report and we went the wrong way. You are right there is no requirement other than the clients whim. Now that we have re-done this I am realy liking our first results.

Also their concern is with hydos and during opperation they are concerned about cold starts. That's why we did one set of tests at 50 F.

Thanks for your imput

Jim

By js55

Date 03-11-2009 18:08

Just my opinion, but imposing 30+ impacts on B9 flux core is stupid. Your wasting your time. You may get lucky and achieve it (though I doubt it) but IMO it will be an upward aberrant, or getting iffy/questionable on procedures, and therefore would be representative of nothing. And I most certainly do not recommend. Representing what is actually in the weld is the whole point. FCAW just can't get that good consistently. Not in my experience.
24, 29, and 30 is very good for FCAW.
The only way to get >30 would be to bump the Ni way up and most specs limit Ni+Mn to 1.5 as well.
If somebody knows a FCAW that can hit +30ft/lbs somebody please tell who's it is because I haven't found it yet and I've tried I believe all of them.

"I just received the report and we went the wrong way." Let me guess, you reduced heat input.

By Jim Hughes (***)

Date 03-11-2009 19:37

Yes. I ran stringers. Here are some of my numbers. .045 wire Amps= 150-155 Volts=26-27 IPM=11-12 Wire Speed=230. Obviously I made some wrong assumptions and did not understand what I needed to do. I believed more beads would inhance tempering. This is incorrect. After talking with Bill Newell of Metrode I believe my IPM should have been more like 5-6. Live and learn.

Jim

By js55

Date 03-11-2009 21:21

You'll look long and hard in futility to find anybody that knows more about Grade 91 than Bill.
Its interesting. The usual procedure is to kick up travel speed thinking in terms of reducing heat input and grain size. But when grain size isn't the primary variable as it isn't with Grade 91(you're not running cold temp impacts), the other way works better. Slowing it down to increase penetration by subsequent beads to temper the martensite of prior beads is more often successful.
But I still believe your earlier results are about as good as you can get it. If you test again and prove me wrong let us know. Or even if Bill's advice gets you going the other way as I'm sure it will.

By Jim Hughes (***)

Date 03-18-2009 11:48

Thanks for the feed back. Looks like what I have learned is our original impacts are above the norm and we should stick with them.

Jim Hughes

By PhilThomas (**)

Date 03-12-2009 20:53

I haven't done impacts during procedure qualification, but I do have experience doing them during product certification testing.

You will be lucky to get 15-20 ft lbs at 72 deg with the flux cored wire. As others have pointed out - running fewer, larger beads will help this a little (as opposed to fast stringers).

hth