It is some thing tricky, and difficult to evaluate the exact cause. Your assumptions regarding HI could be the reason for this at a particular position.
But one thing is not clear to me, you welded this piece in rotating, how do you identify the 12’o clock position, where hardness is more?
Yes your conclusions stated below will help us definitely in due course.
Regarding your query on the previous statement the right vertical line is toe of the weld and left vertical line is toe of the surface temper reinforcing bead, this is mentioned to give a rough idea of surface temper bead placement, please note these surface temper beads may remain in place or may removed by grinding.
The in tempered HAZ as shown with arrow. Attachment in the previous post shows the same for tempering this arrow marked portion.
From: sachin sankhe [mailto:sachin.sankhe@rediffmail.com]
Sent: Monday, July 07, 2008 6:59 PM
To:
Cc:
Subject: Re: [MW:904] Hardness variation on a temper bead welded F65 forging
Dear Mr.Raghuram/Members,
Let me apologise for not putting subject.
Yes I had taken care as mentioned in your mail
As u can see in attached figure that 8th pass was done on 6th pass.
Distance between welding edge of 6th pass & 8th pass(i.e vertical distance in your mail sketch) was 3mm
Yes preheating was done min. 150 deg.C & INTERPASS temp maintained at 180-190 Deg.C
Also why it give high hardness on 12 O'CLOCK POSITION ONLY whereas it was accaptale in 6 O'CLOCK position
Today I could see Macro of all specimen from DNV,Lab(Singapore).I compared weld profile of both 6'O CLOCK & 12 O'CLOCK specimen.I have noticed that fusion line in 12 O'CLOCK was not straight i.e When fusion line deviated far into base metal at that point hardness value was too high.So I think welder shall try to maintain fusion line straight.
Note that 2F position hardenss was OK
So Conclusion is
If hardness is critical to achieve
1.Weld in such aposition that more Heat I/P can be done.In this case preferable position was 2F compare to 5F
2.During capping avoid welding on base metal
3.Grind 1/4th or may be 1/2 of last fill passes before doing capping so that we can get good tempering of last fill pass
4.Last Capping pass(Temper bead technique) shall be not that close to base metal so that it makes its own untempered HAZ in base metal
Views on above concluded points are welcome
I was not clear on your below statement can u be bit more clear on this
"The distance between two vertical lines (as shown in attached sketch) shall be small enough that HAZ of reinforcing bead tempers all of the unaffected HAZ in the base metal, but not so small that it creates its own untempered region."
Regards
Sachin.Sankhe
On Mon, 07 Jul 2008
>Dear members
>
>Request to use appropriate subject line, thou the topic was very
>interesting to discuss, it may be ignored by many in absence of an
>appropriate subject line.
>
>
>
>There are chances that toe of the weld, where no tempering of HAZ has
>occurred, in addition there is weld metal that is also not tempered, it
>may be necessary to add a layer on top of the completed weld and grind
>it off to get the desired results. This results in tempering of the
>remaining untempered weld and HAZ. But be careful not to let this extra
>tempering layer penetrates to base metal, if it, then you may create a
>new untempered HAZ.
>
>The distance between two vertical lines (as shown in attached sketch)
>shall be small enough that HAZ of reinforcing bead tempers all of the
>unaffected HAZ in the base metal, but not so small that it creates its
>own untempered region.
>
>(Remember) Cooling rate during welding : Thicker one cool faster than
>thinner ones, with lower heat input cool rapidly than higher heat input,
>cooler base material cool quicker than hotter ones (did you preheat this
>one?)
>
>
>
>
>
>Invite more discussions, and active participation, irrespective of your
>views whether right or wrong as only in discussion we can improve
>
>________________________________
>
> From:
>[mailto:
>Sent: Saturday, July 05, 2008 6:52 PM
>To:
>Subject:
>
>Dear Friends,
>
>Recently we have come across welding situation as mentioned below
>
>Details are as follows-
>
>1.Material used -API 5L X65 TO A694 F65
>2.Position-5F
>3.Welding Process-GTAW(Root,Hot)/SMAW(Fill, Cap)
>4.Welding consumable-GTAW(ESAB OK 13.09),SMAW(E8016 GH4R)
>5.Welding Technique-Temper Bead Technique
>6Reference Codes-API1104/NACE MR0175/DNV 0S F101
>7.Hardness Requiremnt as per Client Spec-248 HV10
>8.Size(12" O.D X 27.3 mm Thk to 2" O.D X 8.7 mm Thk)
>
>Situation-
>1.We carried out welding procedure qualification and sent for testing
>2.Testing to be carried out-NICK BREAK & HARDNESS
>3.Hardness on capping pass (12 O'CLOCK )at forging side found above 250
>HV10
>4.However at 6 O'CLOCK it was below 248HV10 & hence acceptable
>5.Due to failure at 12 O'CLOCK POSITION,we decided to re-qualify.
>6.This time we maintained high heat input(1.6-2.0 kJ/MM) on caping pass
>at forging side
>7.Hardness result again we found high at same location as
>previous,however on 6 O'CLOCK position it was less then 248 HV10
>8.Due to failure we decided along with client following option
> a)Two procedure to be qualified one in 5F position like prevoiusly but
>this time we decided to rotate the pipe when welding capping pass on
>forging side i.e Welding to be carried out only b/w 9-6-3 o'CLOCK
>POSITION only.Thus avoiding welding in 12 O'CLOCK POSITION
>Also we decided to use even higher heat i/p by using larger dia.
>electrode (3.2 mm)in place of previoiuly used 2.5 mm electrode
> b)Secound procedure we decided to do in 2F position and maintaining
>higher heat i/p(1.8-2.5 kj/mm)on capping pass(Forging side)
>
>9.After hardness testing for 5F position results on 12 O'CLOCK position
>forging side again failed
>10.However in 2F position it was satisfactory with same heat i/p as that
>in 5F position
>
>Would like to know the reason of such behaviour
>
>Sachin.Sankhe
>Engineer-Inspection
>Aker Kvaerner-Malaysia
>
>Email1:Sachin.Sankhe@akerkvaerner.com
>Email2:Sachin.sankhe@rediffmail.com
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