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:
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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