Dear Vaidehi,
If the failure is due to segregation of S P & carbide precipitation.
- Then why it does not happens normally in pressure vessels, Heat exchangers of the same steel grades?
- What about the HAZ of the welding joints for the same pressure vessels which are also under fatigue loadings?
- Wheather solution annealing is recommended by ASME? If then thickness range?
Thanks for the help,
Regards,
PANKAJ
On Sun, Jul 11, 2010 at 8:51 PM, Vaidehi Ganesan <vaidehi@igcar.gov.in> wrote:
It looks like carbides are formed initially. Yes. It is required to do suitable solution annealing treatments to dissolve the carbides in solid solution. Moreover the impurities (P, S, Si ) segregate along the grain boundaries (during service) and reduces the fracture toughness of the material/ weld. We have faced similar problems with HP turbine blades. Failure must be due to carbide precipitation ( fairly big sizes) and segregation of minor elements along G.B.All the best,Thank you,Vaidehi Ganesan.-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Sent: Mon, Jul 12, 10 12:49Subject: Re: [MW:5947] Inservice failureDear Vaidehi,The failed sample at the region of shearing or cracking has got Micro tested & found carbide precipitation in the Heat affected zone . the suraface above welding which is 20 mm far from welding is found ok in Micro.Weather the requirement of solution annealing after welding?as the tube was solution annealed previously.Pankaj
On Sun, Jul 11, 2010 at 5:51 PM, pankaj abhang <pankaj.abhang1@gmail.com> wrote:
On Sun, Jul 11, 2010 at 5:42 PM, pankaj abhang <pankaj.abhang1@gmail.com> wrote:
Dear Vaidehi,Sorry for previous data incorrectly sended.Please find the actual values:-The Chemistry for the Tubes as given belowThe Material Grade is- SA249 TP 304.C (MAX)- 0.08 Observed- 0.054Mn (Max)- 2.00 Observed- 1.14P (Max)-0.045 Observed-0.033S (Max)-0.030 Observed- 0.006Si (Max)-1.00 Observed- 0.42Cr (Max-20 Min-18) Observed- 18.07Ni (Max-11- Min -08) Observed- 8.21Observed UTS Values- 651.4(Mpa)Elongation- 62 mmHardness- 69-70Micro- ASTM Grain size No.7Heat Treatment- Solution annealed at minimum 1040 celcius & rapidly water quenched.PANKAJ
On Sun, Jul 11, 2010 at 4:14 PM, Vaidehi Ganesan <vaidehi@igcar.gov.in> wrote:
--What is the material, compositions?best regards,Vaidehi Ganesan.=============================================================Dr. Vaidehi Ganesan,Metallurgy & Materials Group,IGCAR, Kalpajkkam-603 102, India.=======================================================------- Original Message -----From: pankaj abhangSent: Sat, Jul 10, 10 10:15Subject: [MW:5924] Inservice failureDear Members,We had supplied a Finned tube radiator after 1 year in service the header to tube joint getting shearing off near 10-15 mm from weld joint. what will be the reason for the failure.Details are as given below-Tube inside process fluid- Steam at 200 celciusTube MOC- SA 240 TP 249Tube Thickness-2 mmHeader pipe -3"NB sch10sHeader MOC- SA 240 TP 312Welding Joint- UW 16.1(d)Welding Technique- GTAWWorking pressure- 15 bar(g).
PANKAJ
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