Hi Ashis,
Please see the data sheet for general guidance. Titanium is usually considered immune to SCC. However cold formed bends may require stress relieving to keep the hardness under control, especially in the sour environments.
What's your clients' specific requirements (hardness control) under the given design considerations.
For example MR-15156-Part -3, Table, A-41, requirements are as follows:-
- Specific guidelines shall be followed for successful applications of each titanium alloy specified in this part of ANSI/NACE MR0175/ISO 15156. For example, hydrogen embrittlement of titanium alloys can occur if these alloys are galvanically coupled to certain active metals (e.g., carbon steel) in H2S-containing aqueous media at temperatures greater than 80 °C (176 °F). Some titanium alloys can be susceptible to crevice corrosion and/or SSC in chloride environments. Hardness has not been shown to correlate with susceptibility to SSC/SCC. However, hardness has been included for alloys with high strength to indicate the maximum testing levels at which failure has not occurred.
Thanks.
Pradip Goswami, P.Eng,IWE
Welding & Metallurgical Specialist
Ontario, Canada
pradip_goswami@yahoo.ca
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Raghuram Bathula
Sent: Monday, April 21, 2014 6:19 PM
To: materials-welding@googlegroups.com
Subject: [MW:20642] Re: Stress Relieving of Titanium Grade 2 Tubes
A stress relief treatment is sometimes employed following severe forming or welding to avoid cracking or distortion due to high residual stresses, or to improve fatigue resistance. Cleanliness of titanium parts to be heat treated is important because of the sensitivity of titanium to contamination at elevated temperatures. Titanium fabrications should be cleaned carefully prior to heating, using nonchlorinated solvents or a detergent wash, followed by a thorough water rinse. Handling following cleaning should be minimized to avoid potential surface contamination.
Most titanium grades are typically stress-relieved at about 1000°F (538°C) for 45 minutes and annealed at 1300°F (704°C) for two hours. A slightly higher stress relief temperature [1100°F (593°C), 2 hrs.] and annealing temperature [1450°F (788°C), 4 hrs.] are appropriate for the Grade 5 alloy. Air cooling is generally acceptable.
Although no special furnace equipment or protective atmosphere is required for titanium, a slightly oxidizing atmosphere is recommended to prevent pickup of hydrogen. Direct flame impingement for extended periods, leading to temperatures in excess of 1200°F (649°C), should be avoided because of the potential for contamination and embrittlement. Hydrogen or cracked ammonia atmospheres, also, should never be used, because their use would lead to excessive hydrogen pick-up, and embrittlement.
more info can be found at
http://www.keytometals.com/Article97.htm
http://www.azom.com/article.aspx?ArticleID=1245
On Tuesday, April 22, 2014 3:48:01 AM UTC+5:30, Materials & Welding wrote:
-- Most titanium grades are typically stress-relieved at about 1000°F (538°C) for 45 minutes and annealed at 1300°F (704°C) for two hours. A slightly higher stress relief temperature [1100°F (593°C), 2 hrs.] and annealing temperature [1450°F (788°C), 4 hrs.] are appropriate for the Grade 5 alloy. Air cooling is generally acceptable.
Although no special furnace equipment or protective atmosphere is required for titanium, a slightly oxidizing atmosphere is recommended to prevent pickup of hydrogen. Direct flame impingement for extended periods, leading to temperatures in excess of 1200°F (649°C), should be avoided because of the potential for contamination and embrittlement. Hydrogen or cracked ammonia atmospheres, also, should never be used, because their use would lead to excessive hydrogen pick-up, and embrittlement.
more info can be found at
http://www.keytometals.com/Article97.htm
http://www.azom.com/article.aspx?ArticleID=1245
On Tuesday, April 22, 2014 3:48:01 AM UTC+5:30, Materials & Welding wrote:
Our client requirement states that Stress Relieving of Titanium U bends is mandatory. Our Metallurgy of Tubes is SB 368 Gr. 2 (UNS R50400)
Tube side fluid is sea water and Shell side fluid is sour gas (172 bar Pressure and 170 deg cel at shell side)
In view of above , please let me know , Is it really require to perform SR of Titanium U bends.
NACE states that Titanium is susceptible to Stress corrosion cracking. Vendors are not in opinion of doing SR.
Please provide your valuable input
Thanks
Ashish
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