×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

HIC Material
2

HIC Material

HIC Material

(OP)

Some times for sour services, HIC steel is preferred. In some specifications, simulated post weld heat treatment cycles need to be performed for a certain steel to qualify as HIC steel. For example, three simulated PWHT cycles need to be performed on a test coupon before carrying out detailed chemical analysis and mechanical testing of that coupon. Temperature need to be maintained at 1150°F for a total of three (3) hours.

Question: What happens to the steel when it is held at 1150°F for a long period of time. Why is such a steel which after such simulated PWHT meets certain chemical and mechanical testing criteria, good for sour service?

RE: HIC Material

2
Your question really relates to the effect of post weld heat treatment on material properties (strength and toughness) and HIC resistance of SA-516 plate, as an example.

In general, to enhance HIC-resistance, plate steels like SA-516 are specified to have a lower sulfur content and are heat treated. The heat treatment can be quenched and tempered (Q&T) or normalized (N).

During fabrication of vessels, the application of heat from welding locally alters the original heat treatment condition of the plate (Q&T or N). In some cases, post weld heat treatment (PWHT) is required to reduce residual stress and to decrease the hardness of the base metal heat affected zone from welding, thus reducing susceptibility to in-service cracking ( or HIC). Extensive testing is performed after several or one long PWHT cycle to evaluate the reduction in mechanical properties and HIC-resistance of the plate base material.

If you want more information on this topic, the web site below contains information on HIC-resistant plate steels;

http://www.intlsteel.com/content/products/prod_plate_lit.aspx

RE: HIC Material

Metengr,
Excellent link.  Thanks,

RE: HIC Material

The hardness reduction is principally aimed at sulphide stress cracking resistance (SSC) for the welds rather than HIC resistance of the plate as HIC will occur anywhere in a susceptible material and not just the weld zone that may or may not have been affected by heating.  There is another cracking mechanism, SOHIC (stress oriented HIC)that could be impacted positively by the stress relief.  However, I would say that the test regime is to ensure that mechanical properties are maintained under a possible scenario involving 3 PWHT treatments as may occur with repairs.  

Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources