Mr Karthik,
SA 516/70 plates 1.50 in. [40 mm] and under in thickness are normally supplied in the as-rolled condition. However plates may be ordered normalized or stress relieved, or both.
What was the original heat treatment in the mill, was it normalized ? If plates were normalized then renormalizing following forming may not help much. A normalized 516/70 plate will fall under Curve-D in UCS-66 which by default guarantees better mechanical (impact) properties at lower design temperatures.
UCS -79, specifies, following cold forming heads or vessel parts, shall be heat treated subsequently as per UCS-56, which stress is relieving.
As regarding your query:-
- Normalizing refines the grain, and there would be a change of mechanical properties (betterment) and may cause a drop of hardness, since this hardness values are predominantly due to forming residual stresses. If plates were received as rolled then post forming normalizing would be helpful. But hardness reduction and by how much could only be assessed after simulation HT is done in the lab.
- Since you plan to perform normalizing (if it’s clients requirement), a simulation coupon would help.
- Should the head undergo normalizing; the defect may be ground and repaired later. Otherwise the repair WPS have to undergo a normalizing cycle. It may involve weld metal of higher strength ,ER-80S-G or other consumables, due to the fact that ER-70S-2 may not match the base metal UTS following normalizing.
Hope this provides adequate clarifications to your query.
Thanks
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Karthik
Sent: Saturday, September 18, 2010 5:57 AM
To: materials-welding@googlegroups.com
Subject: [MW:7070] Hardness increased after forming-reg
| Dear All, We found hardness increased on Straight Flange Area (SF) of Head after Spinning(Forming) and linear crack found on the SF area due to improper spinning method Material - SA516 Gr.70, Thk.: 19mm. Hardness found - 240HB to 320HB on SF area only. Con.Code : ASME Se.VIII,Div.1 But there is no maximum hardness value specified in ASME.As our experience,we know the hardness value for carbon steel shall be 187HB maximum.Actually we plan to do Normalising of the heads.The SF area only increased in hardness.The rest of all within the limits. My question is, No.1. If we do normalising of head,is there is any change in grain structure and mechanical properties of the head. No.2. Or if we repair the crack areas by remove the crack by grinding and weld by GTAW and without doing nomalising and staright away we are going for welding with the cap.Is it ok? Or we have some material removed from the SF area of the same head,So we send this matrerial for Mechanical properties confirmation.If it has confirmed we can go as per the No.2. Thanks & Regards, (karthik) Karthikeyan.S QA/QC Manager Getabec Energy Co.,Ltd. 379,Moo6,Soi8,Nikhomphatana, Rayong-21180, Thailand. Phone: 0066 38 897035-8 (Off) Fax: 0066 38 897034 Hand Phone: 0066 892512282 |
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