Sunday, September 19, 2010

Re: [MW:7095] Hardness increased after forming-reg

Dear Karthi
                  Increase in hardness due to strain hardening effect. Remove the crack by grinding  before that drill a hole at both end of the cracks. Do the Normalising you can revert back the original properties. then go for the repair welding.
 
 
 
 
Regards
 
Balaji

On Sat, Sep 18, 2010 at 1:57 PM, Karthik <karthik6684@yahoo.com> wrote:
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?
No.3.
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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