Rolling/forming method for Gr.91 Plate

[Brajendra Singh]

Dear expert's,

Please share the forming/rolling requirements for A387 Gr.91, we have tried cold forming/rolling of shell & dish end but always cracking.

Attaching photographs for refrence.

Thanks in advance

Regards, 

Brajendra Patel

Mob:+917057406907

[PGoswami]

Hi,

What’s the thickness and the diameter involved? It’s not always possible to guess the thickness from photographs due to enlargement. Cold forming generally should be avoided for grade-91 steel.

Grade-91 steel is a high tensile steel. Cold bending could lead to cracking and other metallurgical consequences.

API-TR- 938-B recommendations for cold bending of this steel are  as follows:-

·         The degree of cold working is usually limited to 17 % maximum (wall thickness reduction), if steels are applied at creep range temperatures.

·         Most users would require that cold worked 9Cr-1Mo-V steels be normalized and tempered if the steels are applied in the creep range and the degree of cold working exceeds 17 %.

·         Cold deformation requires heat treatment by most codes for deformation greater than 5 %

 

You need to think about warm forming  to be on the safe side.

 

Appreciate response with details.

 

Thanks.

 

P.Goswami.P.Eng, IWE.

Welding & Metallurgical Specialist

Linkedin: https://www.linkedin.com/in/pradip-goswami-2999855/

Email:pgos...@quickclic.net,pradip....@gmail.com

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[Prakash Hegde]

Hi!

For high alloy steelmaterial edges should be ground and rounded followed by MPT and LPT 

LOADING SHOULD BE GRADUAL and not sudden.during forming

For D.end.it is always better.to go for crown and petal 

Regards

Hegde

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[Brajendra Patel]

Dear sir,

Thanks for your suggestion..

Still i have some query as below.

1. Our dish dia 26", can we make this diameter in crown & petal type.

2. Is hot rolling/bending is better solution for this if it is then what is the recommended temp & precautions for this.

3. Our plate dish cracks multiple locations, is it recommended to weld repair of these cracks, any chances of delayed cracking, please suggest.

Sir your suggestion will be very helpful for us to out of this problem.

  Thanks & regards,

Brajendra Patel

Mob: 7057406907

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[Brajendra Singh]

Dear Sir,

 

Thanks for your valued suggestions.

 

Thickness & dimensions of shell & dish end are as below.

 

For shell: requirement of diameter to be formed is 26” with thickness 18 mm.

 

For Dish End : required diameter is 26”

 

Regards,

 

Brajendra Patel

 

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[PGoswami]

Hi Brejendra,

 

Thanks for sharing the information. A thickness of 18mm may be possible to be cold formed, subject to the heat treatment, mechanical properties and the level of NDE done on the plates  in the mill. Any cold forming with deformation(strain) exceeding the specified value as below should be followed by short stress relieve cycle , prior to  any welding.

 

Or else it better to do warm forming  of the  plates. You may directly approach the manufacturer if procured directly any mill.

 

Irrespective of cold or warm forming, it’s always advisable to have a good shop QA/Q.C , Welding & NDE practices in place while handling Grade 91 steel.

[George Dilintas]

Pls have a look in PG-20 in ASME BPVC Section I

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Dr. Georgios Dilintas,

Dipl. Ing. In Aeronautic and Space Engineering

Ph.D in Mechanics of Solids - Computational Mechanics

A.I.S, A.N.I, IRCA Lead Auditor

Welding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis