Inclusions in casting A216 WCC vs 8620 pressure vessel

[awol]

I have a pressure vessel housing cast with A216 WCC material. Experiencing a lot of inclusions exposed during machining. Foundry wants to change material to 8620 but I cannot verify this 8620 material is pressure quality. This part has internal and external threads so stainless is not an option for me. Thanks, AWOL

 

[metengr]

awol;
If this is a pressure vessel housing, you have several other options for steel or low alloy steel castings under ASTM specifications versus using a cast version of 8620 alloy steel (which does not conform to any of the ASTM casting specifications).

Your options could be various carbon or low alloy steel grades under ASTM A 217, ASTM A 148, ASTM A 27 or other ASTM Casting Specs depending on your specific application.

Is the pressure vessel built to ASME Boiler and Pressure Vessel Code Section VIII, Div 1 requirements?

What is the nature of the housing? Is it welded to the pressure vessel or integral with the vessel?

What are the design service conditions?

 

[arunmrao]

Changing the grade of material is not going to assist in eliminating the inclusion defect observed during machining. The foundry should upgrade its technology to minimise these defects.

8620 grade specification for a casting does not exist. But broadly the castings are manufactured to this chemistry. As suggested earlier there are other grades of cast materials for pressure vessel appplications.

 

[GRoberts]

I would agree with arunmrao, that the material is not in need of upgrading, but foundry practice, NDT, solidification modelling, or other avenues should be investigated.

 

[awol]

Questions asked:


Is the pressure vessel built to ASME Boiler and Pressure Vessel Code Section VIII, Div 1 requirements? No code requirements. Company internal requirements to use pressure grade material or, if using a non pressure grade material, provide documented testing to validate the use of the material in our application.

What is the nature of the housing? Temporarily attached to pipeline like a valve during servicing. Never becomes part of permanent pipeline system. Is it welded to the pressure vessel or integral with the vessel? No, NPT threads.

What are the design service conditions? Test presure 415 psi. MaOP 285 psi. Gas, oil, water.

Of the other material that have been recommended, A148 looks good but will require testing. The others A27 , A487 require HT and / or test with each lot.

I have quotes out to other casting vendors. Thanks for the help.

 

[arunmrao]

ASTM 148 grade 90-60 will be a good choice. However, please include a NDT requirement before accepting the casting,preferably insist on proof machining with hydraulic test also if possible. This will reduce costly rejections after machining. However, I am sure a good foundry should not have problem manufacturing a defect free casting.