Grinding Cracks in Brittle Steel 1

[TangoCleveland]

We have an old pressure vessel analyzed to ASME Div 2, but not originally Code construction. Material is T1 steel, high strength but brittle. We found a spot where an old welded attachment was removed, and we suspect cracks. We will be checking with wet fluorescent mag particle and possibly replication. If we find some small cracks, we can grind about 0.2" without compromising thickness. We are worried that residual stress redistribution during grinding could cause the cracks to run. Any experience here in grinding out cracks, and whether they might get worse? Thanks in advance.....

Larry

 

[metengr]

Could you check the exact material composition for this vessel? If you are referring to USS T1 plate steel, this is a quenched and tempered, high strength low alloy steel. This material should not be brittle. It is weldable.

You need to do two things - (1) verify the vessel material chemical composition and (2) see if you can obtain some hardness values. What was the past process application of the vessel?

Proceed with caution on placing old vessels into service. You need to conduct some type of condition assessment, which would include a review of prior operating history and repairs. Also, you need to assure current operating conditions are suitable for this vessel.

 

[TangoCleveland]

Thanks for the response. One of my previous employers worked on old T1 steel vessels, about 4" thick, built to Code Case 1204.4. Weld repairs were very sensitive to heat input - too much heat caused cracks, so they gave up on weld repairs.

This particular vessel has been assessed, operating history and repairs are known, it's even been inspected by Hartford as a part of its sale to another user. We have material certs, and cut coupons out of a scrap vessel for analysis, which confirmed T1.

Customer is concerned that grinding will alter residual stresses and possible cause cracks to grow. That's the information I'm fishing for.

Larry

 

[metengr]

If you have materials certs, can you list the chemistry and mechanicals - it would help to determine susceptibility to cracking? I am going to check and see if I can find this ASME B&PV code case in Section VIII.

What was the vessel used for – operating temperature and pressure?

 

[unclesyd]

meteng,
When checking on the code case be sure and check the dates as I recall there were some issues with chemistry and physical properties of T-1 before a certain date. There might be a reference to CBI as my boss at the time was working with them on some problems.

My notes from 1965 show ASME code case 1204

 

[metman]

T1 as I recall falls under the categeory of ASTM A514 Low Alloy High Strength Steel. Some of the A514 alloys are susceptible to cracking in the HAZ from welding if thermally stress relieved. Probably the temperatures produced from grinding would not be sustained long enough to produce this kind of embrittlement but it might be good to check if this is one of the susceptible alloys.

 

[TangoCleveland]

Thanks for the replies, gentlemen, but I'm unable to furnish more details. You may possibly see posts here from the actual seller and owner of the vessel; I was just trying to be a middleman here. We are working with contacts at another site who are experienced with similar vessels. They're from a former employer of mine. We're very familiar with the changed properties after a certain date, and of both single wall and autofrettage construction by different manufacturers.

Larry

 

[metengr]

An FYI on this matter;
The ASME B&PV Code, Section II, subcommittee this week approved a code case for using all grades of ASTM A 514 plate in ASEM Section VIII, Div 3 applications. The limitations to this code case are 100 deg F service temperature, allowable stress limited to yield strength, and for a limited range of plate thicknesses, CVN tests, and no welding is permitted.