The issue of forging grades for low-temperature vessels
Thread Content
Section 6.0.8 of HG/T20585-2011 states that when the design pressure is 1.6 MPa or higher, it shall be at least of grade III. And in 6.1.3 of GB150.2-2011, it refers to those that meet condition \"d): steel forgings for low-temperature use with a service temperature below -20 degrees and a nominal thickness greater than 200 mm.\" ”Grade III or IV should be selected. So, when the design pressure is greater than 1.6 MPa, what grade should be used for low-temperature vessel forgings?
Level II can become Level III, which is okay
If I were the designer, I would choose Level III; of course, choosing Level II isn’t wrong either, as HG/T20585 is after all a recommended standard； If your drawings specify design in accordance with HG/T20585, then grade III must be selected
Grade II is sufficient； Grade III is also fine; it’s just more expensive
Look at the cost; use grade III for the critical parts