Problems with impact testing of low-temperature steel per GB20801.2
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In Table 4 of GB/T20801.2, which specifies the requirements for low-temperature steels, under Condition 1: the minimum operating temperature is as given in Table A.1, and impact testing is required. Condition 2: The lowest operating temperature is taken as the lower value between that specified in Table A.1 and -46, and the impact test is waived. The minimum operating temperature for Condition 2 is lower than or equal to that of Condition 1, yet it exempts the impact test. It means that the more severe the operating conditions, the lower the requirements for the material. How should this be understood?
@ZDICK888 @liaifeng The wise are enlightened@The wise are enlightened
There are exemptions, and the materials need not be the same; check all the details
Thank you for the reply, but in the impact test requirements column, there is only “exempted” – no specific requirements listed.
Pay attention to the conditions for exemption from the impact test: only small cross-sections, as well as low temperatures and low stresses, allow exemption from this test
I agree with you, but this table is poorly designed and prone to misunderstanding.
Hello, taking advantage of this question, I’d like to ask another thing: according to this table, if the thickness is ≤15 mm, 20-grade steel can be used at -20°C without the need for impact testing. However, in GB150, the minimum operating temperature for 20-grade steel is 0°C. So, can 20-grade steel actually be used at temperatures below 0°C?
Different standards result in different requirements for shock-free conditions, and they cannot be mixed together.