Industrial seamless pipes

TP304 is an ASME pipe grade, 304L is an ASME sheet grade, and S30403 is a Chinese grade

It is the same material grade with the same properties. But the writing style and standards differ. The first two are generally considered to be American standards ASMT or ASME. Stainless steel seamless tubes can be divided into round tubes and rectangular tubes, with the respective grades being TP304L and MT304L; this applies to steel tubes as well. It is not precise to write only 304L as the grade. The complete grade designation is the standard number plus the material grade. For example: ASTM A312 TP304L. S30403 was originally the material code according to the American standard UNS, while the grade refers to the TP304L material. If it is a US standard, its full designation can also be something like ASTM A312 UNS S30403. However, S30403 is now generally considered to be a material under national standards, simply because the US standard material code was naturally adopted for use. See GB/T14976-2012. Since seamless pipes according to national standards do not require as strict labeling as those per American standards, notation such as S30403 is used. More strictly speaking, national standard pipes should also be labeled with the standard number plus the grade designation. Such as GB/T14976 S30403. In reality, however, there are so many qualified people that people simply write down S30403. In fact, all these refer to the same material; it’s just that different standards apply and the testing procedures vary slightly. Just pay more attention to it. :)