Q345
Thread Content
This post was last edited by adjiang95 on 2010-1-10 21:39. May I ask everyone, Q345 is a low-alloy structural steel; compared to the old standard 1591-88, it corresponds to grades such as 12MnV, 16Mn, 16MnRE, 18Nb, and 14MnNb. What does this mean? Does that mean that the previous materials such as 12MnV, 16Mn, 16MnRE, 18Nb, and 14MnNb are now all referred to as Q345? Is Q345R simply equivalent to the former 16MnR?
The predecessor of the current material standard GB713-08 was GB6654-96 (referring to containers). GB6654-96 specifies 16MnR only; it doesn’t include the other materials you mentioned, so it mainly refers to 16MnR
Take a good look at the preface of GB713-2008!
Q345R is what used to be called 16MnR. Q345 is a structural steel, but it is also a C-manganese steel; there aren’t as many variations as you mentioned. It’s possible that older standards grouped together all steels with a yield strength of 345 under the same category called Q345. I haven’t studied this in detail, but according to the new 1591 standard, Q345 is indeed a C-manganese steel. But this steel is still far inferior to steel used for containers. It’s difficult to compare things that are not part of the same system.
The Q345 mentioned in the introduction is a combination of 16Mn (g, R) and 19Mng; for containers, 16MnR is the main grade used. There aren’t as many other grades as Lz mentioned – it’s likely that the grade you’re referring to is quite old; I’ve never encountered it before
The lower limit value for the standard yield strength is 345 MPa. Q345 and Q345R have different chemical compositions, mainly in terms of P and S. The former is high, the latter is low.
I also read about it on Baidu Baike, where those materials mentioned above were listed
There are many professional forums; taking a casual look at them is enough, no need to search on Baidu