DIFFRENCE BETWEEN P355QH1 AND P355NH

[Krishna_Manyam]

Dear Experts,

Kindly advice on below,

P355QH1(Un assigned group as per ASME IX)where as P355NH assigned group as per ASME IX?
BOTH HAVE SAME CHEMICAL AND MECHANICAL PROPERTIES.

 

[Gr8blu]

https://www.makeitfrom.com/compare/...Alloy-Steel/EN-1.0571-P355QH1-Non-Alloy-Steel

See above link for material properties. Yes, they're close. But what is NOT shown is how good they are at cold temperatures.

Both grades have a "Class" designator (either Class 0, 1, or 2). The higher the class number, the lower the temperature it is good for - and the lower the temperature required for the notch test.

Typically, Class 0 will be good to 0 C, Class 1 to -20 C, and Class 2 to -46 C. But check your supplier's documentation to be sure.



Converting energy to motion for more than half a century

 

[DriveMeNuts]

Q stands for quenched and tempered.
N is for normalised.
H is high temperature.
L is low temp, where L1,2 etc are increasingly low temp.


P355NH is a normalised steel plate for -20° and higher higher.
P355QH1 is quenched and tempered from -40°C and higher temps. It is forging only.
P355QH is quenched and tempered plate or forging with min temp of -20°C and higher temps.

 

[riteshk14]

I think what the enquirer means to ask is: can P355QH1 be considered P-No. 1 too, like P355NH, seeing that both are P355? The answer is no. First, their chemical composition is not same, not even similar. Two, they are classified under different specifications, one under EN 10028-3, another under EN 10222-4.

Section IX specifies the specification along with the classification, in the table QW-422. One should avoid making the mistake of locating the classification alone. When trying to determine P-number, BOTH the classification as well as specification should be matched.

For example, 16Mo3 grade classified under EN 100216-2 specification is a P-No. 3 metal; while 16Mo3 grade specified under EN 10222-2 and EN 10028-2 is an unassigned metal (confirmed by Sec IX through interpretation IX-23-26).

Seeing another way, this is an interesting question however. Some grades are designated with an optional designator. When one comes across a grade having an optional designator, should it be considered of same P-No. as the original grade? Or not?

Can't think of an appropriate example in base metals right now. But in filler metals - E7018 has a F-no. 4 as per ASME Sec IX. I know that E7018-H4R (H4R is an optional designator indicating restricted diffusible hydrogen and restricted moisture content) is also to be considered as F-no. 4. This however, is not spelt out thus anywhere. Does a similar logic apply to base metals too?