P355M and P420M are fine-grain structural steel grades for pressure vessels (EN 10028-5), differing mainly in strength: P355M offers minimum yield strength of 355 MPa (or 345 MPa for thicker plates), while P420M offers higher strength with a minimum yield of 420 MPa, making P420M better for higher pressure/stress applications like pipelines, though P355M is great for storage tanks and general pressure use.
Supplementary Technology: HIC Test | NACE MR0175 | Z15 | Z25 | Z35
Thickness: 6MM to 300MM,
Width: 1500mm to 4050mm,
Length: 3000mm to 15000mm
Chemical Composition
|
EN10028-5 P355M Chemical Composition |
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|
Grade |
The Element Max (%) |
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|
C |
Si |
Mn |
P |
S |
Al |
N |
|
|
P355M |
0,14 |
0,50 |
1,60 |
0,025 |
0,020 |
0,020 |
0,015 |
|
Nb |
V |
Ti |
Ni |
Mo |
|
|
|
|
0,05 |
0,10 |
0,05 |
0,50 |
0,20 |
|
|
|
|
EN10028-5 P420M Chemical Composition |
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|
Grade |
The Element Max (%) |
||||||
|
C |
Si |
Mn |
P |
S |
Al |
N |
|
|
P420M |
0,16 |
0,50 |
1,70 |
0,025 |
0,020 |
0,020 |
0,020 |
|
Nb |
V |
Ti |
Ni |
Mo |
|
|
|
|
0,05 |
0,10 |
0,05 |
0,50 |
0,20 |
|
|
|
Mechanical Property
|
Grade |
P355M Mechanical Property |
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|
Thickness |
Yield |
Tensile |
Elongation |
|
|
P355M |
mm |
Min Mpa |
Mpa |
Min % |
|
6-16 |
355 |
450-610 |
22% |
|
|
16-40 |
355 |
450-610 |
22% |
|
|
40-63 |
345 |
450-610 |
22% |
|
|
Grade |
P420M Mechanical Property |
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|
Thickness |
Yield |
Tensile |
Elongation |
|
|
P420M |
mm |
Min Mpa |
Mpa |
Min % |
|
6-16 |
420 |
500-660 |
19% |
|
|
16-40 |
400 |
500-660 |
19% |
|
|
40-63 |
390 |
500-660 |
19% |
|
Key Differences & Similarities
Strength: P420M has a higher minimum yield strength (around 420 MPa) than P355M (around 355 MPa), making P420M stronger.
Standard: Both fall under EN 10028-5, a standard for flat products for pressure purposes, specifically TMCP steels.
Manufacturing: Both use Thermomechanical Control Process (TMCP), giving them excellent weldability and toughness, allowing for the omission of post-weld heat treatment (PWHT).
Composition: P420M contains elements like manganese (around 1.7%) for strength, but both are controlled low-carbon steels.
Applications: P355M is used in general pressure vessels and tanks, while P420M is suitable for higher-pressure or specific applications like hydrogen/CO2 pipelines.
In Summary: Choose P355M for standard pressure tasks needing good weldability; choose P420M when higher strength is needed for the same application profile, without sacrificing TMCP benefits.
