Steel P355M M+SR
Heat-treated state
EN 1.8821, 10028-5
Use for thick-wall or code-mandated PWHT vessels; expect a small drop in yield and hardness after long soaks.
Values for the M+SR condition
Other P355M tempers and conditions
P355M is listed in 7 conditions; see the grade overview at P355M.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
M | Maximum standard thickness range; check mill capability, through-thickness properties often ordered with Z-quality. | 345 | 495 | 25 | 148 HB | 9 % IACS |
M | Heavy plate for thick-wall shells; slightly lower guaranteed yield and toughness scatter. | 365 | 505 | 25 | 150 HB | 9 % IACS |
M+SRThis page thermomechanically rolled and post-weld stress relieved (~530–580 °C) | Use for thick-wall or code-mandated PWHT vessels; expect a small drop in yield and hardness after long soaks. | 370 | 505 | 27 | 148 HB | 9 % IACS |
M | Mid-thickness plate; yield drops one step per EN 10028-5 thickness table. | 375 | 515 | 26 | 152 HB | 9 % IACS |
MDefault Thermomechanically controlled processed | Standard as-delivered TMCP plate for ambient/moderate-temperature welded vessels; impact tested at 0 °C. | 385 | 520 | 26 | 155 HB | 9 % IACS |
TMCP, low-temperature quality | Pick when the vessel design temperature reaches −20 °C; tighter P/S limits than P355M. | 385 | 520 | 27 | 155 HB | 9 % IACS |
TMCP, extra-low-temperature quality | Cryogenic-leaning option for LPG/ammonia and cold-climate tanks; lowest S/P and best CVN. | 390 | 525 | 28 | 156 HB | 9 % IACS |
What is P355M M+SR?
P355M M+SR is P355M heat treated to M+SR — use for thick-wall or code-mandated PWHT vessels; expect a small drop in yield and hardness after long soaks. P355M M+SR has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 505 MPa (73.2 ksi) — weaker than 70% of steel grades. Elongation at break is 27% and the elastic modulus is 210 GPa (30.5 Msi). P355M M+SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,490°C (2,714 °F). M is the default condition FabDigit quotes; M+SR is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 135 MPa·√m (122.9 ksi·√in), better than 93% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Readily welded — 90/100, better than 90% of steel grades
- Forms and bends easily — 74/100, better than 89% of steel grades
- Ductile — tolerates forming and impact — 27%, better than 86% of steel grades
Limitations
- Hard to polish — 40/100, worse than 96% of steel grades
P355M M+SR properties
Typical room-temperature values for P355M M+SR; 22 are specific to this condition. Other listed values are P355M reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P355M M+SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,490°C (2,714 °F).
Mechanical16
P355M M+SR has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 505 MPa (73.2 ksi) — weaker than 70% of steel grades. Elongation at break is 27% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
P355M M+SR is rated for continuous service to 400°C (752 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
P355M M+SR conducts electricity at 9 % IACS, better than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of P355M M+SR takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability6
P355M M+SR's machinability is good (60/100, better than 83% of steel grades); weldability excellent (90/100); formability very good (74/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P355M M+SR
Is P355M easy to machine?
Machines like HSLA plate — moderate cutting speeds, positive-rake sharp carbide and good chip control; microalloy carbonitrides cause some abrasion and stringy chips.
Can P355M be welded?
Excellent weldability due to low carbon equivalent — SAW/GMAW/SMAW with matching 355-class consumables, low hydrogen, controlled heat input to avoid HAZ softening of the TMCP structure; preheat usually only for heavy sections.
Can P355M be formed, bent or molded?
Good cold formability (press-braking, rolling of shells); avoid hot forming above ~580 °C or re-normalizing, since that destroys the thermomechanical strengthening — re-qualify properties if done.
What surface finishes work on P355M?
No inherent corrosion resistance: blast to Sa 2½ and apply epoxy/zinc-rich primer systems, hot-dip galvanizing or internal lining; readily paintable and weld-seam ground for NDT.
P355M chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cladle analysis, EN 10028-5 | ≤ 0.16 | 0.12 |
| Si | ≤ 0.5 | 0.3 |
| Mn | 1 – 1.7 | 1.4 |
| PML1 ≤0.025, ML2 ≤0.020 | ≤ 0.03 | 0.02 |
| SML1 ≤0.015, ML2 ≤0.010 | ≤ 0.03 | 0.01 |
| Altotal Al; other grain-refining practice permitted | ≥ 0.02 | 0.04 |
| Cr | ≤ 0.3 | 0.05 |
| Ni | ≤ 0.5 | 0.1 |
| Cu | ≤ 0.7 | 0.1 |
| Mo | ≤ 0.1 | 0.02 |
| Nbmicroalloy; Nb+Ti+V ≤ 0.12 total | ≤ 0.05 | 0.03 |
| Ti | ≤ 0.05 | 0.02 |
| V | ≤ 0.1 | 0.03 |
| N | ≤ 0.02 | 0.01 |
| Fe | balance | — |
P355M M+SR — frequently asked
What is P355M M+SR used for?
P355M M+SR is typically used for pressure vessels, boilers, storage tanks and piping. In short: workhorse TMCP vessel plate; low CEV, easy welding; 400 °C service ceiling.
What is the yield strength of P355M M+SR?
P355M M+SR has a typical yield strength of 370 MPa (53.7 ksi) and a tensile strength of 505 MPa (73.2 ksi) — weaker than 70% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is P355M M+SR easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machines like HSLA plate — moderate cutting speeds, positive-rake sharp carbide and good chip control; microalloy carbonitrides cause some abrasion and stringy chips.
Can P355M M+SR be welded?
Yes — weldability is rated excellent (90/100). Excellent weldability due to low carbon equivalent — SAW/GMAW/SMAW with matching 355-class consumables, low hydrogen, controlled heat input to avoid HAZ softening of the TMCP structure; preheat usually only for heavy sections.
What surface finishes work on P355M M+SR?
No inherent corrosion resistance: blast to Sa 2½ and apply epoxy/zinc-rich primer systems, hot-dip galvanizing or internal lining; readily paintable and weld-seam ground for NDT.
Can P355M M+SR be formed, bent or molded?
Good cold formability (press-braking, rolling of shells); avoid hot forming above ~580 °C or re-normalizing, since that destroys the thermomechanical strengthening — re-qualify properties if done.
What is the maximum service temperature of P355M M+SR?
P355M M+SR is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between P355M-M and P355M-ML2?
M is the default condition — standard as-delivered TMCP plate for ambient/moderate-temperature welded vessels; impact tested at 0 °C. ML2: cryogenic-leaning option for LPG/ammonia and cold-climate tanks; lowest S/P and best CVN. Yield strength is 385 MPa in M versus 390 MPa in ML2.
Sources
- EN 10028-5 — Flat products made of steels for pressure purposes: Weldable fine grain steels, thermomechanically rolled — CEN (2009)
- EN 10027-2 — Numerical designation system for steels (1.8821) — CEN (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Thermomechanically rolled pressure-vessel plate (P355M/ML1/ML2) mill datasheets — European plate mills (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.