ASME SA204 Grade B Steel Plate | SA204 Gr.B Mo Vessel Plate
What is ASME SA204 Grade B Steel?
ASME SA204 Grade B is molybdenum-alloy steel plate under ASME SA-204/SA-204M for welded boilers and other pressure vessels. The specification has three grades only: A, B and C. All three are C-0.5Mo. Grade B is the mid-strength line: 485–620 MPa tensile and 275 MPa minimum yield. As Direct Mill Supply by SHH STEEL, the plate is produced to ASME SA-204/SA-204M.
The same plate is written SA204 Grade B, SA204 Gr.B, SA204GRB, SA-204 Grade B, SA204 B and SA 204 Gr B. ASTM A204 Grade B is the companion product spec. Do not treat this page as ASME SA387 Cr-Mo plate, as ASME SA533 Type B Class 1 QT Mn-Mo-Ni plate, or as ASME SA516 carbon vessel plate. Those are different books.
Grade A is 450–585 MPa. Grade C is 515–655 MPa. Molybdenum is the same 0.45–0.60% heat band on all three grades. Strength moves with carbon by thickness, not with extra chromium. Dual marking SA204 / A204 Grade B is available. Certificates can be EN 10204 3.1 or 3.2. Company scope: China steel Mill Agent-SHH STEEL.
Material Specification
| Specification Element | Requirement | SHH STEEL Compliance |
|---|---|---|
| Grade | ASME SA204 Grade B / SA204 Gr.B | Confirmed |
| Product Specification | ASME SA-204/SA-204M | Applied |
| Companion Spec | ASTM A204 Grade B | Dual cert available |
| General Requirements | ASME SA-20 / ASTM A20 | Applied |
| Alloy | C-0.5Mo | Confirmed |
| Intended use | Welded boilers and pressure vessels | As specified |
| Typical Thickness | 8 mm – 150 mm (mill capability beyond by enquiry) | By mill enquiry |
| Certification | EN 10204 3.1 or 3.2 / third-party | As ordered |
This plate sits in the pressure vessel steel plates family. It is not carbon steel plates without molybdenum, not structural steel plates, and not ASTM A36/A36M structural carbon.
Chemical Composition
Chemistry for ASME SA204 Grade B is reported as heat analysis and product analysis. Carbon maximum rises with thickness. Molybdenum stays in one band.
Heat Analysis — ASME SA204 Grade B
| Element | Heat Analysis (%) |
|---|---|
| Carbon (C), max, t ≤ 25 mm | 0.20 |
| Carbon (C), max, 25 mm < t ≤ 50 mm | 0.23 |
| Carbon (C), max, 50 mm < t ≤ 100 mm | 0.25 |
| Carbon (C), max, t > 100 mm | 0.27 |
| Manganese (Mn), max | 0.90 |
| Phosphorus (P), max | 0.025 |
| Sulfur (S), max | 0.025 |
| Silicon (Si) | 0.15 – 0.40 |
| Molybdenum (Mo) | 0.45 – 0.60 |
Product Analysis — SA204 Gr.B
| Element | Product Analysis (%) |
|---|---|
| Carbon (C) | Same maxima as heat analysis |
| Manganese (Mn), max | 0.98 |
| Phosphorus (P), max | 0.025 |
| Sulfur (S), max | 0.025 |
| Silicon (Si) | 0.13 – 0.45 |
| Molybdenum (Mo) | 0.41 – 0.64 |
Grade A and Grade C use the same molybdenum band. They do not use a different alloy. If the ladle has chromium in a Cr-Mo window, the plate belongs under ASME SA387, not SA204. If the ladle is carbon only, look at ASTM A516 or ASME SA515.
SHH STEEL reports heat analysis on every certificate, including molybdenum, and adds product analysis when SA-20 requires it.
Mechanical Properties
Tensile Requirements — ASME SA204 Grade B
| Property | Grade B |
|---|---|
| Tensile strength | 485 – 620 MPa (70 – 90 ksi) |
| Yield strength, min | 275 MPa (40 ksi) |
| Elongation in 200 mm (8 in.), min | 17% |
| Elongation in 50 mm (2 in.), min | 21% |
Grade A is 450–585 MPa and 255 MPa yield. Grade C is 515–655 MPa and 295 MPa yield. Density is 7.85 g/cm³. Charpy is not a hidden default. Write the impact temperature on the order when the vessel specification needs it.
Do not treat 275 MPa yield as a reason to substitute ASTM A572 or high strength low alloy plates. Those are structural routes, not C-0.5Mo boiler plate.
Material Comparison
| Grade | Route | Strength idea | Swap? |
|---|---|---|---|
| SA204 Grade A | C-0.5Mo | 450–585 / 255 MPa | Same family, lower Grade |
| SA204 Gr.B | C-0.5Mo | 485–620 / 275 MPa | This page |
| SA204 Grade C | C-0.5Mo | 515–655 / 295 MPa | Same family, higher Grade |
| ASME SA516 | Fine-grain carbon | No Mo requirement | No |
| ASME SA515 | Si-killed carbon | No Mo requirement | No |
| ASME SA387 | Cr-Mo | Different alloy | No |
| ASME SA533 Type B Class 1 | QT Mn-Mo-Ni | Different family | No |
| ASTM A285 | Low/intermediate carbon PV | No Mo | No |
Nearby vessel pages for comparison also include SA299 Gr.B, SA225 Gr.C and SA455. None of those is C-0.5Mo Grade B.
Molybdenum Vessel Service
ASME SA204 Grade B is selected for welded boilers and process vessels that need a lean molybdenum addition for moderate elevated temperature, without moving into Cr-Mo. Allowable stress comes from ASME Section II Part D for SA-204 Grade B.
Typical use is refinery and petrochemical shells, boiler drums and other welded equipment written to SA-204 Grade B. It is not glass-lining plate like SA562. It is not QT carbon like ASME SA537 or ASTM A537. It is not stainless. Stainless inquiries belong on ASME SA240/SA240M, ASTM A240/A240M or stainless steel sheets and plates.
Weldability
SA204 Gr.B is killed C-0.5Mo. Welding is Code welding.
Procedures are qualified to ASME Section IX. Low-hydrogen practice is the usual shop choice. Carbon rises with thickness, so a 120 mm plate is not welded like a 12 mm plate. Preheat and PWHT follow the qualified WPS and the vessel specification.
Do not copy a SA387 Cr-Mo procedure or a SA533 Type A Class 1 QT procedure onto Grade B without review. The fabricator owns the WPS.
Heat Treatment
The steel shall be killed. Plates 40 mm and under are commonly supplied as-rolled unless the order says otherwise. Plates over 40 mm are commonly normalized. Purchaser-specified normalizing or stress relieving is written on the mill instruction.
This is not the quench-and-temper route used for SA533 Type B Class 2. SHH STEEL reports the actual delivery condition on the MTC.
Delivery Condition
Usual delivery is as-rolled on thinner plate and normalized on thicker plate, or as specified.
The certificate lists ASME SA204 Grade B and, when dual certified, ASTM A204 Grade B; heat number; heat analysis including Mo; product analysis when ordered; tensile results; heat-treatment condition; and supplementary tests. Certificates may be EN 10204 3.1 or EN 10204 3.2.
Dimensions
Usual supply range from SHH STEEL for SA204 Gr.B Mo vessel plate:
- Thickness: 8 mm – 150 mm as regular rolling; thicker plate by mill enquiry when the composition can still meet Grade B tensile
- Width: 1500 mm – 4000 mm
- Length: 3000 mm – 12000 mm
- Cut-to-length shells and nest sizes inside those limits
If the project needs structural sizes rather than vessel plate, look at EN 10025-2 or JIS G3106. If it needs weathering plate, look at EN 10025-5 or Corten A/B. Those pages are not SA204.
Tolerances
Dimensional limits follow ASME SA-20. Thickness, width, length, flatness and camber are vessel-plate tolerances.
Ultrasonic testing to A435 / A577 / A578 is commonly added on thicker Grade B plate. Extra-flatness is a negotiated item.
Supplementary Requirements
Most export ASME SA204 Grade B orders add extras. SHH STEEL does not assume them.
Normalizing. Written when the drawing wants N on all thicknesses.
Charpy details. Temperature, energy, location and orientation.
Simulated PWHT. Same-heat coupons follow the vessel cycle.
NDE. UT to A435 / A577 / A578.
Restricted P, S. Tighter than 0.025% when specified.
Third-party. EN 10204 3.2.
Equivalent Material Grades
| Designation | Standard | Notes |
|---|---|---|
| ASME SA204 Grade B / SA204 Gr.B | ASME SA-204/SA-204M | Code name on this page |
| ASTM A204 Grade B | ASTM A204/A204M | Companion spec |
| SA204 Grade A / Grade C | SA-204 | Same Mo band, different strength |
| EN 10028-2 16Mo3 | EN | Project comparison only |
| JIS G3103 / related Mo vessel | JIS | Confirm Mo and tensile |
| GB 16MoR related | GB | Confirm chemistry |
DIN 17100, EN 10025-3, EN 10025-4 and EN 10025-6 are structural families, not C-0.5Mo boiler plate.
Applications
| Industry | Typical components |
|---|---|
| Boilers | ASME SA204 Grade B drums and SA204 Gr.B shells |
| Petrochemical | SA-204 Gr.B Mo courses |
| Process vessels | ASME SA204 Grade B Mo vessel plate |
| Dual-certified export | SA204 / A204 Grade B plate |
| Fabrication | SA204 Gr.B cut to nest sizes |
Ship plate inquiries belong on shipbuilding steel plates or BV Rules. Weathering inquiries belong on weathering steel plates. Stainless coil and plate inquiries belong on stainless steel products, JIS G4305 or AISI stainless.
Nearby vessel comparisons: SA299 Gr.A, SA225 Gr.D, A455, A562.
Why Choose SHH STEEL
SHH STEEL works as a China Mill Direct Exporter for plates to ASME SA-204/SA-204M. On ASME SA204 Grade B that means mill pricing, dual SA204/A204 marking, C-0.5Mo chemistry with molybdenum in the 0.45–0.60% heat band, recorded as-rolled or normalized condition, Grade B tensile results at 485–620 MPa and 275 MPa yield, 3.1 as standard and 3.2 when specified.
We keep the order on the right grade. Grade B is not Grade A and is not Grade C. SA204 is not SA516. SA204 is not SA387. SA204 Gr.B is not SA533 Type C Class 1. If the drawing names Cr-Mo, we point the inquiry to SA387. If it names carbon vessel plate, we point it to SA516 or SA515.
Company scope: China steel Mill Agent-SHH STEEL.
FAQ
- What names are used for ASME SA204 Grade B?Buyers write SA204 Grade B, SA204 Gr.B, SA204GRB, SA-204 Grade B, SA204 B and SA 204 Gr B. SHH STEEL prints the wording on the purchase order.
- Is ASME SA204 Grade B the same as ASTM A204 Grade B?Chemistry and tensile limits match. ASME SA-204 is the Code version. ASTM A204 is the product spec. As China mill-Direct Supply, SHH STEEL dual-certifies both names when the vessel must be stamped.
- What is the yield strength of SA204 Gr.B?275 MPa minimum. Tensile is 485–620 MPa. Elongation is 17% in 200 mm and 21% in 50 mm.
- Does Grade B have more molybdenum than Grade A?No. Molybdenum is 0.45–0.60% heat on Grades A, B and C. Strength moves with carbon by thickness.
- Is SA204 Grade B the same as SA387 or SA533?No. SA387 is Cr-Mo. SA533 is QT Mn-Mo or Mn-Mo-Ni. SA204 is C-0.5Mo.
- What heat treatment does ASME SA204 Grade B require?Killed steel. Plates 40 mm and under are commonly as-rolled. Thicker plate is commonly normalized unless the order says otherwise.
Conclusion
ASME SA204 Grade B Steel Plate is C-0.5Mo molybdenum vessel plate under ASME SA-204/SA-204M. Whether the inquiry says SA204 Grade B, SA204 Gr.B, SA204GRB or SA-204 Grade B, SHH STEEL supplies plate with molybdenum in the specified band, recorded delivery condition, Grade B tensile results, and EN 10204 3.1 or 3.2 certification.
As a China mill Distributor, SHH STEEL provides ASME SA204 Grade B / SA204 Gr.B Mo Vessel Plate for ASME Section VIII and boiler work.
Contact SHH STEEL for mill rolling, dual SA204/A204 marking, 3.2 inspection or a quotation.
ASME SA204 Grade B Steel Plate, SA204 Gr.B, SA204GRB, SA-204 Grade B, C-0.5Mo vessel plate, Direct Mill Supply by SHH STEEL
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