Steel A204
ASTM A204 · UNS K12822
A204 is a molybdenum-alloyed pressure-vessel plate steel (ASTM A204 Grades A, B and C; UNS K12822) that holds strength at temperature better than plain carbon plate.
Values for the HR condition
A204 tempers and conditions
A204 is supplied in 8 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full anneal / stress-relief annealed plate | Pick when maximum ductility, lowest residual stress and easiest machining/forming are needed. | 290 | 475 | 27 | 145 HB | 8.3 % IACS |
Grade A | Choose Grade A when maximum weldability and ductility matter more than allowable stress. | 290 | 500 | 27 | 140 HB | 44 W/m·K |
HRDefault Hot rolled | Standard stocked condition for thinner A204 plate where as-rolled properties meet the grade minima. | 315 | 520 | 24 | 160 HB | 8.2 % IACS |
Grade B | Most widely stocked A204 grade; default choice for boiler drums and elevated-temperature vessels. | 315 | 540 | 25 | 152 HB | 43 W/m·K |
austenitized and air cooled | Standard condition for heavier plate (and mandatory above certain thicknesses) to refine grain and even out properties. | 325 | 515 | 25 | 155 HB | 8.2 % IACS |
Normalized and tempered | Best balance of strength and notch toughness for code vessels with low-temperature impact requirements. | 330 | 505 | 26 | 155 HB | 8.2 % IACS |
Grade C | Use where the thinnest possible shell is wanted; slightly higher carbon so welding controls are stricter. | 340 | 575 | 23 | 163 HB | 43 W/m·K |
Quenched and tempered | Used for thick sections or when the upper end of the tensile range plus high toughness is required. | 405 | 570 | 22 | 180 HB | 8 % IACS |
What is A204?
A204 is a molybdenum-alloyed pressure-vessel plate steel (ASTM A204 Grades A, B and C; UNS K12822) that holds strength at temperature better than plain carbon plate. It is supplied as normalized or normalized-and-tempered plate for code-built boilers and vessels; the default condition gives 315 MPa yield, 520 MPa tensile, 24 % elongation, 160 HB and service to about 480 °C. The Mo addition gives no corrosion resistance, and code post-weld heat treatment is normally required on thicker sections. For higher temperatures or hydrogen service, move to a 1.25Cr-0.5Mo plate such as A387 Gr 11. A204 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,460°C (2,660 °F). A204 has a yield strength of 315 MPa (45.7 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 82% of steel grades. Elongation at break is 24% and the elastic modulus is 205 GPa (29.7 Msi).
What is A204 used for?
- Boilers
- Storage tanks
- Refinery vessels
Advantages
- High service temperature — 480°C (896 °F), better than 88% of steel grades
Limitations
- Low strength — 315 MPa (45.7 ksi), worse than 82% of steel grades
A204 properties
Typical room-temperature values for A204-HR; bars are the position among steel grades.
Physical3
A204 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,460°C (2,660 °F).
Mechanical16
A204 has a yield strength of 315 MPa (45.7 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 82% of steel grades. Elongation at break is 24% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A204 is rated for continuous service to 480°C (896 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
A204 conducts electricity at 8.2 % IACS, better than 61% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of A204 takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 25%.
Manufacturability8
A204's machinability is good (58/100, better than 75% of steel grades); weldability very good (70/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. A204 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A204
Is A204 easy to machine?
Machines like a 190 HB low-alloy steel — carbide tooling, moderate speeds, good chip control; slightly gummier than plain carbon steel due to Mo.
Can A204 be welded?
Readily welded with matching 0.5Mo consumables (E7018-A1 / ER80S-D2); preheat ~100–150 °C on thick plate and apply PWHT at 620–680 °C per code.
Can A204 be formed, bent or molded?
Cold-form only mild radii; hot form heads at 900–1000 °C and re-normalize afterwards to restore properties.
Manufacturability
The process limits FabDigit applies to A204. Every A204 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better58 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better60 / 100 |
|---|---|
| Weldability | Excellent70 / 100 |
| Bendable | Yes |
A204 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 |
|---|---|---|
| CGr.A ≤0.25, Gr.B ≤0.27, Gr.C ≤0.28 (thickness dependent) | ≤ 0.27 | 0.2 |
| Mnheat analysis max; Gr.C to 0.90 | ≤ 0.9 | 0.7 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.01 |
| Si | 0.15 – 0.4 | 0.25 |
| Mocreep-strengthening addition | 0.45 – 0.6 | 0.5 |
| Fe | balance |
What surface finishes work on A204?
Blast and paint, phosphate or metallize; no anodizing — for corrosive service use stainless weld overlay or roll-bonded clad plate.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel A204 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- K12822
- ASTM
- A204 Grade A/B/CA204 Gr AA204 Gr BA204 Gr C
How much does A204 cost?
A204 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
A204 — frequently asked
What is A204 used for?
A204 is typically used for boilers, storage tanks and refinery vessels. In short: molybdenum pressure plate.
What is the yield strength of A204?
A204 has a typical yield strength of 315 MPa (45.7 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 82% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is A204 easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machines like a 190 HB low-alloy steel — carbide tooling, moderate speeds, good chip control; slightly gummier than plain carbon steel due to Mo.
Can A204 be welded?
Yes — weldability is rated very good (70/100). Readily welded with matching 0.5Mo consumables (E7018-A1 / ER80S-D2); preheat ~100–150 °C on thick plate and apply PWHT at 620–680 °C per code.
What surface finishes work on A204?
Blast and paint, phosphate or metallize; no anodizing — for corrosive service use stainless weld overlay or roll-bonded clad plate.
Can A204 be formed, bent or molded?
Cold-form only mild radii; hot form heads at 900–1000 °C and re-normalize afterwards to restore properties.
What is the maximum service temperature of A204?
A204 is rated for continuous use to about 480°C (896 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does A204 cost?
A204 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in A204?
Yes — A204 is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A204/A204M — Pressure Vessel Plates, Alloy Steel, Molybdenum — ASTM International (2019)
- ASME BPVC Section II Part A (SA-204) and Part D (allowable stresses, physical properties) — ASME (2023)
- EN 10028-2 (16Mo3) — Flat products for pressure purposes, creep-resisting steels — CEN (2017)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.13C / Vol.19 — Corrosion and Fatigue of steels — ASM International (2006)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.