Steel C5
ASTM A217 Grade C5
C5 is a 5Cr-0.5Mo cast alloy steel supplied to ASTM A217 Grade C5, the cast counterpart of wrought P5, alloyed for oxidation and sulfidation resistance in hot hydrocarbon service.
Reference datasheet — C5 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the N+T condition
C5 tempers and conditions
C5 is supplied in 3 conditions, soft to hard. N+T is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full anneal (soft condition for rough machining) | Intermediate softened state used by foundries/machine shops before the final N&T or Q&T qualifying heat treatment. | 380 | 590 | 26 | 9 HRC | 3.3 % IACS |
N+TDefault Normalized and tempered | Standard supply condition for A217 C5 valve bodies and pressure castings; balanced strength, creep resistance and machinability. | 470 | 690 | 22 | 16 HRC | — |
Quenched and tempered | Chosen for heavy sections where a fully transformed, uniform tempered structure and higher toughness through thickness are needed. | 510 | 720 | 21 | 18 HRC | — |
Supply forms, finishes and certifications
Ways C5 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
AW-PWHT | As-welded + PWHT | Surface finish |
What is C5?
C5 is a 5Cr-0.5Mo cast alloy steel supplied to ASTM A217 Grade C5, the cast counterpart of wrought P5, alloyed for oxidation and sulfidation resistance in hot hydrocarbon service. In the normalized-and-tempered default condition it provides 470 MPa yield, 690 MPa tensile, 22 % elongation and 205 HB (16 HRC) with service to 620 °C, and is supplied as pressure-retaining castings such as valve bodies, bonnets and fittings. The alloy air-hardens, so welding requires preheat and mandatory PWHT; atmospheric corrosion resistance is low (28/100) and machinability moderate (45/100), so coating is normally required outdoors. Where higher creep strength is needed, C12 or C12A is the next step. C5 has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 93% of steel grades. It melts at 1,420°C (2,588 °F). C5 has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 57% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi).
What is C5 used for?
- Refinery valve bodies
- High-temperature hydrocarbon service fittings
- Hot oil pump casings
- Catalytic cracking unit piping components
- Valve bonnets for hydroprocessing units
- Cast elbows and tees for hot process lines
Advantages
- High service temperature — 620°C (1,148 °F), better than 99% of steel grades
- Good corrosion resistance — 28/100, better than 94% of steel grades
Limitations
- Limited formability — 10/100, worse than 95% of steel grades
C5 properties
Typical room-temperature values for C5-N+T; bars are the position among steel grades.
Physical3
C5 has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 93% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
C5 has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 57% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
C5 is rated for continuous service to 620°C (1,148 °F). It conducts heat at 36 W/m·K (20.8 BTU/hr·ft·°F), worse than 73% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical2
C5 has an electrical resistivity of 5.5×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is poor (28/100), better than 94% of steel grades.
Sustainability4
Producing a kilogram of C5 takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 75%.
Manufacturability7
C5's machinability is fair (45/100, worse than 65% of steel grades); weldability fair (35/100); formability not recommended (10/100).
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. C5 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C5
Is C5 easy to machine?
Machine in the tempered condition with rigid setups, carbide tooling and moderate speeds (~60–90 m/min); the 5% Cr matrix is abrasive and work-hardens if feeds are too light.
Can C5 be welded?
Use matching 5Cr-0.5Mo (E502/ER80S-B6) consumables with 200–300 °C preheat/interpass and mandatory 700–760 °C PWHT; slow cooling is essential to avoid martensitic cracking.
Can C5 be formed, bent or molded?
Supplied only as castings — control pouring temperature and use generous fillets and risers because the alloy air-hardens and is hot-tear sensitive; never cold form.
C5 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 |
|---|---|---|
| C0.20 max per ASTM A217 | ≤ 0.2 | 0.15 |
| Mn | 0.4 – 0.7 | 0.55 |
| Si | ≤ 0.75 | 0.45 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.05 | 0.02 |
| Cr | 4 – 6.5 | 5 |
| Mo | 0.45 – 0.65 | 0.55 |
| Fe | balance |
What surface finishes work on C5?
Normally shot-blasted and painted or aluminized for outdoor use; hot service parts often left bare since Cr provides a protective oxide, and plating is rarely applied.
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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel C5 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- A217 Grade C5
How much does C5 cost?
C5 is a premium-cost steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
C5 — frequently asked
What is C5 used for?
C5 is typically used for refinery valve bodies, high-temperature hydrocarbon service fittings, hot oil pump casings, catalytic cracking unit piping components, valve bonnets for hydroprocessing units and cast elbows and tees for hot process lines. In short: cast counterpart to P5; 5Cr sulfidation-resistant casting; 620 °C service limit.
What is the yield strength of C5?
C5 has a typical yield strength of 470 MPa (68.2 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 57% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is C5 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the tempered condition with rigid setups, carbide tooling and moderate speeds (~60–90 m/min); the 5% Cr matrix is abrasive and work-hardens if feeds are too light.
Can C5 be welded?
With care — weldability is rated fair (35/100). Use matching 5Cr-0.5Mo (E502/ER80S-B6) consumables with 200–300 °C preheat/interpass and mandatory 700–760 °C PWHT; slow cooling is essential to avoid martensitic cracking.
What surface finishes work on C5?
Normally shot-blasted and painted or aluminized for outdoor use; hot service parts often left bare since Cr provides a protective oxide, and plating is rarely applied.
Can C5 be formed, bent or molded?
Supplied only as castings — control pouring temperature and use generous fillets and risers because the alloy air-hardens and is hot-tear sensitive; never cold form.
What is the maximum service temperature of C5?
C5 is rated for continuous use to about 620°C (1,148 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does C5 cost?
C5 is a premium-cost steel ($$$), cheaper than about 51% 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.
Sources
- ASTM A217/A217M — Steel Castings, Martensitic Stainless and Alloy, for Pressure-Containing Parts, Suitable for High-Temperature Service — ASTM International (2021)
- ASME BPVC Section II Part D — Material Properties (5Cr-1/2Mo) — ASME (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- GB/T 16253 (ZG16Cr5Mo) — SAC (2019)
- API 941 — Steels for Hydrogen Service at Elevated Temperatures — API (2016)
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.