Steel C5 Q+T
Heat-treated state
ASTM A217 Grade C5
Q+T = quenched and tempered
Chosen for heavy sections where a fully transformed, uniform tempered structure and higher toughness through thickness are needed.
Values for the Q+T condition
Other C5 tempers and conditions
C5 is listed in 3 conditions; see the grade overview at C5.
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 | — |
Q+TThis page 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 | — |
What is C5 Q+T?
C5 Q+T is C5 heat treated to Q+T — chosen for heavy sections where a fully transformed, uniform tempered structure and higher toughness through thickness are needed. C5 Q+T has a yield strength of 510 MPa (74 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 65% of steel grades. Elongation at break is 21% and the elastic modulus is 207 GPa (30 Msi). C5 Q+T 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). N+T is the default condition FabDigit quotes; Q+T is available on request or by drawing note.
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 Q+T properties
Typical room-temperature values for C5 Q+T; 10 are specific to this condition. Other listed values are C5 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
C5 Q+T 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 Q+T has a yield strength of 510 MPa (74 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 65% of steel grades. Elongation at break is 21% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
C5 Q+T 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 Q+T 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 Q+T 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 Q+T's machinability is fair (45/100, worse than 65% of steel grades); weldability fair (35/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C5 Q+T
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.
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.
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 | — |
C5 Q+T — frequently asked
What is C5 Q+T used for?
C5 Q+T 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 Q+T?
C5 Q+T has a typical yield strength of 510 MPa (74 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 65% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is C5 Q+T 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 Q+T 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 Q+T?
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 Q+T 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 Q+T?
C5 Q+T 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.