Steel A387 Gr 5 CL2-QT
Heat-treated state
ASTM A387 Gr 5 · UNS S50200
CL2-QT = class 2, Quenched and Tempered
Chosen for heavy sections (>75 mm) where liquid quenching is needed to meet Class 2 strength and toughness through-thickness.
Values for the CL2-QT condition
Other A387 Gr 5 tempers and conditions
A387 Gr 5 is listed in 4 conditions; see the grade overview at A387 Gr 5.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Class 1, Annealed | Softest, most machinable/formable condition for heads and cold-formed parts that will be re-heat-treated or PWHT'd. | 275 | 480 | 28 | 145 HB | — |
Class 1, Normalized and Tempered | Standard lower-strength class for thick refinery vessel shells where creep/oxidation resistance matters more than room-temperature strength. | 300 | 500 | 26 | 155 HB | — |
CL2-NTDefault Class 2, Normalized and Tempered | Most commonly stocked condition: higher design stress for hydroprocessing reactors, exchanger shells and hot piping. | 380 | 570 | 24 | 180 HB | — |
CL2-QTThis page Class 2, Quenched and Tempered | Chosen for heavy sections (>75 mm) where liquid quenching is needed to meet Class 2 strength and toughness through-thickness. | 420 | 600 | 23 | 14 HRC | — |
What is A387 Gr 5 CL2-QT?
A387 Gr 5 CL2-QT is A387 Gr 5 heat treated to CL2-QT — chosen for heavy sections (>75 mm) where liquid quenching is needed to meet Class 2 strength and toughness through-thickness. A387 Gr 5 CL2-QT has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 53% of steel grades. Elongation at break is 23% and the elastic modulus is 207 GPa (30 Msi). A387 Gr 5 CL2-QT has a density of 7.78 g/cm³ (0.281 lb/in³), lighter than 91% of steel grades. It melts at 1,425°C (2,597 °F). CL2-NT is the default condition FabDigit quotes; CL2-QT is available on request or by drawing note.
Advantages
- High service temperature — 600°C (1,112 °F), better than 98% of steel grades
- Tough — resists crack growth — 155 MPa·√m (141.1 ksi·√in), better than 97% of steel grades
- Good corrosion resistance — 25/100, better than 92% of steel grades
Limitations
- Low electrical conductivity — 2.9 % IACS, worse than 93% of steel grades
A387 Gr 5 CL2-QT properties
Typical room-temperature values for A387 Gr 5 CL2-QT; 16 are specific to this condition. Other listed values are A387 Gr 5 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A387 Gr 5 CL2-QT has a density of 7.78 g/cm³ (0.281 lb/in³), lighter than 91% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
A387 Gr 5 CL2-QT has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 53% of steel grades. Elongation at break is 23% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A387 Gr 5 CL2-QT is rated for continuous service to 600°C (1,112 °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).
Electrical3
A387 Gr 5 CL2-QT conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (25/100), better than 92% of steel grades.
Sustainability4
Producing a kilogram of A387 Gr 5 CL2-QT takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
A387 Gr 5 CL2-QT's machinability is fair (42/100, worse than 73% of steel grades); weldability fair (45/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A387 Gr 5 CL2-QT
Is A387 Gr 5 easy to machine?
Machines like a medium-hard alloy steel — rigid setups, carbide inserts, 60–110 m/min in the N&T condition; the 5 % Cr makes it more abrasive and gummier than 2.25Cr grades.
Can A387 Gr 5 be welded?
Weld with matching 5Cr-0.5Mo (E502/ER80S-B6) consumables, 200–260 °C preheat/interpass, low-hydrogen practice, and PWHT at 700–760 °C; control P/Sn/Sb for temper-embrittlement resistance.
Can A387 Gr 5 be formed, bent or molded?
Hot form at 900–1050 °C followed by re-normalizing and tempering; cold forming is limited and should be followed by stress relief.
What surface finishes work on A387 Gr 5?
Not anodizable — protect with high-temperature aluminum/silicone paint, aluminizing or thermal-spray coatings; internal surfaces are often stainless weld-overlay clad.
A387 Gr 5 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 |
|---|---|---|
| Cheat analysis, ASTM A387 Gr.5 | ≤ 0.15 | 0.12 |
| Mn | 0.3 – 0.6 | 0.45 |
| Plower P specified for temper-embrittlement control (API 934) | ≤ 0.03 | 0.01 |
| S | ≤ 0.03 | 0.01 |
| Si | ≤ 0.5 | 0.3 |
| Cr | 4 – 6 | 5 |
| Mo | 0.45 – 0.65 | 0.55 |
| Fe | balance | — |
A387 Gr 5 CL2-QT — frequently asked
What is A387 Gr 5 CL2-QT used for?
A387 Gr 5 CL2-QT is typically used for catalytic reformer piping, high-temperature vessel plate and sulfidic corrosion service equipment. In short: 5 % Cr refinery plate; better sulfidation resistance; service to 620 °C.
What is the yield strength of A387 Gr 5 CL2-QT?
A387 Gr 5 CL2-QT has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A387 Gr 5 CL2-QT easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machines like a medium-hard alloy steel — rigid setups, carbide inserts, 60–110 m/min in the N&T condition; the 5 % Cr makes it more abrasive and gummier than 2.25Cr grades.
Can A387 Gr 5 CL2-QT be welded?
With care — weldability is rated fair (45/100). Weld with matching 5Cr-0.5Mo (E502/ER80S-B6) consumables, 200–260 °C preheat/interpass, low-hydrogen practice, and PWHT at 700–760 °C; control P/Sn/Sb for temper-embrittlement resistance.
What surface finishes work on A387 Gr 5 CL2-QT?
Not anodizable — protect with high-temperature aluminum/silicone paint, aluminizing or thermal-spray coatings; internal surfaces are often stainless weld-overlay clad.
Can A387 Gr 5 CL2-QT be formed, bent or molded?
Hot form at 900–1050 °C followed by re-normalizing and tempering; cold forming is limited and should be followed by stress relief.
What is the maximum service temperature of A387 Gr 5 CL2-QT?
A387 Gr 5 CL2-QT is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A387 Gr 5 CL2-NT and A387 Gr 5 CL1-A?
CL2-NT is the default condition — most commonly stocked condition: higher design stress for hydroprocessing reactors, exchanger shells and hot piping. CL1-A: softest, most machinable/formable condition for heads and cold-formed parts that will be re-heat-treated or PWHT'd. Yield strength is 380 MPa in CL2-NT versus 275 MPa in CL1-A.
Sources
- ASTM A387/A387M — Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum — ASTM International (2021)
- ASME BPVC Section II Part D — Material Properties (5Cr-0.5Mo) — ASME (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- API RP 941 — Steels for Hydrogen Service at Elevated Temperatures — API (2016)
- EN 10028-2 / 1.7362 (X12CrMo5) — CEN (2017)
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.