Stainless Steel CA15M-AC (Spheroidize annealed)
Heat-treated state
ASTM CA15M · UNS J91151
Shipping/intermediate state only — hard, brittle and residually stressed; must be tempered before service.
Values for the AC condition
Other CA15M tempers and conditions
CA15M is listed in 6 conditions; see the grade overview at CA15M.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition for heavy machining or cold straightening before final hardening. | 415 | 640 | 28 | 180 HB | — |
oil/air quench, temper 650–705 °C | Soft-tempered, ≤22 HRC condition for sour service (NACE MR0175) and maximum toughness. | 490 | 690 | 25 | 17 HRC | — |
Homogenized + N&T | For heavy-section or weld-repaired castings needing dendrite/segregation breakdown and uniform properties through thickness. | 540 | 710 | 23 | 19 HRC | 3 % IACS |
NT595Default austenitize ≥1010 °C, air cool, temper 595–650 °C | Standard ASTM A743 supply condition — best balance of strength, ductility and toughness for valve/pump castings. | 550 | 725 | 22 | 20 HRC | — |
ACThis page Spheroidize annealed | Shipping/intermediate state only — hard, brittle and residually stressed; must be tempered before service. | 690 | 900 | 6 | 41 HRC | 2.8 % IACS |
austenitize ≥1010 °C, quench, temper 260–370 °C | Maximum strength/wear condition for pump wear rings and trim; low toughness, not for sour or impact service. | 830 | 1,035 | 12 | 34 HRC | — |
What is CA15M-AC?
CA15M-AC is CA15M heat treated to AC — shipping/intermediate state only — hard, brittle and residually stressed; must be tempered before service. CA15M-AC has a yield strength of 690 MPa (100 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 92% of stainless steel grades. Elongation at break is 6% and the elastic modulus is 200 GPa (29 Msi). CA15M-AC has a density of 7.61 g/cm³ (0.275 lb/in³), lighter than 96% of stainless steel grades. It melts at 1,450°C (2,642 °F). NT595 is the default condition FabDigit quotes; AC is available on request or by drawing note.
Advantages
- High strength — 690 MPa (100 ksi), better than 92% of stainless steel grades
- Conducts heat well — 23.5 W/m·K (13.6 BTU/hr·ft·°F), better than 79% of stainless steel grades
- High electrical conductivity — 2.8 % IACS, better than 79% of stainless steel grades
Limitations
- Limited formability — 3/100, worse than 100% of stainless steel grades
- Limited ductility — 6%, worse than 99% of stainless steel grades
- Low fracture toughness — 30 MPa·√m (27.3 ksi·√in), worse than 99% of stainless steel grades
- Difficult to machine — 20/100, worse than 98% of stainless steel grades
- Difficult to weld — 15/100, worse than 98% of stainless steel grades
CA15M-AC properties
Typical room-temperature values for CA15M-AC; 22 are specific to this condition. Other listed values are CA15M reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
CA15M-AC has a density of 7.61 g/cm³ (0.275 lb/in³), lighter than 96% of stainless steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
CA15M-AC has a yield strength of 690 MPa (100 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 92% of stainless steel grades. Elongation at break is 6% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
CA15M-AC is rated for continuous service to 300°C (572 °F). It conducts heat at 23.5 W/m·K (13.6 BTU/hr·ft·°F), better than 79% of stainless steel grades. Thermal expansion is 10.8 µm/m·K (6 µin/in·°F).
Electrical3
CA15M-AC conducts electricity at 2.8 % IACS, better than 79% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (35/100), worse than 97% of stainless steel grades.
Sustainability4
Producing a kilogram of CA15M-AC takes about 53 MJ of energy and emits 4 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 75%.
Manufacturability7
CA15M-AC's machinability is poor (20/100, worse than 98% of stainless steel grades); weldability poor (15/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CA15M-AC
Is CA15M easy to machine?
Machine in the annealed or high-temper condition with rigid setups, sharp carbide tooling, moderate speeds (60–110 m/min) and heavy coolant; avoid dwelling to prevent work hardening.
Can CA15M be welded?
Weldable with matched 410/410NiMo filler using 200–315 °C preheat, interpass control and mandatory 595–650 °C post-weld temper; underbead martensite cracks without PWHT.
Can CA15M be formed, bent or molded?
Sand or investment cast with generous risering and hot-tearing-tolerant gating; no cold forming — shape by casting plus heat treatment.
What surface finishes work on CA15M?
Takes a good mechanical polish and can be passivated in nitric acid; chrome or electroless-nickel plating requires baking to avoid hydrogen embrittlement in the hardened condition.
CA15M 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 |
|---|---|---|
| CASTM A743 CA15M | ≤ 0.15 | 0.12 |
| Mn | ≤ 1 | 0.6 |
| Si | ≤ 0.65 | 0.5 |
| P | ≤ 0.04 | 0.03 |
| S | ≤ 0.04 | 0.02 |
| Cr | 11.5 – 14 | 12.5 |
| Ni | ≤ 1 | 0.6 |
| Modistinguishes CA15M from CA15 (Mo 0.50 max) | 0.15 – 1 | 0.5 |
| Fe | balance | — |
CA15M-AC — frequently asked
What is CA15M-AC used for?
CA15M-AC is typically used for steam turbine components, high-temperature valve parts, pump impellers and compressor casings. In short: mo-strengthened CA15; better hot strength than CA15; 650 °C service castings.
What is the yield strength of CA15M-AC?
CA15M-AC has a typical yield strength of 690 MPa (100 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 92% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is CA15M-AC easy to machine?
Not especially — machinability is rated poor (20/100, worse than 98% of stainless steel grades). Machine in the annealed or high-temper condition with rigid setups, sharp carbide tooling, moderate speeds (60–110 m/min) and heavy coolant; avoid dwelling to prevent work hardening.
Can CA15M-AC be welded?
Not readily — weldability is rated poor (15/100). Weldable with matched 410/410NiMo filler using 200–315 °C preheat, interpass control and mandatory 595–650 °C post-weld temper; underbead martensite cracks without PWHT.
What surface finishes work on CA15M-AC?
Takes a good mechanical polish and can be passivated in nitric acid; chrome or electroless-nickel plating requires baking to avoid hydrogen embrittlement in the hardened condition.
Can CA15M-AC be formed, bent or molded?
Sand or investment cast with generous risering and hot-tearing-tolerant gating; no cold forming — shape by casting plus heat treatment.
What is the maximum service temperature of CA15M-AC?
CA15M-AC is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between CA15M-NT595 and CA15M-QT315?
NT595 is the default condition — standard ASTM A743 supply condition — best balance of strength, ductility and toughness for valve/pump castings. QT315: maximum strength/wear condition for pump wear rings and trim; low toughness, not for sour or impact service. Yield strength is 550 MPa in NT595 versus 830 MPa in QT315.
Sources
- ASTM A743/A743M — Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application — ASTM International (2019)
- EN 10283 — Corrosion resistant steel castings (GX7CrNiMo12-1, 1.4008) — CEN (2010)
- Steel Castings Handbook, 6th ed. (cast corrosion-resistant alloys) — Steel Founders' Society of America / ASM International (1995)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
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.