Quick Facts
- UNS J91540 is the UNS number for CA6NM, a cast 13Cr-4Ni-Mo martensitic stainless steel (ASTM A352, A487, A743, A757).
- The forged grade is F6NM (UNS S41500). Close equivalents are EN 1.4313 (X3CrNiMo13-4), JIS SCS5 and SS 2385.
- The steel is air hardening, so thick sections have little risk of cracking during heat treatment.
- For sour service, NACE MR0175 sets a hardness limit of 23 HRC max and requires double tempering.
- Supplier: Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory in Jiangyin, Jiangsu, China.
About UNS J91540 / CA6NM / F6NM
CA6NM is a low-carbon martensitic stainless steel with about 12-13% chromium, 4% nickel and 0.5-1% molybdenum. The nickel keeps delta ferrite low. After tempering, the steel has a structure of tempered martensite with some retained austenite. It has good strength, good toughness at low temperatures, and good resistance to cavitation and erosion. It welds better than plain 12% Cr steel and has replaced it in many oil and gas applications.
The name UNS J91540 covers the cast grade only. When the same steel is forged, it is called F6NM (UNS S41500). A forging has no shrinkage cavities or gas porosity, so many valve and pump makers use F6NM forgings instead of CA6NM castings for pressure parts. We can make, mark and certify parts to either grade, as shown on your drawing.
Equivalent Grades
| Standard | Cast grade | Forged / wrought grade |
|---|---|---|
| ACI / ASTM | CA6NM (A352, A487, A743, A757) | F6NM (A182) |
| UNS | J91540 | S41500 |
| EN / DIN | 1.4313 GX5CrNi13-4 | 1.4313 X3CrNiMo13-4 |
| JIS | SCS5 | - |
| SS (Sweden) | SS 2385 | |
| Common names | 13-4, 13Cr-4Ni, 415 | |
Chemical Composition (wt %)
| C | Si | Mn | P | S | Cr | Ni | Mo | Fe | |
|---|---|---|---|---|---|---|---|---|---|
| Min | - | - | 0.50 | - | - | 11.50 | 3.50 | 0.50 | Bal. |
| Max | 0.05 | 0.60 | 1.00 | 0.030 | 0.030 | 14.00 | 5.50 | 1.00 |
Mechanical Properties
Condition: hardened and double tempered
| Property | Imperial | Metric |
|---|---|---|
| Tensile strength | 95 ksi min | 655 MPa min |
| 0.2% proof stress | 75 ksi min | 517 MPa min |
| Elongation | 18% min | |
| Reduction of area | 35% min | |
| Charpy V-notch at -60 °C (-75 °F) | 30 ft·lbf | 40 J |
| Hardness | 23 HRC max (NACE MR0175) | |
Typical Physical Properties
| Density | Thermal expansion (20-100 °C) | Thermal conductivity | Specific heat | Melting range |
|---|---|---|---|---|
| 7.65 g/cm³ | 10.5 µm/m·K | 22.6 W/m·K | 450 J/kg·K | 1399-1467 °C |
Heat Treatment and NACE MR0175
After forging, parts are austenitized, quenched and then tempered twice. For sour service with H₂S or CO₂, NACE MR0175 requires a first temper at about 648-690 °C and a second temper at 595-620 °C. Final hardness must not exceed 23 HRC.
Bringing large 13Cr-4Ni parts below 23 HRC is not easy. Carbon and nitrogen must be kept low in melting, and both tempering steps must be held within a narrow temperature range. We control both of these on every NACE order.
Forged Product Forms
We make parts to your drawing and can deliver them rough machined or finish machined.
Applications
Typical uses are hydro turbine runners, guide vanes and shafts; pump and compressor parts; valve bodies, bonnets, stems and seats for sour oil and gas service; and tooling for pressure die casting.
Inspection and Documents
On request, each order can come with an EN 10204 3.1 mill certificate, ultrasonic testing, hardness and mechanical test reports, and third-party inspection.
FAQ
What is UNS J91540?
UNS J91540 is the UNS number for CA6NM, a cast 13Cr-4Ni-Mo martensitic stainless steel in ASTM A352, A487, A743 and A757. The forged version is F6NM (UNS S41500), close to EN 1.4313 (X3CrNiMo13-4).
What is the difference between CA6NM and F6NM?
CA6NM is the cast grade and F6NM is the forged grade of the same steel. Forgings have no shrinkage or gas porosity, so they are often used for pressure parts and highly loaded parts.
What are the equivalent grades of UNS J91540?
CA6NM, F6NM, UNS S41500, EN 1.4313 (X3CrNiMo13-4, cast GX5CrNi13-4), JIS SCS5 and SS 2385.
Can F6NM be used for NACE MR0175 sour service?
Yes. It must be quenched and double tempered, with a first temper at about 648-690 °C, a second temper at 595-620 °C, and final hardness of 23 HRC max.
Where can I buy F6NM / CA6NM forgings in China?
Jiangyin Jiangnan Metal Co., Ltd., No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Email sales@steelforgepieces.com or call +86-189-2135-9659.
References
- Study of 13Cr-4Ni-(Mo) (F6NM) Steel Grade Heat Treatment for Maximum Hardness Control in Industrial Heats, Metals 2017, 7(9), 351. mdpi.com
- NACE MR0175 / ISO 15156, Materials for use in H₂S-containing environments in oil and gas production.
- ASTM A743, A487, A352, A757 (CA6NM castings); ASTM A182 (F6NM forgings); EN 10250-4 (1.4313 forgings).