Nickel Alloy 925-STA (Solution treated and aged)
Heat-treated state · default condition
UNS N09925
Standard delivery condition for oilfield bar, forgings and fasteners needing ≥760 MPa yield with sour-service hardness control.
Values for the STA condition
Other 925 tempers and conditions
925 is listed in 7 conditions; see the grade overview at 925.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed (≈1010–1040 °C, rapid cool), not aged | Softest condition, supplied for further forming, deep drawing, or customer-performed aging. | 380 | 760 | 45 | 185 HB | — |
Cold drawn | Cold-drawn bar, tube or wire supplied for tight tolerance and moderate strength before customer aging. | 690 | 900 | 25 | 24 HRC | 1.5 % IACS |
API 6ACRA 110 ksi | Sour-service wellhead/valve grade where NACE hardness limits and impact toughness dominate over peak strength. | 810 | 1,100 | 24 | 32 HRC | 1.5 % IACS |
STADefaultThis page Solution treated and aged | Standard delivery condition for oilfield bar, forgings and fasteners needing ≥760 MPa yield with sour-service hardness control. | 830 | 1,210 | 25 | 33 HRC | — |
API 6ACRA 120 ksi | Most common oilfield strength class for 925 bar/forgings in hangers, mandrels and stems. | 880 | 1,170 | 22 | 34 HRC | 1.5 % IACS |
API 6ACRA 140 ksi | High-strength class for smaller cross-sections and fasteners; check NACE hardness/environment limits before sour service. | 1,010 | 1,240 | 19 | 37 HRC | 1.5 % IACS |
Cold worked then aged | Highest-strength condition for spring wire and studs; verify hardness stays within NACE limits for sour environments. | 1,050 | 1,330 | 15 | 40 HRC | 1.5 % IACS |
What is 925-STA?
925-STA is 925 heat treated to STA — standard delivery condition for oilfield bar, forgings and fasteners needing ≥760 MPa yield with sour-service hardness control. 925-STA has a yield strength of 830 MPa (120 ksi) and a tensile strength of 1,210 MPa (175 ksi) — stronger than 88% of nickel alloy grades. Elongation at break is 25% and the elastic modulus is 200 GPa (29 Msi). 925-STA has a density of 8.08 g/cm³ (0.292 lb/in³), lighter than 81% of nickel alloy grades. It melts at 1,315°C (2,399 °F).
Advantages
- Tough — resists crack growth — 140 MPa·√m (127.4 ksi·√in), better than 91% of nickel alloy grades
- High strength — 830 MPa (120 ksi), better than 88% of nickel alloy grades
Limitations
- Limited service temperature — 540°C (1,004 °F), worse than 75% of nickel alloy grades
- Limited formability — 20/100, worse than 75% of nickel alloy grades
925-STA properties
Typical room-temperature values for 925-STA; 17 are specific to this condition. Other listed values are 925 reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
925-STA has a density of 8.08 g/cm³ (0.292 lb/in³), lighter than 81% of nickel alloy grades. It melts at 1,315°C (2,399 °F).
Mechanical15
925-STA has a yield strength of 830 MPa (120 ksi) and a tensile strength of 1,210 MPa (175 ksi) — stronger than 88% of nickel alloy grades. Elongation at break is 25% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
925-STA is rated for continuous service to 540°C (1,004 °F). It conducts heat at 11.1 W/m·K (6.41 BTU/hr·ft·°F), worse than 54% of nickel alloy grades. Thermal expansion is 13 µm/m·K (7.22 µin/in·°F).
Electrical3
925-STA conducts electricity at 1.5 % IACS, better than 59% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (84/100), better than 70% of nickel alloy grades.
Sustainability4
Producing a kilogram of 925-STA takes about 150 MJ of energy and emits 12.5 kg of CO₂ — less than 68% of nickel alloy grades. Typical recycled content is 35%.
Manufacturability6
925-STA's machinability is poor (18/100, worse than 61% of nickel alloy grades); weldability good (55/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 925-STA
Is 925 easy to machine?
Machine preferably in the aged condition with rigid setups, positive-rake carbide, heavy depth of cut, low surface speed (20–35 m/min) and flood coolant to avoid work hardening and glazing.
Can 925 be welded?
GTAW/GMAW with ERNiFeCr-1 (alloy 725/625-type) filler, low heat input, no preheat; re-solution + re-age after welding to restore strength and avoid strain-age cracking in the HAZ.
Can 925 be formed, bent or molded?
Cold form only in the solution-annealed condition (high work-hardening rate, high forming loads); hot work 1010–1180 °C and finish above 950 °C, then solution treat before aging.
What surface finishes work on 925?
Passivation or pickling after descaling restores the Cr-rich film; grinds and polishes well to mirror finish; no anodizing — plating rarely needed as the alloy is inherently corrosion resistant.
925 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 |
|---|---|---|
| Niplus Co in some specs | 42 – 46 | 44 |
| Cr | 19.5 – 23.5 | 21 |
| Mo | 2.5 – 3.5 | 3 |
| Cu | 1.5 – 3 | 2.2 |
| Timain γ′ former | 1.9 – 2.4 | 2.1 |
| Al | 0.1 – 0.5 | 0.3 |
| Mn | ≤ 1 | 0.4 |
| Si | ≤ 0.5 | 0.2 |
| C | ≤ 0.03 | 0.01 |
| S≤0.010 typical for oilfield melts | ≤ 0.03 | 0 |
| P | ≤ 0.03 | 0.01 |
| Febalance, 22 % min | ≥ 22 (balance) | — |
925-STA — frequently asked
What is 925-STA used for?
925-STA is typically used for oil & gas downhole tooling, fasteners in sour service and corrosion-resistant high-strength components. In short: sour-service high-strength CRA; age-hardened Alloy 825; API-140 strength classes.
What is the yield strength of 925-STA?
925-STA has a typical yield strength of 830 MPa (120 ksi) and a tensile strength of 1,210 MPa (175 ksi) — stronger than 88% of nickel alloy grades. Strength varies by condition: see the 7 listed tempers.
Is 925-STA easy to machine?
Not especially — machinability is rated poor (18/100, worse than 61% of nickel alloy grades). Machine preferably in the aged condition with rigid setups, positive-rake carbide, heavy depth of cut, low surface speed (20–35 m/min) and flood coolant to avoid work hardening and glazing.
Can 925-STA be welded?
Yes — weldability is rated good (55/100). GTAW/GMAW with ERNiFeCr-1 (alloy 725/625-type) filler, low heat input, no preheat; re-solution + re-age after welding to restore strength and avoid strain-age cracking in the HAZ.
What surface finishes work on 925-STA?
Passivation or pickling after descaling restores the Cr-rich film; grinds and polishes well to mirror finish; no anodizing — plating rarely needed as the alloy is inherently corrosion resistant.
Can 925-STA be formed, bent or molded?
Cold form only in the solution-annealed condition (high work-hardening rate, high forming loads); hot work 1010–1180 °C and finish above 950 °C, then solution treat before aging.
What is the maximum service temperature of 925-STA?
925-STA is rated for continuous use to about 540°C (1,004 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 925-STA and 925-SA?
STA is the default condition — standard delivery condition for oilfield bar, forgings and fasteners needing ≥760 MPa yield with sour-service hardness control. SA: softest condition, supplied for further forming, deep drawing, or customer-performed aging. Yield strength is 830 MPa in STA versus 380 MPa in SA.
Sources
- INCOLOY alloy 925 technical bulletin — Special Metals Corporation (2004)
- API 6ACRA — Age-hardenable nickel-based alloys for oil and gas drilling and production equipment — API (2020)
- ASTM B805 — Precipitation-hardening nickel alloy (UNS N09925) bar and forgings — ASTM International (2018)
- NACE MR0175 / ISO 15156-3 — Cracking-resistant CRAs for H2S service — NACE/ISO (2020)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
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.