Titanium Ti Grade 21
UNS R58210 · also Beta 21S
Ti Grade 21 (Beta 21S, UNS R58210) is a metastable beta titanium alloy supplied under ASTM B265/B348, strengthened by solution treatment and aging rather than by alpha-beta processing, with silicon and molybdenum additions for oxidation and hot-corrosion resistance.
Reference datasheet — Ti Grade 21 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the ST condition
Ti Grade 21 tempers and conditions
Ti Grade 21 is supplied in 4 conditions, soft to hard. ST is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
STDefault Solution annealed | Softest, most formable condition — pick for cold forming, deep drawing, foil/honeycomb and welding before final aging. | 805 | 830 | 18 | 28 HRC | — |
Solution treated then cold rolled strip/foil | Cold-worked thin strip/foil supplied for honeycomb and springs where extra strength is wanted without aging. | 960 | 1,000 | 8 | 33 HRC | 1.3 % IACS |
STA | Overaged balance condition — lower strength but better ductility, toughness and thermal stability for 500–565 °C airframe/engine parts. | 1,150 | 1,220 | 9 | 39 HRC | — |
STA | Maximum strength condition (≈1400 MPa) for fasteners, springs and highly loaded fittings where ductility and toughness can be traded away. | 1,310 | 1,400 | 6 | 44 HRC | — |
What is Ti Grade 21?
Ti Grade 21 (Beta 21S, UNS R58210) is a metastable beta titanium alloy supplied under ASTM B265/B348, strengthened by solution treatment and aging rather than by alpha-beta processing, with silicon and molybdenum additions for oxidation and hot-corrosion resistance. Engineers choose it for its combination of cold formability in the solution-treated state and strength after aging — 805 MPa yield, 830 MPa tensile, 18% elongation, 28 HRC and 79 GPa modulus — in strip, foil, sheet, bar and thin-gauge honeycomb stock, with service to 425 °C. Limits are poor machinability (score 20), the need to weld before aging, and restricted mill availability compared with Ti-6Al-4V, which remains the default where forming demands are low. Ti Grade 21 has a density of 4.94 g/cm³ (0.178 lb/in³), heavier than 97% of titanium grades. It melts at 1,600°C (2,912 °F). Ti Grade 21 has a yield strength of 805 MPa (117 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 58% of titanium grades. Elongation at break is 18% and the elastic modulus is 79 GPa (11.5 Msi).
What is Ti Grade 21 used for?
- aircraft exhaust and hot structure components
- fuel cell bipolar plates
- high-temperature fasteners
Advantages
- Tough — resists crack growth — 85 MPa·√m (77.4 ksi·√in), better than 91% of titanium grades
- Forms and bends easily — 80/100, better than 90% of titanium grades
- High service temperature — 425°C (797 °F), better than 85% of titanium grades
Limitations
- Low stiffness — 79 GPa (11.5 Msi), worse than 98% of titanium grades
- High embodied carbon — 48 kg CO₂/kg, worse than 95% of titanium grades
Ti Grade 21 properties
Typical room-temperature values for Ti Grade 21-ST; bars are the position among titanium grades.
Physical3
Ti Grade 21 has a density of 4.94 g/cm³ (0.178 lb/in³), heavier than 97% of titanium grades. It melts at 1,600°C (2,912 °F).
Mechanical15
Ti Grade 21 has a yield strength of 805 MPa (117 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 58% of titanium grades. Elongation at break is 18% and the elastic modulus is 79 GPa (11.5 Msi).
Thermal6
Ti Grade 21 is rated for continuous service to 425°C (797 °F). It conducts heat at 7.6 W/m·K (4.39 BTU/hr·ft·°F), worse than 59% of titanium grades. Thermal expansion is 8.6 µm/m·K (4.78 µin/in·°F).
Electrical3
Ti Grade 21 conducts electricity at 1.3 % IACS, worse than 51% of titanium grades.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 53% of titanium grades.
Sustainability4
Producing a kilogram of Ti Grade 21 takes about 700 MJ of energy and emits 48 kg of CO₂ — more than 74% of titanium grades. Typical recycled content is 25%.
Manufacturability8
Ti Grade 21's machinability is poor (20/100, worse than 68% of titanium grades); weldability very good (75/100); formability very good (80/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the titanium family
Yield strength against density for every titanium grade FabDigit runs. Ti Grade 21 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Ti Grade 21
Is Ti Grade 21 easy to machine?
Machine in the solution-treated state where possible: rigid setups, sharp uncoated-carbide or PVD-coated tools, low surface speed (15–30 m/min), heavy feed, flood high-pressure coolant; never dwell — low conductivity concentrates heat in the edge and work-hardened aged material cuts even slower.
Can Ti Grade 21 be welded?
GTAW/plasma/EBW readily in ST condition with full argon trailing and back purge; weld before aging and re-solution/age afterwards, since as-welded aged joints lose ductility and heat tint must be removed by pickling.
Can Ti Grade 21 be formed, bent or molded?
Outstanding cold formability as solution-treated strip and foil (tight bends, deep draws, honeycomb node forming); hot work above the ~800 °C beta transus, then solution treat 870–925 °C and age 8 h at 480–620 °C to set the strength level.
Ti Grade 21 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 |
|---|---|---|
| Moprincipal beta stabilizer | 14 – 16 | 15 |
| Nb | 2.4 – 3.2 | 2.8 |
| Aloxidation resistance / alpha strengthening | 2.5 – 3.5 | 3 |
| Sicreep and oxidation resistance | 0.15 – 0.25 | 0.2 |
| Fe | ≤ 0.4 | |
| O | ≤ 0.17 | |
| C | ≤ 0.05 | |
| N | ≤ 0.05 | |
| H0.020 max for bar/billet per B348 | ≤ 0.02 | |
| Ti | balance |
What surface finishes work on Ti Grade 21?
Pickle in HNO3/HF to remove alpha case and heat tint, then bead blast, passivate, or Type II colour anodize; hard anodize is not applicable — use ion nitriding or coatings for wear/galling surfaces.
Surface treatments FabDigit runs on titanium parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Titanium Ti Grade 21 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- R58210
- Trade names
- Beta 21S
How much does Ti Grade 21 cost?
Ti Grade 21 is a high-cost titanium ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Ti Grade 21 — frequently asked
What is Ti Grade 21 used for?
Ti Grade 21 is typically used for aircraft exhaust and hot structure components, fuel cell bipolar plates and high-temperature fasteners. In short: oxidation-resistant beta alloy; formable then age-hardened; service to 425 °C.
What is the yield strength of Ti Grade 21?
Ti Grade 21 has a typical yield strength of 805 MPa (117 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 58% of titanium grades. Strength varies by condition: see the 4 listed tempers.
Is Ti Grade 21 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 68% of titanium grades). Machine in the solution-treated state where possible: rigid setups, sharp uncoated-carbide or PVD-coated tools, low surface speed (15–30 m/min), heavy feed, flood high-pressure coolant; never dwell — low conductivity concentrates heat in the edge and work-hardened aged material cuts even slower.
Can Ti Grade 21 be welded?
Yes — weldability is rated very good (75/100). GTAW/plasma/EBW readily in ST condition with full argon trailing and back purge; weld before aging and re-solution/age afterwards, since as-welded aged joints lose ductility and heat tint must be removed by pickling.
What surface finishes work on Ti Grade 21?
Pickle in HNO3/HF to remove alpha case and heat tint, then bead blast, passivate, or Type II colour anodize; hard anodize is not applicable — use ion nitriding or coatings for wear/galling surfaces.
Can Ti Grade 21 be formed, bent or molded?
Outstanding cold formability as solution-treated strip and foil (tight bends, deep draws, honeycomb node forming); hot work above the ~800 °C beta transus, then solution treat 870–925 °C and age 8 h at 480–620 °C to set the strength level.
What is the maximum service temperature of Ti Grade 21?
Ti Grade 21 is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Ti Grade 21-ST and Ti Grade 21 STA-H?
ST is the default condition — softest, most formable condition — pick for cold forming, deep drawing, foil/honeycomb and welding before final aging. STA-H: maximum strength condition (≈1400 MPa) for fasteners, springs and highly loaded fittings where ductility and toughness can be traded away. Yield strength is 805 MPa in ST versus 1,310 MPa in STA-H.
How much does Ti Grade 21 cost?
Ti Grade 21 is a high-cost titanium ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B265 — Titanium and Titanium Alloy Strip, Sheet, and Plate (Grade 21) — ASTM International (2020)
- ASTM B348 — Titanium and Titanium Alloy Bars and Billets (Grade 21) — ASTM International (2021)
- TIMETAL 21S (Beta 21S) alloy data sheet — TIMET / Titanium Metals Corp. (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys, Titanium section — ASM International (1990)
- Materials Properties Handbook: Titanium Alloys (beta alloys chapter) — ASM International (1994)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.