Stainless Steel S21640 HF-ANN
Finish state
UNS S21640
HF-ANN = hot Finished and Annealed bar
Large-diameter hot-rolled/forged bar, annealed and descaled — pick for big machined parts and forgings.
Values for the HF-ANN condition
Other S21640 tempers and conditions
S21640 is listed in 7 conditions; see the grade overview at S21640.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
HF-ANNThis page Hot Finished and Annealed bar | Large-diameter hot-rolled/forged bar, annealed and descaled — pick for big machined parts and forgings. | 440 | 710 | 45 | 195 HB | 2 % IACS |
ANNDefault Annealed | Standard stocked condition — maximum corrosion resistance and ductility, yield already ~2× that of 304. | 450 | 725 | 45 | 200 HB | — |
Cold drawn | Light strain-hardening for straightness, close tolerance and better chip control on screw-machine parts. | 620 | 860 | 25 | 24 HRC | — |
Cold Worked, 1/4 Hard | Entry-level high-strength fastener/shaft condition with useful residual ductility. | 690 | 900 | 20 | 26 HRC | 2 % IACS |
Cold Worked, 1/2 Hard | High-strength bolting and pump shafting where ~830 MPa yield is required. | 830 | 1,035 | 15 | 31 HRC | 2 % IACS |
Cold Worked, 3/4 Hard | Near-maximum strength bar/wire for highly loaded fasteners and springs; limited ductility. | 965 | 1,170 | 12 | 35 HRC | 2 % IACS |
Cold Worked, Full Hard | Maximum strength wire/small bar for springs and studs where forming is finished. | 1,100 | 1,275 | 8 | 38 HRC | 2 % IACS |
What is S21640 HF-ANN?
S21640 HF-ANN is S21640 supplied in the HF-ANN condition — large-diameter hot-rolled/forged bar, annealed and descaled — pick for big machined parts and forgings. S21640 HF-ANN has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 710 MPa (103 ksi) — stronger than 68% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 200 GPa (29 Msi). S21640 HF-ANN has a density of 7.86 g/cm³ (0.284 lb/in³), heavier than 59% of stainless steel grades. It melts at 1,370°C (2,498 °F). ANN is the default condition FabDigit quotes; HF-ANN is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
- High service temperature — 815°C (1,499 °F), better than 77% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
Limitations
- Difficult to machine — 25/100, worse than 88% of stainless steel grades
- High embodied carbon — 5.8 kg CO₂/kg, worse than 86% of stainless steel grades
- Low electrical conductivity — 2 % IACS, worse than 77% of stainless steel grades
S21640 HF-ANN properties
Typical room-temperature values for S21640 HF-ANN; 22 are specific to this condition. Other listed values are S21640 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
S21640 HF-ANN has a density of 7.86 g/cm³ (0.284 lb/in³), heavier than 59% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical15
S21640 HF-ANN has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 710 MPa (103 ksi) — stronger than 68% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
S21640 HF-ANN is rated for continuous service to 815°C (1,499 °F). It conducts heat at 15 W/m·K (8.67 BTU/hr·ft·°F), worse than 59% of stainless steel grades. Thermal expansion is 16.2 µm/m·K (9 µin/in·°F).
Electrical3
S21640 HF-ANN conducts electricity at 2 % IACS, worse than 77% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), better than 73% of stainless steel grades.
Sustainability4
Producing a kilogram of S21640 HF-ANN takes about 56 MJ of energy and emits 5.8 kg of CO₂ — more than 59% of stainless steel grades. Typical recycled content is 60%.
Manufacturability8
S21640 HF-ANN's machinability is poor (25/100, worse than 88% of stainless steel grades); weldability very good (70/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with S21640 HF-ANN
Is S21640 easy to machine?
Treat like Nitronic 50: rigid setup, sharp positive-rake carbide, heavy positive feed to cut under the work-hardened skin, ~30 % of 1212 speeds and flood coolant.
Can S21640 be welded?
Readily welded by GTAW/GMAW/SMAW with no preheat and no PWHT; use over-alloyed N-bearing filler (e.g. 209/Nitronic 50 type) and keep interpass low to protect corrosion resistance.
Can S21640 be formed, bent or molded?
Cold forms well but work-hardens very fast — allow extra press tonnage, generous radii and intermediate solution anneals at 1040–1090 °C followed by rapid cooling; hot work 1150–1230 °C.
What surface finishes work on S21640?
Not anodizable; passivate to ASTM A967 (nitric or citric) or electropolish after descaling/pickling for the best pitting performance and mirror finish.
S21640 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 |
|---|---|---|
| Cper UNS S21600 (XM-17); the low-carbon S21603/XM-18 variant is 0.03 max | ≤ 0.08 | 0.05 |
| Mnaustenite stabiliser replacing part of the Ni | 7.5 – 9 | 8.3 |
| Si | ≤ 1 | 0.5 |
| P | ≤ 0.05 | 0.03 |
| S | ≤ 0.03 | 0.01 |
| Cr | 17.5 – 22 | 20 |
| Ni | 5 – 7 | 6 |
| Mopitting resistance | 2 – 3 | 2.5 |
| Nprimary solid-solution strengthener | 0.25 – 0.5 | 0.35 |
| Fe | balance | — |
S21640 HF-ANN — frequently asked
What is S21640 HF-ANN used for?
S21640 HF-ANN is typically used for fasteners, structural hardware and non-magnetic parts. In short: high-strength non-magnetic bar; nitrogen-strengthened Cr-Mn-Ni; weldable without PWHT.
What is the yield strength of S21640 HF-ANN?
S21640 HF-ANN has a typical yield strength of 440 MPa (63.8 ksi) and a tensile strength of 710 MPa (103 ksi) — stronger than 68% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is S21640 HF-ANN easy to machine?
Not especially — machinability is rated poor (25/100, worse than 88% of stainless steel grades). Treat like Nitronic 50: rigid setup, sharp positive-rake carbide, heavy positive feed to cut under the work-hardened skin, ~30 % of 1212 speeds and flood coolant.
Can S21640 HF-ANN be welded?
Yes — weldability is rated very good (70/100). Readily welded by GTAW/GMAW/SMAW with no preheat and no PWHT; use over-alloyed N-bearing filler (e.g. 209/Nitronic 50 type) and keep interpass low to protect corrosion resistance.
What surface finishes work on S21640 HF-ANN?
Not anodizable; passivate to ASTM A967 (nitric or citric) or electropolish after descaling/pickling for the best pitting performance and mirror finish.
Can S21640 HF-ANN be formed, bent or molded?
Cold forms well but work-hardens very fast — allow extra press tonnage, generous radii and intermediate solution anneals at 1040–1090 °C followed by rapid cooling; hot work 1150–1230 °C.
What is the maximum service temperature of S21640 HF-ANN?
S21640 HF-ANN is rated for continuous use to about 815°C (1,499 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between S21640-ANN and S21640 CW-FH?
ANN is the default condition — standard stocked condition — maximum corrosion resistance and ductility, yield already ~2× that of 304. CW-FH: maximum strength wire/small bar for springs and studs where forming is finished. Yield strength is 450 MPa in ANN versus 1,100 MPa in CW-FH.
Sources
- ASTM A276/A276M — Stainless Steel Bars and Shapes — ASTM International (2023)
- ASTM A479/A479M — Stainless Steel Bars and Shapes for Pressure Vessels — ASTM International (2023)
- SAE/ASTM DS-56 (UNS) Metals & Alloys in the Unified Numbering System — SAE International / ASTM (2017)
- 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)
- Nitrogen-strengthened Cr-Mn austenitic stainless bar datasheets (Nitronic-type) — Electralloy / Universal Stainless (2022)
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.