Stainless Steel S31730-3/4 Hard
Supply condition
UNS S31730
3/4 Hard = three-quarter hard
High-strength flat strip for shims and spring washers; forming essentially limited to flat blanking.
Values for the 3/4 Hard condition
Other S31730 tempers and conditions
S31730 is listed in 9 conditions; see the grade overview at S31730.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot Rolled (plate, annealed and descaled) | Heavy plate route for pressure vessels and process tanks; properties essentially those of the annealed condition. | 250 | 570 | 45 | 170 HB | 2.3 % IACS |
AnnealedDefault solution annealed (~1040–1120 °C, rapid cool) | Standard stocked condition for plate, sheet, tube and bar; maximum corrosion resistance and ductility. | 255 | 580 | 45 | 165 HB | — |
weld metal / heat-affected zone, no post-weld heat treatment | Reference condition for fabricated equipment: Ti stabilization keeps the HAZ resistant to intergranular attack without post-weld solution annealing. | 280 | 560 | 35 | 180 HB | 2.2 % IACS |
low-temperature stabilizing/stress relief after cold work or welding | Used on cold-worked or welded assemblies to reduce residual stress and SCC risk while keeping most cold-work strength; Ti stabilization tolerates the hold without sensitization. | 450 | 700 | 30 | 200 HB | 2.3 % IACS |
bar/wire, lightly cold worked and straightened | Choose for machined fittings, shafts and fasteners needing higher yield and better surface than annealed bar. | 550 | 760 | 25 | 220 HB | 2.3 % IACS |
Quarter hard | Light temper rolling when moderate strength must be combined with some bending ability. | 560 | 900 | 20 | 250 HB | 2.3 % IACS |
Half hard | For springy clips, straps and stiff panels where forming is limited to gentle radii. | 800 | 1,070 | 12 | 32 HRC | 2.3 % IACS |
3/4 HardThis page Three-quarter hard | High-strength flat strip for shims and spring washers; forming essentially limited to flat blanking. | 960 | 1,240 | 7 | 37 HRC | 2.2 % IACS |
heavily cold rolled strip | Maximum as-rolled strength for springs and flat gaskets; brittle in bending and prone to distortion on welding. | 1,010 | 1,310 | 4 | 40 HRC | 2.2 % IACS |
What is S31730-3/4 Hard?
S31730-3/4 Hard is S31730 supplied in the 3/4 Hard condition — high-strength flat strip for shims and spring washers; forming essentially limited to flat blanking. S31730-3/4 Hard has a yield strength of 960 MPa (139 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 7% and the elastic modulus is 198 GPa (28.7 Msi). S31730-3/4 Hard has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,375°C (2,507 °F). Annealed is the default condition FabDigit quotes; 3/4 Hard is available on request or by drawing note.
Advantages
- High strength — 960 MPa (139 ksi), better than 98% of stainless steel grades
Limitations
- Limited ductility — 7%, worse than 99% of stainless steel grades
- Limited formability — 20/100, worse than 86% of stainless steel grades
- Limited service temperature — 315°C (599 °F), worse than 85% of stainless steel grades
S31730-3/4 Hard properties
Typical room-temperature values for S31730-3/4 Hard; 24 are specific to this condition. Other listed values are S31730 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
S31730-3/4 Hard has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,375°C (2,507 °F).
Mechanical14
S31730-3/4 Hard has a yield strength of 960 MPa (139 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 7% and the elastic modulus is 198 GPa (28.7 Msi).
Thermal6
S31730-3/4 Hard is rated for continuous service to 315°C (599 °F). It conducts heat at 14.7 W/m·K (8.49 BTU/hr·ft·°F), worse than 69% of stainless steel grades. Thermal expansion is 16.2 µm/m·K (9 µin/in·°F).
Electrical3
S31730-3/4 Hard conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is very good (71/100), better than 70% of stainless steel grades.
Sustainability4
Producing a kilogram of S31730-3/4 Hard takes about 82 MJ of energy and emits 5.4 kg of CO₂ — more than 90% of stainless steel grades. Typical recycled content is 55%.
Manufacturability7
S31730-3/4 Hard's machinability is poor (28/100, worse than 79% of stainless steel grades); weldability good (60/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with S31730-3/4 Hard
Is S31730 easy to machine?
Machine like 316 but expect gummier chips from the TiC particles: rigid setups, positive-rake sharp carbide, 60–90 m/min, heavy feed and flood coolant to avoid work hardening and built-up edge.
Can S31730 be welded?
Readily welded by GTAW/GMAW/SMAW with 318 (ER318/E318) or 316L/347-type filler, no preheat and no post-weld solution anneal needed for corrosion; keep interpass below ~150 °C, back-purge with argon and use low heat input to limit distortion and hot cracking.
Can S31730 be formed, bent or molded?
Good cold formability but higher work-hardening rate than 304 — allow larger press tonnage, generous bend radii, intermediate anneals for severe draws; hot work 1150–1250 °C and always finish with solution anneal after hot forming.
What surface finishes work on S31730?
Pickle and passivate (ASTM A967) or electropolish after fabrication to restore the passive film; not anodizable, and mirror polishing can reveal titanium inclusion streaks, so specify No.4/brushed or bead-blast finishes for cosmetic parts.
S31730 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 |
|---|---|---|
| CTi-stabilized, so carbon need not be extra low | ≤ 0.08 | 0.05 |
| Si | ≤ 1 | 0.5 |
| Mn | ≤ 2 | 1.4 |
| P | ≤ 0.05 | 0.03 |
| S | ≤ 0.03 | 0.02 |
| Cr | 18 – 20 | 19 |
| Ni | 11 – 15 | 13 |
| Mogives pitting resistance above 316 | 3 – 4 | 3.5 |
| Tistabilizer, typically ≥5×C | 0.3 – 0.7 | 0.45 |
| N | ≤ 0.1 | 0.04 |
| Fe | balance | — |
S31730-3/4 Hard — frequently asked
What is S31730-3/4 Hard used for?
S31730-3/4 Hard is typically used for chemical reactors, high-temperature stabilized weldments, process piping and headers for hot acids, heat exchanger tube bundles, expansion joints and bellows and furnace-side ducting and flanges. In short: titanium-stabilized 316/317 grade; as-welded IGC resistance; 870 °C service limit.
What is the yield strength of S31730-3/4 Hard?
S31730-3/4 Hard has a typical yield strength of 960 MPa (139 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 98% of stainless steel grades. Strength varies by condition: see the 9 listed tempers.
Is S31730-3/4 Hard easy to machine?
Not especially — machinability is rated poor (28/100, worse than 79% of stainless steel grades). Machine like 316 but expect gummier chips from the TiC particles: rigid setups, positive-rake sharp carbide, 60–90 m/min, heavy feed and flood coolant to avoid work hardening and built-up edge.
Can S31730-3/4 Hard be welded?
Yes — weldability is rated good (60/100). Readily welded by GTAW/GMAW/SMAW with 318 (ER318/E318) or 316L/347-type filler, no preheat and no post-weld solution anneal needed for corrosion; keep interpass below ~150 °C, back-purge with argon and use low heat input to limit distortion and hot cracking.
What surface finishes work on S31730-3/4 Hard?
Pickle and passivate (ASTM A967) or electropolish after fabrication to restore the passive film; not anodizable, and mirror polishing can reveal titanium inclusion streaks, so specify No.4/brushed or bead-blast finishes for cosmetic parts.
Can S31730-3/4 Hard be formed, bent or molded?
Good cold formability but higher work-hardening rate than 304 — allow larger press tonnage, generous bend radii, intermediate anneals for severe draws; hot work 1150–1250 °C and always finish with solution anneal after hot forming.
What is the maximum service temperature of S31730-3/4 Hard?
S31730-3/4 Hard is rated for continuous use to about 315°C (599 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip — ASTM International (2023)
- ASTM A276/A276M — Stainless Steel Bars and Shapes — ASTM International (2023)
- ASTM A959 — Harmonized Standard Grade Compositions for Wrought Stainless Steels — ASTM International (2022)
- ASTM A666 — Annealed or Cold-Worked Austenitic Stainless Steel Sheet, Strip, Plate and Flat Bar — ASTM International (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Stabilized and Mo-bearing austenitic stainless datasheets (316Ti / 317L / 317LMN) — Outokumpu / Sandvik (2023)
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.