Stainless Steel 302B-3/4 Hard
Supply condition
AISI/SAE 302B · UNS S30215
3/4 Hard = three-quarter hard
High-strength strip for clips and light spring parts; only gentle forming possible.
Values for the 3/4 Hard condition
Other 302B tempers and conditions
302B is listed in 7 conditions; see the grade overview at 302B.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed 1010–1120 °C, rapid cooled | Standard stocked condition for furnace parts, fixtures and formed heat-resisting components. | 275 | 655 | 55 | 165 HB | — |
Hot Rolled (mill finish, not solution treated) | Cheapest plate/bar form for rough furnace hardware where scale and looser properties are acceptable. | 290 | 620 | 45 | 180 HB | — |
Quarter hard | Choose when moderate extra strength is needed and some bending/forming is still required. | 550 | 895 | 25 | 25 HRC | — |
cold-finished bar/wire (annealed then drawn) | Cold-finished bar for machined furnace fasteners and fixtures needing tighter tolerance and higher strength. | 620 | 860 | 25 | 25 HRC | — |
Half hard | For flat springy parts and brackets where strength matters more than bendability. | 790 | 1,070 | 15 | 32 HRC | — |
3/4 HardThis page Three-quarter hard | High-strength strip for clips and light spring parts; only gentle forming possible. | 965 | 1,240 | 10 | 37 HRC | — |
cold rolled to full-hard temper | Maximum as-rolled strength for flat springs and shim stock; essentially not formable. | 1,000 | 1,310 | 7 | 41 HRC | — |
What is 302B-3/4 Hard?
302B-3/4 Hard is 302B supplied in the 3/4 Hard condition — high-strength strip for clips and light spring parts; only gentle forming possible. 302B-3/4 Hard has a yield strength of 965 MPa (140 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 10% and the elastic modulus is 193 GPa (28 Msi). 302B-3/4 Hard has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,400°C (2,552 °F). Annealed is the default condition FabDigit quotes; 3/4 Hard is available on request or by drawing note.
Advantages
- High strength — 965 MPa (140 ksi), better than 98% of stainless steel grades
Limitations
- Limited ductility — 10%, worse than 98% of stainless steel grades
- Difficult to weld — 40/100, worse than 83% of stainless steel grades
302B-3/4 Hard properties
Typical room-temperature values for 302B-3/4 Hard; 19 are specific to this condition. Other listed values are 302B reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
302B-3/4 Hard has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical14
302B-3/4 Hard has a yield strength of 965 MPa (140 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 10% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
302B-3/4 Hard is rated for continuous service to 425°C (797 °F). It conducts heat at 15.9 W/m·K (9.19 BTU/hr·ft·°F), better than 55% of stainless steel grades. Thermal expansion is 16.2 µm/m·K (9 µin/in·°F).
Electrical3
302B-3/4 Hard conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (59/100), worse than 59% of stainless steel grades.
Sustainability4
Producing a kilogram of 302B-3/4 Hard takes about 53 MJ of energy and emits 5 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
302B-3/4 Hard's machinability is poor (28/100, worse than 79% of stainless steel grades); weldability fair (40/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 302B-3/4 Hard
Is 302B easy to machine?
Machines like a gummy 18-8 but the 2–3 % Si is abrasive and work-hardens fast — use rigid setups, sharp coated carbide, positive rake, heavy positive feed and flood coolant; ~40 % of AISI 1212.
Can 302B be welded?
GTAW/GMAW with 309/310-type filler; high Si plus high C raise hot-cracking and sensitization risk, so keep heat input low, avoid restraint and solution anneal afterwards if aqueous corrosion service is intended.
Can 302B be formed, bent or molded?
Cold forms and deep draws reasonably well in the annealed condition but work-hardens faster than 304; hot work at 1150–1200 °C and cool rapidly through 870–425 °C to avoid carbide precipitation.
What surface finishes work on 302B?
Pickle and passivate after hot work — the silicon-rich scale is tenacious and needs longer HF/HNO₃ pickling or grit blasting; takes a good mechanical polish but slightly below 304 due to silicate inclusions.
302B 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 |
|---|---|---|
| Chigh carbon — sensitization prone | ≤ 0.15 | 0.1 |
| Mn | ≤ 2 | 1.2 |
| Sikey addition for scaling resistance | 2 – 3 | 2.5 |
| P | ≤ 0.05 | 0.03 |
| S | ≤ 0.03 | 0.02 |
| Cr | 17 – 19 | 18 |
| Ni | 8 – 10 | 9 |
| Nwhere specified | ≤ 0.1 | 0.05 |
| Fe | balance | — |
302B-3/4 Hard — frequently asked
What is 302B-3/4 Hard used for?
302B-3/4 Hard is typically used for furnace parts, heat-resistant fixtures and high-temperature springs. In short: scaling-resistant 18-8 variant; 1090 °C maximum service; abrasive silicon-bearing grade.
What is the yield strength of 302B-3/4 Hard?
302B-3/4 Hard has a typical yield strength of 965 MPa (140 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 98% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is 302B-3/4 Hard easy to machine?
Not especially — machinability is rated poor (28/100, worse than 79% of stainless steel grades). Machines like a gummy 18-8 but the 2–3 % Si is abrasive and work-hardens fast — use rigid setups, sharp coated carbide, positive rake, heavy positive feed and flood coolant; ~40 % of AISI 1212.
Can 302B-3/4 Hard be welded?
With care — weldability is rated fair (40/100). GTAW/GMAW with 309/310-type filler; high Si plus high C raise hot-cracking and sensitization risk, so keep heat input low, avoid restraint and solution anneal afterwards if aqueous corrosion service is intended.
What surface finishes work on 302B-3/4 Hard?
Pickle and passivate after hot work — the silicon-rich scale is tenacious and needs longer HF/HNO₃ pickling or grit blasting; takes a good mechanical polish but slightly below 304 due to silicate inclusions.
Can 302B-3/4 Hard be formed, bent or molded?
Cold forms and deep draws reasonably well in the annealed condition but work-hardens faster than 304; hot work at 1150–1200 °C and cool rapidly through 870–425 °C to avoid carbide precipitation.
What is the maximum service temperature of 302B-3/4 Hard?
302B-3/4 Hard 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.
Sources
- ASTM A276/A276M — Stainless Steel Bars and Shapes — ASTM International (2023)
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip — ASTM International (2023)
- ASTM A666 — Annealed or Cold-Worked Austenitic Stainless Steel Sheet, Strip, Plate and Flat Bar — ASTM International (2015)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- SAE/ASTM Unified Numbering System (UNS) S30215 listing — SAE International / ASTM (2019)
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.