Steel A321
ASTM A321
A321 is a medium-carbon steel in the 0.25–0.60 % C class (cross-referenced to grade 35), supplied as plate and bar in hot-rolled, normalized, annealed, cold-drawn, quenched-and-tempered (22–26, 28–32 and 33–38 HRC) and induction-hardened conditions.
Reference datasheet — A321 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 HR condition
A321 tempers and conditions
A321 is supplied in 8 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — choose for heavy machining, cold forming or when maximum ductility is needed before hardening. | 270 | 495 | 30 | 143 HB | 51 W/m·K |
HRDefault Hot rolled | Standard stocked plate condition — cheapest, adequate for weldments and machined parts of moderate duty. | 305 | 550 | 18 | 163 HB | — |
Normalized | Pick for uniform fine-grain structure, better toughness and predictable machining before final Q&T or for as-supplied service parts. | 345 | 585 | 25 | 170 HB | — |
Cold drawn | Bar/shaft stock with raised yield, close tolerance and good surface — use where no further heat treatment is planned. | 510 | 600 | 12 | 179 HB | — |
quenched and high-temperature tempered (~600 °C) | Use quenching plus high-temperature tempering near 600 °C for shafts and connecting parts that need 620 MPa yield with 20% elongation and remain reasonably machinable. | 620 | 800 | 20 | 24 HRC | 47 W/m·K |
Induction hardened | Use for journals, spline and cam surfaces needing wear resistance and compressive residual stress over a tough Q&T core. | 640 | 820 | 16 | 52 HRC | 9.5 % IACS |
quenched and tempered (~540 °C) | Choose tempering near 540 °C when moderately loaded shafts, pins and gear blanks in sections under about 40 mm need 780 MPa yield, accepting 17% elongation and slower machining. | 780 | 950 | 17 | 30 HRC | — |
quenched and low/medium tempered (~450 °C) | Maximum practical through-hardened strength for 0.35 %C steel; limited to thin sections and applications tolerating reduced toughness. | 950 | 1,120 | 14 | 35 HRC | — |
What is A321?
A321 is a medium-carbon steel in the 0.25–0.60 % C class (cross-referenced to grade 35), supplied as plate and bar in hot-rolled, normalized, annealed, cold-drawn, quenched-and-tempered (22–26, 28–32 and 33–38 HRC) and induction-hardened conditions. It is specified where moderate strength and hardenability are needed beyond low-carbon structural plate, giving 305 MPa yield, 550 MPa tensile, 18 % elongation and 163 HB in the reference condition. Weldability is only fair (score 48, CE ≈ 0.5) and cold formability is limited (score 45); there is no inherent corrosion resistance. For welded structures, a lower-carbon plate grade is the simpler choice. A321 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). A321 has a yield strength of 305 MPa (44.2 ksi) and a tensile strength of 550 MPa (79.8 ksi) — weaker than 84% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
What is A321 used for?
- machine parts
- medium-strength plate components
- structural reinforcements
- equipment bases
Advantages
- High electrical conductivity — 10.5 % IACS, better than 89% of steel grades
- Conducts heat well — 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades
Limitations
- Low strength — 305 MPa (44.2 ksi), worse than 84% of steel grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 82% of steel grades
A321 properties
Typical room-temperature values for A321-HR; bars are the position among steel grades.
Physical3
A321 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
A321 has a yield strength of 305 MPa (44.2 ksi) and a tensile strength of 550 MPa (79.8 ksi) — weaker than 84% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A321 is rated for continuous service to 400°C (752 °F). It conducts heat at 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
A321 conducts electricity at 10.5 % IACS, better than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of A321 takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 28%.
Manufacturability6
A321's machinability is good (58/100, better than 75% of steel grades); weldability fair (48/100); formability fair (45/100).
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 steel family
Yield strength against density for every steel grade FabDigit runs. A321 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A321
Is A321 easy to machine?
Machines well in normalized or Q&T ≤30 HRC with carbide tooling; annealed material tends to smear, so prefer normalized structure and positive-rake geometry for good finish.
Can A321 be welded?
Weldable with low-hydrogen electrodes but CE ≈ 0.5 demands 150–250 °C preheat, controlled interpass and post-weld stress relief to avoid HAZ hardening and cold cracking.
Can A321 be formed, bent or molded?
Hot forge/roll at 1100–1200 °C; cold bending is limited — use generous bend radii (≥2t) or form in the annealed condition.
A321 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 |
|---|---|---|
| Cmedium-carbon range, GB/T 699 grade 35 / AISI 1035 | 0.32 – 0.4 | 0.35 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.02 |
| Crresidual | ≤ 0.25 | 0.1 |
| Niresidual | ≤ 0.3 | 0.1 |
| Curesidual | ≤ 0.25 | 0.1 |
| Fe | balance |
What surface finishes work on A321?
No inherent corrosion resistance: apply phosphate+oil, zinc plating, black oxide or paint; takes a fine mechanical polish and accepts nitriding or induction hardening for wear surfaces.
Surface treatments FabDigit runs on steel 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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel A321 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 35
How much does A321 cost?
A321 is a budget-cost steel ($), cheaper than about 90% 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.
A321 — frequently asked
What is A321 used for?
A321 is typically used for machine parts, medium-strength plate components, structural reinforcements and equipment bases. In short: mid-strength machinable plate; responds to induction hardening; needs preheat for welding.
What is the yield strength of A321?
A321 has a typical yield strength of 305 MPa (44.2 ksi) and a tensile strength of 550 MPa (79.8 ksi) — weaker than 84% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is A321 easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machines well in normalized or Q&T ≤30 HRC with carbide tooling; annealed material tends to smear, so prefer normalized structure and positive-rake geometry for good finish.
Can A321 be welded?
With care — weldability is rated fair (48/100). Weldable with low-hydrogen electrodes but CE ≈ 0.5 demands 150–250 °C preheat, controlled interpass and post-weld stress relief to avoid HAZ hardening and cold cracking.
What surface finishes work on A321?
No inherent corrosion resistance: apply phosphate+oil, zinc plating, black oxide or paint; takes a fine mechanical polish and accepts nitriding or induction hardening for wear surfaces.
Can A321 be formed, bent or molded?
Hot forge/roll at 1100–1200 °C; cold bending is limited — use generous bend radii (≥2t) or form in the annealed condition.
What is the maximum service temperature of A321?
A321 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A321-HR and A321-IH?
HR is the default condition — standard stocked plate condition — cheapest, adequate for weldments and machined parts of moderate duty. IH: use for journals, spline and cam surfaces needing wear resistance and compressive residual stress over a tough Q&T core. Yield strength is 305 MPa in HR versus 640 MPa in IH.
How much does A321 cost?
A321 is a budget-cost steel ($), cheaper than about 90% 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
- GB/T 699 (grade 35) — SAC (2015)
- ASTM A321 Steel Bars, Carbon, Quenched and Tempered — ASTM (2016)
- ASTM A29/A29M Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol.1: Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4: Heat Treating — ASM International (1991)
- Machining Data Handbook — machinability ratings vs AISI 1212 — Metcut Research (1980)
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.