Steel A4
AISI/SAE A4 · UNS T30104
A4 (T30104) is a manganese- and molybdenum-alloyed air-hardening cold-work tool steel that hardens more deeply in heavy sections than A2 without the distortion risk of an oil quench.
Reference datasheet — A4 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 ANN condition
A4 tempers and conditions
A4 is supplied in 5 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard mill supply condition for machining tool blanks before hardening. | 415 | 745 | 20 | 225 HB | — |
Hardened & tempered 54–56 HRC | Higher-toughness setting for shock-loaded punches, shear blades and heavier forming tools. | 1,560 | 1,800 | 4 | 55 HRC | — |
Hardened & tempered 57–59 HRC | Balanced hardness/toughness setting for general blanking, forming and gauging tools. | 1,700 | 1,950 | 2.5 | 58 HRC | — |
Hardened + deep cryogenic treatment + double temper | Choose for gauges and precision dies where retained austenite must be eliminated for long-term size stability. | 1,800 | 2,050 | 1.5 | 60 HRC | — |
Hardened & tempered 60–62 HRC | Maximum hardness and wear resistance for blanking and forming dies where impact loads are low. | 1,850 | 2,100 | 1.5 | 61 HRC | 24 W/m·K |
What is A4?
A4 (T30104) is a manganese- and molybdenum-alloyed air-hardening cold-work tool steel that hardens more deeply in heavy sections than A2 without the distortion risk of an oil quench. It is machined in the annealed condition at about 225 HB (415 MPa yield, 745 MPa tensile, 20 % elongation, 203 GPa modulus) and then air hardened to 54–62 HRC, with cryogenic treatment available for maximum stability. Weldability (score 25) and cold formability (score 30) are low, corrosion resistance is negligible and service is limited to about 400 °C. A2 remains the choice for thinner sections and easier grinding. A4 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). A4 has a yield strength of 415 MPa (60.2 ksi) and a tensile strength of 745 MPa (108 ksi) — weaker than 56% of steel grades. Elongation at break is 20% and the elastic modulus is 203 GPa (29.4 Msi).
What is A4 used for?
- thick-section blanking dies
- forming dies
- gauges
- cold work punches
Limitations
- Low electrical conductivity — 2.7 % IACS, worse than 96% of steel grades
- High embodied carbon — 2.8 kg CO₂/kg, worse than 90% of steel grades
- Poor heat conductor — 25 W/m·K (14.4 BTU/hr·ft·°F), worse than 88% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
A4 properties
Typical room-temperature values for A4-ANN; bars are the position among steel grades.
Physical3
A4 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
A4 has a yield strength of 415 MPa (60.2 ksi) and a tensile strength of 745 MPa (108 ksi) — weaker than 56% of steel grades. Elongation at break is 20% and the elastic modulus is 203 GPa (29.4 Msi).
Thermal6
A4 is rated for continuous service to 400°C (752 °F). It conducts heat at 25 W/m·K (14.4 BTU/hr·ft·°F), worse than 88% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
A4 conducts electricity at 2.7 % IACS, worse than 96% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of A4 takes about 36 MJ of energy and emits 2.8 kg of CO₂ — more than 89% of steel grades. Typical recycled content is 45%.
Manufacturability8
A4's machinability is good (55/100, better than 62% of steel grades); weldability poor (25/100); formability poor (30/100).
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. A4 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A4
Is A4 easy to machine?
Machine fully in the annealed condition (≈60 % of AISI 1212) with rigid setups and sharp carbide or cobalt HSS; after hardening only grinding, EDM or hard-turning with CBN is practical.
Can A4 be welded?
Weld only for repair: preheat/maintain 200–300 °C, use matched tool-steel or Fe-Cr-Mo filler, minimal stringer beads, then temper immediately at 15–25 °C below the prior tempering temperature.
Can A4 be formed, bent or molded?
Hot work at 900–1050 °C with slow cooling and full anneal at 740–760 °C (furnace cool 15 °C/h to 540 °C); cold forming is limited to light bending of annealed thin stock.
A4 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 |
|---|---|---|
| C | 0.95 – 1.05 | 1 |
| Mnhigh Mn gives deep air-hardening at low austenitizing temperature | 1.8 – 2.2 | 2 |
| Si | ≤ 0.5 | 0.3 |
| Cr | 0.9 – 2.2 | 1.1 |
| Mo | 0.9 – 1.4 | 1.1 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on A4?
Takes a fine ground and lapped finish at 58–62 HRC; protect with black oxide, phosphate, nitriding or TiN/CrN PVD (below the tempering temperature) since bare surfaces rust quickly.
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 A4 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T30104
How much does A4 cost?
A4 is a premium-cost steel ($$$), cheaper than about 51% 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.
A4 — frequently asked
What is A4 used for?
A4 is typically used for thick-section blanking dies, forming dies, gauges and cold work punches. In short: deeper hardening than A2; air hardening, low distortion; for heavy die sections.
What is the yield strength of A4?
A4 has a typical yield strength of 415 MPa (60.2 ksi) and a tensile strength of 745 MPa (108 ksi) — weaker than 56% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is A4 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machine fully in the annealed condition (≈60 % of AISI 1212) with rigid setups and sharp carbide or cobalt HSS; after hardening only grinding, EDM or hard-turning with CBN is practical.
Can A4 be welded?
Not readily — weldability is rated poor (25/100). Weld only for repair: preheat/maintain 200–300 °C, use matched tool-steel or Fe-Cr-Mo filler, minimal stringer beads, then temper immediately at 15–25 °C below the prior tempering temperature.
What surface finishes work on A4?
Takes a fine ground and lapped finish at 58–62 HRC; protect with black oxide, phosphate, nitriding or TiN/CrN PVD (below the tempering temperature) since bare surfaces rust quickly.
Can A4 be formed, bent or molded?
Hot work at 900–1050 °C with slow cooling and full anneal at 740–760 °C (furnace cool 15 °C/h to 540 °C); cold forming is limited to light bending of annealed thin stock.
What is the maximum service temperature of A4?
A4 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 A4-ANN and A4 HT60-62?
ANN is the default condition — standard mill supply condition for machining tool blanks before hardening. HT60-62: maximum hardness and wear resistance for blanking and forming dies where impact loads are low. Yield strength is 415 MPa in ANN versus 1,850 MPa in HT60-62.
How much does A4 cost?
A4 is a premium-cost steel ($$$), cheaper than about 51% 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 A681 — Standard Specification for Tool Steels Alloy — ASTM International (2022)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels, and High-Performance Alloys (Tool Steels) — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- ASM Handbook Vol. 16: Machining — ASM International (1989)
- UNS T30104 alloy record — SAE/ASTM Unified Numbering System (2019)
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.