Steel 4027-A (Solution annealed)
Temper · default condition
AISI/SAE 4027 · UNS G40270
Softest, most machinable and most formable state; the standard stock condition before hardening or carburizing.
Values for the A condition
Other 4027 tempers and conditions
4027 is listed in 10 conditions; see the grade overview at 4027.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefaultThis page Solution annealed | Softest, most machinable and most formable state; the standard stock condition before hardening or carburizing. | 330 | 500 | 30 | 143 HB | — |
Hot rolled | Cheapest bar condition for parts that will be heat treated after machining. | 380 | 585 | 25 | 170 HB | 7.5 % IACS |
Normalized | Uniform fine-grain structure with better strength and toughness than annealed; typical pre-machining or as-supplied condition for forgings. | 415 | 655 | 26 | 179 HB | 7.5 % IACS |
Q&T 650 °C | Softest Q&T condition; maximum ductility and impact toughness where strength demands are low. | 460 | 620 | 27 | 183 HB | 7.5 % IACS |
Cold drawn | Cold-drawn bar for tighter tolerance, better surface and higher as-supplied strength on non-heat-treated parts. | 540 | 640 | 15 | 187 HB | 7.5 % IACS |
Q&T 540 °C | Tough general-purpose condition for shafts, couplings and drive components (~18–22 HRC). | 570 | 720 | 22 | 17 HRC | 7.5 % IACS |
Q&T 425 °C | Balanced strength/toughness for shafts and moderately stressed machine parts (~24–28 HRC). | 670 | 830 | 18 | 24 HRC | 7.4 % IACS |
Carburized and hardened | Choose for gears, cams and pins needing a 58–62 HRC wear-resistant case over a tough ~30 HRC core. | 700 | 950 | 12 | 60 HRC | 7 % IACS |
Q&T 315 °C | High-strength condition for pins and highly loaded fasteners; toughness still modest. | 760 | 950 | 15 | 30 HRC | 7.3 % IACS |
Q&T 205 °C | Maximum hardness/strength condition for small sections where wear resistance matters more than toughness. | 830 | 1,050 | 13 | 34 HRC | — |
What is 4027-A?
4027-A is 4027 in the A temper — softest, most machinable and most formable state; the standard stock condition before hardening or carburizing. 4027-A has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 78% of steel grades. Elongation at break is 30% and the elastic modulus is 205 GPa (29.7 Msi). 4027-A has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Advantages
- Ductile — tolerates forming and impact — 30%, better than 93% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Low strength — 330 MPa (47.9 ksi), worse than 78% of steel grades
4027-A properties
Typical room-temperature values for 4027-A; 11 are specific to this condition. Other listed values are 4027 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4027-A has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
4027-A has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 78% of steel grades. Elongation at break is 30% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4027-A is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
4027-A conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 4027-A takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
4027-A's machinability is good (60/100, better than 83% of steel grades); weldability good (60/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4027-A
Is 4027 easy to machine?
Machines about 60–65 % of 1212 in the annealed state; use rigid setups, carbide at 120–180 m/min, and rough before hardening.
Can 4027 be welded?
Weldable with low-hydrogen electrodes but CE ≈ 0.45–0.5 — preheat 150–250 °C, control interpass and stress relieve/temper after welding.
Can 4027 be formed, bent or molded?
Cold bending and heading only in the annealed condition with generous radii; hot forge 1150–1200 °C, finish above 900 °C, then normalize.
What surface finishes work on 4027?
No anodizing (ferrous) — protect with zinc or manganese phosphate, black oxide, zinc/nickel plating or paint; bake plated parts to avoid hydrogen embrittlement above 1000 MPa.
4027 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 | 0.25 – 0.3 | 0.27 |
| Mn | 0.7 – 0.9 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| Mo | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
4027-A — frequently asked
What is 4027-A used for?
4027-A is typically used for bolts, shafts, axles and couplings. In short: through-hardening moly steel; wide temper range on file; moderate-strength shaft grade.
What is the yield strength of 4027-A?
4027-A has a typical yield strength of 330 MPa (47.9 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 78% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 4027-A easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machines about 60–65 % of 1212 in the annealed state; use rigid setups, carbide at 120–180 m/min, and rough before hardening.
Can 4027-A be welded?
Yes — weldability is rated good (60/100). Weldable with low-hydrogen electrodes but CE ≈ 0.45–0.5 — preheat 150–250 °C, control interpass and stress relieve/temper after welding.
What surface finishes work on 4027-A?
No anodizing (ferrous) — protect with zinc or manganese phosphate, black oxide, zinc/nickel plating or paint; bake plated parts to avoid hydrogen embrittlement above 1000 MPa.
Can 4027-A be formed, bent or molded?
Cold bending and heading only in the annealed condition with generous radii; hot forge 1150–1200 °C, finish above 900 °C, then normalize.
What is the maximum service temperature of 4027-A?
4027-A 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 4027-A and 4027-QT205?
A is the default condition — softest, most machinable and most formable state; the standard stock condition before hardening or carburizing. QT205: maximum hardness/strength condition for small sections where wear resistance matters more than toughness. Yield strength is 330 MPa in A versus 830 MPa in QT205.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- 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)
- UNS G40270 alloy steel property records — SAE/ASTM Unified Numbering System (2020)
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.