Steel 4027
AISI/SAE 4027 · UNS G40270
4027 is a medium-carbon (about 0.27 % C) molybdenum alloy steel (UNS G40270) in the SAE-AISI 40xx family, chosen for through-hardening of moderately stressed parts.
Reference datasheet — 4027 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 A condition
4027 tempers and conditions
4027 is supplied in 10 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault 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?
4027 is a medium-carbon (about 0.27 % C) molybdenum alloy steel (UNS G40270) in the SAE-AISI 40xx family, chosen for through-hardening of moderately stressed parts. The default condition gives roughly 330 MPa yield, 500 MPa tensile, 30 % elongation and 143 HB (78 HRB), with a maximum service temperature around 400 °C and a formability score of 60; it is stocked hot-rolled, annealed, normalized and cold-drawn, and is offered quenched and tempered at 205, 315, 425, 540 and 650 °C as well as case-hardened. With CE around 0.45–0.50 it needs preheat and post-weld tempering, and it has no corrosion resistance. For free-machining work at the same carbon level, 4028 is the direct alternative. 4027 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). 4027 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).
What is 4027 used for?
- bolts
- shafts
- axles
- couplings
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 properties
Typical room-temperature values for 4027-A; bars are the position among steel grades.
Physical3
4027 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 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 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 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 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'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. 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. 4027 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4027
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.
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 |
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.
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 4027 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G40270
How much does 4027 cost?
4027 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.
4027 — frequently asked
What is 4027 used for?
4027 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?
4027 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 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 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?
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 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?
4027 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.
How much does 4027 cost?
4027 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
- 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; 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.