Steel En18-A (Solution annealed)
Temper
Choose for maximum machinability and cold-working before final heat treatment.
Values for the A condition
Other En18 tempers and conditions
En18 is listed in 12 conditions; see the grade overview at En18.
Compare all 12 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AThis page Solution annealed | Choose for maximum machinability and cold-working before final heat treatment. | 400 | 620 | 24 | 187 HB | — |
Hot rolled | Cheapest stock form for parts that will be fully machined and heat treated afterwards. | 430 | 700 | 19 | 16 HRC | 7.9 % IACS |
Normalized | Use as a uniform, moderately strong starting condition for forgings before machining or final Q&T. | 460 | 730 | 20 | 17 HRC | 7.9 % IACS |
Q&T condition R | Lowest hardened-and-tempered class; use for large sections (limiting ruling section ~150 mm) needing toughness over strength. | 560 | 770 | 20 | 20 HRC | — |
Q&T condition S | General-purpose Q&T level for shafts and couplings up to about 100 mm ruling section. | 620 | 850 | 18 | 24 HRC | — |
Cold drawn | Pick for close size tolerance and good surface on shafts and studs used without further hardening. | 660 | 800 | 12 | 22 HRC | 7.8 % IACS |
TDefault Q&T condition T | Most commonly stocked hardened-and-tempered condition for En18 gear blanks, spindles and shafts up to ~63 mm ruling section. | 700 | 920 | 15 | 28 HRC | — |
Induction hardened | Select when a wear-resistant 50+ HRC case with tough Q&T core is needed on journals, gear teeth or splines. | 720 | 950 | 14 | 55 HRC | 7.5 % IACS |
Q&T to 28–32 HRC | Hardness-specified order equivalent to condition T; common for gear and shaft machining shops. | 740 | 950 | 15 | 30 HRC | 7.7 % IACS |
Q&T condition V | For small-section high-strength parts where toughness demands are moderate. | 840 | 1,075 | 12 | 34 HRC | 7.8 % IACS |
Solution heat treated (unstable) | Top strength class, only achievable in thin sections; check impact requirements before specifying. | 920 | 1,150 | 11 | 36 HRC | 7.7 % IACS |
Q&T to 34–38 HRC | Higher-hardness Q&T for wear-loaded small shafts and pins; machining becomes noticeably harder. | 930 | 1,150 | 11 | 36 HRC | 7.6 % IACS |
What is En18-A?
En18-A is En18 in the A temper — choose for maximum machinability and cold-working before final heat treatment. En18-A has a yield strength of 400 MPa (58 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 60% of steel grades. Elongation at break is 24% and the elastic modulus is 207 GPa (30 Msi). En18-A 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). T is the default condition FabDigit quotes; A is available on request or by drawing note.
Advantages
- High service temperature — 450°C (842 °F), better than 86% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
En18-A properties
Typical room-temperature values for En18-A; 13 are specific to this condition. Other listed values are En18 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
En18-A 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
En18-A has a yield strength of 400 MPa (58 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 60% of steel grades. Elongation at break is 24% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
En18-A is rated for continuous service to 450°C (842 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
En18-A conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of En18-A takes about 33 MJ of energy and emits 2.1 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 35%.
Manufacturability7
En18-A's machinability is good (60/100, better than 83% of steel grades); weldability fair (45/100); formability fair (50/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with En18-A
Is En18 easy to machine?
Machines well at 180–300 HB with carbide tooling and rigid setups; above ~34 HRC expect reduced tool life, so rough-machine before final tempering or use hard-turning inserts.
Can En18 be welded?
Weldable with care only — preheat 200–300 °C, low-hydrogen consumables and post-weld temper at 550–650 °C to avoid hard, crack-prone HAZ martensite.
Can En18 be formed, bent or molded?
Hot forge 1050–1200 °C then normalize or anneal; cold forming limited to mild bending in the annealed condition due to the 0.4 % C level.
What surface finishes work on En18?
No anodizing — protect with black oxide, phosphate, zinc or hard-chrome plating; nitriding or induction hardening can be added for wear surfaces, and the fine-grained structure polishes well.
En18 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 |
|---|---|---|
| CAISI 5140: 0.38–0.43 | 0.36 – 0.44 | 0.4 |
| Si | 0.1 – 0.4 | 0.25 |
| Mn530A40 0.60–0.90; 530M40 0.60–1.00; 5140 0.70–0.90 | 0.6 – 1 | 0.8 |
| CrAISI 5140: 0.70–0.90 | 0.9 – 1.2 | 1.05 |
| Smax; 530A40 may specify 0.015–0.040 | ≤ 0.04 | — |
| P | ≤ 0.04 | — |
| Fe | balance | — |
En18-A — frequently asked
What is En18-A used for?
En18-A is typically used for gears, spindles, shafts and bolts. In short: BS equivalent of 5140; economical 1%Cr through-hardener; takes induction hardening well.
What is the yield strength of En18-A?
En18-A has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is En18-A easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machines well at 180–300 HB with carbide tooling and rigid setups; above ~34 HRC expect reduced tool life, so rough-machine before final tempering or use hard-turning inserts.
Can En18-A be welded?
With care — weldability is rated fair (45/100). Weldable with care only — preheat 200–300 °C, low-hydrogen consumables and post-weld temper at 550–650 °C to avoid hard, crack-prone HAZ martensite.
What surface finishes work on En18-A?
No anodizing — protect with black oxide, phosphate, zinc or hard-chrome plating; nitriding or induction hardening can be added for wear surfaces, and the fine-grained structure polishes well.
Can En18-A be formed, bent or molded?
Hot forge 1050–1200 °C then normalize or anneal; cold forming limited to mild bending in the annealed condition due to the 0.4 % C level.
What is the maximum service temperature of En18-A?
En18-A is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between En18-T and En18-A?
T is the default condition — most commonly stocked hardened-and-tempered condition for En18 gear blanks, spindles and shafts up to ~63 mm ruling section. A: choose for maximum machinability and cold-working before final heat treatment. Yield strength is 700 MPa in T versus 400 MPa in A.
Sources
- BS 970-1:1991 (530A40 / 530M40, formerly En18) — BSI (1991)
- SAE J404 / ASTM A29 – alloy steel 5140 — SAE / ASTM (2019)
- ASM Handbook Vol.1: Properties and Selection – Irons, Steels — ASM International (1990)
- ASM Handbook Vol.19: Fatigue and Fracture — ASM International (1996)
- Machinery's Handbook (machinability ratings, heat treatment data) — Industrial Press (2020)
- GB/T 3077 (40Cr equivalent grade) — SAC (2015)
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.