Steel En18
En18 is a BS 970 1% chromium through-hardening alloy steel equivalent to AISI 5140, stocked annealed, normalized, hot-rolled, cold-drawn, in the R to W tempered bands and in 28–32 HRC and 34–38 HRC quenched-and-tempered conditions.
Reference datasheet — En18 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 T condition
En18 tempers and conditions
En18 is supplied in 12 conditions, soft to hard. T is the default FabDigit quotes; the values on this page are for it.
Compare all 12 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
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 |
Supply forms, finishes and certifications
Ways En18 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
U | Q&T condition U | Coating |
What is En18?
En18 is a BS 970 1% chromium through-hardening alloy steel equivalent to AISI 5140, stocked annealed, normalized, hot-rolled, cold-drawn, in the R to W tempered bands and in 28–32 HRC and 34–38 HRC quenched-and-tempered conditions. It is a cost-effective choice for gears, shafts and spindles that need medium hardenability and can be induction hardened or nitrided locally. Typical tempered properties are 700 MPa yield, 920 MPa tensile, 15% elongation, 275 HB (28 HRC), service to 400 °C and a machinability rating of 50. At 0.4% C it is only conditionally weldable and has no corrosion resistance; En19 (4140) is the step up in hardenability for larger sections. En18 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). En18 has a yield strength of 700 MPa (102 ksi) and a tensile strength of 920 MPa (133 ksi) — stronger than 81% of steel grades. Elongation at break is 15% and the elastic modulus is 207 GPa (30 Msi).
What is En18 used for?
- gears
- spindles
- shafts
- bolts
Advantages
- High strength — 700 MPa (102 ksi), better than 81% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
En18 properties
Typical room-temperature values for En18-T; bars are the position among steel grades.
Physical3
En18 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 has a yield strength of 700 MPa (102 ksi) and a tensile strength of 920 MPa (133 ksi) — stronger than 81% of steel grades. Elongation at break is 15% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
En18 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 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
En18 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 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's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (40/100); 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. En18 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with En18
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.
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 |
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.
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 En18 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 5140
How much does En18 cost?
En18 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.
En18 — frequently asked
What is En18 used for?
En18 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?
En18 has a typical yield strength of 700 MPa (102 ksi) and a tensile strength of 920 MPa (133 ksi) — stronger than 81% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is En18 easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% 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 be welded?
With care — weldability is rated fair (40/100). 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?
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 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?
En18 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 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.
How much does En18 cost?
En18 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
- 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; 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.