Steel 826M40
BS 826M40
826M40 is a British Standard nickel-chromium-molybdenum alloy steel close to AISI 4340 but with adjusted alloy content for higher hardenability in heavy sections, supplied quenched and tempered to the T–Z classes or nitrided.
Reference datasheet — 826M40 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
826M40 tempers and conditions
826M40 is supplied in 9 conditions, soft to hard. T is the default FabDigit quotes; the values on this page are for it.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed (softened, ~ max 248 HB) | Softest condition for deep machining, forming or re-heat-treatment of forgings. | 480 | 750 | 22 | 225 HB | — |
Normalized (air cooled from ~870 °C) | Grain-refined intermediate condition for forgings before final Q&T. | 620 | 950 | 16 | 30 HRC | 7.4 % IACS |
TDefault Hardened and tempered, 850–1000 MPa | Most commonly stocked Q&T condition — best balance of strength, toughness and machinability for large shafts. | 730 | 930 | 17 | 29 HRC | — |
Q&T then gas nitrided case | Use when a wear- and fatigue-resistant surface (≈600–700 HV case) is needed on a tough Q&T core. | 810 | 1,000 | 12 | 57 HRC | 7.2 % IACS |
Hardened and tempered, 1000–1150 MPa | General high-duty gear and shaft condition with still-workable machinability. | 900 | 1,075 | 14 | 34 HRC | 7.2 % IACS |
Solution heat treated (unstable) | Choose for highly loaded transmission and landing-gear components needing >1075 MPa. | 985 | 1,150 | 13 | 37 HRC | 7.2 % IACS |
Hardened and tempered, 1150–1300 MPa | High-strength aerospace/racing condition; machining is hard and toughness starts to fall. | 1,060 | 1,225 | 12 | 40 HRC | — |
Hardened and tempered, 1225–1375 MPa | Very high strength; usually finish-ground after heat treatment, hydrogen control essential. | 1,140 | 1,300 | 11 | 42 HRC | — |
Hardened and tempered, 1550 MPa min | Maximum-strength condition for small, well-controlled sections; low ductility and notch sensitivity. | 1,400 | 1,620 | 9 | 49 HRC | — |
Supply forms, finishes and certifications
Ways 826M40 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 | Hardened and tempered, 925–1075 MPa | Coating |
What is 826M40?
826M40 is a British Standard nickel-chromium-molybdenum alloy steel close to AISI 4340 but with adjusted alloy content for higher hardenability in heavy sections, supplied quenched and tempered to the T–Z classes or nitrided. It is used for large shafts, gears and structural components where a uniform tempered structure is required through thick cross-sections; forms include large-diameter bar, heavy forgings and nitrided sleeves. Default-condition values are 730 MPa yield, 930 MPa tensile strength, 17% elongation and 277 HB (29 HRC), with service to 450 °C. Weldability is poor (CE ≈ 1.0) and the steel has no corrosion resistance; 817M40 is the nearest alternative in lighter sections. 826M40 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). 826M40 has a yield strength of 730 MPa (106 ksi) and a tensile strength of 930 MPa (135 ksi) — stronger than 83% of steel grades. Elongation at break is 17% and the elastic modulus is 208 GPa (30.2 Msi).
What is 826M40 used for?
- heavy shafts
- gears
- structural components
Advantages
- High service temperature — 450°C (842 °F), better than 86% of steel grades
- High strength — 730 MPa (106 ksi), better than 83% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- High embodied carbon — 2.5 kg CO₂/kg, worse than 82% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
826M40 properties
Typical room-temperature values for 826M40-T; bars are the position among steel grades.
Physical3
826M40 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
826M40 has a yield strength of 730 MPa (106 ksi) and a tensile strength of 930 MPa (135 ksi) — stronger than 83% of steel grades. Elongation at break is 17% and the elastic modulus is 208 GPa (30.2 Msi).
Thermal6
826M40 is rated for continuous service to 450°C (842 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
826M40 conducts electricity at 7.2 % IACS, worse than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of 826M40 takes about 33 MJ of energy and emits 2.5 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 30%.
Manufacturability8
826M40's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (25/100); formability poor (25/100).
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. 826M40 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 826M40
Is 826M40 easy to machine?
Machine in annealed or T condition with rigid setups, carbide tooling and flood coolant; above ~340 HB use reduced speeds or grind, and rough before final Q&T where possible.
Can 826M40 be welded?
Poor weldability (CE ≈ 1.0) — if unavoidable, use low-hydrogen consumables, 250–350 °C preheat, controlled interpass and immediate post-weld temper/stress relief below the last tempering temperature.
Can 826M40 be formed, bent or molded?
Hot forge 1150–850 °C then slow cool/anneal; cold forming limited to annealed stock and generous bend radii.
826M40 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 | 0.36 – 0.44 | 0.4 |
| Si | 0.1 – 0.4 | 0.25 |
| Mn | 0.45 – 0.7 | 0.57 |
| P | ≤ 0.04 | |
| S | ≤ 0.04 | |
| Cr | 0.5 – 0.8 | 0.65 |
| Mo | 0.45 – 0.65 | 0.55 |
| Ni | 2.3 – 2.8 | 2.55 |
| Fe | balance |
What surface finishes work on 826M40?
No natural corrosion protection: phosphate + oil, paint, zinc or hard chrome plate; bake 190–200 °C for 4–24 h after plating on X/Y/Z conditions to avoid hydrogen embrittlement; nitriding gives a hard wear surface.
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 826M40 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 4340
How much does 826M40 cost?
826M40 is a standard-cost steel ($$), cheaper than about 71% 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.
826M40 — frequently asked
What is 826M40 used for?
826M40 is typically used for heavy shafts, gears and structural components. In short: heavy-section 4340 variant; deepest hardenability in family; poor weldability, CE ≈ 1.0.
What is the yield strength of 826M40?
826M40 has a typical yield strength of 730 MPa (106 ksi) and a tensile strength of 930 MPa (135 ksi) — stronger than 83% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 826M40 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in annealed or T condition with rigid setups, carbide tooling and flood coolant; above ~340 HB use reduced speeds or grind, and rough before final Q&T where possible.
Can 826M40 be welded?
Not readily — weldability is rated poor (25/100). Poor weldability (CE ≈ 1.0) — if unavoidable, use low-hydrogen consumables, 250–350 °C preheat, controlled interpass and immediate post-weld temper/stress relief below the last tempering temperature.
What surface finishes work on 826M40?
No natural corrosion protection: phosphate + oil, paint, zinc or hard chrome plate; bake 190–200 °C for 4–24 h after plating on X/Y/Z conditions to avoid hydrogen embrittlement; nitriding gives a hard wear surface.
Can 826M40 be formed, bent or molded?
Hot forge 1150–850 °C then slow cool/anneal; cold forming limited to annealed stock and generous bend radii.
What is the maximum service temperature of 826M40?
826M40 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 826M40-T and 826M40-Z?
T is the default condition — most commonly stocked Q&T condition — best balance of strength, toughness and machinability for large shafts. Z: maximum-strength condition for small, well-controlled sections; low ductility and notch sensitivity. Yield strength is 730 MPa in T versus 1,400 MPa in Z.
How much does 826M40 cost?
826M40 is a standard-cost steel ($$), cheaper than about 71% 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 970-3: Wrought steels for mechanical and allied engineering purposes (826M40 / EN26) — BSI (1991)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19: Fatigue and Fracture — ASM International (1996)
- EN26 / 826M40 Ni-Cr-Mo alloy steel bar datasheet — UK alloy steel stockists (West Yorkshire Steel / Smiths) (2023)
- Machinery's Handbook — machinability ratings for alloy steels — Industrial Press (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.