Steel 45#
GB 45# · JIS S45C · BS En45
45# is a medium-carbon engineering steel supplied normalized, hot rolled, cold drawn, annealed, turned-ground-and-polished, induction hardened, or quenched and tempered to 217–255 HB, 28–32 HRC or 33–38 HRC; the file also carries a 9260 cross-reference.
Values for the CD condition
45# tempers and conditions
45# is supplied in 8 conditions, soft to hard. CD is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot rolled | Cheapest form for weldments and parts that will be heat treated or fully machined afterwards. | 330 | 580 | 18 | 170 HB | — |
Solution annealed | Softest condition — pick for heavy cold forming, deep boring or maximum dimensional stability before final heat treat. | 340 | 570 | 22 | 163 HB | — |
840–870 °C, air cooled | Standard GB/T 699 delivery condition for bars and forgings: uniform fine pearlite, good toughness, meets Rm ≥ 600 MPa / Rel ≥ 355 MPa. | 375 | 630 | 18 | 179 HB | — |
CDDefault Cold drawn | Most stocked condition for shafts and turned parts: tight tolerance, bright surface, ~530 MPa yield without heat treatment. | 530 | 625 | 12 | 179 HB | — |
Quenched (water/oil 820–860 °C) + high temper 560–620 °C | The classic quench-and-temper condition — water or oil quenched from 820–860 °C, tempered at 560–620 °C — for gears, shafts and couplings; best strength/toughness compromise and still machinable. | 600 | 800 | 16 | 22 HRC | — |
Induction hardened | Pick for wear surfaces — journals, spline flanks, guide rails — where a hard case plus tough core is needed. | 600 | 800 | 14 | 57 HRC | — |
Quench + temper ~500–540 °C | Use the higher-strength quench and temper (~500–540 °C) for keyed shafts, spindles and pins needing 780 MPa yield and some wear resistance, at reduced machinability and weldability. | 780 | 950 | 14 | 30 HRC | — |
Quench + temper ~420–480 °C | Maximum practical through-hardened strength for 45# in sections under ~40 mm; toughness starts to drop. | 900 | 1,100 | 11 | 35 HRC | — |
Supply forms, finishes and certifications
Ways 45# is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
TGP | Turned, Ground & Polished shafting | Surface finish |
What is 45#?
45# is a medium-carbon engineering steel supplied normalized, hot rolled, cold drawn, annealed, turned-ground-and-polished, induction hardened, or quenched and tempered to 217–255 HB, 28–32 HRC or 33–38 HRC; the file also carries a 9260 cross-reference. Engineers use it as the workhorse bar and plate for shafts, crankshafts and fasteners because it machines well (57 % of 1212) and responds to through- and induction hardening. Normalized values are about 530 MPa yield, 625 MPa tensile, 12 % elongation and 179 HB. Carbon equivalent near 0.6 makes welding conditional, cold bending is limited, and there is no corrosion resistance — use 1018 for weldability or 4140 for higher hardenability. 45# 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). 45# has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 625 MPa (90.6 ksi) — stronger than 69% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
What is 45# used for?
- Crankshafts
- Shafts
- Industrial bolts
Advantages
- High electrical conductivity — 10.8 % IACS, better than 94% of steel grades
- Conducts heat well — 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades
Limitations
- Limited ductility — 12%, worse than 84% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 78% of steel grades
45# properties
Typical room-temperature values for 45#-CD; bars are the position among steel grades.
Physical3
45# 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
45# has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 625 MPa (90.6 ksi) — stronger than 69% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
45# is rated for continuous service to 425°C (797 °F). It conducts heat at 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
45# conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 45# takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
45#'s machinability is good (56/100, better than 71% of steel grades); weldability fair (44/100); 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. 45# is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 45#
Is 45# easy to machine?
Good general machinability at 57 % of 1212; turn normalized/CD material at 120–180 m/min with coated carbide, keep hardness ≤255 HB for tapping and expect built-up edge on annealed stock.
Can 45# be welded?
Weldable with care only — CE ≈ 0.6, so preheat 150–250 °C, use low-hydrogen E7018/ER70S-6 and post-weld temper at 600 °C to avoid HAZ martensite and cracking.
Can 45# be formed, bent or molded?
Hot forge 850–1200 °C then normalize; cold bending is limited (min bend radius ≈ 2–3 t) and should be done in the annealed condition.
Manufacturability
The process limits FabDigit's quote engine applies to 45#. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Better56 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better30 / 100 |
|---|---|
| Weldability | Better44 / 100 |
45# 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 |
|---|---|---|
| CGB/T 699 grade 45 | 0.42 – 0.5 | 0.45 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.02 |
| Crresidual | ≤ 0.25 | 0.1 |
| Niresidual | ≤ 0.3 | 0.1 |
| Curesidual | ≤ 0.25 | 0.1 |
| Fe | balance |
What surface finishes work on 45#?
No anodizing; protect with black oxide, phosphate + oil, zinc or hard-chrome plating, nitriding for wear, or primer/paint — bare surfaces rust within days in humid air.
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).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 45# in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does 45# cost?
45# 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.
45# — frequently asked
What is 45# used for?
45# is typically used for crankshafts, shafts and industrial bolts. In short: workhorse medium-carbon plate.
What is the yield strength of 45#?
45# has a typical yield strength of 530 MPa (76.9 ksi) and a tensile strength of 625 MPa (90.6 ksi) — stronger than 69% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 45# easy to machine?
Reasonably — machinability is rated good (56/100, better than 71% of steel grades). Good general machinability at 57 % of 1212; turn normalized/CD material at 120–180 m/min with coated carbide, keep hardness ≤255 HB for tapping and expect built-up edge on annealed stock.
Can 45# be welded?
With care — weldability is rated fair (44/100). Weldable with care only — CE ≈ 0.6, so preheat 150–250 °C, use low-hydrogen E7018/ER70S-6 and post-weld temper at 600 °C to avoid HAZ martensite and cracking.
What surface finishes work on 45#?
No anodizing; protect with black oxide, phosphate + oil, zinc or hard-chrome plating, nitriding for wear, or primer/paint — bare surfaces rust within days in humid air.
Can 45# be formed, bent or molded?
Hot forge 850–1200 °C then normalize; cold bending is limited (min bend radius ≈ 2–3 t) and should be done in the annealed condition.
What is the maximum service temperature of 45#?
45# is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 45#-CD and 45#-HR?
CD is the default condition — most stocked condition for shafts and turned parts: tight tolerance, bright surface, ~530 MPa yield without heat treatment. HR: cheapest form for weldments and parts that will be heat treated or fully machined afterwards. Yield strength is 530 MPa in CD versus 330 MPa in HR.
How much does 45# cost?
45# 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.
Can FabDigit make parts in 45#?
Yes — 45# is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- GB/T 699 (Quality carbon structural steels) — SAC (2015)
- JIS G 4051 (S45C) / EN 10083-2 (C45) — JISC / CEN (2016)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels — ASM International (1990)
- ASM Handbook Vol. 4: Heat Treating (carbon steel Q&T data) — ASM International (1991)
- ASM Handbook Vol. 16: Machining (machinability ratings) — ASM International (1989)
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.