Steel 45# · heat-treated state
Steel 45#-IH
Properties of the IH condition, compared with the other 45# tempers.
Pick for wear surfaces — journals, spline flanks, guide rails — where a hard case plus tough core is needed.
What is 45#-IH?
45#-IH is 45# heat treated to IH — pick for wear surfaces — journals, spline flanks, guide rails — where a hard case plus tough core is needed. 45#-IH has a yield strength of 600 MPa (87 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 77% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi). 45#-IH 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). CD is the default condition FabDigit quotes; IH is available on request or by drawing note.
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
- High strength — 600 MPa (87 ksi), better than 77% of steel grades
Limitations
- Difficult to machine — 12/100, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 79% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
45#-IH properties
Typical room-temperature values for 45#-IH — 11 properties are specific to this condition; the rest are grade-level values shared by every 45# temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
45#-IH 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#-IH has a yield strength of 600 MPa (87 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 77% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
45#-IH 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#-IH conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 87% of steel grades.
Sustainability4
Producing a kilogram of 45#-IH 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#-IH's machinability is not recommended (12/100, worse than 99% of steel grades); weldability not recommended (12/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 45# tempers and conditions
45# is also supplied in 8 other conditions. The full side-by-side table is on the 45# overview.
- CDDefaultMost stocked condition for shafts and turned parts: tight tolerance, bright surface, ~530 MPa yield without heat treatment.530 MPa yield · 179 HB
- Q&T 33-38 HRCMaximum practical through-hardened strength for 45# in sections under ~40 mm; toughness starts to drop.900 MPa yield · 35 HRC
- Q&T 28-32 HRCUse 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 MPa yield · 30 HRC
- Q&T 217-255 HBThe 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 MPa yield · 22 HRC
- IHPick for wear surfaces — journals, spline flanks, guide rails — where a hard case plus tough core is needed.600 MPa yield · 57 HRC
- NormalizedStandard GB/T 699 delivery condition for bars and forgings: uniform fine pearlite, good toughness, meets Rm ≥ 600 MPa / Rel ≥ 355 MPa.375 MPa yield · 179 HB
- ASoftest condition — pick for heavy cold forming, deep boring or maximum dimensional stability before final heat treat.340 MPa yield · 163 HB
- HRCheapest form for weldments and parts that will be heat treated or fully machined afterwards.330 MPa yield · 170 HB
Working with 45#-IH
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.
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.
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 | — |
45#-IH — frequently asked
What is 45#-IH used for?
45#-IH is typically used for crankshafts, shafts and industrial bolts. In short: workhorse medium-carbon plate.
What is the yield strength of 45#-IH?
45#-IH has a typical yield strength of 600 MPa (87 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 77% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 45#-IH easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% 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#-IH be welded?
Not readily — weldability is rated not recommended (12/100). 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#-IH?
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#-IH 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#-IH?
45#-IH 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.
Can FabDigit make parts in 45#-IH?
Yes — 45#-IH 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.