1045 steel (G10450): properties, composition, equivalents
1045 steel (AISI/SAE 1045, UNS G10450): 0.45 % C medium-carbon steel. Hot-rolled ≈ 310 MPa yield / 565 MPa tensile; cold-drawn ≈ 530/625 MPa; flame/induction-hardens to 55–58 HRC. Composition, heat treatment, 1045 vs 4140, C45/S45C/45# equivalents.
What is 1045?
AISI 1045 is the medium-carbon workhorse: 0.43–0.50 % carbon, 0.6–0.9 % manganese, no alloying, UNS G10450 — the American twin of EN C45, JIS S45C and GB/GOST 45. It is the cheapest steel that can be usefully hardened: through-hardening in water works up to about 20–25 mm, and flame or induction hardening gives a 55–58 HRC wear surface on shafts, gears and rollers of any size while the core stays at ~180 HB. Most 1045 is used either as-rolled/cold-drawn for shafting, or surface-hardened.
Cold-drawn 1045 bar reaches roughly 530 MPa yield and 625 MPa tensile — about 40 % above 1018 — and it is the standard material for turned-ground-and-polished (TGP) and induction-hardened chrome-plated shafting used in linear bearings and hydraulic cylinders. Normalized or Q&T it serves for axles, bolts (SAE Grade 5), crankshafts in small engines, spindles, gears, sprockets and machine parts of moderate size.
The price of the higher carbon is weldability: 1045 needs 200–300 °C preheat and post-weld tempering, and it is more prone to quench cracking than 1040. Machinability is still good (≈ 55–60 %).
1045 chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | 0.43 – 0.5 | |
| Mn | 0.6 – 0.9 | |
| P | ≤ 0.04 | |
| S | ≤ 0.05 |
SAE J403 / ASTM A29 (G10450). Si typically 0.15–0.35 (not specified). Compare EN C45 (C 0.42–0.50, Mn 0.50–0.80, Cr/Mo/Ni capped) and C45E (P ≤ 0.030).
1045 mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| Hot rolled — typical | ≈ 310 (≈ 45.0) | ≈ 565 (≈ 81.9) | 16 | ≈ 163 HB |
| Cold drawn, 16–22 mm — typical | ≈ 530 (≈ 76.9) | ≈ 625 (≈ 90.6) | 12 | ≈ 179 HB |
| Cold drawn, 22–32 mm — typical | ≈ 485 (≈ 70.3) | ≈ 600 (≈ 87.0) | 12 | ≈ 170 HB |
| Annealed (790 °C) — typical | ≈ 310 (≈ 45.0) | ≈ 565 (≈ 81.9) | 20 | ≈ 163 HB |
| Normalized (900 °C) — typical | ≈ 410 (≈ 59.5) | ≈ 620 (≈ 89.9) | 22 | ≈ 187 HB |
| Q&T (water), tempered 540 °C, 25 mm — typical | ≈ 530 (≈ 76.9) | ≈ 760 (≈ 110.2) | 18 | ≈ 220 HB |
| Q&T (water), tempered 425 °C — typical | ≈ 620 (≈ 89.9) | ≈ 850 (≈ 123.3) | 15 | ≈ 255 HB |
| Q&T (water), tempered 315 °C — typical | ≈ 700 (≈ 101.5) | ≈ 960 (≈ 139.2) | 12 | ≈ 290 HB |
| As-quenched (water), surface | — | — | — | 55–60 HRC |
Typical values (ASM), 25 mm rounds; hardenability is low so Q&T figures apply to the surface and to sections ≤ 20–25 mm. Induction/flame-hardened surface 55–58 HRC with soft core ≈ 165–190 HB.
Impact toughness
1045 requires a minimum Charpy V-notch energy of 30 J at 20 °C (typical, normalized; ≈ 15 J cold drawn). Medium toughness; not a low-temperature material. Avoid tempering at 230–370 °C.
1045 equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| 080M46 | BS (superseded British) | Identical | BS 970 080M46: C 0.42–0.50, Mn 0.60–1.00. |
| C45 | EN (European) | Identical | 1.0503: C 0.42–0.50, Mn 0.50–0.80; C45E (1.1191) the cleaner version — dual-certified 1045/C45 bar is standard. |
| 45 | GOST (Russia/CIS) | Identical | GOST 1050 Steel 45: C 0.42–0.50, Mn 0.50–0.80. |
| S45C | JIS (Japan) | Identical | JIS G4051 S45C: C 0.42–0.48, Mn 0.60–0.90. |
| 1050 | AISI / SAE | Near | C 0.48–0.55: slightly higher carbon and hardness for the same treatments. |
| 1040 | AISI / SAE | Near | C 0.37–0.44: slightly lower carbon, better weldability. |
| 4140 | AISI / SAE | Functional | Alloyed alternative with deep hardenability for sections > 25 mm and higher toughness. |
| 1144 | AISI / SAE | Functional | Resulfurized 0.44 % C free-machining bar ('Stressproof') for high-volume screw-machine shafts. |
Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for 1045 →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| C1045 | AISI (pre-1960s) | |
| G10450 | UNS | 1045H = H10450 hardenability band. |
| 080M46 / 080A47 | BS 970 | 080M46 ≈ 1045 (Mn 0.60–1.00). |
| C45 / Ck45 / C45E | EN 10083 / DIN 17200 | European twins. |
| XC45 / XC48 | NF A 35-552 |
Product forms and tolerance standards
Product forms: hot-rolled and cold-drawn bar (ASTM A29, A108, A576), turned, ground & polished (TGP) shafting; induction-hardened chrome-plated shafting, plate (A830 1045), forgings (A29 / A521), seamless tube (A519), wire, rail-type sections.
Dimensional tolerances: cold-finished bar: ASTM A108; hot-rolled bar: ASTM A29 / A6; TGP shafting: ASTM A108 + supplier tolerance (typ. h6–h8).
Key property values
1045 steel yield strength
Hot-rolled ≈ 310 MPa (45 ksi); cold-drawn ≈ 530 MPa (77 ksi) in 16–22 mm rounds; normalized ≈ 410 MPa; Q&T tempered 540 °C ≈ 530 MPa, 425 °C ≈ 620 MPa, 315 °C ≈ 700 MPa (≤ 25 mm).
1045 tensile strength
Hot-rolled ≈ 565 MPa (82 ksi); cold-drawn ≈ 625 MPa (91 ksi); normalized ≈ 620 MPa; Q&T 760–960 MPa depending on temper (≤ 25 mm).
1045 hardness
Hot-rolled / annealed ≈ 163 HB; cold-drawn ≈ 179 HB; normalized ≈ 187 HB; Q&T 220–290 HB; as-quenched (water) 55–60 HRC at the surface; flame/induction-hardened surface 55–58 HRC, case depth 1.5–5 mm.
Heat treatment
Anneal 790–870 °C, furnace cool. Normalize 870–925 °C (1600–1700 °F), air. Harden 820–850 °C (1500–1560 °F), water or brine quench (oil for thin, simple shapes); temper 205–650 °C, avoid 230–370 °C. Induction/flame harden to 55–58 HRC, temper 150–200 °C. Stress relieve 550–650 °C. Ac1 ≈ 725 °C, Ac3 ≈ 780 °C, Ms ≈ 340 °C. Ideal critical diameter ≈ 20–25 mm (water).
Machinability
≈ 55–60 % of B1112 (hot-rolled / cold-drawn) — good with carbide; better chip control than 1018. 1144 / 1146 are the free-machining alternatives.
Physical properties
Density 7.85 g/cm³, E = 205 GPa, expansion 11.7 × 10⁻⁶/K, conductivity 49.8 W/m·K, specific heat 486 J/kg·K.
Weldability
Limited weldability (CE ≈ 0.55–0.65): preheat 200–300 °C, low-hydrogen consumables (E7018 / ER70S-6), interpass control, slow cooling, temper or stress-relieve at 550–650 °C afterwards. Weld before hardening; never weld induction-hardened surfaces. For welded assemblies use 1020/A36 for the structure and 1045 only for the machined insert.
Machining, forming and heat treatment
Turning, milling, drilling and threading with HSS or carbide are all routine; cold-drawn and normalized conditions give the best finish. Machine before hardening. Cold forming is limited (annealed condition, generous radii); hot forging 1200–850 °C followed by normalizing. Surface treatments: induction/flame hardening, hard chrome plating (shafting), nitriding (shallow), black oxide, zinc plating.
Typical applications
- TGP shafting, induction-hardened chrome-plated shafts for linear bearings and hydraulic cylinders
- Axles, spindles, drive shafts, pump shafts in general machinery
- Gears, sprockets, ratchets and pinions with induction-hardened teeth
- Bolts and studs SAE Grade 5, threaded rod, U-bolts
- Crankshafts and connecting rods for small engines, compressors
- Hand tools, hammers, wrenches (forged), agricultural wear parts (flame-hardened)
- Rolls, rams, couplings, keys and machine parts up to ~60 mm
1045 compared with related grades
Frequently asked questions
Is 1045 the same as C45?
Yes. AISI 1045 (C 0.43–0.50, Mn 0.60–0.90) and EN C45 (C 0.42–0.50, Mn 0.50–0.80) overlap almost completely; mills dual-certify 1045/C45/S45C. C45E is the cleaner, guaranteed-impact version.
Which is stronger, 1045 or 4140?
4140. Both have ~0.45 % C, but 4140's Cr and Mo let it through-harden in sections up to 50–75 mm and temper to a tougher structure; heat-treated 4140 reaches 900–1600 MPa versus 700–960 MPa for 1045 in thin sections. In the as-rolled condition the difference is smaller (≈ 655 vs 565 MPa tensile). 1045 is cheaper and slightly easier to machine.
Can 1045 be hardened?
Yes: water-quench from 820–850 °C for 55–60 HRC at the surface, through-hardening only to about 20–25 mm; or flame/induction-harden the surface to 55–58 HRC on any size. Temper afterwards (150–200 °C for surface hardening, higher for Q&T).
Is 1045 weldable?
With precautions: 200–300 °C preheat, low-hydrogen filler and post-weld tempering. Without preheat the heat-affected zone hardens and cracks. Use lower-carbon steel where welding is the main joining method.
What is 1045 used for?
Shafts (especially TGP and induction-hardened chrome-plated shafting), axles, gears, bolts, spindles, hand tools and any medium-strength machine part that will be surface-hardened rather than through-hardened.
What is 1045 equivalent to in JIS and GB?
JIS S45C and GB/T 699 grade 45 (45#) are identical; GOST Steel 45 and BS 080M46 as well.
Related grades
Verified against ASTM A29/A29M-20 (SAE J403 chemistry); ASTM A29/A29M-20 Table 1 (G10450); ASTM A108-18; ASM Handbook Vol. 1 (typical properties). Last checked: September 2026.