S45C Carbon Steel Round Bar — Factory Direct Supplier | Huaxia-Steel
Huaxia-Steel is a direct manufacturer and wholesale supplier of the S45C carbon steel round bar, produced under JIS G4051 and supplied globally to machining workshops, forging plants, and OEM component manufacturers. S45C is a medium-carbon structural steel widely used across Japan, Korea, and Southeast Asia, and it is the Japanese Industrial Standard equivalent of AISI 1045 and DIN C45. Our S45C round bars are hot-rolled, forged, or cold-drawn from continuously cast and ingot-rolled billets, then straightened, cut-to-length, and inspected before shipment. With stable hardenability, good machinability in the normalized or annealed condition, and reliable response to quenching and tempering, the S45C carbon steel round bar is the default choice for engineers who need a cost-effective 0.45% carbon grade for shafts, spindles, gears, and general mechanical parts.
We stock and roll diameters from 20 mm up to 300 mm and can supply lengths from 3 m to 12 m, either as mill random length or fixed cut-to-length. Surface conditions available include hot-rolled black, bright (cold-drawn), peeled, and turned-ground-polished. Every order ships with a Material Test Certificate (MTC) per EN 10204 3.1, and third-party inspection (SGS, BV, TÜV) can be arranged on request. This page defines the full technical specification, chemical and mechanical data, international grade equivalents, manufacturing standards, applications, quality assurance, and packaging of our S45C round bars so that purchasers can specify and quote with confidence.
1. Product Overview — S45C per JIS G4051
S45C belongs to the JIS G4051 standard for carbon steel for machine structural use. It is a medium-carbon steel with a nominal carbon content of approximately 0.45%. Compared with low-carbon steels such as S20C or S35C, S45C offers substantially higher strength and hardness after heat treatment, while retaining enough ductility for forging and moderate cold forming. S45C is the Japanese designation; in the United States it corresponds to AISI/SAE 1045, in Germany to DIN C45 (1.0503), and in China to GB 45# (GB/T 699). Because the carbon level sits in the middle of the carbon range, S45C balances machinability, weldability (with preheat and post-weld stress relief), and through-hardening response.
The S45C carbon steel round bar is typically supplied in one of four conditions:
- Hot-rolled black (HR): as-rolled surface, used for rough machining, forging blank, and structural parts where surface finish is not critical.
- Cold-drawn bright (CD): improved dimensional tolerance (h9/h11), better surface, and mild work-hardening for tighter-tolerance components.
- Peeled (turned): surface decarburization and scale removed by rotary peeling, commonly used for further grinding.
- Turned, ground & polished (TGP): highest straightness and finish for precision shafts and chrome-plating base stock.
2. Specification Table
The following table summarizes the standard supply dimensions and tolerances for our S45C carbon steel round bar. Non-standard sizes and special tolerances can be produced on request with extended lead time.
| Parameter | Range / Value | Remark |
|---|---|---|
| Diameter | 20 – 300 mm | Smaller sizes 6–20 mm available as cold-drawn |
| Length | 3 – 12 m | Random mill length or fixed cut-to-length |
| Diameter tolerance | h9 / h11 | h11 for hot-rolled, h9 for cold-drawn/bright |
| Length tolerance | +20 / -0 mm | Cut-to-length standard |
| Straightness | ≤ 1.0 mm per 1000 mm | ≤ 0.5 mm for TGP shaft quality |
| Ovality | ≤ 50% of diameter tolerance | Measured at both ends |
| Surface condition | Black / Bright / Peeled / Turned | Peeled and TGP for machining |
| Decarburization depth | ≤ 0.30 mm (full) | Per JIS G4051 annex |
| Edge / end | Square cut, burr ≤ 2 mm | Chamfer optional |
For diameter measurement, each bar end is checked with a micrometer at two perpendicular positions; the h11 hot-rolled tolerance for a 50 mm bar is ±0.62 mm, while the h9 cold-drawn tolerance is ±0.031 mm, illustrating the precision advantage of the bright-drawn condition. Straightness is verified on a granite flat or by roller rotation, and any bar exceeding the limit is re-straightened before acceptance.
3. Chemical Composition
S45C chemistry is controlled to JIS G4051 with strict limits on sulfur and phosphorus to ensure clean, inclusion-controlled steel suitable for machining and heat treatment. The ladle analysis values below represent our typical melt range.
| Element | Symbol | Content (wt%) |
|---|---|---|
| Carbon | C | 0.43 – 0.48 |
| Silicon | Si | 0.15 – 0.35 |
| Manganese | Mn | 0.60 – 0.90 |
| Phosphorus | P | ≤ 0.030 |
| Sulfur | S | ≤ 0.035 |
| Nickel | Ni | ≤ 0.20 |
| Chromium | Cr | ≤ 0.20 |
| Copper | Cu | ≤ 0.30 |
| Iron | Fe | Balance |
The carbon band of 0.43–0.48% gives S45C its characteristic medium-carbon behavior. Manganese improves hardenability and strengthens the ferrite, while silicon acts as a deoxidizer and contributes to strength. Low phosphorus and sulfur keep the steel clean, reducing the risk of hot shortness and improving surface quality after forging or machining.
4. Mechanical Properties
The mechanical properties of the S45C carbon steel round bar depend on the supply condition. In the annealed or normalized state, the steel is soft enough for high-speed machining. After quenching and tempering (Q&T), tensile strength rises to 700 MPa and above with good toughness. The values below are for the annealed condition unless noted.
| Property | Value | Test Standard |
|---|---|---|
| Yield strength (Rp0.2) | ≥ 355 MPa | JIS Z2241 |
| Tensile strength (Rm) | 570 – 700 MPa | JIS Z2241 |
| Elongation (A) | ≥ 17 % | JIS Z2241 |
| Reduction of area (Z) | ≥ 40 % | JIS Z2241 |
| Hardness (annealed) | 167 – 229 HB | JIS Z2243 |
| Hardness (Q&T, typical) | 200 – 250 HB | After 820–860 °C oil quench, 550 °C temper |
| Impact (Charpy V, RT) | ≥ 35 J | JIS Z2242 |
| Density | 7.85 g/cm³ | — |
Typical heat treatment for S45C is normalizing at 820–870 °C followed by air cooling, or full hardening by quenching from 820–860 °C in oil and tempering between 400 °C and 600 °C depending on the required strength-toughness balance. Surface hardening methods such as induction hardening and flame hardening are commonly applied to shafts to obtain a hard wear-resistant case (up to 55 HRC) over a tough core.
5. Equivalent Grades
Engineers sourcing across regions frequently need to cross-reference S45C with local standards. The table below lists the principal equivalents and notes where chemistry or tolerances differ slightly.
| Standard | Grade | Material No. | Key Note |
|---|---|---|---|
| JIS (Japan) | S45C | — | Base grade, G4051 |
| AISI / SAE (USA) | 1045 | — | Very close carbon band |
| ASTM | 1045 / A29 | — | Bar and rod specification |
| DIN (Germany) | C45 | 1.0503 | Slightly higher Mn tolerance |
| EN (Europe) | C45E / 1C45 | 1.1191 | Improved cleanliness variant |
| GB (China) | 45# | — | GB/T 699 structural carbon |
| ISO | C45E4 | — | ISO 683-1 |
| BS (UK) | 080M46 | — | Close equivalent |
6. Manufacturing Standards
Huaxia-Steel produces and inspects the S45C carbon steel round bar to the following international standards, allowing our bars to be accepted in most procurement specifications:
- JIS G4051 — Carbon steels for machine structural use (base grade definition for S45C).
- ASTM A29 / A29M — Standard specification for general requirements for steel bars, carbon and alloy, hot-wrought.
- ASTM A108 — Standard specification for steel bars, carbon, cold-finished, standard quality.
- GB/T 699 — Quality carbon structural steels (Chinese 45# equivalent).
- EN 10083-2 — Steels for quenching and tempering, unalloyed grades (C45E).
- ISO 683-1 — Heat-treatable steels, alloy steels, and free-cutting steels.
Our melting route is electric arc furnace (EAF) or basic oxygen with secondary refining (LF + VD), continuous casting into billets, and rolling or forging into round bars. This route gives consistent chemistry, low inclusion content, and predictable mechanical response. Process control covers soaking temperature, finish rolling temperature, cooling rate on the cooling bed, and final straightening to guarantee dimensional and metallurgical conformity.
7. Applications
Because of its balanced strength, machinability, and heat-treat response, the S45C carbon steel round bar is used in a broad range of mechanical and structural components:
- Drive shafts and spindles: TGP bars are used as base stock for transmission shafts, pump shafts, and printer/router spindles.
- Gears and pinions: blanked, machined, and surface-hardened for wear resistance.
- Bolts, studs, and fasteners: larger diameter fasteners and anchor bolts where 8.8-class strength is required.
- Connecting rods and cranks: forged and machined for engine and compressor components.
- Machine tool parts: lead screws, guide rods, fixtures, and jigs.
- Automotive components: steering knuckles, axles, and suspension links after forging.
- General machinery: rollers, pins, sleeves, and structural supports.
8. Quality Assurance
Every S45C round bar lot is released only after passing a documented inspection workflow. Our quality system covers incoming billet verification, in-process dimension control, and final release testing.
- Material Test Certificate (MTC): issued per EN 10204 3.1, showing heat number, chemistry, mechanical results, and standard compliance.
- Ultrasonic testing (UT): according to ASTM E587 or EN 10308, for sizes ≥ 40 mm, to detect internal pipe, inclusions, and segregation.
- Hardness testing: Brinell or Rockwell checks on sample ends to confirm the annealed hardness band of 167–229 HB.
- Surface inspection: visual and dye-penetrant where required, checking for cracks, laps, scars, and decarburization depth.
- Dimensional verification: micrometer and straightedge checks for diameter, ovality, length, and straightness against the ordered tolerance.
- Traceability: each bundle is tagged with heat number, size, quantity, and standard so any claim can be traced to the melt.
Optional additional services include SGS/BV/TÜV witnessed inspection, additional charpy impact testing, grain-size evaluation, and microstructure reports on request.
9. Packaging & Shipping
S45C round bars are prepared for export with protection against transit damage and corrosion:
- Bundling: bars of the same size and heat are bundled with a minimum of 4 steel straps (two at ends, two mid-length) to avoid rolling.
- Anti-rust protection: interleaving with anti-rust paper or VCI film, plus end caps where specified, for sea freight.
- Marking: paint stencil or metal tag showing grade, size, heat number, and quantity on each bundle.
- Loading: bundles loaded into 20-ft or 40-ft containers with dunnage and lashing; break-bulk shipment available for large orders.
- Weight: typical bundle weight 2–5 MT depending on diameter and length; maximum single piece length 12 m.
Lead time for stock sizes is generally 7–15 days; made-to-order diameters and special conditions require 25–40 days including rolling and inspection. We arrange FOB, CIF, or CFR shipment from major Chinese ports and can coordinate destination clearance documents.
10. Request a Quote for S45C Carbon Steel Round Bar
If you need the S45C carbon steel round bar for your next production run, contact Huaxia-Steel today with your required diameter, length, surface condition, quantity, and destination port. Our sales engineers will prepare a competitive factory-direct quotation and supply the full Material Test Certificate (MTC) with every shipment. Whether you need a small trial batch of cold-drawn bright bars or a full container of hot-rolled black round bars, we can match the specification to JIS G4051, ASTM A29, GB/T 699, or EN 10083. Reach out to Huaxia-Steel now for S45C round bar quotes, mill test certificates, and technical support on heat treatment and machining of your components.
