S45C and 1045 properties
A plain medium-carbon steel at roughly 0.45 % carbon. There's no significant alloying and no corrosion resistance, but it has enough carbon to harden the surface where a part runs against something.
- TypeUnalloyed medium-carbon steel, roughly 0.42–0.48 % C
- StandardsJIS G4051 S45C · AISI / SAE 1045 · UNS G10450 · EN C45 (1.0503) · GB 45
- Density7.85 g/cm³
- As suppliedHot rolled or normalised, typically 170–210 HB, and machines freely
- TensileAround 570–700 MPa normalised, depending on section size
- YieldAround 340–430 MPa normalised
- InductionHardens to roughly 45–55 HRC on the treated band and leaves the core tough
- Q and TQuench and temper reaches roughly 25–30 HRC in modest sections. Heavier sections do not respond well
- CorrosionNone. Bare S45C shows surface rust within days in Vietnamese humidity
- CertificateMill test certificate to EN 10204 3.1 on request
Show on the drawing where the hardness goes. "45 HRC" on a shaft drawing can mean an induction-hardened running band or a through-hardened part. Those are different processes at different prices. Mark the hardened length and the case depth on the drawing.
S45C and 1045 grade equivalents
| Grade | JIS (Japan) | US (ASTM / AISI / UNS) | GB/T (China) | EN / DIN (Europe) | Cross-reference |
|---|---|---|---|---|---|
| S45C the JIS designation | S45C (JIS G4051) | 1045 · UNS G10450 · ASTM A29 | 45 | C45 · EN 1.0503 · DIN Ck45 (1.1191) | Standard equivalent |
| S50C slightly higher carbon | S50C | 1050 · UNS G10500 | 50 | C50 · EN 1.0540 | Standard equivalent |
| S20C for carburising | S20C | 1020 · UNS G10200 | 20 | C22 · EN 1.0402 | Standard equivalent |
| SS400 structural, not a machining grade | SS400 (JIS G3101) | A36 (similar use, different chemistry) | Q235 | S235JR · EN 1.0038 | Check the MTC |
Designations taken from JIS G4051 and G3101, ASTM A29 and A36, GB/T 699 and EN 10083-2. SS400 is listed because Vietnamese suppliers reach for it when a drawing just says "mild steel". It's a structural grade with a wide chemistry band, not a controlled machining steel, and we don't supply it against an S45C print. Last reviewed 13 September 2026.
When S45C is the right steel
Shafts, pins and rollers
The classic use. Turned to size, then induction hardened on the running surface if the part sees wear, with a tough core left underneath. It's cheap and predictable, and most bar diameters are in stock in Vietnam.
Base plates, jigs and fixture bodies
For parts that need stiffness and thread strength but no corrosion resistance and no hardness. S45C is stiffer than aluminium at a fraction of the material cost, and on a fixture that sits on a bench the extra weight rarely matters.
Not for deep hardening
Plain carbon steel has poor hardenability. Try to through-harden a thick S45C section and you get a hard skin over a soft middle, whether you wanted that or not. If the drawing needs uniform hardness through a heavy section, use SCM440 or 4140.
Not for a wear surface that must be hard everywhere
If the whole surface runs against something and needs 58 HRC or more, S45C won't get there. That part belongs in a carburised low-carbon grade such as S20C, or in tool steel.
Corrosion protection required for export
A container crossing the Pacific is a humidity chamber. Bare S45C arrives with surface rust, and the customer photographs it before reading the packing list. On this material, black oxide, zinc plating or an oil-and-VCI pack has to be written into the specification from the start.
Mild steel is not a grade
If a drawing says only "mild steel" or "carbon steel", we'll come back and ask. The local default is SS400 structural, a different material from S45C with a much wider chemistry band.
Machining process
S45C is easy to cut. When we do get complaints on it, they're about burrs, thread quality or corrosion protection. Tolerances are rarely the issue.
- TurningMori Seiki and Okuma lathes to Ø 310 × 800 mm, including twin-spindle, at ±0.005 mm typical
- MillingDoosan, Haas, Hision and FANUC RoboDrill machining centres, 3, 4 and 5-axis
- GrindingOkamoto and Chevalier surface and NC grinding to 500 × 200 × 250 mm, ±0.005 mm typical, after hardening
- StressNormalising or stress relief before finishing on parts machined heavily from one side. Otherwise the plate moves
- ThreadsCut and rolled, metric and inch. Rolled thread where the fastener is load bearing
- DeburringHand deburr as standard. Put the edge break on the drawing if 0.1 mm and 0.3 mm are not the same to you
- RustParts are oiled at the machine, not at packing, because rust starts in the gap between finishing and protection
- InspectionMitutoyo CRYSTA-APEX V CMM in a climate-controlled lab, reported in inch and millimetre
Typical figures from normal production, not a blanket specification. General tolerance follows ISO 2768 fine or medium class, whichever your print calls out. On hardened parts the tolerance applies to the features ground after heat treatment. Show us which those are on the drawing and we'll plan the sequence around them.
Protecting a steel that rusts
- Black oxideNegligible dimensional change and mild protection, and it needs oil to stay effective
- Zinc platingClear, blue, yellow, black chromate and zinc-nickel to ASTM B633 / ISO 4042
- NickelNickel plating, where a harder and more uniform coating is wanted on a threaded or bored part
- InductionInduction hardening of running surfaces, roughly 45–55 HRC, hardness checked before shipping
- Q and TQuench and temper, commonly written HT on US drawings. Hardness checked on our Mitutoyo QMH 14BX before shipping
- PackingVCI paper and film as standard on unplated steel, ISPM-15 heat-treated pallets for sea freight
Black zinc is not standard zinc plating. A black finish on your print needs black chromate specified, and we confirm that with you before the part goes to plating. Every hardened batch is checked on our Mitutoyo QMH 14BX before it ships. Full finishing and heat treatment list →
Stock and lead time
- BarRound and flat bar widely available from Vietnamese stockists in most sizes
- PlateCommon thicknesses available; oversized and thick plate confirmed per job
- ConditionHot rolled and normalised both available. Tell us which the drawing assumes
- QuoteWithin 24 business hours of a complete RFQ
- Lead timePrototype 3–7 days · small batch 7–14 days · standard 14 days after PO. Hardened parts add a cycle
- CertificateEN 10204 3.1 mill certificate on request, with a dimensional report in inch and millimetre
S45C is the cheapest and easiest steel to buy here, and SS400 often sits in the same rack. If the size your drawing needs is not available in S45C, we tell you what is and wait for your written approval before buying anything.
Common questions
Is S45C the same as 1045?
Yes, for practical purposes. S45C to JIS G4051, AISI 1045 and EN C45 all describe a plain carbon steel at roughly 0.45 % carbon, and they cross-reference cleanly. If a drawing needs the tighter DIN Ck45 residual limits, say so and we buy to that.
Can S45C be hardened to 45 HRC?
On the surface, yes. Induction hardening typically reaches 45–55 HRC on the treated band. Through-hardening a whole section to that value is not realistic in plain carbon steel, and a requirement like that points to 4140 or SCM440.
What does HT mean on an American drawing?
Usually quench and temper. On S45C that typically lands around 25–30 HRC in modest sections. If your drawing says HT with no hardness range, give us the range you actually need and we'll specify the cycle to hit it.
Will the parts arrive rusty?
Bare steel is oiled at the machine and packed with VCI paper and film, and plated or black-oxided parts have the coating to protect them. If the drawing has no finish called out, we ask what protection you want before shipping.
Can you supply SS400 instead? It's cheaper.
Only with your written approval. SS400 is a structural grade with a much wider chemistry band, not a controlled machining steel. We'll quote it if you ask for it.
Do you supply mill certificates for carbon steel?
Yes. EN 10204 3.1 material test certificates on request, together with the dimensional inspection report in inch and millimetre.
Can you weld S45C?
It can be welded with preheat and controlled cooling, but at 0.45 % carbon it's not an easy steel to weld and the heat-affected zone hardens. For welded frames SS400 or a low-carbon grade is usually the better material.
Related information
4140 / SCM440 alloy steel
For sections too thick for plain carbon steel to harden through.
SKD11 / D2 tool steel
Cold-work tool steel at 58–62 HRC for dies, punches and mould components.
Finishing and heat treatment
Black oxide, zinc and nickel plating, and the full heat treatment table.