SUM23 Free-Cutting Steel: JIS Composition & 1215 Interchangeability
SUM23 is a low-carbon sulfur free-cutting steel in JIS G 4804 (sulfur and sulfur-composite free-cutting steels): C ≤ 0.09%, Mn 0.75–1.05%, P 0.04–0.09%, S 0.26–0.35%. It is widely used for fittings, screws and small shafts turned on automatic lathes. AISI/SAE 1215 has identical nominal limits, is likewise lead-free, and is interchangeable with SUM23.
Overview
JIS G 4804 divides free-cutting steels by sulfur and lead content into grades such as SUM21, SUM22, SUM23, SUM24L, SUM25, SUM31 and SUM41. SUM23 sits in the low-carbon, high-sulfur, lead-free slot: carbon is held to 0.09% max and sulfur to 0.26–0.35%. It has lower carbon and phosphorus than SUM22 for a more consistent machined surface; for still higher machinability, the leaded SUM23L and SUM24L are the next step.
1215, common on US drawings (AISI/SAE, SAE J403), has nominal limits identical to SUM23's (C ≤ 0.09%, Mn 0.75–1.05%, P 0.04–0.09%, S 0.26–0.35%), and both are lead-free, so the two are interchangeable. They belong to AISI/SAE and JIS G 4804 respectively. Mill test certificates will be issued for the actual material supplied. Double Steel supplies SUM23 round bar in Ø 13–100 mm; both round and flat bar can be produced to order — please inquire for stock.
Chemical Composition (JIS G 4804)
| Element | Spec Range (%) |
|---|---|
| C (Carbon) | ≤ 0.09 |
| Mn (Manganese) | 0.75 – 1.05 |
| P (Phosphorus) | 0.04 – 0.09 |
| S (Sulfur) | 0.26 – 0.35 |
Same-family comparison (JIS G 4804): SUM22 is C ≤ 0.13%, Mn 0.70–1.00%, P 0.07–0.12%, S 0.24–0.33%; SUM24L is C ≤ 0.15%, Mn 0.85–1.15%, P 0.04–0.09%, S 0.26–0.35% plus Pb 0.10–0.35%.
Mechanical Properties (Reference)
| Condition | Tensile (MPa) | Yield (MPa) | Elongation (%) | Reduction of Area (%) | Hardness (HB) |
|---|---|---|---|---|---|
| Hot rolled | 390 | 230 | 25 | 45 | 121 |
| Cold drawn | 540 | 415 | 10 | 35 | 167 |
JIS G 4804 does not specify mechanical property values. The table quotes SAE J1397 estimated typical values for AISI 1215, which has identical nominal C, Mn, P and S limits — for selection reference only, not guaranteed values. Cold-drawn properties vary strongly with drawing reduction.
Heat Treatment & Processing
Machining
SUM23 produces short, broken chips suited to continuous automatic lathe work and small deep-hole drilling. Versus SUM22, lower carbon and phosphorus make it softer and easier on tools; versus SUM24L, it lacks the lubricating effect of lead, so finish is slightly worse at very high speeds.
Quench & Temper
With C ≤ 0.09%, quenching does not harden SUM23 effectively; it is not a quench-and-temper steel. Parts that need strength should use a medium-carbon or alloy steel.
Carburizing
Carburizing or carbonitriding can add surface wear resistance for lightly loaded pins and sleeves. Sulfides reduce core toughness, so it is not recommended for impact or high-fatigue parts.
Cold Forming & Welding
High sulfur limits cold heading, bending and weldability. Parts that need a cold-headed feature or welding should use an ordinary low-carbon steel such as 1010 or the SWRCH series.
International Standard Comparison
| Standard | Comparable Grade | Correspondence |
|---|---|---|
| JIS (Japan) | SUM23 (G 4804) | Reference standard |
| AISI/SAE (USA) | 1215 (SAE J403) | Identical nominal limits, interchangeable |
| EN (Europe) | 11SMn30 (1.0715) | Near equivalent |
SUM23 and 1215 have identical nominal limits (C ≤ 0.09%, Mn 0.75–1.05%, P 0.04–0.09%, S 0.26–0.35%), are both lead-free, and are interchangeable. They belong to different standards — JIS G 4804 and AISI/SAE (SAE J403) respectively. Mill test certificates will be issued for the actual material supplied. EN 10087 11SMn30 is C ≤ 0.14%, Mn 0.90–1.30%, P ≤ 0.11%, S 0.27–0.33% — not identical to SUM23, so only a near equivalent.
Typical Applications
Automotive & Motorcycle Small Parts
Fuel line fittings, sensor bosses and small turned parts in fuel systems — low load but high machining volume.
Hardware & Fasteners
Machine screws, hex nuts, rivet studs and standoffs produced on automatic lathes.
Appliances & Office Equipment
Small motor shafts, roller shafts and guide bushings needing consistent dimensions and a clean finish.
Hydraulic & Pneumatic Components
Fitting bodies, adjusting screws and plugs where turned threads are the main feature.
Supply Specifications
| Form | Size Range | Stock |
|---|---|---|
| Round bar | Ø 13 – 100 mm | Please inquire |
| Flat bar | Made to order | Please inquire |
Length 5–12 m; cut-to-length available on request. Both round bar and flat bar can be produced to order; please inquire for stock availability.
Material Selection Guide
When choosing a free-cutting steel, check three things: the standard on the drawing (JIS or AISI), whether lead is allowed, and whether the part must be welded or take impact.
Drawing or customer specifies AISI/SAE
Identical nominal limits to SUM23 and likewise lead-free, so the two are interchangeable; 1215 belongs to AISI/SAE (SAE J403). Mill test certificates will be issued for the actual material supplied.
SUM24L
Higher cutting speed needed and lead acceptable
Leaded free-cutting steel with better machinability, comparable to US 12L14.
SUM22
Drawing specifies SUM22
Slightly higher carbon and phosphorus; not directly interchangeable with SUM23 — follow the drawing.
Welding or cold heading required
Ordinary low-carbon steel has far better weldability and cold formability than free-cutting grades.
For technical consultation or a quotation, contact the Double Steel sales team via the inquiry form below or LINE. MOQ, port of loading and Incoterms are agreed case by case.
Related Grades
For cross-standard composition and mechanical property tables, see the technical reference tables.
FAQ
- What is SUM23 steel?
- SUM23 is a low-carbon sulfur free-cutting steel in JIS G 4804: C ≤ 0.09%, Mn 0.75–1.05%, P 0.04–0.09%, S 0.26–0.35%. Manganese sulfides break chips short for automatic lathe production.
- Is SUM23 the same as 1215?
- Their nominal limits are identical (C ≤ 0.09%, Mn 0.75–1.05%, P 0.04–0.09%, S 0.26–0.35%), both are lead-free, and they are interchangeable. The difference is the standard: SUM23 belongs to JIS G 4804 and 1215 to AISI/SAE (SAE J403). Mill test certificates will be issued for the actual material supplied.
- What is the difference between SUM22 and SUM23?
- SUM22 is C ≤ 0.13%, P 0.07–0.12%, S 0.24–0.33%; SUM23 has lower carbon and phosphorus (C ≤ 0.09%, P 0.04–0.09%) and higher sulfur (0.26–0.35%). They are not directly interchangeable.
- What is the difference between SUM23 and SUM24L?
- SUM24L contains 0.10–0.35% lead for better machinability; SUM23 is lead-free. Choose SUM23 where lead is restricted.
- Does SUM23 have specified mechanical properties?
- JIS G 4804 does not specify mechanical properties. SAE J1397 estimates for 1215 (identical nominal C, Mn, P and S limits) are about HB 121 hot rolled and HB 167 cold drawn.
- Can SUM23 be welded or heat treated?
- Welding is not recommended (high sulfur causes hot cracking). It cannot be quench hardened, but can be carburized or carbonitrided for lightly loaded wear parts.
- How do I request a SUM23 quotation from Double Steel?
- Round bar is supplied in Ø 13–100 mm, length 5–12 m with cut-to-length available; both round and flat bar can be produced to order, and stock is by inquiry. Send the grade, form, size, quantity and application through the inquiry form and our sales team will reply.
Or call +886-424078309 or email [email protected]