1215 Free-Machining Steel: Composition, Properties & SUM23 Interchangeability
AISI/SAE 1215 (SAE J403) is a low-carbon resulfurized and rephosphorized free-machining steel with C ≤ 0.09%, S 0.26–0.35% and P 0.04–0.09%. Manganese sulfide inclusions break chips short, making it a standard choice for high-volume automatic lathe parts. JIS G 4804 SUM23 has identical nominal limits, is likewise lead-free, and is interchangeable with 1215.
Overview
1215 is a resulfurized and rephosphorized free-machining steel. Sulfur at 0.26–0.35% combines with manganese to form elongated manganese sulfide (MnS) inclusions that act as chip breakers, giving short, broken chips that do not wrap around the tool. Phosphorus at 0.04–0.09% hardens the ferrite and reduces built-up edge, so the turned surface is cleaner than on ordinary low-carbon steel. The result is higher cutting speeds and longer tool life on automatic and Swiss-type lathes.
Compared with leaded 12L14, 1215 contains no lead — slightly lower machinability, but without lead restrictions. The trade-off of high sulfur is lower transverse toughness, fatigue strength and weldability, so 1215 suits parts that are machined heavily but lightly loaded: fittings, screws, bushings and terminals. Double Steel supplies 1215 round bar in Ø 13–100 mm; both round and flat bar can be produced to order — please inquire for stock.
Chemical Composition (SAE J403)
| 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 |
SAE J403 does not specify silicon for 1215; free-machining steels are usually not silicon-killed so that sulfide morphology stays favorable for machining.
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 |
Estimated typical values for hot-rolled and cold-drawn bars per SAE J1397 — not guaranteed values. SAE J403 specifies chemistry only, not mechanical properties. Actual values depend on size, cold-drawing reduction and processing.
Heat Treatment & Processing
Why It Machines Well
MnS inclusions create stress concentrations in the shear zone so chips break within a short length, and they form a lubricating film on the tool face. Phosphorus strengthens the ferrite and limits built-up edge, improving surface finish compared with ordinary low-carbon steel.
Hardening
With C ≤ 0.09%, 1215 does not respond meaningfully to quench hardening and is not used as a quench-and-temper steel. Where strength after Q+T is needed, choose a medium-carbon grade such as S45C.
Carburizing / Carbonitriding
The low carbon content allows carburizing or carbonitriding for a wear-resistant case, but sulfides reduce core toughness and fatigue strength, so this is only suitable for lightly loaded wear parts.
Welding & Finishing
High sulfur promotes hot cracking, so welding 1215 is generally not recommended. Turned parts are commonly electroplated (zinc, nickel, etc.); the clean machined surface helps plating appearance.
International Standard Comparison
| Standard | Comparable Grade | Correspondence |
|---|---|---|
| AISI/SAE (USA) | 1215 (SAE J403) | Reference standard |
| UNS | G12150 | Identical |
| JIS (Japan) | SUM23 (G 4804) | Identical nominal limits, interchangeable |
| EN (Europe) | 11SMn30 (1.0715) | Near equivalent |
| DIN (Germany, former) | 9SMn28 (1.0715) | Near equivalent |
1215 and SUM23 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 — AISI/SAE (SAE J403) and JIS G 4804 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% — wider ranges, so only a near equivalent.
Typical Applications
Hydraulic & Pneumatic Fittings
Tube fittings, quick couplers and nipples with extensive threading and drilling — the most typical use of 1215.
Precision Turned Parts
Screws, nuts, bushings, pins and spacers made in volume on automatic lathes, where cycle time and dimensional consistency matter most.
Electrical & Electronic Parts
Terminals, connector bodies and small motor shafts — low-load parts that need a clean surface and good plating appearance.
Valve & Instrument Parts
Valve body fittings and instrument housing parts where a good machined finish is needed at low cost.
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
1215 is for parts that are machined in volume and lightly loaded. If a part must be welded, take impact, or be quenched and tempered, a free-machining steel is the wrong choice.
Drawing or customer specifies JIS G 4804
Identical nominal limits to 1215 and likewise lead-free, so the two are interchangeable; SUM23 belongs to JIS G 4804. Mill test certificates will be issued for the actual material supplied.
12L14
Higher cutting speeds and better finish needed
Adds lead (Pb 0.15–0.35%) to the 1215 base for better machinability; check lead restrictions for your market.
Welding, cold heading or cold bending required
Ordinary low-carbon steels without high sulfur have far better weldability and cold formability.
Part needs Q+T strength
A medium-carbon steel that can be quenched and tempered above HB 200 for loaded shafts and structural parts.
For technical consultation or a quotation, contact the Double Steel sales team via the inquiry form below or LINE.
Related Grades
For cross-standard composition and mechanical property tables, see the technical reference tables.
FAQ
- What is 1215 steel?
- AISI/SAE 1215 (SAE J403) is a low-carbon resulfurized and rephosphorized free-machining steel: C ≤ 0.09%, Mn 0.75–1.05%, P 0.04–0.09%, S 0.26–0.35%, designed for high-volume machining on automatic lathes.
- Is 1215 the same as SUM23?
- 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: 1215 belongs to AISI/SAE (SAE J403) and SUM23 to JIS G 4804. Mill test certificates will be issued for the actual material supplied.
- What is the difference between 1215 and 12L14?
- 12L14 adds 0.15–0.35% lead for even better machinability; 1215 is lead-free. Both are free-machining steels for lightly loaded parts.
- What is the hardness of 1215?
- SAE J1397 estimates about HB 121 hot rolled and HB 167 cold drawn. With so little carbon, 1215 cannot be hardened by quenching.
- Can 1215 be welded?
- Generally not recommended — high sulfur promotes hot cracking. Use an ordinary low-carbon steel such as 1010 or 1008 for welded parts.
- Can 1215 be carburized?
- It can be carburized or carbonitrided for a wear-resistant case, but sulfides lower toughness and fatigue strength, so only lightly loaded parts are suitable.
- How do I request a 1215 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]