12L14 Steel
Also: AISI 12L14, SAE 12L14, UNS G12144, leaded steel, free machining steel, screw machine steel, Ledloy, 11SMnPb30 / 1.0718, 11SMnPb37 / 1.0737 (near), 1215 (lead-free cousin)
12L14 is the fastest-machining carbon steel: lead, sulfur and phosphorus give short chips and mirror finishes for screw-machine parts. Not weldable, not for hardening.
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At a glance
| Density | 7.87 g/cm³ (0.284 lb/in³) |
|---|---|
| Tensile strength | 540 MPa (78 ksi) cold drawn |
| Yield strength | 415 MPa (60 ksi) cold drawn |
| Hardness | 163 HB cold drawn |
| Elongation | 10% cold drawn |
| Modulus of elasticity | 200 GPa (29 Msi) |
| Thermal | Melts at about 1,480-1,520 °C (2,700-2,770 °F); lead fumes above about 500 °C (930 °F) during welding or hot work |
| Composition | Fe, up to 0.15% C, 0.85-1.15% Mn, 0.04-0.09% P, 0.26-0.35% S, 0.15-0.35% Pb |
Typical values, Cold drawn (as stocked). Confirm against the mill certificate and the purchase spec.
- MachinabilityExcellent
- About 160-170% of the 1212 benchmark, the best of any steel: short chips, low tool wear, excellent finish at high surface speeds. Sharp positive tooling and a light finishing pass give a near-polished surface.
- WeldabilityNot recommended
- Sulfur and lead cause hot cracking and porosity, and lead fumes are toxic. If a joint is unavoidable, braze or use a mechanical fastener; design the assembly so 12L14 parts are never welded.
- FormabilityPoor
- Low ductility and weak across the grain: it cracks on tight bends, heading and crimping. Thread rolling and light knurling work; bends need a generous radius.
- Corrosion resistancePoor
- Rusts readily and the sulfide stringers pit first. Zinc plate, nickel plate or black oxide with oil are the norm on finished parts.
12L14 is a resulfurized, rephosphorized low-carbon steel with about 0.25% lead added. The manganese sulfides and lead particles break chips short, lubricate the tool and let a Swiss or multi-spindle machine run at speeds no other steel tolerates. Its machinability rating, around 160-170% of the 1212 benchmark, is the highest of any ferrous bar stock, and it leaves an excellent as-turned finish.
It is bought in cold-drawn round, hex and square bar for fittings, bushings, studs, spacers, hose barbs, valve bodies and any part where cycle time on a lathe is the cost. Strength is modest (about 540 MPa / 78 ksi tensile cold drawn), and the inclusions that help the tool make it weak in the transverse direction and brittle when bent or headed.
The additions that make it machine are the additions that ruin it for everything else. It hot-cracks and porosity-fills when welded, the lead fumes are a hazard, it cannot be through-hardened and it case hardens unevenly. Lead also rules it out of RoHS-sensitive assemblies, where 1215 (same idea, no lead) or a free-machining stainless is the substitute.
Heat treatment
Not through-hardenable (about 0.10% carbon) and not a good carburizing steel: the sulfides and lead give an uneven, sometimes cracked case, and lead can embrittle the grain boundaries at hardening temperatures. Where a hard surface is essential, some shops carburize thin cases with care, but 1018, 1117 or 8620 are the right choices for hardened parts. Stress relieve at 540-600 °C (1,000-1,100 °F) only if a heavily machined part must stay straight.
Tempers and conditions
- Cold drawn (as stocked)
- Cold drawn, ground and polished
Stock forms
- Round bar, cold drawn (screw-machine lengths)
- Hex bar
- Square bar
- Ground and polished shafting (limited sizes)
Relative cost
Tier 2 of 5. About 1.3-1.6x 1018 bar by weight, but the cycle-time saving usually makes the finished part cheaper. 1215 is close in price and lead-free.
Typical applications
- Hydraulic and pneumatic fittings, hose barbs and couplings
- Bushings, spacers and standoffs
- Studs, nuts and threaded inserts
- Valve bodies and manifolds for low pressure
- Pins, dowels and shafts under light load
- Electrical terminals and connector bodies (plated)
- High-volume Swiss and multi-spindle screw machine parts
Process compatibility
How 12L14 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.
| Process | Rating | Notes |
|---|---|---|
| Screw Machining | ExcellentExcellent | The reason the grade exists: run at top speed with short chips and a finish that skips secondary polishing. |
| Swiss Machining | ExcellentExcellent | Small precise parts at high volume; the chip control keeps guide bushings clean. |
| CNC Turning | ExcellentExcellent | Highest turning rates of any steel; specify ground or precision cold-drawn bar for collet fit. |
| CNC Machining | ExcellentExcellent | Mills, drills and taps beautifully; taps last several times longer than in 1018. |
| Zinc Plating | ExcellentExcellent | The standard finish on fittings and hardware; low carbon, so no hydrogen bake needed. |
| Electroless Nickel Plating | GoodGood | Uniform coverage on threads and bores for fittings and connectors; clean the sulfide smear well before plating. |
| Nickel Plating | GoodGood | Bright decorative and corrosion finish on knobs, terminals and fittings. |
| Black Oxide | GoodGood | Cheap cosmetic finish for indoor hardware; the finish reads a little duller than on 1018 because of the sulfides. |
| Centerless Grinding | GoodGood | Grinds to close diameters for shafts and pins; the stock is soft, so light passes. |
| Welding | Not recommendedNot recommended | Hot cracking, porosity and toxic lead fumes. Braze, press fit or thread instead, or choose 1018. Can 12L14 steel be welded? |
| Carburizing | PoorPoor | Uneven, crack-prone case and lead embrittlement at temperature; use 1018, 1117 or 8620 for case-hardened parts. |
| Heat Treating | Not recommendedNot recommended | Not enough carbon to through harden and the lead misbehaves at temperature. |
| Press Brake Forming | PoorPoor | Cracks on bends tighter than about 3x thickness; not a forming grade. |
Design and sourcing tips
- Use 12L14 only where the part is turned, drilled and tapped and will never be welded, bent, hardened or highly stressed.
- Check lead restrictions: RoHS, drinking water (NSF/ANSI 61) and some automotive and medical specs forbid it. Specify 1215 or 1144 when lead is a problem.
- Give the shop a good bar size: specify cold-drawn round to the nearest stock diameter so the part comes straight off the bar with minimal roughing.
- Do not tap thin walls hard: the low ductility means threads strip and heads crack; keep wall thickness at least 1.5x thread depth.
- Call the plating out explicitly (zinc per ASTM B633, or electroless nickel); bare 12L14 rusts on the shelf.
Frequently asked questions
- Can 12L14 be welded?
- No, not reliably. The sulfur and lead that make it machine cause hot cracking and porosity in the weld, and the lead vaporizes into toxic fumes. Braze, press fit, thread or rivet 12L14 parts instead, or change the material to 1018 when a weld is required.
- Can 12L14 be hardened?
- Not through the section; it has only about 0.10% carbon. Carburizing is possible but gives an uneven case and the lead can embrittle the part at temperature, so most shops refuse it. For hard parts that still need to machine fast, use 1117 or 1141, or carburize 8620.
- What is the difference between 12L14 and 1215?
- 1215 is the same free-machining chemistry (high sulfur and phosphorus) without the lead. It machines at roughly 130-140% of the benchmark, a little slower than 12L14, but it is RoHS-compliant and has no fume issue. Most new designs specify 1215 unless the last few percent of cycle time matter.
- Is 12L14 RoHS compliant?
- No. Lead at 0.15-0.35% is far above the RoHS 0.1% limit and 12L14 is not covered by the general steel exemption, so it cannot be used in products that must comply. Specify 1215 for the same machinability without lead.
Processes that commonly use it
Related materials
Where to verify these values
- ASTM A108 (cold-finished carbon steel bar)
- SAE J403 and ASTM A29/A29M (chemistry)
- ASM Handbook Vol. 16, Machining (machinability ratings)
- Producer data sheets for 12L14 and 1215 bar
