Manganese Bronze Bushing – The name is misleading, and it matters
Manganese bronze contains no meaningful tin and is not a bronze metallurgically. C86300 and its relatives are high-tensile brasses: a copper-zinc base with aluminium, iron and manganese added, with zinc at roughly 22–28%. The trade name survived because the alloys were developed as stronger replacements for marine tin bronzes. The distinction is practical rather than academic:
- Strength comes from a different mechanism. Zinc in solid solution, plus hard iron-rich and manganese-rich intermetallic particles in a tough matrix, give tensile strength roughly double that of C93200 bearing bronze. Aluminium adds a protective oxide film.
- Dezincification is a real failure mode. High-zinc alloys can lose zinc selectively in certain waters, leaving a porous copper-rich structure. Tin bronzes do not fail this way, and where the medium is warm, stagnant and chloride-bearing this needs addressing at specification stage.
- Thermal expansion is higher. C86300 expands roughly 20–21 µm/m·°C (11–12 µin/in·°F), more than tin bronze and more than steel. Clearance has to reflect that or the bushing closes up as it warms.
C86300 composition
The figures below are the usual compositional windows for C86300 to ASTM B505/B505M and the equivalent casting specifications. Values are weight percent.
| Element | Range (%) | Role |
|---|---|---|
| Copper (Cu) | 60.0 – 66.0 | Base metal |
| Zinc (Zn) | 22.0 – 28.0 | Principal strengthener |
| Aluminium (Al) | 5.0 – 7.5 | Strength, surface film, fluidity in casting |
| Iron (Fe) | 2.0 – 4.0 | Hard particles; wear resistance |
| Manganese (Mn) | 2.5 – 5.0 | Strength and wear resistance |
| Nickel + cobalt (Ni + Co) | 1.0 max | Residual |
| Tin (Sn), lead (Pb) | 0.20 max each | Impurity limits |
Because lead is limited to about 0.2%, C86300 meets most lead-restricted specifications without a special heat — one reason it replaces leaded tin bronze on equipment for markets with tight substance rules — see bronze bushing alloys and European compliance.
Suggested Searches: Copper， Brass， Bronze， Copper Nickel， Manganese， Aluminum
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Mechanical and physical properties
Expect scatter between foundries and section sizes; heavy sections cool slowly and land at the lower end. The values below are the band we design against.
| Property | Typical range | Comment |
|---|---|---|
| Tensile strength | 760 – 830 MPa (110 – 120 ksi) | Among the strongest cast bearing alloys |
| Yield strength | 415 – 480 MPa (60 – 70 ksi) | Resists bore deformation |
| Elongation in 50 mm (2 in) | 12 – 20% | Enough for press fits; less forgiving than tin bronze |
| Brinell hardness | 210 – 250 HB | Demands a hardened shaft |
| Density | ≈ 7.83 g/cm³ (0.283 lb/in³) | Slightly lighter than tin bronze |
| Melting range | 885 – 920 °C (1,625 – 1,690 °F) | Below the copper-tin alloys |
| Thermal conductivity | ≈ 35 W/m·K | Lower than tin bronze; heat leaves slowly |
| Coefficient of thermal expansion | ≈ 20 – 21 µm/m·°C (11 – 12 µin/in·°F) | Greater clearance allowance required |
Grade comparison
C86300 is the grade most buyers mean, but drawings also call up C86200, C86500, C67300 and C67500. They are not interchangeable: zinc, aluminium and tin contents differ enough to change wear and corrosion behaviour.
| Grade | Character | Where it is used |
|---|---|---|
| C86300 (SAE 430B) | Strongest and hardest of the group; needs dependable lubrication | Heavy slow-speed bearings, press rams, trunnion bearings, marine hardware |
| C86200 | Higher tin; good fatigue and impact resistance, slightly lower strength | Start-stop duty, reversing loads, machinery pivots |
| C86500 | Good casting and machining behaviour; balanced strength and wear | General heavy-duty bushings and large cast shapes |
| C67500 | Better corrosion resistance than C86300; lower strength, good castability | Medium-load service with corrosive media, food and chemical plant equipment |
| C67300 | Leaded; improved machinability, lower mechanicals | Machined parts, moderate-load bearings |
Standard product pages: C86300 manganese bronze bushings and related grades.
- High strength and hardness, able to withstand substantial mechanical loads.
- Excellent wear resistance and corrosion resistance, extending service life.
- Good casting and machining properties, allowing for the manufacture of complex shapes.
Due to its unique properties, manganese bronze is widely used in various fields such as maritime, automotive, railway, aerospace, and machinery manufacturing. It is especially used in components that must withstand high loads, heavy wear, and harsh environmental conditions, including bearings, bushings, gears, and valves.
Applications of Manganese Bronze
Selecting by operating condition
| Condition | Grade usually specified | Reason |
|---|---|---|
| High static load, slow motion, reliable grease | C86300 | Highest load capacity; low speed keeps PV in limits |
| Frequent starts, reversals, shock loads | C86200 | Better fatigue and impact behaviour |
| Medium load, corrosive media | C67500 | Better corrosion resistance than C86300 |
| Large cast shapes | C86500 | Good foundry behaviour |
| Seawater immersion or chloride splash | Aluminium bronze instead | High-zinc alloys are weaker here |
| Dirty, marginal lubrication, no re-greasing | Graphite-plugged bronze | Removes the dependence on a grease film |
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Fits, clearance and running-in
- Allow more clearance than for tin bronze. With expansion around 20 µm/m·°C and lower conductivity, the bushing runs hotter and grows more. Start from 0.15–0.25% of shaft diameter plus thermal growth; on a 150 mm (5.9 in) journal that is 0.22–0.38 mm (0.009–0.015 in) before temperature allowance.
- Harden the shaft. At 210–250 HB the alloy will cut a soft journal. We ask for a shaft ideally at 300 HB or better, finished better than Ra 0.8 µm (32 µin).
- Watch the PV product. Design ceilings for lubricated manganese bronze commonly fall in the 1.5–2.6 MPa·m/s band (roughly 43,000–74,000 psi·ft/min). Because conductivity is lower than tin bronze, the real limit is often how fast heat leaves the housing.
- Do not rely on dry running. A plain manganese bronze bushing has no internal lubricant reservoir. If it cannot be greased, specify graphite-plugged construction sized to the duty.
- Measure at a reference temperature. Check bore and wall at 20 °C (68 °F) — see reading and measuring of bearing tolerance.
When manganese bronze is the wrong answer
- Any application sold as “self-lubricating”. Solid C86300 does not release oil and does not contain a lubricant phase. It needs grease, oil or graphite plugs; if the drawing has no lubrication provision and the part cannot be reached for service, this is the wrong alloy.
- High surface speed. Low thermal conductivity and high friction when the film breaks down make it a poor choice for sustained fast rotation. Tin bronze or an aluminium bronze with a proper oil supply runs cooler.
- Soft or rough shafts, and poor alignment. Hardness and low conformability mean the shaft takes the damage. Leaded tin bronze such as C93200 embeds debris and tolerates deflection better.
- Stagnant, warm, chloride-bearing water. Consider dezincification risk. This is a genuine limit of the Cu-Zn system, not a quality issue.
- Ammonia or ammoniacal environments. Brasses are susceptible to stress-corrosion cracking; manganese bronzes are not exempt.
- Elevated continuous temperature. Mechanical properties fall away as temperature rises and the useful ceiling is below that of the aluminium bronzes; above roughly 250 °C (480 °F) continuous, ask us to check the duty.
- Seawater immersion. Use a nickel aluminium bronze — see C95500 or C954 aluminium bronze bushings.
Machining and ordering notes
Manganese bronze machines better than the aluminium bronzes and produces short chips, which helps on long bores. Heavy sections benefit from stress relief before finishing. We leave 2–3 mm (0.08–0.12 in) per side on the OD and 3–4 mm (0.12–0.16 in) on the bore above 150 mm (6 in). Groove geometry belongs on the drawing, because it decides how grease reaches the loaded zone. Capability is described under CNC machining of bronze; see also our bushing material overview.
Frequently Asked Questions (FAQs)
Not sure manganese bronze is right for the load case?
Send the drawing with load, speed, temperature and lubrication method. We will confirm the grade, or say if a tin bronze or aluminium bronze lasts longer.
