Cast Bronze Oilless Materials: Eight Alloy Families
“Oilless” describes a construction, not a single alloy: a cast copper alloy body with solid lubricant embedded in the working surface. Which copper alloy is used decides the load capacity, the corrosion behaviour and the temperature ceiling. This page sets out the eight alloy families produced as cast bronze oilless material, the designations each covers, what the lead content does, and the duties where none of them should be specified.
What the term covers
A cast bronze oilless component is made in two stages. The body is cast — by centrifugal, continuous or sand casting, depending on size and quantity — from a copper alloy chosen for its mechanical and corrosion behaviour. Then holes are drilled or cast in a pattern over the working surface and filled with solid lubricant plugs, usually graphite, sometimes a graphite and MoS₂ blend. In service the plug material transfers to the counter face and forms the film that carries the contact.
The base alloy still carries the load, so its strength and hardness remain governing properties. The method is most useful where fluid lubrication struggles: high load, low speed, oscillating or reciprocating movement, elevated temperature, and places where re-greasing is difficult or impossible.
The eight alloy families
Designations are grouped as they appear on drawings and purchasing specifications. Several trade names (952C, SAE 68, LB2, HTB1) describe a family rather than a fixed composition.
| Family | Designations supplied | Properties and performance | Typical applications |
|---|---|---|---|
| Aluminum bronze | C95210, C95810, 952C, AB1, AB2, SAE 68, CuAl10Fe, CuAl10Ni | High strength, strong corrosion resistance especially in seawater, good wear and fatigue resistance, usable up to about 400 °C (752 °F) | Ship propellers, pump and valve components, mining machinery bearings |
| High-strength brass | C86500, C86300, 865C, 869D, HTB1, HTB3, SAE 43, SAE 430B, CuZn35Al1, CuZn25Al5 | Tensile strength of at least 600 MPa, good machinability, corrosion resistance above standard brass, good hot workability | Heavy-duty gears, marine thrusters, high-stress structural parts |
| Gunmetal | C92610A, C92610, 905C, G1, SAE 62, CuSn10Zn, BC2, BC3 | High fluidity when cast, low shrinkage, pressure-tight in thin-wall castings, good steam corrosion resistance | Pipe valves, fire hydrants, hydraulic system components |
| Lead-tin bronze | C93700, C92710, C93500, 937B, 930D, 935B, LB2, LB3, LB4, SAE 64, CuPb10Sn, CuPb5Sn, C93200, SAE 660, CuSn7ZnPb | Lead particles of roughly 10–20% improve self-lubrication and shock absorption and lower friction; suits boundary lubrication and dusty environments | Plain bearings, bushings, machine tool guideways |
| Phosphor bronze | C90710, C90810, 904D, 907C, PB1, PB2, SAE 65, CuSn12 | Phosphorus raises the elastic limit and resists stress relaxation and acid corrosion; high fatigue strength, non-magnetic | Electrical contacts, spring elements, precision instrument gears |
| Leaded gunmetal | C83600A, C83600, C92410A, 836B, 924B, LG2, LG4, SAE 40, CuSn5ZnPb, CuSn6ZnNi | Lead content of roughly 4–7% improves machinability and gives emergency lubrication; good seawater and salt-spray resistance | Marine pump housings, low-pressure valves, offshore platform piping |
| High-leaded tin bronze | C94100, LB5, 941, C93700, SAE 64, C93800, SAE 67 | Lead content of roughly 20–30% gives strong embeddability of debris and allows oil-starved operation; slow speed and heavy load only, limited PV value | Crusher bearings, mill bushings, agricultural pivot components |
| Tin bronze | C90250, 906D, CT1, CuSn10 | Lead-free, spark-resistant, withstands acid and alkali corrosion over roughly pH 5–12; specified where a biocompatibility reference such as ISO 5832 is requested | Chemical sealing rings, food machinery, tools for hazardous areas |
Families overlap, so where two would both work the decision comes down to lead content, machinability and cost rather than to a strength figure. A broader comparison is kept on the bushing material overview and in common bearing materials.
What the lead content actually changes
Lead is present as discrete particles, not in solution, and the percentage changes behaviour in a predictable way.
| Lead content | Families | What it gives | What it costs |
|---|---|---|---|
| None (lead-free) | Tin bronze, aluminum bronze | Compliance with lead-free requirements, spark resistance, better corrosion behaviour in some media | Lower embeddability; needs a cleaner counter face |
| 4–7% | Leaded gunmetal | Good machinability and emergency lubrication if the oil film is lost | Reduced strength; restricted to low-pressure systems |
| 10–20% | Lead-tin bronze | Self-lubrication, shock absorption, lower friction under boundary lubrication | Lower PV capacity than the harder alloys |
| 20–30% | High-leaded tin bronze | Strong embeddability of dirt; runs under oil-starved conditions | Limited PV value; slow speed and heavy load only |
Lead percentages are nominal for the family. Where a lead-free specification applies — potable water, RoHS, food contact — it has to be stated on the drawing, because several of these designations are normally supplied leaded.
Selecting by duty
| Operating condition | Family usually specified | Reason |
|---|---|---|
| Seawater, brackish water or salt spray | Aluminum bronze, leaded gunmetal | Chloride corrosion resistance; aluminum bronzes carry higher load |
| High load at slow speed with shock | High-strength brass, high-leaded tin bronze | Strength of at least 600 MPa, or embeddability where lubrication is unreliable |
| Elevated temperature up to about 400 °C (752 °F) | Aluminum bronze | Retains strength where tin bronzes soften |
| Dusty or contaminated environment | High-leaded tin bronze, lead-tin bronze | Debris is absorbed instead of scoring the shaft |
| Thin-wall or pressure-tight casting | Gunmetal | Fluidity and low shrinkage fill complex sections |
| Fatigue loading, spring elements | Phosphor bronze | High elastic limit, resists stress relaxation |
| Hazardous area, food or chemical contact | Tin bronze | Lead-free, spark-resistant, tolerant of pH 5–12 |
Grade pages cover the most frequently ordered families: aluminum bronze, C954 aluminum bronze, C86300 manganese bronze, C90500 tin bronze, C91000 phosphor bronze and gunmetal.
Solid lubricant, grooves and delivery forms
- Graphite plugs are standard for dry or marginally lubricated duties; graphite and MoS₂ blends suit long dwell periods under load.
- Oil grooves — straight, figure-eight or spiral — are added where the machine has an intermittent grease supply and the plugs cover the dry intervals, and the two are often combined.
Finished forms include cylindrical and flanged bushings, thrust washers, wear plates, guide sliders and spherical plain bearings; examples are shown under bronze graphite bushings and graphite-impregnated LB2 bushing.
Limits: when cast bronze oilless material is the wrong choice
- High sliding speed. Graphite-plugged construction is designed for high load at low to moderate speed; above that, heat cannot dissipate and the film is stripped faster than it reforms.
- Leaded alloys in high-pressure systems. Leaded gunmetal in particular is restricted to low-pressure service, where exceeding the range risks brittle fracture rather than gradual wear.
- High-leaded alloys in a high-PV duty. The 20–30% lead families trade PV capacity for embeddability and smear rather than wear above their limit.
- Ammonia or acetylene service. Copper alloys are not compatible with either.
- Strongly reducing or sulfidic media. The corrosion behaviour of these alloys is based on oxidising and near-neutral conditions.
- Soft counter faces with high-lead alloys. Embeddability works both ways — a soft shaft is polished unevenly and the leaded surface transfers.
Standards and certification
Composition and mechanical requirements are normally called up against ASTM or DIN/EN designations, and the revision matters — see standards for bronze bearing materials. Each order ships with a material certificate, and the values on it govern over any figure quoted here.
What to send for a quotation. Drawing with dimensions and tolerances, alloy designation or standard, load and speed or oscillation angle, temperature range, mating material and hardness, medium, any lead-free requirement and monthly quantity.
Frequently asked questions
What is the difference between an oilless bronze and a self-lubricating bronze?
In practice the terms describe the same construction: a cast copper alloy with solid lubricant embedded in the working face. Where a distinction is drawn, “oilless” means the component runs with no external oil supply, while “self-lubricating” describes the mechanism.
Can these materials run completely dry?
Yes, when they carry embedded solid lubricant plugs and load and speed stay within the PV limit for the family. A plain cast bronze with only oil grooves is not an oilless material; it needs grease or oil and will score if run dry for long.
Which family should be used where lead is not permitted?
Tin bronze and aluminum bronze are the lead-free families: tin bronze where spark resistance and a wide pH tolerance matter, aluminum bronze where strength and temperature capability matter. The requirement must be stated on the drawing, because the leaded families are the default for many designations.
Can an existing alloy be matched from a sample?
Yes. Where a drawing names a grade that is no longer current, or only a worn part is available, the alloy can be identified from a sample and matched on composition, machining behaviour and wear resistance.
Send the duty and the drawing
Email the operating conditions and either the part drawing or a sample of the existing component. We will confirm which alloy family fits, recommend a designation with typical values, and quote to your drawing.
Built for long-lasting performance, cast bronze oilless materials are perfect for sliding applications in demanding environments.
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