Tin bronze is the original bronze — copper and tin, the alloy that gave an age its name — and all twenty-four grades here are casting alloys. Two variables explain the hub. Tin, from 4.5% to 20%, raises strength and hardness through the hard delta intermetallic and then destroys ductility: C90200 at 7% tin gives 30% elongation, C91300 at 19% gives 0.5% and the lowest machinability rating on this site. Lead, from 0.09% to 27%, is here as a bearing material rather than a machining addition — it gives conformability, embeddability and boundary lubrication, and it is why C94300 carries more than a quarter of its weight in lead. The grades sort into four families: straight tin bronzes, leaded tin bronzes, high-leaded bearing bronzes, and the two precipitation-hardenable nickel-tin bronzes. No grade here appears in ASTM F468 or F467 — those standards cover wrought fastener alloys — and the lead restrictions are the most acute on this site.
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Tin raises strength and hardness and then destroys ductility, and the mechanism is the delta phase. Above roughly 8–10% tin the copper-tin system precipitates a hard intermetallic — conventionally delta, Cu₃₁Sn₈ — dispersed through the softer alpha matrix. Delta is what gives a high-tin bronze its wear resistance, hardness and compressive strength, and equally what makes it brittle and hard to cut. Read the ladder: C90200 at 6–8% tin gives 262 MPa at 30% elongation and 70 HB; C91000 at 14–16% gives 221 MPa at 2% and 105 HB; C91300 at 18–20% gives 241 MPa at 0.5% elongation, 170 HB and a machinability rating of 10, the lowest CDA figure anywhere on this site. Choose the tin against the duty: 5–8% for pressure-tight valve and steam castings that must take shock, 10–12% for loaded gears and worm wheels, 14% and above only where hardness and wear resistance outweigh everything else.
Lead on this hub is not primarily a machining addition — it is a bearing material. That is why the lead contents reach levels found nowhere else in copper metallurgy: C94300 carries 23–27% lead, more than a quarter of the alloy by weight. Lead is insoluble in copper, so it sits as discrete soft globules that do four jobs in a plain bearing: solid lubrication if the oil film breaks down, conformability to a misaligned or out-of-round shaft, embeddability so dirt is absorbed rather than scoring the journal, and incidentally chip-breaking, which takes machinability from 20–30 up to 80. The trade is strength and pressure tightness: C90500 at 0.30% lead gives 276 MPa, C94300 at 27% gives 165 MPa and 48 HB. The high-leaded grades are soft, weak and excellent at being bearings; they are not structural castings.
The lead restrictions are more acute on this hub than anywhere else on this site, and they have closed off traditional applications. The US Safe Drinking Water Act caps lead in drinking-water-contact components at a weighted average of 0.25% of wetted surfaces, with equivalent controls under the European Drinking Water Directive and national acceptance schemes, and RoHS restricts lead in electrical and electronic equipment. Many alloys here are traditional valve, pump and plumbing-fitting materials carrying 6–27% lead — twenty-five to a hundred times that limit. A leaded tin bronze that was the obvious choice for a water fitting thirty years ago is now unusable in that application in most markets. Confirm the position for your market before committing a design, and where potable contact applies consider the unleaded straight grades C90200 to C91300 or the nickel-tin C94700, which holds lead to 0.09%.
The casting method belongs on the order, not just the alloy. Copper-tin has a wide freezing range, so these alloys solidify with interdendritic shrinkage and microporosity rather than concentrated piping — which is why tin bronzes are specified with pressure-tightness requirements, and why the zinc-bearing grades such as C92200 exist at all, zinc being there to deoxidise and improve fluidity and soundness. It is also why continuous cast material is routinely specified stronger than sand cast for the same grade: directional solidification gives a denser, finer structure. C93200 is specified at 207 MPa sand cast and 241 MPa continuous cast; C90700 runs 241 MPa sand cast against 379 MPa permanent mould cast. Two grades invert the pattern — C93800 and C94300 are specified lower on tensile continuous cast — and both pages say so.
Two grades on this hub are precipitation hardenable, and no other alloy here is. C94700 and C94800 carry 4.5–6% nickel, enough to form a coherent nickel-tin precipitate. CDA publish the full cycle: solution treat at 774–802 °C for two hours and water quench, then precipitation treat at 304 °C for five hours (C94700) or six (C94800) and air cool — the TF00 temper. On C94700 that takes the specified minimum from 310 to 517 MPa and hardness from 85 to 180 HB, at the cost of elongation falling from 25% to 5%. As cast, C94700 also carries an Izod of 85 ft-lb, by a wide margin the toughest figure on this site, and at 0.09% maximum lead it is the only grade here CDA rate Good for arc welding. State the condition on the order: as-cast and TF00 are different materials. Note finally that the 2.8–4.0% nickel in C92900 strengthens by grain refinement only and does not make that alloy heat treatable.
This hub spans CDA machinability ratings from 10 to 80, and lead is the variable. At the bottom sits C91300 at 10 — the lowest CDA rating anywhere on this site — then C90200, C90700, C91000 and the nickel-tin C94700 at 20, and C90300 and C90500 at 30. The leaded grades climb to 40–70 and the high-leaded bearing bronzes all reach 80. The unleaded high-tin grades are genuinely hard work, and for a specific reason: the hard delta intermetallic that gives them their wear resistance also abrades tooling and produces a crumbly, discontinuous chip against a soft alpha matrix. Use rigid setups, keen positive-rake carbide, moderate speed with firm feed and flood coolant, and accept short tool life. The leaded grades are the opposite — among the most pleasant copper alloys to turn, with free-breaking chips and excellent finish, which is why bearing bushes are bored and faced from them in volume. One caution on the bearing grades: lead smears. A dull tool or insufficient feed drags lead across the bore and closes the very porosity meant to hold oil. Finish bearing bores with a sharp tool at adequate feed and avoid burnishing.
Composition and machinability data from the Copper Development Association alloy records; tin, lead and nickel figures are read directly from the individual grade pages. Compositions were parsed column-by-column from the source tables, because a positional read mis-assigns minimums where cells are blank. Machinability is on the CDA scale where C36000 free-cutting brass = 100.
| Grade | Designation | Family | Tin % | Lead % | Nickel % | Machinability | Chosen For |
|---|---|---|---|---|---|---|---|
| C90200 | Tin Bronze 7% | Straight | 6.0–8.0 | 0.30 max | 0.50 max | 20 | 30% elongation — most ductile straight grade |
| C90300 | Tin Bronze 88-8-4 | Straight | 7.5–9.0 | 0.30 max | 1.0 max | 30 | Pressure-tight general castings |
| C90500 | Gun Metal | Straight | 9.0–11.0 | 0.30 max | 1.0 max | 30 | The archetypal bronze casting; AMS 4845 |
| C90700 | Tin Bronze 65 | Straight | 10.0–12.0 | 0.50 max | 0.50 max | 20 | Gear bronze, ASTM B427; 379 MPa perm. mould |
| C90800 | Tin Bronze 12% | Straight | 11.0–13.0 | 0.25 max | 0.50 max | — | Gear bronze — no yield or physical data |
| C91000 | Tin Bronze 15% | Straight | 14.0–16.0 | 0.20 max | 0.8 max | 20 | Bell metal range; 2% elongation |
| C91300 | Tin Bronze 19% | Straight | 18.0–20.0 | 0.25 max | 0.50 max | 10 | Machinability 10, 0.5% elongation — brittle |
| C92200 | Navy M Bronze | Leaded | 5.5–6.5 | 1.0–2.0 | 1.0 max | 42 | ASTM B61 steam valve bronze; 10 specs |
| C92300 | Leaded Tin Bronze | Leaded | 7.5–9.0 | 0.30–1.0 | 1.0 max | 42 | C90300 plus lead — machinability 42 |
| C92700 | Leaded Tin Bronze 10-2 | Leaded | 9.0–11.0 | 1.0–2.5 | 1.0 max | 45 | Gun metal with lead — high-duty bearings |
| C92800 | Leaded Tin Bronze 16-5 | Leaded | 15.0–17.0 | 4.0–6.0 | 0.8 max | 70 | 16% tin with 5% lead; 1% elongation |
| C92900 | Leaded Nickel Tin Bronze | Leaded | 9.0–11.0 | 2.0–3.2 | 2.8–4.0 | 40 | Strongest leaded grade — 310 MPa; B427 |
| C93200 | Bearing Bronze 83-7-7-3 | High-leaded | 6.3–7.5 | 6.0–8.0 | 1.0 max | 70 | The universal bearing bronze |
| C93400 | Bearing Bronze 84-8-8 | High-leaded | 7.0–9.0 | 7.0–9.0 | 1.0 max | 70 | Zinc-free C93200 variant |
| C93500 | Bearing Bronze 85-5-9-1 | High-leaded | 4.3–6.0 | 8.0–10.0 | 1.0 max | 70 | Softest-running; 15% IACS, highest here |
| C93600 | Bearing Bronze 80-7-12 | High-leaded | 6.0–8.0 | 11.0–13.0 | 1.0 max | 80 | ASTM B66 car journal bearings |
| C93700 | Bearing Bronze 80-10-10 | High-leaded | 9.0–11.0 | 8.0–11.0 | 0.50 max | 80 | 12 specs — the most on this hub; AMS 4842 |
| C93800 | Anti-acid Metal | High-leaded | 6.3–7.5 | 13.0–16.0 | 1.0 max | 80 | Dilute acid and mine water service |
| C93900 | Bearing Bronze 79-6-15 | High-leaded | 5.0–7.0 | 14.0–18.0 | 0.8 max | 80 | Continuous cast only |
| C94000 | Bearing Bronze 70-13-15 | High-leaded | 12.0–14.0 | 14.0–16.0 | 0.50–1.0 | — | Hardness minimum only — no other data |
| C94100 | Bearing Bronze 76-5-20 | High-leaded | 4.5–6.5 | 18.0–22.0 | 1.0 max | — | ASTM B67 — no yield or hardness data |
| C94300 | Soft Bronze | High-leaded | 4.5–6.0 | 23.0–27.0 | 1.0 max | 80 | 27% lead, 48 HB — softest on the site |
| C94700 | Nickel Tin Bronze | Nickel-tin | 4.5–6.0 | 0.09 max | 4.5–6.0 | 20 | Precipitation hardenable to 517 MPa; Izod 85 ft-lb |
| C94800 | Leaded Nickel Tin Bronze | Nickel-tin | 4.5–6.0 | 0.30–1.0 | 4.5–6.0 | 40 | Precipitation hardenable; machinability 40 |
Read the tin and lead columns together and the four families separate themselves. The straight tin bronzes at 0.50% lead maximum run from ductile C90200 to brittle C91300, with C90500 gun metal the archetype and C90700 the ASTM B427 gear bronze. The leaded tin bronzes add 0.30–6% lead for machinability and pressure tightness — C92200 Navy M is the ASTM B61 steam valve alloy and C92900 the strongest of the group. The high-leaded bearing bronzes run from 6% to 27% lead: C93200 is the universal bearing bronze, C93700 carries twelve specifications — the most on this hub — and C94300 soft bronze is the softest and weakest alloy documented anywhere on this site, which is exactly what it is for. The two nickel-tin bronzes are the only precipitation-hardenable grades here, reaching 517 MPa at TF00. Three grades are shown with gaps rather than borrowed figures: CDA publish no yield or physical data for C90800, only a hardness minimum for C94000, and no yield or hardness for C94100. No grade on this hub is in ASTM F468 or F467 — these are casting alloys, not fastener alloys.
We are committed to delivering zero-defect tin bronze castings and machined cast components. All products undergo rigorous testing including PMI (Positive Material Identification), chemical analysis with tin, lead, zinc, nickel and phosphorus certified explicitly — tin sets strength and delta-phase content, lead governs bearing behaviour, machinability and regulatory acceptability, and nickel determines whether the alloy can be precipitation hardened at all. Pressure testing and radiographic or dye-penetrant examination for interdendritic shrinkage, heat-treatment certification to the TF00 cycle on C94700 and C94800, hardness survey across section, dimensional inspection and full traceability with EN 10204 3.1 certification. Where the casting will contact drinking water, tell us on the enquiry — it governs which grades are available to you.
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