“Manganese bronze” is a misnomer. Every alloy here is a copper-zinc alloy — a brass — with 22–42% zinc plus manganese, iron, aluminium and tin for strength. CDA make the point themselves by filing the wrought grades as Wrought Bronzes and the cast grades as Cast Brasses: High Strength Yellow Brasses. What the name does signal correctly is that these behave nothing like ordinary brass: tensile strength runs 414–758 MPa against a yellow brass's 350–500. Aluminium splits the hub in two — the 0.25–2.0% grades are moderate-strength and machinable, the 3.0–7.5% grades are hard, strong and difficult to cut. Machinability spans the widest range of any family on this site, from 8 at C86300 to 65 at C86400, and it tracks lead rather than strength. C67500 is ASTM F468 Cu 675. Being 22–42% zinc, dezincification is the failure mode to design against — and none of these alloys is inhibited.
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Start with the name, because it misleads. Every alloy on this hub is a copper-zinc alloy — which is to say a brass — with manganese, iron, aluminium and tin added for strength. Zinc runs from roughly 22% to 42%. There is no tin-bronze chemistry here at all; the tin present is a minor 0.20–1.5% addition. CDA then file the two halves of the family in different classes: the wrought grades C67000, C67300, C67400, C67500 and C67600 as Wrought Bronzes, Other Copper-Zinc Alloys, and the cast grades C86100, C86200, C86300, C86400 and C86500 as Cast Brasses: Manganese Bronze and Leaded Manganese Bronze Alloy (High Strength Yellow Brasses). Same chemistry, opposite designation. Use the UNS number on drawings and purchase documents. What the name does signal correctly is that these alloys behave nothing like ordinary yellow brass: manganese, iron and aluminium together lift tensile strength to 414–758 MPa, add real wear and galling resistance, and make the wrought grades exceptionally hot forgeable.
Aluminium splits this hub cleanly in two, and the halves do different jobs. The low-aluminium group at 0.25–2.0% — C67300, C67400, C67500, C67600, C86400 and C86500 — runs 414–634 MPa, keeps 15–33% elongation, and contains every grade here that machines acceptably: valve stems, bushings, marine hardware, general castings. The high-aluminium group at 3.0–7.5% — C67000, C86100, C86200 and C86300 — reaches 621–758 MPa at 180–223 HB with 12–20% elongation and markedly worse machinability: heavily loaded bearings, gears, screw-down nuts, bridge components. C86200 and C86300 make the point exactly — identical in every element except aluminium (3.0–4.9% against 5.0–7.5%), and that one difference takes tensile from 621 to 758 MPa while dropping machinability from 30 to 8.
Machinability spans the widest range of any family on this site, and it tracks lead, not strength. At the bottom, C86300 at 8 — the lowest figure anywhere on this site — then C86500 at 26 and C67400, C67500, C86100 and C86200 all at 30. At the top sit the two deliberately leaded grades: C67600 at 60 with 0.50–1.0% lead and C86400 at 65 with 0.50–1.5%. For reference, C36000 free-cutting brass is the 100, so even the best grade here cuts at two thirds of ordinary free-cutting practice. Forming inverts the picture: the wrought grades are rated Excellent for hot forming and Poor for cold working, and C67400 carries a forgeability rating of 100, equalling C37700, the CDA reference alloy for hot forgeability. Forge or extrude to near net shape, then machine.
Because these are 22–42% zinc brasses, dezincification is the failure mode to design against — and none of them is inhibited. Zinc is selectively leached out, leaving a porous copper residue that retains the original shape of the part: a dezincified valve stem can look sound and fail under hand load. Susceptibility tracks structure, and above roughly 37% zinc the zinc-rich beta phase corrodes preferentially — C86400 at 34–42% and C86500 at 36–42% sit squarely in that range. Unlike C44400 with its antimony addition or C68700 with arsenic, no grade here carries a dezincification inhibitor. The aluminium and manganese help, and the high-aluminium grades do better than the low-aluminium ones, but help is not immunity. For stagnant, warm or chlorinated water, confirm suitability and expect ISO 6509 testing; for continuous seawater immersion the nickel aluminium bronzes are the usual step up. Ammonia stress-corrosion cracking applies too, which is why CDA publish named HR02 stress-relieved tempers for C67400.
The machinability spread across this hub is the widest of any family on this site, and it tracks lead rather than strength. At the bottom sits C86300 at 8 — the lowest CDA rating anywhere on this site — then C86500 at 26 and C67400, C67500, C86100 and C86200 at 30. At the top, the two deliberately leaded grades: C67600 at 60 and C86400 at 65. The unleaded high-aluminium grades are genuinely difficult: tough, work-hardening, with hard intermetallic particles that abrade tooling. Use rigid setups and heavy continuous cuts, keen positive-rake carbide, moderate surface speed with generous feed, and flood coolant — and never let the tool dwell. Forming inverts the picture entirely. CDA rate the wrought grades Excellent for hot forming and Poor for cold working, and C67400 carries a forgeability rating of 100, equalling C37700 forging brass, the CDA reference. C67500 and C67600 follow at 80. Forge or extrude to near net shape, then machine.
Composition, machinability and forgeability data from the Copper Development Association alloy records; zinc, aluminium and lead figures are read directly from the individual grade pages. Machinability and forgeability are on the CDA scales where C36000 free-cutting brass = 100 and C37700 forging brass = 100 respectively.
| Grade | Designation | Form | Zinc % | Aluminium % | Lead % | Machinability | Forgeability | Chosen For |
|---|---|---|---|---|---|---|---|---|
| C67000 | Manganese Bronze B | Wrought | Rem | 3.0–6.0 | 0.20 max | — | — | High-Al forgings — CDA data is composition only |
| C67300 | Leaded Silicon Mn Brass | Wrought | Rem | 0.25 max | 0.40–3.0 | — | — | Anti-galling bushings; widest lead range here |
| C67400 | Silicon Manganese Brass | Wrought | Rem | 0.50–2.0 | 0.50 max | 30 | 100 | Forgeability 100; anti-galling bushings |
| C67500 | Manganese Bronze A | Wrought | Rem | 0.25 max | 0.20 max | 30 | 80 | ASTM F468 Cu 675 — the reference grade |
| C67600 | Leaded Manganese Bronze A | Wrought | Rem | — | 0.50–1.0 | 60 | 80 | C67500 plus lead — machinability doubles to 60 |
| C86100 | Cast Mn Bronze, High Strength | Cast | Rem | 4.5–5.5 | 0.20 max | 30 | — | Highest cast copper content; 655 MPa, 180 HB |
| C86200 | Cast Mn Bronze, 4% Al | Cast | 22.0–28.0 | 3.0–4.9 | 0.20 max | 30 | — | C86300 chemistry at lower Al — 4× the machinability |
| C86300 | Cast Mn Bronze, Highest Strength | Cast | 22.0–28.0 | 5.0–7.5 | 0.20 max | 8 | — | 758 MPa min, machinability 8 — documented on the brass hub |
| C86400 | Leaded Cast Mn Bronze | Cast | 34.0–42.0 | 0.50–1.5 | 0.50–1.5 | 65 | — | Machinability 65, best here; Izod 30 ft-lb |
| C86500 | Cast Mn Bronze, General Purpose | Cast | 36.0–42.0 | 0.50–1.5 | 0.40 max | 26 | — | Most ductile cast grade — 30% elongation |
Read the aluminium column, then the lead column — between them they explain every row. Aluminium splits the hub: the 0.25–2.0% grades are moderate-strength and workable, the 3.0–7.5% grades are hard and strong. Lead sets machinability: C86400 at 65 and C67600 at 60 are the leaded grades, against 8 for C86300 — the lowest CDA machinability figure anywhere on this site. C67500, Manganese Bronze A, is the reference grade and the only one in ASTM F468, as Cu 675: 379–586 MPa with 172 MPa minimum yield and 20% minimum elongation. C67400 carries a forgeability rating of 100, equal to C37700. Note the C67000 row: CDA publish composition, four physical properties and a specification list for it and nothing else — no mechanical, fabrication or thermal data — and we have not substituted figures from the cast high-aluminium grades, which are a different product form. Finally, C86300 is listed here but its page lives on the brass hub, where CDA's own classification places it; that row links there rather than duplicating the page. Every grade on this hub is a 22–42% zinc brass and none is inhibited against dezincification.
We are committed to delivering zero-defect manganese bronze forgings, castings, fasteners and machined components. All products undergo rigorous testing including PMI (Positive Material Identification), chemical analysis with zinc, aluminium, manganese, iron and lead certified explicitly — zinc sets the dezincification exposure, aluminium splits the family into its machinable and high-strength halves, and lead governs machinability and regulatory acceptability under the Safe Drinking Water Act and RoHS. ISO 6509 dezincification testing on request, since no grade in this family is inhibited; low-temperature stress relief on cold-worked and threaded parts; mechanical and hardness verification against the temper or cast condition supplied; dimensional inspection and full traceability with EN 10204 3.1 certification.
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