Phosphor Bronze and Brass for Bearings and Bushings

Two wrought copper families share one commercial habit: they are ordered for bushings because they are available, cheap and easy to machine, not because they were selected against a load calculation. Brass in particular is the most common wrong answer in light-duty bearing work. This page covers the six wrought brasses and the two wrought tin phosphor bronzes that appear in that conversation, with the numbers that show where each one stops working.

Scope: wrought CuSn6.5-0.1 (C51900), wrought CuSn10P (C52400 family) and wrought brasses from CuZn37-CuZn40 down to CuZn10.  |  Sources: CDA alloy database, ASTM B36/B121/B139/B150, EN 12163/12166/12167, GB/T 5231, GB/T 1176.  |  Last reviewed: September 2026.

Grades in this family

The eight grades below are the wrought copper alloys that reach bushing drawings most often without a stated load case. Two of them are bronzes; six are brasses. The distinction matters more than the ordering, because the two bronzes work as bearing materials on their own terms while the six brasses are, with narrow exceptions, structural or conductive materials that also happen to be machinable into a sleeve.

Cross-standard entries are comparable, not identical. The GB/T 5231 H-series and QSn-series designations do not map one-to-one onto the UNS or EN schemes: H62 sits between CuZn37 and CuZn40, and the two QSn grades differ from their nearest western counterparts in residual and phosphorus limits. Where a drawing names a standard, that standard governs.

Where brass belongs, and where it does not

A bushing is a wear part. Its job is to absorb sliding contact, shed heat, tolerate a little misalignment and take the wear instead of the shaft. Brass does the first and the third passably, the second well and the fourth poorly. The reason is structural: brass is a solid-solution copper-zinc alloy. It has no soft phase to embed contamination and no hard phase to resist abrasion, so it cannot bed in to a misaligned shaft and it cannot carry abrasive particles away from the contact. Two consequences follow.

• Brass is limited by speed and by lubrication, not by nominal pressure. Its reference PV ceiling is the lowest in the plain-bearing family, roughly two to three times below a leaded tin bronze and three times below a bearing-grade aluminium bronze. At the pressures a brass sleeve can nominally sustain, the failure mode at excessive sliding speed is scuffing, not plastic collapse.
• Brass transfers wear to the shaft. Hardness of 75-140 HB against a hardened steel journal produces shaft-side polishing or scoring when lubrication is marginal. Tin bronzes of similar nominal strength behave better here because their soft phase protects the counterface.

What brass does well in a bearing assembly is real, and worth stating precisely. It machines to close tolerance without special tooling, it is dimensionally stable, it tolerates intermittent operation, it is non-magnetic, and it is inexpensive. Those properties make it the practical answer for thrust washers, retainer and cage components, bushings in instruments, low-speed pivots, hinge pins, cable and linkage guides, and small electrical or hardware assemblies where the load is measured in newtons rather than kilonewtons.

Composition

The brasses are described by their copper content; the remainder is zinc. The two bronzes contain tin and phosphorus, with no deliberate zinc addition. Impurity windows matter commercially because they drive cost: the tight lead and iron limits of the higher-copper brasses are a large part of why H90 costs roughly twice what H62 costs for the same mass.

Single values are maxima. The wrought and cast phosphor bronze rows are shown separately because their phosphorus windows differ; see the phosphor bronze section below.

Mechanical properties and temper

For wrought copper alloys the temper designation changes the numbers more than the grade does. A hard-temper CuZn30 strip and an annealed CuZn30 tube are the same alloy and differ by roughly 200 MPa in tensile strength and by 50 percentage points in elongation. Any table of wrought properties that omits the temper is therefore only an indication of the grade’s position in the family, not a design input.

Bands are indicative ranges drawn from published product data for the comparable western grades, rounded to 10 MPa. The material certificate supplied against the finished order governs, and measured values for a specific lot usually sit above the lower edge of each band.

Two features of the table are worth reading against each other. First, tensile strength across the yellow brasses H62 to H70 is nearly flat: raising copper from 62 % to 70 % at fixed temper does not buy load capacity. Second, below that band the trend reverses, and the two copper-rich grades H85 and H90 lose about a quarter of the strength of H70 while gaining most of the conductivity. The family is therefore not a strength ladder that can be climbed by paying more; it is a trade between load, conduction and corrosion behaviour.

The two wrought phosphor bronzes

Tin phosphor bronzes are the wrought members of this page that are genuine bearing materials. Phosphorus serves two functions: it deoxidises the melt, and above the solubility limit it forms hard Cu₃P particles that raise hardness and wear resistance at the cost of ductility. Tin provides solid-solution strengthening and, at higher levels, a hard tin-rich phase.

CuSn6.5-0.1 / C51900 / CuSn6P

The 6.5 % tin, low-phosphorus grade is the workhorse of thin-wall wound bushings and precision sleeves. Its combination of moderate tin content with a tightly controlled phosphorus window gives a material that cold-forms well, holds tolerance, runs quietly and shows no magnetic response. Typical duties are machine-tool spindle sleeves, guide bushes, instrument bearings and spring-loaded wear pads. Below 62 dB surface-generated noise levels are quoted for well-finished sleeves in this grade, which is why it appears in measuring and optical equipment where a plain brass or a hardened steel sleeve would transmit more vibration.

CuSn10P / QSn10-1 and the cast counterpart ZCuSn10P1

The 10 % tin grade is the hardest wrought bronze on this page and the one most often specified for solid and continuously cast bushes in medium-speed, high-load service: connecting-rod bushes, worm-wheel rims, rolling-mill and general machine bearings. Its limit in this family is not strength but the phosphorus window.

The practical selection rule between the two bronzes is the one you would expect from their hardness. Where the duty is thin-wall, close tolerance, low load and low noise, the 6.5 % tin grade is the easier material to hold. Where the duty is a solid bush under real specific pressure, the 10 % tin grade carries it and the 6.5 % grade does not.

Conductivity, machining and relative cost

Thermal conductivity is the reason the copper-rich brasses exist, and it is also the property that most often argues for brass in a bearing assembly: a brass sleeve conducts heat out of the contact zone two to three times faster than a tin bronze of similar hardness. That helps at low and moderate sliding speeds. It does not compensate for the absence of a bearing structure at high speed, because the heat generated rises faster than conduction removes it.

Machinability ratings follow the published CDA scale referenced to free-cutting brass C36000 = 100. Supplier literature sometimes quotes higher figures for the H-series; the CDA figures are used here so that the brasses and the bronzes on this page are measured on one basis. Relative cost index is an internal comparison across this site’s material pages, where 5 is the highest-cost group; it is not a price and not a quotation input.

Note the interaction between the last two columns. The two grades with the highest conductivity are also the two that machine least readily, because their low zinc content makes the chip gummy. Machining brass is not the same operation across the family: H62 and H65 cut freely with light feeds and good chip breakage, H90 requires sharper edges, higher rake and more attention to chip control. Where a part must both conduct heat and be produced in volume from bar, the compromise usually lands on H65 or H70 rather than on H90.

Load, speed and PV

Sliding contact is limited by the product of pressure and speed, not by either alone. The figures below are reference ceilings used for first-pass selection in this family. They are not design allowables, and they vary between suppliers, lubrication regimes and shaft finishes.

Reference values, not design allowables. Two conversions and two derating rules apply before use. 1 N/mm²·m/min equals 0.0167 MPa·m/s, so mixed-unit catalogue tables must be converted before comparison. Halve the catalogue PV for a first-pass design, then derate further for oil-free running, elevated temperature, a soft or rough journal, and for oscillating rather than continuous motion. Compare the result against the shaft material and finish as well: a brass sleeve demands a smoother journal than a bronze bush does, because it cannot bed in around a rough profile.

Dezincification and stress-corrosion cracking

Two corrosion mechanisms decide whether a brass part survives a wet environment, and both scale with zinc content. That single fact explains the ordering of the family’s corrosion behaviour, and it is more useful than any qualitative label.

• Dezincification. In stagnant or slowly moving chloride solutions, zinc dissolves selectively and leaves a porous copper-rich layer that retains the original dimensions while losing most of its strength. Risk rises with zinc content and with temperature, so CuZn37-CuZn40 grades in warm seawater or stagnant brackish water are the exposed end of the family. Water-service grades carry small arsenic, antimony or phosphorus additions to inhibit the mechanism; those additions are a water-service feature and do not turn the grade into a bearing material.
• Stress-corrosion cracking. Ammonia and ammonium-bearing environments attack cold-worked or press-fitted yellow brasses along residual tensile stress. Part failures of this type appear as branching cracks, not as general wastage. The standard countermeasures are a stress-relief anneal at about 250-300 °C after forming, avoidance of ammonia-bearing cleaners, fluxes and lubricants, and preference for the low-zinc grades where the environment cannot be controlled. H85 and H90 show the least tendency of the group.

For seawater bearings the honest answer is that this family is the wrong place to look. Aluminium bronze and nickel aluminium bronze exist for that duty, and both the corrosion behaviour and the load capacity are in a different class. See aluminium bronze for bearings for that comparison.

Selection guidance

Two notes that change the numbers

Related material pages

FAQ

Can brass be used for a bushing?

Yes, within limits. Wrought brasses such as CuZn30 (C26000) serve light-duty bushings, thrust washers, retainer cages and low-speed pivots where lubrication is reliable. They carry no hard second phase, so they are limited by speed and by boundary-lubrication conditions rather than by nominal pressure alone. Their reference PV ceiling is the lowest in the plain-bearing family.

What is the difference between H62, H65, H68, H70, H85 and H90?

They are wrought copper-zinc alloys differing mainly in copper content: 60.5-63.5 % (H62), 63.5-68.0 % (H65), 67.0-70.0 % (H68), 68.5-71.5 % (H70), 84.0-86.0 % (H85) and 88.0-91.0 % (H90). Rising copper raises thermal and electrical conductivity and lowers stress-corrosion susceptibility, while tensile strength of the yellow brasses peaks in the 60-70 % copper band and falls again towards H90.

Why do H85 and H90 exist if their strength is the lowest of the group?

Because they are specified for conduction and forming, not for load. CuZn15 (C23000) and CuZn10 (C22000) reach roughly 152-189 W/(m·K) thermal conductivity and 37-44 % IACS, are easily brazed and soldered, and show little tendency to stress-corrosion cracking. They appear in heat-exchanger and condenser tube, electrical terminals and decorative hardware.

Is CuSn6.5-0.1 a bronze or a brass?

It is a wrought tin phosphor bronze, not a brass. The GB/T 5231 designation CuSn6.5-0.1 corresponds closely to copper alloy C51900 and to CuSn6P (CW452K). It contains tin and phosphorus with no deliberate zinc addition. Chinese catalogue listings sometimes group the QSn and H designations together under one heading, which is where the confusion originates.

What is the difference between wrought CuSn10P and cast ZCuSn10P1?

Both are high-tin phosphor bronzes with about 9-11 % tin, but the phosphorus window differs: the cast grade is commonly specified at 0.5-1.0 % P while the wrought designation is quoted at 0.8-1.2 % P. Phosphorus forms hard Cu₃P particles, so the level materially changes hardness and wear behaviour. State the standard on the drawing and do not treat the two as interchangeable without confirming the analysis on the material certificate.

Do brass bushings dezincify in seawater?

Yellow brasses can lose zinc selectively in stagnant or slowly moving chloride solutions, leaving a porous copper-rich layer. Risk rises with zinc content, so CuZn37-CuZn40 grades are the most exposed and CuZn15-CuZn10 the least. Inhibited versions (small arsenic, antimony or phosphorus additions) exist for water service. For seawater bearings, aluminium bronze or a nickel aluminium bronze is the usual route instead.

Why do brass parts crack in service?

Stress-corrosion cracking in ammonia and ammonium-bearing environments. Cold-worked or press-fitted parts carry residual tensile stress, and yellow brasses are sensitive to it. Mitigations are a stress-relief anneal at roughly 250-300 °C after forming, avoidance of ammonia-bearing cleaners and lubricants, and a lower-zinc grade where the environment cannot be controlled.

Which property should be printed on the drawing for a wrought bushing grade?

The temper, alongside the grade. The spread in tensile strength and elongation between the annealed and hard tempers of one wrought copper alloy is wider than the spread between neighbouring grades. A drawing that names only CuZn30 or CuSn6.5-0.1 leaves the strength of the finished part undefined.