UNS C93200 bronze
Selecting leaded tin bearing bronze by casting route, property basis, lubrication system and finished-component requirements.
Tags: materials, copper-alloys, bronze, bearings
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C93200 is a leaded tin bronze commonly called SAE 660 bearing bronze.
Identity and chemistry
Concast's ASTM B505/B505M-23 continuous-cast C93200 lists 35 ksi minimum tensile and 20 ksi minimum yield. St. Paul Foundry's F as-cast summary gives 30 ksi and 14 ksi. Both yield headings use 0.5% extension under load. Confirm casting route and specimen requirements before using either table. Concast continuous-cast properties, St. Paul Foundry F-condition properties
St. Paul Foundry lists C93200 aliases including SAE 660 and 83-7-7-3. Those historical or nominal descriptions are useful identification aids, not substitutes for complete chemistry limits or a current product specification. Its page identifies ASTM B584 as a nearby casting standard and gives separate specification-property and typical-property sections. Preserve the distinction between a standard reference and actual certification of an ordered casting. St. Paul Foundry, C93200 technical data
Wieland Concast's continuous-cast sheet gives 81–85% copper, 6–8% lead, 6.3–7.5% tin and 2–4% zinc, with additional element limits. Its footnote allows nickel to be included when determining minimum copper and says the nickel value includes cobalt. A simplified four-element nominal composition therefore omits important acceptance details. The sheet identifies its chemistry basis as ASTM B505/B505M-23. Concast, C93200 sheet
Casting route changes the property basis
The sources below illustrate different declared bases:
| Source and condition | Minimum tensile strength | Minimum yield strength | Minimum elongation |
|---|---|---|---|
| Concast continuous-cast C93200; B505/B505M-23 basis | 35 ksi / 241 MPa | 20 ksi / 138 MPa | 10% |
| St. Paul Foundry specification summary; F as-cast | 30 ksi | 14 ksi | 15% |
Concast defines yield at 0.5% extension under load, with elongation over 2 inches or 50 mm. It separately lists 65 BHN as typical, using a 500 kg load. These are not all minimum requirements, and the yield result must not be relabeled 0.2%-offset proof stress. Concast, mechanical-property table
St. Paul's heading also defines yield by 0.5% extension under load and elongation over 2 inches. Its typical hardness is separate from the F-condition strength minima. Confirm specimen location and the governing ordered specification before using either supplier summary for acceptance. St. Paul Foundry, specification and typical properties
US Bronze Foundry & Machine's chart presents another information category: a typical mechanical-properties table with a C93200 nominal 83 Cu / 7 Sn / 7 Pb / 3 Zn row and 30,000 psi tensile, 14,000 psi yield, 15% elongation and 65 BHN. Numbers resembling another source's minima remain typical when that is their declared basis. Do not choose the largest published value or erase the casting and test context. US Bronze Foundry & Machine, Bronze Alloy Chart
Lead helps bearing behavior but does not replace lubrication
The Non-Ferrous Founders' Society's Cast Copper Alloy Sleeve Bearings guide discusses leaded tin bronzes' conformability, scoring resistance and tradeoffs with strength and resistance to pounding. It identifies C93200 as a broadly used alloy within that family. Those characteristics do not make every C93200 bearing self-lubricating or establish indefinite operation without oil or grease.
The guide treats boundary, mixed-film and full-film bearing operation separately. Select the lubrication regime against actual motion, lubricant supply and heat removal rather than attaching a single speed or load rating to the alloy name. NFFS, Cast Copper Alloy Sleeve Bearings, hosted by National Bronze
The drawing and operating specification should identify shaft material/finish, bearing length and diameter, installed clearance, housing fit, lubricant and supply method, start/stop frequency, alignment, contamination and allowable wear. A groove layout is part of that design; it should not be copied from an unrelated sleeve solely because its alloy matches.
A calculation is not an operating approval
The NFFS guide defines projected bearing pressure from load divided by projected area and discusses the pressure–velocity product, PV, in bearing assessment. It also shows that bearing temperature, friction and lubrication influence operating limits. PV is therefore a screening quantity, not an independent guarantee of life. NFFS, bearing operating and design considerations
Illustrative calculation only: assume a radial sleeve with 25 mm journal diameter, 25 mm bearing length, 1,000 N steady radial load and 300 rpm. Projected area is 25 × 25 = 625 mm²; average projected pressure is 1.6 MPa. Journal surface speed is π × 0.025 × 300 / 60 = 0.393 m/s, giving PV approximately 0.628 MPa·m/s. This example establishes arithmetic only. It assumes steady load and rotation and omits lubricant-film analysis, temperatures, grooves, misalignment and transient loads. No allowable PV or service life is assigned here.
Exposure, corrosion and finishing
Treat fluid compatibility separately from sliding performance. The bearing guide includes compatibility with working fluids as a material-selection issue; an application's lubricant, process liquid, contaminants and temperature must be considered together. A broad “corrosion-resistant bronze” description cannot qualify arbitrary chemical, seawater or food-contact service. NFFS, material selection and working fluids
For machining and release, inspect the final bore, outside diameter, concentricity, surface finish and groove details against the installed-fit requirements. Specify acceptance of exposed casting discontinuities rather than relying on a raw-stock certificate. Keep joining, coating or impregnation permissions explicit where they affect the application.
Lead-bearing material needs process-specific handling
Concast's Leaded Tin Bronze Alloys SDS number 6, which explicitly includes C93200, is version 03, revised April 29, 2022, originally issued November 5, 2012. It distinguishes massive metal from fine dust and describes dust/fume exposure associated with mechanical work or heating. It calls for avoiding dust accumulation and inhalation, industrial hygiene, protective equipment and exposure controls; fine metallic dust can also present a combustion hazard. Use the applicable SDS and workplace controls for machining, grinding, melting and waste handling rather than treating the intact stock and airborne material as equivalent. Concast, Leaded Tin Bronze Alloys SDS
The intentional lead content also makes “lead-free” substitution a material change. Verify the replacement's machining, dimensional, bearing and application requirements instead of assuming one designation is a universal substitute for another.
Purchase and release record
Retain batch identity, complete chemistry, casting route, standard edition, test definitions and required inspection results. Separate informative typical properties from contractual minima and approved design values. Confirm lubrication, installed geometry and environmental suitability on the finished assembly. No publication dates are inferred from the undated supplier webpages or the bearing-guide filename.