TM23 bronze – high-lead bearing bronze
Cu-Pb-Zn-Sn leaded bronze (≈ 73-15-8-4) for bushings and bearing shells
TM 23 is the trade designation of a high-lead bronze created by Termomecanica, with about 73% copper, 15% lead, 8% zinc and 4% tin (typical manufacturer values). Lead gives semi-self-lubricating behavior: the alloy tolerates poor lubrication, dry starts, high torque and low speed. It has no UNS number of its own; it is sold as bushings, billets, hollow bars and bearing shells.
Designations and equivalents
| System | Designation |
|---|---|
| Trade names | TM 23, TM-23 (Termomecanica), "universal bronze" |
| Others | No official ASTM/SAE equivalent; similar family: leaded bearing bronzes (UNS C93700 / SAE 64, C93800)* |
Standards by product form
| Form | Standard |
|---|---|
| Bar, billet and hollow bar (bushing) | Manufacturer specification (Termomecanica) |
| Cast (bearing shells) | Manufacturer specification; tensile per ASTM E8 |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7407.29.10 | 7407.29 | 7407.29.5000 | 7407 29 00 |
| Hot-rolled bar | 7407.29.10 | 7407.29 | 7407.29.5000 | 7407 29 00 |
Tariff class: other copper alloys (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
Termomecanica – typical values (not a standard range); distributor limits in parentheses
| Element | Range (%) |
|---|---|
| Cu | ≈ 73 (≥ 70) |
| Pb | ≈ 15 (≤ 20) |
| Zn | ≈ 8 (≤ 9) |
| Sn | ≈ 4 (≥ 4) |
Mechanical properties
Cast, round test bar Ø 25 mm – typical Termomecanica values (not guaranteed); bearing shells in parentheses
| Property | Value |
|---|---|
| Tensile strength | 275 MPa (shells: 150 – 230 MPa) |
| Yield strength | 157 MPa (shells: 100 – 150 MPa) |
| Elongation | 23% (shells: 4 – 16%) |
| Reduction of area | 17% |
| Hardness | 75 HB (shells: 55 – 75 HB) |
| Charpy impact | 18 J/cm² |
Typical physical properties
| Property | Value |
|---|---|
| Density | 9.03 g/cm³ |
| Melting point | ≈ 940 °C |
| Thermal conductivity | ≈ 71 W/m·K |
| Electrical conductivity | ≈ 15% IACS |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Not stated by the manufacturer. In bearings, temperature is usually limited by the lubricant; sugar mill shells may have an internal cooling coil to extend service life. |
| Heat treatment | Not hardenable by heat treatment: properties come from composition and casting. Lead stays dispersed as globules in the bronze matrix. |
| Welding | Sources disagree (one distributor cites good weldability). High-lead bronzes tend to hot crack in fusion welding; treat repair of bushings and shells case by case*. |
| Machining | Excellent: lead breaks the chip. One distributor reports better machinability than free-cutting brass. |
Typical applications
- Bronze bearing shells for sugarcane mills
- Bearing bushings with rotating shafts, high torque and low speed
- Bearings with poor lubrication or dry starts
- Machinery for the metallurgical and sugar-ethanol sectors
- Parts machined from billet and hollow bar
Alternatives: TM 620 (Termomecanica, ≈ 87% Cu, 8% Sn, 4% Zn, 1% Pb) when lubrication is good and speed is higher; aluminum bronze C95400 or C63000 for shock loads and severe wear; standardized leaded bronzes (UNS C93700 / SAE 64)* when the order requires an ASTM standard.
TM23 bronze: complete guide
What TM 23 bronze is
TM 23 was created and patented by Termomecanica and got its name because it was the 23rd composition tested, the best performing one. It is a leaded bronze: copper with tin and zinc forming the matrix and lead dispersed as globules. It belongs to the copper alloys used in plain bearings.
Why lead matters in bearings
Lead does not dissolve in copper and stays as small particles. When the oil film fails, as at machine start-up, these particles smear on the surface and reduce friction, preventing shaft seizure. The alloy also has good embeddability: it accommodates hard particles and small shaft misalignments. In exchange, strength is lower than that of tin bronzes and aluminum bronze.
Supply
Dustre quotes bushings, bars and machined parts to drawing, with a material certificate and a clear statement of alloy and origin. To replace TM 23 with an ASTM alloy, tell us the bearing operating conditions (load, speed and lubrication).
Frequently asked questions
What is the chemical composition of TM23 bronze?
Per Termomecanica – typical values (not a standard range); distributor limits in parentheses: Cu ≈ 73 (≥ 70); Pb ≈ 15 (≤ 20); Zn ≈ 8 (≤ 9); Sn ≈ 4 (≥ 4).
Which standards cover TM23 bronze?
Bar, billet and hollow bar (bushing): Manufacturer specification (Termomecanica). Cast (bearing shells): Manufacturer specification; tensile per ASTM E8.
Up to what temperature can TM23 bronze be used?
Not stated by the manufacturer. In bearings, temperature is usually limited by the lubricant; sugar mill shells may have an internal cooling coil to extend service life.
Which materials can replace TM23 bronze?
TM 620 (Termomecanica, ≈ 87% Cu, 8% Sn, 4% Zn, 1% Pb) when lubrication is good and speed is higher; aluminum bronze C95400 or C63000 for shock loads and severe wear; standardized leaded bronzes (UNS C93700 / SAE 64)* when the order requires an ASTM standard.
What is TM 23 bronze?
It is a high-lead bronze from Termomecanica, with about 73% Cu, 15% Pb, 8% Zn and 4% Sn. The name comes from the 23rd composition tested by the company founder, Salvador Arena. It is used in bushings and bearing shells working with little lubrication, high torque and low speed.
Does TM 23 have an ASTM or SAE equivalent?
There is no official equivalent: TM 23 is a trade designation with no UNS number of its own. Standardized leaded bronzes such as UNS C93700 (SAE 64) serve a similar function in bearings, but have a different composition*. If the design calls for an ASTM standard, specify the UNS alloy instead of the trade name.
What is the difference between TM 23 and TM 620?
TM 23 has ≈ 15% lead and suits poor lubrication, high torque and low speed. TM 620 has ≈ 8% tin and only ≈ 1% lead: it is stronger (typical tensile 350 MPa, 92 HB) and suits well-lubricated bearings at higher speed and medium to high loads.
