Plain Bearings – Copper Alloy Bearings with Embedded Solid Lubricants: Technical Requirements, Performance Testing, and Material Selection – An In-Depth Analysis Based on GB/T 23894-2009 (Technical Clarification & Application Guide)

1. Insight: The Role of the Reference Standard and Its Limitations

GB/T 23894-2009, Plain bearings – Copper alloy bearings with solid lubricant, is the core national recommended standard for such products in China. It was issued on May 26, 2009, and came into effect on December 1, 2009, under the supervision of SAC/TC 236 (National Technical Committee on Plain Bearings of Standardization Administration of China). The standard non-equivalently adopts ISO 4379:1993 and specifies the structural types, basic dimensions, technical requirements, and test methods for bearings made by embedding solid lubricants into copper alloy matrices conforming to GB/T 1176.

Revision note: The standard was reviewed on August 6, 2025, with the conclusion “to revise”. The new revision plan No. 20254218-T-604 intends to rename it Plain bearings – Metal‑based bearings with embedded solid lubricants, expanding the matrix from copper alloys to a broader metal base and modifying adoption of ISO 19259:2021.

The standard’s core technical indicators are based on the copper alloy ZCuZn25Al6Fe3Mn3 (high‑strength brass) as the reference matrix material. However, Clause 4.1 explicitly states that “other matrix metal materials shall be agreed upon between the user and the manufacturer.” Therefore, the matrix is not limited to this single alloy. In industrial practice, tin bronzes (e.g., ZCuSn12Ni2), aluminium bronzes (e.g., ZCuAl10Fe5Ni5), and lead bronzes (e.g., ZCuPb20Sn5) are also widely used, each with distinct performance characteristics.

Technical clarification: For products claiming compliance with GB/T 23894-2009 but using a matrix other than ZCuZn25Al6Fe3Mn3, the specific matrix must be agreed upon and documented. The core mechanical properties, permanent compression set, and friction‑wear endurance shall still meet the corresponding requirements of the standard.

2. Dissection: Deep Interpretation of Key Technical Requirements

2.1 Chemical composition of the matrix

The reference material ZCuZn25Al6Fe3Mn3 shall comply with GB/T 1176. Although the standard cites GB/T 1176-1987 (now superseded by GB/T 1176-2013), the grade is retained in the current version. According to GB/T 1176-2013, the chemical composition (wt.%) of ZCuZn25Al6Fe3Mn3 is: Cu balance, Zn 23.0–28.0, Al 5.0–7.0, Fe 2.0–4.0, Mn 2.0–4.0, total impurities ≤1.0%. For other matrices agreed upon, chemical composition is subject to the supply agreement.

2.2 Mechanical properties of the matrix

Regardless of the matrix chosen, the copper alloy must simultaneously meet the following verifiable minimum requirements:

• Tensile strength σb ≥ 740 N/mm²

• Percentage elongation after fracture δ ≥ 10%

• Brinell hardness HB ≥ 210

These values are mandatory and can be verified according to GB/T 228 and JB/T 7925.1.

2.3 Permanent compression set

Using a cylindrical specimen φ15 × 15 mm, apply a compressive stress of 300 N/mm², hold for 30 seconds, then unload. The permanent height reduction shall be ≤ 0.03 mm. Test conditions: platens hardened to ≥55 HRC, specimen ends parallel and perpendicular to axis, light grease on platens, loading increment ≤30 N/mm², final load approx. 53 kN.

2.4 Friction‑wear endurance performance

Test conditions: oscillating angle ±45°, linear speed 1 m/min, bearing pressure 24.5 MPa, test duration 100 h (or earlier termination if friction/temperature surges or temperature limit is reached). Initial lubrication: one‑time application of lithium grease No.2 on the inner surface. Acceptance criteria:

• Coefficient of friction ≤ 0.15

• Wear amount ≤ 0.05 mm (measured as the maximum wall thickness reduction at multiple points)

• Final specimen temperature ≤ 130°C

2.5 Dimensional tolerances and surface roughness

Shaft journal hardness ≥40 HRC, roughness ≤ Ra0.8; bearing working surface roughness ≤ Ra1.6. Coaxiality (outer diameter relative to inner diameter): grade 8 according to GB/T 1184.

2.6 Appearance and solid lubricant bonding

Surface shall be uniform in colour, free from cracks, pores, slag, burrs, sharp edges, significant scratches, impact marks, or rust. The solid lubricant plug shall show no loosening under a 50 N applied force and no cracking on its surface. (Note: The standard does not specify the exact test fixture for the 50 N force; method shall be agreed upon.)

3. Perspective: Multi‑dimensional Comparison of Matrix Materials

3.1 High‑strength brass – reference material

3.2 Aluminium bronzes – high temperature & corrosion resistance

3.3 Tin bronzes – seawater & reduced friction

3.4 Lead bronzes – self‑lubricating & vibration damping

4. Elaboration: Selection Framework & Practical Recommendations

4.1 Four‑dimensional selection matrix

4.2 Updated test method standards

Several test method standards cited have been superseded; use the latest versions (technical values unchanged):

• Tensile/elongation: GB/T 228-2002 → GB/T 228.1-2021

• Tolerances: GB/T 1800.4-1999 → GB/T 1800.2-2020

• Hardness: JB/T 7925.1-1995 → GB/T 231.1 (equivalent)

• Chemical analysis: GB/T 5121 series remains valid.

4.3 Solid lubricant selection note

Common solid lubricants include graphite (dry atmosphere) and PTFE + MoS₂ composites (suitable for underwater or seawater). Lubricant plugs are evenly distributed in holes (typically φ0.5–1.5 mm) covering 20–30% of the bearing surface. The lubricant type should be agreed based on operating temperature, humidity, and medium.

5. Conclusion: Verifiable, Non‑exaggerated Technical Basis

Based on GB/T 23894-2009 and supporting technical data, the following statements are clear, verifiable, and free from exaggeration or inconsistency:

1. Matrix is not limited to ZCuZn25Al6Fe3Mn3 – other copper alloys may be used by agreement, but mechanical properties must meet the standard’s requirements.

2. Mechanical properties are mandatory – σb ≥ 740 MPa, δ ≥ 10%, HB ≥ 210.

3. Permanent compression set ≤ 0.03 mm (300 MPa, φ15×15 specimen) is a clear pass/fail criterion.

4. Friction‑wear endurance – μ ≤ 0.15, wear ≤ 0.05 mm, final temperature ≤130°C – is repeatable on an oscillating test rig.

5. Tolerance and fit system is complete, based on GB/T 1800 series.

6. GB/T 23894-2009 is currently active but under revision (planned as “Metal‑based bearings with embedded solid lubricants”). Users are advised to monitor the revision.

7. Different copper alloys suit different conditions – never select by tensile strength alone; consider corrosion resistance, temperature capability, and cost.

Customised products and material options (e.g., high‑strength brass, tin bronze ZCuSn12Ni2, aluminium bronze ZCuAl10Fe5Ni5, lead bronze ZCuPb20Sn5, with embedded solid lubricants) can be tailored to your actual operating conditions – load, temperature, corrosive environment, lubrication availability. Please consult our engineers for selection assistance.

Disclaimer: This document is a technical summary and clarification based on the public text of GB/T 23894-2009 and related technical sources. It is for engineering reference only and does not constitute a standard interpretation, product warranty, or legal advice. Some referenced standards (e.g., GB/T 1176-1987, GB/T 228-2002, GB/T 1800.4-1999) have been superseded; readers should verify the current valid versions. Material properties may vary depending on casting process, heat treatment, lubricant distribution rate, etc. Actual product design, inspection, and acceptance shall be based on the latest official standard text and the mutual technical agreement. The selection suggestions provided are for reference only; small‑scale validation before mass production is recommended.