Overview
ISO 4381:2011 - Plain bearings - Tin casting alloys for multilayer plain bearings specifies requirements for bearing metals based on tin casting alloys used in multilayer plain bearings. The standard defines the chemical composition and material properties of the original unprocessed casting alloy (representative samples). It notes that test results on finished bearings can differ because of production effects and therefore should not be directly compared with the raw-material data in ISO 4381:2011.
Key topics and requirements
- Material scope: Tin-based casting alloys intended for multilayer plain bearings; principal alloy designated SnSb8Cu4.
- Chemical composition: Element limits are specified (example: Sb 7–8 %, Cu 3–4 %, remainder Sn) and strict impurity limits (Pb, As, Bi, Fe, Al, Zn, Cd, total others). Chemical analysis is decisive for acceptance.
- Material properties: Typical values provided for designers, measured on the unprocessed material. Included properties:
- Brinell hardness at 20 °C and 100 °C (measured per ISO 4384-2)
- Tensile and compressive yield stress and tensile strength at 20 °C (typical mean values)
- Bond strength (to be assessed per ISO 4386-2)
- Rotating bar bending fatigue (tested according to ISO 1143)
- Linear thermal expansion, melting and casting temperatures, and density
- Designation: Example format - Bearing metal ISO 4381 - SnSb8Cu4.
- Selection guidance: Annex A provides practical guidance on use and recommends minimum mating-shaft hardness (for SnSb8Cu4 the shaft minimum is 160 HB) to avoid welding under operating conditions. Lubrication and working conditions affect shaft material choice.
Applications and users
ISO 4381:2011 is relevant to:
- Bearing designers and mechanical engineers working on multilayer plain bearings
- Manufacturers of bearing alloys and multilayer bearing components (casting, bonding, machining)
- Quality and inspection personnel performing material acceptance testing for tin casting alloys
- OEMs in heavy industry (e.g., rolling mills), automotive, and machinery where tin-based bearing layers (good conformability, embeddability and high sliding performance) are specified
Practical use cases include selection of alloy for high-load sliding surfaces, wrapped bushes, thin-walled liners (up to ~3 mm), and thrust washers where SnSb8Cu4 properties are advantageous.
Related standards
- ISO 4384-2 - Hardness testing of bearing metals (solid materials)
- ISO 4386-1, -2, -3 - Testing and inspection of metallic multilayer plain bearings (ultrasonic, destructive bond testing, penetrant testing)
- ISO 1143 - Rotating bar bending fatigue testing
Keywords: ISO 4381:2011, tin casting alloys, SnSb8Cu4, multilayer plain bearings, bearing metals, chemical composition, Brinell hardness, bond strength.
