Cu-Sn-Bi Sliding Material with Nonuniform Bismuth Distribution
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Solution Overview
Problem
Existing Cu-based sliding materials face challenges in recycling due to the presence of lead, which is environmentally hazardous, and require lubricating oil for optimal performance, leading to issues like reduced bonding strength and work hardening during manufacturing.
Innovation Solution
A sliding material with a sintered layer comprising 5-15 mass % elemental Bi nonuniformly distributed in a Cu-Sn alloy matrix, eliminating the need for oil grooves and enhancing bonding strength and lubrication by forming minute depressions for oil accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If lead bronze is used as a Cu-based bearing alloy, then good sliding properties and low cost are achieved, but environmental pollution from lead dissolution occurs
Solution Approach 1:
The patent replaces lead (Pb) with bismuth (Bi) as the lubricating element in the Cu-Sn alloy matrix. This parameter substitution changes the chemical composition while maintaining the functional mechanism where the soft element forms a lubricating film on the sliding surface, providing good sliding properties without lead pollution.
Solution Approach 2:
The patent converts the harmful effect of lead dissolution into a beneficial lead-free composition. By using Bi instead of Pb, the material maintains its self-lubricating capability while eliminating environmental harm, turning a harmful material into a safe alternative with equivalent or superior performance.
2Object-affected harmful factors
If Cu-Sn-Bi sliding alloys are used, then lead-free composition is achieved, but insufficient lubricating effect without lubricating oil occurs
Solution Approach 1:
The patent creates local quality variations by nonuniformly distributing Bi particles in the sintered layer. This results in regions with different Bi concentrations, where some areas provide strong lubrication while others maintain structural integrity, enabling the material to function effectively both with and without external lubricating oil.
Solution Approach 2:
The patent introduces dynamic adaptability by creating a sintered layer that can adjust its lubricating properties based on operating conditions. The nonuniform Bi distribution allows the material to self-regulate lubrication effectiveness, providing sufficient lubricating effect whether lubricating oil is present or absent.
3Stability of the object's composition
If Bi is uniformly dispersed in Cu-based matrix, then homogeneous material structure is achieved, but insufficient oil accumulation capability occurs
Solution Approach 1:
The patent deliberately creates nonuniform Bi distribution with local quality variations. Regions with higher Bi concentration provide oil accumulation zones, while other regions maintain structural stability. This local differentiation enables both homogeneous overall composition and sufficient oil accumulation capability.
4Strength
If sliding parts are made with bearing alloy layer bonded to steel backing plate, then mechanical strength is improved, but recycling difficulty increases
Solution Approach 1:
The patent segments the sliding part into two functional layers: a steel backing plate providing mechanical strength and a Cu-Sn-Bi sintered layer providing sliding properties. This segmentation allows the layers to be manufactured separately and then bonded, facilitating future separation and recycling of each component according to its optimal recycling pathway.
Solution Approach 2:
The patent uses composite material construction with a steel substrate and a copper-based sintered overlay. This composite structure combines the advantages of both materials: the steel provides structural integrity while the copper-based layer provides self-lubricating properties and can be recycled separately from the steel backing plate.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sliding material exhibits superior sliding properties in both lubricated and dry conditions, with increased bonding strength and reduced wear, outperforming traditional lead-based materials without the need for oil grooves.
Implementation Method 1
the lead spreads as a thin layer on the surface of the opposing member and provides good sliding properties by acting as a lubricating oil
Implementation Method 2
Bi performs the same function as Pb in conventional lead bronze, i.e., it forms a thin film covering the surface of the opposing member and acts as a lubricating oil to provide good sliding properties
Implementation Method 3
a first sintering step comprising heating the nonuniform mixed powder and the backing plate to sinter the nonuniform mixed powder to the backing plate
Implementation Method 4
The hard Cu—Sn alloy matrix can support a member being slidably supported by a sliding part (referred to below as 'the opposing member') without wearing
Implementation Method 5
a sliding part made from a conventional copper-based sliding material in which a Cu—Sn—Bi alloy is bonded to a steel plate does not exhibit a sufficient lubricating effect
Data Source
AI summary
A sliding material has a sintered layer formed atop a backing plate. The sintered layer contains 5-15 mass % of Bi nonuniformly distributed in a Cu—Sn alloy matrix consisting essentially of 8-12 mass % of Sn and a remainder of Cu. The sliding material can be manufactured by nonuniformly mixing Cu—Sn alloy powder and Bi powder, dispersing the mixed powder on a backing plate, and sintering the mixed powder to form a sintered layer on the backing plate. The sliding material does not undergo seizing and does not have separation of the sintered layer from the backing plate even when used in severe conditions such as in hydraulic equipment or construction equipment.