Sintered Sliding Member With Copper-Rich Layer
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Solution Overview
Problem
Sintered compact bearings for construction machinery face challenges in achieving both high strength and low friction coefficients due to the melting of copper during high-temperature sintering, which disrupts the intended copper structure on the inner peripheral surface and compromises the strength on the outer peripheral surface.
Innovation Solution
A sliding member with a base layer containing Fe and a low-melting-point metal, where the low-melting-point metal wets Cu particles, allowing Cu to melt at a lower temperature, diffusing into Fe particles to increase strength, and reducing the sintering temperature to prevent Cu from melting, while incorporating alloy elements like Ni, Mo, and Cr for enhanced hardness and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sintering temperature is increased to ensure high strength on the outer peripheral surface, then the strength is improved, but the copper on the inner peripheral surface melts and is pulled into the base layer, compromising the sliding property
Solution Approach 1:
The invention changes the sintering temperature parameter to a specific range (1023K to 1123K, i.e., 750°C to 850°C) that is lower than conventional temperatures. This parameter change prevents copper melting while still achieving adequate strength through optimized sintering conditions and material composition
Solution Approach 2:
The invention uses a composite material structure with a copper-rich sliding layer (containing copper powder and iron powder) and an iron-based base layer. This composite structure allows different regions to have different properties: the copper-rich layer provides low friction and wear resistance, while the iron-based base layer provides structural strength
2Reliability
If the sintering temperature is decreased to prevent copper melting, then the sliding property is improved, but the strength of the sintered compact becomes insufficient
Solution Approach 1:
The invention optimizes multiple parameters simultaneously: sintering temperature (1023K to 1123K), copper powder content (10-30 mass%), iron powder content (70-90 mass%), and sintering time (1-3 hours). This multi-parameter optimization achieves both low friction and adequate strength at lower temperatures
Solution Approach 2:
The invention creates local quality differences between layers: the sliding layer has high copper content (10-30 mass%) for low friction, while the base layer has lower copper content for strength. This local differentiation allows each region to optimize its function without compromising the other
3Reliability
If a two-layered structure with copper-rich inner layer and iron-carbon outer layer is formed, then both sliding property and strength are intended to be satisfied, but copper melts during sintering and is pulled into the base layer, failing to achieve the intended structure
Solution Approach 1:
The invention changes the sintering temperature parameter to remain below copper's melting point (1023K to 1123K, i.e., 750°C to 850°C), preventing copper melting and maintaining the intended two-layered copper-rich/iron-based structure throughout the sintering process
Solution Approach 2:
The invention converts the potential harm of copper melting into a benefit by carefully controlling sintering temperature to be just below copper's melting point. This allows copper to become sufficiently soft and plastic for good bonding while maintaining its structural integrity and preventing unwanted migration into the base layer
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 solution ensures both strength and sliding properties of the sintered compact, reducing the need for post-sintering machining and hardening, thereby lowering costs and enhancing durability under high contact pressure and shock loads.
Implementation Method 1
the low-melting-point metal contained in the base layer is first melted during sintering, and the melt of the low-melting-point metal wets the surface of each Cu particle. Therefore, Cu is melted at a temperature lower than the melting point thereof
Implementation Method 2
the melt of the low-melting-point metal wets the surface of each Cu particle
Implementation Method 3
the molten Cu and the low-melting-point metal permeate Fe particles to diffuse into the Fe particles. With this, the Fe particles are firmly bound together to increase the strength of the base layer
Implementation Method 4
the green compact is sintered at a temperature that is significantly higher than the melting point (1,083°C) of copper
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
A sliding member (1) is formed of a sintered compact. The sintered compact includes: a base layer (3), which mainly contains an Fe-based structure and further contains 1.0 wt% to 5.0 wt% of Cu, a metal having a melting point lower than a melting point of Cu, and C; and a sliding layer (2), which is sintered together with the base layer (3) in a state of being held in contact with the base layer (3) and has a sliding surface (A). The sliding layer (2) mainly contains an Fe-based structure containing at least one kind of alloy element selected from Ni, Mo, Mn, and Cr and further contains Cu and C, and the content of Cu in the sliding layer (2) is larger than the content of Cu in the base layer.