Multi-twisted Steel Cord with Diameter Gradient for Corrosion Resistance
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Solution Overview
Problem
Conveyor belt steel cords face a trade-off between corrosion resistance and weight, where improving corrosion resistance often leads to increased weight due to larger filament diameters, and existing multi-twisted structures have not adequately addressed this issue.
Innovation Solution
A rubber article-reinforcing steel cord with a multi-twisted structure where the core and sheath strands are formed by twisting one or two core filaments and multiple sheath filaments, with specific diameter and tensile strength relationships, and sequential brass and zinc plating to enhance corrosion resistance without increasing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the filament diameter is increased to ensure cord strength, then the strength is improved, but the weight increases and rubber penetration deteriorates
Solution Approach 1:
The steel cord is divided into multiple strands (core strand and sheath strands), each containing multiple filaments. This segmentation allows the use of numerous thin filaments instead of fewer thick filaments, achieving the required cord strength through cumulative filament strength while keeping individual filament diameters small (0.05-0.15mm) to maintain low weight and good rubber penetration.
Solution Approach 2:
The steel cord employs a composite structure combining multiple steel filaments of different diameters arranged in specific patterns (core filaments and sheath filaments). This composite arrangement optimizes the balance between strength and weight by distributing load across multiple filaments with diameters in the range that provides both strength and good rubber infiltration.
2Reliability
If zinc plating is applied to delay corrosion, then the corrosion resistance is improved, but the weight increases
Solution Approach 1:
The plating structure is changed from conventional thick zinc plating to a dual-layer plating system with specific thickness parameters: an inner zinc layer of 5-20μm and an outer brass plating layer of 1-5μm. This parameter optimization provides adequate corrosion protection while minimizing the additional weight compared to conventional plating.
Solution Approach 2:
A composite plating structure is applied combining zinc and brass layers. The zinc layer provides base corrosion protection, while the outer brass layer provides additional corrosion resistance and oxidation protection. This composite plating system achieves superior corrosion protection with controlled weight increase compared to single-layer thick zinc plating.
3Strength
If the filament diameter is increased to ensure cord strength, then the strength is improved, but the rubber penetration deteriorates
Solution Approach 1:
The cord structure is segmented into multiple thin filaments (0.05-0.15mm diameter) arranged in bundles. This segmentation creates numerous small interstices between filaments that allow rubber to penetrate effectively, while the cumulative cross-sectional area of all filaments provides the required cord strength.
Solution Approach 2:
The filament diameter parameter is optimized to the specific range of 0.05-0.15mm. This parameter change is critical: it is small enough to allow good rubber infiltration into the cord structure, yet large enough to provide sufficient strength when numerous filaments are combined in the multi-strand configuration.
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 effectively improves corrosion resistance and tensile strength while maintaining a reduced weight, enhancing the steel cord's durability and performance without increasing its overall dimensions.
Implementation Method 1
corrosion of the filaments can be delayed by allowing the plated zinc to corrode preferentially to the filaments
Implementation Method 2
a multi-twisted structure in which two core filaments are used in a core strand and the diameter of outermost-layer sheath filaments of each sheath strand is controlled
Data Source
AI summary
Rubber article-reinforcing steel cord in which corrosion resistance is improved without an increase in weight. In a rubber article-reinforcing steel cord (1), plural sheath strands (3) each formed by twisting together plural steel filaments are twisted together around at least one core strand (2) formed by twisting together plural steel filaments. Core strand (2) and sheath strands (3) are each formed by twisting together one or two core filaments (2c) and (3c) and plural sheath filaments (2s) and (3s), respectively, and a relationship represented by the following Formula (1) is satisfied when a wire diameter of core filament(s) (2c) of core strand (2), a wire diameter of sheath filaments (2s), a wire diameter of core filaments (3c) of sheath strands (3), and a wire diameter of sheath filaments (3s) are defined as dcc, dcs, dsc and dss, respectively: dcc>dcs≥dsc>dss (1).