Compacted Steel Strand With Metallic Core Coating for Interstice Corrosion
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Solution Overview
Problem
Existing steel strands with circular cross-sections suffer from interstice-related corrosion issues, especially under tensile stress and in humid environments, and existing coatings either fail to fill these gaps or are not heat-resistant, limiting their use in warm conditions.
Innovation Solution
A steel strand with a thick metallic core coating applied via strip cladding or metal extrusion and thin metallic layer coatings via hot dip or electroplating, resulting in a compacted non-circular cross-section that fills interstices and provides corrosion resistance, allowing high-temperature use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymer coating is applied to fill interstices, then corrosion resistance is improved, but heat resistance deteriorates and the coating cannot withstand downstream heat treatment
Solution Approach 1:
The patent changes the material parameter of the core coating from polymer to metal, fundamentally altering the thermal properties. The metal core coating can withstand heat treatment temperatures that would degrade polymer coatings, while still providing corrosion protection through the metallic material properties
Solution Approach 2:
The patent creates a composite structure with a metal core coating and metal layer coatings. This composite metallic system combines the benefits of corrosion resistance with high temperature stability, as both components are metallic and can withstand heat treatment processes
2Reliability
If a metallic coating is applied to provide corrosion resistance, then lifetime is improved, but the coating thickness is insufficient to fill interstices
Solution Approach 1:
The patent divides the coating system into two segments: a thick core coating on the core wire and thin layer coatings on the layer wires. The core coating is specifically designed with sufficient thickness to fill interstices, while the layer coatings provide additional corrosion protection on the outer surface
Solution Approach 2:
The patent applies different coating qualities to different parts of the strand. The core wire receives a thick core coating optimized for filling interstices, while the layer wires receive thin layer coatings optimized for surface corrosion protection. Each part has the appropriate coating thickness for its specific function
3Reliability
If the steel strand is compacted to reduce interstices, then corrosion resistance is improved, but the layer wires develop non-circular cross-sections affecting flexibility
Solution Approach 1:
The patent applies the core coating to the core wire before the strand is compacted. This preliminary coating provides corrosion protection during the compacting process and will subsequently fill the interstices that form during compaction, protecting the wires even as their shape changes
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 fills interstices, preventing moisture ingress and corrosion, enabling the steel strand to withstand tensile forces and high temperatures, suitable for pre- and post-tensioned applications.
Implementation Method 1
The steel strand is compacted so that the steel layer wires have a non-circular cross-section and that said corrosion resistant core coating fills the interstices between the steel core wire and the steel layer wires
Implementation Method 2
The steel layer wires are covered with a corrosion resistant layer coating provided by a hot dip operation or by an electroplating or chemical plating process
Implementation Method 3
The steel layer wires are covered with a corrosion resistant layer coating provided by a hot dip operation or by an electroplating or chemical plating process
Implementation Method 4
The steel layer wires are covered with a corrosion resistant layer coating provided by a hot dip operation or by an electroplating or chemical plating process
Data Source
Figure 1
AI summary
A steel strand (10) comprises a steel core wire (12). This steel core wire (12) is surrounded by steel layer wires (14) that are twisted around the steel core wire(12). The steel core wire (12) is covered with a thick corrosion resistant core coating (16) provided by strip cladding or by metal extrusion. The steel layer wires (14) are covered with a thin corrosion resistant layer coating (18) provided by a hot dip operation or by an electroplating or chemical plating process. The steel strand(10) is compacted so that said steel layer wires (14) have a non-circular cross-section and that the thick corrosion resistant core coating fills the interstices between the steel core wire (12) and the steel layer wires (14) in order to give the steel strand (10) an improved corrosion resistance and increased lifetime.