Composite Concrete Screw With Corrosion-Resistant Mantle
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Solution Overview
Problem
Conventional concrete screws made of martensitic steel suffer from corrosion in acidic environments, leading to material failure, and bimetallic screws with welded components have complex and costly manufacturing processes.
Innovation Solution
A composite screw is manufactured using a continuous casting process that combines a martensitic core section with a corrosion-resistant mantle section, eliminating welding and reducing production costs, with the core section transforming from austenite to martensite through forming processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If martensitic steel is used for the screw tip to ensure hardness for cutting threads into concrete, then the screw achieves high surface hardness and cutting capability, but the screw becomes prone to corrosion in the acidic milieu of concrete leading to material failure
Solution Approach 1:
The screw is designed with different material properties in different regions: the tip section (insertion end) is made of martensitic steel with high hardness for cutting threads, while the drive section is made of corrosion-resistant steel for long-term reliability in the corrosive concrete environment. This local differentiation resolves the contradiction between hardness and corrosion resistance.
Solution Approach 2:
The screw is constructed as a composite structure combining two different steel materials: martensitic steel for the tip and corrosion-resistant steel for the body. This composite approach allows each section to have the optimal material properties for its specific function, simultaneously achieving high hardness at the tip and excellent corrosion resistance along the drive section.
2Reliability
If bimetallic screws are manufactured by welding a tip element to a drive element, then the screw achieves both hardness and corrosion resistance, but the manufacturing process becomes complex and costly
Solution Approach 1:
Instead of manufacturing separate tip and drive elements and welding them together, the invention merges both sections into a single monolithic screw body. The martensitic and corrosion-resistant steels are combined in one casting process, eliminating the need for separate manufacturing and welding operations, thus simplifying the manufacturing process while maintaining the bimetallic structure.
Solution Approach 2:
The continuous casting process produces a composite billet with a martensitic core and corrosion-resistant steel mantle in a single operation. This integrated composite material approach eliminates the need for subsequent welding operations, significantly simplifying manufacturing compared to traditional bimetallic screw production methods.
3Ease of manufacture
If continuous composite casting is used to manufacture the screw, then production costs are reduced and manufacturing is simplified, but the process requires transforming the core material from austenite to martensite through forming processes
Solution Approach 1:
The continuous casting process produces the core section in an austenitic state, which is then transformed to martensite through controlled forming processes. This parameter change in the material's crystalline structure during forming enables the core to achieve the required hardness while maintaining the simplicity and cost-effectiveness of the continuous casting manufacturing method.
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 composite screw achieves high hardness for cutting into concrete while providing excellent corrosion resistance and significantly lower production costs compared to traditional methods.
Implementation Method 1
the core section transforming from austenite to martensite through forming processes
Implementation Method 2
A composite screw is manufactured using a continuous casting process that combines a martensitic core section with a corrosion-resistant mantle section
Data Source
Figure 1
Figure 2~3D
AI summary
A screw (1) having a core section (11) made of a martensitic material and a mantle section (12) surrounding the core section made of a corrosion-resistant steel material and a process for manufacturing such a screw.