Bimetallic Stainless Concrete Screw for Hard Cutting Threads
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Solution Overview
Problem
Concrete screws face challenges in balancing requirements such as high resistance to concrete and steel failure, cutting capability, corrosion resistance, and durability while manufacturing at low cost, due to contradictory material properties like hardenability and hydrogen embrittlement risk.
Innovation Solution
A radially bimetallic screw design where both the shank and screw thread helix are made of different stainless steel grades, optimized for individual requirements, with the screw thread helix having a higher Vickers hardness for enhanced cutting performance and load redistribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the steel material is made harder to improve cutting capability and resistance to concrete failure, then the hardness increases, but the risk of hydrogen embrittlement and brittle failure increases
Solution Approach 1:
The screw features a radially bimetallic construction where the shank is made of one stainless steel grade and the screw thread helix is made of a different stainless steel grade. This allows different regions of the screw to have different material properties optimized for their specific functions: the shank for load bearing and the thread helix for cutting and engagement.
Solution Approach 2:
The invention uses a composite structure combining two different stainless steel materials in a radially bimetallic design. This composite approach enables the screw to simultaneously achieve high hardness for cutting capability in the thread helix while maintaining adequate toughness and resistance to brittle failure in the shank.
2Strength
If the steel material is made harder to improve cutting capability, then the cutting performance improves, but the corrosion resistance decreases
Solution Approach 1:
Different stainless steel grades are used for the shank and screw thread helix, allowing the thread helix to have higher hardness for cutting while the shank maintains corrosion resistance. Both materials are stainless steels, ensuring overall corrosion resistance while achieving localized hardness improvement.
3Ease of manufacture
If a single material is used for the entire screw to simplify manufacturing, then the manufacturing process is simplified, but the performance cannot be optimized for both load bearing and cutting function
Solution Approach 1:
The radially bimetallic design allows different stainless steel grades to be used in different regions (shank vs. thread helix), optimizing each region for its specific function while maintaining a relatively simple overall manufacturing process for a bimetallic construction.
Data Source
AI summary
A screw includes a shank having a tip, a rear end which is disposed opposite the tip, and a longitudinal axis which extends through the tip and through the rear end. The shank consists of a first steel material. A screw thread helix is disposed on the shank and protrudes from the shank. The screw thread helix consists of a second steel material that is different from the first steel material. Both the first steel material and the second steel material are stainless steels.