Hardened Coil Thread Fastener for Concrete Anchoring
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Solution Overview
Problem
Stainless steel fasteners lack the necessary hardness for heavy-duty concrete applications, and existing solutions like bi-metal fasteners are expensive due to complex manufacturing processes, while also compromising on corrosion resistance.
Innovation Solution
A fastener with hardened threads only at the leading edge, where the balance of the threads remain made of corrosion-resistant material, featuring a coil thread made of hardened material attached to the shank, which can be hardened before or after attachment, minimizing the use of less corrosion-resistant material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stainless steel is used for the fastener body, then corrosion resistance is improved, but hardness is insufficient for self-tapping applications
Solution Approach 1:
The fastener applies local quality by using different materials for different portions: the body is made of corrosion-resistant stainless steel (300 or 400 series), while the tip is made of heat-treated carbon steel with superior hardness. This allows each portion to have the material properties optimized for its specific function - corrosion resistance for the body and hardness for self-tapping at the tip.
Solution Approach 2:
The fastener employs composite materials by combining stainless steel and heat-treated carbon steel in a single component. The carbon steel tip is formed separately and then joined to the stainless steel body, creating a composite structure that leverages the advantages of both materials - the corrosion resistance of stainless steel and the hardness of heat-treated carbon steel.
2Strength
If heat treatment is applied to 400 series stainless steel to increase hardness, then self-tapping capability is improved, but corrosion resistance is significantly reduced
Solution Approach 1:
Instead of heat treating the entire fastener, the invention applies local quality by heat treating only the carbon steel tip portion. The stainless steel body remains unheat-treated, preserving its corrosion-resistant properties, while the carbon steel tip is heat-treated to achieve the necessary hardness for self-tapping.
Solution Approach 2:
The fastener is segmented into two distinct portions: the stainless steel body and the carbon steel tip. This segmentation allows independent material selection and processing for each portion - the body can be made from corrosion-resistant stainless steel without heat treatment, while the tip can be made from heat-treated carbon steel optimized for hardness and self-tapping.
3Strength
If a bi-metal fastener with welded carbon steel tip is manufactured, then hardness is improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The carbon steel tip is formed with threads preliminarily before being joined to the stainless steel body. This preliminary threading allows the tip to be prepared independently with the correct thread geometry, simplifying the overall manufacturing process compared to threading after assembly.
Solution Approach 2:
The invention merges the formation of threads and the joining of the tip to the body into a single integrated process step. The pre-threaded carbon steel tip is inserted into the stainless steel body and simultaneously secured, combining multiple operations into one efficient step that reduces manufacturing complexity.
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
This solution reduces manufacturing costs and maintains corrosion resistance by minimizing the use of hardened, less corrosion-resistant material, preventing corrosion-related pressure issues and ensuring effective anchoring in concrete.
Implementation Method 1
The hardened threads are used for creating cuts in the bore
Implementation Method 2
The coil thread is compressed into the groove to secure attachment
Implementation Method 3
heat-hardened carbon steel
Implementation Method 4
heat treatment and hardening
Data Source
AI summary
A method of creating a threaded fastener which includes a shank having a first, threaded portion and a hardened thread portion. The shank includes a thread extending outwardly from a shank body over a first length of the shank. A second portion of the shank includes a groove positioned coincident with the thread and including a turn ratio equal to a turn ratio of the thread. The shank comprises corrosive resistant stainless steel. A coil of hardened steel engages the groove to fill the groove along the second portion.