Rivet Nut Heat Treatment for Crack-Free Crimping Strength
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Solution Overview
Problem
The manufacturing of high-resistance crimp nuts is complex and costly due to the need for double cold heading and localized annealing processes, which require specific equipment and result in nuts that are either brittle or prone to cracking during deformation.
Innovation Solution
A method involving cold forging a steel body with a carbon content of 0.15-0.25% to form a blank, followed by annealing and tapping to create a bendable section with an internal thread, without subsequent quenching, allowing for improved mechanical strength and malleability without cracking, using a heat treatment between 630°C and 720°C for 10-15 minutes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If double cold heading and localized annealing are used to manufacture high-strength rivet nuts, then mechanical strength is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent combines the annealing and threading operations into a single integrated process step. The blank is annealed in its entirety before threading, eliminating the need for separate localized annealing steps and complex equipment while achieving the required mechanical strength and ductility for high-strength rivet nuts
Solution Approach 2:
The patent specifies precise compositional parameters (carbon: 0.15-0.25%, manganese: 0.9-1.2%, boron: 0.0008-0.0050%) and heat treatment parameters (temperature and duration) to achieve the desired balance of strength and ductility. This parameter optimization allows the material to be threaded after annealing without requiring complex localized treatment
2Ease of operation
If low-carbon steel is used for rivet nut manufacturing, then malleability and ease of deformation are improved, but mechanical strength decreases
Solution Approach 1:
The patent uses a composite alloy composition combining low-carbon steel (0.15-0.25% C) with specific amounts of manganese (0.9-1.2%) and boron (0.0008-0.0050%). This composite material approach maintains the inherent malleability of low-carbon steel while the alloying elements enhance mechanical strength and hardenability, allowing the material to be both easily deformed and mechanically strong
Solution Approach 2:
The patent optimizes the chemical composition parameters and heat treatment parameters to transform the material properties. The specific carbon range (0.15-0.25%) provides baseline ductility, while manganese adds strength and boron enhances hardenability. The annealing process parameters are optimized to achieve the desired balance between softness for forming and strength for final performance
3Ease of operation
If the bendable section is annealed to improve ductility, then ease of crimping is improved, but mechanical strength may be reduced
Solution Approach 1:
The patent functionally segments the rivet nut into a bendable section and a threaded section. The entire blank is annealed to ensure the bendable section has sufficient ductility for crimping without cracking. The subsequent threading operation creates work hardening in the threaded section, providing the necessary mechanical strength for load-bearing applications while the annealed bendable section remains ductile for forming
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 method simplifies the manufacturing process, enhances mechanical strength, and allows for effective deformation without cracking, while improving the nut's resistance to tearing and maximum applicable load, with the steel remaining sufficiently ductile for crimping.
Implementation Method 1
applying a heat treatment to the blank
Implementation Method 2
cold forging a steel body to form a blank
Data Source
Figure 1~6
Figure 3~5
AI summary
Method for manufacturing a rivet nut (1), comprising the following steps: - cold forging a steel body having a mass percentage of carbon between 0.15% and 0.25% inclusive, to form a blank comprising a bendable section intended to deform into a riveting bead (8) and an association section (5), - applying a heat treatment to the blank, and - tapping the association section (5) to form an internal thread (7).