Ball Stud Surface Hardening for Wear Resistance Without Neck Cracking
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Solution Overview
Problem
Existing methods for producing ball studs result in low elongation at fracture values, leading to surface cracking in the neck region under high-load conditions, necessitating oversized dimensions to prevent failure, while also compromising on corrosion resistance.
Innovation Solution
A method involving plastic shaping, mechanical machining, thermochemical hardening, selective removal of the surface-hardened layer, oxidation, and polishing to achieve regions with high wear and corrosion resistance for the joint ball and ductility for the shank, allowing for optimal balance between hardness and corrosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ball stud is completely carbonitrided and oxidized to improve corrosion resistance, then the surface has good corrosion protection, but the elongation at fracture decreases and surface cracking occurs under high-load conditions
Solution Approach 1:
The patent applies different surface treatments to different regions of the ball stud. The joint ball receives complete carbonitriding and oxidation for high corrosion and wear resistance, while the neck region has the hardened layer selectively removed to maintain ductility and prevent cracking under stress. This local differentiation resolves the contradiction between needing corrosion resistance and maintaining ductility.
2Reliability
If the neck region is dimensioned larger to prevent incipient cracking, then reliability under high load improves, but the overall weight and material usage increase
Solution Approach 1:
The patent changes the material properties of the neck region by selectively removing the surface-hardened layer, transforming it from a hard, brittle state to a more ductile state. This allows the neck region to undergo elastic deformations without cracking, maintaining reliability without increasing dimensions or weight.
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 produces a lightweight ball stud with a hard, abrasion-resistant joint ball and a ductile shank resistant to cracking under stress, while maintaining sufficient corrosion protection, reducing the risk of incipient cracking and enhancing overall performance.
Implementation Method 1
d) thermochemically hardening the surface of the semi-finished ball stud product
Implementation Method 2
e) removing the surface-hardened layer at least in the neck region and/or the fastening section
Implementation Method 3
f) oxidizing the semi-finished ball stud product
Implementation Method 4
c) rolling the surface of the joint ball
Data Source
AI summary
Method for producing a ball stud with a joint ball and a shank, wherein the shank includes at least a neck region adjoining the joint ball and a fastening section opposite the joint ball, characterized by the steps: a) plastically shaping a semi-finished ball stud product; b) mechanically machining the semi-finished ball stud product; c) rolling the surface of the joint ball; d) thermochemically hardening the surface of the semi-finished ball stud product; e) removing the surface-hardened layer at least in the neck region and/or the fastening section; f) oxidizing the semi-finished ball stud product; g) polishing the joint ball.