Ball Stud Surface Hardening With a Ductile Neck Region
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Solution Overview
Problem
Existing ball pivot manufacturing methods face challenges with low elongation at break in the surface coating, leading to potential cracks under high-load events, necessitating oversized neck areas for prevention, which affects weight and performance.
Innovation Solution
A method involving plastic molding, thermochemical surface hardening, selective removal of the surface-hardened layer, oxidation, and polishing to achieve balanced wear and corrosion resistance, with high ductility in the neck and attachment portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ball stud is completely nitrocarburized and oxidized to improve corrosion resistance and surface hardness, then the surface coating gains wear resistance and corrosion protection, but the elongation at break decreases and the surface becomes prone to cracking under high-load events
Solution Approach 1:
The patent applies different surface treatments to different zones of the ball stud based on their functional requirements. The ball joint receives complete nitrocarburizing and oxidation for maximum wear and corrosion resistance, while the neck area has the surface-hardened layer selectively removed to retain ductility and prevent cracking under high loads. This local differentiation resolves the contradiction by providing hard, corrosion-resistant surfaces where needed while maintaining toughness in critical stress areas.
2Reliability
If the neck area is dimensioned larger to prevent cracking, then the reliability under high-load events improves, but the overall weight of the ball stud increases
Solution Approach 1:
The patent changes the material properties of the neck area by selectively removing the surface-hardened layer through machining or grinding. This parameter change transforms the neck surface from hard and brittle to ductile and tough, enabling it to withstand high-load events without cracking while maintaining the original dimensional specifications. This resolves the contradiction by achieving crack prevention through material property modification rather than increasing dimensions and weight.
3Strength
If selective removal of the surface-hardened layer is performed in the neck area to improve ductility, then the elongation at break increases and crack resistance improves, but additional manufacturing steps are required
Solution Approach 1:
The patent segments the ball stud into functionally distinct zones (ball joint, neck area, fastening section) and applies different surface treatment sequences to each. The neck area undergoes nitrocarburizing followed by selective removal of the hardened layer, while other areas retain the complete treatment. This segmentation approach systematically manages the additional manufacturing steps by organizing them according to functional requirements, making the complex process manageable and justifiable through performance benefits.
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 results in a ball pivot with a hard, abrasion-resistant joint ball and a ductile shank, optimizing weight, wear resistance, and corrosion protection while preventing cracking under high loads.
Implementation Method 1
Rolling of the surface of the ball joint
Implementation Method 2
Rolling of the surface of the ball joint
Implementation Method 3
Thermochemical surface hardening of the ball stud semi-finished product
Implementation Method 4
The listed process steps do not, incidentally, represent a fixed sequence... d) Thermochemical surface hardening of the ball stud semi-finished product
Implementation Method 5
the surface-hardened layer is removed by machining. Turning or grinding are among the methods suitable for this.
Implementation Method 6
e) Oxidizing of the ball stud semi-finished product
Implementation Method 7
g) Polishing of the ball joint
Data Source
Figure 1
AI summary
The invention relates to a method for producing a ball stud (1) having a joint ball (2) and a shank (3), wherein the shank (3) has at least one neck region (4) adjoining the joint ball (2), and a fastening portion (6) on the opposite side from the joint ball (2), characterized by the steps of: a) plastically shaping a semifinished ball-stud product; b) mechanically machining the semifinished ball-stud product; c) rolling the surface of the joint ball (2); d) thermochemically hardening the surface of the semifinished ball-stud product; e) removing the surface-hardened layer at least in the neck region (4) and/or the fastening portion (6); f) oxidizing the semifinished ball-stud product; g) polishing the joint ball (2).