Ball Screw Nut Sleeve Hardening Without Losing Weldability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ball screw nuts made from sheet steel with low carbon content are difficult to harden and create a stable weldable connection with weld-on components due to their martensitic structure and high carbon content, making welded connections challenging or impossible.
Innovation Solution
A profiled nut with a sleeve made of sheet steel, featuring a rolling profile formed without cutting on its inner circumference, is hardened in a heat treatment method, allowing for a non-rolling inner surface with Rockwell hardness between 56 HRC and 64 HRC, while maintaining weldability on the outer surface, enabling a simple connection with a weld-on component. This can be achieved using single-layer or multi-layer composite sheet steels with a copper intermediate layer for better layer connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sleeve is carburized and hardened to achieve high Rockwell hardness (56-64 HRC) for strong rolling contact, then the rolling profile gains sufficient hardness and strength, but the outer surface loses weldability due to high carbon content and martensitic structure
Solution Approach 1:
The patent applies selective carburizing only to the inner lateral surface of the sleeve where the rolling profile is located, while the outer lateral surface and flange areas are intentionally left with low carbon content to maintain weldability. This local differentiation of material properties resolves the contradiction between requiring high hardness for rolling contact and maintaining weldability for external connections.
Solution Approach 2:
The sleeve is functionally segmented into two zones: the inner lateral surface with high carbon content and high hardness for rolling contact, and the outer lateral surface with low carbon content for welding. This segmentation allows each zone to have optimized properties for its specific function without compromising the other.
2Ease of manufacture
If sheet steel with low carbon content is used to maintain weldability, then the material remains weldable and easy to form, but it cannot be hardened sufficiently for the rolling profile to withstand rolling contact
Solution Approach 1:
The patent uses low carbon sheet steel for the entire sleeve to ensure overall weldability and formability, then applies localized carburizing treatment only to the inner lateral surface where the rolling profile requires high hardness. This approach maintains the base material's ease of manufacture while providing localized strength enhancement where needed.
3Strength
If the entire sleeve is carburized to achieve uniform high hardness, then the rolling profile gains sufficient hardness, but the flange and outer surfaces become non-weldable requiring removal of carburized areas
Solution Approach 1:
The patent employs selective carburizing of only the inner lateral surface during the forming process, avoiding carburizing of the outer surfaces and flange areas entirely. This eliminates the need for subsequent removal of carburized areas and simplifies the overall process by preventing the creation of non-weldable zones in the first place.
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 solution allows for economic processing and hardening of the nut, ensuring a strong rolling contact and enabling a firm weldable connection with a weld-on component, as the outer surface remains weldable, even after hardening, facilitating the integration of a flange for secure attachment.
Implementation Method 1
such sheet steels are carburized and the screw nut formed from them is case-hardened
Implementation Method 2
The sleeve is hardened in a heat treatment method at least in the area of the rolling profile
Data Source
AI summary
A profiled nut (1) of a screw drive includes a sleeve (3) produced from sheet steel, has a non-cuttingly formed rolling profile (4) on the inner circumference for rolling contact with rolling bodies and is hardened in a heat treatment method at least in the region of the rolling profile (4). An inner lateral surface of the sleeve (3) having the rolling profile (4) is hardened and has a higher Rockwell hardness. An outer lateral surface of the sleeve (3) is designed such that it can be welded and has a lower Rockwell hardness.