Ball Screw Nut Flange Welding After Case Hardening
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Solution Overview
Problem
Steel sheets with low carbon content are difficult to harden and create a fixed connection with machine parts due to their martensitic structure, making welded connections challenging for ball screw nuts.
Innovation Solution
A method involving forming a sleeve from low-carbon steel sheets using a forming method like roller burnishing, creating a helical ball groove, and applying a diffusion-inhibiting layer to the flange for easy welding to a machine part, allowing for case-hardening and preventing carbon penetration during carburization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-carbon steel sheets are used for forming the sleeve, then ease of manufacture is improved, but hardenability deteriorates
Solution Approach 1:
The patent applies case hardening to create a local quality difference between the sleeve wall and its surface. The inner wall surface is hardened through carburizing and quenching to provide wear resistance for the rolling contact, while the sleeve wall maintains low carbon content for formability. This local differentiation resolves the contradiction between ease of forming and hardenability.
Solution Approach 2:
The sleeve is created as a composite structure with different carbon concentrations at different locations. The base material is low-carbon steel for formability, while the surface layer is enriched with carbon through case hardening to achieve hardenability. This composite approach allows both requirements to be satisfied simultaneously.
2Strength
If the sleeve is case-hardened to improve wear resistance, then strength is improved, but weldability deteriorates
Solution Approach 1:
The case hardening process creates a local quality difference between the sleeve wall and the flange. The sleeve wall surface is hardened for wear resistance, while the flange remains with low carbon content and martensitic structure, making it suitable for welding. This spatial differentiation of material properties resolves the contradiction between wear resistance and weldability.
Solution Approach 2:
The threaded nut is segmented into two functional parts: the sleeve requiring hardening for rolling contact resistance, and the flange requiring weldability for attachment to machine parts. By separating these functions into different components with different material properties, both requirements are satisfied without compromise.
3Ease of manufacture
If a diffusion-inhibiting layer is applied to the flange, then weldability is improved, but manufacturing complexity increases
Solution Approach 1:
The diffusion-inhibiting layer is applied to the flange in advance, before the case hardening process. This preliminary action ensures that during subsequent carburizing, carbon does not penetrate into the flange, preserving its weldability. By performing this protective action beforehand, the need for post-processing or complex manufacturing steps is eliminated.
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
Enables easy production and connection of threaded nuts to machine parts with a thin-walled case-hardened sleeve and a thick-walled flange, ensuring strong and durable threaded drives with reduced material usage and simplified welding processes.
Implementation Method 1
A wobble die is set in a rolling motion, under which the material of the sleeve can flow into its new shape and can generate a thread as a rolling profile
Implementation Method 2
The diffusion-inhibiting layer inhibits the penetration of carbon into the welding surface of the flange during carburization
Implementation Method 3
Case-hardening is a method of surface hardening (boundary layer hardening) consisting of carburizing, hardening and tempering a steel workpiece
Implementation Method 4
Case-hardening is a method of surface hardening (boundary layer hardening) consisting of carburizing, hardening and tempering a steel workpiece
Data Source
AI summary
A method for producing a threaded nut of a threaded drive, includes the following steps: a sleeve is produced from a steel sheet which is suitable for case-hardening; a rolling profile for a rolling contact with rolling bodies is molded on the inner circumference of the sleeve, said rolling profile being wound in a helical manner about the longitudinal axis of the sleeve; a flange is welded to the end face of the sleeve; the flange is provided with a welding surface on the flange end face facing away from the sleeve for welding to a machine part; the welding surface initially has a diffusion-inhibiting layer which inhibits the penetration of carbon; and the welding surface is exposed by removing the diffusion-inhibiting layer after case-hardening the threaded nut. A threaded nut produced according to the method can be part of a ball screw drive, the flange of which can be welded to a provided machine part by the user.