Threaded Shaft Sorbite Structure for Precision Rolling
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Solution Overview
Problem
Current methods for manufacturing mechanical structural members, such as ball threaded shafts and gears, face challenges in achieving high precision and dimensional accuracy due to variations in hardness and metal structure, leading to increased complexity and reduced productivity.
Innovation Solution
A method involving refining steel materials to achieve a sorbite structure with Rockwell hardness between 13 to 28 HRC and a hardness variation within 6 HRC, without annealing, and performing plastic working to form grooves and teeth, ensuring uniform hardness and reduced tool wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional heat treatment (quenching/tempering) is performed on round bar material, then hardness and strength are improved, but hardness uniformity and structural uniformity deteriorate
Solution Approach 1:
The invention changes the heat treatment parameters by performing quenching at 850-950°C followed by tempering at 500-650°C to obtain a sorbite structure with uniform hardness distribution. This specific parameter combination resolves the contradiction by achieving both high hardness (HRC 25-35) and uniform hardness variation (≤6 HRC)
Solution Approach 2:
The invention utilizes phase transition of steel by controlling the transformation from austenite to sorbite structure through controlled quenching and tempering. This phase transition enables the material to achieve uniform microstructure and hardness distribution, resolving the contradiction between strength improvement and hardness uniformity
2Ease of manufacture
If annealing treatment is performed before rolling to improve workability, then machinability is improved, but manufacturing complexity and processing time increase
Solution Approach 1:
The invention merges the heat treatment process with the rolling process by performing quenching and tempering to achieve sorbite structure before rolling. This combination eliminates the need for separate annealing treatment, reducing manufacturing complexity while maintaining good workability for rolling (hardness HRC 25-35 provides optimal balance between strength and ductility)
Solution Approach 2:
The invention performs preliminary heat treatment (quenching and tempering) before rolling to create the optimal sorbite structure. This preliminary action prepares the material with uniform hardness and appropriate ductility, enabling successful rolling without requiring additional annealing treatment afterward
3Manufacturing precision
If multiple heat treatment processes (annealing, nitriding, sulfur-nitriding) are performed to improve precision, then surface hardness and durability are improved, but productivity decreases due to increased processing time
Solution Approach 1:
The invention applies partial hardening action by forming a hardened layer (5-20 μm) on the groove surface through controlled rolling with hardened rolls. This partial hardening is sufficient to achieve the required precision and durability without requiring excessive hardening treatments like multiple nitriding or sulfur-nitriding processes, thus maintaining high productivity
4Productivity
If thread grooves are formed by rolling to improve productivity, then manufacturing efficiency is improved, but tool wear increases due to material hardness variations
Solution Approach 1:
The invention changes the material parameters by achieving uniform hardness distribution (variation ≤6 HRC) through controlled heat treatment before rolling. This parameter optimization ensures consistent material properties that reduce unpredictable tool wear during rolling, extending tool life while maintaining high rolling productivity
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
This approach results in high-precision mechanical structural members with improved processing accuracy and reduced manufacturing costs, enhancing productivity and quality.
Implementation Method 1
the steel materials are subjected to refining by heat treatment (quenching/tempering) to improve machinability, grindability, toughness, wear resistance
Implementation Method 2
a method of refining a round bar material to have a hardness of HRC25 to HRC35, annealing an outer circumferential surface thereof to have a hardness of HRC23 or less
Implementation Method 3
grooves and teeth are formed by plastic working and a hardened layer is formed on a surface of the teeth
Implementation Method 4
a hardened layer is formed on a surface of the teeth
Data Source
AI summary
Provided is a mechanical structural member that can suppress deformation and has high precision and excellent quality. In a mechanical structural member (triangular threaded shaft 31) in which grooves (32) and teeth (33) are formed by plastic working and a hardened layer (31a) is formed on a surface of the teeth (33), the mechanical structural member has a sorbite structure, and Rockwell hardness in a region P excluding the hardened layer (31a) is 13 to 28 (HRC). A variation in the Rockwell hardness in the region P excluding the hardened layer (31a) is within 6 (HRC).