Cold Forging Austenitic Fastener Without Heat Treatment
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Solution Overview
Problem
Conventional methods for manufacturing high-strength fasteners from austenitic 300 series materials are costly and involve multiple procedures, including heat treatment, which can soften the core hardness, lead to corrosion issues, and decrease elongation, affecting screwing security and increasing manufacturing costs.
Innovation Solution
A method involving cold forging to reduce the diameter of a raw shaft, forming a preliminary shank, and subsequently creating a high-strength fastener through sequential head, drill point, and thread formation without heat treatment, enhancing case and core hardness while maintaining corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment and carburizing procedures are used to increase case hardness, then the fastener achieves higher surface hardness for smooth drilling, but the core hardness softens due to high temperature exposure, decreasing elongation and screwing security
Solution Approach 1:
The patent changes the fundamental parameter of heat treatment temperature by eliminating the high-temperature carburizing and quenching process entirely. Instead, it uses cold forging at ambient or lower temperatures, which strengthens the material through plastic deformation and work hardening without thermal softening of the core, thus maintaining both case hardness and core strength
Solution Approach 2:
The patent replaces the thermal field (heat treatment) with a mechanical field (cold forging). The mechanical deformation process during cold forging creates dislocation structures and work hardening that provide both surface hardness and core strength, substituting the need for thermal processing while avoiding its detrimental effects on elongation
2Strength
If conventional heat treatment procedures are applied to enhance fastener strength, then case hardness increases, but manufacturing cost increases and additional corrosion protection processes are required
Solution Approach 1:
The patent merges the forming and strengthening operations into a single cold forging process. The cold forging simultaneously shapes the fastener and work-hardens the material to achieve the required case hardness, eliminating the need for separate heat treatment and corrosion protection steps, thereby reducing manufacturing cost and complexity
Solution Approach 2:
The patent extracts and eliminates the unnecessary heat treatment and corrosion protection procedures from the manufacturing sequence. By using cold forging, the process achieves both shaping and strengthening in one step, removing the extraneous steps that increase cost and complexity
3Productivity
If cold forging is used to reduce raw shaft diameter and form the fastener, then manufacturing cost decreases and production speed increases, but the material must maintain high strength and hardness without heat treatment
Solution Approach 1:
The patent changes the material state parameter by using austenitic 300 series stainless steel, which has superior cold formability and work hardening characteristics. This material parameter selection enables the cold forging process to achieve both high productivity and high strength, as the material can be severely deformed at room temperature and then work-hardened to the required hardness level
Solution Approach 2:
The patent performs preliminary material selection and preparation by choosing austenitic 300 series stainless steel with appropriate chemical composition and initial microstructure before the cold forging process. This preliminary action ensures the material has the necessary ductility for cold forming and the potential for sufficient work hardening to achieve the target strength and hardness
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 a high-strength fastener with improved elongation and corrosion resistance, reducing manufacturing costs and enhancing screwing security by eliminating the need for heat treatment and carburizing, thus providing a more efficient and cost-effective production process.
Implementation Method 1
preparing an austenitic raw shaft and reducing its diameter by cold forging so as to generate a preliminary shank
Implementation Method 2
reducing its diameter by cold forging so as to generate a preliminary shank, which can bear above 1/2 force more than the raw shaft
Data Source
AI summary
The present invention pertains to a method for cold forging high strength fastener with austenitic 300 series material comprising the procedures of initially preparing a raw austenitic shaft and then proceeding through a cold forging method to reduce its diameter for thereafter generating a preliminary shank, which can undertake above ½ force more than the raw shaft; further passing through the following formations of the head, the drilling portion and threads in sequence to build an integral fastener. Thus, the entire cold forging facilitates to fabricate the fastener with high strength and hardness by lower manufacturing cost and with effective corrosion resistance, so as to firmly drill the fastener into objects and increase the screwing security.