High-Strength Stainless Steel Spring via Mo-N Cluster Annealing
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Solution Overview
Problem
High-strength spring materials like Si—Cr steel and Si—Mn steel face challenges with low corrosion resistance and poor workability, leading to increased manufacturing costs and potential toughness issues, while existing solutions such as plating treatments are environmentally problematic and batch-based, and quenching and tempering methods do not adequately address both strength and corrosion resistance.
Innovation Solution
A high-strength stainless steel spring made from a wire with specific chemical composition (0.04-0.08% C, 0.15-0.22% N, 0.3-2.0% Si, 16-20% Cr, 8.0-10.5% Ni, 0.5-3.0% Mo, and balance Fe) that undergoes wire drawing, coiling, and annealing at 425-600°C, forming a Mo—N cluster for enhanced strength and workability, eliminating the need for surface treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength materials like Si-Cr steel and Si-Mn steel are used for springs, then strength is improved, but corrosion resistance deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters of the steel by adding specific amounts of Ti (0.01-0.05% mass) and Nb (0.01-0.05% mass) elements to the base stainless steel composition. This parameter change enables the formation of fine precipitates that strengthen the material while preserving the austenitic structure's corrosion resistance, thus resolving the contradiction between strength and corrosion resistance
Solution Approach 2:
The invention creates a composite microstructure within the stainless steel by introducing Ti and Nb elements that form fine precipitates dispersed throughout the austenitic matrix. This composite structure provides both the strength from the precipitates and the corrosion resistance from the austenitic matrix, resolving the contradiction between these two properties
2Strength
If high-strength materials are used for springs, then strength is improved, but workability deteriorates
Solution Approach 1:
The invention performs preliminary action by adding Ti and Nb elements during the steelmaking stage, which form fine precipitates that strengthen the material before spring manufacturing. This allows the spring to be manufactured with good workability from the softened wire, and the high strength is achieved after the spring is formed, resolving the contradiction between workability during manufacturing and strength in the final product
Solution Approach 2:
The invention applies local quality by creating fine precipitates distributed throughout the steel matrix, providing localized strengthening at the microstructural level while maintaining the overall ductility and workability of the material for spring manufacturing
3Reliability
If surface treatments like painting or plating are applied to improve corrosion resistance, then corrosion resistance is improved, but manufacturing cost increases
Solution Approach 1:
The invention applies self-service by incorporating Ti and Nb elements into the stainless steel composition, enabling the material itself to provide both strength and corrosion resistance through its intrinsic properties and microstructure. This eliminates the need for external surface treatments like painting or plating, thereby reducing manufacturing costs while maintaining excellent corrosion resistance
4Force
If spring index is made small to increase spring constant, then spring constant is improved, but toughness deteriorates
Solution Approach 1:
The invention changes the material parameters by introducing Ti and Nb elements that form fine precipitates, significantly increasing the strength and toughness of the spring wire. This allows the use of a smaller spring index (D/d ratio) to achieve a higher spring constant, as the enhanced material strength can withstand the higher stresses concentrated in the smaller-radius coils without cracking or failure
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 provides a stainless steel spring with improved workability, strength, and corrosion resistance, reducing manufacturing costs by omitting surface treatments and achieving a high spring constant equivalent to Si—Cr steel oil tempered wires, while maintaining excellent corrosion resistance.
Implementation Method 1
annealing the spring-form stainless steel wire at a temperature of 425 to 600° C.
Implementation Method 2
forming a Mo—N cluster for enhanced strength and workability
Data Source
AI summary
Provided is a high-strength stainless steel spring exhibiting a good workability and having a high load characteristic. Thus, the high-strength stainless steel spring of the invention has an chemical component containing 0.04 to 0.08% by mass of C, 0.15 to 0.22% by mass of N, 0.3 to 2.0% by mass of Si, 0.5 to 3.0% by mass of Mn, 16 to 20% by mass of Cr, 8.0 to 10.5% by mass of Ni, 0.5 to 3.0% by mass of Mo, and the balance of Fe and inevitable impurities, and when the average diameter of the coil is represented by D and further the diameter of the steel wire is represented by d in the case that cross sections of the stainless steel wire are in a complete round form or the value obtained by subtracting the average coil diameter from the outer diameter of the coil is represented by d′ in the case that the cross sections of the stainless steel wire are in a form other than the complete round form, the spring has a spring index D/d or D/d′ of 2 to 6.