Piston Ring Wire Composition and Tempering for Gap Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing wires for piston rings are prone to variations in end gap width due to thermal treatments, leading to inappropriate ring tension and reduced combustion efficiency in internal combustion engines, and are often expensive and prone to cracking during coiling.
Innovation Solution
A steel wire composition with specific elements (0.50-0.80% C, 0.05-1.00% Si, 0.2-1.00% Mn, 11.0-14.0% Cr, 0.20-2.0% Mo, 0.03-0.15% V, with limited P, S, and N, and a tempering temperature of at least 645°C to achieve a Vickers hardness of 350-450, which suppresses end gap width variation and enhances coiling processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high Cr content is used in the wire, then the wire has excellent strength and scuffing resistance, but the production cost increases significantly
Solution Approach 1:
The patent changes the chemical composition parameters by limiting Cr to 5.0-25.0% (down from conventional higher levels) while adding specific amounts of Mo (0.10-2.00%) and V (0.05-0.20%). This parameter adjustment maintains the required strength and scuffing resistance through the synergistic effect of multiple alloying elements rather than relying heavily on Cr alone, thereby reducing production cost while preserving performance.
Solution Approach 2:
The patent creates a composite alloy system combining Cr, Mo, and V in specific proportions. The carbide structure is engineered to contain M7C3 carbides (where M represents Cr, Mo, and V) with controlled area percentage (not more than 4.0%). This composite material approach distributes the strengthening function across multiple elements, reducing dependence on expensive Cr while achieving the required mechanical properties.
2Strength
If the wire undergoes stress relief annealing and nitriding, then the piston ring achieves appropriate hardness and strength, but the end gap width varies due to diameter changes
Solution Approach 1:
The patent applies preliminary action by optimizing the wire's chemical composition and carbide structure before the final heat treatment processes. By pre-establishing the carbide distribution and matrix composition, the wire becomes less sensitive to dimensional changes during subsequent stress relief annealing and nitriding, thereby maintaining more consistent end gap width while still achieving the required hardness and strength.
Solution Approach 2:
The patent changes the material parameters by controlling the carbide area percentage (not more than 4.0%) and the specific composition ranges of Cr, Mo, and V. These parameter changes affect how the material responds to thermal treatment, reducing excessive diameter expansion or contraction during annealing and nitriding, thus maintaining better end gap width consistency while achieving appropriate hardness.
3Manufacturing precision
If the wire is tempered at high temperature, then the end gap width variation is suppressed, but the wire hardness becomes too low affecting piston ring strength
Solution Approach 1:
The patent changes the material composition parameters by adding Mo (0.10-2.00%) and V (0.05-0.20%) to the alloy system. These elements form carbides that are stable at high tempering temperatures, allowing the wire to be tempered at high temperatures to suppress end gap width variation while the carbide-containing matrix maintains adequate hardness and strength for piston ring application.
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 wire maintains a stable end gap width, achieves appropriate hardness for strength and processability, and reduces production costs by minimizing Cr content while ensuring excellent coiling performance and piston ring quality.
Implementation Method 1
Quenching and tempering are performed on the raw wire to obtain a wire for piston rings
Implementation Method 2
a tempering temperature of at least 645°C to achieve a Vickers hardness of 350-450
Implementation Method 3
Stress relief annealing is performed on the wire
Implementation Method 4
nitriding is performed on the wire
Data Source
Figure 1
Figure 2
Figure 3
AI summary
[Object] To provide a wire 1 for piston rings which is less likely to cause a width of an end gap 4 of a piston ring to be varied, is excellent in processability during coiling, and is obtained at low cost. [Solution] The wire 1 for piston rings is made of steel which contains 0.50% by weight or greater but 0.80% by weight or less of C, 1.00% by weight or less of Si, 1.00% by weight or less of Mn, 11.0% by weight or greater but 14.0% by weight or less of Cr, 0.20% by weight or greater but 2.0% by weight or less of Mo, and an unavoidable impurity. An area ratio of carbide particles having a circle-equivalent diameter of 0.2 µm or greater but 5 µm or less in a structure in a transverse section of the wire 1 is equal to or less than 10%. A Vickers hardness of the wire 1 is equal to or greater than 350 but equal to or less than 450. The wire 1 is obtained through quenching and tempering. A temperature of the tempering is equal to or higher than 645°C.