Internal combustion engines - Piston rings - Part 3: Keystone rings made of steel
1Key Takeaways
This document specifies the necessary dimensional characteristics of steel wedge rings for piston type internal combustion engines of types T, TB, TBA, TM, K, KB, KBA and KM with nominal diameters from 70 mm to 160 mm.
2Expert Interpretation
An in-depth analysis of the ISO 6624-3:2017 international standard for steel trapezoidal piston rings, covering the technical specifications, dimensional tolerances, surface treatment processes, and mechanical property requirements for eight types of 6° and 15° trapezoidal rings, suitable for reciprocating internal combustion engines with a diameter range of 70-160mm.
Analysis of the core content of the standard
The ISO 6624-3:2017 standard specifies the key technical requirements for steel trapezoidal piston rings, which are suitable for reciprocating internal combustion engines with a cylinder diameter of 70-160mm.
- New technical requirements for PVD coated rings
- Optimized surface treatment process parameters
- Improved mechanical property test methods
Ring type classification and technical characteristics
| Ring type code | Structural characteristics | Cone angle | Typical applications |
|---|---|---|---|
| T/TB/TBA/TM | 6° trapezoidal ring | 6°±20' | Diesel engine top ring |
| K/KB/KBA/KM | 15° Trapezoidal Ring | 15°±30' | High-load Engine |
| Note: B represents barrel surface, A represents asymmetric, and M represents tapered surface | |||
Key Dimensions and Tolerance Control
The standard clearly stipulates the core parameters of trapezoidal ring, such as radial wall thickness (a1), ring width (h1), and closed gap (s1):
- Radial wall thickness tolerance: ±0.15mm (h1≤3mm) to ±0.20mm (h1>3mm)
- Typical Ft/Fd ratio is 1:2.15
- Force tolerance: ±20% (when Ft ≥ 10N) to ±30% (when Ft < 10N)
- Base value of elastic modulus: 210GN/m² (needs to be corrected according to ISO 6621-4)
- When selecting ring types, the material specifications of ISO 6621-4 should be combined
- Inner chamfer design is not recommended for 15° trapezoidal rings
- The taper tolerance of chrome-plated rings needs to be increased by an additional 10'
- The radial wall thickness of the next standard diameter should be selected for maintenance dimensions
| Treatment type | Code | Minimum thickness (mm) | Performance characteristics |
|---|---|---|---|
| Chrome plating | CR2 | 0.10 | Wear resistance increased by 3-5 times |
| Nitriding | NT070 | 0.070 | Surface hardness ≥800HV |
| PVD | PC010 | 0.010 | Friction coefficient reduced by 40% |
Mechanical property requirements
The standard controls the elastic characteristics of the ring through tangential force (Ft) and radial force (Fd):
Implementation recommendations and precautions
Special attention should be paid when applying this standard: