JB/T 6392.2-2017 Crane Wheel Standard: Tread Surface Specifications
JB/T 6392.2-2017, "Cranes — Crane Wheels — Part 2: Wheel Tread," is the dedicated standard governing crane wheel treads. It specifies the technical requirements, heat treatment specifications, and inspection methods for wheel treads.
Wheel Tread Technical Requirements
Kelude supplies crane wheels in all standard specifications. The standard defines the wheel tread as the contact surface between the wheel and the crane rail, which bears significant contact stress and wear. Surface hardening of the tread achieves a hardness of HB300–380, while the core retains its original toughness at HB≤269. The hardened layer depth must be ≥15mm, measured inward from the tread surface. The process uses medium-frequency induction hardening with heating to 880–920°C, followed by water quenching and tempering at 400–500°C. Hardness uniformity across the wheel must not exceed HB40 variation between any two points.
Tread hardness should be properly matched to rail hardness — typically, the wheel is HB30–50 harder than the rail. Excessive wheel hardness accelerates rail wear, while insufficient hardness leads to premature wheel wear. A common pairing is wheel hardness HB300–350 with rail hardness HB250–280 (QU70 or QU80 Crane Rail). The standard also specifies the metallurgical structure of the tread: the hardened layer must consist of fine acicular martensite, transforming to tempered martensite after tempering.
The standard details the inspection methods for tread heat treatment quality — hardness is measured at four evenly spaced points around the tread circumference, with the average taken; the variation between any two points on the same wheel must not exceed HB40. Hardened layer depth is verified using the Vickers hardness method, measuring point-by-point from the tread toward the core until hardness drops to 1.1 times the core hardness. Metallographic inspection involves taking a sample from the wheel cross-section to confirm the hardened layer's microstructure is fine acicular martensite, becoming tempered martensite after tempering. Coarse martensite and retained austenite are not permitted.
The standard also covers operation and maintenance requirements for wheel treads — new wheels must undergo a bedding-in run before being put into operation, running for 2 hours under no-load conditions to ensure proper seating between the tread and the rail. During service, wheel diameter should be measured every 500 working hours to check wear amount, and tread hardness should be verified every 1,000 working hours to confirm it remains within HB300–380. If spalling or indentation deeper than 1mm appears on the tread, the wheel must be taken out of service for repair or replacement. Replacement is also required when flange wear reduces thickness by more than 40% of the original, or when flange height is reduced by more than 50%. The wheel diameter difference between wheels on the same axle must not exceed 0.5mm, otherwise rail gnawing (wheel flange rubbing) may occur.
Hardened Layer Inspection
The hardened layer inspection specified by the standard covers hardness testing (surface HB300–380, gradually decreasing through the transition zone, core HB≤269), hardened layer depth verification (≥15mm), and metallographic examination (fine acicular martensite in the hardened layer, tempered martensite after tempering). Inspection methods — hardness is measured using a Rockwell or Brinell hardness tester, while hardened layer depth is determined by the Vickers hardness method or metallographic analysis. One wheel per batch (minimum one) is sampled for full cross-section hardness distribution measurement.
Surface Hardened
Toughness Retained
Induction Hardened
Above Rail
Spalling/Cracks
Height Red. >50%
| Crane wheel Specification | Material | tread hardness(HRC) | Case Depth(mm) | Wheel load(k N) |
|---|---|---|---|---|
| Φ350×130 | 65Mn | 40~48 | ≥15 | ≤120 |
| Φ400×130 | 65Mn | 40~48 | ≥15 | ≤160 |
| Φ500×150 | 65Mn | 40~48 | ≥15 | ≤250 |
| Φ600×150 | 65Mn | 40~48 | ≥15 | ≤360 |
Wear Limits and Scrapping Criteria
Replace the crane wheel when tread surface wear (diameter reduction) exceeds 5% of the original diameter. Also replace if tread surface shows spalling, indentation deeper than 1 mm, or cracks. Replace when flange wear reduces thickness by more than 40% of the original, or when flange height loss exceeds 50%. The wheel diameter difference between two wheels on the same axle must be ≤ 0.5 mm. During service, measure the wheel diameter and inspect wear amount every 500 working hours.
| inspection items | technical requirements | Method | Cycle |
|---|---|---|---|
| tread hardness | HB300~380 | Hardness Gauge | Per Batch |
| Case Depth | ≥15mm | Metallographic/Vickers | Per Batch |
| wear amount | Reduced Diameter≤5% | Caliper | 500h |
| Wheel flange | Reduced Thickness≤40% | Caliper | 500h |
| Crane wheel Deviation | Concentricity≤0.5mm | Caliper | installation Time |
Per the standard, tread surface hardness is verified by measuring at four evenly spaced points around the circumference and averaging the readings. Hardened layer depth is determined using the Vickers hardness method, measuring from the tread surface inward until the hardness drops to 1.1 times the core hardness. For metallographic inspection, a specimen is taken from the wheel cross-section to confirm that the hardened layer consists of fine acicular martensite.
FAQ: Wheel Tread Hardening & Wear
Q: Why is heat treatment necessary for the wheel tread?
A: The wheel tread is in direct contact with the rail and must withstand significant contact stress and wear. Heat treatment (Surface Hardening) achieves a tread hardness of HB300–380 while maintaining core toughness at HB≤269. A hardened layer depth of at least 15 mm ensures a long service life, helping the tread retain its profile and minimizing wear throughout the wheel's life cycle.
Q: What are the recommended heat treatment parameters for the wheel tread?
A: The process uses medium-frequency induction hardening with a heating temperature of 880–920°C, followed by water quenching and tempering at 400–500°C. The hardened layer depth is ≥15 mm. Tread hardness should be HB300–380, with core hardness at HB≤269. Hardness uniformity across the wheel must not vary by more than HB40 between points.
Q: How should wheel tread hardness be matched with rail hardness?
A: Tread hardness must be properly matched with rail hardness—typically, the wheel should be HB30–50 harder than the rail. If the wheel is too hard, rail wear accelerates; if too soft, the wheel wears out prematurely. A common pairing is a wheel hardness of HB300–350 with a rail hardness of HB250–280.
Q: When should a worn wheel tread be replaced?
A: Replace the wheel when tread wear (measured as diameter reduction) exceeds 5% of the original diameter. Replacement is also required if tread spalling or indentations exceed 1 mm, or if cracks are present. For the wheel flange, replace when thickness reduction exceeds 40% of the original or height loss exceeds 50%. The wheel diameter difference between wheels on the same axle must be kept within 0.5 mm.
