HITACHI 1020265/4388621 ZAX650/ZX650 Track Sprocket Assy / Mining quality - Heavy duty Crawler excavator undercarriage part suppliers and manufacturers-HAN GONG
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Product Specifications
HAN GONG: Advanced ODM Manufacturing for Heavy-Duty Mining Undercarriage – Track Sprocket Assemblies for Hitachi ZAX650/ZX650 (Replaces 1020265, 4388621)
HAN GONG stands at the forefront of ODM (Original Design Manufacturing) for the global heavy mining equipment sector, specializing in the engineering and production of mission-critical undercarriage systems. This technical white paper details our Heavy-Duty ODM Track Sprocket Assembly, an application-engineered solution designed as a superior performance replacement for Hitachi OEM part numbers 1020265 and 4388621, exclusively for the severe-duty cycles of Hitachi ZAX650 and ZX650 super-large mining excavators.
1. Product Definition & Mining Application Context
In mining operations, the track sprocket is the definitive load-transfer component, converting extreme final drive torque into tractive effort under continuous, high-stress conditions. Standard components falter under the trifecta of abrasive wear, high-impact shock loads, and cyclical fatigue endemic to 600-ton-class excavator operation. HAN GONG’s ODM philosophy is rooted in application-specific design augmentation, moving beyond basic dimensional interchangeability to deliver enhanced durability, predictable wear life, and optimized system synchronization for the entire undercarriage.
Target OEM Reference Numbers: Hitachi 1020265, Hitachi 4388621.
Primary Machine Application: Hitachi ZAX650, Hitachi ZX650 Mining Crawler Excavators.
Operational Environment: Engineered for maximum reliability in bulk earthmoving, hard-rock mining, and large-scale quarrying where operational uptime is paramount.
Core Engineering Challenge: To synthesize extreme surface hardness (for wear resistance) with exceptional core toughness and fatigue strength (for impact and crack resistance), thereby extending mean time between failures (MTBF).
2. Engineering Specifications & Material Science
Our design process begins with a forensic analysis of field failure modes, leading to a specification that addresses root causes of premature sprocket degradation in mining.
A. Proprietary Alloy Selection & Metallurgical Design:
We specify a premium, fine-grained low-alloy steel (e.g., a modified 18CrNiMo7-6 or equivalent grade), chosen for its superior hardenability and clean internal structure. This alloy composition is critical for achieving a deep, uniformly hardened case while maintaining a ductile, high-strength core with an ultimate tensile strength (UTS) typically exceeding 1200 MPa. Pre-forging material certification includes spectrographic analysis to guarantee strict adherence to chemical composition limits for key elements like Chromium, Nickel, and Molybdenum.
B. Advanced Forging Process for Structural Integrity:
Each sprocket is manufactured from a precision, closed-die forged blank. This process is non-negotiable for mining-grade components as it:
Optimizes Grain Flow: Aligns the metallic grain structure to follow the complex contours of the teeth and hub, dramatically increasing resistance to fatigue crack propagation.
Eliminates Defects: Produces a denser, more homogeneous microstructure free from the shrinkage cavities and porosity inherent in cast components, ensuring isotropic mechanical properties.
Enhances Impact Strength: Provides a higher Charpy V-notch impact value compared to alternative manufacturing methods, a critical factor for withstanding rock-shock loads.
C. Precision Machining & Profile Optimization:
Post-forging, components undergo a multi-stage CNC machining and gear-cutting regimen.
Tooth Profile Generation: Utilizing CNC gear hobbers and profile grinders, we machine the tooth form to AGMA Class 10 or higher precision. Our ODM design often incorporates a modified tip relief and optimized root fillet radius. This reduces stress concentration at the tooth root—a common failure initiation point—and promotes smoother engagement with the track chain bushing, minimizing impact forces and system vibration.
High-Tolerance Boring & Finishing: The final drive mounting bore and pilot diameters are finish-bored to IT6 tolerance, ensuring absolute concentricity. This precision is vital to prevent radial run-out, which accelerates seal wear and causes uneven load distribution.
Mounting Surface Preparation: All bolt holes, thrust faces, and locating surfaces are machined to provide a perfect, flush mount, eliminating the need for field adjustments and ensuring correct pre-load on mounting hardware.
D. Multi-Stage Heat Treatment for Maximum Durability:
The cornerstone of our product's longevity is a rigorously controlled, multi-phase heat treatment process.
Deep-Case Carburizing: Components undergo computer-controlled gas carburizing in sealed furnaces, creating a deep diffusion layer of carbon.
High-Pressure Gas Quenching: Followed by a high-pressure gas quench, which minimizes distortion compared to oil quenching, while forming a high-hardness martensitic case.
Double Tempering: A dual-stage tempering process stabilizes the microstructure, relieves internal stresses, and develops the final mechanical properties.
Final Specifications:
Effective Case Depth: 6.8 - 8.2 mm at 550 HV (Vickers).
Surface Hardness: 59 - 63 HRC on the tooth working faces.
Core Hardness & Toughness: 40 - 44 HRC with corresponding high impact energy values.
3. Comprehensive Quality Validation Protocol
Every HAN GONG mining sprocket must pass a definitive battery of tests before release, ensuring conformance to our severe-duty standards.
Dimensional & Geometric Inspection: Full 3D scanning via Coordinate Measuring Machine (CMM) verifies global geometry, tooth profile accuracy, pitch error, and all critical interface dimensions.
Hardness & Case Depth Verification: Automated Rockwell testing on tooth flanks and roots, supplemented by micro-hardness traverses to map and certify the exact case depth profile.
Non-Destructive Testing (NDT): 100% Magnetic Particle Inspection (MPI) for surface defects and 100% Ultrasonic Testing (UT) for subsurface imperfections.
Metallographic Analysis: Sample destructively tested to verify core microstructure (tempered martensite) and case microstructure, ensuring the heat treatment process integrity.
Dynamic Run-In Test: Assembled sprockets undergo a supervised run-in cycle to verify smooth operation, correct bearing/seal function, and absence of aberrant noise or vibration.
4. The HAN GONG Value Proposition for Mining Operations
Predictable Performance & Extended Lifecycle: Engineered for severity, our sprockets deliver consistent, extended service life, enabling accurate maintenance scheduling and reducing unscheduled downtime.
System-Wide Wear Harmony: As a full-system ODM manufacturer, we engineer our sprockets, idlers, rollers, and track chains to wear in a synchronized manner, protecting the entire undercarriage investment and optimizing total cost of ownership (TCO).
Technical Collaboration & Support: We engage as a technical partner, offering application analysis and lifecycle management support, not just component supply.
Manufacturing Traceability & Consistency: Complete vertical integration and rigorous process control guarantee batch-to-batch consistency and full material traceability from raw stock to finished product.
Disclaimer: HITACHI, ZAX650, ZX650, and part numbers 1020265 and 4388621 are trademarks of Hitachi Construction Machinery Co., Ltd. HAN GONG is an independent, professional manufacturer of heavy-duty undercarriage components. Our products are the result of our proprietary ODM engineering and are designed to be direct mechanical replacements for the referenced OEM parts. This document implies no affiliation, endorsement, or authorization by Hitachi Construction Machinery.
