In large-scale mining and cement equipment, when the outer diameter of the girth gear is ≥φ4.5m, segmented casting is preferred; when the outer diameter is ≥φ8m, almost all are cast in four or more segments (such as the gear ring of rotary kiln/ball mill with a diameter of φ8-15m). Due to the limitations of long-distance logistics for integral castings and insufficient hoisting space at construction sites, segmented/segmented casting has become the preferred solution for heavy equipment worldwide. This is not only to reduce transportation costs but also to ensure the casting quality of ultra-large thin-walled parts.

Segmented/Segmented Manufacturing Process for Large Girth Gear 

Phase 1: Casting and Blank Production

Process Design: For segmented structures, CAE software is used to simulate the flow and cooling contraction of molten metal, focusing on preventing shrinkage cavities on the segmented surfaces.

Wooden Mold and Molding: Segmented wooden molds are used to ensure consistent geometric dimensions for each segment. High-strength resin sand is used for molding to improve the surface finish and dimensional accuracy of the casting.

Smelting and Casting: Medium-frequency induction furnace is used for melting (such as ZG42CrMo). Strictly control the consistency of chemical composition to minimize hardness and performance deviations between sections.

Sand Removal and Cleaning: Remove risers and adhering sand, and conduct a preliminary visual inspection.

Compared to integral casting, segmented casting significantly improves the fluidity of molten metal by reducing the volume of individual components. This fundamentally reduces the risk of shrinkage cavities and hot cracks common in large ring-shaped parts, resulting in higher density in single-section castings. Second Stage: Heat Treatment (Key to Deformation Control)

Stress-Relief Annealing: Annealing is performed before preliminary rough machining to eliminate casting internal stress and prevent deformation during later finishing.

Temperature Treatment: Overall tempering ensures the hardness and toughness of the matrix.

Third Stage: Precision Machining and Assembly

Half-Surface Rough Machining: Using a large CNC vertical lathe, prioritize machining the joint surfaces (flange faces) of the sections.

Pre-Assembly and Drilling:
Core Step: Pre-assemble two or more sections of the gear ring on specialized tooling, and drill the connecting bolt holes as a whole.

Integral Precision Turning and Gear Hobbing: The outer diameter is precision turned and gears are hobbed while the gears are assembled.

We employ a 'assemble first, then hob' process, solving the installation accuracy problem. This method ensures perfect meshing of the teeth at the segmentation points, eliminates vibrations generated during operation, and achieves more flexible in-situ installation than a single integral gear ring, significantly shortening the customer's downtime maintenance cycle.

Fourth Stage: Inspection and Surface Treatment

Non-destructive Testing: 100% UT (ultrasonic) and MT (magnetic particle) level 2 flaw detection is performed on the tooth root and split surfaces.

Hardness and Dimensional Re-testing: The uniformity of tooth surface hardness is checked, and various tolerances after assembly are measured.

Disassembly, Rust Prevention, and Packaging: The spliced ​​surfaces are marked, and rust-preventive oil is applied after disassembly. Reinforced export wooden crates or steel frames are used for packaging to prevent deformation during long-distance sea transport.

Why do international engineering companies like Metso, FLSmidth, and ThyssenKrupp choose us?

Regarding Precision:

Common Pain Point: Large pitch error at the splicing point, leading to meshing vibration and noise.

Tenfaye Solution: Splice first, then roll the teeth. Ensure tooth profile error at the joint is ≤0.03mm.

Regarding Durability:

Common Pain Point: Uneven material distribution across sections, leading to excessive localized wear.

Tenfaye Solution: Cast in the same furnace. Hardness deviation is controlled within HRC 3, ensuring synchronized wear.

Transparent Inspection System: To meet the requirements of the European and American markets for UT/MT flaw detection, we provide inspection reports, making quality data visible.

If you require a custom-made large gear ring, please contact us.