• Ball Mill Pinion Gear
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Ball Mill Pinion Gear

  • SHILONG
  • Shenyang,China
  • 1~2 month
  • 1000 set / year
This article details the ball mill pinion, a core transmission component that meshes with the bull gear to drive the cylinder, requiring high strength, precision, toughness, and wear resistance, with 20CrMnTi as a common material. It outlines its manufacturing process for 20CrMnTi pinions, including blank forging, rough/semi-finishing (turning, hobbing), carburizing heat treatment, precision machining (tooth grinding, datum grinding), and assembly. Additionally, it specifies comprehensive inspection procedures covering raw materials (composition, forging quality), heat treatment (hardness, carburized layer), tooth accuracy (pitch deviation, runout), and final tests (surface quality, meshing performance, dynamic balance). These ensure the pinion meets transmission efficiency (≥95%) and service life (2-3 years) requirements, supporting stable ball mill operation.

Detailed Introduction, Manufacturing Process, and Inspection Process of Ball Mill Pinions

I. Functions and Structural Features of Ball Mill Pinions

The ball mill pinion is a core component of the transmission system. It meshes with the bull gear (fixed on the cylinder) to transmit power from the motor to the cylinder via the reducer, driving the cylinder to rotate (typically at 15-30 r/min). As a high-speed gear (rotating faster than the bull gear), it directly bears meshing impacts and torque, thus requiring the following properties:


  • High strength: Capable of withstanding torque ranging from tens of thousands to hundreds of thousands of N·m, with high tooth surface hardness (≥55HRC) to resist wear;

  • High precision: Minimal tooth profile error (≤Grade 6 per GB/T 10095) to ensure smooth meshing with the bull gear, reducing vibration and noise;

  • Good toughness: The tooth core must have moderate toughness (hardness 25-35HRC) to avoid impact-induced fracture;

  • Wear resistance: The tooth surface requires hardening treatment (e.g., carburizing, quenching) to extend service life (typically ≥10,000 hours).


Structurally, it is mostly a straight or helical cylindrical gear. Straight teeth are common in small and medium ball mills (simpler to machine), while helical teeth are preferred in large mills (smoother meshing and higher load capacity). The module usually ranges from 8-30mm, with 15-30 teeth.

II. Manufacturing Process of Ball Mill Pinions (Taking 20CrMnTi Carburized Gears as an Example)

20CrMnTi is a common material for pinions due to its excellent carburizing performance (case depth 1.5-3mm). Its manufacturing process is as follows:
1. Blank Forging
  • Raw material: φ100-300mm 20CrMnTi round steel is selected, with spectral analysis verifying its composition (C 0.17-0.23%, Cr 1.0-1.3%, Mn 0.8-1.1%);

  • Forging: Heat to 1100-1150℃, then die-forge into gear blanks (with a machining allowance of 5-8mm). After forging, normalize (920℃×2h, air-cooled) to refine grains and reduce hardness to 180-220HBW.

2. Rough Machining and Semi-Finishing
  • Rough turning: CNC lathes machine the outer circle, end faces, and inner bore (shaft hole or hub hole), leaving a 3-5mm allowance;

  • Gear hobbing: Roughly cut tooth profiles (module 8-30mm) using a gear hobbing machine, with a 0.5-1mm allowance for carburizing and grinding;

  • Drilling and milling: Machine keyways and bolt holes (for split gears) with a positional tolerance of ±0.1mm.

3. Carburizing and Heat Treatment
  • Carburizing: Carburize in a pit-type carburizing furnace at 920-940℃ for 8-16 hours (adjusted by case depth), with a surface carbon content of 0.8-1.2%;

  • Quenching + low-temperature tempering: After carburizing, cool to 850℃ and oil-quench (tooth surface hardness 58-62HRC), then temper at 180-200℃ for 2 hours to relieve stress and stabilize dimensions.

4. Finish Machining
  • Tooth surface grinding: Precision grind tooth profiles using a worm wheel grinding machine, ensuring cumulative pitch error ≤0.05mm/100mm, tooth surface roughness Ra≤0.8μm;

  • Datums grinding: Grind the inner bore (tolerance IT6) and journal (interference fit with bearings, 0.01-0.03mm interference), with end face perpendicularity ≤0.01mm/100mm;

  • Honing: Hone high-precision gears (Ra≤0.4μm) to reduce meshing noise (≤85dB).

5. Surface Treatment and Assembly
  • Non-tooth surfaces are sandblasted for rust removal, then coated with anti-rust paint (thickness ≥60μm);

  • Shrink-fit with the shaft or hub (interference fit), and check radial runout after cooling (≤0.03mm).

III. Inspection Process of Ball Mill Pinions

Inspection complies with GB/T 10095 Accuracy of Involute Cylindrical Gears and JB/T 6396 Large Gears and Gear Ring Forgings, with key steps as follows:
1. Raw Material and Forging Inspection
  • Spectral analysis verifies 20CrMnTi composition (qualified Cr and Mn content);

  • Forgings undergo UT inspection (Grade I qualified), with no internal cracks or shrinkage; tensile tests confirm tensile strength ≥1080MPa.

2. Heat Treatment Inspection
  • Tooth surface hardness: Measured with a Rockwell hardness tester (58-62HRC); core hardness (3mm below the surface) 25-35HRC;

  • Carburized layer inspection: Metallographic analysis measures effective case depth (1.5-3mm), with martensite grade in the hardened layer ≤3.

3. Tooth Profile Accuracy Inspection
  • Gear measuring center tests: Pitch deviation ≤±0.015mm, tooth direction error ≤0.01mm/100mm, total profile deviation ≤0.02mm;

  • Radial runout: Measured with a gear runout tester (≤0.03mm for the gear ring).

4. Final Inspection of Finished Products
  • Surface quality: PT inspection of tooth surfaces (no cracks or pitting); tooth root fillet R≥1.5mm (to avoid stress concentration);

  • Meshing test: Mesh with a bull gear sample and run idle for 1 hour, with no abnormal noise and contact spots (≥60% along tooth height, ≥70% along tooth length);

  • Dynamic balance: For rotational speeds ≥300r/min, unbalance ≤20g·mm/kg.


By strictly controlling tooth profile accuracy, carburizing quality, and assembly tolerances, pinions can ensure a ball mill transmission efficiency of ≥95% and a service life of 2-3 years (depending on working conditions)


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