Forged-Welded Girth Gear for Heavy Industrial Applications

The forged-welded girth gear construction isn't a cost-saving compromise—it's an engineering choice that addresses the fundamental physics of large ring manufacture. When you cast a gear ring above 10 meters in diameter, the solidification process creates coarse grain structures and potential shrinkage porosity in the tooth zone. These defects concentrate stress and reduce fatigue life. Forged-and-welded construction solves this by using a separately forged tooth segment—where grain flow is fine and directional—then welding it to a rolled steel plate ring that provides dimensional stability during heat treatment.

Hanwei's forged-welded girth gears are built with this two-zone approach. The tooth section is rough-forged, machined, and then precision-ground to DIN Grade 6 on our 16 m CNC form grinding machine. The ring body is rolled from premium steel plate, fabricated to exact ring diameter, and welded to the tooth forging using controlled preheat and post-weld heat treatment. The result is a gear with superior tooth fatigue resistance and a ring that stays round during thermal cycling.

We routinely produce forged-welded rings from Φ4 m to Φ16 m. The maximum ring weight we handle exceeds 120 metric tons. For gears in this size class, the weld quality is critical—every circumferential weld undergoes ultrasonic and magnetic particle inspection to ensure zero internal defects. This is why we back forged-welded girth gears with up to 10 years of warranty. We've seen these gears run 15+ years in cement and mining service. Contact our engineering team for a technical discussion on whether forged-welded construction is the right fit for your mill.