Girth Gears: Rotary kiln Girth Gear,ball mill Girth Gear
Girth Gears offered find extensive application in different industry sectors including in sponge iron plants, steel & cement industry, mining industry, wind mills as well as in other industry sectors. These are made available in module range of 10 Module to 70 Module and in minimum diameters of 100 mm to 15000 mm. Further, these comprise maximum weight of 70 MT single pieces. Here the range of hardened & ground gear boxes/gears comprise Worm gear boxes, Helical / Double helical gears/gearboxes, Helical-Bevel gearboxes, Planetary Gearboxes and others.

ZTIC Gear Cutting Machines include:
Ø16m CNC Hobbing Machine
Ø12m Gear Cutting Machine (Switzerland)
Ø10m Hobbing Machine (Germany)
Ø4m CNC High Speed Hobbing Machine (Germany)
Ø1.6m Horizontal CHC Hobbing Machine (Germany)
Ø5m CNC Profile Gear Grinding Machine (Germany)
Ø2.8m CNC Profile Gear Grinding Machine (Germany)
Ø1.25m CNC Profile Gear Grinding Machine (Germany)
Ø1m CNC Profile Gear Grinding Machine (Germany)
Ø0.8m CNC Profile Gear Grinding Machine (Germany)

With more than 1000 girth gears sold over the world CITICIC Gear is a leading supplier in the cement and mineral industry. And as member of AGMA (American Gear Manufacturers Association), we do actively take part in defining the standard for gear rating calculations and service factors. 
We provide girth gears in three different designs
Fabricated steel- forged ring- rolled plate  Cast steel 
Ductile (Nodular) cast iron  
Fabricated gears became more common in the past and are constructed with forged steel gear rim materials and electro welded body structure. The rings are manufactured from a whole block of high resistance alloy steel. After the rough machining of the ring, we carry out hardening and tempering heat treatment in order to improve the mechanical characteristic and therefore its relevant performance.  
Avantages of fabricated girth gears
The forged material structure excludes the risk of inclusions
Structure defects like gas holes, micro shrinkage, pin holes, hot tears, sand and slag inclusions are avoided
Hence, repair welding of the body structure and e.g. grinding of toothed areas is not required.
The fabricated manufacturing procedure excludes the need for patterns and risers
Rim material has higher hardness and higher strength than the material used for the underlying structure (i.e. web, gussets)
These features will reduce the lead time and costs. Fabricated manufacturing ensures a fast delivery.
This is especially beneficial in an emergency situation, where the existing gear rim is suffering from damage   
Features
External teeth 
Maximum diameter: 16000 mm 
Toothed face width: 1700 mm 
Maximum module: 45 by hob 
Maximum module: 65 gear finishing cutter
Internal teeth 
Maximum Diameter: 6500 mm 
Maximum module: 25.4 
Toothed face width: 400 mm

Pinions
ZTIC Gear invested in significant resources and achieved many innovations with pinions. The right combination of material, hardness and finishing between pinion and gear is crucial for a long lifetime of the installed equipment. We design and manufacture pinions to match every customers need, no matter how unique the situation might be. 


Quality assurance documents
The following reports are to be submitted to Quality Assurance:
a. Chemistry report
b. Physical report
c. Heat treatment documents
CITIC HMC  Q/HM 973.2-2007
Specification for Steel Castings for Grinding Mills
1 5
d. Ultrasonic inspection report (before and after repairs)
e. Magnetic particle inspection report (before and after repairs)
f. Dimensional report
g. Weld repair maps
h. Weld procedures and Procedure qualification record
i. Welder qualification
j. Nondestructive testing inspector qualification

 
The technical requirements of a large CITICIC Gear ring:
1) is pretreated before normalizing surface hardening treatment, the hardness should HB210 ~ 250; mechanical performance are the ultimate strength Rb \ 690MPa, yield stress Rs \ 490MPa, elongation D5 \ 11%, reduction of area W \ 25% , impact toughness Ak \ 30J; teeth induction hardened, hardness HRC50 ~ 55; effective hardened layer depth \ 3 ~ 5mm.
2) overall ultrasonic flaw detection, internal quality should meet two requirements GB7233-87 standard requirements; tooth and fillet magnetic particle inspection, quality should meet two requirements GB/T9444-88 standards.
3) Note the casting is not rounded R5 ~ R10.
4) Tooth chamfer at both ends and 1 45b.5) by two and a half ring gear tooth width of each ring coupling along the edge of a whole ring made with high strength bolts, combined with the tooth surface must be at the bottom center.
2 large ring gear manufacturing process

2.1 of rough
Steel casting blank is provided by CITIC Heavy Machinery Co., Ltd. Heavy Forging plant, run by GB11352-89 standard specifies requirements for modeling according to the casting process, smelting, casting, hit boxes, cleaning, dressing castings;. During inspection and acceptance by the drawings and Technical requirements for steel blank
Checks, according JB/T6402-92 standards issued after acceptance
Down procedure.
2.2 roughing
Crossed by drawing and stay out allowance, alignment, connection, processing both inside and outside the circle, combining face milling, drilling and other processes.
2.3 Exploration injury
Overall ultrasonic flaw detection, internal quality should meet the two requirements of GB7233-87 standards.
2.4 normalizing pretreatment
Semi-ring pairs normalizing and tempering treatment, provide a good organization for subsequent surface hardening; press drawings deformation of the half ring gear inspection after heat treatment.
2.5 Machining
First two and a half ring is made with high strength bolts connecting the ring as a whole, the overall process by drawing a circle Quannei Wai teeth and upper and lower end, and then drawing and machining milling process requirements.
2.6 Elimination of processing stress
The overall ring annealed to eliminate stress.
2.7 overall ring surface hardening
IF along the alveolar tooth surface induction hardening, hardness HRC50 ~ 55, effective hardened layer depth \ 3 ~ 5mm.
2.8 Final inspection
First, the detection frequency quenching, the hardness after tempering ring gear cogging meets the requirements of the drawings; secondly, to detect whether the maximum outer diameter larger size D6944 as the deformation \ 3mm, the mechanical correction required until qualified; Thirdly, tooth and fillet magnetic particle inspection, quality should meet two requirements GB/T9444-88 standard requirements; Finally, according to the drawings and technical requirements for final inspection.