Dvostruki spiralni zupčanik valjaonice — podijeljeni sklop ili integralni oblik riblje kosti

Rolling Mill Double Helical Gear — Overview

Among all the industrial applications of double helical gears, the rolling mill environment is arguably the most technically demanding. A hot rolling mill pinion stand must transmit several megawatts through a compact gear set while absorbing instantaneous torque spikes of 3–8× the nominal transmitted torque as each workpiece billet enters the roll gap — an impulse load that occurs hundreds of times per shift, every shift, for the service life of the gear set. The roll drive system must also tolerate severe thermal cycling as heated workpiece material passes within millimetres of the gear housing, and in reversing mill configurations must repeatedly accelerate and decelerate the entire roll-mill inertia train under load. No gear configuration other than the rolling mill double helical gear reliably meets all these requirements simultaneously: the herringbone tooth form provides the high contact ratio and load-sharing that smooth out workpiece-entry impact loads, while the zero-axial-thrust characteristic eliminates the thrust bearing failures that are a common maintenance issue in equivalent single helical roll drive designs.

Korejska kompanija Ever-Power Worm Gear Co., Ltd. proizvodi rolling mill double helical gears in 42CrMo alloy steel (internationally equivalent to AISI 4140, JIS SCM440, DIN 42CrMo4) with high-frequency quenching and tempering to achieve HRC 50-55 on the tooth flanks. This hardness specification — harder than induction-hardened agricultural gears (HRC 40-45) but achieved through high-frequency quench rather than the carburizing-and-grind process of railway or mining gears — is the established industry standard for rolling mill pinion stand gears: sufficient surface hardness to resist the contact fatigue and abrasive wear from scale and lubricant degradation products in the mill environment, with a QT-treated tough core that absorbs workpiece-entry shock without brittle fracture. Both integral (one-piece herringbone) and split assembly configurations are manufactured.

Tehničke specifikacije

Product Specifications — Rolling Mill Double Helical Gear

42CrMo Steel International Grade Equivalents

High-Frequency Quench HRC 50-55 — Why This Heat Treatment for Rolling Mill Gears

Rolling mill gear engineers have developed the HRC 50-55 via high-frequency quench specification as the practical optimum for pinion stand and work roll drive gears after decades of field experience across steel, aluminium, and copper rolling mills. The specification reflects three specific rolling mill operating conditions that distinguish this application from other industrial gear uses:

Workpiece-Entry Impact Loading

When a steel billet, slab, or strip enters the roll gap, the gear train experiences an instantaneous torque spike of 3–8× the steady rolling torque. This impact is repeated at every pass — hundreds of times per shift in a continuous mill. The HRC 50-55 tooth surface is hard enough to resist the pitting and surface fatigue that this cyclic peak stress would cause on a QT soft-tooth gear (HB 220-280), while the tough 42CrMo core (QT treatment maintained in the core by the high-frequency quench process, which heats only the surface layer) absorbs the impulse energy without brittle fracture at the tooth root. This is the fundamental reason HRC 50-55 via high-frequency quench is preferred over full through-hardening: it achieves the surface hardness requirement while preserving the impact toughness of the QT core.

Scale and Abrasive Wear Resistance

Hot rolling mill environments contain iron scale particles and abrasive oxidation products that contaminate the gear lubricant despite filtration. HRC 50-55 tooth flanks resist abrasive wear from these particles substantially better than soft-tooth gears at HB 220-280, extending the time between gear set replacements and reducing the total cost of ownership in terms of unscheduled downtime for gear changes. In comparison, carburized gears at HRC 58-62 would provide even higher abrasive wear resistance but introduce greater brittleness risk under the repeated shock-loading of workpiece entry — making the intermediate HRC 50-55 specification the proven engineering optimum for this specific load combination.

Integral vs Split Assembly — Rolling Mill Configuration Options

Korea Ever-Power manufactures rolling mill double helical gears in two configurations, each suited to different mill stand sizes and installation conditions:

Core Advantages for Rolling Mill Drive Systems

Rolling Mill Application Scenarios

Hot Rolling Mill Pinion Stands and Roughing Drives

Hot strip mill roughing stands receive 200–300mm thick slabs at 1200°C and reduce them to approximately 20–30mm in 5–7 passes. The gear stand pinion must split the motor torque to the two work rolls while absorbing the 3–8× torque spike at each billet entry. The double helical configuration, 42CrMo HRC 50-55 specification, and the split assembly option for large gear bodies make Korea Ever-Power's rolling mill double helical gears a direct engineering match for hot roughing stand applications in Korean POSCO-standard and Japanese JIS-specification hot strip mills. All spiralno rezani zupčanici are produced per customer drawing or sample.

Cold Rolling Mill and Finishing Stand Gears

Cold rolling mill finishing stands operate at higher pitch-line velocities (5–25 m/s) with steadier loads than hot roughing stands, but place tighter requirements on gear accuracy — transmission error at the gear mesh directly appears as periodic thickness variation (gauge wave) in the cold-rolled strip. The optional tooth grinding for rolling mill double helical gears allows finishing stand gears to be ground to higher accuracy class where gauge control requires it. The 42CrMo HRC 50-55 specification provides adequate contact fatigue life at cold rolling mill contact stresses. For the full range of Korean-manufactured proizvođač spiralnih zupčanika products, see Korea Ever-Power's homepage. The dvostruki spiralni zupčanik technology is also widely applied in tandem cold mill configurations.

Aluminium and Copper Rolling Mills

Aluminium foil rolling mills, plate mills, and copper strip mills use double helical pinion stand gears at the same HRC 50-55 specification as steel mills, but with different module and tooth count selections reflecting the softer workpiece materials and different roll force requirements. Korea Ever-Power customises module, helix angle, tooth count, and face width for each mill type. The pužni zupčanik series is available for high-ratio auxiliary drives in the same mill line.

Quality and After-Sale Service

• ✔ 12-month warranty from delivery; replacement parts dispatched by international express within warranty period to minimise mill downtime impact
• ✔ Hardness verification records per tooth flank position (Vickers or Rockwell) supplied with every order; material certificate confirming 42CrMo heat number and chemistry
• ✔ Wooden case packaging with anti-rust treatment appropriate for sea freight to Korean, Japanese, and Southeast Asian steel mill destinations
• ✔ Izrada po crtežu ili uzorku: all major CAD formats (PRO/E, AutoCAD, SolidWorks, UG) accepted; reverse engineering from worn split assembly halves available

Vrste opreme iz Koreje Ever-Power

Korea Ever-Power supplies the full range of gear types used in rolling mill lines and related steel plant machinery:

• ⬡ Jednostruki spiralni zupčanik: For rolling mill auxiliary drives — coiler, uncoiler, entry table, runout table — where double helical cost is not warranted. Full range at spiralno rezani zupčanici.
• ⬡ Zupčanik s čeljustima: Steel mill crane drives, conveyor drives, and slow-speed auxiliary drives in the mill building.
• ⬡ Konusni zupčanik: Right-angle drives for roller table cross-transfers, edger drives, and mill stand roll-change mechanisms.
• ⬡ Pužni zupčanik: High-ratio drives for roll gap adjustment (screw-down) mechanisms and guide beam positioning. See the pužni zupčanik serije.

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