Ring Gear for Wind Turbine – 42CrMo, Mn6 Z109, DIN Cl.7

Ring gears for wind turbines are among the most demanding large-format ring gear applications in industrial power transmission. The wind turbine's main gearbox uses a multi-stage planetary arrangement where the ring gear is the primary structural and load-carrying element — fixed to the gearbox housing while the rotor-connected planet carrier drives multiple planet gears simultaneously. At rated power, a 2 MW wind turbine's first-stage planetary ring gear may carry 1.5–2.5 MNm of reaction torque in continuous operation, exposed to variable loads from fluctuating wind speed, shock loads from gusts, and thermal cycling from ambient temperature changes. Korea Ever-Power manufactures wind turbine ring gears in 42CrMo alloy steel to DIN 3962 Class 7 — with full manufacturing capability to OD 2,500 mm and module up to 45 mm (after tooth grinding).

Ring gears have a diversified industry presence and are typically used in passenger cars, trucks, tractors, earth moving equipment, marine engines, lawn mowers, and industrial/power generation. Wind turbine ring gears represent the largest and most demanding end of this range. Korea Ever-Power is a factory — size per drawing, material and specifications per requirement, free samples available.

Standard Wind Turbine Ring Gear — Basic Data

Technical Detail — Materials and Tolerances

Deep Hardenability

42CrMo's chromium-molybdenum alloying allows the quench hardening effect to penetrate deeply into large cross-sections — a wind turbine ring gear blank may be 200–500 mm thick at the rim. Without adequate hardenability, the centre of the rim would remain soft after quenching, resulting in lower core toughness and risk of brittle fracture initiation at the core under the bending stresses at the tooth root.

Fatigue Resistance at Low Temperature

Wind turbines operate in environments down to −30°C to −40°C in northern climates. At low temperatures, steel's fracture toughness (K1c) decreases — making toughness at low temperature a critical material requirement for wind turbine ring gears. 42CrMo properly heat-treated to 250–350 HB provides adequate fracture toughness at −30°C for wind turbine service, where simpler carbon steels (C45) may be at risk of brittle fracture initiation at the tooth root under high load transients in cold weather.

High Contact Fatigue Strength

Wind turbine ring gears experience over 10⁹ tooth contact cycles in their 20-year design life at a 3 MW rated power site running at average capacity factor of 35%. The contact stress on the tooth surface must remain below the material's endurance limit for pitting fatigue across this very high cycle count. 42CrMo at 280–320 HB provides a contact fatigue endurance limit approximately 25–35% higher than C45 at the same hardness range, directly increasing the ring gear's pitting-free service life.

DIN 3962 Class 7 — Wind Turbine Standard

DIN 3962 (now superseded by DIN ISO 1328 but still specified in many wind turbine gearbox drawings) Class 7 is the minimum accuracy standard for wind turbine main gearbox ring gears. It corresponds approximately to AGMA Class 9 or DIN ISO 1328 Class 7. At this accuracy level, the transmission error of the ring gear pair is low enough that it does not generate significant acoustic emission at the blade-passing frequency harmonics that wind turbine gearboxes are characteristically sensitive to.

Wind Turbine Main Gearbox

42CrMo ring gears Mn=4–8 in the planetary stages of wind turbine main gearboxes for 0.5–5 MW turbines. The first-stage planetary ring gear carries the full low-speed rotor torque — the highest torque point in the wind turbine drivetrain. DIN 3962 Class 7 and tooth grinding to Ra 0.6 are mandatory for the 20-year design life target under variable wind loading.

Pitch and Yaw Actuator Drives

42CrMo or carbon steel ring gears Mn=2–5 in the pitch actuator planetary drives that rotate each turbine blade to control the angle of attack, and in the yaw drive planetary gearboxes that rotate the nacelle to track wind direction. Both drives cycle continuously throughout the turbine's operating life and are exposed to outdoor temperature and corrosion conditions.

Heavy Industrial Gearboxes

Large-module ring gears (Mn=6–26) for industrial planetary gearboxes in rolling mill drives, cement plant kiln drives, mining equipment drives, and ship propulsion planetary gearboxes. The same 42CrMo material and DIN Class 4–8 accuracy capability that serves wind turbines covers the full range of large-module heavy industrial ring gears.

Marine Propulsion

Alloy steel ring gears Mn=4–10 in marine reduction gearbox planetary stages. Marine ring gears share the wind turbine ring gear's requirement for high toughness, adequate hardenability, and resistance to corrosive saltwater atmosphere. 42CrMo with appropriate surface treatment or CrNiMo stainless-clad variants are specified for offshore vessel gearboxes.

Power Generation

Large ring gears in hydroelectric generator planetary stages, tidal power generator gearboxes, and large diesel generator sets. Power generation ring gears share the wind turbine requirement for long service intervals (5,000–20,000 hours between overhauls) driven by the high cost of unplanned power generation outages.

Oil and Gas Equipment

Alloy or stainless steel ring gears Mn=4–20 in oil and gas downhole drilling tool planetary stages, topside pump planetary drives, and wellhead control valve planetary actuators. The 2,500 mm OD capability covers the largest slewing ring gears used in offshore drilling equipment and crane systems.

What is the delivery time for wind turbine ring gears?

For standard configurations in stock: 5–10 days. For custom ring gears (non-standard module, specific tooth count, or special heat treatment not in standard production): 15–20 days depending on quantity. Wind turbine ring gears at large module (Mn=6–10) and OD (500–2,500 mm) require significant forging, rough machining, heat treatment, and final grinding lead time — the 15–20 day delivery window assumes the material is available in stock. For very large ring gears requiring forging from billet, the lead time will be longer and is confirmed at the quotation stage.

Why is tooth grinding required for wind turbine ring gears?

Heat treatment (quenching and tempering, or induction hardening) introduces thermal distortion in the ring gear blank — the tooth profile deforms slightly during the quench as the surface and core cool at different rates. For wind turbine ring gears at DIN 3962 Class 7, the distortion from heat treatment exceeds the allowed tolerance — the gear must be tooth-ground after heat treatment to correct the profile back to the dimensional tolerance. Tooth grinding achieves Ra 0.6 tooth surface finish (vs Ra 3.2 for shaped or milled), which directly reduces the micro-pitting risk at the tooth contact zone over the 20-year service life.

Are free samples available for wind turbine ring gears?

Yes — Korea Ever-Power can offer free samples for wind turbine ring gears, with the freight cost paid by the customer. For large ring gears (above approximately 300 mm OD), the "sample" is typically a smaller-format sample ring gear demonstrating the material, tooth profile accuracy, heat treatment, and surface treatment — not necessarily at full size, unless full-size sampling is requested. For standard module combinations in stock, the sample demonstrates the production standard before the full production order is placed. Contact Korea Ever-Power with the specification to confirm what form the sample will take for your application.

What are the payment terms for wind turbine ring gear orders?

Payment terms depend on order value: for orders ≤ USD 1,000, 100% payment in advance is required. For orders > USD 1,000, the standard terms are 30% T/T in advance (to cover material procurement and production set-up) and the balance (70%) before shipment (after production completion and final inspection). For very large wind turbine ring gear orders where the order value requires additional payment security, Letter of Credit (L/C) payment is also available — contact Korea Ever-Power to discuss at the quotation stage. Contact our team for a quotation.

"We supply wind turbine gearboxes for a 2 MW coastal turbine programme and source 42CrMo ring gears Mn=6, Z=109 from Korea Ever-Power. DIN 3962 Class 7 confirmed on our gear measurement machine — profile deviation within tolerance on all teeth. Tooth surface Ra 0.6 measured by stylus profilometer. Delivery 16 days on our last production order; within the 15–20 day range confirmed at quotation."

Kim Dong-jun  |  Wind Turbine Gearbox Engineer, Incheon Renewable Energy Systems Co.  ·  Q1 2026

"We manufacture yaw drive planetary gearboxes for offshore wind turbines and use alloy steel ring gears Mn=4 from Korea Ever-Power. The ±0.005 mm OD tolerance is confirmed at our incoming CMM — the ring gear interference fit in the gearbox housing is tight and the OD tolerance determines whether the fit is within specification. Free sample confirmed the OD tolerance before we committed the full production order."

Lee Sang-hyeon  |  Offshore Wind Gearbox Engineer, Gyeonggi Offshore Wind Systems Co.  ·  Q4 2025

"We supply large industrial planetary gearboxes for cement plant kiln drives — ring gears Mn=14, OD 1,200 mm. Korea Ever-Power confirmed their tooth grinding capability to OD 2,500 mm and max module 45 mm — covering our size specification with margin. 42CrMo material certificate and Q&T heat treatment report included with delivery. 30% T/T advance payment, balance before shipment — standard terms for our procurement process."

Park Sang-woo  |  Heavy Industrial Gearbox Engineer, Busan Industrial Drive Systems Co.  ·  Q2 2026

"We distribute wind turbine gearbox repair ring gears for the Korean and Southeast Asian wind turbine aftermarket. Korea Ever-Power's 5–10 day stock delivery on standard Mn=6 configurations means we can respond to urgent gearbox failure repairs without the 15–20 day production wait. The 42CrMo material and DIN 3962 Class 7 accuracy match the OEM specification — accepted at all our wind turbine operator customers' maintenance incoming inspections."

Choi Hyeon-jun  |  Wind Turbine Parts Distribution Manager, Daejeon Wind Energy Supply Co.  ·  Q3 2025

"We manufacture marine vessel planetary reduction gearboxes. Korea Ever-Power's tooth grinding capability to 2,500 mm OD and module 45 mm covers our largest marine ring gear specification. 17CrNiMo5 alloy steel substituted for 42CrMo at our request — Korea Ever-Power confirmed the material availability and confirmed the equivalent DIN Class 4 accuracy at the larger module. All material and mechanical test documentation included with delivery for our classification society records."

Yoon Jae-bum  |  Marine Propulsion Gearbox Engineer, Ulsan Marine Drive Systems Co.  ·  Q1 2025