Forging Supplier for Global Wind Energy OEMs: Vestas, Siemens Gamesa, and GE Vernova

August 13, 2026


Vestas (Denmark), Siemens Gamesa (Spain), and GE Vernova (USA) are the world’s three largest wind turbine OEMs together supplying approximately 60% of global wind turbine installations annually. Each wind turbine model requires ring-rolled tower flanges (S355NL, Ø1,500–6,000mm), bearing rings (42CrMo4 slew rings for nacelle rotation and pitch control), and structural fittings that are procured through the OEM’s global supply chains. Indian ring rolling manufacturers with ISO 3834 quality systems, S355NL Charpy at -50°C, and established OEM approval are positioned to supply global wind energy forging demand at 20–30% cost advantage over European ring rolling supply.

OEMKey Turbine PlatformTower Flange ODBearing Ring Material
Vestas (Aarhus)V162-6.2 MW (onshore), V236-15 MW (offshore)Ø2,500mm (V162) / Ø5,500mm (V236)42CrMo4 slew ring
Siemens Gamesa (Zamudio)SG 5.0-145 (onshore), SG 14-236 DD (offshore)Ø2,800mm (SG5.0) / Ø5,500mm (SG14)42CrMo4 slew ring
GE Vernova (Schenectady)GE 3.x series (onshore), Haliade-X 14 MW (offshore)Ø2,500mm (3.x) / Ø5,000mm (Haliade)42CrMo4 slew ring
Envision (Xi’an)EN-156 6.X (onshore)Ø2,400mm42CrMo4 slew ring
Goldwind (Urumqi)GW155/4500 (onshore), GW171-6000 offshoreØ2,600mm42CrMo4 slew ring

Wind turbine tower flanges are among the highest-volume single forging category globally each wind turbine installation requires 3–6 tower section flanges (depending on tower height and section count), plus a transition piece flange connecting the tower to the monopile foundation. At 100,000+ wind turbine installations per year globally, the annual demand for tower flanges is approximately 400,000–600,000 individual ring-rolled forgings in S355NL one of the largest single forging market categories by volume.

The S355NL specification — EN 10025-3 Grade S355NL, a normalised fine-grain structural steel with guaranteed impact properties at -50°C is the near-universal material for wind turbine tower flanges globally. The ‘L’ designation means the material meets a minimum Charpy energy of 27 J at -50°C ensuring adequate toughness in the coldest expected offshore operating conditions. Some offshore wind developers in sub-Arctic regions specify impact testing at -60°C as a supplementary requirement. The Charpy test at -50°C is the primary quality gate that differentiates specification-compliant S355NL ring rolling manufacturers.

Vestas — headquartered in Aarhus, Denmark is the world’s most installed wind turbine OEM with 160+ GW of cumulative installations. Vestas’s flange qualification process requires: ISO 9001 quality management, dimensional compliance with Vestas flange drawings, and Charpy impact testing results at -50°C submitted with each production lot. Vestas approves flange manufacturers through a technical audit process and periodic surveillance.

Siemens Gamesa — formed by the merger of Siemens Wind Power and Gamesa (Spain) supplies offshore wind turbines including the SG 14-236 DD (direct drive, 14 MW, 236 metre rotor diameter). The SG 14-236 DD’s tower base flange is Ø5,500mm above Vinir’s current Ø4,500mm capacity. However, Siemens Gamesa’s onshore platforms (SG 5.0-145, SG 6.0-170) use tower flanges in the Ø2,500–3,500mm range, and intermediate tower section flanges for the SG 14-236 DD are Ø3,500–4,500mm within Vinir’s capacity.

Contact Us

Vinir Capability

  1. Ring rolling to Ø4,500mm OD for S355NL wind turbine tower flanges and 42CrMo4 bearing rings.
  2. S355NL normalised and fine-grain per EN 10025-3 with NABL Charpy at -50°C (minimum 27 J average, no individual below 20 J).
  3. 42CrMo4 through-hardened bearing rings per ISO 6336 with hardness gradient verification 28–34 HRC.
  4. Dimensional tolerances per Vestas, Siemens Gamesa, and GE Vernova flange drawings.
  5. ISO 9001 and AS9100D quality systems both accepted by wind OEMs.
  6. Batch CMM dimensional inspection.
  7. Certificate of conformance per OEM-specific format.
  8. TPI by Bureau Veritas and DNV.
  9. Annual production capacity approximately 3,000 tonnes of S355NL ring-rolled flanges.

Frequently Asked Questions

1.What is the Vestas tower flange qualification process and what must an Indian ring rolling manufacturer demonstrate?+–
Vestas’s flange manufacturer qualification involves: commercial engagement (procurement inquiry, RFQ response, pricing); technical qualification (Vestas quality engineer audit at the manufacturer facility, reviewing process capability, equipment condition, laboratory accreditation, and quality records); qualification lot production (one production run of Vestas-dimensioned flanges with full documentation Charpy at -50°C, dimensional inspection, UT if required, and CoC); Vestas quality review of the qualification lot documentation; and approval as a Vestas-qualified flange manufacturer. The Charpy at -50°C test result is the most scrutinised data point in the qualification. Total qualification timeline: 9–15 months from first contact to approved supplier status.
2.What is the transition piece in offshore wind and what ring-rolled forging components does it contain?+–
The transition piece (TP) is the structural element connecting the monopile (the steel tube pile driven into the seabed) to the wind turbine tower. The TP accommodates the slight angular offset between the monopile (which may not be exactly vertical after driving) and the tower (which must be exactly vertical for turbine operation). The TP’s flange connections to both the monopile and the tower require ring-rolled flanges. The lower TP flange (connecting to the monopile top) is typically Ø4,000–6,000mm OD depending on turbine size; the upper TP flange (connecting to the tower base) is typically Ø3,500–5,500mm OD. Both flanges must be S355NL with Charpy at -50°C.
3.How does the global offshore wind installation programme create forging demand and what volumes are involved?+–
Global offshore wind installations reached approximately 20 GW per year in 2024 and are projected to grow to 50–70 GW per year by 2030 under national government targets. At an average of 10 MW per turbine, 50 GW of annual installations requires approximately 5,000 offshore turbines per year. Each offshore turbine installation requires 4–6 tower section flanges (Ø3,500–5,500mm each), 1–2 transition piece flanges, and 6–12 bearing rings. At 5,000 turbines per year with average 8 ring-rolled forgings per turbine, the global offshore wind ring-rolled forging demand is approximately 40,000 pieces per year worth approximately $500 million–$1 billion annually.
4.What is the Indian domestic offshore wind programme and what ring rolling opportunity does it create?+–
India has announced plans for 100 GW of offshore wind capacity by 2030 the most ambitious offshore wind target in the world after China and the EU. The Indian government has issued tenders for offshore wind projects in the waters off Gujarat and Tamil Nadu. At 1 GW representing approximately 100 offshore turbines in the 10 MW class, each project creates demand for approximately 800–1,000 S355NL tower flanges and transition piece flanges. The Make in India offshore wind policy includes domestic content requirements that will create procurement pressure to source ring-rolled flanges from Indian manufacturers creating a direct domestic market for Vinir’s ring rolling capability.
5. What is the competitive landscape for global wind turbine flange supply and where do Indian manufacturers sit?+–
The global wind turbine flange market is dominated by Arcelor Mittal Gijón (Spain) integrated steelmaker with ring rolling supplying Siemens Gamesa and Vestas; Fabryka Kotłow FAKOP (Poland) major European flange manufacturer; and Dalian Huarui Heavy Industry (China) the largest Chinese flange manufacturer. Chinese ring rolling manufacturers are significant global suppliers at ex-works prices 15–25% below European, they have captured substantial market share in European offshore wind. Indian ring rolling manufacturers are competitive with Chinese pricing on an ex-works basis and have logistics advantages over Chinese suppliers for Middle East, European, and Indian domestic markets.