Open Die Forging Manufacturer India: Large-Section Structural and Shaft Forgings

August 13, 2026


Open die forging — compressing heated metal between flat or shaped dies without a fully enclosing cavity is the production method for the world’s largest and most structurally demanding forged components: power generation rotor shafts, ship propulsion shafts, pressure vessel shell forgings, and mining equipment main shafts. Vinir’s 3,000T hydraulic press with dango manipulator at Bommasandra Unit 2 produces open die shaft forgings to 15,000 kg in carbon steel, alloy steel (4340, EN24, CrMoV, P91), stainless steel, and nickel alloys at 30–40% cost advantage over European and US domestic open die supply.

Forging CategoryMaterialWeight RangeStandard
Shaft forgings (stepped, tapered)4340, EN24, CrMoV alloy steel100–15,000 kgASTM A388, API 20B
Propulsion shaft (marine)4340, C45 carbon steel500–15,000 kgABS / DNV / Lloyd’s Register survey
Pressure vessel shell / nozzle forgingSA-516 Gr.70, 4130, P91, SA-182 F316L200–10,000 kgASME VIII, IBR
Disc and ring blanks (ring-rolled pre-form)S355NL, 42CrMo4, EN36200–8,000 kgEN 10025-3, API 20B
Mining equipment shafts (crusher, mill)4340, EN24, Q&T to 1,200 MPa500–8,000 kgASTM A388, BV/Intertek survey


Open die forging uses a hydraulic or mechanical press to compress and shape a heated billet between flat or contoured dies without a fully enclosing die cavity. The workpiece is manipulated rotated and repositioned between press strokes using a dango (forging manipulator), a powered rail-mounted vehicle that grips the hot billet and positions it precisely under the press. The combination of press force and manipulator motion allows open die forging to produce essentially any shape in any size, limited only by the press force available and the billet weight the manipulator can handle.

The critical metallurgical benefit of open die forging distinct from all other manufacturing methods is the ability to control the accumulated plastic deformation (forging reduction ratio) throughout the cross-section of a large forging. A 10,000 kg turbine rotor shaft forging requires multiple working passes with intermediate reheats to accumulate the total reduction ratio needed to break down the as-cast grain structure of the starting ingot and develop the mechanical properties required by the specification.

Vinir’s 3,000T hydraulic press equipped with a dango manipulator can forge components from small open die shaft sections (100 kg) to large structural forgings approaching 15,000 kg rough-forged weight. The combination of 3,000T press force with precise manipulator control allows open die forging of complex profiles: tapered shafts, stepped diameter shafts, flanged shafts, and ring-like structural cross-sections that serve as pre-forms for subsequent ring rolling.

India’s open die forging cost advantage versus European supply (Saarschmiede Germany at 17,500T, Sheffield Forgemasters UK at 10,000T) is typically 30–40% on ex-works price for equivalent material and quality. For the 500–15,000 kg open die range where Vinir’s 3,000T press is competitive, this cost advantage creates strong commercial cases for procurement requalification from European or Korean sources to Indian supply.

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Vinir Capability

  1. 3,000T hydraulic press with dango manipulator at Bommasandra Unit 2.
  2. Open die forgings 100 kg to 15,000 kg rough-forged weight.
  3. Materials: carbon steel (SA-516 Gr.70, C45), low alloy steel (4340, EN24, 42CrMo4), CrMoV power generation alloy steel, P91 (9Cr-1Mo-V-Nb), SA-508 Grade 3 equivalent, SA-182 F316L stainless, duplex 2205.
  4.  AMS 2750-calibrated heat treatment furnaces for quench-and-temper up to 15,000 kg load.
  5. 100% UT per ASTM A388 with large-section calibration standards.
  6.  NABL Charpy at -20°C, -40°C, and elevated temperature.
  7. Straightness verification for shaft forgings (≤1mm/metre).
  8. Surface MT and PT.
  9. TPI by Bureau Veritas, DNV, and ABS.

Frequently Asked Questions

1.What size range of open die forging can Vinir’s 3,000T press produce and what limits the upper weight?+–
Vinir’s 3,000T hydraulic press produces open die shaft forgings from 100 kg to approximately 15,000 kg rough-forged weight in standard alloy steel. The upper weight limit is determined by: the press force (3,000T) relative to the material flow stress and cross-sectional area being forged; the dango manipulator capacity (maximum weight the manipulator can safely grip and position); and the furnace capacity for intermediate reheats. For nickel alloy and super duplex stainless forgings, the upper weight limit is lower — approximately 5,000 kg because the higher flow stress requires more press force per unit area.
2.What is the forging reduction ratio documentation requirement for pressure vessel and nuclear applications?+–
Forging reduction ratio is the ratio of the original cross-sectional area of the billet to the final cross-sectional area of the forging. API 20B PSL 3, ASME VIII Division 2, and nuclear NQA-1 specifications require that the reduction ratio be documented for each critical forging as a step-by-step record showing the cross-sectional area at each stage of the process. Minimum reduction ratios are typically 3:1 for pressure vessel shell forgings, 4:1 for shaft forgings, and 5:1+ for the most demanding nuclear applications. Vinir’s forging process documentation includes a forging sequence record maintained by the forge shop operator and reviewed by the quality inspector at each intermediate stage.
3.What is the heat treatment sequence for large open die 4340 shaft forgings and how does section thickness affect it?+–
Large 4340 shaft forgings (above 300mm diameter) require carefully managed quench-and-temper. The austenitising temperature is 845–900°C (held approximately 1 hour per 25mm of section thickness). Quenching must be rapid enough to achieve martensite transformation throughout the cross-section for a 500mm diameter shaft, polymer quenching balances quench severity with thermal shock cracking risk. Tempering at 540–650°C follows immediately. The core of a large section cools more slowly than the surface during quenching meaning a 500mm diameter shaft may develop slightly lower hardness at the core than the surface. Hardness measurements at multiple depths confirm adequate through-section transformation.
4.What ABS marine classification survey requirements apply to propulsion shaft forgings?+–
ABS Rules for Building and Classing Steel Vessels govern propulsion shaft forgings for ABS-classed vessels. ABS requires that the forging manufacturer be approved by ABS. For each production lot, ABS survey requires: witness of heat treatment (furnace chart review, thermocouple verification), witness of mechanical testing (tensile and Charpy at the testing laboratory with ABS surveyor present), review of UT report, and issuance of ABS Grade certificate. The ABS Grade for propulsion shafts is typically Grade 3 or Grade 4 specifying minimum tensile strength, yield, elongation, and Charpy requirements. Vinir’s ABS approval covers propulsion shaft forgings in carbon and alloy steel from 500 kg to 15,000 kg.
5.What is a forging manipulator (dango) and how does it improve open die forging quality?+–
A forging manipulator (dango) is a powered rail-mounted vehicle that grips the hot forging billet and can rotate it axially, tilt it, and move it along the rail positioning the billet in three dimensions relative to the press dies. The manipulator allows the press operator to work the entire billet surface systematically: rotating between press strokes to ensure uniform reduction around the circumference and moving axially to work the full length. Without a manipulator, an open die forge shop is limited to very short forgings that can be manipulated manually using tongs. Manipulator control quality directly affects forging shape accuracy and ensures consistent reduction ratio throughout the forging length.