What Titanium Forging Is
Titanium forging is the shaping of billets, bars or preforms by compressive deformation at controlled temperature. The process refines the cast structure, closes internal porosity and develops the wrought microstructure that gives titanium components their fatigue strength and toughness. Forgings are used for critical rotating and load-bearing parts in aerospace, chemical and marine equipment where machined-from-bar parts cannot deliver the required integrity.
Key Standards and Specifications
The primary product standard is ASTM B381, which covers titanium and titanium alloy forgings in all common grades. Aerospace supply adds AMS specifications: AMS 4928 covers Ti-6Al-4V bar, rod and forgings, AMS 4967 covers Ti-6Al-4V forgings, and AMS 2380 defines the approval and control of titanium alloy forging stock. AMS 6931 is the aerospace document for Ti-6Al-4V forgings. Together these documents fix composition, mechanical properties, sampling and marking.
ASTM B381 for general titanium forgings.
AMS 4928 for Ti-6Al-4V bar and forgings.
AMS 4967 for Ti-6Al-4V forgings.
AMS 2380 for forging stock control.
AMS 6931 for Ti-6Al-4V forgings in aerospace service.
Forging Temperature and Beta Transus Control
The beta transus is the temperature above which the material is fully beta phase, and it is the single most important control point in titanium forging. For Ti-6Al-4V the transus sits near 995 degrees Celsius, and forging is normally performed in the alpha-beta field below this line to produce a fine equiaxed structure. Beta forging above the transus gives different fracture toughness and creep properties and is specified only where the design requires it. Temperature uniformity across the billet is essential, since local overheating produces a transformed structure that cannot be corrected by later heat treatment.
Defect Avoidance in Titanium Forging
Titanium is sensitive to surface contamination at forging temperature. Oxygen and nitrogen pick-up forms an alpha case, a hard brittle layer that must be removed by machining or chemical milling before the part enters service. Forging dies, lubricants and heating atmospheres are controlled to minimize contamination, and the finished forging is inspected for surface defects such as laps, folds and cracks.
Inspection and Testing
Forgings are verified by chemical analysis, tensile testing and ultrasonic inspection according to the governing specification. Hardness, microstructure and dimensional checks confirm that the forging meets the ordered class. Traceability is maintained from the ingot heat through the finished component, and the mill test certificate records all results.
Frequently Asked Questions
Q: What is the main standard for titanium forgings?
A: ASTM B381 covers titanium and titanium alloy forgings, while aerospace buyers usually invoke AMS specifications on top of it.
Q: What is the beta transus?
A: The beta transus is the temperature above which titanium is fully beta phase, and it controls whether forging produces an equiaxed or transformed structure.
Q: Why is forging temperature control critical?
A: Forging above the intended range creates a transformed microstructure and surface contamination that cannot be corrected by later heat treatment.
Q: What is alpha case?
A: Alpha case is a hard brittle surface layer formed by oxygen and nitrogen pick-up at high temperature, and it must be removed before service.
Q: Which AMS documents apply to Ti-6Al-4V forgings?
A: AMS 4928 covers bar and forgings, AMS 4967 covers forgings, and AMS 2380 controls the approval of forging stock.
Q: How are titanium forgings inspected?
A: By chemical analysis, tensile testing, ultrasonic inspection and dimensional checks, with full traceability to the ingot heat.
