Grade 3 Titanium Sheet: What GR3 Really Is
Grade 3 (GR3) titanium sheet is a commercially pure, unalloyed titanium product, not a two-phase alloy such as Grade 5 (Ti-6Al-4V). ASTM B265 controls it alongside Grades 1, 2 and 4, and those four grades form a simple strength ladder driven mainly by interstitial oxygen. Grade 1 is the softest and most formable, Grade 4 the strongest and least ductile, and Grade 3 sits in the middle. That middle position is why hot rolled GR3 sheet is specified so often in chemical, medical, marine and desalination fabrication: it provides substantially more yield strength than Grade 2 while retaining enough elongation for rolling, bending, flanging and deep drawing.
A frequent error in procurement documents is to describe GR3 as a titanium alloy. GR3 contains no deliberate aluminium or vanadium addition, and its properties come from oxygen, nitrogen and iron held inside the ASTM B265 limits. If a drawing calls for a 900 MPa tensile sheet, the correct answer is Grade 5 or Grade 23 rather than GR3.
Chemical Composition and Mechanical Properties
ASTM B265 sets maximum interstitial and iron levels for every commercially pure grade. Interstitials are effectively the alloying elements of unalloyed titanium, so raising oxygen from 0.18 percent to 0.35 percent is what converts Grade 1 behaviour into Grade 3 behaviour.
| Grade | Oxygen, max % | Nitrogen, max % | Carbon, max % | Iron, max % | Hydrogen, max % |
|---|---|---|---|---|---|
| Grade 1 | 0.18 | 0.03 | 0.08 | 0.20 | 0.015 |
| Grade 2 | 0.25 | 0.03 | 0.08 | 0.30 | 0.015 |
| Grade 3 | 0.35 | 0.05 | 0.10 | 0.30 | 0.015 |
| Grade 4 | 0.40 | 0.05 | 0.10 | 0.50 | 0.015 |
Typical minimum room-temperature results for annealed sheet and plate are listed below. Values apply to the finished product after the specified anneal, and they are minimums rather than typical mill averages, so a supplier must report actual test results against them.
| Grade | Tensile strength, min | Yield strength, min | Elongation, min |
|---|---|---|---|
| Grade 1 | 240 MPa | 138 MPa | 24 % |
| Grade 2 | 345 MPa | 275 MPa | 20 % |
| Grade 3 | 450 MPa | 380 MPa | 18 % |
| Grade 4 | 550 MPa | 483 MPa | 15 % |
For GR3 the practical consequences are a 450 MPa minimum tensile strength, a 380 MPa minimum yield strength and 18 percent minimum elongation. Density is 4.51 g/cm3, melting point about 1668 C, elastic modulus roughly 105 GPa and thermal conductivity near 21.9 W/(m K). Those figures explain the grade selection logic: GR3 gives about 38 percent more yield strength than Grade 2 while keeping useful ductility.
Hot Rolling Process and Product Condition
Hot rolling is used when the required thickness exceeds what cold rolling can deliver economically, typically above 4 mm to 5 mm, and it is also the route for wide plate. The slab or ingot is heated into the beta or upper alpha-beta field, rolled in several passes, then annealed and descaled. Thickness reduction per pass is limited because titanium work hardens quickly and its low thermal conductivity keeps the surface cool while the core stays hot, so the roll schedule and reheating steps must be controlled to avoid surface laps and edge cracking.
Annealed and pickled (AP): the default delivery condition, with an oxide-free matte grey surface produced by acid pickling after annealing; suitable for forming and welding.
Hot rolled, annealed, un-pickled: a dark mill-scale surface used where the part is to be machined or blasted afterwards.
Ground or polished: thickness-controlled sheet for gasket, medical and vacuum service where surface defects control fatigue life.
Bright annealed: produced under protective atmosphere for a clean surface without pickling, mainly on thinner material.
ASTM B265 covers sheet, strip and plate from roughly 0.4 mm up to 100 mm thickness, and JIS H4600 and GB/T 3620.1 provide the corresponding Japanese and Chinese frameworks for the same commercially pure grades. In GB/T 3620.1 the commercially pure designations are TA1, TA2, TA3 and TA4, which map to ASTM Grades 1 to 4 respectively; TA3 is the usual Chinese equivalent of GR3 and is often the grade quoted on domestic drawings.
Standard Supply Range and Dimensions
Suppliers of hot rolled GR3 sheet normally quote an envelope rather than a single size, and the achievable width shrinks as thickness rises because of rolling mill load limits.
| Item | Typical range | Notes |
|---|---|---|
| Thickness | 0.5 mm to 30 mm | Below 0.5 mm material is normally cold rolled strip |
| Width | 600 mm to 2500 mm | Wider plate is quoted per enquiry |
| Length | 1000 mm to 3000 mm | Cut to length, or supplied as coil for thin sheet |
| Tolerance | Per ASTM B265 / JIS H4600 | Thickness, width, camber and flatness tolerances |
| Edge condition | Mill edge, slit, sheared | Slit and deburred edges for welding lines |
Applications of Hot Rolled GR3 Titanium Sheet
Chemical and petrochemical equipment: pressure vessel linings, column internals, heat exchanger tube sheets and reaction vessels handling chlorides, oxidising acids and hypochlorite.
Desalination and marine: evaporator shells, brine handling plate and seawater piping components where Grade 2 would be marginal on strength.
Medical and pharmaceutical: equipment frames, brackets and non-implant hardware that require corrosion resistance plus autoclave cleaning.
Electronics and electrochemical: electrode plates, anode baskets, plating jigs and current-carrying components where the higher oxygen grade is acceptable.
Aerospace and general engineering: brackets, duct supports and non-critical airframe parts where Grade 5 stiffness or strength is not required.
The common thread is moderate strength combined with excellent resistance to chloride pitting and crevice corrosion, plus a passive oxide film that re-forms immediately after scratching.
How to Specify and Inspect GR3 Sheet
A workable purchase specification for GR3 sheet states the standard, the grade, the condition, the dimensions and the test requirements together, because an ambiguous order is the usual cause of rejected material.
Standard and grade: ASTM B265 Grade 3, JIS H4600 Class 3, or GB/T 3620.1 TA3, quoted explicitly.
Condition: annealed and pickled, annealed and descaled, ground, or bright annealed.
Dimensions: thickness with tolerance class, width, length and edge condition.
Testing: tension test per lot, chemical analysis, hardness where agreed, and ultrasonic inspection for plate used in pressure service.
Documentation: mill test certificate with heat number traceable to the coil or plate, plus dimensional inspection report.
On receipt, verify the heat number against the certificate, measure thickness at several points across the width, check flatness and camber, and confirm the surface is free of laps, scale inclusions and deep grinding marks. Titanium is not magnetic, so material verification relies on chemical analysis or eddy-current sorting rather than magnetic sorting.
Frequently Asked Questions
Q: Is Grade 3 titanium an alloy or a commercially pure metal?
GR3 is commercially pure titanium. It has no deliberate alloying addition; oxygen and other interstitials within ASTM B265 limits provide the strength difference from Grade 2.
Q: What is the difference between Grade 2 and Grade 3?
Grade 3 permits up to 0.35 percent oxygen against 0.25 percent for Grade 2, raising minimum tensile strength from 345 MPa to 450 MPa and minimum yield strength from 275 MPa to 380 MPa, while elongation falls from 20 percent to 18 percent.
Q: Which standards cover hot rolled GR3 titanium sheet?
ASTM B265, JIS H4600 and GB/T 3620.1 are the usual references, with TA3 as the Chinese commercially pure equivalent of the Grade 3 composition.
Q: What thickness range is normally available?
Hot rolled GR3 sheet is typically supplied from about 0.5 mm to 30 mm thick, with width from 600 mm to 2500 mm and cut lengths from 1000 mm to 3000 mm.
Q: Can GR3 sheet be welded?
Yes. GR3 is readily welded by gas tungsten arc and plasma methods, provided the molten pool and hot metal are shielded by inert gas and the joint is clean and oxide-free. Filler metal of matching or slightly lower strength is generally used.
Q: When should Grade 5 be selected instead of Grade 3?
Choose Grade 5 or another alloy when the design needs tensile strength well above 450 MPa, when elevated-temperature strength is required, or when weight saving justifies the higher cost and lower formability of an alloy grade.
