Grade 1 vs Grade 2 Titanium Sheet: Composition, Forming and Application Guide
Nov 26, 2025
Commercially pure titanium sheet is classified into four grades by interstitial content, and Grade 1 and Grade 2 sit at the soft and medium end of that ladder. Both are alpha-phase, both are unalloyed, and both resist chlorides, oxidising acids and seawater through the same passive titanium dioxide film. What separates them is a small chemical difference with a disproportionate effect on how the sheet behaves in the press brake and the forming die.
Chemical Difference Between Grade 1 and Grade 2 Sheet
The two grades differ in oxygen, iron and, indirectly, in the resulting strength. The limits below are the maximum values applied to sheet under the strip, sheet and plate specification ASTM B265.
| Element | Grade 1 (R50250) | Grade 2 (R50400) | Practical meaning |
|---|---|---|---|
| Oxygen, max % | 0.18 | 0.25 | Controls strength and ductility |
| Iron, max % | 0.20 | 0.30 | Secondary strengthener |
| Nitrogen, max % | 0.03 | 0.03 | Same limit in both grades |
| Carbon, max % | 0.08 | 0.08 | Same limit in both grades |
| Hydrogen, max % | 0.015 | 0.015 | Same limit in both grades |
| Titanium | Balance | Balance | No deliberate alloying additions |
Mechanical Properties of the Two Sheets
| Property | Grade 1 sheet | Grade 2 sheet |
|---|---|---|
| Minimum tensile strength | 240 MPa | 345 MPa |
| Minimum yield strength, 0.2% offset | 138 MPa | 275 MPa |
| Minimum elongation in 50 mm | 24 % | 20 % |
| Typical hardness | Around 120 HV | Around 150 HV |
| Minimum bend radius, typical practice | 1.0 to 1.5 times thickness | 1.5 to 2.0 times thickness |
| Cold formability | Excellent, suited to deep drawing | Good, suited to bending and flanging |
The yield-to-tensile ratio is 0.58 for Grade 1 and 0.80 for Grade 2, which explains the difference in forming behaviour better than the strength numbers alone. A low ratio means the material continues to work harden after yielding, distributing strain across the deformation zone instead of concentrating it. That is why Grade 1 survives a tight draw that would tear Grade 2.
Forming, Welding and Machining Behaviour
Grade 1 sheet is the choice for deep drawn cups, expansion bellows, formed liners and explosion-bonded cladding, where the strain path demands the full 24 percent elongation. Grade 2 sheet bends, flanges and roll forms readily, and is used for heat exchanger plates, vessel shells and large fabricated panels. Both grades are welded with inert gas shielding and both must be protected until the cooled metal no longer shows discolouration, which indicates oxygen and nitrogen pickup. Springback is pronounced in both, and denser than in steel, because the elastic modulus is only about 103 GPa for Grade 1 and 105 GPa for Grade 2. Machining behaviour is similarly poor in both grades: low thermal conductivity concentrates heat at the cutting edge, so sharp tooling, modest surface speeds and abundant coolant are needed whether the sheet is Grade 1 or Grade 2.
Corrosion Performance Is Effectively Identical
Buyers sometimes assume that the stronger grade resists corrosion better. It does not. The protective oxide film is the same in both cases, and the interstitial elements that raise strength play no beneficial role in corrosion resistance. Grade 1 and Grade 2 behave almost identically in seawater, brine, hypochlorite and wet chlorine. Where the environment is reducing rather than oxidising, or where a hot chloride is trapped in a crevice, neither grade is the right answer and a palladium-modified grade such as Grade 7 should be evaluated instead.
Temperature behaviour is also common to both: continuous service in air is normally limited to around 300 degrees Celsius, and above about 600 degrees Celsius oxygen diffusion forms an alpha case that must be removed before the component enters service.
Selecting Between Them
The practical rule is to choose Grade 1 when the forming operation is the limiting step in the manufacturing plan, and Grade 2 in every other case. Grade 1 suits deep drawn and severely formed parts, sacrificial anodes and electrode substrates, cladding layers and applications where a soft, highly compliant sheet is required for sealing. Grade 2 suits pressure vessel shells, heat exchanger plates and frames, desalination plant components, marine hardware, medical instrument bodies, architectural panels and electrolyser components. Because the price difference between the two is small, the decision should be driven by manufacturability and design stress rather than by material cost. Where a part is marginal in Grade 1 for strength, moving to Grade 2 is almost always cheaper than redesigning the forming operation.
Ordering and Inspection Notes
Sheet is normally supplied annealed and pickled, with dimensional tolerances and permissible thickness variation set by the same specification that carries the chemistry and mechanical requirements. Thickness tolerance is asymmetric in titanium sheet and varies with nominal thickness and width, so the tolerance class must be stated on the order. Mechanical testing on each heat includes tensile strength, yield strength and elongation, and a bend test is used to confirm ductility on the finished sheet. Buyers should also confirm the condition, whether the sheet was produced by a fully integrated melt route, and whether the certificate identifies the applicable specification revision. Surface condition, including freedom from embedded foreign material and from deep scratches, matters more in titanium than in steel because defects in the sheet surface propagate into formed parts.
Frequently Asked Questions
Q: Can Grade 1 and Grade 2 sheet be mixed within one fabricated assembly?
A: Yes, they weld to each other without difficulty and the joint is metallurgically sound. The lower strength grade controls the design allowable in the joint region, and the welding procedure should be qualified for the thickness combination being joined.
Q: Which grade is better for an explosion-bonded clad plate?
A: Grade 1, because the bonding process requires the metal to deform extensively without cracking. The lower yield strength and higher elongation reduce the risk of interfacial fracture during the collision welding step.
Q: Is Grade 2 sheet worth the extra cost over Grade 1?
A: For any part that must carry load, yes. The 345 MPa minimum tensile strength and 275 MPa minimum yield strength allow thinner sections for the same duty, and the cost difference between the grades is modest compared with the difference between either grade and an alloy such as Ti-6Al-4V.
Q: Does the sheet need stress relief after forming?
A: Where forming strain is high or the part will be machined afterwards, a stress relief anneal reduces distortion and the risk of stress corrosion in chloride service. The treatment is carried out in vacuum or high-purity inert atmosphere to avoid contamination of the surface.
Q: How is thickness tolerance specified on a sheet order?
A: By nominating the applicable specification and tolerance class along with the nominal thickness and width. Titanium sheet has a permitted minus tolerance band of its own, so a buyer who needs a guaranteed minimum thickness should state that requirement explicitly rather than relying on nominal dimensions.
Q: Are there restrictions on the maximum sheet thickness for these grades?
A: Both grades are produced across the sheet range and into plate. Where the product crosses into plate thickness, the applicable mechanical requirements change, particularly the elongation minimum, so the design should be based on the values for the actual product form supplied.
