GRADE PROFILE
Titanium grade 7 — R52400
Grade 7 is unalloyed titanium with 0.12 to 0.25% palladium added. That minimal addition shifts the alloy's behaviour in reducing media, precisely where grade 2 is attacked. It is a titanium for acids.
- Titanium
- PREN: does not apply to this family
When to choose it
In dilute hydrochloric and sulphuric acid, where grade 2 is attacked. In chlorinated chemistry and acid processes, on condensers and heat exchangers in aggressive marine service, in desalination, and in pulp bleaching.
The criterion is the reducing character of the medium. Palladium assists repassivation in conditions where grade 2 no longer repassivates.
When not to choose it
By default in place of grade 2. Palladium makes the grade considerably more expensive and only works in reducing media: in ordinary seawater, grade 2 does exactly the same job.
In oxidising media, where grade 2 is sufficient.
In hydrofluoric acid, even dilute: titanium is attacked there whatever the grade, and palladium changes nothing.
And by specifying "grade 7" where a grade 7H is expected — these are two distinct designations.
Composition
| Element | % | Note |
|---|---|---|
| Ti | ≥ 99.2 | balance |
| Pd | 0.12–0.25 | — |
| Fe | ≤ 0.3 | — |
| O | ≤ 0.25 | — |
| C | ≤ 0.1 | — |
| N | ≤ 0.03 | — |
| H | ≤ 0.015 | — |
Mechanical properties
| Standard | Form | Rm (MPa) | Rp0.2 (MPa) | A (%) | Hardness |
|---|---|---|---|---|---|
| ASTM B338 | tube sans soudure et soudé, état recuit | ≥ 345 | ≥ 275 | ≥ 20 | ≤ 215 HB |
Designations and standards
| Reference | Designation |
|---|---|
| EN (numeric) | 3.7235 |
| EN (symbolic) | — |
| ASTM / AISI | Ti Grade 7 |
| UNS | R52400 |
| JIS | — |
| AFNOR | — |
Tube product standards :
- ASTM B338
- ASME SB338
Availability
Available in welded and seamless tube to ASTM B338. Structured dimensional data for this grade is not yet documented in our reference set: send us your sizes. EN 10204 3.1 material certificates supplied with the goods. As with all titanium, welding requires strict gas shielding.
Related grades
- Titanium grade 2 (3.7035) — the default, far cheaper, outside reducing media.
- C-276 (N10276) — the nickel route for concentrated reducing acids.
- 904L (1.4539) — the stainless route for acids, where chlorides are not the issue.
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Frequently asked questions
- Does palladium really justify the premium?
- Only in reducing media. At 0.12–0.25% it is expensive per kilo of alloy, and outside its domain it adds nothing measurable. The reasoning is the same as for the molybdenum in 316L: the element is only worth paying for when it works.
- Grade 7 or C-276 in hydrochloric acid?
- Grade 7 at dilute concentrations and where aerated chlorides are present; C-276 at high concentrations in reducing conditions. On a borderline application, testing in the real medium settles it better than a table.
- Does PREN apply?
- No, no more than to grade 2: the formula describes stainless steels.