What Material is Grade 7 Titanium

1.What Material is Grade 7 Titanium?

Grade 7 titanium is a commercially pure titanium alloy (CP titanium alloy) classified under the ASTM B265 standard. It is specifically a titanium-palladium (Ti-Pd) alloy, distinguished by its intentional addition of a small amount of palladium to enhance corrosion resistance-especially in reducing environments where unalloyed titanium may struggle. Unlike high-strength titanium alloys (e.g., Grade 5 Ti-6Al-4V), Grade 7 prioritizes corrosion performance over extreme mechanical strength, making it a go-to material for chemical processing, marine, and industrial applications requiring long-term resistance to harsh fluids. It retains the core advantages of pure titanium, such as low density (≈4.51 g/cm³), excellent biocompatibility, and good formability, while addressing the corrosion limitations of unalloyed grades (e.g., Grade 2, Grade 4).

2.What is the chemical composition of grade7 titanium?

The chemical composition of Grade 7 titanium is strictly defined by ASTM standards (ASTM B265, ASTM F67) to ensure consistent performance. Below is the typical and maximum allowable composition (by weight percentage, wt%):

Element	Typical Content (wt%)	Maximum Allowable Content (wt%)
Titanium (Ti)	Balance	Balance
Palladium (Pd)	0.12–0.25	0.10–0.25
Iron (Fe)	≤0.20	0.30
Carbon (C)	≤0.03	0.08
Nitrogen (N)	≤0.015	0.05
Hydrogen (H)	≤0.005	0.015
Oxygen (O)	≤0.18	0.20
Other Elements (Each)	≤0.10	0.10
Other Elements (Total)	≤0.40	0.40

Key Notes: Palladium is the critical alloying element-its presence (even at low levels) significantly improves resistance to hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and other reducing acids by stabilizing the titanium oxide layer. Impurities (e.g., Fe, O, C) are tightly controlled to avoid compromising corrosion resistance or mechanical properties.

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3.What is the hardness of grade7 titanium?

The hardness of Grade 7 titanium depends on its heat treatment state and processing method (e.g., annealed, cold-worked). Below are the typical hardness values for common conditions, measured using standard scales:

1. Annealed State (Most Common)

Annealing (typically 650–750°C for 1–4 hours, followed by air cooling) softens the material for formability while retaining corrosion resistance.

Brinell Hardness (HB): 110–150 HB (using a 3000 kg load and 10 mm diameter tungsten carbide ball).

Vickers Hardness (HV): 120–160 HV (500 g load, 10–15 second dwell time).

Rockwell Hardness (HR): 70–85 HRB (B-scale, for softer metals) or 20–30 HRC (C-scale, less common for annealed Grade 7).

2. Cold-Worked State

Cold working (e.g., rolling, forging, drawing without subsequent annealing) increases hardness by introducing dislocations in the titanium lattice.

Brinell Hardness (HB): 180–220 HB (moderate cold work, ~20–30% reduction in area).

Vickers Hardness (HV): 190–230 HV.

Rockwell Hardness (HR): 85–95 HRB or 30–35 HRC.

3. Key Considerations

Hardness is inversely related to ductility: cold-worked Grade 7 is harder but less formable than annealed material.

Compared to other CP titanium grades: Grade 7 has similar hardness to Grade 2 (annealed: ~120–140 HB) but is slightly harder than Grade 1 (annealed: ~100–120 HB) due to palladium addition and tighter impurity control.

Hardness values are not intended for high-wear applications-Grade 7 is selected for corrosion resistance, not abrasion resistance. For wear-prone uses, titanium alloys with higher alloying (e.g., Ti-6Al-4V) or surface treatments (e.g., nitriding) are preferred.