1. What is Grade 7 Titanium?
Grade 7 titanium is a high-purity, corrosion-resistant variant of commercially pure titanium (CP Ti) , classified under ASTM B265 (the standard for titanium and titanium alloy plate, sheet, and strip) and other industrial standards. It is part of the CP Ti family (alongside Grades 1–4, 7, 11, etc.) but is uniquely distinguished by the addition of a small amount of palladium (Pd, typically 0.12–0.25% by weight) -a noble metal that significantly enhances its resistance to severe corrosion, especially in reducing acid environments where standard pure titanium grades (e.g., Grade 3) may struggle.
Unlike titanium alloys (e.g., Grade 5 Ti-6Al-4V), Grade 7 retains the inherent properties of pure titanium (e.g., excellent biocompatibility, good formability) while addressing a critical limitation: vulnerability to pitting, crevice corrosion, or general corrosion in aggressive media like sulfuric acid, hydrochloric acid, or chloride-rich solutions. This makes it a specialized material for industries where corrosion resistance is non-negotiable, such as chemical processing, oil and gas, and certain medical applications.
2. What is the density of Grade 7 Titanium?
The density of Grade 7 titanium is nearly identical to that of other commercially pure titanium grades, as the small addition of palladium (≤0.25%) has a negligible impact on overall density.
Typical density: 4.51 grams per cubic centimeter (g/cm³)
In imperial units: Approximately 0.163 pounds per cubic inch (lb/in³)
This density is roughly 60% of the density of steel (≈7.85 g/cm³) and 56% of the density of copper (≈8.96 g/cm³), maintaining pure titanium's key advantage of being a lightweight yet strong material.
3. What is the hardness range of Grade 7 Titanium?
The hardness of Grade 7 titanium depends primarily on its temper (heat treatment state) , with the most common temper being annealed (a soft, ductile state used for most forming and fabrication processes). Hardness values are typically measured using the Brinell Hardness Test (HB) or Rockwell Hardness Test (e.g., Rockwell B, HRB).
Typical Hardness Ranges (Annealed State):
Brinell Hardness (HB): 170–210 HB
Rockwell B Hardness (HRB): Approximately 85–95 HRB
For context, this hardness is slightly higher than that of annealed Grade 3 titanium (150–180 HB) but lower than that of titanium alloys like Grade 5 (300–350 HB). The modestly higher hardness compared to standard CP grades is attributed to the small palladium addition, which subtly refines the material's microstructure without compromising its ductility.
If Grade 7 is subjected to cold working (e.g., rolling, drawing) to increase strength, its hardness will rise proportionally-for example, cold-worked Grade 7 may reach 220–250 HB-but annealed hardness remains the industry standard for most applications.
