Titanium Grade 2: Strength and Versatility

Commercially pure Titanium is classified into Grades 1 through 4 depending on yield strength and allowable levels of iron, carbon, nitrogen, and oxygen.

Applications

In saltwater, Grade 2 is fully resistant to corrosion at temperatures up to 600 F, rendering it ideal for a variety of marine uses. It is appropriate for use in evaporators and condensers as well as desalination plants. Aerospace is another sector where titanium is suitable, where corrosion resistance and formability are absolutely crucial. In addition to titanium sheet airframe skins, this Grade 2 is perfect for brackets, ductwork and galley equipment.

Some other Grade 2 Applications:

•             Architecture

•             Automotive

•             Power generation

•             Hydro-carbon processing

•             Medical industry

•             Exhaust pipe shrouds

•             Chlorate manufacturing

•             Electroplating (baskets, jigs, cathodes and starter-sheet)

Commercially pure (CP) titanium is unalloyed. At service temperature it consists of 100% hcp alpha phase. As a single-phase material, its properties are controlled by chemistry (iron and interstitial impurity elements) and grain size. CP Ti Grade 2 has a minimum yield strength of 275 Mpa (40 ksi), and relatively low levels of impurity elements, which places it between Grades 1 and 3 in terms of strength.

Grade 2’s Corrosion Resistance

The corrosion resistance of Titanium Grade 2 is due to the presence of a stable, continuous, tightly adherent oxide layer. This layer forms spontaneously and immediately upon exposure to oxygen and, even if damaged, it re-forms as long as there is some source of oxygen (air or moisture) in the environment. In saline water, it is fully resistant to corrosion at temperatures up to 315ºC (600ºF). The possibility of crevice corrosion must be considered, however, and components should be appropriately designed to avoid tight crevices.

Fallibilities

Conditions under which CP titanium Grade 2 is susceptible to corrosion are strongly reducing acids, alkaline peroxide solutions, and molten chloride salts. Crevice corrosion can occur in hot halide or sulfate solutions (>1000 ppm at 75ºC or higher), which can be a consideration in marine applications. Conditions under which Titanium Grade 2 is vulnerable to stress-corrosion cracking include anhydrous methanol or methanol/halide solutions, red fuming nitric acid, nitrous oxide, liquid or solid cadmium and liquid mercury. There is also a risk of hydrogen embrittlement from the formation of hydrides. Specifications for Grade 2 mill products typically specify a maximum hydrogen limit of 150 ppm, but it is possible for degradation to occur at lower levels, especially in the presence of a notch.

Heat Treatment

The standard heat treatments used for commercially pure titanium are annealing and stress relieving. Annealing is employed to sufficiently soften the material and remove all residual stresses. Precise control of grain size (and mechanical properties) can be achieved by adjusting the anneal temperature. Stress relieving is used to remove the residual stresses from forming, or to recover compressive yield strength after stretching.

Hot and Cold Working

Commercially pure Grade 2 titanium can be processed by conventional techniques such as hot rolling, forging, and hot pressing.  CP Ti Grade 2 has good ductility and can be formed at room temperature by various standard methods including bending, stretch forming, heading, stamping, and drawing. Commercially pure titanium work hardens fairly rapidly, which is a limitation in some operations, such as cold drawing.

Machinability

Grade 2’s machining characteristics are similar to those of austenitic stainless steels. In general, low cutting speeds, heavy feed rates, and copious amounts of cutting fluid are recommended. Sharp tools and rigid setups are also important. Because of the strong tendency of titanium to gall and smear, feeding should never be stopped while the tool and workpiece are in moving contact. Non-chlorinated cutting fluids are generally used to eliminate any possibility of chloride-induced stress-corrosion cracking. It should be noted that titanium chips are highly combustible and appropriate safety precautions are necessary.

Weldability

Titanium Grade 2 can be welded using filler metal. Inert gas shielding techniques must be employed to prevent oxygen pickup and embrittlement in the weld area. Gas tungsten arc welding is the most common welding process for CP Ti. Gas metal arc welding is used for thick sections. Plasma arc welding, spot welding, electron beam, laser beam, resistance welding, and diffusion welding have all been used successfully in CP Ti welding applications.

Properties

For more information about our Grade 2 and other titanium products, call us today on 0800 123 70 10 or send an email: sales@metalsupplies.com and we’ll get back you as soon as we can.