Is pure titanium (TA1, TA2) sufficient for petrochemical equipment? Why isn’t titanium alloy used?
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As I understand it, petrochemical equipment manufacturers generally take advantage of titanium’s corrosion resistance; therefore, the relatively low-cost and easy-to-process pure titanium material is widely used. Compared to stainless steel, titanium alloys actually possess better strength and resistance to high/low temperatures. Additionally, they have a lower density, which reduces the weight of the material used and extends its service life; as a result, the overall cost is not necessarily extremely high. Is it simply because processing and welding are difficult?
In my opinion, TA1 and TA2 are merely industrially pure titanium; essentially, they are still alloys, with only very few elements other than titanium. When selecting materials, the overall cost must be taken into consideration.
However, the mechanical properties of industrially pure titanium are average, and it is relatively soft
The requirement for strength in materials used for pressure equipment is secondary compared to toughness and weldability. After all, insufficient strength can be compensated for by increasing thickness, but poor toughness and weldability are catastrophic. Therefore, even though medium-carbon steel has high strength properties, it is rarely used in the main body of pressure-bearing equipment. Using 45# steel to make tanks is a well-known joke in the pressure vessel industry.
Pure titanium has better corrosion resistance, while titanium alloys are used in specific applications; for example, titanium-palladium alloys exhibit improved corrosion resistance at high temperatures in complex environments containing chlorine dioxide, sulfuric acid, sodium chlorate, and hydrogen peroxide. Alloys such as TC4 have better strength.