SPECIAL STAINLESS ALLOY STEEL

Special Stainless Steel Alloy 316TI UNS No: S31635 DIN: 1.4571 

SS 316Ti is a titanium stabilized version of Type 316 molybdenum-bearing austenitic stainless steel. The Type 316 alloys are more resistant to general corrosion and pitting/crevice corrosion than the conventional chromium-nickel austenitic stainless steels such as Type 304. They also offer higher creep, stress-rupture and tensile strength at elevated temperature. Type 316 stainless steel can be susceptible to sensitization – the formation of grain boundary chromium carbides at temperatures between approximately 900 and 1500 °F (425 to 815 °C) – which can result in rapid corrosion. Resistance to sensitization is achieved in Type 316Ti with titanium additions to stabilize the structure against chromium carbide precipitation, which is the source of sensitization. This stabilization is achieved by an intermediate temperature heat treatment, during which the titanium reacts with carbon to form titanium carbides. This significantly reduces susceptibility to sensitization in service by limiting the formation of chromium carbides. Thus, the alloy can be used for extended periods at elevated temperatures without compromising its corrosion resistance. 316Ti alloy exhibits excellent resistance to oxidation and a low rate of scaling in air atmospheres at temperatures up to 16001650°F (870-900°C).

The molybdenum bearing alloys such as Types 316 and 316Ti stainless steels are more resistant to atmospheric and other mild types of corrosion than the 18Cr-8Ni stainless steels. In general, media that do not corrode 18-8 stainless steels will not attack the molybdenum-containing grades. One known exception is highly oxidizing acids such as nitric acid to which the molybdenum bearing stainless steels are less resistant. Types 316 and 316Ti are considerably more resistant than any of the other chromium-nickel stainless steels to solutions of sulfuric acid. Where condensation of sulfur-bearing gases occurs, these alloys are much more resistant than other types of stainless steels. In sulfuric acid solutions, the acid concentration has a strong influence on the rate of attack.

Resistance of austenitic stainless steels to pitting and/ or crevice corrosion in the presence of chloride or other halide ions is enhanced by higher chromium (Cr) and molybdenum (Mo) content.

What Is AISI 316 Ti?Stainless steel 316Ti has titanium in trace quantities. The percentage of titanium addition is less than 0.5%. Titanium atoms balance the structure of 316 at temperatures higher than 800 ° C. This prevents precipitation of carbide on grain frontiers and protects against corrosion of the metal.

316Ti’s main benefit is its corrosion resistance for a prolonged period of time at high temperatures.  Both 316Ti and 316 have comparable mechanical properties.