One of the problems that are encountered in any aircraft design is that there are numerous parts that are required to be highly resistant to expansion or degradation when heated. This has challenged engineers for decades and recent times have allowed the industry to provide a number of bespoke solutions in regards to tackling this pervasive issue. One such solution can be found in different grades of stainless steel. The two most common variants are 321 and 347 stainless steel tubes. So, what is the difference between these two types and what are they used in?
Primary Differences
As you may have gathered, the primary constituent metals of both of these tubes is stainless steel. However, the main disparity between the two is the metal that they are alloyed with. The 321 variant is combined with titanium. However, the stainless steel 347 tube is a combination of steel and a metal called columbium. In fact, this is the only main difference between the two, as it has been shown that the stress resistances, heat factors and corrosion rates are similar. Still, it is important to note that both derivatives are highly used in the aircraft industry. Why is this the case?
Resistance is Key
Obviously, the components on board an aircraft will be subject to much higher stresses than other land-based machinery. Their failure can be catastrophic, so critical design features need to be strong, reliable and resistant to multiple forms of external variables. This is the benefit of both the 321 and the 347 varieties of this type of tubing. In fact, both of these alloys are resistant to temperatures between 800F and 1500F; thus allowing them to be perfect for use in areas on a plane that will experience notably high temperatures. A few examples of these can include but are not limited to turbines, exhaust manifolds, turbofans and heat sinks.
One of the only issues that is exhibited by the 347 variant is that it is said that this alloy is much harder to come by in the retail and engineering world. Therefore, 321 is more commonly used. Nonetheless, there are various online portals where both types can be encountered. Furthermore, they will frequently be priced much cheaper than through a retailer or a supply warehouse. These are some of the fundamental attributes of the 347 type of tubing that is frequently encountered in modern aircraft designs.
