Stainless steel and aluminium pipes are used everywhere in the industrial, automotive, medical, and research world. When choosing the right tubing for your application, it’s important that you have a solid understanding of what these two materials are all about. This article will discuss the differences between stainless steel and aluminium pipes to help you make an informed decision.
Choosing the right metal for your needs
Stainless steel and aluminium are both considered metals. They come in several different tempers and alloys, with each having their own mechanical and physical properties. One factor to consider when choosing is the strength of the material. In these instances, we suggest using stainless steel tubing which is noted for its good strength-to-weight ratio. Its high-temperature performance makes it suited for such applications. However, if you need to use lightweight components, then aluminium tubing is certainly the better choice. Aluminium generally weighs one-third less than their stainless steel counterparts with the same dimensions.
Another factor worth considering is corrosion resistance. Both stainless steel and aluminium have excellent corrosion resistance and this may vary depending on the alloy used. Thanks to both metals having passive oxidising films, you won’t have to face any corrosion issues between these two materials.
But this passivation comes with a cost. One knock against stainless steel is that it has poor electrical conductivity. Aluminium, on the other hand, provides high electrical conductivity and thermal conductivity that’s three times greater than that of stainless steel. This has led to aluminium being used in power transmission lines. If moving electricity and heat are your top priorities, we recommend using aluminium over stainless steel.
Whether or not your chosen material is intended to conduct heat, you want to ensure it can safely handle the temperatures of its operating environment. Stainless steel contains high amounts of nickel and chromium which makes it excellent for use in high temperatures. On the other side of the spectrum, aluminium has greater tensile strength as the temperature drops, which means it stays stronger at cold temperatures compared to most other steels.
In general, the three main properties you should consider when selecting which metal best fits your applications are:
- Mechanical properties
- Corrosion resistance
- Heat resistance
Once you’ve decided which metal to use, now is the time to choose the exact temper and alloy for your application.
Whichever application you use stainless steel for, you’re sure to find the right grade that works best for you. The most common tube grades used are T304 and T316, both of which are included in the 300 series of stainless steel alloys. T304 is a classic type of steel alloy that’s known for its 18/8 blend of 18% chromium and 8% nickel. T316, on the other hand, is another familiar steel alloy that includes molybdenum and is used in the food and medical industries.
The properties of a steel alloy are mainly dependent on its heat-treatment and history of cold working. When obtaining an exact physical attribute for your tubing, we recommend speaking to a metallurgist to help you out. In regards to the fabrication process and tubing size, tubing specialists can provide you with useful information. Stainless steel ODs range from 0.008 in. for hypodermic applications and 1/16 to 8 in. for tubing.
One aspect of steel tubing that’s often overlooked is its after-life cycle. Although stainless steel is difficult to recycle, its alloying elements like nickel, chromium, and molybdenum can be separated and recovered.
In terms of aluminium alloys, you’re also spoilt with choices such as 2024, 3003, 5052, 6061, and 7075 alloys. Each alloy offers slightly unique physical and mechanical attributes thanks to their alloying elements of copper, manganese, magnesium, silicon, and zinc. Alloys 2024, 6061, and 7075 exhibits good fatigue resistance and high strength-to-weight ratios which has led engineers to use them for aircraft structures.
Alloy 3003 excels in high-corrosion and high strength applications but less so in areas where ductility is needed. 5052 alloy meanwhile, is perfect for applications that rely on multiple joints thanks to its highly weldable characteristics.
Like with steel, the composition of the alloy alone doesn’t paint the entire picture. An aluminium alloy’s exact properties are dependent on its history of heat-treatment and its temper. Tempers beginning in O suggest that the used alloy is annealed at its lowest strength and at its highest ductility while temper T involves heat treatments. Cold working is also done to provide toughness to the metal on either the molecular or grain level.
Once you’ve selected the right aluminium alloy for your needs, the next steps are to specify its size and outlining additional fabrication processes. Aluminium tubing also comes in fractional and metric diameters (ODs) and this ranges anywhere from 0.062 in. to 3.00 in. and 0.010 in. to 0.250 in. for wall thickness. Your chosen aluminium supplier can fabricate, cut, flare, and bend the tubing according to your specifications.
Aluminium tubing enjoys a long service life and the good news it’s a highly recyclable material. The scrap metal is turned into molten aluminium and are remade into large aluminium blocks called ingots.
Stainless steel and aluminium pipes have their fair share of advantages and disadvantages and it’s up to you to weight their characteristics to fit your applications perfectly. Refer to this guide when choosing which material to use for your metal tubing needs.