Aluminum vs. Steel Properties: Strength, Ductility, Cost & ...

Both aluminum and steel are hallmarks of metal manufacturing. Both are useful, commonly used metals. Both don't commonly appear nature like silver or gold. So who wins the battle of aluminum vs. mild steel when it comes to your specific needs?

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Aluminum goes through a few phases before it looks like the shiny silver metal we're all familiar with. The base ingredient of aluminum is a mineral called bauxite, which is mined primarily in tropical areas. The bauxite is ground into a thick paste called alumina, which is then smelted with molten cryolite and shocked with electricity. The ions separate, and the residual liquid cools and becomes the aluminum we know and love.

Steel, on the other hand, is a mixture of the elements iron and carbon. Iron is mined, smelted (forming the intermediate material pig iron), the impurities are removed, carbon is added, and the result is carbon steel. This is the base for other types of steel, such as stainless and chrome-molybdenum.

Knowing the pros and cons of aluminum vs. steel properties gets your project off to the right start. How do you know which one is better for your design?

Aluminum Vs. Steel Properties

Mild/Carbon Steel Stainless Steel Aluminum Cost Low High Medium Weight High High Low Strength High High Low Ductility Low for carbon,
medium for mild High High

Cost

Steel cost vs. aluminum cost is always a hot topic, especially with all the tariffs on imported goods our U.S. administration is throwing around.

Steel tubing varies in price due to the differences in carbon, mild, and stainless steel. Stainless steel alloys are made with a certain percentage of chromium and other trace minerals, which drives the price up.

Basic carbon steels and mild steels are much cheaper, and aluminum's price falls somewhere between carbon and stainless steel. These basic steels win in the cost category.

However, as with most things, there are other sacrifices made if you choose the low prices of carbon steel over aluminum alloys. But, for most components, carbon or mild steel are perfectly acceptable materials, even when taking those sacrifices into account.

Related: 4 Ways to Cut Aluminum Tubing Costs with the Right Vendor

Weight

For steel, one of the biggest sacrifices is in the material's strength-to-weight ratio. Carbon steel is heavy. Aluminum is often preferred for its lightweight composition -- steel is much denser compared to aluminum, which causes its weight to skyrocket.

Mild steel is lighter than its carbon counterpart, but it's much flimsier than aluminum at the same weight. Is stainless steel heavy too? You bet -- aluminum is about 1/3 the weight of basically any steel.

In the weight category, aluminum takes the prize. Overall, it's a very lightweight yet sturdy material.

Strength

How strong is aluminum compared to steel?

Steel tube vs. aluminum tube strength is not even close in most cases. The amount of carbon in steel makes it unyielding (and heavy). This is especially true for carbon steel -- the higher the amount of carbon in an alloy, the harder it becomes.

Mild steel is a "low carbon" steel, which is why it's so flimsy compared to other steels and aluminum (and much cheaper in comparison).

Ductility

Which is more ductile, steel or aluminum? This may be very important if your application will involve electricity.

Carbon steel is NOT very ductile. Carbon, which is a benefit to the strength of the metal, ultimately makes the material harder to manipulate.

Is aluminum ductile? More so than carbon steel and even mild steel. If your project requires a malleable metal, you might be able to get away with mild steel, though.

Steel Vs. Aluminum Is About More Than Just Cost

These are some of the things you should think about when choosing the right type of metal for your project. There may be other factors to consider, but we would suggest not making your decision based on cost alone.

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If you're searching for one of the qualities not mentioned here, such as corrosion resistance, check out this blog post about 316 stainless steel and other related alloys. Or, if you're got materials squared away and are ready to start designing, click below for a free bending guide:

(Editor's note: This article was originally published in September and was recently updated.)

I have seen looking locally to source 1 inch stainless steel tubing but have had no luck. I know very minimal about metal and its properties/strength and came across these 2 types of tubing that I'm guessing are the same or similar? I can get this 1 inch OD (.083 wall thicknes) mechanical tubing at a 20 ft length for $15 and (.120 wall thickness) for $20. My question would be if this would work instead of the stainless steel tubing?

 

Any help I could get from all you would be greatly appreciated!

Thanks all!

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The properties are different, but keeping steel tubing that is as thick or thicker should be OK.

Ensure that you get smooth tubing and keep it smooth and close to circular. Keeping it rust free in the long run is required to keep your machine lasting longer. Basically oil lightly regularly (think keep a small cloth and put a little oil on it and just wipe the tubing regularly. I like to use silicon based liquid lubricant. Let it dry before use, or wipe it after use so it will have time to dry and be clean.

Fighting rust is something that any steel based machinery must do. Often non-moving surfaces/areas are painted, bearing surfaces are cleaned and lubricated.

Whatever decision you make will not be wrong. Just a bit more or less maintenance as long as it is strong enough for the task.

When looking for Stainless Steel tubing - make sure you are trying to source Tubing and Not Pipe. 1" SS Pipe will have an O.D. that is about 5thousands too big for the printed parts. Tubing is definitely more expensive because it has much higher tolerances - ie: it is very flat, very round and very straight. Add in Stainless to the mix and the price goes up. It was the most expensive part of my build (full sheet LR2). I think I paid around $180 for 2 7&#; sections that I found in the drops pile of one of my local steel yards. I also got 304L Seamless Stainless Steel 1" OD tube with a .250" wall thickness. This stuff is fairly heavy but VERY rigid (especially since the longest pieces are the X-Rails and they are only 59" long. This https://www.onlinemetals.com/merchant.cfm?pid=&step=4&showunits=inches&id=312&top_cat=1 is the same tubing I used.

You can definitely go thinner but the wider the table (X Axis) the more flex you will have. I would suggest going .125" wall thickness for a 4&#; wide cutting surface.

The metal that you are showing in the pics seems to be to be a very low carbon steel and will potentially have a lot of flex to it and I would question the &#;roundness&#; of it (especially at longer lengths). The cost really has me concerned about the quality of the metal being used. For comparison, 1" EMT Conduit at Home Depot sells for about $20 for 20&#; and that stuff you can bend if you look at it funny.

If you can&#;t find SS Tubing locally, then check out OnlineMetals or MetalsDepot. Both come decently recommended but are more expensive then local sourcing. I have also found that not all local steel yards stock or order SS Tubing so you might have to shop around. If you ask for it, make sure they are working with 1" OD Tubing and not 1" OD pipe though, as one of the yards I was dealing with didn&#;t realize there was a difference in the actual OD (which is a lot of situations doesn&#;t matter, but it does for us).

Depends on what you want to do, the accuracy you expect, and most importantly, the size of your build.

In the end do I think it matters, no, will I promise anything, nope. I have been getting a lot of flack lately for not having exact specs up so people can directly compare machines. I think you can see the smallest thing makes a difference, 10% less rigid pipe, maybe 1" shorter more than makes up for that, or maybe that ten percent is the difference between 0.1mm and 0.11mm accuracy and that means nothing to you (it shouldn&#;t).

Im just saying, at that price, it is probably isn&#;t the best steel out there. A513 is a fairly &#;brittle&#; steel (if I remember correctly - meaning it tends to break more easily then other steels. Another thing to consider is the surface finish. With SS, you don&#;t have mill scale but you will with other types of steel. It may not be an issue for the LR but it&#;s something to keep in mind. It will also rust on you, even just sitting around, there is enough moisture in the air to cause it to rust. You can get around this by stripping off the mill scale and then painting it, but that another variable in the accuracy of your machine. Honestly, it all depends on what you want to get out of the LR. If you can get the steel you need to $20 bucks, it&#;s worth a try. If it does t work out for you, then you are only out $20 and can just replace it is something else.

What website are you getting that info from, because if their prices are that good, I will order my steel from them (I do welding on the side).

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