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Normally stainless steel is magnetic. But whenever i order stainless steel nozzles from Amazon, they are not magnetic. This makes me think they could be brass coated in something like aluminum. However, there are many types of steel.

I've attached an image of someone who reviewed these nozzles. He says they are not stainless steel because they are not magnetic.

enter image description here

But whenever I order "stainless steel" nozzles, even from other sellers, they are not magnetic. i already returned one pack from another seller and just received a nonmagnetic one from a third seller.

So that's it? Amazon just sells junk now? Or is there a way I can easily tell whether these are something other than colored brass / good for abrasive or high temp printing. Here is the product that was reviewed: AUSTOR 13 Pieces Stainless Steel 3D Printer Nozzles 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm Extruder Nozzle Print Head for E3D Makerbot https://www.amazon.com/dp/B07CHZMGRH/ref=cm_sw_r_cp_apa_i_XtrNDbRMVH8SW

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    $\begingroup$ Stainless steel (at least the versions I've tried) are not magnetic, so I'm pretty sure that's not a way to tell. $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Oct 8 '19 at 23:04
  • $\begingroup$ But a screw (like the reviewer includes in the photo) is stainless steel and is very magnetic. Still, your comment helps.... Does the nonmagnetic kind hold up better than brass? $\endgroup$ – K Mmmm Oct 8 '19 at 23:06
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    $\begingroup$ That's not stainless ... it looks to be zinc plated. Stainless isn't shiny like that ... unless it's in silverware. $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Oct 8 '19 at 23:14
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    $\begingroup$ This bolt is stainless ... this bolt is zinc coated. $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Oct 8 '19 at 23:40
  • $\begingroup$ There's always the Archimedes test. Submerge an equivalent mass of known-real steel in a clear glass of water and note the displacement. Then submerge your hot end. If the displacements are similar, they are the same material. But for what it's worth, Amazon has always sold junk. $\endgroup$ – Joel Coehoorn Oct 11 '19 at 13:36
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Let's preface, that there are a LOT of metal identification methods. For example, I found this guide helpful and I had been at the scrapyard lately, where I have been told that 90+% of the time, steel objects that are non-magnetic are the more valuable stainless steels. The kitchen sink I dropped off? Stainless, non-magnetic steel.

Tempering/Annealing behavior

The very fact that the nozzles do change color to a brassy color that is commonly called straw is proof that it is indeed steel: heating up a piece of steel does alter the steel and also alters the surface color in a process called tempering. The color is only the surface, and the mild straw color would become orange-brown, purple, pale blue teal and yellow if you were to heat it higher. Take a look at the tempering colors of steel here: Steel temper colors

In contrast, brass acts differently when heated and tempering is somewhat different. Subjecting the piece of brass to heat you will not temper but anneal it and you get colors differently. Instead of becoming straw before blue, Brass becomes dark, starting with its pale gold to go over a dark "antique" look to before going green, teal, purple-blue, red and then losing its color like this piece of a polished brass plate shows:

Brass, annealed

Hardness/Chip

Another test that would be easy to conduct is hardness. The base idea of hardness is: An item can scratch a piece of equal or lower hardness, but not of higher hardness. If you have a chisel handy, then you have a piece of steel at hand. Most chisels are rated as HRC 58-62 - which is the Rockwell hardness scale. Brass could be all over the place, depending on work hardening. But the identification is not by the hardness but by how the chisel - or better a graver - cuts.

We expect Brass to get a smooth cut with saw tooth edges while stainless cuts smoothly and has sharp edges to the cut.

Sparktest

If you want to scrap one, get an angle grinder or another power tool to grind at the nozzle. Steel sparks red-orange to whitish and depend on the mix, Carbide sparks very short and orange. Stainless creates a HUGE shower of sparks, yellow-white and dense, no burstes and branching. Copper, aluminium and Brass do not spark. Titanium is very bright white. It can tell you what kind of steel you have.

Drilltest

As we are at destroying a pair of nozzles, why not drill them? we should have done that before subjecting it to heattreating and the grinding, but alas... Basically, we clamp the piece down and take an HSS drill to drill out the center.

Brass needs a different drill type but can be drilled and machined without coolant. Typical HSS drills from the home depot have a positive rake, brass wants neutral or negative rake to drill or machine smoothly. If the piece grabs, creates short spials and dusty small flakes with an unmodified, new drill (or under positive rake machining), it drills like brass, as you see here from a Clickspring video on drilling brass:

HSS on Steel, ft. Clickspring

In contrast, stainless steel doesn't want to be machined without cooling at all and using high speed creates smoke quickly and nearly no chips at all. A moment later your tool starts to glow and gets a dull edge. If your drilling experiment turns a new drill blunt on high speeds or uncooled, you have stainless at your hands. To get chips, you need to work slow and have some sort of cooling. It is still a painfully slow process that needs a lot of pressure, but it gets larger, nesting chips like seen here from a Wayne Canning steel drilling tutorial:

Drilling HSS in Stainless Steel

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    $\begingroup$ A Q&A answerer from the Amazon page that the OP linked to says that they have machined the nozzles and reckons that they are stainless steel, which goes along with the suggestions in your answer to try machining it and see what it's like. $\endgroup$ – Andrew Morton Oct 10 '19 at 19:30
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Stainless steel is created by adding elements (usually Chromium, but also Nickel) to steel. These added elements form an oxide layer with the outside air protecting the steel from corroding.

Whether stainless steel is magnetic or not depends on the added elements and the micro structure of the steel; some are and some aren't magnetic.

From physlink:

As for whether they (red. stainless steels) are magnetic, the answer is that it depends. There are several families of stainless steels with different physical properties. A basic stainless steel has a 'ferritic' structure and is magnetic. These are formed from the addition of chromium and can be hardened through the addition of carbon (making them 'martensitic') and are often used in cutlery. However, the most common stainless steels are 'austenitic' - these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it non-magnetic.

So the answer is that you cannot determine by testing for magnetic properties if the nozzle is stainless steel or not. But if it is not magnetic, it can be stainless steel. Note that discoloration is possible, this is the oxide layer.

To identify if the steel is stainless, you could without sacrificing the nozzle (according to this reference):

Step 1
Stick the magnet on the piece you are testing. If it holds firmly, the metal is possibly stainless steel. If not, it is (red. could be) another metal such as aluminum.

Step 2
Pick a spot on the piece that you don't mind damaging a little.

Step 3
Fill the eye dropper with muriatic acid. Drop a small amount of the acid on the test spot. Wait half an hour.

Step 4
Wipe the acid off the piece. Examine the test spot. If it is discolored, the piece is stainless steel.


Note that the image you posted shows a Zinc plated steel screw, not a stainless steel screw.

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  • $\begingroup$ It seems to me that Step 1 reveals nothing according to previous quote "...that depends," which makes me doubt the muriatic acid (hydrochloric acid) test is valid, especially as it says nothing about the nature of the discolouration (I could be wrong). A better test might be to file a groove in the surface and immerse it in salty water overnight: if it goes rusty, it isn't stainless steel. $\endgroup$ – Andrew Morton Oct 10 '19 at 8:42
  • $\begingroup$ @AndrewMorton I've left it as a quote of the complete steps, but indeed step 1 is not necessary considering the other quote. If I would have left out step one, I would have received comments about "where is step 1". Thanks for the comment, if you have a better reference, please feel free to alter the answer. $\endgroup$ – 0scar Oct 10 '19 at 9:44

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