Silver or Stainless?

[WolfieParticipant @wolfie]

Next silly question! How do I tell the difference between silver steel and stainless steel.

[WolfieParticipant @wolfie]

[SkarvenParticipant @skarven]

Hi,

 

You could start with a magnet. If it’s non-magnetic, it should be stainless.

If it’s magnetic, You could use two pieces of known silver steel and stainless as a reference and make a “Spark test” on a grinding wheel.

 

If you have a low light condition without fluorescent light it is easier to see the difference.

The following link gives some info.

http://en.wikipedia.org/wiki/Spark_testing

Good luck!

[michael howarth 1Participant @michaelhowarth1]

Cut off a small bit, heat to bright red heat then stick it (quench) in cold water, if it is silver steel then it will have hardened to such an extent that you will not be able to file it. After you have identified it, mark it with a paint code.

Some stainless is magnetic, though I believe most is not.

Edited By mick H on 14/10/2011 07:48:42

Edited By mick H on 14/10/2011 07:49:09

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, it can be confusing, even with the ideas mentioned, because you can get martensitic stainless steels which are hardenable. One difference between stainless steels and silver steel is that nearly all stainless steels will not rust, silver steel however will rust. The thing is there are so many stainless steel grades, it is best to know what you have when you purchase it, and mark it accordingly. Only austenitic stainless steels are non magnetic 

 

Regards Nick.

Edited By Nicholas Farr on 14/10/2011 08:33:45

[SkarvenParticipant @skarven]

Some stainless steels are magnetic, some not. The magnetic test will only tell if it is NOT silver steel. If the steel is magnetic, it could be both silver steel and some magnetic stainless steel. Some stainless steels can also be hardened, so this test will not give a simple answer.

 

Most (I think) stainless steel of the 300 type (304,316) containing chromium and nickel are non-magnetic. These are also marked as 18/10 18/8 …for their chromium and nickel content and they are called Austenitic. I think the steel used in propeller shafts of boats is of another type because of the bad frictional characteristic of chromium/nickel steel.

[Ian S CParticipant @iansc]

I have been fooled by a bit of chrome plated brass, non magnetic thought it was stainless. Ian S C

 

[SkarvenParticipant @skarven]

I think the Copper sulfate was part of my first Chemistry set about 40 years ago. It should still be somewhere. It should be a simple test to perform.

 

This is a link with some chemical testing for different types of stainless steel.

The Hydrochloric Acid Test should be useful.

http://www.engineeringtoolbox.com/identification-stainless-steel-d_383.html

However, I still think the spark test is one that everybody can do with their existing equipment. Either a bench grinder or Angle grinder or maybe a Dremel?

If you have a few pieces of known materials to compare with, it’s much easier to do, but there are lots of info on the net:

The following link shows pictures of sparks from different materials:

http://www.wearanswers.com/Instant-Answers/Instant-Answers/Spark-Testing-for-Material-Identification.html

 

I am no expert in this field, but after testing a few pieces of known materials I’m convinced that this is a useful method if you can spare the time to collect a few pieces of different materials, mark them , and look at the sparks.

 

Of course, the best would be to be very clever and mark everything you ever get into your workshop, but who does, and sometimes you find an unknown piece of steel that seems to be exactly right for something, maybe for free!

[SkarvenParticipant @skarven]

I forgot,

The real simple test is to stick it in an orange, leave it outside for some time, and see if there is any rust on it!

[WolfieParticipant @wolfie]

Arrgh I have a jam jar full of thin rod which is mixed silver and stainless. Only one of the dozen rods isn’t magnetic at all and the others are to a varying degree.

 

So the non-magnetic piece is definitely stainless then right??

Edited By Wolfie on 15/10/2011 18:32:54

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Wolfie, yes your non magnetic piece is most likley to be stainlees steel.

 

Regards Nick.

[DMBParticipant @dmb]

Hi all,

If anyone wants some copper sulphate, just put the 2 words into google + you will find several suppliers. I once obtained some by mail order for testing as recommended in this thread and Ialso use it for coating steel b4 marking out.

[michael howarth 1Participant @michaelhowarth1]

In the olden days, when I was a boy and when this was a proper country and people had commonsense it was possible to buy small quantities of all manner of chemicals at Boots and other chemists. About a year ago I tried to buy some copper sulphate at a Boots pharmacy and the pharmacist refused to sell me any in case I wanted to make a bomb with it !!!

 

So careful what you’re doing with that stuff !

[Richard ParsonsParticipant @richardparsons61721]

Copper Sulphate. Go to your garden supplier they sell it. It is main ingredient of ‘Bordeaux Mixture’ for your vines

[michael howarth 1Participant @michaelhowarth1]

Exactly Richard. The pharmacist probably got himself one of those degrees that you get with three tokens from a cornflakes packet.

Edited By mick H on 16/10/2011 19:04:51

[Sub MandrelParticipant @submandrel]

> pharmacist refused to sell me any in case I wanted to make a bomb with it !!!

When I was lad (not that long ago) the chemist sold all sorts of useful compunds, but you had to be careful to buy them one at a time, and have the right excuse handy “It’s for my mum’s fish tank”.

 

Quite how we survived our pyrotechnic experiments without injury, I don’t know, but I reckon half my class would have ended up in Guantanamo Bay these days.

 

One of my adult mentors used to show me his stump of a thumb and warn me against such things. Well he half convinced me of the need to be careful…

 

Neil

[Steve WithnellParticipant @stevewithnell34426]

eBay is a good source of copper sulphate.

[WolfieParticipant @wolfie]

As a matter of interest, why is stainless non-magnetic surely it has plenty of iron in it??

 

And if these 2 materials are so similar, does it matter which I use to make a scriber?

Edited By Wolfie on 18/10/2011 13:19:36

[Steve WithnellParticipant @stevewithnell34426]

Posted by Wolfie on 18/10/2011 13:17:52:

As a matter of interest, why is stainless non-magnetic surely it has plenty of iron in it??

 

And if these 2 materials are so similar, does it matter which I use to make a scriber?

Edited By Wolfie on 18/10/2011 13:19:36

If you heat steels upto a temperature I can’t remember (!) the they become non-magnetic

 

Steve

[Keith Wardill 1Participant @keithwardill1]

Re Wolfies remark about making a scriber, and determining which bit of steel to use. I used a large masonry nail, brazed it into a hole in the end of a bit of steel rod (any rod, silver, stainless, even brass!), then ground the end sharp – its been in use for years, and the thin nail means I get a good view of the tip and line I am scribing – I don’t care if the shank is magnetic, rustless or copper coloured.

[SkarvenParticipant @skarven]

Here is a link with info on magnetic properties of ss.

http://www.azom.com/article.aspx?ArticleID=1140

It seems to be the way the iron is organized on the molecular level that decide the magnetic properties. Interesting to see that coldworking of 304 can make it magnetic, and heating it afterwards can remove the magnetism.

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Wolfie on 18/10/2011 13:17:52:

As a matter of interest, why is stainless non-magnetic surely it has plenty of iron in it??

Hi Wolfie, to understand this fully, you would have to learn a bit of metallurgy. Below is a graph of carbon steels, the temperature on the left and the carbon content at the bottom. The graph shows the metallurgical state that cabon steels are in against temperature.

The next bit is a reply I made in the “Chronos Silver Steel, water or oil quench” thread.

 

Sam, I believe you are describing the allotropy of Iron.

I had to dig out my college notes from 1977 for this one.

Iron can exist in two forms, Ferrite and Austenite. On cooling, it is in its Austenite form at temperatures above the upper transformation line (695 to 920 degrees C)

As cooling continues through the transformation zone (between upper and lower lines) the Austenite changes to Ferrite. During this change Carbon is precipitated from the Austenite, because Carbon is insoluble in (Iron) Ferrite. The precipitated Carbon is in the form of Cementite which goes to form Pearlite, or in the case of steels with over 0.83% Carbon the excess cementite remains on the grain boundries.

Time is needed for these changes to take place. A slow cool will enable the changes to take place and will result in a large grain structure. A faster cool will result in a smaller grain structure.

However, if the cooling rate through the transition range is increased sufficently (i.e. quench) time will not be allowed for the changes from Austenite to Ferrite to take place. In this case there is insufficient time for the Carbon to be precipitated out of solution and this result in the Carbon atoms being forcibly locked in the Ferrite structure. This may be described as a super saturated solid solution of Carbon in Ferrite Iron.

Due to the distortion caused by the Carbon, the grains are acicular (needle like) and are very hard and brittle. The name of this structure is Martensite.

 

As I said earlyer, only Austenitic stainless steels are non magnetic, and this is because there is sufficient Nickel, Nickel and Chromeium or Manganese, to maintain the structure of Austenite.

 

Hope this helps.

 

Regards Nick.

[Sub MandrelParticipant @submandrel]

I think the question then becomes, why is austentite not magnetic…

 

I think (less certainly) that the answer is something to do with the way the atoms are arranged as this affects whether or not their magnetic spins add up or cancel out . if tehy add up, the material is magnetic.

 

I expect wikipedia has the full details…

 

Neil

[Anonymous]

Just to confuse the issue; austentite is magnetic. It is paramagnetic, ie, it has a positive susceptibility to an external magnetic field. But the effect is so small that it cannot be detected with the sort of equipment found at home.

 

What most people call a magnetic material exhibits ferromagnetism where the forces involved are easily observed.

 

Just about every material interacts with a magnetic field; it’s just a question of the strength, characteristics and observability of the interaction.

 

Regards,

 

Andrew

[Gone AwayParticipant @goneaway]

Posted by Ian S C on 14/10/2011 08:46:19:

I have been fooled by a bit of chrome plated brass, non magnetic thought it was stainless. Ian S C

 

 

 

I bet a few people have also been fooled by some of the imported “brass wire brushes”.

 

Many of these will handily stick to a magnet.

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