Stainless steel

[thatguy]

Was thinking back to what a pupil of mine asked me last month.  He asked "How can that be stainless steel?  It's not magnetic!"

I thought some people here might be disappointed in gear they bought which claims to be SS but doesn't attract a magnet.  Only some stainless steels are magnetic, there are ferritic stainless steel and have a very high iron content.  Austensitic SS tend to have higher alloying elements such as chromium (close to 1/5 of the material) nickel, cobalt and others. 

The micro structure is changed depending on the alloy, and this, along with the quantum mechanical nature of the alloy, makes some magnetic and some not.


Long complex piece of metallurgy omitted......




So some are magnetic, some are not....how do we spot the difference between SS and chrome plated brass and aluminium.

1. Aluminium oxidises very fast.  A surface layer will tarnish from bright silver to a dull silver very quickly.  Aluminium is also extraordinarily light for a metal.  Always non magnetic

2. Chrome plated brass - many cheaper clearos/mods made with this.  The big giveaway is that in internal areas or corners, the chrome plating has a tendancy to "bubble" a little giving a rough finish such as you see on  a painted metal fence where the paint is loose.

3.  SS should have a uniform finish and be a bright, and reflective if polished, but can also have a dull finish if not polished.


Basically thought I'd post this so people who paid for SS and tested with a magnet would not instantly assume the product wasn't SS.

[ronaldo]

the highest quality ss is not magnetic and is used for quality cutlery as well as other stuff
the low quality ss has a higher iron content so is magnetic and does eventually rust
so if I buy anything that is stainless steel I test with a magnet and don't want it to be magnetic

[thatguy]

Some of the best SS are magnetic, it depends on the exact content and heat treatment of the material But for cheaper consumer applications, yeah, the non magnetic autensitic SS are the best material for the job. Just wanated to let people know that magnet tests dont mean they have bought an inferior product.

[Ripshod]

tbh I was expecting some of the cheapo chinese clones to be made from chrome-iron. That's not the case, apparently even the chinese won't stoop so low.

[hijack]

I keep some of my various battery and switch magnets wrapped up and store them in the brass and copper small tube sections you get with the mixed mods to shield them and stop everything from sticking to them. It works, up to a point.

[Deleted]

I don't think there is such a thing as a non-magnetic SS, just very, very low. If it looks and feels like stainless and in a magnet test is 'non magnetic' then
it probably is, but it tells you nothing of the grade or quality.

It's important that the grade of stainless is chosen to suit an application. Eg, you'd need a very low level of magnetism if you were building a MRI scanner.
A high level of resistance to the elements in a marine application or the ability to resist an aggressive caustic wash in brewery vessels and couplings.

I don't know about you but I never leave my mod out on the deck of my Yacht while out at sea, and I clean mine with fairy not caustic.
I think the design of the mod, the care taken in precision machining using top quality tooling is more important than having the ultimate grade of stainless.

[fred]

Some of my cutlery is nearly 50 years old (hand me downs from me mam!)
Not a spec of rust on it, although the serrations on the bottom of some of the knives are almost non-existant.
They most certainly are magnetic!

[ronaldo]

Types of Stainless Steel

The three main types of stainless steels are austenitic, ferritic, and martensitic. These three types of steels are identified by their microstructure or predominant crystal phase.

Austenitic:
Austenitic steels have austenite as their primary phase (face centered cubic crystal). These are alloys containing chromium and nickel (sometimes manganese and nitrogen), structured around the Type 302 composition of iron, 18% chromium, and 8% nickel. Austenitic steels are not hardenable by heat treatment. The most familiar stainless steel is probably Type 304, sometimes called T304 or simply 304. Type 304 surgical stainless steel is an austenitic steel containing 18-20% chromium and 8-10% nickel.

Ferritic:
Ferritic steels have ferrite (body centered cubic crystal) as their main phase. These steels contain iron and chromium, based on the Type 430 composition of 17% chromium. Ferritic steel is less ductile than austenitic steel and is not hardenable by heat treatment.

Martensitic:
The characteristic orthorhombic martensite microstructure was first observed by German microscopist Adolf Martens around 1890. Martensitic steels are low carbon steels built around the Type 410 composition of iron, 12% chromium, and 0.12% carbon. They may be tempered and hardened. Martensite gives steel great hardness, but it also reduces its toughness and makes it brittle, so few steels are fully hardened.

There are also other grades of stainless steels, such as precipitation-hardened, duplex, and cast stainless steels. Stainless steel can be produced in a variety of finishes and textures and can be tinted over a broad spectrum of colors.

[VapingBad]

People are often mislead by the the name and should think of it as corrosion resistant. Another good way to tell higher quality is to look for marine grade or A4 (common category with nuts, washers, cable and mesh) as salt water is more corrosive than fresh water. If your not sure leave in water over night.

I always bin any magnetic screw or washers in atties before I use them, a Pulse G atty I got from FT was such bad quality steal it rusted in the ultra sonic cleaner.

[Ripshod]

Jul 24, 2014 9:18:38 GMT ronaldo said:

Types of Stainless Steel

The three main types of stainless steels are austenitic, ferritic, and martensitic. These three types of steels are identified by their microstructure or predominant crystal phase.

Austenitic:
Austenitic steels have austenite as their primary phase (face centered cubic crystal). These are alloys containing chromium and nickel (sometimes manganese and nitrogen), structured around the Type 302 composition of iron, 18% chromium, and 8% nickel. Austenitic steels are not hardenable by heat treatment. The most familiar stainless steel is probably Type 304, sometimes called T304 or simply 304. Type 304 surgical stainless steel is an austenitic steel containing 18-20% chromium and 8-10% nickel.

Ferritic:
Ferritic steels have ferrite (body centered cubic crystal) as their main phase. These steels contain iron and chromium, based on the Type 430 composition of 17% chromium. Ferritic steel is less ductile than austenitic steel and is not hardenable by heat treatment.

Martensitic:
The characteristic orthorhombic martensite microstructure was first observed by German microscopist Adolf Martens around 1890. Martensitic steels are low carbon steels built around the Type 410 composition of iron, 12% chromium, and 0.12% carbon. They may be tempered and hardened. Martensite gives steel great hardness, but it also reduces its toughness and makes it brittle, so few steels are fully hardened.

There are also other grades of stainless steels, such as precipitation-hardened, duplex, and cast stainless steels. Stainless steel can be produced in a variety of finishes and textures and can be tinted over a broad spectrum of colors.

m8, I can only WISH for a memory like that. Good work

[VapingBad]

Jul 24, 2014 9:42:54 GMT Ripshod said:

m8, I can only WISH for a memory like that. Good work

link by why bother typing it

[Ripshod]

*Statement retracted*

I did work as a maintenance engineer at a sheffield cutlery firm a good few years back. We were taught a lot about the various grades of stainless. I would have been able to quote all the specs and blends off the top of my head at one time.

[Deleted]

As VapingBad said the grade A2 and A4 relate to SS fasteners. A2 is basically 304 SS and A4 316 or, as he said 'marine grade'. This has molybdenum added to make it more resistant
to corrosion and suitable for use in a harsh marine environment, and the food industry where aggressive cleaning agents are used. There are different classes of both giving different mechanical properties.

Both are 'non-magnetic' (very low magnetism) and I guess most original mod makers would choose either 304 or 316 SS

[VapingBad]

Jul 24, 2014 9:53:53 GMT Ripshod said:

ronaldo, BUSTED!!

I did work as a maintenance engineer at a sheffield cutlery firm a good few years back. We were taught a lot about the various grades of stainless. I would have been able to quote all the specs and blends off the top of my head at one time.

More Ripshod busted me thinks, you assumed, he never claimed it was original, I'm sure he knew it, but you would have to really like typing if you found something that fits the bill not to copy and paste.

[spikus]

This is like being back at school ! ..... Very informative