how can we identify the grades of stainless steel? 1

[structural1]

I am a Mechanical engineer and i need informations about identifying the grades of stainless steel.
regards.
Wissam Khoury(wkytec@yahoo.com)

 

[NickelMet]

Sorry, but what do you mean by 'identifying'? That is, are you referring to:

1) identifying by numbering/lettering on the part?
2) identifying on a drawing or specification?
3) identifying by analysis?
4) etc. etc.

 

[Watermelon]

Hello Structural1:

One quick test I know of is with a magnet. Grade 312 will be attracted to the magnet. Grade 316 will not.

 

[Rich2001]

Here is some information that might help.

I think that the Carpenter Stainless Steel Manual has directions for chemical spot tests that can be used to identify the various grades of SS.

http://www.cartech.com/

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Test for Moly (distinguishing between type 304 & 316 )

The test for molybdenum in 300 series stainless is to

a) Place equal drops of concentrated hydrochloric acid and concentrated nitric acid on the metal surface. Allow 3 to 4 minutes for reaction and transfer 2 drops to a spot plate.

b) Add 2 drops of 10% potassion thiocyanate.

c) Add 25% sodium thiosulfate dropwise stirring until the red color begins to disappear. A violet color will appear if molybdenum is present.
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Look at ASTM E1916-97 Standard Guide for Identification and/or Segregation of Mixed Lots of Metals

http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/PAGES/E1916.htm?L+mystore+gyfr7769+1042818413

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Your best course of action is to get a chemical spot test kit from Koslow

http://www.koslow.com/

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X-ray Fluorescent Analyzers (a bit more expensive but very handy)




Cianflone Scientific Instruments Corporation.

EDAX Inc.

KevexSpectrace.

Metorex International Oy.

NITON Corporation

http://www.niton.com/

NITON manufacture portable X-ray Fluorescent Analyzers. These instruments are used for a wide variety of analysis problems in the environmental industry, scrap metal and alloy analysis, industrial process and industrial hygiene. X-Ray Fluorescence (XRF) Products: 300Series Lead Analyzer - for lead-based-paint testing, on-site analysis of dust-wipes, air filters, paint chips, and soil. 700Series Multi-Element Analyzer - for multi-element testing of soils, air filters, and thin-film samples (coatings and materials analysis). 800Series Alloy Analyzer - for rapid identification and chemistry of metal alloys, PMI testing, quality assurance, scrap metal sorting and inspection. Also Radon Products and Services: Pico-rad Radon-in-Air Detectors. NITON QA Program for Pico-rad software and vials. Radon-in-Water Analysis introductory kit. Radon-in-Water Collection Vials.

some other manufacturers are:
[ol][li]Cianflone Scientific Instruments Corporation.
[/li][li]EDAX Inc.
[/li][li]KevexSpectrace.
[/li][li]Metorex International Oy.
[/li][li]Quantrad Sensor, Inc. (QSI).
[/li][li]Spectrace Instruments.
[/li][li]Yuzhpolymetal-holding, JSC. (ÀÎÇÒ "Þæïîëèìåòàëë-Õîëäèíã&quot[/li][/ol]

 

[Jeannie]

Bit more info needed Structural 1.

What do you mean by identifying? Do you have a specific part and need to know what grade it is? Unless you have the test certificates for the material, which should ensure some element of traceability back to the manufacturer or supplier chain, then you are a bit todgered.

You could always try sending to a lab to have tested for chemical and mechanical make up.

If just general info you require - have a read...

Austenitic Stainless Steels.
These are the most common and extensive range of stainless steels and are sometimes referred to as 18-8 (18% Chromium and 8% Nickel, though the composition may vary widely from these figures. Their properties may be summarised as follows:
CORROSION RESISTANCE
Austenitics are among the most highly corrosion resistant materials available. They can be susceptible to stress corrosion cracking.

DUCTILITY
Austenitics are ductile and can be formed easily. This applies at both high and low temperatures.

TENSILE STRENGTH
Austenitics have high tensile and yiels strengths. Susceptibility to stress corrosion cracking means that high tensile stresses should be avoided.

HARDNESS
Austenitics cannot be hardened by heat treatment but they do strain harden rapidly when cold worked. Heat treatment is used to provide stress releif after cold working.

WELDABILITY
Good, assuming manufacturers recommendations are followed. Austenitics are less problematic that ferritic and martensitic stainless steels in this respect.

MAGNETISM
Austenitics are non magnetic (This is how you can tell a decent set of stainless steel cutlery from one which is likely to rust in your dishwasher!) Cold working may increase magnetic permeability.

THERMAL EXPANSION
Austenitics have a thermal expansion approximately 50% higher than that of carbon steel

EXAMPLE AUSTENITIC GRADES
Conventional:
Examples include AISI 301, 302, 303, 304, 305, 308, 310, 316, 317.
These are usually furnished in an annealed or cold worked state. Following welding or thermal processing, further annealing may be required to optimise corrosion resistance, softness and ductility. Chromium Carbides, which markedly reduce resistance to intergranular corrosion are disolved during annealing, but may be precipitated during the cooling.
Rapid cooling (water quenching for example) from the anneling temperature prevents this but may cause distortion of thin walled products. This problem is addressed by the stabilised austenitic grades and low carbon alloys.

Stabilised
Examples AISI 321, 347, 348.
These alloys contain controlled amounts of titanium or niobium to render the steel nearly immune to chromium carbide precipitation and its adverse attack on corrosion resistance. Annealing is still used for stress releif, to increase softness and ductility and for additional stabilisation, but rapid cooling is not required to prevent intergranular corrosion.

Low Carbon
Examples AISI 304L, 316L and 317L
The low carbon content of these alloys limits the precipitation of intergranular carbides compared with conventional austenitics. This limited sensitisation is of value when welding and hot working. However, low carbon alloys are not suitable for prolonged service at sentitising temperatures (approx 540 to 760 degrees centigrade) at which carbides may be formed.

Other Grades
Examples AISI 304N, 304LN, 309Cb
These contain varying levels of alloying elements and may be modified for particular requirements such as high temperature service. (Eg. 304H, 310HCb). Super Austenitics (Eg. UNS S31050, S31254) have up to 7% molybdenum, matching contents of chromium and nickel and may also be alloyed with nitrogen. These are most often designed to resist pitting and crevice corrosion in chloride containing environments such as sea water.

There is as much information available on the other types of stainless steel, which I can let you have if you contact me.

These types include DUPLEX STAINLESS STEEL, FERRITIC STAINLESS STEEL and MARTENSITIC STAINLESS STEEL.

There is also an extensive Grades list available.

If you need any other information, please contact with specific questions!

Happy trails,

Jeannie