How to identify stainless steel?

There are many kinds of stainless steel, how do we identify it, this is a problem, in order to solve this problem, we have the following identification methods:

1. Magnetic test

Magnetic test is the simplest method to distinguish annealed austenitic stainless steel from ferritic stainless steel. Austenitic stainless steel is non-magnetic but will be slightly magnetic after cold working at atmospheric pressure, while pure chromium and low alloy steels are highly magnetic.

2. Nitric acid point test

A remarkable characteristic of stainless steel is its inherent corrosion resistance to both concentrated and dilute nitric acid. This property makes it easily distinguishable from most other metals or alloys. However, high carbon 420 and 440 steels are slightly corroded during nitric acid point test, and non-ferrous metals are corroded immediately when exposed to concentrated nitric acid. Dilute nitric acid is highly corrosive to carbon steel.

3. Hardening test

When austenitic stainless steel is cold rolled under high pressure or cold hardening, as a way to distinguish stainless steel - magnetic test method is not applicable. In this case, the sample should be heated to 1850-2000°F (1010-1093 ° C) and water quenched. After such treatment, austenitic stainless steel will completely lose magnetism and its hardness is usually no greater than RB85.

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