Identifying Seamless Stainless Steel Tubes: Four Test Methods

Release Time:

09 May,2024

Author:

Source:

The magnetic test is a straightforward method for distinguishing annealed austenitic stainless steel from ferrous stainless steel. Austenitic stainless steel is non-magnetic but can become slightly magnetic after cold working under high pressure. In contrast, pure chromium steel and low alloy steel are highly magnetic.

Identifying Seamless Stainless Steel Tubes: Four Test Methods

1. Magnetic Test

2. Nitric Acid Point Test

Stainless steel tubes possess inherent corrosion resistance to both concentrated and dilute nitric acid, a characteristic that sets them apart from most other metals or alloys. However, high-carbon 420 and 440 steels exhibit slight corrosion when subjected to nitric acid. Additionally, non-ferrous metals corrode immediately upon contact with concentrated nitric acid, while dilute nitric acid is highly corrosive to carbon steel.

3. Copper Sulfate Point Test

The copper sulfate point test offers a quick and simple way to differentiate between ordinary carbon steel and all types of stainless steel. A 5~10% concentration of copper sulfate solution is typically used for this test. Before conducting the test, ensure the test area is thoroughly cleaned of grease or impurities. Polish a small area with a soft grinding cloth, then use a dropper bottle to drip copper sulfate solution onto the cleaned area. Ordinary carbon steel or iron will form a layer of surface metallic copper within a few seconds, while stainless steel surfaces will not produce copper precipitation or show a copper color.