How to identify seamless stainless steel pipes

Identification of seamless stainless steel pipes

1、 Magnetic test

Magnetic testing is the simplest method to distinguish between annealed austenitic stainless steel and ferritic stainless steel. Austenitic stainless steel is a non-material magnetic steel, but after cold working under atmospheric pressure, it will have a slight magnetism on its own. However, pure chromium stainless steel and low-alloy stainless steel enterprises are both strong magnetic steels.

2、 Nitric acid point test

A notable feature of stainless steel pipes is their inherent corrosion resistance to concentrated and dilute nitric acid. This characteristic makes it easy to distinguish from most other metals or alloys. However, the high carbon 420 and 440 pile foundation Luohe acoustic testing pipes are slightly corroded during the production nitric acid point test, and some non-ferrous metal enterprises will be immediately corroded by society when exposed to concentrated nitric acid. Thin walled stainless steel has strong corrosiveness to carbon steel.

3、 Copper sulfate point test

The copper sulfate point test is a simple calculation method for quickly distinguishing between an ordinary carbon steel and a double flange steel expansion joint of all data types. The concentration of copper sulfate solution used is 5-10%.

Before conducting the spot test, the test area should be thoroughly and effectively cleaned of grease or various impurities on the surface of the 304 stainless steel pipe concrete, and one or a small area should be polished with a soft cloth. Then, we use a dropper to control the dripping of copper sulfate solution into the cleaned area. Ordinary carbon steel or iron forms a layer of metallic copper within seconds, while the surface of double flange steel expansion joints does not produce copper deposits or display copper color.

What is the effect of solid solution treatment on stainless steel seamless pipes

1. Make the arrangement and composition of stainless steel seamless pipes uniform and consistent

This is particularly important for raw materials, as the rolling temperature and cooling rate of each section of hot-rolled pipes are different, resulting in inconsistent microstructure. At high temperatures, atomic economic activity intensifies, and the chemical composition tends to be uniform. After rapid cooling, a more uniform single-phase arrangement is achieved.

2. Eliminate work hardening in order to continue cold working.

Through solid solution treatment, the twisted lattice structure is restored, and the elongated and broken grains begin to crystallize again, eliminating internal stress. The tensile strength of the steel wire continues to decrease, and the elongation gradually increases.

3. Restore the inherent corrosion resistance of stainless steel pipelines.

Due to the formation of carbides and lattice defects during cold processing, the corrosion resistance of stainless steel pipes is reduced. After solution treatment, the corrosion resistance of stainless steel seamless pipes is restored to its optimal state.