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The common place of 304 and 304 alloys
Feb 02, 2018

304 and 304H alloy (UNS S30400 / s30409) are the most widely used "18-8" chromium nickel austenitic stainless steel. The carbon content is controlled in the range of 0.04-0.10% at more than 800 degrees Fahrenheit temperature (427 C). It is a kind of economical and common corrosion resistant alloy, which is suitable for a variety of general purpose.

This is 304H that is dual authentication for 304 and 304H conventions. The high carbon chemical energy 304 meets the requirements of mechanical properties and 304H granularity.

The alloy 304 and 304H have general corrosion resistance similar to 304 / 304L. It is resistant to atmospheric corrosion, as well as a moderate oxidation and reduction environment. However, because of its high carbon content, the alloy 304 and 304H are precipitated by the carbide in the welding heat affected zone.

Alloy 304 and 304H are nonmagnetic in annealing conditions, but can become micromagnetically due to cold processing or welding. It can easily weld and handle the standard workshop manufacturing practice.
Corrosion resistance
Alloys 304 and 304H have good atmospheric corrosion resistance, food and beverage, and many organic and inorganic chemical redox environments. The high chromium content of the alloy is resistant to oxidation solutions, such as nitric acid as high as 55% weight and up to 176 F (80 C).

Alloys 304 and 304H also resist moderately active organic acids such as acetic acid. The nickel in the alloy provides resistance to a moderate concentration of solution, such as pure phosphoric acid in a cold solution and up to 10% diluent hot solutions. The alloy can also in caustic solution containing no chloride or fluoride in the medium temperature running smoothly.

Alloys 304 and 304H do not perform well in highly reduced environments, such as chlorides and sulphuric acid.

Alloys 304 and 304H have good chlorides (less than 100ppm) with low level of fresh water service. At the higher level of chloride, this grade is easily affected by crevice corrosion and pitting. Successful performance of these more serious cases, higher molybdenum content is required such as 316 / 316L alloy 304 and 304H do not recommend services in the marine environment.

In most cases, the corrosion resistance of the alloy 304, 304L, and 30h will be approximately equal in most corrosive environments. However, the low carbon content of the alloy 304L intergranular corrosion in the weld and heat affected areas due to sufficient corrosion is due to its low carbon content.

The corrosion rate of the lowest temperature (F) is more than 5mpy

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