Overview

904L is an austenitic stainless steel. It is harder than 316L, and its molybdenum addition gives it superior resistance to localized attack (pitting and crevice corrosion) by chlorides and greater resistance reducing acids; in particular, its copper addition gives it useful corrosion resistance to all concentrations of sulphuric acid. Its high alloying content also gives it greater resistance to chloride stress corrosion cracking, but it is still susceptible. Its low carbon content makes it resistant to sensitization by welding and which prevents intergranular corrosion.

Limiting Chemical Composition, %,

Nickel...................................................................................................................................................................................23.00-28.00

Chromium............................................................................................................................................................................19.00-23.00

Manganese..............................................................................................................................................................................2.00 max.

Carbon.....................................................................................................................................................................................0.02 max.

Silicon......................................................................................................................................................................................1.00 max.

Sulphur...................................................................................................................................................................................0.035 max.

Phosphorus...........................................................................................................................................................................0.045 max.

Molybdenum............................................................................................................................................................................4.00-5.00

Copper......................................................................................................................................................................................1.00-2.00

Physical properties

Mechanical Properties

Corrosion resistance

Grade 904L stainless steels have excellent resistance to warm seawater and chloride attack. The high resistance of grade 904L against stress corrosion cracking is due to the presence of high amounts of nickel in its composition. Moreover, the addition of copper to these grades develops resistance to sulphuric acid and other reducing agents in both aggressive and mild conditions.

The corrosion resistance of grade 904L is intermediate between super austenitic grades, with 6% molybdenum content, and standard 316L austenitic grades. Grade 904L is less resistant to nitric acid than grades 304L and 310L, which are free of molybdenum. This steel grade needs to be solution treated following cold working, to achieve maximum stress corrosion cracking resistance under critical environments.

Heat treatment

The heat treatment of 904L stainless steel mainly includes solution treatment and stabilization treatment.

The purpose of solution treatment is to fully dissolve alloying elements into the matrix, while eliminating stress and improving the plasticity and toughness of the steel. The temperature of solution treatment is usually selected in the range of 1050-1150 ° C, and the specific temperature and time depend on the composition and thickness of the steel. The cooling method after solution treatment is generally water quenching or rapid air cooling.

The purpose of stabilization treatment is to improve the corrosion resistance and stress corrosion resistance of steel. Stabilization treatment is usually carried out after solid solution treatment, the treatment temperature is 850-950℃, and the holding time depends on the thickness of the steel. Rapid cooling is also required after stabilization treatment, and air cooling is generally used.

It should be noted that the heat treatment of 904L stainless steel should be carried out in professional heat treatment equipment to ensure precise temperature and time control to obtain the best performance. At the same time, the steel parts after heat treatment also need to carry out the necessary mechanical properties and corrosion resistance testing to ensure that they meet the requirements of use.

Available Forms

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● Bar & Rod

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