Stainless Steel 904L

904L grade stainless steel is unlike any other steel. Due to its extra amounts of chromium, molybdenum, nickel and copper, 904L steel features superior resistance to corrosion, rust and acids. While its unique hardness allows it to withstand extreme conditions,

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Description

What is grade 904L stainless steel?
904L stainless steel is a non-stabilized austenitic stainless steel with low carbon content. This high alloy stainless steel is added with copper to improve its resistance to strong reducing acids, such as sulphuric acid. The steel is also resistant to stress corrosion cracking and crevice corrosion.

Stainless Steel 904L, UNS N08904, 1.4539 Chemical composition

Fe, <0.02% C, 19-23% Cr, 23-28% Ni, 4-5% Mo, <2.0% Mn, <1.0% Si, <0.045% P, <0.035% S, 1.0-2.0% Cu

SS 904l Properties

Grade Tensile Strength (MPa) min Yield Strength 0.2% Proof (MPa) min Elongation (% in 50mm) min Hardness
Rockwell B (HR B) Brinell (HB)
SS 904L 490 220 36 70-90 typical 150

 Physical Properties

Grade Density
(kg/m
3)
Elastic Modulus
(GPa)
Mean Co-eff of Thermal Expansion (µm/m/°C) Thermal Conductivity
(W/m.K)
Specific Heat 0-100°C
(J/kg.K)
Elec Resistivity
(nΩ.m)
0-100°C 0-315°C 0-538°C At 20°C At 500°C
SS 904L 7900 190 15 11.5 500 952
Is 904L better than 316L?
The 316L Stainless steel is far less scratch resistant than the stainless steel 904L because it has a much higher Rockwell hardness. … The main advantage of stainless steel 904L over 316L is its resistance to acids: “The addition of copper to this grade gives it greatly improved resistance to strong reducing acids, particularly sulphuric acid.”
What is the difference between 316 and 904L stainless steel?
As you can see, the biggest difference when it comes to using 316L/904L for steel case and bracelet material in watches, is that 904L has a higher percentage of nickel and chromium, as well as the addition of copper.

Corrosion Resistance

SS904L stainless steels have excellent resistance to warm seawater and chloride attack. The high resistance of SUS 904L stainless steel 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 904L is intermediate between super austenitic grades, with 6% molybdenum content, and standard SUS316L austenitic grades. stainless steel grade 904L is less resistant to nitric acid than grades SUS304L and SUS310L, 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.