Enquiry
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
| SS904L 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/m3) |
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.
