Watches are a tool used in everyday life to tell time. Compared to other time-keeping devices, watches are worn directly on the wrist, taking up no space. They are also decorative items and, more recently, status symbols.
Stainless steel is the most widely used material for watches. Watches made of stainless steel have a near-mirror-like luster and a tough, cool feel, making them popular with the public.
A beautifully crafted watch has been considered a piece of high-end jewelry. However, as a piece of jewelry worn on the wrist, it is often subject to wear and tear, often causing scratches and rubbing. Once-delicate markings often become scratched, losing their original elegance.
Therefore, watchmakers have extremely stringent requirements for markings, demanding not only intricate and beautiful patterns but also durability and corrosion resistance.
First, 904L is a super-austenitic stainless steel, meaning it is non-magnetic and cannot be hardened by quenching.
Rolex uses 904L steel, where the “L” stands for Lower Carbon, rather than the previously mentioned aluminum addition. Typically, the “L” alloy has a slightly lower hardness due to the lack of carbon, but this is negligible. However, its corrosion resistance is excellent.
So, what is the hardness of this alloy?
904L 183HV
This is already a relatively soft steel. Even if 904L were Rolex’s own formula, the hardness wouldn’t change much.
Hard platinum jewelry, such as PT900/IR, can scratch both types of steel. Truly hard stainless steels, such as DSN9 or the stainless steel used in Swiss Army knives, have a hardness of 600HV.
As for corrosion resistance, 904L stainless steel is good, but not the best. Many high-molybdenum, high-vanadium, and DSN9 stainless steels are far superior. However, it is sufficient for use in watches.
The 904L stainless steel supplied by Top Bright Metal is a super-austenitic stainless steel with a high chromium, nickel, and molybdenum content, offering excellent corrosion resistance. It offers excellent resistance to uniform corrosion, pitting and crevice corrosion, intergranular corrosion, stress corrosion cracking, and general corrosion, particularly in dilute sulfuric acid.
Because 904L has a very low carbon content (maximum 0.020%), it does not precipitate carbides during standard heat treatment and welding. This eliminates the risk of intergranular corrosion that can occur after standard heat treatment and welding. Due to its high chromium, nickel, and molybdenum content, as well as the addition of copper, 904L can be passivated even in reducing environments such as sulfuric and formic acids.
