904L stainless steel watch strap
There seems to be no brand in the entire watch industry that is more talked about than Rolex. Although Rolex is not the top brand, its status is very transcendent. This brand, which has almost never produced complex functional watches, is committed to taking the basics to the extreme, which is fully reflected in its material selection.
Rolex began gradually replacing its products with 904L stainless steel in 1985, and specifically imported advanced production and processing equipment from Germany due to the high hardness and difficulty of processing 904L stainless steel.
As is well known, Rolex is the only company in the entire bezel that fully uses 904L steel, so 904L steel is also known as "Lao Steel". So compared to 316L steel used by other brands, what are the advantages of 904L steel that make Rolex so fond.
01What are 904L and 316L
904L stainless steel is a low-carbon super austenitic stainless steel, and its special chemical composition and microstructure endow it with excellent corrosion resistance and good processability. This type of steel was originally developed to have excellent corrosion resistance in dilute sulfuric acid. The main components of 904L stainless steel include high chromium (Cr) and nickel (Ni) content, as well as added molybdenum (Mo) and copper (Cu) elements.
Corrosion resistance: 904L stainless steel has excellent corrosion resistance, especially high resistance to chloride interstitial corrosion and stress corrosion cracking. Its carbon content is very low (up to 0.020%), which reduces the risk of intergranular corrosion after heat treatment and welding. In addition, 904L stainless steel has particularly excellent corrosion resistance in dilute sulfuric acid, even in the concentration range of 0-100% and at temperatures up to 95 ° F (35 ° C), it can maintain complete corrosion resistance.
Processing and welding performance: 904L stainless steel has good processing performance and can be subjected to cold and hot processing. Its cold work hardening rate is lower, making machining easier. In terms of welding, 904L stainless steel can be welded in most standard processing, and the solidification after welding will not cause serious element redistribution, so the impact on corrosion resistance is relatively small.
Stress corrosion cracking resistance: Due to its low carbon content and stable nickel content, 904L can resist stress corrosion cracking, making it perform well in high temperature and high stress environments, such as chemical equipment and refining equipment.
Excellent toughness and impact strength: Maintaining good toughness and impact strength at low temperatures, it is very suitable for use in low-temperature conditions, such as refrigeration equipment and marine equipment.
Application areas: commonly used in chemical, petroleum, pharmaceutical, marine engineering, food processing and other fields. It is often used to make equipment and components that require high corrosion resistance and excellent mechanical performance, such as chemical reactors, storage tanks, coolers, furnace tubes, offshore drilling platforms, etc.
316L is an austenitic stainless steel based on molybdenum. Compared with conventional chromium nickel austenitic alloys such as 304 alloy, it has better resistance to general corrosion, pitting corrosion, and crack corrosion. These alloys also have higher ductility, stress corrosion resistance, compressive strength, and high temperature resistance. In addition, 316L stainless steel also has good resistance to chloride corrosion.
Corrosion resistance: It has the same good corrosion resistance as AISI316L and can resist the erosion of various chemical substances.
Low temperature toughness: It has good low-temperature toughness and can maintain stable mechanical and chemical properties at low temperatures.
Heat resistance: able to maintain good mechanical and chemical properties at high temperatures, suitable for use in high-temperature environments.
Strength performance: With high strength, it can withstand significant tensile, compressive, and bending stresses.
Processing performance: Easy to process, cold formed and hot formed, suitable for the production of various shapes and sizes of products.
Application area: 316L stainless steel has a maximum carbon content of 0.03%, which makes it suitable for applications where annealing is not possible after welding and maximum corrosion resistance is required. Its application fields are very wide, including but not limited to pulp and paper equipment heat exchangers, dyeing equipment, film processing equipment, pipelines, and materials for exterior buildings in coastal areas.
904L steel does have strong performance, but that doesn't mean 316L steel is not excellent. 316L steel is the most common type of steel in our daily lives. Due to its low allergenicity, it is commonly used in food processing and medical equipment. Medical surgical knives are made of 316L steel material.
02Difference in Chemical Composition between 316L and 904L
The biggest difference between the two in terms of composition is the content of chromium metal. Chromium metal can form a corrosion-resistant protective film on the surface of steel. Because 904L steel has a higher chromium metal content, it is more corrosion-resistant than 316L. In addition, 904L steel also contains a small amount of copper element, while 316L steel does not contain copper, which means that the corrosion resistance of 904L steel needs to be further improved. Therefore, 904L steel can be used to hold highly corrosive liquids such as sulfuric acid.
03Why did Rolex choose the 904L?
Using 904L steel as the material for the watch case, for consumers, the effect of "promotion" is better than the actual effect of "corrosion prevention" itself. After all, only Rolex uses 904L steel across the entire range, while other brands use "ordinary" and "common" 316L steel. For luxury goods, 'I have what no one has' is a very good promotional point.
In addition, 904L steel has a high chromium metal content, which makes it more likely to cause skin allergies in the human body. Therefore, if you are allergic to metal, it is not recommended to consider watches made of 904L steel.
It has to be said that Rolex watches made of 904L steel have a more beautiful appearance. Many experienced watch repairers have also said that polishing Rolex watches is easier and produces a more shiny effect. Of course, this is mainly due to Rolex's high requirements for steel purity, and the steel used is the most "pure" part. Isn't this Rolex's pursuit of "perfection".