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Marine grade stainless steel 316 has been around for a long time. Now there is a better alternative-445M2 grade from Austral Wright Metals. 445M2 was developed in Japan and has a successful record in Australasia. Compared with 316, it has a real advantage.
Unlike 316, 445M2 has a ferrite microstructure and a higher content of corrosion-resistant element chromium.
This provides the 445M2 level with greater technical advantages than the 316 level, such as:
445M2 grade has excellent stamping, bendability and weldability, making it easy to manufacture. It is made like carbon steel and does not have the strong work hardening of austenitic stainless steels like 316, which makes them difficult to cut and bend.
A typical application for the 445M2 grade is wherever 316 is currently used.
The 445M2 level is very suitable for:
In fact, wherever the corrosion resistance of 316 is used, 445M2 will perform better.
The marine grade 445M2 has 1,219 mm wide and 0.55, 0.7, 0.9, 1.2, 1.5, 1.6, 2.0, 2.5 and 3.0 mm thick coils and sheets-all 1219 mm wide. If you need a narrower material, please consult us. The standard finish is 2B. If you want a lower gloss for architectural applications, please inquire about non-reflective 2DR finishes.
445M2 grade is easier to machine than austenitic stainless steels (such as 316): the work hardening rate is much lower, so the forming load and springback are less. The 445M2 grade also behaves like carbon steel in cutting operations: it provides cleaner cuts, less deformation and longer tool life.
These advantages are essential for the introduction of this grade into roll-formed roofing and cladding, as well as sheet metal mesh and other applications. It is also very useful for perforation to sound insulation screens, etc.
After welding, any oxide scale and color can be removed mechanically or chemically to restore the complete corrosion resistance of the surface. The best corrosion resistance is achieved by pickling to ensure the removal of the low chromium layer formed under the high temperature oxide during the welding process.
Pickling paste can be used: Like other high corrosion resistance grades, 445M2 should generally be pickled at the top of the recommended time.
Nisshin stainless steel, a world-class Japanese steel mill, has carefully formulated this grade to obtain good performance. The ultra-high chromium content (22%) and the added molybdenum provide excellent corrosion resistance. Then add a small amount of niobium and titanium in a balanced way to protect performance when welding steel.
And all the furnaces of 445M2 are made with very low carbon content, which is much lower than the 0.03% carbon in special low-carbon 316L, which is used for better welding corrosion resistance.
Corrosion scientists use PREN (Pit Corrosion Resistance Equivalent Number) to compare the resistance of different grades to localized corrosion. 445M2 has a typical PREN of 26, which has better corrosion resistance than 316 with a typical PREN of 25.
Figure 1. Pitting resistance of 445M2 stainless steel compared to 316 and 305 stainless steel plates.
Table 1. Comparison of chemical composition between 445M2 stainless steel and 316 stainless steel.
Table 2. Comparison of chemical composition between 445M2 stainless steel and 316 stainless steel.
Austral Wright Metals worked closely with the Lockers Group to develop metal meshes for security doors and windows. The existing aluminum mesh has excellent performance in the interior, but has a limited life span under the harsh conditions close to the ocean. The lockers turned to stainless steel as a solution.
Figure 2. The traditional security screen is on the left, and the 445M2 stainless steel substitute is on the right.
However, it is difficult to produce flat meshes in 316, and the tool wears out quickly, resulting in a long downtime for tool sharpening. 445M2 solves these two problems, and has better corrosion resistance to deal with the harsh conditions near the ocean.
Manufacturing Director Peter Lowther said: "The strong sales growth of marine-grade stainless steel safety nets proves that the 445M2 is suitable for this application. We provide our customers with excellent products that use the strength of the 445M2 to provide unobstructed views from the perspective of comfort and safety. . The boys in the tool room love it-they don’t see these tools as often as they used to!"
Stramit Marketing Development Manager Glen Roberts said: "We provide 445 square meters of walls, roofs, gutters and downpipes. We did not encounter tea stains, and when we ran 445M2 on a roller forming machine set for carbon steel, Our set-up time is the shortest-cleanliness is the key. We always clean the machine well to remove any carbon steel contamination.
Figure 3. An exploded view of the 445M2 wall and perforated stainless steel sound-absorbing panel on the right.
We even successfully perforated the 445M2 soundproof screen. When combined with enclosed 50mm soundproof glass wool, Stramit® acoustic panels are an effective noise reduction solution for gyms, factories, public buildings and offices. Wall panels and ceilings add value by providing a "three-in-one" solution that can be used as cladding, sound insulation and thermal insulation materials at the same time. "
445M2 is a first-generation ferritic stainless steel with better corrosion resistance than 316. It has been used in building roofs and exterior walls, hot water applications, and anywhere where high corrosion resistance and stain resistance are required.
445M2 contains 22% chromium and 1.2% molybdenum, giving it excellent corrosion resistance. It contains no nickel additives.
445M2 is provided in annealed condition with clean equiaxed microstructure.
The area per kilogram of 445M2 is 3.5% more than that of austenitic grades such as 316. It also has lower thermal expansion and higher thermal conductivity, so there is less deformation during welding.
The yield strength and hardness of 445M2 are higher than 316, and the tensile strength and elongation are lower.
The work hardening coefficient of 445M2 is much lower than 316. Its formation method is similar to that of carbon steel. The lower springback and easier shearing make the tools and equipment designed for carbon steel have better performance.
Electrochemical tests in chloride solution show that 445M2 is better than 316 to resist pitting corrosion.
Electrochemical tests in chloride solution show that 445M2 is better at resisting crevice corrosion than 316 under supply conditions. The effect after spot welding is much better.
The extremely low carbon content and the stability of niobium and titanium make 445M2 have excellent resistance to intergranular corrosion after sensitization thermal cycling, better than 316.
Unlike grade 316, 445M2 is basically not affected by stress corrosion cracking in chloride-containing water.
In a test that simulates an exposed roof in a marine environment, frequent rain will wash away the salt, and 445M2 has the least rust-much less than 316.
A test that simulates a harsher marine environment—a sheltered area with concentrated salt—shows that 445 square meters of rust is minimal—well below the severe staining of 316.
In the atmospheric exposure test in the severe marine subtropical area (equivalent to Fraser Island), the 445M2 was almost completely free of rust (or tea stains) after 2 years of exposure. 316 was evenly tea stained.
Sulfuric acid is very corrosive to stainless steel because it interferes with the formation of a passive surface film. The corrosion rate of 445M2 in high temperature and low concentration sulfuric acid is about 1/5 of that of 316.
445M2 can be easily welded by TIG or MIG. The steel should be degreased, well protected with argon and the heat input kept low. Use 316L(Si) consumables.
445M2 can be easily welded by spot welding and seam welding.
This information is derived from materials provided by Austral Wright Metals-ferrous metals, non-ferrous metals and high-performance alloys, and has been reviewed and adapted.
For more information on this source, please visit Austral Wright Metals-Ferrous Metals, Non-Ferrous Metals and High Performance Alloys.
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