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Ferritic Stainless Steel
Description of material
X17NBL is a low Carbon and Niobium stabilized ferritic stainless steel with high resistance to stress corrosion cracking, with a good cold deformability and excellent weldability. In addition, this grade offers a good machinability and high magnetic properties after magnetic annealing.
X17NBL is used for welded parts, washing machines, water piping, tanks, heat exchangers, used in food industries, in domestic water heaters, and for screws and bolting. It finds many applications where a good oxidation resistance is required, and in automotive exhausts systems. Thanks to its good magnetic properties, X17NBL can be used for typical magnetic devices (i.e. solenoid valves, relays) with corrosion resistance better than the popular Free Machining ferritic grades.X17NBL is used for welded parts, washing machines, water piping, tanks, heat exchangers, used in food industries, in domestic water heaters, and for screws and bolting. It finds many applications where a good oxidation resistance is required, and in automotive exhausts systems. Thanks to its good magnetic properties, X17NBL can be used for typical magnetic devices (i.e. solenoid valves, relays) with corrosion resistance better than the popular Free Machining ferritic grades.
X17NBL has an excellent resistance to chloride induced stress corrosion cracking and maintains a better corrosion resistance in either fused and heat affected welded zones than type 430 grades. Its resistance to intergranular corrosion is due to a very low carbon content and to stabilization with Niobium which forms a more stable Carbide than Chromium. This is a very important performance in the case of welding processes or slow cooling annealing of rolled/ forged pieces. It should be noted that this grade, as for every kind of stainless steel, surfaces should be free of contaminant and scale, heat tint, and passivated for optimum resistance to corrosion.
X17NBL has a good cold ductility and can be used in cold heading and cold drawing processes. Nevertheless, as with the majority of ferritic grades, X17NBL is brittle at low temperatures and up-setting or cold heading must be carried out, at least, above room temperatures .
X17NBL is easy to machine thanks to its special chemical balance and micro-resulphuring process providing an important increase of productivity if compared to grades type 430/430L. Nevertheless, it should be pointed out that X17NBL is not a Free machining grade, such as type 430F.
Neither pre-heating nor post welding heat treatment is normally required because X17NBL, in the as-welded condition, should be immune to intergranular corrosion. Autogenous high energy welding does not form any martensitic structure in the fused zone thanks to the low content of Carbon, combined with the Nitrogen and Niobium stabilization of X17NBL. Even though Niobium restricts or prevents grain coarsening in heat affected zones, low heat inputs should be used. Parent filler metal supplies a good geometry and metallurgical quality level in the weld (fused) zone. If austenitic fillers were used in order to increase the ductility of the weld, it should be pointed out that the low magnetic permeability of the Austenitic structure of the fused zone dramatically modifies the magnetic flux causing a flux leakage generated by a high difference of magnetic permeability between the two structures. Shielding gas such as Hydrogen and Nitrogen must not be used to avoid a ductility decreasing of the weld. Argon and Helium should be preferred.
X17NBL has a very good hot plasticity thanks to a wide range of possible forging temperatures. Large blooms and ingots may require a suitable preheating to avoid cracks and an air cooling after forging. Avoid overheating and long soaking since could cause grain growth. The last final steps of forging must be carried out at lower temperature range with a suitable reduction in order to obtain a structure with fine and uniform grains. An annealing after forging should be performed in order to restore both corrosion resistance and enhance the ductility.