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Ferritic Soft Magnetic Steel
Description of material
MAGIVAL® MG1 is the best known ferritic free machining stainless steel grade, developed for magnetic applications, and it has high machinability and corrosion resistance similar to type 430F. It is extensively used in the automotive industries and in soft magnetic components. A carefully controlled chemical analysis as well as special metallurgical processes provide a ferritic structure that is very sensitive to magnetic fields. MG1 can be supplied (1) as annealing+ cold finished or (2) annealed+ cold finished + magnetic annealed + cold finished. See Soft Magnetic Steels brochure for more information about magnetic, mechanical and physical properties.
Typical applications of MG1 are solenoid valves, pole pieces, magnetic cores, electromagnetic pumps and devices, fuel injections components, electromagnetic switches and relays, antilock brake systems, sensors in automotive applications, actuators and fuel pumps.
Argon Oxygen Decarburization
It should be well considered that, as with all free machining grades, Sulphur is added to improve machinability and the formation of MnS inclusions could prime points of pitting if exposed to some corrosive environments. MG1 has a good resistance to mildly corrosive environments such as fresh water, crude oil, gasoline, alcohol, some beverages and atmospheres. 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.
MG1 has a very good machinability typical of all Ferritic free machined grades. Productivity gain depends on types of machines, the kind of tools used and their geometry, cutting fluids and kind of machine operations on the pieces produced. It is important to point out that MG1 in the magnetic annealing condition, could have a large grain size and very low hardness. This kind of structure influences the surface finish (roughness) and the chip morphology. Within certain limits, a little bit harder structure typical of annealing+ cold finishing ( such as cold drawing ) offers advantages in some machine operations and better surface roughness, but a vacuum or protective atmosphere annealing of machined parts should be done if an improvement of magnetic properties is required. This grade cannot be heavy cold deformed or upset worked.
MG1, as with other free machining grades with high Sulphur content, is not recommended for welding because the fused zone tends to form porosity. In any case, low heat inputs and a type 430 filler metal should be used. Austenitic fillers, in order to increase the ductility of weld, don’t solve the problems in HAZ unless a PWHT is applied. 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 the high difference of magnetic permeability between the two structures. Autogenous high energy welding shouldn’t form any martensitic structure in fused zone thanks to the low content of Carbon, and Nitrogen of MG1.