MGC- Acciai inox ferritici

Valbruna Grade

MGC

Description of material

MAGIVAL® MGC is a free machining ferritic stainless steel with Molybdenum, stabilized with Niobium, and displays a better corrosion resistance than the MG1, MG2, MG3, MG4 and MG5 grades. Its magnetic properties and machinability is similar to the MG series. A carefully controlled chemical analysis as well as special metallurgical processes provide a ferritic structure that is very sensitive to magnetic fields. MGC 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.

Applications

Typical applications of MGC 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.

Melting practices

Argon Oxygen Decarburization

Corrosion resistance

Even though the Molybdenum content of MGC is able to reduce or avoid pitting corrosion, extending the range of its applications and Niobium Carbides inhibit the precipitation of Cr-carbides on the grain boundaries also in case of welding, it is important to know 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. MGC has a good resistance to mildly chemically corrosive environments such as crude oil, gasoline, alcohol, some beverages, urban- rural atmospheres and fresh water. 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.

Machinability

MGC has a good machinability typical of all Ferritic free machined grades but a little bit lower than MG1/MG2 due to its Molybdenum and Niobium content. Productivity gain depends on types of machines, the kind of tools used and their geometry, cutting fluids and the kind of machine operations on the pieces produced. It is important to point out that MGC in soft magnetic annealing condition, could have a 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 cold deformed or upset worked.

Weldability

MGC, as with other free machining grades with a high Sulphur content, is not recommended for welding because the fused zone tends to form porosity. In any case, low heat inputs and low welding powers with parent filler metal should be used. If austenitic fillers , in order to increase the ductility of weld, are used, it should be pointed out that the lower 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 MGC. PWHT could also be avoided in certain cases. To avoid a ductility decrease in the weld, shielding gases such as Hydrogen and Nitrogen must not be used. Argon and Helium are the preferred choices.

Designations