Soft Magnetic Alloys
Soft magnetic material includes a wide variety of nickel-iron and nickel-cobalt soft magnetic alloys and pure iron for high performance components requiring high initial and maximum permeability coupled with ease of fabrication.
Sophisticated equipment, advanced technology and the expertise developed for producing aeronautical grade alloys are employed for manufacturing, high performance soft magnetic material.
Starting with ultra clean raw materials, special processes and techniques are used for melting and refining this material under controlled atmospheric conditions in the Air Induction Melting, Vacuum Induction Refining and Vacuum Induction Melting furnaces. The final product is manufactured through a combination of forging, hot and cold rolling, wire drawing and heat treatment depending on the customer`s specifications.
Soft magnetic alloys includes two alloy systems:
1. Softmag Alloys
The iron-nickel SOFTMAG alloys exhibit a wide range of magnetic properties in relation to their nickel content. The high nickel alloys have high initial permeability but low saturation, whereas the low nickel alloys are lower in initial permeability but higher in saturation induction. Small amounts of other alloying elements, particularly molybdenum and copper, are added to these alloys and special processing techniques such as annealing in hydrogen are employed in order to develop or accentuate specific characteristics.
Softmag can be broadly classified into six categories:
SOFTMAG 30 Series (30%Ni, Fe rest) – low curie point, temperature compensator alloys. In this type of alloys, by slight compositional variation, the curie point can be brought down to between +40 and +100°C which is mostly used for temperature compensation in magnetic circuit, temperature-sensitive switches and relays.
SOFTMAG 36 Series (36%Ni, Fe rest) – low-permeability, high resistivity alloys. These are two alloys having the same composition but different magnetic properties due to different processing methods.
36A Series is distinguished by the linearity of its magnetic property and finds application in weak fields in the form of laminations.
36B Series is characterized by very high electrical resistivity, good permeability and low electrical loss. This alloy is mostly used in relays and pulse transformers.
SOFTMAG 48 Series (48%Ni, Fe rest) – medium-permeability, high saturation alloys. These are alloys-with similar composition but different magnetic properties.
48A Series is specially heat treated to attain special properties in low fields, for example, to lower the Rayleigh Region coefficient (g/m). This alloy is supplied in finishing heat-treated condition only, in the form of cores and laminations. They are used in telephone equipment and in some measuring devices.
48B Series shows high initial permeability in low fields. It is used for making relays, transformers, solenoids, current transformers, safety plugs for gas applications.
48C Series is a superior version of 48B Series and exhibits very high permeability and low hysteresis loss. It is available in the form of thin strips, cores and laminations. This alloy is used for making electrical components, small sensitive relays, current transformers, differential detectors, transducers, etc.
48D Series is a square loop version of 48B Series produced by adjusting the composition and subsequent rolling and annealing process achieving a high remanence of flux density due to the cube texture. 48D Series alloy is supplied in the form of strips, cores used in magnetic amplifiers, DC-DC transformers, memories, switching devices, etc.
SOFTMAG 53 Series (53%Ni, Fe rest) – high-permeability, medium saturation alloys. 53 Series is a vacuum melted nickel-iron alloy offering a high induction at saturation in conjunction with high permeabilities. It is used only in the form of cores in current transformers, differential detectors, etc.
SOFTMAG 76 Series (76%Ni, Fe rest) – high permeability, low saturation alloys. 76 is an alloy with saturation induction which is higher than that of 78 Series (-8500 G). This alloy has been specially developed for split armature coils of telephones.
SOFTMAG 78 Series (78%Ni, Fe rest) – very high permeability, l ow saturation alloys. This family of alloys shows very high initial and maximum permeability- at low magnetizing forces, low core losses and very good magnetic shielding characteristics. There are six grades of alloys under this series, composed basically of 78% Ni-Fe-Mo and classified according to their permeability characteristics.
78A Series, 78B Series & 78C Series contain small quantities of copper in addition to molybdenum as an alloying element. They are supplied in the form of sheets, strips, cores and laminations.
78D Series & Series 78E are supplied only as tape wound cores in the heat-treated condition to gain optimum magnetic properties higher permeability and reduced losses.
Series 78F is an alloy which exhibits a rectangular hysteresis loop due to special heat treatment. It is obtained from 78D Series heats and is used in the form of cores for magnetic amplifiers, DC transformers, memories, etc.
2. Sofcomag Alloys
The iron-cobalt SOFCOMAG family of alloys are characterized by moderately high permeability and very high saturation induction. While iron-nickel Softmag alloys attain the maximum saturation induction of about 1.5 teslas, the SOFCOMAG alloys can achieve saturation induction values as high as 2.3 teslas. They are also marked by their low electrical resistivity and high hysteresis loss.
SOFCOMAG can be broadly classified into two series:
SOFCOMAG 25 (25% Co, Fe rest)
SOFCOMAG 49 (49% Co, Fe rest)
SOFCOMAG 25 is an alloy which exhibits the highest saturation flux density of all the magnetic alloys. Its high curie point enables its use in areas where the magnetic properties have to remain unimpaired even at high temperatures of about 500°C. This alloy is designed for application in electrical equipment requiring high saturation; induction in high magnetic field as in. electric motor parts of aircraft for which weight is an important consideration. It is also used for magnetic poles of electromagnets.
SOFCOMAG 49A is similar to SOFCOMAG 25 in respect of its high saturation flux density. However, it offers a higher resistivity than SOFCOMAG 25. This yields low eddy current losses at high induction levels. In addition to electric motors for aircraft, SOFCOMAG 49A is also used for its high positive magnetostriction in sonar applications and ultrasonic equipment.
SOFCOMAG 49B is similar to SOFCOMAG 49A but is given special properties due to different processing methods. Hence the hysteresis cycle of this grade is rectangular.