This page describes these alloys: physical and mechanical properties, applications, grades and types of products.
Main information
High-permeability alloys – materials with high permeability and low coercitive force. It is accepted that the coercitive force of the alloys of this class should not exceed 1000-1200 А/m. This is determined by their small hysteresis loop. They quickly magnetize in weak magnetic fields, but also lose their magnetic properties in case of removing the magnetic field. The considered materials belong to one of the most common precision alloys - high-permeability ones.
Iron (Fe) and nickel (Ni) are the main components of the considered materials. Many grades also contain cobalt (Co). Chromium (Cr), molybdenum (Mo), vanadium (V), copper (Cu) and silicon (Si) are used as alloying agents. Alloys of Fe-Ni systems are often called permalloys, Fe-Co alloys - permendurs.
Classification
By main magnetic, electric and mechanical properties so as industrial use high-permeability alloys can be divided into 8 groups.
Table 1
Group
Grade
General specification
Intended use
With the highest permeability
79NiMo 80NiCrSi 77NiMoCu
Highest permeability (μa=20000÷200000, μmax=100000÷1000000); lowest coercitive force from 4 to 0.2 А/m with saturation magnetic induction 0.5-0.8 T
Cores of small-sized transformers, throttles, relays, fault indicators, cartridges of magnetic-tape equipment, magnetic screens
With high permeability and increased nominal resistance
50NiCrSi
High permeability (μa=1500÷6000, μmax=15000÷100000); nominal resistance from 0.9 to 1.0 µΩ·m with saturation magnetic induction 1.0-1.4 T
Cores of communication equipment, throttles and peak transformers
With high permeability and increased saturation magnetic induction
45Ni (EP462) 50Ni (EP467) 50Ni-VI
High permeability (μa=1500÷6000, μmax=15000÷100000); saturation magnetic induction at least 1.5 T
Strip-wound and stamped cores of interstage transformers and small power transformers, throttles, relays and components of magnetic circuits
Square-loop
50NiP 34NiCoMoP 40NiCoMoP 70NiMo
Have a large hysteresis loop (Bτ/Bs=0,85÷0,98); highest maximum permeability (μmax=40000÷1200000) with saturation magnetic induction up to 1.5 T
Cores of magnetic amplifiers, solid-state relays, contact rectifiers, modulator throttles, peak transformers, magnetic elements, computors
With saturation magnetic induction
49CoV 49Co2VA
Highest saturation magnetic induction (2.0-2.4 T); high Curie point
Cores and pole pieces of common and superconductive magnet, electromagnets, small-sized power transformers, throttles, magnetic amplifiers, screens, rotors stators, electrical machines, jockeys, magnetostrictive devices. Cores of peak and broadband transformers
With low remanent induction
47NiCo 64Ni 40NiCoMo 68NiMo 79Ni3Mo
Low remanent induction (5% from Bs); low dependancy of the permeability on the magnetizing field; high property stability in case of temperature changes and effect of magnetic fields
With high corrosive resistance
36CoNiMo
Corrosive stability under increased humidity, in seawater and many other aggressive media
Magnetics cores of different control systems, anchors, electromagnets, pneumatic and hydraulic valves without protective covers in humid and aggressive media
With high magnetostrictive effect
49Co2V
Highest magnetostrictive effect values 35-8010-6 and low coercitive force up to 240 А/m
Cores of magnetostrictive transducers of ultrasound and sonar equipment electromechanical filters delay circuits
Properties of high-permeability alloys
Material properties depend on their chemical composition, production method and other factors. So the properties of high-permeability precision alloys should be considered within the groups described in Classification section. They are given in “General specification” column, Table 1.
Grades
The main grades of high-permeability precision alloys are given in “Classification” section, Table 1. The chemical composition and other requirements are regulated by GOST 10994-74 and GOST 10160-75 standards.
Advantages/drawbacks
Advantages:
have high permeability in weak magnetic fields;
have a low coercitive force.
Drawbacks:
high sensitivity of magnetic properties to stress;
lower saturation magnetic induction if compared with electrical steel;
relatively high cost.
Applications/drawbacks
Permalloys, permendurs and other precision alloys of this category are widely used in magnetic elements of instruments, automatic and wireless devices when working in weak stationary and alternating fields with the frequency up to several tens of kHz or higher (for micronic round products). Examples of applying high-permeability precision alloys are given in “Classification” section, Table 1.
Products/drawbacks
The main types of semi-finished products made of high-permeability alloys are determined by further application of these materials: magnetic and other cores so as similar electrical components. So there are such blanks as sheets, strips (including ones of micron thickness) and rods.