Magnetic irons and steels

All magnetic materials fall into two general classes: they are either permanently or nonper-manently magnetized. The permanently magnetized materials retain their magnetization after being placed in a magnetic field and can be used as a constant source of magnetic field. On the other hand, the nonpermanently magnetized, or soft magnetic materials, retain their magnetization only while a magnetic field is applied to the material.

The basic magnetization process and hysteresis cycle is best understood in terms of the static domain theory, which is applicable under DC excitation. However, most applications of magnetic materials are for AC use. The predominant frequency commercially used in the United States is 60 cycles. For many special applications, particularly in the aircraft and military field, 400 cycles is a common frequency. The AC losses are not simple multiples of the DC hysteresis loss, for in addition to the basic magnetic losses.

Applications

The magnetic alloys used for AC applications are used in sheet form and are most often alloyed so that maximum resistivity is obtained commensurate with the induction required, ability to hot- and cold-work the material, minimum hysteresis loss, and cost.

The number of applications of magnetic materials is so large that a complete listing is not feasible. Furthermore, even for the same general application, such as a motor, many acceptable designs could be made, each requiring different-quality levels of magnetic material. Therefore, no attempt will be made to evaluate all the uses for a given alloy. However, several typical uses will be given. In some instances very special properties of a magnetic material may be required. The most common magnetic materials with their characteristic AC and DC properties are listed in Tables M.3 and M.4.


Tables M.3 and M.4 are designed to give the reader a ready reference source to identify the kinds of materials available and a brief resume of their most important properties. After preliminary selection, reference should be made to the detailed curves available from reputable suppliers before any design is anticipated. Many of the materials listed require special handling and annealing techniques to achieve optimum properties.

TABLE M.3

DC Magnetic Properties

Alloy

Sheet Thick, 0.001 in.

tmp1A-147 tmp1A-148 tmp1A-149 tmp1A-150 tmp1A-151

Iron and Iron Silicon

Comm pure Fe

62.5

0.83a

3600

1530

180

8362

Fe-0.35% Si

25.0

2.0a

1000

1340

176

8500

Fe-0.70% Si

25.0

0.92a

4300c

1400

175

8250

Fe-1.60% Si

25.0

1.00a

3900c

1380

175

7800

Fe-2.80% Si

18.5

0.75a

5000

1380

171

7500

Fe-3.25% Si

18.5

0.50a

6400

1380

171

6600

Fe-3.25% Si (oriented)

12.0

0.095b

16,000

1800

198

12,700

Fe-3.25% Si

14.0

0.095b

15,700

1760

196

12,200

(oriented)

Fe-3.25% Si

5.0

0.70a

5200

1400

7600

Fe-3.25% Si (oriented)

4.0

0.28b

16,000

1800

14,200

Fe-3.25% Si (oriented)

2.0

0.40b

13,200

1630

13,800

Nickel-Iron

50% Ni-50% Fe

14

0.04

13,000

85,000

12,000

9000

tmp1A-152 tmp1A-153 tmp1A-154

50% Ni-50% Fe

2-6

0.07

13,000

15,000

1500

14,000

(oriented)

tmp1A-155 tmp1A-156 tmp1A-157

4% Mo-79% Ni,

20

0.015

40,000

200,000

60,000

5000

Balance Fe

tmp1A-158 tmp1A-159 tmp1A-160

Cobalt-Iron

27% Co-Fe

14

2.0

2000

1500

208

10,500

tmp1A-161 tmp1A-162 tmp1A-163 tmp1A-164

35% Co-Fe

17

1.8

2000

1500

230

9000

tmp1A-165 tmp1A-166 tmp1A-167 tmp1A-168

50% Co-Fe

4

1.0

4400

2000

226

10,000

tmp1A-169 tmp1A-170 tmp1A-171 tmp1A-172

50% Co-2% V

4

0.3

47,000

19,500

216

19,000

tmp1A-173 tmp1A-174 tmp1A-175 tmp1A-176

a Hysteresis loop measured from Bmax. = 10,000 G. b Hysteresis loop measured from Bmax. = 15,000 G. c Permeability at H = 2 oe. d Field at which permeability is measured.

TABLE M.4

AC Magnetic Properties

Sheet Thick,

60 Cycles

40 Cycles

Alloy

0.001 in.

tmp1A-177 tmp1A-178 tmp1A-179 tmp1A-180 tmp1A-181 tmp1A-182

Comm pure Fe

62.5

Fe-0.35% Si

25.0

tmp1A-183 tmp1A-184 tmp1A-185

Fe-0.70% Si

25.0

tmp1A-186 tmp1A-187 tmp1A-188

Fe-1.6% Si

25.0

tmp1A-189 tmp1A-190 tmp1A-191

Fe-2.8% Si

18.5

tmp1A-192 tmp1A-193 tmp1A-194

Fe-3.25% Si

18.5

tmp1A-195 tmp1A-196 tmp1A-197

Fe-3.25% Si (oriented)

12.0

tmp1A-198 tmp1A-199 tmp1A-200 tmp1A-201 tmp1A-202 tmp1A-203

Fe-3.25% Si

5.0

tmp1A-204 tmp1A-205 tmp1A-206

Fe-3.25% Si (oriented)

4.0

tmp1A-207 tmp1A-208 tmp1A-209

Fe-3.25% Si (oriented)

2.0

tmp1A-210 tmp1A-211 tmp1A-212

50% Ni-50% Fe

14.0

tmp1A-213 tmp1A-214 tmp1A-215 tmp1A-216 tmp1A-217 tmp1A-218

50% Ni-50% Fe

2-6

Specialized

use at 0 and 400 cycles requires Constant Current Flux React Test

27% Co-Fe

0.014

tmp1A-219 tmp1A-220 tmp1A-221 tmp1A-222 tmp1A-223 tmp1A-224

27% Co-Fe

0.004

tmp1A-225 tmp1A-226 tmp1A-227 tmp1A-228 tmp1A-229 tmp1A-230

35% Co-Fe

0.017

tmp1A-231 tmp1A-232 tmp1A-233 tmp1A-234 tmp1A-235 tmp1A-236

50% Co-2% V, Balance Fe

0.004c

tmp1A-237 tmp1A-238 tmp1A-239 tmp1A-240 tmp1A-241 tmp1A-242

a Dash indicates alloy is not usually used at this frequency.

b Induction in kilogauss at which loss is measured.

c Field annealed.

Applications

DC devices, i.e., electromagnets, relays, pole pieces

Small motors, intermittently used electrical apparatus

Small motors, fractional horsepower motors

High-quality motors, medium efficiency motors, and generators

Motors and generators, reactors, small transformers

High-efficiency motors and generators, reactors, motors

High-quality, high-power, continuous duty transformers

Aircraft motors and transformers, television transformers Magnetic amplifiers, television transformers, power aircraft

transformers Magnetic amplifiers, pulse transformers

Instrument transformers, magnetic shields, sensitive low-current relays

Magnetic amplifiers, current transformers, pulse transformers

High-temperature generators, high-temperature transformer transducers, aircraft equipment, pole pieces

 

Identification of properties related to the magnetic hysteresis loop. Colored area is the magnetization energy loss in every cycle (hysteresis loss).

FIGURE M.4 Identification of properties related to the magnetic hysteresis loop. Colored area is the magnetization energy loss in every cycle (hysteresis loss).

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