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Soft Iron Base Alloys

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Soft magnetic alloys are ferromagnetic materials that are easily magnetized and de-magnetized. To provide optimal magnetic performance, these soft, iron-based alloys possess very low levels of carbon, nitrogen, and oxygen. They rely on various additions of phosphorus, nickel, and silicon to optimize magnetic induction, permeability, and coercive force. The magnetic properties of all of these alloys benefit from high temperature sintering (HT) above 2200 F (1200 C) in hydrogen, as compared to the standard PM sintering process (ST) in metal mesh belt furnaces at nominally 2050 F (1120 C). Density and grain size increases, while residual levels of carbon, oxygen, and nitrogen are reduced. Typical applications include tone wheels, relays, cores, sensor probes, armatures, solenoid components, and pole pieces.

The following tables contain a list of the materials available. For more complete coverage of properties, reference MPIF Standard 35, ASTM B783, ISO 5755, DIN 30910-4, and JIS Z2550, and download the technical information bulletins of interest. Standard powder metal materials are defined in North America by MPIF Standard 35 and ASTM B783, essentially equivalent standards. German PM steels are listed in DIN 30910-4, or more recently, ISO 5755. Japan steels are listed in JIS Z2550, with grade names changing with the revision from 1989 to 2000.

Type Grade Description
Iron SSI-Iron
MPIF/ASTM F-0000, FF-0000
ISO F-00
DIN Sint-C 00, Sint-D 00, Sint-E 00
JIS SMF 1015, SMF 1020, P1024, P1025, P1026 		Offers the lowest cost solution for high magnetic output where the highest possible magnetic permeability and lowest coercive force is not required.
Iron-Phosphorus
(Fe-0.45%P) 		SSI-45P
MPIF/ASTM FY-4500, FY-8000
ISO F-00P05
DIN Sint-C35, Sint-D 35
JIS P1064, P1065, P1066, P1094, P1086 		Iron with 0.45% phosphorus provides slightly higher magnetic output, increased permeability, and lower coercive force compared to pure iron.
Iron-Silicon
(Fe-3%Si) 		SSI-3Si
ASTM/MPIF FS-0300 		Iron with 3% silicon provides magnetic output similar to phosphorous-iron alloys with higher electrical resistivity.
Iron-Nickel
(Fe-50%Ni) 		SSI-50Ni
ASTM/MPIF FN-5000 		Iron with 50% nickel provides exceptional permeability and extremely low coercive force, at the expense of slightly reduced magnetic output.

Soft Iron Base Alloys – As-sintered

Magnetic Properties at 15 Oe Typical Properties
GRADE Density
g/cm 3		 B m
kG (T)		 B r
kG (T)		 H c
Oe (A/m)		 mmax Tensile Strength
ksi (MPa)		 Yield Strength
ksi (MPa)		 Elongation
%		 Unnotched
Impact Energy
ft-lb (J)		 Apparent Hardness
HRB
FF-0000 7.0
7.2		 10.5 (1.05)
12.0 (1.20)		 9.0 (0.90)
10.5 (1.05)		 2.1 (165)
2.1 (165)		 2,100
2,700		 28 (190)
37 (255)		 17 (115)
22 (150)		 11
16		 - 50 HRF
55 HRF
FY-4500


SSI-45P
SSI-45P-HTS		 7.0
7.2
7.4
7.1
7.3		 11.5 (1.15)
12.5 (1.25)
13.0 (1.30)
12.0 (1.20)
14.0 (1.40)		 9.0 (0.90)
10.0 (1.00)
11.5 (1.15)
10.5 (1.05)
12.6 (1.26)		 1.8 (145)
1.8 (145)
1.8 (145)
1.9 (150)
0.8 (65)		 2,600
2,700
3,200
2,300
6,500		 45 (310)
50 (345)
55 (380)
55 (380)
60 (415)		 32 (220)
35 (240)
38 (260)
40 (275)
39 (270)		 7
7
9
11
25
-

60(80)
>200 (>270)		 45
55
65
58
64
FS-0300


SSI-3Si
SSI-3Si-HTS		 6.8
7.0
7.2
6.9
7.3		 11.0 (1.10)
12.0 (1.20)
13.0 (1.30)
11.6 (1.16)
13.8 (1.38)		 9.0 (0.90)
10.0 (1.00)
11.0 (1.10
9.4 (0.94)
12.6 (1.26)		 1.2 (167)
1.2 (167)
1.0 (80)
1.6 (130)
0.8 (65)		 3,000
4,000
5,000
2,500
6,600		 45 (310)
50 (345)
55 (380)
59 (405)
72 (495)		 30 (205)
35 (240)
40 (275)
45 (310)
51 (350)		 8
10
15
8
23
-


30(40)
>200 (>270)		 65
70
75
62
77
FN-5000

SSI-50Ni
SSI-50Ni-HTS		 7.0
7.4
7.1
7.3		 9.0 (0.90)
12.0 (1.20)
9.5 (0.95)
11.3 (1.13)		 7.5 (0.75)
9.0 (0.90)
6.3 (0.63)
7.6 (0.76)		 0.3 (25)
0.3 (25)
0.25 (20)
0.2 (15)		 8,000
10,000
11,100
19,800		 35 (240)
40 (275)
40 (275)
51 (350)		 20 (140)
25 (170)
21 (145)
22 (150)		 9
15
10
21		 33 (45)
68 (92)
-
-		 28
40
22
26

Density ranges for the materials listed are typically for single-pressed parts. Higher densities can be achieved with double-pressing. “HTS” indicates the material has been “high temperature sintered”, i.e. sintered at a minimum temperature of 2200 F (1200 C).