Home > Materials > Soft Magnetic Iron Base Alloys

Soft Iron Base Alloys

Soft magnetic alloys are ferromagnetic materials that are easily magnetized and de-magnetized. To provide optimal magnetic performance, these 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).