Hot Pressed Magnet

In 1983, John Croat’s team at General Motors Research Laboratory pioneered rapidly solidified Nd-Fe-B, soon developing full-density anisotropic magnets through hot pressing and deformation of these powders. A hot pressed Neodymium magnet rivals sintered Neodymium magnets, pioneered by Masato Sagawa at Sumitomo Special Steel, in magnetic performance. Uniquely, a hot pressed Neodymium magnet achieves grain orientation via plastic deformation at high temperatures without an external magnetic field, enabling innovative designs for specialized motor applications.

This breakthrough fueled extensive research, leading to commercial production of radially oriented ring magnets. Consequently, nearly all hot pressed Neodymium magnets adopt intricate ring shapes. Also known as hot deformed or hot extruded magnets, a hot pressed Neodymium magnet reflects its distinctive processing, offering precision and strength for automotive and industrial motor applications, such as servo and electric power steering (EPS) motors, with robust performance.

Manufacturing Process of Hot Pressed Magnet

A hot pressed magnet begins with rapid quenched powder, cold pressed at room temperature, then hot pressed at ~800°C to form a fully dense, isotropic body. For anisotropic properties, a hot pressed magnet undergoes hot deformation at ~800°C. After deformation, the hot pressed magnet is machined, surface treated, and magnetized, ensuring precision and performance for applications requiring robust magnetic properties in demanding environments.

Magnetic and Physical Properties of Hot Pressed Magnet

Magnetic Properties Chart of Hot Pressed Magnet

Grade	Remanence Br		Coercivity Hcb		Intrinsic Coercivity Hcj		Max. Energy Product (BH)max
Grade	T	kGs	kA/m	kOe	kA/m	kOe	kJ/m³	MGOe
50M	1.40-1.45	14.0-14.5	≥1043	≥13.1	≥1114	≥14	374-406	47-51
45M	1.33-1.37	13.3-13.7	954-1058	12.0-13.1	≥1273	≥16	318-366	40-46
42M	1.29-1.32	12.9-13.2	939-1034	11.8-13.0	≥1273	≥16	302-342	38-43
48H	1.35-1.40	13.5-14.0	1042-1114	13.1-13.6	≥1432	≥18	342-366	43-36
45H	1.32-1.35	13.2-13.5	954-1042	12.5-13.1	≥1432	≥18	318-342	40-43
42H	1.29-1.32	12.9-13.2	931-1010	12.2-13.1	≥1432	≥18	286-326	36-41
40H	1.26-1.29	12.6-12.9	931-1010	11.7-12.7	≥1432	≥18	286-318	36-40
45SH	1.32-1.35	13.2-13.5	954-1042	12.5-13.1	≥1592	≥20	318-342	41-44
42SH	1.29-1.32	12.9-13.2	962-1042	12.2-13.1	≥1592	≥20	302-326	38-41
40SH	1.26-1.29	12.6-12.9	939-1010	11.8-12.7	≥1592	≥20	286-318	36-40
38SH	1.22-1.26	12.2-12.6	923-986	11.6-12.4	≥1592	≥20	278-310	35-39
35SH	1.18-1.23	11.8-12.3	891-962	11.2-12.1	≥1592	≥20	246-286	31-36
38UH	1.22-1.26	12.2-12.6	907-986	11.4-12.4	≥1989	≥25	278-318	35-40
35UH	1.18-1.23	11.8-12.3	891-962	11.2-12.1	≥1989	≥25	246-286	31-36

The above-mentioned data of magnetic properties and physical properties are given at room temperature.
The max working temperature of magnet is changeable due to length-diameter ratio, coating thickness and other environment factors.

Physical Properties Chart of Hot Pressed Magnet

Parameter	Unit	Value
Denstiy / ρ	g/cm³	7.3 – 7.6
Specific Heat / c	J/Kg°C	550
Thermal Conductivity / k	W/m°C	4.8
Coefficient of Thermal Expansion / α	10^-6/°C	C⊥: -0.10 – 0.15 C∥: 7.3 – 7.4
Electrical Resistivity / ρ	10^-8Ωm	135
Vickers Hardness / HV	–	470 – 700
Modulus of Elasticity / λ	MPa	152000
Bending Strength / σ	MPa	C⊥: 200 C∥: 240
Compressive Strength	MPa	C⊥: 740 C∥: 740

Advantages of Hot Pressed Magnets

Hot pressed Neodymium magnets achieve (BH)max values of 240–400 kJ/m³, exceeding sintered radially oriented ring magnets.
It sustains a maximum operating temperature of 200°C.
Suited for small, high L/D ratio, or thin-walled ring magnets, outperforming traditional sintered radially oriented ring magnets.
Its nanocrystalline structure, low Nd-rich phase, and high density provide excellent corrosion resistance.
Hot pressed Neodymium magnets resist cracking from internal stress, offering superior mechanical strength.
Uses 2% less rare earth than sintered Neodymium magnets for equal performance, reducing costs and conserving resources.
Requires fewer heavy rare earth elements to boost coercivity and thermal stability.
Features a short production cycle with near net shape manufacturing, enhancing material efficiency.
Hot pressed Neodymium magnet ensures reliable performance in permanent magnet motors.

Manufacturing Process of Hot Pressed Magnet

Rapid Quenching

Cold Pressing

Hot Pressing

Hot Deformation

Machining

Surface Treatment

Magnetization

Packaging and Shipping

Magnetic and Physical Properties of Hot Pressed Magnet

Magnetic Properties Chart of Hot Pressed Magnet

Physical Properties Chart of Hot Pressed Magnet

Advantages of Hot Pressed Magnets