Heat-resistant isotropic bonded NdFeB magnet and its preparation technology

Abstract

This patent invents a heat-resistant isotropic bonded NdFeB magnet and its preparation technology, belonging to the field of magnetic materials. In present invention, isotropic NdFeB magnetic powders is used as magnetic material, sodium silicate is used as principal binder, and epoxy resin is used as auxiliary binder to prepare heat-resistant isotropic bonded NdFeB magnets. The prepared magnets have greatly increased heat resistance to stand an operating temperature of 200 C., and have advantages of penetration and corrosion resistance. The invented heat-resistant isotropic bonded NdFeB magnets feature good magnetic properties and high operating temperature. During the preparation process, it has the advantage of simple equipment, easy operation, low cost. The technology is easy to large scale production, and has high economic value and huge application prospect in the field of permanent magnetic materials.

Claims

1. A heat resistant isotropic bonded NdFeB magnet comprising about 90-96 mass % of isotropic NdFeB powders, about 3-6.5 mass % of sodium silicate binder, about 0.5-3.3 mass % of epoxy resin binder, about 0.1-0.3 mass % of surfactant, and about 0.1-0.3 mass % of lubricant.

2. The heat resistant isotropic bonded NdFeB magnet according to claim 1, wherein the sodium silicate binder is sodium silicate aqueous solution with modulus of about 3.1-3.4 and Baume degree of 3941.

3. The heat resistant isotropic bonded NdFeB magnet according to claim 1, wherein the surfactant is KH-550 (3-aminopropyltriethoxysilane), KH560 (-(2,3-epoxypropoxy)propytrimethoxysilane), stearic acid, aluminate ester, titanate ester, or a mixture thereof.

4. The heat resistant isotropic bonded NdFeB magnet according to claim 1, wherein the lubricant is paraffin, glycerol, silicate ester, silicone oil, or a mixture thereof.

5. A method for preparing heat resistant isotropic bonded NdFeB magnet according to claim 1, comprising the following steps: (1) mixing isotropic NdFeB magnetic powders with a surfactant and stirring evenly to obtain bonded magnetic powders A; (2) mixing bonded magnetic powders A with epoxy resin binder and stirring evenly until it becomes loose powders to obtain bonded magnetic powders B; (3) mixing bonded magnetic powders B with sodium silicate binder and stirring evenly until it becomes loose powders to obtain bonded magnetic powders C; (4) mixing bonded magnetic powders C with a lubricant and stirring evenly to obtain bonded magnetic powders D; (5) spraying an organic solvent to bonded magnetic powders D to volatilize water of the binder and stirring evenly until it becomes loose powders to obtain bonded magnetic powders E; (6) pressing bonded magnetic powders E in a moulding press machine to obtain an initial green compact F; (7) densifying the initial green compact F in an isostatic pressing machine to obtain a densely compact G; and (8) curing the densely compact G at about 175-200 C. for about 30-40 min to obtain the heat resistant isotropic bonded NdFeB magnet.

6. The method according to claim 5, wherein the epoxy resin binder is diluted and dissolved in acetone before using and immediately mixed with bonded magnetic powders B.

7. The method according to claim 5, wherein the organic solvent is one of acetone, methyl alcohol, ethyl alcohol and ethyl acetate and a mixture thereof.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) The following examples describe this disclosure, but do not limit the coverage of the disclosure.

Example 1: A Method for Preparing Heat Resistant Isotropic Bonded NdFeB Magnets Comprises the Following Steps

(2) Step one: The bonded magnetic powders A1 is obtained by mixing 96 g isotropic NdFeB magnetic powders with 0.3 g KH-550 and stirring evenly;

(3) Step two: The bonded magnetic powders B1 is obtained by mixing bonded magnetic powders A1 prepared in step one with 0.5 g epoxy resin and stirring evenly until it becomes loose powders;

(4) Step three: The bonded magnetic powders C1 is obtained by mixing bonded magnetic powders B1 prepared in step two with 3 g sodium silicate (modulus of 3.1 and Baume degree of 40) and stirring evenly until it becomes loose powders;

(5) Step four: The bonded magnetic powders D1 is obtained by mixing bonded magnetic powders C1 prepared in step three with 0.2 g paraffin and stirring evenly;

(6) Step five: The bonded magnetic powders E1 is obtained by spraying 3 ml acetone to bonded magnetic powders D1 prepared in step four and stirring evenly until it becomes loose powders;

(7) Step six: The initial green compact F1 is obtained by pressing bonded magnetic powders E1 prepared in step five in moulding press machine;

(8) Step seven: The densely compact G1 is obtained by densifying initial green compact F1 prepared in step six in isostatic pressing machine;

(9) Step eight: The heat resistant isotropic bonded NdFeB magnets 1# is obtained by curing densely compact G1 prepared in step seven, wherein the curing temperature is 175 C. and curing time is 40 min.

(10) The sodium silicate binder is replaced by the same mass epoxy resin binder to prepare isotropic bonded NdFeB magnets 1# via the same process as Example One. The temperature coefficients of isotropic bonded NdFeB magnet 1# and 1# are shown in Table 1, and their magnetic properties are shown in Table 2.

(11) TABLE-US-00001 TABLE 1 Temperature coefficients of isotropic bonded NdFeB magnet 1# and 1# Temperature Coefficient of Temperature Coefficient of Remanence 1 (%/ C.) Coercivity 1 (%/ C.) 1# 0.127 (20~200 C.) 0.271 (20~200 C.) 1# 0.095 (20~100 C.) 0.526 (20~100 C.) Note: Bonded magnet 1# with epoxy resin as the only binder has an operating environment temperature of no more than 110 C..

(12) TABLE-US-00002 TABLE 2 Magnetic properties of isotropic bonded NdFeB magnet 1# and 1# Magnetic Energy Remanence Coercivity Product (kGs) (kOe) (MGOe) 1# (Room temperature) 6.245 9.302 8.339 1# (200 C.) 4.817 4.764 3.801 1# (Room temperature) 6.021 9.543 7.820 1# (200 C.) / / / Note: Bonded magnet 1# with epoxy resin as the only binder is broken when it is tested at 200 C.. Therefore, the data is not obtained.

Example 2: A Method for Preparing Heat Resistant Isotropic Bonded NdFeB Magnets Comprises the Following Steps

(13) Step one: The bonded magnetic powders A2 is obtained by mixing 93 g isotropic NdFeB magnetic powders with 0.2 g KH-560 and stirring evenly;

(14) Step two: The bonded magnetic powders B2 is obtained by mixing bonded magnetic powders A2 prepared in step one with 1.5 g epoxy resin and stirring evenly until it becomes loose powders;

(15) Step three: The bonded magnetic powders C2 is obtained by mixing bonded magnetic powders B2 prepared in step two with 5 g sodium silicate (modulus of 3.2 and Baume degree of 39) and stirring evenly until it becomes loose powders;

(16) Step four: The bonded magnetic powders D2 is obtained by mixing bonded magnetic powders C2 prepared in step three with 0.3 g glycerol and stirring evenly;

(17) Step five: The bonded magnetic powders E2 is obtained by spraying 4 ml acetone to bonded magnetic powders D2 prepared in step four and stirring evenly until it becomes loose powders;

(18) Step six: The initial green compact F2 is obtained by pressing bonded magnetic powders E2 prepared in step five in moulding press machine;

(19) Step seven: The densely compact G2 is obtained by densifying initial green compact F2 prepared in step six in isostatic pressing machine;

(20) Step eight: The heat resistant isotropic bonded NdFeB magnets 1# is obtained by curing densely compact G2 prepared in step seven, wherein the curing temperature is 185 C. and curing time is 35 min.

(21) The sodium silicate binder is replaced by the same mass epoxy resin binder to prepare isotropic bonded NdFeB magnets 2# via the same process as Example One. The temperature coefficients of isotropic bonded NdFeB magnet 1# and 2# are shown in Table 3, and their magnetic properties are shown in Table 4.

(22) TABLE-US-00003 TABLE 4 Temperature coefficients of isotropic bonded NdFeB magnet 2# and 2# Temperature Coefficient of Temperature Coefficient of Remanence 1 (%/ C.) Coercivity 1 (%/ C.) 2# 0.129 (20~200 C.) 0.290 (20~200 C.) 2# 0.144 (20~100 C.) 0.432 (20~100 C.) Note: Bonded magnet 2# with epoxy resin as the only binder has an operating environment temperature of no more than 110 C..

(23) TABLE-US-00004 TABLE 4 Magnetic properties of isotropic bonded NdFeB magnet 2# and 2# Magnetic Energy Remanence Coercivity Product (kGs) (kOe) (MGOe) 2# (Room temperature) 5.522 9.460 6.655 2# (200 C.) 4.240 4.522 2.494 2# (Room temperature) 4.281 8.576 4.039 2# (200 C.) / / / Note: Bonded magnet 2# with epoxy resin as the only binder is broken when it is tested at 200 C.. Therefore, the data is not obtained.

Example 3: A Method for Preparing Heat Resistant Isotropic Bonded NdFeB Magnets Comprises the Following Steps

(24) Step one: The bonded magnetic powders A3 is obtained by mixing 96 g isotropic NdFeB magnetic powders with 0.1 g KH-570 and stirring evenly;

(25) Step two: The bonded magnetic powders B3 is obtained by mixing bonded magnetic powders A3 prepared in step one with 3.3 g epoxy resin and stirring evenly until it becomes loose powders;

(26) Step three: The bonded magnetic powders C3 is obtained by mixing bonded magnetic powders B3 prepared in step two with 6.5 g sodium silicate (modulus of 3.4 and Baume degree of 41) and stirring evenly until it becomes loose powders;

(27) Step four: The bonded magnetic powders D3 is obtained by mixing bonded magnetic powders C3 prepared in step three with 0.1 g paraffin and stirring evenly;

(28) Step five: The bonded magnetic powders E3 is obtained by spraying 5 ml acetone to bonded magnetic powders D3 prepared in step four and stirring evenly until it becomes loose powders;

(29) Step six: The initial green compact F3 is obtained by pressing bonded magnetic powders E3 prepared in step five in moulding press machine;

(30) Step seven: The densely compact G3 is obtained by densifying initial green compact F1 prepared in step six in isostatic pressing machine;

(31) Step eight: The heat resistant isotropic bonded NdFeB magnets 3# is obtained by curing densely compact G3 prepared in step seven in vacuum, wherein the curing temperature is 200 C. and curing time is 30 min.

(32) The sodium silicate binder is replaced by the same mass epoxy resin binder to prepare isotropic bonded NdFeB magnets 3# via the same process as Example One. The temperature coefficients of isotropic bonded NdFeB magnet 3# and 3# are shown in Table 5, and their magnetic properties are shown in Table 6.

(33) TABLE-US-00005 TABLE 5 Temperature coefficients of isotropic bonded NdFeB magnet 3# and 3# Temperature Coefficient of Temperature Coefficient of Remanence 1 (%/ C.) Coercivity 1 (%/ C.) 3# 0.132 (20~200 C.) 0.368 (20~200 C.) 3# 0.164 (20~100 C.) 0.667 (20~100 C.) Note: Bonded magnet 3# with epoxy resin as the only binder has an operating environment temperature of no more than 110 C..

(34) TABLE-US-00006 TABLE 6 Magnetic properties of isotropic bonded NdFeB magnet 3# and 3# Magnetic Energy Remanence Coercivity Product (kGs) (kOe) (MGOe) 3# (Room temperature) 4.622 8.640 4.709 3# (200 C.) 3.524 2.917 1.105 3# (Room temperature) 4.281 8.576 4.039 3# (200 C.) / / / Note: Bonded magnet 3# with epoxy resin as the only binder is broken when it is tested at 200 C.. Therefore, the data is not obtained.