Cast ALNICO Permanent Magnets
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Cast ALNICO Permanent Magnets p. 6.1 February 2003 Rev. C ALNICO PERMANENT MAGNETS Introduction For over 50 years an acknowledged leader in any of the other Alnico grades. Alnico 8 pos- the field of permanent magnets, Arnold sesses the highest coercive force of all Alnico Engineering continues its tradition of supe- grades, as well as excellent energy per unit rior quality and value with the full line of volume and a low temperature coefficient. It Alnico products presented in this catalog. is recommended for applications exposed to One of the oldest members of our magnet strong demagnetizing fields, or where space family, Alnico remains the workhorse of the considerations dictate a short magnetic permanent magnet industry and can be relied length. upon to deliver impressive flux density at an ArKomax® 800 and Alnico 9 are premium economical price. Alnico also boasts the grades of Alnico 5 and 8, respectively. The lowest temperature coefficient of any superior magnetic output of these grades is commercial magnet material (.02% per produced by crystal orientation from the degree centigrade) allowing for excellent molten state in the desired direction of stability over a wide temperature range. magnetization. Alnico has experienced renewed interest in Manufacturing processes recent years in such temperature-sensitive Alnico magnets can be produced in a wide applications as hall-effect and MR-based variety of shapes and sizes, ranging in weight automotive and electronic sensors, in addition from less than one ounce (28 grams) to over to the traditional magnetron, TWT amplifiers, 80 pounds (36 kilograms). actuators, motors and instruments applica- tions that have long relied upon Alnico. The majority of magnets are cast in sand molds, following melting in a high-frequency Call Arnold Engineering today for applica- induction furnace. tions engineering assistance, samples or pricing. Magnets weighing less than an ounce (28 grams) may be produced by sintering. In this General characteristics process, the desired mix of metal powders is Alnico permanent magnets form a family of pressed to shape and size in a die, and then alloys whose major constituents are iron, sintered at a temperature of approximately aluminum, nickel and cobalt, though other 2300° F (1260° C) in a hydrogen atmosphere. elements (e.g., copper and titanium) may be The sintering process is well suited to large included in minor amounts. Grades of Alnico volume production and results in parts which vary in cobalt content, which ranges from are structurally stronger than cast magnets. zero (Alnico 3) to 40% (Alnico 8). Relatively close tolerances can be achieved Lower grades (2, 3 and 4) are unoriented— without grinding. magnetic properties are isotropic and equal in Stock items and tooling all directions. Their magnetic output is A variety of shapes and sizes in selected relatively low. Anisotropic grades (Alnico 5, 6, grades of Alnico have become standard over 8 and 9) are designed to produce high the years. A partial list of these parts is magnetic output in a specified direction. provided later in this manual. Arnold Orientation is achieved during heat maintains the required tooling for these parts treatment, by cooling the product from a and in many cases has quantities of them in temperature of about 2000° F (1093° C) at a stock, ready for immediate shipment. controlled rate, within a magnetic field which conforms to the preferred direction of The use of stock items, especially on small magnetization. quantity orders, can result in substantial savings to the user because the need for Alnico 5, the most widely used grade, can costly production tooling is eliminated. usually be depended upon to deliver energy to a magnetic circuit more economically than p. 6.2 February 2003 Rev. C Alnico 2, 3, 4 Magnetic and Physical Properties (Typical Values) Permeance Coefficient Induction at Max. Energy Residual Required Coersive Recoil B/H @ Maximum Product Bd x Hd Induction Br Magnetizing Field Force Hc Permeability (BdHd) Max. Energy Product MGOe KJ/m3 GmTOeKA/m Oe KA/m G/Oe 10-3Tm/KA G/Oe 10-3Tm/KA G mT Alnico 2 1.60 12.7 7200 720 2000 160 560 45 6.2 7.8 12.0 15.0 4400 440 Alnico 3 1.40 11.1 7000 700 2000 160 475 38 5.1 6.4 14.0 17.5 4450 445 Alnico 4 1.35 10.7 5500 550 3000 240 720 57 4.1 5.2 7.0 9.0 3100 310 Typical Demagnetization Curves 16 18 20 22 25 30 40 50 60 100 200 6 2.0 1.0 14 Energy Product BdHd x 10 14 B (kilogauss) 12 12 10 10 8 8 6 ALNICO 2 6 Induction (Kilogauss) 4 4 Slope Bd/Hd - Gausses per Oersted 2 ALNICO 4 2 ALNICO 3 1000 900 800 700 600 500 400 300 200 100 0 -H Demagnetizing Field (oersteds) p. 6.3 February 2003 Rev. C Alnico 2, 3, 4 Magnetic and Physical Properties (Typical Values) Transverse Coefficient Electrical Tensile Modulus of of Thermal Hardness Density Resistivity Strength Rupture Expansion Rockwell C lb./in.3 gr/cm3 25° C (µΩ cm) PSI N/mm2 PSI N/mm2 per ° C x 106 Alnico 2 0.257 7.11 65 3000 20 7200 50 12.4 45 Alnico 3 0.249 6.89 60 12000 80 23000 160 13.0 45 Alnico 4 0.253 7.00 65 9000 60 24000 165 13.1 45 Temperature Effects Alnico 2 Alnico 3 % % B Bd Temp °C d Temp °C 2 2 -50 Bd 0 50 100 150 200 250 300 -50 Bd 0 50 100 150 200 250 300 1 1 X -1 X -1 -2 -2 -3 -3 -4 -4 -5 -5 -6 -6 X -7 Reversible -7 Reversible Irreversible X Irreversible -8 PSymbol -8 PSymbol X -9 6.7 X -9 6.7 X 12 15 -10 -10 56 56 -11 -11 X Alnico 4 % Bd Temp °C 2 -50 Bd 0 50 100 150 200 250 300 1 X -1 X -2 -3 -4 -5 -6 -7 Reversible Irreversible X -8 PSymbol X -9 6.7 X 15 -10 56 -11 X p. 6.4 February 2003 Rev. C Alnico 5, 5cc, 6 & ArKomax® 800, 800 Hi-Hc Magnetic and Physical Properties (Typical Values) Permeance Coefficient Induction at Max. Energy Residual Required Coersive Recoil B/H @ Maximum Product Bd x Hd Induction Br Magnetizing Field Force Hc Permeability (BdHd) Max. Energy Product MGOe KJ/m3 GmTOeKA/m Oe KA/m G/Oe 10-3Tm/KA G/Oe 10-3Tm/KA G mT Alnico 5 5.50 43.8 12500 1250 3000 240 640 51 3.7 4.6 19.0 24.0 10000 1000 Alnico 5cc 6.50 51.7 13200 1320 3000 240 675 54 2.4 3.0 18.5 23.0 11000 1100 Alnico 6 3.90 31.0 10800 1080 3000 240 750 60 5.6 7.0 14.0 17.5 7400 740 ArKomax® 800 8.10 64.5 13700 1370 3000 240 740 59 2.0 2.5 18.0 22.5 12000 1200 ArKomax® 800 Hi-Hc 8.10 64.5 13200 1320 3000 240 810 64 2.0 2.5 15.5 19.5 11200 1120 Typical Demagnetization Curves 16 18 20 22 25 30 40 50 60 100 200 6 8.0 7.0 6.0 5.0 4.0 3.0 14 Energy Product BdHd x 10 14 B (kilogauss) 12 12 10 10 5) ICO ALNICO 6 8 ALN 8 ALNICO 5 6 6 COLUMNAR ALNICO 5CC Induction (Kilogauss) 4 4 (IMPROVED Slope Bd/Hd - Gausses per Oersted 800 2 2 ARKOMAX ARKOMAX 800 Hi-Hc 1000 900 800 700 600 500 400 300 200 100 0 -H Demagnetizing Field (oersteds) p. 6.5 February 2003 Rev. C Alnico 5, 5cc, 6 & ArKomax® 800, 800 Hi-Hc Magnetic and Physical Properties (Typical Values) Transverse Coefficient Electrical Tensile Modulus of of Thermal Hardness Density Resistivity Strength Rupture Expansion Rockwell C lb./in.3 gr/cm3 25° C (µΩ cm) PSI N/mm2 PSI N/mm2 per ° C x 106 Alnico 5 0.264 7.31 47 5500 40 10000 70 11.5 50 Alnico 5cc 0.264 7.31 47 5200 35 9000 60 11.5 50 Alnico 6 0.265 7.34 50 23000 160 45000 310 11.4 50 ArKomax® 800 0.264 7.31 47 5000 35 8000 55 11.5 50 ArKomax® 800 Hi-Hc 0.264 7.31 47 5000 35 8000 55 11.5 50 Temperature Effects Alnico 5 Alnico 5cc Alnico 6 % % B Bd Temp °C d Temp °C 2 2 -50 Bd 0 50 100 150 200 250 300 -50 Bd 0 50 100 150 200 250 300 1 1 X -1 -1 X -2 X -2 -3 -3 X -4 X -4 X X -5 -5 X -6 -6 -7 Reversible -7 Reversible Irreversible Irreversible -8 PSymbol -8 PSymbol -9 6.7 X -9 6.7 X 18 15 -10 -10 56 56 -11 -11 ArKomax® 800 ArKomax® 800 Hi-Hc % B % d Temp °C Bd Temp °C 2 2 -50 Bd 0 50 100 150 200 250 300 -50 Bd 0 50 100 150 200 250 300 1 1 X X -1 -1 -2 X -2 X -3 -3 -4 X -4 X -5 -5 X X -6 -6 -7 Reversible -7 Reversible Irreversible Irreversible -8 PSymbol -8 PSymbol -9 6.7 X -9 6.7 X 18 15 -10 -10 56 56 -11 -11 p. 6.6 February 2003 Rev. C Alnico 8B, 8HE, 8H, 9 Magnetic and Physical Properties (Typical Values) Permeance Coefficient Induction at Max.