Utron's Combustion Driven Compaction (CDC) uses controlled release of chemical energy from combustion of natural gas and air to compact magnetic powders up to 150 tsi for obtaining net shape high-density pressed thermally processed final parts for high performance permanent and soft magnets.
Traditional powder compaction molding (PM) limited to 50-55 tsi and metal injection molding (MIM) produce lower density magnets (e.g., 5.85 to 6 g/cc) with correspondingly lower magnetic properties. Conventional low pressure powder compaction or injection molding lead to relatively higher % of geometrical dimensional changes.
Utron's CDC press operation fills a die with magnetic powder, fills a chamber to high pressure with a mixture of natural gas and air. As the chamber is being filled, the piston or ram moves, pre-compressing and removing entrapped air from the powder. The gas supply is closed, and an ignition stimulus is applied, causing the pressure in the chamber to rise dramatically, further compressing the metal powder to its final net shape. Utron's basic CDC compaction process and CDC 300, 400 and 1000 ton presses compaction presses are manual or automated to fabricate 1 to 6 magnets/minute, depending on part geometry. The Utron CDC magnet compaction process provides high compaction pressures up to 150 tsi, resulting in very high-density magnets with improved properties. In addition to the unique loading sequence and high tonnage the process occurs over a few hundred milliseconds. A typical UTRON's CDC produced load shown in
Permanent magnetic materials are developed for their property attributes of high induction, high resistance to demagnetization, and maximum energy content. Permanent magnets are primarily used to produce magnetic flux fields, which are a form of potential energy). Table 1a provides an overview of several end use applications. Table 1b provides select magnetic property data of commonly used permanent magnets, including those of bonded NdFeB magnets containing resins manufactured by conventional methods of manufacturing.
Magnetic induction (Br) is controlled and limited by alloy composition. Resistance to demagnetization (coercive force Hc) is conditioned to less extent by composition than by shape, or crystal anisotropies, precipitations, strains and other imperfections, including finer particle sizes. Samarium cobalt-based rare earth magnets, as indicated in Table 1b, are for higher temperature use as compared to NdFeB type magnets. Rare earth magnets are the most sturdy type of permanent magnets available at present for various end use applications. These permanent magnets are manufactured by us using several rare earth elements. Owing to the brittle nature of these magnets, especially without any resins, many powder compaction methods involve resin-containing rare earth compounds (e.g., bonded neo compositions have epoxy or similar resins added in various proportions). Conventional metal injection molding and lower pressure powder metallurgical (PM) compaction methods of these bonded magnets are known to provide relatively lower as-pressed/thermally processed densities (e.g., 5.85 to 6 g/cc are common, depending on the bonded neo compositions, type of resins, lubricant additives etc.), with correspondingly relatively lower magnetic properties.
So far in the previous arts as reported in the literature around the world, there are number of attempts by both academia and industry to develop rapidly solidified Nd—Fe-B magnet powders using a variety of rapid solidification followed by suitable milling/grinding etc. However, there has not been any breakthrough scientifically to further advance developing competitive alloy mixes, or compacting mixes uniquely using controlled high pressure above >50-55 tsi and rapid cycle times or milliseconds of pressing cycle time.
Needs exist for improved magnets.
These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings.
a shows graphs of CDC press load force vs. time in micro seconds and magnet densities compared to load forces as well as samples of parts produced by Utron's CDC.
b shows permanent magnet geometries.
c shows improvements 47 in magnets in the last century.
b shows the percentage of springback of CDC high pressure compacted magnetic materials.
c shows the percent of springback of as-pressed CDC magnetic cylindrical disk samples.
d shows CDC high pressure compacted sample #549 with an aspect ratio of 3.21
e shows sample #792 with an aspect ratio of 2.18.
f shows sample #793 with an aspect ratio of 1.99.
g shows sample #794 with an aspect ratio of 1.53.
h shows sample #795 with an aspect ratio of 1.82.
a shows significant improvement of permeabiloity and Q-factor in Utron compacted CDC nanocomposite soft magnetic Fe—Ni with 3 nm SiO2 powders with higher part densities of 5.81 to 6.15 compared to the properties of traditional CoNi-Ferrite materials.
b shows dynamic hysteresis loops of CDC compacted soft magnetic nanocomposite materials up to 1 MHz for FeNi/SiO2 with density of 5.81 g/cc of the same materials with small eddy current losses in the frequency ranges.
a shows CDC high pressure compaction loading profile for bonded neo thin walled ring.
b shows CDC high pressure compaction loading profile for bonded neo thin walled ring.
c shows CDC high pressure compaction loading profile for bonded neo thin walled ring.
As schematically shown in the left of
As the gas 19 fills the chamber at high pressure, the piston 21 and moves the punch or male die 23 into the female die 29, partially compressing the powder 27. Ignition 17 provides a spark or a sapphire window admits a laser beam to ignite and combust the gas and air 19 in combustion chamber 11. The combustion products rapidly drive the piston 21 and the male die 23 into the female die, compressing the powder with several hundreds of force at pressures up to 150 tsi or more.
The combustion chamber housing 13 gas inlet 15 and electric ignition 17 are shown at the right of
This invention provides magnet manufacture using higher pressure up to 150 tsi combustion driven compaction methods to improve not only the densification and magnetic properties. The invention uses innovative material compositions of baseline NdFeB based magnetic powders with up to 2% of other suitable type of epoxy resin additives. As well as the magnetic properties and net-shape attributes the invention fabricates complex shapes such as thin walled, e.g. 0.060 inch wall thickness, using innovative tooling and fabrication techniques.
Bonded NdFeB magnets are strong magnets which are used for various applications such as sensors, electronics, loud speakers, and in large industries. The magnets are manufactured by mixing powder with resin, which is further processed to form the magnets. The epoxy resin is used for compression molding. Using injection molding, large volumes of magnets are produced; however the magnetic value of the magnets so produced are lower. Density of those magnets produced by injection molding of about 5.8 g/cc-5.85 g/cc is typical, as compared to magnets made with compression molding using hydraulic or mechanical pressing methods. At relatively low compaction pressures of about <50-55 tsi about e.g. 6 g/cc is typical because of their relatively low density.
After the new CDC compaction, the surfaces are treated with epoxy coating or nickel-plating to prevent corrosion. To keep the bonded neodymium magnets in good condition, use along with acid, alkali, organic solvent or electrolytes must be minimized. The immersion of a magnet in water or oil may also affect its magnetism. Although bonded NdFeB magnets with protective resins are fairly stable, as compared to the bonded magnets without the resins, the bonded magnets should also be not used in spaces filled with hydrogen, corrosive gases and radioactive rays, as a safety precaution.
The new CDC compacted bonded neodymium magnets have many advantages; The magnets are stable and very efficient. The magnets and other parts may be formed together in a single step. For multi polar applications, there is a free choice of magnetizing direction. The magnets have high dimensional accuracy and are available in different shapes and sizes. The magnets have high resistance to atmospheric corrosion and have the highest magnetic properties among other isotropic magnets.
To improve the corrosion resistance, some bonded neo and other permanent magnets are coated with epoxy, zinc, nickel or gold, and such protection also provides extra firmness.
These magnets are widely used in computer hard drives, fishing reel brakes, audio speakers, bicycle dynamos, and more products. On a relative cost basis, neodymium based magnets are relatively lower in cost as compared to samarium-cobalt alloys due to their complex manufacturing process and their special quality to withstand high temperatures. Commonly fabricated shapes of permanent magnets such as short cylindrical slugs, rings, long cylinder, blocks, segmented shape etc. are shown in
Bonded neodymium-iron-boron magnets are of great value and interest due to their uses for several electrical motors and other applications. Bonded neodymium has unique physical and magnetic characteristics, many of which can be advantageous to a motor's size and performance. Although each motor has its own parameters to fulfill, technical strategies and efforts have generally been steered along the following areas to demonstrate how bonded neodymium can be used to reduce weight, reduced size, improve efficiency, improve performance, Reduce costs and lower eddy current losses.
In many applications, traditional ferrite motors have been replaced with bonded neo magnets, due to their improved magnetic performance and weight reduction, which are attractive for automotive components and other applications as indicated in Table 1a. There are numerous sensors, brushless DC electric motors and other applications in which thin walled magnets are used as well as for fabricating rotors with magnets as one assembly. We have successfully fabricated not only permanent magnets of various materials and compositions but also rotor-magnet assemblies using CDC higher pressure compaction.
Bonded magnet materials can be created through injection molding and can be made from NdFeB, strontium ferrite or a combination of the two. Bonded magnets that are created through injection molding can be molded into complex shapes and also can be molded directly onto components. Bonded magnets also can be created through the process of compression bonding which offer higher magnetic output but are limited to simpler geometries than injection molded materials. Compression bonded magnets can be made from either NdFeB or SmCo powders.
Injection molded neo magnets binders including Nylon/PPS/polyamide have a temperature range of −40 deg C. to 180 deg C., tight tolerances off the tool and reasonable mechanical strength properties.
Compression bonded neo magnets have higher magnetic strength due to higher magnetic particle density. Epoxy binder provides resistance to normal industrial solvents and automotive fluids. Epoxy coating is done after manufacturing to prevent oxidation. Compression bonded neo magnets typically operate in the temperature range of −40 deg C. to 165 deg C., provide tight tolerances off the tool and have better mechanical strength properties than injection molded magnets. Epoxy is a better polymer matrix choice for bonded magnets due to epoxy's unique bonding, curability at low temperatures and strength properties.
Bonded magnet materials are isotropic and can be magnetized in any direction, have a wide range of existing tool sizes and are available in rings, discs and rectangles. Existing multipole magnetizing fixtures provide quick prototyping. Bonded magnets are easily machined. Multipole rings simplify assembly verses using arc segments.
The new invention provides improved results of CDC compacted and processed bonded Nd—Fe-B magnets and their unique improved densification, and higher remnance, coercivity and combined products as compared to those obtained by conventional lower density (5.85 to 6 g/cc) bonded magnets.
CDC higher pressure powder compaction provides many advantages. The higher pressure combustion driven powder compaction (CDC) provides >50 tsi up to 150 tsi and has several advantages as compared to traditional low pressure powder pressing methods. The CDC magnet production employs chemical to mechanical energy conversion (
Tables 1-9 and
Table 1a provides an extensive spectrum of potential applications of permanent magnets in several types of electric motors including brushless motors, magnetic resonance imaging, holding devices, power meters, transducers, magnetic couplings, magnetic separators, transport systems, and host of aerospace, automotive, and other commercial applications. Soft magnet and composites are useful for applications such as solenoids, relays, motors, generators, transformers, magnetic shielding etc. Table 1b provides select representative magnetic properties of permanent materials of various alloys and the bonded NdFeB alloys reveal Br of 9 kG, Hci of 9 kOe and BHmax of 9.5 MG Oe.
CDC compacted magnets using sintered magnetic powders are obtained without any additional bonding resins.
We have compacted successfully metals, ceramics, and composites including macro, micro and nano materials including variety of magnetic materials, bonded Nd—Fe-B magnets, soft Fe—Ni/Nano SiO2 nano composite magnets, SmCo magnets and SmCo with nano Fe. Table 2 provides an overview of both soft and permanent magnetic samples fabricated by CDC higher pressure compaction.
d-4h show compacted samples 54-58 of different compositions and aspect ratios.
CDC has been used for compacted SmCo—Fe composite magnets. For samarium cobalt-containing Fe nanocomposites, low temperature compaction is needed to prevent decomposition of Sm—Co. The reported BHmax energy product for combustion driven compacted Sm—Co with Fe composite is, BHmax of 31.5 MGOe. Such improvement in magnetic property as compared to the properties obtained by other methods such as hot isostatic pressing (HIP) or plasma pressure compacting (P2C) validates not only the scientific breakthrough of the uniqueness of CDC higher pressure 150 tsi cold pressing of the difficult-to-consolidate nanocomposite powders to retain the higher magnet part densities without cracking the sample under optimized compaction process controls and also provides minimal thermal post-process requirements. The following CDC compacted magnetic materials have been evaluated for magnetic properties as shown in
Examples are:
(SmCo5)0.85 Fe0.15:P2C
(SmCo5)0.85 Fe0.15:CDC
(SmCo5)0.80 Fe0.20:HIP
T=300K
Conditions used for compaction using various methods include P2C: Plasma Pressure Compaction (73 MPa, 5 min. 600° C.); CDC: Combustion Driven Compaction (2000 MPa, 550 ms, “20° C.”, Utron, Inc.); HIP: Hot Isostatic Pressing (0.435 MPa, 5 min, 550° C.)
CDC compacted soft magnetic nanocomposites have proved advantageous. Results 60 shown in
The desirable characteristics of soft magnetic materials include higher permeability, high saturation induction (Bs), low-hysteresis loss, low-eddy current loss in alternating flux applications, constant permeability at low field strengths and minimum change in permeability with temperature. The effects of impurities, crystallinity or amorphous nature of the materials all affect properties. Structure insensitive properties are saturation induction (Bs), resistivity and Tc (Curie temperature) and structure sensitive properties which are affected by impurities or alloying elements, residual strain, grain size, etc are permeability (μ), coercive force (Hc), hysteresis loss (Wh), residual induction (Br), and magnetic stability. Controlling structure sensitive properties is accomplished through proper manufacturing process of the alloy and alloy compositions and use of proper thermal processing treatment without affecting the magnetic properties.
Significant improvement of permeability and Q-factor result from the UTRON compacted CDC nanocomposite magnetic Fe—Ni with 3 nm SiO2 powders, with higher part densities of 5.81 to 6.15 g/cc compared to the properties of traditional CoNi-ferrite materials.
CDC higher pressure compacted bonded neo magnets have improved properties.
Table 3 provides the listing of several CDC higher pressure compacted bonded Neo magnetic alloys and compositions. This invention provides CDC higher pressure compaction of up to 150 tsi, with unique compositions of mechanically blended magnetic powders and suitable epoxy resins in various percentages. Varying higher densities is a function of controlling the unique epoxy resin % in both before and after CDC compaction with suitable thermal processing. Select CDC compacted MQLP-B samples 71, 73, 75 are shown in
Due to the higher as-pressed densities, such unique post-process thermal treatment was found to be beneficial in terms of cost-effectiveness. Also, the uniquely processed CDC bonded neo samples were evaluated for densities and magnetic properties and were found to have much higher density improvement and magnetic property improvements as compared to conventional bonded magnets. The unique CDC produced magnets also have much higher improvements in magnetic induction, intrinsic coercive force and BHmax product as shown in Table 6-8 and
We have also compacted and evaluated other higher density bonded magnets using proprietary NdFeB mixes with Magnaquench base powders MQPB and MQPB+ mixes with higher Br (7.7) and BHmax (11.5). Based on geometry needs, Utron can fabricate any shape, ring discs, rectangles, etc.
The CDC higher pressure compacted samples using higher performance magnet (HPM) alloy series developed at UTRON use base alloy magnetic powders provided by Magnaquench series powders with suitable added epoxy procured by Utron Kinetics team independently from another vendor. Resin % at UTRON Kinetics, revealed significant magnetic property improvements of Br (higher remnance or induction) and Hci (higher demagnetization field). The epoxy resin that we used was blended in varying percentages with the baseline powders provided by the magnet baseline powder supplier.
Out of several thermoset polymers such as epoxies, polyesters, polyimides, cyanate esters, and phenolics, epoxy resin in varying % was chosen to be added in the matrix due to their better compatibility with the NdFeB magnetic powders, better firmess in terms of mechanical strength and ductility, and added protection both during and after CDC pressing for intended magnet applications due to the pyrophoric nature of the magnetic baseline powders especially in the fine sizes. Conventional compression molded or injection molded bonded neo magnets typically have higher %, 1.5-2% for example of resins, which may vary depending on the powder supplier and end users of bonded neo magnets.
Based on the unique magnetic property improvement results, one of the suggested powder composition with 1% resin was recommended by the principal scientist to the baseline powder supplier to provide MQLP-B+ together with ˜1% resin weight %, for use in CDC higher pressure compaction. Epoxy resins typically have curing temperatures of 350 deg F, maximum service temperatures of 350 deg F, tensile strength of 8-13 ksi, and elongation of 3-7%. In bonded neo magnets, the properties depend on the % of such epoxy resins.
CDC compacted net shape magnetic ring 81 and steel core 83 assembly is provided for use in brushless electric motor applications.
The manufacturing advantage of layered or functional gradient materials for the CDC higher pressure compacted and processed magnetic outer ring and steel core assembly is new for brushless electric motor applications. Table 9 lists the CDC as-compacted properties of several mechanical samples and other geometries for unique brushless electric motor applications. Much higher densities were determined in all of the samples. Preliminary mechanical durability properties also were much better as compared to mechanical durability of conventional bonded magnets. Another unique way of CDC compacted at 150 tsi and thermally processed assembly of magnetic outer ring and steel composite inner core as shown in
Innovative tooling is conceived and developed for fabricating thin walled net shaped bonded magnet rings with high length to wall thickness aspect ratios and improved magnetic properties.
Popular magnet geometries including thick walled rings with lower aspect ratios are shown in
Using conventional processing methods, there have always been fabrication challenges to fabricate thin walled magnetic geometries using bonded or sintered magnet powders with aspect ratios (ratio between height and sample wall thickness) of >5-6 or higher. Using conventional low compaction pressures, this method has been less successful due to difficulties to firmly hold and eject the low density as-pressed magnetic parts. Injection molding methods produce much lower density parts, typically 5.8 g/cc densities in MIM injection molded parts as compared to 6 g/cc in low pressure compression molding or pressing. Multi-steps were required, such as extrusion of a rod to make a tube, cutting the tube to the final length, post-process grinding to obtain net shape and surface quality, etc. We have successfully used our CDC high pressure 300-Ton compaction press for making net shape high density magnets. We have conceived unique innovative tooling described and shown in Table 10 and
c shows CDC high pressure compaction loading profile for bonded neo thin walled ring (˜140-150 tsi).
We have created continuous, smooth and controlled CDC loading cycles with precombustion load 111 and combustion load 113 shown in
Additional thin walled net shape CDC bonded neo magnet rings in addition to what is reported in Table 10 were fabricated to assure the reproducibility of one of the innovative net shape manufacturing of thin walled (e.g., wall thickness of ˜0.059 inches) rings and also evaluate the properties of statistically acceptable numbers of rings identified a CDC Bonded Neo Magnets 3091-3115.
The invention provides new compositions, products, processes and apparatus for forming permanent, semi-permanent and soft magnets.
Combustion driven compaction at high compaction pressures have been successfully used to fabricate a broad spectrum of soft magnets from FeNi, FeCo-based magnetic materials and permanent magnets from Nd—Fe—B based alloys, SmCo-based alloys, etc., including bonded neo magnetic alloys of various compositions.
The CDC compacted FeNi—SiO2 nanocomposite soft magnets have shown superior magnetic permeability and lower hysteresis losses. CDC compacted SmCo—Fe nanocomposite magnets have yielded far greater resistance to demagnetization, higher coercive force Hci and much higher BHmax product (31.5 MGOe) as compared to those made by other manufacturing methods such as plasma pressure compaction (P2C) and hot-isostatic pressing (HIP).
Bonded permanent magnets have been compacted with innovative varying composition mixes using baseline magnetic powders and a unique epoxy based resin, for example 3M Scotch Cast—265 electrical resin below 1% by weight, called High Performance Magnet Series. The HPMS mixes are subject to changes of baseline powders together with suitable 1% or less epoxy based resin to improve the Br and Hci together with higher BHmax properties and with improved magnetic properties.
Net shape magnetic outer ring/steel composite inner core assembly have been successful as one unit using CDC compaction at 150 tsi and thermally processed assembly for potential brushless electric motor applications. The thermally processed composite steel core has the hardness range of RB 65-68 and showed ultimate tensile strength levels of ˜12627-13093 psi, yield strengths of 6402-5911 psi and 4.5-4.8% ductility at fracture. Baseline magnetic materials of CDC compacted bonded MQLP-B materials provide ˜4000 psi strength levels. The results indicate that the core samples have proven almost three times stronger than the magnetic layers. Bonded steel core magnets have indicated fairly good bonding with no delamination.
Combustion driven high pressure compaction (up to 150 tsi and higher) technology has been successfully used to fabricate intricate thin walled (e.g., 0.059 inch wall thickness) higher density bonded permanent magnet ring geometries with much higher aspect ratios (e.g., Between 16.64 to 17.59 shown in Table 10) than attainable by conventional powder metallurgical compaction methods with typical ratios of 4-5 or less by using innovative tooling development and part fabrication in net shape. The produced parts have been reproduced several times for part consistency and reliable fabricability.
The higher densities for the new net shape thin walled bonded Neo magnetic rings have been reported to be far superior than densities attainable by metal injection molding (MIM), e.g. compression molding or powder pressing methods using conventional hydraulic or mechanical means of methods.
While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention, which is defined in the following claims.
This application claims the benefit of U.S. Provisional Application No. 61/396,231, filed May 24, 2010, which is hereby incorporated by reference in its entirety as if fully set forth herein.
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Number | Date | Country | |
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61396231 | May 2010 | US |