US20090260298A1

US20090260298A1 - Cryogenic Treatment Systems and Processes for Grinding Wheels and Bonded Abrasive Tools

Info

Publication number: US20090260298A1
Application number: US12/425,129
Authority: US
Inventors: Larry L. Benoit; Robert C. Ferrell
Original assignee: Coldfire Technology LLC
Current assignee: Milwaukee Electric Tool Corp
Priority date: 2008-04-16
Filing date: 2009-04-16
Publication date: 2009-10-22
Also published as: WO2009129389A1

Abstract

Embodiments of the invention can provide systems and methods for treating grinding wheels and bonded abrasive tools. A process in accordance with an embodiment of this invention is a cryogenic thermal cycling process for grinding wheels and bonded abrasive tools. Grinding wheels and bonded abrasive tools treated by cryogenic thermal cycling processes in accordance with embodiments of this invention can exhibit improved performance and service life during comparison testing against untreated tools.

Description

RELATED APPLICATION

This application claims priority to U.S. Ser. No. 61/045,517, entitled “Cryogenic Treatment Systems and Processes for Grinding Wheels and Bonded Abrasive Tools”, filed Apr. 16, 2008, the contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to cryogenic thermal cycling treatment of grinding wheels and other bonded abrasive tools. In particular, this invention relates to cryogenic treatment systems and processes for grinding wheels and bonded abrasive tools.

BACKGROUND OF THE INVENTION

Grinding wheels and other bonded abrasive tools are known in the art. Such tools generally are comprised of a tool body or center hub, abrasive grains, and a bond material. The abrasive grains and bond material generally form a solid circular shape, with profiles and cross sections depending upon the intended usage for the wheel. The bond material holds the grains together, supports them as they cut and provides a mode of attachment to the tool body. The type of abrasive grains, type of bond material and percent content of each within the abrasive tool can vary depending upon the intended use.
Types of abrasive grains can include aluminum oxide or alumina; zirconium oxide or zirconia; aluminum oxide and zirconium oxide combinations as a mixture comprised of grains of each type, or wherein each type is present within individual grains or both, also known in the art as zirconia-alumina; silicon carbide; cubic boron nitride; and ceramic aluminum oxide. Aluminum oxide and zirconia-alumina are commonly used in grinding wheels and bonded abrasive tools. U.S. Pat. No. 4,657,563 to Licht et al. relates to grinding wheels that utilize zirconia-alumina abrasive grains. Grinding wheels that utilize zirconia aluminum are available from the Norton Company under the trade name “NorZon”.
Silicon carbide is often used for grinding iron, brass, soft bronze and aluminum, as well as stone, rubber and other non-ferrous materials. U.S. Pat. No. 5,711,774 to Sheldon relates to grinding wheels that utilize silicon carbide materials. Boron nitride can be used for wet or dry grinding of hardened steels and steel alloys. U.S. Pat. No. RE31,883 to Bovenkerk relates to such a grinding wheel. Ceramic aluminum oxide is a more recent development in the art wherein high-purity grains can be manufactured in a gel sintering process. U.S. Pat. Nos. 4,623,364 to Cottringer and 5,282,875 to Wood relate to such gel sintering processes.
The physical size of the abrasive grains is commonly referred to as grit size. Grit size corresponds to the number of openings per linear inch in a sizing screen used to size the abrasive grains. Lower numbers in the range of about ten to twenty-four denote a wheel with coarse grain. Coarse grains are often used for rapid stock removal where finish is not important. Higher numbers in the range of about seventy to one hundred eighty are fine grit wheels, commonly used to produce fine finishes.
Bond materials can be selected to allow the abrasive grains to cut efficiently. The bond material holds the grains during cutting but may also be worn away as the grains themselves are worn, thereby causing worn grains to be expelled and exposing new sharp grains. Bond materials can be selected based upon factors that can include operating speed, materials to be ground and the required precision. Bond materials can be of several types, and can include resinoid, vitrified, and metal. Resinoid bonded abrasive tools utilize organic binders such as phenolics to bond the abrasive particles together. U.S. Pat. Nos. 4,741,743 to Narayanan et al., 4,800,685 to Haynes et al., 5,038,453 to Narayanan et al., and 5,110,332 to Narayanan et al. all relate to such resinoid bonded abrasive tools. In bonded abrasive tools that utilize vitrified bond materials, a glass binder system is used to bond the abrasive particles together. See, for example, U.S. Pat. Nos. 4,543,107 to Rue, 4,898,597 to Hay et al., 4,997,461 to Markhoff-Matheny et al., and 5,863,308 to Qi et al. Metal-bonded abrasive tools can utilize sintered or plated metal to bond the abrasive particles to the tool body.
There is a need in the art for systems and processes to improve the performance and durability of grinding wheels and bonded abrasive tools. There is also a need in the art for systems and processes to improve the performance and durability of grinding wheels and bonded abrasive tools, wherein the improvement process is effective on many different types of abrasive grains and bond materials.
Cryogenic thermal cycling has been utilized for certain materials treatment, and has been used to strengthen and provide increased wear properties for certain articles of manufacture. U.S. Pat. No. 6,332,325 to Monfort relates to an apparatus and method for strengthening articles of manufacture through cryogenic thermal cycling. U.S. Pat. No. 6,314,743 to Hutchison relates to a cryogenic tempering process for printed circuit-board drill bits. U.S. Pat. No. 6,164,079 to Waldmann relates to cryogenic treatment of silicon nitride tool and machine parts. U.S. Pat. No. 5,447,035 to Workman relates to cryogenic treatment of brake pads. U.S. Pat. No. 6,109,064 relates to improvement of optical transmission and mechanical strength properties for silicon dioxide optical fiber. U.S. Pat. No. 7,163,595 to Watson relates to a cryogenic thermal process for treating metals to improve structural characteristics. U.S. Pat. No. 7,297,418 also to Watson relates to cryogenic thermal cycling treatment of carbide materials commonly used for cutting tools, drills and the like. U.S. Patent Application Publication 20050047989 to Watson relates to cryogenic treatment of diamond materials. The above art does not relate to cryogenic treatment of grinding wheels and bonded abrasive tools. The above art does not relate to cryogenic treatment of aluminum oxide materials, zirconium oxide materials, or combinations thereof.
Accordingly, there is a need for certain treatments for grinding wheels and bonded abrasive tools that provide increased cutting performance through increases in strength, hardness, fracture toughness and wear resistance. In particular, there is a need for cryogenic thermal cycling treatments for grinding wheels and bonded abrasive tools comprised of materials including aluminum oxide and zirconium oxide wherein the cryogenic thermal cycling treatments provide increased cutting performance and service life through increases in strength, hardness, fracture toughness and wear resistance.

SUMMARY OF THE INVENTION

Certain embodiments of the invention can address some or all of the above needs. Certain embodiments of the invention can provide systems and methods for treating grinding wheels and bonded abrasive tools. A process in accordance with an embodiment of this invention is a cryogenic thermal cycling process for grinding wheels and bonded abrasive tools. Typically, the process can include introducing a bonded abrasive tool into a cycling chamber, wherein the tool has a temperature of about ambient temperature. The process can also include introducing at least one cryogenic material into the cycling chamber, wherein the internal temperature of the chamber can be controlled by adjusting the flow rate of the at least one cryogenic material. In addition, the process can include decreasing the temperature of the cycling chamber or bonded abrasive tool from about ambient temperature to about −275 degrees Fahrenheit (F) at a rate of about 1 to about 3 degrees F. per minute. Further, the process can include increasing the temperature of the cycling chamber or the bonded abrasive tool to about −80 degrees F. at a rate of about 1 to about 3 degrees F. per minute. Moreover, the process can include decreasing the temperature of the cycling chamber or the bonded abrasive tool to about −275 degrees Fahrenheit (F) at a rate of about 1 to about 3 degrees F. per minute. In addition, the process can include increasing the temperature of the cycling chamber or the bonded abrasive tool to about −80 degrees F. at a rate of about 1 to about 3 degrees F. per minute. The process can also include repeating at least twice the steps of decreasing the temperature of the cycling chamber or the bonded abrasive tool to about −275 degrees Fahrenheit (F) at a rate of about 1 to about 3 degrees F. per minute, and increasing the temperature of the cycling chamber or the bonded abrasive tool to about −80 degrees F. at a rate of about 1 to about 3 degrees F. per minute. Further, the process can include increasing the temperature of the cycling chamber or the bonded abrasive tool to about 225 degrees Fahrenheit (F) at a rate of about 1 to about 3 degrees F. per minute. The process can also include maintaining the temperature of the cycling chamber or the bonded abrasive tool at about 225 degrees Fahrenheit for about 240 minutes before reducing the temperature of the cycling chamber or the bonded abrasive tool to about ambient temperature, resulting in a strengthened bonded abrasive tool.
In another embodiment, a bonded abrasive tool can be provided. The bonded abrasive tool can be selected from a group that comprises at least one of alumina, zirconia, or alumina-zirconia. The bonded abrasive tool can be formed by a process that includes introducing the bonded abrasive tool into a cycling chamber, wherein the tool has a temperature of about ambient temperature. The process can also include introducing at least one cryogenic material into the cycling chamber, wherein the internal temperature of the chamber can be controlled by adjusting the flow rate of the at least one cryogenic material. In addition, the process can include decreasing the temperature of the cycling chamber or bonded abrasive tool from about ambient temperature to about −275 degrees Fahrenheit (F) at a rate of about 1 to about 3 degrees F. per minute. Further, the process can include increasing the temperature of the cycling chamber or the bonded abrasive tool to about −80 degrees F. at a rate of about 1 to about 3 degrees F. per minute. Moreover, the process can include decreasing the temperature of the cycling chamber or the bonded abrasive tool to about −275 degrees Fahrenheit (F) at a rate of about 1 to about 3 degrees F. per minute. In addition, the process can include increasing the temperature of the cycling chamber or the bonded abrasive tool to about −80 degrees F. at a rate of about 1 to about 3 degrees F. per minute. The process can also include repeating at least twice the steps of decreasing the temperature of the cycling chamber or the bonded abrasive tool to about −275 degrees Fahrenheit (F) at a rate of about 1 to about 3 degrees F. per minute, and increasing the temperature of the cycling chamber or the bonded abrasive tool to about −80 degrees F. at a rate of about 1 to about 3 degrees F. per minute. Further, the process can include increasing the temperature of the cycling chamber or the bonded abrasive tool to about 225 degrees Fahrenheit (F) at a rate of about 1 to about 3 degrees F. per minute. The process can also include maintaining the temperature of the cycling chamber or the bonded abrasive tool at about 225 degrees Fahrenheit for about 240 minutes before reducing the temperature of the cycling chamber or the bonded abrasive tool to about ambient temperature, resulting in a strengthened bonded abrasive tool.
Grinding wheels and bonded abrasive tools treated by cryogenic thermal cycling processes in accordance with an embodiment of this invention can exhibit improved performance and service life during comparison testing against untreated tools.
Certain embodiments can provide grinding wheels and bonded abrasive tools that have improved service life and cutting performance.
Certain embodiments can provide grinding wheels and bonded abrasive tools wherein the abrasive particles are better-adhered or better-secured within the bond material.
Certain embodiments can provide grinding wheels and bonded abrasive tools wherein the strength and toughness of the abrasive particles are improved.
Other aspects, features, and embodiments of the invention will become apparent upon a reading of the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example system to treat a bonded abrasive tool using a cycling chamber according to an embodiment of the invention.

FIG. 2 is an example bonded abrasive tool according to an embodiment of the invention.

FIG. 3 is an example process to treat a bonded abrasive tool using a cycling chamber according to an embodiment of the invention.

FIG. 4A is a first comparison of an embodiment of the invention, Cryogenic Cycle 101, with a Cryogenic Cycle 117 and one particular cycle 7 from the Monfort '325 patent.

FIG. 4B is a second comparison of one embodiment of the invention, Cryogenic Cycle 101, with a Cryogenic Cycle 117 and one particular cycle 7 from the Monfort '325 patent.

FIG. 5A is a first comparison of an embodiment of the invention, Cryogenic Cycle 101, with a Cryogenic Cycle 109 and another Cryogenic Cycle 114.

FIG. 5B is a second comparison of an embodiment of the invention, Cryogenic Cycle 101, with a Cryogenic Cycle 109 and another Cryogenic Cycle 114.

FIG. 6 is a comparison of treatment rates used within an embodiment of the invention Cryogenic Cycle 101, a Cryogenic Cycle 109, a Cryogenic Cycle 114, and one particular cycle 7 from the Monfort '325 patent.

FIG. 7A shows an embodiment of the invention that includes six temperature ascent and decent periods.

FIG. 7B shows an embodiment of the invention that includes six temperature ascent and decent periods and also including temperature hold or soak periods.

FIG. 8 shows an embodiment of the invention that includes additional temperature ascent and decent periods and also including temperature hold or soak periods that vary in duration.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the invention. Like numbers refer to like elements throughout.
As used herein, the term “bonded abrasive tool” and its pluralized form should be construed to mean a tool with a plurality of abrasive grains mounted to the tool with at least one bond material. An example bonded abrasive tool is a grinding wheel. Another example of a bonded abrasive tool is a cut-off wheel.
As used herein, the term “ambient temperature” should be construed to mean room temperature.
As used herein, the term “cryogenic material” should be construed to mean oxygen, helium, argon, hydrogen, nitrogen, and any combination thereof.
FIG. 1 is an example system to treat a bonded abrasive tool using a cycling chamber according to an embodiment of the invention. Referring to FIG. 1, a system 100 can include a cycling chamber 102, wherein a bonded abrasive tool, such as 200 in FIG. 2, can be introduced. The system can include at least one valve 104 through which at least one cryogenic material 106 can be introduced into the cycling chamber 102, wherein the temperature of the chamber 102 can be increased or decreased depending on whether the valve 104 is open or closed. In at least one embodiment, other cryogenic materials may be introduced into the chamber 102 to increase or decrease the temperature of the chamber 102. In other embodiments, the chamber 102 can be a multi-walled insulated chamber, a vacuum chamber, or a vacuum-insulated chamber.
As shown in FIG. 1, the system 100 can also include a heat exchanger 108 positioned within the chamber 102 to generate at least one cryogenic vapor within the chamber 102. When the cryogenic material 106 is released into the heat exchanger 108, heat can be absorbed from the chamber 102 and into the heat exchanger 108, wherein a cryogenic vapor can be generated to fill the chamber 102. Examples of suitable cryogenic vapors can include, but are not limited to, oxygen, helium, argon, hydrogen, nitrogen, and any combination thereof. The system 100 can also include at least one processor 110 operable to control introduction of at least one cryogenic material 106 via the at least one valve 104. An example of a suitable valve is a solenoid-operated valve. In the embodiment shown, one or more thermocouples 112, 114 can provide real-time temperature measurement, and feedback to the at least one processor 110. Utilizing the feedback, the at least one processor 110 can follow a pre-programmed profile including temperature targets and rates. Example pre-programmed profiles can include, but are not limited to, an initial descent portion, an intermediate descent portion, a treatment descent portion, a treatment hold or soak portion, a treatment ascent portion, an intermediate ascent portion, a final ascent portion, a repeated portion, and any combination thereof. Any number of pre-programmed profiles can be stored in a memory 116 associated with or otherwise accessible by the at least one processor 110.
Embodiments of a system, such as 100, can facilitate certain cryogenic treatment processes for bonded abrasive tools. Furthermore, certain embodiments of a system, such as 100, can facilitate a process to treat a bonded abrasive tool using a cycling chamber. An example bonded abrasive tool provided by a system, such as 100, is shown as 200 in FIG. 2. Example operations of a system, such as 100 of FIG. 1, and its various components as well as associated methods and processes are described by reference to FIGS. 3-8.
FIG. 2 is an example bonded abrasive tool according to an embodiment of the invention. As shown in FIG. 2, a bonded abrasive tool 200 can be, for example, a grinding wheel. Generally, a bonded abrasive tool can be a tool with a plurality of abrasive grains mounted to the tool with at least one bond material. In other embodiments, a bonded abrasive tool can include, but is not limited to, grinding wheels and cut-off wheels.
FIG. 3 is an example process to treat a bonded abrasive tool using a cycling chamber according to an embodiment of the invention. In the embodiment shown in FIG. 3, the process 300 can begin at block 302.
At block 302, a bonded abrasive tool can be introduced into a cycling chamber, wherein the tool has a temperature of about ambient temperature.
In one aspect of an embodiment, introducing a bonded abrasive tool into a cycling chamber can include introducing a bonded abrasive tool comprising at least one alumina-based material and one bond material of either resinoid or vitrified.
Block 302 is followed by block 304, in which at least one cryogenic material can be introduced into the cycling chamber, wherein the internal temperature of the chamber can be controlled by adjusting the flow rate of the at least one cryogenic material.
Block 304 is followed by block 306, in which the temperature of the cycling chamber or bonded abrasive tool is decreased to about −275 degrees Fahrenheit (F) at a rate of about −1 degree F. per minute to about −3 degrees F. per minute.
Block 306 is followed by block 308, in which the temperature of the cycling chamber or bonded abrasive tool is increased to about −80 degrees F. at a rate of about 1 degree F. per minute to about 3 degrees F. per minute.
Block 308 is followed by block 310, in which the two prior elements are repeated at least twice.
Block 310 is followed by block 312, in which the temperature of the cycling chamber or bonded abrasive tool is further increased to about 225 degrees F. at a rate of about 1 degrees F. to about 3 degrees F.
Block 312 is followed by block 314, in which the temperature of the cycling chamber or bonded abrasive tool is maintained at about 225 degrees F. for about 240 minutes before reducing the temperature of the cycling chamber or the bonded abrasive tool to about ambient temperature, and resulting in a strengthened and toughened bonded abrasive tool.
In one embodiment, a bonded abrasive tool can include, but is not limited to, a grinding wheel or a cut-off wheel.
The example elements of FIG. 3 are shown by way of example, and other process embodiments can have fewer or greater numbers of elements, and such elements can be arranged in alternative configurations in accordance with other embodiments of the invention. It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer such as a switch, a processor or special purpose processor, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functions specified in the flowchart block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational elements or steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide elements for implementing the functions specified in the flowchart block or blocks.
Accordingly, blocks of the block diagrams and flowchart illustrations support combinations of means for performing the specified functions, combinations of elements or steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, can be implemented by special purpose hardware-based computer systems that perform the specified functions, elements, or combinations of special purpose hardware and computer instructions.
Referring to FIGS. 4-8, these diagrams illustrate various embodiments of cryogenic treatment processes for a bonded abrasive tool as well as comparisons to conventional processes. Some or all of the illustrated processes in FIGS. 4-8 according to various embodiments of the invention can be implemented with a system shown as 100 in FIG. 1. Some or all of the illustrated processes in FIGS. 4-8 according to various embodiments of the invention can provide a bonded abrasive tool shown as 200 in FIG. 2.
FIG. 4A is a first comparison of an embodiment of the invention, example cryogenic cycle 400 with another cryogenic cycle 402 and one particular cycle 404 from the Monfort '325 patent. Cryogenic Cycle 402 can be used to cryogenically treat abrasive tools that utilize diamond materials, and has temperature ascent rates and descent rates as slow as about 0.1 degrees F. per minute to about 0.2 degrees F. per minute. The cycle 404 of the Monfort '325 patent has temperature ascent and descent rates of about 5 degrees F. per minute. The Monfort '325 patent relates to temperature ramps as slow as about 0.1 degrees F. per minute during cryogenic processing, and as rapid as about 100 degrees F. per minute. However, Monfort '325 does not relate to any advantages of particular temperature ascent and descent rates for any particular materials or articles of treatment. Monfort '325 does not relate to treatment of grinding wheels or bonded abrasive tools, nor treatment of articles comprised of alumina, zirconia, or zirconia-alumina material combinations. An embodiment of the invention, example cryogenic cycle 400, includes placing a grinding wheel or bonded abrasive tool within a cryogenic treatment apparatus, such as that taught in the Monfort '325 patent, and implementing the following temperature cycle: Lowering the temperature of the grinding wheel or tool from room temperature to about −275 degrees F. at a rate of about 2 degrees F. per minute then holding at about this temperature for about 15 minutes; increasing temperature to about −80 degrees F. at a rate of about 2 degrees F. per minute then holding at this temperature for about 15 minutes; decreasing temperature to about −275 degrees F. at a rate of about 2 degrees F. per minute then holding at this temperature for about 15 minutes; increasing temperature to about −80 degrees F. at a rate of about 2 degrees F. per minute then holding at this temperature for about 15 minutes; decreasing temperature to about −275 degrees F. at a rate of about 2 degrees F. per minute then holding at this temperature for about 15 minutes; increasing temperature to about −80 degrees F. at a rate of about 2 degrees F. per minute then holding at this temperature for about 15 minutes; decreasing temperature to about −275 degrees F. at a rate of about 2 degrees F. per minute then holding at this temperature for about 15 minutes; then increasing temperature to about 225 degrees F. at a rate of about 2 degrees F. per minute and holding at about this temperature for about 240 minutes. According to embodiments of the invention, certain cryogenic treatments with decreasing temperature change rates of about −1 degrees to about −3 degrees F. can have a beneficial effect on the performance of grinding wheels or bonded abrasive tools, in particular those grinding wheels or bonded abrasive tools that utilize alumina or zirconia alumina abrasive particles.
FIG. 4B is a second comparison of one embodiment of the invention, example cryogenic cycle 400, with another cryogenic cycle 402 and one particular cycle 404 from the Monfort '325 patent. In FIG. 4B the timescale is relatively longer to show entire cryogenic cycle 402.
FIG. 5A is a first comparison of an embodiment of the invention, example cryogenic cycle 400, with another cryogenic cycle 500, and yet another cryogenic cycle 502. Temperature ramp rates of cryogenic cycle 500 are about 1 degrees F. per minute. Cryogenic cycle 502 and cycle 400 have temperature ascent rates of about 2 degrees F. per minute. A notable difference between cryogenic cycle 502 and embodiment of the invention, example cryogenic cycle 400, is that the temperature descent rates of cycle 502 are about −3 degrees F. per minute compared to about −2 degrees F. per minute for 101.
FIG. 5B is a second comparison of an embodiment of the invention, example cryogenic cycle 400, with another cryogenic cycle 500, and yet another cryogenic cycle 502. In FIG. 5B the timescale is shorter to allow comparison of the cycles between 0 and approximately 800 seconds.
FIG. 6 is a comparison of treatment rates used within an embodiment of the invention, example cryogenic cycle 400, another cryogenic cycle 500, yet another cryogenic cycle 502, and one particular cycle 404 from the Monfort '325 patent. Cryogenic cycle 500 shows temperature descent rate 602 of about −1 degrees F. per minute that can provide a small benefit or have a detrimental effect such as decreased durability. An embodiment of the invention, example cryogenic cycle 400, shows temperature descent rate 600 of about −2 degrees F. per minute that can provide an increased benefit. Cryogenic cycle 502 shows temperature descent rate 604 of about −3 degrees F. per minute that can provide a relatively smaller benefit or, in some instances, may have a detrimental effect such as decreased durability. The treatment rate 606 of the Monfort '325 patent preferred cycle 404, or a descent rate of about 5 degrees F. per minute is in the region of minimal effect for certain embodiments of the invention.
FIG. 7A shows an embodiment of the invention, example cryogenic cycle 400, that includes six temperature ascent and decent periods 700 a, 700 c, 700 e, 700 g, 700 i and 700 k.
FIG. 7B shows an embodiment of the invention that includes the six temperature ascent and decent periods from FIG. 7A and also including temperature hold or soak periods 700 b, 700 d, 700 f, 700 h and 700 j.
FIG. 8 shows an embodiment of the invention that includes the temperature ascent, descent and hold periods from FIG. 7B and also including additional temperature ascent and decent periods 700 k and 700 m and further including temperature hold or soak periods 700 l and 700 n that can vary in duration.
Certain embodiments of the invention can provide improved cutting performance for grinding wheels and bonded abrasive tools. For example, cutting performance of untreated grinding wheels and cutoff wheels comprised of aluminum oxide and zirconia-alumina has been compared to performance of identical grinding wheels and cutoff wheels treated with embodiment of the invention, Cryogenic Cycle 101, and other cryogenic treatment cycles. In a first instance, 5 untreated cutoff wheels of approximately 3 inch diameter and approximately 0.062 inch thickness from one particular manufacturer (Norton) were compared to 5 identical cutoff wheels treated with embodiment of the invention Cryogenic Cycle 101. These particular cutoff wheels had a composition that included approximately 30% to approximately 80% Aluminum Oxide and approximately 4% to approximately 30% Zirconium Oxide, and could also include a resinoid bond material. The untreated cutoff wheels had an average lifetime of about 275 cuts whereas the cutoff wheels treated according to the present invention had an average lifetime of about 344 cuts, an increase of about 25%. For comparison, identical approximately 4.5 inch cutoff wheels treated with Cryogenic Cycle 109 showed about 4% decrease in average number-of-cuts (about 264 cuts average for sample size of 3), and identical cutoff wheels treated with Cryogenic Cycle 114 showed about 19% improvement in number-of-cuts (about 327 cuts average for sample size of 5). In this first instance, embodiment of the invention Cryogenic Cycle 101 provided excellent results.
In another instance, performance of cutoff wheels with approximately 4.5 inch diameter and approximately 0.045 inch thickness of similar composition from the same manufacturer (Norton) were compared. The untreated cutoff wheels (sample size of 9) had an average lifetime of about 58 cuts whereas the cutoff wheels treated with embodiment of the invention Cryogenic Cycle 101 (sample size of 9) had an average lifetime of about 107 cuts, an increase of about 86%. For comparison, identical approximately 4.5 inch cutoff wheels treated with Cryogenic Cycle 109 showed about 15% improvement in number-of-cuts (about 66 cuts average for a sample size of 5), and identical cutoff wheels treated with Cryogenic Cycle 114 showed about 27% improvement in number-of-cuts (about 73 cuts average for a sample size of 5); both improved as compared to the untreated cutoff wheels but far less improvement than embodiment of the invention Cryogenic Cycle 101.
In another instance, performance of cutoff wheels with approximately 4.5 inch diameter and approximately 0.04 inch thickness from a second manufacturer (Tyrolit) were compared. Cutoff wheels from the second manufacturer had a composition that included approximately 0% to approximately 99% Aluminum Oxide, and could also include a resinoid bond material. The untreated cutoff wheels (sample size of 5) had an average lifetime of about 43 cuts whereas the cutoff wheels treated with embodiment of the invention Cryogenic Cycle 101 (sample size of 5) had an average lifetime of about 54 cuts, an increase of about 25%.
In another instance, performance of cutoff wheels with approximately 4.5 inch diameter and approximately 0.04 inch thickness from a third manufacturer (Dronco) were compared. Cutoff wheels from the third manufacturer had a composition that included approximately 60% to approximately 80% Aluminum Oxide, and could also include a resinoid bond material. The untreated cutoff wheels (sample size of 5) had an average lifetime of about 48 cuts whereas the cutoff wheels treated with embodiment of the invention Cryogenic Cycle 101 (sample size of 5) had an average lifetime of about 56 cuts, an increase of about 17%.
In another instance, performance of grinding wheels with approximately 4.5 inch diameter and approximately 0.25 inch thickness from the first manufacturer (Norton) was compared. Grinding wheels from the first manufacturer had a composition that included approximately 40% to approximately 60% Aluminum Oxide and approximately 30% to approximately 50% Zirconium Oxide, and could also include a resinoid bond material. Grinding wheels from the first manufacturer treated with embodiment of the invention Cryogenic Cycle 101 (sample size of 5) had an average G-ratio of about 122 compared to G-ratio of about 83 for identical but untreated grinding wheels (sample size of 5), about 18% improvement. Note that G-ratio is defined as the cubic volume of grinding stock removed divided by the cubic volume of grinding wheel wear. For comparison, identical approximately 4.5 inch grinding wheels treated with Cryogenic Cycle 109 showed about 7% decrease in G-ratio (average G-ratio of about 96 for a sample size of 5), and identical grinding wheels treated with Cryogenic Cycle 114 showed about 19% decrease in G-ratio (average G-ratio of about 83 for a sample size of 5); both decreased as compared to the untreated cutoff wheels and further decreased as compared to embodiment of the invention Cryogenic Cycle 101.
It can therefore be observed that certain embodiments of the invention can offer some advantages over untreated grinding wheels and other bonded abrasive tools, and grinding wheels and other bonded abrasive tools treated using conventional cryogenic treatment processes.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A process to treat a bonded abrasive tool using a cycling chamber, the process comprising:

(a) introducing a bonded abrasive tool into a cycling chamber, wherein the tool has a temperature of about ambient temperature;

(b) introducing at least one cryogenic material into the cycling chamber, wherein the internal temperature of the chamber can be controlled by adjusting the flow rate of the at least one cryogenic material;

(c) decreasing the temperature of the cycling chamber or bonded abrasive tool to about −275 degrees Fahrenheit (F) at a rate of about −1 degree F. per minute to about −3 degrees F. per minute;

(d) increasing the temperature of the cycling chamber or bonded abrasive tool to about −80 degrees F. at a rate of about 1 degree F. per minute to about 3 degrees F. per minute;

(e) repeating elements (c) and (d) at least twice;

(f) further increasing the temperature of the cycling chamber or bonded abrasive tool to about 225 degrees F. at a rate of about 1 degrees F. to about 3 degrees F.; and

(g) maintaining the temperature of the cycling chamber or bonded abrasive tool at about 225 degrees F. for about 240 minutes before reducing the temperature of the cycling chamber or the bonded abrasive tool to about ambient temperature, and resulting in a strengthened and toughened bonded abrasive tool.

2. The process of claim 1 wherein the temperature rate of element (c) is within the range of about −1 degrees F. per minute to about −2 degrees F. per minute.

3. The process of claim 2, further comprising (c1) maintaining the temperature of the cycling chamber or bonded abrasive tool at about −275 degrees F. for about 15 minutes, and (d1) maintaining the temperature of the cycling chamber or bonded abrasive tool at about −80 degrees F. for about 15 minutes.

4. The process of claim 3, further comprising (e1) maintaining the temperature of the cycling chamber or bonded abrasive tool at about −275 degrees F. for about 260 minutes.

5. The process of claim 1, wherein introducing a bonded abrasive tool into a cycling chamber, comprises introducing an abrasive tool comprising at least one alumina-based material and one bond material of either resinoid or vitrified.

6. The process of claim 1, wherein introducing a bonded abrasive tool into a cycling chamber, comprises introducing an abrasive tool comprising at least one zirconia-based material and one bond material of either resinoid or vitrified.

7. The process of claim 1, wherein introducing a bonded abrasive tool into a cycling chamber, comprises introducing an abrasive tool comprising at least one alumina-zirconia based material and one bond material of either resinoid or vitrified.

8. A bonded abrasive tool comprising:

at least one abrasive material selected from the group that comprises at least one of alumina, zirconia, or alumina-zirconia; wherein the bonded abrasive tool is formed by a process comprising:

(a) introducing the bonded abrasive tool into a cycling chamber, wherein the tool has a temperature of about ambient temperature;

(e) repeating elements (c) and (d) at least twice;

(g) maintaining the temperature of the cycling chamber or bonded abrasive tool at about 225 degrees F. for about 240 minutes, and resulting in a strengthened and toughened bonded abrasive tool.

9. The bonded abrasive tool of claim 8 wherein the temperature rate of element (c) is within the range of about −1 degrees F. per minute to about −2 degrees F. per minute.

10. The bonded abrasive tool of claim 9, further comprising (c1) maintaining the temperature of the cycling chamber or bonded abrasive tool at about −275 degrees F. for about 15 minutes, and (d1) maintaining the temperature of the cycling chamber or bonded abrasive tool at about −80 degrees F. for about 15 minutes.

11. The bonded abrasive tool of claim 10, further comprising (e1) maintaining the temperature of the cycling chamber or bonded abrasive tool at about −275 degrees F. for about 260 minutes.

12. The bonded abrasive tool of claim 8, wherein the element introducing a bonded abrasive tool into a cycling chamber comprises introducing a bonded abrasive tool comprising at least one alumina-based material and one bond material of either resinoid or vitrified.

13. The bonded abrasive tool of claim 8, wherein the element introducing a bonded abrasive tool into a cycling chamber, comprises introducing a bonded abrasive tool comprising at least one zirconia-based material and one bond material of either resinoid or vitrified.

14. The bonded abrasive tool of claim 8, wherein the element introducing a bonded abrasive tool into a cycling chamber, comprises introducing a bonded abrasive tool comprising at least one alumina-zirconia based material and one bond material of either resinoid or vitrified.