Railway wheels and axles – Wheels – Tire fasteners
Reexamination Certificate
1999-12-16
2001-05-08
Stormer, Russell D. (Department: 3617)
Railway wheels and axles
Wheels
Tire fasteners
C295S017000
Reexamination Certificate
active
06227591
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable.
FIELD OF THE INVENTION
The present invention relates to composite metallic articles, and more particularly to a dual alloy railroad wheel.
BACKGROUND OF THE INVENTION
The vast majority of railroad wheels in use today are formed entirely from 0.6 to 0.7 percent plain carbon steel cast in permanent graphite molds. Although formed from a single material, the railroad wheels have different portions that are subjected to different stresses during use and ideally should have different characteristics. For example, the rim of a railroad wheel is in continuous contact with a railroad track and should have good wear resistance. In general, both the rim and body should resist wear and fatigue, but the required wear resistance properties of the rim can compromise the desired level of fatigue resistance of the body portion. Similarly, the desired level of fatigue resistance of the body can reduce the rim wear resistance.
In an attempt to achieve the desired characteristics for the rim and body portions formed from a single material, these portions are processed differently. Conventional railroad wheel fabrication includes processing the rim portion of the wheel through a quenching process. That is, the rim is austenitized at a temperature in a range from about 1700 degrees to 1800 degrees Fahrenheit by rapid cooling with a liquid, such as water spray. The rim quenching process provides a fine perlitic microstructure for the steel and a desirable residual compressive state of stress in the rim about a circumference of the wheel. The fine perlitic structure is harder, and thus generally is more resistant to wear than coarser microstructures and the residual compressive stress on the wheel rim resists cracking due to fatigue and other stresses.
While quenching the rim portion of the wheel provides some contrast in the properties of the body and rim portions of the wheel, there is a limit to the different characteristics that a single material can achieve. Furthermore, there is an inherent tradeoff that is made to balance the desired properties of the different wheel portions.
In addition to providing differing characteristics for the rim and body of the wheel, a fabrication process for making the railroad wheel should be readily adaptable to provide a wheel rim having high traction or low traction depending upon the intended application. For example, a wheel for a locomotive should have a relatively high coefficient of friction with respect to a railroad track for enhancing the load pulling characteristics of the locomotive. Conversely, a freight car should have wheels with a relatively low coefficient of friction for more efficient transport of the freight car.
It would be therefore be desirable to provide a railroad wheel having enhanced wear properties, resistance to fatigue, shelling, and hot spotting. It is further desirable to provide a railroad wheel that can be readily fabricated for relatively high and low traction applications.
SUMMARY OF THE INVENTION
The present invention provides a composite metallic article having enhanced resistance to wear and fatigue. Although the article is primarily shown and described in conjunction with a dual alloy railroad wheel, it is understood that the present invention is applicable to a variety of articles.
In one embodiment, the present invention provides a metallic composite railroad wheel formed from at least two different alloys with each of the alloys having particular properties suited for different portions of the composite article. In an exemplary embodiment, the railroad wheel has a body portion formed from a first alloy and a rim portion formed from a second alloy.
Although it is understood that the rim and wheel body should both be resistant to wear and fatigue, one of ordinary skill in the art will appreciate that a primary characteristic for the first alloy, i.e., the body, is resistance to fatigue cracking and a primary characteristic of the second alloy, i.e., the rim, is resistance to wear. The dual alloy railroad wheel of the present invention provides a wheel with the particular properties that are desired for each of the body and rim portions of the wheel.
In an exemplary embodiment, a method for making a composite railroad wheel of the invention includes casting or forging the body portion from a first alloy steel. A circumferential channel is formed about a perimeter of the body portion. A material, such as sheet metal, is secured about the body portion to form a cavity between the sheet metal and a surface of the body. The cavity is then filled with a second alloy steel powder having desired properties. The cavity is evacuated and hermetically sealed to form a wheel assembly.
The wheel assembly is heated and placed in a hot isostatic press. The wheel assembly is then pressurized with a gas which operates in conjunction with the elevated temperature to densify and diffusion weld the alloy powder to the body portion and provide the rim portion of the wheel. The formed article is then cooled to form the dual alloy railroad wheel.
REFERENCES:
patent: 725999 (1903-04-01), Slattery
patent: 856675 (1907-06-01), Blair, Jr.
patent: 925394 (1909-06-01), Slattery
patent: 950500 (1910-03-01), Woods
patent: 950501 (1910-03-01), Woods
patent: 3978712 (1976-09-01), Cowan et al.
patent: 4183456 (1980-01-01), Shilling et al.
patent: 4426236 (1984-01-01), Sugino et al.
patent: 5290507 (1994-03-01), Runkle
patent: 5312075 (1994-05-01), Kuhn
patent: 5496004 (1996-03-01), Kuhn
patent: 5531943 (1996-07-01), Sudani et al.
patent: 5629101 (1997-05-01), Watremez
patent: 7802742 (1982-11-01), None
Nutter & McClennen & Fish LLP
Stormer Russell D.
Ultraclad Corporation
LandOfFree
Dual alloy railroad wheel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dual alloy railroad wheel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dual alloy railroad wheel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2462510