Roll or roller – Single annular member – per se – Specific nonmetallic composition
Reexamination Certificate
1999-11-03
2001-01-09
Jones, Deborah (Department: 1775)
Roll or roller
Single annular member, per se
Specific nonmetallic composition
C428S627000, C428S034400, C428S698000, C428S612000, C428S697000, C428S472000, C501S087000
Reexamination Certificate
active
06171224
ABSTRACT:
FIELD OF THE INVENTION
The invention relates in general to a method for finishing tungsten carbide surfaces and to articles having a finished tungsten carbide surface. In particular, the invention is directed to a method of finishing tungsten carbide surfaces by contacting the tungsten carbide surface with a series of increasingly finer abrasive members.
BACKGROUND OF THE INVENTION
Tungsten carbide compositions have been useful for providing hard, durable surfaces. One particularly important application for such surfaces is tools, such as calender rolls for use in manufacturing. However, many tools require surfaces with very smooth finishes. In particular, calender rolls used to apply magnetic coatings on tape have very exacting smoothness requirements, for example, an RMS (root-mean-square) surface roughness of about 25 nm (about 1 microinch) or less. The RMS surface roughness is a measurement of the typical surface structure found on the object. Surface deformities in the calender roll, such as pits and peaks (e.g., particles sticking out of the surface) will be transferred to the magnetic coating during the coating process. However, the surface of the magnetic tape, after the magnetic coating has been applied, should be very smooth to reduce noise caused by the surface deformities.
Other manufacturing processes also require calender rolls that, although they often do not need the precision of magnetic tape rolls, should have a relatively smooth surface. Furthermore, smooth surfaces made using a hard, durable material may be useful in other applications, such as optics.
Currently, calender rolls in the magnetic film industry have chrome coatings, which also have relatively smooth surfaces. However, these coatings are relatively soft and wear out rapidly. Furthermore, chrome surfaces also tend to have cracks that give the surface the appearance, under a microscope, of a dry lake bed. These cracks may be transferred to the magnetic tape. Moreover, chrome has been recognized to be environmentally hazardous and is now regulated. Thus, there is a need for an alternative.
One potential substitute for chrome is tungsten carbide, which forms a harder and more durable surface coating for calender rolls and other tools. Suitable tungsten carbide coatings often include up to 40 wt. % of other metals, such as chromium, cobalt, and nickel. The addition of these metals often gives the tungsten carbide coating improved properties, such as durability, hardness, and enhanced bond strength with the substrate.
However, these tungsten carbide coatings are often sensitive to current finishing methods and there has been difficulty achieving the necessary surface roughness requirements; in particular, when a relatively uniform profile must be obtained. One danger when trying to finish tungsten carbide is overworking (e.g., using many passes to finish the surface). Overworking a tungsten carbide surface typically increases the porosity of the surface as portions of the surface are removed. This results in an increased RMS surface roughness and possibly introduction of pits into the surface. A method is needed for finishing tungsten carbide surfaces to obtain the desired smoothness without overworking the surface and defeating the desired goal.
SUMMARY OF THE INVENTION
One embodiment of the invention is a method for finishing a tungsten carbide surface on a cylinder which includes contacting the tungsten carbide surface with a first abrasive member while the cylinder is rotating. The first abrasive member is coated with grit particles and is positioned between a support and the tungsten carbide surface. The support and the abrasive member oscillate back and forth across the tungsten carbide surface at a first rate. This oscillation forms a first pattern of markings on the tungsten carbide surface at a first angle relative to the axis of rotation. Subsequently, the tungsten carbide surface is contacted with a second abrasive member which has grit particles that are finer than the grit particles of the first abrasive member. The second abrasive member is positioned between a support and the tungsten carbide surface. The support and the second abrasive member oscillate back and forth across the surface at a second rate to form a second pattern of markings on the surface at a second angle relative to the axis of rotation of the cylinder. The first and second angles differ by at least 15 degrees and one of the first and second angles ranges from about 60 to about 90 degrees and the other of the angles ranges from about 15 to about 75 degrees.
Another embodiment of the invention is a method of producing a tungsten carbide surface having a root-mean-square (RMS) surface roughness of about 25 nm (1 microinch) or less which includes contacting the tungsten carbide surface with an abrasive member having grit particles. The abrasive member is held between a support and the tungsten carbide surface. The support and the abrasive member oscillate back and forth across the tungsten carbide surface. These steps are repeated for each abrasive member in a series of abrasive members until the tungsten carbide surface has an RMS surface roughness of about 25 nm (1 microinch) or less. At least one of the abrasive members in the series has grit particles with an average diameter of 3 &mgr;m or less.
A further embodiment of the invention is a finished article which includes a substrate and a surface layer over the substrate. The surface layer is made with a tungsten carbide composition which contains about 12 to about 26 wt. % chromium. The surface layer has an RMS surface roughness of about 25 nm (1 microinch) or less.
Another embodiment is a cylindrical article which has a substrate and a surface layer on the substrate. The surface layer is formed from a tungsten carbide composition. The surface layer has an RMS surface roughness of about 25 nm (1 microinch) or less, as determined by light scattering, and a surface profile which varies by about ±0.013 mm (±0.0005 inches) or less.
The above summarizes various aspects of particular embodiments incorporating principles of the present invention. This summary discussion is not intended to summarize or describe every embodiment or every feature of the present invention.
REFERENCES:
patent: 3203139 (1965-08-01), Giese
patent: 3836341 (1974-09-01), Saltzman et al.
patent: 4826734 (1989-05-01), Jackson et al.
patent: 4841683 (1989-06-01), Williams
patent: 4842633 (1989-06-01), Kuribayashi et al.
patent: 4953385 (1990-09-01), Aoki et al.
patent: 4963183 (1990-10-01), Hong
patent: 5075129 (1991-12-01), Jackson et al.
patent: 5141571 (1992-08-01), DuBois
patent: 5148639 (1992-09-01), Sakai et al.
patent: 5223332 (1993-06-01), Quets
patent: 5269683 (1993-12-01), Hickok et al.
patent: 5480695 (1996-01-01), Tenhover et al.
patent: 5485890 (1996-01-01), Cawthorne et al.
patent: 5535838 (1996-07-01), Keshavan et al.
patent: 5616426 (1997-04-01), Tenhover et al.
patent: 6004189 (1999-12-01), Phillips
patent: 359472 (1930-04-01), None
patent: 434786 (1933-12-01), None
patent: 407290186A (1995-11-01), None
“Calender Rolls—Thermal spray coatings reduce wear and corrosion on calender rolls,” Phillips and Knapp,Tappi Journal, vol. 78, No. 10, Oct. 1995, pp. 196-205.
Case History of GEM Microfinisher, Grinding Equipment & Machinery Co., Inc., Youngstown, OH, dated prior to Sep. 15, 1997.
Paper entitled “What is a Microfinisher?” from Grinding Equipment & Machinery Co., Inc., Youngstown, OH, dated prior to Sep. 15, 1997.
Imation Corp.
Jones Deborah
Levinson Eric D.
Stein Stephen
LandOfFree
Finishing of tungsten carbide surfaces does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Finishing of tungsten carbide surfaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Finishing of tungsten carbide surfaces will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2473784