Efficient degradation of materials is important to a variety of industries including the pavement, mining, and excavation industries. In the pavement industry, pavement may be degraded using attack tools, and in the mining industry, attack tools may be used to break minerals and rocks. Attack tools may also be used when excavating large amounts of hard materials. In pavement milling, often, a drum supporting an array of picks may rotate such that the picks engage a paved surface causing it to break up.
U.S. Pat. No. 6,733,087 to Hall et al., which is herein incorporated by reference for all that it contains, discloses an attack tool for working natural and man-made materials that is made up of one or more segments, including a steel alloy base segment, an intermediate carbide wear protector segment, and a penetrator segment comprising a carbide substrate that is coated with a superhard material. The segments are joined at continuously curved interfacial surfaces that may be interrupted by grooves, ridges, protrusions, and posts. At least a portion of the curved surfaces vary from one another at about their apex in order to accommodate ease of manufacturing and to concentrate the bonding material in a region of greatest variance. The carbide used for the penetrator and the wear protector may have a cobalt binder, or it may be binderless. It may also be produced by the rapid omnidirectional compaction method as a means of controlling grain growth of the fine cobalt particles. The pats are brazed together in such a manner that the grain size of the carbide is not substantially altered. The superhard coating may consist of diamond, polycrystalline diamond, cubic boron nitride, binderless carbide, or combinations thereof.
In one aspect of the invention, a pick adapted to degrade man-made or natural formations has a steel body comprising a shank adapted for attachment to a driving mechanism. The pick also has a leading edge opposite the shank which has an inside edge. A bore is disposed in the steel body proximate the inside edge. A cemented metal carbide core is press fit into the bore. A reentrant is at least partially formed in the bore. In some embodiments, the reentrant joins the leading edge and the bore. In other embodiments, the reentrant is formed in proximate a base of the bore.
The cemented metal carbide may be press fit into the steel body with an interference of between 0.0005 and 0.004 inch. In some embodiments, the leading edge may comprise a surface with a hardness of at least 58 HRc. The surface may comprise a material selected from the group consisting of chromium, tungsten, tantalum, niobium, titanium, molybdenum, carbide, natural diamond, polycrystalline diamond, vapor deposited diamond, cubic boron nitride, TiN, AlNi, AlTiNi, TiAlN, CrN/CrC/(Mo, W)S2 TiN/TiCN, AlTiN/MoS2, TiAlN, ZrN, diamond impregnated carbide, diamond impregnated matrix, silicon bounded diamond, and/or combinations thereof In other embodiments, a carbide ring may be fixed to the leading edge.
A distance from the leading edge to an end of the reentrant may be 0.05 to 0.20 inch. A superhard material, selected from the group consisting of diamond, cubic boron nitride, or combinations thereof, is bonded to the cemented metal carbide. The diamond may be infiltrated diamond. Metallic binder from the cemented metal carbide may diffuse into the superhard material. The distance from the leading edge to the end of the reentrant may be 25 to 100% of a thickness of the diamond.
In another aspect of the invention, the cemented metal carbide has first and second regions comprising different metal concentrations. A superhard tip bonded to the first region has a hardness over 4,000 HV. The second region is attached to the steel body. The metal concentration of the first region may be lower than the second region. The second carbide region may be brazed to the steel body or may be press fit into the steel body. The cemented metal carbide may be tungsten carbide, titanium carbide, niobium carbide, vanadium carbide, hafnium carbide, zirconium carbide, molybdenum carbide, tantalum carbide, chromium carbide or combinations thereof. The cemented metal carbide may also comprise a metallic binder selected from the group consisting of cobalt, tantalum, nickel, vanadium, chromium, niobium, or combinations thereof. The first region may comprise 2 to 12 weight percent of metallic binder whereas the second region comprises 5 to 25 weight percent of metallic binder. It is believed that the region with the lower metallic binder composition may have a greater wear resistance than the region with the higher metallic binder composition. The region with the higher metallic binder composition may better withstand impact than the region with the lower metallic binder composition. The first region may be 1 to 5 mm thick. The two regions may comprise two cemented metal carbide segments. The two cemented metal carbide segments may be brazed together. A chamfer or a reentrant may be disposed in the steel body proximate a leading edge opposite the shank.
In the preferred embodiment, the first and second regions 203, 204, may comprise two cemented metal carbide segments. The two segments may be brazed together. The steel body 200 may also comprise a washer 206 such that when the pick 100 is inserted into a holder, the washer 206 protects an upper surface of the holder and in some cases facilitates rotation of the pick 100. The pick may also be disposed in a protective sleeve 207 such that the protective sleeve 207 protects the pick while it is being press fit into the holder and allowing the pick to rotate.
An exploded diagram of an embodiment of a pick 100 is shown in
Referring now to
A reentrant 301 disposed in the pick 100 from the bore 302 to the leading edge 300 may have different geometries as shown in various pick embodiments in
Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.
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20080284234 A1 | Nov 2008 | US |