Cast abrasion resistant hollow balls

#1. Field of the Invention

#The present invention relates in general to cast abrasion resistant hollow balls and more particularly to a hollow pulverizer ball formed on a hollow ceramic core.

#2. Description of the Related Art

#The various features of novelty characterizing the invention are pointed out in particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, the operating advantages attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.

#In the drawings:

#FIG. 1 is an exterior view of a hollow ball cast in accordance with the present invention;

#Hollow metal balls have been successfully used in the operation of a pulverizer of the general type shown in U.S. Pat. No. 2,275,595. In the present invention, one such use for the cast hollow balls is a similar use for these types of pulverizers. The ball has an exterior diameter of approximately 121/4 inch with a wall thickness of approximately 31/2 inch thick. Other hollow balls of varying exterior diameters may be made with the method of the present invention ranging from 61/2 inch or smaller to 401/4 inch with metal wall thicknesses ranging from 11/4 inch to 10 inch thick. Of course, larger or smaller diameter balls having a greater or lesser thickness may also be cast with the method of the present invention. These balls are cast from highly abrasion resistant ferrous metals such as ASTM A532M-93A Class I through III or A128M93 grades "A" through "F" and/or other suitable materials. These may be heat treated to obtain desired physical and metallurgical characteristics. The size of the ball being determined by the use to which they are adapted and the balls may be used in other types of pulverizers or applications. Experience has shown that hollow balls as described herein when heat treated for service in a pulverizer resist impact stresses and heat effects better than solid balls formed from the same material and similarly heat treated.

#In manufacturing the hollow ball (10) shown in the figures, a hollow ceramic core (12) is made from a highly refractory material such as fused silica for example or other high temperature ceramic materials. The ceramic core (12) is fired at temperatures in excess of 1500.degree. F. or a temperature high enough to eliminate any trace of organic material in the ceramic core (12). Advantageously, the present invention uses a ceramic hollow cast or blown core as opposed to the core material disclosed in U.S. Pat. No. 3,254,849 which is a consumable core material and generates gases during the metal casting process. The present invention employs the hollow ceramic cast or blown core (12) which when fired prior to the casting process eliminates any trace of organic material and results in a core (12) which generates no gas when surrounded by the liquid metal during the solidification of the metal and the casting process.

#U.S. Pat. No. 3,254,849 is hereby incorporated by reference. Unlike the casting process as disclosed in that patent, the present invention does not employ the consumable core material nor does it employ hollow arms 11 as disclosed in that patent. Rather, the present invention advantageously produces an improved cast hollow ball which may be employed as a pulverizer ball as described in that patent, but the core material (12) in the instant invention is a ceramic cast or blown spherical hollow core (12) which uses at least one refractory bar or support (14) which is solid. There are no openings or holes in the ceramic support (14) due to the fact that the hollow ceramic sphere core (12) is composed of an inert refractory material which eliminates any gases being generated during the pouring and solidification of the liquid metal during the casting process.