US2173955A

US2173955A - Apparatus for casting cylindrical rolls

Info

Publication number: US2173955A
Application number: US193008A
Authority: US
Inventors: John S Zahn
Original assignee: OHIO STEEL FOUNDRY CO
Current assignee: OHIO STEEL FOUNDRY CO
Priority date: 1938-02-28
Filing date: 1938-02-28
Publication date: 1939-09-26
Anticipated expiration: 1956-09-26

Description

Sept. 26, 1939. J, s ZAHN 2,173,955

APPARATUS FOR CASTING CYLINDRICAL ROLLS Filed Feb. 28, 1938 I f ,EMC/mo j ldd/w55.' u @/UMQ. Zeb/n) www www5' Patented Sept. 26, 1939 2,173,955 APPARATUS FORl CASTING CYLINDRICAL ROLLS JohnfS. Zahn, Lima, Ohio, assgnor to The Ohio Steel Foundry Company, Lima, Ohio, a corporation of Ohio Application February 28, 1938, Serial No. 193,008

4 Claims.

This invention relates to improvements in methods and apparatus Afor producing hollow' rolling mill rolls and similar tubular metal castings. Among the objects of the invention is to provide a simple and economical method and apparatus in connection with the usual foundry molding processes to extend an auxiliary heat conducting medium such as a pipe through the hollow cylin- ,drical mass so as to aid in cooling the interior l0 surface of the casting while in the mold.

It has been generally recognized that hollow mill rolls have certain advantages over said rolls, particularly as to more uniform grain structure and responsiveness to heat treatment in smallersectioned masses, giving them greater resistance to breakage and failure than with solid castings, in which excessive internal stresses are more likely to be set up. One of the principal diiiculties in the production of such hollow rolls, however, has been that of introducing'in the mold satisfactory means for equalizing the temperature of the interior and exterior surfaces of the hollow casting while it is cooling in the mold.

This problem can be better understood when it `is explained that in casting such heavy rolling mill rolls, it is customary to stand them on end and provide what is known as a swirl gate near the bottom so that the metal enters the mold tangentially to the bottom cylindrical portion of the mold. The hot metal thus enters the mold with a spiral motion about the axial core. It has been proposed to introduce a cooling medium such as a pipe for air, steam, water or the like, through the center core, made of usual core sand, but this has been-found unsatisfactory because the swirling motion of the metal soon erodes the sand, and the metal reaches the pipe in places making it difficult to remove the pipe, and also causing some of the core sand to be burned into the casting. Attempts to dispense with a core sand covering have only increased the diiculty of removing the pipe to a point where it often has had to be machined out of the casting after the latter has been removed from the mold.

In carrying out my invention, I utilize a plurality of annular baked clay sections of high refractory value, which are arranged end-to-end to form a continuous sleeve over the central pipe, and thus provide a core capable of resisting erosion of the metal and yet which is relatively easy to remove. The invention may best be understood by reference to the accompanying drawing, in which Fig. 1 illustrates the application of my improved process and apparatus to a molding ask and shows the ilask and hollow roll in longitudinal section, but with the core and center pipe shown in part elevation.

Fig. 2 is an enlarged detail section taken on line 2-2 of Fig. 1. 5 Fig. 3 is an enlarged detail longitudinal section showing the arrangement of the pipe and center core construction.

Referring to details of the apparatus illustrated in the drawing, a ask I0 of the usual form 10 is shown with a cylindrical mold or impression II therein formed in molding sand in the usual manner. ,A gate of the usual swirl type, not shown, may be connected to the lower end of the impression, but need not be described in detail as 15 it forms no part of the present invention.

In place of the usual center core made of baked sand, I provide a composite core structure, herein consisting of a length of hollow metal pipe I5, and surrounded by a hollow tile covering, 20 consisting of a plurality of baked clay sleeve sections IB, IE arranged in end-to-end relation along said pipe, as shown in Fig. 1. Each of the clay sleeve sections I6 is preferably interlocked with l adjacent sections, as by a tongue I'I fitting into 25 annular grooves I8 formed in the abutting ends of said sleeves, as is best shown in Fig. 3. The clay sleeve sections IB are preferably mounted 0n the pipe with a loose fit so as to leave a space therebetween, as indicated at I9 in Fig. 3.

Said sleeves are preferably made of baked clay, having a relatively high refractory value similar to the material used in tiles employed in pouring ladles and other refractory furnace structures. I have found that such baked clay sleeves have 35 ample strength to withstand considerable pressures at high temperatures, and yet have sutilcient plasticity to withstand erosion of the hot metal as it is introduced in the mold.

Means are also provided for holding the sleeves 40 together under yielding pressure, and yet permit expansion during the molding operation, In the form shown herein, the lower end of the pipe I5 has nuts 20 and 2l mounted thereon, and adjustable on opposite sides of the bottom wall IIIa of 45 the iiask. When tightened against said wall said nuts provide an anchor for one end of the pipe relative to said flask. A washer 22, preferably recessed at I'Ia to receive the tongue I1 of the adjacent clay section, is seated above the inner ad- 50 justing nut 2|, and the lowermost clay sleeve I6 abuts against said washer, as shown in Fig. 1. The uppermost clay sleeve I 6 projects through the upper end of the iiask, but is supported in lateral engagement with the topmwall thereof.

Cil

A washer 23 engages the outer end of the uppermost clay sleeve, and is urged downwardly thereagainst by coil spring 24 which has its upper end engaged with an adjustable nut 25 threaded on the pipe l5. The cooling medium such as water, air or steam, can be supplied for circulation through the pipe by any suitable connections such as the T-

members

26 and 21 at the bottom and top of the ilask as shown in Fig. 1.

With the construction and arrangement above described, the several sleeve sections are maintained under suicient yielding pressure longitudinally of the core to keep them in snug engagement with each other, but permitting longitudinal expansion orcontraction of the core during the molding process. It will be understood that in filling the mold with molten steel, the core is progressively heated from the bottom of the mold toward the top. By building up Vthe core of individual sleeve sections as herein disclosed, each section is permitted to expand independently of the others and thus accommodates itsef to rapid changes in temperature without transmitting the resulting stresses to'adjacent parts of the core. As a result the core structure is capable of withstanding the thermal shocks imposed thereon during the molding process, and it expands or `contracts longitudinally under yielding compression of the spring 24 as required by changing temperature conditions.

While the mold is being lled, the cooling medium can be passed through the pipe as required to reduce the temperature of the interior of the casting, as is desirable with hollow castings of this character. The clay sections are readily removable, usually being comparatively brittle after cooling to atmospheric temperatures so that they are easily broken up. Due to the clearance or space maintained between the outside of the pipe and the inside of the sleeves during the pouring and cooling operations, the pipe is also quite loose within the sleeves, and therefore readily removable from the casting after the latter has been cooled and is taken from the mold.

While the preferred embodiment illustrated in the drawing has a hollow pipe for conducting a cooling medium such as Water, air, steam or the like, through the hollow roll, it will be understood that under some conditions the pipe may be replaced by a solid metal bar passing through the hollow clay tile core, and the thermal capacity of said metal bar can be utilized to carry oi the heat by conduction from the interior of the mold.

Although I have shown and described certain embodiments of my invention, it will be understood that I do not wish to be limited to the exact construction shown and described, but that various changes and modifications may be made Without departing from the spirit and scope of my invention as defined in the appended claims.

I claim as my invention:

1. In an apparatus for casting hollow steel rolls and in combination with a mold body, a central core structure therefor consisting of a pipe extending through the mold body and projecting at the end thereof to dissipate heat from the casting,

and a sleeve made of refractory tile surrounding said pipe in independent self-supporting relation therewith to provide sufficient clearance to permit endwise removal of said pipe independently of said sleeve after the casting is formed.

2. In an apparatus for casting hollow steel rolls and in combination with a mold body, a central core structure therefor consisting of a pipe extending through the mold body having connections for passing a cooling medium therethrough, and a baked clay sleeve tting loosely around said pipe and having suflicient strength and heat resistance to withstand the pouring temperature of steel and permit endwise removal of said pipe from within said sleeve after the casting is formed.

3. In an apparatus for casting hollow steel rolls and in combination with a mold body, a central core structure therefor consisting of a pipe extending through the mold body having connections for passing a cooling medium therethrough, and a plurality of baked clay sleeve sec tions disposed in abutting relation to each other and forming a self-supporting sleeve surrounding said pipe to permit endwise removal of the latter from said sleeve after the casting is formed.

4. In an apparatus for casting hollow steel rolls and in combination with a mold body, a central core structure therefor consisting of a metallic cooling member extending through the mold body and projecting at opposite ends thereof, a baked clay sleeve fitting loosely around said cooling member, means adjacent one end of said mold body forming an abutment for one end of said clay sleeve, and yielding means adjacent the end of said cooling member beyond the opposite end of said mold lbody for holding said sleeve against said abutment, but permitting longitudinal I expansion of said sleeve relative to said cooling member.

JOHN S. ZAHN.