US3146504A

US3146504A - Mold plug

Info

Publication number: US3146504A
Application number: US172745A
Authority: US
Inventors: Willis C Mellott; Carl A Woleslagle
Original assignee: Eureka Fire Brick Works
Current assignee: Eureka Fire Brick Works
Priority date: 1962-02-12
Filing date: 1962-02-12
Publication date: 1964-09-01
Anticipated expiration: 1981-09-01

Description

P 1964 w. c. MELLOTT ETAL 3,146,504

MOLD PLUG Filed Feb. 12, 1962 //A/GOT MOL D 16 REF/PAC 7-way INVENTORS W/LZ/S C. MELLOTT; (419A 4. WOLESLAGLE United States Patent 3,146,504 MGLD PLUG Willis C. Mellott, Connellsville, and Carl A. Woleslagle, Uniontown, Pa., assignors to Eureka Fire Brick Works, Mount Braddock, Pa., a corporation of New Jersey Filed Feb. 12, 1962, Ser. No. 172,745 3 laims. (Cl. 22148) This invention relates to an improved mold plug for ingot molds, especially the big-end-up ingot molds.

In forming steel ingots, molten steel is poured into a cast iron ingot mold, allowed to solidify therein, and thereafter removed as a unitary mass by inserting an expulsion element through a bottom opening in the ingot mold. The bottom opening is closed during the actual pouring of molten steel by means of a mold plug which is formed to fit tightly into the opening. Each mold plug has a single usei.e., for the pouring of a single ingot of steel. The ingot mold itself may be utilized for the pouring of many ingots, as many as forty ingots being considered a satisfactory life expectancy for an ingot mold.

Mold deterioration is greatest in the bottom regions of the ingot mold above the mold plug and results from the splashing of the initial moiety of molten steel against the mold plug and thence against the inner walls of the ingot mold. The very hot molten steel impinges against the relatively cool cast iron bottom and side walls of the ingot mold and quickly causes deterioration of the ingot mold walls through erosion and thermal shock. The undesirable splashing also causes rapid solidification of the splashed steel moiety with an accompanying segregation of its components with the result that the metallurgical composition of the resulting ingot becomes non-uniform. The solidified particles of cooled steel on the bottom and side walls create what is known as a scabby ingot surface. The embedded solidified particles of splashed steel must be ground off the ingot before the remaining steel of the ingot can be processed.

According to the present invention, a mold plug is provided for ingot molds which appears to minimize the splashing of the initial moiety of molten steel entering into the ingot molds. The results of using the present mold plug are:

An increased life of the ingot mold by twenty percent or more, i.e., each ingot mold can be used to produce about forty-eight ingots rather than merely forty ingots as heretofor obtained;

The metallurgical segregation in the resulting ingot is significantly decreased. Formation of scabby ingot surfaces is minimized.

Thus the principal object of this invention is to provide a mold plug for a big-end-up ingot mold which will decrease the deterioration of the ingot mold and improve the metallurgical quality of the resulting ingot.

This objective is accomplished by providing a novel surface configuration in the upper surface of the mold plug which includes:

A central spherical-surfaced portion;

An intermediate annular toroidal portion; and

A peripheral rim portion.

The top of the spherical central portion is disposed beneath a horizontal plane of the peripheral rim portion and the intermediate annular toroidal portion comprises an annular depression of semi-circular cross-section.

The invention will be understood by reference to the following detailed description and the accompanying drawings in which:

FIGURE 1 is a cross-section illustration of a typical big-end-up ingot mold having a hot-top affixed at its top and a mold plug of this invention secured in its bottom opening;

FIGURE 2 is a cross-section illustration of the present mold plug; and

FIGURES 3 and 4 are cross-section illustrations of typical mold plugs heretofor employed in ingot molds.

Referring to FIGURE 1 there is a cast iron ingot mold 10 which customarily has slightly tapering side-walls 11 which join with a bottom wall 12 which has a central opening 13 having the configuration of a conical frustum. A hot-top 14 is fitted over the upper end of the ingot mold 10 under normal circumstances. The hot-top 14 has a central opening 15 which is positioned vertically above the bottom opening 13.

A mold plug 16 of conical frustum configuration is placed in the bottom opening 13 to plug that opening against egress of molten steel during the pouring of the ingot. Mold plugs normally are formed from cast iron, ceramic materials and graphite. The present mold plug may be fabricated from any of those materials.

An ingot expulsion element (not shown) is rammed against the mold plug 16 after the ingot has solidified in order to discharge the ingot and mold plug from the ingot mold 10. The mold plug 16 is discarded after a single use.

Heretofor mold plugs have had upper surfaces as shown in FIGURES 3 and 4 (as well as other configurations) wherein the upper surface 17 of the mold plug 16a is fiat (FIGURE 3) and the upper surface 18 of the mold plug 16b (FIGURE 4) is concave.

When mold plugs of the type shown in FIGURES 3 and 4 have been employed, the ingot mold 10 experiences severe deterioration in the region indicated by the arrows A as a result of splashing of molten steel against the relatively cool bottom walls 12 and the lower portion of the side walls 11.

The present mold plug 16, as seen in FIGURE 2, has a circular upper rim 19, a circular lower rim 20 and conically tapered side walls 21. The upper surface includes a central portion 22 and a rim portion 23 separated by an intermediate annular portion 24.

It will be observed that the central portion 22 has the cross-section of a spherical surface having its center at the point B. The intermediate annular portion 24 has a toroidal surface having a circular-arc cross-section which has its circular center locus along the horizontal circle represented by the points C in FIGURE 2. The uppermost portion of the central portion 22 (identified by the letter D in FIGURE 2) is disposed beneath a horizontal plane represented by the letter E. The are of the toroidal intermediate annular portion 24 is tangential to the spherical surface of the central portion 22. The horizontal circle which defines the toroidal intermediate annular portion 24 (indicated by the points C) likewise is disposed beneath the horizontal plane E.

From the foregoing description, it will be apparent that a conical side wall portion 25 is provided which joins the circular rim 20 with the intermediate annular portion 24 and which is tangential to the toroidal surface thereof.

If desired, one or more slots 26 may be provided within the body of the mold plug 16 to facilitate stripping of the mold in the manner described in US. Patents 2,444,- 140, 2,798,268 and 3,008,203. The mold-stripping slots 26 may be cut in the central portion 22 or in the intermediate annular portion 24 i.e., they may communicate with the upper surface of the mold plug 16 anywhere within the circular rim 20.

By virtue of the widespread use of hot-tops, the pouring of molten steel is substantially at the direct center of the ingot molds because of the relatively narrow opening 15 in the hot-top 14. Hence the liquid metal descends in a relatively narrow stream directly against the center portion 22 of the present mold plug 16. It is postulated that the splashing which occurs is directed upwardly against the descending stream of molten metal rather than against the side walls 12 in the region indicated by the arrows A as heretofor encountered. The controlled splashing pattern appears to result from the use of the present mold plug as will be apparent from the following description of results.

Examples The operating results achieved through the use of the present mold plug are quite significant.

The use of the present mold plug (as opposed to the use of a prior art plug of the type shown in FIGURES 3 and 4) increased the life of ingot molds by more than twenty percent in a series of actual commercial operations with stainless steel. In all of the described commercial operations, hot-tops were employed so that the molten metal was poured into the ingot molds at precisely the center thereof. Throughout the commercial operations which have been described, the ingot molds were inspected at intervals to observe the surface condition.

Through fourteen heats there was no detectable difierence in the ingot mold surfaces. Thereafter the ingot molds which utilized the prior-art mold plugs started to wash out and to develop fire-checks.

After thirty heats had been poured in the ingot molds, there was a considerable difference in the condition of the bottom portions of the ingot molds.

After forty heats, the ingot molds utilizing the present mold plugs were only slightly washed out and exhibited only very light fire checks. In contrast, the ingot molds which utilized the prior-art mold plugs were badly washed out after forty heats and had developed heavy fire-checks over their bottom portions. Those ingot molds were discarded after forty heats. When an ingot-mold is badly washed-out in its bottom portion, the removal of the solidified ingot becomes troublesome. Throughout the series of commercial operations, the ingots made in those ingot molds having the present mold plugs were removed with no difficulty.

The ingot molds utilizing the present mold plugs continued in service through forty-eight heats and were considered at that time to be still in condition for additional use.

According to the provisions of the patent statutes, we have explained the principle, preferred construction, and mode of operation of our invention and have illustrated and described what we now consider to be its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. An improved plug for a big-end-up ingot mold adapted for insertion into the base of said mold for closing the lower opening thereof, said mold plug having a circular upper rim and a circular lower rim and being in the form of a conical frustum, the upper surface of said mold plug having a spherical central portion, an intermediate toroidal annular portion and a circular rim portion, the said central portion being disposed beneath the said rim portion, and the said intermediate annular portion comprising a circular depression.

2. An improved mold plug for a big-end-up ingot mold adapted for insertion into the base thereof for closing the lower opening thereof, said mold plug having a circular upper rim and a circular lower rim and being in the form of a conical frustum,

the upper surface of the said mold plug having a circular rim portion,

a central portion of spherical outer surface, the highest point of which is disposed beneath a horizontal plane defined by said outer circular rim portion, and

an intermediate annular portion of toroidal outer surface, the said toroidal outer surface being tangential with the said spherical outer surface, and

a conical side wall extending from the said upper circular rim portion and being tangential with the said toroidal outer surface.

3. The mold plug of claim 2 wherein at least one slot is provided within the body of the said mold plug communicating with the upper surface of the said mold plug within the outer circular rim portion.

References Cited in the file of this patent UNITED STATES PATENTS 107,766 Dunfee Sept. 27, 1870 2,113,445 Estep Apr. 5, 1938 2,444,140 Messler June 29, 1948 2,572,754 Patterson Oct. 23, 1951 2,798,268 Whitacre July 9, 1957 2,863,189 Beck Dec. 9, 1958 3,008,203 Dagenhard Nov. 14, 1961