Abstract:
An arrangement of operating stations and equipment for the rapid preparation and transport of molten metal ladles and pouring tanks with covers to a pouring station of a pressure-pouring operation, and a method of providing the moving, placement and transport of the ladles and pouring tanks for the minimization of the loss of time between end of the first stage of pouring and initiation of the second stage of pouring.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to method and apparatus for moving molten metal ladles between a cover position, a ladle-load position and a pouring position at a casting station. More particularly, a method and an apparatus are taught which enhance a pressure casting process to expedite the movement from the pouring station of a molten-metal evacuated ladle and the positioning of a molten-metal filled ladle at the pouring station without the intermediate delays associated with ladle covering and uncovering. 
     Casting and casting practices generally involve the use of molten metals at elevated temperatures. This molten metal practice requires the use of heavy apparatus for the holding and transport of the metal. Specifically, molten metal for casting is frequently held in large steel or cast-iron ladles lined with refractory brick. In a pressure-casting or pouring operation, the ladle is placed in a pouring tank and a tank cover is placed atop the pouring tank. This tank cover is equipped with a pouring tube as well as ports to elevate the gas pressure above the molten metal. Avoidance of fracture of the pouring tube and refractory linings generally involves maintaining or preheating the pouring tank cover and pouring tube. A holding or heating furnace is frequently utilized for this purpose. However, the physical act of positioning the pouring tank cover atop the pouring tank and thereafter securing the pouring tank cover are time-consuming operations and an inhibition to a rapid production operation. 
     A presently known operation utilizes a single pouring or casting station in cooperation with twin ladle-loading stations. These ladle-loading stations use pressure-pouring tanks on transfer cars for holding the hot-metal ladles, and for transporting the ladles between the ladle-loading stations and the pouring station. In this operation, a ladle of molten metal is transported to a pressure-pouring tank at a ladle-loading station for subsequent transfer of the ladle containing pouring tank to the pouring station. At the pouring station, a pressure-pouring tank cover is positioned on and secured to the pressure pouring tank by the pouring crane. After pouring of the molten metal from the ladle, the pressure pouring tank cover is removed using the pouring crane. The pressure pouring tank is then transported to the first ladle-loading station for eventual filling with another ladle of molten metal. A second molten-metal-filled ladle in a pressure pouring tank is then transported to the pouring station from the second ladle-loading station and a pressure pouring tank cover is positioned and secured to the second pressure pouring tank at the pouring station, as described above. 
     The time delays in pressure pouring tank covering and the use of the pouring crane at the pouring station are significant when measured in terms of daily lost production of large castings. Accordingly, it is an object of the present invention to provide a more efficient pressure pouring arrangement. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus to provide a more efficient arrangement for bottom-pressure casting. In this method, the pressure pouring tank cover is secured on a first pressure pouring tank at a ladle-load station prior to moving the covered pressure pouring tank with a full ladle into the pouring-station position. Further, subsequently but prior to the emptying of the first ladle, a second metal-filled ladle in a second pressure pouring tank is positioned in a second ladle-load station with its pressure pouring tank cover secured. The second covered pressure pouring tank is ready for immediate movement into the pouring station after emptying of the first ladle and the removal of the first pouring tank from the pouring station without removal of the first pressure pouring tank cover. The pressure pouring tank covers are moved onto the pouring tanks at the ladle-load stations by a jib crane or overhead crane. The pressure pouring tank covers with their pouring tubes are maintained at an elevated temperature at cover station ovens within the range of motion of the jib crane or overhead crane. The second pressure pouring tank is available for immediate placement into the pouring station to continue production as soon as the first pressure pouring tank with its empty ladle has been moved a distance adequate to provide the necessary clearance for the second pressure pouring tank transfer-car bearing a second metal-filled ladle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawings, 
     FIG. 1 is a schematic outline of the locations of the pressure pouring tank positions of the prior art practice, and 
     FIG. 2 is a schematic plan view of the locations of the several positions for the pressure pouring tanks of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Known bottom-pressure casting practice in the industry utilizes a two-ladle-load-station practice to transfer molten-metal filled ladles to a single pouring station, which practice was considered an improvement over the older practice of a single pouring station and a single ladle-load station. It is recognized that molten metal is provided from steel manufacturing furnaces, such as basic oxygen furnaces or electric arc furnaces, which furnaces and furnace practice are known but not shown. 
     This casting process is directed to the bottom-pressure pouring and casting of railroad wheels. The railroad wheels are steel castings weighing upwards of six hundred pounds and produced from molten steel poured at about 2900° F. 
     Referring now to FIG. 1, a prior art bottom pressure casting pouring station with two ladle-loading stations is shown. 
     The single pouring station is shown at  112 , with track  122  leading to ladle-loading station  114  and track  124  leading to ladle-loading station  116 . Pouring crane  127  is seen to move laterally along bridge  118  which itself moves transversely along support rails  126 ,  128 . 
     In a known pouring operation utilizing the prior art arrangement of FIG. 1, ladle  134  of molten metal is placed in pouring tank  135  in tank transfer car  136  at ladle-loading station  114 . Tank transfer car  136  is rolled across track  122  into pouring station  112 . 
     Pouring tank cover  129  is then placed on pouring tank  135  utilizing pouring crane  127 . Pouring tank cover  129  is kept in a holding oven located transversely from pouring station  112  within support rails  126 ,  128 . 
     When ladle  134  is empty, pouring crane  127  is utilized to remove pouring tank cover  129 . Pouring tank transfer car  136  is then rolled out of pouring station  112  back to ladle-loading station  114 . 
     Another pouring tank transfer car  146  with pouring tank  145  on it and with fill ladle  144  within pouring tank  145  has been prepared at ladle-loading station  116 . Tank transfer car  146  is rolled across track  124  into pouring station  112 . Another pouring tank cover identical to cover  129  is then placed on pouring tank  145  utilizing pouring crane  127 . Pouring tank cover  129  is left in a holding oven located transversely from pouring station  112  within support rails  126 ,  128 . 
     Positioning pouring tank cover  129  over pouring tank  135  at pouring station  112  generates a delay in initiating actual casting of railroad wheels. It is estimated that this delay can be between eight and 10 minutes. In a casting practice manufacturing one casting per minute, this is considered a significant time loss when placed in the context of approximately forty-five ladles of molten steel being poured per day. 
     In FIG. 2, an arrangement in accordance with the present invention is shown. Pouring station  12  is operatively connected to ladle-load-stations  14  and  16  by tracks  60  and  62 . Jib crane  28  with center pivot  30  is located between, and offset from, ladle-loading stations  14  and  16 . In this configuration, jib crane  28  may be rotated about center  30  and extends over ladle-loading stations  14  and  16 . Alternatively, overhead crane  70  along tracks  72 ,  74  can be utilized to transfer ladles from ladle-loading stations  14 ,  16  to pouring station  12  and pouring tank covers to and from cover holding ovens  50 ,  52  to ladle-loading stations  14 ,  16 . 
     First pouring tank cover holding oven  50  and second pouring tank cover holding oven  52  are displaced from pouring station  12 , as well as ladle-load stations  14  and  16 . Pouring tank cover holding ovens  50  and  52 , and ladle-load stations  14  and  16  are symmetrically arranged, but this is merely illustrative and not a limitation. Pouring tank cover  20  and its pouring tube are preheated to avoid thermal shock at introduction of the pouring tube into a molten metal in ladle  21 . Jib crane  28  or overhead crane  70  is operable to grasp pouring tank cover  20  from either of pouring tank cover ovens  50  and  52 , and to move pouring tank cover  20  over either pouring tank  23  or  29  at ladle-load station  14  or  16 . 
     In an illustrative operation, a pressure-pouring tank transfer car  33  with a molten-metal filled ladle  21  in pouring tank  23  is positioned at ladle-load station  14  in preparation for transfer to pouring station  12 . Pouring tank  23  with ladle  21  therein will have pouring tank cover  20  positioned and secured thereon with a pouring tube extending into molten metal bath in ladle  21  by the use of jib crane  28  or overhead crane  70 . Thereafter, pouring tank  23  is transferred to pouring station  12  on transfer car  33  over rails  60  for continuation of the casting operation. 
     After casting the metal in ladle  21  at pouring station  12 , evacuated ladle  21  and transfer tank car  33  are returned to ladle-load station  14  for removal of pouring tank cover  20 . Simultaneously, a full ladle  27  in pouring tank  29  covered with pouring tank cover  39 , having been installed by jib crane  30  or overhead crane  70 , has been readied at second ladle-load station  16 . Covered pouring tank  29  at second ladle-load station  16  is then moved into position at pouring station  12  along tracks  62  on second transfer car  31  as soon as first transfer car  33  has moved a distance from station  12  adequate to provide clearance to pouring station  12  for second tank transfer car  31 . 
     It can be appreciated that the covering and uncovering of pouring tank  22  is now conducted at ladle-load stations  14  and  16  instead of pouring station  12 , which greatly lessens the interruption of pouring operations at pouring station  12 . For example, the total turnaround time for transfer of a ladle  134  with the transfer system of the prior art required eight to ten minutes with the above-described ladle handling procedure at pouring station  112 . With the present invention and use of ladle-load stations  14  and  16  and holding ovens  50 ,  52 , the calculated time for removal of pouring tank  23  with ladle  21  from pouring station  12  and the placement of covered pouring tank  29  from ladle-load station  16  to pouring station  12  is three minutes, a saving of at least five minutes.