GB2102927A

GB2102927A - Apparatus for curing and heating the refractory lining

Info

Publication number: GB2102927A
Application number: GB08219192A
Authority: GB
Inventors: Masahiro Hayase; Shozo Kanamitsu; Shigeru Okuda; Noriaki Morishita
Original assignee: Shinagawa Refractories Co Ltd; Shinagawa Shiro Renga KK; Nippon Kokan Ltd
Current assignee: Shinagawa Refractories Co Ltd; Shinagawa Shiro Renga KK; JFE Engineering Corp
Priority date: 1981-07-07
Filing date: 1982-07-02
Publication date: 1983-02-09
Also published as: FR2509453B1; DE3225034A1; DE3225034C2; KR880001928Y1; JPS586200U; GB2102927B; KR840000720U; JPS6030718Y2; FR2509453A1

Abstract

An uncured amorphous refractory lining (1) formed on the inner surface of a vessel adapted to receive hot molten metal, such as a ladle can be uniformly heated by an apparatus including a pipe (5) for directing hot air to and thus heating the lining surface, either directly or through a mold (3) holding the lining in the vessel. The hot air issues from an exit (6) over the surface of the bottom lining (2) in the vessel. A first hot air guide plate (7a) is mounted near the exit end of the pipe and at least one additional plate (7b, 7c) is mounted at a distance from the first plate. By the operation of these guide plates, the hot air is guided over the surface of the lining mounted in the vessel, and the hot air may ascend uniformly from the bottom and along the overall inner periphery of the vessel through the gaps (8a, 8b, 8c) between the guide plates and the lining. <IMAGE>

Description

SPECIFICATION Apparatus for curing and heating the refractory lining This invention relates to an apparatus for curing and heating a refractory lining and more particularly to an apparatus for curing a refractory lining of a vessel used in iron making for transporting or reacting molten iron or steel or the like hot molten metal, such as ladle, iron ladle, tapping spout, tundish, vessel or vacuum degasing and other vessels for reception of molten metal, especially such refractory lining obtained by casting an amorphous refractory material.

The molten metal vessels provided with a refractory lining cannot be used immediately after application of such lining, but the molten metal can only be received in the vessels after termination of curing and heating of the refractory material. The purpose of curing is to afford a certain quality to the lining by hardening the lining to a predetermined hardness. Such curing is especially important when the lining is obtained by casting an amorphous refractory material containing 6 to 8 percent moisture. A certain quality of the lining can be attained by curing for a certain time at a temperature of 40 to 1000C.

The purpose of heating the lining following curing is to preheat the refractory material to a higher temperature close to the temperature of the molten metal for several tens of hours in accordance with a predetermined temperature rising curve. By such heating, the refractory lining may be safeguarded against cracks, peeling or breakage due to heat shock that the lining may undergo when the molten iron or steel is poured into the vessel.

Heretofore, such curing was allowed to occur spontaneously at the ambient temperature at the site of manufacture. In the case of a ladle, the refractory lining was allowed to stand for 20 to 30 hours since the time it is cast and the mold is taken off when the lining has apparently hardened.

Heretofore, a castable, refractory material was used as amorphous refractory for casting. Usually, alumina cement was added in an amount higher than 10 wt. percent, and the castable was hardened through the hydrating reaction of alumina cement. However, alumina cement leaves much to be desired as a bonding agent for the refractory lining of a molten metal vessel because it exhibits inferior hot properties in the higher temperature range higher than 12000C and a poor mechanical strength due to dehydration in the intermediate temperature range of 800 to 12000C.

In order to avoid such defect, a castable with an addition of about 10 wt. percent of kibushiclay, Kaolin or similar finely powdered refractory clay as a bonding agent has been devised.

However, when subjected over an extended time to repeated heat cycles of heating to elevated temperature and cooling in the course of the operation of the molten metal vessel, the refractory is liable to peel off from the vessel thus reducing the service life of the vessel.

There has recently been devised a castable which may be hardened through chemical reaction of an additive other than alumina cement and refractory clay. For example, a castable with cement contents of 1 to 5 percent as hardener has been devised. However, since the hardening process depends appreciably on the ambient temperatures, it is difficult, especially in winter, to harden the cast refractory and develop a structural strength within a shorter time interval.

In this consideration, it may be conceived to heat and elevate the temperature of the refractory material by a burner. However, the optimum curing temperature for the refractory material is in the range of 40 to 800C and, if flame heating by direct combustion of fuel is resorted to, it is nearly impossible to control the temperature and heat the inner wall of the large capacity vessel uniformly and to a temperature lower than 1000C.

This invention envisages to obviate the above problems and to provide an apparatus whereby the inner wall of the refractory lining can be warmed uniformly by hot air and curing can be terminated promptly without regard to climatic conditions.

The apparatus according to the present invention for heating and elevating the temperature of an uncured lining formed on the inner surface of a reception vessel for hot molten metal by casting an amorphous refractory material compriscs:- a hot air inlet pipe arranged vertically in said reception vessel with the foremost hot air exit downwards for directing hot air to the surface of a bottom lining of the vessel through, by way of an example, of a mold; a flange-like first hot air guide plate mounted in the vessel to the foremost part of said inlet pipe and spaced from the surfaces of the bottom lining and the inner peripheral lining in said vessel or from the surface of the mold placed thereon; and one or more flange-like second hot air guide plate(s) mounted to said inlet pipe at a certain interval from said first hot air guide plate, with the peripheral edge(s) thereof spaced apart from the surface of the inner peripheral lining in the vessel or from the surface of the mold placed thereon.

The annular interstices which the peripheral edges of the first and second hot air guide plates define with the surface of the inner peripheral lining or the surface of the mold placed thereon represent a passage way on which the hot air ejected from the hot air exit at the end of the inlet pipe onto the bottom lining in the vessel and caused to flow radially on the surface of the bottom lining by virtue of the first guide plate is channeled towards the upper opening of the vessel along the surface of the inner peripheral lining in the vessel. Hence, the size of these interstices should be adjusted on purpose.Thus, in order that the distribution of hot air flowing along the surface of the inner peripheral lining of the vessel may be uniform over the entire peripheral surface, preferably the size of the interstices is so selected that the further a given interstice is spaced apart from the bottom surface of the vessel, the lesset is the size of the interstice.

In case that the vessel to be used in conjunction with the curing apparatus is of a fixed inside dimension, the first and second hot air guide plates can be mounted fixedly to the inlet pipe. However, in case the curing apparatus is used in conjunction with vessels of variable size and shape, hot air guide plates of correspondingly variable size and shape must be used and mounted detachably to the pipe.

In addition, the second hot air guide plate or plates may be movable axially of the inlet pipe so that a particular portion or zone of the lining may be heated more pronouncedly than the remaining portion.

These and other objects, features and advantages of the present invention will be more apparent from the following description of a preferred embodiment thereof especially when read in conjunction with the accompanying drawing.

The single drawing is a longitudinal crosssection showing a preferred embodiment of the invention when placed in the vessel.

Referring to the drawings, which illustrates the present apparatus in longitudinal cross-section, the numeral 1 denotes a side wall lining of a vessel for molten metal obtained by casting an amorphous refractory material. The numeral 2 denotes a bottom lining of the vessel, equally obtained by casting the amorphous refractory material. The numeral 3 denotes a casting mold employed for forming the lining. In case the vessel is a ladle, the mold 3 is frusto-conical in crosssection and, in case the vessel is a tapping spout, tundish or an equalizing furnace and hence of a substantially rectangular cross-section, the mold 3 is of a box-like shape with a substantially rectangular cross-section.The function of this mold 3 is to hold the amorphous refractory material of the side wall lining 1 and the bottom lining 2 while it is not hardened and the mold 3 is taken off or separated after termination of hardening of the refractory material. The numeral 4 denotes a curing apparatus of the present invention mounted substantially centrally within the mold 3. The numeral 3 denotes a hot air inlet pipe and the numeral 6 a hot air exit at the lower end of the pipe. The numerals 7a, 7b, 7c are flange-like hot air guide plates mounted horizontally or at right angles with respect to the pipe and the numerals 8a, 8b, 8c are annular interstices defined between these guide plates and the mold.

In the present embodiment, the first hot air guide plate 7a is mounted to the lower end of the pipe 5 and two second guide plates 7b, 7c are mounted in the similar manner to the pipe 5 at certain intervals above said guide plate 7a and from each other.

Taking an example of a ladle having a 300-ton capacity, the pipe 5 shown in Fig. 1 has an inside diameter of 600 mm, with a vertical section 9 and a horizontal section 10 thereof being approximately 4 meters and 3 meters, respectively. A connection flange 1 2 is provided to the end of the horizontal section 10 for interconnecting a hot air supply pipe 11 and the inlet pipe 5, with the lower end of the vertical section 9 being opened to provide the hot air exit 6 which is spaced about 1 50 mm above the ladle bottom.

When assumed that the inlet pipe is connected by the flange 12 to the supply pipe and that the hot air of 2000C obtained by heat exchange with coke-oven gas, converter gas or waste gas is supplied through supply pipe 11 at a rate of 80 m3 per minute, the hot air is discharged at the exit 6 through the pipe 5 in a jet with a velocity of 4 to 5 meters per second.

The feature of the present invention resides in the structure such that the hot air may be caused to ascend uniformly along the overall inner periphery of the mold 3. The hot air guide plates 7a, 7b, 7c in the form of discs may for example be heat-resistant steel discs about 10 mm in thickness, and are mounted at substantially right angles to the vertical section 9 of the pipe 5. The annular interstices 8a, 8b, 8c of 80 to 100 mm width are defined between the outer ends of the guide plates 7a, 7b, 7c and the inner surface of the mold 3, with the widths of the interstices 8a, 8b, 8c being narrower towards the upper end of the vessel. The lowermost guide plate 7a is mounted close to the hot air exit 6 of the pipe 5 and the intervals between the plates 7a and 7b and between the plates 7b and 7c are equal and about 1.5 meter in the present embodiment.

In the above construction, the hot air discharged from the exit 6 at a rate of 4 to 5 meters per second is dispersed radially by the guide plate 7a over the entire bottom of the ladle so that the refractory material of the bottom lining 2 is heated uniformly to about 5000C through the steel plate of the mold 3. The hot air then travels uniformly over the entire inner surface and through the annular interstice 8a at a rate of 1.3 to 1.6 meter per second. The hot air enters the space between the hot air guide plates 7a and 7b transiently, but if is guided by the guide plate 7b radially outwards and travels uniformly over the entire inner peripheral surface and through the annular interstice 8b. The hot air then travels uniformly through the annular interstice 8c in the similar manner. Since the hot air heats the entire inner surface of the steel plate mold 3 uniformly and from the inner side, the side wall lining and the bottom lining may be heated therethrough substantially uniformly to a temperature of 40O to 50"C.

According to the curing apparatus of the present invention, as mentioned above, the curing effect may be exhibited uniformly and the curing step which has to be continued about 30 hours in winter with the use of the conventional apparatus can be completed in about three hours. With the curing step of such short duration, the side wall lining 1 and the bottom wall lining 2 can be completely hardened and the mold 3 can be removed in a shorter time while cracks in the refractory lining may be prevented from occurring.

It has aiso been clarified that, in accordance with the present apparatus, the curing can always be completed within a certain time irrespective of the ambient air temperature, thus allowing to perform a stable ladle operation.

When the ladle capacity is changed, effective curing can be achieved by increasing or decreasing the diameters or the number of the hot air guide plates. Moreover, when the refractory lining is partly repaired thus requiring curing only of a portion of the lining, such partial lining can be made by suitably changing the vertical mounting position or mounting intervals of the hot air guide plates. Thus the guide plates may preferably be capable of being displaced, dismounted or exchanged as desired. The guide plates need not be mounted at right angles to the inlet pipe, but may be suitably changed in dependence upon the flow velocity or volume of hot air or the desired curing duration.

According to the curing apparatus of the present invention, mentioned above a refractory lining of an excellent strength can be obtained with the use of a simple and inexpensive setup composed of a hot air inlet steel pipe and several hot air guide plates in the form of flat plates mounted substantially at right angles thereto. The refractory lining may be heated uniformly through use of waste heat and the mold can be removed in a shorter time without regard to climitic conditions.

Depending on the kinds of the cast-in amorphous refractory material, the curing apparatus of the present invention can be used only at the ultimate curing phase and thus following preliminary curing and removal of the mold used for such preliminary curing.

The apparatus of the present invention can be used not only with the refractory lining for the ladle, but with the refractory lining for other molten metal vessels, subject to design changes of the shape or number of hot air guide plates, the diameters and number of the hot air inlet pipe and the flow velocity or volume of hot air.

Claims

1. An apparatus for heating an uncured lining of amorphous refractory material formed on the inner surface of a vessel adapted to receive hot molten metal, which apparatus comprises:- a hot air inlet pipe adapted to be arranged vertically in said vessel having a downwardlydirected hot air exit at its end for directing hot air to the surface of a bottom lining; a flange-like first hot air guide plate mounted at the exit end of said inlet pipe and adapted to be spaced when in use from the surfaces of the bottom lining and inner peripheral lining in said vessel; and one or more flange-like second hot air guide plates each mounted on said inlet pipe at a predetermined distance from said first hot air guide plate, with the peripheral edge of each of said plates being adapted to be spaced apart from the surface of the inner peripheral lining in said vessel, when said apparatus is in use.

2. An apparatus as claimed in Claim 1 wherein the distances between the edges of the first and second guide plate and the surface of the inner peripheral lining of the vessel decrease as the distance of the plates from the vessel bottom increases.

3. An apparatus as claimed in Claim 1 wherein the first and second hot air guide plates are mounted removably on said inlet pipe.

4. An apparatus as claimed in Claim 1 wherein the second hot air guide plate is mounted on said pipe in a manner allowing adjustment of the axial position of the second guide plate on the pipe.

5. An apparatus as claimed in Claim 1 and substantially as hereinbefore described with reference to the single Figure of the accompanying drawing.