GB2032083A

GB2032083A - Sliding gate valves

Info

Publication number: GB2032083A
Application number: GB7931944A
Authority: GB
Original assignee: Didier Werke AG
Current assignee: Didier Werke AG
Priority date: 1978-09-16
Filing date: 1979-09-14
Publication date: 1980-04-30
Also published as: DE2840398C2; FR2435986A1; JPS5541395A; IT7925756A0; CA1143921A; BE878789A; GB2032083B; IT1123183B; FR2435986B1; JPS5823550B2; DE2840398A1

Abstract

A sliding gate valve 1 for metallurgical vessels, such as Siemens-Martin ovens, having a substantially horizontal outlet passage 2 includes an inlet sleeve 4, a base plate 5, a sliding plate 6 and an outlet sleeve 7 which together define a passage extending through the valve. The passage 9 within the inlet sleeve is lined with a pipe 11 of ceramic oxide material having a slot 10 extending along its length. <IMAGE>

Description

SPECIFICATION Sliding gate valves The invention relates to sliding gate valves for use with metallurgical vessels.

German Patent No. 2523928 discloses a vessel from which the molten metal flows out not vertically but substantially horizontally. Various parts of the gate valve come into contact with the slag and are therefore subject to considerable asymmetric wear. This is in particular so when the parts subject to wear, such as the inlet sleeve, base plate, sliding plate and outlet sleeve are of relatively iarge dimensions because the passage extending through them has a large diameter of, for example, 1 70 mm, and therefore have to be formed by casting, e.g. from refractory cement, as disclosed in German Offenlegungsschrift No.

2624299. In such cases ridges can occur, particularly at the connection of the gate valve to the outlet of the vessel due to wear, and such wear may be of up to 5 mm per charge. This formation of ridges leads to undesirable turbulence in the flow of metal discharged from the vessel. Attempts have been made to reduce this wear by using an inlet sleeve with a different geometry, e.g. with an eccentric passage, or by arranging the gate valve so that its height is adjustable. Both measures, however, are extremely expensive and not very successful.

An object of the present invention, therefore, is to provide a sliding gate valve in which excessive or uneven wear is prevented, particularly of the inlet sleeve in the region of its connection to the outlet of the metallurgical vessel.

According to the present invention there is provided a sliding gate valve for metallurgical vessels having a substantially horizontal outlet passage including an inlet sleeve, a base plate, a sliding plate and an outlet sleeve which together define a passage extending through the valve in which the passage within the inlet sleeve is lined with a pipe of ceramic oxide material having a slot extending along its length.

The pipe inserted into the passage within the inlet sleeve is made from high-grade material which is therefore very resistant to wear. Since the pipe may have relatively thin walls in comparison to the total volume of the valve component or components which it is desired to protect, the cost of materials for production of the gate valve is not significantly increased.

In the past it had been considered that the use of a wear-resistant pipe in, for example, the inlet sleeve was not practical because of the differing coefficients of thermal expansion of the materials of the inlet sleeve and the pipe. However, use of a pipe of ceramic oxide material with a longitudinal slot not only simplifies the production of the inlet sleeve and pipe to a suprising degree but also obviates the problem of the differing coefficients of thermal expansion. Thus, in the preferred embodiment of the invention the inlet sleeve of the valve, and optionally also the base plate, sliding plate and outlet sleeve are made of refractory cement. The inlet sleeve can therefore be formed by moulding around the ceramic oxide pipe.The shrinkage of the refractory cement in which the pipe is embedded as a "lost core" during formation of the inlet sleeve is compensated for by the longitudinal slot, since during pouring a wedge-shaped member which somewhat enlarges the external diameter of the pipe is inserted into the slot and then withdrawn before the refractory cement hardens. This means that the shrinking cement can contact the pipe but does not induce excessive compressive stress due to its reduction in cross section during the molding process. When in position, the longitudinal slot in the pipe serves to compensate for the differing expansions of the ceramic oxide material and the refractory cement during heating. In other words, the longitudinal slot acts as an expansion joint.

Thus the inlet sleeve not only has a greater resistance to steel melts and slag but also has an improved reliability in operation. Furthermore, the slot improves the resistance of the pipe to changes in temperature. A continuous pipe which is suddenly heated from inside develops tangential tensile stresses on its relatively cold exterior which can exceed the strength of the material and lead to thermal fracture. A slotted pipe, however, can expand under the effect of an increase in temperature so that the tensile stress is considerably reduced and the pipe is less sensitive to thermal shock. The pipe made from ceramic oxide material does not exhibit substantial wear which would necessitate alteration of the gate valve or the base plate.The ceramic oxide pipe in the bore of the inlet sleeve serves to concentrate or direct the flow of metal and thus also reduces excessive wear on the base plate sliding plate and outlet sleeve.

Wear in the region of the base plate may be particularly reduced if the inlet sleeve and base plate are constructed as one piece and the pipe made from ceramic oxide material, optionally with an unslotted section, extends into the passage within the base plate, or a separate slotted pipe made of ceramic oxide material is inserted therein.

If desired one or more of the passages within the base plate, sliding plate or outlet sleeve may also be line with such a slotted pipe.

The longitudinal slot which, in use, conveniently lies uppermost where it comes into less contact with the molten metal and the slag, is preferably 1 to 2 mm wide. This width has proved to be sufficient both to compensate for the shrinkage and the associated compressive stress during setting of the refractory cement on the pipe and to compensate for thermal expansion, in use, and improve the resistance to changes in temperature without it being necessary to check for excessive wear of the material of the gate valve in the region of the longitudinal slot.

An average thickness of between 10 and 20 mm is sufficient for the pipe, but its wall thickness preferably decreases from its inlet end to the outlet end, e.g. from approximately 20 mm to approximately 5 mm so that the outer surface of the wall of the pipe and the surface of the passage of the inlet sleeve, (or other components containing such a pipe) are tapered in the intended direction of flow of metal. In this way the flow of metal ensures that expulsion of the pipe from the inlet sleeve can not occur.

The ceramic oxide material preferably comprises one or more oxides having a melting point of above 19500 C. Such oxides may comprise one or more of MgO, Cr2O3, Awl203 and ZrO2 with less than 1% by weight of other oxides with the exception of ZrO2-stabilising additives.

The invention also extends to a metallurgical vessel having a substantially horizontal outlet passage defined by two or more refractory runner bricks communicating with such a sliding gate valve, and to a slotted ceramic oxide pipe for such a valve.

Further features and details of the invention wili be apparent from the following description of two specific embodiments which is given by way of example with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic sectional elevation of a sliding gate valve connected to a metallurgical vessel; Figures 2 and 2a are longitudinal and transverse sections respectively through the ceramic oxide pipe; and Figures 3a and 3b are diagrammatic sectional elevations on a larger scale of two' different embodiments of the invention.

The sliding gate valve 1 seen in Figure 1 is connected to the tap-hole in a side wall 13 of a Siemens-Martin oven or electric furnace, the walis of which have a refractory lining 14. Interfitting runner bricks 3 define an outlet passage 2 within the lining 1 4. An inlet sleeve 4, which in this case is of unitary construction with a stationary base plate 5, is fitted on the outer end of the outermost runner brick 3. A sliding plate 6 with an associated collector nozzle or outlet sleeve 7 is connected to the outer surface of the base plate 5 and can be slid in a conventional manner in a frame relative to the base plate 5 between the closed and open positions. The passages within the inlet sleeve 4, base plate 5, sliding plate 6 and outlet sleeve 7 together form an outlet channel 8.A pipe 11 made from ceramic oxide material is inserted into the passages 9 and 12 within the inlet sleeve 4 and the base plate 5. As shown in Figure 2a the wall thickness of the pipe 11 is tapered externally from its inlet or upstream end to its outlet or downstream end and fits into the inlet sleeve 4 and base plate 5, which are, for example, cast in one piece from refractory cement using the pipe 11 as a lost core. As shown in Figure 2b the pipe 11 has a longitudinal slot 10 extending along its entire length which compensates for the shrinkage of the refractory cement during setting and for thermal expansion when the valve is in use, and increases its resistance to changes in temperature.

When the pipe 11 has an internal diameter of for example 1 70 mm the longitudinal slot 10 is preferably 1 to 2 mm wide. The wall thickness of the pipe 11 is then preferably between 10 and 20 mm.

Figure 3a shows the gate valve of Figure 1 in the region of the inlet sleeve 4 and base plate 5 on a somewhat larger scale. Figure 3b on the other hand shows a modified construction in which the pipe 11 of ceramic oxide material is only within the bore 9 of the inlet sleeve 4 which, in this construction, is separate from the base plate 5.

Nevertheless the pipe 11 effectively concentrates or directs the flow from the oven and thus reduces wear not only of the inlet sleeve 4 itself but also of the base plate 5 and the other parts subject to wear in the region of the passage 12. In exceptional cases, e.g. when the components are to be subjected to extreme wear, the sliding plate 6 and the outlet sleeve 7 can also be provided with an appropriately dimensioned inner pipe or lining of ceramix oxide material.

In one specific construction a mixture of 50% by weight of Awl203 and 50% ZrO2 is used as a starting material for the ceramic oxide pipe. In a ceramic oxide pipe of this type the following properties were obtained after pressing at approximately 1 7500C: Total porosity : 9.1% Open porosity: 5.2% Cold compressive strength : greater than 3000 kp/cm2 Gas Permeability : 0 Refractoriness under load : initial temperature at which softening occurs is greater than 1 7400C Modulus of elasticity (static) : 438,300 kp/cm2 Bending strength :848 kp/cm2 Hot bending strength at 15000C 1 500 C: 137 kp/cm2 Thermal expansion (maximum thermal expansion at 1 500 C): 0.89% Pressure flow (24 hours, 1 5000C, 24 kp/cm2) 0.2% Bending strength after 25 quenchings: 56 kp/cm2 The refractory cement used for the inlet sleeve and/or outlet sleeve and/or base plate and/or sliding plate may conveniently have the following percentage composition by weight: Al2O3 : 94.5 SiO2 0.5 Se2O3 : 0.2 TiO2 : 0.1 CaO : 4.2 MdO : 0.1 Na2O : 0.3 K2O : 0.1 In the preferred embodiment the valve R for the ceramic oxide material, which is equal to BS/V x a where BS is the bending strength, V is the V modulus (bending modulus) and athe coefficient of thermal expansion, is greater than 350C.

Claims

1. A sliding gate valve for metallurgical vessels having a substantially horizontal outlet passage including an inlet sleeve, a base plate, a sliding plate and an outlet sleeve which together define a passage extending through the valve in which the passage within the inlet sleeve is lined with a pipe of ceramic oxide material having a slot extending along its length.

2. A valve as claimed in Claim 1 in which the base plate is integral with the inlet sleeve and positioned between the inlet sleeve and the sliding plate, and in which the pipe extends into the passage within the base plate.

3. A valve as claimed in Claim 1 or Claim 2 in which one or more of the passages within the sliding plate, base plate or outlet sleeve is also lined with a slotted tube of ceramic oxide material.

4. A valve as claimed in any one of the preceding Claims in which the inlet sleeve, base plate, sliding plate and outlet sleeve are made of refractory cement.

5. A valve as claimed in any one of the preceding Claims in which the slot is between 1 and 2 mm wide.

6. A valve as claimed in any one of the preceding Claims in which the pipe has an average wall thickness of between 10 and 20 mm.

7. A valve as claimed in any one of the preceding Claims in which the wall thickness of the pipe decreases from its inlet end to its outlet end.

8. A valve as claimed in Claim 7 in which the wall thickness decreases from about 20 mm to 5 mm.

9. A valve as claimed in any one of the preceding claims in which for the ceramic oxide material the value R = BS/V x a where BS is the bending strength, V the V modulus (bending modulus) and a the coefficient of thermal expansion is greater then 350C.

10. A valve as claimed in any one of the preceding claims in which the ceramic oxide material comprises one or more oxides having a melting point of above 1 95O0C.

1 A valve as claimed in Claim 10 in which the oxides comprise one or more of MgO, Cr2O3, Awl203 and ZrO2 with less than 1% by weight by other oxides with the exception of ZrO2-stabilising additives.

12. A sliding gate valve substantially as specifically herein described with reference to Figures 1, 2a, 2b and 3a or Figure 3b of the accompanying drawings.

1 3. A metallurgical vessel having a substantially horizontal outlet passage defined by two or more refractory runner bricks communicating with a sliding gate valve as claimed in any one of the preceding claims.

14. A pipe of ceramic oxide material having a slot extending along its length for a sliding gate valve as claimed in any one of Claims 1 to 12.