CA1174463A - Renovation or adaptation of refractory valve plates for molten metal pouring - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Techniques are disclosed for renovating sliding gate valve plates of for adapting conventional plates for use with problem-beset metals. Stationary plates (1) have their orifices (2) bored out to downwardly-tapering form and correspondingly tapered pre-fabricated refractory insert rings (3) are then cemented in place, the rings having axial depths equal to the plate thicknesses. An orificed plate (7) furnished with an integral depending nozzle (12) has its flow passage (13) bored out such that an upper bore portion extending through the plate (7) and part way along the nozzle (12) is transversely larger than the following downstream bore portion.
A prefabricated refractory insert ring (9) is cemented into the upper bore portion, ring (9) being substantially as deep axially as the said bore portion. The downstream bore portion is lined with cementitious, metal-reinforced material (14). Materials for the insert rings (3,9) and cementitious lining (14) are chosen to suit the pouring conditions and metals to be poured.

Description

The present invention relates to methods for the reno-vation or adaptation of refractory valve plates used in slide gate valves for casting ladles or tundishes for controlling molten metal pouring.
Various methods are known for repairing valve plates, according to which there are inserted into the bores of the worn plates annular parts which have exactly the same thickness as the plates themselves. For valve plates having an integral "nose" or ! nozzle, it is known for the bore in the latter to be filled with a cement-like filling compound.
Ring-shaped inserts which have been used in prior art methods have comprised two cylindrical portions having different outside diameters, the portion having the larger outside diameter being the upper part of the ring insert~
The known prior art methods have disadvantages, the most serio~s of which will be now mentioned. Firstly, the ring insert for a stationary plate can extend downwardly therefrom and press on the movable plate. Secondly, the upper part of the ring insert for the stationary plate is very frequently oversized, so that the periphery of the ring insert is undesirably close to the annular recess provided, in the upper surface of the stationary plate, for sealing engagement with a refractory discharge outlet member of the associated pouring vessel. This results in the plate area between the new ring insert and the recess being considerably reduced, which may lead to leakage of molten metal.
For the movable plates, the disadvantage of a ring-shaped insert having a length equal to the plate thickness consists in ,~ ~

~'7'.~3 that the flowing metal can seep between the lower end of the ring insert and the abutting face of the cement lining of the "nose", and thus along the contact surface between the plate and the "nose".
Such may happen particularly when metal is tapped under throttling conditions with the valve only partly open, when the metal flow will possess a horizontal flow component.
The cementitious compound used for the lining of the "nose"
of the movable plate is a refractory material, whose poor elasticity may l~ad to crack formation in the surface as well as in the body of the lining.
Valve plate repair techniques disclosed herein can equally well be employed for adapting conventional valve plates to suit them for use with special steels which may give rise to difficulties when pouring thro1lgh conventional valve plates.
The present invention aims, inter alia, to provide a method of renovating or adapting the valve plates, both stationary and movable, of sliding gate valves, which method avoids the disadvan-tages of the prior art discussed above.
' According to one aspect of the present invention there is provided a method of renovating or adapting a valve plate set of a sliding gate valve for use in controlling molten metal flow, the plate set including a stationary, orificed upper plate and an orificed lower plate furnished with an integral, depending dis-charge nozzle, the method including the steps of:
(a) boring out the stationary plate orifice to form a downwardly-tapering opening and securing a pre-fabrica~ed refractory insert ring in the resulting opening, the ring being tapered to match the "~

~:~ '7'~3 tapering opening and having an axial length equal to the thickness of the stationary plate;
(b) boring ou~ the flow passage which extends through the lower plate and its lntegral nozzle to remove areas of wear and to form a stepped bore, a larger diameter portion of said bore piercing the plate and extending part way along the nozzle, while the smaller diameter portion extends through the remainder of the nozzle;
(c) securing a prefabricated refractory insert ring in the larger bore portion, the ring having an axial length greater than the plate thickness; and (d) positioning an elongated tubular former concentrically inside the smaller bore portion and filling the space between the former and the confronting inside wall of the nozzle with cementitious material to form a nozzle liner, the former having an ou~er diameter enabling it to fit snugly into the insert ring in the larger bore portion.
According to another aspect of the invention, there is provided a method of renovating or adapting an orificed lower valve plate of a sliding gate valve for use in controlling molten metal flow, the plate being furnished with an integral, depending dis-charge nozzle, wherein the method includes the steps of:
(a) boring out the flow passage which extends through the lower plate and its integral nozzle to remove areas of wear and to form a stepped bore, a larger diameter portion of said ~ore piercing the plate and extending part way along the nozzle, while the smaller diameter portion extends through the remainder of the nozzle;
(b) securing a prefabricated refractory insert ring in the larger bore portion, the ring having an axial length greater than the plate thickness; and (c) positioning an elongated tubular former concentrically inside the smaller bore portion and filling the space between the former and the confronting inside wall of the nozzle with cementitious material to form a nozzle liner, ~he former having an outer dia-meter enabling it to fi~ snugly into the insert ring in the larger bore portion.
According to a further aspect of the invention, there is provided a method of renovating or adapting a stationary, orificed upper valve plate of a sliding gate valve for use in controlling molten metal flow, the plate being held in a metal can or tray, and the method including the steps of:
(a) checking the can or tray for unevenness or distortion;
(b) eradicating any such unevenness or distortion by a pressing operation; and (c) boring out the plate orifice to form a downwardly-tapering opening and securing a pre-fabricated refractory insert ring in the resulting opening, the ring being tapered to match the tapering opening and having an axial length equal to the thickness of the stationary plate.
The invention embraces valve plates when renovated or adapted by the methods according to the invention.
Initial preparation of used valve plates may involve re-moval of adhering metal and slag.
Then, the evenness of the metal cans containing the plates may be checked and, if necessary, rectified by a pressing operation.
Sliding surfaces of the plates can be repaired as necessary with refractory material; suitable patching compositions are already . ~.

known.
Finally, the repaired parts can be pre-dried, after-treated, dried again, and if desired tarred and graphited.
Further details of the present invention are now given by way of illustrative example in the following description.
Turning first to the stationary valve plate of a sliding gate valve setl the pour opening in the sta~ionary plate is bored out so as to taper conically in the down-stream flow direction.
For this tapered opening, a correspondingly tapered ring insert is required, its internal diameter being equal to the diameter of the original flow opening in the plate, although it could differ.
The outer surface of the ring insert should have the same conical taper as the conically-bored opening, but its dimensions are such that a gap of appxoximately one millimetre is left between the ring and the plate opening.
The opening in the stationary plate is bored to a dimension which is such that a distance of at least 2mm is kept between the tapered opening and the ring-shaped recess, mentioned earlierl in the upper plate surface.
The passage opening in the movable plate and in its "nose"
can be bored out to the same diameter, but preferably the movable plate and nose are counterbored to provide a larger bore in the plate per se and a smaller bore in the "nose". The larger bore should be carried into the nose.
The ring insert for the movable plate usually has the ~ame inside diameter as the original plate orifice~ though it could differ.

t7~

This ring insert is longer than the movable plate is thick and thus overlaps the contact line between the movabl~ plate and its nose, the insert extending part way down the nose.
The outside diameter of the ring insert is approximately two millimetres smaller than the corresponding diameter of the receiving opening bored therefor in the movable plate and in its nose.
When the opening in the movable plate and in its nose is ~ bored, care must be taken that the inner wall of the nose remains thick enough to withstand possible seepage of molten metal into the joint between the lower end face of the ring insert and the upper edge of a sleeve-shaped lining of the nose.
The thickness of the refractory wall of the nose should preferably not be less than ~ mm.
The ring inserts should be produced from a refractory material whose physical and mechanical characteristics are at least equal to those of the corresponding plate material.
In order to renew the opening in the nose of the movable plate downstream of the insert thereof, a tube is used whose out-5ide diameter corresponds to the required internal diameter of thenose. The space between the tube and the bored out nose is filled with a refractory type of cement by the casting or ramming methods.
The type of cement used for this purpose also must have characteristics comparable with the material of the nose, that is to say it must b~ suitable for use in contact with the metal to be cast. Aclvantageously, the cement mixture with which the space hetween the tube and th~ bore is to be filled contains reinforcing strands or needles e.g. in stainless steel which are 0.2 to 5 mm ., , thick and are not long~r than the thickness of the required sleeve-shaped lining of the nose.
The weight proportion of the steel needles may range from

2~ to 20% of the total weight of the filling, preferably from 8% to 15%.
The main or sliding surfaces of both plates should also be repaired, as necessary, with a refractory cement which, after dry-ing, has a high strength against mechanical stresses, as well as a good resistance to abrasion, erosion and to chemical agents at a high temperature. When the cement coating has set, it is ground and treated as usual for the original plates.
Some movable plates have noses exhibiting small extensions which project from the metal cans or sleeves encasing the nozzles.
Such an extension is so shaped that it mates with a protective tube which isolates the molten metal stream from the atmosphere as the metal is teemed into a receiving vessel.
In applying the present invention to such plates, the extension of the nose is first completely removed. Then, onto the metal sleeve another metal housing is welded, the latter being as long as the original extension. Now it is possible with the aid of a tube or former whose outside diameter corresponds to the required inside opening diameter completely to fill with refractory cement the space between the internal wall of the nose and the tube or between the tube and the metal housing extension. The refractory cement illing can be introduced by the casting or ramming methods.
The technique just described may also be used to adapt new plates if the quality of the steel necessitates refractory materials of a special type which are different from the materials ,, .

'7~ 3 conventionally used for the production of refractory plates.
By following the teaching of this invention, molten metal e.g. steel will in fact only come into contact with refractory material of a suitable type, that is to say a material which with-stands bsth chemical stressing at a high temperature and the fric-tion or erosion caused by the flowing metal. The refractory materials can be tailored to the exact steel to be poured. Thus, materials can be chosen for avoiding deposition, caused by eutectic formation, which reduces the opening cross section.
The advantages of this invention include from the following.
Thanks to the downwardly conically tapering ring insert for the stationary plate and to the correspondingly shaped opening there-for, thermal expansion and displacement of the insert is in the up-ward direction rather than downwardly against the movable plate.
Thus a potential source of leakage is avoided.
Cement for fastening the ring inserts in place absorbs radial expansion of the ring inserts.
The presence of stainless steel needles in the refractory cement mixture for the filling of the nose imparts to the sleeve-shaped nose lining sufficient elasticity to prevent the formationof surface and internal cracks in the lining during casting.
Thanks to the ring insert in the movable plate being longer than the thickness of the plate, molten metal is prevented from seeping between the plate and nose.
The material strength between the casting opening in the stationary plate and the ring-shaped recess in its surface ensures an adequate mechanical strength of the crown and thus the function ~a'7~ 3 of the original flow trough system.
If the evenness of ~he metal cans is checked and remedied and surface defects in the refractory plates are repaired, the renovated plates will offer maximum reliability and freedom from leakage~
Advantageously the tube or former around which the nose liner is formed is perforated to allow the water in the cement mixture more easily to evaporate hefore the tube is removed. Uni-form hardening of the sleeve-shaped lining is also facilitated.
To provide a better understanding of this invention/ two applications will now be described by way of example, reference to be made to the accompanying drawings, in which:
Figure 1 is a vertical se~tion through a stationary valve plate, Figure 2 is a verkical section through a movable plate having an integral nose or collector nozzle, and Figure 3 i5 a vertical section through a second movable plate having an integral nozzle for mating with an elongated pour-ing tube.
After any metal and slag particles which may be adhering to the plates have been removed, first the evenness of the hori-zontal surfac~s of the metal boxes 6 and 15 of the stationary plate 1 and the movable plate 7 are checked and, if necessary, rectified by pressing.
Subsequently, any de~ects in the sliding surfaces of the plates are repaired by patching cement. Next, the opening in the stationary plate 1 is conically bored, as shown in Figure 1.

The upper diameter ~1 is larger than the lower diameter 02, the cone angle being at least 5.
The diameter ~1 has been chosen so that the distance d between the upper edge of the opening ~ and the internal edge of the ring-shaped recess 5 is a~ least thr~e millimetres.
The ring insert 3, of a suitable refractory material, has the same depth as t~e plate thickness in the zcne of the opening 2, and has a bore defining a flow orifice equal to the diameter of the opening originally in the plate. The ring insert has the same taper as that of the opening bored in the plate 1.
The opening and insert are so dimensioned that between the inner face of the opening 2 and the outer face of the xing insert

3 there is a gap of one millimetre for cement 4 to fasten the insert in positionO
The opening 8 in the movable plate 7 and in the upper part of the,nose, which is shown in Figure 2, is bored out to the dia-meter ~3 for a distance hl from the sliding surface of the plate 7 while the remaining lower part of the nose is bored out to the diameter ~4 which is smaller than 03. Distance hl is greater than the plate thickness.
The ring insert 9 which is to be accommodated in the larger opening por~ion contained in the plate and the upper part of the nose, has an outside cliameter two millimetres smaller than ~3. The resulting gap is filled with cement 10.
It clearly emerges from Figure 2 that the ring insert 9 extends far beyond the contact line between the plate 7 and the nose 12, since its climension hl considerably exceeds the thickness '~-~ ~ 7 L~ L~

h2 of the plate.
The inside diameter of the ring insert 9 has the same di-mension as the opening originally in the plate 7.
The sleeve 14, with which the opening 13 of the nose 12 is lined, is made of a cementitious material which contains 12% by weight of very thin needles in stainless steel.
The cement mixture is pressed into the opening 13 after the ring insert 9 and the perforated tube 16 (only shown in Figure 3) have been insert~d.
The thickness of the cement lining 14 is chosen to be such that the opening defined thereby for metal flow has the same dia-meter as the inside diameter of the ring insert 9 D
The diameter 04 is chosen such that all the worn material is removed from the plate and the nose while leaving the wall of the nose with a thickness of 5 mm.
In Figure 3, there is shown a novable plate 7 whose nose originally had a refractory matexial ext:ension 19 which occupied the entire surface beneath the line A-A.
The ring insert 9 of the height hl, which is larger than the thickness h2 of the plate 7, is placed into the opening having the diameter 03 of the plate and into the upper part of the nose.
After the original refractory extension 19 has been re-moved, a metal sleeve extension 17 is secured to the lower part of the sleeve 15' by a weld 18. The sleeve extension has the same shape as the original refractory material extension.
The entire space between the perforated tube 16 and the opening of the nose as well as between the tube 16 and the sleeve extension 17 can be filled with the already-mentioned cement mixture.

.~ . ,.

Claims (19)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of renovating or adapting a valve plate set of a sliding gate valve for use in controlling molten metal flow, the plate set including a stationary, orificed upper plate and an orificed lower plate furnished with an integral, depending dis-charge nozzle, the method including the steps of:
(a) boring out the stationary plate orifice to form a downwardly-tapering opening and securing a pre-fabricated refractory insert ring in the resulting opening, the ring being tapered to match the tapering opening and having an axial length equal to the thickness of the stationary plate;
(b) boring out the flow passage which extends through the lower plate and its integral nozzle to remove areas of wear and to form a stepped bore, a larger diameter portion of said bore piercing the plate and extending part way along the nozzle, while the smaller diameter portion extends through the remainder of the nozzle;
(c) securing a prefabricated refractory insert ring in the larger bore portion, the ring having an axial length greater than the plate thickness; and (d) positioning an elongated tubular former concentrically inside the smaller bore portion and filling the space between the former and the confronting inside wall of the nozzle with cementitious material to form a nozzle liner, the former having an outer dia-meter enabling it to fit snugly into the insert ring in the larger bore portion.

2. A method of renovating or adapting an orificed lower valve plate of a sliding gate valve for use in controlling molten metal flow, the plate being furnished with an integral, depending discharge nozzle, wherein the method includes the steps of:
(a) boring out the flow passage which extends through the lower plate and its integral nozzle to remove areas of wear and to form a stepped bore, a larger diameter portion of said bore piercing the plate and extending part way along the nozzle, while the smaller diameter portion extends through the remainder of the nozzle;
(b) securing a prefabricated refractory insert ring in the larger bore portion, the ring having an axial length greater than the plate thickness; and (c) positioning an elongated tubular former concentrically inside the smaller bore portion and filling the space between the former and the confronting inside wall of the nozzle with cementitious material to form a nozzle liner, the former having an outer diameter enabling it to fit snugly into the insert ring in the larger bore portion.

3. A method according to claim 1, wherein the cementitious material for filling the said space is reinforced with metallic needles.

4. A method according to claim 3, wherein said needles are of stainless steel, have a thickness in the range of 0.2 to 5 mm and have a length no greater than the thickness of the liner to be formed from the cementitious material, the needles being 2 to 20%
by weight of the mixture of needles and cementitious material.

5. A method according to claim 4, wherein the weight per-centage of the needles in the mixture is in the range of 8 to 15%.

6. A method according to any of claims 1 to 3, wherein each insert and its corresponding opening are dimensioned so as to provide a gap therebetween for cement used to secure the insert in position.

7. A method according to any of claims 1 to 3, wherein the tubular former used is perforated to assist de-watering and setting of the cementitious lining material.

8. A method according to any of claims 1 to 3, wherein the nozzle is metal jacketed and a portion of the nozzle protrudes downwardly therefrom, and the method includes the further steps of removing the protruding nozzle portion, securing an extension piece to the metal jacket, thereafter installing a tubular former which is long enough to extend through the nozzle and through the extension piece, and lastly filling with the cementitious material the space between the former, the confronting nozzle inside wall and the confronting inside wall of the extension piece.

9. A method according to any of claims 1 to 3 including a preliminary step of removing metal or slag deposits from the slid-ing surface of the or each plate.

10. A method according to any of claims 1 to 3, including a preliminary step of eradicating defects in the sliding surface of the or each plate using a cementitious patching composition.

11. A method according to any of claims 1 to 3, wherein the or each plate is held in a metal can or tray, and the method includes preliminary steps of checking the can or tray for uneven-ness and of eradicating any defects therein by a pressing operation.

12. A method of renovating or adapting a stationary, orificed upper valve plate of a sliding gate valve for use in controlling molten metal flow, the plate being held in a metal can or tray, and the method including the steps of:
(a) checking the can or tray for unevenness or distortion;
(b) eradicating any such unevenness or distortion by a pressing operation; and (c) boring out the plate orifice to form a downwardly-tapering opening and securing a pre-fabricated refractory insert ring in the resulting opening, the ring being tapered to match the tapering opening and having an axial length equal to the thickness of the stationary plate.

13. A method according to claim 12, wherein the plate has an annular groove in its upper surface concentric with the opening formed in the plate and the boring step is so performed as to obtain a minimum spacing of 2 mm between the radially inner edge of the groove and the adjacent edge of the opening.

14. A method according to claim 12 wherein the insert and its opening are dimensioned so as to provide a gap therebetween for cement used to secure the insert in position.

15. A method according to claim 12, 13 or 14, including a preliminary step of removing metal or slag deposits from the sliding surface of the plate.

16. A method according to claim 12, 13, 14 including a preliminary step of eradicating defects in the sliding surface of the plate using a cementitious patching composition.

17. A plate set produced by the method claimed in claim 1, 3 or 4.

18. A valve plate, furnished with an integral nozzle, when produced by the method as claimed in claim 2.

19. A stationary upper valve plate, when produced by the method claimed in any of claims 12, 13 and 14.