US3593773A

US3593773A - Method and apparatus for supervising casting of steel tubes

Info

Publication number: US3593773A
Application number: US830296A
Authority: US
Inventors: Gerd Vogt; Josef Glaser; Manfred Strohschein; Johannes Kurth; Rudolf Schwitzgobel
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1968-06-07
Filing date: 1969-06-04
Publication date: 1971-07-20
Anticipated expiration: 1988-07-20
Also published as: BE733639A; SE342755B; DE1758466A1; FR2011906A1; GB1228071A; AT282090B; DE1758466C3; DE1758466B2

Abstract

Method and equipment for supervising the continuous casting of steel tubes is disclosed. The tubes are water cooled as they leave the die and the steam pressure is used as an indicator for the forming of cracks to control retarding or stopping of the casting process at an early stage of crack forming.

Description

United States Patent m1 3,593,773

[72] Inventors Gerd VOgt {51] lnt.Cl .B22d 13/10 Krefeld; [50] FieldofSearch. l64/4,85,

Josef Glaser, Gelsenkirchen; Manfred Strohschein. Gelsenkirchen; Johannes Kurth, Gelsenkirchen; Rudolf Schwitzgobel, Gelsenkirchen, all of. Germany 1 2| Appl. No. 830,296

{22] Filed June 4,1969

[45] Patented July 20, 1971 [73] Assignee Mannesmann Aktiengesellschaft Dusseldorf, Germany [32] Priority June 7, 1968 [33] Germany [54] METHOD AND APPARATUS FOR SUPERVISING CASTING OF STEEL TUBES l 1 Claims, 2 Drawing Figs. [52] US. Cl. 164/4, 164/154, 65/86, 65/16] 65/190, 65/191 150, I51, I52, I53, 281, I54; 264/40, 173, 209; 122/504; 65/29. 86, 1611, I87, I88, 189, 190, l9l,

[56] References Cited UNITED STATES PATENTS 2,145,438 l/l939 Thulin 164/152 2,853,754 9/1958 Paddock... 164/85 3,327,761 6/1967 Rowell 122/504 X Primary Examiner-J. Spencer Overlholser Assistant Examiner-John S. Brown Attorney-Smyth, Roston & Pavitt ABSTRACT: Method and equipment for supervising the continuous casting of steel tubes is disclosed. The tubes are water cooled as they leave the die and the steam pressure is used as an indicator for the forming of cracks to control retarding or stopping of the casting process at an early stage of crack formmg.

METHOD AND APPARATUS FOR SUPERVISING CASTING OF STEEL TUBES The present invention relates to a method and equipment for improving the continuous casting of steel tubes which are cooled from the interior by spraying water onto the inner surface of a tube when leaving the die, and more particularly the invention relates to supervision of such casting process.

During continuous casting, the rods or tubes, as the case may be, are only partially solidified as they leave the die. In fact, there is barely a solid shell or mantle while the interior is still liquidous. The solid portion grows in thickness with increasing distance of tubing from the die, but even at an appreciable distancefrom the die the interior of the tube walls, or even more so the interior of a rod, is still in the liquid state. The cross-sectional dimension of this liquid core decreases until the entire tube or rod has solidified remote from the die. It is now possible, however, that the already solidified portion of the tube or rod cracks and that some of the still liquidous in terior core pours out and over tube, die and other casting equipment. It is needless to say that should such cracking occur, it interrupts operation and renders considerable portions of the cast tube or rod unusable.

Aside from the danger to equipment and product resulting directly from the outflow of liquid steel the employment ofinterior water cooling equipment for causing water to be sprayed upon the interior surface of a cast tube, establishes an additional source of considerable danger, particularly for the personnel. As the tube cracks and liquidous steel pours through the crack the amount of water vapor and steam developed is suddenly increased. The pressure in the tube increases accordingly, and may well lead to explosion. Unfortunately, it is yet unknown how to recognize the initial conditions leading to the formation of such cracks, sufficiently early to positively prevent at all any cracking of the cast product prior to its complete solidification. Such cracks develop too sudden and under basically unforeseen circumstances.

It is an object of the present invention to establish method and equipment for continuously casting of steel tubes in which at least the production of a crack in the interior of a tube is recognized in the developing stage, i.e., sufficiently early so that continued development of the crack and enlargement thereof can be at least materially impeded.

In accordance with the preferred embodiment of the invention, it is suggested to continuously measure the steam pressure in the interior of a cast and to control the casting process in accordance with that pressure. It was found to be of particular advantage to measure the vapor pressure directly in the region of spraying within the tube. It was found in particular that for a constant rate of flow of spray water the steam pressure increases drastically as soon as a crack begins to form in the interior wall surface of the tube. Such a crack in the interior of the tube exposes still hot portions of the solidified portion of the tube closer to the still liquidous core in the tube wall, and even exposes liquid steel to the spray water. As soon as a crack begins to form, liquid steel begins to seep into and through the crack. As a consequence, the rate of vaporization of spray water increases rapidly as compared with undisturbed operation.

Sudden and steep increase of the water vapor pressure is, therefore, a certain sign for the creation ofa crack and which, if not stopped, could possibly lead to a complete breakage in the tube. In accordance with the increase in vapor pressure, for example, the casting process is changed. For example, the flow or metal into the die is throttled as soon as the water vapor pressure increases. Moreover, in case a particular threshold pressure has been reached, and/or in case the rate of pressure increase is steep and persistent, it is advisable to interrupt the casting process completely. Additionally, the flow of water to be sprayed is subject to control in accordance with the current steam pressure. Excess pressure will result in a complete throttling of the supply to prevent explosion.

It was found that with aid of the inventive method it is actually possible to monitor the beginning of the formation of a crack in the interior of'the tube at such an early state that by appropriate and speedy control an enlargement of that crack can be prevented. Moreover, the early detection permits taking of adequate measures against any catastrophic effects of an outpour of liquid steel through a large crack and even against the outpour itself by speedily impeding the formation of a large crack. The casting of a tube is intended as an illustrative example. The invention will find utility for continuously casting of hollow objects with internal cooling.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which;

FIG. i there is illustrated somewhat schematically a cross section through a continuous casting equipment for the casting of steel tubes; and

FIG. 2 illustrates a modification of the equipment shown in FIG. ll.

The equipment illustrated in FIG. ll includes a water-cooled die member I having a die cavity which actually has ringshaped configuration; because a water-cooled, hollow mandrel 2 projects centrally into the die cavity. Liquid steel is fed into the die from a container or hopper 111 having an aperture Ila which can be closed by a movable plug or stopper element 10. A continuous hollow product, i.e., a cast tube 3 leaves the bottom die, i.e., the steel normally continuously pouring from hopper 11 into die 11 leaves the bottom thereof as a formed tube 3.

Tube 3 when directly leaving the die is only partially solidified by operation of the cooling process involving die and mandrel. In particular, the tube has initially very thin solid wall portions 312; there is an inner wall portion forming a thin tube and circumscribing the hollow interior of tube 3 and there is an outer wall portion also forming a thin tube. These two wall portions 3b are separated by an essentially ringshaped liquid core 3a. At greater distance from the die, core 3a is reduced in cross-sectional dimension and vanishes when inner and outer portions 3b merge at large distance from the die.

It is conventional to spray water upon the outer surface of the tube to increase rapidly the thickness of its solidifying outer wall portion. Equipment for spraying water on the outer tube surface is now shown and is not considered to be a part of the invention. Also, it is conventional to provide rollers for the transporting the formed tube away from the die; as this is likewise known and does not constitute a part of the invention these rolls are, therefore, likewise not illustrated in detail.

The interior wall of the tube, particularly the inner surface of the cylindrical cavity defined by the tube is cooled by continuously spraying water through nozzles 5. Water is fed to nozzles 5 through a pipe 4 which traverses the hollow mandrel 2 and is'under control ofa valve 112 for controlling the amount of water supplied to the nozzles. The water is directly sprayed onto the hot inner surface of the tube and partially vaporizes. Water vapor thus produced escapes from the interior of tube 3 through the hollow flow space of mandrel 2 communicating on one end with tube 3 and being on the other end connected to a steam pipe 6. A suction device 7 sucks steam from pipe 6 to be discharged in the surrounding atmosphere.

A measuring or sensing pipe 8 likewise traverses the hollow space of mandrel 2 and extends down into the region where the tube 3 leaves the die. The pipe 3 opens particularly to the zone adjacent the inner surface of the tube upon which coolant is sprayed. Measuring and probing pipe 8 is connected to a pressure measuring instrument It outside of the steam zone. In lieu of employing the special measuring pipe 8, pressure instrument 9 could also be connected directly to the pipe 6 for purposes of monitoring the pressure therein as representation of the pressure in the interior of mandrel 2 and in the space defined by the interior of tube 3.

During normal operation and for a constant rate of water flow as passing through pipe 4 and nozzles 5 for spraying, instrument 9 will indicate a constant value. The value is particularly determined by the rate of spray water flow and by the relative low pressure in pipe 6. Should the pressure increase suddenly, instrument 9 will respond immediately. lf the casting process itself did not change, nor was there any change in the flow of cooling and spray water then such pressure increase clearly represents that a crack is about to form and is in the initial state of formation. After the pressure increase has been detected, the casting process is changed so that further increase of a crack is impeded. Such an impediment can be produced in a controlled manner as follows:

For example, the pressure in the spray zone as monitored by probing pipe 8 acts upon an adjusting piston 13. It may be advisable to interpose, for example, a fluid amplifier in the connection path between probing pipe 8 and adjusting element 13. This way the control can be conducted at a particular characteristic as to when steel flow from hopper 11 is to be interrupted. The piston 13 may normally be in retracted position but is then actuated as a result of an increase in pressure of probing pipe 8. Piston l3 actuates a lever 14 which in turn moves stopper toward a more closing position.

Normally, the lever 14 is balanced by a weight 15 such that the stopper 10 is retracted from hopper opening 11a so that casting proceeds at a particular speed and rate of steel flow. Should the pressure in pipe 8 exceed a particular value causing piston 13 to be actuated, stopper 10 drops and the steel supply is diminished or even interrupted.

A similar arrangement could possibly be provided for the control of the spray water flow. As shown in FIG. 2, a pressure responsive transducer 23 is connected to probe 8 responding to the pressure therein operating a control box 24 which in turn causes valve 12 to throttle the amount of water in case the steam pressure increases. If a threshold pressure value is exceeded, the spray water flow is turned off completely.

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included.

lclaim:

1. A method of supervising the continuous casting of steel tubes which are cooled in the interior during casting by spraying of water comprising the steps of:

measuring the pressure of the steam resulting from vaporization of the sprayed water, and

controlling the casting process in accordance with that pressure.

2. The method as set forth in claim 1 the control step including throttling of the water supply for spraying, upon sudden increase of the pressure.

3. The method as set forth in claim 1 the control of the casting process including the step of controlling the supply of liquid steel for the casting process.

4. Apparatus for supervising the continuous casting of steel tubes which includes means for cooling the cast tubes in the respective interior by spraying of water, comprising:

means for measuring the pressure of the steam resulting from vaporization of the sprayed water; and

means for controlling the casting process in accordance with that pressure.

5. Apparatus as set forth in claim 4, the means for measuring including a probing pipe extending into the interior of the cast tube.

6. Apparatus as set forth in claim 5, the probing pipe extending to a region adjacent an interior surface portion of the cast tube towards which water is sprayed.

7. In an apparatus for continuously casting a steel tube, the cast tube leaving a die cavity, there being means in communication with the interior of the cast tube during the casting process;

the apparatus further including means for spraying cooling water onto the inner surface of the cast tube, the improvement comprising:

first means in communication with the interior of the cast tube to be responsive to the pressure of developing steam in the tube; and

second means operatively connected to the first means to retard the casting process in response to development of pressure indicative ofa crack forming in the tube.

8. In an apparatus as set forth in claim 7 the second means including means for controlling the flow of liquid steel into the die cavity.

9. in an apparatus as set forth in claim 8, the means included in the second means stopping flow of liquid steel into the die cavity when the steam pressure exceeds a particular value.

10. In an apparatus as set forth in claim 7 including third means connected to the first means and responsive to the pressure in the tube to control the flow of water for spraying the interior of the tube.

11. In an apparatus as set forth in claim l0 the third means throttling the flow of spray water when the pressure exceeds a danger limit.

Claims

1. A method of supervising the continuous casting of steel tubes which are cooled in the interior during casting by spraying of water comprising the steps of: measuring the pressure of the steam resulting from vaporization of the sprayed water, and controlling the casting process in accordance with that pressure.

4. Apparatus for supervising the continuous casting of steel tubes which includes means for cooling the cast tubes in the respective interior by spraying of water, comprising: means for measuring the pressure of the steam resulting from vaporization of the sprayed water; and means for controlling the casting process in accordance with that pressure.

7. In an apparatus for continuously casting a steel tube, the cast tube leaving a die cavity, there being means in communication with the interior of the cast tube during the casting process; the apparatus further including means for spraying cooling water onto the inner surface of the cast tube, the improvement comprising: first means in communication with the interior of the cast tube to be responsive to the pressure of developing steam in the tube; and second means operatively connected to the first means to retard the casting process in response to development of pressure indicative of a crack forming in the tube.

11. In an apparatus as set forth in claim 10 the third means throttling the flow of spray water when the pressure exceeds a danger limit.