CS199235B2 - Equipment for manufacture of tubes with spiralshaped ribs by electroslag remelting - Google Patents

Abstract

1352815 Continuous casting; casting processes MITSUBISHI JUKOGYO KK 10 April 1972 [9 April 1971] 16474/72 Heading B3F A tube having internal and/or external longitudinal fins (the fins on the tube being either all spiral or all straight) is continuously cast with the use of a core 6 and mould 7 either or both being finned and the metal being provided by an electroslag arrangement, e.g. with consumable electrodes 5 of arcuate shape, Fig. 5(a), the molten metal being vibrated, as by vibrators 11 contacting a tubular starter 9. As shown in Fig. 6, the latter has internal spiral fins like those of a tube to be cast and with the cast tube it is rotated by a motor 16 and table 14 as a supportÀ ing plate 17 is lowered. If the fins are straight, withdrawal rolls extract the starter and casting. Cooling water passes to and from the mandrel 6 and mould 7 through pipes 8. At the start, molten slag 12 is retained in the tapered inlet of the cavity by the top of the starter 9 as shown. The top of the starter also melts when the metal melts. During casting, mushy slag forms a heatinsulating and lubricating layer between the metal and casting surfaces. The vibration of the metal facilitates filling of the casting cavity and imparts grain uniformity.

Description

The present invention relates to an apparatus for producing spiral rib tubes by electroslag remelting, in which molten metal is continuously fed into the mold and the solidified product is drawn at the lower end of the mold.

For the reaction of ammonia, hydrogen and petrochemicals, such as ethylene, at high temperatures, · cylindrical tubes are generally used. These tubes are also used in the treatment of these substances or in the recovery of the heat released by them, where the tubes convey the heat recovery medium inside by heat exchange and are heated externally. It is known that finned tubes are the most suitable for such purposes.

Since the temperature of the external heat source is to be as high as possible with respect to the highest thermal efficiency of the device, the tubes used for this purpose are today usually made of alloy steels which are characterized by good thermal stability. Produced from these materials. however, tubes of complex cross-sectional shapes using conventional methods, such as extrusion, are extremely difficult.

British Patent No. 1-250,910 discloses a process for making finned tubes suitable for forming alloyed steels using electroslag remelting and the molten metal in the mold is in the form of a solidified product at the other end of the mold. linearly pulled. This method has largely eliminated the shortcomings of the prior art. However, it is only applicable to pipes with a constant cross-section which can be achieved by linear pipe withdrawal. On the other hand, this known method and the devices designed for its implementation do not make it possible to produce helically wound tubes which, as is known, are even more effective than ribbed tubes of constant cross-section for increasing the heat exchange surface area of the tube. SUMMARY OF THE INVENTION It is therefore an object of the invention to develop the idea of the aforementioned British patent and to provide a device which makes it possible to produce tubes with spirally wound ribs.

The principle of the apparatus for producing spiral ribs by electroslag remelting, in which the molten metal is continuously fed into the mold and at the lower end of the mold, the solidified product is withdrawn, the apparatus comprising a cooled mold and a drawing table. According to the invention, the drawing table is supported at the same time - vertically displaceable and - rotating - around the axis of the withdrawn pipe, the total speed of the resulting downward movement of the drawing table being equal to the withdrawal speed of the pipe from the mold on a vertical helical path .

Such a device makes it possible, due to the helical pulling movement of the drawing table, to produce tubes with helically wound ribs as opposed to the straight running ribs of the linearly drawn tubes according to the prior art. The tubes manufactured on this device can be used for a variety of purposes, such as processing and reaction of petrochemicals, heat exchangers, boilers, heating radiators, etc.

The invention is explained in more detail with reference to the accompanying drawings, in which:

FIG. 1 shows an example of a tube made on the device according to the invention with external helically wound ribs, in cross-sectional view;

FIG. 2 shows an example of a tube made on the device according to the invention with internal helically wound ribs, also in cross-sectional view;

FIG. 3 is an axial section through an example of the apparatus of the invention for manufacturing the pipe of FIG. 2.

As can be seen from FIG. 3, the basic part of the device according to the invention is a mold 1, generally consisting of an outer mold part 2 and an inner core 3. As can be seen from the figure, the core 3 has a profile. corresponding to the internal profile of the pipe to be produced. In the part away from profile а — а to profile b — b, the core 3 taperes so that there is no more undulation at the location of profile b — b. The other part of the core 3 from the profile b-b towards the profile c-c is of a conical shape without undulating. Opposite to the profile a — a, the core 3 has a constant diameter, allowing the manufacture of the product of the desired dimensions in any cross section of this part, up to the profile a‘ — and ‘. In the section from the profile α-a to the profile d-d, the core 3 has a conical shape as shown in the figure.

With respect to the inner surface of the outer mold part 2, the portion of the profile b-b to the profile s-c at the upper end towards the apex has a cross-section which gradually increases. The part between the profile b-b and the profile d-d is regularly cylindrical and the inner diameter of the outer mold part 2 is adapted in this part to the outer shape of the article.

Both the core 3 and the outer mold part are made of copper and are provided with cooling tubes 4, 6 for water cooling. The core 3 and the outer mold part 2 are arranged coaxially and constructed such that the profile of the formed finned tube with the desired corrugation of the inner surface is formed by the gap defined by the core and the outer mold part 2. The core 3 and the outer mold part 2 are supported of sufficient height to produce a tube of the desired length, each of the two mold parts maintaining their fixed position. For example, the outer mold part 2 is supported on the stand support 5 and the core 3 is carried by a water cooling tube 4 attached to its top.

A trigger tube 7 is inserted into the gap between the outer mold part 2 and the core 3 by means of which the formation of the pipe to be produced is initiated. This trigger tube 7 is screwed into the part of the gap between the two mold parts 1 which lies between the profile a-a and the profile b-b.

The purpose of this tube is to pull out the product that is formed above it while descending and rotating about its own axis. Therefore, the device according to the invention has a rotation mechanism comprising a drawing table 8, a reduction gear 9, a drive motor 10 and a drawing base 11 for moving the product downward at a speed corresponding to the drawing speed.

The ribbed tubes of FIG. 1, which have a corrugation on their outer surface, are manufactured on a similarly designed device, with the variation that the core 3 has a cylindrical shape and the outer mold part 2 is provided with a rib corrugation on the inner surface.

The device according to the invention functions as follows. A power supply source 13 is connected to the electrodes 12 of the tube-forming metal disposed in the upper part of the mold 1 and introduced from above into its cavity. The resistive heat induced by the electrical resistance of the slag 14 then causes a phenomenon called electroslag melting, which melts the end of each electrode 12 to form spheres of molten metal. The balls descend with the molten slag 14 to the upper end of the trigger tube 7. The upper end of the trigger tube 7 and its adjacent part also melts as a result. Thus, the balls accumulate between the profile a-a and the profile b-b, forming the annulus of the tube formed.

As the melt bath gradually increases in volume, the trigger tube 7 is pulled in a helical motion by means of a draw table 8 at a controlled speed downwards. With the gradual lowering of the tube 7, the gap between the core 3 and the outer mold part 2 is simultaneously filled with melt, with the vibrating effect of the vibrators 15 assisting the downward passage of the melt balls. contact with the walls of the mold gradually solidifies, so that at the bottom of the mold 1, a stiffened tube with spirally wound ribs is gradually withdrawn by the trigger tube.

Claims (1)

object of the invention Apparatus for producing spiral rib tubes by electroslag remelting, wherein molten metal is continuously fed into the mold and a solidified product is drawn at the lower end of the mold, the apparatus comprising a cooled mold and a drawing table, characterized in that the drawing table (8) is The total speed of the resulting downward movement of the drawing table (8) from the mold (1) is equal to the speed of the withdrawal of the pipe from the mold (1) on a vertical helical path.