JPS5858960A - Production of hollow steel ingot - Google Patents

Abstract

PURPOSE:To produce superior hollow steel ingots having roughly uniform wall thickness in high yields by charging molten steel into a mold from below and drawing the formed solidified shell upward. CONSTITUTION:In a mold 2, molten steel 4 is charged therein from below, and is cooled with a cooling jacket 20. While the solidification of the steel 4 is under progression, a holding metal 8 is immersed into the steel 4 in the position where a solidified shell 6 forms, and the metal 8 is solidified and captured in the shell 6. At the point of the time when the prescribed shell 6 is formed, the metal 8 is pulled upward, and the shell 6 is removed easily from the inside of the mold 2. The replenishing of the steel 4 according to drawing of the shell 6 is accomplished by providing an intermediate vessel 12 below a ladle 10, and communicating the mold 2 and the vessel 12 with a bottom charging runner 14. The level of the molten steel in the mold 2 to be charged with the molten steel is maintained at a specified position easily by maintaining the level of the molten steel in the vessel 12 at the same level as the height of the specified position where the molten steel is charged in the mold 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a hollow steel ingot, and particularly to a method for manufacturing a hollow steel ingot that can be easily mass-produced.

Conventionally, hollow steel ingots have been manufactured by a centrifugal casting method or a core method. Centrifugal casting fLFi, bath 'A in cylindrical mold
This method uses centrifugal force to produce a hollow body by press-fitting the molten steel into a cylindrical mold and rotating it at high speed. This method is suitable for producing thin-walled hollow bodies, but in the case of thick-walled hollow bodies, segregation occurs. This promotes the density in the thickness direction.7) The open radicals of the cloth become large, causing quality problems.

In addition, the equipment cost is high, and the amount of melting per time is 1001
There is a drawback that installing casting equipment suitable for the above-mentioned large smelting furnace requires a large amount of equipment cost.

The core method is more suitable for manufacturing thick-walled hollow bodies than the centrifugation method, and the core method is suitable for manufacturing thick-walled hollow bodies. In this method, a water-cooled core that rotates once is provided, molten steel is supplied between the mold and the core, and after the solidified shell in contact with the core has grown to a certain extent, the core is continuously raised and pulled out. Furthermore, a metal plate core with a circular or irregular horizontal cross section is installed in the center of the cast lid, and the interior of the metal woven plate core is made hollow by water cooling, cooling gas injection, or filling with a radiant heat absorber. There is also a method of adjusting the coagulation conditions till the end.

These core methods have problems such as the complexity of core manufacturing and installation, poor surface quality of the hollow steel ingot, and cracks on the inner surface, and have drawbacks that make it difficult to say that it is a practical method suitable for mass production. .

An object of the present invention is to solve the problems of the prior art described above and to provide a method for manufacturing a hollow steel ingot without using a core.

The above objects of the present invention are achieved by the following two inventions.The gist of the first invention is as follows. That is, it is characterized by comprising the steps of injecting molten steel into the mold, and pulling the solidified shell upward when the desired solidified shell is formed by solidification from the mold wall. A method for manufacturing hollow steel ingots.

The gist of the second invention is to inject molten steel into a mold in the same manner as the first invention, and after drawing out the solidified shell, pour the molten steel into the mold in an amount corresponding to the amount of drop in the melt level in the mold due to the withdrawal of the solidified shell. 171. A method for producing a hollow steel ingot, comprising the steps of: injecting the steel into the mold; and repeating the vertical drawing and the injection of molten steel into the mold.

Conventionally, the method of producing hollow steel ingots by discharging unsolidified molten steel is well known, but since it is impossible to effectively utilize unsolidified molten steel without using special equipment, a hollow steel ingot manufacturing method using the discharging method has been adopted. could not be a practical method.The present inventors have extensively investigated these problems and have discovered a method that can effectively utilize unsolidified molten steel for manufacturing hollow steel ingots.

1. Hydraulics of the present invention is based on the idea opposite to the above-mentioned molten steel discharge method, and when molten steel is injected into a mold with a normal circular or rectangular cross section and the desired solidification thickness is obtained. In this method, instead of discharging molten steel, a hollow steel ingot consisting of a solidified shell is pulled upward from the mold at high speed. At this time, the level of the unsolidified molten steel remaining in the mold will drop to the extent that the solidified shell is pulled out, but molten steel equivalent to the amount pulled out will be added to form the next solidified shell. I can do it. If this method is used, it is not possible to economically manufacture a large number of hollow steel ingots by sequentially drawing out the solidified shells from one mold.

A feature of the present invention is that the solidified shell is pulled upward at high speed, thereby preventing solidification adhesion between the end face of the lower end of the solidified shell being pulled out and the unsolidified molten steel, and improving the surface quality of the solidified shell that is subsequently generated. It has an improving effect.

In order to pull the solidified shell upward, as shown in the attached drawing, while the molten steel 4 is solidifying in the mold 2, the holding fitting 8 is immersed from the upper part of the mold 2 into the molten steel at the position where the solidified shell 6 is generated. The holding fitting 8 is solidified and captured in the solidified shell 6. When the desired solidified shell 6 is formed, the solidified shell 6 can be easily taken out from within the leg mold 2 by pulling up the holding fitting 8.

Oxidized scales that form on the inner surface of hollow steel ingots are generally undesirable, although this varies depending on the purpose of opening the hollow steel ingot.These 7. It is possible to prevent IE from mkA by adhering to the inner surface of the solidified shell when the solidified shell is pulled out.

Note that a mold with a wide top is desired in order to facilitate upward drawing of the solidified shell used in the practice of the present invention.

In addition, in order to produce a large number of hollow steel ingots with a constant Mitt shell thickness from the same mold, it is necessary to keep the thermal conditions of the mold as constant as possible throughout the operation. For this purpose, it is desirable to use a mold made of copper, which has excellent heat conductivity, and is filled with water.

Reduces the friction between the mold and the solidified shell when drawing the solidified shell,
In order to facilitate high-speed drawing, the inner surface of the mold needs to be machined to have a smooth surface with no irregularities.From this point of view, a steel mold machined by 4m is preferable, and is effective in preventing thermal deformation of the mold. At this point, it is necessary to install sufficient water cooling equipment.

Regarding the molten steel replenishment method associated with solidified shell drawing, please refer to Bottom Pour K.
For this purpose, as shown in the attached drawing, an intermediate container 12 is provided below the Ml[10].
By making the molten metal level in the mold 2 the same as the injection position height in the mold 2, it is possible to easily set the injection position inside the mold 2 at the specified height.

Embodiments of the present invention will be described with reference to the accompanying drawings.

This example has a diameter of 300 mm, a wall thickness of approximately 60 wm, and a diameter of 200 mm.
This invention relates to the production of a 0+w hollow cylindrical steel ingot.

The inner diameter of the lower surface is 300 m on the cast iron surface plate 16, and the inner diameter of the F surface is 3.
A cylindrical steel mold 2 with a diameter of 40 mm is set upright, and a surface plate with a diameter of 16 mm is installed.
Set the runner brick 17 made of fireworks, and place the intermediate container 12.
A bottom pouring runner 14 between the mold 2 and the mold 2 was made. A slide-in cooling jacket 20 is provided between the intermediate container 12 and the bottom pouring channel 14 to control the amount of molten steel poured into the mold 2, resulting in a water-cooled structure. Refractory bricks 22 were embedded in the lower setting plate 16.

In the above device 11, C: 0.13chi, S i
: 025chi1, \ln :0.78%, P: 0.
018%, S: 0.008%, At: 0.035
% of the molten steel was injected into the intermediate container 12 from the weir @10, and at the same time as the injection of a predetermined amount of molten steel into the intermediate container 12 was completed, the sliding gate 18 was fully opened and molten steel #44 was injected into the mold 2.

At the same time, a holding fitting 8 for drawing out the solidified steel ingot from the upper surface of the mold 2 was inserted into the part of the mold 2 where the solidified shell was to be formed.It takes about 30 seconds to inject a predetermined amount of molten steel into the mold 2. did. After standing still for 240 seconds, the holding metal fitting 8 was pulled upward at a speed of about 500 xy' sec using a solidified shell pulling device, and the solidified shell 6 was taken out from the mold 2. At the same time, an amount equivalent to the solidified shell that has been pulled up is refilled into the mold 2 by making the level of the molten steel in the intermediate container 12 the same as the height of the fixed injection position in the mold 2, and a separately prepared holding metal fitting is used to replenish the mold 2. 8 was set on the top of M type 2 again. After being left still for 240 seconds, the solidified shell 6 was pulled upward at the same speed as the previous time using a pulling device, and the above operation of 0 or more was repeated 9 times to produce 9 hollow steel ingots. As is clear from the contents, the unsolidified molten steel could be used effectively during the process.

The ingot obtained by the above method, excluding the initial steel ingot, had an average wall thickness of 58.4 rm within the range of 56.8 to 60.3'-, and #'! ! was a hollow steel ingot with uniform wall thickness. The first steel ingot is removed from the mold 2 from the intermediate container IO, and because the mold 2 has not reached a steady temperature distribution.
Due to the large heat loss up to this point, the solidification rate within the casting W2 was large (the wall thickness was 58.5 to 61.3 m+).

Surface defects were observed with the naked eye on the surface and inner surface of the steel ingot, and it was found that there were no defects such as cracks, and a hollow steel ingot of sufficiently satisfactory quality could be obtained.

As is clear from the above examples, the present invention was able to produce excellent hollow steel ingots with a high yield and substantially uniform wall thickness using simple equipment and methods.

[Brief explanation of drawings]

The accompanying drawing is a sectional view of a casting apparatus showing an embodiment of the present invention. 2... Mold 4... Molten steel 6... Solidification fi 8... Holding metal fittings 12...
・Intermediate container 14...Bottom pouring runner agent medium
Takeo Michi

Claims (3)

[Claims] (1) It is characterized by comprising the steps of injecting molten steel into the mold, and pulling the solidified shell upward when the desired solidified shell is formed by solidification from the walls of the silent mold. A method for producing a hollow steel ingot. (2) A step of injecting molten steel into the mold, a step of pulling out the core solidified shell upward when the desired solidified shell is formed by solidification from the mold wall, and a step of pulling out the solidified shell K from the mold. A hollow steel ingot comprising the steps of: injecting molten steel into the core mold in an amount corresponding to the amount of drop in the melt level in the core mold; and repeating the solidified shell drawing and the injection of molten steel into the mold. manufacturing method. (3) The injection of the molten steel is performed by the bottom pouring method, an intermediate container is provided to accommodate the molten steel, the intermediate container and the mold are communicated through a bottom pouring runner, and the level of the molten steel in the intermediate container is raised. Manufacturing a hollow steel ingot according to claim 1 or 2, wherein the molten steel is injected to the same position in the mold by keeping the height the same as the height of the injection position in the mold. Method.