JPS5823536A - Production of double layered hollow steel ingot - Google Patents

Abstract

PURPOSE:To produce a double layered hollow steel ingot having excellent adhesive strength by placing a mold and a steel pipe which forms an inner layer for a double layered hollow steel ingot on a molding board, constituting a flow passage for a cooling gas in said steel pipe, and charging the molten steel for forming an outer layer between the mold and the steel pipe by bottom pouring. CONSTITUTION:A mold 2 is placed on a molding board 1, and the 1st steel pipe 6 of>=5mm. thickness for forming an inner layer of a composite hollow steel ingot is erected in the central part of the mold 2. The 2nd steel pipe 7 and the 3rd steel pipe 9 are provided concentrically in the pipe 6 to form a flow passage 4 for a cooling gas, whereby a core 3 is formed. A refractory material 8 is packed between the pipe 6 and the pipe 7 and a hydrocarbon type resin 12 is coated on the outer side of the pipe 6. Molten steel 13 for forming an outer layer of the double-layered hollow steel ingot is charged into the spacing between the mold 2 and the pipe 6 through the sprue 14 of the board 1 by bottom pouring. The steel 13 charged therein is cooled with the board 1, the mold 2 and the core 3 having the passage 4, whereby the steel is solidified. Thus the double- layered hollow steel ingot consisting of the pipe 6 as the inner layer and the steel 13 as the outer layer and having good adhesive strength is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a multi-layer hollow steel ingot, and more particularly to a method for producing a multi-layer hollow steel ingot that allows inner-coated steel materials to be produced at low cost.

The reaction vessels and transport pipes of chemical reaction plates are made of stainless steel or other highly corrosion-resistant steel coated on the inside. Currently, these coatings are made by welding, but the manufacturing cost is very high.

Also, as a method for manufacturing conventional internally coated steel materials.

In addition to the sensuous welding method, there are rolling methods, explosive crimping methods, and methods for manufacturing multilayer steel ingots, but all of them have drawbacks such as problems with the adhesion between multilayer metals and high manufacturing costs. Ta.

An object of the present invention is to solve the problems of the prior art and to provide a method for manufacturing a multi-layer hollow steel ingot, which can produce internally coated steel materials at low cost.

The gist of the present invention is as follows.

In other words, place the bottom pouring mold on the surface plate! RN and
erecting a first steel pipe with a thickness of 5 mm or more made of the inner layer of the laminated hollow steel ingot in the center of the mold; and erecting a concentric second steel pipe inside the first steel pipe, and filling the gap with a refractory material; further inside the second steel pipe, a concentric third steel pipe having a connection KrIIUii with the surface plate is erected, and the third steel pipe is lowered from its upper part to form a gap with the second steel pipe; forming a cooling gas flow path for ascending the first steel pipe; coating the outside of the first steel pipe with a hydrocarbon-based or fluorocarbide-based resin; FIG. 1 shows a longitudinal cross-sectional view of a mold apparatus for producing a multi-layer hollow steel ingot according to the present invention. It is a diagram. That is, the casting lid device in the method of the present invention includes a bottom pouring mold 2 placed on a surface plate 1, a core 3 placed in the center of the casting 112, and a mold provided inside the round of the core 3. It is composed of a core cooling gas flow path 4. These cores 3 and core cooling gas passages 4 are placed in the casting 11 so that they do not float in the molten steel.
It is fixed to the upper end of 2 by a support fitting 5.

In the method of the present invention, first, the bottom pouring casting m2 is placed on the surface plate 1, and then the first steel pipe 6, which is the outermost layer of the core 3, is erected in the center of the mold. This first steel pipe 6 is the core of the present invention, and has the composition of the inner layer of the target multilayer hollow steel ingot, and has a thickness of 5 m or more. A second steel pipe 7 is installed concentrically inside the first steel pipe 7, and the connection between the first steel pipe 6 and the i-th steel pipe 7 is filled with a refractory material 8 such as foundry sand.

The core cooling gas passage 4 provided inside the core 3 is formed using a third steel pipe 9 provided further inside the second steel pipe 7 and concentrically therewith. That is, a gap 1110 is provided between the lower end of the third steel pipe 9 and the surface plate l, and a gap 1110 is provided between the lower end of the third steel pipe 9 and the surface plate l.
1f: 413 is introduced above the steel pipe 9, descends through the third steel pipe 9, passes through the interface with the surface plate 1, rises between the second steel pipe 7 and the third steel pipe 90, and is discharged upward. The inner side 1 of the second steel pipe 7 forms the core cooling gas flow path 4 as a whole.
A hydrocarbon-based or hydrogen fluoride-based resin 12 is coated or pasted on the outer surface of the zero-order first steel pipe 6, which cools the core 3 by cooling.

Note that all of the above operations do not necessarily need to be performed within the mold. Second. It goes without saying that the core structure formed by the third steel pipes and the refractory may be manufactured in advance as a single piece, and then placed upright in the mold.

After the preparation of the mold apparatus is completed as described above, the molten steel 13 having the composition that will become the outer layer of the desired multilayer hollow steel ingot is cast! l! 1 and the first steel pipe 6. The molten steel 13 is poured by the bottom pouring method, which causes less fluctuation of the molten metal surface during pouring and less risk of breaking the core 3. Therefore, the upper sprue 14 of the annular molten steel 13 in the surface plate 1 is placed in the mold 2. and the first steel pipe 60.

When injecting molten steel 13, as shown in FIG.
The hydrocarbon or fluorocarbide resin 12 coated on the outer surface of the mold is injected into the casting 112 through the upper sprue 14, heated by the steel 13, and releases gas 15 by thermal decomposition. Due to the movement of the hot water caused by the gas 15, the scum 16 floating on the hot water surface is kept away from the surface of the core 3, and does not become a drop. Furthermore, the released gas 15 creates a non-oxidizing atmosphere above the molten metal near the first steel pipe 6, thereby preventing contamination of the molten steel by oxidation. The thicker the resin 12 is, the larger the amount of gas generated is, so it is preferable to round it, but in practice, Q, 1 wA or more is sufficiently effective.

The molten steel 13 poured into the mold 2 is cooled and solidified by the core 3 having a surface plate 1, a casting mold, and a core cooling gas passage 4. Air nitrogen, albo/etc. are usually used as cooling gas.

In this way, the outer layer of the core 3'rjHOK1 steel pipe 6 is used as the inner layer.

A multilayer hollow steel ingot is formed with the injected molten steel 13 as an outer layer, and due to the effect of the resin 12 coated on the outer surface of the all steel pipe 6), the outer surface of the first steel pipe 6 and the solidified molten steel are completely welded, and the solidified molten steel is completely welded to the outer surface of the first steel pipe 6. It is possible to obtain a multi-layer hollow steel ingot that does not contain harmful impurities at the boundary.

The material or composition of the first steel pipe 6 is the one required for the inner coating material of the 11-grade steel material, so if corrosion resistance is required, stainless steel is selected as the material for the first steel pipe 6. When ordinary steel is cast, a multi-layer hollow steel ingot is produced in which the inner layer is stainless steel and the outer layer is ordinary steel.
If this is further pipe-formed, a normal steel pipe whose inner surface is coated with stainless steel can be obtained.

The thickness of the #11 steel pipe 6 is not only not eroded during the injection of the molten steel 13, but also not removed by oxidation when the multilayer hollow steel ingot is heated into a round shape by hot working such as forging, rolling, or drawing. In addition, the thickness of the remaining portion after processing deformation and cutting must be greater than the thickness required as the inner coating layer thickness of the product steel material. Oxidation loss during heating varies depending on the material.

The amount of processing deformation and cutting varies depending on the shape and weight of the product and the processing ratio from the steel ingot to the product, so the first steel pipe 6
Although the thickness cannot be determined uniformly, it is possible to ensure a minimum thickness of 3 cm due to oxidation, a minimum thickness of 1/2 due to processing deformation, and a minimum inner coating layer thickness of 1 cm without cutting the inner surface. The thickness of the first steel pipe 6 is required.

Next, the upper limit of the thickness of the first steel pipe 6 must be such that it has enough plasticity to absorb the solidification shrinkage of the outer layer of the steel ingot, which is a requirement for manufacturing multilayer hollow steel ingots (1), and has sufficient heat capacity. It is determined from the relationship with the weight of the steel ingot within a small range where the temperature rises easily. For example, as a result of testing a 200 tt steel ingot, it was found that if the thickness was 50 m or more, radial cracks would occur on the inner surface of the ingot, making it unsuitable for use as a hollow steel core. is desirable.

As described above, the method of the present invention produces a nine-layer hollow steel ingot with excellent e-layer properties by using the first steel pipe as the outer surface of the core during injection of molten steel and finally as the inner layer of the multi-layer hollow steel ingot. be able to.

Example 1 The outer layer is a steel pipe with a thickness of 25 cm and the composition shown in Table 1.
A core with a diameter of 2000 m+ was installed using the method of the present invention, and the thickness was 0.
．． A multilayer hollow steel ingot with an outer diameter of 760 wwn, a body height of 2900 wwn, and a total weight of 2001 mm including a boiler was manufactured by pasting a 2 m long fluorocarbon resin film and casting molten steel having the composition shown in Table 1. Next, this medium steel ingot was forged and the outer diameter was 4.235.
mm, inner diameter turtle 265 kaku.

Table 1: A cylindrical steel material with a length of 409m-v was manufactured, and the condition of the coating layer was investigated.As a result, the thickness of the entire inner surface of the steel material was 7mm.
It was confirmed that the coating layer No. 5- was formed in a completely defect-free state.

The method of the present invention is clear from the above examples.

By using the outer layer of the core as the inner layer of a multilayer hollow steel pile, it was possible to produce a multilayer hollow steel ingot with good adhesion at a low cost.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a casting apparatus according to the present invention immediately after injection of molten steel, and FIG. 2 is a partially enlarged schematic sectional view of the casting apparatus illustrating the liquid level situation during injection of molten steel according to the present invention. l... Surface plate 2... Mold 4... Cooling gas flow path 6... First steel pipe 7... $
2 steel pipe 8... refractory material 9... third steel pipe
10... Gap for gas flow path 12... Resin
13... Molten steel agent Takeo Nakaji Figure 1 Figure 2

Claims (1)

[Claims] (1) placing a bottom pouring mold on a surface plate, and erecting a first steel pipe with a thickness of 5 m or more made of the composition of the inner layer of a multilayer hollow steel pipe in the center of the mold; A concentric second steel pipe is erected inside the first steel pipe and a refractory material is filled in the joint 11 between the two, and a concentric second steel pipe having a gap between the surface plate and the second steel pipe is further inside the second steel pipe. 3. A step of erecting a #11 steel pipe, descending from the top of the pipe, and forming a cooling gas flow path rising through the gap with the #11 steel pipe; and a step of under-pouring molten steel having a composition that will become the outer layer of the multi-layer hollow steel ingot into the space formed by the mold and the first steel pipe. A method for producing multilayer hollow steel ingots.