JPS61238974A - Manufacture of composite pipe - Google Patents

Abstract

PURPOSE:To reduce the amount of FeO remaining in produced ceramics when a thermit reaction is causes in a rotating mother pipe to form produced layers in the pipe, by substituting Cr or Mn oxide for part of iron oxide in a thermit agent used. CONSTITUTION:An oxide such as Cr2O3, MnO2 or MnO is substituted for part of iron oxide (FeO or Fe3O3) in a thermit agent. The amount of the oxide substituted is 5-30%. The resulting thermit agent is put in a mother pipe in the form of a layer and ignited in the field of centrifugal force to cause a thermit reaction. The iron oxide is preferentially reduced by the thermit reaction.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an improvement in the manufacturing method of a composite tube in which a metal layer and a ceramic layer are integrally coated on the inner surface of the mother tube by a thermite reaction. This is to reduce the amount of FeO that inevitably remains.

(Prior art) Composite tubes made by coating the inner surface of the mother tube with a ceramic layer are suitable for use as transportation tubes for various fluids and for industrial use because the ceramic layer exhibits good properties such as heat resistance, abrasion resistance, and corrosion resistance. It has common uses as a piping member.

As a manufacturing method for this kind of composite pipe, for example,
The so-called centrifugal thermite method, which utilizes centrifugal force and thermite reaction, has been proposed as disclosed in Japanese Patent Publication No. 40219, Japanese Patent Publication No. 59-27747, and the like.

The content of this centrifugal thermite method is to apply alumina (^901) to the inner surface of a cylindrical tube made of iron or iron alloy, such as a steel tube, by utilizing the thermite reaction between aluminum and iron oxide.
An overview of the ceramic layer that is integrally coated is that the inner surface of a metal frame that can be rotated at high speed is coated with a mold release agent in advance to prevent the metal cylindrical tube from seizing and to provide resistance when taking out the product. Place a metal cylindrical tube with an outer diameter slightly smaller than the inner diameter of the metal frame, that is, a mother tube, and insert it into the metal frame.
Both ends of the main tube in the axial direction are supported by bands (holding lids) fixed to the metal frame side, and aluminum (81), iron oxide (Fez 11) or Fe3.04) powders or particles are placed inside the main tube. A thermite agent consisting of a mixture of a certain ratio is spray-loaded through the center hole of the band, and is ignited in the centrifugal field caused by the high speed rotation of the metal frame to induce the known thermite reaction.This exothermic reaction produces thermite. Molten metal (
Fe) and molten ceramics (A I2x Os ) are separated by specific gravity, and the inner surface of the main tube is integrally coated with a ceramic layer via a metal layer.

(Problems to be Solved by the Invention) However, the conventional centrifugal thermite method has the following problems.

In the conventional manufacturing method described above, the produced ceramic becomes extremely porous if only a normal thermite agent is used, so a densification aid such as silicic acid (SiOz) is added to a maximum of about 10-odd percent to prevent it from becoming porous. In other words, densification is being achieved. However, due to the rapid cooling process from instantaneous melting to solidification due to thermite reaction, Fez Ox (Fe3.04) is not completely reduced in the thermite agent, and a considerable amount of Fez Ox (Fe3.04) is inevitably contained in the resulting ceramics. FeO components remain. This FeO component exists in the grain boundaries of alumina, and when exposed to, for example, high-temperature acidic hot water, FeO gradually dissolves and corrosion progresses over time. In order to obtain good thermal and chemical properties, it is essential to reduce this FeO.

(Means for Solving the Problems) In order to reduce the amount of FeO that inevitably remains in the produced ceramics, the present invention charges an iron oxide-based thermite agent in the mother tube, and uses the thermite in a centrifugal force field. In the method for manufacturing a composite tube in which the inner surface of the mother tube is integrally coated with a metal layer and a ceramic layer generated by the chillmint reaction by igniting the agent layer to cause a chillmint reaction, the iron oxide ( Fez 01 or F
e304) and Cr, which is slightly less reducible than Cr
It is intended to manufacture a composite tube using a thermite agent substituted with an oxide such as 20t, Mn01Mn0z, etc.

(Function) When the thermite reaction is carried out, iron oxide is preferentially reduced, and then oxides other than iron oxide are reduced.

(Example) A part of the iron oxide of the thermite agent used in the present invention is Cr201, Mn
Examples include O, Mn0t, etc.

Here, the composition ratio of the oxide to be reduced in the thermite agent is:
According to the experimental results of the present inventors, iron oxide is 70 to 95% by weight.
, 5 to 30% by weight of the front oxide is preferred. In this way, when a thermite agent is prepared by mixing a predetermined amount of Af and the oxide to be reduced, and a thermite reaction is caused by the known centrifugal thermite method, the easily reduced iron oxide in the oxide to be reduced is preferentially reduced. As a result, the amount of FeO remaining in an unreduced state in the produced ceramics could be significantly reduced. In addition, during implementation, oxides such as Cr201 and M
Compared to Pe5o1, nO□ has a lower calorific value during the chillmint reaction and tends to be somewhat lacking in heat, so to compensate for this, oxidizing metals such as octaβ, Mg, and St are added to the blending system. It is best to add a little too much.

Specific examples of the present invention will be shown below.

Example 1> Diameter 101', 6 * x φ x thickness 4.2 + ux length 250 * Fe20 in x steel pipe): 1076 g
, Cr; 401: 266 g (20% of the oxide to be reduced), ^It: 512 g, SiO□: 3
A thermite agent consisting of a mixture of 6 g was spread to a substantially equal thickness, and the thermite reaction was induced under rotation of 100 G.

The FeO content in the resulting ceramic was 5.1%.

<Example 2> Fez Oy: 1278 g, Mn0t: 6 in a steel pipe with diameter 101.6+nx thickness 4Jmx length 25On
4g (5% of the oxide to be reduced), A7! : 458
g, Si: A thermite agent consisting of a mixture of 40 g was spread in a substantially equal thickness, and a thermite reaction was induced under high speed rotation of GNoloo.

FeO contained in the obtained ceramic was 4.7%.

<Comparative Example> After carrying out a thermite reaction under the same conditions except that CrzO) was not mixed in the thermite agent in Example 1 and MnO□ was not mixed in Example 2, the amount of FeO in the ceramic was investigated. However, the former was 12%;
The latter was 17%.

(Effects of the Invention) The present invention is a method of inducing a thermite reaction in a main tube rotating at high speed and forming a ceramic layer in the main tube. By replacing it with a specific oxide, it was possible to reduce the amount of FeO that inevitably remained in the produced ceramics, and as a result, it was possible to provide a composite tube with good thermal and chemical properties.

Claims (1)

[Scope of Claims] 1. By loading an iron oxide-based thermite agent into the main tube and igniting the thermite agent layer in a centrifugal force field to cause a thermite reaction, a thermite reaction is generated on the inner surface of the main tube. In the manufacturing method of a composite tube in which a metal layer and a ceramic layer are integrally coated, a part of the iron oxide (Fe_2O_3 or Fe_3O_4) of the thermite agent is replaced with Cr_2O_3, MnO, which is slightly less reduced.
A method for manufacturing a composite tube, characterized in that a thermite agent substituted with an oxide such as , NnO_2, etc. is used. 2. The method for manufacturing a composite pipe according to claim 1, wherein the amount of the metal oxide that is difficult to reduce is 5 to 30%.