JPH0151330B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing an insulating corrosion-resistant tube, and in particular, a method of manufacturing an insulating corrosion-resistant tube, and in particular, a method of manufacturing an insulating corrosion-resistant tube, and in particular, a method of manufacturing an insulating corrosion-resistant tube, and in particular, a method of manufacturing an insulating corrosion-resistant tube. - This invention relates to a method of manufacturing an insulating corrosion-resistant pipe in which a coating layer is formed of an inorganic composite material made of mica plastic.

[Prior art]

Glass-mica plastics are made from a mixture of vitreous powder and mica powder, heated to a temperature where the glass in the raw material softens and flows under pressure, and then pressurized in the heated state. An inorganic composite material obtained by molding, which will be detailed later, is an insulating and corrosion-resistant material.

In petroleum-related or chemical factories, gases or liquids that hardly corrode metals at room temperature but corrode rapidly when the temperature rises are transported in metal pipes at room temperature, but the temperature is increased during transport.
Since extremely high transport efficiency can be obtained by raising the temperature to 200 to 300°C, there is a demand in various places for metal tubes whose outer peripheral surfaces are coated with insulation for safety reasons. In order to meet the above requirements, in order to ensure mechanical strength, insulating corrosion-resistant pipes (hereinafter referred to as Corrosion-resistant pipes) are required. Much research has been conducted to obtain such corrosion-resistant tubes. The main ones are as follows.

First, there is one in which a coating layer of a heat-resistant organic material is formed on the inner and outer peripheral surfaces of a metal tube. Among heat-resistant organic materials,
Teflon or peak resins have extremely excellent properties in terms of heat resistance and corrosion resistance, but when the operating temperature rises, the coating layer expands and deforms due to the essential difference in the coefficient of thermal expansion, leading to a peeling phenomenon. do. Incidentally, the coefficient of thermal expansion of the organic material is at least 5 to 10 times that of the steel pipe.
As mentioned above, all of the above organic materials cannot be used because their unavoidable characteristics become fatal defects.

Next, regarding inorganic materials, the one that is considered to have the greatest potential is steel pipes coated with enamel.
When applying enamel coating to steel pipes, it is essential that the enamel glaze has a coefficient of thermal expansion of 10.5 to 12.0×10 ^-6 . In order to achieve the above coefficient of thermal expansion, it is necessary to use a composition containing a large amount of oxides of alkali metals such as lithium, potassium, and sodium. This enamel material is used for tableware etc.
It has considerable corrosion resistance against water at around 100℃, but when the hot water temperature exceeds 100℃ and it is an acidic liquid, its corrosion resistance properties decrease rapidly, resulting in a fatal flaw in corrosion resistance. be.

As mentioned above, the reality is that none of the conventionally known materials can be used.

In this regard, corrosion-resistant pipes with glass-mica plastic bodies formed as coating layers on both the inner and outer circumferences can be used at temperatures up to 200°C.
Even at temperatures up to 300℃, there is no deformation or peeling phenomenon, and the glass-mica plastic body itself contains 50-70% by volume of mica powder, which has extremely excellent corrosion resistance properties. Therefore, it has extremely excellent corrosion resistance in terms of hot water resistance, acid resistance, alkali resistance, etc., as well as high electrical insulation properties.Furthermore, it is possible to form a thick coating layer, and it is non-porous. , it is ideal as a coating layer material for corrosion-resistant pipes used for the above purpose.

However, such corrosion-resistant pipes have a fatal defect in that long products cannot be obtained using conventional manufacturing methods.

Below, the characteristics of the glass-mica plastic body and the conventional manufacturing method of corrosion-resistant pipes will be explained. First of all, glass
The characteristics of mica plastic bodies are largely controlled by the characteristics of the raw material glass used. For example, in terms of heat resistance, if a glass material with a transition temperature of about 400°C is used, it will not change even at a temperature of about 300°C, and its electrical and mechanical strength will also hardly change. Maintains the same characteristics as at room temperature. Furthermore, the coefficient of thermal expansion has a large influence, and by changing the properties of the glass, a coefficient of thermal expansion of 8 to 11×10 ^-6 can be obtained. Furthermore, there is a close relationship with respect to corrosion resistance properties, and there are many advantages such as the ability to improve the corrosion resistance properties by using glass itself that is highly corrosion resistant.

Next is the raw material mica. Natural mica contains crystal water and has a low thermal decomposition temperature, and there are many varieties.
Since it is difficult to obtain a product with stable characteristics, it is not preferred as a raw material mica. On the other hand, synthetic mica does not have this tendency, has a high heat resistance, and is easy to obtain products with stable characteristics. Therefore, synthetic mica powder is used exclusively, and synthetic fluorine-containing gold mica is particularly suitable. .

Now, a corrosion-resistant tube obtained by a conventional manufacturing method and having a coating layer formed of glass-mica plastic material on both the inner and outer circumferential surfaces will be explained with reference to FIG. In Fig. 1, a corrosion-resistant tube A includes a metal tube 1, an inner circumferential coating layer 2, and an outer circumferential coating layer 3.
Consists of.

Next, a conventional manufacturing method will be explained with reference to FIG. A mold is used for manufacturing. The molding die includes a frame 4, a divisible wall portion 6 having a raw material loading chamber 5 at the top, a support metal 7 having a convex portion 7-1 for holding a core metal fitting 9 and a metal tube 1 in the center, and a processing die. It is composed of four parts of the pressure metal 8.

The raw material glass has a composition of PbO: 70, B ₂ O ₃ :
16, SiO ₂ : 14W% with a dislocation temperature of 400℃
Use by crushing into 200 pieces. Raw material mica is
Use synthetic fluorine-containing gold mica powder with a particle size of 60 to 100 mesh. Mix 50W% of such glass powder and 50W% of mica powder to prepare raw material powder,
Approximately 5W% of moisture was added to this mixed raw material powder to make it moist, and it was formed into a cylindrical body that could be loaded into the raw material loading chamber 5 by cold pressing (the mold is not shown), and then dried to remove the moisture. It is used as a preform 10.

The molding is carried out by assembling the frame 4, wall part 6 and support metal 7 in a mold as shown in FIG.
is heated to 550℃ without assembly, and core metal fitting 9 and metal tube 1 are heated to 550℃ without assembly.
is heated to 600°C, and the preform 10 is heated to 800°C. When heating is completed, the core metal fitting 9 and the metal tube 1
is loaded onto the support 7 within the wall 6, and then the preform 10 is loaded into the raw material loading chamber 5. The state at this time is shown in FIG. 2a. Next, the pressure metal 8 is placed on the preform 10, and a pressure molding machine (not shown) is used.
The pressurized metal 8 is pressurized and the preform 10 is press-fitted into the space 11 constituted by the metal tube 1 and the core fitting 9 and the space 12 constituted by the metal tube 1 and the wall 6 to form the inner peripheral coating layer 2 and The outer peripheral coating layer 3 is formed. The state at this time is shown in FIG. 2b. Covering layer 2, 3
temperature is 380℃ (lower than the transition temperature of glass)
The molding die is disassembled, the molded product is taken out, and the core fitting 9 is removed by machining to form the corrosion-resistant tube A shown in FIG. 1 to complete the manufacturing process.

However, when using the above-mentioned conventional manufacturing method, ideal characteristics can be obtained for corrosion-resistant tubes A with a short length, but it is not possible to manufacture ideal characteristics when the length is long. There was an unavoidable fatal flaw. The reason for this will be explained below. The raw material, a mixture of glass and mica powder, has extremely high viscosity even when heated, and this viscosity is largely controlled by temperature, decreasing as the temperature rises and rapidly increasing as the temperature decreases. . In addition, if the heating temperature of the preform 10 during molding is increased, the viscosity will be lowered, but as the temperature rises, the erosion of the vitreous mica becomes more intense, so there is naturally a limit to the heating temperature, which is 800 to 850°C. is the limit. The temperature of the molding die is also related to mechanical strength, and is limited to 550°C. During pressure molding, the preform 10 pressurized by the presser metal 8 flows into the spaces 11 and 12, but the leading end contacts the core metal fitting 9, the metal tube 1, and the wall portion 6. As it flows, its temperature decreases. Then, as the temperature decreases, the viscosity increases rapidly, the fluidity deteriorates, and the length of the product becomes longer.
1 and 12-1 are not completely filled with the preform 10, and the density does not increase. Therefore, uniform inner and outer coating layers 2 and 3 could not be obtained.

Since the above phenomenon was unavoidable in the conventional method, a long product could not be obtained, and a process of cutting and removing the core metal fitting 9 of the molded product by machining was required, which required a considerable amount of effort. This was one of the major flaws, as it required a rise in price.

[Summary of the invention]

This invention was made with the aim of solving the various problems in the conventional manufacturing methods as described above, and includes a lower metal plate having a divisible lower metal plate and a raw material loading chamber with a through hole formed in the horizontal direction. A preforming mold is used, and a molding jig that has a core metal with a tapered outer periphery and holds a metal tube is used.The molding jig is fitted into a through hole, and the preforming is loaded into a raw material loading chamber. The preform is pressurized and made to flow in the heated state of a body, a mold for molding, a jig for molding, etc., and a glass-mica plastic body is formed on the inner and outer peripheral surfaces of a metal tube in which an inflow path and a discharge path are formed. The present invention provides a method for manufacturing an insulating corrosion-resistant tube that enables manufacturing of a long corrosion-resistant tube by forming a coating layer, eliminates the need for machining, and realizes a reduction in price.

[Embodiments of the invention]

First, the molding die used in this manufacturing method will be explained with reference to FIGS. 3a and 4a. The molding die is composed of a molding part B and a pressurizing metal C. The molding part B consists of a stack of three parts: an upper metal 13, a lower metal 14 divided into an upper part 14-1 and a lower part 14-2, and a base metal 15, and each contact surface is a preformed body 16 under pressure. Manufactured to prevent leakage. Upper gold 13
A rectangular parallelepiped raw material loading chamber 17 is provided in the upper part of the raw material loading chamber 17, and a plurality of oblong outflow passages 18 are provided in the lower part of the raw material loading chamber 17, penetrating from the bottom of the raw material loading chamber 17 to the lower surface thereof. Figure 3a
In the embodiment shown in , nine outflow passages 18 are provided. The lower metal 14 has an upper part 14-1 and a lower part 14-
A through hole 19 is formed in the lateral direction centering on the contact surface of 2.
The upper part 14-1 has the same shape and the same number of filling passages 20 communicating with the outflow passage 18 of the upper metal 13, reaching the through hole 19, and the lower part 14-2 has a rectangular reservoir 21.
However, a plurality of oval flow passages 22 reaching the through hole 19 are provided in the upper part of the reservoir 21 . In the embodiment shown in FIG. 3, nine flow passages 22 are provided.

The base metal 15 is arranged at the bottom of the lower metal 14 and the reservoir part 21
The upper metal plate 13 and the lower metal plate 14 are fixed to each other. The pressurizing metal C is adapted to fit into the raw material loading chamber 17.

Next, the forming jig D for holding the metal tube 23 will be explained with reference to FIG. The outer diameter of the metal tube 23 is smaller than the inner diameter of the through hole 19 of the molding die, and the metal tube 23 is arranged so as to face the flow path 22 of the lower mold 14 in one direction.
The same number of discharge passages 24 are provided, and the number of inflow passages 25 is fewer than the filling passages 20 so as to face the filling passage 20 of the lower metal 14 in the facing part, and in the case of this embodiment, there are nine discharge passages 22. , five inflow passages 25 are provided. The material of the metal tube 23 may be any material as long as it maintains mechanical strength to withstand pressure when heated to about 500° C., and a steel tube is preferable.

26 is a metal core, which has a center hole 27 and a tapered outer circumference 28, and the outer diameter of the thick part is the same as that of the metal tube 23.
It is smaller than the inner diameter of. The constituent material used must have a coefficient of thermal expansion (in this case, coefficient of thermal contraction, hereinafter referred to as coefficient of thermal expansion) that is larger than the coefficient of thermal expansion of the glass-mica plastic body (coefficient of thermal expansion below the transition temperature of the raw glass). , stainless steel, copper alloy, etc. are preferably used. Reference numeral 29 denotes a side plate, the outer diameter of which is sized to fit into the through hole 19 of the molding die, has a center hole 30, and a convex portion for holding the metal tube 23 and the core bar 26 in the center. A section 31 is provided. There are no particular restrictions regarding the material. 32 is a bolt, and its constituent material has a thermal expansion coefficient of glass.
A material smaller than a mica plastic body is used, and titanium or the like is preferable. 33 is a washer, which may be a disc spring or a spring washer, a core bar 26, and a metal tube 2.
Used to assemble without applying strong tightening pressure to 3. 34 is Natsu.

The following molding jig D is assembled and used by holding the core bar 26 and the metal tube 23 at the center, as shown in FIG.

Next, the manufacturing process will be explained. The raw materials used are the same as those used in the conventional manufacturing method, and first, a preform 16 that can be loaded into the raw material loading chamber 17 is prepared.
Prepare.

For molding, the integrated molding part B and pressurizing metal C are 550 mm
The molding jig D is heated to 500°C, and the preform 16 is heated to 800°C. When the heating is completed, the molding jig D holding the metal tube 23 is moved so that the inflow path 25 is connected to the filling path 20 and the discharge path 24 is connected to the flow path 22.
It is fitted into the through hole 19 of the lower metal part 14 so as to face it.

Next, the preform 16 is loaded into the raw material loading chamber 17. The state at this time is shown in FIGS. 3a and 4a.

Then, the pressurized metal C is placed on the preform 16,
Pressure molding machine (not shown) pressurizes the pressurized metal C to cause the preformed body 16 to flow. Preformed body 1
6 passes through the outflow path 18 and the filling path 20 and reaches the space 35 formed by the metal tube 23 held in the molding jig D, the side plate 29, and the wall of the through hole 19, and a part of it passes through the inflow path. 25 and reaches a space 36 formed by the core bar 26, the side plate 29, and the metal tube 23. The flowing preform 16 further includes a metal tube 23 and a core bar 2.
Proceed by branching left and right along the surface of 6, and proceed to space 3
5 fills the space 36, flows down the space 36 and joins at the lower part, passes through the discharge path 24, flows down the flow path 22 via the space 35, and reaches the reservoir 21.
reach. Further, the leading portion that flows through the space 35 and joins at the lower part similarly flows down the flow path 22 and flows into the reservoir 21.
, the reservoir 21 is filled and the flow stops. Thereafter, the density of the preform 16 is further increased by applying pressure with the pressurizing metal C, and the inner circumferential coating layer 37 and the outer circumferential coating layer 38 made of the glass-mica plastic body are applied to the metal tube 2.
It is formed and adhered to the inner and outer peripheral surfaces of 3. The state at this time is shown in FIGS. 3b and 4b.

Thereafter, the molding die is cooled until the temperature of the coating layers 37 and 38 reaches 380° C., and the molding die is disassembled to take out the molded product. Filling path 20 and distribution path 22
The thin plate-shaped molded piece that is sometimes formed is broken off and removed, and the molded product shown in FIG.
obtained with. Next, the nut 34 is loosened and the washer 33, side plate 29 and bolt 32 are removed. Since the coefficient of thermal expansion of the core bar 26 below 400°C, which is the transition temperature of the raw glass, is greater than that of the inner peripheral coating layer 37, the core bar 26 exhibits a shrinkage phenomenon in the circumferential direction and the axial direction. A slight gap is generated between the outer peripheral surface and the inner peripheral surface of the inner peripheral coating layer 37, and the core metal 2
Since the taper 28 is provided on the surface of the tube 6, the core bar 26 can be easily removed, and the corrosion-resistant tube E shown in FIG.
is obtained. This completes the manufacturing.

Next, the features of the manufacturing method according to the present invention and the manufactured corrosion-resistant tube will be explained. In the case of this manufacturing method, the flow distance of the heated preform 16 is short and the temperature drop is extremely small, so the phenomenon that the density at the tip does not increase as in the conventional manufacturing method is completely eliminated. Ru. This effect is particularly significant because the leading portion of the fluidized preform 16 flows out into the reservoir 21 provided at the bottom of the mold. That is, the preform 16 passes through the outflow path 18 and the filling path 20 and reaches the upper part of the metal tube 23.
flows branching to the left and right sides of the metal tube 23, and collides and coalesces at the bottom thereof. Although the temperature of this combined part has decreased, it passes through the flow path 22 to the reservoir part 21, and after passing through the outflow part 18 and the filling part 20, it passes through the inflow part 21.
5 reaches the upper part of the core metal 26, branches to the left and right, flows, collides and coalesces at the lower part, and is discharged through the discharge path 2.
4. From the flow path 22 to the reservoir 21 via the space 35
Therefore, the molded inner and outer coating layers 37 and 38 do not include any portions where the temperature has decreased. Therefore, the density of each portion is uniform, and a coating layer with stable characteristics can be obtained.

As mentioned above, a major feature of the manufacturing method of the present invention is that the reservoir 21 is provided at the bottom of the molding die, and the leading end of the preform 16, whose temperature has decreased due to flow, flows out of the product. be.

Next, regarding the length of the corrosion-resistant tube E to be manufactured, even if it becomes longer, there are no changing conditions regarding the filling conditions of the coating layers 37 and 38, so it is essentially possible to mold a long product. Matters related to the removal of the core metal 26 occur. This point will be explained below. This problem is related to the molding jig D and can be solved by considering the following matters. First, the difference in thermal expansion coefficient between the core bar 26 and the glass-mica plastic body is to be made as large as possible, and the second purpose is to increase the taper 28 and to avoid the occurrence of adhesion between the core bar 26 and the inner peripheral coating layer 37. . Increasing the taper 28 will cause a difference in the wall thickness at both ends of the coating layer, but this can be solved by grinding the inner circumferential surface of the thicker part by machining after molding. It is possible to make it into a food tube.

Next, regarding the problem of adhesion between the core metal 26 and the inner peripheral coating layer 37, it is a useful method to use a copper alloy for the core metal 26. When the core metal 26 is made of a copper alloy, a copper oxide film is formed on the surface when heated, but since this film hardly adheres to the base metal, it becomes effective as a mold release agent. It is also effective to apply copper plating to the surface of the core metal 26.

In addition, in the forming jig D, the reason why the bolt 32 is made of a material with a small coefficient of thermal expansion and the washer 33 is used to reduce the tightening pressure of the nut 34 as much as possible is that the side plate 29 is used during cooling after forming. This is a measure to prevent tightening pressure from being applied to the coated layers 2 and 3.

〔Effect of the invention〕

In the corrosion-resistant tube manufactured by the above manufacturing method according to the present invention, the molded coating layer is composed of a glass-mica plastic body containing a large amount of mica powder, which has extremely high corrosion resistance, and has extremely high insulation properties. At the same time, it maintains excellent properties in terms of high temperature hot water resistance, acid resistance, salt water resistance, etc.
In addition, the coefficient of thermal expansion is similar to that of metal pipes, so
Not only does it not deform even at high temperatures of 200 to 300 degrees Celsius, it always maintains a perfect bond with the metal pipe, and is non-porous, so there is no leakage phenomenon. While maintaining properties equivalent to corrosion-resistant tubes obtained using conventional manufacturing methods, such as having high impact strength, it is possible to manufacture long products that could not be obtained using conventional manufacturing methods. It is possible to completely eliminate the fatal and unavoidable flaws of

The above explanation refers to insulating corrosion-resistant pipes that carry gases or liquids that are highly corrosive to metals under high-temperature conditions of 200 to 300°C, and that have high mechanical strength and can maintain insulation properties. However,
The uses are not limited to the above, but it is widely useful as an insulating tube under room temperature to high temperature conditions, or repeated conditions.
Its practical and technical effects are extremely large. Note that it is also a useful effect that the price can be significantly reduced.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of a conventional corrosion-resistant pipe, and Figure 2 is a vertical cross-sectional view for explaining the conventional manufacturing method.
Figure 3b shows the state immediately before pressure forming, Figure b shows the state after pressure forming is completed, and Figs. In the figure, a shows the state immediately before pressure forming, b shows the state after pressure forming is completed, FIG. 5 is a longitudinal cross-sectional view of the molding jig used in this example, and FIG. It is a longitudinal cross-sectional view of the corrosion-resistant pipe in the final step. In the figure, B is the molding part, C is the pressure metal, D is the molding jig, 13 is the upper metal, 14 is the lower metal, 15 is the base metal, 16
17 is a preform, 17 is a raw material loading chamber, 18 is an outflow path, 19 is a through hole, 20 is a filling path, 21 is a reservoir,
22 is a flow path, 23 is a metal pipe, 24 is a discharge path, 2
5 is an inflow path, 26 is a core metal, 27 is a center hole, 28 is a taper, 29 is a side plate, 32 is a bolt, 35, 36
37 is an inner peripheral coating layer, and 38 is an outer peripheral coating layer. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A method for manufacturing an insulating corrosion-resistant tube by forming a coating layer made of a glass-mica plastic material on the inner and outer circumferential surfaces of a metal tube, comprising: (a) forming a vitreous powder by cold pressing; a first step of creating a preform consisting of a mixture of mica powder and mica powder; a lower metal part having a through hole and which is separable; an upper metal part having a raw material loading chamber in its bottom part connected to an outflow passage communicating with the filling passage and connected to the upper surface of the lower metal part; a second step of preparing a molding mold comprising: a pressurizing mold that fits into the chamber; The metal tube has a smaller number of inflow passages and a greater number of discharge passages than the number of inflow passages on the other side, and a central hole whose maximum outer diameter is smaller than the inner diameter of the metal tube and whose outer peripheral surface is tapered. A molding device that holds the metal tube by inserting the core metal into the metal tube and a pair of side plates that are to be fitted into the through hole and placing them at both ends of the core metal and tightening them with bolts. a third step of preparing a jig; (d) heating the preform, the molding die, and the molding jig to respective predetermined temperatures; fitting into the through hole with the inflow path facing the filling path,
The preform is loaded into the raw material loading chamber, and the preform is pressurized by the pressurizing metal to move the preform from the space between the metal tube, the through hole, and the core metal to the reservoir. The fluid,
(e) cooling and disassembling the molding die to take out the molding jig; disassembling the molding jig and filling the inner and outer peripheral surfaces with the glass-mica plastic body; A method for manufacturing an insulating corrosion-resistant tube, comprising: a fifth step of obtaining the metal tube on which a coating layer is formed. 2. A patent for using a forming jig equipped with a core bar made of a metal having a coefficient of thermal expansion greater than that of the glass-mica plastic body at a temperature below the transition temperature of the raw glass and a bolt made of a metal having a coefficient of thermal expansion smaller than that of the glass-mica plastic body. A method for manufacturing an insulating corrosion-resistant pipe according to claim 1.