JPS6047088B2 - Manufacturing method of vinyl chloride lined galvanized metal pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a galvanized metal tube whose inner surface is lined with vinyl chloride.

This type of galvanized metal pipe is used for water pipes, etc., and its manufacturing method has conventionally been as shown in FIG. 1.

That is, the galvanized metal pipe Z shown in figure a is carried into the production line, and then an adhesive is applied to the outer surface of the vinyl chloride pipe V shown on the left side of the figure using an adhesive applicator A, and the galvanized metal pipe Z is Apply adhesive to the inner surface of the
Adhesive is applied to the inner surface of the galvanized metal pipe Z using an adhesive applicator B, and then a vinyl chloride pipe V is inserted into the galvanized metal pipe Z as shown in Fig. c, and then a plug P is placed in a heating furnace H. The PVC pipe V is expanded in diameter while being pulled out and glued together (Fig. d), and finally cut into a predetermined length by a saw cutter S (Fig. e) to produce a product. However, in this method, (1) the lining material is vinyl chloride pipe with a low softening temperature, so the temperature inside the heating furnace cannot be raised, and therefore it takes a long time to soften the vinyl chloride pipe. (2) Since the hot processing is carried out in a heating furnace, the fuel consumption rate is poor.
3) In order to prevent the adhesive strength from decreasing due to cooling shrinkage of the PVC pipe after heat forming, adhesive must be applied to the outside surface of the PVC pipe as well as the inside surface of the galvanized metal pipe, and a large amount of adhesive is used. There are problems such as being uneconomical.

The present invention solves these problems all at once, and its purpose is to substantially enable cold working, reduce the thermal energy required for processing, and increase production efficiency.
An object of the present invention is to provide a method for manufacturing a galvanized metal pipe lined with vinyl chloride, which also reduces the amount of adhesive used.

The processing method of the present invention is significantly different from the conventional method.

That is, the present invention, when adhering a vinyl chloride pipe to the inner surface of a galvanized metal pipe, inserts the vinyl chloride pipe into the galvanized metal pipe, then brings the inner surface of the galvanized metal pipe to a temperature below the softening temperature of vinyl chloride, and The outer surface is intensively heated to a temperature at which the base metal to zinc alloy layer exhibits sufficient ductility, and the diameter is reduced by drawing with a die to bond the galvanized metal pipe and the vinyl chloride pipe. It is characterized by Next, to explain the present invention in detail, as in the conventional method, galvanized metal pipes (hereinafter referred to as galvanized pipes) are carried into the production line, and adhesive is applied to the outer surface of the PVC pipe or galvanized Apply adhesive to the inner surface of the tube.

Thereafter, after inserting the vinyl chloride pipe 2 into the galvanized pipe 1, drawing is performed using a die 3 as shown in FIG. In this drawing, only the outer surface of the galvanized tube 1 is intensively heated and drawn using a high-frequency induction heating coil 4 just before the die 3, thereby reducing the diameter of the galvanized tube 1, and converting it into polyvinyl chloride. They are crimped from the outside of the tube 2 and glued together. After that, it is made into a product through a cutting process. According to the method of drawing using the die 3 while heating when bonding the galvanized pipe 1 and the vinyl chloride pipe 2, the outer surface of the galvanized pipe 1 is intensively heated in advance. has been done.

Therefore, when the galvanized pipe 1 is drawn and reduced in diameter, along with the Zn layer on the outer surface layer, Zn and base metal such as F
e(7) Fe-Zn alloy layer exhibits high ductility. As a result, the difference in ductility between the Fe base metal layer and the Fe-Zn alloy layer is reduced,
It is possible to prevent Zn plating from peeling off from the base metal. By the way,
Galvanizing when the inner surface temperature of galvanized 1 was set to room temperature and the outer surface temperature was changed. When the presence or absence of peeling was examined, the results shown in FIG. 3 were obtained. In this case, the plating thickness was 489 to 581 g1d, and the processing rate was 18.5%. From FIG. 3, it is clear that peeling occurs at temperatures below 50°C. Although a ring burner or the like may be used to intensively heat the outer surface of the galvanized pipe 1, the high frequency induction heating method of the above example is most suitable for the purpose of rapid concentrated heating.

As shown in FIG. 3, if the temperature of the outer surface of the galvanized pipe 1 is 50'C or higher, the Zn plating will not peel off if the temperature of the base metal is around room temperature.

However, at this time, the inner surface temperature of the galvanized pipe or the temperature of the vinyl chloride pipe should be at least below the softening temperature of vinyl chloride, that is, about 50° C., depending on the grade.
The reason for this is that when drawing with dies, the diameter of the vinyl chloride pipe is reduced along with the galvanized pipe, but the present invention aims to have the effect that after the processing, the vinyl chloride pipe recovers its elasticity and adheres strongly to the inner surface of the galvanized pipe. On the other hand, if the temperature is raised to a high temperature, the PVC pipe will soften, the elastic restoring force of the PVC pipe after processing deformation will be weak, and the adhesive strength between the galvanized pipe and the PVC pipe will decrease. It is from. On the other hand, if heating is carried out so as to raise the inner surface temperature of the galvanized pipe, not only will it not be possible to expect the above-mentioned elastic restoration effect of the PVC pipe, but it will also be unfavorable in terms of heating energy consumption, and It has been found that when the temperature of the base metal is increased, for example, the ductility of the base metal is increased and peeling of the Zn plating occurs even if the temperature difference between the base metal and the outer surface is high. In other words, the cause of the peeling of galvanizing is the vibration base metal and Fe-
This is caused by the difference in ductility with the Zn alloy layer. Therefore, if the base metal is also heated, the ductility of the base metal will increase more than the ductility of the Fe-Zn alloy/gold layer, and the difference in ductility will increase, causing peeling of the Zn plating. . Therefore, the optimum mode is to keep the base metal temperature at approximately room temperature by high-frequency induction heating or the like, and heat the outer surface intensively to raise the temperature to 50° C. or higher. Since the present invention cleverly utilizes the elastic recovery effect of PVC pipes after processing deformation, it is not necessary to apply adhesive to both the inside surface of the PVC pipes as well as the outside surface of the PVC pipes as in the conventional method. Basically, it is not necessary, and it is sufficient to apply the adhesive to the outer surface of the PVC pipe or only to the inner surface of the galvanized pipe.

The adhesion strength between the galvanized pipe and the vinyl chloride pipe (lining layer) is 12 to 17k9 knots for the conventional product made using the conventional method, while the adhesive strength of the product of the present invention is approximately the same or higher, at 12 to 20k9 knots. Demonstrates strength and fully satisfies standard values. Although the adhesive may be applied only to the inner surface of the galvanized pipe, it is preferable to apply the adhesive to the outer surface of the vinyl chloride pipe. Figures 4 to 6 show the results of a peelability test of zinc plating.

Figure 4 shows no heating in front of the die and no lubrication.
2gmmφ→26? φ with a total elongation rate of 11%. Figure 5 shows a galvanized tube outer surface temperature heated to 110° C. in front of the die, and otherwise processed under the same conditions. From these comparisons, it can be seen that heating is necessary to prevent the plating from peeling off. Figure 6 shows the drawing process performed without heating using a lubricant at a total elongation rate of 83%, but peeling of the zinc plating is observed. As described above, in the present invention, the inner surface of the galvanized metal pipe is made to be below the softening point temperature of vinyl chloride, and the diameter of the galvanized metal pipe is drawn and contracted using a die, so that the vinyl chloride pipe is elastically restored after processing. It can be bonded to the inner surface of galvanized metal pipes with desired strength.

Therefore, it is sufficient to apply the adhesive to one side, and the amount of adhesive used can be reduced. In addition, the outer surface of the galvanized metal pipe is
Since the base metal and zinc alloy layer are heated intensively to a temperature at which they exhibit sufficient ductility, peeling of the zinc plating can be reliably prevented, and the outer surface of the galvanized metal pipe can be virtually removed by cold working. Since only a small amount of heating is required, only a small amount of heating energy is required, and processing can be performed in a short heating time, significantly improving production efficiency.

[Brief explanation of the drawings] Figures 1 a-e are schematic diagrams showing the conventional method in the order of steps, Figure 2 is a cross-sectional view showing the method of the present invention, and Figure 3 is a diagram showing the method for changing the outer surface temperature of galvanized metal pipes. 4 to 6 are photographs showing the state of adhesion of zinc plating due to differences in processing conditions. 1... Galvanized pipe, 2... PVC pipe, 3...
・Dice, 4...High frequency induction heating coil.

Claims (1)

[Claims] 1. When bonding a vinyl chloride pipe to the inner surface of a galvanized metal pipe, the vinyl chloride pipe is inserted into the galvanized metal pipe, and then the inner surface of the galvanized metal pipe is brought to a temperature below the softening temperature of vinyl chloride, and the outer surface is bonded to bare metal. ~ With the outer surface heated intensively to a temperature at which the zinc alloy layer exhibits sufficient ductility,
A method for manufacturing a vinyl chloride-lined galvanized metal pipe, which comprises drawing and reducing the diameter using a die, and bonding a galvanized metal pipe and a vinyl chloride pipe.