JPS6230076B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention involves forming steel, surface-treated steel strips made of plated steel, or other metal strips as raw materials, and then stacking two or more metal strips by welding to form pipes at the same time or in a separate process. The present invention relates to a method for manufacturing a multilayer pipe, in which two or more types of pipes are combined and drawn to form a pipe. Compared to single-layer pipes, multi-layer pipes have superior corrosion resistance, heat resistance, heat retention, and sound deadening properties, so they solve problems in applications where single-layer pipes have been used up until now.
For example, demand is increasing for parts such as automobile exhaust system pipes and chemical plant piping, which require noise prevention and heat retention. Accordingly, conventional methods for manufacturing multilayer pipes can be broadly classified into two types. For example, in the case of a double-layer pipe,
The first method is to form and weld a metal strip consisting of an outer tube and an inner tube at the same time on the same tube-making line, and the second method is to form the outer tube and inner tube separately,
This is a method in which the pipe is made by welding, the inner pipe is inserted into the outer pipe, and the inner and outer pipes are drawn simultaneously to integrate them. However, when multi-layered pipes are manufactured at the same time using conventional pipe-making methods, the inner bead formed on the inner surface of the outer pipe and the outer bead formed on the outer surface of the inner pipe overlap in the same area. Pressure on the welded part of either the outer or inner pipe, press fit into the welded part, and cracks occur. Even if the positions of the welded parts of the outer and inner tubes are different, or even if the inner and outer tubes are made in separate processes like the latter, the inner bead of the outer tube has a convex shape. If this is the case, a cavity will be created between the inner and outer tubes near the welded part, or the roundness will be poor. When a convex bead is generated on the contact surface between the outer tube and the inner tube as described above, the strength, shape, and other characteristics of the tube are significantly deteriorated. That is, for example, Fig. 1 shows a schematic cross-sectional view of a welded part of a pipe manufactured by a conventional method at the time of forming and after welding. Depending on the type of butt shape on each joint surface 3 of 2,
I-I type, V-V type, inverted V-inverted V type,
It is classified into the Y-Y type, and the reverse Y-inverted Y type.
As is clear from the figure, the inner surface bead 5 of the outer tube 1 and/or the outer surface bead 6 of the inner tube 2 generated from at least one of the outer tube 1 and the inner tube 2 is press-fitted into the welded part of the other one. . At the same time, a portion of the metal oxide produced by welding, a substance previously coated on the material plate before welding, or its oxide is also press-fitted into the welded part. Furthermore, a bead is formed protrudingly in the gap where the outer tube 1 and the inner tube 2 meet, pushing both tubes apart and forming a cavity near the welded part, which significantly deteriorates the shape and mechanical properties of the tube. It makes things worse. In FIG. 1, reference numeral 4 indicates an outer bead of the outer tube 1, and 7 indicates an inner bead of the inner tube 2. In addition, in the case of plated metal materials or clad materials, if the slit material is left as it is, the plated or clad metal remains wrapped around both end surfaces of the slit. If such slit material is used as it is for pipe making, the residual metal will be trapped in the weld, resulting in defects in the weld, deteriorating the corrosion resistance and workability of the pipe, and significantly impairing the properties of the pipe. Furthermore, as a method to prevent the occurrence of defects as described above, the amount of set-up is reduced to reduce the amount of beads generated, but if the amount is even slightly insufficient, welding will not be possible, and if it is even slightly larger, internal damage will occur. Beads occur on the outer surface, making adjustment extremely difficult. In addition, in order to prevent dissimilar metals and oxides from being trapped in the weld, there is a method of increasing the amount of upset and forcing them out of the weld.
Large beads occur. Even if multilayer pipes are manufactured using such conventional methods, it is difficult to obtain a pipe with a satisfactory shape and welding strength. Therefore, when manufacturing multilayer pipes using conventional methods, a high degree of skill and skill is required, and the quality of the obtained products varies widely. As a result of intensive research into the manufacturing method of multilayer pipes, the inventors of the present invention have found that there is no entrainment of dissimilar metals or their oxides in the welded parts, and that there is no bead formation on the contact surfaces of the outer pipe and the inner pipe. The aim of this study was to find a method for manufacturing multilayer pipes that generates extremely little amount of oxidation, has an excellent butt joint surface shape, and has excellent workability at welded parts. That is, the gist of the present invention is to widen at least a portion of the portion facing another metal band in the band thickness direction of the abutting portion of both edges of each metal band toward the surface of the other metal band for forming a multilayer tube. After cutting it down, it is formed into a pipe. The present invention will be explained below based on embodiments shown in the drawings. FIG. 2 is a schematic cross-sectional view of the metal strip according to the present invention at the time of forming and after welding. As shown in the figure, in order to prevent excessive beads from forming on the inner surface of the outer tube and the outer surface of the inner tube during welding, at least a portion of the abutting portions of both edges of the metal strips of the outer tube 1 and the inner tube 2 are removed. This depends on the method of removal. That is, in the first embodiment, as shown in FIG. 2, in order to prevent excessive weld beads from being generated at the weld contact surface between the outer tube 1 and the inner tube 2, in the pre-tube manufacturing process,
The abutting portions of both edges of each metal strip to be joined are spread out toward the surface of the other metal strip along the thickness direction of the strip (inverted V shape).
-Cut it off using a cutter or grinder so that it becomes V-shaped. Then, the pipe is formed so that the shaved portions face each other and butt against each other. As a result, as shown in Fig. 2, the metal part heated and melted by the high-frequency heater becomes a bead due to the pressure of the squeeze roll and protrudes from the outer tube 1 and the inner tube 2. Since it protrudes only on the side surface and the inner surface of the inner tube as beads 4 and 5, respectively, it does not protrude between the contact surfaces of both tubes. In addition, as the shape of both butt parts of the metal strip, the second
Various shapes shown in the figures are also applicable.
That is, in the second embodiment shown in Fig. 2, the shaved shapes of the outer tube and the inner tube are respectively inverted Y-Y type, the third embodiment is inverted V-V type, and the fourth embodiment is inverted. The tube is of Y-V type, and both the outer tube and the inner tube, including the first embodiment, are effective by using thick plates and thin plates. In the XX type of the fifth embodiment shown in Figure 1, both corners of the joining portion of the plates are shaved off, which is difficult to do with thin plates but easy to do with thick plates, and is advantageous in that respect. In addition, no beads are generated on both the inner and outer surfaces, and drawing processing is easy. In addition, there is no need to remove the bead after welding, and the coating metal does not peel off from the surface near the weld, so it has excellent rust prevention effects. Therefore, it is advantageous to apply it to surface-treated steel sheets and the like. Furthermore, in the reverse YX type of the sixth embodiment, a thick plate is advantageous for the inner tube, and both thick and thin plates can be applied for the outer tube.
In particular, there is no bead formation on the inner surface of the inner tube, which is advantageous for drawing processing. The XY type of the seventh embodiment is advantageous when the inner tube is made of thick and thin plates and the outer tube is made of thick plates, and no outward beading of the outer tube occurs. If there is a bead, it must be cut to a width of 4 to 5 mm, but since there is no bead, bead cutting can be omitted, and the rust prevention effect is excellent as described above. The X-V type of the eighth embodiment is advantageous when the outer tube is made of a thick plate and the inner tube is made of both thick and thin plates, and since beads are not formed on the outer surface, it is suitable for surface-treated steel pipes, etc., as described above. Also,
The inverted V-X type of the ninth embodiment shown in Fig. 1 is advantageous when the outer tube is made of thick and thin plates and the inner tube is made of thick plates, and the drawing process is easy because no bead occurs on the inner surface of the inner tube. . As described above, in all of the above embodiments, since the abutting portions of both edges of the metal strip were scraped off in a shape that widened toward the surface of the other metal strip, the molten metal was transferred to the scraped portions by the squeezing pressure of the squeeze roll. , so that the beads hardly protrude from the inner surface of the outer tube and the outer surface of the inner tube. To create the shape of both end faces of the joint, use a knife to scrape it off.
A method of grinding with a grinder or other methods may be used. The amount of cutting or grinding must be determined based on the appropriate amount of upset during pipe making. Further, the step of cutting or grinding may be incorporated into any of the steps of slitting the metal strip to a predetermined width, a separate step after slitting, or a tube-making line step. Next, a typical test example for manufacturing a double-layer pipe according to the present invention will be explained. Test Example As shown in Table 1, the butt shape of the present invention is an inverted V-V type (Fig. 2 1), an inverted Y-Y type (Fig. 2 2)
and reverse MY type (Fig. 2, 3). Then, a molten aluminum plated steel strip with a rimmed steel plate thickness of 1.2 mm (plating weight: 80 g/
m ² ) was used as the outer pipe material, and a cold-rolled steel plate with a thickness of 1.2 mm was used as the inner pipe material. A metal band coil A, in which these tube materials were slit to a predetermined width according to the tube diameter, was made into a tube according to the tube making line shown in Figure 3. That is, as shown in FIG. 3, when the metal strip A1 is pulled out from the coil A through the guide rolls 11, 11, both widthwise ends of the metal strip A1 are cut into the shape of the end surface by the cutter 12 at the middle part of the front and rear guide rolls. Be taken. Subsequently, the metal strip A1 is sequentially pressed and bent into a circular tubular shape via a large number of forming rolls 13, and the tubular metal strip A1 is heated and melted from the outer periphery by a high-frequency induction heater 14, and horizontally rolled by a squeeze roll 15. Pressure is applied from both sides in the diametrical direction, and the abutting portions of both edges of the metal band A1 are welded to form a pipe. The formed rough pipe 10 is cut with an external bead cutter 16
The outer bead is scraped off using a cooler 17, and then cooled by a cooler 17. Then, the outer shape is corrected by passing through a large number of sizing rolls 18, and finally the cutting machine 19,
The single-layer pipe is completed by cutting to a predetermined length. Next, in order to manufacture a double-layer pipe using these single-layer pipes, two types of single-layer pipes are used on a drawing line as shown in Figure 4, and a small-diameter pipe is inserted into a large-diameter pipe to form an outer pipe. 1. The inner tube 2 is formed into a desired diameter by drawing it through a die 21. The bead of the inner tube 2 collapses at the same time as it is pulled out and becomes extremely thin. In this way, a two-layer pipe consisting of a hot-dip aluminum-plated steel pipe and a cold-rolled steel pipe with an outer diameter of 50.8 mm was manufactured.
Note that the reference numeral 22 shown in FIG. 4 is a plug of the ball core type. According to the inspection by cutting the welded part after pipe making, in the pipe according to the present invention, as shown in Table 1, no excessive beads were observed on the contact surface between the outer pipe and the inner pipe due to welding. As a result, there was no evidence that beads generated from the outer tube or the inner tube were press-fitted into the welded portion of the other tube, and therefore, no cracks were generated due to press-fitting of excessive beads. In addition, the contact surface near the welded part is in close contact with no cavities, and the shape is excellent. Therefore, both the outer tube and the inner tube were well welded, and good values were obtained in the flattening test and the spreading test. On the other hand, the outer tube manufactured by the conventional method, that is, the butt shape is, for example, I-I type (Fig. 1 1) and V-V type (Fig. 1 2), is a molten aluminum-plated steel tube, an inner tube. In the case of a double-layer pipe made of cold-rolled steel pipe (all of which are made of the same material as the examples of the present invention), the outer bead of the inner pipe was press-fitted inside the welded part of the outer pipe.
As a result, the wall thickness of the welded portion of the outer tube was reduced, and a cavity was also created at the contact surface near the welded portion of the outer tube and inner tube.

[Table] Furthermore, in another manufacturing method included in the present invention, a plurality of metal strips (Fig. 3 A, A') are overlapped and simultaneously bent and formed in the same manner as above, and heated to form a pipe. In the manufacturing method, the welds overlap on the same part, but even in this case, there are almost no beads on the inner surface of the outer tube 1 or on the outer surface of the inner tube 2, so the same results as in the above example were obtained. It will be done. The present invention is applicable not only to the two-layer pipe of the above embodiment, but also to a multi-layer pipe of three or more layers. As described above, the method for manufacturing a multilayer pipe of the present invention involves sequentially pressing and bending a metal strip into a circular tube shape through a large number of forming rolls, and heating both abutting portions of the metal strip with a high-frequency heater. After that, a tube is formed by squeezing it with squeeze rolls, and a small diameter tube is inserted into the large diameter tube of the plurality of tubes formed and drawn, or the same as above is carried out at the same time with a plurality of metal strips stacked on top of each other. In the method for producing a multilayer pipe, at least a portion of the portion facing another metal strip of the abutting portion of both edges of each metal strip in the thickness direction of the strip is flared toward the surface of the other metal strip. After scraping it off, it is molded into a tube. Therefore, in the multilayer pipe according to the present invention, excessive beads on the inner surface of the outer tube and beads on the outer surface of the inner tube that are generated due to welding are extremely rare, so that excessive beads are generated at the welded part of the inner and outer tubes and in the vicinity thereof. Defects are removed. In other words, there is no deterioration in properties such as strength, roundness, spreadability, and corrosion resistance caused by the press-fitting of beads or oxides into the weld, and there is no formation of cavities at the contact surface of the two pipes near the weld. It exhibits high industrial value, with excellent strength and processability compared to conventional methods, and good quality characteristics.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of a welded part of a pipe manufactured by the conventional method at the time of forming and after welding. FIG. 4 is a system diagram of a pipe-making line for carrying out the present invention, and is a vertical sectional view of the main part of the drawing line. DESCRIPTION OF SYMBOLS 1...Outer tube, 2...Inner tube, 3...Joint surface, 4...Outer surface bead of outer tube, 5...Inner surface bead of outer tube, 6...Outer surface bead of inner tube, 7...Inner surface bead of inner tube, 12...Knife , 13... Forming roll, 14... High frequency induction heating machine, 15... Squeeze roll, 21... Dice, A... Metal band coil, A1... Metal band.

Claims (1)

[Claims] 1. A metal strip is sequentially pressed and bent into a circular tube shape through a large number of forming rolls, and both abutting portions of the metal strip are heated using a high-frequency heater, and then squeezed with squeeze rolls to form a tube. In a method for producing a multilayer pipe, a method for producing a multilayer pipe includes inserting a small diameter pipe into a large diameter pipe of a plurality of pipes and drawing the pipe, or forming a pipe in the same manner as described above while stacking a plurality of metal bands. It is characterized in that at least a part of the part of the metal band where both edges abut, facing the other metal band, in the band thickness direction is shaved off in a shape that widens toward the surface of the other metal band, and then formed into a pipe. Method for manufacturing multilayer pipes.