JPH0586284B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a metal tube with spiral fins used as a heat transfer tube for a heat exchanger or the like. [Prior Art] As shown in FIG. 3 (perspective view), a method for manufacturing such a metal tube with a spiral fin is to transport a cylindrical metal tube 31 in the axial direction while rotating the axis, and to rotate the outer peripheral surface of the metal tube 31 in the axial direction. A method of continuously supplying the strip plate material 32 so that one edge of the strip material 32 is in contact with the metal tube 31, spirally wrapping the strip plate material 32 around the outer circumferential surface, and high-frequency welding the joint between the metal tube 31 and the strip plate material 32. There is (Unexamined Japanese Patent Publication 1983-
No. 9715). When manufacturing a metal tube with a spiral fin by such a method, there are the following problems: a large driving force is required for winding the strip plate material 32, it is difficult to speed up the winding process, and it is difficult to wrap the metal tube 31 around the metal tube 31. The band-shaped plate material 32 is prone to cracking due to tensile stress generated on the outer circumference side, and compressive stress is generated on the inner circumference side, which tends to cause wrinkles, folds, and waving phenomena. It is difficult to weld the joints reliably, and when the obtained metal tube with spiral fins is used as a heat transfer tube, the heat transfer characteristics are poor due to the uncertain welding of the joints, etc. , there were various drawbacks. On the other hand, a method using plastic working has also been proposed as a method for obtaining a metal tube with spiral fins as an integral body. For example, as shown in FIG. 4 (front view) and FIG. 5 (side view showing an enlarged cross-section taken along the - line in FIG. 4), three rollers are arranged around the pass line of the hollow metal pipe 44. rolling roll 41,
42 and 43, the metal tube 44 is rolled in a cold or hot manner (Plasticity and Processing Vo110 No.
105 P732). However, metal tubes with spiral fins can be manufactured using the above method only when the material is a soft metal with excellent workability, such as aluminum or copper. There is a problem in that the above-mentioned method is difficult to apply when the material is ordinary steel, as well as when the material is alloy steel, stainless steel, etc. In addition, when using this method, there is almost no stretching in the longitudinal direction of the tube axis. Therefore, the present inventors proposed a method for manufacturing a metal tube with spiral fins by plastic working, which is different from the method described above. That is, Fig. 6 (front view) and Fig. 7
As shown in the figure (a side view showing an enlarged cross-section taken along the - line in Figure 6), grooves for forming fins are formed around the outer circumferential surface at intervals that gradually become wider from the inlet side of the metal tube toward the outlet side. Using a cross-type inclined rolling mill in which three (or four) rolling rolls 61, 62, 63 formed in a plurality of directions are arranged around a pass line,
By hot feeding the hollow metal tube 64 between the rolling rolls 61, 62, and 63 while placing a mandrel 65 in the hollow part, the metal tube 64 is heated.
We proposed a method for forming spiral fins on the outer circumferential surface of No. 4 by performing inclined rolling.
−263439). According to this method, a spiral fin can be formed on the outer circumferential surface of a metal pipe made of common steel. [Problems to be Solved by the Invention] However, when manufacturing a metal tube with spiral fins by the above-mentioned method, the flesh of the metal tube pushed away by the rolling rolls mainly flows in the axial direction. As the metal tube flows, fins are formed on the metal tube and it extends in its axial direction. Therefore, metal tubes with spiral fins that have thin and tall fins that require the flesh of the metal tube to flow in the radial direction, specifically, fins that have an outer diameter larger than the outer diameter of the metal tube. When manufacturing a metal tube with a spiral fin (hereinafter referred to as a hyphen tube), there was a problem in that the above-mentioned method could not be used effectively. Incidentally, when manufacturing a high-fin inch tube using the above-mentioned method, it becomes necessary to use a hollow metal tube with an outer diameter as large as the outer diameter of the fins. When the above-mentioned method is carried out using the above-mentioned method, the machining energy during inclined rolling increases, and machining that requires a large number of man-hours to remove the inner part of the metal tube is required.
Since the manufacturing cost increases significantly due to a decrease in material yield, etc., the above-mentioned method is not applied, and the conventional method shown in FIG. 3 is usually applied. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method suitable for manufacturing a high-finish tube at low cost. [Means for Solving the Problems] The method for manufacturing a metal tube with spiral fins according to the present invention includes rolling a rolling roll having a plurality of annular grooves formed in the circumferential direction of the outer peripheral surface for forming fins along a pass line. Using three or four intersecting inclined rolling mills arranged around the circumference, the metal blank tube is hot fed between the rolling rolls to perform tilt rolling on the metal blank tube, and In the method for manufacturing a metal tube with a spiral fin in which a spiral fin is formed on the outer circumferential surface, a metal tube having a small-diameter pilot hole bored in the center is used as the metal tube, and the pilot hole of the metal tube is inserted into the metal tube. Insert a plug with a larger diameter to perforate the metal pipe,
The method is characterized in that fins having an outer diameter larger than the outer diameter of the metal tube are formed by diameter-expanding rolling and filling the grooves of the rolling rolls with the flesh. [Operation] In the case of the method of the present invention, since a metal pipe having a small-diameter pilot hole is used as the metal pipe, machining that requires a large number of man-hours is required to manufacture the metal pipe, that is, to drill the pilot hole. Moreover, by drilling a pilot hole, the thermal load on the plug tip can be reduced, and melting and wear of the plug tip can be prevented. In addition, since a plug with a larger diameter than this is inserted into the pilot hole of the metal tube to perform drilling and diameter expansion rolling, the pilot hole serves as a guide for the plug, suppressing uneven thickness.
This stabilizes the height of the spiral fin, and the wall thickness of the raw pipe flows in its radial direction, which fills the grooves of the rolling rolls, so the shape of the grooves should be made to correspond to the desired fin shape. Accordingly, it is possible to easily form a fin having an outer diameter larger than the outer diameter of the metal tube. [Example] The present invention will be described in detail below based on drawings showing an example of the case where the number of rolls is three. FIG. 1 is a front view showing the main part (roll section) of the apparatus used to carry out the method of the present invention together with the material to be rolled (the roll grooves are omitted), and FIG. 2 is taken along the - line in FIG. 1. It is a side view which expands and shows a cross section. In the figure, reference numeral 4 denotes a metal tube as a material to be rolled, which has a small-diameter pilot hole 4a bored in its center.
A set of three cone-shaped rolling rolls 1 are installed at the rolling position of the pass line while the plug 5 is inserted into the
It is designed to be rolled at steps 2 and 3. The rolling rolls 1, 2, and 3 each have the same surface angle α (see Figure 2), and their axes are inclined so that the shaft ends on the same side face toward the same side in the circumferential direction (this axis line The angle β with respect to the path line of , the intersection angle γ when the roll axis separates from the pass line on the exit side is defined as positive). A plurality of annular grooves, for example 10 to 20 grooves, are cut in the circumferential direction on the outer circumferential surfaces of the rolling rolls 1, 2, and 3 at appropriate distances in the axial direction. In addition, the groove is
It may be formed by cutting the outer peripheral surface of a one-piece roll, or it may be formed by overlapping a plurality of disc-shaped rolls and fitting them onto a single shaft to integrate them. It's okay. The positions, intervals, widths, and depths of the grooves differ among the rolling rolls, as shown in part in Fig. 2, and the intervals, width, and depth of each rolling roll also differ depending on the material entry side. It is different from the beginning to the exit side. Note that the positions and intervals of the grooves are determined depending on the height and interval of the fins to be formed and the shape of the plug 5, and the above-mentioned angles α,
β, γ, etc. have been determined. In addition, the position and depth of the grooves are changed appropriately from the material input side to the output side, taking into consideration the spiral metal flow during inclined rolling and the metal flow in the radial direction of the fins formed in the gaps between the roll grooves. It is being The fins coming out of one of the rolling rolls 1, 2, and 3 having grooves as described above are guided to the grooves of the next rolling roll and are successively formed. The width and depth of the grooves are substantially the same between the rolling rolls. Note that the groove depth in each rolling roll is appropriately changed from the entry side to the exit side so as to obtain a desired fin height at the exit end. In addition, the inclination angle of each groove with respect to the roll axis in the depth direction is such that when the fins to be formed are perpendicular to the surface of the metal tube, the angle of the center line of the groove is It is tilted at the same angle as the intersection angle γ. That is, when the fins are formed on the material surface so as to be inclined at a predetermined angle, the intersection angle γ and the inclination angle of each groove with respect to the roll axis in the depth direction are made different. When manufacturing a high-finish tube using a cross-type inclined rolling mill equipped with such rolling rolls, first, the metal tube 4 having a small-diameter pilot hole 4a bored in the center is heated to a predetermined temperature in a heating furnace (not shown). (for example, 1200° C. in the case of medium carbon steel), and then transferred to the cross-type inclined rolling mill, where the metal tube 4 is pierced and rolled as shown in FIG. That is, when rolling of the metal tube 4 is started in the cross-type inclined rolling mill, the metal tube 4 is rolled by the rolling rolls 1,
After being successively bitten by the holes 2 and 3, they are rolled at three locations in the circumferential direction, and the diameter of the pilot hole 4a is enlarged by the plug 5, and the hole 4a is punched and rolled. The flesh of the metal tube 4 flows in its radial direction and fills the grooves of the rolling rolls 1, 2, and 3, so that the metal tube 4 can be formed into a desired high inch tube. [Numerical example] The material has the same composition as STBA24 and the outer diameter is 65
mmφ and an inner diameter of 10 mmφ (in other words, a pilot hole with a hole diameter of 10 mmφ is drilled in the center) is inclined rolled under the rolling conditions shown in Table 1, and the fin spacing is is 7mm and the outer diameter of the fin is 75mmφ
A high-fin inch tube with a fin valley diameter of 38 mmφ, an inner diameter of 31 mmφ, and a wall thickness of 3.5 mm was manufactured.

[Table] As a result, it was possible to easily manufacture the high tube as a single piece, which was conventionally difficult to manufacture using plastic working and was manufactured using a plate-wrapping welding method. In the above example, the roll intersection angle γ was set to 0°, but the roll intersection angle γ is not limited to this, and can be set to either a positive or negative angle depending on the specifications and structure of the rolling mill. can do. Incidentally, the roll crossing angle γ is 1°, and the roll face angle α is
If it is 6° and 1° on the exit side, the roll reduction surface angle with respect to the pass line will be 5° on the inlet side and 2° on the exit side as in the above example, which is equivalent to the high-end angle obtained in the above example. The hyphen inch was obtained. However, the angle of the roll groove was tilted by 1° toward the entry side so that it was perpendicular to the axis of the metal tube, with the roll crossing angle being 1°. [Effects] As described above, according to the method of the present invention, a metal tube having a small-diameter pilot hole drilled in the center is pierced using a plug with a larger diameter than the pilot hole and rolled to expand its diameter. The pilot hole serves as a guide for the plug, suppressing uneven thickness of the metal tube, which in turn prevents variations in the height of the spiral fin, making it possible to manufacture high-finish tubes with a high and narrow pitch in one process. In addition, it is possible to reduce the frictional force between the plug tip and the metal tube, which has a small volume and low heat capacity, reducing the heat load, and making it possible to process stainless steel and carbon steel, easing restrictions on the material of the tube. The present invention has excellent effects, such as being able to significantly reduce the tool consumption of the plug.

[Brief explanation of drawings]

Fig. 1 is a front view showing the main parts of the device used to carry out the method of the present invention, Fig. 2 is an enlarged side view of the cross section taken along the - line in Fig. 1, and Fig. 3 is a conventional spiral fin-equipped device. FIG. 4 is a perspective view showing a method for manufacturing a metal tube; FIG.
The figure is a side view showing an enlarged cross-section taken along the - line in Fig. 4, Fig. 6 is a front view showing the main parts of a cross-type inclined rolling mill, which is a conventional spiral fin-equipped metal tube manufacturing device, and Fig. 7 is a side view showing an enlarged cross-section taken along the - line in Fig. FIG. 7 is a side view showing an enlarged cross section taken along the line - in FIG. 6; 1, 2, 3...Rolling roll, 4...Metal raw pipe,
4a...center hole, 5...plug.

Claims (1)

[Scope of Claims] 1. Using a cross-type inclined rolling mill in which three or four rolling rolls each having a plurality of annular grooves for forming fins formed in the circumferential direction on the outer peripheral surface are arranged around a pass line, In the method for manufacturing a metal tube with a spiral fin, the metal tube is hot fed between the rolling rolls to perform inclined rolling on the metal tube to form a spiral fin on the outer peripheral surface thereof, As the metal tube, a tube with a small-diameter pilot hole drilled in the center is used, and a plug with a larger diameter than this is inserted into the pilot hole of the metal tube to drill and expand the metal tube. By radially rolling and filling the grooves of the rolling roll with the meat,
A method for manufacturing a metal tube with spiral fins, the method comprising forming fins having an outer diameter larger than the outer diameter of the metal tube.