JPH0428402A - Internal high-fined tube and manufacture of internally high-finned type double tube - Google Patents

Abstract

PURPOSE:To obtain a internally high-finned tube by hardening by drawing work because the strength of a thin-walled round tube which is extruded from a billet is low like an annealed material and forming longitudinal fins on the inside of the hardened thin-walled round tube with a grooved mandrel and roll of a pilger mill. CONSTITUTION:The metallic billet (base stock) 1 of copper, copper alloy, etc., is extruded from a hot extruder 10 and made into a thin-walled extruded tube 2. The extruded tube 2 is drawn with a cold drawing device 20 and made into a drawn tube 3. Because the extruded tube 2 is low strength like the annealed material and is a thin-walled tube, the extruded tube is deformed by a feed chuck when feeding and rotation are applied to this tube as it is with the pilger mill 30 to work inner fins. Therefore, the extruded tube is hardened by performing cold drawing for the purpose of increasing the strength of the extruded tube so as not to be deformed. The drawn tube 3 is made into the internally high-finned tube with the longitudinal fins 4a on the inside by being rolled with the pilger mill 30.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a high-fin inner surface tube and a high-fin inner surface double tube useful as a heat exchange tube for a condenser or the like.

[Prior Art] Conventionally, a combination of isostatic extrusion and drawing has been used to manufacture copper and copper alloy tubes with high internal fins, but the cost is very high. The reason for using the hydrostatic extrusion method is that it is difficult to produce multiple products using the method described above. For example, hot extrusion Lll has the ability to extrude large-sized pipes, but has the disadvantage that the drawing process to produce small-diameter pipes is long.

In addition, the inner surface of the circular tube is prepared by cold drawing from the circular tube. ``Even if you try to form fins, there is a drawback that you cannot obtain fins with a predetermined height.

Also, regarding the method of producing and covering the inner surface of finned tubes using a pilger rolling mill, attempts have been made for some shapes of iron-based materials, but they are thin, narrow and high. Regarding the fin type, one drawback is that the grooved man 1r rail used in the pilger rolling mill has a short lifespan and becomes obsolete.

In addition, as prior art material for this application, Japanese Patent Publication No. 36-1781
0, Japanese Patent Application Laid-Open No. 60-166108, and Japanese Patent Application Laid-Open No. 62-212006.

[Problems to be Solved by the Invention] This invention is easier to manufacture than the conventional hydrostatic extrusion method, has a lower manufacturing cost, has a longer mandrel life, and can easily produce a wide variety of products. An object of the present invention is to provide a method for manufacturing a heffin tube and a double tube with a high inner surface.

[Technical Means for Solving the Problems 1] In order to solve the above problems, the present invention includes (1) a first process of forming a thin-walled circular tube from a billet by hot extrusion; in'? '47. : Cold drawing of H flesh circular tube 1
The second step is to harden the tube in the second step, and the circular tube hardened in the second step is rolled using a pilger rolling machine to form a finned tube with longitudinal fins on the inner surface. (2) billet]
- a first step in which the thin-walled circular tube obtained in the first step is cold-drawn and hardened; a second step in which the thin-walled circular tube obtained in the first step is hardened; The circular tube is rolled by a pilger rolling machine to form an inner finned tube with longitudinal fins on the inner surface, and the final full wall thickness of the inner finned tube is transferred to the mandrel of the pilger rolling mill. A third step is to make the wall thickness the same as that at the contact start position, and a fourth step is to hold the inner tube at the tip of the fin of the fin tube to the inner surface obtained in the third step by cold drawing and joint drawing.
The present invention has a method for manufacturing a double-walled pipe with high internal fins, which comprises the following steps.

[Function] In the first invention, since the thin-walled circular tube extruded from the billet has low strength like the annealed material, it is hardened by the drawing operation in the second step. In the third step, the hardened thin-walled circular tube is formed with longitudinal fins on its inner surface using a grooved mandrel and a roll of a pilger rolling mill.

In the second invention, the inner fin tube obtained in the first invention is used as an outer tube, the inner tube is inserted into the outer tube and cold drawn, and the inner tube is held at the inner end of the fin by matching drawing. Turn it into a double pipe with high fins on the inside.

[Example J] The present invention will be described below with reference to the drawings without referring to Examples. 1st
Figures 3 to 3 show the manufacturing process of the inner surface fin tube, and Figure 4 shows the inner surface high fin type double tube in which a small diameter circular tube is inserted and fixed inside the inner surface fin tube obtained in Figures 1 to 3. Manufacturing method not shown. In FIG. 1, a billet (raw material) 1 of metal such as copper or copper alloy is extruded from a hot extrusion device 10 shown in FIG. 1(a) to become a thin-walled extruded tube 2 shown in FIG. 1(b). The reason why the extruded tube 2 is made in this way is that if the finned tube is made directly from the billet 1 to the inner surface by hot extrusion, the fin ridges of the mandrel used for manufacturing may become softened and deformed.

The extruded tube 2 is drawn out by the cold drawing device 20 shown in FIG. 2(a) to become the drawn tube 3 shown in FIG. 2(b). The reason why the cold drawing process is 1" is because the extruded tube 2 has low strength like annealed material and is a thin-walled tube, so it is fed and rotated by a pilger rolling mill 30 to be described later in order to process the inner surface with fins. The extruded tube is deformed by the feed chuck.Also, if the grip force of the feed chuck is lowered to avoid deformation, the extruded tube ends up slipping and the desired feed cannot be obtained.

Therefore, in order to increase the strength of the extruded tube so that the extruded tube is not deformed, light cold working (cold drawing in this example) is performed to harden the extruded tube. (20-30% with reduction
) The drawn tube 3 is rolled by a pilger rolling mill 30 shown in FIG. 3(a) to become a high-fin inner tube 4 having longitudinal fins 4a on the inner surface. This inner high fin tube 4 has an outer diameter of 2
0~50Φ, wall thickness 1゜Oyvn, fin height 3
~5rNrI.

The pilger rolling mill 30 has a grooved mandrel 31 and a roll 3.
It is composed of 2.

The grooved mandrel 31 (a) has a curved shape such that the cross-sectional area reduction rate at each cross-section is approximately constant, as shown in FIG. ing.

(b) Since it is difficult to form grooves over the entire length of the mandrel 31 in terms of processing and accuracy, the grooves are formed in the minimum length required for forming the fins.

(C) The groove 318 provided in the mandrel 31 to form the fin 4a on the drawn tube 3 is formed so that the width of the groove tapers toward the tip of the mandrel 31 as shown in FIG. 5(C). However, since it is impossible to remove the mandrel 31 from the tube at the end of rolling, the groove is a straight groove with a constant width as shown in FIG. 5(d).

Regarding the drawn pipe 3 (a) As mentioned above, the groove 31a of the mandrel 31 is provided from the middle of the mandrel 31 to the tip.
In the region of the mandrel 31 where no 8 is provided, the drawn tube 3 becomes an air-rolled region L1 where only the outer diameter is reduced without contacting the mandrel 31, as shown in FIG.

(b) In this air rolling region L1, the wall thickness of the drawn tube 3 tends to increase, and as shown in FIG. 7, the wall thickness increase rate Rt (
%) increases approximately in proportion to the outer diameter reduction rate Rd (%). In addition, To and D in FIG.

are the wall thickness and diameter of the drawn pipe 3, respectively. Also lower 1SD
i is the wall thickness and diameter of the drawn tube 3 at any position in the empty rolling region L1, respectively. Further, this rate of increase differs slightly depending on the wall thickness/outer diameter (To/Do) of the drawn tube 3.

(C) As a necessary condition for forming a predetermined fin, it has been empirically determined that the final total thickness T satisfies To (=T+H)≦T. That is, the wall thickness TS of the drawn tube 3 at the position of the mandrel 31 where the drawn tube 3 contacts the mandrel 31 and starts forming fins is equal to the bottom of the inner surface high fin tube 4 after rolling by the required Pilger rolling 1fi30. The total thickness is equal to or greater than the total thickness including the thickness T and the height H of the fins 4a.

(d) In the case of T,>T, fin breakage 11 and lack of thickness 12 occur as shown in FIG.

(e) In the case of Tn x T, it is advantageous for fin formation, but as shown in FIG. 9(a), the fin 4a is
This fills the groove 31a and strongly presses the bottom of the groove 31a, reducing the life of the mandrel 31. Therefore, the fins 4a should be prevented from filling the groove 31a as shown in FIG. 9(b). For this, T. =T, is the limit condition,
Wall thickness T of drawn pipe 3. can be found from Figure 7.

The high-fin inner surface tube 4 is drawn by the cold drawing and matching drawing device 40 shown in FIG.

In this inner high fin type double pipe 5, the inner high fin pipe 4 becomes the outer pipe 6.

When forming a double pipe 5 with high fins on the inner surface (a>Pilger)
There is also a method of forming a double pipe by subjecting the internally high-finned tube 4 obtained by the rolling mill 30 to assembly and drawing as is, but usually a die 41 and a grooved plug 42 are used as shown in FIG.
Cold drawing is performed to product size using

(b) However, if the entire surface of the grooved plug 42 is brought into contact with the fins 4a of the inner high fin tube 4, the frictional force will increase and it will be difficult to pull it out.
As shown in Figure 1, a part of the fin 4a has a grooved lug 42.
or by using a coring method that contacts the leakage plug 42.
Use the empty search method that does not use .

(C) In the case of item 1-, the fin portion extends in the longitudinal direction, so the height Hi of the fin decreases as shown in FIG.

1~]. is the height of the fins 4a of the inner high fin tube 4. Therefore, the rolling dimensions based on the pilger rolling mill are determined by considering the relationship shown in FIG.

(d) By the way, when drawing circular tubes made of various materials such as titanium, SUS, copper, etc. with inner tubes, it is important to check the degree of crushing and machining of the joint horns and fins with the inner high fin tube 4, which is the outer tube. I empirically set the fin height to 0.3 due to the ease of
For 0.5 seconds, I was under pressure as if I was being crushed.

(e) Figures 13 (a) to (d) show the deformation of the inner high fin type two-way pipe 1° (a) The inner high fin type 20 pipe 5a is almost the same as the inner high fin type double pipe 5. (b) In the case where the inner tube 7b has one outward facing fin between the fins 6a of the outer tube 6, the inner surface high fin type double tube 5b of (c) has a high inner surface fin type double tube 5G. In the case where the inner tube 7G has three outward facing fins G, m between the fins 6a, the twin type double tube 5d with high inner surface of (d) has one high inner surface fin inside the twin 6a of the outer tube 6. We accept the case where type double pipe 8 is incorporated-3
, [Effect J Since this invention has the above configuration, it has the following excellent effects.

(b) (Hot extrusion) - (Cold drawing) of the high fin inner tube, which is the outer tube of the double tube with high inner fins, which could previously only be manufactured using the high-cost hydrostatic extrusion method. )
-(Pilger-tan) = (cold bow-pulling) makes the process longer, but it is easy and inexpensive.

(b) If the material of the inner tube is titanium, SUS, copper, etc., it is easy and inexpensive to manufacture various two-way tubes with high fins on the inner surface, so it has a wide range of uses.

(c) Part of the equipment used to carry out this invention, such as the mandrel, can be used for a longer period of time, leading to a reduction in the cost of the product.

[Brief explanation of drawings]

Figure 1 (a) shows the hot extrusion device (), Figure 2 (b)
shows a sectional view of an extruded tube extruded by the apparatus of FIG. 1(a). Figure 2 (a) shows the cold drawing equipment;
Figure 3 (b) shows a cross-sectional view of a cold-drawn pipe cold-drawn by the apparatus shown in Figure 2 (a); Figure 3 (a) shows a rolling mill with pilger grooves; ) shows an inward high fin tube rolled by the apparatus shown in FIG. 3(a). FIG. 4(a) shows a cold drawing and joint drawing device, and FIG. 4(b) shows a cross section of a double-walled pipe with high internal fins obtained by the device of FIG. 4(a). Figure 5 (a) shows a grooved mandrel used in a pilger grooved rolling mill, Figure 5 (b) shows an end view of the grooved mandrel (), and Figure 5 (c) shows a taper. FIG. 5(D) shows a straight groove type mandrel. FIG. 6(a) shows the position and dimensional relationship between the cold drawn pipe and the grooved mandrel, and FIG. 6(eye) shows an end view of FIG. 6(a). FIG. 7 shows the relationship between the outer diameter reduction rate and the wall thickness increase rate of the cold-drawn pipe in the air-rolled section of FIG. 6. FIG. 8 shows a perspective view of fin breakage and underfilling occurring in the fins of the inner high fin tube. FIG. 9(a) shows the case where the fins are completely filled in the groove of the mandrel, and FIG. 9(b) shows the case where the groove is not filled. 10th
The figure shows a cold drawing device for internally high fin tubes. FIG. 11 shows the contact relationship between the fins of the inner high fin tube and the grooved plug, where the broken lines indicate the fins before handling, and the diagonal lines indicate the portions of the fins that actually come into contact with the grooved plug. FIG. 12 shows the relationship between the reduction rate of the outer diameter of the tube and the height of the fins when the tube with high internal fins is subjected to cold drawing. Figures 13(a) to 13(d) show modified examples 1' of a double pipe with high internal fins. 1... Fillet 1- 2... Extruded pipe 3... Drawn pipe 4... Inner surface ^ twin tube 5... Inner high fin type double tube 30... Pilger rolling machine 40... Cold drawing and combined drawing equipment

Claims (2)

[Claims] (1) A first step of hot extruding the billet into a thin-walled circular tube, a second step of hardening the thin-walled circular tube obtained in the first step by cold drawing, and hardening in the second step. The circular tube thus obtained is rolled using a Pilger rolling machine to produce a high-finned inner tube with longitudinal fins on the inner surface, and the final total wall thickness of the high-finned inner tube is reduced by contacting the high-finned inner tube with the mandrel of the Pilger rolling mill. A method for manufacturing a high-fin inner surface tube comprising a third step of making the wall thickness the same as that at the starting position. (2) A first step of hot extruding the billet into a thin-walled circular tube, a second step of hardening the thin-walled circular tube obtained in the first step by cold drawing, and hardening in the second step. The circular tube thus obtained is rolled using a Pilger rolling machine to produce a high-finned inner tube with longitudinal fins on the inner surface, and the final total wall thickness of the high-finned inner tube is reduced by contacting the high-finned inner tube with the mandrel of the Pilger rolling mill. The third step is to make the wall thickness the same as that at the starting position, and the fourth step is to hold the inner tube at the inner end of the fins of the inner high fin tube obtained in the third step by cold drawing and joint drawing.
A method for manufacturing a double-walled pipe with high internal fins, comprising the steps of: