JPH0547296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a seamless branch pipe having a branch pipe, such as a T-type branch pipe joint (hereinafter abbreviated as T-joint) used at a branch part of piping.

The above T-joint consists of a main pipe 2 and a branch pipe 3, as shown in Fig. 1, and is the most typical example of a branch pipe.The manufacture of this T-joint will be described below as an example. Proceed with the explanation.

Now, among the methods for manufacturing T-joints, the simplest method is the direct drawing method. This method is illustrated in FIG. That is, first, as shown in A (a is a longitudinal side view, b is a front view, and the same applies hereinafter), a true round blank pipe (straight pipe) with the same outer diameter and approximately the same length as the target product main pipe 2 is shown. ) 5, a through hole (hereinafter referred to as a pilot hole) 6 is made in the planned branching area (the area where the branch pipe 3 is planned to be formed), and then the area around the pilot hole or the entire base pipe is heated, and then
It is set on a drawing die 7 which has a die hole 8 having a shape that is approximately the same as the outer shape of the branch pipe of the target product (Dice hole diameter ≒ Branch pipe outer diameter D ₂ ), and is inserted into the pipe through the pilot hole 6 from the die hole 8. A pull-out plug 10 having an outer diameter _dp smaller than the inner diameter _d2 of the target product branch pipe 3 by the finishing allowance is connected and fixed to the drawn-out rod 9. Then, the drawing rod 9 is pulled downward as shown in B, and the drawing plug 10 passes through it to enlarge the prepared hole 6. At the same time, the portion around the prepared hole is bent to open the die hole 6.
In this way, a fully formed part 3' for a branch pipe (hereinafter referred to as branch pipe part) is obtained.

However, in this forming method, when forming the branch pipe portion 3',
Outer diameter: dp (outer diameter of the pull-out plug 10), inner diameter: d ₀ (diameter of the prepared tube hole 6), height: T ₀ (the Since only the material within the cylindrical region with a wall thickness (wall thickness) is used, the height _H'2 of the branch pipe portion 3' to be formed is restricted. In the case of something like a T-joint, the height _H2 of the branch pipe 3 is determined from the viewpoint of workability when welding pipes, etc. to the branch pipe, and also to keep the root of the branch pipe, which is important for strength, away from the welded part. In terms of meaning as well, it is desired to be as large as possible, and therefore the fact that only a low branch pipe section 3' can be obtained is a major drawback. Normally, the base pipe wall thickness T ₀ should be the same as the product main pipe wall thickness T ₁ , or
Make the base tube wall thickness T ₀ larger than the product mother tube wall thickness T ₁ ,
There is also a method of increasing the volume (amount of material) of the A section. However, in this method, the main pipe portion 2 becomes unnecessarily thick, which is disadvantageous in terms of yield. Another related drawback of the direct drawing method is that it is difficult to form the branch pipe portion 3' if the wall thickness T ₀ of the raw pipe is extremely thick. That is, according to the experience of the present inventor, when T ₀ falls within the range of T ₀ /D ₂ > 0.8 (D ₂ : diameter of die hole 8), bending around the prepared hole 6 becomes difficult. As shown in FIG. 3, the expanded deformation of the prepared hole 6 occurs preferentially due to the plug drawing process, and the height _H'2 of the branch pipe portion 3' becomes rather small. In the direct drawing method, the height H′ ₂ of this branch pipe section is generally considered to be approximately 0.3 times the die hole diameter D ₂ as the forming limit.

In order to obtain a branch pipe 3 with a large height, it is necessary to forcibly flow the material into the die hole 8.
As molding methods that take this point into consideration, the bulge molding method and the diameter reduction-pulling method are known. That is, first of all, regarding the bulge forming method, this is generally carried out cold, and as shown in FIG. While applying internal pressure to the raw tube 11 using hydraulic pressure or the like, the raw tube is set in a pair of upper and lower dies 12, 12' having an inner surface shape identical to the outer shape of the target product, and pistons 13, 13 are applied to the raw tube from both pipe ends. axial compression is applied to the die hole 8 provided in the branch pipe forming side die 12'.
Then, as shown in Figure B, the material is pushed in and introduced.
A main pipe portion 2′ of L′ ₁ that is longer than the target product main pipe length L ₁ by the finishing allowance (meaning the completed forming part for the main pipe);
A semi-finished product 14 having a raised portion 3'' with a height H′ ₂ greater than the height H ₂ of the branch pipe is obtained.The closed head of the raised portion 3″ of this semi-finished product is cut off to form a branch pipe portion.

This processing method can efficiently form the protrusion 3'' by applying internal pressure and axial compressive force to the base pipe, but the desired branch pipe diameter D ₂ and main pipe diameter D ₁ As the ratio D ₂ /D ₁ (hereinafter referred to as the diameter ratio) decreases, the ratio of the raw pipe wall pressure T ₀ to the die hole diameter D ₂ decreases.
As T ₀ /D ₂ becomes larger, it becomes difficult for material to flow into the die hole 8, and therefore, the range of D ₂ /D ₁ >0.4 and T ₀ /D ₂ <0.2 is usually effective in practice.

On the other hand, the diameter reduction-drawing method is a processing method in which a raw pipe is compressed in the circumferential direction to form a raised part for a branch pipe, and hot working is basically used. Usually, the target product main tube outer diameter _D1 is 1.2~
Using a raw tube with an outer diameter of about 1.4 times, it is first flattened so that the cross-sectional minor axis (outer diameter) is the product mother tube diameter D ₁
A flat tube approximately equal to , as shown in FIG.
Pressure is applied in the long diameter direction with a press to compress in the circumferential direction, and the branch pipe forming side die 16'
A raised part 3'' is obtained by pouring the material into the die hole 8 provided in the figure, as shown in FIG. ) is applied to form the branch pipe portion 3'.

Similarly to the bulge forming method, in this diameter reduction-pulling method, as the diameter ratio D ₂ /D ₁ becomes smaller, T ₀ /
As D ₂ becomes larger, it becomes difficult to push the material into the die hole 8, so in this case as well, its application is essentially within the condition range of D ₂ /D ₁ > 0.3 and T ₀ /D ₂ < 0.3. Limited.

A method for obtaining a T-joint with dimensions that cannot be manufactured using the above-mentioned pipe forming method is to use forging and machining. As shown in Fig. 6 (a), a solid block with an outer shape approximately sized to allow a product T-joint to be obtained is made by forging, and the product is machined from this block, or as shown in Fig. 6 (b), a branch pipe forming part is formed. 17 is forged into a hollow block with a convex shape,
There is a method of cutting the product out of it, but this type of cutting process is not only time-consuming and inefficient, but also involves forging the inner surface of the pipe at the branch pipe and crotch part, which is important for strength. The degree of this is significantly inferior to the above-mentioned methods in which a tube is used as a raw material and the shape is formed by molding.

In view of the above, the present invention uses a pipe as a material,
The purpose of this method is to provide a method for manufacturing branch pipes that cannot be manufactured using conventional methods such as the bulge forming method or the diameter reduction-drawing method. , insert the mandrel 25 with the plug 24 attached laterally, set the plug 24 on the flat tube body 23 in the major diameter direction, and press the flat tube body 23 in the major diameter direction so that the long side direction is A secondary flat tube 27 is formed in the short side direction, and its pressing force pushes the plug 2 through the mandrel 25.
4 is pressed in the thickness direction from the inner surface of the tube to form a protrusion 28 on the outer surface of the tube, and then the preformed tube body 38 is processed to correct its flatness. The mandrel 25 and the plug 24 are removed, and then, with the protruding part 28 tightly fitted into the die hole 8 of the die 7, the protruding part 28 is subjected to branching processing by a plug pulling method. It's a method.

Hereinafter, the method of the present invention will be explained in detail step by step.

A perfectly circular blank pipe (straight pipe) is prepared and first flattened to obtain a primary flat pipe. That is, the seventh
As shown in Figure A, the outer radius (1/
A pair of upper and lower flat dies 21 and 22 each having a groove 20 having an arcuate cross section with a radius of curvature R larger than 2D ₀ ).
The upper die 21 is lowered using a press (not shown) as shown in FIG. get. The degree of this flattening is determined by the mandrel 25 and plug 2 described later.
4 is the range that can be set inside the pipe. The outer diameter of the raw pipe 19 used is desirably about 1.02 to 1.05 times D ₁ from the viewpoint of reducing the circumference by flattening and correcting the roundness by molding, which will be described later. Further, its length may be set to the target product main pipe length L ₁ with a slight finishing allowance. The selection of the raw pipe wall thickness T ₀ has a particularly important meaning in the method of the present invention, and this T ₀ is determined from the target product main pipe wall thickness T ₁ and the volume of the product branch pipe 3.
This point will be explained in detail later.

Note that this flattening process can be performed by either cold or hot process.

Next, this primary flat tube 23 is preformed to form a protrusion for a branch pipe on the outer surface of the tube. As shown in FIG. A tool with a plug 24 attached thereto is inserted into the primary flat tube 23 and set. Next flat tube 23
As shown in the figure, a die hole 2 with a diameter approximately equal to the target product branch pipe diameter D ₂ provided in the lower die 22 is
6 so as to correspond to the planned branching portion, and the tool positions the plug 24 in the longitudinal direction of the primary flat tube 23 on the inner surface of the tube in the planned branching portion corresponding to the die hole 26. The mandrel 25 and the plug 24 to be used are connected by a small diameter bolt or spot welding so that they can be separated relatively easily. The diameter dp of the plug 24 will be described later. Mandrel 25 opposite side from the plug installation side (back side) 2
5' is the back side 2 during the plug pushing process described below.
In order to avoid deformation of the inner surface of the raw tube that comes into contact with 5', it is recommended to use a suitable circular arc surface.

In the state set as above, the upper die 21 is lowered by a press as shown in FIG.
The primary flat tube 23 is pressed in the long diameter direction, and the inner surface of the tube is pressed against the back surface 25' of the mandrel 25, and the plug 2
4 from the inner surface of the tube in the thickness direction, thereby pushing the material into the die hole 26 and forming a raised portion 28 at the portion of the outer surface of the tube where branching is planned. At this time, the major axis direction and the minor axis direction of the obtained secondary flat tube 27 are opposite to those shown in FIG. 7B. Volume of raised portion 28
V ₂ must be able to cover the volume of the target product branch 3. Note that since the plug pressing operation is performed via the mandrel 25,
The reaction force F of pushing the plug in is transmitted to the tube inner surface 29 in contact with the mandrel back surface 25' in a distributed manner as shown by f in FIG. It is stopped and is not a problem.

The above is the basic procedure up to preforming, and the following can be said about the above preforming. That is, to explain with reference to FIG. 9A, the plug 24
The volume V ₂ of the raised portion 28 formed on the outer surface of the tube by preforming by pushing increases as the volume V ₁ of the raw tube material removed by pushing the plug 24 (hereinafter referred to as excluded volume) increases. It is obvious that this ratio of V ₂ and V ₁ is V ₂ /V ₁ × 100 (%)
(Extrusion efficiency) depends on the ratio dp/ _D2 of the plug diameter dp and the die hole diameter _D2 . Figure B is based on experimental results.
Regarding the relationship between V ₂ /V ₁ and dp/D ₂ , as is clear from the figure, the extrusion efficiency V ₂ /V ₁ ×100 (%) is dp/D ₂
It improves linearly as the value of increases.
In other words, for the same excluded volume V ₁ , a larger ridge volume V ₂ can be obtained by increasing dp/D ₂ , and according to this experimental result, dp/D ₂ ≒ 1.1
By doing so, a ridge volume V ₂ which is the same as the excluded volume V ₁ , ie, an extrusion efficiency of 100% is achieved.

In addition, in the above experimental results, the material flow when the value of dp/D ₂ is smaller than 1.1 is the 11th
The state shown in the figure will be reached. That is, the value of dp/D ₂ is 1.1
If it is smaller than V ₁ >V ₂ , the material of V ₁ −V ₂ appears as a bulge 41 around the plug 24 . Also, even if the value of dp/D ₂ is set to 1.1 or more,
V ₁ /V ₂ cannot be greater than 1 (100%). That is, as shown in Figure 12, the value of dp/D ₂ is 1.1.
When dp is increased to exceed , the plug pushing force becomes extremely large, and the material bulges around the plug 24. In other words, as dp increases, the material around the plug is further away from the die hole, so it becomes difficult to flow into the die hole, and the material around the plug becomes difficult to flow into the die hole.
The number swells around number 4. Therefore, making dp larger than necessary will only worsen the efficiency.

Now, in the case of the method of the present invention, in this preforming, it is necessary to ensure that the volume V ₂ of the raised portion 28 is enough to cover the volume of the target product branch pipe 3. Therefore, as a practical condition, The plug diameter dp, its pushing depth h, and the raw tube wall thickness _T0 are determined as follows. First, dp is extrusion efficiency V ₂ /V ₁ × 100 (%) 100%
In order to do this, dp/D ₂ may be determined to be approximately 1.1. Then, h is the plug depression depth h corresponding to the required removal volume V ₁ (=V ₂ ) by calculating the volume of the raised part V ₂ that is sufficient to cover it from the volume of the target product branch pipe.
Calculate and use this as the implementation condition. T ₀ is a value obtained by adding this calculated h value to the target product main tube wall thickness T ₁ and taking into account a slight cutting allowance.

Note that the volume of the target product branch pipe is the volume of a virtual cylinder created by rotating the branch pipe cross section shown in the shaded area around the branch pipe axis p in the center cross section of the product branch pipe shown in FIG. This is the volume of the target product branch pipe.

The secondary flat tube 27 whose flattening direction has been reversed by the above preforming is then hot molded using a pair of upper and lower dies 35, 35, as shown in FIG. 7E and F. The dice 35, 35 used are
As shown in Fig. 10, the main body part 2 of the secondary flat tube
9 and the grooves 36, 3 corresponding to the raised portions 28, respectively.
7, the groove shape approximately matches the target product outline shape, and the tool (mandrel 25
With the plug 24) still attached, set the secondary flat tube 27 with its major diameter facing the die (vertical), and press it in the major diameter direction by operating the die using a press (not shown) to form the secondary flat tube. 27
A process is performed to correct the flatness of the main body part 29 to form a perfectly circular main pipe part 2'. As stated earlier, the outer diameter of the base tube _D0 is 1.02 to _1.05D1 ( _D1 : target product mother tube diameter)
If this is done, a high correction effect can be obtained by this processing.

After this straightening process, the mandrel 25 and plaque 24 are removed from the straightened preformed tube 38. First, the back surface 25' of the mandrel 25 is separated from the inner surface of the tube by the above-mentioned straightening process (see FIG. 7), and then the mandrel 25 is pressed in the longitudinal direction as shown in FIG. (not shown), the bolted or spot welded joint with the plug 24 is sheared off, and the plug 24 is left in place and removed. Next, a pilot hole 39 is drilled in the center of the protrusion 28 to perform the plug extraction process described later until it reaches the plug 24, and then a punch 4 is inserted into the pilot hole 39 as shown in FIG.
Remove it by inserting it into the straightened preformed tube 38 and pushing it out. Punching out the plug with this punch can be performed extremely easily if a slight draft angle is provided on the side surface of the plug 24.

After removing the mandrel 25 and the plug 24, the plug extraction method as described above is applied to the raised portion 28 of the straightened preformed tube 38 to obtain a branch tube portion. That is, as shown in FIG. 7L, the preformed tube 38 is set in a die 7 having a die hole 8 having the same diameter as the target product branch pipe diameter D ₂ so that its raised portion 28 fits into the die hole 8. A pull-out plug 10 is connected to the tip of the pull-out rod 9, which is exposed to the inside of the tube through a prepared hole 39 formed in the raised portion 28. As the pull-out plug 10, one whose outer diameter dp is smaller than the inner diameter of the target product branch pipe by the finishing allowance is used. After setting, by pulling the pull-out rod 9 downward and passing the pull-out plug 10 through the pilot hole 39, the pilot hole 39 is enlarged to the outside diameter dp of the plug, and the raised portion is The branch pipe portion 3' is formed by ironing between the plug 10 and the inner wall of the die hole 8 from the inner and outer surfaces. As a result, a roughly finished product 42 is obtained. Since this plug drawing process is performed while the outer periphery of the raised portion 28 is completely restrained by the inner wall of the die hole 8, all the material removed as the plug 10 advances during the drawing process increases the height of the branch pipe portion 3'. Shift in direction. In other words,
This means that all of the material forming the raised portion 28 can be used to form the branch pipe without any waste. In short, the formation of the raised portion 28 by preforming requires the following steps:
The amount of material necessary for forming the target product branch pipe 3 is secured in advance by protruding from the outer surface of the base pipe, and moreover, the material of this portion is made to be effectively used for forming the branch pipe in the plug drawing process. It's meaningful.

In addition, even if the raw pipe wall thickness T ₀ is thick,
At the stage before the plug drawing process shown in FIG. Therefore, when the protruding portion 28 is subjected to the plug drawing process, the material of the protruding portion 28 is squeezed between the plug 10 and the inner wall of the die hole 8, and the material of the protruding portion 28 is squeezed between the plug 10 and the inner wall of the die hole 8, and forms a branch pipe that extends long in the plug drawing direction and has a large height. can be formed.

Accordingly, according to the method of the present invention, the expansion deformation of the prepared hole as shown in FIG. 3 described above occurs preferentially, and the problem that the height of the branch pipe portion becomes small does not occur.

The rough finished product 42 obtained in the above manner is finished by cutting the main pipe part 2' and the branch pipe part 3' to the target product dimensions, respectively, to become a product. Note that if the protrusion 28 is high enough to collect the product branch pipe 3 at the stage shown in FIG. Of course, it is also possible to perform finishing processing and make it into a product.

The method of the present invention described above achieves a diameter ratio D ₂ /
This makes it possible to manufacture a T-joint that requires a thick pipe with a small D ₁ (<0.3) and T ₀ /D ₂ >0.3.

In the method of the present invention, the portion of the raw pipe where the branch is to be branched is raised in advance by pushing a plug into the inner surface, but the idea of pressing the portion where the branch is to be branched from the inner surface of the tube is not known in the past. ing. However, in the past, for example,
As shown in No. 52-139664 and Japanese Patent Application Laid-open No. 57-142725, the push-in plug is made by moving a jig that engages with the plug through a wedge or the like in the axial direction of the tube. ), and such machining methods require complicated tools and are difficult to apply to thick-walled pipes that require large machining forces due to the strength of the tools. As mentioned above, the method of the present invention moves and pushes the plug in the wall thickness direction by flattening the raw pipe itself by applying press pressure.The method of the present invention is as simple as attaching the plug to a mandrel as a tool. Moreover, since the external pressure from the press is directly used as the processing force, it has the advantage that it can be applied to raw pipes of any thickness.

Although the explanation has been limited to the manufacture of T-joints, the method of the present invention is widely applicable not only to the manufacture of T-joints, but also to the manufacture of branch pipes having many branch pipes such as header pipes. be.

As is clear from the above explanation, the method of the present invention makes it possible to manufacture branched pipes using pipes as raw materials, which cannot be manufactured by the bulge forming method or the diameter reduction-drawing method. It also avoids the disadvantages in terms of product quality that are seen under the law, and its practical value is extremely large.

[Brief explanation of drawings]

Figure 1 is a perspective view showing the shape of the T-joint, Figure 2 A and B are process diagrams showing the conventional plug extraction method, and Figure 3 is a perspective view showing the shape of the T-joint.
The figure is a partial view showing the forming situation around the pilot hole of the raw tube when the plug drawing method is applied to a thick-walled raw tube.
Figures 5A to 5C are process explanatory diagrams showing the reduction-drawing method, and Figures 6A and 6B illustrate the forging and cutting method, showing two types of material blocks after forging and before cutting. is a solid block, and b is a hollow block. Figures 7A to 7 are process diagrams showing the molding method of the present invention, Figure 8 is an explanatory diagram showing the state of action of plug reaction force in the preforming (expansion molding of a raised part) process based on the method of the present invention, and Figure 9 Figure A is the same as above for preforming.
A diagram showing the relationship between dp/D ₂ and extrusion efficiency V ₂ /V _1. Figure 10 is a schematic diagram to explain the shape change of the raw tube in the preforming process. Figure 10 is a mold based on the method of the present invention. FIG. 11 is a perspective view showing a mold die used for inserting and straightening processing, in preforming based on the method of the invention,
FIG. 12 is a diagram illustrating the shape change of the raw pipe material when the value of dp/D ₂ is small, and FIG. 12 is a diagram explaining the shape change of the raw pipe material when the value of dp/D ₂ is large.
FIG. 13 is a diagram illustrating the volume of the target product branch pipe. In the figure: 1: T-joint, 2: Main pipe, 3: Branch pipe, 5: Base pipe, 9: Pull-out rod, 10: Pull-out plug, 21,2
2: flat die, 24: plug, 25: mandrel, 35: molding die.

Claims (1)

[Claims] 1. When branching out a part of the tube, in the primary flat tube 23 formed with a flat cross section,
Attach the plug 24 to the mandrel 25 at right angles to it.
Insert the tool with which the plug 24 is attached, and align the plug 24 in the long diameter direction of the tubular body 23 to correspond to the planned branching portion. A secondary flat tube 27 is formed as a direction, and the plug 24 is pushed in the wall thickness direction from the inner diameter of the tube through the mandrel 25 with the pressing force at that time, so that the planned branching portion is raised 28 toward the outer surface of the tube. Preforming is performed, and then this secondary flat tube body 27
After processing to correct the roundness, the used mandrel 25 and plug 24 are removed, and then the raised part is inserted into the die hole 8 of the die 7 against the raised part 28 of the straightened preformed tube 38. A method for manufacturing a branch pipe, characterized by performing branching processing by pulling out a plug while the branch pipe is tightly fitted into the pipe.