JPS5841130B2 - Method for manufacturing a curved pipe joint in which relatively long straight pipe parts are integrally and continuously formed at both ends - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Conventionally, in piping around marine equipment, curved front joints with straight pipe portions have been manufactured with a range of 12 to 30 elbows, depending on the diameter of the elbow used.

To give an overview of this conventional manufacturing method of a curved front joint with a straight pipe part, as shown in Fig. 1, first, a raw material pipe P of a required diameter is cut to a required length, and the head part is cut into a circular cross section. The tube is expanded and curved while being press-fitted through the elephant nose-shaped mandrel m1, which is the guide portion rn1g, to form a curved tube P2 having a circular cross section and a required circumference.

Then, the end g of the curved tube P2 is cut so that the end length of the curved tube P2 in the axial direction with the designated angle as the reference plane is the same length l for both the back and abdomen, and then the core metal is attached to both ends of the curved tube P2. m2
A curved pipe P2 is formed by straightening only the bend at the end from the direction of the bending radius r using a two-split mold d1 and d2 in which molding grooves el and e2 with semicircular cross sections are formed so as to face each other. A straight pipe portion V having a required length l was formed at both ends of the pipe.

In this way, in the conventional manufacturing method, the curved pipe P2 with a circular cross section is formed by forming grooves el with a semicircular cross section facing each other,
Two-split mold d1 with e2. d2 to straighten only the bend at the end into a straight pipe shape, it is necessary to insert core metal m2 at both ends of the curved pipe P2. Unless the length 1 is made extremely short, it will be difficult to insert the core metal m2.

For these reasons, the length l of the straight pipe part V of the curved front joint manufactured by the conventional manufacturing method has to be extremely short. The range of use of curved front fittings with part V is limited,
There was a drawback that the demand for it suddenly decreased.

Therefore, it was necessary to weld a short straight pipe of the required length to the straight pipe part (■) to meet widespread demand. Since high accuracy is required for the finish roughness on the inner surface of the welded part between the welded part and the short straight pipe, the straight pipe part (2) without such a welded part is long (Max.

There was a strong demand for the development of a curved front joint (200mm).

In addition, as a result of the recent requirement for ultrasonic testing (UT) of welded parts of piping systems for nuclear power generation to be inspected during use, it has become necessary to There has been a demand for the development of joints.

Under these circumstances, a method of manufacturing a curved front joint in which relatively long straight pipe parts are integrally and continuously formed at both ends according to the present invention was devised. A curved tube with an elliptical cross section with a length equal to the circular circumference, a total length equal to the total length of the product pipe joint, and an elliptical cross section curved over the entire length with the same curvature as the product pipe joint is formed from the raw material pipe. The curved pipe having an elliptical cross section is formed by using a two-split mold in which molding grooves each having a semicircular cross section are formed to face each other, and a straight pipe molding groove of a required length is connected to both ends of the curved pipe forming groove. The gist of the invention is to press the curved pipe with the elliptical cross section in opposite directions using a molding die on the major diameter axis of the ellipse, thereby correcting the curved pipe having the elliptical cross section into a desired shape and a circular cross section with a desired diameter.

The illustrated embodiments will be described in more detail below.

The method for manufacturing a curved front joint according to the present invention includes a curved pipe having an elliptical cross section obtained from a raw material pipe as an intermediate molded product for obtaining a curved front joint as a final product, and the major axis of the ellipse being the curved front joint. There is a vertical ellipse method in which the ellipse is formed so as to extend in the direction of the radius of curvature, and a horizontal ellipse method in which the major axis of the ellipse is formed in a direction perpendicular to the direction of the radius of curvature of the curved tube.

First, to explain the vertical ellipse method, as shown in FIG.
2 is fixed to the tip of the support rod Q, and is composed of a tube expansion section M2e and a guide section M2g for the raw material tube P.

The expanding section M2e has a cross section from the inlet side of the circular section toward the guide section M2g, so that the cross section becomes a vertical ellipse with the short axis S2 and the long axis T2 shaped like a dog. The radius of curvature r2 on the ventral side and the radius of curvature r1 on the dorsal side are curved at different curvatures.

The guide portion M2g is curved as a whole with the same curvature radius R2 of the central axis on both the ventral side and the dorsal side while maintaining the same longitudinal elliptical cross section E2 as the distal end cross section of the expanded tube portion M2e.

Then, using another device (not shown), a raw material tube P having a required diameter and length is force-fitted into the elephant nose-shaped core metal M2 in the direction of the arrow and expanded and curved. As shown in FIG. 2B, a curved tube B2M having an elliptical cross section with a required circumference and a curved shape in which the major axis T2 of the ellipse is directed in the direction of the radius of curvature R2M of the curved tube is obtained as an intermediate molded product.

Furthermore, as shown in FIG. 2C, the curved tube B2M with an elliptical cross section as an intermediate molded product is corrected into a circular cross section with a desired shape (and a desired diameter) to obtain a curved front joint as a final product. The molds D21 and D22 are divided into two parts, each having a molding groove E with a semicircular cross section facing each other.
21 + E2□ is provided.

This molding groove E21) E2□ has a curved pipe B2 in the center.
Curved tube forming groove B2 for forming a curved portion B2 of a desired shape in M
11 B2□ is also provided with straight tube forming grooves L2□ and L22 of a required length, respectively, at both ends thereof.

Therefore, the molding groove E21. of such molding die D21 t D2□. A curved pipe B2M with an elliptical cross section as an intermediate molded product is inserted into E2□, and this is formed into a molding die D2□.

Due to D2□, arrow F2 is drawn on the major axis T2 of the ellipse.
When pressed in opposite directions, the curved tube B2M with an elliptical cross section forms the molding groove E2□ of the molding die D21 j D2□.

E22, the straight pipe portion L2.E22 is corrected into a circular cross section of a desired shape and diameter, and a straight pipe portion L2. A curved front joint B2J is obtained as a final product in which L3 is integrally and continuously formed.

Next, to explain the horizontal ellipse method, as shown in FIG. 3A, an elephant nose-shaped core bar M2 for expanding and curving the material tube P is fixed to the tip of the support rod Q, and the material tube P It is composed of a tube expansion section M3e and a guide section Mag.

The expanding section M3e has a circular cross section from the inlet side toward the guide section M3g, so that the cross section becomes a horizontal ellipse with the short axis S3 and the long axis T3 shaped like a dog. The radius of curvature r4 on the ventral side and the radius of curvature r3 on the dorsal side are curved at different curvatures.

The guide portion Mag is curved as a whole with the same curvature radius R3 of the central axis on both the ventral side and the dorsal side while maintaining the same horizontal elliptical cross section E3 as the distal end cross section of the expanded tube portion M3e.

Then, using another device (not shown), a raw material tube P having a required diameter and length is force-fitted and passed through the fish-like core metal M3 in the direction of the arrow, and the tube is expanded and curved. As shown in FIG. 3B, a curved tube B3M having an elliptical cross section with a required circumference and a major axis S3 of the ellipse oriented in a direction perpendicular to the radius of curvature R3M of the curved tube is obtained as an intermediate molded product. It will be done.

Furthermore, as shown in FIG. 3C, a molding tool is used to correct the curved pipe B3M, which has an elliptical cross section as an intermediate molded product, into a circular cross section with a desired shape and diameter to obtain a curved front joint as a final product. Mold])at t D32 is divided into two parts, each having a molding groove E with a semicircular cross section facing each other.
31 t Ea□ is provided.

This molding groove E31 r E3□ has a curved pipe B3 in the center.
Curved tube forming groove B3 that forms a curved portion B3 of a desired shape in M
1 + B3□, and a straight pipe part L of the required length at both ends.
2. Straight pipe forming grooves L31 j and L32 for forming L3 are arranged in succession, respectively.

Therefore, the molding groove E31. of such molding die D31 + D3□. Insert the curved pipe B3M with an elliptical cross section as an intermediate molded product into E3□, and insert it into the molding die D31°D3□.
If the curved pipe B3M with an elliptical cross section is pressed in the direction of the arrow F3 on the major axis T3 of the ellipse, the curved tube B3M with the elliptical cross section is formed into the desired shape, the required diameter, and the required shape by the forming grooves E31JE32 of the molding die I) The curved front joint as a final product is corrected to have a circular cross section with a diameter, and a straight pipe portion L3 + L3 of a relatively long required length is integrally and continuously formed at both ends thereof, as shown in Fig. 3D. B3J is obtained.

As described above, the manufacturing method according to the present invention includes the vertical ellipse method and the horizontal ellipse method, but when manufacturing a curved front joint in which the straight pipe portion is to be extremely or relatively long, the horizontal ellipse method is preferred. , in the molding molds D3□ and D32, a curved pipe B3 as an intermediate molded product is placed in the straight pipe forming groove L31 + L3□.
This is inconvenient because both ends of M cannot be inserted due to its curvature, but even in such cases, with the vertical ellipse method, the above-mentioned inconveniences do not occur, and it is possible to insert A relatively long curved front joint can be manufactured.

In addition, as a means for forming a curved tube with an elliptical cross section from a raw material tube, in the above embodiment, a method is shown in which the raw material tube is passed through a fish-like core metal. There is no problem in obtaining a curved pipe with an elliptical cross section by deforming it into a tube and then bending this straight pipe with an elliptical cross section.

As described above, according to the manufacturing method of the present invention, unlike conventional manufacturing methods, there is no need to cut both ends of the curved pipe in advance, and there is no need to insert a core metal at both ends. It is possible to obtain a curved front joint in which the straight pipe part is integrally and continuously formed, and the range of its use is wide without being limited due to the extremely short length of the straight pipe part, which is the case with conventional manufacturing methods. Can be supplied as a curved front joint with various uses.

Further, there is no need to further weld a short straight pipe of a required length to the straight pipe portion as in conventional manufacturing methods, and high accuracy is not required for the finish roughness on the inner surface.

Furthermore, since the curved front joint according to the present invention is capable of performing UT, it can be used for nuclear power generation piping diameters.

As described above, the present invention first forms the curved part of the elliptical cross section of the required length and length by the molding process using the fishy core metal,
This intermediate molded product is corrected into the desired final shape in a single molding process using a molding die that is split into two and has molding grooves of the desired shape with a semicircular cross section. This made it possible to economically produce a curved front joint with a continuous pipe section.

In other words, the present invention should be highly praised for its inventiveness, as it achieved an inexpensive and high-precision product by specifically selecting and combining two molding methods that are well-experienced, stable, and inexpensive. It is.

Further, as an example of the effect of implementing the present invention in terms of product precision in terms of roundness, the following table shows that the present invention has achieved an extremely large effect.

Incidentally, when comparing the results obtained by the method of the present invention with several manufacturing methods that the present applicant has tried in the past for the purpose of obtaining products of the same form, the diagrams in FIGS. 4 and 5 show that As can be seen, the method of the present invention proves to be particularly superior.

The target product pipe joint is a 90° curved front joint as shown in Figure 4 A, and the product dimensions are an outer diameter of 1e! '(406im) Thickness 4
This is an extremely thick piece for a two-stage nuclear reactor, making it extremely difficult to bend.

The four methods from Kuchinoni 1 to A4 in the figure are as follows.

Part 1: Bending a perfectly round straight pipe (R = 1.5D) L, straightening a perfectly round curved pipe by splitting it into two molds &2: Using the method of the present invention, bending an elliptical cross section curved pipe (R = 1.5D) )
Straighten by splitting into two molds 3: Split a perfect circular straight pipe into two molds into three stages (1st stage R = 3I), 2nd stage R2 2D, 3rd stage R = 1.5D ) A4: Split an elliptical straight pipe into two molds to form three stages (1st stage R = 3D, 2nd stage R = 2D, 3rd stage R = 1.5D).The processing conditions are as follows: The circumference of the raw material pipe should be increased by 1.5 times the circumference of the product pipe joint (if it increases by about 5mm, burrs will occur on the outside, and if it increases by about 3φ, burrs will occur on the inside, which is not preferable.

In addition, the ratio of the major axis to the minor axis of the elliptical tube was 1.15.

The ellipticity of each position (maximum outer diameter (dmax) and minimum outer diameter (dmax)
The difference in min) is as shown in Figure 4, and A2 of the present invention is the best, resulting in a nearly perfect circle.

This is followed by A1, followed by A4, and then A3, with A3 having the largest outer diameter ellipticity.

Regarding uneven thickness, the A2 method of the present invention is the best for each position, followed by the A1 method, but in the black 3 and A4 methods, wrinkles occur on the ventral side at the curved part of the product joint tube, and at the same time, the dorsal side becomes thicker. is damaged and cannot be used.

Therefore, if we show the wall thickness changes in each part (the difference between the standard wall thickness of 42 mm and the wall thickness of the product pipe joint) for only the two methods AI and A2, it is as shown in Figure 5 at 42. It can be seen that this method is extremely superior to the first method.

As mentioned above, it may be possible to achieve low cost by specifically selecting and combining two inexpensive forming methods that are experienced, stable, and stable in their own right: ``forming a curved tube with an elliptical cross section'' and ``correction using a two-split mold.'' As a result of extremely high product precision, the present invention deserves to be highly evaluated both from the point of view of the idea and from the point of view of effectiveness.

[Brief explanation of the drawing]

FIG. 1 shows an outline of the process for forming a curved pipe joint in which straight pipe parts are integrally and continuously formed at both ends by a conventional method. A group of drawings from FIG. 2A to FIG. 2D show the main steps of an embodiment of the manufacturing method according to the present invention, and the third
A group of drawings from Figure A to Figure 3D show the main steps of another embodiment of the manufacturing method according to the present invention. In addition, Figures 4 and 5 compare the product results of the method (A2) of the present invention with other methods (AI, A3, 44) tried by the applicant, and A in Figure 4 is a comparison of the product results. Figure 5A shows the comparison of the ellipticity at each position of the product, and Figure 5A shows the comparison of the shape of the product and each comparison position. , Q is the side portion, and R is the back portion). Among these drawings, FIGS. 2A and 3A show the relationship between the raw material tube and the fishy core, and FIGS. 2B and 3B show a curved tube with an elliptical cross section as an intermediate molded product. 2nd C
The figure and FIG. 3C show the relationship between the curved tube and the molding die in the process of correcting the curved tube with the elliptical cross section using the molding die to form the required pre-bent pipe joint with the circular cross section, and further,
FIG. 2D and FIG. 3D show a perspective view of the curved pipe joint as a final product. In addition, in the drawings, in the conventional manufacturing method, P ~ raw material tube, m ~ fishy core bar, m1g ~ circular cross section guide part of its head, P2 ~ curved pipe expanded and curved, g ~ cutting rn2 - core metal, dl, d2 - mold, el, e2 - molding groove, r - bending radius, l - required length of both ends of curved pipe P2, V - straight pipe part. Furthermore, in the manufacturing method according to the present invention, P~raw material tube, M22M3~elephant nose-shaped mandrel, Q~support rod, M2e,
M3e ~ tube expansion part, M2g2 M3g ~ guide part, r1 ~ radius of curvature on the dorsal side of guide part M2g and tube expansion part M2e, r2
~Same radius of curvature on the ventral side of tube expansion section M2e, r3~Same radius of curvature on the dorsal side of guide section M3g and tube expansion section M3e, R3-Same radius of curvature of the solid axis, r4~Same radius of curvature on the ventral side of tube expansion section M3e , E2~expansion part M2e tip or guide part M
2g elliptical cross section, E2 to expanded tube part M3e tip to guide part M
3g elliptical cross section, T2 to elliptical cross section E2 and curved pipe B2
Vertical diameter (major axis diameter) of M, 82 ~ Similarly, its horizontal diameter (minor axis diameter)
, T3 ~ longitudinal diameter (major axis diameter) of elliptical cross section E3 and curved pipe B3M, 83 ~ also its transverse diameter (short axis diameter), R2M ~ radius of curvature of curved pipe B2M, R3M ~ radius of curvature of curved pipe B3M, D2 ,. D22 ~ Mold for the precept, F211 E22 ~ Its molding groove,
BB211 B2□~Curved pipe forming groove, L211 L2□
~Straight pipe oval groove, F31,' D3□~Mold for oval shape, F
31 + E3□ ~ Its forming groove, F311 B3□ ~ Curved forming groove, LSI j L3□ ~ Straight pipe forming groove, B2J ~
Curved pipe joint, B2 - its curved part, L2 - its straight pipe part, B
3J - curved pipe joint, B3 - its curved part, L3 - its straight pipe part, F2. F3 to the pressing direction of the ceremonial mold D21 j D2 □ and F311 F32.

Claims (1)

[Claims] 1. An elliptical cross section with a circumference equal to the circular circumference of the product pipe joint, a total length equal to the total length of the product pipe joint, and the same curvature as the curved pipe portion of the product pipe joint. There is an intermediate forming process in which a curved pipe with an elliptical cross section curved in the shape of a circular arc is formed from a raw material pipe, and a semicircular cross-section in which straight pipe forming grooves of the required length are connected to both ends of the curved pipe forming groove. The curved pipe with the elliptical cross section obtained by the intermediate forming process is avoided from the straightening process in which the curved tube with the elliptical cross section obtained by the intermediate forming process is pressed facing each other on the major axis of the ellipse using a two-split molding die in which forming grooves are formed facing each other. Straight pipe parts are continuously formed at both ends of a curved pipe with an elliptical cross section by a straightening process, and the straight pipe parts are straightened into a circular cross section of a required diameter, and relatively long straight pipe parts are integrally continuous at both ends. A method for manufacturing the formed curved front joint. 2. A curved tube with an elliptical cross section is formed such that the major axis of the ellipse is directed in the direction of the radius of curvature of the curved tube, as set forth in claim 1, wherein relatively long straight tube sections are integrally formed at both ends. A method for manufacturing a curved front joint that is continuously formed. 3. A straight pipe with comparatively long ends at both ends as set forth in claim 1, characterized in that the curved pipe with an elliptical cross section is formed such that the major axis of the ellipse is directed in a direction perpendicular to the direction of the radius of curvature of the curved pipe. A method for manufacturing a curved front joint in which parts are integrally and continuously formed.