JPH0545331B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention utilizes the so-called diameter reduction-plug drawing method to produce a tee or cross joint with a straight pipe section (hereinafter collectively referred to as a pipe joint). ), and particularly relates to a method for manufacturing stepped pipes thereof.

[Conventional technology]

As shown in Fig. 4, a Tee joint with a straight pipe part has a branch pipe 2 extending from the main pipe ₁ with a straight pipe part 1a to one end, and a cross joint with a straight pipe part has a shape as shown in Fig. 5. As shown in FIG. 2, branch pipes 2 protrude from both sides of a main pipe 1 with a straight pipe portion 1a, and these are used at T-junctions and crossroads of piping.

Demand for this type of pipe joint has recently increased, particularly for use in nuclear reactors. This is because, particularly in piping related to nuclear reactors, there is a demand to minimize the number of welded parts that are disadvantageous in terms of strength and corrosion protection. The specific dimensions of the Tee joint with straight pipe for nuclear reactors are: main pipe outer diameter 609mmφ, same wall thickness 39mm, branch pipe outer diameter 356mmφ, same wall thickness 46mm, same height 200mm, overall length.
There are various types such as 6000mm, straight pipe length (up to the center of the branch pipe) 5470mm.

Incidentally, in the case of this type of joint, not limited to those related to nuclear reactors, it is desired that the branch pipe height H be larger. This is because it is advantageous for the above-mentioned H to be larger in terms of work when welding another pipe to the end of the branch pipe, and also in the sense of keeping the root of the branch pipe, which is important for strength, away from the welded part. It is.

As one method for obtaining a joint with a large pipe height H, the diameter reduction-plug drawing method is known. That is, to explain this method using the case of a Tee joint with a straight pipe section as an example, first, as shown in Fig. 6, a stepped element having a large diameter section M ₁ on one end side which is larger in both the inner and outer diameters than the other parts is used. Prepare tube M. In the forming process, first, the large diameter part M ₁ of this stepped blank tube M is flattened to form an elliptical part M ₁ ' as shown in Fig. 7A, and this stepped blank tube M is assembled into a pair of upper and lower parts. The elliptical part M1' is compressed in the circumferential direction by pressurizing the elliptical part _M1 ' in the long diameter direction.
The material M ₁ ' is poured into the die hole 4 provided in the lower die 3 to obtain the raised portion 2' as shown in FIG. 3 (diameter reduction process). Next to this raised portion 2', a through hole 5 is drilled as shown in FIG.
By drawing the plug through the plug using the drawing rod 7 connected thereto, the through hole is expanded to form the branch pipe 2 as shown in FIG. 2D (plug drawing step).

In the case of a cross joint, the raised parts 2' are formed on both sides of the elliptical part _M1 ' during the diameter reduction process,
Plug withdrawal will be carried out for each of its ridges 2'.

By the way, the following two methods are conventionally known as methods for making the stepped blank tube M used in such a diameter reduction-die drawing method. That is, by using the Erhard-Putschubsch pipe manufacturing method, which is known as a method for producing seamless pipes, a hollow material _mA with a large wall thickness and equal thickness as shown in FIG. We decided to use the method of cutting out the stepped tube M by machining (hereinafter referred to as method A) and the same Erhard-Putschübench pipe manufacturing method, and punch out a stop in the final stage of multiple punches. Therefore, as shown in FIG. 12, a stepped material m B with a step on the outer surface side and a thick wall part m _B ′ left on one end side is formed in advance, and from there, the step material m _B shown in the dashed-dotted line is formed in the same manner. A method of cutting out a stepped blank pipe M (hereinafter referred to as method B).

[Problem that the invention seeks to solve]

However, all of the above methods require considerably large machining allowances S and S', resulting in very low manufacturing yields. Method B is somewhat better than Method A, but it is still only 50% better at most, and for this reason, the overall yield for manufacturing pipe fittings with straight pipe parts by the diameter reduction-plug drawing method is extremely low. I felt bad for being so low.

The present invention is intended to improve the yield of manufacturing a pipe joint with a straight pipe section by a diameter reduction-plug drawing method by particularly devising the manufacturing method of the stepped blank pipe M.

[Means to solve the problem]

That is, the present invention uses a hollow material m _p with a bottom made by punching with a vertical press or one or more horizontal presses, and has a required diameter d _x smaller than the inner lumen diameter D _np ′ of the material. mandrel 8
By performing punching at least once while leaving _one end unprocessed using
A stepped hollow material m _c with m _c1 is created, and this is finished to the required dimensions by cutting the bottom and cutting the inner and outer surfaces to create a stepped blank pipe M with a large diameter part M ₁ on one end side.
Then, the large diameter portion M ₁ is flattened to form an elliptical portion M ₁ ′, and then the elliptical portion is formed by diameter reduction processing.
The planned branch pipe portion on the long diameter side of M ₁ ′ is bulged and raised outward to form a raised portion 2′, and this raised portion 2′ is subjected to branching processing by pulling out a plug to form the branch pipe 2. Accordingly, a tee or cross joint is obtained by using _{the small diameter portion M 2 other} than the large diameter portion M 1 as the straight pipe portion 1 _a .

Hereinafter, the method of the present invention will be explained specifically and in detail with reference to the drawings.

FIGS. 1A to 1C show a procedure for manufacturing a stepped blank tube M according to the present invention, and the procedure will be explained with reference to the figures as follows.

Basically, like the conventional method, the Erhard-Putschübench tube-making method is used. First, the hollow material with a bottom shown in Fig. A is _obtained through one or more punching operations using a vertical press or a horizontal press. .
The dimensions of this material are its inner and outer diameters D _np ′,
Both _Dnp and Dnp are sizes that take into account the machining allowances S and S' for later cutting work on the inner and outer diameters D _M1 ' and D _M1 of the large diameter portion _M1 of the target stepped blank pipe M, respectively. length
Regarding L _np , consideration is given so that the target length of the stepped blank pipe M can be obtained after processing in the intermediate stop punching process described below. The presence or absence of punching and the number of times punching is performed can be determined as appropriate depending on the _shape of the hollow material with a bottom to be obtained.
Needless to say, punching is done hot.

This bottomed hollow material m _p is then horizontally pressed to reduce the inner diameter D _np ′ of the material as shown in the diagram.
Using a mandrel 8 with an outer diameter _dx smaller than
A stepped hollow material m _c is produced in which a large diameter portion M _{c1, which is larger in both inner and outer diameters than m c2 ,} is formed on one end side. The length L _nc1 of the large diameter part m _c1 to be left unprocessed must be long enough to extract the large diameter part M ₁ of the target stepped blank pipe M from that part, and the length of the processed part m _c1 As for the length L _nc2 , it is assumed that the small diameter part M ₂ can also be taken, and its inner and outer diameters D _nc2 ′, D _nc2 ′ are the same as the inner and outer diameters D _M2 ′, D _M2 of the same small diameter part M ₂ and the machining allowance in the following cutting process. The size should take into account S and S'. The outer diameter d _x of the mandrel 8 used is therefore smaller than the above-mentioned small diameter portion inner diameter D _M2 ' by an amount S'×2 of the inner surface machining allowance. The number of times this halfway stop punching process is performed may be one or more times, and is appropriately selected depending on the required amount of work. The inner diameter d _y of the ring die 9 used for the final punching is the outer diameter D _M2 of the small diameter part.
It is clear from the above that the dimension is obtained by adding the outer surface cutting allowance S×2 to the above. It is the same as in the case of using hot processing as push technique.

By the way, when _the mandrel 8 with _the outer diameter _d It may be difficult to ensure uniform machining in the circumferential direction due to eccentricity. In order to deal with such a situation, as shown in FIG _{.
A large} diameter portion 8' with _an outer diameter _d d _s
A ring-shaped centering jig 13 having a diameter is attached, and during punching, this large diameter portion 8' or the centering jig 13 is used to hold the rear side m' of the material in a normal state where its center coincides with the punching center 0. By doing so, non-uniformity in the circumferential direction of machining can be avoided as much as possible.

Next, the stepped material m _c obtained in this way is cut off at the bottom as shown by the dashed-dotted line j in Figure C to make the entire length the target length L _M , and also as shown by the dashed-dotted line i. By cutting the inner and outer surfaces m _i ′, m _i to obtain the target inner and outer diameters D′, D, a step with a large diameter portion M ₁ on one end as shown in FIG. Finished with an attached tube M. The purpose of cutting the inner and outer surfaces is to ensure dimensional accuracy, and the machining allowances S and S' are expected to be as small as possible within the range permitted to guarantee dimensional accuracy.

The steps for producing a stepped blank tube according to the present invention are as described above, and this method is considerably more advantageous in terms of yield than the two methods shown as conventional examples. That is, as shown in FIGS. 11 and 12, the conventional method involves cutting from a material m _A with straight inner and outer surfaces, or from a material m _B with steps only on the outer surface. The method is based on both the inside and outside of the material.
Since m _i ′, m _i are formed into a stepped shape before being cut out, the cutting allowances S, S′ for cutting out can be much smaller in the present invention.

Regarding the yield, the method according to the present invention (hereinafter referred to as C
An example of a quantitative comparison of the conventional A and B2 methods is as follows.

Three methods A, B, and C were applied to manufacture the stepped blank tube M having the dimensions shown in FIG. 10. As method A, vertical press - 1 time full length extrusion - 2 times cutting, as B method, vertical press - 1 time full length extrusion - 3
Rotating stop punching (using the same mandrel throughout the entire process) - Cutting out, C method: Vertical press - 1 full length punching - 3 half stop punching (between full length punching and halfway stop punching) (change the mandrel diameter) - start cutting,
Each step was adopted.

As a result, the yield was 40% for conventional method A and 40% for method B.
In contrast, method C of the present invention recorded a high yield of 60%.

Note that the target dimensions of the stepped pipe M are set as follows based on the dimensions of the product pipe joint to be finally obtained. That is, the outer diameter of the large diameter part M ₁
D _n1 is calculated based on the product main pipe 1 considering the type of product pipe joint (T joint, cross joint) and the height H of its branch pipe.
Set the outer diameter D _p of the small diameter part M 2 to be larger than the outer diameter D ₂ of the small diameter part M ₂
is approximately equal to the outer diameter D _p of the product main pipe 1.
The wall thickness t of the large diameter portion M ₁ is approximately equal to that of the product main pipe 1, t _p , and the lengths L ₁ and L ₂ are L ₁ + L ₂ ≒
The total length of the product main pipe 1 is L _p , and L ₁ is set so as to cover at least the portion directly affected by the diameter reduction/plug drawing process described below.

The method of the present invention uses the stepped blank pipe M obtained as described above and performs diameter reduction and plug extraction to produce a pipe joint with a straight pipe section. Diameter reduction
The process of pulling out the plug is basically the same as described above, but the details are as follows. Here, too, the explanation will first be given using the case of a Tee joint with a straight pipe section as an example.

First, as shown in FIG. 7A, the large diameter portion M ₁ of the stepped blank tube M prepared above is flattened to form an elliptical portion M ₁ ′. The elliptical portion M ₁ ′ is made such that its minor axis D _s is approximately the same as the outer diameter D _p of the product main pipe 1 .

This stepped blank tube M is then set in a pair of upper and lower dies 3, 3', and the elliptical portion M1 _' is compressed in the circumferential direction by pressurizing it in the long diameter direction. The dies 3 and 3' used have an inner shape that is almost the same as the outer shape of the product main pipe 1, and one die 3 has an inner shape that is almost the same as the outer shape of the product branch pipe 2. A soybean hole 4 is provided. Through this processing, as shown in (B), the material of the elliptical portion M ₁ ' is forced out and flows into the die hole 4, and the material is pushed out into the product branch from a portion approximately corresponding to the protruding position of the product branch pipe 2 (from the large diameter end). tube 2
The protrusion 2' is formed at a distance approximately corresponding to the distance _Lz from the central main tube end 1'. In addition, the material near the part corresponding to the overhanging position of the branch pipe 2 flows into the die hole 4 to form the raised part 2' as described above, but the material flows into the die hole 4 in the part away from the said part. Because it does not, the wall thickness becomes thicker. This thick portion is ground using a grinder or the like, if necessary.

This processing is carried out at least on the elliptical part of the stepped tube M.
It is common to heat M ₁ ′ as a whole, but
When a particularly large branch pipe height H is required, after heating the whole part as described above, only the side opposite to the formation of the protuberance is cooled to a partially heated state, and then the diameter is reduced (partial heating method). ). If this partial heating method is adopted, the forming force during processing will be concentrated on the heated ridge formation side, and the height H' of the ridge formed will be higher.

In addition to this, as a means to further increase the height H' of the raised portion, as shown in FIG. There is a method in which the plug 10 is inserted into the die hole 4 (plug combination method). This method is related to a previous application by the same applicant, and in the process of forming the raised portion 2', the portion is always supported in a tendency to be pushed out from the inside of the tube, thereby increasing the height of the raised portion 2'.
This is an effective method to make a larger H′ appear. In addition, when the method of using a plug in combination is adopted, after forming the raised portion 2', the plug 10 and the mandrel 11 are cut and separated from their connecting portion and taken out to the outside.

After forming the raised portion 2' in this way,
As shown in Figure C, there is a through hole 5 in the center of the raised part 2'.
is bored and set in the lower die 3 having the die hole 4, and the drawing rod 7 is connected to the plug 6 in the tube through the through hole 5. And this pulling rod 7
is pulled downward as shown in Figure 2, and the through hole 5 is forced and expanded by the passage of the plug 6, thereby obtaining the branch pipe 2.
The diameter d _p of the plug 6 used is the inner diameter of the product branch pipe.
approximately match D _z ′.

In the case of a cross joint with a straight pipe section, as mentioned above, it is sufficient to form the raised parts 2' on both sides of the raw pipe and pull out the plug from each of them. , 2' will be briefly explained below. A pair of upper and lower dies used for diameter reduction processing is one in which die holes 4 are provided in both the upper die 3' and the lower die 3, as shown in Fig. 9.
Basically, two raised portions 2', 2' are created at the same time with this die. However, when applying the above-mentioned partial heating method, as is clear from the concept, the processing is divided into two steps, first, only one of the raised portions 2' is formed in the first step, and the remaining ridges are formed in the second step. A two-step method will be adopted in which the first raised portion 2' is formed. Further, the plug combination method described above can be similarly carried out in the case of this cross joint. As shown in FIG. 9 above, a tool 12 equipped with plugs 10, 10 at both upper and lower ends may be used, and machining may be performed using dies 3, 3' in the same manner.

〔Effect of the invention〕

As mentioned above, the method of the present invention, when manufacturing the stepped blank pipe M, uses a bottomless hollow material manufactured by vertical press-punching by punching with a stop in the middle, leaving one end unprocessed. Since a stepped hollow material with a large inner and outer diameter is created at one end and the material is machined from there, the yield drop due to the process of milling is much greater than in the conventional method mentioned above. This results in a significant improvement in the yield throughout the entire manufacturing process of pipe joints with straight pipe parts by reducing the diameter and pulling out the plug.

[Brief explanation of the drawing]

Figures 1A to 3C are process diagrams showing the process for manufacturing a stepped blank pipe according to the present invention, and Figures 2 and 3 are process diagrams showing the process for punching out a stepped blank pipe in the manufacturing process for a stepped blank pipe according to the present invention, respectively. 4 and 5 are cross-sectional views showing the upper half of a pipe joint with a straight pipe section, and FIG. 4 is a Tee joint, and FIG. 5 is a cross joint. Figure 6 is a sectional view of the upper part showing a stepped blank pipe for a pipe joint with a straight pipe part, and Figures 7 A to D show the manufacturing process of a Tee joint with a straight pipe part using the diameter reduction-plug drawing method. The process diagrams shown in Figures 8 and 9 show the diameter reduction process using the plug combination method, and Figure 8 is for manufacturing a Tee joint with a straight pipe section, and Figure 9 is for manufacturing a cross joint with a straight pipe section. In both figures, A shows a longitudinal side view and B shows a longitudinal front view. Fig. 10 is a dimensional diagram of a stepped blank pipe for a pipe joint with a straight pipe section actually manufactured using the method based on the present invention and the conventional method for yield comparison, Fig. 11, Fig. 12 2A and 2B are cross-sectional views showing the shape of the material before cutting, respectively, to explain a conventional method for manufacturing a stepped blank pipe. In the figure, 1: main pipe, 2: branch pipe, 3, 3': upper and lower dies, 4: die hole, 5: through hole, 6: plug,
7: Drawing rod, 8: Mandrel, 9: Ring die, 10: Plug, 11: Mandrel, M: Stepped tube.

Claims (1)

[Claims] 1 Using a hollow material m _p with a bottom made by perforation with a vertical press or punching with one or more horizontal presses, a mandrel 8 with a required diameter d _x smaller than the inner diameter D _np ′ of the material is formed. By performing punching that leaves one end unprocessed at least once using the punched part m _c2
We created a stepped hollow differential material m _c with a large diameter part m _c1 that is larger in both the inner and outer diameters, and finished it to the required dimensions by cutting the bottom and cutting the inner and outer surfaces to create a stepped hollow material m c with a large diameter part m _c1 on one end. Obtain a blank tube M, then flatten the large diameter portion M ₁ to form an elliptical portion M ₁ ′,
Subsequently, the planned branch pipe portion on the longer diameter side of the elliptical portion M ₁ ′ is bulged and raised outward by diameter reduction processing to form a raised portion 2′, and this raised portion 2′ is subjected to branching processing by pulling out a plug. A tee or cross joint with a straight pipe part is obtained by forming a branch pipe 2 with a straight pipe _{part 1a} using a small diameter part _M2 other than the large diameter part M1 as a straight pipe part 1a. Production method.