JP6767200B2 - Method of forming the insertion port protrusion of the metal tube - Google Patents

Description

The present invention relates to a method for forming an insertion port protrusion of a metal pipe such as a cast iron pipe manufactured by a centrifugal casting method, and in particular, an insertion port protrusion of a metal pipe such as a seismic pipe having a detachment prevention function and an expansion / contraction function in a joint portion. It relates to a method of forming a part.

Cast iron pipes used for water pipes, etc. consist of a cylindrical straight part with a constant inner and outer diameter, a socket provided at one end of the pipe and a larger inner and outer diameter than the straight part, and an insertion port provided at the other end. Many are used (see FIG. 11 of the present application).
Among the cast iron pipes, there are those called seismic pipes whose joints have a detachment prevention function and an expansion / contraction function, and the types include GX type, S type, US type, NS type, S50 type and the like. These joints have an insertion port that prevents detachment from the receiving port, and in addition, can be expanded and contracted (removable) within a required range.

For example, in the joint portion shown in FIG. 11, the insertion port 1 of one pipe P is inserted into the receiving port 2 of the other pipe P, and the water stop ring (water stop ring) is formed all around between the insertion port 1 and the receiving port 2. The structure is such that the rubber ring) 3 and the lock ring 4 are fitted. In this joint portion, the protrusion 6 on the outer periphery of the tip of the insertion port 1 can move between the inner end 2a of the receiving port 2 and the lock ring 4, and exerts the function of expanding and contracting the moving length of the protrusion 6. By locking the lock ring 4, the insertion port 1 exerts a detachment prevention function of preventing the insertion port 1 from detaching from the receiving port 2. In FIG. 11, the portion extending from the left side of the insertion port 1 to the receiving port 2 is the straight portion 5 (see FIG. 12).

On the other hand, this type of seismic tube P is usually made of a ductile cast iron pipe made of spheroidal graphite cast iron, and in its manufacture, for example, in centrifugal casting of the ductile cast iron pipe P shown in FIG. 12, a cylindrical mold 11 is rolled. Rotated by 12, the molten metal c is sent from the ladle 13 to the casting trough 15 via the triangular ladle 14, and the trough 15 is moved in the axial direction in the mold 11 to cast the molten metal c in the mold 11. It is poured (pouring) to form a cylindrical molten metal layer (cast iron pipe) P having a required thickness (see Patent Document 1, paragraph 0025, FIG. 8).

It is very difficult to form the protrusion 6 of the insertion port 1 by this centrifugal casting. Therefore, as one means of providing the protrusion 6 on the outer periphery of the tip of the insertion port 1, as shown in FIG. 13, a metal ring 21 that is split and tightened by one in the circumferential direction is fitted (wound) on the outer periphery of the tip of the insertion port 1. ), Both peripheral surfaces of the ring 21 are fillet welded by an arc, and the fillet welded portions 22 and 22 are shaped into a required shape by grinder processing or lathe processing to provide a protrusion 6 (patented). References 2 paragraphs 0005 to 0008, see FIG. 5).

As another means, as shown in FIG. 14, a ring 24 having a groove cutting process 23 on the outside is wound around the outer periphery of the tip of the insertion port 1, the groove 23 is melted down by an arc, and the ring 24 is attached to the insertion port 1. Some have a protrusion 6 (see Patent Document 2, Abstract, FIG. 1 and the like).

Further, as another means, as shown in FIG. 15, the insertion port 1 of the cast iron pipe is heated to a forgingable temperature 80 to 100 ° C. lower than the solid phase line, and the insertion port 1 is used as a clamp die 31. In some cases, the protrusion 6 is formed by stationary forging using the sliding mandrel 32 (see Patent Document 3, Summary, FIG. 1, etc.).

As another means, as shown in FIG. 16, the insertion port 1 of the cast iron pipe P is heated to a temperature at which the insertion port 1 can be plastically deformed and the cementite does not crystallize in the pipe wall structure after quenching, and the insertion port is heated. Using the outer mold 35 and the stopper 36, the pipe P is compressed in the pipe axial direction by the piston rod 38 via the backing plate 37, and the insertion port 1 is bulged and plastically deformed in the radial direction of the pipe and cooled as it is. In some cases, a protruding portion 6 is formed (see Patent Document 4, claim 1, FIGS. 1 to 4, etc.).

Further, as shown in FIG. 17, the insertion port 1 is cast to be thicker than the straight portion (FIG. 17A), and the outer peripheral surface of the insertion port 1 having the thickness is cut (mesh portion). Some form a protrusion 6 (see Patent Document 5, Summary, FIG. 1, FIG. 2, etc.).

Japanese Unexamined Patent Publication No. 2005-288475 JP-A-9-122910 JP-A-9-96386 Japanese Unexamined Patent Publication No. 2004-344903 Japanese Unexamined Patent Publication No. 2014-188571

In the arc welding of the rings 21 and 24 shown in FIGS. 13 and 14, since the welded portion is rapidly heated and rapidly cooled, the welded portion is affected by heat and material and mechanical changes occur, resulting in welding deformation and welding. Residual stress is generated. Therefore, it is necessary to set appropriate welding conditions, and depending on the material, heat treatment after welding may be required. That is, the formation of the protrusions 6 by the rings 21 and 24 by arc welding requires a welding material and a ring, and also requires heat treatment, which is costly. Further, in the protrusion 6 shown in FIG. 14, since a gap is formed around both sides of the ring 24, it is necessary to paint the gap. For this reason, workability is also poor.

In the method shown in FIGS. 15 and 16, since a compressive force is generated in the direction of the pipe axis of the pipe P, it is necessary to firmly fix the pipe P so that it does not move. If this is not done, the insertion port 1 end May not be formed into a required shape, and a protrusion 6 having an appropriate shape may not be formed, or the linear state of the pipe P may not be guaranteed.
Further, in the method of FIG. 16, similar to the deformation of the outer peripheral surface of the insertion port 1, the inner surface side of the pipe is also curved (deformed), and the inner surface of the pipe may not be straightened over the entire length.
Incidentally, the outer mold 35 of FIG. 16 is for "making the amount of bulging of the bulging portion (protruding portion) 6 constant" as described in paragraph 4, paragraph 0023, lines 5 to 6 of the Patent Document (protruding portion 6). (Not a forging mold).
In the method of FIG. 17, since the protrusion 6 is formed by cutting, the workability is poor, and since the inner surface of the insertion port 1 bulges inward, the inner diameter thereof is the other portion (straight portion 5). ) Is smaller in diameter.

An object of the present invention is to provide another molding method for the protrusion 6 under the above-mentioned actual conditions.

In order to achieve the above object, the present invention has decided to form a protrusion by forging the insertion port with an inner / outer mold. In the case of forging, welding deformation and welding residual stress do not occur unlike arc welding, and because it depends on the inner and outer molds, the insertion port is supported and fixed by the forging mold, and force in the pipe axial direction is unlikely to be generated. Straightness can be easily ensured, the protrusion can be formed according to the mold, and workability is good.

As a specific configuration of the present invention, a cylindrical straight portion having a constant inner and outer diameter, a receiving port provided at one end of the straight portion and having an inner and outer diameter larger than the straight portion, and a socket provided at the other end of the straight portion. It consists of an insertion port with an outer diameter that can be fitted into the socket, and the insertion port is inserted into the socket, and the protrusion on the outer periphery of the tip of the insertion port is locked to the lock ring in the socket, so that the insertion port can be inserted from the socket. In the method for forming the insertion port protrusion of a metal tube manufactured by a centrifugal casting method, which exerts a detachment prevention function for preventing detachment, the outer periphery of the insertion port end portion manufactured by the centrifugal casting method is covered with the above. An outer mold having a concave portion having a shape corresponding to the protrusion is applied, an inner mold is applied to the inner circumference of the insertion port end to which the outer mold is applied, and the inner and outer molds are used to attach the insertion end to the insertion port. It is possible to adopt a structure in which the tip of the insertion port having the protrusion is formed by forging.
In this configuration, it is preferable that the inner and outer diameters of the insertion port end portion are the same as those of the straight portion, and that the inner diameter of the outer mold is the same as the outer diameter of the straight portion from the concave portion to the straight portion side.

When forging the insertion port end portion with the inner and outer molds, various conventional modes may be adopted as means for applying the forging pressure. For example, to the inner circumference of the insertion opening end portion of the inner mold. The pressing surface of is gradually reduced in diameter from the same outer diameter as the inner diameter of the straight portion in the axial direction of the insertion port, and with the outer mold fixed, the inner mold is moved in the axially reduced diameter direction. , It is possible to adopt a configuration in which the end of the insertion port is forged with an inner and outer mold.
As another means, the inner mold is divided into a plurality of pieces in the circumferential direction, and the divided pieces are moved in the radial direction of the metal pipe to forge the insertion port end portion by the inner and outer molds. Can be done. At this time, a long pressing rod in the axial direction is provided in the inner mold, the pressing rod is moved in the axial direction, and the divided piece is divided into the radius of the metal pipe by the tapered surface in the axial direction of the outer peripheral surface of the pressing rod. It is possible to adopt a configuration in which the end of the insertion port is forged by moving in the direction with an inner and outer mold.

As another means, the inner mold is divided into a plurality of pieces in the circumferential direction, and the divided surface of each of the divided pieces is a tapered surface that is inclined in the circumferential direction toward the inner mold axial direction, and the taper facing the inner mold. One divided piece and the other divided piece having the same direction in which the distance between the surfaces is narrowed are divided, and the one divided piece and the other divided piece are relatively moved in the axial direction, so that one and the other are divided. It is possible to adopt a configuration in which the divided pieces are moved in the radial direction of the metal pipe and the end of the insertion port is forged with an inner / outer mold.
Further, as another means, the inner mold is used as a roller, the inner peripheral surface of the insertion port end to which the outer mold is applied is rolled by the roller, and the insertion end is formed by the inner and outer molds. A forging configuration can be adopted. At this time, it is also possible to adopt a configuration in which the outer mold is also a roller and the insertion port end is rolled and forged by the inner and outer rollers.

In each of the above configurations, the insertion port end side is cast thicker than the straight portion, the outer mold is applied to the outer periphery of the insertion opening end portion of the wall thickness, and the insertion port end portion of the wall thickness is applied. An inner mold having a pressing surface having the same outer diameter as the inner diameter of the straight portion is applied to the inner circumference of the inner circumference, and the tip of the insertion port having the protrusion is forged with the inner and outer molds. It is possible to form a part.
By doing so, the inner and outer diameters of the insertion port can be made to be the same as that of the straight portion, and it becomes easy to fit the insertion port into the receiving port.
Further, in each of the above configurations, the tip of the insertion port can be removed (cut) from an unnecessary portion to obtain the required length from the protrusion, or can be made a downward tapered surface toward the tip, if necessary. .. The tapered surface may be formed by casting during centrifugal casting.

In the present invention, as described above, since the protrusion is formed by forging with the inner and outer molds, the protrusion can be easily formed while ensuring the straightness of the pipe.

Partial sectional view for explaining the insertion port casting according to the embodiment of the method for forming the insertion port protrusion according to the present invention. It is explanatory drawing of the protrusion formation of the same embodiment, (a) is the front view of cutting the main part before forging, and (b) is the front view of cutting the main part after forging. Front view of the main part for explaining the formation of the same protrusion It is explanatory drawing of the protrusion formation of each other embodiment, (a) is the front view of the cut of the main part which also formed the tip taper surface of the insertion port after forging, (b) is the post-forging that did not make the insertion opening thick. Front view of cutting the main part It is explanatory drawing of the protrusion formation of another embodiment, (a) is the front view of cutting the main part before forging, (b) is the side view of cutting the main part. Front view of the main part cut after forging of the same embodiment It is an explanatory view of the protrusion formation of still another embodiment, (a) is a front view of cutting a main part before forging, (b) is a front view of cutting a main part during forging, and (c) is a cutting of a main part after forging. Front view The inner mold of the same embodiment is shown, (a) is a perspective view of the inner mold and its pusher, and (b) is an exploded perspective view of the inner mold. It is an explanatory view of the protrusion formation of still another embodiment, (a) is a front view of cutting a main part before forging, and (b) is a right side view of cutting the main part. Front view of the main part cut after forging of the same embodiment It is an explanatory view of the protrusion formation of still another embodiment, (a) is a front view of cutting a main part before forging, and (b) is a right side view of cutting the main part. Front view of the main part cut after forging of the same embodiment Cross-sectional view of an example of a metal pipe joint Schematic cross-sectional view of an example of a centrifugal casting apparatus according to the present invention. Front view of the main part of the protrusion of the conventional example Front view of the main part of the protrusion of the conventional example Front view of the main part of the protrusion of the conventional example Front view of the main part of the protrusion of the conventional example An example of forming a conventional protrusion is shown, (a) is a front view of cutting a main part during centrifugal casting, and (b) is a front view of cutting a main part for explaining the formation of a protrusion.

An embodiment of a method for forming an insertion port protrusion of a metal pipe according to the present invention is shown in FIGS. 1 to 3, and this embodiment is a ductile cast iron pipe, which is the GX type, S type, US type, and NS type. , S50 type, etc. have a function to prevent detachment of the joint structure.
The cast iron pipe P is manufactured by centrifugal casting shown in FIG. 12 as in the conventional case. At the time of casting, as shown in FIG. 1, the amount of hot water poured into the insertion port 1 of the mold 11 is increased as compared with the straight portion 5 and the like, the mold 11 is water-cooled from the outside, and the molten metal poured into the mold 11 is showered. By cooling with water or the like, the cooling rate of the molten metal is increased, and the inside of the insertion port 1 is inflated to be thicker than the straight portion 5.

Next, the cast iron pipe P after demolding is set in the forging apparatus shown in FIG. Its forging, cold forging, hot forging, or may employ molten metal forging and the like, inserted port 1 of the temperature is malleable temperature of the casting pipe P, for example, soluble hot forging of semi-solidified state after casting or it is preferable that the hot forging on 600 ° C. or more after annealing.

The forging device is composed of a cylindrical outer die (outer die) 51 made of rigid metal and an inner die (inner die) 52, and the inner peripheral surface of the outer die 51 is a recess (cavity) corresponding to a protrusion 6. ) 53 is formed on the entire circumference, and the front-rear direction (straight side and tip side direction) from both ends of the recess 53 has the same inner diameter as the outer diameter of the straight portion 5. The inner mold 52 is composed of a truncated cone-shaped pressing portion 52a and a drawer rod 52b protruding from its minor axis surface, and as shown in FIGS. 2A to 2B, the drawer rod 52b is oriented in the direction of the arrow. The inner surface of the insertion port 1 is pressed by pulling it out.
At this time, as shown by the arrow a, the end face of the insertion port 1 and the end face of the outer mold 51 are pressed and fixed to prevent the insertion port 1 and the outer mold 51 from moving, and the outside of the insertion port 1 (right side in FIG. 2). ) Can prevent the force of swelling. In this way, the bulge (material bulge) of the insertion port 1 into the recess 53 is promoted, and the formation of the protrusion 6 becomes smooth.

By pressing the inner mold 52, as shown by the arrow in FIG. 2A, the outer surface of the thick insertion port 1 is plastically deformed into the recess 53 to form the protrusion 6 (FIG. 2B). )). That is, the protrusion 6 is formed by forging.
After that, the mold is removed, and if necessary, the outer surface of the protrusion 6 and the tip of the insertion port 1 are cut to obtain the required shape of the protrusion 6 and the tip downward taper surface 1a (FIG. 3). .. In addition, the residual stress generated by the processing is appropriately removed by annealing heat treatment.
The outer peripheral surface 52a ₁ of the pressing portion 52a of the inner die 52 does not have to be linear in the axial direction (solid line in FIG. 2A), but may be arcuate as shown by the chain line in the figure. Further, the linear shape and the arc shape may be formed into an arc shape or a straight taper shape after extending a certain distance toward the drawer rod 52b with the same diameter as the inner diameter R of the straight portion 5 (insertion port 1). The constant distance is appropriately set in consideration of the pulling force and the degree of plastic deformation of the insertion port 1.

Other embodiments are shown in FIGS. 5 and 6, and the forging apparatus of this embodiment is composed of a cylindrical outer mold 51 made of a rigid metal, an inner mold 52, and a pressing rod 54, similarly to the above embodiment. The inner mold 52 is divided into a plurality of pieces in the circumferential direction. The number of divisions is arbitrary, such as 2 or more, 3, 4, 5, 6, ..., And equal division is preferable. In this embodiment, it is divided into eight equal parts. The gap t of each of the divided pieces 52c becomes as narrow as possible when the inner mold 52 expands in diameter, the divided pieces 52c do not interfere with each other, and the insertion port 1 is pressed (when contacting pressure). Set appropriately by experiment etc. so that a step does not occur. The inner mold 52 is restricted (blocked) from moving in the length direction by the receiving plate 55.

The pressing rod 54 has a truncated cone shape from the middle, and its conical surface 54a corresponds to the conical surface 52d of the inner surface of the inner mold 52 (divided piece 52c) (the conical surface has almost the same inclination). ), As shown by the white arrow, when the pressing rod 54 is pulled out, the divided pieces 52c of the inner die 52 move in the radial direction with the two conical surfaces (tapered surfaces) 54a and 52d, and press the insertion port 1. (Fig. 6). The tapered surfaces 54a and 52d are formed in opposite directions (in the tapered surface 52d, the direction in which the tapered surfaces 52d expand to the right in FIG. 5A), and the pressing rod 54 is pushed in to move the divided piece 52c of the inner die 52 in the radial direction. Can be done.

By this pressing, as shown by the arrow in FIG. 5, the outer surface of the thick insertion port 1 portion is plastically deformed in the recess 53 to form the protrusion 6 (FIG. 6). At this time, similarly, as shown by the arrow a in FIG. 5A, a pressing force is applied to the tip surface of the insertion port 1 to prevent the force of bulging to the outside of the insertion port 1 (on the right side in the figure). can do. Further, when the protrusion 6 shown in FIG. 6 can be forged, the diameter R'of the truncated cone-shaped straight portion of the pressing rod 54 is such that the total length of the inner surface of the insertion port end portion is the same as the inner diameter of the straight portion 5. It is preferable to set to.
After that, the mold is removed, and if necessary, the outer surface of the protrusion 6 and the tip of the insertion port 1 are cut to obtain the required shape of the protrusion 6 and the tip downward taper surface 1a (FIG. 3). ..

In the above embodiment, as shown in FIGS. 2 and 4A, the inner surface of the outer end of the outer mold 51 can be used as a downward tapered surface 51a to form the tapered surface 1a during forging. At this time, as compared with the outer mold 51 shown in FIG. 5 (a) in which the inner surface without the tapered surface 51a is straight (flat), the outer mold 51 having the tapered surface 51a has a material flow during forging, which is the tapered surface 51a. It is hindered by, and the force required for forging becomes large.
Further, when the pipe thickness of the insertion port 1 may be reduced, as shown in FIG. 4B, the insertion port 1 has the same thickness as the straight portion 5 as in the conventional case without the above-mentioned wall thickness. It can be made thick and forged with an inner mold 52 whose outer peripheral surface bulges in an arc shape.

Still other embodiments are shown in FIGS. 7 and 8, and the forging apparatus of this embodiment is a cylindrical outer mold 51 made of a rigid metal, an inner mold 62, and a pusher for the inner mold thereof, as in the above embodiment. It consists of 63a and 63b.
The inner mold 62 is divided into a plurality of parts in the circumferential direction, and the divided surfaces of the divided pieces 62a and 62b are tapered surfaces 62c that are inclined in the circumferential direction toward the axial direction of the inner mold 62. A group of divided pieces 62a and the other one (in FIG. 7, the tapered surfaces 62c and 62c are approaching to the left in the same direction) in which the intervals between the opposing tapered surfaces 62c and 62c are narrowed. It is divided into a group of divided pieces 62b (the tapered surface 62c whose adjacent tapered surface 62c is approaching to the right).

The tapered surface 62c of the divided pieces 62a and 62b may have any angle as long as the diameters of the divided pieces 62a and 62b described later are smoothly expanded, but for example, with respect to the axial direction (tube axial direction) of the insertion port 1. It is set to "15 degrees", "-15 degrees", and the like. Further, the number of divisions of the division pieces 62a and 62b is arbitrary, such as an even number of 4 or more, 6, 8, 10, ..., And equal division is preferable. In this embodiment, it is divided into eight equal parts, and both divided pieces 62a and 62b are grouped into four pieces, respectively.
The inner mold pushers 63a and 63b are provided with teeth 63'on the side surface of the annular body, and the number of the teeth 63'corresponds to the number of divisions of the inner mold 62, and is four in this embodiment. There is.

In the forging device of this embodiment, as shown in FIG. 7A, the insertion port 1 is inserted into the outer die 51, the inner die 62 is loaded into the insertion slot 1, and one of the inner die 62 is loaded. One pusher 63a is applied to the end face of the split piece 62a, and the other pusher 63b is applied to the end face of the other split piece 63b via the teeth 63'.
In this state, when one pusher 63a is fixed and the other pusher 63b is pushed in as shown by the arrow F in each figure of FIG. 7, FIG. 7 (a) → the figure (b) → the figure (c). As shown in the above, each of the divided pieces 62a and 62b expands (moves) in the radial direction of the insertion port 1 via the tapered dividing surface 62c, and the outer surface of the thick insertion port 1 portion is in the recess 53 accordingly. The protrusion 6 is formed by plastic deformation (FIG. 7 (c)). When the diameters of the divided pieces 62a and 62b are expanded, the gap t shown in FIG. 5B does not occur between the adjacent divided pieces 62a and 62b.
After forging the protrusion 6, the mold is removed, and similarly, the outer surface of the protrusion 6 and the tip of the insertion port 1 are cut as necessary to obtain the required shape of the protrusion 6 and the tip downward taper. Let surface 1a (Fig. 3).

The forging device of this embodiment is incorporated into a press machine and inserted into a ductile cast iron pipe (FCD420-10) having an outer diameter of 117 mm and a pipe thickness of 8.5 mm under the conditions of a pipe temperature of 750 ° C. and a press load of F: 280 ton. When the mouth 1 was forged, the protrusion 6 having a height h: 2.5 mm could be smoothly formed (see FIG. 7 (c)).

Further, as shown in FIG. 9A, the forging device of another embodiment has an inner mold as a roller 72, and the roller 72 presses the inner peripheral surface of the insertion port 1 end to which the outer mold 51 is applied. As shown in FIG. (B), while rotating the insertion port 1 together with the outer die 51 (arrow), the roller 72 is pressed against the outer die 51 through the insertion port 1 to roll.
By this rolling, as shown in FIG. 9B, the outer surface of the thick insertion port 1 portion is plastically deformed into the recess 53 to form the protrusion 6.
In this embodiment, as shown in FIG. 10A, the outer mold 51 is also a cylindrical (cylindrical) roller 71, and the insertion port 1 is rolled by both rollers 71 and 72, and as shown in FIG. 10B, a thick insertion port is used. It is also possible to form the protrusion 6 by plastically deforming the outer surface of one portion into the recess 53.

Not limited to the centrifugal cast iron pipe of the above embodiment, the present invention can be adopted in various cast pipes having a protrusion 6 and having a detachment prevention function. Further, even in the case of the instep pipe and the second pipe, the protrusion 6 can be formed at the insertion port portion in the same manner.
Further, it goes without saying that the present invention can be adopted not only for cast iron pipes but also for forged metal pipes.
Thus, it should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

P Casting pipe (metal pipe)
c Molten metal 1 Insertion port 2 Receptacle 3 Water stop ring (rubber ring)
4 Lock ring 5 Straight part 6 Protrusion part 11 Centrifugal casting mold (mold)
51 Outer mold 52 Inner mold 52a Inner mold pressing part 52b Same drawer rod 52c Same division piece 53 Cavity (recess)
54 Inner mold pressing rod 55 Receiving plate 62 Inner mold 62a, 62b Divided piece 62c of inner mold 62 Tapered split surface 63a, 63b pusher 71 of inner mold 71 Roller forming inner mold 72 Roller forming inner mold

Claims (8)

A cylindrical straight portion (5) having a constant inner and outer diameter, a receiving port (2) provided at one end of the straight portion (5) and having an inner and outer diameter larger than that of the straight portion (5), and a socket (2) provided at the other end thereof. It is composed of an insertion port (1) having an outer diameter that can be fitted into the socket (2), the insertion port (1) is inserted into the socket (2), and a protrusion on the outer periphery of the tip of the insertion port (1). Centrifugal casting that exerts a detachment prevention function of preventing the insertion port (1) from detaching from the socket (2) by locking the lock ring (4) in the socket (2). A method for forming the insertion port protrusion (6) of a cast iron metal tube (P) manufactured by a casting method.
An outer mold (51) having a recess (53) having a shape corresponding to the protrusion (6) is applied to the outer periphery of the insertion port end portion manufactured by the centrifugal casting method, and the outer mold (51) is applied. An inner mold (52) is applied to the inner circumference of the broken insertion slot end, and the insertion slot end is subjected to molten metal forging or annealing treatment in a semi-solidified state after casting with the inner and outer molds (51, 52). After that , hot forging at 600 ° C. or higher is performed, and the end of the insertion port is plastically deformed into the recess (53) by pressing the inner mold (52) to form the tip of the insertion port having the protrusion (6). A method for forming an insertion port protrusion of a metal tube, which is characterized by forming. A cylindrical straight portion (5) having a constant inner and outer diameter, a receiving port (2) provided at one end of the straight portion (5) and having an inner and outer diameter larger than that of the straight portion (5), and a socket (2) provided at the other end of the straight portion (5). It is composed of an insertion port (1) having an outer diameter that can be fitted into the socket (2), the insertion port (1) is inserted into the socket (2), and a protrusion on the outer periphery of the tip of the insertion port (1). Centrifugal that exerts a detachment prevention function of preventing the insertion port (1) from detaching from the socket (2) by locking the lock ring (4) in the socket (2). A method for forming the insertion port protrusion (6) of a metal tube (P) manufactured by a casting method.
An outer mold (51) having a recess (53) having a shape corresponding to the protrusion (6) is applied to the outer periphery of the insertion port end portion manufactured by the centrifugal casting method, and the outer mold (51) is applied. Apply the inner mold (52) to the inner circumference of the end of the inserted opening,
The pressing surface of the inner die (52) against the inner circumference of the insertion port (1) end gradually shrinks in the axial direction of the insertion port (1) from the same outer diameter as the inner diameter of the straight portion (5). With the diameter and the outer mold (51) fixed, the inner mold (52) is moved in the axial direction to reduce the diameter, and the inner and outer molds (51, 52) are used for the insertion port. A method for forming an insertion port protrusion of a metal tube, which comprises forging an end portion to form an insertion port tip having the protrusion (6) . The inner mold (52) is divided into a plurality of pieces in the circumferential direction, the divided pieces (52c) are moved in the radial direction of the metal pipe (P), and the inner and outer molds (51, 52) are used to forge the end of the insertion port. The method for forming an insertion port protrusion of a metal tube according to claim 1, wherein the method is performed. An axially long pressing rod (54) is provided in the inner mold (52), and the pressing rod (54) is moved in the axial direction to taper the outer peripheral surface of the pressing rod (54) in the axial direction. (54a) The method for forming a metal tube insertion port protrusion according to claim 3, wherein the divided piece (52c) is moved in the radial direction of the metal tube (P). A cylindrical straight portion (5) having a constant inner and outer diameter, a receiving port (2) provided at one end of the straight portion (5) and having an inner and outer diameter larger than that of the straight portion (5), and a socket (2) provided at the other end of the straight portion (5). It is composed of an insertion port (1) having an outer diameter that can be fitted into the socket (2), the insertion port (1) is inserted into the socket (2), and a protrusion on the outer periphery of the tip of the insertion port (1). Centrifugal that exerts a detachment prevention function of preventing the insertion port (1) from detaching from the socket (2) by locking the lock ring (4) in the socket (2). A method for forming the insertion port protrusion (6) of a metal tube (P) manufactured by a casting method.
An outer mold (51) having a recess (53) having a shape corresponding to the protrusion (6) is applied to the outer periphery of the insertion port end portion manufactured by the centrifugal casting method, and the outer mold (51) is applied. Apply the inner mold (62) to the inner circumference of the end of the opening
The inner mold is divided into a plurality of pieces in the circumferential direction, and the divided surfaces of the divided pieces (62a, 62b) are formed as tapered surfaces (62c) inclined in the circumferential direction toward the axial direction of the inner mold (62). One divided piece (62a) and the other divided piece (62b) having the same direction in which the distance between the opposing tapered surfaces is narrowed are divided into one divided piece (62a) and the other divided piece (62b). Is relatively moved in the axial direction, and one and the other divided pieces (62a, 62b) are moved in the radial direction of the metal tube (P), and the insertion port end is used with the inner and outer molds (51, 62). A method for forming an insertion port protrusion of a metal tube, which comprises forging a portion to form an insertion port tip having the protrusion (6) . The inner mold is a roller (72), and the inner peripheral surface of the insertion port end to which the outer mold (51) is applied is rolled by the roller (72), and the inner and outer molds (51, 72) are used. The method for forming an insertion port protrusion of a metal tube according to claim 1, wherein the insertion port end portion is forged. The metal tube insertion according to claim 6, wherein the outer mold is also a roller (71), and the outer mold roller (71) and the inner mold roller (72) are used to forge the end portion of the insertion port. How to form a mouth protrusion. It is assumed that the insertion port end portion is bulged inward from the straight portion (5) and cast to a thick wall, and the inner mold has a pressing surface having the same outer diameter as the inner diameter of the straight portion (5). With the inner and outer molds (51, 52), the end of the insertion port is forged to form the tip of the insertion port having the protrusion (6), and the total length of the inner surface of the end of the insertion port is the inner diameter of the straight part (5). The method for forming an insertion port protrusion of a metal tube according to any one of claims 1 to 7, wherein the diameter is the same as that of the above.

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