JP2022142383A - Method for manufacturing heating hot forming material - Google Patents

Abstract

To provide a method for manufacturing a hot forging material, which can increase productivity while suppressing bending of a forging blank at the time of heating during hot forging.SOLUTION: This method for manufacturing the hot forging material, which hot-forges a large diameter part of a rod-like forging blank having large and small diameter parts, includes: inserting the small diameter part of the forging blank into a hole of a blank holding tool having the hole for inserting the forging blank; heating the large diameter part to a heated temperature to form a heated material; after pulling-out of the heated material from the blank holding tool, inserting the small diameter part of the heated material into a hole of a hot forging mold having the hole for inserting the heated material; and executing hot forging for pressing the large diameter part in an axial direction to form a hot forging material.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing hot forged materials.

For example, among aircraft engine parts and power generation parts, there are some that are formed into a shaft shape by processing a long bar material. In order to manufacture these products, an ingot adjusted to a predetermined composition is used to form a billet or rough ground by hot forging, which is then hot forged into the final product shape. For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 6-238387), the one end of a bar having a swaged portion and a shaft portion having a ratio L1/D of length L1 to outer diameter D of 1 to 3 After upset forging the swaged portion to a swage ratio of 1/2u or more, the shaft portion is reheated to a recrystallization temperature or less, and the shaft portion is forged and stretched with a forging ratio of 2s or more using a four-sided forging machine. There is an invention of a long steel forging method that is suitably applied to the manufacture of long shafts for large aircraft engines, etc., in which the length L2 is 2000 mm or more.

JP-A-6-238387

According to the long steel forging method described in Patent Document 1, the forging material used in the upset forging for forming the flange is in the form of a cylindrical round bar. Then, the forging material is heated to a predetermined temperature and inserted into the hole provided in the lower hot forging die, and the end face of the forging material is pressed against the portion not restrained by the hole with the upper hot forging die. It is intended to perform upsetting forging.
When hot forging a portion of this material, if the entire forging material to be hot forged is heated to the heating temperature, the portion not hot forged is also heated at a high temperature. In particular, the heating temperature is high in hard-to-work materials such as Ni-base superalloys that are strengthened by precipitates such as the γ' (gamma prime) phase.

By the way, by heating the entire forging material, the forging material or the hot forged material after hot forging may have poor bending, and the hot forged material after hot forging may be damaged by the lower die for hot forging. There is a problem that it becomes difficult to get out of the provided hole and the productivity is lowered. Defective bending not only increases machining costs, but also leads to defects in the product itself.
For example, even if it is a round bar-shaped forging material, in a long and stepped forging material with different diameters such that a large diameter portion and a small diameter portion are integrally molded, in the heating process before hot forging, forging If the material is placed horizontally, the small diameter portion may be bent. As a result, it becomes difficult to insert the small-diameter portion into the hole formed in the hot forging lower die in the subsequent hot forging step.
Further, when hot forging is performed by pressing the large diameter portion while constraining the small diameter portion with a hole formed in the lower hot forging die, the small diameter portion thermally expands and is difficult to insert into the hole. After forming the large diameter portion into a predetermined shape by hot forging, the large diameter portion and the cavity portion of the lower mold are brought into close contact with each other due to the pressing force of the hot forging. may be removed with In this case, the impact of the knockout pin is applied to the small-diameter portion, which may cause deformation of the small-diameter portion. In order to prevent this, if the diameter of the small-diameter portion and the diameter of the hole are close to each other, the space for deformation will be narrowed. , the hole diameter cannot be reduced excessively. Therefore, the temperature of the lower die for hot forging and the small-diameter portion may be readjusted before removal, which reduces productivity.
SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a hot forged material capable of increasing productivity while suppressing bending of a forging material during heating during hot forging.

The present invention has been made in view of the problems described above.
That is, the present invention relates to a method for manufacturing a hot forged material by hot forging the large diameter portion of a rod-shaped forging material having a large diameter portion and a small diameter portion, wherein the material holder has a hole into which the forging material is inserted. The small-diameter portion of the forging material is inserted into the hole of the jig, the large-diameter portion is heated to a heating temperature as a heating material, and the heating material is removed from the material holding jig, and then the heating material is removed. The small-diameter portion of the heating material is inserted into the hole of the hot forging lower die having a hole for insertion, and hot forging is performed by pressing the large-diameter portion in the axial direction with the hot forging upper die. This is a method for producing a hot forged material as a forged material.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress the bending of a forging material at the time of heating at the time of hot forging, and also to improve productivity.

1 is a schematic diagram of a stepped rod-shaped forging material and a heating jig for heating the forging material; FIG. It is a cross-sectional schematic diagram when inserting a stepped rod-shaped forging material into the through-hole of the heating jig. It is a cross-sectional schematic diagram when inserting a stepped rod-shaped forging material into a non-penetrating hole in a heating jig. It is a cross-sectional schematic diagram when the large-diameter portion of the heating material inserted into the lower mold is hot forged by pressing the upper mold.

The present invention will be described in detail below. In addition, the "heating material" described below refers to the material before being charged into the heating furnace, the "heating material" refers to the material heated to a predetermined temperature in the heating furnace, and the "hot forging material "" means a formed material formed into a predetermined shape by a hot forging device.
In addition, the "hot forging" referred to in the present invention means that a lower die for hot forging (sometimes simply referred to as "lower die") and an upper die for hot forging (simply referred to as " (sometimes referred to as "upper die") presses the heating material to carry out hot plastic working.
<Forged material>
The forging material 1 used in the present invention is a stepped bar having a large diameter portion 11 and a small diameter portion 12 as shown in FIG. Forming into the shape of the forging material 1 is performed by forging and stretching a rod-shaped material, which is the forging material, by repeating the operation of extending the entire length by pressing from four directions over the entire length while rotating it intermittently in the circumferential direction. It is better to perform radial forging with a four-sided forging machine. Since the end face of the large-diameter portion of the forging material is pressed by the upper die, the length of the forging material should be three times or less the diameter D of the large-diameter portion so as not to cause buckling. preferable. In addition, the "large diameter" and "small diameter" referred to in the present invention include, for example, a polygonal shape of hexagon or more in addition to the circular shape. For the diameter D in the case of a polygon, it is preferable to obtain the diameter D from its circumscribed circle.
In addition, the material of the forging material used in the present invention is strengthened with precipitates such as γ' (gamma prime) phase suitable for aircraft engine parts and power generation parts, Ni-based super heat-resistant alloys containing the most Ni, and It is assumed to be applied to aging steel.

<Material holding jig>
In the present invention, a material holding jig 2 as shown in FIG. 1 is used as a jig for heating the large diameter portion 11 of the forging material 1 described above. The purpose of using the material holding jig 2 is to heat only the large diameter portion 11 as much as possible and reduce the direct heating area of the small diameter portion 12, thereby suppressing the thermal expansion of the small diameter portion. can be easily performed.
A plurality of holes 21 are formed in the material holding jig 2 shown in FIG. The number of holes 21 formed in the material holding jig 2 may be one. It is better to leave It should be noted that the material of the material holding jig may be a heat insulating material having a heat insulating effect, such as a heat-resistant brick or mortar. The hole diameter of the hole 21 formed in the material holding jig 2 can be made smaller than the diameter D of the large diameter portion 11 of the forging material 1 .
Further, as shown in FIG. 1, when the forging material 1 is inserted into the hole 21 of the material holding jig 2, it is preferable to insert it from the side direction. is preferably deeper (longer) than the small diameter portion of the This structure is used because, for example, when the large-diameter portions 11 of a plurality of forging materials 1 are to be heated at the same time, even if there is some variation in the length of the small-diameter portions 12 of the forging materials 1, the large-diameter This is because the portion 11 can be heated, and thermal expansion due to heating of the small-diameter portion 12 can be suppressed. Further, if the structure is such that it is inserted from the lateral direction, the forging material can be easily inserted and removed by the manipulator, and productivity can be improved. Insertion and withdrawal from above may require a crane, and it takes too much time from withdrawal to the start of hot forging.

2 and 3 are schematic cross-sectional views when the small diameter portion 12 of the forging material 1 is inserted into the material holding jig 2. FIG. The material holding jig 2 may be a through hole (hole 21) as shown in FIG. 2, or a non-through hole 21 having a bottom portion 22 as shown in FIG. In the case of heating the large-diameter portion, the effect of suppressing the temperature rise of the small-diameter portion inevitably increases when the non-through hole 21 having the bottom portion 22 shown in FIG. 3 is used. is. Therefore, it is preferred in the present invention to use a blank holding jig having a blind hole 21 with a bottom portion 22 .
In the present invention, the construction of the most preferable material holding jig is as follows.
A material holding jig for heating the large-diameter portion of a rod-shaped forging material having a large-diameter portion and a small-diameter portion, wherein the holding jig has a plurality of small-diameter portions of the forging material inserted into the side surfaces of the holding jig. A material holding jig, comprising a plurality of non-penetrating holes, the length of the holes being longer than the length of the small-diameter portion.

<Large-diameter portion heating process>
In the present invention, the small-diameter portion 12 of the forging material 1 is inserted into the hole 21 provided in the material holding jig 2, and the large-diameter portion 11 of the forging material 1 is heated to the heating temperature to form a heating material.
In order to partially heat the forging material 1 and set the large diameter portion 12 to a predetermined heating temperature, for example, there is a method of using high frequency heating. In this case, each forging material is heated. Become. Further, since it takes time to sufficiently raise the temperature of the entire large-diameter portion, it is preferable to select a method capable of heating a plurality of forging materials at once. Therefore, in the present invention, when performing the heating process for the large diameter portion, the material holding jig is installed in advance in the heating furnace (not shown), and after the heating furnace is heated to a predetermined temperature, the forging is performed. It is preferable to select the method of inserting the small diameter portion 12 of the material 1 into the hole 21 provided in the material holding jig 2 .
The material holding jig 2 installed in the heating furnace preferably has a non-through hole 21 having a bottom portion 22 as shown in FIG. For example, if the material of the forging material is a Ni-based super heat-resistant alloy, which is a difficult-to-work material, the heating temperature may be 850 to 1050°C. At this time, when the through hole (hole 21) as shown in FIG. 2 is used, the temperature of the central portion of the small diameter portion is about 50 to 180° C. lower than the temperature of the large diameter portion. On the other hand, in the case of the non-through hole 21 structure having the bottom portion 22 as shown in FIG. The thermal expansion of the small-diameter portion can be reliably suppressed, and bending failure of the small-diameter portion due to heating can be suppressed.

<Hot forging process>
In the large-diameter portion heating step, after the heating material heated to a predetermined temperature is removed from the material holding jig, the small diameter heating material is inserted into the hole provided in the lower mold having a hole for inserting the heating material. A hot forged material is obtained by inserting a portion into the forged portion and pressing the large-diameter portion in the axial direction with an upper die.
FIG. 4 is a schematic cross-sectional view when the small-diameter portion of the heating material 3 obtained by heating the forging material 1 to a predetermined temperature is inserted into the hole 41 provided in the lower die 4 . As described above, in the large-diameter portion heating step, the thermal expansion of the small-diameter portion is suppressed by suppressing the temperature rise of the small-diameter portion 12, so that the insertion of the small-diameter portion into the hole 41 provided in the lower die 4 is also possible. easier.
In addition, since the heating material 3 has a stepped rod shape having a large diameter portion and a small diameter portion in the present invention, the diameter of the large diameter portion of the heating material 3 is the same as the hole 41 provided in the lower die 4. By being larger than the diameter, the stepped portion 31 of the large diameter portion is utilized to bring the stepped portion 31 into contact with the lower die (the stepped portion 31 is supported by the lower die) so that the end face of the small diameter portion is downward. It can be configured as if it is floating in the air without contact with the bottom of the mold. Moreover, since the temperature of the small-diameter portion is lower than that of the large-diameter portion and thermal expansion is suppressed, for example, the gap between the diameter of the hole 41 provided in the lower mold 3 and the diameter of the circumscribed circle of the small-diameter portion 12 is No need to make it too big. Also, if the central axes of the heating material 3 and the hole 41 provided in the lower mold 4 are aligned, the small diameter portion of the heating material 3 inserted into the hole 41 of the lower mold 4 does not contact the inner peripheral surface of the hole 41. It is also possible to

As described above, the small-diameter portion of the heating material 3 is inserted into the hole 41 provided in the lower mold 4, and the stepped portion 31 of the large-diameter portion is brought into contact with the lower mold 4 (the stepped portion 31 is brought into contact with the hole of the lower mold 4). 41), the upper die 5 is lowered while the end face of the small diameter portion is kept out of contact with the bottom of the lower die, and the hot forged material 6 is pressed axially against the large diameter portion of the heating material 3. and Further, since the small-diameter portion can be kept out of contact with the bottom of the lower die 4, deformation such as bending of the small-diameter portion can be suppressed when the large-diameter portion 11 is pressed by the upper die. Even after forming the hot forged material 6 , the thermal expansion of the small-diameter portion remains suppressed, and the hot forged material 6 can be smoothly removed from the lower die 4 .
According to the hot forging method of the present invention, the large-diameter portion to be hot-forged is preferentially heated, and the temperature rise of the small-diameter portion can be suppressed, so that the small-diameter portion can be prevented from bending during the heating process. In addition, since thermal expansion due to temperature rise in the small diameter portion can be suppressed, the heating material can be smoothly inserted into and removed from the lower die, thereby improving productivity.

(Example 1)
A stepped rod material of 18% Ni maraging steel (class 250) was prepared as a forging material for molding into aircraft engine parts. The forging material is radially forged by a four-sided forging machine that repeats the operation of extending the entire length by pressing from four directions over the entire length while intermittently rotating in the circumferential direction to form the circumscribed circle of the large diameter portion. is 180 to 205 mm, the length of the large diameter portion is 440 to 550 mm, the circumscribed circle of the small diameter portion is 118 to 139 mm, and the length of the small diameter portion is 1380 to 2150 mm.
Using the above-mentioned forging material, defects in bending during heating of the large-diameter portion were confirmed. The material holding jig used in the large-diameter portion heating step had a through hole (hole 21) shown in FIG. 2 and a non-through hole 21 having a bottom portion 22 shown in FIG. Inventive example A having a non-penetrating hole 21 having a bottom portion 22 shown in FIG. Write down.

The diameter of the hole 21 of the material holding jig 2 into which the small diameter portion 12 of the present inventions A and B of the forging material 1 is inserted is approximately 200 mm, and the depth (length) of the hole 21 is approximately 2500 mm in the case of a non-through hole. , the material holding jig 2 was provided with four holes. The number of holes 21 in the material holding jig 2 having through holes is also the same.
As shown in FIG. 1, the material holding jig is installed in a heating furnace so that the forging material 1 can be inserted from the side when inserting the forging material 1 into the hole 21 of the material holding jig 2. was heated and held at a predetermined temperature, the large diameter portion 11 of the forging material 1 was held in the hole 21 of the material holding jig 2 with a manipulator, and the small diameter portion 12 was sequentially inserted into the hole 21 .
The heating temperature in the furnace for hot forging was set to approximately 900° C., and the large diameter portions 11 of the forging materials 1 of the present invention A and the present invention B were selectively partially heated.
When the large-diameter portion 11 was sufficiently heated, the temperature near the center of the length of the small-diameter portion 12 was measured after extraction from the heating furnace. Table 1 shows the results. Temperature was measured using a radiation thermometer. The temperatures shown in Table 1 are the results of measurement of four samples, and the comparative example is the result of heating in a furnace without using the heating jig of the present invention.

As shown in Table 1, the temperature of the small-diameter portion of the present invention A is 300° C. or more lower than the temperature of the large-diameter portion, and is suppressed to a temperature of 500° C. or less. The temperature of the small-diameter portion of the present invention B is 60 to 180° C. lower than the temperature of the large-diameter portion, and is suppressed to 800° C. or less. From this fact, the effects of the present invention can be achieved by applying the methods of the present invention A and the present invention B in particular. In addition, in the case of the present invention A, there was almost no bending of the small-diameter portion after heating.

(Example 2)
Based on the results of Example 1 described above, hot forging was performed by applying the large-diameter portion heating process applied to the present invention A and the present invention B. The material, shape and dimensions of the forging material used and the material holding jig were the same as those shown in the first embodiment. The heating temperature for hot forging was set to approximately 900° C., and the forging material 1 of the present invention A and the present invention B was partially heated for 2 to 7 hours by selectively heating the large diameter portion 11 . Subsequently, after removing the heating material heated to about 900° C. from the material holding jig, the small diameter portion of the heating material is inserted into the hole provided in the lower mold having a hole for inserting the heating material, and the upper Hot forging was performed by pressing the large-diameter portion in the axial direction with a die 5 to obtain a hot forged material.
Hot forging was performed by inserting the small-diameter portion of the heating material 3 into the hole 41 provided in the lower die 4, as shown in FIG. Since the heating material 3 is a stepped rod-shaped heating material 3 having a large-diameter portion and a small-diameter portion, the stepped portion 31 of the large-diameter portion is utilized to separate the stepped portion 31 and the lower die. (the stepped portion 31 is supported by the lower mold), the end surface of the small diameter portion is suspended in the air without contact with the bottom of the lower mold, and the heating material 3 and the lower mold 4 are provided with The small-diameter portion of the heating material 3 inserted into the hole 41 of the lower die 4 and the inner peripheral surface of the hole 41 are kept out of contact with each other by aligning the center axis with the hole 41 . In the large-diameter portion heating step, the thermal expansion of the small-diameter portion is suppressed by suppressing the temperature rise of the small-diameter portion 12, and the occurrence of bending is also suppressed. Insertion of the part was also easy.
Further, since the small diameter portion is not in contact with the bottom of the lower mold 4, deformation such as bending of the small diameter portion can be suppressed when the large diameter portion 11 is pressed by the upper mold. Even after forming the hot forged material 6 , the thermal expansion of the small-diameter portion was still suppressed, and the hot forged material 6 could be removed smoothly from the lower die 4 .

When 100 or more hot forged materials were produced by the above hot forging, the defect rate due to bending could be suppressed to 0% for the invention A and less than 1% for the invention B.
From the above, according to the hot forging method of the present invention, the large diameter portion to be hot forged can be preferentially heated and the temperature rise of the small diameter portion can be suppressed, so the bending of the small diameter portion in the heating process can be suppressed. Furthermore, since the thermal expansion due to the temperature rise of the small diameter portion can be suppressed, the heating material can be smoothly inserted into and removed from the lower mold, and the productivity can be improved.

REFERENCE SIGNS LIST 1 forging material 2 material holding jig 3 heating material 4 lower die 5 upper die 6 hot forged material 11 large diameter portion 12 small diameter portion 21 hole 31 stepped portion of large diameter portion

Claims (1)

A hot forged material manufacturing method for hot forging the large diameter portion of a rod-shaped forging material having a large diameter portion and a small diameter portion,
inserting the small-diameter portion of the forging material into the hole of the material holding jig having a hole for inserting the forging material, and heating the large-diameter portion to a heating temperature to obtain a heating material;
After removing the heating material from the material holding jig, the small diameter portion of the heating material is inserted into the hole of the hot forging lower die having a hole for inserting the heating material, and the hot forging upper die A method for producing a hot forged material, characterized by performing hot forging in which the large diameter portion is axially pressed to obtain the hot forged material.

Images