JP5963041B2 - Hot forging method - Google Patents

Description

  The present invention relates to a hot forging method.

When hot forging a difficult-to-work material such as a Ti alloy or a Ni-base superalloy, it is important to ensure sufficient lubricity for hot forging while ensuring hot workability.
When hot-forging this difficult-to-work material, the glass-based lubricant that has been used as a lubricant has a problem of lubrication. Therefore, for example, Japanese Laid-Open Patent Publication No. 4-13434 (Patent Document 1) proposes a method of isothermal forging in which a metal foil is present together with a lubricant between a workpiece and a forging die.

JP-A-4-13434

In the combination of the lubricant and the metal foil disclosed in Patent Document 1, the rigidity of the metal foil is high. When the metal foil is arranged on the lower mold, it is difficult to understand the shape of the mold engraved surface, and the material to be forged. Positioning becomes difficult. If it does so, the temperature of a to-be-forged material will fall, and there exists a concern about the fall of the hot workability of a to-be-forged material.
It is an object of the present invention to more reliably perform hot forging lubrication of difficult-to-work materials, and to easily position the to-be-forged material to be placed in the lower mold, and to ensure sufficient hot workability of difficult-to-work materials. A sustainable hot forging method is provided.

The present invention has been made in view of the above-described problems.
That is, the present invention relates to a hot forging method in which a heated forging material is disposed between an upper die and a lower die and forged, and the lubricant is applied to the ceramic fiber sheet on the die-cut surface of the lower die. A lubricating sheet impregnated with a flexible material is arranged so as to follow the shape of the die-carved surface , and the ceramic fiber sheet is not arranged on the surface in contact with the upper die of the columnar forged material. , A hot forging method in which the forged material is hot stamped and forged into a disk shape by the upper die and the lower die heated to 200 to 450 ° C.

  According to the present invention, lubrication during hot forging can be performed more reliably, positioning of the forging material arranged in the lower die is easy, and hot workability of difficult-to-work materials can be sufficiently maintained. Even if the material to be forged is a difficult-to-work material, it is possible to prevent hot forging defects such as seizure between the material to be forged and the mold and cracking of the forged material.

It is a schematic diagram which shows the hot forging method of this invention.

An important feature of the present invention is that a lubrication sheet in which a fiber sheet is impregnated with a lubricant and provided with flexibility is placed along the shape of the mold carved surface on the mold carved surface of the lower mold. There is forging.
In the present invention, the lubricating sheet is disposed on the die-cut surface for the following reason.
(1) Prevention of temperature drop due to direct contact of forged material with mold.
(2) Giving sufficient lubrication effect during hot forging.
(3) Hot forging defects such as seizure between the material to be forged and the mold and cracking of the hot forged material are prevented.
(4) Since the fiber sheet is used, the lubricant is impregnated uniformly, so that it is difficult for the lubrication to become non-uniform during hot forging, and the effect of improving the life of the mold can be obtained at the same time.
Is the main reason.

In addition, since the lubricating sheet of the present invention is a fiber sheet impregnated with a lubricant to provide flexibility, the lubricating sheet can be arranged so as to follow the shape of the engraved surface.
This makes it easy to position the forging material to be placed in the lower mold, so it is possible to prevent the hot workability of the forging material from being deteriorated, and hot forging such as cracking of the hot forging material. Defects can be prevented.
In the present invention, the fiber sheet is required to be a ceramic fiber sheet.
This is because the ceramic fiber sheet has a heat insulation property, so that the heat insulation property can be further secured by arranging it between the lower mold and the material to be forged, where temperature drop is a concern. This is because the temperature drop can be further prevented. Further, since the lubricity can be expected from the ceramic fiber sheet itself, the lubricity can be greatly improved.

Next, a typical hot forging method using the above-described lubricating sheet of the present invention will be described with reference to the drawings.
In the hot forging method of the present invention, for example, as shown in FIG. 1, a lower mold 4 and an upper mold are used by using a lubricated sheet 2 in which a heated forging material 1 is impregnated with a lubricant to enhance flexibility. 3 and forging. The lubricating sheet provided with flexibility is arranged so as to follow the shape of the engraved surface.
The conditions for hot forging may be a conventional method. Specifically, the forged material 1 is heated to a recrystallization temperature or higher. The heating temperature of the material to be forged for hot forging is preferably not less than the recrystallization temperature and not more than the solidification temperature.
And hot forging is performed using the forging material heated to the above-mentioned temperature range. At this time, the upper mold and the lower mold is, for example, your clauses heated to 200~450 ℃. This is for preventing damage to the mold and reducing the heat loss of the material to be forged.

Next, in the present invention, the lubricating sheet 2 impregnated with the lubricant is disposed on the die-cut surface of the lower mold 4 so as to be interposed between the forged material 1 and the lower mold 4. Thereby, the to-be-forged material 1 can prevent the to-be-forged material's heat loss by contacting the lower metal mold | die 4 directly.
In the present invention, since the fiber sheet impregnated with the liquid lubricant is disposed as the lubricating sheet, the mold carved surface can be visually confirmed. Therefore, it becomes easy to position the forging material, it is possible to prevent forging defects such as lacking due to displacement, and at the same time, it is possible to shorten the time until the forging material is installed at a suitable position, It is also possible to prevent a temperature drop of the material to be forged.
In addition, the impregnation of the fiber sheet with the lubricant may be performed by, for example, immersing the fiber sheet in a container filled with a lubricant such as an aqueous lubricant such as a white lubricant or an oil lubricant such as a graphite lubricant. This is the simplest method.
In addition, since the lubricating sheet of the present invention is provided with flexibility as described above, it can be arranged along the mold carved surface when arranged on the carved surface, and the shape is on the lubricating sheet. It can be confirmed from. Therefore, it gives sufficient lubrication effect during hot forging, prevents seizure between the material to be forged and the mold and prevents hot forging defects such as cracks in the hot forging, and lubrication during hot forging. It is difficult to become non-uniform, and the effect of improving the life of the mold can be obtained at the same time.
Moreover, although a ceramic fiber sheet can be used as the fiber sheet, the use of a glass fiber sheet can improve lubricity as well as an excellent heat insulating effect.

  Using the above-described lubricating sheet, the forged material can be more reliably lubricated during hot forging by hot forging the upper forged material with the upper die and the lower die, and placed in the lower die. Is easy to position and the hot workability of difficult-to-work materials can be maintained sufficiently, so that even if the forged material is difficult-to-work material, seizure between the forged material and the mold or hot Hot forging defects such as cracking of the forged material can be prevented.

Hereinafter, the present invention will be described with reference to examples.
As the material to be forged, Waspaloy (registered trademark of United Technologies) equivalent alloy of difficult-to-work material was prepared. The size of the material to be forged was a cylindrical shape having a diameter of 140 mm × 300 mm (T). This forged material was heated to 1050 ° C. and preheated before hot forging. The hot forging was a die forging, and a disk-shaped forged material was obtained.
The lubricating sheet used for hot forging is a ceramic fiber sheet of heat-insulating glass cloth (250 mm (W) x 250 mm (L) x 1.5 mm (T)) that is large enough to cover the entire engraved surface of the lower mold. Was prepared and immersed in an aqueous lubricant of Lubcaster (R) manufactured by Nikka Chemical Co., Ltd. to obtain a lubricating sheet.
In addition, although it tried to apply the method of patent document 1 as a comparative example, when metal foil is installed on a mold-carved surface, alignment of a carved surface and a to-be-forged material is difficult, and there is a possibility of lack of thickness. In addition, the disk-shaped carved surface has irregularities and partial inclinations, so it takes too much time to place the metal foil along the carved surface. In consideration of safety, we gave up hot forging.
Therefore, a normal hot stamping forging method without using a lubricating sheet was used as a comparative example.

The upper mold 3 and the lower mold 4 as shown in FIG. 1 were heated to 350 ° C. Thereafter, the lubricating sheet 2 was placed on the mold carved surface of the lower mold 3, and the forged material 1 taken out from the preheating furnace was placed on the lubricating sheet.
At this time, since the lubrication sheet 2 has flexibility, it could be arranged along the mold carved surface of the lower mold 3, so the shape of the mold carved surface of the lower mold 1 was visually confirmed. We were able to. Therefore, since it did not take time to align the forged material 1, it was possible to suppress the temperature drop of the forged material. In addition, the temperature at the time of the hot work start of a forging material was about 1030 degreeC, and was the temperature which can fully maintain the hot workability of a difficult-to-work material.
Next, the hot to-be-forged material 1 was arrange | positioned between the upper metal mold | die 3 and the lower metal mold | die 4, and hot stamping forging was performed. Sufficient lubrication was ensured by the lubricant impregnated in the lubricating sheet and the ceramic fiber sheet, and no new lubricant was supplied during hot stamping forging.
In the disk material obtained by the hot stamping forging, forging defects such as seizure between the material to be forged and the die, cracking of the hot forging material, lack of wall thickness and uneven thickness were not observed.

As a comparative example, hot stamping forging was performed under the same conditions as described above except that a lubricating sheet was not used. In this case, the lubricant was sprayed on the lower mold.
In the hot stamping forging of the comparative example, a temperature drop of the forging material in contact with the lower die was observed. As a result, cracks spreading in the radial direction occurred on the lower surface of the forged material. In addition, in order to suppress cracking, when the material to be forged was once put into the preheating furnace during the hot stamping forging and the hot stamping forging was performed again, the crystal grains became coarse compared with the examples. .

  The hot forging method of the present invention is particularly promising as a hot forging method for difficult-to-work materials because it is excellent in lubricity and is expected to have a heat insulating effect. Moreover, since it is possible to install a lubricating sheet along the shape of the die-carved surface of the mold, it is particularly suitable for obtaining a hot forged material having a complicated shape.

1 Forging material 2 Lubrication sheet 3 Upper die 4 Lower die

Claims (1)

In a hot forging method in which a heated material to be forged is placed between an upper mold and a lower mold and forged, a ceramic fiber sheet is impregnated with a lubricant on the mold carved surface of the lower mold for flexibility. The lubricating sheet provided with the property is arranged so as to follow the shape of the die-sculpted surface , and the ceramic fiber sheet is not disposed on the surface that contacts the upper die of the columnar forged material. A hot forging method, wherein the material to be forged is hot stamped and forged into a disk shape by the upper die and the lower die heated to the same temperature .