JP2653157B2 - Forging method of heat-resistant alloy - Google Patents

Description

The present invention relates to a method for forging a heat-resistant alloy such as WASP.

[Background Art] For example, when manufacturing a ring used as a component of a gas turbine or the like, a heat-resistant alloy called WASP (Waspalloy: trade name) has recently been used.

This WASP is a Ni-Cr-Al-Ti alloy and is excellent in heat resistance, but is hard at a temperature of about 980 ° C or less and easily cracks due to crystal precipitation.

Therefore, conventionally, when manufacturing the above-mentioned ring with this WASP, the cylindrical burette obtained by forging is heated red by reheating, quickly set in a forging press device, and forged at high pressure in a short time. To make a disk. Further, a method of forming the disk into a ring shape using a ring mill has been adopted.

[Problems to be Solved by the Invention] However, in the above-described conventional forging method, even if the burette in the red hot state is quickly set in the press device, the contact surface to the press device is prevented from cooling immediately after that. I can't. For this reason, it becomes relatively hard near the contact surface where the temperature is low, and the burette after forging deforms like a drum instead of a perfect disk, and not only the structure becomes non-homogeneous, but also near the contact surface. When a portion having a temperature of 980 ° C. or lower occurs, the low-temperature portion may be broken. Furthermore, since the burette must be forged in a relatively hard state, a large driving force is required for the press device, which increases the size of the device and increases the manufacturing cost, and also heats the buret contact surface of the press. And the life of the device is shortened.

"Means for solving the problem" The present invention has been made to solve the above problems,
A liquid ceramic-based heat-insulating solvent is applied to the surface of the heated heat-resistant alloy material, and the ceramic-based heat-insulating fiber sheet is fixed to a contact surface with a forging press device, and then forging is performed.

 Hereinafter, the present invention will be described specifically.

In this method, first, a ceramic heat-insulating solvent such as Serum Guard (trade name) is applied to the entire surface of a buret made of a heat-resistant alloy such as WASP in the red hot state immediately after being formed by forging using a brush or a spray gun. Apply to a substantially uniform thickness. This ceramic-based heat-insulating solvent is obtained by dissolving ceramic fine powder in a slurry form with a liquid such as water.
Desirably, it is about 0.1 to 0.5 mm. If the thickness is less than 0.1 mm, a sufficient heat insulating effect cannot be obtained, and the heat insulating effect does not increase even if applied thicker than 0.5 mm.

The temperature of the buret before application is preferably 900 to 1100 ° C. in the case of WASP, for example. If the temperature is lower than 900 ° C., cracks may occur during forging, and if the temperature is higher than 1100 ° C., the ceramics may melt and flow.

Next, a ceramic insulating fiber sheet such as kao wool (trade name) is laid on the lower press upper surface of the forging press device,
The buret on which the application of the heat-insulating solvent has been completed is quickly placed on the heat-insulating fiber sheet. Further, a similar ceramics heat insulating fiber sheet is placed on the upper surface of the burette, and forging is rapidly performed. If possible, the heat insulating fiber sheet may be wound around the entire surface of the burette. This can further enhance the heat insulating effect.

The ceramic insulating fiber sheet does not dissolve even at the above-mentioned temperature, and asbestos or the like can be used in addition to the above-mentioned kao wool. Further, in the case of kao wool, for example, the thickness of the sheet is desirably about 10 to 20 mm in a natural state where no pressure is applied. If the thickness is smaller than this range, the heat insulating effect is insufficient and the conventional problem cannot be solved. If the thickness is larger than this range, the forging accuracy may decrease due to the thickness of the sheet.

The forging method of the present invention is applicable not only to WASP but also to heat-resistant alloys such as U-710, which have similar problems.

[Operation] In the above method, the ceramic insulating fiber sheet laid between the burette and the press does not escape from the abutment portion of the buret even when press pressure is applied, and the fiber has a certain thickness even when compressed. However, since a high heat insulating effect is obtained, it is possible to prevent heat transfer from the high temperature burette to the press, and to prevent local cooling and hardening of the burette. Therefore, forging can be efficiently performed with a relatively small pressing pressure, and the structure of the obtained forged product is uniform, cracks and shape defects due to a decrease in temperature do not occur, and there is no fear of press deterioration due to heat transfer.

On the other hand, the ceramic-based heat-insulating solvent not only exerts its own heat-insulating effect, but also forms a heat-insulating layer between the burette and the heat-insulating fiber, preventing the heat-insulating fiber from directly welding to the high-temperature buret, and further solidifying. After that, applied strain is generated at the contact interface with the forged product due to the difference in thermal expansion coefficient from the heat-resistant alloy, and the insulating fiber is easily peeled off from the forged product by providing heat insulating fibers, so that the removal is extremely simple.

By the way, if the ceramic insulating fiber sheet is put on the glowing burette without using the ceramic insulating solvent, the insulating fiber sheet is welded to the burette due to the high temperature of 1000 ° C or higher and the pressing pressure, and it is easy to solidify after the solidification. Cannot be peeled. Also, if the burette is simply coated with a ceramic-based heat-insulating solvent and no heat-insulating fibers are used, the heat-insulating solvent escapes from the burette surface during forging, and the press and buret come into direct contact. In addition, inconveniences such as contamination of the press device with the heat insulating solvent also occur.

"Examples" Next, the effects of the present invention will be demonstrated with examples. WASP
Was used as a raw material to cast a cylindrical burette of 36 cmφ × 120 cm. Then, while in the glowing state, the buret was applied with a brush with a brush to a thickness of about 0.3 mm, and the entire upper and lower surfaces were sandwiched with kao wool having a thickness of 10 mm (natural state) and forged with a press device. The obtained forged product is 48cmφ × 60
It is a column of cm.

As a result, the press pressure required for forging was 200 kg / cm ² . After natural cooling, an attempt was made to peel off the serum guard and kao wool from the forged product, and the chao wool solidified into a plate shape with the serum guard and peeled off easily. Further, the serum guard attached to the outer peripheral surface could be easily peeled off due to the difference in coefficient of thermal expansion from the heat-resistant alloy. The forged product had an almost perfect cylindrical shape, no cracks or drum-like deformations, and had a homogeneous structure.

On the other hand, as Comparative Example 1, a burette that was glowed in the same manner as described above was directly set in a press device and forged. As a result, a pressing pressure of 1020 kg / cm ² was required to obtain a forged product of the same size as above, and the forged product had a drum-like shape and cracks occurred radially on the lower surface.

Further, as Comparative Example 2, the same chao wool as above was sandwiched over the entire upper and lower surfaces of the red-hot burette, and as a result of forging press, a pressing pressure of 200 kg / cm ² was required. Although the forged product had a substantially perfect cylindrical shape, kao wool was welded to the upper and lower surfaces, and removal was troublesome, and was not practical.

Further, as Comparative Example 3, a serum guard was sprayed on the entire surface of the red-heated burette to the same thickness as in the above example, and the forging press was performed as it was. As a result, the serum guard sprayed on the upper and lower surfaces of the burette flowed from the contact surface, and the upper and lower surfaces of the buret were cooled, and the forged product became drum-shaped. In addition, the serum guard adhered to the press device, solidified, and took time to remove.

As described above, according to the heat-resistant alloy forging method according to the present invention, the ceramic insulating fiber sheet laid between the burette and the press maintains a certain thickness even when compressed, Due to the high heat insulating effect, the heat transfer from the hot burette to the press is significantly reduced, and local cooling and hardening of the burette can be prevented. Therefore,
Forging can be performed efficiently with a relatively small press pressure, the cost required for the driving force can be reduced, and the structure of the obtained forged product is uniform, and cracks and shape defects due to a decrease in temperature do not occur. Further, deterioration of the press due to heat transfer can be prevented.

On the other hand, the heat-insulating solvent not only exerts the heat-insulating effect itself, but also forms a heat-insulating layer between the burette and the heat-insulating fiber, thereby preventing the heat-insulating fiber from directly welding to the high-temperature buret, and after solidification. Due to the difference in the coefficient of thermal expansion from the heat-resistant alloy, stress strain occurs at the contact interface with the forging. Therefore, according to this method, both the heat-insulating solvent and the heat-insulating fiber can be easily peeled off from the forged product, and an excellent effect that post-processing after forging can be extremely easily performed can be obtained.

Claims (1)

(57) [Claims] A liquid ceramic-based heat-insulating solvent is applied to the surface of a heated heat-resistant alloy buret, and at least a surface in contact with a forging press is covered with a ceramic-based heat-insulating fiber sheet. Forging a heat-resistant alloy.