JPH06254648A - Thermostatic die forging method - Google Patents

Abstract

PURPOSE:To prevent a burning between a die and a part to be forged, to control a chemical reaction and to prevent an oxidation corrosion by coating a die of a nickel base heat resistant alloy with a graphite base lubricant or a nitride boron base release agent and executing with thermostatic die forging in an atmospheric environment of a specific temperature range. CONSTITUTION:A material to be forged M composed of a nickel base powder super alloy is arranged on a lower die 2, and together both dies are closed by descending an upper die 1, on one side, the temperature of the upper and lower dies 1, 2 is increased in an atmospheric environment by inputting a heater through an input controller. In this time, an oxidation corrosion of the dies is prevented by coating the dies with a graphite base lubricant or a nitride boron base release agent. Further, the thermostatic die forging can be stably realized under the atmospheric environment of the temperature range 1100-1200 deg.C by preventing a burning crack caused on the temperature increase of the die under the temperature increasing condition where at every time of increasing the temperature of the die of the max. 250 deg.C, the die is kept within the time min. 30 minutes in the temperature rising condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant temperature die forging method for forming a hard plastic working material such as a nickel base alloy or an intermetallic compound.

[0002]

2. Description of the Related Art Heat-resistant high alloys such as nickel-base alloys and intermetallic compounds used for turbine disks and blades for aircraft engines are extremely difficult to plastically work due to their material properties. isothermal forging method is applicable to, and in its isothermal forging, using a very fine material of the crystal grains, the high temperatures these materials exhibit superplastic behavior (1000 ° C. or higher) and low distortion rate (10 ^{- 2}
Molding is performed in the region of ~ 10 ^-4 / sec).

On the other hand, in the constant temperature die forging, the die is
Since it is exposed to severe conditions of high temperature of 1000 ° C. or higher for a relatively long time, a heat-resistant alloy such as molybdenum-based alloy and fine ceramics, or a nickel-based heat-resistant superalloy is used.

[0004]

By the way, in recent years, as heat resistant high alloys used for aircraft engine members, etc.,
In order to improve the performance, more excellent high temperature strength is required, and its plastic working tends to be more difficult.
Therefore, the temperature range for superplastic forming these materials is 1,10
Many of them reach 0 ℃ to 1,200 ℃, and constant temperature die forging is required to be performed efficiently in a higher temperature range.

However, molybdenum-based alloys have high strength even at high temperatures of 1100 ° C. or higher, but their strength is significantly reduced by oxidation in the air atmosphere. Therefore, when these alloys are used as a die for isothermal die forging. However, it is necessary to forge in a vacuum or in a non-oxidizing atmosphere to prevent oxidation. Therefore, it is necessary to provide an exhaust device, a chamber, and the like, and accordingly, not only does the device structure become large, the equipment cost rises, but also it is difficult to put in and take out the workpiece, and the productivity is lowered.

Further, fine ceramics have high strength without being oxidized even in a high-temperature atmosphere, but they are inferior in toughness, so that it is difficult to form them as a mold by themselves, and they are used in combination with a metal member for backing them up. It is necessary, and when it is used for a complicated mold with many irregularities or a relatively large mold, the mold is divided into multiple parts from the corners etc. in order to prevent damage from stress concentration parts such as the corners of the impression. In addition to the need for an assembled structure, the structure becomes complicated and the manufacturing cost rises, and a heavy burden is imposed on maintenance.

On the other hand, the nickel-base heat-resistant superalloy integrated mold is said to be usable in a constant temperature atmospheric atmosphere near 1000 ° C. If it can be used for constant temperature die forging at 1100 ° C. or higher, equipment And it is very advantageous in terms of mold cost and production efficiency.

However, a die made of a nickel-base heat-resistant superalloy easily seizes with the material to be forged at 1000 ° C. or higher, which deteriorates the useful life of the die and the quality of the product. In order to apply the above isothermal die forging, it is necessary to prevent seizure between the die and the material to be forged, but a concrete method for preventing the seizure has not yet been known. For example, in a constant temperature die forging in the atmospheric atmosphere near 1000 ° C. using a die made of a conventional nickel-base heat-resistant superalloy, in order to prevent seizure between the die and the material to be forged, a glass-based lubricant is usually used. However, these glass-based lubricants tend to heat up and scatter at 1000 ° C and to be transformed at the same time, and in the air atmosphere at 1100 ° C or higher, they chemically react with the nickel-base heat-resistant superalloy. Since it causes the oxidative corrosion of the mold and significantly shortens the service life, it cannot be used as a lubricant in the atmosphere of 1100 ° C or higher.

Furthermore, the nickel-base heat-resistant superalloy, like the molybdenum-base alloys and fine ceramics, has a higher thermal embrittlement than ordinary hot die steels, so that cracks easily occur due to thermal stress during temperature rise. To apply a mold made of nickel-base heat-resistant superalloy to isothermal die forging, from room temperature to 11
It is necessary to prevent mold cracking when the temperature is raised to a high temperature range of 00 ° C or higher, but a quantitative method for surely preventing the cracking has not yet been known.

That is, in isothermal forging in a constant temperature die forging in the temperature range of 1100 ° C to 1200 ° C, a die made of a nickel-base heat-resistant superalloy is used, which reduces equipment and die costs and improves production efficiency. To prevent this, seizure between the mold and the material to be forged is prevented by a lubricant or mold release agent, and the chemical reaction between the lubricant or mold release agent and the mold is suppressed to prevent oxidative corrosion of the mold. It is necessary to newly define a method for preventing the above, and a method for raising the temperature of the mold from room temperature to a high temperature range of 1100 ° C. or higher without causing thermal stress cracking.

The present invention has been made to solve the above-mentioned problems, and uses a die made of a nickel-base heat-resistant alloy, and prevents seizure between the die and the material to be forged by applying a lubricant or a release agent. In addition, the chemical reaction between the lubricant and mold release agent and the mold can be suppressed to prevent oxidative corrosion of the mold.
Providing a constant temperature die forging method that can achieve constant temperature die forging with high production efficiency in the atmospheric temperature range of up to 1,200 ° C, and a die made of a nickel-base heat-resistant alloy from room temperature to 1100
A constant temperature die forging method that can raise the temperature to a high temperature range of ℃ or higher without generating cracks, and can stably achieve constant temperature die forging in the atmosphere of the temperature range of 1100 ° C to 1200 ° C. And aim.

[0012]

In order to achieve the above object, the present invention has the following constitution. That is, the isothermal die forging method according to the first invention, when isothermal die forging is performed using a die made of a nickel-base heat-resistant alloy, a graphite-based lubricant or a boron nitride-based release agent is applied to the die, It is characterized by constant temperature die forging in an air atmosphere in the temperature range of 1100 ° C to 1200 ° C.

The isothermal die forging method according to the second aspect of the invention is such that, when the isothermal die forging is performed using a die made of a nickel-base heat-resistant alloy, the die temperature is raised every 250 ° C. at maximum. Under the temperature rising condition of keeping the temperature for at least 30 minutes, the temperature is raised stepwise from room temperature to the temperature range of 1100 ° C to 1200 ° C, and then a constant temperature type is set in the atmosphere of the temperature range of 1100 ° C to 1200 ° C. Characterized by forging.

[0014]

[Function] 1100 using a mold made of nickel-base heat-resistant alloy
In the case of constant temperature forging in the atmospheric temperature range of ℃ ~ 1200 ℃, as a lubricant or mold release agent used to prevent seizure between the mold and the material to be forged, Those that cause a chemical reaction with the mold to accelerate the oxidative corrosion of the mold not only reduce the service life of the mold but also reduce the product quality, and therefore must be avoided. The present inventors have studied various lubricants and mold release agents from this viewpoint, and can apply a graphite-based lubricant and a boron nitride-based mold release agent, which are chemically stable even in a high temperature range. It is listed as a candidate for various lubricants or release agents.

In order to confirm the chemical reaction of these with the nickel-base heat-resistant alloy material as the die material in the high temperature range, Mo: about 10 wt% (others, W: about 12 wt%, A
l: about 6 wt%), the balance consists essentially of Ni, and γ
Phase is 30-75vol%, γ'phase is 25-60vol%, α phase is 2.5
A test piece made of nickel-base super heat-resistant alloy material having a phase of ~ 11 vol% and improved high-temperature strength characteristics as a die material (thickness
10 mm, width 10 mm, length 50 mm, surface roughness 6S) are prepared, and graphite lubricant and boron nitride release agent are applied to these test pieces, and the test pieces are heated and corroded in the atmosphere. Experiment was conducted. For comparison, a glass-based lubricant was applied to the test piece and an experiment under the same conditions was performed. Graphite-based lubricant and boron nitride-based release agent are applied by spray coating, and glass-based lubricant is applied by brush coating on the entire surface of the test piece.
After heating to a temperature of 00 ° C. and holding for about 4 hours, it was allowed to cool, and then the surface condition of each test piece was examined closely.

As a result, deposits were formed on the surface of the test piece coated with the glass-based lubricant, and the surface roughness of the test piece after removing the deposit was significantly increased as compared with that before heating. It was Also, the deposit was identified as an oxide of the main component of the test piece, and from this fact, most of the lubricant was heated and scattered when heated at high temperature, while promoting oxidative corrosion with the test piece. It was confirmed that a chemical reaction of

On the other hand, a dense and thin film layer is formed and remains on the surface of the test piece coated with the graphite-based lubricant, and the surface roughness of the test piece after the thin film layer is removed. Was almost unchanged from before heating. In addition, the thin film layer was identified as consisting of graphite, which is the main component of the lubricant, and from this fact, the lubricant was partly heated by high-temperature heating and scattered, but partly from graphite. It was confirmed that a thin film layer was formed to remain on the surface of the test piece and no chemical reaction occurred with the test piece. On the surface of the test piece coated with the boron nitride release agent, the coating film layer of the same release agent remained without much change, and the surface roughness of the test piece after the film layer was removed. Was almost unchanged from that before heating, and it was confirmed from this that the same release agent did not cause a chemical reaction with the test piece by high temperature heating. Further, the film layer peeled off much more easily than the thin film layer formed in the example in which the graphite-based lubricant was applied. That is, since the graphite-based lubricant and the boron nitride-based mold release agent form a film layer with almost no chemical reaction with the nickel-base superheat-resistant alloy in the air atmosphere in the high temperature region, they are made of the nickel-base superheat-resistant alloy. When performing constant temperature die forging in an air atmosphere in the temperature range of 1100 ° C to 1200 ° C using a die, it plays a sufficient role as a lubricant or mold release agent that prevents seizure between the die and the material to be forged. It turned out to be a reward.

The first invention was completed based on the conditions grasped by the above experiment, and a mold made of a nickel-base heat-resistant alloy is provided with a graphite-based lubricant or a boron nitride-based release agent. By applying, it is possible to suppress the chemical reaction between the lubricant and mold release agent and the mold to prevent oxidative corrosion of the mold, and also to prevent seizure between the mold and the forged material. It is possible to achieve isothermal die forging in the atmospheric atmosphere in the temperature range of 1200 ° C.

The graphite-based lubricant in the first invention is mainly composed of graphite, and additionally contains K, Si, Na, S, Cl, Al, etc. alone or in combination. The above-mentioned boron nitride-based mold release agent is mainly composed of boron nitride, and further contains O, Al, C, etc. alone or in combination. Things are used.

On the other hand, the destruction of the mold due to the temperature rise is caused by the generation of excessive tensile thermal stress during the temperature rise, and the thermal stress value generated during the temperature rise is the heat history for preheating the mold. It is possible to control the temperature to be low by setting the maximum temperature rise value in 1) and the minimum holding time value in each temperature rise stage. In order to quantify the suitable temperature rising conditions based on this viewpoint, the present inventors have determined that Mo: about 10 wt% (others: W: about 12 wt%, Al: about
6 wt%), the balance consists essentially of Ni, and the γ phase is
30-75vol%, γ'phase 25-60vol%, α phase 2.5-1
Using the integrated upper and lower molds made of nickel-base super heat-resistant alloy material with 1vol% phase and improved high-temperature strength characteristics as a mold material, fracture experiments by its temperature rise and numerical analysis of its thermal stress were performed. went.

The temperature of the mold is raised and the set value of the holding time in each temperature raising stage is variously changed, and the temperature is raised from room temperature to 1100 ° C. to 1200 ° C. repeatedly. When the presence or absence of cracks on the inner surface of the mold was scrutinized, when the maximum temperature rise value in one step was 300 ° C or higher, the frequency of cracking was high and it was difficult to apply it to actual operation. In some cases, it was found that the frequency of occurrence of cracks decreased and it could withstand practical use. Also, when the thermal stress generated inside the mold was determined, the maximum temperature rise value in one step was 250 ° C or less, and if the temperature was maintained for 30 minutes, the temperature rise in that step It was revealed that almost all of the generated thermal stress was released and relaxed and did not remain in the next heating step.

The second invention is completed based on the conditions grasped by the temperature rising fracture test of the mold and the analysis of the thermal stress, and is performed at a constant temperature using a mold made of a nickel-base heat-resistant alloy. When forging a die, the die can be
Under each temperature raising condition, each time the temperature is raised by 50 ° C, the temperature is maintained at that temperature for at least 30 minutes, and the temperature is raised stepwise from room temperature to 1100 ° C to 1200 ° C. The thermal stress generated in the mold can be suppressed to a low level that does not cause cracking, and the generated thermal stress can be released and relaxed at each temperature rising stage, thus preventing cracking due to the temperature rise of the mold, resulting in 1100 ° C. It is possible to stably achieve isothermal die forging in an air atmosphere in the temperature range of up to 1200 ° C.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a drawing showing a schematic configuration of a mold and a constant temperature forging apparatus used in the constant temperature forging method of the embodiment of the present invention.

In FIG. 1, (1) is an upper mold, (2) is a lower mold, and these upper and lower molds (1) and (2) are especially M
o: about 10 wt% (others, W: about 12 wt%, Al: about 6 wt%)
Contained, the balance consisting essentially of Ni, and the γ phase of 30-75v
ol%, γ'phase is 25 to 60vol%, α phase is 2.5 to 11vol%, and it is made of nickel-base super heat-resistant alloy material with improved high temperature strength characteristics, and is used for normal closed die forging. In this example, a pair of impressions for molding a die-forged product (in this example, a turbine disk) is provided on the opposing kiss surface sides.

Reference numeral (3) is a constant temperature forging apparatus, and this constant temperature forging apparatus (3) is an open-air type pressing apparatus provided with a heater (4) for surrounding and bending the working portion. Where lower mold (2)
Is attached to the lower anvil (3b) of this isothermal forging device (3) and is located inside and below the heater (4), while the upper die (1) is attached to the reduction anvil (3a). Lower mold
The material to be forged (M) placed in the impression with the lower die (2) is pressed at a low strain rate while being pressed toward (2) and under constant temperature by the heater (4). Further, the heater (4) is connected to an input control device (not shown here), and the output is controlled by the input control device so that the upper and lower molds (1) and (2) are predetermined. It is said that the temperature can be raised under the conditions and can be maintained at a constant temperature in a predetermined high temperature range.

In the present embodiment, under the above-mentioned constitution, the forging material (M) made of the nickel-base powder superalloy was isothermally forged in the atmosphere to form the desired turbine disk material. Prior to the isothermal die forging, the following die temperature raising experiment was conducted.

First, a model material made of nickel-base powder superalloy is placed on the lower die (2), and the upper die (1) is lowered to close both, while an input control device (not shown) is used. To the heater (4) to heat the upper and lower molds (1) and (2) in the atmosphere, and from room temperature to 1100 ℃, 1150 ℃ and
Each heating experiment up to 1175 ° C was conducted. In addition, in these heating experiments, each time the upper and lower molds (1) and (2) were heated by 250 ° C, the above set temperature was maintained for 30 minutes at that temperature. The temperature was raised stepwise.

Then, while repeating several temperature rising experiments,
The upper and lower molds were thoroughly examined for cracks after each heating experiment.The upper and lower molds were kept in a very good condition even after repeating several heating tests. From the results, each time the mold was heated up to 250 ° C, the temperature was raised from room temperature to
It was possible to confirm the excellent effect of the method of the present invention in which the temperature was raised stepwise to the temperature range of 00 ° C to 1200 ° C.

Next, as a first example, the upper and lower molds (1),
On the impression surface of (2) and the entire surface of the material to be forged (M),
Graphite lubricant (in this example, 99 wt% crystalline graphite as the main component, K: 0.2 wt%, S
i: 0.2 wt%, Na: 0.2 wt%, S: 0.1 wt%, Cl:
Lubricants containing 0.1 wt% and Al: 0.1 wt% were spray-coated to perform isothermal die forging.

As a second example, the upper and lower molds (1), (2)
A boron nitride-based mold release agent (in this example, 86 wt% of boron nitride as the main component, O: 5.4
wt%, Al: 4.1 wt%, C: 3.1 wt%), and the same graphite lubricant as above is spray-coated on the entire surface of the material to be forged (M). Forged.

Further, the materials to be forged in the constant temperature forging
The pressure molding of (M) is set to a low strain rate selected from the range of 10 ^-2 to 10 ^-4 / sec, while the holding temperature during pressure molding by the heater (4) is 1100 ° C and 1150 ° C. The temperature was changed to 1175 ° C and the temperature was changed to 1175 ° C, but all of the turbine disk materials obtained by constant temperature die forging had a good shape, and the surface condition was extremely smooth without any seizure with the die. The mold after repeating the isothermal die forging was also kept in a healthy state without any abnormality such as oxidative corrosion. From these facts, it was possible to confirm the excellent effect of the method of the present invention.

In the above two examples, the graphite-based lubricant was applied to the material to be forged, but this is to prevent seizure between the die and the material to be forged more reliably. As long as the graphite-based lubricant or the boron nitride-based release agent is applied, needless to say, the application of the graphite-based lubricant to the material to be forged can be omitted without impairing the effects of the present invention.

[0033]

As described above, according to the constant temperature die forging method of the present invention, a die made of a nickel-base heat-resistant alloy is used, and seizure between the die and the material to be forged is prevented by a lubricant or separation. It is possible to prevent oxidation corrosion of the mold by suppressing the chemical reaction between the lubricant and mold release agent and the mold while preventing it by applying the mold agent.
Therefore, constant temperature die forging can be achieved with high production efficiency in the air atmosphere in the temperature range of 1100 ° C to 1200 ° C.
The mold can be heated from room temperature to a high temperature range of 1100 ° C or higher without cracking.
The constant temperature die forging can be stably achieved in the atmosphere of the temperature range of ℃ to 1200 ℃, so it can be applied to the constant temperature die forging of heat resistant high alloy members made of nickel-base alloys and intermetallic compounds that have poor plastic workability. And can greatly contribute to the improvement of the productivity.

[Brief description of drawings]

FIG. 1 is a plan view showing a schematic configuration of a die and a constant temperature forging apparatus used in a constant temperature die forging method according to an embodiment of the present invention.

[Explanation of symbols]

 (1) --Upper mold (2) --Lower mold (3) --Constant temperature forging machine (3a)-Upper anvil (3b)-Lower anvil (4) --Heater.

Claims (2)

[Claims] 1. At the time of constant temperature forging using a die made of a nickel-base heat-resistant alloy, a graphite-based lubricant or a boron nitride-based release agent is applied to the die, and the temperature is 1100 ° C. to 12 ° C.
A constant temperature die forging method characterized by performing constant temperature die forging in an atmosphere of a temperature range of 00 ° C. 2. When performing constant temperature die forging using a die made of a nickel-base heat-resistant alloy, the die must be kept at the elevated temperature for a minimum of 30 minutes each time the temperature is raised to a maximum of 250 ° C. In the above, the isothermal die forging method is characterized in that after the temperature is raised stepwise from room temperature to a temperature range of 1100 ° C to 1200 ° C, the isothermal die forging is performed in the atmosphere of the temperature range of 1100 ° C to 1200 ° C.