JPH05115939A - Die forging method of high alloy steel - Google Patents

Abstract

PURPOSE:To provide the die forging method of high alloy steel which controls the temperature. CONSTITUTION:In the die forging time by heating the die 1 and the billet 4 composed of high alloy steel of Ni base heat resistance alloy, etc., the heating temperature of the die 1 is set lower than the heating temperature of the billet 4, the ratio is made within the range 0.6-0.8 and the forming is completed while the temperature relation is kept during forging. As compared with the conventional method which heats the die to a comparative low temperature, because the growing of chill layer from the surface part and the generation of inner strain are prevented, the post process of machining, etc., is eliminated, and the yield is good. In the other hand, as compared with the isothermal forging, the heating device for the die is simplified and the heating time can be shortened and together the complicated operation for the large equipment to be used becomes needless.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die forging method for high alloy steel.

[0002]

2. Description of the Related Art Conventionally, a material made of a high alloy steel such as a Ni-base heat-resistant alloy is used, and when a product such as a disk for a gas turbine is die forged, the material and the die are heated together. It is being appreciated. Such a die forging method is
Generally, the material is heated to a temperature suitable for forging and the mold is heated to a relatively low temperature. The heating of this mold has a relatively low impact value at a low temperature of the mold material. Preheated to ~ 200 ° C.

However, in such a conventional die forging method, the die preheating temperature is low, the temperature of the material made of high alloy steel is rapidly lowered during forging, and a chill layer develops from the surface layer portion. Moreover, since internal strain remains, it is difficult to obtain uniform internal properties. In particular, high alloy steel requires cracking because it causes cracking, which is troublesome and the yield is poor.

Further, as known from Japanese Patent Publication No. 63-21737, there is isothermal forging (constant temperature forging) in which the temperature of the material and the die are the same, and a dense structure is obtained, but it takes a long time to heat each forging operation. In addition to requiring large-scale equipment, it is costly. For example, when the die is heated to 1050 ° C., which is the same as the material, a large-scale heating device that generally combines a gas burner and an electric heater is required, and TZM, which is a usual die material, has poor oxidation resistance. The mold must be placed in a vacuum or in an inert gas to prevent oxidation-induced deterioration of the mold. As a result, the isothermal forging device is large and complicated, and its workability is poor.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional technical problems, and its constitution is a material and a mold made of a high alloy steel such as a Ni-base heat-resistant alloy. When heating together and forging the mold, set the mold heating temperature lower than the material heating temperature, and set the ratio to 0.6-
It is a die forging method for high alloy steel in which the range is set to 0.8 and the forming is completed while maintaining the above temperature relationship during the forging operation.

[0006]

[Operation] According to the die forging method of this high alloy steel, the die is
It is heated to a predetermined heating temperature (T ₁ ) using a heating device, and the material is heated to a predetermined heating temperature (T ₁ ) by a forging heating furnace.
Heat to ₂ ). Therefore, this temperature relationship is established by setting the heating temperature of the raw material to the normal hot forging temperature and setting the heating temperature of the mold to a temperature slightly lower than that of the isothermal forging.

In this state, the forging work is started, and the material is formed with a die. Since this forging work can be completed in a short time,
The temperature of the mold and the material during the forging operation is usually completed while maintaining the above relationship (T ₁ / T ₂ = 0.6 to 0.8). If the temperature of the mold is instantly decreased due to the low ambient temperature and the above temperature relationship is not maintained during the forging operation, the heating device is activated to prevent the mold temperature from decreasing. However, care should be taken to maintain the above temperature relationship even at the finishing temperature. Such maintenance of the temperature relationship can be easily realized when the material has a certain amount of heat capacity and the die does not cause a sudden temperature drop.

According to such a die forging method, the die is sufficiently heated as compared with the conventional die forging method which is performed by heating the die at a relatively low temperature. A layer can be prevented from developing and a product with uniform internal properties without defects can be obtained. On the other hand, compared to isothermal forging, the time required to heat the die is shortened.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. Mold 1
Is composed of an upper mold 2 and a lower mold 3. The lower mold 3 is fixed to a forging machine base (not shown), and the upper mold 2 is fixed to a press ram (not shown). Then, the material 4 is inserted between the molds 2 and 3. The material 4 is made of a high alloy steel such as a Ni-based heat-resistant alloy or a titanium-based alloy, and the height of the cylindrical material 4 is H and the diameter is D, and H / D = about 1.5. Further, a gas burner 5 as a heating device is arranged around the mold 1 so that both molds 2 and 3 can be heated to a predetermined temperature described later.

By using such a forging device, the following temperature control is performed during the forging operation. That is, the heating temperature of the mold 1 is T ₁ , and the heating temperature of the material 4 is T _{1 which is} higher than the recrystallization temperature.
₂ is set in the range of T ₁ / T ₂ = 0.6 to 0.8. Mold 1, using the gas burner 5 was heated to a predetermined heating temperature (T _1), the material 4, by the forging furnace consisting of a continuous furnace or a non-continuous furnace connexion predetermined heating temperature (T ₂ )
Heat to. As for this temperature relationship, the heating temperature of the material 4 is set to the normal hot forging temperature, and the die 1
The heating temperature is set to be slightly lower than the isothermal forging.

Specifically, when the material 4 made of a Ni-base heat-resistant alloy is die-forged into, for example, a disk for a gas turbine, the material 4 is heated to 1050 ° C. and the die 1 is 700 to 8.
Heat to 00 ° C. In this state, the forging work is started, and the material 4 is formed between the upper die 2 and the lower die 3. Since this forging operation can be completed within a short time of about 2 seconds, the temperatures of the mold 1 and the material 4 during the forging operation are usually the above-mentioned relation (T ₁ / T
₂ = 0.6 to 0.8) is maintained and completed. Then, when the temperature of the mold 1 is instantly lowered due to the reason that the ambient temperature is low and the above temperature relationship is not maintained during the forging operation, the gas burner 5 is operated to lower the temperature of the mold 1. Therefore, the above temperature relationship should be maintained even at the finishing temperature. Maintaining such a temperature relationship is
This can be easily realized when the material 4 has a certain amount of heat capacity and the material 1 does not cause a sudden temperature drop due to the mold 1. The above-mentioned disk for gas turbine has a diameter of 1 m.
Yes, with the required heat capacity.

According to such a die forging method, the die 1 is sufficiently heated as compared with the conventional die forging method which is performed by heating the die at a relatively low temperature (150 to 200 ° C.). As a result, the chill layer is prevented from developing from the surface layer,
It is possible to obtain products with uniform internal properties without defects. On the other hand, compared to isothermal forging (constant temperature forging), the mold 1
It is not necessary to prevent the deterioration of the mold 1 due to the oxidation by arranging the mold 1 having poor oxidation resistance in a vacuum or in an inert gas while shortening the time required for heating. In addition, the die forging method of the above-described embodiment has been described as the case where the material 4 is formed into a product by one forging operation. Can also be applied to.

[0013]

As can be understood from the above description,
According to the die forging method of the high alloy steel according to the present invention, as compared with the conventional method of heating the die at a relatively low temperature, the development of the chill layer from the surface layer portion and the occurrence of internal strain are prevented,
Post-processes such as machine shaving are omitted, and the yield is good. On the other hand, compared with the isothermal forging, the heating device for the mold is simplified and the heating time can be shortened, and it is not necessary to arrange the mold in vacuum or in an inert gas. As a result, the complicated work of using a large-sized facility is unnecessary, and the cost can be reduced. Furthermore, since the heating temperature of the mold is low, the durability of the mold can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a partial cross section of a forging device used in a die forging method for high alloy steel according to an embodiment of the present invention.

[Explanation of symbols]

1: Mold, 2: Upper mold, 3: Lower mold, 4: Material, 5: Gas burner (heating device).

Claims (1)

[Claims] 1. When heating a material made of a high alloy steel such as a Ni-base heat-resistant alloy and a die together and forging the die, the heating temperature of the die is set lower than the heating temperature of the material, and the ratio is 0. A die forging method for high alloy steel, characterized in that the forming is completed within the range of 6 to 0.8 while maintaining the above temperature relationship during the forging operation.