JP6941283B2 - Manufacturing method of materials for turbine blades - Google Patents

Description

The present invention relates to a method for producing a material for a turbine blade using hot forging.

In recent years, demand for large-sized hot forged products that make up jet engines for medium- and large-sized aircraft, steam turbines for power plants, etc. has increased significantly. For example, in steam turbines, the length of turbine blades used for them has been increasing due to the demand for higher efficiency. When manufacturing a long material for turbine blades exceeding about 1500 mm, a preformed body (rough ground) is sandwiched between the upper and lower dies and forged with a large press to form a material for turbine blades. The method is mainstream.
Further, nickel-based super heat-resistant alloys, titanium alloys and the like used in the above-mentioned applications are difficult-to-process materials. Therefore, in those forgings, in order to suppress the temperature drop of the heated preformed body and avoid the shape defect, hot die forging using a heated die and the temperature of the die are controlled within a predetermined range. Constant temperature forging, etc. for forging is applied.

For example, in Japanese Patent Application Laid-Open No. 2002-96134 (Patent Document 1), as a method for heating a forging die, an upper die holder and a lower die holder, and an upper die holder and a lower die holder are installed in the upper die holder and the lower die holder, respectively. A configuration is disclosed in which a mold is heated by a heater installed in each die holder and a heating jig sandwiched between an upper mold and a lower mold. It is also described that the heating temperature of the mold can be raised to a temperature higher than the conventional one, for example, about 300 ° C. by such a configuration.
Further, in Japanese Patent Application Laid-Open No. 4-46651 (Patent Document 2), which aims to solve shape defects and the like, a material heated to 920 ° C. is forged with a die heated and held at about 920 ° C. At that time, a method of fitting the engaged portion formed in the material into the engaging portion formed in the mold and setting the material in a regular position is disclosed.

JP-A-2002-96134 Japanese Unexamined Patent Publication No. 4-46651

The method disclosed in Patent Document 1 described above heats the mold using a heating jig, but at the same time, it is necessary to heat the upper die holder and the lower die holder, and the heating efficiency is low and the upper die holder is heated. There is a problem that the configuration for heating the die holder or the like becomes large and complicated. The lengthening of the turbine blades described above makes such a problem even more remarkable, and makes it more difficult to take measures against shape defects such as lack of meat.
Further, in Patent Document 2, the mold is heated to the same temperature as the material, and the configuration related to heating becomes larger and more complicated. Further, since it is necessary to use a heat-resistant alloy that can withstand a high temperature of about 920 ° C. as the mold material, the mold cost also increases.
In view of this problem, the present invention has simplicity that is advantageous for cost reduction when manufacturing a material for turbine blades, which is strongly required to be long, by hot forging, and has a shape defect such as lack of meat. An object of the present invention is to provide a method for producing a material for a turbine blade that can be suppressed.

The present invention has been made in view of the above-mentioned problems.
That is, the present invention is a method for manufacturing a material for a turbine blade having a blade portion and a root portion, wherein the preformed body is coated with a glass lubricant and then heated to a hot forging temperature, and a die apparatus. The preformed body is hot-forged using a second step of obtaining a material for a turbine blade having a blade portion and a root portion, and the mold apparatus is an alloy tool for a hot mold. A steel upper mold and lower mold, and an upper die set and a lower die set that support the upper mold and the lower mold are provided, and in the second step, the upper mold and the lower mold are Before being installed on the upper die set and the lower die set, it is preheated to a temperature of 550 ° C. or lower, and the hotness of the plurality of preformed bodies is in a state where the temperature of the upper mold and the lower mold is 350 ° C. or higher. When forging is performed and the temperatures of the upper and lower dies are less than 350 ° C., the next preformed body is not hot forged.
Further, in the method for manufacturing a material for a turbine blade, it is preferable that a heat insulating material is arranged between the upper mold and the lower mold and the upper die set and the lower die set.
Further, the preformed body has a main body portion in which a first portion corresponding to the wing portion and a second portion corresponding to the root portion are integrated, and the main body portion from an end portion of the first portion. The lower mold has a first protrusion protruding to one side in the longitudinal direction of the main body and a second protrusion protruding from the end of the second portion to the other side in the longitudinal direction of the main body. Is provided with a protrusion accommodating portion for accommodating the first and second protrusions and positioning the preformed body, and the first and second protrusions are accommodated in the protrusion accommodating portion. It is preferable to start hot forging with at least a part of the main body in contact with the lower mold and the first and second protrusions separated from the bottom of the protrusion storage portion.

According to the present invention, when a material for turbine blades, which is strongly required to be lengthened, is manufactured by hot forging, it has simplicity that is advantageous for cost reduction and can suppress shape defects such as lack of meat. It is possible to provide a method for manufacturing a material for a turbine blade.

It is a figure which shows an example of the preformed body for a turbine blade. It is a figure which shows an example of a mold. It is sectional drawing which shows an example of the mold apparatus. It is sectional drawing which shows the other example of a mold apparatus. It is a figure which shows an example when the preformed body for a turbine blade is placed on a mold (lower mold). It is a partial cross-sectional view at the position of line BB of FIG.

The method for manufacturing a material for a turbine blade according to the present invention is a method for manufacturing a material for a turbine blade having a blade portion and a root portion, wherein the preformed body is coated with a glass lubricant and then heated to a hot forging temperature. It has one step and a second step of hot forging a preformed body using a mold device to obtain a material for a turbine blade having a blade portion and a root portion. The mold apparatus used includes an alloy tool steel upper and lower dies for hot dies and an upper and lower die sets that support the upper and lower dies. Further, in the second step, the upper mold and the lower mold are preheated to a temperature of 550 ° C. or lower before being installed on the upper die set and the lower die set, and the temperature of the upper mold and the lower mold is 350. Hot forging of the preformed body is performed at a temperature of ° C. or higher.
Alloy tool for hot dies By using steel upper and lower dies, the mold cost can be kept low. Further, since the upper mold and the lower mold are heated separately from the upper die set and the lower die set and installed on the upper die set and the lower die set, the upper mold and the lower mold can be heated efficiently. In addition, since it is not necessary to provide a heating mechanism such as a heater in the mold device, the mold device is simplified. Further, by coating the preformed body with a glass lubricant and performing hot forging at a mold temperature of 350 ° C. or higher, it is possible to simultaneously suppress shape defects such as lack of meat.

Hereinafter, embodiments of the method for producing a material for turbine blades according to the present invention will be specifically described with reference to the drawings, but the present invention is not limited thereto. In addition, the configurations described in the present embodiment can be combined with each other as long as their functions are not impaired.

<Pre-molded body>
FIG. 1 shows an example of a preformed body for a turbine blade. The preformed body (rough ground) is a forging material that has been prepared into a predetermined shape through hot working or the like. The preformed body 100 has a rod-shaped main body portion 3 in which a first portion 1 corresponding to a wing portion and a second portion 2 corresponding to a root portion are integrated, and a main body from an end portion of the first portion 1. A first protruding portion 4-1 projecting to one side in the longitudinal direction of the portion 3 and a second protruding portion 4-2 projecting from the end portion of the second portion 2 to the other side in the longitudinal direction of the main body portion 3. And have. The first portion 1 and the second portion 2 are formed continuously and integrally as different portions of the main body portion 3. The first part 1 is a part that becomes a blade part of the material for turbine blades by hot forging, and the second part 2 having a diameter larger than that of the first part 1 is a root part of the material for turbine blades by hot forging. Is the part that becomes. In the example shown in FIG. 1, the preformed body 100 has a cross section perpendicular to the longitudinal direction (the direction of the central axis indicated by the alternate long and short dash line in the figure, that is, the direction in which the first portion 1 and the second portion 2 are connected). Is a circular rod shape, but the shape of the preformed body is not limited to this, and a preformed body having an elliptical cross-sectional shape, a polygonal shape, or the like can also be used. Further, the change in the size of the cross-sectional shape in the longitudinal direction is not limited to the configuration shown in FIG. For example, a shape in which the diameter is changed in the middle of the first portion 1 corresponding to the wing portion and a step is further provided can be applied.

The first protrusion 4-1 and the second protrusion 4-2 (hereinafter, also simply referred to as “protrusions”) protruding from the main body 3 in opposite directions in the longitudinal direction are preformed with respect to the mold. Although it is for positioning the body 100, such a protrusion is not essential, and a preformed body having no protrusion can also be used. However, in order to more reliably avoid the misalignment of the preformed body during hot forging, it is advantageous to use the preformed body having protrusions. Hereinafter, an example using preforming having a protrusion will be described.

A rod-shaped protrusion having a smaller diameter (cross-sectional area) than the main body 3 can be formed continuously and integrally with the main body 3, but is joined to the main body as a separate part from the main body 3. Is more preferable. Unlike the so-called "grasping allowance", the protrusion functions as a "positioning member", so the position accuracy of providing the protrusion is important. For example, if the main body 3 and the protrusion are to be formed as an integral body by hot working such as hot forging, it is difficult to provide the protrusion with high position accuracy. On the other hand, if the protrusion is joined to the main body as a separate part, the protrusion can be joined more accurately at a desired position. The position of the protrusion is preferably the center of the surface on which the protrusion protrudes. More preferably, it is on the central axis of the main body. As a result, it is possible to more reliably prevent misalignment and defects such as lack of meat due to the misalignment. As a method of joining the protrusions, fitting with screws and / or welding is convenient. When joining the protrusions only by welding, it is more preferable to apply friction welding that can increase productivity.

The dimensions of the protrusions may be determined according to the size (diameter, etc.) of the material for turbine blades, and for example, a columnar one having a diameter of about 30 to 60 mm can be used. The columnar shape is used because it can be easily accommodated in the protrusion accommodating portion formed in the lower mold, which will be described later. When joining the protrusions as separate parts, it is preferable that the material of the protrusions is the same as the material of the main body. This is because the protrusions can be reused as a raw material for recycling together with burrs after being removed together with burrs from the material for turbine blades after hot forging.

As the main body, heat-resistant alloys such as Ni-based super heat-resistant alloys and Ti alloys (titanium alloys) and Fe-based alloys can be used, of which Ti alloys are preferable. Since it is expected that the blades will become longer and larger in the future, Ti alloy, which is advantageous for weight reduction, is suitable for the preformed body for turbine blades (material for turbine blades). As the Ti alloy, for example, Ti-6Al-4V can be used.

<Mold device>
The mold apparatus used in the method for manufacturing a material for a turbine blade will be described below with reference to FIGS. 2 to 4. FIG. 2A is a plan view of a mold (lower mold), FIG. 2B is a side view of the mold (lower mold), and FIG. 3 is a mold (lower mold) shown in FIG. It is a cross-sectional view of the mold apparatus which was used, and is the cross-sectional view at the position of line AA in FIG. 2A showing the lower mold. The upper mold corresponding to the lower mold and the upper die set supporting the upper mold are not shown. Further, even when the upper die set is on the upper side and the upper die set is on the lower side in the state where the mold device is configured like the upper mold and the upper die set, the upper mold is fixed to the upper die set. As long as the upper die set is treated as "supporting" the upper mold.

The lower mold 200 has a die-engraved surface 5 formed according to the shape of the material for the turbine blade, and first protrusions 4-1 and second protrusions at both ends of the preformed body 100 for the turbine blade. It accommodates 4-2 and includes protrusion accommodating portions 6-1 and 6-2 for positioning the preformed body 100. The protrusion accommodating portions 6-1 and 6-2 are formed as groove-shaped recesses. The upper mold also has a die-engraved surface formed according to the shape of the material for the turbine blade, but is not provided with a protrusion accommodating portion.

The mold device includes an upper mold and a lower mold (hereinafter, also simply referred to as a mold), and an upper die set and a lower die set (hereinafter, simply referred to as a die set) that support the upper mold and the lower mold. Be prepared. Note that FIG. 3 shows a portion of the mold apparatus related to the lower mold, and the portion related to the upper mold is not shown. In the example shown in FIG. 3, the lower mold 200 is housed and fixed in the recess formed in the lower die set 7. The lower mold 200 is fixed to the lower die set 7 by a fixing jig (not shown) such as a bolt or a clamp.
FIG. 4 shows another example of a mold device, which is for the mold device of FIG. 3 and further insulates between the upper and lower molds and the upper and lower die sets. Equipped with materials. A heat insulating material 8 having a lower thermal conductivity than these is arranged between the lower mold 200 and the lower die set 7, and due to this configuration, the lower mold 200 accommodated in the lower die set 7 after heating. The temperature drop can be suppressed. In the example shown in FIG. 4, a recess is further provided on the bottom surface of the recess of the lower die set 7 by engraving, and the plate-shaped heat insulating material 8 is housed in the recess. When the lower die 200 is placed on the lower die set 7, a part of the bottom (back surface) of the lower die 200 is in contact with the heat insulating material 8 and a part is in contact with the lower die set 7. Since a part of the lower die set 7 can be directly received by the lower die set 7, it is possible to cope with a higher forging load than the configuration in which the entire bottom surface of the lower die 200 is in contact with the heat insulating material. Further, since the opening edge of the recess is inside the outer edge of the bottom surface of the die and the heat insulating material is accommodated so as to be fitted into the recess, even if the heat insulating material is cracked during hot forging, the die is replaced. The risk of movement and scattering is small at times, and it is possible to prevent the work at the time of mold replacement from becoming complicated. The recess for accommodating the heat insulating material can be formed by engraving directly into the die set as described above, or can be formed in a plate material prepared separately from the die set. In the latter case, a plate material in which a heat insulating material is fitted in the recess is housed in the recess of the die set. The heat insulating material 8 may be composed of one plate material or may be composed of a plurality of individual pieces. The mold and the heat insulating material may be arranged in contact with each other, or may be arranged via a cover member or the like. However, since the heat insulating effect is higher when the mold and the heat insulating material are in direct contact with each other, for example, the cover member may not be arranged in the lower die set, but may be arranged so that the heat insulating material is exposed on the lower mold side.

Alloy tool steel for hot dies is used as the material for the upper and lower dies. The type of alloy tool steel for hot dies is not particularly limited, and in consideration of strength and cost, alloy tool steel for hot dies such as SKD61 and SKT4 specified by JIS G4404 and The improved steel can be used. SKD61 has C: 0.35 to 0.42, Si: 0.08 to 0.12, Mn: 0.25 to 0.50, P: 0.030 or less, S: 0.020 or less in mass%. It is defined by the composition of Cr: 4.80 to 5.50, Mo: 1.0 to 1.5, V: 0.80 to 1.15, balance Fe and impurities, and SKT4 is C: 0.50 by mass%. ~ 0.60, Si: 0.10 to 0.40, Mn: 0.60 to 0.90, P: 0.030 or less, S: 0.020 or less, Ni: 1.50 to 1.80, Cr : 0.80 to 1.20, Mo: 0.35 to 0.55, W :, V: 0.05 to 0.15, the composition of the balance Fe and impurities. Since these alloy tool steels have high versatility and low material cost, the cost of the entire mold apparatus can be suppressed.
The materials of the upper die set and the lower die set are not particularly limited. For example, alloy tool steel for the hot mold similar to the upper mold and the lower mold can be used.

The heat insulating material 8 is not particularly limited as long as it is a material having a lower thermal conductivity than the alloy tool steel for hot molds. For example, since the thermal conductivity of hot mold steel such as SKD61 is about 30 W / (m · K), a material having a thermal conductivity smaller than that may be used. A heat insulating material having a thermal conductivity of 10 W / (m · K) or less, more preferably 1 W / (m · K) or less is used. As the heat insulating material, for example, an inorganic heat insulating material such as ceramics, a composite heat insulating material of glass fiber and resin, or the like can be used.

<First step>
The preformed body to be subjected to hot forging is coated with a glass lubricant and then heated to the hot forging temperature (first step). By coating at least a part of the preformed body with a glass lubricant, it contributes to reducing the forging load and obtaining a preformed body having a sounder shape. The glass lubricant can partially cover a portion where lubrication is likely to run out, but if the entire preformed body is covered with the glass lubricant, the lubricity becomes more reliable. Further, since the glass lubricant also has a heat insulating effect, it is possible to suppress a temperature drop until the preformed body is taken out from the heating furnace, placed on the mold, and forging is started. From this point of view, it is desirable to coat the entire preformed body with a glass lubricant.

The method of coating the glass lubricant is not particularly limited. For example, a slurry-like mixture containing a glass composition and a medium can be placed on the surface of a preformed body as a film by a method such as coating, spraying, or dipping. Coating is preferable from the viewpoint of simplification of work / equipment, and spraying is preferable from the viewpoint of uniformity of film thickness. After coating or the like, unnecessary media is removed by drying, and the surface of the preformed body is coated with a glass lubricant.
The thickness of the coating of the glass lubricant placed on the surface of the preformed body is not particularly limited as long as the lubricating ability is exhibited, but in order to more reliably suppress the increase in the forging load. It is preferably 200 μm or more. On the other hand, if the glass lubricant is made excessively thick, the risk of the glass lubricant peeling off increases when the preformed body is heated. From this point of view, the thickness is preferably 500 μm or less. The thickness of the glass lubricant may be measured by an eddy current film thickness meter. The type of glass lubricant is not particularly limited as long as it retains the lubricating ability during hot forging. For example, a glass lubricant whose main component of glass is borosilicate glass can be used.

The preformed body is heated to a predetermined hot forging temperature using a heating furnace or the like. The hot forging temperature of the preformed body may be set according to the material of the preformed body. For example, in the case of a Ni-based superheat-resistant alloy, 850 to 1150 ° C., and in the case of a Ti alloy, 800 to 1100 ° C. is a practical range.

<Second process (hot forging process)>
The hot forging step, which is the second step, is performed using the above-mentioned mold device and the preformed body for the turbine blade that has undergone the first step. In the second step, the upper and lower molds are preheated to a temperature of 550 ° C. or lower before being installed on the upper and lower die sets. The preheating temperature is specified to be 550 ° C. or lower in order to make it lower than the tempering temperature of the alloy tool steel for hot dies. In the range of 550 ° C. or lower, the higher the mold temperature, the more preferable. Since the preformed body is hot forged at 350 ° C. or higher as described later, the die is preheated at at least 350 ° C. or higher. A more preferable preheating temperature is 450 ° C. or higher. The mold is preheated using a heating furnace or the like, and the heated mold is installed on a die set to form a mold device.

As shown in FIG. 5, the heated preformed body 100 is placed on the heated lower die 200, and hot forging is performed. After the forging of one preformed body is completed, the next preformed body is continuously forged with the same mold device. This is repeated to perform hot forging of a plurality of preformed bodies, but since the above-mentioned mold device does not have a heating mechanism such as a heater, the temperature of the mold gradually decreases. On the other hand, it is important to perform hot forging of the preformed body in a state where the temperature of the die is 350 ° C. or higher. This is because if hot forging is continued when the temperature of the die is less than 350 ° C., shape defects such as lack of meat will occur. The above-mentioned configuration in which the heat insulating material is arranged between the mold and the die set contributes to maintaining the mold temperature of 350 ° C. or higher for a longer period of time. Productivity is improved by maintaining the mold temperature of 350 ° C. or higher for a longer period of time and increasing the number of preformed bodies to be hot forged during that time. It is preferable to perform hot forging of the preformed body 10 times or more, preferably 15 times or more for one assembly of the die apparatus.
If the mold temperature is less than 350 ° C, the next hot forging of the preformed body is not performed. In this case, the die is removed from the die set and preheated again and then installed in the die set, or another preheated die is installed and the next hot forging is performed. The mold temperature may be measured each time hot forging is performed on the surface of the mold having a die carved surface.

In the above-mentioned hot forging, unlike Japanese Patent Application Laid-Open No. 2002-96134 (Patent Document 1) and Japanese Patent Application Laid-Open No. 4-46651 (Patent Document 2), a heating mechanism is not provided in the die device, so that the die device is not provided. Is simplified. Further, when the mold is heated and the mold temperature is maintained at 350 ° C. or higher, it is not necessary to heat the die set having a large heat capacity, so that the heating efficiency for heating the mold is high. Further, when the mold is heated via the die set, the temperature of the die set is higher. Therefore, in order to raise the mold temperature, it is necessary to use a material with higher heat resistance for the die set, while when trying to use a material with heat resistance similar to that of the mold for the die set, the mold temperature is low. I have no choice but to become. The former causes an increase in the cost of the mold device, and the latter makes it difficult to maintain the mold temperature at a high temperature such as 350 ° C. or higher. A method of maintaining and managing a mold temperature of 350 ° C. or higher for a longer period of time by using a heat insulating material can solve such a problem.

Hereinafter, a more preferable embodiment with respect to the above-described embodiment will be described.
<Die set heating / die set temperature>
Preheating the upper and lower die sets with heated dummy material before installing the upper and lower molds on the upper and lower die sets, respectively, further suppresses the drop in mold temperature. can do. Here, the "dummy material" refers to a member separate from the die used in the hot forging in the second step, and for example, the die and specifications (material, shape, dimensions) used in the hot forging are defined. The same mold, molds with different specifications, steel materials without a work surface, etc. By arranging a heat insulating material between the mold and the die set, it is possible to suppress a decrease in the mold temperature, but it cannot be reduced to zero. Therefore, in order to further suppress the decrease in the mold temperature, it is effective to raise the temperature on the die set side and lower the heat gradient by using the dummy material heated as described above. Since no load is applied to the dummy material, it can be used by heating it to a temperature higher than the heating temperature of the mold.
More specifically, it is preferable to perform hot forging of the preformed body in a state where the temperature of the upper die set and the lower die set is 50 ° C. or higher. The purpose of setting the temperature to 50 ° C. or higher is to secure a significant difference in heating with respect to a room temperature of about 25 ° C. In particular, it is preferable that the temperature of the die set is 50 ° C. or higher from the time of the first hot forging after installing the heated die. The temperature of the die set may be measured on the side surface of the die set.

<Placement form of preformed body>
A preferable form regarding the mounting form of the preformed body will be described with reference to FIG. In the example shown in FIG. 5, when the preformed body 100 is placed on the mold (lower mold) 200, the first and second protrusions 4-1 and 4-2 are the protrusion housing portions 6-1 and 6. The main body of the preformed body 100 is in contact with the lower mold 200 while being housed in -2. Hot forging is started in this state. As a form in which the preformed body having the protrusions is placed on the lower mold, a configuration in which the premolded body is supported only by the protrusions and the main body portion does not come into contact with the lower mold is also applicable. However, as will be described later, a configuration in which the main body of the preformed body is in contact with the lower mold as in the example shown in FIG. 5 is more effective in suppressing the shape defect of the turbine blade material from the viewpoint of positioning. It is advantageous.
On the other hand, since the main body is in contact with the lower die, there is also a disadvantage that heat easily escapes from the preformed body to the lower die before the start of forging. On the other hand, if heat conduction from the preformed body to the die is suppressed by using a heat insulating material or the like and then hot forging is performed at the predetermined temperature or higher described above, such a disadvantage can be compensated. be. That is, it is particularly preferable to combine the configuration having the mold device shown in FIG. 4 and the like with the configuration in which the main body portion is in contact with the lower mold. In the example shown in FIG. 5, a part of the first part corresponding to the wing part and the second part corresponding to the root part of the main body part of the preformed body 100 are in contact with the lower mold 200, but the main body It suffices that at least a part of the portion is in contact with the lower mold 200.

Among the mounting forms of the preformed body, the configuration and effect of the protrusions will be further described. As shown in FIG. 2 and the like, the lower mold 200 accommodates the first and second protrusions 4-1 and 4-2, and the protrusion housing portions 6-1 and 6- for positioning the preformed body 100. 2 is provided. The protrusion accommodating portions for positioning the preformed body using the protrusions are provided in advance on both sides of the die-carved surface on which the load of the press during hot forging is not applied. The protrusion accommodating portion is a groove-shaped recess extending in the longitudinal direction (x direction) of the preformed body arranged on the engraved surface. FIG. 6 is a partial cross-sectional view taken along the line BB seen from the x direction of FIG. 5, showing the positional relationship between the protrusion and the protrusion accommodating portion. The protrusion 4-1 is constrained by the groove-shaped protrusion accommodating portion 6-1 in the y direction (vertical direction (pressurization direction for forging) and direction perpendicular to the longitudinal direction of the preformed body) through an appropriate clearance. And positioned. If it is necessary to restrain the preformed body with the protrusion from the longitudinal direction, the tip of the protrusion should be restrained by the inner surface of the recess of the die set, the stepped surface provided in the protrusion accommodating portion, or the like. It should be. It is also possible to arrange the protrusions and the protrusion accommodating portions on only one side of the main body, but in order to position the preformed body under forging with high accuracy, the protrusions are provided on both sides of the main body in the longitudinal direction. And it is preferable to provide a protrusion accommodating portion.
On the other hand, since the preformed body is in contact with the lower mold at the main body from the time when it is placed on the lower mold, the protrusion 4-1 is separated from the bottom of the protrusion accommodating portion 6-1 and is moved up and down. It is in a free state that is not constrained in the direction (z direction: forging pressurization direction). If the main body does not come into contact with the lower die and only the protrusion is supported by the lower die when it is placed on the lower die, the protrusion will be deformed first when forging starts. The positioning function is weakened. Therefore, it is preferable to adopt a configuration in which the main body is in contact with the lower mold when it is placed on the lower mold. When the amount of vertical movement of the protrusion during forging is small, it is possible to apply a configuration in which the main body is in contact with the lower mold and the protrusion is also in contact with the bottom of the protrusion accommodating portion. However, if the bottom surface of the protrusion accommodating portion is in contact with the protrusion, the contact surfaces may rub against each other during hot forging, or the protrusion may be caught on the bottom surface of the protrusion accommodating portion, resulting in the main body of the preformed body. There is a risk that it will deviate from the specified position. Therefore, as shown in FIG. 6, it is preferable that the bottom portion of the protrusion accommodating portion and the protrusion portion are in a non-contact state.

The protrusion accommodating portion shown in FIGS. 2 to 6 is continuously integrally formed with the lower mold, but it can also be configured by fixing a component separate from the lower mold to the lower mold. As a method of constructing the protrusion accommodating portion continuously and integrally with the lower mold, there is a method of carving a groove by processing. However, when the mold for manufacturing a material for a large turbine blade is directly processed, the weight of the mold is, for example, several tons, and a great deal of labor and cost are required for transportation and processing. On the other hand, if the protrusion accommodating portion is configured by using another detachable part, it is possible to correspond to various protrusion shapes by exchanging only the protrusion accommodating portion according to the shape and size of the protrusion. ..
In both cases where the protrusion accommodating portion is continuously integrated with the lower mold and the protrusion accommodating portion is configured by using different parts, the bottom portion of the protrusion accommodating portion is the working surface of the lower mold (mold engraving surface 5). It is more preferable that the height is the same as that of the peripheral surface of the surface, that is, flush with each other. This is to ensure the maximum degree of freedom of movement of the protrusion in the vertical direction.
Further, it is preferable to provide a flat or curved chamfer on the upper corner portion of the groove-shaped protrusion accommodating portion so that the projection accommodating portion can be smoothly accommodated.

The configuration including the protrusions and the protrusion housing described above more reliably prevents the preformed body 100 for turbine blades from being misaligned in the mold during hot forging, especially from misalignment in the y direction. can do. In particular, in the case of hot forging with a large load of tens of thousands of tons and one blow, if the pressing is not started sequentially from the target place in the die, defects such as lack of meat are likely to occur. In order to place the preformed body at a desired position of the mold and perform hot forging in order from a desired pressing location during hot forging, the positioning configuration by the protrusion and the protrusion accommodating portion is particularly effective.

A Ti alloy (Ti-6Al-4V) was hot-worked to prepare a preformed body for turbine blades having the same outer shape as the main body shown in FIG. For turbine blades that have protrusions by grinding the wing side end face and root side end face on the extension line of the central axis of the preformed body and joining the Ti alloy for columnar protrusions to such surfaces by friction welding. A preformed body of the above was prepared. The Ti alloy of the protrusions 4-1 and 4-2 and the Ti alloy of the main body 2 have the same composition.

Next, a mold device having the same configuration as that shown in FIG. 5 was prepared. The position and dimensions of the groove-shaped protrusion storage portion formed in the lower mold are set so as not to come into contact with the groove bottom when the preformed body is placed. The total clearance between the side surface of the protrusion accommodating portion and the protrusion was about 2 mm on both sides. On the working surface of the lower die, a die carved surface forming a wing portion and a root portion was formed by hot forging with one blow to obtain a material for a turbine blade having a near net shape. Alloy tool steel (SKD61) for hot dies was used for the dies and dies. Further, a heat insulating plate having a thermal conductivity of 0.2 W / (m · K) was used as a heat insulating material between the mold and the die set.
The mold was heated to 500 ° C. in a heating furnace, and the die set was preheated with a dummy material (separate mold) heated to 500 ° C. After removing the separate mold, the heated mold was installed to prepare the mold device.
The preformed body was coated with a borosilicate glass-based glass lubricant to a thickness of 350 μm and heated to a forging temperature of 1000 ° C. (first step). The preformed body covered with the glass lubricant softened by heating at such a forging temperature was placed on the lower mold of the mold device prepared as described above. Hot forging was started with the protrusions housed in the protrusion housing and a part of the main body was in contact with the lower die to obtain a material for turbine blades having wings and roots (second step). ). At this time, the surface temperature of the die before hot forging was 450 ° C. The temperature of the die set at the start of hot forging was measured on the side surface (the lateral position of the die indicated by the arrow in FIG. 4) and found to be 50 ° C. While measuring the temperature of the mold, such hot forging was repeated to obtain materials for a plurality of turbine blades.

As a result of repeating the hot forging as described above, when the hot forging was performed at a mold temperature of 350 ° C. or higher, a material for turbine blades having no problem of defects such as lack of meat could be obtained. On the other hand, when hot forging was performed in a state where the mold temperature was lower than 350 ° C., it was confirmed that meat shortage occurred.
In the above-described embodiment, hot forging under the condition that the mold temperature is 350 ° C. or higher, which is necessary for obtaining a normal material for turbine blades, is carried out 18 times or more for one assembly of the mold device. I was able to.

1 1st part 2 2nd part 3 Main body part 4-1 1st protrusion 4-2 2nd protrusion 5 type carved surface 6-1 1st protrusion accommodating portion 6-2 2nd protrusion accommodating Part 7 Die set 8 Insulation material 100 Preformed body 200 Lower mold

Claims (2)

A method for manufacturing a material for turbine blades having wings and roots.
The first step of coating the preformed body with glass lubricant and then heating it to the hot forging temperature, and
It has a second step of hot forging the preformed body using a mold device to obtain a material for a turbine blade having the blade portion and the root portion.
The mold apparatus includes an alloy tool steel of the upper and lower molds for hot die, and a die set and the lower die set upper supporting said upper die and lower die, the upper A heat insulating material is arranged between the mold and the upper die set and between the lower mold and the lower die set.
In the second step,
The upper mold and the lower mold are preheated to a temperature of 550 ° C. or lower before being installed on the upper die set and the lower die set, and the temperature of the upper mold and the lower mold is 350 ° C. or higher. When the temperature of the upper die and the lower die is less than 350 ° C. after hot forging of a plurality of the preformed bodies, the material for the turbine blade which is not hot forged of the next preformed body is used. Production method. The preformed body has a main body portion in which a first portion corresponding to the wing portion and a second portion corresponding to the root portion are integrated, and a length of the main body portion from an end portion of the first portion. It has a first protrusion protruding to one side in the direction and a second protrusion protruding from the end of the second portion to the other side in the longitudinal direction of the main body.
The lower mold accommodates the first and second protrusions and includes a protrusion accommodating portion for positioning the preformed body.
The first and second protrusions are housed in the protrusion accommodating portion, at least a part of the main body portion is in contact with the lower mold, and the first and second protrusions are of the protrusion accommodating portion. method for producing a material for the turbine blade according to claim 1, wherein the starting hot forging in a state of being separated from the bottom.

Images