JP6471444B2 - Manufacturing method of hot forging die - Google Patents

Description

  The present invention relates to a method for manufacturing a hot forging die.

In hot forging, a forging material is plastically processed in a high temperature range of approximately 900 ° C. or higher. Among these, die forging is a process of plastic working into a predetermined shape with a pair of upper and lower hot forging dies formed with a die-sculpting surface having a specific shape.
In this die forging, for example, as described in Japanese Patent Application Laid-Open No. 2007-892 (see Patent Document 1), JIS-SKD61, SKT4, or the like is used as a die base material. Overlay welding is performed at the expected location to improve the die life.

JP 2007-892 A

In the hot forging in the above-mentioned die forging, recently, a large-scale forging apparatus having a scale of 50,000 tons has started operation. The die for hot forging used for it is also enlarged, and in addition, forging materials to be hot forged, difficult-to-work alloys such as Ni-base super heat-resistant alloys and Ti alloys are used, and hot for large turbine parts etc. Forging is performed.
The die for hot forging used in this large forging device is subjected to a large load compared to the conventional one or overlay welding is performed on the die engraving surface of the die for hot forging. It is necessary to improve the service life.
In general, when the weight of a hot forging die is small for this overlay welding, even if tensile or compressive stress is generated inside the hot forging die due to overlay welding, The mold itself is deformed, and stress such as tension and compression remaining in the hot forging die is reduced. However, when the weight of the hot forging die is increased, the hot forging die is not deformed, and there is a possibility that tensile or compressive stress is accumulated inside and the hot forging die is destroyed. . In particular, the stress that causes cracking, etc. is tensile stress, which reduces the tensile stress during build-up welding or localizes the balance of the tensile stress inside the hot forging die that occurs during build-up welding. It is necessary to perform overlay welding so that a place with a high tensile stress is not generated. If cracks due to the tensile stress inside the hot forging die occur at the end of overlay welding, the amount of damage will be great.
However, conventionally, there is no overlay welding method that provides an appropriate tensile stress for a hot forging die used in a hot forging device having a scale of several tens of thousands of tons.
An object of the present invention is to provide a method for manufacturing a hot forging die that can appropriately balance the tensile stress generated during overlay welding on a large hot forging die.

The present invention has been made in view of the above-described problems.
That is, the present invention relates to a method for manufacturing a hot forging die that performs overlay welding on a hot forging die base material to form an overlay layer.
The region where the build-up layer is formed has one end in the first width direction, the other end, and an intermediate portion between the one end and the other end,
In the build-up welding, the first build-up weld is formed by performing continuous welding on the one end portion, then the first build-up weld and the next continuous weld on the intermediate side. And performing the overlay welding toward the intermediate portion by sequentially repeating the continuous welding, forming a continuous overlay layer, and stopping the overlay welding before the intermediate portion Welding process;
Continuous welding is performed on the other end portion to form the first build-up weld, then the first build-up weld is performed, the next continuous weld is performed on the intermediate side, and the continuous welding is performed. Positions of 1 to 8 mm apart from the built-up layer formed in the first build-up welding step by successively performing overlay welding in the direction of the intermediate portion to form a continuous built-up layer A second overlay welding process for stopping the overlay welding at
A third build-up welding step of performing build-up welding on the interval portion of the intermediate portion;
After the first to third overlay welding steps, a heat treatment step of performing heat treatment at 540 to 620 ° C. for 1 to 10 hours on the hot forging die that has been overlay welded,
It is a manufacturing method of the metal for hot forging which performs.
This method is suitable for forming a rectangular welding region.

The present invention also relates to a method for manufacturing a hot forging die, which performs overlay welding on a hot forging die base material to form an overlay layer.
The region where the overlay layer is formed has an outer peripheral end, an inner peripheral end, and an intermediate portion between the outer peripheral end and the inner peripheral end,
In the build-up welding, continuous welding is performed on a portion to be either one of the outer peripheral end portion or the inner peripheral end portion to form a first build-up weld portion, and then the first build-up weld portion is formed. Continuously, the next continuous welding is performed on the intermediate portion side, the continuous welding is sequentially repeated, and overlay welding is performed toward the intermediate portion to form a continuous overlay layer, before the intermediate portion. A first overlay welding process for stopping the overlay welding at
Continuous welding is performed on a portion which is the other end of the outer peripheral end or the inner peripheral end to form an initial build-up weld, and then continuous to the first build-up weld, the intermediate portion The next continuous welding is performed on the side, the continuous welding is sequentially repeated, and overlay welding is performed toward the intermediate portion to form a continuous overlay layer, which is formed in the first overlay welding process. A second build-up welding step for stopping the build-up welding at a position where the distance from the built-up layer is 1 to 8 mm;
A third build-up welding step of performing build-up welding on the interval portion of the intermediate portion;
Including
After the first to third overlay welding steps, a heat treatment step of performing heat treatment at 540 to 620 ° C. for 1 to 10 hours on the hot forging die that has been overlay welded,
It is a manufacturing method of the metal for hot forging which performs.
This method is suitable for forming a ring-shaped weld region.

Furthermore, the present invention relates to a method for manufacturing a hot forging die in which overlay welding is performed on a die base material for hot forging to form an overlay layer.
The area where the build-up layer is formed has an outer peripheral end portion, a central portion, and an intermediate portion between the outer peripheral end portion and the central portion,
In the build-up welding, continuous welding is performed on a portion that is one of the outer peripheral end portion or the center portion to form an initial build-up weld portion, and then continuous with the first build-up weld portion, The next continuous welding is performed on the part side, the continuous welding is sequentially repeated, and overlay welding is performed toward the intermediate part to form a continuous overlay layer, and the overlay welding is performed before the intermediate part. A first overlay welding process to stop;
Continuous welding is performed on the other end portion of the outer peripheral end or the central portion to form a first build-up weld portion, and then continuous to the first build-up weld portion, and next to the intermediate portion side. Welding, successively repeating the continuous welding and performing overlay welding toward the intermediate portion, forming a continuous overlay layer, and the overlay layer formed in the first overlay welding step; A second build-up welding process in which the build-up welding is stopped at a position where the interval is 1 to 8 mm;
A third build-up welding step of performing build-up welding on the interval portion of the intermediate portion;
Including
After the first to third overlay welding steps, a heat treatment step of performing heat treatment at 540 to 620 ° C. for 1 to 10 hours on the hot forging die that has been overlay welded,
It is a manufacturing method of the metal for hot forging which performs.
This method is suitable for forming a circular weld region.

Preferably, it is a manufacturing method of the hot forging die which repeats the said 1st-3rd build-up welding process sequentially, and makes a build-up layer multilayer in the thickness direction.
More preferably, it is a method for manufacturing a hot forging die in which the bead width in the first and second build-up welding steps is 10 mm or more.
More preferably, it is a method for manufacturing a hot forging die in which the material of the build-up layer is a Ni-based superalloy.
Further, the present invention is suitable for a hot forging die base material having a weight of 500 kg or more.
Preferably, the method is a hot forging die manufacturing method in which the build-up welding is arc welding.

  According to the present invention, since the balance of the tensile stress generated at the time of overlay welding to a large hot forging die can be made appropriate, it is possible to more reliably prevent cracking at the time of overlay welding. .

It is a schematic diagram which shows the magnitude | size and direction of the stress which remain | survives in the forming direction of a build-up layer, and the metal mold | die for hot forging. It is a schematic diagram which shows the magnitude | size and direction of the stress which remain | survives in the forming direction of a build-up layer, and the metal mold | die for hot forging. It is a schematic diagram which shows the magnitude | size and direction of the stress which remain | survives in the forming direction of a build-up layer, and the metal mold | die for hot forging. It is a schematic diagram which shows the magnitude | size and direction of the stress which remain | survives in the forming direction of a build-up layer, and the metal mold | die for hot forging. It is a schematic diagram of a build-up layer cross section. It is a schematic diagram of the metal mold | die for hot forging. It is a perspective view which shows an example of the metal mold | die for hot forging. It is a perspective view which shows an example of the metal mold | die for hot forging. It is a perspective view which shows an example of the metal mold | die for hot forging.

First, the present inventors investigated the tensile and compressive stress generated during overlay welding in a hot forging die that forms an overlay weld layer on the die-carved surface. The material of the hot forging die used for the investigation was JIS-SKD61, and a hollow portion simulating a die-carved surface was formed by cutting.
Overlay welding was performed on the recesses by several methods using an alloy equivalent to Udimet 520 (Udimet is a registered trademark of Special Metals). After the overlay welding was completed, a strain relief heat treatment at 600 ° C. for 2 hours was performed, and the investigation die was cut to investigate the residual stress. The residual stress was evaluated using a strain gauge. The remaining amount of stress is shown as a schematic diagram in FIGS.
1-3, the arrow in the overlay layer indicates the direction in which the overlay layer is formed. The overlay layer is subjected to a predetermined length of first continuous welding at a portion that becomes an end portion in the width direction, and then a next continuous welding that is continuous to the first continuous welded portion. It is a built-up layer with a width. Thickness is repeated as the above-described overlay is laminated.
The amount of stress of the mold is indicated by the length of the arrow, and the arrow length serving as the reference (20 MPa) is indicated. The direction of the arrow indicates the direction of the stress distribution. When the length of the arrow is long, a large stress remains.
The arrow shown in the overlay layer 2 formed on the hot forging die 1 indicates the direction of overlay welding. Moreover, the place shown as the circle | round | yen 1-5 in the metal mold | die for hot forging is a measurement place of residual stress. In the arrow of the stress amount, a solid line indicates a tensile stress, and a broken line indicates a compressive stress.

FIG. 2 is a diagram showing a change in stress when strain relief annealing is performed on the hot forging die shown in FIG. Thus, it turns out that the residual strain amount of the die base material 3 for hot forging is reduced by performing the strain relief heat treatment after the overlay welding. Moreover, it turns out that the magnitude | size of the residual stress changes with the direction of overlay welding.
Among them, while performing overlay welding from both ends shown in FIG. 3 toward the center portion, providing an interval (root interval) portion at the center portion, and finally performing a method of overlay welding the interval portion in sequence. It can be seen that in the case of overlay welding on multiple layers, the tensile stress that causes cracking is reduced, and the balance of residual stress is almost balanced.
From the above results, it can be seen that the build-up welding method shown in FIG. 3 can properly balance the tensile stress generated during build-up welding to a large hot forging die. Therefore, in the present invention, the order of overlay welding shown in FIG. 3 is adopted.

As described above, in the present invention, the build-up welding process is divided into three processes in order to reduce the tensile stress and balance the stress remaining in the hot forging die base material. It is. The present invention is described in detail below. First, a build-up welding method when the welding area is rectangular will be described. The “rectangular shape” refers to a shape when the hot forging die is viewed from above as shown in FIG.
5 and 7 show an embodiment showing the method of overlay welding shown in FIG. 3 in detail, FIG. 5 is a schematic sectional view, and FIG. 7 is a perspective view. First, a die base material 3 for hot forging that performs overlay welding is prepared. The build-up welding is performed on the die-carved surface side that performs plastic working of the forging material into a predetermined shape during hot forging. In addition, the hot forging die base material is preheated to a temperature range lower than the tempering temperature of the hot forging die base material with a lower limit of 250 ° C. to prevent cracking during overlay welding. Is good. Preferably, it is the range of 300-tempering temperature minus 100 degreeC. Note that the preheated hot forging die base material can more reliably prevent cracking of the hot forging die base material by maintaining the temperature until the formation of the build-up layer described later.
And a 1st overlay welding process is performed. First, continuous welding is performed for a predetermined length on a portion that becomes one end portion in the first width direction of the build-up layer 2 to form a first build-up weld, and then, continuous with the first build-up weld. The next continuous welding is performed on the intermediate portion side, and the continuous welding is sequentially repeated so that the first build-up weld portion and the next continuous weld overlap in the length direction, and directed toward the intermediate portion of the build-up layer. Then, overlay welding is performed to form a continuous overlay layer, and the overlay welding is stopped before the intermediate portion to form the first overlay layer 4 (build-up layer A ′).

After the first overlay welding process, the second overlay welding process is performed.
In the second build-up welding process, continuous welding is performed for a predetermined length on the part that becomes the other end of the build-up layer 2 to form the first build-up weld, and then connected to the first build-up weld. The next continuous welding is continued to the first build-up weld so that the next continuous weld overlaps in the length direction on the intermediate side, and the continuous welding is sequentially repeated in the middle direction of the build-up layer. Build-up welding is performed to form a continuous build-up layer, and the build-up welding is stopped at a position of 1 to 8 mm from the build-up layer formed in the first build-up welding step. Then, the second build-up layer 5 (build-up layer A) is formed. Further, in the present invention, the interval is set to 1 to 8 mm so that the edge of the built-up layer formed in the first build-up welding process and the edge of the built-up layer formed in the second build-up welding process are sufficiently melted. Because. The upper limit of the preferable interval is 7 mm, more preferably 6 mm.
And as a 3rd build-up welding process, build-up welding used as the 3rd build-up layer 6 is performed to the space | interval part of the said intermediate part, and it is set as the 3rd build-up layer 6 (build-up layer A "). In addition, in this invention, when forming a 3rd build-up layer, after forming the 2nd build-up layer made into the space | interval of 1-8 mm, build-up welding is once interrupted. Change the angle of the torch or hot forging die base material and readjust it so that build-up welding is possible at the center of the interval, then once from the vertical direction of the hot forging die base material It is preferable to form the third build-up layer by overlay welding, thereby preventing the occurrence of poor weld such as overlay welding or blow hole.
The balance of the tensile and compressive stresses during overlay welding can be made substantially uniform by the order of overlay welding defined in the present invention described above.
In the hot forging die, the weldability of the hot forging die base material and the overlay is improved between the hot forging die base material and the overlay layer as the work surface. The intermediate layer 7 that relaxes the stress generated between the layers may be build-up welded. Even in that case, it is preferable to form the intermediate layer in the order of overlay welding according to the present invention. The effect of forming the intermediate layer is the same when a ring-shaped or circular weld region, which will be described later, is formed.

Next, the overlay welding method in the case of forming a ring-shaped welding region will be described with reference to FIG. Basically, it is the same as the above-described rectangular area build-up, but in the case of a ring shape, the area where the build-up layer is formed is the outer peripheral end, the inner peripheral end, the outer peripheral end and the inner peripheral And an intermediate portion with the end portion. The first built-up layer 4 (built-up layer A ′) is formed from either the outer peripheral end or the inner peripheral end, and the second built-up layer 5 (built-up layer A) is formed from the other side. . The third built-up layer 6 (built-up layer A ″) is formed in the middle part. In this case as well, the distance between the first built-up layer 4 and the second built-up layer 5 is 1 to 8 mm. The third built-up layer 6 is formed in the intermediate portion that is spaced apart.
Moreover, the base material for hot forging to be used typically has a ring shape as shown in FIG. In this case, it is easy to perform overlay welding while rotating the base material for hot forging in the circumferential direction.
In addition, "ring shape" means the shape when the hot forging die is viewed from above as shown in FIG.

Next, a method of overlay welding when forming a circular welding region will be described with reference to FIG. Basically, it is the same as the above-described rectangular area or ring-shaped area build-up, but in the case of a circular shape, the area where the build-up layer is formed is the outer peripheral end, the center, the outer peripheral end, and the It has an intermediate part with a center part. The first build-up layer 4 (build-up layer A ′) is formed from either the outer peripheral end or the center portion, and the second build-up layer 5 (build-up layer A) is formed from the other side. The third built-up layer 6 (built-up layer A ″) is formed in the middle part. In this case as well, the distance between the first built-up layer 4 and the second built-up layer 5 is 1 to 8 mm. The third built-up layer 6 is formed in the intermediate portion that is spaced apart.
Moreover, the die base material for hot forging to be used has a truncated cone shape or a columnar shape. In this case, it is easy to perform overlay welding while rotating the die base material for hot forging in the circumferential direction.
The “circular shape” means a shape when the hot forging die is viewed from above as shown in FIG.

Next, in this invention, after the said build-up welding process, the heat processing for 1 to 10 hours is performed at 540-620 degreeC to the metal mold | die for hot forging welded as a heat treatment process. The main purpose is to reduce the stress generated during overlay welding. When the heat treatment temperature for stress relaxation is less than 540 ° C., the stress of tension or compression cannot be sufficiently reduced. On the other hand, in the temperature range exceeding 620 ° C., the tempering temperature of the hot forging die base material may be exceeded, and the hardness of the hot forging die base material is lowered. Therefore, the temperature range of the heat treatment step performed in the present invention is limited to 540 to 620 ° C.
Moreover, in order to perform sufficient stress relaxation in the above-mentioned temperature range, it is necessary to make the time appropriate. If the heat treatment time is less than 1 hour, the tensile or compressive stress cannot be sufficiently reduced. On the other hand, even if the heat treatment time exceeds 10 hours, the improvement of the stress relaxation effect cannot be expected. For example, when the heat treatment temperature is 600 ° C. or higher, the hardness of the die base material for hot forging is slightly lowered. There is a risk that. Therefore, the upper limit of the heat treatment time is 10 hours.
According to the configuration of the present invention described above, the balance of the tensile stress generated during the overlay welding described with reference to FIG. 2 can be made appropriate, and the stress generated during the overlay welding can be reduced.

In addition, in this invention, when making the build-up layer 2 into a multilayer, it is preferable to repeat the said 1st-3rd build-up welding process sequentially, and make a build-up layer into a multilayer in the thickness direction. This is because the balance of tensile stress generated during overlay welding can be made appropriate.
In the first and second build-up welding processes, it is preferable that the width of the weld bead formed by the one-time continuous welding is 10 mm or more. By setting the bead width to 10 mm or more, the bead shape becomes smooth, and the shape and the build-up quality when the layers are stacked can be stabilized. The upper limit of the bead width is not particularly specified, but for example, if it exceeds 35 mm, the width of the weaving becomes wide, and air may be mixed into the arc atmosphere due to insufficient shielding. The upper limit is preferably 35 mm.
Furthermore, the material of the overlay layer used in the present invention is preferably a Ni-based superalloy. This is because the high temperature strength in the temperature range where hot forging is performed is very excellent, and the oxidation resistance of the striking surface under high temperature is excellent. The “Ni-base superalloy” according to the present invention refers to an alloy that contains the most Ni and is excellent in oxidation resistance and high-temperature strength. Specifically, typical alloys include the aforementioned Udimet 520 equivalent alloy and an alloy having a composition shown in JIS-G4901 or G4902. These can strengthen (harden) the alloy by precipitating intermetallic compounds such as γ ′ phase.
The overlay welding is preferably arc welding. This means that a similar build-up layer can be obtained even with high-energy beam welding, but the welding equipment costs are expensive. Moreover, it is because the shape and dimensions of the workpiece are limited.

  The method for manufacturing a hot forging die of the present invention described above is suitable for a method for manufacturing a hot forging die for a large-scale hot forging device having a scale of tens of thousands of tons, for example. When a hot forging die for a large hot forging device is used, the weight thereof is 500 kg or more. As described above, when the weight of the hot forging die is increased, the hot forging die according to the present invention is usually damaged due to accumulation of tensile or compressive stress inside the hot forging die. According to the mold manufacturing method, the balance of tensile stress generated during overlay welding can be made appropriate, and problems such as cracking during overlay welding can be more reliably prevented.

The following examples further illustrate the present invention.
A die base material 3 for hot forging produced by JIS-SKD61, which was quenched at 1000 ° C. × 1 hour and tempered at 600 ° C. × 5 hours, was prepared. The die base material for hot forging weighs about 3000kg, and the work surface is machined with a die forging surface for disk forging. It is manufactured for a large hot forging machine with a maximum load of 50,000 tons. It is a thing. A schematic cross-sectional view is shown in FIG. As shown in FIG. 6, the present hot forging die is an assembly of a ring-shaped hot forging die 1a and a frustoconical hot forging die 1b.
The above-mentioned hot forging die base material was heated to 400 ° C. in a heating furnace, and overlay welding was performed. In addition, the base material for hot forging was heat-retained at 300 degreeC until the completion of overlay welding.
For overlay welding, an arc welding apparatus is used, and for the overlaying powder, an intermediate layer is made of Hastelloy-C276 equivalent alloy (Hastelloy is a registered trademark of Haynes International), and Udimet 520 equivalent alloy is used as a work surface on the intermediate layer. Overlay welding was performed.

First, the manufacturing process of the ring-shaped hot forging die 1a will be described.
As the first build-up welding process, continuous welding is performed for a predetermined length on the inner peripheral end portion to form the first build-up weld, and then the first build-up weld is continued to the intermediate portion. The next continuous welding is performed on the side, and the continuous welding is sequentially repeated so that the first overlay welding and the next continuous welding overlap in the length direction (circumferential direction), and overlay welding is performed toward the intermediate portion. Then, a continuous built-up layer was formed, and welding was stopped in front of the intermediate portion to form a first built-up layer 4 (build-up layer A ′) as shown in FIG. The schematic diagram shown in FIG. 5 has a V-shaped cross section, but actually has a cross sectional shape as shown in FIG. 6 and is simply described with reference to FIG.
Next, after the first build-up welding step described above, continuous welding is performed for a predetermined length on the portion that becomes the outer peripheral end portion to form the first build-up weld portion, and then the first build-up weld portion is formed. The next continuous welding is performed continuously to the first overlay weld so that the next continuous welding overlaps in the length direction (circumferential direction) on the intermediate portion side, and the continuous welding is sequentially repeated to repeat the intermediate portion. Overlay welding is performed in the direction to form a continuous buildup layer, and the welding is stopped at a position where the distance from the buildup layer formed in the first buildup welding process is 5 mm. The build-up layer 5 (build-up layer A) was formed.
Next, as a third build-up welding step, build-up welding that becomes the third build-up layer 6 is performed on the interval portion of the intermediate portion, and the third build-up layer 6 (build-up is 3 mm thick). The bead width in the first and second build-up welding steps was 22 mm. The third build-up layer was formed in the vertical direction of the die base material for hot forging. From this, it was set as one overlay welding.

Next, overlay welding was performed on the intermediate layer using an alloy equivalent to Udimet 520. The welding sequence, route interval, and bead width were the same as in the above-described overlay welding of the intermediate layer, and four layers of Udimet 520 equivalent alloy were laminated to produce a ring-shaped hot forging die shown in FIG.
Overlay welding during this time was overlaid sequentially while rotating the ring-shaped hot forging base material.
Thereafter, the hot forging die subjected to overlay welding was subjected to heat treatment at 600 ° C. for 2 hours to reduce the stress generated during overlay welding.
The ring-shaped hot forging die thus obtained was extremely large with a diameter of 1400 mm and an inner diameter of 300 mm. However, there were no problems such as cracking during the above-described overlay welding process and heat treatment process. Did not occur.

Next, the manufacturing process of the frustoconical (circular when viewed from above) hot forging die 1b will be described.
As the first build-up welding process, continuous welding is performed for a predetermined length on the outer peripheral end portion to form the first build-up weld, and then the first build-up weld is connected to the intermediate portion side. To the first weld overlay, and the successive welds are sequentially repeated so that the next continuous weld overlaps in the length direction (circumferential direction) on the intermediate portion side. Overlay welding is performed in the direction to form a continuous overlay layer, and the welding is stopped in front of the intermediate portion, and the first overlay layer 4 (build-up layer A ′) as shown in FIG. ) Was formed.
Next, after the first build-up welding process described above, continuous welding is performed at the center for a predetermined length to form the first build-up weld, and then the first build-up weld is continued to the intermediate The next continuous welding is continued to the first build-up weld so that the next continuous welding overlaps in the length direction (circumferential direction) on the part side, and the continuous welding is sequentially repeated toward the intermediate part. The build-up welding is performed to form a continuous build-up layer, and the second build-up layer is stopped by stopping the welding at a position of 5 mm from the build-up layer formed in the first build-up welding process. 5 (built-up layer A) was formed.
Next, as a third build-up welding step, build-up welding that becomes a third build-up layer is performed at the interval portion of the intermediate portion, and a third build-up layer 6 (build-up layer) having a thickness of 3 mm. A ″) was formed. The bead width in the first and second overlay welding processes was 22 mm. The third overlay layer was formed from the vertical direction of the hot forging die base material. One overlay welding was performed.

Next, overlay welding was performed on the intermediate layer using an alloy equivalent to Udimet 520. The welding sequence, route interval, and bead width were the same as in the above-described overlay welding of the intermediate layer, and four layers of Udimet 520 equivalent alloy were laminated to produce a ring-shaped hot forging die shown in FIG.
Overlay welding during this time was overlaid sequentially while rotating the ring-shaped hot forging base material.
Thereafter, the hot forging die subjected to overlay welding was subjected to heat treatment at 600 ° C. for 2 hours to reduce the stress generated during overlay welding.
The obtained frustoconical hot forging die had a large diameter of 300 mm, but no problems such as cracking occurred during the build-up welding process and the heat treatment process.
The ring-shaped hot forging die and the frustoconical hot forging die are combined by shrink fitting, and the forging surface is machined and hot forging as shown in FIG. We were able to manufacture a metal mold.

  From the above results, there is a possibility that tensile or compressive stress is usually accumulated inside and the hot forging die may be destroyed. According to the method for manufacturing a hot forging die of the present invention, overlaying is performed. It becomes possible to make the balance of the tensile stress produced at the time of welding appropriate. In addition, even a large hot forging die can more reliably prevent problems such as cracks during overlay welding.

DESCRIPTION OF SYMBOLS 1 Hot forging die 2 Overlay layer 3 Hot forging die base material 4 1st overlay layer 5 2nd overlay layer 6 3rd overlay layer 7 Intermediate layer

Claims (8)

In the method for manufacturing a hot forging die for forming a buildup layer by performing overlay welding on a hot forging die base material,
The region where the build-up layer is formed has one end in the first width direction, the other end, and an intermediate portion between the one end and the other end,
In the build-up welding, the first build-up weld is formed by performing continuous welding on the one end portion, then the first build-up weld and the next continuous weld on the intermediate side. And performing the overlay welding toward the intermediate portion by sequentially repeating the continuous welding, forming a continuous overlay layer, and stopping the overlay welding before the intermediate portion Welding process;
Continuous welding is performed on the portion to be the other end portion to form a first build-up welded portion, then continuous to the first build-up weld portion, and the next continuous welding is performed on the intermediate portion side, and the continuous welding is performed. Are sequentially repeated toward the intermediate part direction to perform overlay welding to form a continuous overlay layer, and the interval between the overlay layer formed in the first overlay welding step is 1 to 8 mm. A second overlay welding process for stopping the overlay welding at a position;
A third build-up welding step of performing build-up welding on the interval portion of the intermediate portion;
Including
After the first to third overlay welding steps, a heat treatment step of performing heat treatment at 540 to 620 ° C. for 1 to 10 hours on the hot forging die that has been overlay welded,
A method for producing a hot forging die, characterized in that: In the method for manufacturing a hot forging die for forming a buildup layer by performing overlay welding on a hot forging die base material,
The region where the overlay layer is formed has an outer peripheral end, an inner peripheral end, and an intermediate portion between the outer peripheral end and the inner peripheral end,
In the build-up welding, continuous welding is performed on a portion to be either one of the outer peripheral end portion or the inner peripheral end portion to form a first build-up weld portion, and then the first build-up weld portion is formed. Continuously, the next continuous welding is performed on the intermediate portion side, the continuous welding is sequentially repeated, and overlay welding is performed toward the intermediate portion to form a continuous overlay layer, before the intermediate portion. A first overlay welding process for stopping the overlay welding at
Continuous welding is performed on a portion which is the other end of the outer peripheral end or the inner peripheral end to form an initial build-up weld, and then continuous to the first build-up weld, the intermediate portion The next continuous welding is performed on the side, the continuous welding is sequentially repeated, and overlay welding is performed toward the intermediate portion to form a continuous overlay layer, which is formed in the first overlay welding process. A second build-up welding step for stopping the build-up welding at a position where the distance from the built-up layer is 1 to 8 mm;
A third build-up welding step of performing build-up welding on the interval portion of the intermediate portion;
Including
After the first to third overlay welding steps, a heat treatment step of performing heat treatment at 540 to 620 ° C. for 1 to 10 hours on the hot forging die that has been overlay welded,
A method for producing a hot forging die, characterized in that: In the method for manufacturing a hot forging die for forming a buildup layer by performing overlay welding on a hot forging die base material,
The area where the build-up layer is formed has an outer peripheral end portion, a central portion, and an intermediate portion between the outer peripheral end portion and the central portion,
In the build-up welding, continuous welding is performed on a portion that is one of the outer peripheral end portion or the center portion to form an initial build-up weld portion, and then continuous with the first build-up weld portion, The next continuous welding is performed on the part side, the continuous welding is sequentially repeated, and overlay welding is performed toward the intermediate part to form a continuous overlay layer, and the overlay welding is performed before the intermediate part. A first overlay welding process to stop;
Continuous welding is performed on the other end portion of the outer peripheral end or the central portion to form a first build-up weld portion, and then continuous to the first build-up weld portion, and next to the intermediate portion side. Welding, successively repeating the continuous welding and performing overlay welding toward the intermediate portion, forming a continuous overlay layer, and the overlay layer formed in the first overlay welding step; A second build-up welding process in which the build-up welding is stopped at a position where the interval is 1 to 8 mm;
A third build-up welding step of performing build-up welding on the interval portion of the intermediate portion;
Including
After the first to third overlay welding steps, a heat treatment step of performing heat treatment at 540 to 620 ° C. for 1 to 10 hours on the hot forging die that has been overlay welded,
A method for producing a hot forging die, characterized in that:   The method for producing a hot forging die according to any one of claims 1 to 3, wherein the first to third build-up welding steps are sequentially repeated, and the build-up layer is formed into a multilayer in the thickness direction. .   The method for producing a hot forging die according to any one of claims 1 to 4, wherein a bead width in the first and second build-up welding steps is 10 mm or more.   The method for manufacturing a hot forging die according to any one of claims 1 to 5, wherein the material of the build-up layer is a Ni-based superalloy.   The method of manufacturing a hot forging die according to any one of claims 1 to 6, wherein the weight of the hot forging die base material is 500 kg or more. The method for manufacturing a hot forging die according to any one of claims 1 to 7, wherein the build-up welding is arc welding.