Divided die for hot forging

Abstract

To provide a divided mold for hot punch forging which is effective for preventing a surface of a forged product from being injured.SOLUTION: In a divided mold for hot punch forging which constitutes a design surface integrated for forming a forging raw material by combining a plurality of mold pieces which has the divided design surfaces, the divided mold for hot punch forging has a difference caused by a boundary face I which is substantially parallel to a direction where the boundary face of adjacent mold pieces presses the forging raw material, so that a design surface SB becomes downstairs, between the design surface SA of a mold piece A of a side that is earlier brought into contact with the forging raw material and the design surface SB of a mold piece B of a side that is later brought into contact with the forging raw material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a segmented die that can be used in the field of hot die forging. [Background technology]

[0002] Hot die forging, which involves forging a material heated to a hot working temperature, uses a die with a "design surface" that has been pre-cut to the desired shape of the forged product. Compared to free hot forging, it can produce finer shapes and is also advantageous for mass production of identically shaped products. Furthermore, by using a "divided die" for hot forging, which combines multiple die pieces having divided design surfaces to form an integrated design surface for shaping the forging material, it becomes unnecessary to manufacture such a die by machining it as a single piece from a large block of die material. As a result, even large hot forging dies used for shaping aircraft jet engine discs and power generation gas turbine discs can be manufactured with a high yield (Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2013 / 147154 Brochure [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, in recent hot die forging, high-strength materials such as nickel alloys and titanium alloys are used as the forging material. And some of the various disc products mentioned above are over 1 meter in diameter. When forging such large forged products, especially using high-strength materials, the deformation load during hot die forging becomes an extremely large pressing force, exceeding 150 MN. And in such hot die forging, when a "split die" is used as the die, significant defects sometimes occur on the surface of the forged product. The object of the present invention is to provide a split die for hot forging that is effective in suppressing the occurrence of defects on the surface of forged products. [Means for solving the problem]

[0005] The present invention relates to a divided die for hot die forging, which combines multiple die pieces having divided design surfaces to form an integrated design surface for shaping a forging material. At the interface I where the interface between adjacent mold pieces is approximately parallel to the direction in which the forging material is pressed, the design surface S of mold piece A, which is the one that first contacts the forging material, A The design surface S of the mold piece B that will come into contact with the forged material. B Between this design surface S B This is a divided die for hot forging, having a step created by the interface I described above, such that the lower side is the lower level. [Effects of the Invention]

[0006] The present invention is effective in suppressing the occurrence of defects on the surface of forged products when forging material is hot-forged using a split die. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram showing an example of a cross-section including the interface of the split die for hot forging according to the present invention. [Figure 2] This is a schematic diagram showing an example of a cross-section including the interface of a conventional split die for hot forging. [Figure 3] This is a diagram explaining the mechanism by which defects occur on the surface of a forged product when hot die forging is performed using a conventional split die for hot die forging. [Figure 4] This is a substitute drawing photograph showing an example of the surface of a forged product produced using the split die for hot die forging of the present invention. [Figure 5] This is a substitute drawing photograph showing an example of the surface of a forged product produced using a conventional split die for hot die forging. [Figure 6] This is a schematic diagram showing a cross-section along the pressing direction of the split die for hot die forging used in the examples.

MODE FOR CARRYING OUT THE INVENTION

[0008] (1) The split die for hot die forging of the present invention is such that the boundary surface between adjacent die pieces includes "boundary surface I that is substantially parallel to the direction of pressing the forging material". Figure 2 shows an example of a cross-section including the boundary surface of a conventional split die for hot die forging, which satisfies the above (1). In the case of Figure 2, the individual die pieces are arranged and combined in the horizontal direction with respect to the vertical direction (the direction of pressing the forging material), so that the boundary surface between adjacent die pieces is substantially parallel to the direction of pressing the forging material. In a hot die forging die, the direction of pressing the forging material is usually the vertical direction. There are various types of hot die forging, such as closed forging, semi-closed forging, and closed die forging. In any type of die forging, it is common to press the forging material placed on the lower die vertically with the upper die. And, to give a specific example of such a split die for hot die forging, the hot forging die of Patent Document 1 is such that "a plurality of ring-shaped die pieces are combined and fixed concentrically with each other, the axial direction of the ring-shaped die pieces becomes the pressing direction when forging the forged material, and a die engraved surface is formed at the portion of the hot forging die that contacts the forged material", which is one form that satisfies the above (1).

[0009] Furthermore, the term "approximately parallel" in this invention does not mean that the angle between the "direction in which the forging material is pressed" and the "boundary surface of adjacent die pieces" is zero degrees. In other words, when the forging material is pressed with a split die, the reaction force pushes the die pieces in the direction of the die holder. Considering the mechanism by which defects occur on the surface of the forged product, as described later, it is sufficient that the reaction force acts along the boundary surface at an angle that allows it to function along the boundary surface. This angle can be, for example, in a range of approximately plus or minus 45 degrees from zero degrees, or in a range of plus or minus 30 degrees. Patent Document 1 also discloses a hot forging die in which the boundary surface has a predetermined angle with respect to the axial direction of the ring-shaped die piece. Furthermore, the "divided die for hot forging" of the present invention is not limited to being an upper die or a lower die, and the "die piece" according to the present invention may be a punch or, for example, a knockout pin that can move along the interface. In addition, the "design surface" of the die piece according to the present invention or the "step" described later may be subjected to build-up welding of, for example, a nickel-based superalloy.

[0010] (2) The split die for hot forging of the present invention is such that, at the position of the interface surface I described above, "the die piece A whose design surface contacts the forging material first and the die piece B which contacts the forging material later are adjacent to each other." Figure 2 shows an example of a cross-section of a conventional hot-die forging split die, including its interface I, and satisfies (2) above. In Figure 2, the die piece B on the left side of the paper and the die piece A on the right side are combined with the interface I in between. The design surface S of die piece A A The overall shape is that of the design surface S of mold piece B. B It has a "convex shape" relative to the other side. In this regard, the hot forging die described in Patent Document 1 also shows a relationship of convexity and concaveness on the design surfaces of the ring-shaped die pieces that are combined with each other. Note that when die piece A and die piece B are combined, it does not matter whether the die piece becomes the "center side" or the "outer circumference side" of the divided die (the direction in which the forging material flows does not change).

[0011] When the design surface of the split mold is like this, when die forging is started, the forging material first contacts the design surface S of the mold piece A A and "first". Then, as the die forging progresses and the forging material is deformed by the design surface S A , the forging material is pushed out toward the design surface S of the mold piece B B , and the forging material contacts the design surface S B "later", and finally, it is formed into the shape of the forged product on the design surface of the entire mold. And the inventor found that when hot die forging is carried out due to the behavior of such a forging material, significant defects may occur on the surface of the forged product. And the mechanism by which defects occur on the surface of this forged product was clarified as follows.

[0012] That is, when die forging is performed with a conventional split mold for hot die forging (Figure 2), first, at the start, the forging material contacts the design surface S of the mold piece A A . And the forging material deformed by die forging by the design surface S A flows toward the design surface S of the mold piece B B as well, and then forging by the design surface S B is started (because the design surface S B contacts the forging material), so until then, the reaction force corresponding to the deformation load concentrates on the design surface S of the mold piece A A . And when the deformation load at this time is large, the pressurized mold piece A elastically deforms, and the design surface S A is pushed into the die holder side more than the original position before the start of forging. As a result, the design surface S A is lower than the design surface S B before the forging material flows to the design surface S B (or when it is flowing). And at the boundary surface I, as shown in Figure 3 (the circled part. There is an enlarged view), an edge by the mold piece B is formed facing the direction in which the forging material flows.

[0013] Design surface S AThe fact that the material is pushed towards the die holder from its original position before the start of forging may not affect the overall dimensions of the forged product. However, when the above edge is formed on the interface I, the material passes through the interface I while this edge cuts away at the material during die forging. As a result, scratches (gouges) are formed on the surface of the forged product at the position corresponding to this interface I, as shown in Figure 5, which adversely affects the quality of the product. Therefore, the hot die forging split die of the present invention suppresses the occurrence of these scratches by the following requirement (3).

[0014] (3) The divided die for hot forging of the present invention has the above-mentioned design surface S A and design surface S B Between, the design surface S B The floor is lower, and therefore "has a step due to the boundary surface I described above." In this invention, in the initial stages of die forging, the design surface S of the die piece A is A Anticipating that it would deform and move downward towards the die holder, the design surface S at the interface I was prepared before the start of die forging. B The position of the design surface S A The surface is lowered in advance to the position where it is expected to decrease. In other words, the hot die for forging division of the present invention has a design surface S as shown in Figure 1. A and design surface S B Between, the design surface S B A "step" is provided on the boundary surface I such that the lower level is located below. By doing this, in the initial stages of die forging, the design surface S of the die piece A A Even if the position shifts downward towards the die holder, the pre-set step mentioned above will remain in place on the design surface S. A The displacement caused by the downward movement is absorbed, mitigating the formation of the edge by the mold piece B. Then, the forged material is formed on the design surface S. B When flowing, the design surface S at the position of the interface I A and design surface S B Since the height difference is reduced (because the edge height due to mold piece B is low), the occurrence of defects caused by the above can be suppressed, as shown in Figure 4.

[0015] Furthermore, the above-mentioned "design surface S" B Regarding the "step that is the lower level," the "lower level" refers to the direction in which the forging material is pushed (in other words, the side closer to the die holder), regardless of whether the mold is the upper or lower mold. Furthermore, the "design surface S" according to the present invention B Regarding the step that results in a lower floor, the specific form of this step can be anything other than what is shown in Figure 1. For example, it could be a part that can become the edge of mold piece B, a part of mold piece A that is opposite it, or a step itself that has been chamfered. In this way, the design surface S A However, whether the temperature drops more than expected, or less than expected, it is effective in mitigating the aggression of the mold piece edges on the forging material.

[0016] The nature (shape and height) of the step according to the present invention can be determined by performing an elastic analysis of the mold. For example, based on the results of the elastic analysis of the entire mold, the optimal nature of the step is determined such that deformation of mold piece A does not affect the surface of the forged product. Then, the parts that can become the edge of mold piece B and the parts of mold piece A that are opposite it can be modified so that the step takes on such a nature. The height of the step can usually be kept within the range of 1 to 5 mm. [Examples]

[0017] Two identical hot-die forging split dies made from JIS-SKD61 equivalent material were prepared. Figure 6 shows a cross-section of these split dies along the pressing direction. The split die 0 in Figure 6 consists of a total of four die pieces 1, with one cylindrical die piece at the center and three ring-shaped die pieces fitted concentrically around it. The outermost part is a fixing jig 2 for securing the die pieces 1. These divided dies have an "interface I" that is approximately parallel to the direction in which the forging material is pressed. At the position of this interface I, a "die piece A" whose design surface contacts the forging material first and a "die piece B" whose design surface contacts the forging material later are adjacent to each other. In one of these divided dies, the design surface S is located at the position of the interface I. BA step was created by the boundary surface I so that the lower level would be below (Figure 1).

[0018] Using these divided dies and the opposing dies, a roughly disc-shaped forging material made of a nickel alloy equivalent to Alloy 718 was forged to produce a disc-shaped forged product with a diameter of approximately 1 meter. The heating temperature of the forging material was set to 1000°C. The deformation load during forging exceeded 150 MN. The appearance of the manufactured forged products was visually inspected. As a result, in the case of the split mold without the step described above on the interface I, scratches (gouges) were formed on the surface of the forged product at the location corresponding to interface I, as shown in Figure 5. In contrast, in the case of the split mold with the step described above on the interface I, no such scratches were found on the surface of the forged product at the same location, as shown in Figure 4. [Explanation of Symbols]

[0019] 0-part mold 1 mold piece 2 Fixing fixture

Claims

[Claim 1] In a divided die for hot die striking, which combines multiple die pieces having divided design surfaces to form an integrated design surface for shaping a forging material, At the interface I where the interface between adjacent mold pieces is approximately parallel to the direction in which the forging material is pressed, the design surface S of mold piece A, which is the one that first contacts the forging material, Ａ The design surface S of the mold piece B that will come into contact with the forged material. Ｂ Between, the design surface S Ｂ The boundary surface I provides a step so that the lower floor is located. A split die for hot die forging, characterized in that, at the position of the interface I, the edge portion of the die piece B, the portion of die piece A facing the edge portion of die piece B, or the step created by the interface I is chamfered.

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