JP4819352B2 - Manufacturing method of forging die, forging die and forged product - Google Patents

Description

  The present invention relates to a method for producing a forging die for producing a forging die made of an aluminum alloy, a forging die, and a forged product forged using the forging die.

  There are three basic issues in cutting: high accuracy, high efficiency, and low cost. Of these three issues, increasing the cutting speed is required as a means for realizing high-efficiency machining. When the cutting speed is increased, the cutting efficiency is improved accordingly, but there is a problem that the tool life is shortened and the tool cost is increased. When the tool life is reduced, the frequency of tool change increases, so there is a problem that productivity is deteriorated, and it is difficult to realize high-efficiency machining.

  In particular, today, where high-precision molded products are required, molds are also required to have high precision. As a method for producing high-speed, high-precision molds, direct replacement to the conventional electric discharge machining has been performed. A method of manufacturing a mold by the engraving method has been studied.

For example, in Patent Document 1 below, the CBN sintered body contained in the CBN sintered tool is set to 75% or more, the cutting speed is set to 1500 m / min or more, and a plurality of CBN sintered tools are mounted. A face mill is configured, the cutting speed of the face mill is set to 1500 m / min or more, and the feed amount of one CBN sintered tool per one face mill rotation is 0.2 mm / rev to 0.4 mm / rev. A method for preventing the tool life from being reduced even if the cutting speed is increased by cutting is disclosed.
JP-A-11-170102

Further, in Patent Document 2 below, C: 0.28 to 0.55 mass%, Si: 0.15 to 0.80 mass%, Mn: 0.40 to 0.85 mass%, P: 0.0. 020 mass% or less, S: 0.018 mass% or less, Cr: 2.5 to 5.7 mass%, Mo: 1.4 to 2.8 mass%, V: 0.20 to 0.90 mass%, W: 0.01 to 1.65% by mass, Co: 0.03 to 0.89% by mass, Ni: 0.01 to 1.65% by mass, with the balance being substantially Fe and inevitable impurities N of the inevitable impurities is regulated to 0.009% by mass or less, Ti is controlled to 0.003% by mass or less, B is controlled to 0.012% by mass or less, and the cleanliness of nonmetallic inclusions is JIS dA 0.005% or less. And d (B + C) is 0.020% or less, and the directionality of the martensite structure after the heat treatment is 17 With hot tool steel characterized by being in the range of 33 to 33%, the tool life during tool cutting and the variation in tool life when manufacturing a die by direct carving are improved significantly by improving the machinability. In addition, it is disclosed that the finished surface is excellent when ultra-fine cutting is performed, and the lapping time can be shortened.
JP 2003-268486 A

In Patent Document 3 below, C is 0.25 to 0.45 wt%, Si is 0.05 to 0.6 wt%, Mn is 0.2 to 0.8 wt%, and Cr is 4. 0 to 6.0 wt%, Mo 1.0 to 3.0 wt%, V 0.3 to 1.0 wt%, Al 0.005 to 0.040 wt%, and S 0.001 to A mold containing 0.004% by weight, the balance consisting of Fe and inevitable impurities, and having a hardness of HRC 41 to 45, and a mold having the above component composition, and then molding the mold A manufacturing method of the mold, wherein a plastic working is performed on a corner portion having a rounded surface of the sculpture using a pressurizing tool having a radius of curvature smaller than the corner radius so that the equivalent total strain of the surface is 5% or less. By using it, the manufacturing cost is the same as that of the conventional hot forging die made of JIS SKT4 or SKD61. It is disclosed that there is provided a forging die having a low strike and having excellent durability that can be manufactured under a favorable working environment as compared with these conventional dies.
JP-A-8-188852

  However, in the case of Patent Document 1, the CBN sintered body is cut at a cutting speed of 1500 m / min or more with a tool that makes the CBN sintered body 75% or more, but this is a special condition that is impossible with a general machine tool. The tools presented are expensive and impractical.

  Further, in Patent Document 2, although examinations are made from materials, specific optimum processing conditions are not examined.

  Further, Patent Document 3 discusses materials, and discloses a method for applying a compressive stress to a corner portion. However, specific processing conditions for a cutting method are not studied.

  And in the case of direct engraving, it has the following subjects regarding processing conditions. That is, it is required to increase the protruding length of the tool and deepen it so that it can correspond to various shapes, but conventionally, the conditions are determined by trial and error of the rotation speed and feed rate, When the tool protrusion length was increased, the optimum condition was not achieved. For example, the rotation speed is set as large as possible, and then the feed and cutting (pitch) are determined by calculation based on the required surface roughness. However, if this calculated value is left as it is, problems such as tool vibration will occur. Has a problem and needs to be fixed. Conventionally, it has been generally encouraged that lowering the feed rate can improve the finish, and it takes trial and error to find the conditions for actually bringing the finish to the best state. Took time.

  In addition, in the mold production by the conventional direct engraving method, the polishing process is indispensable when the cutting process is inadequate when cutting at high speed. It was a factor that raised the cost and lengthened the production time. In addition, polishing is generally hand-finished and has become a major cause of defects. Therefore, development of a direct engraving process of a mold that can obtain a surface finish that can omit or simplify the polishing process has been studied.

  The present invention has been proposed in view of the above, and can be cut at a high speed in the production of a forging die, maintain the tool life, omit the polishing step, and can be manufactured with high efficiency as a whole. It is an object of the present invention to provide a method for producing a forging die, a forging die and a forged molded product forged using the forging die.

To achieve 1) above object, the first invention is a method for producing a forging die, small
At least rough cutting, heat treatment, finish cutting, shape cutting, and shape cutting
Then, a ball end mill whose surface is reinforced is used as a cutting tool, the protrusion length L (mm) of the tool, the radius R (mm) of the edge of the ball end mill, and the tool rotation speed A (rpm)
And the tool feed speed B (mm / min) satisfying (B / A) ² × (L / (2 × R)) = 0.01 to 0.05 , the hardness is HRC 45 or more 62 Cutting edge of the following mold material by direct engraving , cutting oil at the time of cutting, the core thickness / outer diameter of the cutting tool is 60 to 80%, and the runout is 5 μm or less during idling Is ejected from at least two directions, and is supplied by being flowed down from above the blade edge so that at least 5 mm from the tip of the blade is always immersed in the cutting oil, and cutting is performed in at least three stages. In order to equalize the variation in the machining allowance to 10 to 30 μm or less or 20 to 80% by the second stage treatment, 1.2 to 2: 0.2 to 0.5: 0.03 to 0.05, At least one of contour line processing and loop processing as the tool feed direction It is characterized by including .

2) In addition to the configuration of the invention described in 1) above, the second invention includes the above contour line processing and the above.
Combining the two processes of the rounding process, contours the part near the standing wall of the mold material.
Then, the flat part is rounded and processed, and the angle between the contact surface and the horizontal plane is about 30 to 50 °.
It is characterized by being able to switch between positions .

In the present invention, cutting oil is supplied by flowing down from above the cutting edge of the cutting tool during cutting .

At least rough machining, heat treatment, finishing machining, shaped portion cutting, those shape-portion cutting comprises at least three steps, the tool radial direction pitch ratio at that three stages, 1
. 2 to 2: 0.2 to 0.5: a 0.03-0.05, feeding direction of the tool is Nde contains at least one of the feed direction of the circulating processing contour line processing.

Moreover, in the manufacturing process of the forging die, it is preferable to cut the concave corners of the processed surface into a shape including the composite R. Here, the shape including the composite R is the straight portion of the processing surface of the mold material.
In addition to the radius (R1) of the specified dimension of the concave portion, the curved portion and the straight line
At least one curve with a radius (R2) that is greater than 1 times R1 and less than 4 times R1.
It refers to the shape cut in addition to the above.

3) The third invention is a forging die, which is manufactured by the forging die manufacturing method described in 1) or 2) above.

4) In the fourth aspect of the invention , in addition to the structure of the invention described in the above item 3) , the surface roughness is Rma.
x5μm or less, the specified dimension of the recess in the recess of the corner composed of the straight part and the curved part of the processed surface
In addition to the radius of (R1), the radius that is more than 1 times of R1 and less than 4 times at the place where the curved part and the straight part are connected
A molding hole having a composite R shape to which at least one curve of (R2) is added is formed.

5) The fifth invention is a forged molded product, characterized by being forged using the forging die described in the above item 3) or 4) .

In the present invention, in direct engraving production of a forging die, the die material is cut in a state where the protruding length of the tool, the edge radius of the ball end mill, the tool rotation speed, and the tool feed speed satisfy a predetermined relationship. I tried to do it . Specifically, at least rough cutting, heat treatment, finish cutting, shape
In the shape part cutting process, the ball end mill whose surface is reinforced is processed.
As a cutting tool, the tool protrusion length L (mm) and the ball end mill edge
The relationship between the diameter R (mm), the tool rotation speed A (rpm), and the tool feed speed B (mm / min) is
(B / A) ² × (L / (2 × R)) = cutting a die material having a hardness of HRC45 or more and 62 or less by direct engraving while satisfying 0.01 to 0.05, and cutting Sometimes the cutting oil is sprayed from at least two directions to the tip of the cutting edge where the core thickness / outer diameter of the cutting tool is 60 to 80% and the runout is 5 μm or less during idling, and at least 5 mm from the tip of the cutter is always cut. While flowing down from the upper edge of the blade so as to be immersed in oil, cutting is performed in at least three stages, and the tool radial pitch ratio in the three stages is 10-30 μm or less in the machining allowance due to the second stage processing. Or 1.2 to 2: 0.2 to 0.5: 0.03 to 0.05 for uniformizing to 20 to 80%, and including at least one of contour line processing and rounding processing as the feed direction of the tool As a result , the optimum machining conditions are easy. In addition, it is possible to cut at high speed, maintain the tool life, omit the polishing step, and as a whole, the forging die can be manufactured with high efficiency.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a sketch of an example of a forging die produced by the method of the present invention. As an example of a forging die manufactured by the method of the present invention, a die 1 having a semi-cylindrical forming hole 2 as shown in FIG. 1 will be described as an example. The semi-cylindrical shape is an example of a shape that requires machining or deep engraving that changes the inclination of the machining surface.

  First, the material of the mold 1 is preferably mold steel or high-speed tool steel having a hardness HRC (Rockwell hardness C) in the range of 45 to 62 (preferably 46 to 55). For example, SKD61 and matrix high speed can be mentioned. By using such a material, a mold having a long life and accuracy can be manufactured, and the effects of the present invention can be sufficiently exhibited.

  An example of the manufacturing process of the mold 1 will be described. A manufacturing process can be made into the process of (a) roughing-> (b) heat processing-> (c) finishing cutting-> (d) shape part cutting-> (e) polishing processing-> (f) inspection. Hereinafter, the steps (a) to (f) will be described in order.

  (A) Rough cutting The rough cutting is performed by a general method. For example, using a lathe and a milling machine, a die outer shape portion, a positioning hole, and the like are cut. The semi-cylindrical portion may be carved about 80% of the whole by a ball end mill.

  (B) Heat treatment Heat treatment is performed to adjust toughness and wear resistance. For example, in SKD61, the heat treatment condition is to hold at 900 to 1100 ° C. (preferably 1000 to 1050 ° C.) for 30 minutes to 1 hour, and then rapidly cool and hold at 500 to 700 ° C. (preferably 560 to 600 ° C.) for 3 to 5 hours. Is preferred. The holding time is adjusted according to the size of the mold.

  (C) Finishing cutting In finishing cutting, the outer shape of the die is finished to a predetermined dimension using a lathe. Machining that is difficult with lathe processing may be performed using a grinding machine or a wire-cut electric discharge machine.

  (D) Shaped part cutting Using a ball end mill whose surface is reinforced, the molded hole part of the mold is cut into a final shape. It is preferable to have a plurality of stages, for example, at least three stages of cutting processes, and satisfy cutting conditions described later. Furthermore, it is preferable that the feeding direction includes contour line processing and / or circulation processing.

  FIG. 2 is an explanatory diagram of contour line processing, and FIG. 3 is an explanatory diagram of circulation processing. In these drawings, when cutting the forming hole 2 into the final shape, the cutting edge of the tool advances from the point P1 (x1, y1, z1) in the order of (1) → (2) → (3) → (4). Then, when moving to the point P2 (x2, y2, z2), in (5), the progress is different between the contour line process and the circulation process.

  In the contour line processing, as shown in FIG. 2, in (5), a Z coordinate value is determined by giving a difference b between the Z coordinate value z2 of the point P2 and the Z coordinate value z1 of the point P1, and then the X coordinate. The value x2 calculates a point corresponding to the Z coordinate value z2 on the L line, determines (x2, y2, z2), moves to the point P2 at that position, and resumes the movement from the point P2 to (6). . Contour line processing is a process that specifies the machining pitch in the Z direction (depth direction) for a shape with a standing wall shape, and gradually cuts from top to bottom or from bottom to top. This is preferable in that a sharp shape can be processed efficiently.

  In one rounding process, as shown in FIG. 3, in (5), the difference a between the X coordinate value x2 of the point P2 and the X coordinate value x1 of the point P1 is given to determine the X coordinate value. The Z coordinate value z2 calculates a point corresponding to the X coordinate value x2 on the L line, determines (x2, y2, z2), moves to the point P2 at that position, and moves from the point P2 to (6). Resume. In the rounding process, the machining pitch in the XY direction (horizontal direction) is instructed for a shape close to a flat surface, and the shape is cut from outside to inside or from inside to outside. It is preferable in that it can be processed well.

  For complex shapes, it is preferable to combine two processes, contour line processing and rounding process. For example, in contour line machining with a constant machining pitch in the Z direction, a place near the standing wall can be machined cleanly, but it is almost flat. By the way, since the processing pitch becomes rough, in order to compensate for this, a rounding process is used in the vicinity of the flat portion.

  In the case of engraving a semi-cylindrical shape that is an example having a shape in which the inclination angle of the machining surface changes, it is preferable to perform the contour processing on the shallow upper portion and the circulation processing on the deep lower portion. These treatments are preferably switched at a position where the angle between the contact surface of the semi-cylindrical shape and the horizontal plane is 30 to 50 °, since the pitches of both processes are almost equal. Also, it is preferable to overlap both processes by 0.1 to 1 mm because it is possible to prevent uncut parts from being generated at the switching boundary.

  The shape portion cutting is so-called direct engraving, and depending on the shape, a finer part can be left behind with a small blade (tool radius R 0.2 to 1 mm, preferably 0.5 mm).

  (E) Polishing If necessary, the surface roughness after processing is increased as required. For example, the surface is polished using a grindstone, then diamond paste is applied to the surface, and the surface is polished using felt buff or wood. It can be omitted depending on the state of the shape portion cutting process.

  (F) Finally, the finished state is inspected. The inspection items are a three-dimensional measuring machine, a caliper, a dimensional inspection using a gauge, a dimensional inspection using a shape measuring device, a hardness inspection using a hardness meter, and a surface roughness inspection using a surface roughness meter.

  Next, the shape part cutting process of the present invention will be described. Initially, the tool used for the shape part cutting process of this invention is demonstrated.

  FIG. 4 is a view showing an example of a tool used in the present invention. As the tool 3 used in the present invention, any tool can be used as long as the surface is subjected to a strengthening treatment (surface hardening treatment). For example, a hardened layer is provided on the surface of the base material. Examples of the material of the hardened layer include TiAlN (titanium aluminum nitride), TiSiN (titanium silicon nitride), and CrSiN (chromium silicon nitride). In particular, those having a low coefficient of friction with the mold material and a high oxidation start temperature of the reinforcing coating are preferable from the viewpoint of tool life.

  The tip shape of the tool 3 is preferably a ball end mill shape and has a core thickness / outer diameter of 60 to 80%, from the viewpoint of improving the tool rigidity. The number of blades is not particularly limited, but 2-3 blades can be used.

  In order to enable deep engraving, the tool diameter D (= 2R) is μ0.4 to 10 mm, preferably μ0.5 to μ6 mm, and the protruding length L is 5 to 20 mm (more preferably 5 to 17 mm). Is preferred.

  Further, in order to engrave a minute shape, the tool diameter D (= 2R) is preferably μ0.2 to 2 mm, more preferably μ0.4 to 2 mm.

  In particular, it is preferable that the relationship of L / 2R (= L / D) is 3 to 20 (preferably 3.5 to 15) because the effect of the present invention is well exhibited.

  The cutting surface has a good runout during cutting. For this purpose, it is preferable to suppress the runout of the blade to 5 μm or less during idling (when the blade is rotated without being processed in that state). For example, use a device with a small spindle runout, for example, a runout of 2 μm or less, a collet holder for attaching the cutter to the machine spindle, and a collet chuck for gripping the cutter to a shrinking type Or any combination thereof.

  Next, cutting conditions will be described.

In the present invention, the relationship between the protruding length L (mm) of the tool, the blade end radius R (mm) of the ball end mill, the tool rotation speed A (rpm), and the tool feed speed B (mm / min) is (B / A) ² × (L / (2 × R)) = Cutting is performed in a state satisfying 0.01 to 0.05.

  In the past, conditions were determined by trial and error in the number of rotations and feed speed, but the conditions were not optimal, such as when the protruding length of the tool enabling deep engraving was increased.

  The rotation speed can be set as large as possible, and the feed and depth of cut (pitch) can be calculated from the desired surface roughness. However, if this calculated value is used as it is, problems such as tool vibration will occur. However, in order to find out the conditions to actually make the finished surface the best, it is generally recommended that the feed rate be lowered to improve the finish. Trial and error was necessary.

The inventor found out that, even if the feed speed was lowered too much, incompleteness in the finished state was a factor that made it difficult to find the optimum state, and (B / A) ² × (L / This can be avoided by managing the value of (2 × R)).

  This mechanism is presumed as follows. When the surface state after cutting was investigated, as shown in FIG. 5, so-called macroscopic blade type transfer and microscopic blade type transfer remain, and these states are related to the quality of the surface finish state. found.

  When the feed rate is increased with respect to the rotational speed, the cutter bite, which is considered to be a macroscopic blade type transfer, is minutely chipped by the cutter, and the bite mark tends to remain.

  When the feed rate is reduced with respect to the number of rotations, scissors-like traces of the blade, which are considered to be microscopic blade type transfer, tend to remain. In particular, when the tool is used for a long time, the occurrence of a scissors-like mark is likely to occur.

  Therefore, it is necessary to set conditions while looking at these balances. However, it has been found that the radius of the cutting edge of the tool, L / 2R, must be taken into account, not simply by the ratio between the rotational speed and the feed rate.

The inventor paid attention to the value of (B / A) ² related to the kinetic energy of the tool and the value of (L / 2R) indicating the state of the tool. As a result, control is possible even when the tool radius is small or when L / 2R is large.

  In this way, the tool material is cut in a state where the tool protrusion length, the blade end radius of the ball end mill, the tool rotation speed, and the tool feed speed satisfy the predetermined relationship. Can be easily set, and the surface finish is good and cutting can be performed at high speed. In particular, even if the tool protrusion length is increased and deep engraving is performed, the finish is improved. As a result, the chatter of the tool is suppressed and the cutting state is stable, so that there is an effect that the tool life is extended, and further, the polishing process can be omitted, and the forging die is manufactured with high efficiency as a whole. Will be able to.

  In accordance with the shape of the cutting surface, especially when the tool traveling direction changes by 35 ° to 45 ° or more in the corner-shaped part, the feed rate is reduced by 30 to 40% from 0.2 to 0.5 mm before the change point. Is preferred.

  The shape part cutting process preferably has at least three cutting steps, and the feed direction of the tool includes a contour line process and / or a round process. In this case, it is preferable that the radial pitch ratio of the tool is set to 1.2-2: 0.2-0.5: 0.03-0.05 in order from the first stage. The unevenness of the cutting allowance remaining in the entire surface by the second stage processing is made uniform to 10-30 μm or less and the third stage processing is performed, thereby suppressing unevenness in the finished state of the cutting processing in the third stage. Because it can. The variation of the remaining machining allowance of the entire surface by the second stage treatment is made uniform to 20 to 80% of the final machining allowance, and the third stage treatment is performed, so that the cutting treatment in the third stage is performed. This is because unevenness of the finished state can be suppressed. By doing so, the cutting allowance in the third step for increasing the finishing accuracy becomes uniform, the cutting in the third step is stabilized, and the dimensional accuracy for the design is improved.

  In particular, in the case of a semi-cylindrical shape, it is preferable to combine the contour line process and the circulation process after the second and third stages.

For example, in the first stage, contour processing is performed, and the radial pitch is 1.2 to 2 mm, preferably 1.8.
mm, the cutting depth is 0.15 to 0.25 mm, preferably 0.2 mm, and in the second stage, the contour line treatment and the rounding treatment are used together, and the radial pitch is 0.2 to 0.5 mm, preferably 0.4 m.
m, the cutting depth is 0.3 to 0.5 mm, preferably 0.4 mm, and in the third stage, the contour line treatment and the rounding treatment are used together, and the radial pitch is 0.03 to 0.05 mm, preferably 0.05 m.
m and the cutting depth can be 0.04 to 0.06 mm, preferably 0.05 mm.
Here, the relationship between the radial pitch and the cutting depth is as shown in FIG.

  As the cutting oil (lubricant), a water-insoluble cutting oil can be used, and examples thereof include a sulfurized fatty oil-based cutting oil for carbon steel or alloy steel. The supply temperature is preferably 15 ° C to 30 ° C. A preferred flow-down method of the present invention will be described. The supply amount is preferably 15 to 25 liters (L) / min.

  Conventionally used air blow systems can blow off chips to some extent, but have insufficient cooling ability.

  The conventionally used mist method is a method in which water-insoluble cutting oil is made into a mist and sprayed onto the blade together with air. The supply amount is, for example, mist 0.2 L / min and air 200 L / min. In this method, there is usually one ejection nozzle, and if the tip of the cutter is behind the workpiece, the mist does not reach the tip of the cutter directly, and the effect may be reduced or not obtained.

  The preferred flow-down method of the present invention is a method in which cutting oil is ejected from at least two directions and is supplied so that at least 5 mm from the tip of the blade is always applied to the cutting oil. In this method, even if the cutter hides behind the workpiece, the tip is always immersed in the cutting oil, so the effect of the cutting oil is not lost. In the present invention, since the tool is rotated at a high speed, a sufficient cooling effect by this flow-down method is preferable because the tool life can be extended.

  The supply direction is preferably from the upper edge of the blade. In particular, it is preferable from the viewpoint of eliminating the shortage of supply when machining the vicinity of the standing wall shape that the direction of flow is from all directions centering on the tool. Specifically, for example, it can be realized by arranging cutting oil injection nozzles in four directions around the tool.

  Inappropriate swarf condition may cause adverse effects on the tool, increase tool wear, shorten tool life, increase cutting resistance, reduce cutting speed and promote tool wear. To do. In particular, if chip discharge becomes inappropriate, tool chattering may occur, which may promote the deterioration of the quality of the finished surface and the deterioration of the tool. Since the discharge state of cutting powder becomes favorable, it is preferable. Since the discharge processing of the chips becomes smooth, the adhesion of the chips to the tool and the occurrence of biting are suppressed, the chatter of the tool can be suppressed, and the cutting state is stabilized.

  Next, the composite R will be described. The compound R is a radius of the specified dimension of the concave portion (R1) in the shape of the concave portion of the corner portion composed of the straight portion and the curved portion, and more than 1 times R1 at the place where the curved portion and the straight portion are connected. It is made into the shape which added at least 1 or more of the curve of radius (R2) below 1.5 times, preferably 1.5 times-2.5 times. Thereby, it becomes the shape which suppressed the rapid change of the contact area of a tool. The compound R can be similarly considered when a draft is provided in the standing wall portion.

  7, 8, and 9 are cross-sectional shape diagrams showing examples of the shape of the corner concave portion provided with the composite R. FIG.

For example, the concave shape of the corner portion provided with the composite R shown in FIG. 7 can be set as follows.
(1) Lv and Lh are determined from the shape of the molded product as the cross-sectional contour shape of the wall surface sandwiching the corner portion.
(2) Ra is determined from the shape required for the corner of the molded product. For example, it can be a radius of curvature of a corner portion of a given product shape.
(3) “Composite R index α” is given. α may be 0.5 Ra or less. For example, a tolerance value x (0.5 to 2) of a corner shape of a molded product is given as α.
(4) An imaginary circle (A) having a radius Ra is drawn around a point (Xa (= Ra), Ya = (Ra + α)) whose center position is from Lv to Ra and is Ra + α from Lh.
(5) The virtual circle (B) in contact with the virtual circle (A) and Lh is obtained. The virtual circle (B) can be obtained by numerical calculation or drawing under the condition of “contact”. When a plurality of solutions are obtained, the one with 4 times or less of Ra is adopted.
(6) Here, the relationship between the virtual circle (A) and the virtual circle (B) is a characteristic of the composite R, but the virtual circle (A) is in an inscribed state where it touches inside the virtual circle (B). is there.
(7) The center position is from Lh to Rb, the center position of the virtual circle (B) in contact with the virtual circle (A) is (Xb = (Rb−β), Yb = (Rb)), and its radius is Rb Become.
Here, Rb and β are constants obtained in step (5) from the condition of “contact”.
(8) A circular arc (BB) in contact with the virtual circle (A) and Lh is drawn with a radius Rb around (Xb, Yb).
(9) An arc (AA) in contact with the arc (BB) and Lv is drawn with a radius Ra around (Xa, Ya).
(10) Connect the Lv, the arc (AA), the arc (BB), and Lh to form the corner recess shape having the composite R.

In FIGS. 7 and 8, 痾 is a dimensional tolerance of Ra, Ra is an arc that touches Lv, Rb is an arc that touches Lh and Ra, and Xa and Xb are dimensions that are automatically determined from other dimensions. In FIG. 7, the corner concave portions are formed in a multi-stage shape by connecting the straight portions Lh and Lv and the curved portion having the designated dimension radius Ra with a curved line having a radius Rb so as to be in contact with both. In FIG. 7, Rb is provided so as to contact Ra and Lh, but Rb may be provided so as to contact Ra and Lv.

Furthermore, in the case of obtaining a combined corner recess shape, it is possible to add a virtual circle between the virtual circles (A) and (B).

For example, a virtual circle (C) having a radius Rc and a center position (Rc, Rc + αc) is provided so as to contact the virtual circle (A). Here, αc = mαa and Rc = nRa. αa is α of the virtual circle (A), m is a value less than 1, for example 0.5, and n is a value greater than 1, for example 2.

Then, by providing a virtual circle (B) between the virtual circle (C) and Lv, the corner portion is formed into a concave shape based on the virtual circles (A), (B), and (C). I can do it.

  FIG. 8 shows a case where a draft angle is provided. Similarly to FIG. 7, the corner concave portion has a radius Rb so that the corner concave portions are in contact with each other between the straight portions Lh and Lv and the curve of the designated dimension radius Ra. It is formed in a multi-stage shape by connecting the parts. Although Rb is provided so as to contact Ra and Lh in FIG. 8, Rb may be provided so as to contact Ra and Lv. It is preferable because it is easy to escape the contact of the tool in the standing wall portion.

  Moreover, in FIG. 9, a corner part recessed part leaves 60%-85% from the corner part center as a shape by designation | designated R, and the remaining part is a curve with a curvature changing continuously, and a curvature changes continuously. An example of a composite R is shown.

  In this way, by forming the corner concave portion with the composite R, as shown in FIG. 10, for example, the tool 3 comes into contact with (i.e., touches) the processing surface, but a rapid change in the contact range between the tool and the processing surface is suppressed. Therefore, the feeding of the tool can be stabilized and the occurrence of chatter can be suppressed. As a result, the finished state can be made better. Concave corners are difficult to polish uniformly in shape, and this has been a problem in production. However, using such a composite R is preferable because the polishing step can be omitted and simplified. Furthermore, because it is a composite R, the contact area between the mold and the blade is small, so that the chip is small and a large space for discharging the chip can be taken, the discharge state of the chip becomes good, and it is discharged once more. This is preferable since the biting that is a state in which the chip is sandwiched between the blade and the workpiece is less likely to occur.

  In the case where the inclination angle of the concave portion of the corner portion in the machining shape is changed (for example, in the case of the machining shape as shown in FIG. 1, the concave portion position of the corner portion in the semi-cylindrical shape (reference numeral D in FIG. 1)). In FIG. 1, the concave portion is a semi-cylindrical tangentially inclined surface.) A height distance (for example, symbol F in FIG. 1) from the lowest part (for example, symbol E in FIG. 1) to the highest part of the corner portion. On the other hand, it is preferable that the shape of the concave portion at the corner portion in the height range of at least 20% (for example, symbol G in FIG. 1) also includes the composite R. This is because the contact state of the tool with the workpiece in that range affects the finished state (surface shape, surface roughness, dimensional accuracy) of the workpiece.

  A machining center can be used for direct engraving in the shape cutting process. The machining center is a numerically controlled machine tool that mainly uses a rotary tool, is equipped with an automatic tool changer, and performs various types of machining without changing the setup for changing the workpiece. In particular, the one used for direct engraving preferably has a spindle speed of 20,000 or more.

  The design of the mold shape portion is mainly performed using three-dimensional CAD. Based on the designed shape model, the number of machining stages, the type of cutting tool used at each stage, machining feed, cutting, and pitch are set, the tool trajectory (machining method) is calculated using CAM, and output as NC data. To do. The created NC data is transferred to the machining center through a LAN cable or the like, and the machining center executes cutting based on the NC data.

  The cutting conditions of the present invention, the processing method of the shape portion cutting, and the like are set as conditions in the CAM. The shape of the composite R is designed by CAD.

  The forging die manufactured by the above manufacturing method can be manufactured in a single time with a forming hole having a surface roughness of Rmax 5 μm or less (preferably 3 μm or less) and a concave corner having a composite R shape. In addition, it is a mold with excellent surface finish. The molded product forged using this mold has a good surface finish, and particularly has a good surface finish at the corner.

  As the forging method using the mold, known methods such as cold forging and warm forging can be used. A case where a material made of an aluminum alloy is used will be described as an example.

  The above-mentioned mold is shrink-fitted into the mother mold as necessary, and installed in the forging device as a lower mold. A material for forging is obtained by cutting an extruded material, a continuous casting rod, or the like into a predetermined length. Lubricate the material and put it into the mold. If necessary, it is preferable to heat the material and mold. The upper die is lowered and forged. In the case of deburring and forging, trimming processing for deburring is further performed. The molded product is heat-treated as necessary. Although the example of the lower mold has been described, it can be used for the upper mold according to the shape of the molded product, or can be used for both the upper mold and the lower mold.

  Thus, the forged molded product forged using the above-mentioned mold has a good surface finish surface to which the surface state of the mold is transferred. In particular, the surface finish is good at the corners. For example, since the mold is not divided at the corner portion, no insertion burr occurs. In addition, when a mold that is a composite R is used, the curve at the convex corner becomes smooth and the appearance is excellent.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

  The material of the mold was SKD61, and the hardness was HRC48 ± 2. The tool uses a ball end mill of R0.5 to R2, and the surface treatment film is CrSiN. Other conditions are shown in Tables 1 and 2.

The surface finish after cutting was evaluated by observing with a loupe. The evaluation results are shown in Table 1. Table 2 shows a comparison between the conventional method and the present invention.

As apparent from Table 1 above, even when the tool diameter (2R) and the tool overhang length (L) are the same value, the tool rotation number (A) and the feed amount (B) are appropriately selected, and (B / A) ² × By setting (L / 2R) to a range of 0.01 to 0.05, a casting mold having a good finished surface can be manufactured with high efficiency.

It is a sketch of an example of the metal mold | die manufactured with the method of this invention. It is explanatory drawing of a contour line process. It is explanatory drawing of a circulation process. It is a figure which shows an example of the tool used for this invention. It is a conceptual diagram explaining the cutting state. It is a conceptual diagram explaining a cutting process. It is a figure which shows the example of the corner part recessed part shape which provided the composite R. FIG. It is a figure which shows the example of the corner part recessed part shape which provided the composite R. FIG. It is a figure which shows the example of the corner part recessed part shape which provided the composite R. FIG. It is a conceptual diagram explaining the cutting state in a corner part.

Explanation of symbols

1 Forging die 2 Molding hole 3 Tool

Claims (5)

In the method for producing a forging die,
At least rough cutting, heat treatment, finish cutting, shape cutting,
In the shape part cutting process,
A ball end mill whose surface is reinforced is used as a cutting tool, the protruding length L (mm) of the tool, the blade edge radius R (mm) of the ball end mill, the tool rotation speed A (rpm),
The relationship with the tool feed speed B (mm / min) is
(B / A) ² * (L / (2 * R)) = 0.01-0.05
A die material with hardness of HRC45 or more and 62 or less is cut by direct engraving while satisfying the conditions
Cutting oil is used for cutting, and the core thickness / outer diameter of the cutting tool is 60 to 80%.
At least 5 m from the blade tip, ejected from at least two directions to the blade tip that is 5 μm or less
As m always flows into the cutting oil, it is supplied by flowing down from above the cutting edge,
Cutting at least in three stages, and the tool radial pitch ratio in the three stages is processed in the second stage
In order to make the variation in the machining allowance uniform within 10-30 μm or 20-80%
1.2 to 2: 0.2 to 0.5: 0.03 to 0.05, and contour line treatment as the feed direction of the tool
Including at least one of reasoning and rounding,
A method for producing a forging die characterized by the above. Combining the two processes of the contour line process and the round process, it is close to the standing wall of the mold material.
Contour lines are processed at the corners, circular processing is performed on the flat part, and these processes are performed at the angle between the contact surface and the horizontal plane.
The method for producing a forging die according to claim 1 , wherein the degree is switched at a position of 30 to 50 ° . It is manufactured by the method for manufacturing a forging die according to claim 1 or 2.
Mold. Roughness of the surface is Rmax 5 μm or less, and the concave portion of the corner portion is composed of a straight portion and a curved portion of the processed surface.
In addition to the radius (R1) of the specified dimension of the concave portion, the portion where the curved portion and the straight portion are connected is 1 times R1
A composite R shape having at least one curve with a radius (R2) exceeding 4 times and less than 4 times.
The forging die according to claim 3, wherein a shaped hole is formed. A forged molded product forged using the forging die according to claim 3.

Images