JP2017170543A - Spired metallic machine component and manufacturing method of spired metallic machine component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a spired metallic machine component capable of preventing or suppressing a condition impacted by segregated distribution which may cause deterioration in strength of a spired part.SOLUTION: A spired metallic machine component 1 is formed of a steel bar 3 by a cutting step, after the steel bar is provided by a hot-working step. The spired metallic machine component 1 comprises a spired part 2 which is arranged at one end side along a center axis Q, and which has a diameter thinner than that at the other end side. A center axis S of the spired part 2 is configured to be arranged deviated from a segregation center axis P of center segregation in the steel bar 3 so as to prevent or suppress a condition impacted by a segregation distribution which may cause deterioration in strength of the spired part 2.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a metal mechanical part having a spire portion on one end side along the axial direction, and a method of manufacturing the spire type metal mechanical part.

  Conventionally, a metal mechanical part having a spire-shaped structure in which the diameter on one end side (acting part side) in the axial direction is smaller than the diameter on the other end side (reaction part side) It is used in various fields in industry as a punch for tablet machines used for molding, an engine valve for automobiles, and the like.

  A metal machine part having such a spire-type structure is a relatively large-diameter part and a relatively small-diameter spire part from a steel bar or wire that is a thicker material than the steeple-type metal machine part. It is manufactured by shaving. These steel bars and wire rods are materials formed by hot-rolling slabs obtained by solidifying molten steel with adjusted components by continuous casting or by performing cold working such as drawing after hot rolling. .

  By the way, in the casting process, it is known that the cast material starts to solidify with volume shrinkage from the outside, and the central portion in the cross section solidifies last. In this way, solidification progresses from the outside to the inside. At that time, impurities and the like are also concentrated toward the inside, and therefore, in the vicinity of the central portion that solidifies last inside the cross section, it is called segregation or inclusion. Concentration of a specific element and concentration of foreign matters such as oxide, carbide or sulfide are observed. In addition, when the vicinity of the center of the slab solidifies, the periphery of the center has already been solidified. In response, free volume shrinkage accompanying cooling is prevented, and a large tensile force acts on the center. As a result, pores called porosity are formed in the vicinity of the center (for example, see Non-Patent Document 1 below).

  Although defects caused by such segregation can be reduced by adjusting the solidification structure by remelting, they cannot be completely removed, and are not possible in materials such as steel bars and wire rods. (See, for example, Non-Patent Document 2 below).

  In addition, such foreign matter concentration and voids that occur near the center of the solidified slab may be reduced in the process of reducing the cross-sectional area of the slab by hot rolling or subsequent cold drawing. Although it is reduced, it still remains. As a result, abnormal structures (defects) due to segregation, inclusions, or residual porosity are also observed in the vicinity of the axis of the columnar bar or wire.

  In the following description, the steel bars and wires that are the materials (base materials) for scraping the spire-shaped metal machine parts are collectively referred to as “bar steel”, and as shown in FIG. “Steel bar central axis”.

  In this figure, a scale showing how the distribution including all defects such as segregation, inclusions, precipitates, porosity, etc. appearing in the steel bar 3 during or after the casting process becomes “segregation distribution”. The presence / absence and strength of the segregation distribution is schematically shown in association with the cross section of the steel bar 3. As can be seen from the figure, in the small circle with the radius r centered on the steel bar central axis P ', there is a high probability that an abnormal structure due to segregation or other defects remains. That is, the portion having a high segregation distribution strength is contained in a circle having a radius r centered on the steel bar central axis P ′. On the other hand, almost no residual abnormal structure is observed outside the radius r centered on the steel bar central axis P ′ (the intensity of the segregation distribution is zero or substantially zero). From the above, it can be understood that the portion where the abnormal structure remains is limited to the range of a circle having a small radius r centered on the steel bar central axis P ′.

  Here, in FIG. 13, a photograph of a 15 mm diameter material (a metal mechanical part at the time before forming the spire portion) cut out from a steel bar having a diameter of 32 mm and subjected to polishing treatment and corrosion treatment, is observed with an optical microscope. Indicates. The spot at the tip of the arrow in FIG. 6A is the remaining abnormal tissue, and the region where the presence of this abnormal tissue is observed (region showing a strong segregation distribution) is as shown in FIG. In the region of about 3 mm in diameter centered on the central axis of the material (metal mechanical part before the spire portion was formed). That is, the region where the presence of an abnormal structure is observed (region showing a strong segregation distribution) is “a diameter about one tenth of the diameter of the steel bar” centered on the steel bar central axis. This is the same even when the radius is taken as a reference. Referring to FIG. 12, the radius r of the region centered on the central axis P ′ of the steel bar and where the presence of the abnormal structure is observed is the radius R of the steel bar 3. It is about 1/10 of. Here, if the center of a circle with a radius r where the presence of an abnormal structure is observed is defined as a “segregation center”, the segregation center coincides with the geometric center of the steel bar 3. When the segregation center of each cross section is connected to the axial direction of the steel bar 3 as a “segregation central axis”, the segregation central axis coincides with the geometric axis P ′ of the steel bar 3.

The mechanical strength of the portion where the abnormal structure remains (the inner portion of the circle having the radius r centered on the steel bar central axis P ′) is equal to the portion where the abnormal structure does not remain (radius r centered on the steel bar central axis P ′). It is far inferior to the mechanical strength of the outer part of the circle. However, the area πr ² of the cross section of the portion where the abnormal structure remains in the steel bar 3 is not so large as compared to the area πR ² of the cross section of the steel bar 3. As described above, in the normal steel bar 3, the radius r centered on the steel bar central axis P ′ is 1/10 or less of the radius R of the steel bar 3, for example, the radius R of the steel bar 3 is about 5 mm to 32 mm. Considering the range, the radius r centered on the steel bar central axis P ′ is about 0.5 mm to 3.2 mm corresponding to the range of the radius R of the steel bar 3.

That is, the maximum value of “r / R”, which is the ratio of the radius r centered on the central axis P ′ of the steel bar where the residual abnormal structure remains, and the radius R of the steel bar 3 is 0.1, and the area ratio ( (πr ² / πR ² ) is 0.01 or less. Therefore, in the material stage (the state of the steel bar 3) before the cutting process is performed, the cross-sectional area of the portion where the abnormal structure remains is much smaller than the cross-sectional area of the material (the steel bar 3). Almost no influence on the average strength of the material (bar 3).

That is, it is represented by a portion of a radius r centered on the steel bar central axis P ′ so that it can be represented by the formula “(πr ² ) ÷ (πR ² ) = (r / R) ² ≦ 0.01”. The presence of an abnormal structure (trace of central segregation) has little effect on the average strength of the steel bar 3 as a whole.

Edited by Japan Iron and Steel Institute: “Steel Manufacturing Method (1st volume, steelmaking and steelmaking)”, Maruzen, p. 682-695, p. 724-727, 1972 Jun Sato, Koji Iwanaga, Atsushi Tomioka, Katsushi Nishiguchi, Hiroki Nakajima, Hitoshi Ishida: “High-quality roll manufacturing technology using new ESR”, Kobe Steel Technical Report, Vol. 60, No. 2, p. 15-19, 2011.8

  By the way, as shown in FIG. 12, the relatively large diameter portion and the relatively small diameter steeple portion 20 are cut out from the steel bar 3 where the abnormal structure remains in the central axis P ′ and the vicinity thereof. When manufacturing and processing the steeple-shaped metal machine part 10, the steel bar center axis P ′ and the center axis S of the steeple portion 20 are usually processed coaxially. As a result, in the steeple-type metal mechanical part 10, abnormal portions due to segregation or other defects are observed in the thinned portion indicated by the radius α in FIG. That is, the axis of the steeple-type metal machine part 10 (the center axis R of the steeple-type metal machine part 10) coincides with the steel bar center axis P ′ in FIG. The inner side has a higher segregation distribution than the outer side. As described above, the mechanical strength of the material in the portion where the strength of the segregation distribution is high (the portion where the abnormal structure remains) is inferior to the average mechanical strength of the steel bar 3.

Therefore, if the radius r centered on the steel bar central axis P ′ is larger than the radius α of the steeple part 20, that is, if the relationship of “α <r” is satisfied, the entire region of the steeple part 20 is made of the steel bar 3. Of these, the mechanical strength of the spiers 20 is greatly affected by the mechanical strength of the material having the high-strength segregation distribution and is significantly reduced. It will be. As a result, there is a high possibility that the spire portion 20 will be chipped or broken during use of the spire-type metal machine part 10, and if chipping or breakage occurs, the replacement frequency of the spire-type metal machine part 10 is increased. Not only that, but the machine (equipment) on which the spire-type metal machine part 10 is mounted breaks down and the risk of leading to a major accident increases. This tendency becomes more prominent as the cross sectional area πr ² of the spire portion 20 becomes smaller.

  The present invention has been made paying attention to such points, and the main purpose thereof is a spire-type metal machine capable of preventing / suppressing the influence of the segregation distribution that causes the deterioration of the strength of the spire. It is an object of the present invention to provide a part and a method for producing such a spire-type metal machine part.

  That is, the present invention relates to a spire-type metal machine part formed by cutting a steel bar provided through hot working. Here, the “bars” in the present invention are all materials (base materials) for cutting out steeple-type metal machine parts such as rods and lines provided from cast materials through hot working such as rolling and forging. (Concept). Note that the “bar” in the present invention is not only provided through hot working, but also provided through cold working such as cold drawing after hot working, It is a concept including what is provided by performing a heat treatment after cold working.

  And the spire type metal machine part according to the present invention has a spire part having a diameter smaller than that of the other end part on one end side along the central axis of the spire type metal machine part. The center axis is deviated from the center axis of segregation in the steel bar. Here, “center segregation” in the present invention refers to defects such as segregation that are distributed in a circle with a radius in a certain range in a cross section of a steel bar subjected to hot working or cold working after hot working. This is an abnormal structure resulting from the “segregation central axis”, which is an axis passing through the center of the central segregation. In other words, if the center of the radius circle where the presence of abnormal structures due to defects such as segregation is observed (the radius circle with a high segregation distribution strength) is the “segregation center”, the segregation center of each cross section of the steel bar is The axis connected in the axial direction of the steel bar is the “segregation central axis”.

  The inventor found that the cause of the problem that occurs in the case of a conventional spire-type metal machine part is the geometric center of the spire portion when manufacturing a spire-type metal machine part by cutting a steel bar as a raw material. The center axis of the spire metal machine that matches the axis matches the center axis of the steel bar.As a result, the segregation center axis of the segregation center of the steel bar and the center axis of the spire metal machine part It was found that the point is in agreement with. That is, the inventor of the present invention has a conventional configuration in which the portion of the steeple portion in the steeple-type metal machine part including the center of the steel bar and an abnormal structure in the vicinity thereof (the portion with a high segregation distribution strength) is included in the spire portion. The cause of strength deterioration was investigated.

  Therefore, in the present invention, a configuration is adopted in which the central axis of the spire portion is displaced from the segregation central axis of the central segregation in the steel bar. With such a spire-type metal machine part according to the present invention, the situation in which abnormal tissue remains in the spire portion can be completely avoided, or the ratio of the remaining portion of abnormal tissue existing in the spire portion can be significantly reduced. It is possible to realize a spire-type metal machine part that can prevent or suppress the situation of being affected by the segregation distribution that causes the strength deterioration of the spire portion.

  In particular, in the present invention, in order to reliably avoid the configuration in which the abnormal structure exists in the spire portion, the deviation amount of the central axis of the spire portion relative to the segregation central axis of the steel bar is set to 10 minutes of the radius of the steel bar. It is preferable to set it to 1 or more. This is because, as shown in FIG. 12, the portion where the abnormal structure due to segregation or other defects remains in the cross section of the steel bar is within the range of a circle with a small radius r centered on the segregation central axis P of the steel bar. The point limited to the above, and the value of the radius r around the segregation central axis P of the steel bar is about one-tenth of the steel bar radius R, and the above points are focused on. Naturally, the maximum value of the amount of deviation of the central axis of the spire portion is such that the target spire-type metal machine part can be reliably obtained from the steel bar as the base material by cutting.

  Furthermore, in the present invention, as shown in FIG. 3, the deviation δ of the central axis of the spire portion relative to the segregation central axis of the steel bar is obtained by adding 1/10 of the radius R of the steel bar to the radius α of the spire portion. If a configuration satisfying the equation “δ ≧ α + (R / 10)” is employed, the amount of deviation δ of the central axis of the steeple portion relative to the segregation central axis of the steel bar is calculated as It is set in such a manner that a region having a large amount of segregation is excluded from the inside of the part, and a configuration in which abnormal tissue due to a defect such as segregation exists in the spire part can be avoided with high probability. And a portion excluding a portion where the intensity of the segregation distribution is high, which is limited to the inside of the predetermined radius centered on the segregation central axis of the steel bar, that is, a portion outside the predetermined radius centered on the segregation central axis of the steel bar By adopting a configuration in which the spire portion is formed and the segregation center axis and the center axis of the spire portion are displaced, it is possible to eliminate the influence of the segregation distribution from the spire portion.

  The present invention also relates to a method of manufacturing a steeple-type metal machine part from a steel bar through a cutting process, and in the cutting process, the center axis of the steeple-type metal machine part is displaced from the segregation central axis of the center segregation in the steel bar. The spire-type metal machine parts are cut out and manufactured by cutting them.

  With such a method for manufacturing a spire-type metal machine part, it is possible to manufacture a spire-type metal machine part that has no or almost no abnormal tissue that causes strength deterioration in the spire part. It is possible to manufacture a spire-type metal mechanical part having a spire portion having a strength equivalent to the average mechanical strength in the cross section of the above.

  As described above, according to the present invention, in the metal machine part having the spire portion, the configuration in which the center axis of the spire type metal machine part is displaced from the segregation center axis of the center segregation in the steel bar is adopted. Therefore, it is possible to prevent the deterioration of the mechanical strength of the spire part, and to make the strength of the spire part the same as the average strength of the steel bar that is the base material, and the stable strength of the spire-type metal machine parts Guarantees can be realized. Therefore, since it is possible to prevent the spire portion from being broken or broken, which can occur frequently, it is possible to reduce the replacement frequency of the spire-type metal machine parts, and to reduce the spire-type metal machine parts. It becomes possible to guarantee the stable operation of the used machine (device).

  Also, in the process of cutting out the spiers, the smaller the spiers, that is, the smaller the radius of the spiers, the lower the strength of the spiers, and the probability of a breakage accident when cutting However, according to the present invention, such a breakage accident can be prevented in advance, and various losses such as material loss and energy loss required for manufacturing a spire-type metal machine part can be prevented. Occurrence can be suppressed.

1 is an overall schematic diagram of a steeple-type metal machine part according to an embodiment of the present invention. The whole schematic diagram of the steel bar in the embodiment. The figure which shows the relative positional relationship (how to cut out the spire type metal machine part from the bar steel) in the same embodiment corresponding to FIG.1 and FIG.2. The figure which shows the strength test method of the test piece (spiral type metal machine parts) of a present Example and a comparative example. The figure which shows the time of the spire part of a test piece breaking at the root in the test corresponding to FIG. The figure which shows the relative positional relationship of the test piece and steel bar seen from the axial direction in each case of the test. The figure which shows the component of the steel bar (SNCM477) used by the same test. The figure which shows the test result of case 1 and case 2 in the same test. The figure which shows the test result of case 1 and case 2 in the same test with a graph. The figure which shows the test result of case 3 and case 4 in the same test. The figure which shows the test result of case 3 and case 4 in the same test with a graph. The figure which shows typically the relative positional relationship (how to cut out from a bar steel of a spire type metal machine part) of the conventional spire type metal machine part and a steel bar. A photograph showing segregation in the vicinity of the axis of a conventional spire-type metal machine part.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the spire-type metal machine component 1 according to the present embodiment is set to have a smaller diameter at one end side along the central axis Q of the spire-type metal machine component 1 than at the other end side. The spire portion 2 is provided. Such a spire-type metal machine part 1 is used, for example, as a punch of a tableting machine, and can be formed by compressing powder at the spire portion 2 during actual use. Therefore, the spire part 2 functions as an action part. That is, the steeple-type metal machine part 1 according to the present embodiment has the steeple part 2 on the action part side along the central axis Q of the steeple-type metal machine part 1.

  The steeple-shaped metal machine part 1 is a machined part formed by cutting from, for example, a steel bar 3 shown in FIG. 2 provided through hot working. As shown in FIGS. 1 and 3, the steeple part The center axis S of 2 coincides with the center axis Q of the spire-type metal machine part 1. And the spire-type metal machine part 1 which concerns on this embodiment has shifted the central axis S of the spire part 2 from the segregation central axis P of the center segregation in the steel bar 3. FIG.

  Here, the part where the abnormal structure remaining due to defects such as segregation, inclusions, precipitates, porosity, etc. appearing in the steel bar 3 during the casting process or after the casting process (part where the strength of the segregation distribution is high) is Of these, the radius r is limited within the range of the center axis P ′ of the steel bar 3 in FIGS. 2 and 3. In FIGS. 2 and 3, similarly to FIG. 12 described above, the presence / absence and strength of segregation distribution is schematically shown in association with the cross section of the steel bar 3. Thus, the abnormal structure resulting from defects such as segregation distributed in a circle with a radius r in a certain range in the cross section of the steel bar 3 that has undergone hot working is the center segregation, and the strength of the segregation distribution is high. The axis passing through the center of the radius r is the “center segregation segregation central axis”. In the present embodiment, the segregation center axis P coincides with the center axis P ′ of the steel bar 3.

And the spire type metal mechanical component 1 which concerns on this embodiment has the characteristics in the point which is comprised so that the range of the said radius r among the steel bars 3 may not be included in the spire part 2. Using a steel bar 3 in which the central axis P ′ of the steel bar 3 and the segregation central axis P coincide with each other, the central axis S of the spire part 2 is displaced from the segregation central axis P of the central segregation in the steel bar 3. As one means for making the machine part 1, in this embodiment, the distance δ between the center axis Q of the spire-type metal machine part 1 and the segregation center axis P satisfies the relationship of the following formula 1. It is set.
δ ≧ (α + r) (Formula 1) where α is the radius of the spire portion 2 (see FIGS. 1 and 3).

  Thus, in the case of the steel bar 3 in which the central axis P ′ of the steel bar 3 and the segregation central axis P coincide with each other, the distance δ between the central axis Q of the spire-type metal machine part 1 and the segregation central axis is expressed by the equation When the relationship 1 is satisfied, the spire portion 2 does not have a portion in which abnormal tissue due to segregation or the like remains, and the strength of the spire portion 2 can be prevented from being reduced.

  That is, since the spire-type metal mechanical component 1 according to the present embodiment employs a configuration in which the abnormal tissue that causes the strength deterioration does not exist in the spire portion 2, the deterioration of the mechanical strength of the spire portion 2 occurs. Without this, the spire portion 2 having a strength equivalent to the average mechanical strength in the cross section of the steel bar 3 can be obtained. Therefore, the spire-type metal mechanical component 1 according to the present embodiment has an operational effect that chipping or breakage of the spire portion 2 is reduced.

  Hereinafter, test contents and test results conducted to verify the strength of the spire-type metal machine part 1 according to the present embodiment will be described with reference to FIGS. 4 to 11.

  In this test, an elongated test piece X corresponding to a spire-type metal machine part is cut out from a steel bar 3 which is a hot-rolled black bar material, and as shown in FIG. With the appropriate pressing tool Z from the direction perpendicular to the axial direction, the tip of the spire portion 2 is gripped by the appropriate gripping tool Y at equal pitch intervals in the circumferential direction. The time point shown in FIG. 5, that is, the time point at which breakage occurred at the base of the spire portion 2 was defined as “the time point when the breakage was reached”, and the amount W of push-in at this “time point when the breakage occurred” was compared and examined. 4 is a schematic diagram viewed from the A direction in FIG. 4, and the spire portion 2 of the test piece X is formed by the gripper Y at equal pitch intervals in the circumferential direction. It is a figure which shows the state which has hold | gripped the part of the side which is not. The steel bar 3 used in this test has a center axis that coincides with the segregation center axis. In this test piece X, the diameter of the portion on which the spire portion 2 is not formed is set to 15 mm, the length of the same portion along the axial direction is set to 29 mm, the diameter of the spire portion 2 is set to 3 mm or 5 mm, and the axial direction The length of the spire part 2 along the line is set to 30 mm. Further, in this test, the value of y (the distance from the root of the spire portion 2 to the gripping tip position by the gripper Y) shown in FIG. 4 is set to 10 mm, and the value of z (from the tip of the spire portion 2 to the pressing tool z) is set. Is set to 5 mm.

  The method of cutting out the test piece X in this test is four patterns shown in FIG. In case 1, the center of the steel bar 3 having a diameter d1 of 32 mm and the center of the test piece X having a diameter d2 of 15 mm (the center of the spire-type metal mechanical part 1) are matched, and the diameter d3 of the spire portion 2 is set. The case 2 is formed by shifting the center of the steel bar 3 having a diameter d1 of 32 mm and the center of the test piece X having a diameter d2 of 15 mm by 8 mm (deviation amount δ: 8 mm). The diameter d3 of the part 2 is set to 3 mm.

  In addition, the case 3 is a case in which the center of the steel bar 3 having a diameter d1 of 32 mm and the center of the test piece X having a diameter d2 of 15 mm are matched, and the diameter d3 of the spire portion 2 is set to 5 mm. 4, the center of the steel bar 3 having a diameter d1 of 32 mm and the center of the test piece X having a diameter d2 of 15 mm are displaced by 6 mm (deviation amount δ: 6 mm), and the diameter d3 of the spire portion 2 is set to 5 mm. It is a thing.

  Here, in the present test in which the center axis P of the center segregation in the steel bar 3 coincides with the axis passing through the center of the steel bar 3, the center of the steel bar 3 and the center of the test piece X are deviated. Is the test piece X according to the present embodiment (the spire-type metal machine part 1 according to the present invention), and the case 1 and the case 3 in which the center of the steel bar 3 and the center of the test piece X coincide with each other are the case 2 and the case 3, respectively. 4 is a test piece X according to Comparative Example 4;

  In addition, each test piece X applied in this test is manufactured by turning from a hot rolled finish SNCM447 material (chromium molybdenum steel SNCM447) having a diameter of 32 mm, which is a steel bar 3. The component range in the JIS standard regarding chromium molybdenum steel SNCM447 is as shown in FIG.

  The test results are as shown in FIGS. That is, the center of the steel bar 3 having a diameter d1 of 32 mm and the center of the test piece X having a diameter d2 of 15 mm (the center of the spire-type metal machine part 1) are matched, and the diameter d3 of the spire portion 2 is set to 3 mm. As a result of conducting a total of 6 tests for the set case 1, the average value of the pushing amount W at the time when the fracture was reached (when the breakage occurred at the base of the spire portion 2) was 6.73 mm (see FIG. 8 and FIG. 8). (See FIG. 9). On the other hand, a total of 6 tests were conducted on Case 2 in which the center of the steel bar 3 having a diameter d1 of 32 mm and the center of the test piece X having a diameter d2 of 15 mm were displaced by 8 mm and the diameter d3 of the spire portion 2 was set to 3 mm. As a result, the average value of the push-in amount W at the time of rupture was 11.68 mm (see FIGS. 8 and 9).

  In addition, the test relating to Case 3 in which the center of the steel bar 3 having a diameter d1 of 32 mm and the center of the test piece X having a diameter d2 of 15 mm are matched and the diameter d3 of the spire portion 2 is set to 5 mm is performed a total of three times. As a result, the average value of the push-in amount W at the time when the fracture occurred was 3.7 mm (see FIGS. 10 and 11). On the other hand, a total of three tests on case 4 in which the center of the steel bar 3 having a diameter d1 of 32 mm and the center of the test piece X having a diameter d2 of 15 mm are offset by 6 mm and the diameter d3 of the spire portion 2 is set to 5 mm are performed. As a result, the average value of the push-in amount W at the time of rupture was 4.0 mm (see FIGS. 10 and 11).

  From the above test results, the value of the push-in amount W at the time of rupture in the case 2 and the case 4 of the present example in which the center of the steel bar 3 and the center of the test piece X are decentered is It was found to be larger than Case 1 and Case 3 in which the centers of the pieces X were matched. That is, in this test in which the segregation center axis P of the center segregation in the steel bar 3 coincides with the axis passing through the center of the steel bar 3, the axis of the test piece X is deviated from the segregation center axis P of the steel bar 3. Thus, it was found that the value of the indentation amount W until breakage increases and the strength increases.

  As a result of microstructural observation, the presence of a slightly abnormal structure was confirmed in addition to the region of radius r centered on the segregation central axis P of the steel bar 3, although not as close to the central axis P ′ of the steel bar 3. It was. Due to this influence, in each case of this test, as shown in FIGS. 8 to 11, even if the case number is the same, the “value of the push amount W at the time of rupture” varies for each test number. I can guess.

  However, in the test results for each case, when the average value of the push-in amount W until rupture is seen, even if the diameter d3 of the spire portion 2 is 3 mm or 5 mm, the shaft core of the test piece X is made of the steel bar 3 It can be understood that the breaking strength of the test piece X (spiral metal machine part) is improved by shifting from the axis P ′ (that is, the segregation center axis P).

  Further, from the test results on cases 1 to 4, the strength of case 2 in which the diameter d3 of the spire portion 2 is set to 3 mm is higher than the case 4 in which the diameter d3 of the spire portion 2 is set to 5 mm. Turned out to be great. This is because when the segregation center axis P of the steel bar 3 and the center axis S of the spire portion 2 coincide with each other (case 1, case 3), if the diameter d3 of the spire portion 2 is 3 mm, the strength of the segregation distribution is high. This is presumably because all of the spire portion 2 is included in a region having a particularly strong distribution even within a range of 5 mm in diameter around the central axis P ′ of the steel bar 3.

  As described above, when the segregation center axis P of the center segregation in the steel bar 3 coincides with the axis passing through the center of the steel bar 3, the center axis S of the spire portion 2 is deviated from the center axis P ′ of the steel bar 3. According to the spire-type metal mechanical part 1 according to the present embodiment configured to deviate the center axis S of the spire portion 2 from the segregation center axis P of the steel bar 3, the spire portion 2 is segregated or the like. The situation in which abnormal tissue remaining due to the defect of the spire can be completely avoided, or the ratio of the abnormal tissue (defect portion) present in the spire portion 2 can be remarkably reduced, and the cause of the strength deterioration of the spire portion 2 It is possible to prevent or suppress the situation affected by the segregation distribution.

  In particular, when the segregation central axis P of the center segregation in the steel bar 3 is coincident with the axis passing through the center of the steel bar 3, as shown in FIG. The value of the radius r where the abnormal structure remains is limited to about one-tenth of the radius R of the steel bar 3, which is limited to the range of a circle with a small radius r centered on the central axis P ′ of the steel bar 3. By paying attention to the above points, the deviation amount δ of the central axis S of the spire portion 2 with respect to the segregation central axis P of the steel bar 3 is set to 1/10 or more of the radius R of the steel bar 3, A configuration in which abnormal tissue is present in the spire portion 2 can be reliably avoided. In both cases 2 and 4, the deviation amount δ (8 mm, 6 mm) of the center axis S of the spire portion 2 with respect to the segregation center axis P of the steel bar 3 is 10 minutes of the radius R (16 mm) of the steel bar 3. 1 (1.6 mm) or more is set.

Furthermore, the deviation amount δ of the center axis S of the spire portion 2 with respect to the segregation center axis P of the center segregation in the steel bar 3 is a value obtained by adding 1/10 of the radius R of the steel bar 3 to the radius α of the spire portion 2. By adopting the configuration set above, that is, the configuration satisfying the following formula 2, the deviation amount of the central axis S of the spire portion 2 with respect to the central segregation center axis P of the central segregation in the steel bar 3 is set large. Further, a configuration in which abnormal tissue exists in the spire portion 2 can be avoided with a higher probability.
δ ≧ α + (R / 10) (Formula 2)

  In the case 2 described above, the deviation δ (8 mm) of the center axis S of the spire portion 2 with respect to the segregation center axis P of the center segregation in the steel bar 3 is set to the radius α (1.5 mm) of the spire portion 2. It is not less than a value (3.1 mm) obtained by adding 1/10 (1.6 mm) of the radius R (16 mm). Further, in the case 4 described above, the deviation δ (8 mm) of the center axis S of the spire portion 2 with respect to the segregation center axis P of the center segregation in the steel bar 3 is set to the radius α (2.5 mm) of the spire portion 2. It is equal to or more than a value (4.1 mm) obtained by adding one-tenth (1.6 mm) of the radius R of 3 (16 mm). Therefore, the case 2 and the case 4 are configured to satisfy the above-described expression 2.

  Further, in the cutting process, the spire type metal machine part 1 is cut out and manufactured by shifting the center axis Q of the spire type metal machine part 1 from the segregation center axis P of the center segregation in the steel bar 3. If this method is used, it is possible to manufacture the spire-type metal machine part 1 in which the abnormal tissue that causes the strength deterioration does not exist at all or in the spire portion 2, and an average in the cross section of the steel bar 3 can be obtained. It becomes possible to manufacture the spire-type metal machine part 1 having the spire portion 2 having the same strength as the mechanical strength.

  In addition, this invention is not limited to embodiment mentioned above. For example, even if it is a structure which does not satisfy | fill the conditions of the above-mentioned Formula 1 and Formula 2, if the center axis | shaft of a spire part is deviated from the segregation center axis | shaft of the center segregation in a steel bar, the spire type | mold which concerns on this invention Corresponds to metal machine parts.

  In addition, the ratio of the diameter of the spire portion to the ratio of the height dimension of the spire portion to the height dimension of the entire spire-type metal machine part can be changed as appropriate.

  In addition, the spire-type metal machine part according to the present invention has the same center axis of the spire part as that of the spire-type metal machine part, and the center axis of the spire part deviates from the segregation center axis of the center segregation in the steel bar. It is sufficient that it is positioned, and instead of a complete columnar spire portion, for example, a spire portion having a constricted portion recessed radially inward at a predetermined location along the axial direction, or along the axial direction It is also possible to apply a spire portion having a projecting portion protruding radially outward at a predetermined location, and a spire portion having a tip portion set in a conical shape or a spherical shape.

  As a specific material of the steel bar, a material other than the above-described chromium molybdenum steel SNCM447 can be applied.

  In addition, the spire-type metal mechanical parts according to the present invention can be used and utilized in various fields in the industry, such as automobile engine valves, in addition to the use as a punch of a tableting machine for forming tablets such as medicines. Is possible.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Spire-shaped metal machine part 2 ... Spire part 3 ... Steel bar P ... Segregation center axis P 'of center segregation in bar steel ... Center axis Q of steel bar ... Center axis R of spire-type metal machine part ... Radius S of steel bar ... Center axis α of the spire part ... Radius δ of the spire part ... Deviation of the central axis of the spire part with respect to the central axis of the steel bar

Claims (4)

A spire-type metal machine part formed by cutting a steel bar provided through hot working,
On one end side along the central axis of the spire-type metal machine part, it has a steeple portion having a diameter smaller than that of the other end side, and the central axis of the spire portion is separated from the segregation central axis of the central segregation in the steel bar. Spire-type metal machine parts characterized by being displaced. The spire-type metallic machine part according to claim 1, wherein a deviation amount of the central axis of the spire portion with respect to the segregation central axis is set to 1/10 or more of a radius of the steel bar. The amount of deviation of the central axis of the spire portion with respect to the segregation central axis is set to a value equal to or greater than a value obtained by adding 1/10 of the radius of the steel bar to the radius of the spire portion. Spire-type metal machine parts. A method of manufacturing a spire-type metal machine part from a steel bar through a cutting process,
In the cutting step, the spire type metal machine part is cut out and manufactured by shifting the center axis of the spire type metal machine part from the segregation center axis of the center segregation in the steel bar. A method for manufacturing a spire-type metal machine part.

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