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    • 专利摘要:
    The present invention provides a powder forged part in which the fatigue strength is improved because its machinability is ensured without increasing its hardness and its tensile strength after fracture division can be ensured, a method of making the same and a fracture type crank using the powder forged part. The powder forged part is obtained by forging a sintered preform at high temperature, the sintered preform is formed by subjecting a powder mixture to preliminary compaction and then sintering the compacted preform, the sintered preform has a proportion of free Cu of 10% or less at the beginning of the forging, the forged the composition of the powder part after forging is composed of C: 0.2 to 0.4% by weight, Cu: 3 to 5% by weight and Mn: 0.5% by weight or less (excluding 0), and the remainder iron with unavoidable impurities, and the The powder forged part has a ferrite content of 40 to 90%.
    公开号:SE535027C2
    申请号:SE0900121
    申请日:2007-07-04
    公开日:2012-03-20
    发明作者:Masaaki Sato；Minoru Takada；Kentaro Takada；Zenji Lida；Ryosuke Kogure
    申请人:Kobe Steel Ltd；
    IPC主号:
    专利说明:

    535,027 2 alloying elements such as Ni and Mo (see patent document 2) are shown as another method for increasing the fatigue strength of the machine part. However, the former method increases the number of processes and the latter method uses expensive alloys, which increases the cost of the part and increases the hardness of the part as well as in the method of increasing the content of C. This causes a disadvantage by reducing machinability. In the conventional methods described above, the toughness of a part, for example a connecting rod, decreases with the increase of the hardness, causing the breaking surface of the part to tend to become flat. When the part is manufactured using a fracture splitting method included in the connecting rod or the like, a particular problem is caused by the fact that position change of the part, when assembling the part, is easily generated (i.e. reduction of self-consistency).
    Patent Document 1: Japanese Unexamined Patent Publication No. 61-117203 Patent Document 2: Japanese Unexamined Patent Publication No. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION It is an object of the present invention to provide a powder forged member with improved fatigue strength while ensuring its machinability without increasing its hardness and securing the toughness after fraying. , a method of making the same, and a splitting-type connecting rod using the powder-forged part.
    MEASURES FOR SOLVING THE PROBLEMS In accordance with a first aspect of the present invention, a powder forged detail has excellent machinability and fatigue strength, the powder forged part is obtained by forging a sintered preform at high temperature, the sintered preform is formed by subjecting a powder mixture to preliminary 535 02 3 compaction and then sintering of the compacted preform, the sintered preform has a proportion of free Cu of 10% or less at the beginning of forging, the component composition of the forged powder part after forging is composed of C: 0.2 to 0.4% by weight, Cu: 3 to 5% by weight and Mn: 0.5% by weight or less (excluding 0), and the remainder iron with unavoidable impurities, and the powder forged part has a ferrite content of 40 to 90%. In the powder forged part, relative density relative to theoretical density is preferably 97% or more.
    In the powder forged part, it is preferred that the hardness is HRC 33 or less, and the partially pulsating tensile strength is 325 MPa or more.
    It is preferred that the powder forged part contains at least one machining material in a total amount of 0.5 to 0.6% by weight, the machining material being selected from the group consisting of MnS, MoSg, 8203 and BN. In accordance with a second aspect of the present invention, a fracture split type connecting rod rod is fabricated using the powder forged member of the first aspect.
    According to a third aspect of the present invention, a powder mixture is used as the raw material for the powder forged part according to the first aspect, wherein a component composition in addition to a lubricant is composed of C: 0.1 to 0.5% by weight, Cu : 3 to 5% by weight, Mn: 0.4% by weight or less (excluding 0), 0: 0.3% by weight or less and the remainder iron with unavoidable impurities.
    It is preferred that the powder mixture for powder forging is obtained by adding a grating powder, a copper powder and a lubricant in an iron-based powder composed of C: less than 0.05% by weight, 0: 0.3% by weight or less and the remainder iron with unavoidable contaminants. According to a fourth aspect of the present invention, a powder mixture is used as a raw material for the powder forged part according to the first aspect, wherein a component composition in addition to a Lubricant contains C: 0.1 to 0.5% by weight, Cu: 3 to 5% by weight, Mn: 0.4% by weight or less (excluding 0), 0: 0.3% by weight or less, and also at least one process-enhancing material in a total amount of 0.05 to 0, 6% by weight, and the remainder iron with unavoidable impurities, the processability-improving material is selected from the group consisting of MnS, MoSg, 8203 and BN.
    It is preferred that the powder mixture for powder forging is obtained by adding a grating powder, a copper powder, at least one machinability enhancing material selected from the group consisting of MnS, MoS 2, 5203 and BN, and a lubricant in an iron-based powder composed of C: less than 0 .05 wt%, 0: 0.3 wt% or less and the rest iron with unavoidable impurities.
    According to a fifth aspect of the present invention, a method of manufacturing the powder forged part having excellent machinability and fatigue strength according to the first aspect, the method includes: a compaction and sintering step of subjecting the powder mixture to powder forging according to the third aspect. for preliminary compaction and then sintering the exposed compacted preform to form a sintered preform; and a forging step of forging the sintered preform at a high temperature to form a powder forged part.
    In accordance with a sixth aspect of the present invention, a method of making the powder forged part having excellent machinability and fatigue strength according to the first aspect includes: a compaction and sintering step of subjecting the powder mixture to powder forging according to the fourth aspect of preliminary compacting and then sintering the compacted preform to form a sintered preform; and a forging step of forging the sintered preform at a high temperature to form a powder forged part.
    POWER OF THE INVENTION In the present invention, the content of Cu is increased compared to conventional products, and the content of C in the powder forged part is reduced as compared with conventional products, and the proportion of free Cu is limited in the sintered preform at the beginning of forging. Thereby, since soft ferrite is increased by decreasing the content of C to suppress the increase in hardness, the machinability can be ensured and the toughness can be maintained to guarantee self-strength after fracture division. In addition, since the amount of diffusion of Cu into the inferrite is increased by increasing the content of Cu and limiting the proportion of free Cu for solid solution enhancement, the fatigue strength is also drastically improved.
    Cracks in the powder forged part during forging can be avoided by limiting the proportion of free Cu.
    BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 (a) is a perspective view showing the shape and size of a test detail of a powder forged part used for fatigue testing of examples, and Fig. 1 (b) is a cross-sectional view showing a section taken along the line A-A.
    Fig. 2 is a cross-sectional view showing an applied state of a fracture load on a test portion of a powder forged part in fatigue test.
    Fig. 3 is a diagram showing the relationship between the proportion of free Cu and the fatigue limit.
    Fig. 4 is a cross-sectional view showing the microstructure of a powder forged part.
    DESCRIPTION OF EMBODIMENTS Hereinafter, the present invention will be further described in detail.
    [Composition of powder forged part] First, the reason for limiting the composition of a powder forged part will be described according to the present invention, i.e. the component composition, structure, density and proportion of free Cu in a sintered preform.
    C: 0.2 to 0.4% C is an indispensable element for ensuring the strength of a base steel. Conventionally, the hardness and strength of the base steel have been increased by increasing the content of C to reduce ferrite and increase perlite in the structure of the base steel. In contrast, in the present invention, the content of C is reduced to 0.4% or less in order to suppress the increase in the hardness of the base steel. However, since the strength of the base steel cannot be sufficiently ensured even if the content of Cu is increased when the content of C is greatly reduced, the content of C is set to 0.2% or more. Therefore, the content of C is set to 0.2 to 0.4%.
    Cu: 3 to 5% Cu is an element which dissolves in the ferrite phase in the structure of a base steel on heating during sintering and forging to form a solid solution to exhibit a solid solution-strengthening effect, and is partially precipitated on cooling to increase the strength of the base steel. In the conventional product, Cu is used in an amount of about 2% of the solid solution limit in the iferrite phase near the eutectoid temperature of the Fe-C system. On the other hand, the limit of solid solution for Cu in the austenitic phase is about 8%. 3% Cu or more can be dissolved sufficiently in the base steel to form a solid solution by increasing the heating temperature compared to that of the conventional product and / or extending the heating time. In the present invention, a larger amount of the Cu in the austenitic phase is dissolved to strengthen the solid solution of the ferrite phase generated in a cooling method than in the conventional product. A content of Cu less than 3.0% may not show a sufficient intended solid solution-strengthening effect. On the other hand, if the content of Cu exceeds 5.0%, it causes free Cu to easily remain. Prolongation of heating time, for example extension of sintering time, is required to limit the proportion of free Cu to 10% or less, and consequently productivity is reduced. Therefore, the content of Cu is set to 3 to 5%, and preferably 3 to 4%. 535,027 Mn: 0.5% or less (excluding 0) Mn is an element which has a deoxidizing effect on the base steel and is useful for increasing the hardenability and improving the strength of the base steel. However, Mn has a high affinity for oxygen and reacts with oxygen in the atmosphere in a powder-producing process or in a sintering process of a product subjected to preliminary compaction and causes light oxide. A content of Mn exceeding 0.5% makes it difficult to reduce an Mn oxide and significantly reduces the quality characteristics of the powder forged part such as reduction in density and strength caused by the Mn oxide. Therefore, the content of Mn is set to 0.5% or less (excluding 0), and preferably 0.4% or less (excluding 0). Remaining: iron and unavoidable impurities The powder forged part according to the present invention may contain P, S, Si, O, N and other elements as unavoidable impurities.
    The proportion of free Cu: 10% or less As described above, the content of Cu in the present invention is almost twice the Cu content used to strengthen the solid solution of the ferrite phase in the conventional product and undissolved Cu (ie free Cu) remains readily in the bass steel.
    Therefore, forging cracks can be generated by hot embrittlement during forging. In severe cases, the risk of damage to the sintered preform is increased when handling between a forming sintering process and a forging process. Therefore, in the present invention, the proportion of free Cu in the sintered preform is set to 10% or less at the start of forging. Here, the proportion of free Cu, which means the proportion of undissolved Cu in the base steel, can be quantified by the following method. That is, the cross section of the sintered preform as a detail to be measured is ground from paper a polishing disc and then etched with picric acid. Three positions having an area of 0.2 mm> <0.3 mm are photographed at 400x magnification using an optical microscope, and the total area of areas of copper color is measured by image processing. On the other hand, the total area of copper color areas of a reference material is measured by the same method. As reference material 535 027 8 is used a product obtained by sintering a compacted product compacted in the same component compositions, shape and forming pressure as those of the part to be measured under the condition of 1000 ° C for 20 minutes where Cu is not substantially the base steel. The proportion of free Cu can be calculated using the following formula: The proportion of free Cu (%) A = [total area of areas of Cu color of the part to be measured] / [total area of areas of Cu color of reference material]> <100.
    Ferrite content: 40 to 90% When the powder-forged part has a ferrite content of less than 40%, the powder-forged part has insufficient toughness and insufficient rigidity after fracture division. On the other hand, when the powder-forged part has a ferrite content exceeding 90%, the powder-forged part has excessively high toughness and large elongation, which causes the deformation at the fracture division to impair dimensional accuracy. Therefore, the ferrite content of the powder forged part is set at 40 to 90%.
    Relative density relative to theoretical density: 97% or more When the relative density relative to the theoretical density is less than 97%, the degree of reduction in fatigue strength of the powder forged part becomes large. Therefore, the relative density relative to the theoretical density of the powder forged part is preferably 97% or more. When the relative density is set to 97% or more, the hardness of the powder forged part becomes HRC 33 or less and the partial pulsating tensile strength limit becomes 325 MPa or more. Therefore, a powder forged part is provided which has ensured machinability and excellent fatigue strength.
    Machinability-improving material: Total amount of 0.05 to 0.6% "A machinability-enhancing material can be added during preliminary compaction (ie to a powder mixture for powder forging) to improve the machinability of the powder forged part. As machinability-improving material, for example. a powder composed of MnS, MoSg, 8203 or BN can be used, either individually or in combination with two or more substances, when the amount of the process-enhancing material to be added is less than 0,05% of the On the other hand, when the amount of the machinable material to be added exceeds 0.6%, the area occupied by the iron material is reduced, and non-metals constituting the starting point for fatigue cracks are increased, exhibiting the total amount. a tendency of deterioration in fatigue strength.Therefore, the total amount of processability enhancing materials to be added are preferably 0.05 to 0.6% of the total amount.
    [Component composition of powder mixture for forging] In the following, the reason for limiting the component composition of the powder mixture for forging (hereinafter only referred to as a "powder mixture") will be described.
    C: 0.1 to 0.5% It is necessary to adjust the content of C in the powder mixture taking into account the amount of oxygen in the powder mixture and the type of atmospheric gas during sintering so that the content of C of the powder forged part finally obtained is set to 0.2 to 0.4%.
    That is, when inert gas atmosphere such as Ng gas is used in the sintering process, C is oxidized and consumed by oxygen in the powder mixture and contaminates oxygen in the atmospheric gas. The content of C of the sintered preform (i.e. the powder forged part) is lower than that of the powder mixture. Dawid adjusts the content of C of the powder mixture to more than 0.2% and 0.5% or less, which is higher than that of the powder forged part. On the other hand, when the atmospheric gas has a high carbon potential such as the use of endothermic gas, carbonization caused by the atmospheric gas usually amounts to more than the amount of oxidation consumption of C by oxygen in the powder mixture, and the content of C of the sintered preform the detail) becomes higher than that of the powder mixture. In this case, the content of C in the powder mixture is adjusted to 0.1% or more and less than 535 O2 0.4% which is lower than that of the powder forged part. Therefore, the content of C of the powder mixture can be set in the range of 0.1 to 0.5%, since the change of the content of C is predicted according to the content of oxygen of the powder mixture and the type of atmospheric gas during sintering.
    0: 0.3% or less The variation of the amount of C consumed is also greater when the content of oxygen of the powder mixture is higher, and it becomes difficult to set the content of C of the powder forged part to the target of 0.2 to 0.4. %. Thereby, the content of oxygen in the powder mixture is set to 0.3% or less.
    Other components Cu, Mn and the process-enhancing material are not consumed or produced by sintering as in C. The content of each of the components in the powder mixture is fi nied as the same as the content of each of the components in the powder forged part (even if the value of the content of each of the components changes extremely little by increasing and decreasing the amount of C during sintering in the same way, the value is within an ignoreable range).
    [Method for producing powder forged details] Next, a method for producing the powder forged part that meets the composition above will be described.
    First, the change in the content of C during sintering is predicted according to the content of oxygen in an iron-based powder and the type of atmospheric gas during sintering. A graphite powder in which the content of C of the powder mixture is in the range of 0.1 to 0.5% so that the content of C after sintering is set to 0.2 to 0.4%, a copper powder in which the content of Cu is 3 to 5%. %, and the processability-enhancing material of the total amount of 0.05 to 0.6% is added, if necessary, in an iron-based powder. A suitable amount of a lubricant is further added thereto to produce a powder mixture. This powder mixture is subjected to preliminary compaction by a pressure compaction machine to produce a compacted preform.
    When the iron-based powder used in the production of the powder mixture shows less compressibility, the density of the compacted preform is hardly increased during preliminary compaction. The inside of the sintered preform is oxidized during high temperature transport to the forging process after sintering, and a phenomenon in which the strength of the sintered preform is reduced by an oxide film occurs even if the sintered preform is forged. Therefore, in order to soften the iron-based powder and increase the density of the compacted preform to avoid internal oxidation of the compacted preform, the content of C of the iron-based powder is set to less than 0.05%, preferably 0.04% or less. , and more preferably 0.02% or less.
    This compacted preform is then sintered at a high temperature to produce a sintered preform. Here, referring to the sintering condition, higher temperature and longer time are preferred because the diffusion of Cu continues and the amount of free Cu decreases as the temperature becomes higher or the time longer.
    However, when the content of Cu is, for example, 4%, the proportion of free Cu can be set to 10% or less by sintering the preform at 1190 ° C or more for 10 minutes.
    This sintered preform is immediately forged with a predetermined forging pressure at a high temperature without cooling the sintered preform to obtain a powder forged part. Higher forging pressure is preferred because the density of the forged part becomes higher and the strength is increased because the forging pressure is higher.
    However, when a connecting rod having a shape and size shown in, for example, Fig. 1 is formed, the relative density relative to the theoretical density can be set to 97% or more by forging the preform at a pressure of 6.0 tons / cmz or more, resulting in the powder forged part exhibiting excellent machinability and fatigue strength. Although the example describes immediate forging of the preform using the temperature after sintering in the producing method, the preform can be cooled after it has been sintered and reheated to forge. In this case, the preform is heated twice during sintering and forging and the heating time will inevitably be longer. Therefore, even when the heating temperature is a temperature (about 1050 ° C to about 1120 ° C) further lower than the lower temperature limit (1190 ° C), the proportion of free Cu can be set to 10% or less.
    A crankcase-type connecting rod produced by using this forged part has reduced tool wear during machining and suppresses the cost increase of parts and has excellent fatigue strength and intrinsic strength when assembled after fracture division.
    Example 1 (Effect of the proportion of free Cu) A briar powder and a copper powder were added in a pure iron-based powder having a component composition shown in Table 1 so that the contents of C and Cu after sintering were 0.3% and 4%, respectively. 0.75% zinc stearate was further added as a lubricant and they were mixed for 30 minutes to produce a powder mixture. The powder mixture was subjected to preliminary compaction with a compaction expression of 6 tons / cm 2 to produce a compacted preform.
    [Table 1] Components C Mn PS Si ON Content (wt%) 0.001 0.19 0.01 0.009 0.01 0.12 0.004 This compacted preform was dewaxed at 600 ° C for 10 minutes in N 2 gas atmosphere and filtered then at various temperatures of 1110 to 1260 ° C for 10 minutes to produce a plurality of sintered preforms. The proportion of free Cu of each of some sintered preforms was measured using the method described in the above-mentioned [owder forging composition]. The remaining sintered preforms were immediately forged at a forging pressure of 10 tons / cm 2 to produce test details of powder forged parts imitating the shape of a connecting rod. Beards on each of the test details were removed, and the surface shell was removed by blasting or the like to provide test details for a pulsating tensile fatigue test. F ig. 1 shows the shape and size of each of the test details used for the fatigue test. Fig. 2 shows an applied condition of a tensile load on each of the test details in the fatigue test.
    Table 2 and fi g. 3 shows measurements and test results. Which is obvious from Table 2 and fi g. 3 when the sintering temperature is higher, the proportion of free Cu decreases and the fatigue limit increases. When the sintering time is 10 minutes, the proportion of free Cu is 10% or less at the temperature of 1190 ° C or more, and the fatigue limit of 325 MPa or more is reached. Fig. 4 shows comparatively cross-sectional microstructures of a reference material having a free Cu proportion of 100%, a comparative material having a proportion of 15% and a material of 3% according to the invention. lfig. 4 has parts to which "net hatching" is applied existing free Cu.
    [Table 2] Test- Sintering- Rate Fatigue- Note detail temperature of free Cu limit no (° C) (%) (MPa) 101 1 1 10 82 245 102 1 140 56 275 Comparative 103 1170 43 294 examples 104 1 180 19 324 105 1190 9.8 353 Inventing 106 1200 4.6 353 according to 107 1230 2.1 363 Example 108 1260 1, 4 373 In the exemplary invention, the ferrite content of the powder forged part was approximately 70% at each sintering temperature.
    Example 2 (Effect of the contents of C and Cu) A briar powder and a copper powder were added in a pure iron-based powder having the same component composition as in Example 1 shown in Table 1 with varying amounts of added briar powder and copper powder so that the content of C and Cu after forging were 0.1 to 0.6% and 2 to 5%, respectively, to produce a powder mixture. The powder mixture was subjected to preliminary compaction under the same conditions as that described in Example 1 above to form a compacted preform. This compacted preform was dewaxed at 600 ° C for 10 minutes under N 2 gas atmosphere and then sintered at 1120 ° C for 30 minutes under N 2 gas atmosphere to produce sintered preforms. The sintered preforms were heated at 1050 ° C for 30 minutes under an N 2 gas atmosphere and then forged at a forging pressure of 10 tons / cm 2 to produce test details of powder forged parts mimicking the shape of the same connecting rod as described in Example 1 above.
    These test details were subjected to a tensile fatigue test under the same conditions as those in Example 1 described above, and the HRC hardness of each of the surfaces of the test details was measured after machining.
    Furthermore, the following test was performed in order to quantify the intrinsic strength after fracture division. That is, a disc-shaped test part of a powder-forged part having a diameter of 90 mm> <a thickness of 40 mm was produced under the same conditions as in the description above. This was machined to produce an annular test piece having an outer diameter of 80 mm, an inner diameter of 40 mm> <a thickness of 20 mm and having a V-notch having a depth of 1 mm and an angle of 45 degrees at a diagonal line on the inner ring. This test detail was subjected to tensile fracture in the deep direction and perpendicular direction of the groove. An actual area including micro-irregularities on the fracture surface was measured using an optical three-dimensional measuring device (produced by GFMesstchnik Company, type: MicroCAD 3> <4), and a proportion relative to a flat projection surface ignoring the irregularity (referred to as an "area proportion in fracture division"). Furthermore, the presence or absence of displacement of the intervening position of the fracture surface after fracture division was visually examined.
    Table 3 shows the test results. The proportion of free Cu in each of the test details before forging (at the start of forging) exceeds 10% in test piece no. 222 which has the content of Cu exceeding 5%. However, the proportion was 10% or less in the other test details. 535 027 1 5 [Table 3] Test- Chemical Hardness Fatigue- Ferrite- Fracture- Self-strength Note detail detail- (HRC) percentage of partition- no setting limit (%) area- (weight%) (MPa) proportion C Cu (-) 201 0.10 2.0 11.7 200 97 1.54 xdeformation caused 202 0.10 2.5 12.8 209 97 1.53 x fiformation caused 203 0.10 3.0 14.0 218 97 1 , 56 x: deformation caused 204 0.10 3.5 15.2 227 96 1.55 xïdeformation caused 236 o, 1o 4.0 16.4 236 96 1.54 xnefermanen fäåwáe caused example 206 0.10 4.5 17 , 5 245 97 1.52 xdeformation caused 207 0.10 5.0 18.7 255 98 1.51 xxieformation caused 208 0.20 2.0 16.2 235 83.6 1.54 x: deformation caused 209 0, 20 2.5 17.4 244 84.1 1.53 xzdeformation caused 210 0.20 3.0 18.5 307 84.6 1.51 O Upp fi n- 211 0.20 3.5 19.7 316 85.1 1.50 O nings- 212 0.20 4.0 20.9 325 85.6 1.49 O according to 213 0.20 4.5 22.1 334 36.1 1.43 o Example 214 0.20 5, 0 23.2 341 86.6 1.46 O 215 0.30 2.0 20.7 270 66.9 1.46 O Jam- 216 0.30 2.5 21.9 280 67.4 1.45 O leading example 217 0.30 3.0 23.1 340 67.9 1.47 O Upp fi n- 218 0.30 3.5 24.3 346 68.4 1.45 O nings- 219 0.30 4.0 25.4 352 68.9 1.44 O according to 22o 0.30 4.5 26.6 357 69.4 1.43 o Example 221 0.30 5.0 27.8 360 69.9 1.42 O 222 0.30 6.0 28.0 306 70.1 Not measured Not measured Jam- 223 0.40 2.0 25.3 315 50.2 1.44 O leading 224 o, 4o 2.5 26.4 360 50.7 1.43 o Example 225 0.40 3.0 27.6 363 51.2 1, 42 O Upp fi n- 226 0.40 3, 5 28.8 365 51.7 1.41 O nings- 227 0.40 4.0 30.0 366 52.2 1.39 O according to 223 o, 4o 4.5 31.1 367 52.7 1.33 o Example 229 0.40 5.0 32.3 322 53.2 1.37 O 230 0.50 2.0 29.8 343 33.5 1.40 O 231 0 .50 2.5 32.5 347 34 1.37 O 232 0.50 3.0 33.1 349 34.5 1.36 x Displacement caused 233 0.50 3.5 33.3 358 35 1.36 x Displacement caused 234 0, 50 4.0 34.5 367 35.5 1.35 x displacement caused 235 0.50 4.5 35.7 376 36 1.34 x fi displacement Jám_ caused driving 236 0.50 5.0 36.8 357 36 , 5 1.32 x offset example caused 535 02 16 237 0.60 2.0 34.3 366 16.8 1.35> <: offset caused 238 0.60 2.5 35.5 375 17.3 1.34 xz offset caused 239 0.60 3.0 36 .7 384 17.8 1.32 xz displacement caused 240 0.60 3.5 37.8 394 18.3 1.31 x fi displacement caused 241 0.60 4.0 39.0 403 18.8 1.30 xz displacement caused 242 0.60 4.5 40.2 412 19.3 1.29 x displacement caused 243 0.60 5.0 41.4 200 19.8 1.28 x displacement caused As shown in Table 3, the following is confirmed. Each of the inventive examples in which the levels of C and Cu, the ferrite content and the proportion of free Cu were within the range defined in the present invention, which had hardness of HRC 33 or less, had no problems in processability. Each of the inventive examples had a fatigue limit of 300 MPa or more, specifically 325 MPa or more, in addition to some of the inventive examples (Test Details Nos. 210, 211). In the inventive examples, no displacement was observed in the fracture surface after fracture division and they had no problems in self-strength.
    The examples according to the invention simultaneously met machinability, fatigue strength and intrinsic strength after fracture division. On the other hand, in comparative examples in which the component composition and / or the ferrite content fall outside the range as they are denoted in the present invention, comparative examples which have hardness of HRC 33 or less, which have fatigue limits up to 300 MPa in addition to certain comparative examples (test details no. 230, 231) and causes deformation due to elongation in fracture division to reduced dimensional accuracy (test details Nos. 201 to 209). On the other hand, comparative examples having a fatigue limit of 300 MPa or more, the comparative examples having hardness exceeding HRC 33 have impaired machinability, causing intervening positional displacement of the fracture surface to cause a problem of intrinsic strength. Therefore, it has been found that it is very difficult to simultaneously obtain a powder-melted part which satisfies machinability, fatigue strength and intrinsic strength after fracture division. 535 02 As shown in Table 3, the surface ratio in fracture division can be used as an index to represent strength. When the fracture splitting area ratio is less than 1.37, the intervened displacement of the fracture splitting surface is easily caused. On the other hand, when the fracture pitch surface ratio exceeds 1.51, it has been found that deformation caused by the elongation becomes noticeable and the dimensional accuracy deteriorates.
    Example 3 (Effect on relative density) Next, test parts were produced from powder forged parts having the same component composition (C: 0.3%, Cu: 3.5%) as that of test part No. 218 of Example 2 under the same conditions as that of Example 2. except that only one forging pressure was changed varying in the range of 2.5 to 10 tons / cm 2. the effect of the relative density of the powder forged part exerted on the fatigue limit was investigated. While the fatigue limit was measured, the HRB hardness of each of the test details was also measured. Table 4 shows the test results.
    [Table 4] Test- Forging- Relative Hardness Fatigue detail Pressure density (HRB) Limit No. (ron / cmz) (%) (MPa) 218 10 99 105.0 346 301 7.5 98 100.0 338 302 9, 5 99 101.5 340 303 6.0 97 97.0 329 304 4.0 95 91.5 316 305 3.5 94 86.5 299 306 2.5 93 80.0 286 As shown in Table 4 above, it is confirmed that the fatigue limit of 325 MPa or more could be ensured when the relative density relative to the theoretical density was 97% or more. Example 4 (Influence of machinability-improving materials) Next, test parts were produced from powder-forged parts having the same component composition (C: 0.3%, Cu: 3.5%) as that of test part No. 218 of Example 2 as in Example 2. 3 was produced in the same manner as in Example 2 except that various processability enhancing materials were added with the amount of additive changed. Impacts on processability were investigated. Referring to machinability, an impact force was measured when a hole was formed from the surface of the test part at a number of rotations of 200 rpm and a cutting speed of 0.12 mm / revolution using a SKH drill having a diameter of 5 mm. This was used as an index for machinability. Table 5 shows the test results.
    As can be seen in Table 5, the impact force is reduced by increasing the amount of additive of the machinability-enhancing material to improve machinability. However, when the amount of additive of the processability-improving material exceeds 0.6%, the large reduction trend of the fatigue limit is also observed in all processability-improving agents.
    [Table 5] Test- Processing Improvement Shock force Hardness Fatigue detail material (N) (HRC) nings- no. Type Added limit amount (MP8) (% by weight) 218 - 0.0 770 24.3 346 401 0.2 765 24 .8 351 402 MnS 0.4 755 25.2 350 403 0.6 750 26.2 335 404 0.8 750 26.5 306 405 MoSz 0.8 750 25.5 308 406 0.6 750 25.8 338 407 B20; 0.6 739 24.3 334 408 0.8 744 25.4 299 409 BN 0.6 746 24.9 336 410 0.8 749 26.3 316 535 027 19 Example 5 (Effect of oxygen content of powder mixture) Next For example, the oxygen content of a powder mixture was changed by using an iron-based powder having different levels of oxygen, and test details of powder-forged parts were produced under the same conditions as in that described in Embodiment Example 1 above. The levels of C and Cu of the powder mixture after forging were set to 0.3% and 4% respectively as targets, and the addition of briar powder was set to 0.3% + (content of oxygen of iron-based powder - 0.05%) x 3 / 4 to adjust the content of C. Referring to this test detail, the content of C and the fatigue limit were measured, and the effect of the oxygen content of the powder mixture thereon was examined.
    Table 6 shows the results. As shown in Table 6, when the oxygen content of the iron-based powder (ie, the powder mixture) was 0.3% or less (Test Details Nos. 501 to 503), the C content of the powder-forged part was an approximate target content of C. However, , when the oxygen content of the iron-based powder (ie the powder mixture) exceeded 0.3% (test part No. 504), it was found that the content of C of the powder-forged part was significantly shifted from the target content of C and fell outside the approximate range (0 , 2 to 0.4%) of the content of C de ier denied in the present invention to drastically reduce the fatigue strength.
    [Table 6] Test- Chemical composition of Powder forging detail Note detail Iron-based powder (% by weight) Component- Fatigue- no composition (weight%) limit C Mn PS Si OC Cu (MPa 501 0.001 0.19 0.01 0.009 0.01 0.012 0.31 4.00 352 Invention 502 0.001 0.18 0.01 0.009 0.01 0.020 0.29 4.05 353 according to 503 0.001 0.18 0.01 0.009 0.01 0.030 0, 4.00 351 êXeml-ïel 504 0.001 0.19 0.01 0.009 0.01 0.040 0.15 3.95 267 Comparative Example 535 027 Example 6 (Effect of the content of C in iron-based powder) Next, an iron-based powder was used. powders having different levels of C, and a powder mixture having the same component composition were produced by adjusting the addition amount of bead powder.Compacted preforms and test details of powder forged parts were produced under the same conditions as in Embodiment 1 described above.The levels of C and Cu after forging were respectively set at 0.3% and 4% as targets.The densities of the compacted preforms and powder forging the details were measured as well as the fatigue limit of the powder forged part.
    Table 7 shows the test results. As can be seen from Table 7, the decreasing trend of the density of the compacted preform is shown with the increase of the content of C of the iron-based powder. When the content of C of the iron-based powder is 0.05% (test part No. 604), it was found that the fatigue strength is drastically reduced even if the density of the powder-forged part after forging is almost the same as the cases where the content of C is less than 0.05 % (Test Details Nos. 601 to 603).
    [Table 71 Test- Component composition of Compact- Powder forging Note detail iron-based powder (wt%) terated detail no. .19 0.01 0.009 0.01 0.12 7.05 7.83 353 Invent- 602 0.005 0.18 0.01 0.008 0.01 0.12 6.90 7.83 352 nings- 603 0.02 0 .19 0.01 0.009 0.01 0.13 6.60 7.81 335 according to example 604 0.05 0.20 0.01 0.009 0.01 0.12 6.30 7.79 279 Comparative example
    权利要求:
    Claims (11)
    [1] 1. l. Zäpowderforgedmemberhavingexcellentnmchinabilityand fatigue strength, the powder forged member obtained by forging a sinteredpreform at a high temperature, the sintered preform.formed bysubjecting a powder mixture to preliminary compacting andthereafter sintering the subjected compacted preform, the sintered preform having a ratio of free Cu of 10% orless upon the start of the forging, thecomponentcompositionofthepowderforgedmemberafterthe forging composed of, C: 0.2 to 0.4% by mass, Cu: 3 to 5%by mass, Mn: 0.5% by mass or less (excluding O) , and the balanceiron with inevitable impurities, and the powder forged.member having a ferrite ratio of 40 to
    [2] 2. The powder forged member having excellentmachinabilityandfatiguestrengthaccordingtoclahnl,wherein a relative density to theoretical density is 97% or more.
    [3] 3. The powder forged member having excellentmachinabilityandfatiguestrengthaccordingtoclahn2,whereina hardness is HRC 33 or less, and a partial pulsating tensile fatigue limit is 325 MPa or more. 32
    [4] 4. The powder forged member having excellentmachinabilityandfatiguestrengthaccordingtoanyoneofclaims1 to 3, wherein the powder forged member contains at least onemachinability-improving material in a total amount of 0.05 toO.6%bymass,themachinability-improvingmaterialselectedfrom the group consisting of MnS, MoS2, Bfih and BN.
    [5] 5. Afracturesplittypeconnectingrodproducedbyusingthe powder forged member according to any one of claims l to 4.
    [6] 6. A powder mixtureused as a raw material for a powderforged member according to any one of claims 1 to 3, whereina component composition except a lubricant is composed of, C:0.1 to O.5% by mass, Cu: 3 to 5% by mass, Mn: O.4% by mass orless (excludingífl, O: 0.3%kn/masscnïless andifluabalance iron with inevitable impurities.
    [7] 7. The powder mixture for powder forging according toclaim 6, wherein the powder mixture is obtained by adding agraphite powder, a copper powder and a lubricant into aniron-based powder composed of, C: less than 0.05% by mass, O:O.3% by mass or less and the balance iron with inevitable impurities. 33
    [8] 8. A powder mixture for powder forging used as a rawmaterialforapmwderforgedmemberaccordingtoclamn4,whereina component composition except a lubricant contains, C: 0.1 to0.5%bymass,Cu:3to5%bymass,Mn:0.4%bymassorless(excluding0), O: 0.3% by mass or less, and at least onemachinability-improving material in a total amount of 0.05 to0.6% bylnass, and the balance iron with inevitable impurities,the machinability-improving material selected from the group consisting of MnS, MOS2 and B2O3 and BN.
    [9] 9. The powder mixture for powder forging according toclaim 8, wherein the powder mixture is obtained by adding agraphite powder, a copper powder, at least onemachinability-improving material selected from the groupconsisting of MnS, MoS2, BAL and BN, and a lubricant into aniron-based powder composed of, C: less than 0.05%% by mass orless, O: 0.3%% bylnass or less or less and the balance iron with inevitable impurities.
    [10] 10. . A method for producing a powder forged member havingexcellent machinability and fatigue strength according to anyone of claims l to 3, the method comprising: a compacting and sintering step of subjecting a powdermixtureforpowderforgingaccordingtoclahn6or7topreliminary compacting and thereafter sintering the subjected compacted 34 preform to form a sintered perform; anda forging step of forging the sintered preform at a high temperature to form a powder forged member.
    [11] 11. ll . A method for producing a powder forged member havingexcellent machinability and fatigue strength according to claim4, the method comprising: a compacting and sintering step of subjecting a powdermixture for powder forging according to claim7 or 8 to preliminarycompacting and thereafter sintering the subjected compactedpreform to form a sintered perform; and a forging step of forging the sintered preform at a high temperature to form a powder forged member.
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    同族专利:
    公开号 | 公开日
    CN101506401B|2011-05-18|
    WO2008004585A1|2008-01-10|
    KR101186445B1|2012-09-27|
    CA2658051C|2018-07-17|
    KR20090034373A|2009-04-07|
    JP2008013818A|2008-01-24|
    JP4902280B2|2012-03-21|
    US20130192414A1|2013-08-01|
    CN101506401A|2009-08-12|
    US20090311122A1|2009-12-17|
    CA2658051A1|2008-01-10|
    SE0900121L|2009-02-03|
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    法律状态:
    2021-03-02| NUG| Patent has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    JP2006186927A|JP4902280B2|2006-07-06|2006-07-06|Powder forged member, mixed powder for powder forging, method for producing powder forged member, and fracture split type connecting rod using the same|
    PCT/JP2007/063377|WO2008004585A1|2006-07-06|2007-07-04|Member produced by powder forging, powder mixture for powder forging, process for producing member by powder forging, and fracture splitting connecting rod obtained from the same|
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