JP4188970B2 - Cam lobe material, camshaft using the same, and method of manufacturing cam lobe material - Google Patents

Description

  The present invention relates to a cam lobe material used in an internal combustion engine, a camshaft using the cam lobe material, and a cam lobe material manufacturing method.

  As a camshaft of a valve operating apparatus used in an internal combustion engine (engine), an assembly type camshaft having a cam lobe on the shaft is known. The cam lobe provided in this camshaft is divided into a cam follower (roller follower) that makes rolling contact and a cam follower (slipper follower) that makes sliding contact (sliding contact). For example, see Patent Document 1).

  In such an internal combustion engine, parts such as a camshaft and a rocker arm slide at high speed during operation, and thus sliding characteristics are required. In particular, the cam lobe that uses the roller follower that is in rolling contact as described above has a small contact area with the roller follower and has excellent sliding properties such as wear resistance, pitting resistance, and scuffing resistance on the outer peripheral surface thereof. Is required.

  For this reason, a camshaft having a chill cam in which a hard white cast iron structure is formed on the surface portion of the cam nose by rapidly solidifying the cam nose portion with a cooling metal during casting has been used. Since this chill cam shaft has a hard chill structure on the outer peripheral surface, it has excellent wear resistance and scuffing resistance.

On the other hand, in the assembly type camshaft, a technology is known that improves the density of the cam piece by warm forming the cam piece and solves the problem that the cam piece breaks during the diameter expansion process of the shaft (for example, Patent Document 2).
: JP-A-2001-240948 : JP 2003-14085 A

  However, the chill cam shaft has a problem that it has poor pitting resistance. For this reason, the chill camshaft has a problem that it is difficult to use for a high load engine.

  In addition, there is a limit to improving the density of the cam piece by warm forming, and there is a problem that it is difficult to use for an engine with a high load, like the chill cam shaft.

  Accordingly, the present invention solves these problems, has excellent sliding characteristics such as wear resistance, pitting resistance and scuffing resistance, and is a cam lobe material that can be suitably used for a high-load engine, and a cam using the same It is an object of the present invention to provide a method for manufacturing a shaft and a cam lobe material.

The cam lobe material of the present invention that solves the above problems is Ni: 0.3-5.0 mass%, C: 0.5-1.2 mass%, and at least one of B and P: 0.02-0.3. The mass% and the balance are made of an iron-based sintered alloy containing inevitable impurities, the outer peripheral surface hardness is HRC50 or more, and the density is 7.5 g / cm ³ or more.

  According to this invention, since the cam lobe material is produced from the iron-based alloy having a specific component composition, a cam lobe material having high hardness and high density can be provided. In particular, when at least one of B and P is contained, a liquid phase is generated during sintering, and the density of the manufactured cam lobe material can be increased. As a result, the cam lobe material of the present invention has excellent sliding characteristics such as wear resistance, scuffing resistance, and pitting resistance. Therefore, it is possible to provide a cam lobe that can be suitably used for an engine with a high load, for example, an engine with a surface pressure about twice that of a normal engine.

  In the cam lobe material of the present invention, the iron-based sintered alloy further contains Mo: 2.5% by mass or less. According to this invention, in addition to the above-mentioned action, a cam lobe material is obtained in which the hardenability of the sintered cam lobe material is enhanced and the solid solution effect of the iron alloy base is promoted.

  In the cam lobe material of the present invention, the cam lobe material has a roller follower as a counterpart material. According to this invention, since the cam lobe material has improved repeated contact fatigue strength due to its toughness and hardness, it is a counterpart material for a roller follower that requires repeated contact fatigue strength typified by pitting resistance. Can be suitably used.

  The camshaft of the present invention that solves the above-described problems is characterized by including a cam lobe made of the cam lobe material of the present invention. According to the present invention, it is possible to provide a camshaft that is excellent in sliding characteristics such as wear resistance, scuffing resistance, and pitting resistance, and that can be suitably used for a high-load engine.

  Furthermore, a cam lobe material manufacturing method for solving the above-described problems is the cam lobe material manufacturing method according to the present invention, wherein an iron-based alloy powder prepared to have the composition of the iron-based sintered alloy is added to a predetermined cam lobe material. A compression molding step for compression molding into a shape and a sintering step for sintering the compression molded body are repeated twice or more, and the sintered sintered body is quenched and tempered. .

According to the present invention, the dimensional accuracy before and after the last sintering step is high, and it is not necessary to cut after the cam lobe manufacturing or the cutting amount is small. Therefore, the labor and cost for manufacturing the cam lobe can be reduced. Furthermore, the outer peripheral surface hardness of the cam lobe after manufacture can be set to HRC50 or more, and the density can be set to 7.5 g / cm ³ or more. Therefore, the cam lobe material after manufacture can have high hardness and high density, and can have excellent sliding characteristics such as wear resistance, scuffing resistance, and pitting resistance. Therefore, it is possible to provide a cam lobe that can be suitably used even for an engine with a high load, for example, an engine with a surface pressure about twice that of a normally used engine.

  The manufacturing method of the cam lobe material of the present invention is characterized in that shot blasting is performed on the outer peripheral surface of the cam lobe material. According to the present invention, the shot blasting can improve the pitting resistance of the cam lobe material.

  As described above, according to the cam lobe material of the present invention, since it is manufactured from an iron-based alloy having a specific component composition, it is possible to provide a cam lobe material having high hardness and high density. In particular, when at least one of B and P is contained, a liquid phase is generated during sintering, and the density of the manufactured cam lobe material can be increased. As a result, the cam lobe material of the present invention has excellent sliding characteristics such as wear resistance, scuffing resistance, and pitting resistance. Therefore, it is possible to provide a cam lobe that can be suitably used for an engine with a high load, for example, an engine with a surface pressure about twice that of a normal engine. The cam lobe material of the present invention is suitably used as a counterpart material for a roller type cam follower.

Further, according to the method of manufacturing the cam lobe material of the present invention, the dimensional accuracy before and after the final sintering step is high, and it is not necessary to cut after the cam lobe material is manufactured, or the cutting amount is small. Therefore, it is possible to reduce labor and cost for manufacturing the cam lobe material. Furthermore, the outer peripheral surface hardness of the cam lobe material after manufacture can be set to HRC 50 or more, and the density can be set to 7.5 g / cm ³ or more. Therefore, the cam lobe material after production can have high hardness and high density, and has excellent sliding characteristics such as wear resistance, scuffing resistance, and pitting resistance. Therefore, it is possible to provide a cam lobe that can be suitably used for an engine with a high load, for example, an engine with a surface pressure about twice that of a normal engine.

FIG. 1 is a perspective view showing an embodiment of a valve operating apparatus for an internal combustion engine provided with a cam lobe material of the present invention and a plan view of a camshaft of the present invention.
FIG. 2 is a schematic view of a two-cylinder contact tester used for evaluation of examples of the present invention.
FIG. 3 is a graph showing the density of a cam lobe material with respect to the Ni (nickel) content for an example of the present invention.
FIG. 4 is a graph showing the hardness of the cam lobe material with respect to the Ni content in Examples of the present invention.
FIG. 5 is a graph showing the number of occurrences of pitching of the cam lobe material with respect to the Ni content in Examples of the present invention.
FIG. 6 is a graph showing the dimensional change rate of the cam lobe material with respect to the Ni content in Examples of the present invention.
FIG. 7 is a graph showing the cam lift error of the cam lobe material with respect to the Ni content in the example of the present invention.
FIG. 8 is a graph showing the density of the cam lobe material with respect to the C (carbon) content in Examples of the present invention.
FIG. 9 is a graph showing the hardness of the cam lobe material with respect to the C content in Examples of the present invention.
FIG. 10 is a graph showing the density of the cam lobe material relative to the P (phosphorus) content for the examples of the present invention.
FIG. 11 is a graph showing the hardness of the cam lobe material with respect to the P content in Examples of the present invention.
FIG. 12 is a graph showing the number of occurrences of pitching of the cam lobe material with respect to the P content in Examples of the present invention.
FIG. 13 is a graph showing the density of a cam lobe material with respect to B (boron) content in an example of the present invention.
FIG. 14 is a graph showing the hardness of the cam lobe material with respect to the B content in Examples of the present invention.
FIG. 15 is a graph showing the density of a cam lobe material with respect to the Mo (molybdenum) content for an example of the present invention.
FIG. 16 is a graph showing the hardness of the cam lobe material with respect to the Mo content in Examples of the present invention.

Explanation of symbols

1 Cam lobe material (for rotating contact)
2 Camshaft 3 Roller follower (cam follower for rotating contact)
4 Valve operating device for internal combustion engine 5 Cam lobe material (for sliding contact)
6 Slipper follower (cam follower for sliding contact)
7 Shaft 8 Cam lobe test piece 9 Cylindrical test piece 10 Lubricating oil 11 Load

  The cam lobe material, cam shaft, and cam lobe material manufacturing method of the present invention will be described below.

The cam lobe material of the present invention has Ni: 0.3-5.0% by mass, C: 0.5-1.2% by mass, at least one of B and P: 0.02-0.3% by mass, and the balance It is made of an iron-based sintered alloy containing inevitable impurities, has an outer peripheral surface hardness HRC of 50 or more, and a density of 7.5 g / cm ³ or more. The iron-based sintered alloy may further contain Mo: 2.5% by mass or less.

  First, the iron-based sintered alloy will be described.

  Ni (nickel) has an effect of increasing strength and toughness. The Ni content is 0.3-5.0% by mass. If Ni is less than 0.3% by mass, sufficient strength and toughness cannot be obtained. On the other hand, if Ni exceeds 5.0% by mass, the amount of dimensional change during sintering increases, resulting in poor accuracy. Ni is preferably contained in an amount of 1.0 to 3.0% by mass.

  C (carbon) has an effect of obtaining a cam outer peripheral surface hardness that satisfies wear resistance. The C content is 0.5-1.2% by mass. When C is less than 0.5% by mass, it is difficult to obtain a desired cam outer peripheral surface hardness after quenching and tempering treatment, and wear resistance is poor. On the other hand, when C exceeds 1.2% by mass, the compressibility is remarkably lowered and the density is not increased. C is preferably contained in an amount of 0.8 to 1.0% by mass.

  B (boron) and P (phosphorus) have the effect of promoting sintering by producing a low-melting ternary eutectic liquid phase with Fe (iron) and C. At least one of B and P is included in the iron-based sintered alloy used for the cam lobe material of the present invention. The content of at least one of B and P is 0.02-0.3% by mass. When at least one of B and P is less than 0.02% by mass, the above-described action is small, and the density and hardness described later may not be obtained. On the other hand, if at least one of B and P exceeds 0.3% by mass, the amount of shrinkage during sintering increases, and the dimensional accuracy of the cam lobe material deteriorates. At least one of B and P is preferably contained in an amount of 0.05-0.20% by mass. In addition, when both B and P are contained, the content ratio of B and P is not particularly limited, but is usually about B: P = 2: 1-1: 2.

  Mo (molybdenum) added arbitrarily has the effect of enhancing the hardenability and promoting the solid solution effect of the iron-based alloy base. The Mo content is 2.5% by mass or less. The effect is obtained little by little from the content of about 0.05% by mass of Mo, but if Mo exceeds 2.5% by mass, the compressibility is remarkably deteriorated and the density is not increased. Mo is preferably contained in an amount of about 0.2 to 1.5% by mass or less.

  The remaining inevitable impurities include not only a trace amount of impurities mixed in the raw material powder, but also residues of lubricants such as zinc stearate added to the sintering powder and other additive components.

  Next, the physical properties of the cam lobe material using the iron-based sintered alloy will be described.

  The outer peripheral surface hardness of the cam lobe material is HRC50 or more. If it is less than HRC50, the wear resistance cannot be satisfied. The upper limit of the outer peripheral surface hardness of the cam lobe material is not particularly limited, but is usually about HRC60. The outer peripheral surface hardness is preferably HRC50-55. Here, the outer peripheral surface of the cam lobe material refers to a surface that slides with the cam follower when used as a cam shaft as a cam lobe.

The density of the cam lobe material is 7.5 g / cm ³ or more. If the density is less than 7.5 g / cm ³ , the strength of the cam lobe material is lowered and the pitting resistance is deteriorated, so that the engine cannot be used for a heavy load engine. The upper limit of the density of the cam lobe material is not particularly limited, but is usually about 7.7 g / cm ³ . The density is preferably 7.5-7.6 g / cm ³ .

  As described above, since the cam lobe material of the present invention has a high density and high hardness, it has high pitting resistance in contact with the cam follower. For this reason, the cam lobe made of the cam lobe material of the present invention can be suitably used for an engine with a high load. Furthermore, the cam lobe material of the present invention is excellent in wear resistance and scuffing resistance and has excellent sliding characteristics.

  Further, the cam lobe material of the present invention is suitably used as a counterpart material for a roller type cam follower (roller follower). Here, FIG. 1A shows a valve operating apparatus for an internal combustion engine showing a mode in which a camshaft 2 provided with a cam lobe 1 of the present invention and a roller follower (rolling contact type cam follower) 3 are in contact with each other. 4 is a perspective view. A cam lobe 5 and a slipper follower (sliding contact type cam follower) 6 provided on the camshaft 2 are shown on the front side of FIG.

  Examples of the roller follower 3 include a roller tappet and a roller rocker arm. In such a roller follower 3 and the cam lobe material 1 as the counterpart material, repeated contact fatigue strength typified by pitting resistance is required. In the present invention, a liquid phase is generated by the B or / and P component during the sintering of the cam lobe material, thereby densifying the cam lobe material and improving the density. Thus, the toughness and hardness of the cam lobe material are improved, and the repeated contact fatigue strength is improved. Therefore, the cam lobe material of the present invention can be suitably used as a counterpart material for a roller follower.

  In addition, the cam shaft 2 as shown to FIG. 1 (a) and FIG.1 (b) can be provided by using the cam lobe material of the above-mentioned this invention. The mode and manufacturing method of the camshaft 2 will be described later.

  Next, a method for producing the cam lobe material of the present invention will be described. This manufacturing method is for the cam lobe material of the present invention described above.

  The manufacturing method of the cam lobe material of the present invention uses an iron-based alloy powder blended and prepared so as to become an iron-based sintered alloy having the above composition, and repeats the compression molding step and the sintering step twice or more, and quenching and tempering The processing is performed. Furthermore, shot blasting can be performed on the outer peripheral surface of the cam lobe material.

  The composition, blending ratio, action, etc. of the elements added to the iron-based alloy powder are the same as those in the description of the cam lobe material. After sintering, an iron-based alloy powder is blended and prepared so that the composition ratio is within the above range.

  A compression molding process will be described in which such iron-based alloy powder is mixed so that each component is evenly mixed and compression molded into a predetermined shape. This compression molding process is performed twice or more. The second and subsequent compression molding steps are performed after the sintering step.

This compression molding step is performed using a conventionally known compression molding apparatus, and usually press molding is performed using a mechanical press or the like. The surface pressure at the time of compression molding is usually about 5-7 ton / cm ^{2 in the} compression molding process (temporary molding) excluding the last compression molding process. Moreover, in the last compression molding process, it is usually about 7-12 ton / cm < ² >, and is set as a surface pressure higher than temporary molding. In addition, the temperature in a compression molding process is the same as normal temperature, and is performed at about 20-40 degreeC.

  After the iron-based alloy powder is compression-molded as described above, a sintering process for sintering the compact will be described. This sintering process is performed twice or more.

  In the sintering step, a conventionally known sintering apparatus can be used, and it is usually performed using a vacuum sintering furnace or the like. The temperature in the sintering step is usually about 650-850 ° C. in the sintering step (temporary sintering) excluding the final sintering step. Moreover, in the last sintering process, it is about 1100-1200 degreeC normally, Preferably it is set to about 1130-1180 degreeC, and is set as temperature higher than temporary sintering. The atmosphere around the molded body in the sintering step is the same as that during normal sintering, and is not particularly limited, but sintering is performed under an atmosphere such as Ax gas, Rx gas, or vacuum. The time required for sintering the molded body of the cam lobe material is the same as the normal time and is not particularly limited, but is about 30 to 90 minutes.

  Next, the sintered body of the cam lobe material obtained in the final sintering step is subjected to quenching / tempering treatment. The quenching treatment is usually performed by holding at 800-950 ° C. for about 30-150 minutes in a heat treatment furnace or the like and then rapidly cooling to about 30-100 ° C. using oil, water or the like. The tempering treatment is usually performed by holding at 120-200 ° C. for about 30-150 minutes and then cooling to about 10-40 ° C. at a rate of about 2-10 ° C./minute after the above-described quenching treatment. . According to the quenching / tempering treatment, the hardness of the outer peripheral surface of the cam can be increased and the wear resistance of the cam lobe material can be improved.

Furthermore, it is preferable to perform shot blasting on the outer peripheral surface of the sintered body of the cam lobe material. By performing shot blasting, residual compressive stress is generated on the outer peripheral surface of the cam lobe material, and the pitting resistance can be improved. Shot blasting usually involves rotating the cam lobe material, adjusting the nozzle so that it can be shot on the outer peripheral surface, and hitting the outer surface of the cam lobe material with a grid of steel, glass beads, etc. at a pressure of about 5 kg / cm ^2. The processing is performed.

  Note that the cam lobe material manufactured by the method of manufacturing a cam lobe material of the present invention has a dimensional change rate of about-(±) 0 to 0.5% before and after the final sintering step. This dimensional change rate is measured by using a three-dimensional measuring machine, and measuring at least one point every 1 ° over 360 ° of the outer shape of the green body before the final sintering step and the sintered body after the sintering step. Then, by superimposing both shapes traced from the measurement point, the dimensional change rate of each measurement point is obtained, and the maximum value is indicated.

Thus, according to the method of manufacturing the cam lobe material of the present invention, since the compression molding process and the sintering process are performed at least twice, the dimensional accuracy before and after the final sintering process is high, Either no cutting or no cutting amount. Therefore, it is possible to reduce labor and cost for manufacturing the cam lobe material. Furthermore, the outer peripheral surface hardness of the cam lobe material after manufacture can be set to HRC 50 or more, and the density can be set to 7.5 g / cm ³ or more. Therefore, the cam lobe material after manufacture can have high hardness and high density, and can have excellent sliding characteristics such as wear resistance, scuffing resistance, and pitting resistance. As a result, it is possible to provide a cam lobe material that can be suitably used for an engine with a high load, for example, an engine with a surface pressure about twice that of a normal engine.

  The assembled camshaft 2 as shown in FIG. 1B is obtained by assembling and fixing the cam lobe material thus manufactured to the shaft. Such a camshaft 2 can be obtained, for example, by being assembled and fixed at a predetermined position of the shaft 7 made of a material such as S45C at a predetermined angle by shrink fitting or cold fitting. As a method of assembling and fixing the cam lobe material to the shaft, the above-mentioned shrink fitting and cold fitting are preferable in terms of assembly accuracy and inexpensive equipment costs, but it is also possible to use other methods such as press fitting and diffusion bonding. Is possible. The camshaft 2 may be provided with only the cam lobe 1 made of the cam lobe material of the present invention, or suitable for the cam lobe 1 according to the present invention and the sliding type cam follower 6 as shown in FIG. It is good also as what is provided with the cam lobe 5 which has an appropriate sliding characteristic. The camshaft produced in this way requires no or even very little grinding of the cam lobe. Thus, it is possible to provide a camshaft that is excellent in sliding characteristics such as wear resistance, scuffing resistance, and pitting resistance, and that can be suitably used for a high-load engine.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

(Example 1-30)
Each element was added to the iron powder so as to have the final component composition shown in Table 1, to prepare a powder for sintering, and compression molded into a cam lobe shape with a surface pressure of 6 ton / cm ² , and then at 700 ° C. Sintering was performed for 90 minutes. Further, compression molding was performed at a surface pressure of 10 ton / cm ² , and then sintering was performed at 1140 ° C. for 60 minutes. Subsequently, this sintered body was heated at 900 ° C. for 100 minutes, and then quenched by oil cooling. Furthermore, this sintered body was heated at 150 ° C. for 60 minutes, and then tempered by air cooling. Thereafter, shot blasting was performed to produce the cam lobe material of Example 1-30.

(Comparative Example 1)
Each element was melted so as to have the final component composition shown in Table 1, poured into a mold having a cooling metal, quenched, and solidified to obtain chilled cast iron. By polishing this, the cam lobe material of Comparative Example 1 was produced.

(Comparative Example 2-5)
Each element was added to the iron powder so as to have the final component composition shown in Table 1 to prepare a powder for sintering, compression-molded into a cam lobe shape with a surface pressure of 5 ton / cm ² , and then at 1100 ° C. By performing sintering for 60 minutes, a cam lobe material of Comparative Example 2-5 was produced.

(Evaluation method and results)
For the cam lobes obtained in the examples and comparative examples, (1) density, (2) Rockwell hardness HRC of the outer peripheral surface, (3) number of occurrences of pitching and wear, (4) dimensional change rate, (5 ) Cam lift error was measured. Each measurement method will be described below, and each measurement result is shown in Table 2.

(1) Density The test piece of the obtained cam lobe material was sealed with paraffin, and the density was measured by Archimedes method.

(2) Rockwell hardness of outer peripheral surface Using a Rockwell hardness meter, measure the outer periphery of the cam nose of the obtained cam lobe specimen on the C scale at five points, calculate the average value, and lock the outer peripheral surface. Well hardness.

(3) Pitching occurrence number and wear amount Pitching occurrence number and wear amount were measured as follows. Using the two-cylinder contact testing machine shown in FIG. 2, the rotating surfaces of the cam lobe test piece 8 and the counterpart cylindrical test piece 9 rotating at a constant speed are brought into contact with each other, and lubricating oil 10 is dropped on the contact surfaces of both test pieces. While rotating by applying a predetermined load 11, the number of rotations until the occurrence of pitching was measured, and the number of occurrences of pitching was determined. Similarly, each test piece 8 was rotated, and the amount of wear subsidence (μm) per certain number of rotations (1 × 10 ⁵ times) was measured to obtain the amount of wear.

(Measurement condition)
Measuring device: Two-cylinder contact test machine rotation speed: 1500rpm
Lubricating oil: Engine oil 10W30
Oil temperature: 100 ° C
Oil amount: 2 × 10 ⁻⁴ m ³ / min
Load: 3000N
Sliding rate: 0%
Opponent material: SUJ2
Judgment method: AE (acoustic emission) was used to detect cracks in which pitching occurred, and an SN curve was created using the number of contacts at that time as the number of times pitching occurred, and compared with each test piece.

(4) Dimensional change rate Using a three-dimensional measuring machine, measure the outer shape of the secondary compact and secondary sintered compact every 360 ° over 360 °, and overlay both shapes traced from the measurement point. In addition, the dimensional change rate at each measurement point was determined, and the maximum value among them was specified as the dimensional change rate of the secondary sintered body relative to the secondary compact. In addition, about Comparative Example 2-5, since shaping | molding and sintering were performed only once, the dimensional change rate was measured about the outer periphery shape of a primary molded object and a primary sintered compact.

(5) Cam lift error The cam lift error was measured for the test piece after quenching and tempering the secondary sintered body and further shot blasting. The cam profile was measured using a cam profile measurement program ad call, and compared with the target profile, the error was detected and taken as a lift error. In Comparative Example 2-5, since molding and sintering were performed only once, the cam lift error was measured for the specimen after quenching and tempering the primary sintered body.

(Consideration of measurement results)
(I) Effect of Ni (nickel) amount (Examples 1-8, 16)
Examples 1 to 8 and 16 in Table 2 show the test results of the density, hardness, pitching occurrence number, wear amount, dimensional change rate, and cam lift error of alloys having different Ni amounts.
The density, the hardness, and the number of occurrences of pitching tend to increase as the Ni amount increases from 0.5% to 5.0%. As shown in FIG. 3, the density tends to increase gradually from 7.52 to 7.58 g / cm ³ . As shown in FIG. 4, the hardness is also 52.5 to 55.5 HRC and tends to increase little by little like the density. Also, the number of occurrences of pitching tends to increase from 1.2 × 10 ^{6 to} 6.0 × 10 ^{6 as} shown in FIG.
The wear amount is stable with relatively little change, 0.19 to 0.23 μm / 1 × 10 ⁵ times when the Ni amount is 0.5% to 5.0%.
As shown in FIG. 6, the dimensional change rate tends to increase gradually from −0.1 to −0.5% when the Ni content is 0.5% to 5.0%. Further, as shown in FIG. 7, the cam lift error tends to increase gradually from 0.02 to 0.05 mm when the Ni amount is 0.5% to 5.0%, similarly to the dimensional change rate.

(B) Effect of C (carbon) amount (Examples 9 to 12, 24, 25)
Examples 9 to 12, 24, and 25 in Table 2 show the test results of the density, hardness, pitching occurrence number, wear amount, dimensional change rate, and cam lift error of alloys having different C amounts.
As shown in FIG. 8, the density is as high as 7.55 g / cm ³ when the amount of C is as low as 0.5%. As the amount of C increases, the density tends to decrease, and the amount of C is 1.2. When it is as high as%, the density is as low as 7.51 g / cm ³ . Contrary to the density, the hardness tends to increase to 51.5 to 56.0 HRC when the C content is 0.5% to 1.2%, as shown in FIG.
Pitting number, until C of 0.5% to 1.2%, relatively unchanged it is less stable with ^{1.5 × 10 6 ~3.5 × 10 6} . Like the number of occurrences of pitching, the wear amount is stable with relatively little change of 0.16 to 0.25 μm / 1 × 10 ⁵ times when the C amount is 0.5% to 1.2%. The dimensional change rate tends to increase slightly to -0.1 to -0.4% when the C content is 0.5% to 1.2%. The cam lift error is stable with relatively little change of 0.01 to 0.03 mm up to a C amount of 0.5% to 1.2%.

(C) Effect of P (phosphorus) amount (Examples 1, 13 to 15)
Examples 1 and 13 to 15 in Table 2 show the test results of the density, hardness, pitching occurrence number, wear amount, dimensional change rate, and cam lift error of alloys having different P amounts.
The density, hardness, and number of occurrences of pitching relating to the P amount show the same tendency as Ni. As shown in FIG. 10, the density tends to increase gradually from 7.51 to 7.54 g / cm ³ when the P content is 0.05% to 0.3%. As shown in FIG. 11, the hardness is 52.0 to 54.0 HRC in the amount of P from 0.05% to 0.3%, which is increasing little by little like the density. Further, as shown in FIG. 12, the number of occurrences of pitching tends to increase from 8.5 × 10 ^{5 to} 1.5 × 10 ⁶ when the P amount is 0.05% to 0.3%.
The wear amount is stable with relatively little change of 0.20 to 0.23 μm / 1 × 10 ⁵ times when the P amount is 0.05% to 0.3%. Similar to the wear amount, the dimensional change rate is stable with relatively little change of -0.1 to -0.2% up to 0.05% to 0.3% of the P amount. The cam lift error is stable with relatively little change of 0.02 to 0.03 mm up to a P amount of 0.05% to 0.3%.

(D) Influence of B (boron) amount (Examples 10 and 17 to 19)
Examples 10 and 17 to 19 in Table 2 show the test results of the density, hardness, number of occurrences of pitching, wear amount, dimensional change rate, and cam lift error of alloys having different B amounts.
As shown in FIG. 13, the density is stable with little change of 7.51 to 7.53 g / cm ³ when the B content is 0.02% to 0.3%. As shown in FIG. 14, the hardness is stable with little change from 53.0 to 54.0 HRC and a density of B from 0.02% to 0.3%, similar to the density.
The number of occurrences of pitching is stable with relatively little change of 2.0 × 10 ^{6 to} 3.2 × 10 ⁶ when the B amount is 0.02% to 0.3%. The wear amount is also stable with relatively little change, 0.21 to 0.24 μm / 1 × 10 ⁵ times, when the B amount is 0.02% to 0.3%. Similar to the amount of wear, the dimensional change rate is stable with relatively little change of -0.2 to -0.4% when the B amount is 0.02 to 0.3%. The cam lift error is stable with relatively little change of 0.02 to 0.04 mm until the B amount is 0.02 to 0.3%.

(E) Effect of Mo (molybdenum) amount (Examples 6, 20 to 23, 26 to 30)
Examples 6, 20 to 23, and 26 to 30 in Table 2 show the test results of the density, hardness, number of pitching occurrences, wear amount, dimensional change rate, and cam lift error of alloys having different Mo amounts.
As shown in FIG. 15, the density is as high as 7.54 g / cm ³ when the amount of Mo is as low as 0.3%. As the amount of Mo increases, the density tends to decrease. When it is as high as%, the compressibility is remarkably deteriorated, so the density is as low as 7.50 g / cm ³ . As shown in FIG. 16, when the Mo amount is 0.3% to 2.5%, the hardenability is increased and the hardness is as high as 55.5 to 56.5 HRC, and the change is stable with little change.
The number of occurrences of pitching is stable with relatively little change of 1.8 × 10 ^{6 to} 2.5 × 10 ⁶ when the Mo amount is 0.3% to 2.5%. The wear amount is as low as 0.16 to 0.21 μm / 1 × 10 ⁵ times when the Mo amount is 0.3% to 2.5%, and is relatively stable with little change. The dimensional change rate is stable with relatively little change of 0 to -0.3% when the Mo amount is 0.3% to 2.5%. The cam lift error is stable with a relatively small change of 0.02 to 0.04 mm, when the Mo amount is 0.3% to 2.5%.

(F) Various combinations of Ni, B, and Mo (Examples 24-29)
Examples 24 to 29 in Table 2 show the test results of the density, hardness, number of occurrences of pitching, wear amount, dimensional change rate, and cam lift error of alloys having different amounts of Ni, B, and Mo, respectively.
Consider each test result in a combination of Ni amount 1.0% to 3.5%, B amount 0.05% to 0.2%, Mo amount 0.3% to 2.0%.
Since the density is affected by Mo, even if the elements of Ni and B are changed, there is almost no effect, and the density changes from 7.50 to 7.54 g / cm ³ , which is relatively low to medium. The hardness is relatively high at 55.5 to 56.5 HRC because the amount of C is high and affected by Mo.
The number of occurrences of pitching is in a wide range of 1.8 × 10 ^{6 to} 3.5 × 10 ⁶ because the density is affected by Mo and the influence of Ni. The amount of wear is high because the amount of C is high, and the hardness is affected by the synergistic effect of C and Mo, so the hardness is high, 0.16 to 0.21 μm / 1 × 10 ⁵ times relatively low. It has transitioned to.
Since the dimensional change rate is affected by Ni, it changes over a wide range of 0 to -0.4%. Like the dimensional change rate, the cam lift error is affected by Ni, and thus has a wide range of 0.01 to 0.04 mm.

(G) Combination of B and P (Example 30)
Example 30 in Table 2 shows the test results of the alloy density, hardness, number of pitching occurrences, wear amount, dimensional change rate, and cam lift error of the combination of B and P.
Because the amount of C and Mo is high, the density is low and the hardness is high, and the number of occurrences of pitching and the amount of wear are about the middle of the ranges of the above-mentioned embodiments, and the dimensional change rate is low. The cam lift error was high. Thus, even when B and P were combined, the density and hardness within the range of the present invention were obtained, and other good results were obtained.

(H) About Comparative Example Example 1-30 was superior to any of Comparative Examples 1-5.
Comparative Example 2 is not included in the present invention in that it does not contain B and P. As a result, in Comparative Example 2, the density and the number of occurrences of pitching were lower than in each Example, and the pitting resistance was inferior. Moreover, the comparative example 2 had a larger abrasion amount than each Example, and its abrasion resistance was inferior. Since Comparative Example 2 was manufactured by one-time compression-one-time sintering (hereinafter referred to as 1P1S), the dimensional change rate was higher than in each example, and the cam lift error was also higher than in each example. there were. Thus, Comparative Example 2 was inferior in both dimensional change rate and cam lift error.
Comparative Example 3 is not included in the present invention in that it does not contain Ni. As a result, in Comparative Example 3, the density and the number of occurrences of pitching were lower than in each Example, and the pitting resistance was inferior. Moreover, since the comparative example 3 was lower in density and hardness than each Example, the amount of wear was larger than each Example, and its abrasion resistance was inferior. Since Comparative Example 3 was manufactured by 1P1S, the dimensional change rate was higher than that of each example, and the cam lift error was also higher than that of each example. Thus, Comparative Example 3 was inferior in both dimensional change rate and cam lift error.
In Comparative Example 4, the contents of C, Ni, and P are lower than the specified amounts of the present invention, and are not included in the present invention. As a result, in Comparative Example 4, the density and the number of occurrences of pitching were lower than in each Example, and the pitting resistance was inferior to that of Comparative Examples 2 and 3 described above. Moreover, since the comparative example 4 was lower in density and hardness than each Example, the abrasion loss was larger than each Example and the above-mentioned Comparative Examples 2 and 3, and abrasion resistance was very inferior.
In Comparative Example 5, the contents of C, Ni, and P are all higher than the specified amount of the present invention and are not included in the present invention. As a result, in Comparative Example 5, as in Comparative Examples 2 and 3, the density and the number of occurrences of pitching were lower than in each Example, and the pitting resistance was inferior. Moreover, since the comparative example 5 was lower than each Example in both a density and hardness, the amount of wear was larger than each Example, and its abrasion resistance was inferior. Furthermore, since the comparative example 5 was manufactured by 1P1S, the dimensional change rate was extremely higher than each Example, and the cam lift error was also extremely higher than each Example. Thus, Comparative Example 5 was inferior in both dimensional change rate and cam lift error.

Claims (6)

Ni: 0.3-5.0 mass%, C: 0.5-1.2 wt%, at least one of B and P: 0.02-0.3 wt%, and the balance Fe and unavoidable impurities A cam lobe material comprising an iron-based sintered alloy having an outer peripheral surface hardness of HRC50 or more and a density of 7.5 g / cm ³ or more.   2. The cam lobe material according to claim 1, wherein the iron-based sintered alloy further contains Mo: 2.5% by mass or less.   The cam lobe material according to claim 1, wherein the cam lobe material has a roller follower as a mating material.   A camshaft comprising a cam lobe made of the cam lobe material according to any one of claims 1 to 3. A manufacturing method of the cam lobe member according to any one of claims 1 to 3, compressing the iron-based alloy powder prepared so as to have the composition of the iron-based sintered alloy in a predetermined cam lobe shape A cam lobe material characterized in that a compression molding step for molding and a sintering step for sintering the compression molded body are repeated twice or more, and the sintered sintered body is quenched and tempered. Production method.   6. The method of manufacturing a cam lobe material according to claim 5, wherein shot blasting is performed on an outer peripheral surface of the cam lobe material.

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