JP5063019B2 - Abrasion resistant titanium - Google Patents

Description

  The present invention relates to a wear-resistant titanium member.

  In internal combustion engines typified by automobiles and motorcycles, from the viewpoint of improving performance and reducing environmental load, there is a constant demand for weight reduction of parts in order to improve efficiency by improving the limit rotational speed and reducing friction. The effect is great when parts made of conventional steel are replaced with titanium materials having excellent specific strength.

  However, since the titanium material has a strong affinity with itself and other elements, seizure easily occurs by sliding. For this reason, the surface treatment which provides favorable slidability to a titanium material is calculated | required.

  As a surface treatment of titanium material, the technology of coating the surface with TiN, CrN, etc. by ion plating is known, and since this coating provides a non-metallic surface, it is seized with wear resistance. Can be improved (see, for example, Patent Document 1).

In addition, a technique is known in which the surface of a metal material is shot peened and then filled with a filler to give compressive residual stress to increase the pitting resistance of the metal material and smooth the surface. (For example, refer to Patent Document 2).
JP-A-4-171206 No. 7-8803

By the way, as for the technique of the said patent document 1, the film thickness is about 3-5 micrometers, and adhesiveness will fall in the thickness beyond it. Since such a 3-5 μm coating is formed on the surface of a relatively soft titanium material, the titanium material may be deformed when sliding at a high surface pressure, and there are restrictions on the application site.
Here, as a similar wear-resistant surface treatment, Ni composite plating is known, but although a sufficient plating thickness of 20 μm or more can be ensured, adhesion strength at the interface between the titanium material and the plating phase Therefore, the plating layer may be peeled off by severe sliding, and the application site is also limited.

Further, as a surface treatment different from these coatings, there is an oxidation treatment which is a diffusion treatment. This oxidation treatment is advantageous in terms of cost because the titanium material is basically only heated in the atmosphere. Moreover, since it is a diffusion treatment, the adhesion is good, and the thickness of the cured layer can be set by selecting the treatment conditions.
However, in this oxidation treatment, the hardened layer can be made thicker as the treatment temperature is raised and the treatment time is lengthened, but at the same time, the surface layer becomes brittle, and particularly the pitting resistance is lowered.

  On the other hand, the technique of Patent Document 2 can improve the pitting resistance of a metal material by shot peening. However, the surface has irregularities, and a filler for smoothing the irregularities formed on the surface is used. It is necessary and it is difficult to improve productivity.

  This invention is made | formed in view of the subject mentioned above, The objective is to provide the abrasion-resistant titanium member excellent in abrasion resistance and pitting resistance.

To achieve the above object, wear resistant titanium member of the invention according to claim 1, the alloy composition, the Fe and 0.2 to 0.5 wt% of O of 0.5 to 1.5 mass% It is formed of a titanium alloy containing the balance Ti and the inevitable impurities, and at least the contact surface with other members is oxidized and the surface hardness Hmv (load 0.1 kg) is set to 550 or more and less than 800, and then shot. The surface hardness Hmv (load 0.1 kg) is set to 800 or more and 1000 or less by performing peening .

According to a second aspect of the present invention, in addition to the configuration of the first aspect , the shot peening is performed using a medium having a particle size of 0.03 mm to 0.1 mm.

The invention according to claim 3 is characterized in that, in addition to the structure of claim 1 or 2 , an α case layer having a thickness of 5 μm to 20 μm is formed by the oxidation treatment.

The invention according to claim 4 is characterized in that, in addition to the structure of any one of claims 1 to 3 , the shot peening is performed with a coverage of 100 to 500%.

According to a fifth aspect of the present invention, in addition to the structure of any one of the first to fourth aspects, the titanium member is a titanium valve spring retainer having a contact surface with which the valve spring contacts.

According to a sixth aspect of the present invention, in addition to the structure of any one of the first to fourth aspects, the titanium member is a titanium valve lifter having a contact surface on which the cam slides.

According to the invention according to claim 1, after the wear-resistant titanium member is subjected to an oxidation treatment at least on the contact surface with the other member, the surface hardness Hmv (load 0.1 kg) is set to 550 or more and less than 800, Shot peening was performed to make the surface hardness Hmv (load 0.1 kg) 800 or more and 1000 or less. As a result, the contact surface with the other member can obtain a hardened layer having a sufficient thickness by an oxidation process having good adhesion at a low cost and improve the wear resistance, and can remain by the shot peening process. Pitting resistance can be improved by applying stress, and a wear-resistant titanium member having good slidability even under severe sliding conditions can be obtained.
Further , the alloy composition is Fe: 0.5 to 1.5 mass% (hereinafter, mass% is expressed as wt%), O: 0.2 to 0.5 wt%, the balance titanium and titanium composed of inevitable impurities. By using an alloy, the balance between strength and workability can be improved, and an α case layer formed by oxidation treatment compared to other alloys can be secured in a short time with a sufficient thickness. It is possible to easily obtain the effect of improving the wear resistance and pitting resistance by shot peening.

According to the invention according to claim 2 , by performing shot peening using a medium having a particle size of 0.03 mm or more and 0.1 mm or less, unevenness on the treated surface subjected to shot peening can be suppressed as much as possible, and wear resistance is increased. The sex can be further improved.

According to the invention of claim 3 , by forming an α case layer having a thickness of 5 μm or more and 20 μm or less by oxidation treatment, the effect of shot peening is maximized, and the wear resistance and pitting resistance are good. The balance can be improved.

According to the invention according to claim 4 , since shot peening is performed with a coverage of 100 to 500%, it is possible to improve the pitting resistance by shot peening and the fatigue strength due to the compressive residual stress applied concomitantly. Further, it is possible to maintain the wear resistance by securing the thickness of the α case layer.

According to the invention of claim 5 , since the titanium member is a titanium valve spring retainer having an abutting surface against which the valve spring abuts, the valve spring retainer with improved wear resistance and pitting resistance is harsh. Good slidability can be provided even under sliding conditions.

According to the invention of claim 6 , since the titanium member is a titanium valve lifter having a contact surface on which the cam slides, the valve lifter with improved wear resistance and pitting resistance can be used under severe sliding conditions. Can also provide good slidability.

  Hereinafter, a wear-resistant titanium member according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, for example, an engine body 1 of a DOHC type internal combustion engine includes a cylinder block 2 having a cylinder bore 4 and a cylinder head 3 coupled to the cylinder block 2, and is slidable on the cylinder bore 4. A combustion chamber 6 that faces the top of the piston 5 to be fitted is formed between the cylinder block 2 and the cylinder head 3.

  The cylinder head 3 is provided with an exhaust valve port 7 that opens to the ceiling surface of the combustion chamber 6, and an exhaust port 8 that communicates with the exhaust valve port 7. A stem 9 a of the exhaust valve 9 that opens and closes the exhaust valve port 7 is provided in the cylinder head 3. The guide cylinder 10 provided in the cylinder head 3 is slidably fitted.

  A valve spring retainer 12 is fixed to an end portion of the stem 9 a protruding from the guide cylinder 10 via a cotter 11 divided between the valve spring retainer 12 and a spring receiving member 13 supported by the cylinder head 3. In the meantime, a coiled valve spring 14 surrounding the stem 9a is contracted, and the exhaust valve 9 is urged in the valve closing direction by the spring force exerted by the valve spring 14.

  The upper part of the stem 9a, the upper part of the valve spring 14, and the valve spring retainer 12 are covered with a valve lifter 15 formed in a bottomed cylindrical shape. The upper end of the stem 9a is connected to the inner shim on the inner surface of the closed end of the valve lifter 15. It is contact | abutted coaxially via 25. The valve lifter 15 is slidably fitted in a guide hole 16 provided in the cylinder head 3.

  A valve operating cam (cam) 18 provided on the camshaft 17 is slidably contacted with the outer surface of the closed end portion of the valve lifter 15, and the valve cam 18 is slidably contacted with the rotation of the camshaft 17 through the valve lifter 15. Thus, the stem 9a is pushed down against the spring force of the valve spring 14, whereby the exhaust valve 9 is opened.

  As shown in FIG. 2A, the valve spring retainer 12 includes a disk-shaped large-diameter portion 12a and a small-diameter portion coaxially connected to one end of the large-diameter portion 12a with a larger axial thickness than the large-diameter portion 12a. 12b and a taper portion 12c coaxially connected to one end of the small diameter portion 12b so that the diameter decreases as the distance from the small diameter portion 12b increases. Between the large diameter portion 12a and the small diameter portion 12b, a valve An annular seat surface (contact surface) 19 for receiving the upper end of the spring 14 is formed.

  The valve spring retainer 12 is provided with a tapered hole 20 for fixing the stem in the axial direction, and is interposed between the stem 9a inserted through the tapered hole 20 and the valve spring retainer 12. In this way, the split cotter 11 is fitted into the tapered hole 20.

  On the other hand, as shown in FIG. 2B, the valve lifter 15 has a cylindrical portion 21 inserted into the guide hole 16 of the cylinder head 3 and a closed end portion 22 that closes one end of the cylindrical portion 21. The outer surface of the closed end 22 is a sliding surface (contact surface) 23 on which the valve cam slides, and a central projection 24 is formed on the inner surface of the closed end 22 so that the inner shim 25 contacts.

  The valve spring retainer 12 and the valve lifter 15 which are wear-resistant titanium members are made of a titanium alloy formed by cold forging. The composition of the titanium alloy is Fe: 0.5 to 1.5 wt%. , O: 0.2 to 0.5 wt%, the balance is composed of Ti and inevitable impurities.

  Further, the valve spring retainer 12 and the valve lifter 15 are heated in the atmosphere, whereby the entire surface thereof is oxidized. As a result, the surface hardness Hmv (load 0.1 kg) of the valve spring retainer 12 and the valve lifter 15 subjected to this oxidation treatment is set to be 550 or more and less than 800.

  Further, the valve spring retainer 12 and the valve lifter 15 are subjected to shot peening at least at sliding portions with other members. Here, the sliding portion that performs shot peening on the valve spring retainer 12 is a sliding surface that includes a seat surface 19 with which the valve spring 14 abuts, and the sliding portion that performs shot peening on the valve lifter 15 includes: A sliding surface 23 with which the valve cam 18 is slidably contacted.

The valve spring retainer 12 and the valve lifter 15 are formed by forming an α case layer having a thickness of 5 μm or more and 20 μm or less on the surface by oxidation treatment, and subjecting the seating surface 19 and the sliding surface 23 to shot peening. The hardness Hmv (load 0.1 kg) is increased to 800 or more and 1000 or less.
The valve spring retainer 12 and the valve lifter 15 used for an intake valve (not shown) that opens and closes an intake valve port (not shown) have the same configuration.

  Next, the surface treatment method for the valve spring retainer 12 and the valve lifter 15 will be described. Here, a description will be given by taking the valve spring retainer 12 as an example.

  First, Fe: 0.5 to 1.5 wt%, O: 0.2 to 0.5 wt%, oxidized on the surface of the valve spring retainer 12 formed by cold forging from a titanium alloy having the balance of Ti and inevitable impurities. Apply processing. In the oxidation treatment, for example, the valve spring retainer 12 is placed in an atmosphere having oxygen, for example, in an atmospheric furnace, and heated at about 600 to 800 ° C. for several minutes to several hours.

  In this way, as shown in FIG. 3, oxygen diffuses on the surface of the base material of the valve spring retainer 12, and the oxide scale layer 31, the α case layer 32, and the oxygen diffusion layer 33 are formed in this order from the outer surface side. . Here, the oxygen diffusion layer 33 has no change in structure, and the hardness is higher than that of the base material before processing due to the diffusion of oxygen. In addition, the α case layer 32 has a thickness of 5 μm or more and 20 μm or less, has a large amount of oxygen diffusion, changes the titanium structure to the α phase, and has a significantly higher hardness than the base material before processing. It has excellent wear resistance. That is, by subjecting the valve spring retainer 12 made of a titanium alloy to oxidation treatment, a hardened layer composed of the α case layer 32 and the oxygen diffusion layer 33 is formed on the valve spring retainer 12, and the surface hardness Hmv (load) 0.1 kg) is 550 or more and less than 800.

  Next, a shot peening process is performed on the seating surface 19 of the valve spring retainer 12 that has been subjected to an oxidation process as described above to make the surface hardness Hmv (load 0.1 kg) 550 or more and less than 800. In the shot peening process, for example, an air nozzle type shot peening apparatus is used to project a medium made of fine particles toward the seating surface 19 of the valve spring retainer 12.

  The processing conditions of the shot peening process include the projection pressure, projection distance, media type (shape, material), nozzle speed, work rotation speed, number of passes, etc. By controlling these conditions, arc height ( Shot peening intensity) and coverage (media dent rate) are determined. In addition, the medium made of fine particles used in the shot peening treatment preferably has a particle size of 0.03 mm or more and 0.1 mm or less in consideration of the unevenness of the treatment surface.

  FIG. 4 shows an example of shot peening processing in the manufacturing process of the valve spring retainer 12. In order to perform the shot peening process on the valve spring retainer 12, first, the support rod 41 that is vertically arranged is stacked through the tapered holes 20 of the plurality of valve spring retainers 12 with the seating surface 19 facing upward.

  In this state, while rotating the valve spring retainer 12 together with the support rod 41, the medium is shot from the nozzle 42 of the shot peening device inclined downward by about 45 degrees to the seat surface 19 of the uppermost valve spring retainer 12. Project.

  When shot peening to the uppermost valve spring retainer 12 is completed, the support rod 41 and the nozzle 42 are moved relative to each other, and shot peening is sequentially performed on the stacked valve spring retainers 12 from the upper side.

  When the shot peening process is performed on the valve spring retainer 12 in this manner, the oxide scale layer 31 that is a scale on the processing surface is removed. Further, the α case layer 32 is increased in hardness by the fine particles to be projected, the surface hardness Hmv (load 0.1 kg) is set to 800 or more and 1000 or less, and a compressive residual stress is applied, thereby fatigue. Strength is increased and pitting resistance is improved.

  Further, as described above, when the medium is projected onto the seating surface 19 of the valve spring retainer 12 from an oblique direction, the media is also projected onto the corner 19a between the seating surface 19 and the wall portion adjacent to the seating surface 19. As a result, the fatigue strength at the corner 19a is also greatly increased.

  Here, FIG. 5 is a graph showing the relationship between the wear resistance and the pitting resistance with respect to the thickness of the α case layer 32 before the shot peening process. As shown in FIG. 5, in the valve spring retainer 12 made of a titanium alloy, the pitting resistance improves as the thickness of the α case layer 32 decreases, but the wear resistance decreases. On the contrary, the wear resistance improves as the thickness of the α case layer 32 increases, but the pitting resistance decreases. This is considered to be because when the α case layer 32 is thick, the surface becomes brittle and pitching occurs from minute cracks.

  However, when the shot peening process is performed after the oxidation process, the α-case layer 32 is given a residual stress to greatly improve the pitting resistance, thereby suppressing a decrease in the pitting resistance even when the thickness is increased. It is done. Thereby, after the shot peening treatment, for example, even when the thickness of the α case layer 32 is 20 μm, the pitching resistance substantially equivalent to the case of the thickness of 5 μm or less can be obtained. In addition, as the surface hardness is increased by the shot peening process, the wear resistance is also greatly improved.

  In addition, when the thickness of the α case layer 32 exceeds 20 μm, the grain boundary of the recrystallized crystal grains easily breaks and pitching occurs, and the pitting resistance can be sufficiently improved even when the shot peening treatment is performed. Can not. For this reason, it is preferable that the thickness of the α case layer 32 be 5 μm or more and 20 μm or less in consideration of wear resistance and pitting resistance.

  FIG. 6 is a graph showing the relationship between the surface hardness of the base material and the thickness of the α case layer 32 with respect to the coverage in the shot peening process. If the coverage is less than 100%, the improvement of the fatigue strength due to the pitting resistance and the accompanying compressive residual stress is small and it is difficult to obtain sufficient surface hardness, and the coverage is more than 500%. Then, the α case layer 32 is scraped to reduce the thickness, and the wear resistance is reduced. Therefore, the coverage in the shot peening process is preferably in the range of 100 to 500%.

  In addition, also when performing the surface treatment to the valve lifter 15, the same treatment as the surface treatment to the valve spring retainer 12 is performed. Thereby, also in the case of the valve lifter 15, the surface hardness Hmv (load 0.1 kg) on the sliding surface 23 is increased to 800 or more and 1000 or less by the shot peening process after the oxidation process, and the pitting resistance as well as the wear resistance is increased. Be improved.

  The alloy composition is a titanium alloy composed of Fe: 0.5 to 1.5 wt%, O: 0.2 to 0.5 wt%, the balance Ti and inevitable impurities. Within this composition range, the balance between strength and workability is good, and the α case layer 32 formed by oxidation treatment compared to other alloys can be secured in a sufficient thickness in a short time. The effect of improving the wear resistance and pitting resistance by shot peening is easily obtained.

  As described above, according to the titanium valve spring retainer 12 and the valve lifter 15 according to the present embodiment, the seating surface 19 with the valve spring 14 and the sliding surface 23 with the valve cam 18 are subjected to oxidation treatment and surface. After setting the hardness Hmv (load 0.1 kg) to 550 or more and less than 800, shot peening was performed to set the surface hardness Hmv (load 0.1 kg) to 800 or more and 1000 or less. Thereby, it is possible to obtain a cured layer composed of the α case layer 32 and the oxygen diffusion layer 33 having a sufficient thickness by an oxidation process having good adhesion at a low cost, and to improve the wear resistance, and also to perform shot peening treatment. Therefore, the pitting resistance can be improved by applying the residual stress, and the titanium valve spring retainer 12 and the valve lifter 15 can have good slidability even under severe sliding conditions.

  Further, by performing shot peening using a medium having a particle size of 0.03 mm or more and 0.1 mm or less, unevenness on the treated surface subjected to shot peening can be suppressed as much as possible, and wear resistance can be further improved. .

  Further, by forming the α case layer 32 having a thickness of 5 μm or more and 20 μm or less by the oxidation treatment, it is possible to maximize the effect of shot peening and improve the wear resistance and pitting resistance in a good balance. it can.

  Further, since shot peening is performed with a coverage of 100 to 500%, the shot peening can improve the pitting resistance and fatigue strength due to the accompanying compressive residual stress, and the thickness of the α case layer 32. It is possible to maintain wear resistance by ensuring the above.

  Furthermore, the balance of strength and workability can be achieved by making the alloy composition a titanium alloy composed of Fe: 0.5 to 1.5 wt%, O: 0.2 to 0.5 wt%, the balance Ti and inevitable impurities. The α case layer 32 formed by oxidation treatment as compared with other alloys can be ensured in a short time with a sufficient thickness, and can be improved in wear resistance and resistance by shot peening. The effect of improving the pitching property can be easily obtained.

In addition, this invention is not limited to the thing of the said embodiment, A change or improvement etc. are possible suitably.
In the present embodiment, the valve spring retainer and the valve lifter are shown as the wear-resistant titanium member. However, the present invention is not limited to these, and for various products in addition to engine parts such as a crankshaft and a rocker shaft. It is applicable.

Further, in the valve lifter of this embodiment, shot peening is applied to the sliding surface with the cam. In addition to this sliding surface, shot peening is also applied to the sliding surface with the guide hole of the cylinder head. Also good.
Furthermore, the composition of the titanium member of the present invention is not limited to that described above, and may be Ti-6Al-4V alloy, Ti-3Al-2.5V alloy, JIS class 2 pure titanium, or the like.

(Test 1)
First, the wear resistance and pitting resistance of the valve spring retainer were tested according to the oxidation treatment conditions and the presence or absence of shot peening. As a sample, a valve spring retainer was produced by cold forging from a rod of 10 mm in diameter made of a Ti-1Fe-0.3O (wt%) alloy, and the processing conditions were 500 ° C. × 5 hours, 600 ° C. × 5 The oxidation treatment was performed at different times, 700 ° C. × 5 hours, 800 ° C. × 5 hours, and 900 ° C. × 5 hours. Furthermore, a valve spring retainer was prepared in which shot peening was performed on the contact surface with the valve spring. Shot peening was performed on media with the conditions of # 400 high speed, distance 200 mm, projection pressure 0.5 MPa, and coverage 300%.

  The surface hardness was 10 points measured at a load of 100 g with a micro Vickers hardness meter after removing irregularities on the surface lightly by buffing using 0.3 μm alumina abrasive particles, and an average of 8 points excluding the upper and lower points. Values were used. Wear resistance and pitting resistance were evaluated by a motoring durability test using a burr valve spring in the vicinity of the terminal. Table 1 shows the results of the motoring endurance test.

X in Table 1 indicates that severe wear or pitting occurred, Δ indicates that wear or pitting was observed, and ○ indicates that wear or pitting did not occur and good slidability was exhibited. It is. As a result, the wear resistance and the pitting resistance are compatible when the oxidation treatment is performed at 600 ° C. × 5 hours to 800 ° C. × 5 hours and the shot peening treatment is performed. The surface hardness Hmv (load 0.1 kg) of these valve spring retainers was 800 or more and 1000 or less.
The valve spring retainer that was oxidized at 900 ° C. for 5 hours was not evaluated because a large amount of oxidized scale was generated on the surface after the oxidation and the surface was extremely rough.

(Test 2)
Next, the diameter of the media used for the shot peening process was changed, and the valve spring retainer was tested for wear resistance and pitting resistance. As in the test 1, a valve spring retainer was produced by cold forging from a 10 mm diameter rod made of a Ti-1Fe-0.3O (wt%) alloy as in Test 1. This was subjected to an oxidation treatment at 700 ° C. for 5 hours, followed by shot peening by changing the diameter of the media and evaluated in a motoring durability test in the same manner as in Test 1. The conditions are the same as in Example 1 except that the diameter of the medium is changed. Table 2 shows the results of the motoring durability test.

  As a result, in the media having a particle size of 0.03 mm or more and 0.1 mm or less, both the wear resistance and the pitting resistance were good. It can be seen that the cured layer itself is damaged and does not give good results.

(Test 3)
Next, a test was conducted on the wear resistance and pitting resistance of the valve spring retainer depending on the thickness of the α case layer which varies depending on the oxidation treatment conditions. As in the test 1, a valve spring retainer was produced by cold forging from a 10 mm diameter rod made of a Ti-1Fe-0.3O (wt%) alloy as in Test 1. The valve spring retainer was oxidized under various conditions, and then shot peened under the same conditions as in Test 1. After the motor spring endurance test was performed on the valve spring retainer thus manufactured in the same manner as in Test 1, each valve spring retainer was cut, embedded in a polishing resin, and polished to obtain the thickness of the α case layer on the surface. I investigated. The α case layer is a portion in which the structure of titanium is changed to an α phase by oxygen that has entered and diffused from the surface to become a hard layer, and appears white on the microscope by etching. It should be noted that there is a so-called oxygen diffusion layer whose hardness is increased by diffusion of oxygen, although there is no change in the structure in the region inside the α case layer. Table 3 shows the results of the motoring endurance test.

  As a result, when the thickness of the α case layer was 2 μm, the wear resistance itself was inferior, and when it was 24 μm, the grain boundaries of the recrystallized crystal grains were easily broken and pitching occurred. On the other hand, good results were obtained when the thickness of the α case layer was 5 μm or more and 20 μm or less.

(Test 4)
Next, the wear resistance and pitting resistance of the valve lifter according to the oxidation treatment conditions and the presence or absence of shot peening were tested. As a sample, a valve lifter was manufactured by forging and machining from a rod material having a diameter of 30 mm made of a Ti-1Fe-0.3O (wt%) alloy. The oxidation was performed by changing the treatment conditions to 500 ° C. × 5 hours, 600 ° C. × 5 hours, 700 ° C. × 5 hours, and 800 ° C. × 5 hours. In addition, about 900 degreeC x 5 hours, since it was already known that it was not worthy of evaluation in Test 1, it was not implemented. In addition, a valve lifter with shot peening on the sliding surface with the cam was prepared. The surface hardness measurement method and shot peening conditions are the same as in Test 1.

  The wear resistance and pitching resistance of the valve lifter were evaluated by preparing a camshaft with a cam width reduced by 25% and performing a motoring durability test. Table 4 shows the results of the motoring endurance test.

  X in Table 4 indicates that severe wear or pitching occurred, △ indicates that wear or pitting was observed, and ○ indicates that wear or pitting did not occur and good slidability was exhibited. It is. The wear resistance and the pitting resistance are compatible when the oxidation treatment is performed at 600 ° C. × 5 hours to 800 ° C. × 5 hours and the shot peening treatment is performed. And the surface hardness Hmv (load 0.1kg) of those valve lifters was 800 or more and 1000 or less. Thus, in the case of the valve lifter, the same result as that of the valve spring retainer was obtained.

(Test 5)
Next, the diameter of the media used for the shot peening treatment was changed, and the valve lifter was tested for wear resistance and pitting resistance. As in the test 4, a valve lifter was produced by forging and machining from a 10 mm diameter rod made of a Ti-1Fe-0.3O (wt%) alloy in the same manner as in Test 4. This was subjected to an oxidation treatment at 700 ° C. for 5 hours, followed by shot peening by changing the diameter of the media, and evaluated by a motoring durability test in the same manner as in Test 4. The conditions are the same as in Example 4 except that the diameter of the medium is changed. Table 5 shows the results of the motoring durability test.

  As a result, the media having a particle size of 0.03 mm or more and 0.1 mm or less showed good results in both wear resistance and pitting resistance. It can be seen that the cured layer itself is damaged and does not give good results. Thus, in the case of the valve lifter, the same result as that of the valve spring retainer was obtained.

(Test 6)
Next, a test was conducted on the wear resistance and pitting resistance of the valve lifter according to the thickness of the α case layer, which varies depending on the oxidation treatment conditions. As in the test 1, a valve spring retainer was produced by cold forging from a 10 mm diameter rod made of a Ti-1Fe-0.3O (wt%) alloy as in Test 1. The valve spring retainer was oxidized under various conditions, and then shot peened under the same conditions as in Test 1. After the motor spring endurance test was performed on the valve spring retainer thus manufactured in the same manner as in Test 1, each valve spring retainer was cut, embedded in a polishing resin, and polished to obtain the thickness of the α case layer on the surface. I investigated. Table 6 shows the results of the motoring durability test.

  As a result, when the thickness of the α case layer was 2 μm, the wear resistance itself was inferior, and when it was 24 μm, the grain boundaries of the recrystallized crystal grains were easily broken and pitching occurred. On the other hand, good results were obtained when the thickness of the α case layer was 5 μm or more and 20 μm or less. Thus, in the case of the valve lifter, the same result as that of the valve spring retainer was obtained.

(Test 7)
Next, the test was performed by changing the alloy composition of the valve spring retainer or the valve lifter. If the alloy composition is Fe: 0.5 to 1.5 wt%, O: 0.2 to 0.5 wt%, the balance is Ti and inevitable impurities, and both Fe and O are in this composition range, the addition It was found that the amount and tensile strength were almost proportional. However, in this composition range, the fatigue strength is not different from the tensile strength and is very advantageous for mass production management. Further, it was found that this composition makes it easier to utilize the effects of the present invention because the α-case layer can be made thicker than other alloys.

(Test 8)
Next, the abrasion resistance and pitting resistance depending on the oxidation treatment conditions and the presence or absence of shot peening were tested using a Fabry abrasion tester. First, a Fabry abrasion test piece was produced by machining from a bar having a diameter of 10 mm made of a Ti-1Fe-0.3O (wt%) alloy. The test piece was subjected to oxidation treatment by changing the treatment conditions to 500 ° C. × 5 hours, 600 ° C. × 5 hours, 700 ° C. × 5 hours, 800 ° C. × 5 hours, and 900 ° C. × 5 hours. Further, a sample to which shot peening was added was prepared. In the wear test, the wear resistance was evaluated when the test material was used on the block side, and the pitting resistance was evaluated when the test material was used on the pin side. The counterpart material was an SCM carburized material with a surface hardness Hmv (load 0.1 kg) of about 750. The method for measuring the surface hardness of the test piece and the shot peening conditions are the same as in Test 1. The test results are shown in Table 7.

  X in Table 7 indicates that severe wear or pitting occurred, Δ indicates that wear or pitting was observed, and ○ indicates that wear or pitting was not observed and good slidability was exhibited. It is. In the case where both wear resistance and pitting resistance were compatible, the shot peening treatment was performed at an oxidation treatment of 600 ° C. × 5 hours to 800 ° C. × 5 hours. And the surface hardness Hmv (load 0.1kg) of those test materials was 800 or more and 1000 or less. Note that the test material of 900 ° C. × 5 hours was not able to be evaluated because a large amount of surface oxide scale was generated after the oxidation treatment, and the surface was extremely rough.

(Test 9)
Next, the diameter of the media used for the shot peening treatment was changed, and the valve lifter was tested for wear resistance and pitting resistance. In the same manner as in Test 8, a Fabry wear test piece was produced by machining from a 10 mm diameter rod made of a Ti-1Fe-0.3O (wt%) alloy. The test piece was subjected to an oxidation treatment at 700 ° C. for 5 hours, followed by shot peening by changing the diameter of the media, and the influence was evaluated by a wear test. Shot peening is the same conditions as in Example 1 except that the diameter of the media is changed. The test results are shown in Table 8.

  From this test result, the media having a particle size of 0.03 mm or more and 0.1 mm or less showed good wear resistance and pitting resistance, but at 0.3 mm or more, the cured layer itself was damaged by the oxidation treatment. It turns out that a good result is not obtained.

(Test 10)
Next, the wear resistance and the pitting resistance due to the thickness of the α case layer, which varies depending on the oxidation treatment conditions, were tested using a Fabry abrasion tester. In the same manner as in Test 8, a Fabry wear test piece was produced by machining from a 10 mm diameter rod made of a Ti-1Fe-0.30 (wt%) alloy. The test piece was subjected to oxidation treatment under various conditions, and then subjected to shot peening treatment under the same conditions as in Test 8. After the wear test, each specimen was cut, embedded in a polishing resin and polished to examine the thickness of the surface α case layer. The test results are shown in Table 9.

  When the thickness of the α case layer was 2 μm, the wear resistance itself was inferior, and when it was 24 μm, the grain boundaries of the recrystallized crystal grains were easily cracked and pitching occurred. Good results were obtained when the thickness of the α case layer was 5 μm or more and 20 μm or less.

(Test 11)
Next, using a Ti-6Al-4V alloy, a Ti-3Al-2.5V alloy, and JIS type 2 pure titanium, the oxidation treatment conditions were set to 700 ° C. × 5 hours, and the other conditions were the same as in Example 8 and tested. went. As a result, all the titanium materials showed good wear resistance and pitting resistance with shot peening. The surface hardness Hmv (load 0.1 kg) after shot peening was 910, 884, and 818, respectively.

(Test 12)
Next, shot peening was performed on the rocker shaft made of Ti-6Al-4V alloy and used by oxidation treatment under the conditions of Example 4, and a bench durability test was performed. The conventional oxidation treatment condition is 600 ° C. × 6 hours. The rocker shaft of the present invention showed durability of 10 times or more of the conventional specification in the ultimate durability test, and it was confirmed that the effect of the present invention was great even in actual parts.

It is a principal part longitudinal cross-sectional view of an internal combustion engine. (A) is an enlarged vertical sectional view of a valve spring retainer, and (b) is an enlarged vertical sectional view of a valve lifter. It is sectional drawing which shows the composition of the base material surface of the titanium alloy which performed the oxidation process. It is a schematic side view which shows the method of the shot peening process to a valve spring retainer. It is a graph which shows the relationship of the abrasion resistance and the pitching resistance with respect to the thickness of (alpha) case layer before a shot peening process. It is a graph which shows the relationship between the surface hardness of the base material with respect to the coverage in a shot peening process, and the thickness of (alpha) case layer.

Explanation of symbols

14 Valve spring 12 Valve spring retainer 15 Valve lifter 18 Valve cam (cam)
19 Seat (contact surface)
23 Sliding surface (contact surface)
32 α case layer

Claims (6)

Alloy composition, and containing Fe and 0.2 to 0.5 wt% of O of 0.5 to 1.5 wt%, is formed of a titanium alloy consisting of the balance Ti and unavoidable impurities, those with at least another member The contact surface is subjected to oxidation treatment to make the surface hardness Hmv (load 0.1 kg) from 550 to less than 800, and then shot peened to make the surface hardness Hmv (load 0.1 kg) from 800 to 1000. A wear-resistant titanium member. The wear-resistant titanium member according to claim 1 , wherein the shot peening is performed using a medium having a particle size of 0.03 mm to 0.1 mm. Wear resistant titanium member according to claim 1 or 2, wherein the α case layer thickness of less than 5μm or 20μm by oxidation is formed. The wear-resistant titanium member according to any one of claims 1 to 3 , wherein the shot peening is performed with a coverage of 100 to 500%. The wear resistant titanium member according to any one of claims 1 to 4 , wherein the titanium member is a titanium valve spring retainer having the abutting surface with which the valve spring abuts. Wherein the titanium member is wear resistant titanium member according to any one of claims 1 to 4, characterized in that a titanium valve lifter having a contact surface which cam slides.