JP2000080451A - Sintered body for wear resistant ring and wear resistant ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wear resistant ring in which the problem of the coagulation of aluminum to a piston ring is not generated, the wear of top ring grooves is reduced, and the problems of cast-in ability with a piston body, thermal conductivity, workability or the like are solved. SOLUTION: As to a sintered body composed of circular openings and base phases, a sintered body for a wear resistant ring in which the compsn. of the base phases is composed of, by weight, 0.5 to 1.5% C, one or >= two kinds among Cu, Ni, Mo and Cr by 1.0 to 10%, and the balance substantially Fe is used as the stock, and the stock is cast-in to a piston ring 3, and machining is executed to compose a wear resistant ring 10. In the sintered body, preferably, the porosity is 15 to 50 vol.%, hard particles having 500 to 1,300 Hv hardness are contained by 0.5 to 30 wt.%, and a solid lubricant is contained by 0.1 to 10 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered body for wear-resistant rings and a wear-resistant ring, and more particularly to a sintered body for wear-resistant rings and a wear-resistant ring suitable for use in diesel engines and high-output gasoline engines.

[0002]

2. Description of the Related Art In recent years, engines made of aluminum alloy have become popular for the purpose of reducing the weight and heat radiation of engines, and pistons are also made of aluminum alloy. On the other hand, with the demand for higher output of the engine, the engine is exposed to a higher temperature combustion environment, and the piston ring material is also required to have severe wear resistance. Therefore, since the piston ring groove for mounting the piston ring is hit by the end face of the piston ring having high hardness, the normal aluminum alloy may cause the piston ring groove to be set or deformed. In particular, since the combustion pressure directly acts on the top ring of a diesel engine, the top ring groove is worn and worn due to repeated impact of the piston ring, and if gas leakage or oil leakage occurs, the engine output will decrease. Becomes

In order to solve this problem, a configuration has been proposed in which a wear ring made of a material having a higher strength than the piston material is fixed to the piston ring groove, and the piston ring is supported by the wear ring. For example, in the case of a piston for a diesel engine, a niresist cast iron insert (wear ring) is inserted into the top ring groove, and the wear ring prevents the piston ring groove from being worn when the piston slides in the cylinder. Things are mainstream.

Japanese Patent Application Laid-Open No. 58-93835 discloses a wear-resistant ring made of an aluminum-based MMC material (metal matrix composite material) in which alumina-silica fibers are composited. The gazette discloses a sliding member comprising a carbonaceous powder, a solid lubricant coated with a metal, and an aluminum-based metal. Also, JP-A-8-319504
The publication discloses that at least one of Cr, Mo, V, W, Mn, and Si is 2-70%, carbon is 0.07-8.2%, and iron-based raw material powder having an unavoidable impurity composition is used. A metal comprising a porous metal sintered body whose hardness is set to Hv200 to 800 by micro-Vickers hardness, and a light metal impregnated into pores and solidified. Sintered composite materials have been proposed.

Japanese Patent Application Laid-Open No. Hei 9-143639 discloses that
It is composed of a skeleton of 55% perforated Fe-based sintered alloy, and
A lightweight aluminum alloy piston body casting whose head is reinforced with a cast-in material consisting of a porous Fe-based sintered alloy having an overall specific surface area of 300 to 2000 cm ² / cm ³ and an overall porosity of 80 to 97% is proposed. Have been.

[0006]

However, the wear-resistant ring made of niresist cast iron is a cast product, so the yield is low despite the high material cost, the cost is high, and the castability is improved. Therefore, aluminizing treatment is indispensable, and the density is increased due to the iron alloy, which causes a decrease in engine performance. In addition, thermal conductivity is still insufficient.

The reason why the wear ring is made of aluminum-based MMC material is that the piston ring groove is softened by the high temperature and the tapping due to the recent increase in the output of the diesel engine and the accompanying temperature rise of the piston ring groove. It is feared that the phenomenon of sticking (adhesion) to the surface (called aluminum adhesion) becomes apparent. This aluminum adhesion occurs notably on the lower surface side of the piston ring (the side not facing the combustion chamber).

Further, in the sliding member disclosed in Japanese Patent Application Laid-Open No. 6-264079 and comprising a carbonaceous powder, a solid lubricant coated with a metal and an aluminum-based metal, a heat-resistant ring for the top ring groove is heat-resistant. Is not enough, and the strength is not enough. Further, in the porous metal sintered body described in JP-A-8-319504, a large amount of alloying elements such as Cr, Mo, and V are added so that air quenching can be performed, which is economically disadvantageous. Becomes There was also a problem that the groove workability after casting the piston was deteriorated.

Further, when the piston is reinforced with the cast-in material disclosed in Japanese Patent Application Laid-Open No. 9-143639, there is a problem that the iron-based sintered alloy portion is as small as 3 to 20% and the wear resistance is deteriorated. Was. Therefore, the present invention does not cause the problem of aluminum adhesion to the piston ring, reduces wear of the top ring groove, and has problems of castability with the piston body, heat conductivity, workability, and the like, and problems of boundary separation. It is an object of the present invention to provide a wear ring that solves the problem of economy.

[0010]

Means for Solving the Problems As a result of earnest studies to achieve the above object, the present inventor has conceived of forming a wear ring using an iron-based sintered material having a certain amount of pores. .
By doing so, the holes are sealed with a molten Al base metal by high-pressure die casting at the time of casting of the piston, and the bondability between the ring and the piston body is improved, and the thermal conductivity of the ring is also improved. The coefficient of thermal expansion of the wear ring can be close to the value of the piston body. Hard particles can be added from the viewpoint of wear resistance, and a solid lubricant can be added from the viewpoint of machinability and wear resistance.

The present invention is further studied based on the above idea.
The gist of the experiment was as follows. (1) A sintered body composed of vacancies and a base phase, wherein the composition of the base phase is C: 0.5 to 1.5 wt%, and one or more of Cu, Ni, Mo, and Cr are total: 1.0 to 10 wt% %, Balance: Fe-substantially sintered body characterized by being substantially Fe.

C is an element added to promote sintering diffusion, but if it is less than 0.5 wt%, sintering hardly proceeds.
If the content exceeds 1.5 wt%, carbides precipitate and the toughness and machinability deteriorate, so the content is set to 0.5 to 1.5 wt%. Cu, Ni, Mo, and Cr are elements that are added individually or in combination to stabilize the pearlite structure. However, if the content is less than 1.0 wt%, the effect is not obtained, and if it exceeds 10 wt%, the effect is saturated and Since the austenitic structure is increased and the wear resistance is inferior, the amount added alone or in combination is set to 1.0 to 10% by weight. In addition,
Preferably, the amount added alone or in combination is 2 to 8 wt%. (2) The sintered body for ring bearing according to (1), which has a porosity of 15 to 50 vol%.

The holes are filled with a molten Al alloy at the time of casting, as described above, to improve the bonding between the sintered body and the piston body, and at the same time, to improve the thermal conductivity and thermal expansion properties of the sintered body. Is effective to improve the porosity (vacancy abundance) of 15
If the content is less than 50% by volume, the effect is poor. If the content is more than 50% by volume, the strength and hardness of the sintered body are reduced, and the wear resistance is poor.
vol%. In addition, it is preferably 20 to 40 vol%. (3) Further, 0.5 to 30 wt% of hard particles having a hardness of Hv500 to 1300
The sintered body for ring bearing according to (1) or (2), which is contained.

Hard particles improve abrasion resistance, but have an Hv50
If it is less than 0, the effect is small, and if it exceeds Hv1300, machinability deteriorates. As hard particles, Fe-Mo alloy particles, C-Cr-
Fe alloy particles, Cr-Mo-Co alloy particles, JIS SKH-based steel particles, JIS SKD-based steel particles, and the like are suitable. The hard particles preferably have a particle size of 20 to 100 μm. If the content of the hard particles is less than 0.5% by weight, the wear resistance is poor. On the other hand, if it exceeds 30 wt%, workability and strength become problems. Therefore, the content of the hard particles is preferably limited to the range of 0.5 to 30 wt%. In addition, more preferably, 1.0 to 1
0.0 wt%. (4) Further contains 0.1 to 10 wt% of solid lubricant (1) to
(3) The sintered body for ring bearing according to any of (3).

Solid lubricants have an effect on machinability and abrasion resistance, but when the amount is less than 0.1% by weight, the effect is small, and when it exceeds 10% by weight, the strength is poor. As solid lubricants, graphite,
Sulfides (MoS ₂ , WS ₂ , MnS, etc.), fluorides (CaF ₂ , LiF, etc.) are suitable. (5) A wear-resistant ring obtained by casting the sintered body for wear-resistant rings according to any one of (1) to (4) into a piston and cutting the piston.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the use of the wear ring of the present invention will be described with reference to FIGS. FIG. 2 shows a main part of the diesel engine, in which a cylinder body 4 having a cylinder liner 6 pressed into the inner peripheral surface side is provided in a cast crankcase 2, and a piston made of an aluminum alloy is provided in the cylinder liner 6. 3 are slidably guided. A water jacket 5 for cooling the cylinder is formed on the outer periphery of the cylinder body 4. A cylinder head 1 is provided at an upper portion of the crankcase 2, and a combustion chamber is defined between the cylinder head 1 and an upper surface of the piston 3. A plurality of piston rings 7 are mounted on the upper side of the piston 3.

As shown in FIG. 1, a ring groove 8 for receiving a piston ring 7 is formed on the outer peripheral surface of the piston 3. The ring groove 8 is on the upper surface,
The ring groove 8 has a U-shaped wear ring 10 formed of a sintered material having a higher strength than the piston and is fixed to the ring groove 8. Piston 3
As the piston ring 7 slides, a relative movement occurs between the piston ring 7 and the ring groove 8, but the wear-resistant ring 10 can prevent the ring groove 8 from being worn, set or deformed.

Now, the method for producing the sintered body for wear-resistant rings of the present invention will be described. First, pure iron powder, C powder, and Cu
One, two or more of powder, Ni powder, Mo powder, and Cr powder, or if necessary, the above hard particle powder and / or solid lubricant powder are blended and kneaded so as to have the above composition.
At this time, zinc stearate or the like may be blended as a lubricant. Instead of using pure iron powder and one or more of Cu powder, Ni powder, Mo powder and Cr powder, iron pre-alloyed with one or more of Cu, Ni, Mo and Cr Powder or steel powder may be used.

Next, the kneaded powder is filled in a mold,
It is compressed and molded into an annular shape by a molding press or the like to obtain a green compact.
At this time, to make the porosity of the sintered body 15 to 50 vol%,
It is desirable to adjust the pressing force so that the density of the green compact is 5.5 to 6.0 g / cm ³ . Next, this green compact is sintered to obtain a sintered body. As this sintering method, it is preferable to heat the green compact to 1100 to 1200 ° C. in a non-oxidizing atmosphere. 11
If the temperature is lower than 00 ° C, the sintering diffusion is insufficient and the strength is reduced.
In the case of exceeding, the hard particles are excessively diffused and wear resistance is deteriorated.
In order to make the atmosphere non-oxidizing, it is preferable to use an ammonia decomposition gas.

The thus obtained annular sintered body is mounted on a portion corresponding to a ring groove in a mold used for high-pressure die-casting of a piston, and molten aluminum alloy is poured into the mold to perform high-pressure die-casting of the piston. The sinter is cast-in. Thereby, the pores of the sintered body are sealed with the aluminum alloy. Then, the sintered body after casting is cut into a predetermined size to complete the wear ring.

[0021]

EXAMPLES As examples of the present invention and comparative examples, sintered bodies shown in Table 1 were produced in accordance with the above-mentioned production method (sequential steps of blending various powders, kneading, pressing, and sintering). In addition, pure iron powder and graphite powder were used as the raw material powder of the base phase, and one or more of Cu powder, Ni powder, Mo powder, and Cr powder were partially used. 1.0 part by weight of zinc stearate was added as a lubricant to parts by weight, and the porosity was adjusted by changing the density of the green compact. In the sintering process, the green compact is charged into an ammonia decomposition gas atmosphere furnace.
Heated to 1150 ± 20 ° C.

The obtained sintered body is subjected to a sealing treatment for encapsulating pores with a molten Al alloy, and then processed into a test piece, which is then subjected to a tester shown in FIG. ) 11 was set as a piston side member (simulated wear-resistant ring) 13, and a sliding tap test was performed using the same testing machine 11. The composition of the molten Al alloy was JIS AC8A. The above-mentioned "sliding and tapping test" means that the simulated wear ring 13 is fixed so as not to be movable in the axial direction with respect to the testing machine 11, and the ring material 12 equivalent to the piston ring is simulated.
13 is concentrically attached to the ring material 12, and the piston side member 13 is rotated while rotating the ring material 12 by reciprocating a cast iron circular rod 15 equivalent to a cylinder liner provided on the inner peripheral surface side of the ring material 12 in the axial direction. This is a test for giving a hitting operation mode. Testing machine 11
Has a heater 14 for heating the test material, can reproduce the high temperature state during combustion in the engine without actually burning the fuel, and can simulate the state change of the wear ring.

The test conditions were as follows. Piston side material temperature 340 ° C Repetition rate 1500 times / min Rotation (ring material rotation speed) 3.0 rpm Surface pressure 20 kg / cm ² Test time 10h On the other hand, the following ring material 12 was used.

Ring material A: JIS FCD (spheroidal graphite cast iron)
Ring material B: Cr-plated outer surface with Si-Cr steel as base material Ring material B: Gas-nitrided 17Cr stainless steel as base material Table 1 Example 4 materials shown in the following,
The test was performed by processing a test piece in the same manner as the comparative example. Conventional example 1
Is an Al forged drawn material having the composition shown in Table 1, and Conventional Example 2 is
Al material (JIS AC8A) green material, Conventional Example 3 is a raw material obtained by subjecting the raw material of Conventional Example 2 to alumite treatment, and Conventional Example 4 is a niresist cast iron material.

By this test, wear on the piston side (amount of wear of the simulated wear-resistant ring), ring wear (amount of wear of the ring material), and adhesion of aluminum to the ring material were evaluated. Table 1 shows the results.

[0026]

[Table 1]

In Table 1, as for the wear, the smaller the wear amount (mg), the better. Naturally, the symbol ◎ in the aluminum adhesion column indicates “no aluminum adhesion and good surface condition”, and the symbol “a” indicates aluminum. “No adhesion”, × means “with aluminum adhesion”. However, since Conventional Example 4 does not contain Al, it was excluded from the evaluation of aluminum adhesion. From Table 1, Examples 1 to
No. 5 is much better than Conventional Examples 1 to 3 in terms of piston-side wear regardless of the type of mating material (ring material), and is equal to or greater than Conventional Example 4. In addition, the ring wear is better than any of Conventional Examples 1 to 3, and in comparison with Conventional Example 4, Examples 2 and 3 are slightly inferior when the mating material is ring material A. All others are better than Conventional Example 4. In addition, aluminum adhesion is superior to Conventional Examples 1 and 2, and is equal to or greater than Conventional Example 3.

Among the examples, in particular, when the amount of the alloy element is 1 to
In the case of Examples 1 to 9 as small as 4 wt%, the abrasion on the piston side is better than that of Comparative Example 2. On the other hand, in Comparative Example 1, one or more of Cu, Ni, Mo, and Cr in the base phase (referred to as a third element) was less than 1.0 wt% in total, so that the pearlite structure became unstable. Since the total amount of the third elements in the base phase exceeds 10.0 wt%, the austenite structure increases, and all of them are inferior to the examples in terms of wear on the piston side. Comparative Example 3
Has a porosity of less than 15 vol%, so that bonding with the Al base material is insufficient. Comparative Example 4 has a porosity of more than 50 vol%, so that the strength and hardness of the sintered body are lowered, and the sintered body is inferior to the embodiment in the point of piston side wear.

[0029]

As described above, according to the present invention, not only the wear resistance of the wear ring itself is improved, but also the amount of wear on the piston side can be reduced and the occurrence of aluminum adhesion can be prevented. In addition, since iron-based sintered material is used, the holes are sealed with a molten Al base metal by high-pressure die-casting when the piston is inserted, and the jointability between the ring and the piston body is improved. The conductivity is improved, and the coefficient of thermal expansion of the wear ring can be close to the value of the piston body.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a piston provided with a wear-resistant ring.

FIG. 2 is a sectional view showing an internal combustion engine to which a wear ring is mounted.

FIG. 3 is a partially cutaway perspective view showing a testing machine for performing a property test of a wear ring.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Crankcase 3 Piston 4 Liner 5 Water jacket 6 Cylinder liner 7 Piston ring 8 Ring groove 10 Wear ring 11 Test machine (High temperature valve seat wear test machine) 12 Ring material 13 Piston side material (simulated wear ring) 14 Heater 15 Cast iron rod

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02F 3/00 302 F02F 3/00 302Z F16J 9/00 F16J 9/00 A

Claims (5)

[Claims] 1. A sintered body comprising pores and a base phase, wherein the composition of the base phase is C: 0.5 to 1.5 wt%, Cu, Ni, Mo,
One or more types of Cr: a total of 1.0 to 10 wt%, and the balance: substantially Fe. 2. The sintered body for wear-resistant rings according to claim 1, wherein the porosity is 15 to 50 vol%. 3. Hard particles having a hardness Hv of 500 to 1300 are further added to a hard particle.
3. The sintered body for wear-resistant rings according to claim 1, which contains 5 to 30% by weight. 4. The sintered body for a ring bearing according to claim 1, further comprising 0.1 to 10% by weight of a solid lubricant. 5. A wear-resistant ring obtained by casting the sintered body for wear-resistant ring according to claim 1 into a piston and cutting it.