JP2002226949A - Wear-resistant ring for piston made of aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive wear-resistant ring for a piston made of aluminum alloy. SOLUTION: The wear-resistant ring has a groove for fitting a piston ring therein and is cast in a piston made of aluminum alloy. This collar is constituted of an austenitic stainless steel material having a composition containing, by mass, 3.5-17.0% Ni and 15.0-20.0% Cr, and the structure of the surface layer of the groove is composed of strain-induced martensite. Further, nitriding is applied to the surface layer to form a nitride case.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear ring for an internal combustion engine piston, and more particularly to a wear ring excellent in wear resistance suitable for use with an aluminum alloy piston.

[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 engine output, the engine is exposed to a higher temperature combustion environment, and the piston ring 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, there is a possibility that the piston ring groove may be set or deformed in a normal aluminum alloy. In particular, high combustion pressure acts directly on the top ring of a diesel engine. For this reason, the top ring groove is apt to be worn due to repeated tapping by the piston ring, causing gas leakage and oil leakage, resulting in a decrease in engine output.

[0003] In order to solve this problem, there has been conventionally proposed a configuration in which a wear-resistant 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 mounted. For example, in a piston for a diesel engine, an insert (abrasion ring) made of niresist cast iron is inserted into the top ring groove, and the abrasion ring prevents wear of the piston ring groove due to sliding of the piston in the cylinder. Things are mainstream. Niresist cast iron is Ni-Cu-Cr austenitic cast iron,
FCA-NiCuCr 1562 defined in JIS G 5510.

However, when the wear-resistant ring is made of niresist cast iron, the material cost is high, the yield is low because it is a cast product, the cost is high, and an aluminizing treatment is indispensable to improve the cast-in property. . It is also H _B 200 about the hardness, with high output power and increase in size of the recent engine, the wear resistance becomes insufficient. To solve such a problem, for example, Japanese Patent Application Laid-Open No. H11-182333 describes that C:
A wear ring for an internal combustion engine piston formed of a sintered body of austenitic steel having a density of not less than 6.0 g / cm ³ and containing 0.1 to 1.0% by weight has been proposed.

Japanese Patent Application Laid-Open No. Hei 8-151954 discloses that a wear ring of an aluminum alloy material containing particles of silicon carbide SiC is cast into an aluminum alloy piston, and a joint interface between the wear ring and the piston is laser level. There has been proposed a piston for an internal combustion engine in which remelting is joined by a heat source having an energy density to improve adhesion.

[0006]

The wear ring according to the technique described in Japanese Patent Application Laid-Open No. H11-182333 improves the adhesion to the piston and makes it easier to cast into the piston than Niresist cast iron. In addition, the wear resistance is almost the same as that of Niresist cast iron, and the wear resistance is still insufficient to cope with recent demands for higher output and larger engines. Further, in the wear-resistant ring according to the technology described in Japanese Patent Application Laid-Open No. 8-151954, the piston ring groove (wear-resistant ring) is hit at a high temperature and hits due to the recent increase in the output of the engine and the accompanying temperature rise of the piston ring groove. There is a concern that the phenomenon of softening and sticking (adhesion) to the end surface of the piston ring (called aluminum adhesion) will become apparent.

Accordingly, the present invention provides an inexpensive wear-resistant ring for an aluminum alloy piston which does not cause the problem of aluminum adhesion to the piston ring, can reduce the wear of the piston ring groove, is excellent in wear resistance, and is inexpensive. The purpose is to do.

[0008]

Means for Solving the Problems The present inventor has made intensive studies to achieve the above-mentioned object, and as a result, the wear ring is made of an austenitic stainless steel material having a thermal expansion coefficient close to that of an aluminum alloy. Occasionally, it was conceived that the surface layer had a hard martensite structure due to the process-induced transformation. Thereby, it has been found that the thermal expansion of the wear ring can be made similar to that of the aluminum alloy piston, and at the same time, the wear resistance is improved.

The present invention has been made based on the above findings, and has been further studied and experimented. The gist of the present invention is as follows. (1) A wear-resistant ring which is cast in an aluminum alloy piston and has a groove for mounting a piston ring, and has a mass%
And contains Ni: 3.5 to 17.0%, Cr: 15.0 to 20.0%, preferably C: 0.08% or less, Si: 1.00% or less, Mn: 2.00%
A wear-resistant ring for an aluminum alloy piston, comprising: an austenitic stainless steel material having the following composition, with the balance being Fe and unavoidable impurities, wherein the structure of the groove surface layer is work-induced martensite. (2) The wear-resistant ring for an aluminum alloy piston according to (1), wherein the thermal expansion coefficient of the work-induced martensite is 15 × 10 ⁻⁶ / ° C. or more. (3) The wear-resistant ring for a piston made of an aluminum alloy according to (1) or (2), wherein the surface layer of the groove has a nitrided layer. (4) A wear-resistant ring which is cast in an aluminum alloy piston and has a groove for mounting a piston ring, and has a mass%
And contains Ni: 3.5 to 17.0%, Cr: 15.0 to 20.0%, preferably C: 0.08% or less, Si: 1.00% or less, Mn: 2.00%
A wear-resistant ring for an aluminum alloy piston, comprising: an austenitic stainless steel material having the following composition, with the balance being Fe and unavoidable impurities, and having a nitride layer on the surface of the groove. (5) An aluminum alloy piston for an internal combustion engine obtained by casting the wear-resistant ring according to any one of (1) to (4) into an aluminum alloy piston and subjecting it to groove finishing. (6) In mass%, Ni: 3.5 to 17.0%, Cr: 15.0 to 20.0%, preferably C: 0.08% or less, Si: 1.00% or less,
Austenitic stainless steel material containing Mn: 2.00% or less, with the balance being Fe and unavoidable impurities, is forged or drawn into a predetermined shape, and is further processed into a groove for mounting a piston ring by cutting and polishing. A method for producing a wear-resistant ring for an aluminum alloy piston, wherein a work-induced martensite structure is provided in the groove surface layer by the forging or drawing. (7) In the method of (6), after the groove is processed, a nitriding treatment is performed. (8) In mass%, Ni: 3.5 to 17.0%, Cr: 15.0 to 20.0%, preferably C: 0.08% or less, Si: 1.00% or less,
Austenitic stainless steel material containing Mn: 2.00% or less, with the balance being Fe and unavoidable impurities, is forged or drawn into a predetermined shape, and is further processed into a groove for mounting a piston ring by cutting and polishing. A method for producing a wear-resistant ring for an aluminum alloy piston, the method comprising: after forming the groove, performing a nitriding treatment.

[0010]

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,
It has a U-shaped cross section consisting of a lower side surface and a bottom surface, and a wear ring 10 having a U-shaped cross section is cast into and fixed to the ring groove 8. Piston ring 7 with sliding of piston 3
Movement occurs between the ring and the ring groove 8, but the wear ring 10
This can prevent the ring groove 8 from being worn, set or deformed.
First, the reasons for limiting the composition of the steel material constituting the wear ring of the present invention will be described.

The wear ring of the present invention has a Ni content of 3.5 to 3.5% by mass.
It is composed of an austenitic stainless steel having a composition containing 17.0% and Cr: 15.0-20.0%. The composition of the austenitic stainless steel material is as follows: Ni: 3.5 to 17.0%, Cr: 1
5.0 to 20.0%, preferably C: 0.08% or less, S
i: 1.00% or less, Mn: 2.00% or less, or further Mo: 6% or less, Cu: 4% or less, Nb: 1% or less, Ti: 0.
It is preferable that the composition contains one or two or more of 6% or less and N: 0.3% or less, and has a balance of Fe and unavoidable impurities. P and S as inevitable impurities are P: 0.
045% or less, S: 0.030% or less is preferable from the viewpoint of ductility.

Ni: 3.5 to 17.0% Ni has an effect of stabilizing the austenite phase and has a thermal expansion coefficient of 15 × 10 ⁻⁶ / ° C. of the work-induced martensite.
In order to ensure the above, a content of 3.5% or more is required. In addition, Ni has the effect of preventing the intrusion of nitrogen into austenitic stainless steel, and if it exceeds 17.0%,
The nitriding time is long. Therefore, in the present invention, Ni is 3.
Limited to the range of 5 to 17.0%.

Cr: 15.0 to 20.0% Cr is important for improving the wear resistance by increasing the hardness of the nitrided layer and improving the wear resistance by combining with nitrogen invading into the austenitic stainless steel to form chromium nitride of high hardness. Element. On the other hand, if the Cr content is less than 15%, it is difficult to obtain sufficiently high-hardness chromium nitride, and a high-hardness nitrided layer cannot be obtained. Also,
Cr also has an effect of preventing nitrogen from penetrating into austenitic stainless steel, although not as much as Ni, and if it exceeds 20.0%, the nitriding time becomes long. Therefore, in the present invention, Cr is limited to 15.0 to 20.0%.

The reasons for limiting the components other than Ni and Cr are as follows.
It is. C: 0.08% or less, C increases the strength and stabilizes the austenite phase
However, if contained in large amounts, the strength becomes too high
Workability is reduced and thermal expansion coefficient is 15 × 10 ^-6/ ℃ or less
It will drop below. Therefore, C is limited to 0.08% or less
Is preferred.

Si: 1.00% or less Si is an element necessary as a deoxidizing agent in the steelmaking process, but is a ferrite-forming element. A large amount of Si deteriorates the mechanical properties. In the present invention, up to 1.00% is acceptable. Mn: 2.00% or less Mn forms a solid solution in steel to improve the strength and has an effect of stabilizing the austenite phase. However, if it exceeds 2.00%, the strength becomes too high, and the machinability decreases. Therefore, Mn is 2.00
% Is preferable.

One or more of Mo: 6% or less, Cu: 4% or less, Nb: 1% or less, Ti: 0.6% or less, N: 0.3% or less Mo, Cu, Nb, Ti, N It is an element that improves corrosion resistance, strength and workability, and can be selected as necessary and contained in the above-described range. Thermal expansion coefficient: 15.0 × 10 ⁻⁶ / ° C. or more Since the wear ring of the present invention is cast in an aluminum alloy piston, the difference in thermal expansion coefficient poses a problem when put to practical use. Within the above-described steel material composition range of the present invention, the thermal expansion coefficient of the wear-resistant ring becomes 15 to 18 × 10 ⁻⁶ / ° C.,
Thermal expansion coefficient of aluminum alloy (JIS AC8A): 19 × 10 ^-6
/ ° C, and there is no inconvenience in use.

Further, the coefficient of thermal expansion of the work-induced martensite formed in the groove surface layer of the wear-resistant ring can also follow the thermal expansion of the aluminum alloy piston.
It is preferable that the temperature be 15.0 × 10 ⁻⁶ / ° C. or higher.
It is preferable to adjust the content of each component within the above-described composition range of the austenitic stainless steel material so as to have the above-mentioned coefficient of thermal expansion.

In the wear ring of the present invention, the structure of the surface layer of the groove is made to be hard martensite by work-induced transformation. By making the surface layer of hard work-induced martensite, the hardness of the wear-resistant ring surface layer is increased, and wear, settling, and deformation due to the piston ring due to sliding of the piston can be prevented. By making the surface layer work-induced martensite, an increase in hardness up to about Hv400 is recognized within the steel composition range of the present invention.

Further, in the wear ring of the present invention, it is preferable that the surface layer be a work-induced martensitic phase and a nitride layer be further formed. The thickness of the nitrided layer is preferably 30 to 70 μm. By forming the nitrided layer in addition to the formation of the work-induced martensite phase, the wear resistance is significantly improved. Note that the nitride layer may be formed on the entire surface of the wear-resistant ring surface, or may be formed only in the groove portion that comes into contact with the piston ring. Note that a nitrided layer may be formed without forming a work-induced martensite phase on the surface layer according to the required degree of wear resistance.

Next, a method for producing a wear-resistant ring of the present invention will be described. First, an austenitic stainless steel material having the above-described composition and having a size capable of collecting a predetermined wear-resistant ring is forged or drawn to have a predetermined shape. At that time, a work-induced martensite phase is precipitated by forging or drawing. After forging or drawing, further cutting and polishing are performed. In the present invention, it is important that at least the surface layer of the groove in which the piston ring is mounted has a work-induced martensite phase.

In order to further increase the hardness,
After performing grooving by cutting, nitriding is performed,
Preferably, a nitride layer is formed. As the nitriding treatment, any of the conventionally known nitriding treatments such as gas nitriding, ion nitriding, salt bath nitriding, and sulphonitriding are suitable. The thickness of the nitrided layer formed by the nitriding treatment is preferably 30 to 70 μm.

When the hardness requirement is low, the steel material may be grooved without forging or drawing. In this case, in order to increase the hardness, a nitriding treatment may be performed to form a nitrided layer to have a desired hardness.
The anti-friction ring obtained in this way is mounted on the ring corresponding to the ring groove in the mold used for high-pressure die-casting of the piston, the molten Al alloy is poured into the die, and the piston is high-pressure die-casted to cast the ring. I do. The properties of the formed work-induced martensite are not significantly changed by the heat history at the time of casting.

After casting, groove finishing is performed and finished to a predetermined size to complete an aluminum alloy piston in which a wear-resistant ring is cast.

[0025]

EXAMPLE An austenitic stainless steel material having the composition shown in Table 1 was used as a material and processed into test pieces to form a piston side material (simulated wear ring) 13 of a testing machine (high-temperature valve seat wear testing machine) 11 shown in FIG. A sliding tap test was performed using the same testing machine 11. Here, the `` sliding test '' means that the simulated wear ring 13 is fixed immovably in the axial direction with respect to the testing machine 11, the ring material 12 equivalent to the piston ring is concentrically mounted on the simulated wear ring 13, and the ring material This is a test for imparting an operation mode in which the ring member 12 is rotated and hits the piston side member 13 by reciprocating the cast iron circular rod 15 equivalent to the cylinder liner provided on the inner peripheral surface side of the ring member 12 in the axial direction. . The test machine 11 has a heater 14 for heating the test material, and 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. it can.

The processing conditions for the portion (groove equivalent) of the test piece (simulated wear-resistant ring) that comes into contact with the ring material were as follows: forging, polishing by cutting, and polishing by cutting.

After processing the test piece, the presence of a work-induced martensite phase on the test piece surface was confirmed by an X-ray diffraction method. The coefficient of thermal expansion including the process-induced martensite is determined by thermo-mechanical analysis TM
A. After processing into test pieces, some test pieces were subjected to a nitriding treatment at a portion (corresponding to a groove) in contact with the ring material to form a nitrided layer. The thickness of the nitrided layer was measured by obtaining a hardness distribution using a hardness tester.

The test conditions of the "slip and tap test" 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: Si-Cr steel as base material and Cr-plated outer circumferential surface Ring material C: 17Cr stainless steel gas-nitrided Conventional material As examples, four types of materials shown in Table 1 were used as examples,
The test was performed by processing a test piece in the same manner as in 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, the wear on the piston side (amount of wear of the simulated wear ring) and the ring wear (the amount of wear of the ring material) were evaluated. Table 2 shows the results.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

In Table 2, as for the wear, the smaller the wear amount (mg), the better. In any of the working examples of the present invention (piston side materials No. 1 to No. 17), good results can be confirmed in slipping test results with the current niresist cast iron (piston side material No. 35). The coefficient of thermal expansion is also larger than 15.0 × 10 ⁻⁶ / ° C.

In the comparative examples (piston side materials No. 18, No. 24, No. 26, No. 27) out of the range of the present invention, the thermal expansion coefficient is smaller than 15.0 × 10 ⁻⁶ / ° C. Has become. In each of the comparative examples (piston side materials No. 18 to No. 31), the wear resistance of the ring B material was larger than that of the conventional Niresist cast iron (piston side material No. 31) because the piston side wear was large. ing. This is a ring-resistant material and ring B material (Si-Cr
It is considered that the compatibility between the ring material and the steel material was poor, and the ring material had a high aggressiveness against the piston material, causing the piston side material to be worn. According to the results of the sliding wear test, a decrease in the wear amount of the piston side material was observed in the ring A material and the ring C material by performing the nitriding treatment, but the wear amount of the ring material was reduced by Niresist cast iron (piston side material No. 35). ) Is not suitable because it is equal to or higher than.

From Table 2, it can be seen that the example of the present invention is much better than the conventional examples (piston side materials No. 32 to No. 34) in terms of piston-side wear regardless of the type of mating material (ring material). It is also better than the conventional example (piston side material No. 35). In terms of ring wear, the conventional example (piston side material No. 32
To No. 35).

[0037]

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. Further, the coefficient of thermal expansion of the wear ring can be made close to the value of the piston body. The present invention also relates to an Ink Turbo or Diesel engine.
In a high-temperature atmosphere in a GR (exhaust gas recirculation system), it is particularly effective in improving abrasion resistance.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a piston provided with a wear 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 F02F 3/00 G F16J 1/00 F16J 1/00 9/00 9/00 A

Claims (12)

[Claims] An austenitic ring having a groove which is cast in an aluminum alloy piston and has a groove in which a piston ring is mounted, and which has a composition containing, by mass%, Ni: 3.5 to 17.0% and Cr: 15.0 to 20.0%. A wear-resistant ring for a piston made of an aluminum alloy, comprising a stainless steel material, wherein the structure of the groove surface layer is work-induced martensite. 2. The austenitic stainless steel material,
In mass%, C: 0.08% or less, Si: 1.0% or less, Mn: 2.0
The wear ring for a piston made of an aluminum alloy according to claim 1, wherein the wear ring comprises: 3. The wear-resistant ring for a piston made of an aluminum alloy according to claim 1, wherein the thermal expansion coefficient of the work-induced martensite is 15.0 × 10 ⁻⁶ / ° C. or more. 4. The wear-resistant ring for an aluminum alloy piston according to claim 1, further comprising a nitride layer on the surface of the groove. 5. A wear-resistant ring having a groove in which a piston ring is mounted by being cast in an aluminum alloy piston, and having a composition containing, by mass%, Ni: 3.5 to 17.0% and Cr: 15.0 to 20.0%. A wear-resistant ring for a piston made of an aluminum alloy, comprising a stainless steel material and having a nitride layer on the surface of the groove. 6. The austenitic stainless steel material,
C: 0.08% or less, Si: 1.0% or less, Mn: 2.0% by mass%
The wear-resistant ring for an aluminum alloy piston according to claim 5, comprising: 7. An aluminum alloy piston for an internal combustion engine, wherein the wear ring according to any one of claims 1 to 6 is cast in an aluminum alloy piston and subjected to groove finishing. 8. In mass%, Ni: 3.5 to 17.0%, Cr: 15.0%
In forming an austenitic stainless steel material having a composition containing up to 20.0% into a predetermined shape by forging or drawing, and further, by cutting and polishing, forming a groove for mounting a piston ring to form a wear-resistant ring. A method for producing a wear-resistant ring for a piston made of an aluminum alloy, characterized by having a work-induced martensite structure in a groove surface layer by drawing. 9. The austenitic stainless steel material,
C: 0.08% or less, Si: 1.0% or less, Mn: 2.0% by mass%
The method for producing a wear-resistant ring for an aluminum alloy piston according to claim 8, comprising: 10. The method for producing a wear-resistant ring for an aluminum alloy piston according to claim 8, wherein a nitriding treatment is further performed after the groove is processed. 11. In mass%, Ni: 3.5 to 17.0%, Cr: 15.0
Austenitic stainless steel having a composition of up to 20.0% is forged or drawn into a predetermined shape, and then, by cutting and polishing, forming a groove for mounting a piston ring to form a wear-resistant ring. After that, a nitriding treatment is applied to the method for producing a wear-resistant ring for an aluminum alloy piston. 12. The austenitic stainless steel material,
C: 0.08% or less, Si: 1.0% or less, Mn: 2.0% by mass%
12. The method for producing a wear-resistant ring for a piston made of an aluminum alloy according to claim 11, comprising: