WO2016152967A1

WO2016152967A1 - Sliding component and sliding structure

Info

Publication number: WO2016152967A1
Application number: PCT/JP2016/059355
Authority: WO
Inventors: 精心上田; 久保田　邦親
Original assignee: 日立金属株式会社
Priority date: 2015-03-26
Filing date: 2016-03-24
Publication date: 2016-09-29
Also published as: CN107429356A; JPWO2016152967A1; EP3276031A4; EP3276031A1; JP6424951B2; KR20170118904A; CN107429356B

Abstract

Provided is a sliding component which has excellent wear resistance. Also provided is a sliding structure which is provided with this sliding component. A sliding component which has a constituent composition containing, in mass%, 0.7-1.6% of C, 0.5-3.0% of Si, 0.1-3.0% of Mn, 0.05% or less of P, 0.01-0.12% of S, 0.3-1.5% of Ni, 7.0-13.0% of Cr, Mo and/or W in such amounts that (Mo + 1/2W) is 0.5-1.7%, 0-0.70% of V, 0.1-1.0% of Cu, 0.10-0.70% of Al and 0-0.30% of Nb, with the balance made up of Fe and impurities, and which has a hardness of 52 HRC or more but less than 58 HRC. A sliding structure which is configured such that the above-described sliding component is in sliding contact with a sliding surface of a counterpart component in an environment where a lubricant is present on a sliding surface of this sliding component.

Description

Sliding parts and sliding structures

The present invention relates to a sliding component used in various sliding environments such as an oil ring and a cam lobe incorporated in an internal combustion engine. Then, the present invention relates to a sliding structure such as an internal combustion engine configured by incorporating these sliding parts.

Conventionally, sliding parts constituting sliding structures such as oil rings, cam lobes, tappets, piston pins, cylinder liners, mission gears, thrust plates and vanes, which are constituent parts of internal combustion engines, are made of JIS steel as the material. SUJ2 and SKD11 which have been used have been used. SKD11 is a steel type that can achieve a high hardness of 60 HRC or higher by quenching and tempering, and also has abundant carbides in the structure, and therefore has excellent wear resistance. And the press metal mold | die which gave the sliding characteristic (self-lubrication characteristic) excellent in the raw material and improved abrasion resistance by improving the component composition of the raw material is proposed (patent document 1).

JP 2007-002333 A

The press die disclosed in Patent Document 1 has excellent wear resistance due to its self-lubricating properties. However, it has not been considered to apply the material of the press die of Patent Document 1 to the components of the internal combustion engine.

An object of the present invention is to provide a sliding part having excellent wear resistance. And it is providing the sliding structure which comprised this sliding component.

The present invention, in mass%, C: 0.7-1.6%, Si: 0.5-3.0%, Mn: 0.1-3.0%, P: 0.05% or less, S : 0.01 to 0.12%, Ni: 0.3 to 1.5%, Cr: 7.0 to 13.0%, one or two of Mo and W: (Mo + 1 / 2W) In the relational expression, 0.5 to 1.7%, V: 0 to 0.70%, Cu: 0.1 to 1.0%, Al: 0.10 to 0.70%, Nb: 0 to 0.30 %, Remaining Fe and impurities, and a hardness of 52 HRC or more and less than 58 HRC.

Further, the present invention is configured such that the above-described sliding component of the present invention slides with the sliding surface of the mating component in an environment where lubricating oil is present on the sliding surface of the sliding component. It is a sliding structure characterized by these.

According to the present invention, the wear resistance of the sliding part can be improved.

It is a figure which shows an example of the relationship between hardness and fatigue strength of the sliding component of the example of this invention and a comparative example. It is a figure which shows an example of the result of the friction coefficient measured by the ball-on-disk test of the sliding parts of the example of the present invention and the comparative example. It is a figure which shows an example of the relationship between the fatigue strength of the sliding parts of the example of this invention, and a sliding distance when the friction coefficient measured by the ball-on-disk test reaches 0.20.

Many of the sliding parts that make up various types of sliding structures, such as oil rings and cam lobes, are represented by components of internal combustion engines. Used by sliding with sliding surface. In this environment, the sliding component of the present invention has been found to exhibit self-lubricating properties effectively and improve the wear resistance of the sliding component. Hereinafter, the configuration requirements of the present invention will be described.

(1) The sliding component of the present invention is, in mass%, C: 0.7 to 1.6%, Si: 0.5 to 3.0%, Mn: 0.1 to 3.0%, P: 0.05% or less, S: 0.01 to 0.12%, Ni: 0.3 to 1.5%, Cr: 7.0 to 13.0%, one or two of Mo and W : 0.5 to 1.7% in the relational expression of (Mo + 1 / 2W), V: 0 to 0.70%, Cu: 0.1 to 1.0%, Al: 0.10 to 0.70%, Nb: 0 to 0.30%, balance Fe and impurity components.
In the above component composition, particularly, the sliding component of the present invention is characterized by “co-addition of S and Cu” which greatly contributes to the expression of the self-lubricating property. Conventionally, S and Cu are elements that are not actively added in most steel materials because they are elements that inhibit the hot workability of steel materials. Hereinafter, the effect of the component composition of the sliding component of the present invention will be described.

C: 0.7 to 1.6% by mass (hereinafter simply referred to as “%”)
C is an element that dissolves in the base and imparts strength to the sliding component. Moreover, it is an element which forms carbide and enhances the wear resistance and seizure resistance of the sliding component. However, when C increases excessively, the amount of C dissolved in the base increases, and the machinability when finishing into the shape of the sliding part deteriorates. Further, coarse carbides are generated, and the heat treatment size change during quenching is increased. Therefore, C is set to 0.7 to 1.6%. Preferably it is 0.9% or more. Moreover, Preferably it is 1.3% or less. More preferably, the content is 1.1% or less.

・ Si: 0.5-3.0%
Si is an element that improves the high-temperature softening characteristics of the sliding component. However, when there is too much Si, the formation of delta ferrite in the structure becomes remarkable, and the maintenance of the hardness of the sliding part is hindered. Therefore, Si is 0.5 to 3.0%. Preferably it is 0.9% or more. Moreover, it is preferably 2.0% or less. More preferably, it is 1.5% or less. More preferably, it is 1.1% or less.

・ Mn: 0.1-3.0%
Mn is an element that enhances hardenability. However, if too much, the machinability deteriorates. Therefore, Mn is set to 0.1 to 3.0%. Preferably it is 0.3% or more. More preferably, it is 0.4% or more. Further, it is preferably 1.0% or less. More preferably, it is 0.6% or less.

-P: 0.05% or less P is an element contained inevitably even if it does not usually add. And it is an element which inhibits the toughness of a sliding component. Therefore, it is made 0.05% or less. Preferably it is 0.03% or less. More preferably, the content is 0.02% or less.

・ S: 0.01-0.12%
S is an element that contributes to the improvement of the self-lubricating property of the sliding component of the present invention together with Cu described later. This inventor investigated the phenomenon which has arisen on the sliding surface, when the sliding component which has the component composition of patent document 1 was used in the environment where lubricating oil intervened in the sliding surface. As a result, during this use, when the sliding surfaces of the sliding part and the mating part come into contact with each other at such a high surface pressure that the seizure occurs, organic components in the lubricating oil adsorbed on the sliding surface of the sliding part Has been dehydrogenated, and this has been found to change to substances such as diamond and graphite. Among these diamonds and graphites, “graphite intercalation compounds” having a structure in which sulfate ions or sulfuric acid molecules are periodically sandwiched improve the self-lubricating properties of the sliding parts, so It was found that the friction coefficient can be kept low.

Then, S in the sliding part is oxidized on the sliding surface in use to generate sulfate ions. The generated sulfate ions are sandwiched between the graphite layers to promote the formation of the graphite intercalation compound. Alternatively, the generated sulfate ions combine with the hydrogen ions generated by the dehydrogenation of the lubricating oil to form sulfuric acid molecules, which are sandwiched between the graphite layers to promote the formation of the graphite intercalation compounds. . This increases the interplanar spacing of the graphite in the C-axis direction, suppresses the graphite from undergoing an allotropic transformation into diamond in a nano-level state, increases the degree of freedom of sliding, and improves the lubricity. However, when S in the sliding component becomes excessive, excessive sulfate ions are generated on the sliding surface so as not to be sandwiched between the graphite layers. This excess sulfate ion promotes damage to the sliding surface and inhibits the expression of self-lubricating properties. Therefore, S is set to 0.01 to 0.12%. Preferably it is 0.03% or more. More preferably, it is 0.04% or more. More preferably, it is 0.05% or more. Moreover, Preferably it is 0.09% or less. More preferably, it is 0.08% or less.

・ Ni: 0.3-1.5%
Ni is an element that contributes to the maintenance of the hardness of the sliding component by binding to Al, which will be described later, in the quenching and tempering process, thereby precipitating a Ni—Al intermetallic compound. However, if there is too much Ni, the machinability when processing into the shape of the sliding component in the annealed state before quenching and tempering deteriorates. Therefore, Ni is set to 0.3 to 1.5%. Preferably it is 0.4% or more. Further, it is preferably 1.0% or less. More preferably, it is 0.8% or less. More preferably, it is 0.6% or less.

・ Cr: 7.0 to 13.0%
Cr is an element that enhances the hardenability of the base. Moreover, it is an element which forms the above-mentioned C and a carbide | carbonized_material, and improves the abrasion resistance and seizure resistance of a sliding component. However, the increase in carbides deteriorates machinability. Therefore, Cr is set to 7.0 to 13.0%. Preferably it is 7.5% or more. More preferably, it is 8.0% or more. Moreover, it is preferably 11.0% or less. More preferably, it is 10.0% or less. More preferably, it is 9.0% or less.

・ One or two of Mo and W: 0.5 to 1.7% in the relational expression of (Mo + 1 / 2W)
Mo and W are elements that form fine carbides in the structure after quenching and tempering and impart fatigue strength to the sliding component. However, if too much, machinability and toughness are reduced. Mo and W can be added alone or in combination. The addition amount at this time can be defined together by the relational expression of (Mo + 1 / 2W) since W is an atomic weight approximately twice that of Mo. In the present invention, the value of (Mo + 1 / 2W) is 0.5 to 1.7%. Preferably it is 0.7% or more. More preferably, it is 0.9% or more. More preferably, it is 1.0% or more. Further, it is preferably 1.5% or less. More preferably, it is 1.3% or less. More preferably, it is 1.2% or less.

・ V: 0 ~ 0.70%
V can be contained for improving hardenability. However, since V forms hard VC carbide, the inclusion of excess V inhibits machinability. Therefore, in the present invention, even when V is contained, the content is made 0.70% or less. Preferably it is 0.50% or less. More preferably, it is 0.30% or less. More preferably, it is 0.20% or less.

Cu: 0.1 to 1.0%
Cu, together with S described above, is an element that contributes to the improvement of the self-lubricating characteristics of the sliding component of the present invention. That is, Cu is an element that exhibits a catalytic action for producing the above-mentioned “graphite intercalation compound”. Cu can deposit a very small amount on the sliding surface of the sliding part after quenching and tempering. Then, Cu deposited on the sliding surface has a function of a catalyst that promotes the formation of the above-mentioned “graphite intercalation compound”. However, when Cu is contained excessively, red hot embrittlement of the material is caused and hot workability is deteriorated. Therefore, Cu is made 0.1 to 1.0%. Preferably it is 0.2% or more. More preferably, it is 0.3% or more. Further, it is preferably 0.8% or less. More preferably, it is 0.6% or less. More preferably, it is 0.5% or less.

・ Al: 0.10 to 0.70%
Al is an element that combines with the above Ni to form a Ni—Al-based intermetallic compound and contributes to maintaining the hardness of the sliding component. However, when there is too much Al, the formation of delta ferrite in the structure becomes remarkable, and the maintenance of the hardness of the sliding part is hindered. Therefore, Al is made 0.10 to 0.70%. Preferably it is 0.15% or more. More preferably, it is 0.25% or more. Moreover, Preferably it is 0.50% or less. More preferably, it is 0.45% or less.

・ Nb: 0 to 0.30%
Nb, like V, can be contained to improve hardenability. However, excessive Nb content inhibits machinability. Therefore, in the present invention, even when Nb is contained, the content is made 0.30% or less. Preferably it is 0.20% or less. More preferably, it is 0.15% or less. A preferable content for obtaining the above effect is 0.03% or more. More preferably, it is 0.05% or more. More preferably, it is 0.07% or more.

With the above component composition, the self-lubricating property of the sliding component of the present invention is exhibited by utilizing the “deformation behavior due to friction” of the lubricating oil present on the sliding surface. Therefore, in order to develop the self-lubricating characteristics according to the present invention, it is only necessary to intervene with a counterpart component in use, for example, a hydrocarbon-based lubricating oil. Material) can be selected.

(2) The sliding component of the present invention has a hardness of 52 HRC or more and less than 58 HRC.
In general, it has been considered that reducing the hardness of a sliding component leads to a decrease in wear resistance of the sliding component. Therefore, the conventional sliding component has been adjusted to a hardness of 60 HRC or higher. However, the sliding component of the present invention has higher fatigue strength than the conventional SKD11 due to the above-described component composition. And the value of the fatigue strength improves more notably by reducing the hardness of a sliding component moderately. That is, as shown in FIG. 1, the conventional SKD11 (x mark in FIG. 1) had a fatigue strength of about 560 MPa when adjusted to 60 HRC, which is the hardness of a general sliding component. And the value of the fatigue strength increases only to about 600 MPa even if the hardness is lowered. On the other hand, in the case of the material of the component composition according to the present invention (circle mark in FIG. 1), the fatigue strength value shows a high fatigue strength of about 630 MPa when the hardness is lowered to 58 HRC. Thereafter, the high fatigue strength is maintained in a low hardness region.

In the sliding component of the present invention having the above-described component composition, the friction coefficient in use exhibited by the sliding component is effectively reduced as the fatigue strength value of the sliding component increases, and the present invention Lubricating characteristics are synergistically improved (see FIG. 3). As the fatigue strength that can stably obtain this synergistically improved self-lubricating property, the present invention aims at a sliding component having a fatigue strength exceeding 600 MPa, which is difficult to achieve with the conventional SKD11. The fatigue strength is preferably over 630 MPa. And the hardness of the sliding component of this invention shall be less than 58HRC as a range which can achieve this fatigue strength exceeding 600 MPa easily. Preferably it is 57 HRC or less.

However, when the sliding component of the present invention is used, assuming that the hardness of the counterpart component is high, it is not a good idea to reduce the hardness of the sliding component of the present invention. For example, when SUJ2, which is a bearing steel of the JIS steel type, is used as the mating part, the hardness is usually adjusted to 60 to 62 HRC, which is higher than the sliding part of the present invention. SUJ2 is a “high carbon chrome bearing steel” standardized by JIS-G-4805, and its component composition is as follows in mass%.
C: 0.95 to 1.10%, Si: 0.15 to 0.35%, Mn: 0.50% or less, P: 0.025% or less, S: 0.025% or less, Cr: 1. 30 to 1.60%, remaining Fe and impurities

If the sliding component of the present invention is an oil ring or cam lobe, the sliding surface slides with the sliding surface of the counterpart component in an “intermittent” contact mode such as rotation or reciprocation. In such a contact form, when the hardness of the sliding component of the present invention is significantly lower than that of the counterpart component, the applied Hertz stress increases. When this Hertz stress exceeds the fatigue strength of the sliding component, fine plastic deformation occurs on the sliding surface. Then, the sliding wear of the sliding parts is induced, the friction coefficient between the sliding surfaces is increased, and the self-lubricating property of the present invention is hindered. Therefore, the lower limit of the hardness of the sliding component of the present invention is 52 HRC. In this lower limit, it is preferably 53 HRC. More preferably, it is 54HRC. More preferably, it is 55HRC.
Under these conditions, for example, a metal material such as SUJ2 can be used as the material of the counterpart part, and a long-life sliding structure that achieves both suppression of seizure (adhesion) damage and improvement of fatigue life The body mechanism can be obtained.

Sample No. in Table 1 Respective sliding

parts

1 and 2 having component compositions of 1 and 2 were prepared. Sample No. 2 is SKD11.

Next, for each of the sliding

parts

1 and 2, those in which the target hardness was adjusted to three types of A: 50 HRC, B: 55 HRC, and C: 60 HRC were prepared. At this time, the actual hardness of each sliding component is 50.4 HRC for sliding component 1-A, 56.2 HRC for 1-B, 62.0 HRC for 1-C, 50.0 HRC for 2-A, 2-B was 55.8 HRC and 2-C was 61.0 HRC. The sliding component 2-C made of SKD11 having a target hardness of 60 HRC corresponds to a conventional sliding component. And the fatigue strength of these sliding parts was measured. The fatigue strength was measured by processing each sliding part into a rotating bending fatigue test piece and performing an Ogoshi type rotating bending fatigue test on this. The surface stress of the test piece was adjusted by adjusting the secondary moment of the cross section determined from the shape of the test piece and adjusting the weight of the weight suspended in the center of the parallel part of the test piece. The stress amplitude was set so that the tensile stress and the compressive stress were equal in one rotation of the specimen (referred to as an amplitude ratio −1). The rotation speed of the test piece was 50 Hz (3,000 rpm). And the stress at the time of reaching the fracture | rupture of a rotation bending fatigue test piece was made into fatigue strength. The results are shown in FIG.

Then, a ball-on-disk test was performed on each sliding component to evaluate the self-lubricating characteristics of each sliding component. The test conditions are as follows. The change in the coefficient of friction was continuously measured until the sliding distance reached 100 m. The results are shown in FIG.
Equipment: CSM friction and wear tester Test piece:
・ Disk (sliding part): Diameter 20mm x thickness 5mm
・ Ball (mating part): SUJ2 (diameter 6mm, hardness 62HRC)
Ball load: 10N
Disk rotation speed: 500rpm
Sliding radius: 3.3mm
Sliding distance: 100m
Oil amount: 0.1 μl
Oil type (lubricant):
・ Base oil: Commercial paraffin oil ・ Formic acid: Amount 2.9 × 10 ⁻⁴ ppm

As shown in FIG. 2, the sliding components 2-A, 2-B, and 2-C, which have component compositions that do not exhibit self-lubricating properties, have increased friction coefficients and measured friction coefficient values exceeding 0.30. . In the sliding parts 2-B and 2-C, seizure occurred before the sliding distance reached 100 m, and the friction coefficient rapidly increased.

In contrast, sliding parts 1-A, 1-B, and 1-C, which are component compositions that exhibit self-lubricating properties, did not cause seizure during a sliding distance of 100 m. In addition, the sliding components 1-A and 1-B maintained the coefficient of friction therebetween being 0.30 or less. In addition to the component composition that exhibits the above self-lubricating characteristics, the sliding component 1-B of the present invention in which the hardness is adjusted to “52 HRC or more and less than 58 HRC” synergistically improves the self-lubricating characteristics, The coefficient of friction was further reduced, and the value was 0.20 or less.

FIG. 3 shows the relationship between the fatigue strength of each sliding component and the sliding distance when the friction coefficient measured above reaches 0.20. Here, as described above, the value of the friction coefficient of “0.20” is an index of the friction coefficient when the sliding component exhibits a synergistic self-lubricating property under the test conditions of this example. From FIG. 3, the sliding component 1-B of the present invention has a fatigue strength of over 600 MPa. Even when the sliding distance reached 100 m, a low coefficient of friction of 0.20 or less was maintained (in FIG. 3, for convenience, it is shown at the position “100 m”). The sliding component 1-B of the present invention has improved self-lubricating properties (smaller friction coefficient) than the sliding components 1-A and 1-C, and the improved self-lubricating properties are: It was stably maintained over a long sliding distance.

Claims

In mass%, C: 0.7 to 1.6%, Si: 0.5 to 3.0%, Mn: 0.1 to 3.0%, P: 0.05% or less, S: 0.01 0 to 0.12%, Ni: 0.3 to 1.5%, Cr: 7.0 to 13.0%, one or two of Mo and W: (Mo + 1 / 2W) 0.5 to 1.7%, V: 0 to 0.70%, Cu: 0.1 to 1.0%, Al: 0.10 to 0.70%, Nb: 0 to 0.30%, balance Fe And a sliding component characterized by having a component composition of impurities and having a hardness of 52 HRC or more and less than 58 HRC.
The sliding component according to claim 1, wherein the sliding component is configured to slide with the sliding surface of the counterpart component in an environment where lubricating oil is present on the sliding surface of the sliding component. A moving structure.