JPS60228650A - Sliding parts and their manufacture - Google Patents

Abstract

PURPOSE:To improve the wear resistance of the sliding surface of cast iron contg. graphite as a base material by forming a surface layer having a structure contg. an islandlike alpha-iron phase dispersed in a phase of M7C3 carbide contg. Cr on the sliding surface. CONSTITUTION:An Fe-Cr alloy is welded to cast iron contg. graphite in the structure as a base material by build-up welding at 10-80% rate of dilution with a plasma gas welding machine or a TIG welding machine. The part built up on the surface of the base material and the part melted under the surface of the base material are agitated to form a uniform chemical structure, and the resulting surface layer on the sliding surface of the base material has a uniform structure contg. an islandlike alpha-iron phase dispersed in a phase of M7C3 carbide and/or M23C6 carbide contg. Cr. By this method the wear resistance of the sliding surface is considerably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION ■Field of Industrial Application The present invention relates to a sliding component and a method for manufacturing the same. The present invention relates to an improved sliding part and a method for manufacturing the same.

2. Prior Art For example, among the parts of an internal combustion engine, camshafts, rocker arms, tappets, etc. slide with their mating parts under severe conditions, so they are required to have wear resistance and rigidity.

Cast iron is widely used as such sliding parts, and in order to impart wear resistance, (a) a cold metal is used during casting to coat the sliding surface with a surface layer of white cast iron structure. (b) A method of irradiating the sliding surface with a laser beam or electron beam, etc. to remelt it and solidify it to form a surface layer of white cast iron structure on the sliding surface, (c) The above (b) In addition to the above method, the wear resistance is further improved by adding alloying elements such as chromium, molybdenum, and nickel to the cast iron base material. Conventionally, a method of creating a stitched iron structure has been adopted.

(2) However, in the method (d) above, not only the sliding surface but also other parts have a white cast iron structure, making the material brittle, making machining difficult, and further increasing the cost. The methods (a), (b), and (c) above still provide insufficient wear resistance, especially under severe sliding conditions. Taking the method described above as an example, the structure of the sliding surface layer is described as follows:
As shown in the micrograph (50x magnification, picral corrosion), the molten layer 1 on the outermost surface solidifies and becomes a white cast iron structure, and this molten layer 1 and the base material (spheroidal graphite cast iron in this example) 3
Sandwiched between the layers, a layer 2 is observed in which the base material becomes martensite by being heated during surface melting and then rapidly cooled by the heat taken away by the base material. As can be seen from the high magnification (1000x) micrograph in Figure 2, the above molten layer consists of pearlite and cementite crystallized in needle-like or dendritic shapes, similar to ordinary white cast iron.
Fe3C). Cementite has the effect of making materials brittle, and when it crystallizes in the form of needles or branches, this brittleness becomes noticeable (3), making the surface of sliding parts brittle and causing severe damage. Under sliding conditions, a wear phenomenon occurs in which the surface layer is chipped away little by little during sliding.

3. Purpose of the invention The present invention solves the problems of conventional sliding parts as described above,
The object of the present invention is to provide a sliding component that does not exhibit sufficient wear resistance even when used under severe sliding conditions such as high load and high friction speed, and a method for manufacturing the same.

4. Structure of the invention, that is, the first invention of the present invention is to provide at least one of chromium-containing M, C3 carbide, and chromium-containing M□C=carbide on at least the sliding surface of a cast iron base material having graphite in its structure. Alternatively, the present invention relates to a sliding component in which a surface layer is formed having a structure in which an α-iron phase exhibiting an island shape is dispersed in a phase consisting of both. The second invention is characterized in that overlay welding is performed using an iron-chromium alloy as an overlay material at a dilution rate of 10 to 80% on at least the sliding surface of a cast iron base material having graphite in its structure.
The present invention relates to a method for manufacturing a sliding component according to the first invention.

(4) In the present invention, cast iron having graphite in its structure refers to gray cast iron, spheroidal graphite cast iron, and malleable cast iron, and does not include white cast iron with crystallized carbides.

Furthermore, sliding refers to moving in contact with and relative to a mating part; it does not only refer to movement in contact with a stationary mating part; It also includes movement of the mating part.

Moreover, here, the above M represents a metal atom such as iron and chromium, the above C represents a carbon atom, and the above dilution ratio is a value given by the following formula.

The cross-sectional area, A, represents the cross-sectional area of the welded and solidified portion below the surface of the base metal.

5. Effects of the Invention The surface layer in the first invention is composed of chromium-containing MqC3 carbide and/or chromium-containing M2]Ch carbide (hereinafter, these carbides are simply referred to as M, C, carbide or M, IC & carbide (5) .

It is called. ), in which island-like α-iron phases are dispersed. In addition to the above carbides, iron-chromium-carbon alloys also contain M, C carbides, and Fe5C called cementite (however, in this case, chromium is dissolved in solid solution).
However, since carbides generally cause embrittlement, the crystallization of these carbides is preferably structured, so the surface layer is less likely to become embrittled, and since these carbides are hard, they do not form on the surface layer of sliding parts. It is suitable as a carbide to be present. Furthermore, by forming such a structure, the corrosion resistance is significantly improved, so that it is extremely effective as a component for internal combustion engines and the like.

In the surface layer structure as described above, the relationship between the carbon content and chromium content in the surface layer is 0.2XCr@weight%≧C weight%≧(0.1XCr-4)
fiii% (obtained by 21. (Hereinafter, weight % will be simply expressed as "%".) When 0% > 0.2XCr%, M, C carbides or cementite will crystallize and the surface layer will become brittle. As a result, the wear resistance also deteriorates.If 0%<(0,IXCr-4)%, carbon is insufficient and the amount of carbide crystallization is small, and the effect of improving the wear resistance is not sufficiently achieved. Or, if too much chromium is present, an FeCr intermetallic compound called σ phase precipitates, making the surface layer brittle, and the effect of improving wear resistance cannot be sufficiently achieved. The surface layer structure as in invention 1 can be obtained by overlaying an iron-chromium alloy on a cast iron base material at a dilution rate of 10 to 80%.A more suitable range of dilution rate is 50%. ~70%. If the dilution rate is outside the range of 10 to 80%, the composition of the surface layer will no longer satisfy the above formula (2), and as a result, the surface layer as in the first invention A layered structure cannot be obtained.

The surface layer (7) of the resulting sliding part has a uniform structure. Therefore, even if the portion protruding from the surface due to build-up is removed by grinding or the like, the above-mentioned surface layer still remains on the surface, so that there is no difference in direction.

Note that the build-up is preferably performed using a plasma gas welding machine or a TIG welding machine.

6. Example 3. 60% C, 2, 58% Si, 0.35% Mn, 0.
02%P10.01% S, O, OA The base material is spheroidal graphite cast iron with a pearlite base containing some ferrite having a chemical composition of 0.01% Mg, 45% Cr on the surface of the base material, and the remainder substantially consisting of Fe. A welding rod was used as the overlay material, and overlay was performed using a TIG welding machine at a dilution rate of 60%.

The structure of this built-up area and its surroundings is shown in the micrograph (50x, vicral corrosion) in Figure 3.The surface layer 4 where the welding rod penetrated into the base metal does not contain graphite, but contains lead. Layer 5, which has become a remaining chill structure, was heated during build-up, and the base metal has lost heat and rapidly cooled, and the base has become maru (8). Layer 6, which has become a rutin site, has not cooled rapidly enough to be hardened. First, a layer 7 in which the base is only pearlite is observed.

Furthermore, below it is the remains of the structure of the base material spheroidal graphite cast iron,
This part is included in the drawing (4 g of copper sulfate, 20 g of concentrated hydrochloric acid)
m7! , a corrosive solution for stainless steel prepared at a rate of 20 mA of water) is a micrograph at a magnification of 1000 times. In the figure, α-iron phase 9, which is rounded and exhibits an island shape, is observed in carbide phase 8.

Figure 5 shows the results of line analysis from the base material to the surface layer using an X-ray microanalyzer (magnification: 200I).
No obvious change was observed in the content of Fa, Cr content increased in the surface layer, and C content decreased in the surface layer.

Figure 6 shows the results of line analysis of the surface layer at a magnification of 1000 times, and the contents of Cr and C are correspondingly up and down, and
It can be seen that, conversely, the content of e is low in areas where Cr and C are high, and is high in areas where Cr and C are low (9).

In addition, in the rules of Figures 5 and 6, the ground is the primary electron Crzl.
It can be understood that c4 is clearly detected, Cr5C, Fexc, and the rounded island-like phase 9 observed in the figure are α iron, and the surrounding 8 are M2O3, M, and SO4.

In this way, the surface layer in the present invention has 1yyit≠M,
Since it has a structure in which rounded island-like α-iron phases are dispersed in a phase consisting of +2 and/or M, C4 carbides,
It can be seen that the embrittlement effect of carbides is not apparent and the material is strong.

In addition, as shown in Figure 3, the surface layer is not corroded by the corrosive liquid (Kral) that is normally used for speculum of steel materials, but is treated with the strongly acidic marble corrosive liquid used for speculum of stainless steel (Fig. 4). It can be seen from the appearance of the structure shown that it has extremely excellent corrosion resistance (10).

Above this, the structure of the surface layer in the present invention is shown in Figure 1.
This structure is completely different from the white cast iron structure of the conventional surface layer shown in FIG.

The hardness of the surface layer is Hv (500 g) 450 to 700, which is a fairly high hardness.

Next, the padded surface of this sample was polished to a flat surface, and this surface was used as a friction surface for the stator, and a mating rotor was coated with Cr, Ni, and Mo, respectively, using a super-immersion type wear tester. 0.5%, and the rest was made by casting a molten metal with a general cast iron composition using a chilled metal, and the surface had a white cast iron structure.The friction distance was 600 m and the final load was 18.9 kg. A wear test was conducted at a speed of 0.15 to 2.0 m/sec.

The test results are shown in FIG.

The figure shows a stator with 1.5% Cr for comparison.

A molten metal containing 1.5% Ni and 0.6% MO and other general cast iron composition was cast using a chilled metal and the surface had a white cast iron structure, and the same conditions as above were used. The results of the test are also listed.

(11) From the same figure, the amount of wear of the comparative stator changes greatly depending on the friction speed, whereas the amount of wear of the stator of the present invention changes very little depending on the friction speed, and the amount of wear changes significantly. It can be seen that the sliding part of the present invention has extremely excellent wear resistance.

Next, an example in which the present invention is applied to a camshaft will be described.

As shown in FIG. 8, on the surface of the cam nose portion 11, which slides and moves the cam piece fixed to the shaft 12 with the rocker arm or tappet (not shown) of the mating part,
A surface layer 4 having the structure shown in FIG. 4 was prepared in the same manner as above.
The camshaft 10 was formed and finished by grinding.

From the results of the wear test, it can be seen that this camshaft has extremely excellent wear resistance and exhibits sufficient durability even when used under harsh conditions for a long period of time.

It goes without saying that the present invention is applicable to rocker arms, tappets, valve seats, floating (12) seals, mechanical seals, etc. in addition to camshafts.

7. As described in detail, the sliding component of the present invention has MヮC3 and/or M, at least on the sliding surface of the cast iron base material containing graphite.
Since a surface layer is formed with a structure in which island-like α-iron phases are dispersed in a phase consisting of Q carbide, the surface layer is tough, has excellent wear resistance, and is resistant to harsh sliding. It has sufficient wear resistance even when used under dynamic conditions.

Moreover, the manufacturing method has great utility in that it builds up at least the sliding surface of a cast iron base material having graphite in its structure with an iron-chromium alloy as a build-up material at a dilution rate of 10 to 80%.

[Brief explanation of drawings]

Figure 1 is a 50x micrograph showing the surface layer and surrounding structure of a conventional sliding component, and (13) a 1000x micrograph. Figures 3 to 8 show examples of the present invention; Figure 3 is a 50x micrograph showing the surface layer and surrounding structure of the sliding component of the present invention; and Figure 4 is the sliding component of the present invention. 1000 indicating the structure of the surface layer of
This is a micrograph at 2x magnification. Figure 5 is the surface layer of the sliding part of the present invention and its surroundings Figure 6 is a 1000x photograph taken by an X-ray microanalyzer showing the element concentration in the surface layer of the sliding part of the present invention, Figure 7 is wear A graph showing the test results, and FIG. 8 is a cross-sectional view of a camshaft to which the present invention is applied. In addition, in the symbols shown in the drawings, 3・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・Base material cast iron (14) 4・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・Surface layer 5.6.7・・・・・・・・・・・・
・・・・・・・・・・・・Middle class 8・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・Carbide phase 9・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・α Iron phase 10・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・Camshaft 11
・・・・・・・・・・・・・・・・・・・・・・・・
...This is the cam nose part. Representative patent attorney Hiroshi Osaka (1 other person) (15) 50 1oo0 area <) Manabuaki Shiga, Commissioner of the Japan Patent Office +059, Patent Application No. 8444B 2, Name of sale, - 1 Sliding parts and their manufacturing method 3, Person making amendments Related to the case Patent applicant address Chiyoda, Tokyo Kudankita-ku, 13-5 Name: Riken Co., Ltd. 4, Agent 6, Number of inventions increased by amendment 7, Subject of amendment” “’°°”°”“”’°゛°I? 18. Contents of amendment 7' (+1 Specification page 13, line 19, same page, line 20, same page 1
First, add ``metal'' before ``organization'' in line 5 on page 4 and line 6 on the same page. (2) “Photo-
Next to 1, first add [photographs showing the X-ray intensities of Fe, Cr, and C as oscilloscope waveforms]. -I-To- (2) 279-

Claims (1)

[Claims] 1. At least the sliding surface of the cast iron base material having graphite in its structure contains chromium-containing M? C, carbide and chromium-containing M2ρ,
A sliding component having a surface layer having a structure in which island-like alpha iron phases are dispersed in a phase consisting of one or both of carbides. 2. At least on the sliding surface of a cast iron base material having graphite in its structure, an iron-chromium alloy is used as a build-up material at a dilution rate of 10 to 8.
Chromium-containing M
7CJ carbide and chromium containing M2. A method for manufacturing a sliding component in which a surface layer is formed having a structure in which island-like alpha iron phases are dispersed in a phase consisting of one or both of c6 carbides.