JPS5943864A - Nitrided cast iron parts subjected to sealing treatment and its production - Google Patents

Abstract

PURPOSE:To obtain nitrided cast iron parts having improved corrosion resistance and sliding characteristics by polishing the surface of a nitrided cast iron base material and sealing the clearances between the exposed graphite and the base material by using a resin contg. a solid lubricant. CONSTITUTION:When a cast iron blank material is subjected to a soft nitriding treatment, a compd. layer 10 is formed on the surface thereof and build-ups are produced in the parts 12 of graphite simultaneously with hardening, thus forming clearances between said parts and a base material part 14. After the build-ups on the surface are polished away, a resin such as epoxy resin which contains 30-80vol% a solid lubricant and does not decompose at <=250 deg.C is coated thereon and is rubbed. The material is then subjected to a heat treatment to form a resin layer 15 on the surface of the material 14 and to seal the clearances. Even if the layer 15 is collapsed by sliding with a piston or the like, the layer remains as a resin part 16 in the exposed part of the graphite 12 and provides a sealing effect.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides nitrogen oxide Ti', 3 with improved corrosion resistance.
Concerning I information and its manufacturing method.

It is well known that nitriding (Is) treatment is performed to improve the wear resistance of cast iron. For example, to improve the wear resistance of the cast iron cylinder wall of an automatic engine, the surface is treated with nitriding. Words are an effective means of hardening.

However, when the nitriding process was completed, the rising part of the filler at the edge of the exposed graphite part was missing due to the polishing process, and this missing sound was caused by the thinning of the graphite due to the nitriding process. A gap is created between graphite and the vowel i. In a gasoline IJ engine, this gap also becomes an oil pocket, and rather unpleasant results can be expected, but in a diesel engine, the fuel contains a large amount of sulfur, which causes corrosion.

It is common knowledge to seal surface defects in general cast iron products by impregnating them with water glass, etc., but this method has a heat resistance and abrasion resistance of 75%; The purpose of the present invention is to
It is an object of the present invention to provide a nitrided cast iron product having improved corrosion resistance, wear resistance and heat resistance due to improved sliding properties, and a method for producing the same.

The nitrided cast iron product of the present invention has a nitrided layer on the surface, and the gap between the graphite exposed on the surface and the surrounding base material is 30 to 8 Q.
The pores are sealed with a resin that does not decompose below 250° C. and contains a solid lubricant of vol.%. In addition, this method for manufacturing nitrided cast iron products involves nitriding the surface of a cast iron material, polishing the nitrided surface, and forming a gap between the graphite exposed on the polished surface and the base material. 25 containing 30-80 vol,% solid lubricant in
The method is characterized in that a resin that does not decompose at temperatures below 0° C. is applied, and the resin is heat-treated to seal the gap.

In the nitrided cast iron product of the present invention, resin is embedded in the gap between the graphite and the base material that is formed on the surface during the nitriding treatment and subsequent polishing. Therefore, the hardness of this nitrided cast iron product increases through nitriding treatment, and the surface wear resistance is improved. At the same time, the openings are covered with a resin that has a certain heat resistance, and the matrix (A) is no longer exposed on the surface. 4 Corrosion resistance is improved. As a result, the nitrided cast iron product of the present invention can be used for diesel engine cylinders, etc. After the nitrided cast iron product is polished, a resin is applied, and the resin is coated with a resin. By applying a certain heat treatment, a sufficient sealing effect can be obtained.In other words, a nitrided cast iron product with improved wear resistance and corrosion resistance can be obtained by a relatively simple method.

Preferred basic properties of the 1-distillate fat used in the present invention are as follows.

(1) Not altered by fuels such as gasoline and diesel oil, sulfuric acid, oil, and water.

(2) No thermal decomposition occurs at 250°C.

(3) Easy to apply at room temperature.

Examples of resins that meet these conditions include evoquino resin,
Phenol resin, polyimide resin, polyamide resin,
There are polyimide amide resins and fluororesins.

In the present invention, the resin used for the above-mentioned sealing treatment is 60%
It contains ~80 vol. of solid lubricant, and this solid lubricant has the effect of ensuring the lubricity of the resin portion exposed to the surface by the sealing treatment and increasing the wear resistance of this portion. Therefore, when this nitrided cast iron product is used in the cylinder liner of an automobile ennon, the piston slides smoothly, which has the advantage of reducing wear on the nitrided cast iron product and reducing wear on the piston. As this solid lubricant, molybdenum disulfide, tungsten disulfide, Teflon, graphite, BN, etc. are suitable, and the content thereof is 30 to 80 vol. % is preferred. This is because if it is less than 30%, the abrasion resistance effect will be weak, and if it exceeds 80%, it will be difficult to mix uniformly with the resin for sealing treatment, and the viscosity will become high, making coating difficult. Further, the particle size is preferably about 74 microns or less. The reason for this is that if the particle size is larger than this, it will be difficult for the solid lubricant to enter the sealing portion, and the wear resistance of this portion will be reduced.

In a preferred embodiment of this resin-based pore sealing treatment, after removing the bulges on the surface of the base material around the graphite caused by the nitriding treatment by grinding or other means, a resin containing a lubricant is applied to the solid material, and after drying, 0.5 To,! //Cll12 or higher pressure. Perform infiltration treatment at a temperature of 100 to 400 degrees Celsius, depending on the resin used, in the atmosphere.
Heat treatment is performed for 0.5 hours or more. The reason for limiting the flow rate of this heat treatment is that if it is below 100°C, the resin will not harden sufficiently and a sufficient sealing effect cannot be obtained, and if it exceeds 400°C, the nitrided cast iron will decompose. This is because wear resistance decreases. Table 1 shows the relationship between each resin and its appropriate heating temperature.

Table 1 Also, nitriding treatments include gas nitriding, ion nitriding,
Gas soft nitriding, tuftride, etc. can be used, and when performing gas soft nitriding treatment for engine cylinders, 550
From the viewpoint of preventing deformation, etc., it is preferable to carry out the process under the conditions of 600° C. for 30 minutes to 30 hours.

Example 3.5%C, 1.8%St, 0.7%Mn, 0.2%C
A cylindrical sample (inner diameter 89 mm, outer diameter 98 m, A length of 160 rran) was prepared. Next, this sample was subjected to soft nitriding treatment at 570° C. for 3 hours under the conditions of 50% RX and 150% NH3. At this time, as schematically shown in Fig. 1, a layer of compounds with nitrogen is formed on the surface of the cast iron product, hardening the surface, and at the same time, a bulge occurs in the graphite portion 12, which is the composition of the cast iron product. . Also, this graphite 12
There is a gap between the base material 14 and the base material 14 due to the thin graphite. Next, the protrusions on the surface of the nitrided cast iron product were removed by honing, and as shown in FIG. Kin resin was applied, dried, rubbed with a rubber grindstone, and heated in the air at 170° C. for 1 hour. As a result, a resin layer 15 is formed on the surface of the nitrided cast iron product. Even if this resin layer collapses due to sliding of a piston or the like, it remains as a resin portion 16 on the exposed portion of the graphite 12, as shown in FIG. 4, and has a sealing effect.

Figure 8 (a), (b), (C), (d)
A photograph of the surface condition of a piece of 70% tsukisui after sealing treatment is shown. FIG. 8(a) is an electron micrograph of the surface after sealing, magnified 400 times, and the black area is the puncture area.

An X-ray photog (4oo times) of this state reveals that only the Fe component is present.
Figures 8(b) and 8(a) show images of only the MO component. The white dots in FIG. 8(b) are the Fe component, and the white dots in FIG. 8(b) are the Mo component. From now on, Figure 8(b)
The MO component shown in FIG. 8(b) is present in the black part that is not the Fe component. In other words, it can be said that Mo S 2 exists in the gap. Moreover, FIG. 8(d) shows an optical micrograph (400x) of a longitudinal section after the sealing treatment, in which the white layer on the surface is a nitride layer and the black layer on the surface is Mo S 2
Graphite exists underneath the epoxy resin layer.

Next, the samples obtained according to the above method were tested together with the samples that were not subjected to the sealing treatment.

The samples tested are shown in Table 2.

Table 2 (Continued from Table 2) (1) Basic dry abrasion test The outline of the test apparatus is shown in FIG. 5. The specimen 20 which has been nitrided and sealed by the method described above is
It is fixedly placed on a base 22 installed on the floor 18 with the t-side facing up.

This test piece 20 is cut out from a cylindrical sample formed in the shape of an en-shin cylinder liner. This specimen 20 is, for example, Ii] i 5 nun y length 75
Can you drill a bolt hole with a size of about mn iz +l? It is fixed to the base with a bolt etc. A contact member 24 cut out from a part of an engine piston ring is attached to the two sides of this sample.
are in contact with each other, and this contact member 24 is held by a holder 26. This holder is attached to the tip of an arm 28, and this arm 28 is connected to a motor 34 via connecting members 30 and 32. The fulcrums 36, 38, 40 of the connecting members are all rotatable, and the motor 34
The rotational motion of is transmitted as a reciprocating motion of the holder 26,
The contact member 24 slides on the upper surface of the specimen 20. A predetermined load P is applied to this holder in the direction of the arrow in the figure, thereby generating a certain surface pressure between the contact member 24 and the specimen 20.

The main conditions of the test are as follows: Atmosphere: In the atmosphere Friction speed near 00 cycles/min Number of frictions: 2 x 104 times Load P: 1.2 to 20 kl Surface pressure: 0, 4 k! / nm2 Sliding width: 10 nun Method of measuring wear amount: Gravimetric method Note that corrosive lubricant was used in K1-1 between the contact member 24 and the specimen 20 to promote wear.

The results are shown in FIG.

The lower graph shows the amount of wear on the mating material, that is, the contact member 24. According to the results, the amount of wear of the samples BX (and DX E according to the present invention) is reduced compared to the conventional sample A for both the sample and the counterpart A2.

(2) Corrosion test Corrosion id'H of the inner wall of the diesel ennon cylinder
Assuming that it was due to the 2SO4 system, the specimen was immersed in sulfuric acid water for a certain period of time, and the amount of weight loss was measured. The results of these three tests are shown in FIG. In this figure, the corrosion loss represents the loss (pr9) in the area of specimen 1C7n2 per hour. In the figure, A, B, C,
D and E are the same as those in FIG. In this test, sample 8. The weight loss of C, D, and E is smaller than that of the conventional sample A.

[Brief explanation of the drawing]

Figure 1 is an enlarged partial sectional view schematically showing the cross section of the cast iron product after nitriding treatment, and Figure 2 is the same view as in Figure 1 after removing the bulges on the surface of the cast iron product in Figure 1. Figures 3 and 4 are similar to Figure 1 after sealing with resin, Figure 5 is a schematic diagram of the abrasion test equipment, and Figure 6 is the abrasion test sample. The graph showing the results, FIG. 7, is a graph showing the corrosion test, but does not show the test results. Figure 8 (a) (b) (C) (d
) are an electron micrograph of the surface metal structure when sealed with Mo S 2 -containing resin, an X-ray photograph of the Fe component, an X-ray photograph of the MO component, and an optical microscope photograph of the longitudinal section (all 400 Satoru). This is a drawing substituted for a photo. DESCRIPTION OF SYMBOLS 10... Compound layer, 12... Graphite, 14... Matrix part, 20... Sample, 24... Contact member, 34... Motor. Patent applicant Toyo Kogyo Co., Ltd.: 1 \ 11i% ('d sentence 1 [1 1 1 -11- '1 □ ''': l l j,・1・,・1−(11(
糟く: ゛・ 〒′、-n′
Do\j1'・ , 1 ゛・・ , 1 entry:,: '1 list 11 m f-1,, i:,). 3re7]) - Figure (()) (X400) (1 (X/JOO) ((゛) (xzi○0) (['') (×4(tsu())

Claims (2)

[Claims] (1) A sagging resin that has a nitrided layer on its surface and that the gap between the graphite exposed on the surface and the base material is 30 to 80 vol.% solid lubricant that does not decompose below 250°C. A nine-grade cast iron product characterized by having its pores sealed by. (2) The surface of the cast iron material is nitrided, the nitrided surface is polished, and 30 to 80 vol.
A method for producing a nitrided cast iron product, comprising applying a resin that does not decompose at 250° C. or lower and containing a solid debris inhibitor, and heat-treating the resin to seal the gap.