JPS6140036B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) This invention relates to a method for removing burrs from the inner surface of a cast iron cylinder, which removes burrs generated during grinding. (Prior Art) In general, the inner surface of cylinder parts such as cast iron cylinder blocks or liners used in internal combustion engines is required to have high surface properties such as smoothness and low friction resistance for high speed rotation. Therefore, conventionally, cast iron cylinder parts are subjected to grinder grinding and rubber honing in the final machining stage, but such grinding creates plastic flow on the processed surface and creates burrs. Since the graphite in the matrix layer is covered, not only does the lubricating effect of graphite not occur, but also this burr breaks off and burrs during high-speed operation, causing so-called abrasive wear, and furthermore, this burr fuses, a so-called scuffing phenomenon. There were problems such as causing Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 54-143741, a method for solving the above problem has been to immerse a ground cast iron sliding member in a corrosive liquid and apply vibration to the surface. There are ways to remove the burrs that occur. However, in the above prior art,
Since a nitric acid alcohol solution is used as the corrosive liquid, this nitric acid alcohol solution acts on the iron surface and dissociates it as Fe→Fe ²⁺ +2e ^- 5H ⁺ +2e ^- →H ₂ , as shown in Figure 1. iron surface 1
However, due to the local cell reaction that produces the anode portion 2 and the cathode portion 3, local corrosion of the iron surface 1 progresses unevenly, thereby significantly impairing the surface properties of the iron surface 1. Moreover, the carbides contained in cast iron remain uncorroded and protrude from the iron surface 1, causing abrasive wear and scuffing phenomena similar to burrs. On the other hand, when a picric acid/alcohol mixture, picric acid/caustic soda mixture, etc. is used as a corrosive liquid, there are drawbacks such as the carbon content consisting of graphite and carbides being severely corroded, leaving depressions. Ta. (Object of the Invention) This invention has been made to improve the above-mentioned drawbacks, and by applying chemical treatment and ultrasonic vibration, it is possible to eliminate burrs that occur on the inner surface of the cylinder without significantly damaging the surface characteristics of the inner surface. The purpose of the present invention is to provide a method for removing burrs from the inner surface of a cast iron cylinder. (Structure of the Invention) That is, the present invention provides a local battery as described above by immersing a cast iron cylinder block or liner whose inner surface is ground into a nitric acid aqueous solution containing an amine corrosion inhibitor. By suppressing the local progress of the reaction, the burrs formed on the inner surface of the cylinder are corroded and weakened, and in this state, minute ultrasonic vibrations are applied to fully fatigue break the weakened burrs and remove them. The above amine corrosion inhibitor dissolves carbides protruding from the iron surface and improves its surface properties. In other words, when corroding the inner surface of a cast iron cylinder containing carbides, a carbide dissolving agent is required because the carbides must be dissolved along with the iron as mentioned above. Since the additive has not only a corrosion inhibiting effect but also a carbide dissolving effect, it can be said to be a more preferable additive. Examples of such amine-based corrosion inhibitors include cyclohexylamine, benzylamine, morpholin, and ethylamine, but these have recently been recognized as carcinogenic, and are also preferable from the standpoint of water pollution and environmental pollution. do not have. Therefore, as the amine-based corrosion inhibitor used in this invention, for example, hexamethylenetetramine is suitable as it has little toxic effect on the human body. When a ground cast iron cylinder is immersed in a nitric acid aqueous solution containing hexamethylenetetramine, the inner surface of the cylinder is uniformly corroded, and the burrs caused by the grinding are weakened and become brittle. This phenomenon occurs when hexamethylenetetramine dissociates in an aqueous nitric acid solution to produce an organic amine, and the positively charged nitrogen in this organic amine is electrostatically attracted to the cathode part 3 formed on the inner surface 1 of the cast iron cylinder. As shown in Fig. 2, this cathode part 3 is covered to make it difficult for current to pass through, and as a result, the release of hydrogen ions is suppressed, the progress of the above-mentioned local battery reaction is inhibited, and corrosion is made uniform. It is understood that (Example) Hereinafter, this invention will be specifically explained with reference to Examples. However, the following Examples and Comparative Examples were all carried out under the following conditions. Note that hexamethylenetetramine is abbreviated as HMTA. Ultrasonic oscillator: Ultrasonic oscillator manufactured by Shimada Rika Co., Ltd. (frequency range 5 to 50KC) Dynamic friction coefficient measurement conditions: Pin disc friction tester, load 1Kg, sliding speed 0.5mm/S Example 1 Performing rubber honing processing A test piece measuring 10 cm x 10 cm was prepared by cutting out a portion of the cast iron cylinder liner. Figure 3 is a microscopic photograph (300
times), A indicates the cross section, and B indicates the surface. In A, the white part that appears to be raised from the surface, and in B, the part that appears as a white wavy pattern are burrs caused by the rubber honing process, and were observed in large numbers. The surface roughness of this test piece is
3.5μ, and the dynamic friction coefficient was 0.4 to 0.54. Next, this test piece was immersed in a corrosive solution consisting of 100 c.c. of water, 3 c.c. of HNO ₃ and 0.2 g of HMTA (approximately 0.19 (weight)%), and subjected to ultrasonic vibration at a frequency of 30 KC for 60 seconds. I let it happen. Figure 4 is a microscopic photograph (300
times), A indicates the cross section, and B indicates the surface. That is,
The burrs were removed, local corrosion was hardly observed, and the surface was smooth. The surface roughness of this test piece is 3.0μ, and the coefficient of dynamic friction is 0.265~
It was 0.325. Comparative Example A 10 cm x 10 cm test piece was prepared by cutting out a portion of a rubber honed cast iron cylinder liner, and this test piece was heated to 100 c.c. of water and 3 c.c. of HNO ₃ .
A corrosion test was conducted by immersing the sample in a nitric acid aqueous solution consisting of: When the surface was observed, it was found that many matrix structures were exposed due to local corrosion. Moreover, the surface roughness of the surface was 3.5μ, and the coefficient of dynamic friction was 0.465. Examples 2 to 3 A portion of a cast iron cylinder liner that has been rubber honed is cut out and each is 10cm x
10 cm test pieces were prepared, and the following corrosion tests were conducted using these test pieces.

[Table] The burrs seen on the surfaces have been removed, and no local corrosion was observed. The surface was smooth. The surface roughness of the test pieces obtained in both Examples was 3.2μ and 2.8μ, respectively, and the coefficient of dynamic friction was 0.3-0.355 and 0.255-0.3, respectively. Example 4 80φ×140mm rubber honed
We conducted a physical verification experiment using 15 cast iron cylinder liners. These cylinder liners were supported upright and spaced from each other in a 400 x 500 x 200 mm stainless steel water tank, containing 100 c.c. of water, 3 c.c. of HNO ₃ and
It was immersed in a corrosive solution containing 0.4 g (0.39 (weight)%) of HMTA, and subjected to ultrasonic vibration at a frequency of 30 KC for 60 seconds. In both cases, the burrs found on the inner surfaces were removed, no local corrosion was observed, and the surfaces were smooth. Also, the average value of the surface roughness of the inner surface of the liner is
2.9μ, and the average value of the dynamic friction coefficient was 0.3. In other words, it was confirmed that the effects of the above-mentioned example using the test piece were reproduced with almost the same tendency for the solid cylinder. Figure 5 shows the surface roughness obtained from each of the above experiments.
Figure 6 shows the relationship between the amount of HMTA added, and Figure 6 shows the relationship between the surface roughness and the coefficient of dynamic friction, and it can be seen that both characteristic values are significantly improved by the method of this invention. Furthermore, when the coefficient of kinetic friction is 0.4 or more, abrasive wear becomes noticeable due to the separated burrs, whereas at 0.2 to 0.3, almost no abrasive wear occurs. The surface condition can be evaluated. As is clear from the above examples, the amount of hexamethylenetetramine added is preferably 0.2 to 0.8% (by weight) relative to the 1 to 3% (by volume) nitric acid aqueous solution.
If it exceeds 0.9% (by weight), it will become supersaturated and no significant effect can be expected. Also, 0.2 (weight)
% or less, the improvement in surface properties is not so great. In addition, the ultrasonic vibration removes the burrs on the inner surface of the cylinder weakened by the corrosive liquid and removes the grinding powder attached to the inner surface.
50KC, action time 30-60 seconds is preferred. Note that the burr removal method according to the present invention is performed after grinding with a grinder and rubber honing, but even if this corrosion treatment is performed as the next step after grinding with a grinder and the rubber honing is omitted, a sufficiently smooth surface can be obtained. can do. (Effects of the Invention) As detailed above, the method of this invention suppresses the uneven progress of local corrosion by immersing a cast iron cylinder block or liner in a nitric acid aqueous solution containing an amine corrosion inhibitor. By weakening the part and applying ultrasonic vibration, the weakened burr part is sufficiently fatigue-broken, and at the same time, the grinding powder is removed, and in addition, the above amine-based corrosion inhibitor is used to remove carbides protruding from the iron surface. It is possible to provide a method for burring the inner surface of a cast iron cylinder by melting and obtaining a uniform inner surface of the cylinder with significantly improved surface properties.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a mechanism for forming local batteries by conventional corrosion treatment, FIG. 2 is an explanatory diagram showing a mechanism for suppressing the formation of local batteries according to the present invention, and FIG.
The figure and Figure 4 are micrographs (300x) of the inner surface of a cast iron cylinder liner, and Figures 3A,
B is a cross section and surface showing an example of the inner surface of the liner immediately after rubber honing;
Figure 5 is a diagram showing the relationship between the surface roughness of the inner surface of the liner and the amount of hexamethylenetetramine added, and Figure 6 is a diagram showing the relationship between the surface roughness of the inner surface of the liner and the amount of hexamethylenetetramine added. It is a relationship diagram with a coefficient.

Claims (1)

[Claims] 1. A cast iron cylinder block or liner whose inner surface has been ground is immersed in a nitric acid aqueous solution containing an amine corrosion inhibitor, and ultrasonic vibration is applied to remove the burrs formed on the inner surface of the cylinder. A method for removing burrs from the inner surface of a cast iron cylinder.