JPS59107081A - Method for etching cylinder made of aluminum alloy - Google Patents

Abstract

PURPOSE:To etch uniformly the Al matrix of a cylinder and to improve the wear resistance by etching the inner wall of the cylinder with an aqueous soln. contg. prescribed percentages of NaOH and H2O2 to expose Si particles and by carrying out etching further with an aqueous soln. of HNO3 having a prescribed concn. CONSTITUTION:The inner wall of a cylinder made of an Al alloy contg. Si is polished, and the Al matrix of the inner wall is etched with an aqueous soln. contg. 5-10wt% NaOH and 0.05-0.35wt% H2O2. The etched inner wall is washed with water to expose Si particles, and the surfaces of the exposed Si particles are made smooth by etching with an aqueous soln. contg. 3-7wt% HNO3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of etching an aluminum alloy cylinder.

Aluminum alloy cylinders are commonly used for the purpose of reducing the weight of engines, but they have a problem in that they have lower wear resistance than cast iron cylinders and are more likely to seize. Therefore, attempts have been made to increase the silicon content of aluminum alloy cylinders and expose silicon particles on the inner wall surface of the cylinder to improve wear resistance.

For example, in JP-A-67-10/700, the inner wall surface of the cylinder is electrolytically etched to make silicon particles stand out from the inner wall surface of the cylinder, and the silicon particles improve wear resistance. A proposal is described to improve the lubricating oil holding power by using recesses between the two.

However, in the case of electrolytic etching, in order to make the etching amount uniform, the distance between the electrode inserted into the cylinder pore and the cylinder inner wall surface must be constant, and it is difficult to maintain this distance constant. , machining, and the amount of ching may become uneven, resulting in a large amount of silicon particles protruding (so much that the silicon particles may fall off when the piston ring slides, or the corners of the silicon particles may become uneven). There was a problem with some parts missing.

Other etching methods include acid etching using strong acids such as sulfuric acid, nitric acid, and phosphoric acid, and alkaline earth metal etching using highly concentrated sodium hydroxide.
In the case of the ching method, there is a problem that the silicon particles are dissolved or the boundary between the silicon particles and the aluminum base is dissolved, making it easy for the silicon particles to fall off or be missing.

On the other hand, in the case of the alkalini-ching method, the aluminum substrate is dissolved without dissolving the silicon particles, but metal components such as copper and magnesium are difficult to dissolve, so they remain on the surface, and the molten aluminum becomes aluminum hydroxide. There is a problem in that it adheres to the aluminum base and inhibits uniform etching.

In view of this point, the present invention first prepares the inner wall surface of the cylinder for 5 to 50 minutes.
70 wt% NaOH and θo,3;~θ3j wt% H2
We provide an etching method in which silicon particles are raised by etching with an aqueous solution mixed with O2, and after washing with water, the surface of the silicon particles is dissolved and smoothed with a 3 to 7% by weight aqueous solution of HNO3, thereby uniformly etching an aluminum base. The purpose of this invention is to improve wear resistance by preventing silicon particles from falling off or missing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below based on embodiments with reference to the drawings.

The example consists of two steps, and Figure 1 shows the second step and the second step.
The figure shows the state of the inner wall of the aluminum alloy cylinder 1 after the third step, and FIG. 3 shows the state of the inner wall of the aluminum alloy cylinder 1 after the fifth step. 2 is an aluminum base, and 6 is a silicon particle. The composition (weight %) of the aluminum alloy casting constituting the cylinder 1 is Sj
, 77%, Cu4t, 6% Ni/6%9M8/%
, POO is 6%, and the balance is Aμ, and the primary silicon particles 6 are refined by the addition of P.

In the first step, the cylinder 1 after casting is subjected to heat treatment. That is, the cylinder 1 is heated at 500 DEG C. for 5 hours, water-cooled (quenched), and then tempered at 720 DEG C. for 3 hours.

In the second step, the inner wall surface 4 of the cylinder 1 is polished. That is, first, the inner wall surface 4 of the cylinder 1 is honed and then lapped using abrasive grains. The state after processing is shown in FIG. 1, and the surface roughness of the inner wall surface 4 is /6μ or less.

In the third step, the aluminum base 2 of the cylinder inner wall surface 4 is etched. The etching solution is
It is a mixed solution of NaDH (~/θ weight%), H2O2 (θθj~θ36% by weight), and remaining water, the liquid temperature is 30~60°C, and the processing time is 70~3θ seconds.Etching treatment This aspect is shown in Fig. 7. In the figure, 5 is a felt made of glass fiber or other material that is resistant to etching treatment liquid, and is attached to the support member. The upper part is fitted into a support cylinder 7, and the felt 5 is configured to move up and down together with the support member 6.The support cylinder 7, together with the felt 5 and the support member 6, is connected to a storage tank (not shown) in which an etching solution is stored. It is configured to reciprocate between the cylinder 1 and the cylinder 1.

For etching, first, the felt 5 is soaked in the etching solution in the storage tank to impregnate the felt 5 with the etching solution, and then the felt 5 is heated in the bore of the cylinder 1 for 10 to 3
Slide it up and down for 0 seconds.

As shown in FIG. 2, on the inner wall surface 4 of the cylinder 1, only the aluminum base 2 is etched with NaOH, and the silicon particles 6 are not dissolved. That is, the surface of the silicon particles 60 is in an uneven state as it has been subjected to the polishing process in the second step, and the exposed area of the silicon particles 3 is 20 to 30 degrees on the inner wall surface 4 of the cylinder.
%. Furthermore, the oxidizing power of H2O2 prevents the generation of smut and scale. The amount of corrosion of the aluminum base 2, that is, the embossed height of the silicon particles B is set to be slightly higher than the final embossed height (/:, ff-4μ) described later.

In this process, smut and scale generation
The optimal conditions for etching only the aluminum base 2 while preventing corrosion are as follows. That is, the etching solution contains 5% by weight of NaOH and Q0% by weight of H.
The etching solution is a mixed solution of 2O2 and remaining water, and the temperature of the etching solution is 50 DEG C. and the processing time is 10 to /j seconds.

In the embodiment, by using the felt 5 for etching, it was possible to perform the etching process only on the inner wall surface 4 of the cylinder 1.
(You may also use a method of immersing the film in an etching solution and etching it.)

Next, in the second step, the cylinder 1 is washed with water. This is to remove the etching solution remaining on the inner wall surface 4 of the cylinder 1 in the third step.

In the ffl process, the silicon particles exposed from the inner wall surface 4 of the cylinder 1 are etched. The etching solution is a mixture of 3 to 7% by weight of HNO3 and residual water, the temperature of the solution is 30 to 0°C, and the processing time is 20 to 20 seconds. The etching process is performed in the same manner as the third step.

As shown in FIG. 3, on the inner wall surface 4 of the cylinder 1, only the silicon particles 6 are etched, leaving the aluminum base 2 intact. That is, the silicon particles 6 have their surface peripheries dissolved by low concentration nitric acid, and the surface unevenness disappears, making it smooth. And aluminum base 2 of silicon particle filter
The height of the protrusion from the surface is about 76 μm to μ μ.

The optimum conditions for etching in this step are as follows. In other words, the concentration of HNO3 in the etching solution is 36% by weight, the solution temperature is 50°C, and the processing time is:
20 to 0 seconds.

In the second step, the cylinder 1 is washed with water to remove the etching solution.

Next, the wear resistance of the cylinder according to the method of the present invention will be explained based on test results.

<Test/> In this test, the example of the present invention was compared with the conventional example regarding the relationship between the number of times the ring material slid with respect to the cylinder H and the wear volume of the cylinder material.

The cylinder materials used in the test are shown in the table below.
The ring material used was cast iron with chrome plating.

In the above table, in the method of the present invention, the etching solution having the optimum conditions in the third and fifth steps was used. Also,
The conventional method is the acid enotinic method, and the treatment liquid is
It is a mixture of H3PO4/g% by weight HNO3 and 2J% by weight water. The liquid temperature was C and θ℃, the processing time was 30 to θ seconds, and the water was removed after etching. did. Nao,
FCH/ji C, Si, Mn.

It is an alloy cast iron containing p, S, and Cr.

FIG. 5 shows a cylinder material 8 and a ring material 9 as test materials. Cylinder material 8 +i is a flat plate. The ring material 9 is a rectangular parallelepiped, with a length LC/θ and a width W/m.
It is m. Further, the reciprocating distance S of the ring material 9 is 70 cylinders.

The test conditions were the number of times the ring material 9 was slid back and forth for 7 minutes at 7θ.
θ times, and the contact surface pressure between cylinder material 8 and ring material 9 is 2
7/-, and machine oil #10 was used as the lubricating oil. Note that the contact pressure is the normal piston ring surface pressure (θ/~/
Kg/tsJ) higher G1° test results are shown in Figure 6.

As shown in the figure, in the case of the example of the present invention, the conventional example/,
It can be seen that the wear volume is smaller than both of No. 2, and the wear resistance is excellent. '<test! 〉 This test compared the example of the present invention and the conventional example regarding the relationship between contact surface pressure and wear volume.

The cylinder materials are those shown in the column of the invention example and conventional example/ in the table of test/, and the ring material is the one shown in the column of test/
is the same as In addition, the number of times the ring material is slid is 30.
x10' times, the lubricating oil was machine oil #10. The test results are shown in Figure 7.

As shown in the figure, in the case of the example of the present invention, the wear volume is lower than that of the conventional example. The contact surface pressure that causes the material to fall off, etc., is also higher in the example of the present invention.

Therefore, it can be seen that when the surface of the silicon particles is made smooth as in the present invention, not only the wear resistance but also the durability of the silicon particles increases.

<Test 3> This test looked at the relationship between the protrusion height of silicon particles according to the present invention and the amount of wear, and the test results are shown in FIG. 2.

In sample A, the cylinder material is shown in the column of the invention example in the table of test/, and the ring material is the same as test/.

Further, the contact surface pressure was i J' KSI/mA, the lubricating oil was machine oil #10, and the number of sliding movements was 200 x 70 times.

As shown in Figure 2, the amount of wear increases rapidly as the height of the silicon particles decreases or increases on both sides of the boundary between 6tt and μ. It has become. In other words, when the protrusion height is less than 7.5μ, the lubricating oil is poorly retained between the silicon particles, and the amount of wear increases due to adhesion due to contact between the aluminum base and the ring material. On the other hand, when the embossment height exceeds Zμ, the embedding depth of the silicon particles into the aluminum ground becomes shallow (as a result, the silicon particles tend to fall off,
Further, the corners of the silicon particles are easily chipped and the amount of wear is large. Therefore, it is most preferable that the raised height of the silicon particles is in the range of X6 to Guμ.

As described above, according to the present invention, since H2O2 is mixed into the etching solution for the aluminum base, the generation of smut and scale is prevented, and the aluminum base can be uniformly corroded. Since the surface of the silicon particles is made smooth by applying this process, the excellent effect of improving wear resistance compared to the conventional method can be obtained.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention, and FIGS. 1 to 3 are cross-sectional views showing the state of the inner wall of the cylinder at each stage of the processing process, FIG. 7 is a cross-sectional view showing an aspect of the etching process, and FIG. The figure is a perspective view showing the aspect of the wear test, Figure 4 is a graph showing the relationship between the number of sliding movements and wear volume, Figure 7 is a graph showing the relationship between contact pressure and wear volume, and Figure 2 is a graph showing the relationship between contact surface pressure and wear volume. is a graph diagram showing the relationship between the protrusion height of silicon particles and the amount of wear. 1...Cylinder, 2...Aluminum ground, 6...Silicon particles, 4...Inner wall surface Figure 1 Figure 21 Zo No. 41

Claims (1)

[Claims] (1) After polishing the inner wall of the aluminum alloy cylinder, apply j~/θ weight ■% to the aluminum base of the inner wall.
Etching is performed with a mixture of 905 to 036% by weight of NaOH, 905 to 036% by weight of H2O2, and the remainder water, and then the inner wall is washed with water, and the surface of the silicon particles exposed on the inner wall is etched with 3 to 7% of the surface of the silicon particles exposed on the inner wall.
A method for etching an aluminum alloy cylinder, characterized in that etching is performed using a mixed solution of HNC13 and remaining water in an amount of % by weight.