JP2002302755A - Post thermal spraying treatment method for cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a post thermal spraying treatment method for a cylinder by which low-adhesion sprayed coating or flying particles adhering to the inner surface can be efficiently removed and abrasives entering the inside can be recovered. SOLUTION: The post thermal spraying treatment method for a cylinder by which the sprayed coating 15 or flying particles 151 adhering to the each inner wall surfaces 17, 19 of the cylinder which has the port parts 17, 19 penetrating from port holes 7 formed in the inner surface 3 of a bore toward outside can be removed comprises the following steps: a step where a cylindrical member 5 for masking which is capable of being inserted into the above inner surface 3 of the bore and in which openings 9 are formed in the positions corresponding to the above port holes 7, respectively, is inserted into the inner surface 3 of the bore and then the openings 9 and the port holes 7 are fitted together; and a step where abrasive blasting or shot treatment is performed from the inside of the cylindrical member 5 for masking toward the respective inner wall surfaces 17, 19 of the cylinder 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder block having a port portion, such as a two-cycle cylinder, which removes scattered particles and a sprayed coating having a small adhesive force attached to the port portion when the inner surface of the bore is subjected to thermal spraying. The present invention relates to a post-spraying treatment method of a cylinder for performing spraying.

[0002]

2. Description of the Related Art In general, a two-cycle type aluminum cylinder has a bore formed in the axial direction thereof.
A scavenging port section and an exhaust port section are provided on the side of the bore. FIG. 18 is a cross-sectional view showing thermal spraying on a bore inner surface 103 of a cylinder 101 by a conventional method.
3 is the bore inner surface 1 because the piston reciprocates violently.
By spraying 03 to form a thermal spray coating,
Improves wear resistance. When performing this thermal spraying, since the scavenging port portion 105 and the exhaust port portion 107 are open to the inside, as shown in FIG. Particles 151 adhere. These scattered particles 151 are sprayed coating 1
If it falls off during operation of the engine due to insufficient adhesion to the piston 55, the piston and the bore inner surface 10 that reciprocate violently will reciprocate.
There is a possibility that the piston and the inner surface 103 of the bore may be worn out, etc. For this reason, conventionally,
The following measures are mainly adopted.

(1) In the technique described in Japanese Patent Publication No. 55-42861, after the port holes 113 of the port portions 105 and 107 are closed with a filling or the like, wire explosion spraying is performed on the inner surface 103 of the bore. The scattering particles 151 are prevented from adhering to the ports of the two-cycle cylinder. (2) The technology described in Japanese Patent Publication No. Hei 3-9822 is
This is a method of cutting a pipe material of a sliding portion by casting a pipe material having a thermal spray coating 155. That is, first, a pipe material having good machinability and plastic workability is deformed so as to conform to the shapes of the bore inner surface 103 and the port portions 105 and 107, and thermal spraying excellent in sliding and lubricating performance is performed on the outer periphery of the pipe material. A film 155 is formed. Next, the thermal spray coating 155
After forming the cylinder material by casting the pipe material formed with the aluminum alloy into a cylinder material, the pipe material of the portion that becomes the sliding surface of the cylinder 101 is cut to expose the spray coating, thereby producing the cylinder 101 of two cycles. are doing. For this reason, inside the port portions 105 and 107, the pipe material appears on the innermost side to prevent the thermal spray coating 155 from being exposed.

(3) In Japanese Patent Publication No. Hei 4-47027,
The port portions 105 and 107 are formed with a coating or the like to which the scattered particles 151 do not easily adhere, and if necessary, the port portions 105 and 10 are formed.
After filling and masking by inserting the filling into the inner surface of the bore
By performing the wire explosion spraying on 3, the scattering particles 151 are prevented from adhering to the inside of the port.

[0005] However, the conventional technique has the following problems. (1) According to the technology of Japanese Patent Publication No. 55-42861,
In two-cycle engines, the shapes of the ports 105 and 107 are narrow and complicated, and there are many places where filling is impossible. Further, even if the port portions 105 and 107 are filled, there is a problem that the attachment and removal of the filling material is difficult and takes a long time, so that the productivity of the cylinder 101 is reduced. The port 10
If there is a gap between 5,107 and the filling, the blast material of the blasting process, which is the pre-spraying treatment, accumulates in this gap. There was a problem of up.
Furthermore, if the blast material remains in the port portion, the piston and the bore inner surface 103 may be worn during operation of the engine.

(2) According to the technique disclosed in Japanese Patent Publication No. 3-9822, the bore inner surface 103 and the port portions 105 and 107 of the two-stroke engine have many complicated shapes. It was very difficult to deform the pipe material so as to conform to the shape of 107. On the other hand, when determining the shape of the port portion, giving priority to the shape of the pipe material that is easily deformed,
The degree of freedom in the design of 05 and 107 is reduced. Also,
This method has a problem that the steps are complicated and the number of steps is increased.

(3) According to the technique disclosed in Japanese Patent Publication No. Hei 4-47027, a coating film to which scattering particles 151 are less likely to adhere before a blast treatment as a thermal spraying pretreatment is formed.
There was a problem that the coating film was peeled off in the surface roughening step by blast treatment, and the effect of preventing the scattering particles 151 from adhering was reduced. When filling is performed in the port portion in order to prevent the peeling of the coating film, there is a possibility that the productivity may decrease and the material cost may increase due to the removal of the blast material, as in the case of Japanese Patent Publication No. 55-42861. . If the coating is performed after the blasting, which is the pre-spraying treatment, the inner surface 10 of the bore to be blasted is treated.
Because the paint must not adhere to 3,
Painting work was very troublesome.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and efficiently removes a sprayed film and scattered particles having low adhesion adhered to the inner surface of the port portion without filling or painting the port portion. Another object of the present invention is to provide a post-spraying treatment method for a cylinder capable of recovering the blast material that has entered the port portion.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention is directed to a cylinder having a port portion penetrating outwardly from a port hole formed in an inner surface of a bore and attached to an inner wall surface of the port portion. In the post-spray treatment method of a cylinder for removing the sprayed coating or scattered particles, a masking cylindrical member insertable into the bore inner surface and having an opening formed at a position corresponding to the port hole is inserted into the bore inner surface. ,
The step of matching the opening to the port hole; and the step of performing blasting or shot processing from inside the masking cylindrical member toward the inner wall surface of the port portion of the cylinder.

In the blasting or shot processing, a blast material or a shot material composed of a plurality of small hard particles (ceramic particles, steel particles, etc.) is sprayed toward the inner wall surface of the port portion, and the blast material or the shot material adheres to the inner wall surface. This is a process to remove thermal spray coatings and flying particles with insufficient force. According to this method, since the inner surface of the bore is covered by the masking cylindrical member, the thermal spray coating on the inner surface of the bore is not damaged, and the processing can be performed only in the port portion. In addition, since the masking cylindrical member has a simple structure, it can be manufactured at low cost and can be easily attached and detached. The hard particles used for the blasting or the shot treatment are of appropriate size and material depending on the thickness of the thermal spray coating. For example, if the thickness of the thermal spray coating is 200
In the case of μm, the size of the hard particles is preferably 0.05 to 1 mm.

[0011] In one aspect of the present invention, the opening of the cylindrical member is formed to be larger by 10% to 500% of the thickness of the thermal spray coating than the diameter of the port hole on the inner surface of the bore. 100% to 250%. Thus, the thermal spray coating on the edge of the port hole can be chamfered. By this chamfering effect, it is possible to prevent the piston ring from being caught on the end face of the port hole, and
The sprayed coating does not peel off during honing.

Further, in another aspect according to the present invention, the blast processing or the shot processing is performed while performing suction and exhaust from the outer end of the port and the end of the bore. The suction and exhaust can be performed using, for example, a cylinder set jig. That is, when the cylinder is fixed to the cylinder set jig, the outer end of the port and the end of the bore communicate with each other so as to be combined into one space,
Suction and exhaust may be performed in this state. As a result, a smooth airflow is generated in the port and bore, and during spraying, turbulence does not occur and fumes can be prevented from being caught in the sprayed coating. There is no risk of occurrence. And also in the blast processing,
The blast material does not remain in the port portion having a complicated shape, and the bore inner surface is not worn by the residual blast material during operation of the engine.

In still another aspect of the present invention, after the inner surface of the bore is subjected to thermal spraying with the shielding plate inserted in the port portion, post-thermal spraying is performed by the above-described post-processing method. According to this method, the thermal spray coating and the scattered particles can be prevented from adhering to the inner wall surface of the port portion as much as possible, and even if they adhere, the adhesion can be suppressed near the port hole. Therefore, post-spray processing can be performed easily and in a short time.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A post-spray processing method for a cylinder according to an embodiment of the present invention will be described below in detail with reference to the drawings.

[Outline of Thermal Spraying and Post-Spraying Treatment] In the post-spraying treatment method according to the present invention, after the port inner portion is subjected to thermal spraying on the inner surface of the bore of the cylinder by a usual method without filling or painting the port portion, the port is sprayed. Blast processing or shot processing is performed inside the unit. As shown in FIG. 1, these processes are performed by forming a masking cylindrical member 5 on the inner surface 3 of the bore of the cylinder 1.
Is carried out in a state where is inserted.

The outer diameter of the masking cylindrical member 5 is formed in a size corresponding to the inner diameter of the bore inner surface 3, and an opening 9 corresponding to the port hole 7 of the cylinder 1 is provided on a side portion. . After the cylindrical member 5 is inserted into the bore inner surface 3 as masking, as shown in FIG. 2, the inner surface of the bore 3 is subjected to blasting or shot processing so that the inside of the scavenging port portion 17 and the exhaust port portion 19 are adhered to each other. Removes thermal spray coatings and scattered particles with insufficient force.

At this time, since the thermal spray coating formed on the inner surface of the bore 3 is covered with the masking cylindrical member 5, no damage is caused by blasting or shot processing.
Further, as shown in FIG. 2C, when the opening 9 to be opened in the masking cylindrical member 5 is formed larger than the diameter of the port hole 7 of the cylinder 1 by a dimension a (for example, about 1 mm), the port end face is The chamfer 13 can be formed on the thermal spray coating 15 at the same time. As a result, film peeling due to the protrusion of the thermal sprayed film 15 during honing is eliminated, and the scavenging port portion 17 and the exhaust port portion 19 are opened in the bore inner surface 3 even after honing. The ring protrudes slightly and does not get caught on the end face of each port. After the masking shielding plate 39 described later is inserted into the port portion of the cylinder 1, thermal spraying is performed on the bore inner surface 3, and thermal spraying is performed so that the thermal spray coating 15 and the scattered particles 151 do not adhere to the port portion as much as possible. By performing the above-mentioned post-spraying treatment, the effect of this post-treatment can be further improved.

[Outline of Manufacturing Process of Cylinder Block] First, machining oil adhering during machining of the cylinder 1 is washed. Next, as shown in FIG.
In order to fix the cylinder 1 to 1 and improve the adhesion of the thermal spray coating 15, the entire inner surface of the bore 3 is subjected to blasting as a pretreatment using a blasting device equipped with a blast gun, and the inner surface of the bore 3 is roughened. Become Thereafter, as shown in FIG. 4, a spray coating having excellent wear resistance and slidability is formed on the bore inner surface 3 by using the inner diameter spray gun 25 without filling or painting the scavenging port portion 17 and the exhaust port portion 19. 15 are formed. When the formation of the thermal spray coating 15 is completed, as shown in FIG. 5, the outer diameter matches the inner diameter of the bore after thermal spraying, and the shape of the port holes 7 of the scavenging port portion 17 and the exhaust port portion 19 is formed. Is inserted into the bore inner surface 3 after the thermal spray coating is formed, and only the scavenging port portion 17 and the exhaust port portion 19 are blasted in this state. After the blasting, the masking cylindrical member 5 is removed, and finally the bore inner surface 3 is honed to finish.

By inserting a masking shielding plate, which will be described later, into the scavenging port portion 17 having a narrow and complicated shape, the area of the thermal spray coating 15 and the scattered particles adhering to the wall surface of the scavenging port portion 17 can be reduced as much as possible. This makes it possible to more easily and quickly remove the thermal spray coating 15 and scattered particles by blasting. In this case, since the shielding plate has an elongated shape, the port 1
If the suction is performed from the lower ends of 7, 19, the air flow 27 generated during thermal spraying is not obstructed.

[Cylinder for Masking] If the outer diameter of the masking cylindrical member 5 is made slightly smaller than the inner diameter of the bore after the thermal spray coating 15 is formed, the cylindrical member 5 can be smoothly inserted into the bore. The difference between the outer diameter of the cylindrical member 5 and the inner diameter of the bore is preferably 0.2 to 1.0 mm,
Of these, 0.5 mm is most preferable. The length of the cylindrical member 5 is set to a length capable of covering the bore inner surface 3 when the cylindrical member 5 is inserted into the bore of the cylinder 1, and the opening 9 cut out according to the shape of the port hole 7 has a chamfering effect on the port end face. For example, 0.5 mm more than port hole 7
And so on.

When the masking cylindrical member 5 is set in the bore of the cylinder 1, the port hole 7 and the cylindrical member 5
In order to prevent the opening 9 from being displaced from the opening 9, a bolt hole 33 for fixing the cylinder head is provided as a positioning hole as shown in FIG. 6, and as shown in FIG. Preferably, a pin 35 is provided.
The material of the cylindrical member 5 for masking is not limited to metals such as iron, aluminum, and copper, and is not particularly limited as long as it is not lost by blasting or shot processing. preferable. Further, in order to improve the durability and wear resistance of the cylindrical member 5, the inner surface thereof may be subjected to a surface treatment.

[Cylinder Set Jig] As shown in FIGS. 3 to 5 described above, when the cylinder 1 is set, the ends of the bore, the scavenging port portion 17 and the exhaust port portion 19 are cylinders. It is configured to communicate with the suction / exhaust pipe 37 of the set jig 21,
When suction is performed from the suction / exhaust pipe 37, a downward airflow 27 toward the suction / exhaust pipe 37 is generated in the bores and the sweep / exhaust ports 17 and 19.

As shown in FIG. 8, since the masking shielding plate 39 is fixed to the cylinder set jig 21, when the cylinder 1 is mounted on the cylinder set jig 21, three narrow portions are simultaneously formed. The shielding plate 39 is inserted into the scavenging port portion 17. Here, the material of the masking shielding plate 39 is not limited to a metal plate such as an aluminum alloy material, an iron material, or a copper material, and is not particularly limited as long as it does not wear or disappear by blasting or shot processing. Further, the masking shielding plate 39 may be subjected to a surface treatment for providing durability. In addition, the scavenging port section 17 is provided by blasting for pre-treatment and blasting for scattered particles.
If there is a possibility that the masking shielding plate 39 inserted into the cylinder may be worn, as shown in FIGS. 9 and 10, insert the insertion portion 41 into the hole of the set jig 21 connected to the scavenging port portion 17 of the cylinder 1. It is preferable to provide the masking shield plate 39 so that it can be easily attached and detached by inserting and removing it.

[Blast conditions or shot conditions] The blast conditions are preferably in the range shown in Table 1 below.

[0025]

[Table 1]

As shown in FIG. 11 (b), the blast material or shot material 51 scatters with spreading at the time of injection, but since the blast material or shot material 51 follows the trajectory through which the thermal spray frame 53 passes. The spray angle θ1 of the blast material or the shot material 51 is preferably set to an angle close to the spray angle θ2, and the spray angle θ1 and the spray angle θ2
More preferably,

The operation of the above configuration will be described below. According to the present invention, since the port portions 17 and 19 are not filled, the blast material or the shot material 51 for the thermal spraying pretreatment is rarely deposited, and the port portions are connected via the cylinder set jig 21 and the suction exhaust pipe 37. By suctioning from the lower ends of the ports 17 and 19, a smooth airflow 27 is generated in the ports, and the blast material or shot material 51 does not remain in the ports 17 and 19 having a complicated shape. As a result, wear of the bore inner surface 3 due to the residual blast material or shot material 51 does not occur. Also, a smooth airflow 27
Therefore, turbulence does not occur during thermal spraying, fumes are prevented from being entangled in the thermal spray coating 15, and the adhesion of the thermal spray coating 15 does not decrease.

Further, as shown in FIG.
When the masking shielding plate 39 is inserted into the inside of FIG.
As shown in FIG. 19, the thermal spray coating 15 is hardly formed in the scavenging port portion 17, but when the masking shielding plate 39 is not provided, the thermal spray coating 15 and the scattering Particles 151 adhere.

[0029]

Next, the present invention will be described more specifically with reference to examples. [Pretreatment Step] First, the processing oil attached during the cylinder processing was washed, and the cylinder 1 was fixed to the cylinder set jig 21. Next, in order to impart adhesion to the thermal spray coating 15,
Under the conditions shown in Table 2, the inner surface 3 of the bore of the cylinder 1 was blasted by using a blast gun 23 to roughen the inner surface 3 of the bore.

[0030]

[Table 2]

[Spraying Stage] Thereafter, under the conditions shown in Table 3, the scavenging port portion 17 was
Without filling the exhaust port portion 19, the bore inner surface 3
A Fe-Al composite sprayed coating excellent in wear resistance and slidability was formed.

[0032]

[Table 3]

[Post-Treatment Step] When the formation of the thermal spray coating 15 is completed, the cylindrical member 5 having an opening 9 corresponding to the bore inner diameter after thermal spraying and conforming to the shape of the port hole 7 is sprayed for masking. It was inserted into the bore after the film was formed, and blasting was performed only on the portions inside the ports 17 and 19 under the same conditions as in Table 2 above. Here, in the above-mentioned blast processing of the pre-spraying processing, the processing was performed over the entire length of the bore, but in the post-processing, the blast processing was performed only in the vicinity of the port hole 7. After the blast treatment, the masking cylindrical member 5 was removed, and finally, the bore inner surface 3 was honed to finish.

[Results] FIGS. 14 to 17 show the port portion 1 before and after blasting as a post-spraying process.
7 and 19 show cross sections of wall surfaces. As can be seen from these, before the blast treatment for removing scattered particles,
The scattered particles 151 adhered to the wall surface of the port 19, whereas the scattered particles 1
51 did not adhere (part Q in FIG. 15). It can also be seen that the chamfering effect is obtained also at the end faces of the port portions 17 and 19 (portion P in FIG. 15). There was no residue. Further, in FIG. 17A, the scattered particles 15 adhered to the surface of the aluminum alloy material are shown.
1 was sufficiently removed by the blast treatment as shown in FIG.

The masking cylindrical member 5 and the cylinder set jig 21 used in the embodiment will be briefly described below. [Cylinder Member for Masking] The cylinder member 5 for masking
As shown in FIG. 7, the outer diameter is made smaller by 0.5 mm than the inner diameter of the bore after the thermal spray coating is formed, and the length of the cylindrical member 5 covers the bore inner surface 3 of the cylinder 1 to be processed when set in the cylinder 1. 155 mm. The opening 9 cut out according to the shape of the port hole 7 was made 0.5 mm larger than the port hole 7 in order to obtain a chamfering effect. As the material of the masking cylindrical member 5, an iron material having little wear due to the treatment was used.

[Cylinder Set Jig] As shown in FIGS. 8 to 10, when the cylinder 1 is set, the cylinder bore, the scavenging port section 17 and the exhaust port section 19 are connected to the cylinder set jig 21. It is configured to communicate with the suction / exhaust pipe 37 at the lower part of. When the cylinder is set, the three narrow scavenging port sections 17 have a plate thickness of 1 mm.
The shielding plate 39 is set on the set jig 21 so that the masking shielding plate 39 made of
Was fixed. Further, since the shielding plate 39 inserted into the scavenging port portion 17 may be worn by the pre-processing blasting process and the scattered particle blasting process, the opening hole of the set jig 21 connected to the scavenging port portion 17 of the cylinder 1 is considered. The insertion portion 41 is provided at 55, and the shielding plate 39 is configured to be replaceable with one touch.

[0037]

According to the present invention, it is possible to efficiently and simply remove a sprayed coating and scattered particles having insufficient adhesion adhered to a port portion of a cylinder. As a result, the sprayed coating and the scattered particles do not fall off during the operation of the engine to cause wear on the inner surface of the piston and the bore.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a shielding cylindrical member is inserted into a bore of a cylinder.

FIG. 2A is a cross-sectional view showing a state in which a post-spraying process according to the present invention is performed on a bore surface; FIG.
3A is an enlarged cross-sectional view of a portion A of FIG. 3A, and FIG. 3C is an enlarged cross-sectional view of a B portion of FIG.

FIG. 3 is a cross-sectional view showing a state in which a pre-spraying process is performed on a bore surface of a cylinder.

FIG. 4 is a cross-sectional view showing a state where thermal spraying according to the present invention is applied to a bore surface.

FIG. 5 is a cross-sectional view showing a state where a post-spray treatment according to the present invention is performed on a bore surface.

6A is a plan view of a cylinder, and FIG. 6B is a cross-sectional view taken along line CC of FIG. 6A.

7A is a plan view of a masking cylindrical member, and FIG. 7B is a cross-sectional view taken along line DD of FIG. 7A.

FIG. 8 is a side view of a cylinder set jig used in the present invention.

FIG. 9 is a plan view of FIG.

FIG. 10 is an enlarged plan view of a portion E in FIG. 9;

FIG. 11A is a schematic diagram showing an injection angle of a sprayed powder, and FIG. 11B is a schematic diagram showing an injection angle of a blast material or the like.

FIG. 12 is a cross-sectional view showing a state where thermal spraying is performed in a state where a shielding plate is inserted into a port portion of a cylinder.

FIG. 13 is an enlarged sectional view of a portion F in FIG. 12;

FIG. 14 is a cross-sectional view of a cylinder that has been subjected to post-spray processing in the example.

FIG. 15 is a photograph showing a structure of a cross section of a P part and a Q part of FIG. 14;

FIG. 16 is a cross-sectional view of a cylinder that has been subjected to post-spray processing in the example.

FIG. 17 is a photograph showing a cross section of an R part in FIG. 16;
(A) shows the case without the blast for removing scattered particles, and (b) shows the case with blast for removing the scattered particles.

FIG. 18 is a cross-sectional view showing a state where a bore surface is being thermally sprayed by a conventional method.

FIG. 19 is an enlarged sectional view of a portion S in FIG. 18;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 3 Bore inner surface 5 Masking cylindrical member 7 Port hole 9 Opening 13 Chamfer 15 Thermal spray coating 17 Scavenging port portion 19 Exhaust port portion 21 Cylinder set jig 23 Blast gun 25 Inner diameter spray gun 27 Air flow 33 Bolt hole for fixing cylinder head 35 Positioning Pin 37 Suction / Exhaust Pipe 39 Masking Shield 41 Insertion Section 51 Blast Material, Shot Material 53 Thermal Spray Frame 55 Opening Hole

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02F 1/00 F02F 1/00 R 1/22 1/22 DF Term (Reference) 3G024 AA21 AA22 AA32 DA12 EA01 FA06 FA14 GA01 GA04 4K031 AA02 AB02 AB08 CB09 CB26 DA04 FA04

Claims (4)

[Claims] 1. A post-spray treatment method for a cylinder for removing a spray coating or scattered particles attached to an inner wall surface of a port portion of a cylinder having a port portion penetrating outward from a port hole formed in an inner surface of the bore. A masking cylindrical member insertable into the bore inner surface and having an opening formed at a position corresponding to the port hole, and inserted into the bore inner surface to match the opening with the port hole; and Performing a blast process or a shot process from the inside of the cylinder member toward the inner wall surface of the port portion of the cylinder. 2. An opening of said cylindrical member is made 10 to 500% of a thickness of a sprayed coating more than a diameter of a port hole in an inner surface of said bore.
The post-spray treatment method for a cylinder according to claim 1, wherein the cylinder is formed large. 3. The blast processing or the shot processing,
3. The post-spraying method according to claim 1, wherein suction and exhaust are performed from an outer end of the port portion and an end of the bore. 4. After the thermal spraying is applied to the inner surface of the bore with the shielding plate inserted in the port portion, post-thermal spraying is performed by the method according to any one of claims 1 to 3. Post-spray treatment method for cylinders.