JPH0770729A - Flame spraying method for inside surface - Google Patents

Abstract

PURPOSE:To form a flame sprayed layer which is relieved in remaining of tensile stress and is improved in adhesion on the inside surface of a pipe. CONSTITUTION:A planar shielding material 6 is arranged near the surface to be flame sprayed of the inside surface of a cylinder 1 and a flame sprayed layer is formed on this inside surface in this method. The flame spraying is executed by rotating this shielding material 6 at every one time of flame spraying at need. The flame sprayed layer formed by the shielded part is parted by parting parts in an axial direction. The residual tensile stress of the flame sprayed layer is relieved by the parted parts, by which the adherence strength of the flame sprayed layer is improved. The flame spraying is executed by rotating this shielding material 6 at every one time of flame spraying, by which the parting layers formed on the flame sprayed layer are dispersed and only the prating layer formed by the final flame spraying remains on the surface of the flame sprayed layer and, therefore, this method is applicable even to a member which is small in the degree of relaxation of the thermal tensile stress but with which the difference in the level of the flame sprayed layer is undesirable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner surface thermal spraying method for thermally spraying a metal or ceramics on the inner surface of a cylindrical member such as a cylinder.

[0002]

2. Description of the Related Art To form a sprayed layer of alloy or ceramics on the inner surface of a cylinder, plasma spraying method, gas flame spraying method, electric arc spraying method, etc. are used to spray heat-melted sprayed particles on the inner surface of the cylinder. It is formed by continuously repeating the step of rapidly cooling and solidifying, and the thermal sprayed layer thus formed has tensile residual stress.

As described above, since residual tensile stress is present in the thermal spray layer formed on the inner surface of the cylinder, the adhesive strength of the thermal spray layer is low, and the thermal spray layer often peels off due to thermal mechanical stress. To this end, it has been proposed to use Japanese Patent Laid-Open No. 60-266.
The invention of the inner surface thermal spraying method of Japanese Patent No. 56, in which a plurality of projections having a triangular or trapezoidal cross-sectional shape are formed between the inner surfaces of a cylinder, and thermal spraying is performed so that the thickness of the thermal spray coating is not less than the height of these projections. Then, the inner surface of the cylinder is processed to be smooth, and the residual stress is dispersed by the protrusions, so that the peeling resistance is improved.

[0004]

However, according to the above-mentioned prior art, it is difficult to machine the protrusions on the inner surface of the cylinder, which increases the processing cost, and the formed protrusions are destroyed by the blast treatment before the thermal spraying. There is a problem that the expected effect cannot be obtained.

The present invention has been made in order to solve the above-mentioned problems in forming a sprayed layer by spraying an alloy or ceramics on the inner surface of a cylinder. It is an object of the present invention to provide an inner surface thermal spraying method capable of forming.

[0006]

The inventor has found that the reason why tensile stress remains in the sprayed layer formed on the inner surface of the cylinder is that the sprayed layer is solidified integrally. Therefore, we conceived of dividing the sprayed layer by some method, and succeeded in dividing the sprayed layer by arranging a shielding material in the axial direction near the sprayed surface when forming the sprayed layer to achieve this. Then, the present invention was completed.

The inner surface thermal spraying method of the present invention is the method of forming a thermal sprayed layer on the inner surface of a cylinder as claimed in claim 1, wherein a linear or plate-shaped shield is arranged near the surface to be sprayed on the inner surface of the cylinder. The point is to form a layer. Further, the gist of the invention of claim 2 is that the shield is rotated and sprayed each time it is sprayed.

The shield for shielding the surface to be sprayed may be a plate material or a wire material. The shield is arranged at two or more places that equally divide the circumference, but the upper and lower ends of the shield are fixed to an annular member in advance and used as a shield jig.

It is desirable that the shielding material is arranged 1 mm or more and 5 mm or less from the surface to be sprayed. This is because if the thickness is less than 1 mm, it is difficult to attach / detach the shielding jig, and if it is 5 mm or more, the shielding effect of the spray particles decreases. Depending on the film to be produced, the division (step) of the film layer on the inner peripheral surface may not be preferable. In this case, the thermal spraying is performed while rotating the cylindrical material or the shielding jig during the thermal spraying.

[0010]

According to the method of claims 1 and 2, since the surface to be sprayed is shielded by the shielding material, the sprayed coating layer formed by the shielded portion is divided in the axial direction and is shielded. The tensile residual stress of the thermal spray coating layer is relaxed by the divided portions, and the adhesion strength of the thermal spray layer is improved.

According to the second aspect of the present invention, since the shield is rotated and sprayed every time the thermal spraying is performed, the split portions formed in the coating sprayed layer are dispersed, and the split portions formed in the final spraying. Since only the thermal spray coating layer remains on the surface of the thermal spray coating layer, it can be applied to a member that has a small degree of relaxation of thermal tensile stress but does not have a step in the thermal spray layer.

[0012]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, in order to form the sprayed layer 4 on the inner surface of the cylinder 1, the four shield lines 6 are located 5 mm inward from the sprayed surface at positions that divide the sprayed surface into four equal parts. Then, as shown in the perspective view of the shielding jig of FIG. 3, the shielding jig 2 in which the upper end and the lower end of the shielding wire 6 were fixed to the annular member was produced. As shown in FIG. 1, the outer diameter of the upper annular member 7 is larger than the outer diameter of the cylinder 1, and the lower annular member 9 has a guide hole 8 into which the cylinder 1 fits. It is smaller than the inner diameter and can be inserted into the cylinder 1.

In this way, the thermal spray gun 3 was inserted into the cylinder 1 to which the shielding jig 2 was fixed, and the inner surface was sprayed by the thermal spray gun 3 while rotating the cylinder 1 (or rotating the thermal spray gun). As shown in the cross-sectional view of the cylinder 1 in FIG. 4, the formed sprayed layer 4 is divided in the axial direction by four dividing portions 5, whereby the residual tensile stress of the sprayed layer 4 is dispersed,
It was possible to improve the adhesion strength of the sprayed layer 4.

(Embodiment 2) In Embodiment 1, the shielding jig 2 is installed not to be fixed to the cylinder 1 but to be rotatable arbitrarily, and a constant angle is set every time the thermal spray gun 3 forms one layer of the thermal spray layer 4. The sprayed layer 4 was formed while rotating the jig 2 one by one. In this embodiment, the sprayed gun 3 was reciprocated 3 times to produce the target sprayed film. However, as shown in the partial cross-sectional view of FIG. 5, the relative position of the cylindrical member 1 and the jig 2 may be changed for each reciprocation. Then, the coating was divided for each layer, but there was no fault 5 where the base material 1 was exposed in the final coating. As a result, it was confirmed that the thermal sprayed layer 4 can be applied to a member having an undesired step.

In the embodiment described above, the case where the shield is a wire is shown, but the same thing can be obtained by using the shield which is the shield plate 10 as shown in the shield jig 2 of FIG. The effect is obtained. When the shield is the shield plate 10, the area of the divided portion of the coating layer increases and the material yield on the coating surface decreases, but the unit sprayed area also decreases, so the shrinkage force of the sprayed layer can be further reduced, and the adhesion strength The improvement effect of can be increased.

[0016]

As described in detail above, the inner surface thermal spraying method of the present invention forms a thermal spray layer by arranging a linear or plate-shaped shield near the surface to be sprayed on the inner surface of the cylinder. If necessary, the shield is rotated and sprayed once every spraying, and the sprayed layer formed by the shielded portion is
It is divided in the axial direction by a dividing portion, and this dividing portion relieves the tensile residual stress of the thermal sprayed layer and improves the adhesion strength of the thermal sprayed layer. Further, by rotating and spraying the shield for each thermal spraying, the splitting layers formed in the sprayed layer are dispersed and only the splitting layers formed in the final spraying remain on the surface of the sprayed layer. Also, the present invention can be applied to a member in which the degree of relaxation of thermal tensile stress is small but the step of the sprayed layer is not preferable.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which an inner surface of a cylindrical material is thermally sprayed by the method of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a perspective view of a shield jig.

FIG. 4 is a cross-sectional view of a cylindrical material after inner surface thermal spraying.

FIG. 5 is a partially enlarged cross-sectional view of the cylindrical material and the sprayed surface after the inner surface is sprayed on the cylindrical material according to the invention of claim 2.

FIG. 6 is a perspective view of a shielding jig whose shield is a plate material.

[Explanation of symbols]

 1 Cylindrical material 2 Shielding jig 3 Thermal spray gun 4 Thermal spray layer 5 Minute fault 6 Shielding line 7 Upper annular member 8 Guide hole 9 Lower annular member 10 Shielding plate

Claims (2)

[Claims] 1. A method for forming a sprayed layer on the inner surface of a cylinder, wherein a liner or plate-shaped shield is arranged near the surface to be sprayed on the inner surface of the cylinder to form the sprayed layer. 2. The inner surface thermal spraying method according to claim 1, wherein the shield is rotated and sprayed every time the thermal spraying is performed once.