JP2017141483A - Method of forming spray coating on outer peripheral surface of cast iron pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the yield of a spray coating material.SOLUTION: After a spray coating is formed on an outer peripheral surface of a cast iron pipe P, a spray coating is further formed again on the spray coating. Normally, the outer peripheral surface of the cast iron pipe is roughened by blast processing etc., before the spray coating is formed, so when the spray coating is formed on the roughened surface, unevenness of the spray coating is generated in addition to unevenness of the former cast iron pipe surface. Consequently, anchor effect on the spray coating increased by forming the coating again. At this time, it is preferred that a speed of feeding of the cast iron pipe along its axis and a speed of rotation on the axis are made slower in the spray coating formation than in the former spray coating formation, namely, a latter spray coating speed is slower than a former spray coating speed. The reason is that although it takes a sufficient time for finishing with the latter (next) spray coating, the former spray coating is only for forming a base and thereby may be rough. Consequently, a work time can be shortened.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for forming a thermal spray coating on an outer peripheral surface of a cast iron pipe for water and sewage etc. buried in soil.

When cast iron pipes are buried in the soil, they are exposed to corrosion from moisture in the soil and fluid flowing inside. For this reason, it is common that the outer peripheral surface and inner peripheral surface of a cast iron pipe are subjected to anticorrosion treatment.
As an anti-corrosion treatment on the outer peripheral surface of the cast iron pipe, a thermal spray coating made by heating and melting a metal such as zinc-aluminum silicon (Zn-AlSi) pseudo alloy is sprayed from the spray gun onto the outer peripheral surface of the cast iron pipe to form a thermal spray coating. (See Patent Document 1, paragraphs 0030 to 0031 and FIG. 1b).

JP, 2014-133908, A

The conventional thermal spray coating forming method will be described, for example, with reference to FIG. 5 of the present application. A cast iron pipe P is supported on a carriage 2 traveling on a rail 1 via a support roller 3 so as to be rotatable around its axis. Then, the cast iron pipe P is moved in the axial direction while rotating, the spray material c is sprayed from the spray gun (spray machine) G, and the spray material c is spray coated on the outer peripheral surface of the cast iron pipe P.
In this thermal spray coating, if the sprayed material c has a large scattering amount (scattering amount), the yield (hereinafter referred to as “yield” as appropriate) is poor, resulting in a problem in productivity. For this reason, it is common to prevent scattering by means for reducing (approaching) the distance S between the spray gun G and the cast iron pipe P and reducing the spray pattern (see c ′ in FIG. 4).
However, this means has some effect, but if the distance S is too close, the spray pattern c ′ becomes small and a sufficient spray pattern cannot be obtained, and the rotational speed of the cast iron pipe P and the axial direction thereof are not obtained. In many cases, a spiral pattern is formed on the thermal spray coating due to the movement speed.
For this reason, conventionally, since the thermal spraying is performed with a sufficient distance S so that the spiral pattern does not occur, there is a problem that the yield of the thermal spray material c is poor. From today's depletion of resources, it is preferable that the yield is as high as possible.

  This invention makes it a subject to raise the yield of a thermal spray material under the above actual condition.

In order to achieve the above object, in the present invention, after the thermal spray coating is performed on the outer peripheral surface of the cast iron pipe P, the thermal spray coating is further performed on the thermal spray coating.
Usually, before spray coating, the outer peripheral surface of the cast iron pipe is roughened by blasting or the like, so when the thermal spray coating is formed on the rough surface, in addition to the irregularities on the surface of the cast iron pipe, As a result, the anchor effect on the thermal spray coating increases during re-coating.
Further, in the respraying coating, a part of the pre-spraying coating (spraying surface layer) is remelted by respraying and the adhesion with the particles being sprayed is promoted, so that the particles being sprayed are hardly peeled off.
From the above, the yield rate of the thermal spray material is increased.

  Incidentally, the spray gun G is also reciprocated in the axial direction of the cast iron pipe P (see Patent Document 1, paragraph 0030, line 6, FIG. 1B). In this invention, after the entire thermal spray coating in the range of thermal spray coating is performed, the thermal spray coating is not further performed on the thermal spray coating.

As a configuration of the present invention, in the method of forming a thermal spray coating by spraying a thermal spray material from a thermal spray gun on the outer peripheral surface of the cast iron pipe, the thermal spray coating in the range of the thermal spray coating from one end of the cast iron pipe to the other end is performed. Thereafter, a configuration in which spray coating (re-spray coating) is further performed on the spray coating can be employed.
The thermal spray coating is performed by relatively moving the spray gun and the cast iron pipe in the axial direction, but the relative movement is performed by moving either the spray gun or the cast iron pipe in the axial direction with respect to the other. Just do it. In addition, re-spray coating is performed by reciprocating movement between one end and the other end in the axial direction, or by spraying from one end of the cast iron pipe to the other end and then returning from one end to the other end. That is, the thermal spray coating from the other end to the one end or from the one end to the other end of the range to be spray coated can be further performed.
Furthermore, the spraying speed of the spray gun (spraying amount per unit time to the cast iron pipe) is determined by the axial feed rate of the cast iron pipe and the rotational speed around the axis (hereinafter referred to as appropriate). , Simply referred to as “feeding speed” and “rotational speed”), the spraying speed is determined by adjusting both speeds. At this time, if the rotation speed is slowed (lowered), the influence of the airflow on the cast iron pipe surface is less likely to be affected, which is preferable from the viewpoint of yield.

In this configuration, the thermal spray coating of the entire outer peripheral surface from one end to the other end of the spray coating range of the cast iron pipe, and the entire outer periphery from the other end to the one end or the same end to the other end of the subsequent thermal spray coating range In the spray coating on the surface, the feed rate and the rotation speed for the spray gun can be made different. At this time, it is preferable to increase the feed rate and rotation speed in the former spray coating with respect to the feed rate and rotation speed in the latter re-spray coating, that is, to lower the next spray rate with respect to the previous spray rate. .
As described above, since the subsequent spray coating is finished in order to reduce the speed of the next spray coating relative to the spraying speed of the previous spray coating, it is necessary to secure a sufficient time for the finishing. On the other hand, the above-mentioned thermal spray coating is for making a base and may be rough.

  In addition, it is conceivable to change the spraying amount of the thermal spray material to ensure the finishing degree. In that case, however, the thermal spray gun (spraying machine) is usually sprayed at a maximum capacity (for example, medium capacity) or less. In order to reduce the amount, the working time becomes longer in order to obtain a thermal spray coating layer having a required thickness with a guaranteed finish. On the other hand, as described above, if the spraying is to slow down the subsequent spraying speed with respect to the previous spraying speed, the ability of the spraying gun is maximized, and the sprayed coating layer of the required thickness is formed by adjusting the spraying speed. Therefore, even if two thermal spray coating operations are performed, the operation time can be shortened as a result. This is efficient and reduces work time.

  Since this invention is comprised as mentioned above, the yield rate of a thermal spray material can be made high.

Schematic of one embodiment of a method for forming a thermal spray coating on the outer peripheral surface of a cast iron pipe according to the present invention Schematic of the other embodiment Schematic of yet another embodiment Thermal spray pattern Schematic diagram of conventional example

  One embodiment of the thermal spray coating apparatus for the outer peripheral surface of the cast iron pipe according to the present invention is shown in FIG. In this embodiment, a cast iron pipe P is supported by a carriage 2 traveling on a rail 1 via a support roller 3 so as to be rotatable around its axis, as in the prior art. A fixed spray gun G is opposed to the moving cast iron pipe P. The cast iron pipe P on the carriage 2 has an outer peripheral surface roughened by blasting or the like.

In this thermal spray coating apparatus, as shown in FIG. 1, a cast iron pipe P rotating around an axis is moved in the left-right direction by a carriage 2, and a thermal spray material in which the metal such as zinc is heated and melted from a thermal spray gun G. c is ejected. Therefore, the cast iron pipe P is thermally sprayed on the entire outer peripheral surface from one end (right end in the figure) to the other end (left end in the figure) (FIG. 1 (a) → same (b) → same ( c)).
When the thermal spray coating is performed and the thermal spray coating reaches the other end of the cast iron pipe P (when the thermal spray gun G faces the other end of the cast iron pipe P) as shown in FIG. And move in the opposite direction. Therefore, the cast iron pipe P is thermally sprayed on the entire outer peripheral surface from the other end toward the one end (FIG. 1 (c) → same (d) → (same e)).

  When spray coating is performed up to one end of the cast iron pipe P (state of FIG. 1 (e)), that is, when the cast iron pipe P is reciprocated with respect to the spray gun G and spray coating is performed, The spraying of the thermal spray material c is stopped, and the thermal spray coating operation of the cast iron pipe P is completed. Thereafter, the carriage 2 moves to the next process, and a new blasted cast iron pipe P is fed into the thermal spray coating apparatus, and thermal spray coating is performed by the above-described action.

  In this thermal spray coating operation, the thermal spray range L is the entire length of the cast iron pipe P or a part of the cast iron pipe P as shown in FIG. In the latter case, for example, as shown in FIG. 2, the insertion opening portion L ′ is left about 60 to 70 mm (not sprayed), and the insertion opening portion L ′ is subjected to zinc rich coating or the like.

  Table 1 shows the “spraying yield (yield)” in which both the one-way spraying (FIG. 5) and the reciprocating spraying (FIG. 1) have the same feed rate and the same rotational speed of the cast iron pipe P. . At this time, a test was performed on 30 ductile cast iron pipes P having a nominal diameter of 100 mm, and the amount of spraying from the spray gun G was adjusted so that the spray coating thickness would be the same value. 1 (c) As shown by a chain line, a single-sided sandblast plate piece T (for example, 1.6 mm thickness × 150 mm × 50 mm) is fixed to a cast iron pipe P before spray coating by a magnet or the like, and after the spray coating, the plate piece T The thermal spray coating weight on the surface of the plate piece T was divided by the weight of the thermal spray material c ejected (used) on the surface of the plate piece T. Further, the distance S (see FIGS. 1 (a) and 5) between the spray port of the spray gun G and the outer surface of the cast iron pipe P is 150mm at the straight portion because the height of the spray gun G is fixed. Became 120 mm.

  From Table 1, it can be understood that reciprocating spraying is superior in terms of “spraying yield” because reciprocating spraying is improved by about 3% in comparison with one-way spraying.

  Next, in the reciprocating spraying, the example of Table 1 is set as “benchmark (BM)”, and the feed speed and the rotational speed of the cast iron pipe P are different forward and backward (fast and slow) in the forward path and the return path with the BM as a reference point. Tables 2 and 3 below show the “spraying yield” in the case of being applied. Also in this test, the cast iron pipe P is made of ductile cast iron having a nominal diameter of 100 mm, the “spraying yield” is also calculated by the above plate piece T, and the nozzle of the spray gun G and the cast iron pipe are used. Similarly, the distance S between the outer surface of P and the height of the spray gun G was fixed, the straight part was 150 mm or 155 mm, and the receiving part was 120 mm or 125 mm. In BM, “spraying yield” differs between Table 2 and Table 3 because the distance S between the spray port of the spray gun G and the outer surface of the cast iron pipe P is as follows: Table 2: 150 mm, Table 3: 155 mm This is because they are different.

From the comparison between conditions 1 and 2 in Table 2, it can be seen that when the rotational speed is lowered, the “yield” is improved due to the decrease in the scattering of the thermal spray material c.
Further, from comparison between the same condition 3 and the same condition 4, it can be seen that the “yield” is improved when the return speed of the cast iron pipe P (speed of the carriage 2) is slowed down with respect to the forward path.
Further, from the comparison of conditions 7 to 13 in Table 3, the spraying speed determined from the feed speed and the rotation speed of the cast iron pipe P in the spray coating on the return path is determined from the feed speed and the rotation speed in the spray coating on the outbound path. It can be seen that the “spraying yield” is improved when the spraying speed is reduced. However, from the comparison between conditions 8 and 9, and 12 and 13, even if only the rotational speed of the cast iron pipe P is simply reduced, the “yield” is not necessarily improved in relation to the same feed speed of the cast iron pipe P. I understand that I will not. From this, it is preferable to determine appropriately by data collection of experiments and actual operations so as to obtain an “optimal yield” as an effective spraying speed with the rotational speed and feed speed of the cast iron pipe P. Can understand.

  In the above-described embodiment, the cast iron pipe P is moved in the axial direction by the carriage 2 with respect to the spray gun G. However, the cast iron pipe P is rotated and reciprocated while gripping both ends (insertion, receiving port), As shown in FIG. 2, the spray gun G may be reciprocated with respect to the cast iron pipe P. In this case, the carriage 2 supports the cast iron pipe P through the support roller 3 so as to be rotatable around its axis, and serves only for conveyance to the front and rear processes. Further, although spray coating is performed by reciprocating movement, after spraying from one end to the other end of the cast iron pipe (spraying range L), it can be performed by returning to the same end and spraying from one end to the other end (FIG. 1 (a)). ) → (b) → (c) and (a) → (b) → (c)).

Furthermore, as shown in FIG. 3, if the front and rear in the axial direction of the cast iron pipe P are covered with a plurality of spray guns G, G such as two, the spray distance in the axial direction per one spray gun G can be increased. The working time can be shortened by shortening, and for example, when the spraying conditions in the straight part and the receiving part are different, the conditions can be changed. In the case of the difference, the spray amount and the distance S of the thermal spray material c in the straight part and the receiving part are different.
In each of the above embodiments, the direction of rotation of the cast iron pipe P at the time of the previous thermal spray coating and the time of the subsequent thermal spray coating can be made different. Further, the distance (distance S) between the spray gun G and the cast iron pipe P is appropriately determined based on experiments and actual operations so that the spiral pattern does not occur in relation to the feed speed and the rotational speed of the cast iron pipe P. Of course, it is determined to be a short distance S.

Incidentally, in actual operations and various tests, the thermal spray coating film thickness is measured using a bipolar film thickness meter or the like, and is set at three or more locations such as the middle and both ends in the length direction of the cast iron pipe P. . The suitability of the thermal spray coating is evaluated by a cross-cut method or the like.
Further, the thermal spray coating can be made not only to reciprocate within the range L, but also to cover more than three layers. Further, in the spraying range L, the entire range L can be changed to a plurality of layers by performing reciprocating spraying in small increments (for example, by 1/5 × L reciprocating spraying coating).

1 Rail 2 Traveling Cart 3 Cast Iron Pipe Support Roller G Thermal Spray Gun L Thermal Spray Range P Cast Iron Pipe c Thermal Spray Material c ′ Thermal Spray Pattern

As a configuration of the present invention, in a method of forming a thermal spray coating by spraying a thermal spray material from a thermal spray gun on an outer peripheral surface of a cast iron pipe, a range of the thermal spray coating from one end to the other end of the cast iron pipe with the same thermal spray material after the spray coating, the over spray coating, further spray coating (re spray coating) to have a row, cast iron pipe plurality of spray coating layer formed to the same thermal spraying material consisting of the same spraying material on the outer peripheral surface of the The structure which raises the yield rate of can be employ | adopted.
The thermal spray coating is performed by relatively moving the spray gun and the cast iron pipe in the axial direction, but the relative movement is performed by moving either the spray gun or the cast iron pipe in the axial direction with respect to the other. Just do it. In addition, re-spray coating is performed by reciprocating movement between one end and the other end in the axial direction, or by spraying from one end of the cast iron pipe to the other end and then returning from one end to the other end. That is, the thermal spray coating from the other end to the one end or from the one end to the other end of the range to be spray coated can be further performed.
Furthermore, the spraying speed of the spray gun (spraying amount per unit time to the cast iron pipe) is determined by the axial feed rate of the cast iron pipe and the rotational speed around the axis (hereinafter referred to as appropriate). , Simply referred to as “feeding speed” and “rotational speed”), the spraying speed is determined by adjusting both speeds. At this time, if the rotation speed is slowed (lowered), the influence of the airflow on the cast iron pipe surface is less likely to be affected, which is preferable from the viewpoint of yield.

When the thermal spray coating is performed up to one end of the cast iron pipe P (state shown in FIG. 1 (e)), that is, the two layers of thermal spray coating made of the same thermal spray material c are performed by reciprocating the cast iron pipe P with respect to the thermal spray gun G. When performed, the spraying of the thermal spray material c from the thermal spray gun G is stopped, and the thermal spray coating operation of the cast iron pipe P is completed. Thereafter, the carriage 2 moves to the next process, and a new blasted cast iron pipe P is fed into the thermal spray coating apparatus, and thermal spray coating is performed by the above-described action.

Claims (3)

  In a method for forming a thermal spray coating by spraying a thermal spray material (c) from a thermal spray gun (G) to the outer peripheral surface of a cast iron pipe (P), from one end of the spray coating range (L) of the cast iron pipe (P) After the thermal spray coating of the entire outer peripheral surface to the other end, on the thermal spray coating, the range from the other end to the one end or the one end to the other end of the spray coating range (L) of the cast iron pipe (P) A method for thermal spray coating on cast iron pipes, characterized by further performing thermal spray coating on the entire outer peripheral surface.   Thermal spray coating of the entire outer peripheral surface from one end to the other end of the spray coating range (L) of the cast iron pipe (P), and the other end to one end of the subsequent spray coating range (L) or the other from the same end In the spray coating on the entire outer peripheral surface to the end, the feed rate in the axial direction of the cast iron pipe (P) with respect to the spray gun (G) and the rotational speed around the axis of the cast iron pipe are different. The thermal spray coating method to the cast iron pipe according to claim 1.   Thermal spray coating of the entire outer peripheral surface from one end to the other end of the spray coating range (L) of the cast iron pipe (P), and the other end to one end of the subsequent spray coating range (L) or the other from the same end In the thermal spraying coating of the entire outer peripheral surface to the end, the thermal spraying speed determined by the feed rate in the axial direction of the cast iron pipe (P) in the thermal spraying coating and the rotational speed around the axis is set in the latter thermal spraying coating. The thermal spray coating method for a cast iron pipe according to claim 2, wherein the thermal spray speed is determined with respect to a thermal spray speed determined by an axial feed speed of the cast iron pipe (P) and a rotational speed around the axis.

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