JP5922822B1 - Tube manufacturing method and powder coating method - Google Patents

Abstract

A method of manufacturing a tubular body for forming a powder coating film having a uniform film thickness is provided. A tube body 900 includes a receiving port 910 having an earthquake-resistant structure and a straight portion 920 continuing to the receiving port 910. A recess 993 for accommodating the lock ring 720 is formed in the inner peripheral surface 951 of the receiving port 910. In the tube manufacturing method, the nozzles 11 and 12 for discharging powder in the tube axis direction of the tube body 900 and the tube body 900 are relatively moved, and the nozzles 11 and 12 and the tube body 900 are moved around the tube axis. A step of discharging the powder to at least the concave portion 993 while rotating relatively is provided. The peripheral speed in the recess 993 when the powder is discharged to the recess 993 is set to 50 m / min or more and 200 m / min or less. [Selection] Figure 4

Description

  The present invention relates to a pipe manufacturing method, a pipe manufactured by the pipe manufacturing method, and a powder coating method.

  In recent years, ductile cast iron pipes (iron pipes), which are mainly used for water pipes, are joined by inserting the joints of one cast iron pipe into the socket of one cast iron pipe even during an earthquake. Part) does not leave, and it is required to maintain the water flow function as a lifeline. For this reason, a member such as a lock ring for preventing the joint part from being detached or a rubber ring for maintaining the water stoppage of the joint part is mounted on the inner peripheral surface of the cast iron pipe as a member for realizing them. There are provided a plurality of concave portions for the purpose and convex portions for causing the member to function. Further, a long tubular portion called a straight portion exists between the receiving port located at both ends of the cast iron tube and the insertion port.

  By the way, cast iron pipes, which are metal pipes, are coated on the inner and outer peripheral surfaces for reasons of anticorrosion, etc., but the inner peripheral surfaces are used to respond to consumer demand for delicious water. In many cases, powder coating is applied.

  However, when powder coating is applied to the inner peripheral surface of the receptacle having such a concavo-convex shape, a uniform powder coating film can be formed because the ease of adhesion of the paint differs between the bottom surface and the wall surface of the concavo-convex portion. Have difficulty. Therefore, an excessive amount of powder paint adheres depending on the part. As a result, the size of the concave portion does not fall within a predetermined tolerance range, and there is a possibility that troubles may occur when the rubber ring, the lock ring, or the like is attached or when the recess is joined. Therefore, the powder coating is mainly targeted for the smooth portion of the inner peripheral surface of the straight part, and the powder coating has not been applied to the uneven shape of the inner peripheral surface of the receiving port.

  Therefore, when painting the inner peripheral surface of the receiving port, it is difficult to completely eliminate painting work by skilled workers, which has been a burden on the painting process.

  For example, Patent Document 1 discloses a method of performing powder coating on the inner surface of an iron pipe having a receiving port at one end and an insertion port at the other end as an example of powder coating on the inner peripheral surface of a tube body. ing. The coating method of Patent Document 1 is a method of forming a uniform coating film on the inner peripheral surface of the receiving port by discharging a charged powder paint from a nozzle.

  Patent Document 2 discloses a method for forming a uniform coating film on the inner peripheral surface of a receiving port by using a nozzle that sprays paint onto a cone-shaped spray pattern while rotating a metal tube. .

JP 2010-269243 A JP 2003-53220 A

  However, depending on the rotational speed of the tube during powder coating, a coating film having a uniform film thickness may not be formed on the inner peripheral surface of the receiving port.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is a tube manufacturing method for forming a powder coating film having a uniform film thickness, and a tube manufactured by the tube manufacturing method. It is in providing a body and a powder coating method.

  According to the first aspect of the present invention, there is provided a method of manufacturing a tubular body comprising: a tubular body having a powder coating film formed by powder coating on an inner peripheral surface of a tubular body having no powder coating film formed thereon. Executed to manufacture. The tubular body includes a receiving port having an earthquake-resistant structure and a straight portion continuing to the receiving port. A housing portion for housing the lock ring is formed on the inner peripheral surface of the receiving port. The tubular body manufacturing method includes at least housing while relatively moving the nozzle and the tubular body that discharge powder in the tubular axis direction of the tubular body and relatively rotating the nozzle and the tubular body around the tubular axis. A step of discharging powder to the part. The peripheral speed in the container when discharging powder to the container is set to 50 m / min or more and 200 m / min or less.

  According to the invention of claim 2, the peripheral speed in the container when discharging powder to the container is set to 50 m / min or more and 100 m / min or less.

  According to the invention of claim 3, in the step of discharging the powder, the powder is also discharged to a part of the straight part. The peripheral speed in the container when discharging powder to the container is set slower than the peripheral speed in the container when discharging powder to a part of the straight part.

  According to the invention of claim 4, the tube is manufactured by the tube manufacturing method according to claims 1 to 3.

  According to invention of Claim 5, the powder coating method is performed with respect to a pipe body provided with the receiving port which has an earthquake-resistant structure, and the straight part which continues to a receiving port. A housing portion for housing the lock ring is formed on the inner peripheral surface of the receiving port. In the powder coating method, the nozzle that discharges powder in the tube axis direction of the tube body and the tube body are moved relatively, and the nozzle and the tube body are relatively rotated around the tube axis, A step of discharging the powder to at least a part of the inner peripheral surface and the container. The peripheral speed in the container when discharging powder to the container is set to 50 m / min or more and 200 m / min or less.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the pipe body provided with the tubular body in which the powder coating film of uniform film thickness was formed, and the said tubular body.

It is a figure for demonstrating the structure of a pipe line and a pipe body. It is a figure showing the structure of the coating system for performing powder coating with respect to the internal peripheral surface of the receiving opening of a tubular body with a coating device. It is a figure for demonstrating the discharge state of the powder at the time of powder coating. It is a figure for demonstrating the connection state of the pipe body in a pipe line, and a pipe body. It is a figure for demonstrating the position (henceforth a "measurement point") which measures the film thickness of a powder coating film. It is a figure showing the investigation result of flowability and gel time, and the evaluation with respect to the film thickness of the powder coating film formed by powder coating about 29 types of powder coatings. FIG. 7 is a graph in which the values of flowability and gel time shown in FIG. 6 are plotted by classification according to evaluation with the flowability as a horizontal axis and the gel time as a vertical axis. It is a figure showing evaluation with respect to the film thickness of the powder coating film formed by powder coating about the peripheral speed of 7 steps. It is a figure showing the measurement result for 1 time about the peripheral speed of six steps except 25 m / min as an example of a measurement result.

  Hereinafter, a tubular body according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  In the following description, an iron pipe body having a receiving port (as an example, a ductile cast iron pipe for water supply) will be described as an example of a coating object. In addition, the material of the pipe body used as the coating object is not limited to iron as long as powder coating is possible. For example, the coating object may be a metal tube other than iron.

<A. Outline of tube>
FIG. 1 is a diagram for explaining the structure of a pipe line and a pipe body. Referring to FIG. 1, a pipe line 2000 is formed by connecting a pipe body 900 and a pipe body 900A.

  The pipe bodies 900 and 900A are ductile iron pipes (joints) having an earthquake resistance function. In addition, although the tubular bodies 900 and 900A are general ductile iron pipes, the structure of the tubular bodies 900 and 900A is demonstrated below for convenience of explanation.

  The tubular bodies 900 and 900A are connected to each other when the insertion opening 921 of one tubular body 900A is inserted into the receiving opening 910 of the other tubular body 900. Tube 900 and tube 900A have the same structure.

  In more detail, the tubular bodies 900 and 900A are configured so that even if ground deformation occurs due to an earthquake or the like due to the lock ring 720, the lock ring holder 730, and the protrusion 922 provided at the tip of the insertion opening 921 in the tubular body 900A. The insertion opening 921 is prevented from being detached from the receiving opening 910. Further, the insertion end 921 of the tubular body 900 </ b> A is regulated so as not to enter the tubular body 900 by the tip of the tubular body 900 </ b> A hitting the bottom portion 940 of the tubular body 900. The rubber ring 710 prevents leakage of liquid (for example, water) or gas that passes through the inside of the tubular bodies 900 and 900A to the outside.

  Hereinafter, for convenience of explanation, the tubular body 900 will be described focusing on the tubular body 900, 900A.

<B. Composition of painting system>
FIG. 2 is a diagram illustrating an example of a configuration of a coating system 1000 for performing powder coating on the inner peripheral surface of the receiving port 910 of the tubular body 900 by the coating apparatus 1. With reference to FIG. 2, the coating system 1000 includes a coating apparatus 1, a pipe body 900 as an object to be coated, and a rotating apparatus 800. The coating apparatus 1 includes a powder discharge mechanism 10, a drive device 20, a control device 30, a powder supply device 40, and a hose 50.

  The powder discharge mechanism 10 includes a nozzle 11 and a lance 16. The lance 16 is a pipe (paint supply pipe) for supplying powder to the nozzle 11. The nozzle 11 is provided at the tip of the lance 16. The nozzle 11 discharges powder onto the concave and convex inner peripheral surface of the receiving port 910 of the tube body 900.

  The drive device 20 includes a housing 21 for fixing the powder discharge mechanism 10 and a support base 22 that supports the housing 21 so as to be movable. The support base 22 has a drive mechanism for reciprocating the casing 21 in the axial direction of the tube body 900 (that is, the X-axis direction). The powder discharge mechanism 10 moves in the same direction and speed as the casing 21 as the casing 21 moves.

  The control device 30 controls the moving direction, moving speed, and moving distance of the casing 21 by sending a command to the driving device 20. That is, the control device 30 controls the moving direction, moving speed, and moving distance of the powder discharge mechanism 10. The moving direction, moving speed, and moving distance of the casing 21 are set in advance by the user of the coating apparatus 1 according to the dimensions of the tube body 900 and the like. The control of the moving speed will be described later. The control device 30 instructs the powder supply device 40 to start and stop supplying powder.

  The control device 30 moves the housing 21 in the direction of arrow A (X-axis positive direction) and arrow B (X-axis negative direction). More specifically, the control device 30 moves the casing 21 relative to the support base 22 so that the nozzle 11 enters the receiving port 910 of the tube body 900 and then the nozzle 11 emerges from the receiving port 910.

  The powder supply device 40 is connected to the lance 16 by a hose 50. Thereby, the coating apparatus 1 can discharge powder from the nozzle 11.

  The rotating device 800 rotates the tube body 900 in the circumferential direction of the tube body 900. More specifically, the rotating device 800 rotates the tubular body 900 at a constant speed in the direction of arrow C as an example. Thereby, the coating apparatus 1 can discharge the powder to the entire area of the inner peripheral surface of the receiving port of the tubular body 900.

<C. Powder discharge>
FIG. 3 is a diagram for explaining the discharge state of the powder during powder coating. Referring to FIG. 3, the inner peripheral surface 951 of the receiving port 910 of the tubular body 900 has an uneven shape. On the other hand, the inner peripheral surface 952 of the straight part 920 continuing to the receiving port 910 does not have an uneven shape. Hereinafter, the structure of the inner peripheral surface 951 of the receiving port 910 will be described in detail.

  A plurality of recesses are formed on the inner peripheral surface 951. Specifically, the inner peripheral surface 951 has a recess 991 in which the heel portion 7101 (see FIG. 4) of the rubber ring 710 is accommodated and a recess 992 in which the valve portion 7102 (see FIG. 4) of the rubber ring 710 is accommodated. And a recess 993 in which the lock ring 720 and the lock ring holder 730 are accommodated.

  The concave portion 991 has a wall surface 961 on the opening side (front side) of the receiving port 910 of the tube body 900 and a wall surface 962 on the back side of the tube body 900. The concave portion 991 has a bottom surface 971 between the wall surface 961 and the wall surface 962. The recess 992 has a wall surface 963 on the opening side of the tube body 900 and a wall surface 964 on the back side of the tube body 900. Further, the recess 992 has a bottom surface 972 between the wall surface 963 and the wall surface 964. The recess 993 has a wall surface 965 on the opening side of the tube body 900 and a wall surface 966 on the back side of the tube body 900. The concave portion 993 has a bottom surface 973 between the wall surface 965 and the wall surface 966.

  The wall surfaces 961, 962, 964, and 966 are substantially parallel to a cross section perpendicular to the axial direction of the tube body 900. The bottom surfaces 971, 972, and 973 are substantially perpendicular to a cross section perpendicular to the axial direction of the tube body 900.

  The wall surface 963 is inclined at a predetermined angle with respect to a cross section perpendicular to the axial direction of the tubular body 900 in consideration of deformation of the rubber ring 710 and the like. More specifically, the wall surface 963 is inclined with respect to the cross section so that the angle formed between the bottom surface of the recess 992 and the wall surface 963 becomes an obtuse angle.

  The wall surface 965 is inclined at a predetermined angle with respect to a cross section perpendicular to the axial direction of the tube body 900 in order to apply a force in the central direction of the tube body 900 to the lock ring 720. More specifically, the wall surface 965 is inclined with respect to the cross section so that the angle formed between the bottom surface of the recess 993 and the wall surface 965 becomes an obtuse angle.

  As described above, the inner peripheral surface 951 of the receiving port 910 has a plurality of recesses 991, 992, and 993 each having two wall surfaces (rising portions).

  Of the two wall surfaces in the recesses 992 and 993, the wall surfaces 963 and 965 on the tube axis direction opening opening side are inclined so that the angle formed with the bottom surface is an obtuse angle. Is an unreasonable force applied to the rubber ring abutting against the wall surface 963 by expanding the diameter to reduce the insertion force (force required for insertion) when the protrusion 922 at the distal end of the insertion port passes through the inner peripheral surface of the rubber ring 710. For this reason, the diameter of the lock ring that comes into contact with the wall surface 965 when a force is applied to cause the insertion port to be separated from the receiving port during an earthquake or the like is reduced. is there.

  On the other hand, the two wall surfaces 961 and 962 of the recess 991 near the opening of the receiving port are both flat surfaces perpendicular to the tube axis because the heel portion of the rubber ring 710 attached to the receiving port inner peripheral surface. An annular portion having a rectangular cross section is fitted, and both wall surfaces of the recess 991 are held so that the rubber ring 710 receiving a force in the depth direction in the tube axis direction is held in a predetermined position when the insertion opening 921 passes through the inner peripheral surface of the rubber ring 710. The reason is that the heel portion is securely gripped by 961 and 962.

  For these reasons, the inclination angle is different between the wall surface on the inner side in the tube axis direction and the opening side wall surface, and the wall surface on the inner side in the tube axis direction is perpendicular to the tube axis. In many cases.

  The recess 991 is generally referred to as a “heel portion accommodating portion”. The concave portion 992 is generally referred to as a “valve portion accommodating portion”.

<D. Details of connected state>
FIG. 4 is a diagram for explaining a connection state between the pipe body 900 and the pipe body 900 </ b> A in the pipe line 2000. Referring to FIG. 4, when the insertion opening 921 is inserted into the receiving opening 910 of the tube body 900, the rubber ring 710 is deformed and a force acts on the valve portion 7102 of the rubber ring 710, and the tip end portion of the valve portion 7102. Enters the recess 992. Note that the heel portion 7101 of the rubber ring 710 remains in the recess 991.

  In this state, when a liquid (typically tap water) flows into the pipe line 2000 constituted by the pipe body 900 and the pipe body 900A, the liquid flows into the recess 993. In addition, the liquid flows into the recess 992 except for the region filled with the valve portion 7102 of the rubber ring 710. The rubber ring 710 can prevent the liquid flowing in the tube bodies 900 and 900A from flowing out of the tube bodies 900 and 900A.

  In addition, as described above, the tubular body 900, 900A has the insertion opening 921 separated from the receiving opening 910 even if ground deformation occurs due to an earthquake or the like due to the lock ring 720, the lock ring holder 730, and the protrusion 922. To prevent it. For example, when the projection part 922 exerts a force on the lock ring 720 due to the relative movement between the tube body 900 and the tube body 900A due to ground fluctuation, the lock ring 720 contacts the wall surface 965.

<E. Flowability and gel time>
Each of the plurality of powder coatings was evaluated whether the film thickness of the powder coating film on the inner peripheral surface 951 of the receiving port 910 satisfies a predetermined standard under predetermined coating conditions. Specifically, it was confirmed whether the film thickness at a plurality of measurement points satisfied 300 μm or more and 500 μm or less. Prior to evaluation, the flowability and gel time of each powder coating were investigated.

(E1. Investigation method of flowability and gel time of powder coating)
(1) Flowability The flowability of each of the 29 types of powder coatings was investigated under the following conditions (i) to (iv). The investigation of flowability is in accordance with JIS K 5600-9-2 (inclined melt flow test).

(I) 0.5 g of the powder coating was poured into a tablet molding machine (diameter 13 ^mm), molded at a pressure of ^{1kg / cm 2 ~5kg / cm 2} .

  (Ii) A cold rolled steel sheet (SPCC-SB, thickness 2 mm) specified in JIS G3141 is placed on a jig having a 45 ° inclination and heated at 180 ° C. for 20 minutes using an oven. Thereafter, the tablet is placed on the heated steel plate, and after 5 minutes, the steel plate is taken out of the oven, and the length L (mm) of the cured product is measured.

(Iii) The value K is calculated using the following formula (1).
K = (L-13) / 13 (1)
(Iv) The average value of the three values K obtained when the operations (i) to (iii) are performed three times is defined as flowability.

(2) Gel time The gel time was investigated under the following conditions (i) to (iv) for each of the above 29 kinds of powder paints. The investigation of gel time is in accordance with JIS K 5600-9-1 (Method for measuring gel time of thermosetting powder paint at a predetermined temperature).

  (I) About 0.1 g of powder coating is placed on the center of the plate of a gelation tester having a surface temperature of 200 ° C. as much as possible. Fifteen seconds after the powder coating is completely melted, the stirring of the powder coating is started with a Teflon (registered trademark) rod with a sharpened tip.

  (Ii) Measure the time from when the powder coating is completely melted until when the powder coating is lifted with a Teflon (registered trademark) rod until no yarn is pulled.

  (Iii) The above operations (i) and (ii) are repeated five times, and an average value of three measurement times after removing the maximum value and the minimum value one by one is obtained.

  (Iv) The above operations (i) to (iii) are performed twice, and the average value of the average values of the three measurement times obtained in the above operation (iii) is taken as the gel time.

(E2. Coating conditions, number of tests, measurement points)
Using the coating apparatus 1 having two nozzles (see FIG. 2), powder coating was performed on the inner peripheral surface 951 of the receiving port 910 of the tube body 900 under the following coating conditions (i) to (iv). The coating was performed without charging the powder by applying no electric charge from the outside (coating without static electricity).

(I) Test tube: receiving port 910 (nominal diameter: 100 mm) of the tubular body 900
(Ii) Paint used: 29 types of epoxy powder paint (iii) Target film thickness: 300 μm to 500 μm
(Iv) Discharge amount: 140 g / min (v) Peripheral speed: 100 m / min (The peripheral speed represents a measured value at the concave portion 993. Specifically, the peripheral speed represents a measured value at the bottom surface 973)
In addition, each of the 29 kinds of powder coatings was tested 30 times. That is, test coating was performed 870 times (= 30 times × 29 types).

  FIG. 5 is a diagram for explaining a position at which the film thickness of the powder coating film is measured (hereinafter also referred to as “measurement point”). With reference to FIG. 5, twelve measurement points were set in order from the end surface 919 of the receiving port 910 to the straight portion 920 on the inner peripheral surface 951 of the receiving port 910. Furthermore, 36 other measurement points P13 to P48 (not shown) were set.

  The measurement points P13 to P24 are positions obtained by rotating the measurement points P1 to P12 by 90 degrees in the circumferential direction along the inner peripheral surface 951. The measurement points P25 to P36 are positions obtained by further rotating the measurement points P13 to P24 by 90 degrees in the circumferential direction along the inner peripheral surface 951. The measurement points P37 to P48 are positions obtained by further rotating the measurement points P25 to P36 by 90 degrees in the circumferential direction along the inner peripheral surface 951. That is, the measurement points P1, P13, P25, and P37 are set in this order and at equal intervals on the circumference of the inner peripheral surface 951.

  The measurement point P1 is set on the upper surface 981 between the end surface 919 and the wall surface 961. The measurement point P2 is set on the wall surface 961. The measurement point P3 is set on the upper surface 982 between the wall surface 962 and the wall surface 963. The measurement point P4 is set on the bottom surface 972.

  The measurement point P5 is set on the wall surface 964. The measurement point P6 is set on the upper surface 983 between the wall surface 964 and the wall surface 965. The measurement point P7 is set on the wall surface 965. The measurement point P8 is set on the bottom surface 973. The measurement point P9 is set on the wall surface 966. Measurement points P10, P11, and P12 are set on the inner peripheral surface 984 of the bulging portion 918 of the receiving port 910.

(E3. Survey results and evaluation)
FIG. 6 is a diagram showing the flowability and gel time investigation results and the evaluation of the film thickness of the powder coating film formed by powder coating for 29 types of powder coatings.

  Referring to FIG. 6, powder coating materials # 1, # 3, # 7, # 8, # 18, # 20, # 23, # 24, and # 25 were A evaluations. A rating indicates that the result was “particularly good”. Specifically, in the A evaluation, all of the measurement results (that is, the measurement results of 360 times) when the film thickness of the coating film is measured 30 times at the 12 measurement points P1 to P12 are 300 μm or more and It represents that it was 500 μm or less.

  Powder coating materials # 9, # 10, # 15, # 19, and # 26 were evaluated as B. B evaluation represents that the result was "good". Specifically, the B evaluation is performed at 95% or more and less than 100% of the measurement results when the film thickness of the coating film is measured 30 times each at the measurement points P1 to P12 (that is, 342 times or more and 360 times). This indicates that the measurement result (that is, the film thickness) of less than 300 times was 300 μm or more and 500 μm or less.

  Powder coatings # 2, # 4 to # 6, # 11 to # 14, # 16, # 17, # 21, # 22, # 27 to # 29 were C evaluations. The C evaluation represents that the result was “bad”. Specifically, in the C evaluation, a measurement result of less than 95% (that is, less than 342 times) of the measurement results when the film thickness of the coating film is measured 30 times at the measurement points P1 to P12 is 300 μm. It represents that it was above and 500 micrometers or less. In other words, the C evaluation indicates that the conditions of 19 times or more and the film thickness of 300 μm or more and 500 μm or less were not satisfied.

  The relationship between the evaluation results of the paints # 1 to # 29 and the flowability and gel time will be described later.

(E4. Consideration)
FIG. 7 is a graph in which the values of the flowability and gel time shown in FIG. 6 are plotted by classification according to evaluation, with the flowability as the horizontal axis and the gel time as the vertical axis.

  With reference to FIG. 7, the minimum value of the gel time of 14 powder coating materials obtained A evaluation and B evaluation was 19.1 seconds, and the maximum value of the gel time was 38.1 seconds. In addition, the minimum value of the flowability (measured value in the gradient melt flow test) of the 14 powder coatings that obtained A evaluation and B evaluation was 0.5, and the maximum value of the flowability was 3.6. there were.

  Moreover, the minimum value of the gel time of nine powder coating materials obtained A evaluation was 19.7 seconds, and the maximum value of the gel time was 35.4 seconds. In addition, the minimum value of the flowability (measured value in the gradient melt flow test) of the 14 powder paints that obtained A evaluation and B evaluation was 0.7, and the maximum value of the flowability was 2.7. there were.

  As described above, in order to form a powder coating film having a uniform film thickness on the inner peripheral surface 951 of the receiving port 910, the gel time is 19.1 seconds or more and 38.1 seconds or less, and the flowability is 0.00. It is preferable to use a powder coating of 5 or more and 3.6 or less. Further, in order to form a powder coating film having a uniform film thickness on the inner peripheral surface 951 of the receiving port 910, the gel time is 19.7 seconds or more and 35.4 seconds or less, and the flowability is 0.7. It is more preferable to use a powder paint having a viscosity of 2.7 or less.

  It should be noted that the region where the powder coating film is formed using the paint having the characteristics described above does not necessarily have to be the entire region of the inner peripheral surface 951 of the receiving port 910. A powder coating film may be formed on at least a part of the inner peripheral surface 915 of the receiving port 910 using a paint having the above characteristics. In particular, since the recesses 991, 992 in which the rubber ring 710 is accommodated and the recesses 993 in which the lock ring 720 and the lock ring holder 730 are accommodated require uniformity of the film thickness, It is preferable to use a paint having the following characteristics. It is preferable to use a paint having the above characteristics at least in the concave portion 993 that requires particularly high accuracy.

  In consideration of the JIS standard and the fact that the film thickness is not too thick, the thickness of the powder coating film on the inner peripheral surface 951 of the receiving port 910 is preferably 300 μm or more and 500 μm or less.

  Further, in consideration of the uniform film thickness, the difference between the maximum value and the minimum value of the thickness of the powder coating film on the inner peripheral surface 951 of the receiving port 910 is preferably 200 μm or less.

  On the other hand, the powder coating film formed on at least a part of the inner peripheral surface 952 of the straight part 920 of the tube body 900 has a gel time of 30.0 seconds or more and 50.0 seconds or less and a flowability of 2. It is preferably formed using a powder coating of 0 or more and 8.0 or less.

  When the gel time is 30.0 seconds or more and the flowability is 2.0 or more, it can be said that a paint that is harder than the receiving port 910 and is easy to flow is used, but by using such a paint, When coating is performed while rotating at the straight part 920 having no irregularities such as the receiving port 910, the powder paint melted by the heat of the tube body 900 is likely to spread on the inner face of the straight part. This is because smoothing becomes possible. If the gel time is too large, it takes time to cure and the productivity is poor. Therefore, the gel time is preferably 50.0 seconds or less. On the other hand, if the flowability is too high, the powder coating is likely to spread too much, so that it is difficult to make the film thickness uniform. Therefore, the flowability is preferably 8.0 or less.

  As described above, although the coating material for uniformizing the film thickness of the receptacle 910 having the concave portion and the coating material for uniformizing the film thickness of the straight portion 920 are the same coating material, in terms of gel time and fluidity The preferred ranges are completely different and the reasons for specifying those ranges are also completely different.

<F. Peripheral speed>
Next, the influence of the peripheral speed on the uniformity of the film thickness was examined. Specifically, the film thickness uniformity was evaluated by changing the peripheral speed of the recess 993 in which the lock ring 720 and the lock ring holder 730 are accommodated (specifically, the peripheral speed of the bottom surface 973).

(F1. Coating conditions, number of tests, measurement points)
Using the coating apparatus 1 (see FIG. 2), powder coating was performed on the inner peripheral surface 951 of the receiving port 910 of the tubular body 900 under the following coating conditions (i) to (v). The coating was performed without charging the powder by applying no electric charge from the outside (coating without static electricity).

(I) Test tube: receiving port 910 (nominal diameter: 100 mm) of the tubular body 900
(Ii) Paint used: Powder paint # 1 shown in FIG.
(Iii) Target film thickness: 300 μm to 500 μm
(Iv) Discharge amount: 140 g / min (v) Peripheral speed: Seven stages of peripheral speed between 25 m / min and 300 m / min (peripheral speed represents a measured value in the recess 993. Specifically, the peripheral speed is The measured value at the bottom surface 973 is represented.)
In addition, 30 tests were performed for each of the above seven stages of peripheral speeds. That is, the test coating was performed 210 times (= 30 times × 7 stages).

  The measurement points are the measurement points P1 to P12 shown in FIG. 5 and the 36 measurement points P13 to P48 (not shown) described above. That is, the film thickness measurement was performed 1440 times (= 12 × 4 × 30 times) for each of the seven peripheral speeds.

(F2. Evaluation and discussion)
FIG. 8 is a diagram showing an evaluation with respect to the film thickness of the powder coating film formed by powder coating for the seven peripheral speeds.

  Referring to FIG. 8, A evaluation was performed when the peripheral speed in recess 993 was 50 m / min and when 100 m / min. A rating indicates that the result was “particularly good”. Specifically, in the A evaluation, all of the measurement results (that is, the measurement results of 1440 times) when the film thickness of the coating film is measured 30 times each at the 48 measurement points P1 to P48 are 300 μm or more and It represents that it was 500 μm or less.

  The case where the peripheral speed was 150 m / min and the case of 200 m / min were B evaluations. B evaluation represents that the result was "good". Specifically, the B evaluation is performed by measuring 95% or more and less than 100% of the measurement results when the film thickness of the coating film is measured 30 times at measurement points P1 to P48 (that is, 1368 times or more and 1440 times). This indicates that the measurement result (that is, the film thickness) of less than 300 times was 300 μm or more and 500 μm or less.

  The evaluation was C when the peripheral speed was 25 m / min, 250 m / min, and 300 m / min. The C evaluation represents that the result was “bad”. Specifically, the C evaluation has a measurement result of less than 95% (that is, less than 1368 times) of the measurement results when the film thickness of the coating film is measured 30 times at each of the measurement points P1 to P48. It represents that it was above and 500 micrometers or less. In other words, the C evaluation represents that the conditions of 73 times or more and the film thickness of 300 μm or more and 500 μm or less were not satisfied. In particular, when the peripheral speed was 25 m / min, a spiral powder coating film was generated in relation to the moving speed of the lances 16 and 17.

  FIG. 9 is a diagram showing measurement results for one time with respect to six peripheral speeds excluding 25 m / min as an example of measurement results. Referring to FIG. 9, when the peripheral speed is 50 m / min and 100 m / min, the film thickness is 300 μm or more and 500 μm or less at each of twelve measurement points P1 to P12. For example, when the peripheral speed is 300 m / min, the film thickness is thinner than 300 μm at the measurement points P2, P5, P7, P9, P10, and P12, and the measurement points P1, P3, P4, P8, In P11, the film thickness is thicker than 500 μm.

  As described above, as described above, the tube manufacturing method for manufacturing the tube 900 on which the powder coating film is formed includes the nozzles 11 and 12 that discharge powder in the tube axis direction of the tube 900 and the tube. And a step of discharging powder onto the inner peripheral surface 951 of the receiving port 910 while relatively moving the nozzle 900 and rotating the nozzles 11 and 12 and the tube body 900 around the tube axis. . The peripheral speed in the recess 993 when the powder is discharged onto the inner peripheral surface 951 is set to 50 m / min or more and 200 m / min or less. By setting the peripheral speed in this way, a powder coating film having a uniform film thickness can be obtained on the inner peripheral surface 951. Specifically, a powder coating film having a thickness of 300 μm or more and 500 μm or less can be formed on the inner peripheral surface 951.

  The peripheral speed in the recess 993 when discharging powder to the inner peripheral surface 951 is preferably set to 50 m / min or more and 100 m / min or less. By setting the peripheral speed in this way, a powder coating film having a more uniform film thickness can be obtained on the inner peripheral surface 951.

  The region where the powder coating film is formed at the peripheral speed as described above does not necessarily have to be the entire region of the inner peripheral surface 951 of the receiving port 910. A powder coating film may be formed on at least a part of the inner peripheral surface 951 of the receiving port 910 using a paint having the characteristics described above. In particular, since the recesses 991, 992 in which the rubber ring 710 is accommodated and the recesses 993 in which the lock ring 720 and the lock ring holder 730 are accommodated require uniformity of the film thickness, It is preferable to perform powder coating at such a peripheral speed. It is preferable to perform powder coating at the peripheral speed as described above at least in the concave portion 993 where accuracy is particularly required.

(F3. Comparison with powder coating on inner peripheral surface 952 at straight part 920)
When the powder is discharged onto the inner peripheral surface 951 (especially the concave portion 993) of the receiving port 910, the peripheral speed in the concave portion 993 is such that the powder is discharged onto all or part of the inner peripheral surface 952 of the straight portion 920. It is preferable that it is set to be slower than the peripheral speed in the recess 993 when the operation is performed. The reason for this is as follows.

  When powder coating is performed on the inner peripheral surface 952 of the straight part 920, the powder coating is uniformly diffused on the inner peripheral surface 952 by a strong centrifugal force from the viewpoint of forming a uniform powder coating film. It is necessary to let On the other hand, when powder coating is performed on the inner peripheral surface 951 (particularly, the recesses 991, 992, and 993), when a strong centrifugal force is applied, the powder coating adhered to each of the wall surfaces 961 to 966 There is a possibility that the powder flows into the adjacent bottom surfaces 971 to 973 (see FIG. 3), and a powder coating film having a uniform film thickness cannot be formed. From such a viewpoint, the peripheral speed in the concave portion 993 when applying powder to the inner peripheral surface 951 is set slower than the peripheral speed in the concave portion 993 when applying powder to the inner peripheral surface 952. It is preferable that

  In addition, as a peripheral speed in the recessed part 993 when apply | coating powder with respect to the internal peripheral surface 952, it can be set to 270 m / min, for example.

  In the above description, the case where powder coating is performed without charging the powder by applying no electric charge from the outside has been described as an example. That is, the coating conditions capable of forming a uniform powder coating film without charging the powder have been described. However, the present invention is not limited to this, and the above numerical values and numerical ranges are also applicable when powder coating (electrostatic powder coating) is performed by charging the powder by applying an external charge. it can.

  The embodiment disclosed this time is an exemplification, and the present invention is not limited to the above contents. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Coating apparatus, 10 Powder discharge mechanism, 11 Nozzle, 16 Lance, 20 Drive apparatus, 21 Housing | casing, 22 Support stand, 30 Control apparatus, 40 Powder supply apparatus, 50 Hose, 600 Powder, 710 Rubber ring, 720 Lock ring, 730 Lock ring holder, 800 rotating device, 900,900A tube, 910 receiving port, 915, 951, 952, 984 inner peripheral surface, 918 bulging portion, 919 end surface, 920 straight portion, 921 insertion port, 922 Projection, 940 Bottom, 961, 962, 963, 964, 965, 966 Wall surface, 971, 972, 973 Bottom surface, 981, 982, 983 Top surface, 991, 992, 993 Recess, 1000 Coating system, 2000 Pipe line, 7101 Heel part, 7102 Valve part.

Claims (5)

A pipe body in which the powder coating film is formed by performing powder coating using a powder coating material in which powder is not charged on the inner peripheral surface of the pipe body in which the powder coating film is not formed. A tube manufacturing method for manufacturing,
The tubular body includes a receiving port having an earthquake-resistant structure and a straight portion continuous to the receiving port,
An accommodating portion for accommodating the lock ring is formed on the inner peripheral surface of the receptacle,
The tube manufacturing method includes:
While relatively moving the nozzle that discharges the powder paint in the tube axis direction of the tube and the tube, and relatively rotating the nozzle and the tube around the tube axis, at least A step of discharging a powder coating material to the housing portion;
Peripheral speed of the receiving portion at the time of discharging the powder coating to the accommodating portion is set below min rate 50m or more and minute speed 200 meters,
The gel time of the powder coating material discharged to the housing part is 19.1 seconds or more and 38.1 seconds or less,
The method of manufacturing a tubular body, wherein the flowability of the powder coating material discharged to the housing portion is 0.5 or more and 3.6 or less . The gel time of the powder coating material discharged to the storage unit is 19.7 seconds or more and 35.4 seconds or less,
The tubular body manufacturing method according to claim 1, wherein the flowability of the powder coating material discharged to the housing portion is 0.7 or more and 2.7 or less . The tubular body manufacturing method according to claim 1 or 2 , wherein a peripheral speed in the housing portion when discharging the powder coating material to the housing portion is set to 50 m / min or more and 100 m / min or less. . In the step of discharging the powder coating, also ejecting said powder coating to a part of the straight portion,
Peripheral speed of the receiving portion at the time of discharging the powder coating to the accommodating portion is slower than the peripheral speed of the receiving portion at the time of discharging the powder coating to a part of the straight portion Is set ,
The gel time of the powder coating material discharged to a part of the straight part is 30.0 seconds or more and 50.0 seconds or less,
The pipe body manufacturing method according to any one of claims 1 to 3, wherein the flowability of the powder coating material discharged to a part of the straight part is 2.0 or more and 8.0 or less . A powder coating method for a tubular body comprising a receiving port having an earthquake-resistant structure and a straight part continuous to the receiving port,
An accommodating portion for accommodating the lock ring is formed on the inner peripheral surface of the receptacle,
The powder coating method is:
While relatively moving the nozzle that discharges the powder paint in the tube axis direction of the tube and the tube, and relatively rotating the nozzle and the tube around the tube axis, A step of discharging a powder paint that is not charged with powder to at least a part of the inner peripheral surface of the straight part and the housing part,
Peripheral speed of the receiving portion at the time of discharging the powder coating to the accommodating portion is set below min rate 50m or more and minute speed 200 meters,
The gel time of the powder coating material discharged to the housing part is 19.1 seconds or more and 38.1 seconds or less,
The powder coating method, wherein the flowability of the powder coating material discharged to the housing portion is 0.5 or more and 3.6 .

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