JP2017177268A - Processing method for shot-peening of structural steelwork and method for preventive maintenance of structural steelwork - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method for shot-peening of a structural steelwork by which a construction period can be significantly shortened, and further, a cost can be significantly reduced, and a method for preventive maintenance of a structural steelwork.SOLUTION: In a preventive maintenance construction method with use of a circulation type blast device 1 which can inject grit and shot, blast treatment for a steel bridge K is performed by use of grid, shot-peening is performed by use of shot in order to increase a fatigue strength of a blast-treated portion, and thereafter, final finish coating for a shot-peening treated portion is performed, and further, broken shot is so made as to be capable of being re-used as grid.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a shot peening treatment method for a steel structure in a steel structure such as a steel bridge, a tunnel, and a factory plant, and a preventive maintenance method in the steel structure.

  Conventionally, steel structures such as steel bridges, regardless of whether they are newly installed or existing, are used to prevent the occurrence of rust, etc., or in particular for existing steel structures, to renew the coating that has been corroded due to aging. In addition, preventive maintenance is provided. As described above, since preventive maintenance requires removing rust and the like and removing old paint films, in recent years, rust and paint films are removed by blasting (one kind of keren), and then a new coating is applied. Things have been done.

  Usually, the abradant used for such blasting treatment uses an almandite garnet made of natural minerals, iron-made slag made of minerals, or the like. However, when such an almandite garnet or iron slag is used for the abrasive, the abrasive is crushed during the blasting process, and enormous waste is generated. In particular, when PCB (polychlorinated biphenyl) or lead is used for the old coating film, it becomes specially controlled industrial waste including not only the old coating film removed but also the abrasive used for blasting, This process is very expensive.

  For example, Japanese Patent Application Laid-Open No. H10-228561 discloses that after the scouring material and dust are collected in a collection tank, the scouring material and dust are separated and classified in the collection tank. A structure surface polishing system that collects dust and the like while reusing the separated abrasive is disclosed.

  Further, apart from the above problem, the steel structure may be uneven in strength at the welding location. Here, for example, in the case of steel road bridges, fatigue cracks may occur from welds where the strength is biased by the entire bridge being shaken or vibrated when a vehicle passes or strong winds blow. The problem that occurs occurs. For this reason, the actual situation is that a huge expense is required for the repair.

  For example, Patent Document 2 discloses a method for preventing the occurrence of cracks by applying a primer to a structural discontinuity caused by a welded joint of a steel structure.

  Patent Document 3 discloses a method for improving the fatigue performance of a welded joint in which ultrasonic peening is performed on the end face of the welded joint and the weld toe at the end of the welded joint.

JP-A-11-207624 JP 2006-102738 A JP 2006-142367 A

  However, the conventional configuration as described above still has a long construction period and of course the cost is enormous.

  Accordingly, an object of the present invention is to provide a shot peening treatment method for a steel structure and a preventive maintenance method for the steel structure that can significantly reduce the work period and thereby reduce the cost.

  The present invention is a shot peening treatment method for a steel structure in which a shot is projected onto a steel structure, wherein the shot has a hardness to be crushed by an impact when colliding with the surface of the steel structure. It is a shot peening processing method for steel structures.

  In such a configuration, the stress applied to the surface of the steel structure is increased by cracking (breaking) the shot that has collided with the steel structure (which may be a new steel structure or an existing steel structure). Thus, fatigue strength and stress corrosion cracking resistance can be effectively improved.

  A preventive maintenance method for a steel structure including the shot peening treatment method for a steel structure, wherein the crushed used shot obtained by the shot peening treatment method for a steel structure is projected as a grit onto the steel structure. A preventive maintenance method for steel structures characterized by including a blasting method for steel structures is proposed.

  In such a configuration, the crushed shot obtained by executing the shot peening process can be reused as a grit, and the construction cost can be greatly reduced.

  Furthermore, in order to adjust the base material for the steel structure, the process A for performing a blasting process using grit as an abrasive, and the steel structure for improving the fatigue strength with respect to the portion subjected to the base material adjustment Including a step B for executing the shot peening treatment method, and after performing the step A and the step B, including a step C for applying a final finish coating to the portion to be subjected to the substrate adjustment, In the step A, a configuration including using the crushed used shot obtained in the step B as a grit is proposed.

  Here, in general, when so-called type 1 keren is constructed, a scaffold is built on the steel structure, or a dustproof sheet is stretched to prevent dust from leaking outside. Although temporary curing equipment is provided, in the above-described present invention, a common temporary curing equipment is used for the steel structure with the process A for performing the blasting process and the process B for performing the shot peening process. Can do. Therefore, it is not necessary to separately perform the process A and the process B, the work process is not wasted, the work period can be effectively shortened, and the cost can be drastically reduced. In addition, by reusing the crushed used shot as grit, a small amount of new grit is required for the blasting process in step A, thereby further reducing the cost.

In addition, it is desirable that the Vickers hardness H of the shot to be projected is 650 kgf / mm ² ≦ H ≦ 950 kgf / mm ² . The Vickers hardness is preferably measured according to JIS Z 2244.

Here, as a shot of the hardness to be crushed by impact when colliding with the surface of the steel structure, a shot of the above conditions is suitable, but if the hardness H is less than 650 kgf / mm ² , the shot peening effect is obtained. It cannot be obtained sufficiently, and the crushed shot is pulverized, making it difficult to reuse it as grit. On the other hand, when the hardness H exceeds 950 kgf / mm ² , it becomes difficult to crush at the time of projection.

  The shot peening treatment method of the present invention can effectively improve fatigue strength and stress corrosion cracking resistance. Moreover, the cost can be significantly reduced by reusing the shot crushed by the shot peening processing method as a grit by the blast processing method.

  Moreover, since the preventive maintenance method of the steel structure of the present invention can reuse the crushed shot as grit, the cost can be drastically reduced.

It is a flowchart which shows the procedure of the preventive maintenance of a steel bridge. It is an outline explanatory view explaining a circulation type blast device. It is explanatory drawing which cuts and shows a separation chamber.

  Hereinafter, embodiments embodying the present invention will be described in detail. In addition, this invention is not limited to the Example shown below, A design change is possible suitably.

  As shown in FIG. 1, as a preventive maintenance (repainting) procedure for an existing steel bridge (steel structure), first, a temporary curing facility is installed on the steel bridge that is the target of preventive maintenance. Specifically, a scaffold is temporarily installed on the steel bridge, and a dustproof sheet is stretched so that dust does not leak outside. Further, pre-preparation (S101) is performed for curing an unpainted portion and installing an apparatus for performing a blasting process and a shot peening process.

  Thereafter, the type and thickness of the old paint applied to the steel bridge, the situation of the steel bridge, etc. are investigated (S102). Then, based on the investigation result, the type of grit and shot to be used, the injection speed, and the like are determined.

At this time, the shot to be selected (spherical) has a Vickers hardness H of
650 kgf / mm ² ≦ H ≦ 950 kgf / mm ²
Use one. A material is not specifically limited, Well-known things, such as a metal, an ore, and a ceramic, are applicable suitably.

  A blast process is first performed using the grit determined in S102 (S103). Specifically, peeling of the coating film or the like to be peeled from the steel bridge and adjustment of the base of the portion to be ground adjusted are performed. By such blasting, step A in the present invention is configured. In addition, although the coating film, rust, etc. peeled off by the blast treatment and used grit are generated as dust, since the dustproof sheet is stretched in S101, the dust does not leak to the outside, and the dust Will accumulate at the work site.

  Subsequently, the shot determined in S102 is loaded in place of the grit to the blasting apparatus that has injected the grit so that the shot can be injected (shot replacement step). Here, temporary scaffolds and dustproof sheets are used continuously without being removed.

Then, a shot peening process is performed on the blasted portion (that is, the substrate adjustment portion) formed by the blasting process using the blasting apparatus replaced with the shot (S104). By such treatment, a process B is formed in which the fatigue strength and stress corrosion cracking resistance of the base material are improved. The shot used in the shot peening process has a Vickers hardness H of
650 kgf / mm ² ≦ H ≦ 950 kgf / mm ²
Since the working pressure (air pressure) at the time of projection is 0.6 MPa to 0.7 MPa, the shot is crushed by the impact when colliding with the projected surface, and is directly on the work site. , Depositing while being mixed with the used grit in S103. By the way, the shot peening process may be performed on all the ground surfaces on which the blasting process has been performed, or may be performed appropriately on the periphery of the welded part, a part where the strength is uneasy, or the like.

  Thereafter, the ground surface on which the blasting process and the shot peening process have been performed is confirmed (S105). Such confirmation includes not only visual confirmation but also comparison using, for example, an ISO8501 blast photo book, or roughness confirmation using a surface roughness measuring instrument. As a result, it is confirmed whether an unexfoliated coating film remains, or whether the roughness of the ground surface is within the specification, and an appropriate process is performed on an insufficient portion. For example, the base adjustment is performed using a hand tool or the like in a portion where the blasting process cannot be performed.

  In this way, the final finish coating for forming the final coating film is performed on the portion where the ground surface has been confirmed (S106). By such a coating process, the process C according to the present invention is configured. Such coating is generally applied in layers such as undercoating as an anticorrosion coating, intermediate coating for protecting the anticorrosion coating, and topcoating as the final finish coating. .

  When the painting is completed, the confirmation (S107) is performed. Such confirmation includes not only confirmation of the film thickness after the coating has dried, but also confirmation of the wet film thickness using a wetness gauge during the painting operation, for example. Further, such confirmation is performed not only after the top coat which is the final finish paint, but also during the undercoat and intermediate coats.

  When the painting operation is completed by the confirmation, the site is cleaned up (S108). Specifically, the preventive maintenance is completed by collecting the scaffold, dustproof sheet, and the like, and withdrawing the blast-shot peening injection device.

  In addition to the above procedure, a dust collecting step is executed (S110). Specifically, the used grit generated in the blasting process (S103), the used shot generated in the shot peening process (S104), and dust containing exfoliation and rust generated in each process are separated. While collecting.

  The collected used grit and the crushed material of the shot can be reused as blasting grit. In addition, shots that are not crushed by the shot peening process (maintaining a spherical shape) can be reused as shots for the shot peening process. In particular, the crushed material of the shot can be effectively reused as a grit for blasting. Therefore, there is almost no need to input new grit at one work site, and it is very economical, and the amount of waste can be greatly reduced by separating it from the peeled film and other foreign matters. .

  Hereinafter, it is possible to inject the grit and the shot with a common device, and also to collect the used grit, the used shot, the peeled coating film, and the like, and to circulate the blasting device 1 This will be described as an example.

  As shown in FIG. 2, the circulating blast apparatus 1 includes an apparatus main body 2 that is installed adjacent to a work site α of a steel bridge K that is a work target. Furthermore, the apparatus main body 2 includes a pressure feeding hose 4, and an injector 3 is connected to the tip of the pressure feeding hose 4. Grit g and shot s are ejected from the injector 3. Moreover, the said apparatus main-body part 2 comprises the suction hose 5, and the front-end | tip of this suction hose 5 is arrange | positioned at the work site (alpha). Thus, the used grit g ′ generated at the work site α, the crushed material sg of the shot (hereinafter simply referred to as the crushed material sg), and the shot s ′ that has not been crushed (hereinafter used) through the suction hose 5. Dust X consisting of foreign matter D including a shot s ′) and a peeled coating film or rust can be sucked. In order to prevent the dust X from leaking outside, a dustproof sheet (not shown) is stretched on the work site α, and a blower, a dust collector, and the like are also installed as appropriate.

  As shown in FIG. 2, a grit hopper tank 10 and a shot hopper tank 20 are disposed adjacent to each other in the apparatus main body 2 of the circulating blast apparatus 1. More specifically, the grit hopper tank 10 has a function of storing grit g, used grit g ', and crushed material sg (hereinafter, a mixture thereof is referred to as grit G). The shot hopper tank 20 has a function of storing shots s and used shots s' (hereinafter, a mixture thereof is referred to as shot S). The grit hopper tank 10 is connected to a grit pressure tank 11 for pressure-feeding the grit G stored in the grit hopper tank 10 to the work site α. Similarly, the shot hopper tank 20 is connected to a shot pressurizing tank 21 for pressure-feeding the shot S stored in the shot hopper tank 20 to the work site α.

  Further, a dry compressed air supply means 30 is connected to the grit pressure tank 11 and the shot pressure tank 21 via a dry compressed air pipe 31. The dry compressed air supply means 30 includes an air compressor and an air dryer for supplying dry compressed air. Further, the dry compressed air pipe 31 is provided with a switching valve 32 so that the dry compressed air can be selectively supplied to the grit pressurizing tank 11 or the shot pressurizing tank 21, and shot instead of the grit. Can be loaded in such a way that it can be jetted.

  The pressure feeding hose 4 is connected to the grit pressure tank 11 and the shot pressure tank 21. And by this structure, the grit G or the shot S is injected from the injector 3 through the pumping hose 4 by the air pressure by the dry compressed air supplied from the dry compressed air supply means 30, and the steel bridge K to be operated In addition, blast processing or shot peening processing can be executed.

  Dust X including foreign matter D such as used grit g ′, crushed material sg, used shot s ′, and peeled coating film deposited on the work site α is sucked together from one end of the suction hose 5. . The dust X sucked by the suction hose 5 reaches the separation chamber 40 disposed above the grit hopper tank 10 and the shot hopper tank 20.

  In addition, a dust hose 51 is attached to the separation chamber 40, and a dust recovery unit 50 as a release coating film recovery unit is connected to the dust hose 51. Further, an air suction device 60 as a dust suction means is connected to the dust collection unit 50. Therefore, the dust X can be sucked by the air suction force of the air suction device 60.

  Here, as shown in FIG. 3, the separation chamber 40 has a channel 41 that is horizontally long and airtight, and an inlet 42 on the upstream side (left side in FIG. 3) of the channel 41. Is provided. In addition, a reflection plate 43 that is inclined with respect to the flow path direction of the flow path 41 is attached to the downstream side. Further, a discharge portion 44 is provided below the reflecting plate 43. In addition, a used grit collection unit 45 is disposed on the upstream side with respect to the discharge unit 44, and a used shot collection unit 46 is disposed on the upstream side of the used grit collection unit 45. The discharge part 44 is connected to the dust hose 51 and is connected to the air suction device 60 via the dust recovery part 50, and the air flow in the separation chamber 40 takes the suction port 42 upstream. The discharge part 44 is located downstream.

  Here, the dust X introduced into the flow path 41 from the suction hose 5 via the suction port 42 is maintained in the flow path 41 while maintaining a predetermined speed by the air suction force of the air suction device 60. move on. Then, the foreign matter D such as a peeled coating film or rust having a low specific gravity is directly discharged to the discharge portion 44 along the air flow in the flow path 41. The discharged foreign matter D is introduced into the dust collecting unit 50 through the dust hose 51 and accumulated in the dust collecting unit 50, and is discharged into the waste bag 52 at a desired timing and processed as industrial waste. .

  Further, the used grit g ', the crushed material sg, and the used shot s' have a high specific gravity, and in a state where a predetermined speed is given, the flow path 41 does not follow the air flow but goes straight in accordance with inertia. It collides with the reflector 43. At this time, the used shot s' rebounds most efficiently because it has a spherical shape as described above. On the other hand, since the used grit g 'and the crushed material sg have an angular shape, the rebound is smaller than that of the used shot s'. Based on the difference in the rebounding distance, the used grit collection part 45 is provided near the reflector 43 near the lower part of the flow path 41 and closer to the suction port 42 than the discharge part 44. The used shot collection unit 46 is provided farther from the reflector 43 (closer to the suction port 42) than the used grit collection unit 45. With this configuration, the dust X is used to remove the used grit g ′ and the crushed material sg, the used shot s ′, and the peeled coating by only the air suction force of the air suction device 60 without using a mechanical operation such as a vibration sieve. The foreign matter D including the film can be separated from each other. The used grit g 'and the crushed material sg thus separated are returned to the grit hopper tank 10 below the sorting chamber 40 and reused. Similarly, the used shot s ′ is also returned to the shot hopper tank 20 below the sorting chamber 40 and reused. In this way, the grid G and the shot S can be circulated and used continuously.

  Of the crushed material sg, a material crushed so small that it cannot be used as a grit is discharged to the discharge unit 44 in the same manner as the foreign matter D. Therefore, the used grit collection unit 45 and the There is no return to the grit hopper tank 10 or the shot hopper tank 20 via the used shot collection unit 46.

  In addition to the configuration described above, the present invention can be modified as appropriate. For example, the switching valve 32 may be provided in the work site α so that the worker H at the work site α can perform switching operation, or may be remotely operable. Further, the injector 3 and the suction hose 5 may be separate or may be integrated (vacuum blast type). Further, the dry compressed air supply means 30 may be provided separately for the grit pressurization tank 11 and the shot pressurization tank 21, respectively. Further, the pressure feeding hose 4 may be provided separately for grit and shot. Similarly, the injector 3 may be divided into a grit and a shot. Moreover, the separation chamber 40 does not need to be disposed immediately above the grit hopper tank 10 and the shot hopper tank 20, and the position is not particularly limited. In addition, the method for realizing the airtight space in the flow path 41 is not particularly limited. For example, the hopper tanks 10 and 20 may be in an airtight state while communicating with the grit hopper tank 10 and the shot hopper tank 20, or a dedicated tank for temporarily storing the grit G or the shot S may be disposed at a desired timing. Thus, the grid G and the shot S may be supplied to the hopper tanks 10 and 20. In addition, it is desirable to be able to supply a new product when the grit amount or shot amount in the circulating blast device 1 is less than a specified value. Further, the apparatus main body 2 may be placed on a vehicle and movable, for example. Moreover, you may apply the preventive maintenance method of this invention not only at the time of the repainting of a steel structure but to the steel structure newly constructed. For example, for a newly constructed steel structure, the process A is performed to remove rust and the like on the surface that has not yet been painted, and then the process such as the scaffold used during the execution of the process A is not removed. B is executed, and Step C is executed. Even in such a configuration, the anticorrosion performance can be improved, and the construction period can be greatly shortened, whereby the cost can be greatly reduced.

  Note that the preventive maintenance in the present invention includes a maintenance work performed to prevent corrosion of a steel structure when newly installed or an existing steel structure. Blast processing, grit, and shot are defined in JIS Z 03120: 2004 “General rules of blast processing method for substrate adjustment”, respectively. Specifically, the blasting process is “to remove the oxides or deposits on the steel surface by causing a grinding material having a large kinetic energy to collide with the surface of the steel material to be treated, and finely cutting and striking the steel surface. To clean and roughen the surface. " The grit is “an angular shape having a ridge angle (ridge angle) in a state before use, and a round portion having less than half of the particle”. A shot is “a spherical particle having a major axis (ridge angle), a crushing surface, or other sharp surface defects and having a major axis within twice the minor axis before use”. In the blasting process, the “grinding material” is synonymous with the “abrasive material” described above. Moreover, in JIS B 2711: 2013 “Spring shot peening”, shot peening is “improvement of fatigue strength and stress corrosion cracking resistance by hitting the surface layer of the spring with spherical hard particles at high speed. “A cold working method that gives compressive residual stress to the surface and hardens the surface.” In the present invention, grit corresponds to the abrasive used for performing the blasting process, and shot corresponds to the hard particles used for performing the shot peening process. In addition, what is called a steel cut wire may be employ | adopted as a grit. Moreover, what is called a round cut wire may be employ | adopted as a shot.

G Grit S Shot K Steel bridge (steel structure)

Claims (4)

A shot peening treatment method for a steel structure in which a shot is projected onto the steel structure,
The shot peening treatment method for a steel structure, characterized in that the shot has a hardness to be crushed by an impact when colliding with a surface of the steel structure. A preventive maintenance method for a steel structure including the shot peening treatment method for a steel structure according to claim 1,
A preventive maintenance method for a steel structure, comprising: a blasting method for a steel structure that projects the crushed used shot obtained by the shot peening method for a steel structure onto a steel structure as grit. A process A for performing a blasting process using a grit as an abrasive material in order to adjust the substrate for the steel structure;
A step B of executing the shot peening treatment method for a steel structure in order to improve fatigue strength with respect to a portion to be subjected to the substrate adjustment;
Including
After performing the step A and the step B, including a step C for applying a final finish coating to the portion to be subjected to the substrate adjustment,
In the said process A, the preventive maintenance method of the steel structure of Claim 2 including using the crushed used shot obtained by the said process B as a grit. Vickers hardness H of the shot to be projected
650 kgf / mm ² ≦ H ≦ 950 kgf / mm ²
The shot peening method for a steel structure according to claim 1.

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