JPH02139125A - Descaling method for steel pipe - Google Patents

Abstract

PURPOSE:To eliminate a scale safely in a highly efficient manner by applying an insulative stone onto an outer circumferential surface and/or an inner circumferential surface of a steel pipe, while making an electrolytic current flow in a gap between the steel pipe and an electrode body via a pastelike electrolyte, and moving either of the steel pipe or the electrode body in the longitudinal direction as rotating it. CONSTITUTION:A descaling device is supported by an optional supporting means (unillustrated herein), and it is constituted so as to perform contact operation to an outer circumferential surface of a steel pipe P. Then, when a scale on the outer circumferential surface of the steel pipe P is eliminated, an insulative stone 3 is applied onto the outer circumferential surface of the steel pipe P, and while feeding the outer circumferential surface of the steel pipe P with a pastelike electrolyte 7, the steel pipe P is set down to an anode and the electrode body 2 to a cathode, respectively, via this paste electrolyte 7, thus an electrolytic current is made to flow between them. Then, the insulative stone 3 is rotated, while the steel pipe P is moved in the longitudinal direction as being rotated, thus the scale on the outer circumferential surface of the steel pipe P is electrochemically and mechanically eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for removing scale from steel pipes.

1-Prior Art" Conventionally, scales on the outer circumferential surface and/or inner circumferential surface of a steel pipe are generally removed by pickling, grinding with a grinder, or the like.

``Problems to be Solved by the Invention'' By the way, in the method of removing scale on the outer and/or inner circumferential surfaces of steel pipes by pickling, there are problems such as a poor working environment due to fumes of the pickling solution and a long processing time. This causes problems such as lower efficiency, higher costs, and especially in the case of stainless steel pipes, because the scale is tight, it takes additional processing time.

In addition, when using a grinder to remove scale from the outer and/or inner circumferential surface of a steel pipe, the scale removal ability is affected by the contact pressure of the grinder against the outer and/or inner circumferential surface of the steel pipe. In the case of steel pipes, the scale is tight, so when mechanically grinding with a grinder, there are problems in that the scale gets stuck in the grinder's eyes and that it is difficult to remove the scale due to the hard scale.

The present invention has developed a scale removal method that solves the problems of the conventional steel pipe scale removal method.

"Means for Solving the Problems" The gist of the present invention is to bring an insulating grindstone provided in an electrode body into contact with the outer circumferential surface and/or inner circumferential surface of a steel pipe, and to remove the insulating grindstone from the electrode body. While supplying a paste electrolytic agent to the outer circumferential surface and/or inner circumferential surface of the steel pipe, an electrolytic current is passed between the steel pipe and the electrode body through this paste electrolytic agent, and the electrolytic current is passed between the steel pipe and the electrode body. A method for removing scale from a steel pipe, which comprises moving at least one of the pipes in the longitudinal direction while rotating the pipe.

"Operation" As described above, an insulating grindstone provided on an electrode body is brought into contact with the outer circumferential surface and/or inner circumferential surface of the steel pipe, and the insulating grindstone is penetrated from the electrode body to the outer circumferential surface of the steel pipe and/or While supplying a paste electrolyte to the inner peripheral surface, an electrolytic current is passed between the steel pipe and the electrode body through the paste electrolyte,
By rotating and moving at least one of the steel pipe and the electrode body in the longitudinal direction, scale on the outer peripheral surface and/or the inner peripheral surface of the steel pipe can be electrochemically and mechanically removed.

"Example" Next, an example of the method for removing scale from a steel pipe according to the present invention will be described below based on the drawings.

FIG. 1 schematically shows an apparatus for removing scale from the outer circumferential surface of a steel pipe P, which includes a motor 1, an electrode body 2 connected to a rotating shaft 1a of the motor 1, and an electrode body 2 connected to a rotating shaft 1a of the motor 1.
It consists of an insulating grindstone 3 that is integrally provided on the lower surface of the grindstone.

The rotating shaft 1a of the motor 1 and the electrode body 2 are covered by a cover 4.

An arbitrary number of through holes 5 are bored across the electrode body 2 and the insulating grindstone 3, and a paste electrolyte supply tank 6 is provided.
The paste that is supplied and stored in the cover 4?
1 ipH agent 7 is supplied to the outer circumferential surface of the steel pipe P from the through hole 5.

A conductive brush 8 is provided on the rotating shaft 1a of the motor 1, and the negative side of the DC power is applied to the electrode body 2 through the conductive brush 8, and the negative side of the DC power is applied to the steel pipe P. The positive side of the DC Li source is applied via the conductive brush 9.

It is assumed that the motor 1 and the rotating shaft 1a are electrically insulated.

Further, the scale removing device shown in FIG. 1 is supported by an arbitrary supporting means (not shown), and is capable of contacting the outer circumferential surface of the steel pipe P.

Therefore, in order to remove scale on the outer peripheral surface of the steel pipe P,
As shown in FIG. 1, an insulating grindstone 3 is brought into contact with the outer circumferential surface of the steel pipe P, and while a paste electrolytic agent 7 is supplied to the outer circumferential surface of the steel pipe P, the steel pipe P is anodized through the paste electrolytic agent 7. Then, an electrolytic current is applied using the electrode body 2 as a cathode, the insulating grindstone 3 is rotated, and the steel pipe P is rotated and moved in the longitudinal direction to electrochemically and mechanically remove the scale on the outer peripheral surface of the steel pipe P. It removes it.

FIG. 2 schematically shows an apparatus for simultaneously removing scale on the outer and inner circumferential surfaces of a steel pipe P, which includes an external cylindrical electrode body 11 that surrounds the outer periphery of a required length of the steel pipe P, It is integrally provided on the inner peripheral surface of this external cylindrical electrode body 11, and
An external cylindrical insulating grindstone 12 that is brought into contact with the outer peripheral surface of the external cylindrical insulating grindstone 12 constitutes an outer peripheral surface descaling device.

An arbitrary number of through holes 13 are bored across the external cylindrical electrode body 11 and the external cylindrical insulating grindstone 12, and from these through holes 13, a paste electrolyte supply tank 14 is passed from the paste electrolyte supply tank 14 to the outer peripheral surface of the steel pipe P. A paste electrolyte 15 is supplied.

Also, the steel pipe P corresponding to the installation position of the external cylindrical electrode body 11
Inside is a mandrel 1 supported by a mandrel bar 16.
7 is fitted into the mandrel 17, and an internal cylindrical electrode body 18 is integrally provided on the outer peripheral surface of this mandrel 17.

An internal cylindrical insulating grindstone 19 that contacts the inner peripheral surface of the steel pipe P is integrally provided on the outer peripheral surface of the internal cylindrical electrode body 18. An arbitrary number of through holes 20 are bored across the electrode body 18, and the paste electrolyte 15 from the paste electrolyte supply tank 14 is passed through the mandrel bar 16, the mandrel 17, and the through holes 20 to the steel pipe P. The inner circumferential surface scale removing device is configured such that the descaling device is supplied to the inner circumferential surface of the scale.

The external cylindrical electrode body 11 and the internal cylindrical electrode body 18 are configured to receive the negative side of the DC power, and the steel pipe P is configured to receive the positive side of the DC power.

Further, it is assumed that the external cylindrical P4 scraper 11 and the mandrel bar 16 are each supported by arbitrary support means (not shown).

When removing scale from the outer and inner circumferential surfaces of the steel pipe P using the scale removing device shown in FIG. 2, the steel pipe P is rotated and moved in the manual direction. The scale on the surrounding surface is removed electrochemically and mechanically.

As the paste electrolyte, for example, 1O%NatS
Oa, 1O%LSOn-10%1hPOa, etc. may be used.

Further, as the insulating grindstone, for example, an abrasive nonwoven fabric containing abrasive grains may be used.

Furthermore, the electrolytic conditions include a voltage of 5 to 50 V, a current density of 2
It may be in the range of 0 to 300 mA/-.

Table 1 below shows the results of the method of the present invention, the conventional pickling method, and the mechanical polishing method.
The data for descaling of previous duplex stainless steel pipes are shown below.

Table 1 As shown in Table 1 above, it can be seen that the method of the present invention is extremely superior in removing scale from steel pipes than the conventional method.

"Effects of the Invention" According to the method for removing scale from steel pipes according to the present invention described above, scale can be removed more efficiently than the conventional pickling method or mechanical grinding method, and moreover, it is possible to remove scale more efficiently than the conventional pickling method or mechanical grinding method. Scale removal work can be carried out safely without the problem of deterioration of the working environment due to pickling liquid fume.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram showing an embodiment of the method of the present invention for removing scale from the outer circumferential surface of a steel pipe, and Fig. 2 shows an embodiment of the method of the present invention for simultaneously removing scale from the outer circumferential surface and inner circumferential surface of a steel pipe. FIG. P...steel pipe, l...motor, la...rotating shaft,
2... fi14 body, 3... Insulating grindstone, 4... Cover 5... Through hole, 6... Paste electrolyte supply tank, 7... Paste electrolyte, 11...・External cylindrical 1! Scraping body, 12... External cylindrical insulating grindstone, 13...
・Through hole, 14... Paste electrolyte supply tank, 1
5... Paste down type N agent, 16... Mandrel bar 117... Mandrel, 18... Internal cylindrical electrode body, 19... Internal cylindrical insulating grindstone, 20... Through hole

Claims (1)

[Claims] (1) An insulating grindstone provided on an electrode body is brought into contact with the outer circumferential surface and/or inner circumferential surface of the steel pipe, and the insulating grindstone is passed from the electrode body to the outer circumferential surface and/or inner circumferential surface of the steel pipe. While supplying a paste electrolyte, an electrolytic current is passed between the steel pipe and the electrode body through the paste electrolyte, and at least one of the steel pipe and the electrode body is moved in the longitudinal direction while rotating. A distinctive method for removing scale from steel pipes.