JPH0394407A - Demagnetization apparatus of large-diameter pipe and the like - Google Patents

Abstract

PURPOSE:To simply execute a demagnetization operation of largesized products such as large-diameter steel pipes and the like by a method wherein a plurality of demagnetizing coils whose cross-sectional shape can pass a product to be demagnetized are installed at prescribed intervals, a direct-current power supply is connected in series with the coils and a magnetism is attenuated while polarities of a direct current of the direct-current power supply are changed over alternately. CONSTITUTION:A product 1 to be demagnetized is stopped in a position inside coils 2 by using a conveyor 4; then, a direct-current attenuation electric current is made to flow to the coils 2 from a direct-current power supply 3; polarities of the direct- current electric current are changed over alternately. At this time, the product 1 is magnetized simultaneously as a whole. However, since the electric current is of an attenuation type, a magnetism of the product itself is attenuated gradually. When the electric current is cut out finally, the magnetism is reduced to a definite residual magnetism and the product is demagnetized. Since the direct current is used in this case, the magnetism is permeated up to the inside of the product 1 and the product is demagnetized perfectly. Thereby, large-sized products such as large-diameter pipes and the like can be demagnetized simply, quickly and perfectly.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a demagnetizing device for large diameter and long products such as large diameter pipes. (B) Prior art In the past, demagnetizing devices for general products can be roughly divided into AC type and DC type, and each of these types includes through type, planar type, damping type, interpolar type, etc. There is. However, both devices are applied to relatively small products and cannot be used as is for large products such as large diameter steel pipes.

(c) Problems to be Solved by the Invention The problem to be solved by the present invention is to obtain a demagnetizing device that can easily demagnetize large products such as large-diameter steel pipes. (2) Means for Solving the Problems The device for demagnetizing large-diameter pipes, etc. of the present invention includes a plurality of demagnetizing coils having a cross-sectional shape that allows the passage of the product to be demagnetized at predetermined intervals. The above problem is solved by means of connecting the coil in series with a DC power source and attenuating the DC power while alternating the polarity of the DC power. (E) Embodiment An embodiment of the demagnetizing device for large-diameter pipes, etc. of the present invention will be described with reference to FIG. The demagnetizing device of the present invention includes a plurality of demagnetizing coils 2 having a cross-sectional shape that allows the product 1 to pass through the demagnetizing coils 2 at predetermined intervals (
In this embodiment, the operation of the device of the present invention will be explained, in which four coils are connected in series to a DC power source 3, and the polarity of the DC power of the DC power source 3 is alternately changed and attenuated. First, as shown in FIG. 1, the product 1 to be demagnetized is stopped at a position inside the coil 2 by the conveyor 4. Then,
A DC decay current (Figure 2) is passed from DC power supply 3 to coil 2 for about 60 seconds. The polarity of direct current alternates. At this time, the entire product 1 is magnetized at the same time, but because the current is of an attenuated type, the magnetism of the product itself gradually attenuates (Figure 2), and when the current is finally cut off, a residual amount of about 0 to 15 Gauss remains. It becomes magnetic and is demagnetized. Since direct current is used, the magnetism passes through to the inside of product 1.
The product is completely demagnetized. In the case of alternating current, only the surface is demagnetized due to the skin effect. The device of the present invention uses a stationary demagnetizer, so it is easy to work with, and since it uses synchronized coils, it can completely and uniformly demagnetize large products instantly. ．． For example, a pipe that has an average strength of about 30 Gauss (G) before being demagnetized can be demagnetized to 15 G or less using the apparatus of the present invention. The time required for demagnetization is 60 seconds for demagnetization + 60 seconds for handling, totaling 120 seconds. Figure 3 (A) shows the residual magnetism of the pipe before demagnetization, and Figure 3 (B) shows the residual magnetism of the pipe after demagnetization by the device of the present invention. Demonstrates magnetic effect. (f) Effects According to the present invention, large products such as large diameter pipes can be easily demagnetized.
Can be implemented quickly and completely. In addition to large diameter pipes, it can also be applied to H-beam steel, etc.

[Brief explanation of drawings]

Figure 1 is a schematic explanatory diagram of the demagnetizing device of the present invention. Figure 2 is a graph showing the demagnetization process using the device of the present invention. Figure 3 is a graph showing the demagnetizing effect of the device of the present invention. 1: Demagnetized product 2: Coil 3: DC power supply 4: Conveyor

Claims (1)

[Claims] A plurality of demagnetizing coils having a cross-sectional shape that allows the product to be demagnetized to pass through are provided at predetermined intervals, and the coils are connected in series to a DC power source, and the polarity of the DC power of the DC power source is alternately changed. A demagnetizing device for large diameter pipes, etc., characterized by attenuation.