JPH06262254A - Mill scale removing device for producing large diameter welded steel tube - Google Patents

Abstract

PURPOSE:To efficiently remove a mill scale over all the length and over all the internal surface of a large diameter welded steel tube by providing a stripping machine and an air blow nozzle on a moving machine through a boom. CONSTITUTION:A rotary wire brush 2 and an air blow nozzle 3 are provided on a tip of a boom 4 in a steel tube, the boom 4 is provided on a mill scale removing truck 5, and all the device can be moved. Before welding the steel tube 1, the mill scale stuck inside the steel tube 1 is stripped from the one end with the rotary wire brush 2, and successively the air is made to blow from the air blow nozzle 3 provided on the rear side. The mill scale stripped with the wire brush 2 and the mill scale stripped and piled from the internal surface of the steel tube at the time of forming the steel tube is discharged from the other end, and sucked with a dust collector 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the entire length of a large diameter welded steel pipe,
The present invention relates to a mill scale removing device for removing mill scale over the entire inner surface very efficiently and surely, and for producing a material of a welded portion of a large-diameter welded steel pipe in an excellent condition.

[0002]

2. Description of the Related Art Applications of large-diameter welded steel pipes include line pipes for transporting oil and natural gas. Recent resource development areas have moved to polar regions, deep seas, and remote areas, and the resources themselves are inferior in quality, including hydrogen sulfide. Therefore, strict composite characteristics such as high strength, high toughness, and sour resistance are required for large-diameter welded steel pipes for line pipes.

However, the material of the welded portion of the large diameter welded steel pipe,
In particular, it is well known that the toughness value varies in a relatively wide range. Experiments revealed that the cause of this is not only the test characteristics, but also the rolling mill scale, which inevitably occurs in iron, mixes into the groove to deteriorate the material quality and contribute to this variation. . (Figure 3)

The mechanism is that mixing of the iron oxide mill scale into the groove increases the amount of oxygen in the weld metal and produces a large amount of inclusions. At the same time, the additive elements in the weld metal are trapped and hardenability is increased. Is caused by increasing the crystal grain size. In the past, only the mill scale accumulated on the inner bottom surface of the pipe was blown away only by air blow from a nozzle fixed to the pipe end before welding. (Fig. 2) Therefore, even after air blowing, the mill scale adhering to the inner surface of the pipe peels off during conveyance of the pipe and accumulates on the bottom of the pipe, or the mill scale once blown up by air blowing blows. This is also because it is deposited on the bottom surface of the pipe.

[0005]

Therefore, the above-mentioned method has a problem that mill scale remains after air blowing, mixes with the weld metal, and deteriorates the toughness value of the weld metal. The form of penetration of this mill scale into the weld metal will be described below. The mill scale existing on the inner surface of the steel pipe due to peeling is collected in the groove by the magnetic force during welding that occurs in the vicinity of the groove at the same time when welding starts, and the mill scale that does not collect in the groove also passes through the welding electrode and The magnetic force pulls it toward the welding electrode all at once and enters the molten pool. The scale attraction by the welding magnetism was such that the mill scale was supplied to the toe of the molten pool, so that the stirring of the molten metal was weak, so that oxygen was likely to remain in the weld metal.

[0006] The present invention advantageously solves the above-mentioned problems by extremely efficiently and surely removing mill scales over the entire length and the entire inner surface of a large diameter welded steel pipe, and the welded portion of the large diameter welded steel pipe is extremely reduced. The purpose is to manufacture well.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a mill for removing the mill scale adhering to the inner surface of a steel pipe in an apparatus for removing the mill scale generated by forming a large diameter welded steel pipe before welding. A scale stripper, an air blow nozzle behind the stripper, which blows off the milled scale that has been stripped out of the pipe to blow off the entire inner surface of the steel pipe where the stripper is located, and the stripper and the air blow nozzle. Is a mill scale removing device for steel pipes, which is installed on a moving device via a boom.

The present invention will be described in detail below with reference to examples. FIG. 1 shows an embodiment of a mill scale removing device for steel pipe according to the present invention. Reference numeral 1 is a steel pipe, in which a rotary wire brush 2 and an air blow nozzle 3 are provided at the tip of a boom 4, and the boom 4 is installed on a mill scale removing carriage 5 so that the entire apparatus can move. A dust collector 6 is provided at the end of the steel pipe 1 on the air blow outlet side.

[0009]

Before welding the steel pipe, the mill scale adhering to the inside of the steel pipe 1 is peeled off from one end of the steel pipe 1 by the rotary wire brush 2, and then air is blown out from the air blow nozzle 3 installed behind the steel pipe. The mill scale separated by the brush 2 and the mill scale separated and accumulated from the inner surface of the steel pipe during the molding of the steel pipe are discharged from the other end of the steel pipe and sucked by the dust collector 6. Here, the number of the air blow nozzles 3 is one or more, and the number and arrangement of the nozzles are set so that the air blow is supplied in a range covering the entire surface of the cross section where the rotary wire brush separates the mill scale. In this embodiment, four nozzles are arranged.
Here, the number of nozzles may be one or two, or a method in which the nozzle rotates in the circumferential direction to cover the entire area of the cross section where the mill scale is peeled off may be used. This can prevent the once-up mill scale from remaining behind the blow nozzle and accumulating again on the inner surface of the steel pipe.

Wire brush 2 and air blow nozzle 3
Is installed on the mill scale removing carriage 5 via the boom 4, and the scale removing carriage 5 travels to remove and remove the mill scale in the steel pipe from one end to the other end of the steel pipe 1 over the entire length of the steel pipe. Can be done. As a result, the mill scale on the entire inner surface of the steel pipe can be efficiently and reliably separated and removed.

Although the rotary wire brush is adopted as a method for removing the mill scale attached to the steel pipe, the present invention is not limited to this, and another method such as hammering may be used.

[0012]

Industrial Applicability According to the present invention, the mill scale deposited on the inner surface of the steel pipe is reliably removed, and the mill scale peeled off by the transportation of the steel pipe is also eliminated. Further, after the blow, the mill scale floats and is deposited again in the steel pipe. There was no mill scale that was used, and there was no mill scale mixed in the weld metal. As a result, variations in the material of the welded portion of the steel pipe are suppressed, and it has become possible to manufacture a large-diameter steel pipe in a stable manner even with strict requirements for the quality of the welding members.

[Brief description of drawings]

FIG. 1 is a mill scale removing device for a large diameter welded steel pipe according to the present invention.

FIG. 2 is a mill scale removing device for large diameter welded steel pipes by a conventional method.

FIG. 3 is a graph showing the relationship between the amount of mill scale in the groove and the toughness value of weld zone.

[Explanation of symbols]

 1 Steel Pipe 2 Rotary Wire Brush 3 Air Blow Nozzle 4 Boom 5 Mill Scale Removal Cart 6 Dust Collector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyoshi Mashima 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Steel Co., Ltd. (72) Inventor Toshihiro Nagase 1 Kimitsu, Chiba Prefecture Sankyu Co., Ltd. In the 2nd sub-center (72) Inventor Moruichi Ikuta 1 Kimitsu, Kimitsu-shi, Chiba Shin Nippon Steel Co., Ltd. Kimitsu Steel Co., Ltd. (72) Inventor Hideki Miyazaki 1 Kimitsu, Chiba Shin Nippon Steel Co., Ltd. Company Kimitsu Works

Claims (1)

[Claims] 1. A device for removing mill scale generated by forming a large-diameter welded steel pipe before welding, a mill scale peeling machine for peeling mill scale adhering to the inner surface of the steel pipe, and a peeling machine behind the peeling machine. Characterized in that an air blow nozzle for discharging the mill scale outside the pipe and covering the entire inner surface of the steel pipe where the peeling machine is located, and blowing out the peeling machine and the air blow nozzle are installed in a moving device via a boom. Steel pipe mill scale removal device.