JPH01118313A - Method for removing scale in manufacturing stage of forge welded steel pipe - Google Patents

Abstract

PURPOSE:To prevent defects from occurring in a butt forge welded part by blowing air to an edge part of a skelp before local heating to remove scale. CONSTITUTION:An air blow equipment 6 is provided in front of an induction heating coil to perform local heating and at the rear of #1V forming roll 3. Skelp 2 continuously heated in a heating furnace 1 is formed by a #1V forming roll 3 and a #1H forming roll 4 nearly into a circular form. In this case, before the skelp is heated locally and melted, air is blown by a blow device 6 to the scale. Since scale is not in a molten state, the release properties are kept excellent and the atmosphere at a but forg welded part is improved. Therefore, defects by inclusion of scale are prevented from occurring in the butt welde part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for removing scale before forge welding in the manufacturing process of forge welded steel pipes.

[Conventional technology]

As shown in the example in Figure 3, the conventional method for removing scale in the manufacturing process of forge welded steel pipes is to use a welding horn 8VC air blower immediately before butt forge welding if the local heat method using an induction heating coil is not used. There is a method of installing equipment and removing scale. 1 in the figure is a heating furnace,
2 is Skelp (strip steel), 3 is +1v forming roll, 4 is ◆
In addition, as shown in the example of FIG. 4, there is also a method in which air is blown with an air blower 6 in front of the forming stand on the exit side of the heating furnace. Further, a method similar to the conventional method shown in FIG. 3 is a method described in Japanese Patent Application Laid-open No. 53-90148. In this method, an air blower is attached to the welding horn, and air is blown onto the welding surface to blow away scale, followed by reheating with oxygen.

[Problems to be solved by the invention] In the conventional manufacturing process of forge-welded steel pipes, as shown in Fig. 3, air blowing is performed at the welding horn 8 to remove scale at the abutting edge. Ta. Recently, in order to reduce the fuel consumption in heating furnaces, a manufacturing method has become common in which an induction heating coil 7, as shown by the two-dot chain line in Fig. 3, is installed before butt forging to locally heat only the edges. It has been adopted. In this case, the scale generated during the molding stage becomes molten by the induction solar coil, and the scale becomes molten.
It sticks to the edges of the Even if air blowing is carried out in this state, the effect of removing scale will hardly be obtained, and the scale may be caught in the weld as it is, resulting in butt forge welding, resulting in unwelded state.

In addition, as shown in Fig. 3, if air blowing is performed before the forming stands 3 and 4 on the outlet side of the heating furnace, the brick waste generated from the caloric furnace 1 can be removed, but the skelp 2 is a flat plate. Therefore, the scale is difficult to peel off, and it is not very effective in terms of scale removal.

[Means for solving problems]

The present invention solves the above-mentioned problems, and its gist is to form a continuously heated skelp into a substantially circular shape, and locally heat the edges of the formed skelp using an induction heating coil. After that, in the process of manufacturing a forge-welded steel pipe by blowing oxygen to the edge to heat it and then butt-welding the edge, air is blown to the edge of the skelp that is being formed before local heating to forge-weld it. This is a method for removing scale in the manufacturing process of forge-welded steel pipes, which is characterized by removing scale that is generated near the part.

The scale removal method of the present invention will be explained in detail below with reference to an embodiment shown in FIG.

As shown in the figure, a nozzle 6' with a flat tip is installed between the +1V forming roll 3 and +IH forming roll 40 in the process of forming the skelp 2 in the pipe making process, so that air piping and both edges can be uniformly blown. Install a scale removal air blower f6 with In addition, this air blow device 6
A lifting mechanism is provided for position adjustment to accommodate the size of manufactured steel pipes.

The configuration of the apparatus for carrying out the present invention will be explained below with reference to FIGS. 1 and 2.
This will be explained in detail based on the example shown in the figure.

In FIG. 1, at the stage where the scale 2 between the +1'i' forming roll 3 and the +IH forming roll 4 is formed, that is, at the stage where the scale is most likely to peel off, the scale at the edge part is locally removed by the induction heating coil 7. Skelp 2 is heated by an air blower 6 before it is heated and melted.
Remove scale from the edges. In the embodiment shown in FIG. 1, the air blowing device lt6 is located between the na1v forming roll 3 and the IH forming roll 4, but if there is space, it can be placed between the IH forming roll 4 and the induction heating coil 7. This air blowing device 6 may be installed between the nozzle 6' and air piping (the outer diameter size of the pipe is 3/4") so that both edges of the stell 120 can be evenly blown.
It is preferable to use a stainless steel tube in consideration of heat resistance. Furthermore, since the height of the edge part changes depending on the size of the steel pipe to be manufactured, it is effective to provide a lifting mechanism to accommodate this and always blow from the same distance to the edge part of Skelp 2. . This elevating mechanism is designed to automatically operate and ascend even if some trouble occurs during pipe making and an emergency stop occurs.

Also, the air pressure is naturally approximately O~5 Kf.
Although it is possible to adjust up to 2 KIi/m, in an actual machine, it is preferably about 2 KIi/m because there is a risk of temperature drop at the edge.

[Examples and effects]

Next, embodiments of the present invention will be described with reference to embodiments shown in FIGS. 1 and 2.

In the pipe-making process of forge-welded steel pipes, first, the skelp 2 heated continuously from the heating furnace 1 is passed through the +IV forming roll 3 and the φIH
It is formed into a substantially circular shape using forming rolls 4. The edges of the molded skelp 2 are locally heated by an induction heating coil 7, and further heated by oxygen blowing from a welding horn 8. Immediately after this, both edge portions heated by the forge welding roll 5 are welded against each other. In order to remove the scale generated at the edge part during this pipe-making process, the scale is locally heated and before it becomes molten, in other words, at the position in front of the induction heating coil 7, and during the forming process, the scale is peeled off. An air blower ft6 is provided at a position after the IV forming roll 3 to make it easier.

This air blowing device 6 is provided with a lifting mechanism so that the height can be adjusted according to the size of the manufactured steel pipe.

〔Effect of the invention〕

The method for removing scale in the manufacturing process of forge-welded steel pipes according to the present invention has the following effects compared to conventional methods.

An example of a conventional scale removal method is to blow air at the welding horn, but immediately before this, the edges are locally heated with an induction heating coil, so the scale is melted. If this is not removed, butt forge welding may result in serious quality defects.
In addition, when air blowing is performed immediately after leaving the heating furnace, the scale is not formed into a plate shape, so there is a drawback that the scale is difficult to peel off. By performing air blowing, scale removal properties are greatly improved.
The atmosphere of the butt forge welded part is improved, preventing defects in the butt part due to scale encroachment, and has a great effect on the quality of the forge welded pipe.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a scale removing device implementing the present invention, FIG. 2 is a partial perspective view of FIG. 1, and FIGS. 3 and 4 are explanatory diagrams showing an example of a conventional scale removing device. It is. 1...Heating furnace 2...Skelp (steel strip)
3...φIV forming roll 4...÷IH forming roll 5...÷2 forge welding roll 6...Scale removal air blow device 7...Induction heating coil 8...Felding horn Fig. 3■ Heating furnace 2 Skelp (12 steel) 3: #l' forming roll 4: #l"l forming roll 5: #2 forge welding roll 6° scale removal air blowing equipment F (7. Induction heating coil 8 welding horn Fig. 4 Procedural amendment 1 Indication of the case Showa year Patent application No. U/φ Yunu λ Address (residence) Kyoto (! Nihu: z-- 謬, hand round 2nd round 6th place 3rd place)
-1 Name (665) Ne1 Nippon Steel Corporation 4, Representative Address 330 Marunouchi Shigesu Building, 2-6-2 Marunouchi, Chiyoda-ku, Tokyo Name (3667) Teru Taniyama -11'' 8 , Details of the amendments The following matters in the specification and drawings will be amended as shown in the attached document. Note 1, page 7, insert the following sentence between lines 12 and 13. [Next, the results of a test to confirm the effectiveness of the present invention will be explained using figures. First, case 1 is a case in which the scale removing air blow device of the present invention is arranged as shown in FIG. In case 2, case 3 is the case where the air of the scale removal air blowing device is stopped, the eddy current flaw detection results and scale encroachment rate are shown in Figures 5 and 6 (a), (0), and (8). This was the result. That is, as shown in FIG. 1, case 1, which is the method of the present invention, has the best eddy current flaw detection (ECT) results, and naturally, case 3 has the worst. In addition, when looking at the scale encroachment rate in terms of scale intervening length (*), Case 1, Case 2, Case 3
It can be seen that the method of the present invention is the best. 2. On page 8, line 16, it says "This is an explanatory diagram showing an example." An explanatory diagram showing an example, Figures 5 and 6 ((), (0
). (8) is a diagram showing the results of an effect confirmation test in the present invention and a comparative example. ” he corrected. 3. Newly add "Figure 5" and "Figure 6 (A), (B). (8)" in the drawings. Figure 5 Ska-1 Ginzai length (%) Ska-1 Ginzai length (%) Ska-1 Ginzai length (%)

Claims (1)

[Claims] The continuously heated skelp is formed into a substantially circular shape, the edges of the formed skelp are locally heated using an induction heating coil, and then the edges are further heated by being blown with oxygen, and then the edges are butt-forge welded. In the process of manufacturing forge-welded steel pipes, air is blown onto the edges of the skelp that is being formed before local heating to produce a skelp near the forge-welded abutment.
A method for removing scale in the manufacturing process of forge-welded steel pipes, characterized by removing scale that flakes off.