JPH0438516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing an electric resistance welded pipe.

[Prior Art] The material used to manufacture electric resistance welded steel pipes is generally slit hot rolled coils.

Both edges 1a of the slit coil 1 are thinner than the central part of the coil due to edge sag (Fig. 7) during slitting, and the coil edges 1a are compressed during forming by breakdown rolls 5a and 5b (Fig. 7). (Fig. 8), and the thickness is becoming thinner. Figure 9 shows the wall thickness distribution of the hot-rolled coil, slit coil, and before finpass.

When the coil edge portions in this state are butted and welded, the cross section of the edge portion after welding is as shown in FIG. 10.

In other words, there is a beat 1 on the inner and outer surfaces due to reduction by welding.
Although portions a and 1b are respectively raised, the concave portion 1c on the side of the bead 1a remains thin.

This bead 1a will be cut and removed in a later process, but
When cutting as shown by B without leaving the recess 1c,
To prevent dimensional defects of the inner bead cutting marks (bead cutting side wall thickness - bead cutting part wall thickness exceeding the standard value or exceeding the lower limit of wall thickness standard value) and conversely, dimensional defects of the new bead cutting marks. When cutting as shown in A, there is a quality problem in that a concave groove 1c remains.

[Problems to be Solved by the Invention] For this reason, the aim is to increase the thickness of the edge portion by increasing the reduction in the fin pass, but the amount of thickness increase on the edge end surface is There is a problem that the thickness near the edges is less effective in preventing concave grooves than near the edges, and the thickness near the edges is outside the standard value. (FIG. 11) [Means and effects for solving the problem] Before forming, thickened portions are formed on both ends of the material plate for an ERW tube using tapered rolls, and an ERW tube is manufactured.

In this manner, thickened portions are formed at both end portions using tapered rolls before molding, and thickening is promoted using fin passes to prevent dimensional defects and concave grooves from occurring after the inner bead is removed.

[Example] An example of an edge offset apparatus 10 for carrying out the method of the present invention will be explained with reference to FIGS. 1 to 3. As shown in FIG. 1, the edge upset device 10 is provided in front of a molding machine such as a breakdown 5 and a fin pass 6. As shown in FIG.
It is constructed by disposing a pair of edge upset rolls 12, 12 facing each other, and the interval between these upset rolls 12, 12 is determined by a screw shaft 13 driven by a motor.
It can be adjusted by The frame 11 is placed on the bed 14 via roller bearings 15 and is movable in a direction perpendicular to the line. The edge offset roll 12 is a tapered roll having a tapered surface 12a whose diameter increases upward as shown in FIG.

Material 1 with edge sagging due to slits
is rolled down from both sides by the upset roll 12 as shown in FIG. 3, and the portion C in contact with the tapered surface 12a is deformed to form a thickened portion D on the upper side.
On the other hand, the F portion on the lower side of the end remains almost unchanged without undergoing major deformation.

In this case, since the frame 11 can be moved in a direction perpendicular to the line, the unbalance in the reduction amount on both sides of the material is within 10% as shown in FIG. 4a. A comparative example in which the frame 11 is fixed is shown in FIG. 4b. In this case, due to meandering of the coil camber, etc., the reduction on both sides of the edge becomes uneven, resulting in an unbalance of about 30% in the amount of reduction.

Then, the material plate with the thickened portion D formed at the end portion is formed by a breakdown 5 and then squeezed by a fin pass 6. In this case, when the edge end is straight as in the conventional case, the end face fully contacts the fin pass roll 6a as shown in FIG. Nakatsuta. However, in the case of the method of the present invention, when the edge enters the fin pass, only the F part of the edge contacts the fin pass roll 6a as shown in FIG. This promotes thickening of the C part. The wall thickness distribution of the edge end at the exit of the fin path 6 is shown in FIG. 6a. Compared to the conventional case shown in FIG. 6b, there is no thinner part at the edge end.

In this way, the concave portion 1c (the first
0) can be obtained.

[Effects of the Invention] The method of manufacturing an electric resistance welded pipe of the present invention as described above can prevent dimensional defects and concave grooves from occurring after the inner bead is removed.

[Brief explanation of drawings]

Figures 1 to 3 show an example of an apparatus for carrying out the method of the present invention; Figure 1 is a layout diagram;
The figure is an explanatory diagram of the edge upset device, Figure 3 is an explanatory diagram showing the upset roll in use, and Figures 4 a and b are the D side and F side of the edge when the frame is movable and when the frame is fixed. Figures 5a and b are explanatory diagrams showing the relationship between the side rolling reduction amount, and Figures 5a and b are diagrams that illustrate the contact state between the edge end face and the fin pass roll in the method of the present invention and the conventional method. Figures 6a and b are diagrams showing the relationship between the method and the conventional method. An explanatory diagram of the wall thickness distribution at the edge end in the conventional method,
Figure 7 is an explanatory diagram of the edge end after slitting, Figure 8
The figure is an explanatory diagram of breakdown, and Figure 9 is an explanatory diagram of wall thickness distribution at the edge end in each process in the conventional method.
FIG. 10 is an explanatory diagram of the cross-sectional shape of a butt weld in the conventional method, and FIG. 11 is an explanatory diagram of the wall thickness distribution at the edge end when the aperture in the fin pass is changed in the conventional method. 1...Material board, 1a...Edge part, 1
2...Edge upset roll, 12a...Tapered surface.

Claims (1)

[Claims] 1. A method for manufacturing an electric resistance welded tube, which comprises forming thickened portions on both ends of a material plate for electric resistance welded tubes using tapered rolls before forming the electric resistance welded tube.