JP2002275537A - Hearth roll type annealing furnace for continuously annealing pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous annealing furnace for continuously annealing pipes in which the pipes are moved by hearth rolls, in which the pipe is passed through straight in the furnace to eliminate troubles such as stubbing in the furnace, and the annealing efficiency and the efficiency of straightening any bend in the following step by preventing generation of the bend during the cooling can be improved. SOLUTION: A plurality of hearth rolls are disposed in the direction orthogonal to the pipe traveling direction, and the angle of a plurality of V-shaped grooves provided in the surface of the hearth rolls are set to 80-100 deg.. The pipes can be traveled in the furnace while restricting and straightening the bend caused by the thermal distortion in the V-shaped grooves, and the bend is less even when the pipes are cooled in water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous annealing furnace for continuously annealing a pipe while traveling by a hearth roll.

[0002]

2. Description of the Related Art Steel pipes such as welded pipes are annealed in a continuous annealing furnace after processing in order to homogenize quality. As shown in FIG. 1, a pipe P placed on an entrance roller table 2 is sequentially inserted into an annealing furnace 1 by rotation of a roll, and is annealed by receiving heat. It is taken out from the side roller table 4. As described above, when performing continuous annealing, the furnace is run in the furnace while rotating the pipe to be heated from the viewpoint of performing uniform heating. As shown in FIG. 2, the furnace hearth roll 5 is attached at an angle of about 3 ° with respect to the vertical direction of the pipe running direction, and by rotating the hearth roll 5, the heated pipe P is rotated while rotating the hearth roll 5. Is running. Also,
A V-shaped groove is provided on the hearth roll to suppress bending and allow the vehicle to run straight.

[0003]

When pipes are continuously annealed in such a hearth roll type continuous annealing furnace, when the pipe to be annealed enters the furnace, heat distortion occurs at the tip due to heating. Pipes may bend. When the vehicle is run in a bent state, it travels in the vertical direction of the hearth roll, which is out of the V-shaped groove and is inclined by 3 °, hits the furnace wall and leads to occurrence of a pipe trouble. Also, when traveling,
It is often the case that the original V-shaped groove is detached and then successively inserted into the adjacent V-shaped groove, and the pipe at the side end strikes the side wall of the annealing furnace, leading to a trouble in piping. For this reason, the V-shaped groove near the side wall of the annealing furnace in the direction in which the bending is expected (upward in FIG. 2) is preliminarily provided with two or three V-shaped grooves, that is, the number of passages is reduced to perform the annealing. Is decreasing. Furthermore, when the bent pipe is cooled by water cooling on the outlet side of the furnace, the bending is further increased, which makes it difficult to perform the bending correction work in the next step.

The present invention has been devised in order to solve such a problem. In a furnace in which a pipe is continuously annealed while being run on a hearth roll, the pipe is passed straight through the furnace. It is an object of the present invention to provide a continuous annealing furnace which can eliminate troubles such as plunging of the steel, and can improve the annealing treatment efficiency and the bending correction processing work efficiency in the next process by preventing the occurrence of bending during cooling. And

[0005]

Means for Solving the Problems A hearth roll type annealing furnace for continuous pipe annealing according to the present invention has the following objects.
A plurality of hearth rolls are arranged in a direction perpendicular to the pipe running direction, and the angle of the plurality of V-shaped grooves provided on the surface of the hearth roll is set to 80 to 100 °. In addition, one end of the hearth roll is supported by the side wall of the annealing furnace so as not to be movable in the axial direction, and the other end is supported by the other side wall of the annealing furnace so as to be movable in the axial direction. Avoided the effects of expansion. Furthermore, the hearth rolls are divided into multiple groups, and the rotation speed of the hearth roll in the rear group is faster than the rotation speed of the hearth roll in the preceding group, and tension is applied to the pipe toward the outlet side. did.

[0006]

In the conventional hearth roll type annealing furnace for continuous pipe annealing, as described above, the hearth roll is installed at a slight angle to the direction perpendicular to the direction of travel of the pipe, and the pipe runs while rotating. And uniform heating was performed. The present invention is based on the idea that even if a bend is generated by thermal stress due to heating without rotating the pipe during traveling, the bend is corrected by the constraint of the V-shaped groove of the pipe. First, the hearth roll 5 was arranged at right angles to the pipe running direction (not shown). Therefore, when the hearth roll is rotated in parallel with the pipe running direction, the heated pipe runs without being rotated. For this reason, the pipe inserted into the furnace along the V-shaped groove is heated and generates thermal stress, which is likely to bend. However, this bend is constrained by the side wall of the V-shaped groove, and the pipe is weighed by its own weight. Let it be corrected.

FIG. 3 shows the angle of the V-shaped groove formed on the surface of the hearth roll. Conventionally, the groove angle of the V-shaped groove in (a) was about 120 °, but in the present invention (b),
The angle was set to 80 to 100 °. The smaller the angle is, the larger the ratio of the stress load in the inward direction of the V-shaped groove due to the weight of the pipe increases, and the effect of correcting the bending of the pipe increases. However, if the angle is less than 80 °, the bent pipe tends to strike against the wall of the V-shaped groove, and there is a possibility that smooth running may not be achieved. On the other hand, if it exceeds 100 °, the ratio of the stress load in the inward direction becomes small, and the correction effect is reduced due to its own weight.

FIG. 4 illustrates the state of the support of the hearth roll at the furnace wall. Conventionally, (a) the hearth roll shaft is axially movably supported by a cylindrical bearing 8 so as to allow thermal expansion in the axial direction, and a sprocket 9 for rotation is attached to a tip of the shaft. 6 has been rotated. Since both ends of the hearth roll are supported so as to be movable in the axial direction, when receiving heat, the hearth rolls are not unified but expand in a desired direction. For this reason, when viewed from the pipe running in the furnace, the V-shaped grooves on each hearth roll do not line up in a straight line, but form a zigzag shape, which hinders smooth running of the pipe and applies extra stress to the pipe. And it was supposed to promote the bending of the pipe.

Therefore, in the present invention (b), the spacer 12 is fitted on the hearth roll shaft between the cylindrical bearing 8 at one end of the furnace wall and the hearth roll. The spacer 12 was also fitted between the bearing 8 and the sprocket 9. The other end of the hearth roll shaft is movably supported in the axial direction by a cylindrical bearing without fitting a spacer as in the related art. In this way, by supporting the one end so that it cannot move, the thermal expansion of the hearth roll shaft is aligned in one direction only in the non-fixed direction, so the V-shaped groove on the surface moves uniformly in one direction. I do. When viewed from the running pipe, the V-shaped grooves are aligned, and the pipe runs smoothly, making it difficult for the pipe to bend.

In a further preferred embodiment of the present invention, as shown in FIG. 5, a plurality of hearth rolls (nine in the drawing) are divided into a plurality of groups (three in the drawing, three groups). The hearth roll rotation speed of the rear group in the traveling direction of the pipe is higher than the hearth roll rotation speed of the previous group (1-2% faster than the group in the drawing and 1% higher than the group in the drawing). ~ 2% faster). Specifically, by changing the number of sprockets that rotate the hearth rolls one by one, the rotation speed of each hearth roll can be changed without changing the speed of the drive chain (detailed drawings are omitted). By increasing the rotation speed of the hearth roll in the later stage, tension acts on the running pipe in the outlet side direction, and the straightness of the running of the pipe is further improved.

As described above, by changing the installation angle of the hearth roll and the shape of the V-groove provided on the hearth roll, and changing the hearth roll fixing method and the driving method, 10 months after the practice of the present invention, However, there is no running trouble caused by the pipe sticking in the furnace. In addition, bending during cooling was almost eliminated. Further, since it is not necessary to provide an empty space near the side wall of the annealing furnace, the processing capacity is increased by 20%. conventionally,
When the small-diameter pipe is passed, the pipe runs obliquely at a rate of 70 to 80% due to the occurrence of a bend, and runs into a furnace wall to cause a trouble, so that monitoring in the furnace was necessary. This improvement eliminated running troubles and reduced the workload for monitoring work.

[0012]

As described above, according to the present invention, by changing the setting angle of the hearth roll and the groove angle of the V-shaped groove, the pipe is made to pass straight without rotating, and the pipe is struck in the furnace. To solve the problems of
The efficiency of annealing treatment and the prevention of bending at the time of cooling were able to be greatly improved, and the efficiency of the bending correction processing work in the next step could be greatly improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of annealing performed in a hearth roll type continuous annealing furnace.

FIG. 2 is a diagram showing a conventional hearth roll installation state of a hearth roll type continuous annealing furnace.

FIG. 3 is a longitudinal section showing the V-angle of a V-shaped groove provided on the surface of a hearth roll, the conventional one, (a) and the present invention (b).

FIG. 4 is a cross-sectional view showing a supporting structure of a hearth roll at an end of a furnace wall, a conventional one (a) and a one according to the present invention (b).

FIG. 5 is a conceptual diagram illustrating a hearth roll driving method.

[Explanation of symbols]

P: Annealed pipe 1: Annealing furnace 2: Inlet roller table 3: Water cooling section 4: Outlet roller table 5: Hearth roll
6: Drive chain 7: Line direction 8: Bearing 9: Sprocket
10: Cooling water hole 11: Cooling water entering side 12: Spacer 13: Cap 14: Bolt

Claims (3)

[Claims] 1. A plurality of hearth rolls are disposed in a direction perpendicular to a pipe running direction, and a plurality of V-shaped grooves provided on a surface of the hearth roll have a groove angle of 80 to 100 °. Hearth roll annealing furnace for continuous pipe annealing. 2. The hearth roll has one end pivotally supported by the side wall of the annealing furnace so as not to be movable in the axial direction, and the other end supported by the other side wall of the annealing furnace so as to be movable in the axial direction. 2. A hearth roll type annealing furnace for continuous pipe annealing according to 1. 3. The pipe according to claim 1, wherein the plurality of hearth rolls are divided into a plurality of groups, and the hearth roll rotation speed of the rear group in the traveling direction of the pipe is higher than the hearth roll rotation speed of the preceding group. Hearth roll type annealing furnace for continuous annealing.