JP3691909B2 - Forged steel pipe manufacturing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a forged steel pipe and an apparatus therefor. More specifically, the present invention relates to a technique for improving yield by processing skelp existing in a heating furnace without loss as much as possible when an operation is interrupted due to size change or the like in a forged steel pipe manufacturing process.
[0002]
[Prior art]
As shown in FIG. 1, the forged steel pipe manufacturing process is performed by unwinding a pipe-forming material steel strip (skelp) 10 from a coil with an uncoiler 1, cutting it with a shear 2 to a width according to the steel pipe dimensions, and then steel strip welder 3. Connected to the preceding steel strip, sent to the pre-tropical zone 11 of the heating furnace through the looper 4 and preheated to about 700 ° C., and then heated to a high temperature of about 1350 to 1400 ° C. in the heating zone 12 of the heating furnace, It is forged by machine 6 to form a steel pipe, and cut into a standard length by hot saw 7 to obtain a product. As an example, the length L ₁ of the heating furnace is several tens of meters, and the length L ₂ of the working process from the pipe making machine 6 to the hot saw 7 is about 20 m.
[0003]
In such a forged steel pipe manufacturing process, when the pipe making size is changed or the pipe making operation is interrupted, the conventional working method is shown in FIG. FIG. 3 shows a process of a length L ₁ from the entrance to the exit of the heating furnace and a length L ₂ from the exit of the heating furnace to the hot saw exit. When the forged steel pipe production line is stopped, the skelp 10 is gas-cut at the outlet position (point B) of the heating furnace, and the skelp 10 having a length L ₁ heated at a high temperature in the heating furnace 12 is provided on the heating furnace inlet side. The scrap coiler 5 is wound up as indicated by an arrow 13 while being hot and becomes scrap. Meanwhile Sukerupu 10a of the cut downstream of the L ₂ portion is also scrap processed.
[0004]
Next, when the operation is resumed, the skelp 10 on the upstream side of the scrap coiler 5 is passed through the heating zone 12 of the heating furnace to resume the pipe making.
[0005]
[Problems to be solved by the invention]
As described above, in the conventional forged steel pipe manufacturing process, the skelp of the portion existing in the heating zone of the heating furnace and the portion up to the hot saw downstream thereof is scrapped.
The present invention aims to reduce such scrap as much as possible and improve the product yield.
[0006]
Another object of the present invention is to solve the problem of unsafety caused by winding a skelp heated at a high temperature with a scrap coiler.
[0007]
[Means for Solving the Problems]
The present invention preheats the skelp and heats it to a high temperature to produce a welded steel pipe. When the pipe making operation is interrupted, the skelp is cut on the upstream side from the high temperature heating step and the skelp is fed upstream from the cutting position. the stops, Sukerupu the downstream side of the cutting position is applied to the manufacturing method of the forged against steel you pipe formation.
[0008]
The apparatus of the present invention is a forged steel pipe manufacturing apparatus in which a skelp running cutting machine is disposed downstream of the pre-tropical zone of the heating furnace and upstream of the heating zone, and the running cutting machine has a cutting blade attached thereto . A pair of rollers facing each other is rotated at the same speed, cut, and retracted out of the line when not in use. The running cutting machine is installed downstream from the pre-tropical zone of the heating furnace and upstream from the heating zone. This is because the skelp in the pre-tropical zone is low in temperature, so that it can be used again for normal operation after a short stop, and there is no need to perform the plate operation when the operation is resumed. The running cutting machine is located downstream from the pre-tropical zone of the heating furnace and upstream from the heating zone, so it is evacuated from the line to the outside of the line when not in use.
[0009]
Conventionally, a forged steel pipe production line is temporarily stopped, a high-temperature skelp is gas-cut on the outlet side of the heating furnace, and a downstream side thereof is cut with a hot saw through a pipe making machine to scrape the irregular tail end steel pipe. On the other hand, the skelp in the heating furnace was scraped by being wound up by a scrap coiler on the heating furnace entrance side.
In the present invention, the skelp running on the inlet side of the heating furnace is cut while running, and the skelp downstream from the cut portion, that is, the skelp during the heating process is piped by the pipe making machine. And the tail end part of the pipe making part is scrapped.
[0010]
Almost 2/3 of the first half of the skelp in the heating furnace after the running cut is a normal product. And about 1/3 of the tail end side is scrapped. This is substantially comparable to the conventional tail end length L ₂ shown in FIG.
The numerical value of about 2/3 is the length of the part that can be manufactured normally and can be commercialized, and the numerical value of about 1/3 on the tail end side is determined by the length of the irregular steel pipe. It is not a strictly limited numerical value.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 shows a process explanatory diagram of the example. L ₁ and L ₂ are the same as those in FIG. The forged steel pipe production line is decelerated, and the skelp 10 is cut by a running cutting machine 21 provided on the inlet side (point A) of the heating furnace. Simultaneously with the cutting, the skelp on the upstream side of the cutting part stops the conveyance. The downstream skelp continues to be transported as it is and is piped by a pipe making machine. Steel pipe length L ₂ from the furnace outlet to Hottoso outlet becomes normal product. Further, the length L ₁ skelp in the heating furnace is continuously produced by a pipe making machine. About 2/3 of the first half of the length L ₁ can be commercialized. About 1/3 of the latter half of the length L ₁ is free from the tail end of the skelp, resulting in poor weld jointing and scrapping.
[0012]
The running-cutting machine 21 cuts a pair of opposed rollers, to which cutting blades are attached, rotating at the same speed. When not in use, it is retracted from the line by an air cylinder. In the example, the cutting speed was 60 m / min at the maximum.
About 2/3 length of the skelp in the heating furnace, which has conventionally been scrap due to cutting between the runs, and the tube-forming part from the heating furnace outlet to the hot saw become the product, so that the product yield is improved and the scrap coiler 5 Since it is no longer necessary to take up the wire, it has been possible to reduce the time required to change the pipe size. In one example to which the present invention is applied, the amount of work time reduction is 7 minutes for each winding and threading (threading at the time of resuming operation), and a total of 2.9 hours per month. In addition, the actual recovery amount of products that were scraps as conventional products was an average of 489 km / time, 25 times / month, resulting in a yield improvement of 0.2%. Moreover, the target collection amount and the actual collection amount for each pipe diameter are shown in FIG. The target value was almost achieved.
[0013]
【The invention's effect】
According to the present invention, in the forged steel pipe manufacturing process, the change in the pipe making size effectively makes the skelp existing in the heating furnace when the work is interrupted, which contributes to the improvement of the yield and the reduction of the work time. can do.
[Brief description of the drawings]
FIG. 1 is an overall process diagram of a forged steel pipe manufacturing method.
FIG. 2 is a process explanatory diagram of an example.
FIG. 3 is a diagram for explaining a conventional process.
FIG. 4 is a graph showing the effect of the example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Uncoiler 2 Shear 3 Steel strip welding machine 4 Looper 5 Scrap coiler 6 Pipe making machine 7 Hot saw 10, 10a Skelp 11 Pre-tropical zone 12 Heating zone 13 Arrow 21 Running distance cutting machine

Claims (1)

In the welded steel pipe manufacturing apparatus, a skelp running cutting machine is arranged downstream from the pre-tropical zone of the heating furnace and upstream from the heating zone. An apparatus for manufacturing a forged steel pipe, comprising a mechanism for rotating at the same speed to cut and retracting to the outside of the line when not in use.

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