JPS6247420A - Rolling material cooler in continuous hot rolling line - Google Patents

Abstract

PURPOSE:To prevent the generation of uneven cooling of rolling material and to improve the quality of the rolling material by injecting cooling water from spray nozzles at the inlet and outlet of a cooling pipe in the stage of passing a hot rolled steel bar, wire, etc., through the inside of the cooling pipe and cooling the same. CONSTITUTION:A steel billet is heated to a rolling temp. in a heating furnace 20 and is passed through a roughing mill train 21 consisting of rolling mills 1-8, an intermediate rolling mill train 22 consisting of rolling mills 9-12, an intermediate cooling zone 24, a finishing mill train 23 consisting of rolling mills 13-16, a rear cooling zone 25, and a cooling bed 26, by which the billet is rolled and cooled. The cooled material is taken out. The rolling material such as steel bar or steel wire is passed through the cooling pipe 41 in which the cooling water is passed by which the rolling material is cooled in the intermediate cooling zone 24. The four spray nozzles 45 are disposed near the apertures at the end thereof to inject the cooling water to the rolling material moving into and out of the pipe 41. The water ejected therefrom is brought into collision against the cooling water discharged and splashed from the aperture at the end of the pipe 41, by which the non-uniform falling of the splashed cooling water to the rolling material 46 is prevented and the material is uniformly cooled in the circumferential direction. The uneven cooling is thus prevented and the steel bar, wire, etc., having uniform quality are produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a cooling device for rolled material in a continuous hot rolling line, and is intended to prevent uneven cooling of the rolled material.

(Prior Art) In continuous rolling lines for steel bars, wire rods, etc., rolled materials are cooled by forced water cooling in order to improve their structure and mechanical properties, suppress scale formation, and the like.

Among these, the most important is so-called controlled rolling and controlled cooling, which obtain a desired finishing temperature by controlling the flow rate of cooling water and rolling speed in order to refine the grains and improve toughness and strength of the rolled material.

The cooling device for controlled rolling and controlled cooling includes cooling pipes installed between rolling mill rows and on the rolling line after the rolling mill row.
A cooling pipe is used in which the rolled material is cooled by cooling water inside the cooling pipe. In that case, the cooling water used for cooling was discharged from the opening for the rolled material inlet and outlet at the end of the cooling pipe.

(Problems to be solved by the invention) Generally, during forced water cooling for controlled rolling and controlled cooling,
It is important to cool the rolled material as uniformly as possible in the circumferential direction within the cross section. However, regardless of whether controlled rolling or controlled cooling is performed, non-uniform cooling portions such as uneven cooling structures, that is, uneven cooling, often occur in the cross section of a rolled material subjected to water cooling.

For example, if medium-strong cooling is required in the intermediate cooling zone in order to obtain the target finished temperature during controlled rolling, the temperature at the surface layer will inevitably be low and uneven cooling will occur in the circumferential direction within the cross section. It remains as a homogeneous tissue. Such cooling unevenness is particularly harmful to controlled rolled materials that are subjected to processing such as direct cutting without heat treatment in the secondary processing step.

Furthermore, uneven cooling during controlled cooling to form a hardened layer on the surface layer by strong cooling, that is, non-uniform cooling in the circumferential direction, causes failure to obtain a uniform hardened layer.

Factors that cause uneven cooling of rolled materials include temperature distribution and surface properties in the circumferential direction of the rolled material before cooling, dimensions of the rolled material, flow rate of cooling water, position of the rolled material within the cooling pipe, and cooling discharged from the cooling pipe. Water may be scattered onto the rolled material, etc. The inventors of the present application investigated the influence of these factors on cooling unevenness through an experiment simulating an actual machine.

As a result, it was found that the cooling water discharged from the opening at the end of the cooling tube and splashing on the rolled material had a large effect on cooling unevenness. In other words, the scattered cooling water is not uniformly sprinkled onto the rolled material, and the influence of uneven cooling due to the scattered cooling water is particularly strong in areas where the surface temperature of the rolled material is low, resulting in a suitable cooling structure, that is, uneven cooling, within the cross section of the rolled material. It was something that would occur. Further, even in directly hardened materials in controlled cooling in which a hardened layer is formed on the surface layer of the rolled material by strong water cooling, a uniform hardened layer cannot be obtained due to non-uniform cooling caused by scattered cooling water.

In view of the above, an object of the present invention is to provide a rolled material cooling device that can prevent uneven cooling of rolled material caused by scattered cooling water discharged from a cooling pipe, and can also prevent uneven cooling caused by other factors. .

(Another Means for Solving the Problems) The present invention is characterized by the technical means taken to solve the problems of the prior art. A rolling material cooling device,
The end opening of the cooling pipe is used as the entrance and exit for the rolled material to be conveyed,
The rolled material is cooled by cooling water inside the cooling pipe, and the cooling water is discharged from the end opening of the cooling pipe,
The present invention is characterized in that a means for ejecting fluid is provided at the entrance and exit of the rolled material to prevent non-uniform cooling of the rolled material.

(Function) By colliding the jetted fluid with the scattered cooling water, it is possible to prevent the scattered cooling water from scattering unevenly on the rolled material and to cool the rolled material uniformly.

Moreover, the rolled material is cooled by the ejected fluid, and non-uniform cooling of the rolled material can be corrected and the material can be cooled uniformly.

(Example) Embodiments of the present invention will be described below based on the drawings.

Fig. 1 shows a cooling pipe of a basic cooling experiment device having a drainage port in the center of the cooling pipe cylinder body, in which a material to be cooled according to the present invention is sprayed at equidistant recessed positions in the circumferential direction near the outlet end opening. This is the cross-sectional structure of the material to be cooled (501,548C) after a cooling experiment with a nozzle arranged and water used as the ejecting fluid (cooling start temperature 940"C, cooling water flow rate 50 m/hr, cooling time 2.5 sec + spray Total flow of debris i5.5 m/
hr).

In FIG. 1, the distribution of the suitable cooling structure in the surface layer is uniform. This is because ■ The water jetted from the spray nozzle almost eliminates the waste water (splattered cooling water) that would scatter unevenly on the rolled material when there is no spray nozzle, and the flow of this sprayed cooling water is axially symmetrical, that is, circumferentially. It is presumed that this is because the uniformity in the circumferential direction improves the cooling ability of the portion with low cooling ability centered on the lower part, and the material to be cooled is cooled uniformly in the circumferential direction.

In Figure 2, in the conventional cooling method (without spray nozzle), the cooling ability of the upper part of the ion to be cooled is increased by the scattered cooling water from the opening at the end of the cooling tube, so the suitable cooling structure is unevenly distributed in the upper part. ing.

These results confirmed that the material to be cooled was cooled uniformly in the circumferential direction when the method according to the present invention was used.

FIG. 6 shows a hot continuous rolling line, in which 2o is a heating furnace for heating billets, followed by a rough rolling mill row 21, an intermediate rolling mill row 22, and a finishing rolling mill row 23 arranged in series. . These rolling mill rows 21, 22, and 23 are composed of first to sixteenth rolling mills 1 to 16. 24 is an intermediate cooling zone provided between the intermediate rolling mill row 22 and the finishing rolling mill row 23; 25 is a rear cooling zone provided between the finishing rolling mill row 23 and the cooling bed 26; Obi 24
, 25 is a cooling device 27.2 that supplies cooling water to the rolled material.
8 are provided, and the amount of cooling water in each of the cooling devices 27 and 28 is controlled by a control device including a process control computer 29. 30 is a thermometer that measures the surface temperature of the rolled material on the entry side of the ninth rolling mill 9; 31 is a finishing rolling mill row 23;
32 is a thermometer that measures the surface temperature of the rolled material after forced water cooling on the exit side of the latter cooling zone 25.

In the intermediate cooling zone 24, cooling water is supplied under automatic control by a computer 29 in order to make the microstructure of rolled materials such as steel bars and wire rods fine and uniform, and to improve mechanical properties such as high toughness and strength. Controlled rolling is performed in which the temperature of the rolled material is controlled. Further, in the latter stage cooling zone 25, controlled cooling is performed in which cooling water is supplied to the product after controlled rolling to cool it.

FIG. 5 shows the configuration of each cooling zone 24, 25, 41 is a cooling pipe arranged in a row on the rolling line, 42 is a conveying roller for rolled material, 35 is a cooling water supply pipe to the inside of the cooling pipe 41, 43 44 is an ON-OFF valve for cooling water flow, and a flow control valve for cooling water. Here, the cooling water supplied into the cooling pipe 41 is discharged from the rolled material entry/exit opening at the end of the cooling pipe 41, or from the rolled material entry/exit opening and the drain port provided in the cooling pipe cylindrical body. Ru.

As shown in FIGS. 3 and 4, four spray nozzles 4 are installed near the end opening of each cooling pipe 4I.
5 are arranged at equidistant positions in the circumferential direction on the circumference surrounding the rolling line. In this embodiment, water is sprayed from each spray nozzle 45 toward the rolling line.

In the above configuration, a billet with a mouth of 155 fins is rolled by machine rows 21 and 22 of I46 dragon bar 46 (548C
), and controlled rolling was performed in which this was cooled in an intermediate cooling zone 24. Cooling start temperature 925℃, cooling water flow rate 2
4Q m/h, and the cooling time was 2.2 seconds. And the total flow from the spray nozzle 45 if 30 n?
/ h of water is ejected and the ejected water is discharged from the end opening of the cooling pipe 41 and collides with the scattered cooling water, so that the scattered cooling water is unevenly distributed on the steel bar 46 being conveyed on the line. This prevents this and improves uneven cooling in the circumferential direction. In this case, the rolled material is also cooled by water from this spray nozzle, but this cooling is uniform in the circumferential direction of the rolled material, and the cooling capacity is determined in advance and the cooling pipe is used to finish it at the target temperature. Supply cooling water flow rate to 220 r
r? /hr. The cross-sectional structure of the product thus obtained is shown in FIG. FIG. 8 shows the cross-sectional structure of the product when the scattered cooling water is non-uniformly sprinkled as before. As can be seen by comparing the two, the one on which the scattered cooling water was sprinkled non-uniformly has a suitable cooling Mi texture on the surface layer. In conventional technology, when the cooling water supplied to the cooling pipes is adjusted (reduced) to prevent uneven cooling (unevenly cooled parts such as properly cooled tissue), the required amount of adjustment increases, making it difficult to achieve the specified temperature drop. Therefore, the target finishing temperature, that is, the rolled material structure cannot be achieved. In the device according to the present invention, which prevents the scattered cooling water from sprinkling unevenly, cooling is uniformly performed in the circumferential direction, so there is no uneven cooling.
As shown in FIG. 10, a fine and uniform ferrite/pearlite structure was obtained. FIG. 9 is a micrograph (X100) of the surface layer, and FIG. 10 is a micrograph (X100) of the center.

In the above embodiment, a so-called immersion cooling pipe is used to fill the cooling pipe 41 with cooling water, and the cooling water is discharged from openings at both ends, or from openings at both ends and drain ports provided in the cylindrical body of the cooling pipe. Although the present invention is applied, the present invention can also be applied to a so-called spray cooling pipe in which cooling water is sprayed within the cooling pipe, and the cooling water is discharged from the outlet side opening end. Further, other fluid such as air may be ejected from the spray nozzle. Further, since the flow rate of the water jetted from the spray nozzle can be easily adjusted, by understanding the cooling capacity of the rolled material by the jetted water in advance, it is possible to prevent uneven cooling of the rolled material due to other factors.

In other words, uneven cooling due to misalignment of the rolled material relative to the cooling pipe 41, contact between the rolled material and the conveyance roller, etc.
This problem can be solved by cooling the rolled material with water jetted from the spray nozzle 45 and correcting it by making the cooling capacity uniform in the circumferential direction.

Further, even when the present invention was applied to controlled cooling in which direct quenching was performed using strong water cooling, a uniform quenched layer was obtained on the cross section of the rolled material.

Eliminating such uneven cooling of the rolled material is also effective in reducing bending of the rolled material.

(Effects of the Invention) According to the present invention, it is possible to prevent uneven cooling of the rolled material due to the ejected fluid, and it is possible to improve the quality of the rolled material.

[Brief explanation of drawings]

Fig. 1 is a metallographic diagram of a cross section of a steel bar cooled by a basic cooling device using the present invention, Fig. 2 is a metallographic diagram of a cross section of a bar cooled by a basic cooling device using the conventional method, and Fig. 3 is a metallographic diagram of a cross section of a steel bar cooled by a basic cooling device using the present invention.
Enlarged side view of main parts of the cooling device according to the embodiment of the present invention, No. 4
The figure is an enlarged front view of the main parts, Figure 5 is a side view explaining the overall configuration, Figure 6 is a schematic diagram explaining the configuration of the continuous hot rolling line,
The figure is a metallographic diagram of a cross section of a steel bar cooled by the cooling device of the present invention, Figure 8 is a metallographic diagram of a cross section of a steel bar cooled by a conventional cooling device, and Figures 9 and 10 are metallographic diagrams of a rolled material. It is. 27.28...Cooling device, 41...Cooling pipe, 45.
...Spray nozzle. Patent applicant: Kobe Steel, Ltd. Dobishoku■ =

Claims (1)

[Claims] 1. A rolled material cooling device having a cooling pipe installed on a continuous hot rolling line, in which the opening at the end of the cooling pipe is used as the entrance and exit for the rolled material being conveyed, and the rolled material is cooled by cooling water inside the cooling pipe. and the cooling water is discharged from the end opening of the cooling pipe, characterized in that the outlet and outlet of the rolled material are provided with means for ejecting fluid to prevent uneven cooling of the rolled material. A rolling material cooling device for a continuous hot rolling line.