JPH0344128B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for cooling steel pipes. [Prior Art] As one method for increasing the tensile strength, toughness, or other high-grade treatments for steel pipes, quenching and tempering treatments are performed in the same manner as other steel products. In the tempering process of steel pipes, due to the downsizing and shortening of production lines in recent years, the temperature range (200 to 300
An increasing number of lines are installing water-cooled floor equipment, which cools the product from below (℃ or below) to around room temperature. To briefly explain the steel pipe tempering process using a diagram, in FIG. Vertical feed)
After that, the steel pipe is passed through a shaping machine 4 whose main purpose is to finish the roundness and outer diameter of the steel pipe, and then a straightening machine 5 whose main purpose is to straighten the bends of the steel pipe. It is corrected while being rotated and conveyed, and then delivered to the cooling bed 6. The steel pipe that is tempered through the above steps is heated to a temperature of approximately 500 to 700°C in the heating furnace 1, so various conditions such as the outer diameter, wall thickness, and transportation time of the steel pipe to be processed are determined. Although there are some temperature fluctuations depending on the temperature, the temperature of the steel pipe at the entrance of the cooling bed 6 is approximately
The temperature is approximately 500° C., and the material is cooled to room temperature on the cooling bed 6 in order to be transported to the next step of finishing or inspection. The water cooling zone 7 is determined based on the size such as the outer diameter and wall thickness of the steel pipe to be processed on the cooling bed 6 and the line capacity.
Temperature range in which no material change occurs in treated steel pipes (approximately 200℃
It is installed at an appropriate position on the cooling bed 6 so that it can be water-cooled from a temperature of about 300°C. However, the general methods that have been practiced so far have had the following problems. The problem will be explained with reference to FIGS. 4 and 5. Figures 4 and 5 are diagrams showing the water cooling zone structure in detail, and are views taken in the vertical direction at an arbitrary point on the longitudinal axis of the steel pipe, and are identical in the longitudinal direction. It is a structure. In addition, Figure 4 shows an example of a chain conveyor system, which is designed to convey continuous flow, as the method of transporting the steel pipes to be processed, and Figure 5 shows an example in which a walking beam system is similarly adopted as the transport method. . First, the procedure of transport and processing in this water cooling zone will be explained with reference to the drawings. First, in Figure 4, the first stage radiation cooling (in the atmosphere) zone 20
The steel pipe 2, which has been cooled to a temperature where there is no problem in terms of quality even if it is cooled with water, is transferred to the reversing conveyor 12 and the dog 14.
While being rotatably supported by the conveyor 13, it is continuously conveyed laterally into the water cooling zone 7. In the water cooling zone 7, the upper water cooling header 8
A predetermined amount of cooling water is injected in advance by the lower water cooling header 9, and the steel pipe 2 flows through this water cooling zone 7.
It is cooled down to the required temperature and continuously discharged to the downstream process. On the other hand, in Fig. 5, steel pipe 2
is held by the fixed beam 17 and conveyed by the moving beam 18 at one pitch or an arbitrary number of pitches in the saddle of the fixed beam 17, and is cooled to a predetermined temperature in the same manner as shown in FIG. 4 above. The biggest problem with these conventional methods is as shown in FIG. 6, which shows the bending behavior of the steel pipe at the time the steel pipe enters the water cooling zone 7. It is. That is, in the prior art, when the steel pipe 2 enters the water cooling zone, cooling water is continuously injected by the upper water cooling header 8 and the lower water cooling header 9. The resulting temperature difference in the circumferential direction of the steel pipe induces bending in the steel pipe 2, causing transportation troubles, and also causes residual bending after cooling. There were serious problems with the quality of the steel pipes, such as the need to re-straighten the steel pipes and, depending on the material, reheat treatment. As a countermeasure against this problem, in order to reduce the temperature difference in the circumferential direction at the start of the water cooling of the steel pipe, for example, a method of increasing the rotation speed during cooling of the steel pipe and a method of increasing the rotation speed of the conveyor 13 as disclosed in Japanese Patent Application Laid-Open No. 140330/1983 are available. There are ways to increase the speed, but this will significantly increase the power required for conveyance, and if the rotational speed or conveyance speed of the steel pipe is too high, the steel tube will fluttering and the conveyance state will become unstable. It has the disadvantage of becoming. [Problems to be Solved by the Invention] The present invention solves various problems that occur when cooling steel pipes, and provides a method for cooling steel pipes that is particularly advantageous in preventing bending during cooling. [Means for Solving the Problems] The present invention has been made in view of the problems caused by conventionally commonly used cooling methods. However, when cooling the steel pipe by injecting cooling water from the upper and lower parts of the steel pipe, when the steel pipe enters the water cooling zone, the water in the upper water cooling header and the lower water cooling header is temporarily stopped, and the steel pipe cools. After completely entering the water cooling zone, cooling water is injected toward the steel pipe from the upper water cooling header and lower water cooling header in conjunction with the transport of the steel pipe, and cooling water is intermittently injected to cool the entire circumference of the steel pipe. A method for cooling steel pipes is characterized in that: In other words, in the present invention, if cooling water is continued to be spouted while the steel pipe is being transported, a temperature difference will inevitably occur in the circumferential direction of the steel pipe at the entrance of the water cooling zone, as shown in FIG. 6, and this will cause the steel pipe to bend. To avoid this, when the steel pipe enters the water cooling zone, temporarily stop the water in the upper water cooling header and the lower water cooling header, and after the steel pipe completely enters the water cooling zone,
Intermittent injection of cooling water is performed to start water cooling, and in this way, generation of temperature differences in the circumferential direction of the steel pipe is avoided. As shown in FIG. 1, even if the conveyor 13 is not in pitch conveyance, that is, in continuous conveyance, the upper water cooling header and If intermittent injection is performed by repeating the operation of starting and stopping the cooling water jet from the lower water-cooled header, the same functional effect as that of the present invention can be obtained. Furthermore, it is desirable to rotatably cool the steel pipe during cooling in the same way as when it is left to cool. If the steel pipe is cooled without rotating, the cooling water in the upper water-cooled header 8 and lower water-cooled header 9 shown in Fig. 1 may not reach the side of the steel pipe depending on the size of the steel pipe, resulting in insufficient cooling. Generates a temperature difference in the circumferential direction. The number of revolutions required to be applied to the steel pipe in order to avoid the occurrence of this temperature difference varies depending on the size of the steel pipe, but is about 1 to 10 revolutions per minute, as in the case of cooling. [Example] Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a cooling zone when cooling a steel pipe according to the present invention, taken in a direction perpendicular to the longitudinal axis of the steel pipe, and the structure is the same in the longitudinal direction of the steel pipe. First, the process will be explained using an example in which steel pipes to be treated are transported intermittently. The steel pipe 2 is heated to a predetermined temperature in a heating furnace, passed through a straightening machine, etc., and conveyed from the previous process (conveyed in a direction perpendicular to the plane of the drawing). It is temporarily stopped on the conveyance roll 21, and then the dispensing unit 22
The material is delivered onto a cooling bed, and is held by the conveyor 13 and dog 14, which are stopped and waiting at this time. The reversing conveyor 12, which circulates in the opposite direction to the conveyor 13, is constantly operated to continuously rotate the steel pipes 2 on the conveyor 13 in the cooling bed. If the steel pipe 2 on the conveyor 13 is not rotated, a temperature difference in the circumferential direction (mostly a temperature difference between the upper and lower surfaces in the circumferential direction) will occur in the steel pipe while it is being cooled, and it may also cause the end of the steel pipe to bend. Therefore, steel pipe 2
need to be rotated. The rotational speed given to the steel pipe 2 varies depending on the size of the steel pipe, but it gives a rotation of about 1 to 10 revolutions per minute. Of course, the number of rotations of the steel pipe may be increased as long as the steel pipe can be conveyed in a stable state without causing eaves in the steel pipe even if the steel pipe is rotated more than this. Next, the conveyor 13 equipped with a large number of dogs 14 arranged at regular intervals is started and operated for a single pitch or an arbitrary number of dog pitches, and the steel pipes 2 from the previous process are sequentially received onto the cooling bed. The steel pipe 2 is rotatably cooled on a cooling zone 20 to a temperature where there is no problem with the material even if it is cooled with water. On the other hand, the steel pipe 2A, which has been left to cool to the temperature immediately before water cooling, is conveyed by a single pitch or an arbitrary number of pitches of the dog 14 in synchronization with the steel pipe 2 sent from the previous process, and is transported to the position 2B in the water cooling zone 7. transported. At this time, the cooling water injection from the nozzle 15 of the upper water-cooled header 8 and the nozzle 15 of the lower water-cooled header 9 in the water cooling zone 7 is stopped while the steel pipe 2A is being conveyed, and the
Immediately after A is completely fed into the water cooling zone 7, that is, when the steel pipe reaches the position 2B where cooling water can be injected over the entire circumferential direction of the steel pipe 2A, the injection of cooling water is started and water cooling is started. Begins. In this way, continuous operation is performed intermittently in synchronization with the reception of the steel pipe 2 from the previous process into the cooling bed. Note that the start/stop control of the transport motor 25 and the cooling water on/off valve 27 is performed via the controller 26. The steel pipe cooled in the water cooling zone 7 is discharged onto a conveyor roll 23 by a discharge kicker 24.
In FIG. 1, 19 is a curtain for preventing water scattering. Next, a specific example of cooling a steel pipe by implementing the present invention will be described. In the rotary cross-feed type water cooling bed shown in Fig. 1, when the steel pipe to be cooled enters the water cooling zone based on the specifications shown in Table 1, the water from the upper water cooling header and the lower water cooling header is After the cooling water injection is stopped and the steel pipe completely enters the water cooling zone, the conveyance of the steel pipe and the start of the cooling water injection are matched so that the cooling water is spouted from the upper water cooling header and the lower water cooling header. A series of tempering operations were carried out. As a result, no bending of the steel pipes occurred during transportation, and stable operations could be carried out.

【table】

〔Effect of the invention〕

According to the present invention, the water cooling start timing in the circumferential direction of the steel pipe 2 is performed almost simultaneously over the entire circumference, so uniform cooling of the entire circumference of the steel pipe is possible, which prevents bending of the steel pipe and quality defects. The effect is that stable cooling operation can be performed without any problems.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view showing the state of a cooling zone when a steel pipe is cooled by implementing the present invention, and FIG. 2 is an explanatory diagram showing an intermittent injection state of cooling water in the method of the present invention. Figure 3 is a schematic side view showing the steel pipe tempering process, Figures 4 and 5 are longitudinal sectional front views to explain the conventional steel pipe cooling method, and Figure 6 is the bending behavior of the steel pipe during cooling. FIG. In the figure, 1 is a steel pipe, 7 is a water cooling zone, 8 is an upper water cooling header, 9 is a lower water cooling header, 12 is a reversing conveyor, 13 is a transport conveyor, 14 is a dog, 20 is a radiation cooling zone, 21 is a transport roll, Reference numeral 22 is a dispensing screw, 25 is a conveyance motor, 26 is a controller, and 27 is an opening/closing valve.

Claims (1)

[Claims] 1 When a steel pipe is conveyed horizontally and cooled by injecting cooling water from the upper and lower parts of the steel pipe, when the steel pipe enters the water cooling zone, the upper water cooling header and the lower water cooling header are temporarily blocked. After the water has been stopped and the steel pipe has completely entered the water cooling zone, cooling water is injected toward the steel pipe from the upper water-cooled header and the lower water-cooled header in conjunction with the transport of the steel pipe, cooling the entire circumference of the steel pipe. A steel pipe cooling method characterized by intermittent injection of cooling water.