JPH0211325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an annealing device in a cooling bed configured so that the cooling in the cooling bed for hot rolled steel can be used selectively depending on the purpose.

(Prior Art) Steel materials are usually produced by hot rolling to give them various desired shapes and then air cooling them on a cooling bed while preventing the occurrence of bending. Currently, these steel materials are subjected to softening heat treatment in order to improve properties such as machinability and cold stage properties in the subsequent cutting or cold working process. However, this softening heat treatment not only requires a great deal of labor and time, but also consumes a lot of energy for heating and cooling, resulting in a large cost.

On the other hand, it is known that it is possible to soften the rolled material by reducing the cooling rate after hot rolling to a predetermined rate or less and performing slow cooling. Processing can be omitted, leading to significant cost reductions.

For the purpose of this direct heat treatment, for example,
-42335 publication or Japanese Patent Application Laid-Open No. 58-93510 have been proposed.

However, although Utility Model Publication No. 56-42335 has a sealed structure with heat insulating materials on the top, bottom, left and right, since both the front and rear surfaces, which are the passing direction of the moving rolled material, are open, there is a gradual cooling effect due to radiant heat dissipation, but it is due to convection. Heat dissipation cannot be prevented, and there is a limit to slowing down the slow cooling rate. In addition, since it has a sealed structure, it is sufficient to use manufacturing equipment exclusively for slow cooling, but in order to suppress the surface scale of materials that cannot be slow-cooled or materials that do not require slow-cooling, it is necessary to install equipment for each production line that produces a variety of products. Since a part of the transfer device is in a sealed structure, it takes a lot of time to remove and rearrange the installation, and there are problems such as large production problems. Furthermore, as a solution to the above problem, Japanese Patent Application Laid-open No. 58-93510 uses a structure in which the four circumferences of the cover are sealed with heat-resistant curtains to reduce convective heat dissipation, and a structure is adopted in which both the upper and lower covers can be retracted.

(Problems to be Solved by the Invention) However, by employing this mechanism, the following problems occur particularly in the cooling bed lower mechanism.

a) By installing a retractable lower cover at the bottom of the retsuhen that supports the rolled steel material, the lower cover can have an almost airtight structure, but since the retsuhen is located in a slow cooling device, it is exposed to high temperatures and is subject to loads. As a result, thermal deformation is likely to occur, which leads to design restrictions such as shortening the retchen support span. In addition, in order to manufacture softened steel materials by slow cooling, in addition to the cooling rate equivalent to slow cooling,
It is necessary to ensure the slow cooling time and slow cooling end temperature, and the short width of the slow cooling device limits the production amount and hinders productivity. In addition, the retouchen causes creep deformation, and the retouche supporting the steel material must be replaced frequently, increasing running costs. Also, if you want to lengthen the support span of the retsuhen, you will need to increase the height of the retsuhen.
There is also the disadvantage that the distance between the steel material and the lower cover is large, which tends to cause convection within the cover, and the cooling rate is accelerated by air entering through the gap in the lower cover.

b) If a retractable lower cover is to be installed directly under the steel material in order to ensure strength and prevent convection, the lower cover must be installed within the height range of both the movable and fixed handles. In order to avoid interference with each retsuhen, it became necessary to divide the lower cover, resulting in a lower cover drive structure with hundreds of strips, resulting in a large capital investment, lower equipment reliability, and a very large gap between the movable lower cover and the retsuhen. However, the cooling rate required to obtain the desired slow cooling effect was also limited.

As mentioned above, under certain restrictions or productivity,
It is possible with conventional technology to manufacture small quantities of easily softened steel at the expense of equipment durability, etc., but in a large-scale production line for a wide variety of products, it is difficult to produce a predetermined amount of softened steel while ensuring productivity and equipment durability. There were many problems in manufacturing.

In addition, conventional thermal covers employ a sealed structure in which ceramic fibers or the like are placed on the inner surface of the rolled material and the outer skin is fixed with iron plates, etc., to prevent heat dissipation due to heat conduction from the cover and to achieve slow cooling. In order to further increase efficiency, there are examples of using a highly reflective stainless steel plate with a glossy inner surface to actively reduce heat dissipation due to radiation. However, both of these have the effect of reflecting radiant heat, and when the material cannot be slowly cooled or does not require slow cooling, if the lower heat insulating cover is left in place, the cooling rate of the lower part of the rolled material will be much slower than that of the upper part. This causes bending during rolling on the floor. This phenomenon can be avoided by installing the lower heat insulating cover at a location away from the rolled material, but as described above, problems such as thermal deformation of the retsuhen and slow cooling effects due to convection occur during slow cooling.

(Means for Solving the Problems) The object of the present invention is to eliminate the drawbacks of the conventional methods as described above, and to enable slow cooling and other cooling of hot rolled steel products to be carried out efficiently and effectively online. This provides gradual cooling in a cooling bed.

The gist of the present invention is to provide a black body or an approximation thereof (hereinafter referred to as a black body plate) in which the lining facing the steel material in a cooling bed is made of a material with good heat absorption.
It has the structure of a heat insulation cover with a heat insulating material with good heat insulation properties placed on the back side, and such heat insulation covers are installed directly above and directly below the steel material conveyance line on the cooling floor, and furthermore, the heat insulation cover is installed above and below the steel material conveyance line. The structure is such that it is covered with a heat-resistant curtain to prevent heat dissipation from all four sides between the covers. In this way, it is possible to prevent radiant heat dissipation and convective heat dissipation of steel materials, and to enable gradual cooling of rolled steel materials.In addition, when cooling materials that cannot be slow-cooled or materials that do not need slow-cooling, the structure is such that the heat-insulating cover directly above the cooling bed can be removed. By doing so, it is possible to perform such processing. At this time, the heat insulation cover directly under the cooling bed has a black body board installed on its inner surface, and has a structure that improves insulation and secures some ventilation, making it easy to use in terms of equipment.
Another feature is that it is possible to use a fixed type with excellent equipment durability and reliability, and has a structure that allows operation without production problems. The structure of the lower heat insulating cover that ensures a certain degree of air permeability here means that appropriate holes and gaps are provided to penetrate the black body plate, the heat insulating material, and the outer shell.

(Example) An example of the present invention will be described below with reference to the drawings in the case of a steel bar rolling line.

FIG. 1 is a side view showing an embodiment of a cooling device according to the present invention. FIG. 2 is an enlarged sectional view of the main part taken along the line AA in FIG.

After hot rolling, the steel bar 1 is cut into specified lengths, and then is continuously transported laterally from left to right in the drawing by fixed recesses 2 and movable recesses 3 of the cooling bed. The movable retsuchen 3 moves over a certain range by circular or elliptical motion via an interlocking beam 5 by a driving device 4 provided below the cooling bed, and the steel bar 1 is temporarily stopped in a groove on the fixed retsuchen 2. are sequentially moved to the adjacent right groove.

In the conventional Retzchen type cooling bed having such a structure, the slow cooling device according to the present invention is constructed as follows. That is, a retractable upper heat-insulating cover 6 is provided directly above the cooling bed, and a heat-resistant curtain 7 or a movable heat-resistant shield plate is provided around the four circumferences of the upper heat-insulating cover, and the upper heat-insulating cover 6, the fixed layer 2, and the right side are provided. It has a structure that closes the gap with the moving steel bar 1 and prevents the dissipation of convection heat and radiant heat, and the lower heat insulation cover 8 is fixedly installed directly under the groove on the upper part of the fixed retsuhen 2 to reduce the convection effect and dissipate heat. The structure is designed to reduce the

As shown in FIG. 2, the upper heat insulation cover 6 and the lower heat insulation cover 8 have a black body plate 9 on the inner surface facing the steel material, that is, the steel bar 1, and a heat insulating material 10 and an outer skin 11 are sequentially stacked on the outer surface of the black body plate 9. It has a laminated structure.

Ideally, the black body board 9 should be a completely black body, but
Materials having similar properties within a feasible range can be used. According to the experience of the present inventors, ultrathin steel sheets with black oxidized surfaces have similar characteristics,
I found out that it can be used. This is thought to be due to the blackening of the surface and extremely small heat capacity, which quickly absorbs heat and approaches the temperature of the opposing steel material.

The heat insulating material 10 may be any commonly used fire-resistant heat insulating material, such as ceramic fiber. Reference numeral 11 denotes an outer skin, which is a mechanically strong outer frame, and is made of a steel structure. The black body plate 9 and the heat insulating material 10 may be attached to the outer skin 11 by an appropriate method.

Reference numeral 7 is a heat-resistant curtain hanging from the upper heat insulation cover 6, but it may also be made of asbestos cloth or a similar flexible heat-resistant material, or a heat-resistant shielding plate having such properties. The heat-resistant curtain 7 has a drapery structure that hangs down from the four circumferences of the upper heat-insulating cover, and it is effective if its lower end reaches the lower heat-insulating cover 8.

Figure 3 shows the lower heat insulating cover viewed from above. The lower heat retaining cover 8 has a sealed structure in the fixed part 2, and it is necessary to leave a gap 18 in the movable part 3 in order for the movable part 3 to operate. In addition, the lower heat insulation cover 8 is provided with small holes 19 to maintain cooling when slow cooling is not required.
They are installed with appropriate opening area and placement to prevent the steel bars from bending. The total opening area of the above-mentioned gap 18 and small hole 19 is 2 to 10 times the effective area of the lower heat insulation cover.
It is said to be about %.

Next, the retraction structure of the upper heat retaining cover 6 will be explained with reference to FIG.

12 is a support body for the upper heat insulation cover 6, and 13 is a support frame. The support frame 12 is rotatably attached to the support frame 13 by pins 14. It has a structure in which it is suspended by a wire 15 from approximately the center of the upper heat insulation cover. 16 is a sheave, and 17 is a wire winding drum. At the time of evacuation, the wire 15 is wound up by the winding drum 17, so that the upper heat insulation cover 6 looks up with the pin 14 as a fulcrum,
Retract to the position shown at 6'.

(Function) Since the present invention is configured as described above, the upper and lower heat insulation covers have black body plates on their inner surfaces, so they absorb the radiant heat from the rolled steel material without reflecting it, but the heat capacity thereof is small. The combination of this and having a heat insulating material on the back surface causes the temperature to rise quickly, increasing heat retention efficiency. Therefore, when slowly cooling steel materials on a cooling bed,
The upper heat insulation cover is rolled down and formed to cover the upper surface of the steel material being transported. At this time, since the gap between the upper and lower heat-insulating covers is shielded by the heat-resistant curtain 7, the amount of air entering through the gaps and small holes provided in the lower heat-insulating cover is extremely small, and no internal convection occurs. Due to the curtain structure, the steel materials can be freely entered and exited.

Further, when the material is not to be slowly cooled, the cooling process can be performed at the same cooling rate as a normal cooling bed by simply rolling up and retracting the upper heat insulation cover 6. At this time, the presence of gaps and small holes in the lower heat insulating cover contributes to the absence of the upper heat insulating cover, and convection cooling by the surrounding air is active.

FIG. 4 shows the influence of the lower heat retaining cover on the cooling rate when the upper heat retaining cover is retracted. In the figure, A represents the cooling rate in the original cooling bed without any covers, and B represents the cooling rate in the present invention.
C is a material with good reflectivity that has been used in the past and has holes,
This is a curve showing the situation when convection is prevented without providing any gaps. As you can see from this figure, if the conventional lower heat insulation cover is left in place, there will be a difference in cooling rate of 0.1 to 0.2°C/sec, which will cause a large temperature difference between the top and bottom surfaces of the steel material, causing the product to bend. occurs. On the other hand, as in the present invention, if a black body board is provided with holes, gaps, etc. that absorb heat and generate convection, even if such a black body board is installed, the difference in cooling rate will be at most 0.05℃/ sec, which is within a range that does not have any effect on product bending or cooling capacity (productivity).

On the other hand, regarding the cooling rate during slow cooling, the influence of the opening ratio in the upper and lower heat retaining covers of the present invention will be explained with reference to FIG.

A significant gradual cooling effect can be obtained by installing upper and lower thermal covers. The effect increases as the opening ratio of the lower heat insulation cover is reduced, but the heat insulation cover according to the present invention can achieve a slow cooling rate that is sufficient to soften alloy steel such as SCM, and the lower heat insulation cover can be fixed. It is possible.

(Effects of the Invention) As described above, according to the present invention, the lower heat insulation cover can be fixed, the equipment is simple, and creep deformation of the retsuhen can be prevented, improving equipment durability and reliability. This makes it possible to realize online softening treatment of steel without hindering productivity on a large-scale, multi-product production line.

In addition, the black body plates provided on the inner surfaces of the upper and lower thermal covers according to the present invention have good heat absorption properties, and by reducing the heat capacity, the temperature difference between the steel material and the surrounding objects is quickly reduced, and it is possible to reduce the temperature difference during slow cooling. It has good steady-state characteristics and also has the effect of reducing the amount of dummy rolled material in front of the material to be annealed compared to slow cooling by conventional methods.

[Brief explanation of drawings]

Fig. 1 is a side view showing the structure of the present invention, Fig. 2 is an enlarged sectional view taken along the line A-A of the main part of Fig. 1, Fig. 3 is a sectional view taken along the line B-B of Fig. 2, and Fig. 4 is a cross-sectional view of the cover. A chart showing the difference in the cooling rate of steel materials depending on the presence or absence and type of steel material for each size of steel material. Figure 5 is a chart showing the cooling rate of steel material depending on the presence or absence of a lower cover and its type for each size of steel material. 2: Fixed retsuhen, 3: Movable retsuhen, 4: Drive device, 5: Interlocking beam, 6, 6': Upper heat insulation cover,
7: Heat-resistant curtain, 8: Lower heat insulation cover, 9:
Black body board, 10: heat insulating material, 11: outer skin, 12: support frame, 13: support frame, 14: pin, 15: wire, 16: sheave, 17: winding drum.

Claims (1)

[Scope of Claims] 1. A retsuchen-type cooling bed in which hot-rolled steel is cooled while sequentially moving on a fixed retsuchen in a movable retsuchen that moves in a circular or elliptical manner via interlocking beams by a drive device, An upper heat insulating cover configured to be retractable is provided directly above the cooling bed, and a lower heat insulating cover covering the cooling bed is provided directly below the cooling bed, and the upper heat insulating cover and the lower heat insulating cover are made of a material with good heat absorption. It is lined with a certain black body or its approximation, and is formed by arranging a heat insulating material on the back side, the lower heat insulating cover has a small hole passing through it, and a heat resistant cover is provided between the upper heat insulating cover and the lower heat insulating cover. An annealing device in a cooling bed for hot rolled steel, characterized by a structure formed by vertically installed curtains.