JP2007152423A - Rake type cooling bed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling bed which is simple, the cost of equipment of which is not increased and cooling can be performed while effectively suppressing the bend of a hot-rolled steel such as a flat bar and leaf-spring material. <P>SOLUTION: In this rake type cooling bed, shield plates 7 are installed between the bearing parts 4-1 of a fixed lakes 4 and in the spaces between the bearing parts 4-1 and the bearing part 5-1 of a moving lake 5 and a thermally insulating material composed of a material the thermal conductivity of which is smaller than that of the construction material of each lake is attached to the surfaces of the fixed lakes and the moving lakes. In this cooling bed, it is desirable that the thermally insulating material is austenitic stainless steel. By this cooling bed, because even the steel which is not rotated like the flat bar and the leaf-spring material can be uniformly cooled, the generation of the bend is suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steel plate after hot rolling, that is, a Rechen type cooling bed that cools a hot steel material while conveying it. This cooling floor is particularly suitable for uniformly cooling hot steel materials having a shape that cannot be rotated during conveyance on the cooling floor, such as flat steel and leaf spring materials, and preventing the bending thereof. .

  Hot rolled steel such as flat steel and leaf spring material (hereinafter collectively referred to as hot steel) is cooled while being transported on the cooling floor, and processed through cutting, binding, inspection, etc. Become. If the steel material bends during this cooling process, the length becomes uneven when the product is cut or when the product is cut before the secondary processing. In order to avoid this, measures are taken to add a straightening process to straighten the bend or scrap the bent product.

  As described above, the bending of the hot steel material requires an extra process of correction, or causes a decrease in product yield due to scrapping. Therefore, prevention of bending in the cooling process is an important solution.

  A method for suppressing bending when a hot steel material is conveyed on a cooling floor is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 8-174037). The method is a method of transporting using a progressive chain conveyor and a reverse chain conveyor (or a fixed rail). In this method, round steel can be rotated in the form of a cooling floor, but square steel simply moves without rotating. Therefore, uniform cooling of the square steel is difficult.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 8-197129) discloses a method of slowly cooling a steel material by providing a heat insulating cover with a tropical zone on the upper and lower portions of a cooling bed. However, the installation of such a heat insulating cover requires a large facility cost, and it is also necessary to consider the temperature control in the tropical zone and the prevention of deformation due to the heat of Rechen. Therefore, this method is never practical.

JP-A-8-174037 JP-A-8-197129

  An object of the present invention is to provide a cooling bed that can be cooled while effectively suppressing the bending of a hot steel material that does not rotate, such as flat steel and leaf spring material, with a simple and inexpensive facility cost. It is in.

  The gist of the present invention is that “a shielding plate that restricts ventilation is provided in the space between the support portions of adjacent lakes, and the surface of the lake is made of a material having a lower thermal conductivity than the constituent material of the lake. It is in a “Rechen-type cooling bed” characterized in that a heat shield is attached.

  In the above cooling floor, the heat shield attached to the surface of the lake is preferably austenitic stainless steel.

  If the cooling bed of the present invention is used, uniform cooling can be realized even with a steel material such as a flat steel or a leaf spring material that does not rotate during conveyance, and the bending thereof can be reduced. According to the present invention, it is possible to reduce the incidence of defective steel materials and improve the product yield.

  In order to investigate the cause of bending after cooling of flat steel and leaf spring materials, flat steel and leaf spring materials etc. (hereinafter referred to as “products”) that have been bent after cooling. When the product with no bending was examined, it was found that the former product had non-uniform hardness in the circumferential direction of the cross section.

  FIG. 1 shows the measurement results of the hardness distribution of a SUP9 leaf spring material having a thickness of 8 mm and a width of 60 mm. The leaf spring material was cooled in a normal Rechen type cooling bed after hot rolling.

  For the product after cooling, measure the hardness (Hv) at intervals of 5 mm on the upper and lower surfaces of the leaf spring material 1 as shown in FIG. 2 at the cross section of the bent portion and the non-bent portion. did.

  FIG. 1A shows the hardness distribution of the portion where the bending occurs. The left end and the right end are positions 2 and 3 in FIG. 2, respectively. The surface (upper surface) is a surface that is not in contact with the cooling bed (Rechen), and the surface (lower surface) is a surface that is in contact with the cooling bed (Rechen). As shown in the figure, the hardness difference between the left end and the right end is large, and the hardness difference between the upper surface and the lower surface is also larger than that in FIG. In addition, the difference between the maximum hardness and the minimum hardness is remarkably large at about 60. Such unevenness in hardness is considered to be a cause of bending.

  FIG. 1B shows the hardness distribution of a portion where no bending occurs. Here, there is no significant difference in hardness between the left end and the right end, and the hardness difference between the upper surface and the lower surface is small. The difference between the maximum hardness and the minimum hardness is about 34.

  When the product is cooled while being conveyed on the cooling bed, the cooling rate is different between the lower surface that contacts the lake of the cooling bed and the upper surface that does not contact the lake. That is, the heat removal by the rake and the cooling by the air flowing in from the bottom of the cooling floor are added to the lower surface, and the cooling speed is large, and the cooling speed of the upper surface is small. Uniformity occurs.

  In addition, uneven cooling rates occur in the left and right direction of the product. This is because, as shown in FIG. 4, the left end of the product is in contact with the slope of the lake, so that it is easy to remove heat and the cooling rate increases. Furthermore, when a plurality of products are arranged and cooled, if their lengths are not uniform, there will be a difference in the radiant heat from the adjacent products at the end in the length direction. It will be different and bend.

  The uneven cooling rate as described above causes a difference in the metal structure of the product cross section, and this appears as the hardness difference shown in FIG.

  Based on the above knowledge, the present inventor has completed the present invention considering that uniform cooling of the product is essential to prevent the product from bending. Hereinafter, the structure of the cooling bed of the present invention will be specifically described with reference to the accompanying drawings.

  FIG. 3 is a view of a part of the Rechen-type cooling bed as viewed from the side. The Rechen-type cooling floor has a fixed rake 4 with notches at regular intervals and a moving rake 5 with notches at the same interval. This is a device that conveys a product 6 (for example, a bar steel or a flat steel) 6 in the notch.

  The product 6 in FIG. 3 is placed in a notch portion of the fixed rake 4. When the moving rake 5 rises, the product 6 is lifted by the moving rake 5 so as to exceed the apex of the notch portion of the fixed rake 4, and is carried toward the next notch of the fixed rake 4 (direction perpendicular to the paper surface). By repeating this process, the product is conveyed and cooled.

  When the product is conveyed on the Rechen-type cooling bed as described above, if the product has a circular cross section such as a steel bar, the product is rotated during the conveyance, so that the cooling is performed uniformly. However, if the cross section is rectangular, especially if the flatness is large, such as flat steel or leaf spring material, rotation during conveyance cannot be expected. That is, the lower surface of the product is always in contact with the surface of the rake and is conveyed in a state where it is exposed to ventilation from below. Therefore, uneven cooling rates appear in the circumferential direction of the steel material cross section, and bending occurs.

  In the cooling bed of the present invention, as shown in FIG. 3, between the support part 4-1 of the fixed lake 4 and between the support part 4-1 of the fixed lake 4 and the support part 5-1 of the moving lake 5. A ventilation shielding plate 7 is installed in the space. This shielding plate is for preventing air from flowing in from below the cooling floor and excessively cooling the lower surface of the product. Therefore, the shielding plate 7 may have a structure that blocks ventilation, and the material thereof is not particularly limited, but an inexpensive steel material such as SS400 is preferable. The thickness may be about 1 to 3 mm. The support structure of each lake may be the same as before, and the shielding plate 7 may be attached by any method that does not hinder the movement of the moving lake.

  FIG. 4 is a view showing a state in which the heat shielding material 8 is attached to the upper surface of the notch portion of the rake. The heat shielding material 8 plays a role of cutting off direct contact between the product 6 placed thereon and the rake surface and preventing excessive heat removal from the steel material to be cooled by the rake. Therefore, it is necessary to produce the heat shielding material with a material having a lower thermal conductivity than at least a lake material (usually carbon steel). Suitable materials are austenitic stainless steels such as SUS304, 316, 310, etc. The thickness is desirably 3 to 5 mm, and mounting is performed by pinning or the like. Desirably, the heat shield is attached to both the fixed and moving rake surfaces. Although not shown, it is desirable to attach a heat shield to the left inclined surface of the rake notch, but this is not essential.

  If the cooling floor comprised as mentioned above is used, even if it is a steel material which does not rotate like a flat steel or a leaf | plate spring material, the excessive cooling of the steel material lower surface by the ventilation from the cooling floor lower part can be prevented. Moreover, the excessive cooling of the steel material lower surface by directly touching a cold rake can also be prevented. As a result, the non-uniform cooling rate and the accompanying non-uniform hardness in the circumferential direction of the steel material cross section as described above are eliminated, and the bending of the steel material is reduced.

  Hereinafter, the effects of the present invention will be specifically described by way of examples.

  As shown in FIGS. 3 and 4, the leaf spring material was cooled using a Rechen type cooling floor provided with a ventilation shielding plate and a heat shielding material. The ventilation shield plate is SS400 with a thickness of 1 mm, and the heat shield is made of austenitic stainless steel (SUS304) with a thickness of 3 mm. Each was attached as shown in FIG. 3 and FIG. The leaf spring material has various sizes of SUP9 having a thickness of 7 to 41 mm and a width of 54 to 150 mm. The total number of cooling is about 200,000 corresponding to the conventional example (of which about 160,000 are those with a thickness of 9 mm or less), and the total number of cooling is about 380,000 (of which the thickness is 9 mm or less). About 340,000).

  The cooling was performed by cooling a steel material at 700 to 1020 ° C. to room temperature. For comparison, cooling by a conventional Rechen type cooling bed having no ventilation shield and heat shield was also performed.

  FIG. 5 shows the occurrence of bending. In the same figure, the case where the whole leaf spring material having cooled the “bending scrap defect rate” is used as a parameter and the case where the thickness is 9 mm or less is used as a parameter. In addition, the “bending waste defective rate” is a value that is determined as “curving occurrence” when warpage of 3 mm or more per 1 m of length occurs, and out of the number of cooled pieces, the number of bending occurrences is expressed as a percentage. is there.

  As shown in FIG. 5, when the cooling bed of the present invention is used, the “bent scrap defect rate” is conspicuously reduced. This is a result that the cooling rate of the upper and lower surfaces of the leaf spring material is substantially the same by the ventilation shielding plate and the heat shielding material, and the hardness difference in the circumferential direction of the cross section is eliminated. In particular, when the thickness is 9 mm or less, the “curved scrap defect rate” is large in the conventional cooling bed, but when the cooling bed of the present invention is used, it is remarkably lowered.

  The cooling bed of the present invention can be constructed by simply modifying an existing one. And if this cooling floor is used, even if it is steel materials, such as a flat steel and a leaf spring material which do not rotate during conveyance, uniform cooling can be realized and the bending can be reduced. Therefore, the incidence of defective products due to bending can be reduced and the product yield is greatly improved.

It is a figure which shows the hardness distribution of the cross section of the part which the bending generate | occur | produced and the part without a bending of the product cooled with the Rechen type cooling floor. It is a figure which shows the hardness measurement position of a product cross section. It is a side view of a part of the cooling floor of the present invention. It is a side view which shows the state which attached the heat shielding material to the lake surface of the cooling floor of this invention. It is a figure which shows the bent waste generation rate of the product at the time of using the cooling bed of this invention, and the conventional cooling bed.

Explanation of symbols

1: leaf spring material, 2: left edge of leaf spring material, 3: right edge of leaf spring material, 4: fixed rake,
5: Moving lake, 6: Product, 7: Ventilation shielding plate, 8: Heat shield

Claims (2)

  A shielding plate that restricts ventilation is provided in the space between the adjacent lake support parts, and a heat shielding material made of a material having a lower thermal conductivity than the constituent material of the lake is attached to the surface of the lake. Rechen type cooling floor characterized by The Rechen-type cooling bed according to claim 1, wherein the heat shielding material attached to the surface of the lake is austenitic stainless steel.

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