JPH07224326A - Water cooling method and equipment after heat treatment of stainless steel channel steel - Google Patents

Abstract

(57) [Summary] [Purpose] Elimination of cooling strain that is seen in water cooling of stainless steel channel steel after heat treatment. [Structure] In the cooling zone provided continuously to the continuous heat treatment apparatus, the web portion of stainless steel channel steel is located on the lower surface and the tip of the flange portion is located on the upper surface to form a pool of cooling water in the groove portion of the channel steel. Cool with water.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a water cooling method and apparatus after heat treatment of stainless steel channel steel. In particular, the present invention relates to a method and a device for easily and inexpensively improving the accuracy of a product shape.

[0002]

2. Description of the Related Art Recently, stainless steel has come to be used in a wide range of industrial fields, and in particular, for structural steel, the demand for structural materials has been increasing due to the trend of approval for structural materials. . In particular, the use of stainless steel channel steel is expanding as a structural material for large-scale plants, and in the future, it is required to improve the accuracy of its size and shape.

By the way, stainless steel is usually its composition,
Various heat treatments are performed according to the type and application. For example, in the case of a general hot-rolled material of 18-8 series stainless steel, the original characteristics are impaired due to the formation of the rolling structure by hot rolling, so that the structure is generally returned to a normal structure by heat treatment.

Regarding the water cooling condition among the heat treatment conditions, in the case of the above-mentioned 18-8 series stainless steel, rapid water cooling is required to maintain the austenite structure, and as a method therefor, water tank cooling, spray cooling and the like are performed.

In this water-cooling process, the cooling rate is different depending on the product cross-sectional shape and the product length, so that cooling distortion occurs. This is particularly likely to occur when the cross-sectional shape is asymmetric, when the plate thickness is partially different, or when the shape is complicated.

[0006] In the case of cooling in a water tank, the outer layer of steel cools sharply at the time of charging, but there are problems such as slow cooling of the central part of the steel where the surroundings of cold water are slow, and distortion is likely to occur.
Spray cooling is considered in order to control this cooling distortion and is suitable for line operation, and is widely used especially in continuous heat treatment equipment.

However, in the spray method, it is difficult to secure the amount of cooling water, and it is difficult to perform uniform rapid cooling because of restrictions on installation of the spray. Shaped steels, especially grooved steels in particular, cause variations in the contacting of cooling water with the simple spray method, and the original product shape is greatly impaired by cooling distortion, causing problems in the post-correction process. It was easy to do.

[0008]

In the case of stainless steel channel steel, the cross-sectional shape is three sides (two sides for angle steel) and multiple sides, and the coefficient of linear expansion is high, so that the cooling strain is constant. do not do. This distortion can be corrected by using multiple stages of rollers in the next step, but if the distortion is large, it will have a large effect on both the equipment scale and work standards, and a single correction will make the web,
In some cases, the flange may be wavy, bent, or twisted and may not meet the specifications. In this case, re-correction is required, which may result in defective scraps, which causes a cost increase.

It is an object of the present invention to improve the accuracy of the product shape of water-cooled stainless steel channel steel after heat treatment, and reduce the cooling distortion to reduce the need for straightening in the next step. (EN) It is intended to provide a water cooling method after heat treatment of stainless steel channel steel and a device therefor which can be produced at the lowest possible cost and at a low cost.

[0010]

DISCLOSURE OF THE INVENTION As a result of studying spray cooling conditions after heat treatment of stainless steel channel steel, the present inventors have found that cooling water pools are generated in the channel portion of channel steel to cool it. It was found that a large amount of cooling water can be brought into contact with the inner surface of the channel steel, and cooling strain is reduced.

Here, the gist of the present invention is that the web portion of stainless steel channel steel is located on the lower surface and the tip of the flange portion is located on the upper surface in the cooling zone provided continuously to the continuous heat treatment apparatus. This is a water cooling method after heat treatment of stainless steel channel steel, which is performed by forming a pool of cooling water in the channel portion of the channel steel.

[0012] From still another aspect, the present invention is a water cooling device provided in a cooling zone following a continuous heat treatment device for stainless steel channel steel, comprising a plurality of water cooling devices provided along a channel steel moving direction. A water cooling device comprising a nozzle and a high pressure air nozzle that is provided upstream and downstream with respect to the direction of movement of the channel steel of the water cooling nozzle and that causes a pool of cooling water in the groove portion of the channel steel. is there.

[0013]

Next, the apparatus and method of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic explanatory view showing one example of a water cooling device according to the present invention, and FIG. 2 is a- of FIG.
It is an a'sectional view.

In the figure, a water cooling device 10 of the present invention provided in a cooling zone following the outlet of a continuous heat treatment furnace 22 comprises a plurality of water cooling nozzles 1 located at the center and a water cooling pipe 2 for supplying water to the water cooling nozzles. I have it. In the illustrated example, five water-cooling pipes 2 are arranged from above the channel steel in the water-cooling zone, three below the channel steel, and between the transport rollers 21, and the upper portion is increased to secure the amount of water. The direction of the water-cooling nozzle 1 is inclined so that it is concentrated in the center.

Further, the water-cooling device 10 of the present invention comprises a first high-pressure air nozzle 3a for preventing backflow of cooling water to the continuous heat treatment furnace 22 upstream of the steel moving direction of the water-cooling nozzle 1 and cooling in the traveling direction downstream thereof. A second high-pressure air nozzle 3b for preventing water outflow and high-pressure air pipes 4a and 4b for supplying air to the first and second high-pressure air nozzles, respectively.

Each high-pressure air nozzle has its jetting direction inclined toward the water-cooling zone (water-cooling nozzle) by an angle indicated by θ in order to improve the efficiency of generation of a pool of cooling water.

In the water cooling method of the present invention, the channel steel 11
Arranges the web portion 12 on the lower side and the flange portion 13 on the upper side. Moreover, the direction of the water cooling nozzle 1 and the directions of the first and second high pressure air nozzles 3a and 3b are inclined so that water easily collects in the upper portion of the web portion 12. Therefore, the inside of the groove is water-cooled while water is accumulated on the upper portion of the web portion 12.

As described above, even if the inner surface of the channel steel, which is liable to be insufficient in cooling water in the conventional simple spray method, can be brought into contact with a large amount of cooling water by forming a pool of water, and uniform and rapid cooling is possible. .

The lower surface (web) and the side surface (flange) are water-cooled from the outside by a water-cooling nozzle in which the angle of spraying is set so that the corners come to the center. The present invention will be described below based on specific numerical values.
This is merely an example of preferable numerical values, and the present invention is not limited to specific cooling conditions as long as cooling with distortion as small as possible is performed.

In the actual operation, the important points are the amount of cooling water and the air pressure, and the amount of water from the water cooling nozzle depends on the specific shape of the shaped steel, the wall thickness, etc. 20-25 liters from the top, from the bottom
7 to 8 liters is preferable, and if it is less than this, the cooling rate becomes slow and thermal strain is likely to occur, and if it exceeds this, it is not preferable from the viewpoint of partial strain generation due to reverse flow of water to the continuous heat treatment furnace and water unit.

Specifically, the air pressure from the high-pressure air nozzle is preferably ²⁰ to 50 kgf / cm ² , and if it is less than this, partial strain may occur due to reverse flow of water into the continuous heat treatment furnace. If it exceeds the range, distortion may occur due to local air cooling.

Specifically, the angle of the first and second high pressure air nozzles shown as θ in FIG. 1 is preferably 20 to 45 ° from the vertical plane, and if the angle is less than or equal to this, the water blocking effect is lowered and Accumulation is less likely to occur. Regarding the number of water cooling nozzles, the upper water cooling nozzle is preferably 17 to 20 per channel steel, and the lower water cooling nozzle is preferably 6 to 10 per channel steel.

Cooling Distortion When a metal material is heated and cooled with water, cooling distortion (bending, twisting, etc.) occurs for each lot, for the following reason.

(I) In each part of the cross-sectional shape, cooling speed and shrinkage difference occur due to the difference in shape and wall thickness. (Ii) In the water cooling process, water cooling is not necessarily uniform not only in the cross-sectional direction but also in the longitudinal direction. In the present invention, the temperature difference is minimized and the strain is reduced by quenching as described below.

(1) By concentrating the water cooling nozzles as much as possible, the effect of cooling to room temperature in a short time is improved. (2) In order to promote (1), a nozzle is placed directly above the thin steel that is the material to be cooled, and the amount of water is secured. (3) Further, the water flowing out along the groove is held at a high pressure in the water cooling zone by the air nozzle.

(4) The air pressure is increased by increasing the air pressure from the upstream high-pressure air nozzle to prevent the cooling water from flowing in the direction opposite to the steel moving direction and flowing back into the furnace. The air pressure from the downstream high-pressure air nozzle is set to be slightly lower so that the pool flows in the line direction.

By concentrating and strengthening the water cooling zone as described above, the temperature gradient in the longitudinal direction of the treated material becomes sharp, the intermediate temperature range is narrowed, and the uneven strain during this period is reduced.

Further, the scattering area of water droplets is also narrowed by the effect of air, so that it is possible to prevent local cooling and prevent partial waving distortion. Next, the operation of the present invention will be described in more detail with reference to Examples.

[0029]

EXAMPLE A water cooling test was performed on stainless steel channel steel after heat treatment using the water cooling apparatus shown in FIG. The steel types, shapes, and cooling conditions used in this example are as follows.

1. Steel type, dimensions (common to working examples and conventional examples) SUS304, channel steel 6 × 50 × 100 (mm) × 6 m 2. Heat treatment temperature: 1050 to 1150 ° C. (common to working examples and conventional examples) 3 . the present invention cooling conditions pressure = 3.5 kg / cm ² for example, water = 33 liters / steel 1Kg air pressure = 20 to 50 kg / cm ² (nozzle 3a = 50 kg / cm ^2, the nozzle
3b = 30kg / cm ² ) 4. Cooling condition of conventional example Water pressure = 3.5 kg / cm ² , without air supply.

The product shape after water cooling and the product shape after straightening in the case of being water cooled by the method of the present invention and the case of being water cooled by the conventional method were compared. However, the heat treatment and the straightening device are performed under the same conditions, and the main specifications are diameter 300 (mm) ×
7-step roller straightening was used.

The results are summarized in Table 1.

As shown in Table 1, a clear difference was found in the occurrence of strain, and in the conventional example, the necessity of re-correction due to a defective shape after correction occurred, but it was solved in the example of the present invention. Of course, even in the conventional example, a part of the solution can be achieved by increasing the capacity of the straightening equipment (roller diameter and number of roller steps), but according to the present invention, it is obvious that this problem can be solved without significantly increasing the equipment capacity. .

[0034]

[Table 1]

[0035]

As described above, according to the present invention,
With a simple means, it is possible to reduce the occurrence of cooling distortion that is observed during water cooling of stainless steel channel steel, to substantially eliminate the burden of the straightening process, and to improve the product shape.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an example of a cooling device according to the present invention.

FIG. 2 is a sectional view taken along the line a-a ′ of FIG.

[Explanation of symbols]

1: Water cooling nozzle 2: Water cooling pipe 3a: High pressure air nozzle (upstream side) 3b: High pressure air nozzle (downstream side) 4a: High pressure air pipe (upstream side) 4b: High pressure air pipe (downstream side) 10: Water cooling of the present invention Device 11: Channel steel 12: Web 13: Flange 21: Conveyor roller 22: Continuous heat treatment furnace

Claims (2)

[Claims] 1. A cooling zone continuously provided in a continuous heat treatment apparatus, wherein the web portion of stainless steel channel steel is located on the lower surface and the tip of the flange portion is located on the upper surface, and cooling water pools are placed in the groove portions of the channel steel. Water cooling method after heat treatment of stainless steel channel steel. 2. A water cooling device provided in a cooling zone following a continuous heat treatment device for stainless steel channel steel, comprising a plurality of water cooling nozzles provided along a channel steel moving direction, and the grooves of the water cooling nozzle. A water cooling device comprising: a high-pressure air nozzle, which is provided upstream and downstream with respect to the moving direction of the shaped steel, and which creates a pool of cooling water in the groove portion of the grooved steel.