A system for inhibiting the formation of surface iron oxide scale on a slab

Abstract

The utility model discloses a system of inhibiting the generation of the surface scale of the slab, including two cold room, and the direction of each of two cold room's out of the blank mouth is provided with the series of multiple pull straightening machine, wherein, the slab sent from two cold room is in turn through each pull straightening machine, and the import of each pull straightening machine is provided with the shower nozzle, and the shower nozzle is towards the slab and is used to spray water to the slab, the utility model discloses through adding the shower nozzle before the pull straightening machine import, can spray water cooling to the slab, thereby control the temperature -rising speed of the slab, inhibit the generation amount of the surface scale of the slab, to avoid the cutting device cutting process and produce " tempering", improve automatic cutting success rate.

Description

Technical Field

[0001] This utility model belongs to the field of continuous casting technology in iron and steel metallurgy, and particularly relates to a system for suppressing the formation of iron oxide scale on the surface of slabs. Background Technology

[0002] In the continuous casting process of steelmaking, the billet is initially solidified in the crystallizer to form a slab. After being forcibly cooled in the secondary cooling chamber, the slab enters the straightening machine for straightening and is finally cut into slabs of predetermined specifications.

[0003] However, iron oxide scale is easily generated on the surface of the slab during the process of being sent from the secondary cooling chamber to the cutting device. When the iron oxide scale is thick, it will cause "tempering" during the cutting process, resulting in the failure of automatic cutting by the cutting device and requiring manual cutting, which greatly reduces production efficiency. Utility Model Content

[0004] The purpose of this invention is to provide a system for suppressing the formation of iron oxide scale on the surface of slabs, thereby reducing the amount of iron oxide scale generated on the surface of slabs.

[0005] The present invention adopts the following technical solution: a system for suppressing the generation of iron oxide scale on the surface of slabs, comprising a secondary cooling chamber, wherein multiple straightening machines are connected in series in each direction of the billet outlet of the secondary cooling chamber; wherein the slabs sent out from the secondary cooling chamber pass through each straightening machine in sequence;

[0006] Each straightening machine is equipped with a nozzle at its inlet, which is directed toward the slab and used to spray water onto it.

[0007] Furthermore, the nozzle is located above the slab, and the water mist sprayed from the nozzle covers the slab in the width direction.

[0008] Furthermore, the distance between the nozzle and the slab is proportional to the width of the slab.

[0009] Furthermore, a temperature measuring device is installed at the entrance of each tension leveling machine.

[0010] Furthermore, the temperature measuring device is oriented towards the upper surface of the slab and is used to measure the temperature of the upper surface.

[0011] Furthermore, all temperature measuring devices are connected to a controller, which is also connected to a regulating valve, which is installed on the pipeline connected to the nozzle downstream of the temperature measuring device.

[0012] The beneficial effects of this utility model are: by adding a nozzle before the inlet of the straightening machine, water can be sprayed onto the slab to cool it down, thereby controlling the slab's reheating rate and suppressing the amount of iron oxide scale generated on the slab surface, so as to avoid "backfire" during the cutting process of the cutting device and improve the success rate of automatic cutting. Attached Figure Description

[0013] Figure 1 This is a side view of a system for suppressing the formation of iron oxide scale on the surface of a slab, according to an embodiment of the present invention.

[0014] Figure 2 This is a top view schematic diagram of a system for suppressing the formation of iron oxide scale on the surface of a slab, according to an embodiment of the present invention.

[0015] Among them: 10. Slab; 20. Straightening machine; 30. Secondary cooling chamber; 40. Nozzle. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] During the straightening process of slabs, the formation of iron oxide scale originates from the secondary oxidation of the high-temperature slabs exposed to air. First, the iron on the surface of the slab is oxidized to FeO (dominated by high temperature), and then Fe3O4 and Fe2O3 are gradually generated as the slabs cool. Iron oxide scale can easily lead to defects on the surface of the slab.

[0018] Therefore, it can be seen that excessively rapid cooling will exacerbate oxidation. On the one hand, the heat conduction in the core of the slab 10 after the rapid cooling of the inner surface of the secondary cooling chamber 30 leads to "warming up", which prolongs the high-temperature oxidation time; on the other hand, the atomic oxygen ([O]) generated by the vaporization of cooling water accelerates the reaction. After an oxide layer is formed on the surface of the slab, the uneven shrinkage of the oxide layer and the slab matrix forms microcracks, which further promotes oxygen penetration.

[0019] This utility model discloses a system for suppressing the formation of iron oxide scale on the surface of slabs, such as... Figure 1 and Figure 2 As shown, the system includes a secondary cooling chamber 30, and multiple straightening machines 20 arranged in series are provided in each outlet direction of the secondary cooling chamber 30. The slab 10 sent out from the secondary cooling chamber 30 passes through each straightening machine 20 in sequence. Each straightening machine 20 is provided with a nozzle 40 at its inlet, which faces the slab 10 and is used to spray water onto the slab 10.

[0020] In this embodiment, the secondary cooling chamber 30 refers to the secondary cooling chamber in the continuous casting process. Its main function is to spray water to cool the high-temperature slab pulled from the crystallizer, while sealing off the steam to prevent water vapor from overflowing and affecting the operating environment. Typically, each secondary cooling chamber 30 outputs multiple streams of slabs 10, and each stream of slabs 10 passes through multiple straightening machines 20 in sequence.

[0021] The full name of the 20-ton stretching and bending straightening machine is also known as the billet straightening machine or scale breaking machine. It is a key piece of equipment in the continuous casting and cold / hot rolling strip steel processing line of steel. It is mainly used to stretch and straighten the billet or strip steel to eliminate defects such as waviness, wavy, longitudinal bending, and transverse bending, and to ensure that the plate shape is flat and the quality meets the standards.

[0022] Because slab 10 typically has a certain thickness and width, the reheating rate of slab 10 output from the secondary cooling chamber 30 is relatively high, usually exceeding 100℃ / m, resulting in the formation of iron oxide scale on the surface, with a production amount reaching 1.6Kg / t. This not only directly affects the steel consumption index but also has a certain impact on the next process, increasing the labor cost of slag removal during maintenance.

[0023] Based on this, the present invention adds a nozzle 40, which is located above the slab 10, and the water mist sprayed by the nozzle 40 covers the slab 10 in the width direction. This allows the nozzle 40 to spray water to cool the slab 10, and because the nozzle 40 has a large coverage area, it can achieve a better surface cooling effect and prevent the surface of the slab 10 from warming up too quickly.

[0024] In addition, the distance between the nozzle 40 and the slab 10 is proportional to the width of the slab 10. Therefore, the distance between the nozzle 40 and the slab 10 can be adjusted according to the size of the slab 10 to increase its spray range. At the same time, the water pressure in the water pipe can be increased appropriately to further ensure the cooling effect.

[0025] In one embodiment, a temperature measuring device is provided at the inlet of each straightening machine 20. The surface temperature of the slab 10 can be measured by the temperature measuring device. By comparing the detected temperature with the temperature detected by the previous temperature measuring device, if the temperature recovery rate is less than a predetermined threshold, the next nozzle 40 can be left unactivated. If the temperature recovery rate is greater than or equal to the predetermined threshold, the next nozzle 40 needs to be activated to spray water for cooling.

[0026] Typically, to ensure more accurate temperature measurements, the temperature measuring device is positioned facing the upper surface of the slab 10 and is used to measure the temperature of the upper surface. Furthermore, to prevent water spray from the nozzle 40 from interfering with the normal operation of the temperature measuring device, a waterproof cover can be added around the device (especially at the top).

[0027] More specifically, the temperature measuring devices are all connected to the controller, which is in turn connected to the regulating valve, which is installed on the pipeline downstream of the temperature measuring device where the nozzle is connected. With this setup, the water spray volume of the nozzle 40 can be adjusted according to the temperature measuring structure of the temperature measuring device.

[0028] In one embodiment, after the billet exits the secondary cooling chamber 30 and enters the continuous casting straightening machine area, nozzles 40 are added at specific positions on stands 1#, 2#, 3#, and 4#. In order to control the surface temperature of the billet within a reasonable range, each nozzle 40 draws water from the main pipe of the secondary cooling chamber 30 and distributes it to each stream. On the wide face of the billet in the straightening area, multiple sets of nozzles 40 are installed in sequence for each stream to control the temperature recovery of the red billet. In this embodiment, the distance between two nozzles 40 is designed to be 1.5m. After implementation, six points were selected in the straightening area for temperature measurement (point ① was located at the inlet of the first straightening machine 20, point ② at the inlet of the second straightening machine 20, point ③ at the inlet of the third straightening machine 20, point ④ at the outlet of the third straightening machine 20, point ⑤ at the inlet of the fourth straightening machine 20, and point ⑥ at the outlet of the fourth straightening machine 20; because the third and fourth straightening machines in the workshop are far apart, there are temperature measurement points at the inlet and outlet of the third and fourth straightening machines). The measured temperatures were ① 962℃, ② 975℃, ③ 968℃, ④ 940℃, ⑤ 910℃, and ⑥ 902℃, respectively. This shows that the slab temperature was stably controlled within a reasonable linear range (e.g., less than or equal to 50℃ / m).

[0029] Therefore, the system of this invention can control the cooling rate while preventing the billet from reheating and causing the surface temperature of the billet to rise, resulting in the formation of iron oxide scale.

[0030] Furthermore, this method was applied to slabs produced on the No. 2 continuous casting machine in the rolling mill. The slab specifications were 165×355-575 mm. Before installing the nozzle, a 7.9-meter-long slab was hoisted out and allowed to cool. After cooling, all the iron oxide scale on the slab surface was cleaned off and weighed. The measurement showed that the iron oxide scale was approximately 1.6 kg / t of steel. Using the same measurement method, after installing and using the nozzle, a 7.9-meter-long slab of the same specifications was measured, and the iron oxide scale was found to be 1.0 kg / t of steel, resulting in a reduction of 0.6 kg / t in iron oxide scale production. Therefore, this method significantly reduces the generation of iron oxide scale.

[0031] In summary, this invention controls the temperature drop of the billet in the straightening zone, keeping it below 50°C per meter. This method reduces the formation of iron oxide scale on the billet surface by 60%, and lowers cutting losses by 15% (e.g., losses due to increased kerf width). By suppressing secondary oxidation, the surface quality pass rate is increased to 98%, improving production efficiency, reducing cutting losses, and increasing the billet cutting rate by 10% (i.e., cutting success rate). Only simple cooling nozzles need to be installed at suitable locations on the existing straightening machine; no additional large equipment is required.

Claims

1. A system for suppressing the formation of iron oxide scale on the surface of a slab, characterized in that, The system includes a second cooling chamber (30), and each of the two cooling chambers (30) is equipped with multiple straightening machines (20) connected in series in the direction of each billet outlet; wherein the billet (10) sent out from the second cooling chamber (30) passes through each straightening machine (20) in sequence. Each of the tension leveling machines (20) is provided with a nozzle (40) at its inlet, the nozzle (40) being directed toward the slab (10) and used to spray water onto the slab (10); The nozzle (40) is located above the slab (10), and the water mist sprayed by the nozzle (40) covers the slab (10) in the width direction.

2. The system for suppressing the formation of iron oxide scale on the surface of a slab as described in claim 1, characterized in that, The distance between the nozzle (40) and the slab (10) is proportional to the width of the slab (10).

3. A system for suppressing the formation of iron oxide scale on the surface of a slab as described in claim 1 or 2, characterized in that, A temperature measuring device is provided at the entrance of each of the aforementioned straightening machines (20).

4. The system for suppressing the formation of iron oxide scale on the surface of a slab as described in claim 3, characterized in that, The temperature measuring device is oriented toward the upper surface of the slab (10) and is used to measure the temperature of the upper surface.

5. The system for suppressing the formation of iron oxide scale on the surface of a slab as described in claim 4, characterized in that, The temperature measuring devices are all connected to a controller, which is also connected to a regulating valve. The regulating valve is installed on the pipeline connected to the nozzle downstream of the temperature measuring device.

Images