Cooling method for roller hearth open flame heat treatment furnace

Abstract

The application discloses a cooling method of a roller hearth open flame heat treatment furnace, which comprises the following steps: operating the roller hearth open flame heat treatment furnace; cooling the roller hearth open flame heat treatment furnace by alternately circulating the even-numbered burners and the odd-numbered burners of a burner cooling circulation system to generate cooling alternating pulse circulation, and making the pressure of the burner cooling circulation system be 5.5KPa-7.5KPa. The cooling method of the roller hearth open flame heat treatment furnace can cool the cold air blowing in the roller hearth open flame heat treatment furnace by alternately circulating the even-numbered burners and the odd-numbered burners of the burner cooling circulation system to generate cooling alternating pulse circulation, so that the uniformity of the cooling in the furnace is good, and the cooling rate is consistent. The cooling rate is greatly improved, the process switching time of the roller hearth open flame heat treatment furnace is reduced, and the production cost is reduced.

Description

Technical Field

[0001] This application belongs to the technical field of steel processing equipment control methods, and particularly relates to a cooling method for a roller hearth open flame heat treatment furnace. Background Technology

[0002] Improving the mechanical properties of ordinary steel through heat treatment is the most direct way to achieve lightweighting and thus energy conservation and emission reduction. Roller hearth open flame heat treatment furnaces are key equipment in steel plate heat treatment production lines, highly automated, and widely favored by major steel companies.

[0003] Currently, heat treatment production lines produce a wide variety of steel grades and specifications, with varying heat treatment requirements for different steel grades, leading to frequent furnace temperature switching. Sudden component failures within the heat treatment furnace itself may also necessitate sudden shutdowns for maintenance, such as damage to the heating unit. Furthermore, if the steel plate raw material is not thoroughly shot-blasted, surface oxides and rust can accumulate on the roller bottom during heating in the heat treatment furnace, causing defects such as pits on the steel plate surface after exiting the furnace. This also requires furnace shutdown for cooling and roller grinding. Without artificial intervention for rapid cooling, the natural cooling process of the heat treatment furnace is extremely lengthy. For example, under natural cooling conditions, it takes 66 hours to reduce the temperature from 600℃ to 200℃, severely impacting the production efficiency and flexibility of the heat treatment furnace and resulting in high production costs.

[0004] Furthermore, the inconsistent cooling rates across different sections of the furnace result in poor temperature uniformity within the heat treatment furnace after cooling, significantly impacting the mechanical properties of the steel plate. Existing technology presents a method for rapid cooling in heat treatment furnaces, but this method does not control the cooling air pressure, affecting the cooling rate. Moreover, the cooling air control is singular and cannot achieve odd / even pulse control, leading to poor cooling uniformity. Furthermore, when applied to open-flame heat treatment furnaces, this method causes a continuous increase in pressure within the furnace, compromising its safety. Summary of the Invention

[0005] This application provides a cooling method for a roller hearth open flame heat treatment furnace, which can improve the cooling rate and furnace temperature uniformity of roller hearth open flame heat treatment under normal conditions, thereby improving industrial production efficiency and reducing production costs.

[0006] In a first aspect, this application provides a cooling method for a roller hearth open flame heat treatment furnace, comprising:

[0007] Operating a roller hearth open flame heat treatment furnace;

[0008] The burner cooling circulation system of the roller hearth open flame heat treatment furnace uses alternating pulse cooling cycles to cool the furnace, with the burners in even and odd positions, so that the pressure of the burner cooling circulation system is 5.5 kPa to 7.5 kPa.

[0009] In one embodiment of this application, the cooling method for a roller hearth open flame heat treatment furnace further includes:

[0010] Increase the negative pressure suction air volume in the furnace chamber of the roller hearth open flame heat treatment furnace.

[0011] In one embodiment of this application, the step of increasing the negative pressure cooling air volume of the furnace chamber of the roller hearth open flame heat treatment furnace includes raising the height of the loading and unloading furnace door of the roller hearth open flame heat treatment furnace to increase the negative pressure cooling air volume of the furnace chamber and cool the furnace chamber.

[0012] In one embodiment of this application, the cooling method for a roller hearth open flame heat treatment furnace further includes:

[0013] Increase the frequency of the exhaust fan to make the internal pressure of the roller hearth open flame heat treatment furnace lower than the external pressure. The pressure difference between the internal and external pressures of the roller hearth open flame heat treatment furnace is 5.5 Pa to 55.5 Pa.

[0014] In one embodiment of this application, the cooling method for a roller hearth open flame heat treatment furnace further includes:

[0015] The steel plate to be heat-treated is fed into a roller hearth open flame heat treatment furnace for circulating cooling.

[0016] In one embodiment of this application, the step of placing the steel plate to be heat-treated into a roller hearth open flame heat treatment furnace for circulating cooling includes heat-treating the steel plate to be treated to a size not exceeding the design dimensions of the roller hearth open flame heat treatment furnace, so as to achieve rapid heat absorption and obtain a better cooling effect.

[0017] In one embodiment of this application, the cooling method for a roller hearth open flame heat treatment furnace further includes:

[0018] The frequency of the circulating fan at the top of the roller hearth open flame heat treatment furnace is set to 35Hz to 42Hz to accelerate the turbulence of hot gas inside the furnace.

[0019] The cooling method of the roller hearth open flame heat treatment furnace in this application embodiment utilizes the alternating pulse cooling cycle of burners in even and odd positions in the burner cooling circulation system to cool the cold air blowing into the roller hearth open flame heat treatment furnace, which can achieve good uniformity of cooling in the furnace and a consistent cooling rate.

[0020] In addition, this application also accelerates cooling by drawing in a large amount of cold air through negative pressure in the roller hearth open flame heat treatment furnace; exhausting the hot air in the furnace through the exhaust fan; reducing the furnace temperature by absorbing heat from the cold steel plate to be heat treated; and rapidly reducing the furnace temperature by increasing the circulation frequency of the circulating fan to accelerate turbulence.

[0021] Compared with existing cooling technologies, the cooling method of the roller hearth open flame heat treatment furnace in this application embodiment can significantly improve the cooling rate, reduce the process changeover time of the roller hearth open flame heat treatment furnace, and lower production costs within the same time frame after treatment by the above-mentioned cooling method. Furthermore, the cooling is more uniform than that of traditional heat treatment furnaces, resulting in varying degrees of improvement in product performance and quality. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic flowchart of a cooling method for a roller hearth open flame heat treatment furnace provided in one embodiment of this application;

[0024] Figure 2 This is a comparison chart of the cooling rates of a roller hearth open flame heat treatment furnace under normal cooling mode and cooling method of the roller hearth open flame heat treatment furnace of this application.

[0025] Figure 3 This is a schematic diagram of the steel plate sampling locations for testing the properties of heat-treated steel plates in embodiments and comparative examples of this application. Figure 3 The arrow shown indicates the direction in which the steel plate moves forward during heat treatment.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1. Heat-treated steel plate; 2. Edge; 3. Middle. Detailed Implementation

[0028] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0029] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0030] To address the problems of the prior art, this application provides a cooling method for a roller hearth open flame heat treatment furnace. The cooling method for the roller hearth open flame heat treatment furnace provided in this application will be described below.

[0031] Cooling methods for roller hearth open flame heat treatment furnaces include:

[0032] Operating a roller hearth open flame heat treatment furnace;

[0033] The burner cooling circulation system of the roller hearth open flame heat treatment furnace uses alternating pulse cooling cycles to cool the furnace, with the burners in even and odd positions, so that the pressure of the burner cooling circulation system is 5.5 kPa to 7.5 kPa.

[0034] The cooling method of the roller hearth open flame heat treatment furnace in this application embodiment utilizes the alternating pulse cooling cycle of burners in even and odd positions in the burner cooling circulation system to cool the cold air blowing into the roller hearth open flame heat treatment furnace, which can achieve good uniformity of cooling in the furnace and a consistent cooling rate.

[0035] Odd and even positions refer to the burners in the roller hearth open flame heat treatment furnace being arranged in a certain order. The burners in odd and even positions are equipped with a system to cool themselves, namely the burner cooling system. The burners are alternately cooled by the odd and even burner cooling systems, which makes the temperature inside the furnace of the roller hearth open flame heat treatment furnace more uniform.

[0036] In one embodiment of this application, the step of setting the pressure of the burner cooling circulation system to 5.5 kPa to 7.5 kPa involves simultaneously turning on two exhaust fans and ensuring that their frequencies are consistent when one exhaust fan cannot meet the pressure requirement, so as to obtain the required pressure for rapid cooling of the roller hearth open flame heat treatment furnace.

[0037] When two exhaust fans are running simultaneously, it is essential to ensure that the frequencies of the two exhaust fans remain consistent to prevent the frequency converters of the fans from malfunctioning due to uneven suction.

[0038] In one embodiment of this application, the cooling method for a roller hearth open flame heat treatment furnace further includes:

[0039] Increase the negative pressure suction air volume in the furnace chamber of the roller hearth open flame heat treatment furnace.

[0040] In one embodiment of this application, the step of increasing the negative pressure cooling air volume in the furnace chamber of a roller hearth open flame heat treatment furnace includes raising the height of the loading / unloading furnace door of the roller hearth open flame heat treatment furnace to increase the negative pressure cooling air volume in the furnace chamber and cool the furnace chamber. The height of the loading / unloading door of the roller hearth open flame heat treatment furnace can be raised to a height higher than the normal operating height, up to the highest position, and the highest position.

[0041] In one embodiment of this application, the cooling method for a roller hearth open flame heat treatment furnace further includes:

[0042] Increase the frequency of the exhaust fan to make the internal pressure of the roller hearth open flame heat treatment furnace lower than the external pressure. The pressure difference between the internal and external pressures of the roller hearth open flame heat treatment furnace is 5.5 Pa to 55.5 Pa.

[0043] During normal production, the furnace pressure of a roller hearth open-flame heat treatment furnace is 0 Pa to 10 Pa. This application increases the frequency of the exhaust fans to reduce the internal pressure of the furnace to 5.5 Pa to 55.5 Pa less than the external pressure, effectively controlling the pressure difference between the internal and external atmospheric pressures to between 5.5 Pa and 55.5 Pa. This ensures that the furnace has sufficient negative pressure differential to draw in external cold air. If the power of one exhaust fan is insufficient, both exhaust fans can be turned on to ensure that the furnace pressure remains within a controllable range.

[0044] In one embodiment of this application, the cooling method for a roller hearth open flame heat treatment furnace further includes:

[0045] The steel plate to be heat-treated is placed in a roller hearth open flame heat treatment furnace for circulating cooling.

[0046] In one embodiment of this application, the step of feeding the steel plate to be heat-treated into a roller hearth open flame heat treatment furnace for circulating cooling includes heat-treating the steel plate, which does not exceed the design size of the roller hearth open flame heat treatment furnace, to achieve rapid heat absorption and obtain a better cooling effect. The size of the steel plate to be treated should be selected as large as possible to achieve the purpose of rapid heat absorption.

[0047] In one embodiment of this application, the cooling method for a roller hearth open flame heat treatment furnace further includes:

[0048] The frequency of the circulating fan at the top of the roller hearth open flame heat treatment furnace is set to 35Hz to 42Hz to accelerate the turbulence of hot gas inside the furnace.

[0049] The frequency of the circulating fan used in the furnace top in the existing technology is generally 10Hz to 20Hz. After changing it to 35Hz to 42Hz, it can accelerate the turbulence of hot gas in the furnace, thereby rapidly cooling the roller hearth open flame heat treatment furnace.

[0050] This application also accelerates cooling by drawing in a large amount of cold air under negative pressure within the roller hearth open flame heat treatment furnace; exhausting the hot air from the furnace through an exhaust fan; reducing the furnace temperature by allowing the cold steel plate to be heat-treated to absorb heat; and rapidly reducing the furnace temperature by increasing the circulation frequency of the circulating fan to accelerate turbulence. The above steps for cooling the roller hearth heat treatment furnace can be used individually or in combination.

[0051] Example

[0052] The technical solutions and advantages of this application will be further explained below through specific side embodiments.

[0053] Figure 1 A schematic flowchart of a cooling method for a roller hearth open flame heat treatment furnace according to an embodiment of this application is shown. Figure 1 As shown, the cooling methods for roller hearth open flame heat treatment furnaces include:

[0054] S1. Operating roller hearth open flame heat treatment furnace;

[0055] S2. The operator first switches the loading / unloading furnace door of the roller hearth open flame heat treatment furnace to manual mode and raises the loading / unloading furnace door to the highest position to ensure air circulation between the inside and outside of the roller hearth open flame heat treatment furnace, so as to increase the negative pressure suction air volume of the furnace and cool the furnace.

[0056] S3. On the HMI interface of the roller hearth open flame heat treatment furnace, ensure the internal pressure of the furnace is 5.5 Pa to 55.5 Pa lower than the external pressure. Specifically, increase the frequency of the exhaust fan to adjust the furnace pressure to the aforementioned value, allowing external cold air to easily enter the roller hearth open flame heat treatment furnace for cooling. If one exhaust fan cannot guarantee the aforementioned pressure difference, start the standby exhaust fan according to the above steps, setting the frequencies of the two started exhaust fans to be consistent and setting the exhaust fans to automatic operation mode, automatically adjusting the fan frequency while maintaining negative pressure. The HMI interface is the operation and control interface of the roller hearth open flame heat treatment furnace.

[0057] S4. Set the pressure of the burner cooling circulation system of the roller hearth open flame heat treatment furnace to 5.5 kPa to 7.5 kPa and set it to automatic operation. Turn on the burner cooling circulation system. During the opening process, first turn on the odd-numbered burners to cool the roller hearth open flame heat treatment furnace. After 5 minutes, switch to the even-numbered burners to cool the roller hearth open flame heat treatment furnace. The system will automatically switch at this frequency for pulse circulation. The pressure of the burner cooling circulation system is actually the pressure of the cold air from the combustion fan.

[0058] S5. Set the frequency of the circulating fan at the top of the roller hearth open flame heat treatment furnace to 35Hz~42Hz, and then make the circulating fan run automatically to accelerate the turbulence of hot air inside the roller hearth open flame heat treatment furnace and cool down the roller hearth open flame heat treatment furnace.

[0059] S6. Prepare 15 steel plates with a specification of 25*2000*1000mm to be heat-treated. According to the heat treatment time of 10 minutes in the furnace, send the steel plates to be heat-treated into the roller hearth open flame heat treatment furnace for circulating cooling.

[0060] Comparison of test data

[0061] A comparative cooling test was conducted using a roller hearth open-flame heat treatment furnace (198 meters long) from a domestic steel plant, operating under its standard mode, and comparing it with the cooling method for a roller hearth open-flame heat treatment furnace proposed in this invention. Data was collected and analyzed for rapid cooling using both the standard cooling method and the method proposed in this application. Since the heat treatment furnace has 54 zones, the average furnace temperature was used for comparison. Specific comparative data are as follows:

[0062] Table 1. Comparison of cooling data between the standard mode and the cooling method of this application.

[0063]

[0064] Plot the test data in Table 1 as a line graph, such as... Figure 2 As shown, it is obvious that the cooling method of the roller hearth open flame heat treatment furnace according to the embodiments of this application has a faster cooling rate at the beginning, and can cool down the roller hearth open flame heat treatment furnace more quickly. When the temperature drop range is 400℃-300℃ and 300℃-200℃, the cooling rate slows down, but still exceeds the cooling rate of the ordinary method. Based on the above data comparison, it can be concluded that the cooling method of the roller hearth open flame heat treatment furnace according to the embodiments of this application can cool down the roller hearth open flame heat treatment furnace more quickly.

[0065] Steel plates of grade LG960QT produced by Lianyuan Iron and Steel Group, with specifications of thickness * width * length = 10 * 2000 * 12000 mm, were subjected to rapid cooling heat treatment using both the conventional cooling method in a roller hearth open flame heat treatment furnace and the cooling method using a roller hearth open flame heat treatment furnace according to the embodiments of this application. Figure 3 The sampling locations shown are the steel plates taken from the edge and middle of the cross face for mechanical property testing. The mechanical properties of the edge and middle of the cross face are shown in Table 2 below:

[0066] Table 2. Test results of mechanical properties of the edges and middle sections of the cross face of specimens 1 and 2.

[0067]

[0068] From Table 2, we can conclude that:

[0069] After being heat-treated and cooled using conventional methods, the tensile strengths of the edge and middle of sample 1 were 990 MPa, 970 MPa, and 991 MPa, respectively, with a difference of at least 2.06% between the tensile strengths of the middle and the edge. The yield strengths of the edge and the middle were 994 MPa, 1080 MPa, and 990 MPa, respectively, with a difference of at least 0.4% between the yield strengths.

[0070] After heat treatment using the cooling method of the roller hearth open flame heat treatment furnace of the present application embodiment, the tensile strength of the edge and the middle of sample 2 were 981 MPa, 984 MPa and 985 MPa, respectively, with a maximum difference of 0.41%; the yield strengths were 1006 MPa, 1008 MPa and 1004 MPa, respectively, with a maximum difference of 0.4%.

[0071] The above experimental results show that the steel plate has more stable transverse mechanical properties after being treated by the cooling method of the roller hearth open flame heat treatment furnace of this application.

[0072] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the corresponding processes in the foregoing method embodiments can be referred to, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A cooling method for a roller hearth open flame heat treatment furnace, characterized in that, include: Operating a roller hearth open flame heat treatment furnace; The burner cooling circulation system of the roller hearth open flame heat treatment furnace is used to cool the furnace by alternating pulse cooling cycles between even-numbered and odd-numbered burners, so that the pressure of the burner cooling circulation system is 5.5 kPa to 7.5 kPa. Increase the negative pressure cooling air volume in the furnace chamber of the roller hearth open flame heat treatment furnace, including raising the height of the loading / unloading furnace door of the roller hearth open flame heat treatment furnace to increase the negative pressure cooling air volume in the furnace chamber.

2. The cooling method according to claim 1, characterized in that, Also includes: Increase the frequency of the exhaust fan to make the internal pressure of the roller hearth open flame heat treatment furnace lower than the external pressure, with a difference of 5.5 Pa to 55.5 Pa.

3. The cooling method according to claim 1, characterized in that, Also includes: The steel plate to be heat-treated is fed into a roller hearth open flame heat treatment furnace for circulating cooling.

4. The cooling method according to claim 3, characterized in that, The step of sending the steel plate to be heat-treated into the roller hearth open flame heat treatment furnace for circulating cooling includes heat-treating the steel plate to be treated to a size not exceeding the design size of the roller hearth open flame heat treatment furnace in order to quickly absorb heat and cool down.

5. The cooling method according to claim 1, characterized in that, Also includes: The frequency of the circulating fan at the top of the roller hearth open flame heat treatment furnace is set to 35Hz to 42Hz to accelerate the turbulence of hot gas inside the furnace.

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