Control method for reducing oxidation burning loss of double-heat-storage walking beam furnace
By optimizing temperature control, combustion atmosphere and heating time in a dual-heat storage stepper heating furnace, the problem of oxidation and burning loss in steel rolling production is solved, and the effect of reducing oxidation and burning loss rate and improving production efficiency is achieved.
Patent Information
- Application Number
- CN202411516299.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-29
- Publication Date
- 2025-02-11
AI Technical Summary
Double heat storage stepper heating furnaces will inevitably face oxidation and burning problems in steel rolling production, resulting in an oxide layer forming on the surface of the steel, affecting product quality and increasing energy consumption.
By controlling the furnace temperature, adjusting the combustion atmosphere and heating time, specific measures include: controlling the temperature ranges of different heating sections, optimizing the CO content and flue gas residual oxygen content in the mixed gas, adjusting the empty coal ratio, and distinguishing between hot and cool blanks heating time.
It effectively reduces the oxidation burn rate from 0.8% to 0.5%, extends the cleaning interval of heating slag, reduces gas consumption, and improves production efficiency and product quality.
Smart Images
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Figure BDA0005106779990000051
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of double-heat storage walking beam heating furnaces, and in particular relates to a control method for reducing oxidation and burning loss of a double-heat storage walking beam heating furnace. Background Art
[0002] The double heat storage walking beam heating furnace is a steel heat treatment industrial equipment that combines a double heat storage system and walking beam heating. The double heat storage walking beam heating furnace effectively reduces fuel consumption and carbon emissions by recovering flue gas waste heat and storing it in the heat storage body; it also ensures uniform heating, optimizes temperature control, prevents overheating or underheating, and improves product quality by moving materials step by step.
[0003] When producing plain carbon steel Q235B, the double regenerative walking beam heating furnace will inevitably face the problem of oxidation and burning. Oxidation and burning in steel rolling production refers to a metal loss phenomenon that occurs during high-temperature heating and rolling of steel. When the steel is exposed to a high temperature environment in the heating furnace or during the rolling process, its surface will react chemically with the oxygen in the air to form iron oxide. This process not only causes a rust-like oxide layer to form on the surface of the steel, but also causes weight loss of the material, affecting the surface quality of the product. The degree of oxidation and burning is affected by many factors, including heating temperature, duration, oxygen content in the air, and the composition of the steel itself.
[0004] Oxidation burning is a common technical problem that is common in all heating furnaces. Because as long as steel is in contact with oxygen-containing atmosphere at high temperature, oxidation reaction will inevitably occur. Oxidation burning causes many harms to the steel heating production process, including: First, due to the oxidation of the steel surface, iron scale falls off, which directly leads to weight loss of the slab, reduces the yield rate, and causes waste of raw materials; secondly, the oxidation process increases heat consumption, resulting in increased gas consumption and increased energy costs; thirdly, the shed iron oxide scale accumulates at the bottom of the furnace, and the slag needs to be cleaned frequently, which not only increases the maintenance workload, but also affects the normal production rhythm; finally, the presence of iron oxide scale affects the uniform heating of steel, causing uneven temperature distribution, thus affecting product quality.
[0005] Therefore, there is an urgent need for a method to reduce oxidation and burning loss in large slab heating furnaces. Summary of the invention
[0006] The object of the present invention is to provide a control method for reducing oxidation and burning of a double-regenerative walking beam heating furnace, so as to solve the technical problem of oxidation and burning in steel rolling production proposed in the above background technology.
[0007] In order to achieve the above object, the present invention provides the following technical solutions:
[0008] A control method for reducing oxidation and burning loss of a double heat storage walking beam heating furnace, comprising:
[0009] According to the slab rolling specifications, the furnace temperature is controlled, the temperature of the first heating section is controlled at 1000℃~1050℃, the temperature of the second heating section is controlled at 1150℃~1200℃, the temperature of the third heating section is controlled at 1250℃~1300℃, and the soaking temperature is controlled at 1250℃~1280℃; this helps to heat the slab evenly and reduce oxidation and burning caused by uneven temperature;
[0010] Controlling the CO content in the high-speed mixed gas to 26% to 32% can ensure a proper reducing atmosphere; controlling the residual oxygen content in the flue gas to less than 8% can reduce the occurrence of oxidation reactions. The combination of these two parameters can effectively inhibit oxidation and burning.
[0011] Control the air-coal ratio of the first heating section to 0.8-0.95, the air-coal ratio of the second heating section to 0.8-0.95, the air-coal ratio of the third heating section to 0.9-1.0, and the air-coal ratio of the equalizing section to 0.8-0.9; control the atmosphere in the furnace, reduce oxidation and burning losses, and optimize combustion efficiency.
[0012] Cold billets and hot billets are loaded into the furnace separately. The time of hot billets in the furnace is controlled at 120 minutes to 140 minutes, and the time of cold billets in the furnace is controlled at 160 minutes to 180 minutes. Differentiate the heating time of hot billets and cold billets to avoid unnecessary oxidation and burning caused by too long heating time. Ensure that billets at different temperatures can achieve the appropriate heating effect
[0013] Preferably, the slab rolling specifications include above 3.0 mm and below 3.0 mm; different temperature control strategies are adopted for different thicknesses.
[0014] Preferably, when the slab rolling specification is above 3.0 mm, the furnace temperature is controlled according to the lower limit to avoid overheating.
[0015] Preferably, when the slab specification is below 3.0 mm, the upper limit of the furnace temperature is controlled to ensure sufficient heating.
[0016] Preferably, the temperature of the first heating section is 1000°C or 1050°C, the temperature of the second heating section is 1150°C or 1200°C, the temperature of the third heating section is 1250°C or 1300°C, and the soaking temperature is 1250°C or 1280°C.
[0017] Preferably, the CO content in the high-speed mixed coal gas is 26% or 32%.
[0018] Preferably, the air-coal ratio of the first heating section is 0.8 or 0.95, the air-coal ratio of the second heating section is 0.8 or 0.95, the air-coal ratio of the third heating section is 0.9 or 1.0, and the air-coal ratio of the equalizing section is 0.8 or 0.9.
[0019] Preferably, the hot billet is kept in the furnace for 120 minutes or 140 minutes, and the cool billet is kept in the furnace for 160 minutes or 180 minutes.
[0020] Preferably, a slab temperature greater than 500°C is a hot slab, and a slab temperature less than 500°C is a cold slab; avoiding mixing hot and cold slabs can ensure the stability of the heating process and facilitate precise control of the heating time and temperature.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] The present invention provides a control method for reducing oxidation and burning of a double heat storage walking beam heating furnace, which solves the technical problem of oxidation and burning in steel rolling production. By rationally optimizing the key parameters in the combustion process, the present application greatly reduces the adverse effects of oxidation and burning, and improves the overall production efficiency and product quality.
[0023] The present invention achieves precise control of the heating process and avoids oxidation and burning caused by overheating by precisely controlling the temperature ranges of different heating sections (1st heating section 1000-1050°C, 2nd heating section 1150-1200°C, 3rd heating section 1250-1300°C, soaking section 1250-1280°C), and adopts different temperature control strategies according to the slab specifications (with 3.0mm as the boundary). The present invention creates a suitable heating environment and reduces the occurrence of oxidation reaction by controlling the atmosphere in the furnace, including the CO content of the mixed coal gas (26%-32%), the residual oxygen content of the flue gas (<8%), and the air-coal ratio of each heating section. The present invention distinguishes between hot billets (>500°C) and cold billets (<500°C) and adopts different furnace time controls (120-140 minutes for hot billets and 160-180 minutes for cold billets), and avoids mixing hot and cold billets, thereby optimizing the heating time, ensuring the heating quality, and avoiding overheating.
[0024] Through the comprehensive application of the above technical means, the present invention not only effectively reduces the oxidation loss from 0.8% to 0.5%, and extends the cleaning interval of the heating slag from six months to eight months, but also reduces the gas consumption, improves the production efficiency and product quality, and ultimately achieves the purpose of reducing costs and increasing efficiency. DETAILED DESCRIPTION
[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.
[0026] A control method for reducing oxidation and burning loss of a double heat storage walking beam heating furnace, comprising:
[0027] According to the rolling specifications of the slab, the furnace temperature is controlled, the temperature of the first heating section is controlled at 1000℃~1050℃, the temperature of the second heating section is controlled at 1150℃~1200℃, the temperature of the third heating section is controlled at 1250℃~1300℃, and the ambulating temperature is controlled at 1250℃~1280℃.
[0028] Specifically, the main purpose of the first heating section is to heat the slab from room temperature or starting temperature to a higher temperature to start initial uniform heating; through this heating section, the slab obtains sufficient heat energy to reduce the temperature difference between its surface and interior in the subsequent stages. The temperature of the first heating section is controlled at 1000℃~1050℃. This temperature range is to ensure that the slab can effectively absorb heat energy without overheating or early oxidation on the surface and near the surface. Too high initial temperature may cause the surface oxide scale to thicken or micro cracks to appear on the material surface.
[0029] The main purpose of the second heating section is to continue to increase the temperature of the slab and promote the anisotropic phase transformation process in the steel, such as the transformation to the austenite phase. The temperature of the second heating section is controlled at 1150℃~1200℃. This temperature range provides sufficient energy for the material to reduce the resistance to plastic deformation and make the slab easier for subsequent plastic rolling operations. Similarly, temperatures higher than this may quickly lead to local overheating and oxidation, while temperatures lower than this may not be fully heated.
[0030] The main purpose of the three heating sections is to heat the slab to a temperature close to or reaching plastic deformation, so as to provide efficient rolling deformation capacity for the subsequent rolling. The temperature of the three heating sections is controlled at 1250℃~1300℃. Within this temperature range, the plasticity of the steel is greatly enhanced, the flow stress is reduced, and the deformation force required for rolling is minimized. This enables smooth large deformation rolling and improves the microstructure inside the metal. For example, it promotes grain refinement.
[0031] The main purpose of the soaking section is to provide sufficient time to ensure that the temperature is uniform throughout the cross section of the slab, thereby eliminating the temperature difference between the inside and outside and harmful stress concentration. The soaking temperature is controlled at 1250℃~1280℃. Maintaining it in this temperature range can eliminate the inhomogeneity of the microstructure and improve the overall mechanical properties and ductility of the material.
[0032] The slab rolling specification is divided by 3.0mm. When the slab rolling specification is above 3.0mm, it is controlled according to the lower limit of the furnace temperature; when the slab specification is below 3.0mm, it is controlled according to the upper limit of the furnace temperature. Thick plates require longer time to conduct heat from the surface to the core, so lower temperatures are required at the beginning to slowly accumulate heat to avoid surface problems; thin plates respond to temperature changes more quickly, and high temperatures are set at each stage to optimize time and energy efficiency.
[0033] That is, the rolling specification is 4.0mm, the furnace temperature is controlled, the first heating temperature is 1000℃~1010℃, the second heating temperature is 1150℃~1060℃, the third heating temperature is 1250℃~1260℃, and the average heating temperature is 1250℃~1260℃; the rolling specification is 2.8mm, the furnace temperature is controlled, the first heating temperature is 1050℃, the second heating temperature is 1190℃~1200℃, the third heating temperature is 1290℃~1300℃, and the average heating temperature is 1270℃~1280℃.
[0034] Control the CO content of high-speed mixed gas to 26% to 32%, and control the residual oxygen content of flue gas to less than 8%;
[0035] Specifically, during the slab heating process, the CO content of the high-speed mixed coal gas and the residual oxygen content of the flue gas are important factors affecting the heating efficiency and quality.
[0036] CO (carbon monoxide) is an important component of heat energy generated during the combustion process. Controlling the appropriate CO content range can ensure sufficient and efficient combustion. High CO content can increase the temperature in the furnace, increase the combustion rate and heat transfer efficiency, thereby achieving faster and more uniform slab heating. Too low CO content may mean incomplete combustion, which will lead to low thermal efficiency, energy waste, and may even produce harmful unburned gases. Too high CO content may cause safety hazards, increase the risk of explosion, and may combine with excessive oxygen to produce additional heat losses. The range of 26% to 32% is a balanced state that can take into account both safety and combustion efficiency.
[0037] Residual oxygen content refers to the amount of oxygen in the flue gas after combustion that does not participate in combustion. Low residual oxygen indicates that the combustion of the fuel is close to complete, thereby reducing the waste of unburned components. Controlling the residual oxygen content to less than 8% helps to optimize fuel use, reduce energy loss, and show good heat absorption efficiency in the furnace. If the residual oxygen content is higher than 8%, it usually means that there is a problem of excess air in the combustion process, which will cause a decrease in thermal efficiency and may also cause overheating of materials and equipment. By keeping the residual oxygen content less than 8%, it is ensured that only the necessary oxygen participates in the reaction, avoiding oxidation damage and heat loss.
[0038] By strictly controlling the CO content in the high-speed mixed gas and the residual oxygen content in the flue gas, the heating furnace can be ensured to operate in an efficient and safe state. This ensures that the slab obtains uniform and appropriate heat during the heating process to support the subsequent rolling process and material quality. At the same time, it also optimizes the combustion efficiency and energy utilization in the furnace to the greatest extent, reducing environmental impact and economic costs.
[0039] The relationship between CO content, calorific value and air-fuel ratio in coal gas is shown in Table 1 below:
[0040] Table 1 Relationship between CO content, calorific value and air-fuel ratio
[0041]
[0042]
[0043] The air-coal ratio of the first heating section is controlled to be 0.8-0.95, the air-coal ratio of the second heating section is controlled to be 0.8-0.95, the air-coal ratio of the third heating section is controlled to be 0.9-1.0, and the air-coal ratio of the equalizing section is controlled to be 0.8-0.9.
[0044] Specifically, in the first heating stage, the appropriate air-coal ratio ensures that the gas is fully burned to provide the necessary heat for the initial heating of the slab. The air-coal ratio in the first heating stage is (0.8-0.95). A lower air-coal ratio (such as 0.8) indicates a larger amount of air, which is conducive to complete combustion, but may cause part of the heat to be used for heating of excess air, which is not conducive to energy utilization. A higher ratio (such as 0.95) increases the proportion of gas and improves the calorific value, which helps to enhance the thermal effect and lay the foundation for the subsequent heating stage. At this stage, the air-coal ratio is flexibly adjusted to ensure that the combustion is both sufficient and does not lose thermal efficiency due to excessive air, in order to meet different furnace temperature requirements.
[0045] The second heating section needs to continue to ensure that the temperature in the material rises evenly and promotes the internal structural phase change. The air-coal ratio (0.8-0.95) in the second heating section is controlled in the same ratio range as the first heating section to maintain a stable combustion state, continuously provide sufficient heat, and support uniform temperature rise. The stability of combustion can prevent uneven heating caused by local air flow fluctuations.
[0046] The three heating stages are used to raise the temperature to the deformation optimization level, laying the foundation for plastic deformation and structural homogenization. The three heating stages have an air-to-coal ratio (0.9-1.0). A higher air-to-coal ratio (such as 0.9-1.0) means a higher fuel supply, which helps to meet high temperature requirements. A ratio close to 1.0 focuses on supplying sufficient fuel to achieve a higher heat output, so that the slab reaches the optimal state before processing. Careful control is required to avoid oxidation damage caused by excessive fuel.
[0047] The soaking section is used to ensure the uniformity of the temperature of the material cross section and achieve the final temperature balance. The air-coal ratio in the soaking section is (0.8-0.9). A lower air-coal ratio (such as 0.8) effectively prevents abnormally high heat caused by excessive combustion during the homogenization process, which may damage the toughness of the material. A moderate ratio (such as 0.9) ensures that the heat is maintained under low oxidation risk, making the temperature inside the slab more balanced, providing a guarantee for the final mechanical properties.
[0048] By adjusting the air-gas ratio in different heating stages, the optimized combustion state of gas is achieved between each stage, ensuring the efficient use of thermal energy and precise control of the slab heating process. This not only meets the performance requirements of slabs of different thicknesses and materials before rolling, but also exerts the thermal effect of the furnace through the optimal energy configuration, which helps the economy, environmental protection and quality consistency of production.
[0049] Cold billets and hot billets are loaded into the furnace separately. Billets with a temperature greater than 500°C are hot billets, and billets with a temperature less than 500°C are cold billets. The time that hot billets stay in the furnace is controlled at 120 to 140 minutes, and the time that cold billets stay in the furnace is controlled at 160 to 180 minutes.
[0050] The slab temperature is hot when it is greater than 500℃, and cold when it is less than 500℃. In many steel materials, 500℃ is a relatively critical temperature, because after exceeding this temperature, the microstructure of the material gradually begins to change. For example, the ferrite of some steels begins to transform into austenite within this range. In order to ensure that the material's organization is balanced and stable during hot processing, especially in the rolling process, this temperature point is usually used as a reference to determine whether the material is at a high temperature.
[0051] The initial temperatures of hot and cold slabs are quite different. If they are mixed in the same furnace, it will lead to uneven heating. Hot slabs may be overheated, while cold slabs may not reach the required heating temperature. Mixing will complicate process control and increase the risk of defective products. Heating slabs with different initial temperatures separately can optimize the heat distribution in the furnace, improve energy efficiency, and reduce unnecessary energy waste.
[0052] The hot billet in the furnace time is controlled at 120 to 140 minutes. Since the hot billet already has a high initial temperature, a shorter time in the furnace can quickly achieve uniform heating and ensure good plasticity in subsequent rolling. The cold billet in the furnace time is controlled at 160 to 180 minutes. The cold billet needs a longer time to heat from a lower temperature to the required rolling temperature. The longer time in the furnace ensures that the internal temperature of the slab is uniform, reducing the risk of thermal stress and deformation. By strictly distinguishing and controlling the heating process of hot billets and cold billets, the heating efficiency can be improved, energy utilization can be optimized, and the quality and performance of the final product can be ensured.
[0053] The data basis of this embodiment comes from the production of Q235B plain carbon steel in a double heat storage walking beam heating furnace. Through the control method for reducing oxidation and burning loss in a double heat storage walking beam heating furnace described in this embodiment, the oxidation and burning loss rate of the production of Q235B plain carbon steel is reduced from 0.8% to 0.5%, and the cleaning interval of the heating furnace slag is extended from six months to eight months.
[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A control method for reducing oxidation and burning loss in a double heat storage walking beam heating furnace, characterized in that: include: According to the slab rolling specifications, the furnace temperature is controlled, the temperature of the first heating section is controlled at 1000℃~1050℃, the temperature of the second heating section is controlled at 1150℃~1200℃, the temperature of the third heating section is controlled at 1250℃~1300℃, and the soaking temperature is controlled at 1250℃~1280℃; Control the CO content in high-speed mixed gas to 26% to 32%, and control the residual oxygen content in flue gas to less than 8%; Control the air-coal ratio of the first heating section to 0.8-0.95, the air-coal ratio of the second heating section to 0.8-0.95, the air-coal ratio of the third heating section to 0.9-1.0, and the air-coal ratio of the equalizing section to 0.8-0.9; The cold billets and hot billets are loaded into the furnace separately. The time of the hot billets in the furnace is controlled at 120 minutes to 140 minutes, and the time of the cold billets in the furnace is controlled at 160 minutes to 180 minutes.
2. The control method for reducing oxidation and burning loss of a double-regenerative walking beam heating furnace according to claim 1 is characterized in that: The slab rolling specifications include above 3.0 mm and below 3.0 mm.
3. The control method for reducing oxidation and burning loss of a double-regenerative walking beam heating furnace according to claim 2 is characterized in that: When the slab rolling specification is above 3.0 mm, the furnace temperature is controlled according to the lower limit.
4. The control method for reducing oxidation and burning loss of a double-regenerative walking beam heating furnace according to claim 2 is characterized in that: When the slab specification is below 3.0 mm, the furnace temperature is controlled according to the upper limit.
5. The control method for reducing oxidation and burning loss of a double-regenerative walking beam heating furnace according to claim 1 is characterized in that: The temperature of the first heating section is 1000°C or 1050°C, the temperature of the second heating section is 1150°C or 1200°C, the temperature of the third heating section is 1250°C or 1300°C, and the average heating temperature is 1250°C or 1280°C.
6. The control method for reducing oxidation and burning loss of a double-regenerative walking beam heating furnace according to claim 1, characterized in that: The CO content in the high-speed mixed gas is 26% or 32%.
7. The control method for reducing oxidation and burning loss of a double-regenerative walking beam heating furnace according to claim 1 is characterized in that: The air-coal ratio in the first heating section is 0.8 or 0.95, the air-coal ratio in the second heating section is 0.8 or 0.95, the air-coal ratio in the third heating section is 0.9 or 1.0, and the air-coal ratio in the equalizing section is 0.8 or 0.
9.
8. The control method for reducing oxidation and burning loss of a double-regenerative walking beam heating furnace according to claim 1 is characterized in that: The hot billet in the furnace time is controlled to be 120 minutes or 140 minutes, and the cool billet in the furnace time is controlled to be 160 minutes or 180 minutes.
9. The control method for reducing oxidation and burning loss of a double-regenerative walking beam heating furnace according to claim 1, characterized in that: A slab temperature greater than 500°C is a hot slab, and a slab temperature less than 500°C is a cool slab.