Silicon steel oxidation system of normalizing furnace

Abstract

The invention belongs to the technical field of steel production, and relates to a normalizing furnace silicon steel oxidation system which comprises an inlet sealing chamber, a preheating section, a non-oxidation heating section, a furnace throat, a follow-up normalizing treatment furnace section and an outlet sealing chamber. The furnace throat is connected with the non-oxidation heating section and the follow-up normalizing treatment furnace section, the follow-up normalizing treatment furnace section is connected with the outlet sealing chamber, the preheating section is connected with afterburning air and a smoke exhaust device, the follow-up normalizing treatment furnace section is connected with a diffusion flue, and the diffusion flue is connected with the furnace throat. And the inlet sealing chamber, the furnace throat, the subsequent normalizing treatment furnace section and the outlet sealing chamber are respectively connected with nitrogen. According to the silicon steel oxidation system of the normalizing furnace, smoke of the non-oxidation heating section can be effectively prevented from flowing backwards to the follow-up furnace section of the furnace throat, and strip steel oxidation can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, and in particular to a normalizing furnace silicon steel oxidation system. Background Art

[0002] Silicon steel is an important soft magnetic alloy that is indispensable in the power, electronics and military industries, and is also the soft magnetic material with the largest consumption. Silicon steel products are often figuratively called "crafts" among steel products, especially oriented silicon steel among silicon steels. Due to its complex manufacturing process and equipment, strict composition control, long manufacturing process and many factors affecting performance, its quality is often considered an important indicator of a country's special steel manufacturing technology level.

[0003] The normalizing pickling unit is an essential production process for the production of high-end non-oriented silicon steel and oriented silicon steel. Its purpose is to improve the uniformity of the hot-rolled plate structure, coarsen the grains, adjust the size and distribution of precipitates, remove the iron oxide scale on the surface of the hot-rolled coil, and improve the magnetic properties and surface quality of the product.

[0004] Normalizing furnace generally consists of preheating section, non-oxidizing heating section, radiant tube heating section, soaking section and cooling section. When normalizing silicon steel in normalizing furnace, the dew point of subsequent furnace sections increases due to the supplementary combustion air in preheating section and the flue gas after combustion in non-oxidizing heating section. The water vapor and residual air in the flue gas react with the strip to form dense oxide composed of Si, Fe, etc. on the surface of hot-rolled plate substrate, and the iron oxide scale thickens sharply. It is difficult to completely remove it in the subsequent shot blasting and pickling process. After pickling, there is obvious iron oxide scale residue on the surface of the strip, resulting in pickling defects.

[0005] In order to completely remove the iron oxide scale, it is generally adopted to reduce the production speed and increase the pickling time or increase the shot blasting machine, increase the length of the pickling section to improve the shot blasting and pickling capacity to achieve the removal of the iron oxide scale. However, the above method has the problems of low production efficiency, large investment and increased production cost. It is obviously not applicable in high-speed continuous normalization treatment, so it needs to be improved. Summary of the invention

[0006] In view of this, the present invention provides a normalizing furnace silicon steel oxidation system.

[0007] Specifically, the present invention is achieved through the following technical solutions:

[0008] According to a first aspect of the present invention, a normalizing furnace silicon steel oxidation system is provided, comprising: an inlet sealed chamber, a preheating section, a non-oxidizing heating section, a furnace throat, a subsequent normalizing treatment furnace section and an outlet sealed chamber, wherein the preheating section is respectively connected to the inlet sealed chamber and the non-oxidizing heating section, the furnace throat is respectively connected to the non-oxidizing heating section and the subsequent normalizing treatment furnace section, the subsequent normalizing treatment furnace section is connected to the outlet sealed chamber, the preheating section is respectively connected to supplementary combustion air and a smoke exhaust device, the subsequent normalizing treatment furnace section is connected to a venting flue, and the inlet sealed chamber, the furnace throat, the subsequent normalizing treatment furnace section and the outlet sealed chamber are respectively connected to nitrogen.

[0009] Optionally, the supplementary combustion air is introduced at the head of the preheating section.

[0010] Optionally, the subsequent normalizing treatment furnace section includes one or more sections of a radiant tube heating section, a radiant tube cooling section, a radiant tube cooling\heating section, an electric soaking section, and a protective gas jet cooling section.

[0011] Optionally, a control valve is provided on the emission flue.

[0012] Optionally, the pressure difference between the subsequent normalizing treatment furnace section and the tail of the non-oxidation heating section is 5-50Pa.

[0013] Optionally, the pressure difference between the subsequent normalizing treatment furnace section and the tail of the non-oxidation heating section is 10-30Pa.

[0014] Optionally, the furnace pressure of the preheating section is 20-40Pa.

[0015] Optionally, the furnace pressure of the inlet sealing chamber is 5-20Pa.

[0016] Optionally, the furnace pressure of the outlet sealing chamber is 80-200Pa.

[0017] Optionally, the dew point of the subsequent normalization treatment furnace section is -60 to -10°C, and the concentration of carbon monoxide is 0-500 ppm.

[0018] The technical solution provided by the present invention brings at least the following beneficial effects:

[0019] The silicon steel oxidation system of a normalizing furnace provided in the present application can effectively prevent the flue gas of the non-oxidizing heating section from flowing toward the subsequent furnace section of the furnace throat, thereby reducing the oxidation of the strip steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0022] Figure 1 A schematic diagram of a normalizing furnace silicon steel oxidation system provided in an embodiment of the present invention

[0023] Figure 2 A schematic diagram of furnace pressure distribution of a normalizing furnace silicon steel oxidation system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Figure 1 A normalizing furnace silicon steel oxidation system suitable for an embodiment of the present invention is schematically shown.

[0026] Reference Figure 1 As shown, the present application provides a normalizing furnace silicon steel oxidation system, comprising: an inlet sealed chamber, a preheating section, a non-oxidation heating section, a furnace throat, a subsequent normalizing treatment furnace section and an outlet sealed chamber, wherein the preheating section is respectively connected to the inlet sealed chamber and the non-oxidation heating section, the furnace throat is respectively connected to the non-oxidation heating section and the subsequent normalizing treatment furnace section, the subsequent normalizing treatment furnace section is connected to the outlet sealed chamber, the preheating section is respectively connected to supplementary combustion air and a smoke exhaust device, the subsequent normalizing treatment furnace section is connected to a venting flue, and the inlet sealed chamber, the furnace throat, the subsequent normalizing treatment furnace section and the outlet sealed chamber are respectively connected to nitrogen.

[0027] In the embodiment of the present application, after the hot-rolled raw material plate of silicon steel is obtained, it needs to be subjected to a normalizing process, including uncoiling, straightening, welding, normalizing, shot blasting and phosphorus removal, pickling and coiling processes. A normalizing furnace is required when normalizing silicon steel. The normalizing furnace is provided with an inlet sealing chamber, a preheating section (PH), a non-oxidizing heating section (NOF), a furnace throat, a subsequent normalizing furnace section and an outlet sealing chamber in sequence along the running direction of the strip, wherein the furnace pressure of the normalizing furnace has the following distribution law: the furnace pressure gradually increases from the inlet sealing chamber along the running direction of the strip, the furnace pressure at the tail of the normalizing furnace is the highest, and the furnace zone atmosphere flows from the tail to the head in the opposite direction of the running direction of the strip.

[0028] Exemplarily, the supplementary combustion air is introduced at the head of the preheating section.

[0029] In the embodiment of the present application, the supplementary combustion air is introduced at the head of the preheating section (PH) to prevent the supplementary combustion air from oxidizing the strip steel.

[0030] Exemplarily, the subsequent normalizing treatment furnace section includes one or more sections of a radiant tube heating section, a radiant tube cooling section, a radiant tube cooling\heating section, an electric soaking section, and a protective gas jet cooling section.

[0031] In an embodiment of the present application, the subsequent normalizing treatment furnace section includes a combination of one or more sections of a radiant tube heating section (RTF), a radiant tube cooling / heating section (RCF), an electric soaking section, a radiant tube cooling section (ATC), and a protective gas jet cooling section (RJC).

[0032] Exemplarily, a control valve is provided on the emission flue.

[0033] In the embodiment of the present application, the inlet sealed chamber, the furnace throat, and the outlet sealed chamber are filled with protective gas nitrogen, and the preheating section (PH), the non-oxidation heating section (NOF) and the subsequent normalizing furnace section are isolated from the atmosphere by a nitrogen curtain. Two nitrogen routes are introduced into the furnace section between the furnace throat and the outlet sealed chamber, one route is common low-pressure nitrogen, and the other route is high-pressure nitrogen. A furnace atmosphere venting flue and a control valve are added to the head of the subsequent normalizing furnace section adjacent to the downstream of the furnace throat. By adjusting the nitrogen intake of the subsequent normalizing furnace section and the opening of the control valve of the furnace atmosphere venting flue, the pressure difference between the subsequent normalizing furnace section and the tail of the non-oxidation heating section (NOF) is controlled to achieve the furnace pressure distribution.

[0034] Exemplarily, the pressure difference between the subsequent normalizing treatment furnace section and the tail of the non-oxidizing heating section is 5-50Pa.

[0035] In the embodiment of the present application, the pressure difference between the subsequent normalizing treatment furnace section and the tail of the non-oxidation heating section is 5-50Pa, which can prevent the flue gas from the non-oxidation heating section (NOF) from escaping to the downstream furnace section of the furnace throat, thereby protecting the strip steel in the subsequent furnace section of the furnace throat from being oxidized.

[0036] Exemplarily, the pressure difference between the subsequent normalizing treatment furnace section and the tail of the non-oxidation heating section is 10-30Pa.

[0037] In the embodiment of the present application, the pressure difference between the subsequent normalizing treatment furnace section and the tail of the non-oxidation heating section is 10-30Pa, which can better prevent the flue gas from the non-oxidation heating section (NOF) from escaping to the downstream furnace section of the furnace throat, thereby protecting the strip steel in the subsequent furnace section of the furnace throat from being oxidized.

[0038] Exemplarily, the furnace pressure of the preheating section is 20-40Pa.

[0039] In an embodiment of the present application, the furnace pressure detection control position of the preheating section (PH) is moved from the head to the tail, and the furnace pressure is set to 20-40Pa, which can enhance the smoke exhaust capacity of the non-oxidation heating section (NOF) and reduce the furnace pressure of the non-oxidation heating section (NOF) under high load of the normalizing furnace.

[0040] Exemplarily, the furnace pressure of the inlet sealed chamber is 5-20Pa, and the furnace pressure of the outlet sealed chamber is 80-200Pa.

[0041] In the embodiment of the present application, the inlet sealed chamber and the outlet sealed chamber are respectively filled with protective atmosphere nitrogen, the furnace pressure of the inlet sealed chamber is set to 5-20Pa, and the furnace pressure of the outlet sealed chamber is set to 80-200Pa, which can maintain a positive pressure in the furnace and prevent outside air from entering the normalizing furnace.

[0042] Exemplarily, the dew point of the subsequent normalizing treatment furnace section is -60 to -10°C, and the concentration of carbon monoxide is 0-500 ppm.

[0043] In an embodiment of the present application, the dew point of the subsequent normalizing treatment furnace section is -60 to -10°C, and the concentration of carbon monoxide is 0-500ppm. A dew point detector and a carbon monoxide analyzer are arranged at the head of the subsequent normalizing treatment furnace section along the running direction of the strip to monitor the furnace atmosphere of the subsequent normalizing furnace section to avoid the occurrence of flue gas from the non-oxidizing heating section (NOF) leaking to the furnace section downstream of the furnace throat.

[0044] like Figure 1 As shown, the supplementary combustion air of the preheating section (PH) was originally introduced at the tail of the preheating section (PH). When the strip speed is low, the plate temperature of the strip reaching the tail of the preheating section (PH) has exceeded 300°C. When the plate temperature is above 300°C, the silicon steel plate can be oxidized. At this time, if a large amount of supplementary combustion air is introduced at the tail of the preheating section (PH), it will inevitably cause the surface oxidation of the strip, making the oxide layer of the hot-rolled raw material plate thicker. In this application, the supplementary combustion air of the preheating section (PH) is introduced from its head, and the plate temperature is low at this time, which can effectively prevent the supplementary combustion air from oxidizing the strip.

[0045] like Figure 2 As shown, along the running direction of the strip steel, furnace pressure (furnace pressure refers to the pressure inside the furnace) is detected at the entrance sealing chamber (point a), the tail of the preheating section (PH) (point A), the tail of the non-oxidation heating section (NOF) (point B), the head of the subsequent normalizing furnace section (point C), the tail of the subsequent normalizing furnace section (point D), and the exit sealing chamber (point d). The furnace pressure at the tail of the preheating section is the pressure control reference point of the non-oxidation heating section (NOF), and the pressure difference between the head of the subsequent normalizing furnace section and the tail of the non-oxidation heating section (NOF) is the pressure control reference point of the subsequent furnace section at the throat.

[0046] exist Figure 2 In the original furnace pressure distribution shown in the left part, when the normalizing furnace switches the product specifications, varieties, speed or process, the combustion load of the non-oxidation heating section (NOF) changes, which will cause furnace pressure fluctuations. In particular, as the combustion load of the non-oxidation heating section (NOF) increases, the flue gas in the non-oxidation heating section (NOF) cannot be discharged through the exhaust fan in time, resulting in an increase in the furnace pressure of the non-oxidation heating section (NOF). The furnace pressure is greater than the furnace pressure of the furnace section downstream of the furnace throat, causing the flue gas from the non-oxidation heating section (NOF) to flow backward to the furnace section downstream of the furnace throat. The unburned air in the flue gas and the H2O produced after combustion react with the high-temperature strip to cause secondary oxidation of the hot-rolled strip in the normalizing furnace, resulting in a thickening of the oxide layer on the surface of the strip after normalization.

[0047] like Figure 2 The new furnace pressure provided by the present application shown in the middle right part has the following distribution: it gradually increases from the inlet sealing chamber along the running direction of the strip, the furnace pressure at the tail of the normalizing furnace is the highest, and the furnace zone atmosphere flows from the tail to the head in the opposite direction of the running direction of the strip. In order to prevent the flue gas from the non-oxidation heating section (NOF) from flowing back to the furnace section downstream of the furnace throat and protect the strip from being oxidized in the subsequent furnace sections of the furnace throat, along the running direction of the strip, the pressure difference between the subsequent normalizing furnace section and the tail of the non-oxidation heating section (NOF) is controlled to be 5-50Pa, preferably 10-30Pa.

[0048] like Figure 1 As shown, in the present application, two nitrogen protective gases are introduced into the furnace section between the furnace throat and the outlet sealing chamber, one of which is commonly used low-pressure nitrogen with a nitrogen pressure of 0.5-1 bar, and the entry points are all furnace sections between the furnace throat and the outlet sealing chamber, each furnace section has 3-5 entry points, and the entry point spacing is arranged in principle at 20m / piece, to ensure that there is sufficient nitrogen intake during normal production of the normalizing furnace, and the furnace pressure of the subsequent normalizing furnace section is greater than the tail furnace pressure of the non-oxidizing heating section (NOF); the other is high-pressure nitrogen with a nitrogen pressure of 3-4 bar, and the entry point is the last furnace section (generally the cooling section) of the normalizing furnace, each furnace section has 3-4 entry points, and the entry point spacing is arranged in principle at 20m / piece, to ensure that during abnormal production such as process transition and specification transition, high-pressure nitrogen is introduced due to changes in the normalizing furnace load and the amount of commonly used low-pressure nitrogen is insufficient to maintain the furnace pressure, so as to ensure that the furnace pressure of the subsequent normalizing furnace section is greater than the tail furnace pressure of the non-oxidizing heating section (NOF), and to avoid flue gas backflow. High-pressure nitrogen is introduced into the last furnace section (usually the cooling section) of the normalizing furnace instead of the heating section or the soaking section. This can effectively reduce energy loss, play a cooling role, and reduce the cooling load of the cooling section.

[0049] like Figure 1As shown, in the present application, a furnace atmosphere discharge flue and a control valve are added at the head of the subsequent normalizing treatment furnace section, and the pressure difference between the subsequent normalizing treatment furnace section and the tail of the non-oxidizing heating section (NOF) is controlled by adjusting the nitrogen intake of the subsequent normalizing treatment furnace section and the opening of the control valve of the furnace atmosphere discharge flue to achieve the furnace pressure distribution.

[0050] Specifically, the fuel supplied by the open flame burner of the non-oxidation heating section (NOF) burns in a furnace of limited volume, and the smoke generated by the combustion and the smoke exhausted by the smoke exhaust fan are controlled to be balanced, so that the furnace pressure of the preheating section (PH) can be controlled at the reference point. The present application moves the detection and control position of the furnace pressure of the preheating section (PH) from the head to the tail, and sets the furnace pressure to 20-40Pa, thereby enhancing the smoke exhaust capacity of the non-oxidation heating section (NOF), reducing the furnace pressure of the non-oxidation heating section (NOF) under a large load of the normalizing furnace, and reducing the nitrogen supply to the subsequent furnace sections of the furnace throat. The furnace pressure at the tail of the preheating section (PH) should not be set lower than 20Pa. If it is set too low, it will result in a lower furnace pressure in the inlet sealed chamber, resulting in an increase in the amount of nitrogen introduced into the inlet sealed chamber.

[0051] In the present application, the inlet sealed chamber and the outlet sealed chamber are filled with protective atmosphere nitrogen, the furnace pressure of the inlet sealed chamber is set to 5-20Pa, and the outlet sealed chamber is set to 80-200Pa, which can maintain a positive furnace pressure and prevent outside air from entering the normalizing furnace.

[0052] like Figure 1 As shown, a dew point detector and a carbon monoxide analyzer are arranged at the head of the subsequent normalizing treatment furnace section along the running direction of the strip to monitor the atmosphere in the subsequent normalizing treatment furnace section. The dew point control range is -60--10°C, and the carbon monoxide concentration range is 0-500ppm. The atmosphere in the subsequent normalizing furnace section can be monitored to avoid the occurrence of flue gas from the non-oxidizing heating section (NOF) leaking to the furnace section downstream of the furnace throat.

[0053] Example:

[0054] The following takes the normalization production of high-grade non-oriented silicon steel with a silicon content of 2.5% as an example to further illustrate the technical solution of the present invention. After normalization by different control normalization methods, the thickness of the iron oxide scale detected before and after normalization and the pickling quality are as follows:

[0055] Table 1: Comparison of the control method of the normalizing furnace of the present invention and the original control method after normalization

[0056]

[0057] The silicon steel oxidation system of a normalizing furnace provided in the present application can effectively prevent the flue gas of the non-oxidizing heating section from flowing toward the subsequent furnace section of the furnace throat, thereby reducing the oxidation of the strip steel.

[0058] It should be noted that, in the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0059] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0060] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0061] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0062] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A normalizing furnace silicon steel oxidation system, characterized in that: include: An inlet sealed chamber, a preheating section, a non-oxidation heating section, a furnace throat, a subsequent normalizing treatment furnace section and an outlet sealed chamber, wherein the preheating section is respectively connected to the inlet sealed chamber and the non-oxidation heating section, the furnace throat is respectively connected to the non-oxidation heating section and the subsequent normalizing treatment furnace section, the subsequent normalizing treatment furnace section is connected to the outlet sealed chamber, the preheating section is respectively connected to supplementary combustion air and a smoke exhaust device, the subsequent normalizing treatment furnace section is connected to a venting flue, and the inlet sealed chamber, the furnace throat, the subsequent normalizing treatment furnace section and the outlet sealed chamber are respectively connected to nitrogen.

2. The normalizing furnace silicon steel oxidation system according to claim 1, characterized in that: The supplementary combustion air is introduced into the head of the preheating section.

3. The normalizing furnace silicon steel oxidation system according to claim 1, characterized in that: The subsequent normalizing treatment furnace section includes one or more sections of a radiant tube heating section, a radiant tube cooling section, a radiant tube cooling\heating section, an electric soaking section, and a protective gas jet cooling section.

4. The normalizing furnace silicon steel oxidation system according to claim 1, characterized in that: A control valve is arranged on the flue gas vent.

5. The normalizing furnace silicon steel oxidation system according to claim 1, characterized in that: The pressure difference between the subsequent normalizing treatment furnace section and the tail of the non-oxidizing heating section is 5-50Pa.

6. The normalizing furnace silicon steel oxidation system according to claim 1, characterized in that: The pressure difference between the subsequent normalizing treatment furnace section and the tail of the non-oxidizing heating section is 10-30Pa.

7. The normalizing furnace silicon steel oxidation system according to claim 1, characterized in that: The furnace pressure of the preheating section is 20-40Pa.

8. The normalizing furnace silicon steel oxidation system according to claim 1, characterized in that: The furnace pressure of the inlet sealing chamber is 5-20Pa.

9. The normalizing furnace silicon steel oxidation system according to claim 1, characterized in that: The furnace pressure of the outlet sealing chamber is 80-200Pa.

10. The normalizing furnace silicon steel oxidation system according to claim 1, characterized in that: The dew point of the subsequent normalization treatment furnace section is -60 to -10°C, and the concentration of carbon monoxide is 0-500ppm.

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