Process for reducing oxidation burning loss of medium plate heating furnace

Abstract

The invention discloses a process for reducing oxidation burning loss of a medium-thickness plate heating furnace, which belongs to the technical field of ferrous metallurgical equipment maintenance and production processes, and specifically comprises the following steps: (1) arranging a charging organization for production in a manner that a steel billet discharged from a continuous casting machine is directly conveyed in a hot charging manner or is conveyed in a hot charging manner or is conveyed in a hot charging manner, and a cold charging blank is used as an auxiliary manner; (2) a low-temperature heating process is adopted, and the heating temperature is controlled to be 1120-1160 DEG C; (3) the in-furnace time of the cold charging blank is controlled to be larger than or equal to 8 min / cm, and the in-furnace time of the hot charging blank of hot charging direct conveying or hot charging hot conveying is controlled to be larger than or equal to 6 min / cm; and (4) the residence time of each section of the heating furnace is controlled, the residence time of the heating section is smaller than or equal to 45 min, and the residence time of the soaking section is smaller than or equal to 40 min. According to the structure of the heating furnace, through reasonable production organization, optimization of the heating process and control of time nodes, the oxidation burning loss of the surface of the steel billet in the heating process is reduced to the minimum, and the production efficiency is improved. And meanwhile, the shutdown time of a production line is shortened, and the comprehensive economic benefits of the production line are improved.

Description

Technical Field

[0001] The invention relates to a process for reducing oxidation and burning of a heating furnace, in particular to a process for reducing oxidation and burning of a medium and thick plate heating furnace, and belongs to the technical field of iron and steel metallurgical equipment maintenance and production process. Background Art

[0002] During the long-term service of the heating furnace, due to aging equipment, inadequate maintenance, unreasonable production organization, slow process update and other reasons, the iron scale on the surface of the steel billet is relatively thick and the oxidation and burning is serious during the heating process of the heating furnace. The iron scale on the lower surface of the steel billet falls to the bottom of the furnace and under the roller. When the long-term accumulation reaches a certain thickness, it not only increases the fuel consumption of the heating furnace, but also affects the movement of the walking beam of the heating furnace. In severe cases, it causes the walking beam to move out of place or get stuck, and it is also easy to cause the accumulation of iron scale under the steel-out furnace door and the steel-out roller of the heating furnace. The top tilted furnace door and the steel-out roller are often blocked. During normal maintenance time, only the trench outside the furnace door and the bottom of the steel-out roller can be cleaned, and the blocking of the walking beam requires the furnace to be stopped to clean the oxidized slag at the bottom of the furnace. Usually, the oxidized slag at the bottom of the furnace is cleaned once a year for overhaul. In fact, the oxidized slag accumulated at the bottom of the furnace 7-9 months after the overhaul increases fuel consumption and affects the movement of the walking beam. The cleaning of the slag in the furnace requires the furnace to be shut down for treatment. Each shutdown for cleaning the slag takes about 7 days. Most medium and thick plate production lines are equipped with two heating furnaces, one large and one small. The long shutdown time has a series of impacts on the production line. Barely maintaining production until the annual overhaul time, various conditions of the heating furnace occur from time to time, production is intermittent, product quality is difficult to guarantee, and the output and energy consumption loss of the production line are relatively large, causing huge economic losses to the company.

[0003] Before the improvement, our production was mainly cold-charged billets, supplemented by hot-charged direct delivery and hot-charged hot delivery. The heating process temperature range of each steel grade is different, ranging from 1100-1230℃, and the range reaches 130℃; the furnace time requirements vary by 50 minutes. During the heating process of multiple steel grades entering the furnace one after another, there are frequent high and low temperature conversions. The heating furnace operator needs to frequently adjust the heating target temperature and air-fuel ratio. The shutdown time requirements of each steel grade in the heating section and the soaking section are also different, resulting in some steel grades The heating time is too long, the heating furnace frequently rises and falls, and the probability of oxidation and burning on the surface of the steel billet increases, resulting in excessive oxidation and burning.

[0004] Therefore, there is an urgent need for a process to reduce the oxidation and burning of the billet surface to extend the slag cleaning cycle of the heating furnace. Summary of the invention

[0005] In view of the above-mentioned technical problems, the present invention overcomes the shortcomings of the prior art and provides a process for reducing oxidation and burning of medium and thick plate heating furnaces. According to the structure of the heating furnace itself, through reasonable production organization, optimization of the heating process and control of time nodes, the oxidation and burning of the surface of the steel billet during the heating process is reduced to a minimum, thereby extending the shutdown cycle of the heating furnace and slag cleaning, while reducing the heating time of the production line that is not enough to wait for the temperature and the downtime of the heating furnace due to failure, thereby improving the comprehensive economic benefits of the production line.

[0006] In order to solve the above technical problems, the present invention provides a process for reducing oxidation and burning loss in a medium and thick plate heating furnace, which specifically includes the following steps: (1) The steel billets coming out of the continuous casting machine are sent to the heating furnace by hot charging and direct delivery or hot charging and hot delivery as the main method, with cold charging as the auxiliary method; (2) Using low temperature heating process, the heating temperature is controlled in the range of 1120-1160℃; (3) The time of cold-charged billets in the furnace is controlled to be ≥8 min / cm, and the time of hot-charged billets in the furnace for hot-charged direct delivery or hot-charged hot delivery is controlled to be ≥6 min / cm; (4) Control the residence time of each section of the heating furnace, where the residence time of the heating section is 30-45 minutes, and the residence time of the soaking section is 25-40 minutes.

[0007] The technical solution further defined in the present invention is: Furthermore, in the aforementioned process for reducing oxidation and burning loss in the heating furnace for medium and thick plates, the temperature of the steel billet entering the furnace in the hot charging and direct delivery method is 500-700°C.

[0008] In the aforementioned process for reducing oxidation and burning loss in the heating furnace for medium and thick plates, the temperature of the steel billets entering the furnace in the hot charging and hot delivery method is 250-500°C.

[0009] In the aforementioned process for reducing oxidation and burning loss in a heating furnace for medium and thick plates, the temperature of the billets entering the furnace in the cold charging method is 0-250°C.

[0010] In the aforementioned process for reducing oxidation and burning loss in a heating furnace for medium and thick plates, when the hot-charged steel billet is directly delivered in step (1), the temperature at which the hot-charged steel billet enters the furnace is 600°C.

[0011] In the aforementioned process for reducing oxidation and burning loss in a heating furnace for medium and thick plates, in step (3), the time in the furnace for cold-charged billets is controlled to be 8-10 min / cm, and the time in the furnace for hot-charged billets by direct hot charging or hot-charging and hot-charging is controlled to be 6-8 min / cm.

[0012] In the aforementioned process for reducing oxidation and burning loss in a heating furnace for medium and thick plates, in step (4), the residence time of each section of the heating furnace is controlled, wherein the residence time of the heating section is 30-35 minutes, and the residence time of the soaking section is 30-35 minutes.

[0013] The beneficial effects of the present invention are: The present invention adopts the form of hot charging and direct delivery or hot charging and hot delivery as the main method and cold charging and hot delivery as the auxiliary method to organize batch production of steel billets by hot charging and direct delivery or hot charging and hot delivery. The hot charged steel billets enter the furnace at a high temperature, the heating difficulty is reduced, and the heating time of the heating furnace is shortened. The heating time of 150mm billets is shortened from ≥120 minutes to ≥90 minutes, thereby reducing the heating time to avoid excessive oxidation and burning, and at the same time reducing the energy consumption of the heating process and the downtime of the rolling mill waiting for temperature due to insufficient heating process time.

[0014] Medium and thick plates refer to steel plates with a thickness between 4.5mm and 100.0mm. Within this thickness range, medium and thick plates are classified by use and include: steel for high-rise buildings, steel for engineering machinery, ship plates, steel for bridges, wear-resistant steel, Q550-Q1100 high-strength steel, steel for pipelines, low-alloy steel plates, boiler steel plates, pressure vessel steel plates, patterned steel plates, automobile beam steel plates, certain parts of tractors and welded components, etc. The present invention implements a low-temperature heating process for ordinary plates, and reduces the steel-out temperature range of structural steel, ship plates, steel for engineering machinery, pressure vessels, etc. from the original 1100-1230 degrees to 1120-1160 degrees, narrows the heating temperature range, stabilizes heating, reduces frequent heating and cooling of the heating furnace, avoids large temperature fluctuations in the furnace caused by high temperature / low temperature reciprocating switching, and reduces the probability of oxidation and burning of the billet surface.

[0015] The process of the present invention reduces the oxidation and burning of the surface of the steel billet during the heating process to a minimum through reasonable production organization, optimization of the heating process and control of time nodes according to the structure of the heating furnace itself, and can effectively reduce comprehensive indicators such as fuel consumption, water consumption and electricity consumption of the heating furnace, and extend the period of stopping the heating furnace to clean the oxidized slag at the bottom of the furnace by 3-5 months, while reducing the downtime and energy consumption loss of the production line, greatly reducing the impact of long downtime on production output, energy consumption and economic benefits, and improving the comprehensive economic benefits of the production line.

[0016] After tracking and comparing the process performance before and after implementation, the comprehensive performance indicators of the products produced by the new process organization meet the process requirements and are consistent with the performance indicators before the improvement. At the same time, the rolling rhythm and rolling output have been greatly improved, and the fuel consumption of the heating furnace and the time for waiting for temperature due to insufficient process time have been reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the relative positions and structures of various areas of a medium and thick plate slab heating furnace in an embodiment of the present invention; In the figure: 1-steel-discharging furnace door, 2-steel-loading furnace door, 3-steel-discharging roller table, 4-steel-discharging machine support arm, 5-walking beam, A-heating furnace tail, B-preheating section, C-heating section, D-soaking section. DETAILED DESCRIPTION

[0018] To make the present invention more clearly understood, a process for reducing oxidation and burning loss in a medium and thick plate heating furnace of the present invention is further described below in conjunction with the accompanying drawings. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Example 1

[0019] This embodiment provides a process for reducing oxidation and burning loss in a heating furnace for medium and thick plates. Taking batch hot-shipping plate A billet of 150×2560×8200mm and subsequent structural steel S355J-2 billet of 150×2650×8100mm, with a billet temperature of 600°C as an example, the process specifically includes the following steps: (1) After the steel billets come out of the continuous casting machine, they are charged into the furnace and organized for production in the form of hot charging and direct delivery or hot charging and hot delivery as the main method, and cold charging and hot delivery as the auxiliary method. According to the production situation of the on-site continuous casting machine, the hot charging and direct delivery or hot charging and hot delivery priority principle is met. If the continuous casting machine cannot keep up with the abnormality, cold charging and hot charging are arranged to be charged into the furnace. In this embodiment, hot charging and direct delivery of steel billets are organized for batch production. The temperature of the hot charging steel billets entering the furnace is 600°C, and the heating time of 150mm billets is shortened to 90-100 minutes. (2) Using the low-temperature heating process for ordinary plates, the relative positions and structural diagram of each area of ​​the medium and thick plate slab heating furnace are as follows: Figure 1 As shown, the two ends are the steel-out furnace door 1 and the steel-loading furnace door 2. The slab is moved by the walking beam 5, lifted out of the heating furnace by the steel-out machine support arm 4, and finally transported to the next process by the steel-out roller 3. The heating furnace includes the heating furnace tail section A, preheating section B, heating section C and soaking section D from the steel-loading furnace door 2 to the steel-out furnace door 1. The soaking section D of the heating furnace is heated according to the target steel-out temperature of 1120-1160℃, and the heating temperature range is unified, which reduces the frequent temperature rise and fall of the heating furnace and reduces the probability of oxidation and burning of the steel billet surface. (3) Shorten the time in the furnace. The time in the furnace for cold-charged billets is shortened from 10 minutes / cm to 8 minutes / cm, and the time in the furnace for hot-charged billets is shortened from 8 minutes / cm to 6 minutes / cm. This batch of billets is 6 minutes / cm, which is calculated to be 90 minutes. (4) Control the residence time in each section of the heating furnace, especially the residence time in heating section C and soaking section D. The residence time in heating section C is controlled at 35 minutes, and the residence time in soaking section D is controlled at 35 minutes.

[0020] The present invention is mainly used in the heating process of the slab heating furnace of the hot-rolled medium and thick plate production line. It is optimized reasonably according to the conventional slab heating process requirements, and the oxidation and burning degree of the heated slab is controlled by optimizing the temperature and organizational form of the billet entering the furnace, the time in the furnace, the steel burning temperature, and the steel-out rhythm. In this way, the thickness of the slag accumulation at the bottom of the heating furnace is reduced, the cleaning cycle of the slag at the bottom of the heating furnace is extended, the oxidation and burning ratio of the heated slab is reduced, the energy consumption of the heating furnace is reduced, the finished product rate and the yield rate of the rolled piece are increased, and the comprehensive economic benefits of the production line are finally improved.

[0021] According to tracking statistics: the fuel consumption per ton of steel has been reduced from the original 1.47GJ / t to 1.39GJ / t, and the oxidation loss has been reduced from 9‰ to 5‰, which has improved the metal recovery rate of the billet and effectively delayed the time and cycle of slag cleaning at the bottom of the heating furnace; reduced the downtime of the rolling mill due to insufficient heating furnace temperature, and increased the machine hourly output from the original 230t / h to 248t / h, bringing economic benefits to the enterprise.

[0022] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A process for reducing oxidation and burning loss in a medium and thick plate heating furnace, characterized in that: The specific steps include: (1) The billets coming out of the continuous casting machine are charged into the furnace and organized for production by direct hot delivery or hot delivery as the main method, supplemented by cold charging of billets; (2) Use low temperature heating process, and control the heating temperature at 1120-1160℃; (3) The time of cold-charged billets in the furnace is controlled to be ≥8 min / cm, and the time of hot-charged billets in the furnace for hot-charged direct delivery or hot-charged hot delivery is controlled to be ≥6 min / cm; (4) Control the residence time of each section of the heating furnace, where the residence time of the heating section is 30-45 minutes, and the residence time of the soaking section is 25-40 minutes.

2. The process for reducing oxidation and burning loss in a medium and thick plate heating furnace according to claim 1 is characterized in that: In the hot charging and direct delivery method, the temperature of the steel billet entering the furnace is 500-700°C.

3. The process for reducing oxidation and burning loss in a medium and thick plate heating furnace according to claim 1 is characterized in that: In the hot charging and hot delivery method, the temperature of the steel billet entering the furnace is 250-500°C.

4. The process for reducing oxidation and burning loss in a medium and thick plate heating furnace according to claim 1 is characterized in that: The furnace entry temperature of the cold-charged billet is 0-250°C.

5. The process for reducing oxidation and burning loss in a heating furnace for medium and thick plates according to claim 1 is characterized in that: When the hot charging and direct delivery method is adopted in step (1), the temperature of the hot charged steel billet entering the furnace is 600°C.

6. The process for reducing oxidation and burning loss in a medium and thick plate heating furnace according to claim 1 is characterized in that: In the step (3), the time that the cold-charged blank stays in the furnace is controlled to be 8-10 min / cm, and the time that the hot-charged blank is directly delivered or hot-charged and hot-delivered is controlled to be 6-8 min / cm.

7. The process for reducing oxidation and burning loss in a heating furnace for medium and thick plates according to claim 1 is characterized in that: In the step (4), the residence time of each section of the heating furnace is controlled, wherein the residence time of the heating section is 30-35 minutes, and the residence time of the soaking section is 30-35 minutes.

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