Method for reducing chromatic aberration of cold-rolled steel coil after bell-type furnace annealing

Abstract

The invention provides a method for reducing chromatic aberration of a cold rolled steel coil after bell-type furnace annealing, which specifically comprises the following steps after emergency purging of a bell-type furnace: (1) adjusting an annealing heating program of the bell-type furnace to an initial stage according to annealing process requirements, when the temperature in the bell-type furnace is reduced to 400-300 DEG C, a heating cover of the bell-type furnace is buckled on the cold-rolled steel coil, and an annealing heating program of the bell-type furnace is started; (2) the temperature in the bell-type furnace is controlled to be increased to 450-550 DEG C, the heating time is 1.5-2.5 h, after heat preservation is conducted for 1.5-2.5 h, 20 m < 3 > / h-30 m < 3 > / h of hydrogen is blown into the bell-type furnace for 3-4 h, and the annealing atmosphere in the bell-type furnace is converted into the hydrogen atmosphere; and (3) after the annealing heating procedure is completed, starting the cooling procedure of the bell-type furnace and moving away the heating cover, so that the cold-rolled steel coil is naturally cooled. According to the technical scheme, color difference after annealing can be prevented, and repair is prevented.

Description

Technical Field

[0001] The present invention relates to the field of cold rolling technology, and in particular to a method for reducing color difference of cold-rolled steel coils after annealing in a bell-type furnace. Background Art

[0002] At present, the bell-type furnace annealing unit in the cold rolling mill is prone to emergency purge and other failures when entering the factory due to various reasons during the production process. After the emergency purge, the annealing atmosphere in the bell-type furnace is changed from hydrogen to nitrogen, which will lead to poor reduction of the surface of the steel coil after annealing, and the surface quality will be black and not bright. Figure 1 As shown, serious problems require spot purchase or repair. Summary of the Invention

[0003] Based on the above technical problem that the surface quality of the product is affected after the cold-rolled steel coil is annealed in a bell furnace, a method for reducing the color difference of the cold-rolled steel coil after bell furnace annealing is provided.

[0004] The technical means adopted in the present invention are as follows: A method for reducing color difference of cold-rolled steel coils after bell-type furnace annealing, after an emergency purge of the bell-type furnace occurs, specifically comprising the following steps: (1) Adjust the annealing heating program of the bell-type furnace to the initial stage according to the annealing process requirements, and when the temperature in the bell-type furnace drops to 300℃-400℃, buckle the heating cover of the bell-type furnace onto the cold-rolled steel coil and start the annealing heating program of the bell-type furnace; (2) Control the temperature in the bell-type furnace to 450℃-550℃, heat for 1.5h-2.5h, keep warm for 1.5h-2.5h, and then purge 20m into the bell-type furnace. 3 / h-30m 3 / h of hydrogen for 3h-4h to convert the annealing atmosphere in the bell-type furnace into a hydrogen atmosphere; (3) After completing the annealing heating process, start the cooling process of the bell furnace and remove the heating hood to allow the cold-rolled steel coil to cool naturally.

[0005] Furthermore, before step (1), the method further includes: checking whether the inner cover of the heating cover is leaking; if leakage occurs, increasing the working pressure of the bell-type furnace to restore the pressure inside the furnace to the standard working pressure of the bell-type furnace.

[0006] Furthermore, after the emergency purge of the bell furnace occurs, the temperature in the bell furnace drops to 350°C-450°C and then enters step (1).

[0007] Compared with the prior art, the present invention has the following advantages: The method for reducing color difference of cold-rolled steel coils after annealing in a bell-type furnace provided by the present invention can prevent color difference after annealing, prevent rework and spot goods from being produced, and achieve cost reduction and efficiency improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0009] Figure 1 This is a surface quality diagram of the cold-rolled steel coil after annealing obtained after an emergency purge of the bell-type furnace without using the method in Example 1.

[0010] Figure 2 The surface quality map of the cold-rolled steel coil after annealing is obtained using the method in Example 1. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions 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 only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0012] The present invention provides a method for reducing color difference of cold-rolled steel coils after bell-type furnace annealing, which specifically includes the following steps after emergency purging of the bell-type furnace: (1) Adjust the annealing heating program of the bell-type furnace to the initial stage according to the annealing process requirements, and when the temperature in the bell-type furnace drops to 300℃-400℃, buckle the heating cover of the bell-type furnace onto the cold-rolled steel coil and start the annealing heating program of the bell-type furnace; (2) Control the temperature in the bell-type furnace to 450℃-550℃, heat for 1.5h-2.5h, keep warm for 1.5h-2.5h, and then purge 20m into the bell-type furnace. 3 / h-30m 3 / h of hydrogen for 3h-4h to convert the annealing atmosphere in the bell-type furnace into a hydrogen atmosphere; (3) After completing the annealing heating process, start the cooling process of the bell furnace and remove the heating hood to allow the cold-rolled steel coil to cool naturally.

[0013] Furthermore, before step (1), the method further includes: checking whether the inner cover of the heating cover is leaking; if leakage occurs, increasing the working pressure of the bell-type furnace to restore the pressure inside the furnace to the standard working pressure of the bell-type furnace.

[0014] Furthermore, after the emergency purge of the bell furnace occurs, the temperature in the bell furnace drops to 350°C-450°C and then enters step (1).

[0015] By adopting the method for reducing color difference of cold-rolled steel coil after annealing in a bell-type furnace provided by the present invention, the annealing atmosphere is changed from nitrogen to hydrogen annealing, thereby avoiding color difference after leaving the furnace and rework, and generating spot goods.

[0016] Example 1 The method for reducing color difference of cold-rolled steel coils after bell-type furnace annealing provided in this embodiment specifically includes the following steps after an emergency purge of the bell-type furnace occurs: (1) Adjust the annealing heating program of the bell-type furnace to the initial stage according to the annealing process requirements, and when the temperature in the bell-type furnace drops to 350°C, buckle the heating cover of the bell-type furnace onto the cold-rolled steel coil and start the annealing heating program of the bell-type furnace; (2) Control the temperature in the bell-type furnace to 500℃, heat it for 2 hours, keep it warm for 2 hours, and then purge the bell-type furnace for 30m. 3 / h of hydrogen for 4h to convert the annealing atmosphere in the bell-type furnace into a hydrogen atmosphere; (3) After completing the annealing heating process, start the cooling process of the bell furnace and remove the heating hood to allow the cold-rolled steel coil to cool naturally.

[0017] Furthermore, before step (1), the method further includes: checking whether the inner cover of the heating cover is leaking; if leakage occurs, increasing the working pressure of the bell-type furnace to restore the pressure inside the furnace to the standard working pressure of the bell-type furnace.

[0018] Furthermore, after the emergency purge of the bell furnace occurs, the temperature in the bell furnace drops to 450° C. and then enters step (1).

[0019] After a steel plant adopted the method provided in this embodiment, the monthly repair rate decreased by 25%, and the monthly economic benefit obtained was: monthly repair volume × reduction in repair rate × repair price difference × contribution coefficient = 510 tons × 25% × 200 yuan / ton × 0.2 = 29,900 yuan; the total annual economic benefit was: 29,900 yuan × 12 months = 358,800 yuan.

[0020] The surface quality of the cold rolled steel coil obtained without the method described in this embodiment is as follows: Figure 1 As shown, the surface quality is black and not shiny, with obvious color difference. In the actual production of the steel plant, an average of 15-20 furnaces need to be repaired each month, and the repair output is about 1350 tons to 1800 tons. The surface quality of the cold-rolled steel coil obtained by the method described in this embodiment is as follows Figure 2As shown, there is no obvious color difference. When applied in actual production, it does not need to be repaired after being taken out of the furnace, and then repaired during the annealing process (about 8-10 hours), which takes up 300-400 tons of production and can save 1050 tons to 1400 tons of annealing production.

[0021] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reducing color difference of cold rolled steel coil after bell furnace annealing, characterized in that: After the bell-type furnace has an emergency purge, the following steps are included: (1) Adjust the annealing heating program of the bell-type furnace to the initial stage according to the annealing process requirements, and when the temperature in the bell-type furnace drops to 300℃-400℃, buckle the heating cover of the bell-type furnace onto the cold-rolled steel coil and start the annealing heating program of the bell-type furnace; (2) Control the temperature in the bell-type furnace to 450℃-550℃, heat for 1.5h-2.5h, keep warm for 1.5h-2.5h, and then purge 20m into the bell-type furnace. 3 / h-30m 3 / h of hydrogen for 3h-4h to convert the annealing atmosphere in the bell-type furnace into a hydrogen atmosphere; (3) After completing the annealing heating process, start the cooling process of the bell furnace and remove the heating hood to allow the cold-rolled steel coil to cool naturally.

2. The method for reducing color difference of cold rolled steel after bell furnace annealing according to claim 1, characterized in that: Before step (1), the method further includes: checking whether the inner cover of the heating cover is leaking; if leakage occurs, increasing the working pressure of the bell-type furnace to restore the pressure inside the furnace to the standard working pressure of the bell-type furnace.

3. The method for reducing color difference of cold rolled steel after coil bell furnace annealing according to claim 1, characterized in that: After the emergency purging of the bell furnace, the temperature in the bell furnace drops to 350°C-450°C and then enters step (1).

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