Production method for heating high-strength medium-thickness plate based on bogie-hearth resistance furnace

Abstract

The invention relates to a production method for heating a high-strength medium-thickness plate based on a bogie-hearth resistance furnace, and belongs to the technical field of medium-thickness plate production in the metallurgical industry. According to the technical scheme, the method is operated according to the following steps that firstly, one or more layers of refractory bricks are laid on a steel casting furnace bottom plate of the trolley type high-temperature resistance furnace; 2, wrapping the four side edges, the upper surface and the lower surface of the plate blank with high-temperature refractory cotton or refractory felt, and fixing the plate blank with adhesive tape or ropes after wrapping; and thirdly, the wrapped plate blank is hoisted to a trolley on which refractory bricks are laid, pushed into a resistance furnace to be heated and subjected to heat preservation, and then discharged out of the furnace to be rolled. The method has the beneficial effects that the trolley type resistance furnace is used for replacing a traditional stepping type or steel pushing type gas heating furnace to heat the plate blank, the inherent defects of the resistance furnace for heating the plate blank are overcome, and the rolling success rate of the continuous casting blank reaches 100%; and the straightness of the produced finished steel plate can be stably controlled within 8mm / 2m, so that high-standard requirements for special purposes are met.

Description

Technical Field

[0001] This invention relates to a production method for high-strength medium-thick plates based on trolley-type resistance furnace heating, belonging to the technical field of high-strength medium-thick plate production equipment in the metallurgical industry. Background Technology

[0002] An electric resistance furnace is an industrial furnace that uses electric current to heat heating elements inside the furnace, thereby heating workpieces or materials. Compared with traditional flame furnaces, electric resistance furnaces have advantages such as uniform furnace temperature, precise temperature control, high thermal efficiency, and a better operating environment. Currently, electric resistance furnaces are widely used in metal heat treatment, brazing, powder metallurgy sintering, and other fields.

[0003] However, in the large-scale continuous production of medium and heavy plates in large steel enterprises, walking beam or pusher-type gas-fired heating furnaces are commonly used, and trolley-type resistance furnaces are rarely used for heating and rolling continuously cast billets or steel ingots. This is mainly because the heating method of resistance furnaces is primarily through radiation and conduction, which is fundamentally different from that of flame furnaces. The following technical challenges exist when using trolley-type resistance furnaces to heat large-section slabs: (1) Uneven heating of slab leads to rolling warping: The slab is placed directly on the metal furnace bottom plate. Its lower surface is heated by contact conduction, while the upper surface and sides are heated by radiation, resulting in a huge temperature gradient inside the slab, especially the temperature difference between the upper and lower surfaces. During the rolling process, the metal on the lower surface, which has a higher temperature and better ductility, flows faster, causing the steel plate to warp or buckle uncontrollably, which seriously affects the rolling stability and yield. (2) The main heat transfer direction is singular: the heat conducted from the bottom plate of the furnace is transferred from bottom to top, which aggravates the non-uniformity of the internal structure and properties of the slab; (3) Mismatch in rolling process: The traditional rolling process designed based on the characteristics of flame furnace heating cannot adapt to the temperature change law of resistance furnace heating slab, which leads to further deterioration of warping problem.

[0004] Therefore, developing a method that can overcome the above-mentioned defects and is suitable for producing high-quality medium and heavy plates, especially high-strength steel with high temperature sensitivity, using a bogie-type resistance furnace has important industrial application value. Summary of the Invention

[0005] The purpose of this invention is to provide a production method for high-strength medium-thick plates based on trolley-type resistance furnace heating. This method uses a trolley-type resistance furnace to replace the traditional walking beam or pusher-type gas heating furnace for heating the slab and optimizes the rolling process, thereby solving the problems existing in the background technology.

[0006] The technical solution of this invention is: A production method for high-strength medium-thick plates based on heating in a bogie-type resistance furnace, comprising the following steps: Step 1: Lay one or more layers of refractory bricks on the cast steel furnace bottom plate of the bogie-type high-temperature resistance furnace. Step 2: Wrap the four sides and top and bottom surfaces of the slab with high-temperature refractory cotton or refractory felt, and then fix it with tape or rope. Step 3: The wrapped slab is hoisted onto a trolley lined with refractory bricks, pushed into the electric resistance furnace for heating and heat preservation, and then taken out of the furnace for rolling.

[0007] In step one, the thickness of the refractory bricks laid is 60mm-120mm.

[0008] In step one, the refractory bricks are laid in a thick arrangement with a certain spacing.

[0009] In step two, the thickness of the refractory cotton or refractory felt is 10-30mm.

[0010] In step three, the slab is slowly and evenly heated to 800℃~1200℃ in an electric resistance furnace and held at that temperature for a certain period of time.

[0011] In step three, during slab rolling, the single-pass reduction rate of the first two passes is controlled at 5%-10%, the single-pass reduction rate of the middle passes is controlled at 15%-25%, and the rolling force of the last three passes gradually decreases, with the difference in rolling force between passes controlled within 10000KN.

[0012] The beneficial effects of this invention are: (1) High success rate: It solves the inherent defects of heating slabs in resistance furnaces, and makes the rolling success rate of continuous casting slabs reach 100%; (2) Excellent quality: The flatness of the finished steel plates produced is excellent and can be stably controlled within 8mm / 2m, meeting the high standard requirements for special purposes; (3) Low cost and easy to implement: This invention does not require the purchase of expensive equipment. It can be achieved simply by adding refractory bricks to the existing bogie furnace, wrapping the slab with common refractory materials, and optimizing the rolling process. It can be made from local materials and is very suitable for promotion and application in factories with bogie-type resistance furnaces. (4) Wide applicability: This method is not only applicable to high-strength steel, but also has important reference value for the production of medium and heavy plates of other alloy steels, high-strength steels and ultra-high-strength steels. Attached Figure Description

[0013] Figure 1 Rendering of a refractory brick laying process on a cast steel furnace bottom plate; Figure 2 Image showing the effect of pre-treatment for wrapping slabs; Detailed Implementation

[0014] The invention will be further described below with reference to the accompanying drawings and examples.

[0015] See attached document Figure 1 , 2 A production method for high-strength medium-thick plates based on heating in a bogie-type resistance furnace, comprising the following steps: Step 1: Lay one or more layers of refractory bricks on the cast steel furnace bottom plate of the bogie-type high-temperature resistance furnace. Step 2: Wrap the four sides and top and bottom surfaces of the slab with high-temperature refractory cotton or refractory felt, and then fix it with tape or rope. Step 3: The wrapped slab is hoisted onto a trolley lined with refractory bricks, pushed into the electric resistance furnace for heating and heat preservation, and then taken out of the furnace for rolling.

[0016] In this embodiment, refer to the appendix Figure 1 , 2 The core of this high-strength medium-thick plate production method lies in the use of a trolley-type high-temperature resistance furnace for heating, and includes the following steps: Step 1: Improve the existing bogie-type high-temperature resistance furnace like Figure 1 As shown, a layer of standard refractory bricks is laid flat on the pressure-resistant and high-temperature-resistant cast steel furnace bottom plate of a bogie-type high-temperature resistance furnace to form a solid load-bearing surface. The thickness of the refractory bricks can be selected according to the weight of the slab and the heating temperature, usually between 60mm and 120mm. This allows the slab to be placed on the refractory bricks, rather than in direct contact with the metal furnace bottom plate. This transforms the contact conduction heating method of the slab's lower surface into radiation and indirect conduction heating through the suspended refractory bricks, significantly reducing the temperature difference between the upper and lower surfaces of the slab, fundamentally changing the heating method of the slab, and solving the problem of rolling warping caused by overheating of the lower surface. Step 2: Slab Pretreatment like Figure 2 As shown, high-temperature refractory cotton or refractory felt with a thickness of 10-30mm should be used to tightly wrap the four sides and top and bottom surfaces of the slab. After wrapping, it can be fixed with tape or rope. This measure aims to equalize the heating conditions of each surface of the slab, reduce radiative heat loss from the sides and ends, and make the heating mode of each surface of the slab more consistent during the heating process in the resistance furnace, thus ensuring the uniformity of the overall temperature of the slab. Step 3: Heating and Rolling 1. Loading and Heating: The wrapped slab is hoisted onto a trolley lined with refractory bricks and pushed into the furnace. A heating curve is set, and the slab is slowly and evenly heated in the resistance furnace to a rolling temperature of 800℃~1200℃, and held at that temperature for a certain period of time to ensure uniform temperature between the core and surface of the slab. 2. Adaptive rolling: The heated slab is taken out and sent into the rolling mill for rolling; 3. Initial passes: The single-pass reduction rate of the first two passes is controlled at 5%-10%. Based on the rolling conditions of the two passes, the warping situation of the billet during the rolling process is confirmed. The extension height of the lower cylinder of the rolling mill and the speed difference between the upper and lower working rolls are adjusted appropriately. At the same time, a small straightening torque is applied to the billet, and the flowability of the upper surface metal is balanced by the speed difference to suppress warping that may be caused by residual temperature difference. 3. Intermediate passes: After the overall temperature of the slab is more uniform, the normal rolling process is resumed. The single-pass reduction rate can be increased to 15%-25%, so that the rolling force can fully penetrate into the core and achieve the effect of refining the core grains. 4. Final rolling passes: Adjust the rolling force of the last three passes to make the rolling force of the last three passes show a decreasing trend, and control the difference in rolling force between passes within 10000KN. This is to improve the rolling difficulty caused by the low temperature of the final rolling passes, while also leveling the steel plate shape to ensure the stability of the steel plate rolling process and the straightness of the steel plate.

[0017] Effect verification The high-strength medium-thick plates produced using the method of this invention were produced in 10 consecutive batches, totaling 20 steel plates. The rolling process was stable, with no accidents such as steel jamming or scrapping caused by warping, and the rolling success rate reached 100%. The flatness of the finished steel plates was tested, and the unevenness was less than 8mm / 2m, fully meeting the high standard requirements.

Claims

1. A production method for high-strength medium-thick plates based on trolley-type resistance furnace heating, characterized in that: Follow these steps: Step 1: Lay one or more layers of refractory bricks on the cast steel furnace bottom plate of the bogie-type high-temperature resistance furnace. Step 2: Wrap the four sides and top and bottom surfaces of the slab with high-temperature refractory cotton or refractory felt, and then fix it with tape or rope. Step 3: The wrapped slab is hoisted onto a trolley lined with refractory bricks, pushed into the electric resistance furnace for heating and heat preservation, and then taken out of the furnace for rolling.

2. The production method of high-strength medium-thick plates based on trolley-type resistance furnace heating according to claim 1, characterized in that: In step one, the thickness of the refractory bricks laid is 60mm-120mm.

3. The production method of high-strength medium-thick plates based on trolley-type resistance furnace heating according to claim 2, characterized in that: In step one, the refractory bricks are laid in a thick arrangement with a certain spacing.

4. The production method of high-strength medium-thick plates based on trolley-type resistance furnace heating according to claim 1, characterized in that: In step two, the thickness of the refractory cotton or refractory felt is 10-30mm.

5. The production method of high-strength medium-thick plates based on trolley-type resistance furnace heating according to claim 1, characterized in that: In step three, the slab is slowly and evenly heated to 800℃~1200℃ in an electric resistance furnace and held at that temperature for a certain period of time.

6. The production method of high-strength medium-thick plates based on trolley-type resistance furnace heating according to claim 5, characterized in that: In step three, during slab rolling, the single-pass reduction rate of the first two passes is controlled at 5%-10%, the single-pass reduction rate of the middle passes is controlled at 15%-25%, and the rolling force of the last three passes gradually decreases, with the difference in rolling force between passes controlled within 10000KN.

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