Method for improving steel billet heating temperature uniformity of pusher-type heating furnace

Abstract

The invention relates to the technical field of heating of pusher-type heating furnaces, in particular to a method for improving temperature uniformity of heated billets of a pusher-type heating furnace, heat conduction and heat transfer quantity q1 and radiation heat transfer quantity q2 of the billets are obtained according to Tz and Tb, the radiation heat transfer quantity q2 of the billets is larger than the heat conduction and heat transfer quantity q1, the adjacent billets are separated, heat radiation and heat transfer of the side faces of the billets are increased, and heat transfer efficiency is improved. The heat transfer quantity difference value delta Q is obtained through the heat conduction and heat transfer quantity q1 and the radiation heat transfer quantity q2, finally the heating time tX of the steel billet meeting the temperature uniformity requirement is obtained, the heating time t of the steel billet is larger than or equal to tX, and the steel billet tapping temperature requirement is met. The problem that the overall temperature uniformity is poor is solved, the heat transfer capacity is improved, the heating time is shortened, the billet heating temperature uniformity is improved, and the heating in-furnace time is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of heating in pusher-type reheating furnaces, and particularly to a method for improving the temperature uniformity of billets heated in pusher-type reheating furnaces. Background Art

[0002] The temperature uniformity of a pusher-type reheating furnace is an important process parameter, which directly affects the heating quality of billets and the stability of the subsequent rolling process.

[0003] However, when the pusher-type reheating furnace is operating, there is no gap between the billets being heated in the furnace, which results in a temperature difference across the cross-section of the billets. Since the transfer and distribution of heat between the billets are restricted, it is difficult to ensure that each billet is uniformly heated. This temperature difference may cause non-uniform deformation and internal stress in the billets during the heating process, affecting the quality of the final product.

[0004] To improve the temperature uniformity of the pusher-type reheating furnace, some measures can be taken. For example, optimizing the heating regime, adjusting the temperature distribution, heating time, and heating speed of the reheating furnace so that each part of the billet reaches the predetermined heating temperature. Despite these improvement measures, the pusher-type reheating furnace may still have certain limitations in terms of temperature uniformity. Summary of the Invention

[0005] To overcome the deficiencies of the prior art, the present invention provides a method for improving the temperature uniformity of billets heated in pusher-type reheating furnaces. According to T z and T b the heat transfer by conduction q1 and the heat transfer by radiation q2 of the billet are obtained. The heat transfer by radiation q2 of the billet > the heat transfer by conduction q1. The adjacent billets are separated to increase the heat transfer by thermal radiation on the side of the billets. The heat transfer difference ΔQ is obtained through the heat transfer by conduction q1 and the heat transfer by radiation q2. Finally, the heating time t required for the billet to meet the temperature uniformity requirement is obtained as t X The heating time t of the billet ≥ t X This not only meets the requirement of the billet's furnace outlet temperature but also effectively reduces the problem of low side temperature caused by the billets being close to each other in the pusher-type reheating furnace and poor overall temperature uniformity.

[0006] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0007] A method for improving the temperature uniformity of billets heated in pusher-type reheating furnaces, the method for improving the temperature uniformity of billets heated in pusher-type reheating furnaces specifically includes the following steps:

[0008] S1. Collect the data of the furnace temperature T L of the soaking section of the billet;

[0009] S2. Through on-line temperature testing of the steel billet, it is obtained through testing that the average temperature T at the center of the soaking section of the steel billet z ; the surface temperature T of the steel billet b is calculated by the following empirical formula:

[0010] T b = 0.995 × T L T L < 1000 °C;

[0011] T b = 0.95 × T L 1000 < T L ≤ 1200 °C;

[0012] T b = 0.9 × T L T L > 1200 °C;

[0013] Establish a relational database of T z and T b ; obtain T b through T z ;

[0014] S3. The thermal conductivity of the steel billet at T z is λ z ; the thermal conductivity of the steel billet at T b is λ b ; the average thermal conductivity is λ:

[0015]

[0016] S4. The heat transfer by conduction from the surface to the center of the steel billet is where h is the thickness of the steel billet;

[0017] S5. The heat transfer by radiation from the heating furnace to the steel billet is where C is the heat radiation coefficient;

[0018] S6. When the steel billet moves to the discharge furnace door, separate the adjacent steel billets to increase the heat radiation heat transfer on the side of the steel billet and shorten the heating time;

[0019] S7. When the steel billet moves to the discharge end and is about to be discharged from the furnace, collect the residence time t of the soaking section of the steel billet in the furnace; calculate the difference in the heat transfer amount between radiation heat transfer and heat conduction at the same time: ΔQ = (q2 - 2q1)t;

[0020] S8. The heat supply gap for the steel billet at the discharge end to meet the temperature uniformity requirement is ΔQ, and the heating time required for the steel billet to meet the temperature uniformity requirement is t X ; it is obtained through calculation that: t X = ΔQ / q2;

[0021] S9. When the heating time t of the steel billet in the furnace satisfies t ≥ t X , the temperature requirement of the steel billet when it leaves the furnace is met; when the heating time t of the steel billet is less than t X , the heating time of the steel billet in the heating furnace is extended to t X -t.

[0022] Further, the different steel grades and specifications include the thickness h of the steel billet and the density ρ of the steel billet.

[0023] Further, the relationship between the T z and T b is obtained through on-line temperature testing of the steel billet.

[0024] Further, in step S6, the steel billet at the discharge furnace door moves forward 30 - 40 cm, separating the originally adjacent steel billets, changing the heat transfer from conduction on the side to radiation heat transfer, and increasing the heat transfer amount.

[0025] Further, the units of q1 and q2 are KJ / m 2 ·h.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. The radiation heat transfer amount q2 of the steel billet is greater than the conduction heat transfer amount q1, increasing the heat radiation transfer on the side of the steel billet, increasing the heat transfer amount, shortening the heating time, improving the temperature uniformity of the steel billet during heating, and reducing the heating time in the furnace.

[0028] 2. It effectively reduces the low temperature on the side caused by the close contact of the steel billets in the pusher-type heating furnace, changes the conduction heat transfer amount to the radiation heat transfer amount, ensures the time in the furnace, and solves the problem of poor overall temperature uniformity of the steel billets. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the control flow chart of improving the temperature uniformity of the steel billet in the pusher-type heating furnace described in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following further describes the specific embodiments of the present invention:

[0031] As Figure 1 shown, it is known that the average charging temperature of the steel billet is T z = 30°C, the thickness h of the steel billet is 150 mm, the density ρ of the steel billet is 7800 kg / m 3 , and the furnace temperature in the soaking section is T L = 1280°C.

[0032] Through on-line temperature testing of the steel billet, it is obtained that the average temperature T z at the center of the soaking section of the steel billet is 1100°C; the surface temperature T of the steel billetb Calculated by the following empirical formula,

[0033] T b = 0.995 × T L , where T L < 1000 °C;

[0034] T b = 0.95 × T L when 1000 < T L ≤ 1200 °C;

[0035] T b = 0.9 × T L when T L > 1200 °C;

[0036] [[ID=3I]]The soaking section billet surface temperature T is obtained as b = 1280 °C × 0.9 = 1152 °C.

[0037] According to the material handbook, the thermal conductivity of the billet at T z is λ z = 102.56 KJ / m·h·°C, and the thermal conductivity of the billet at T b is λ b = 105.49 KJ / m·h·°C. The average thermal conductivity is λ.

[0038] The heat transfer by conduction from the surface to the center of the billet is:

[0039]

[0040] The radiant heat transfer of the heating furnace to the billet is known as C = 10.5 KJ / m 2 ·h·K 4 :

[0041]

[0042] When the heating furnace heats the billet, the radiant heat transfer q1 of the billet is greater than the conductive heat transfer q2. When the billets are close to each other, heat transfer occurs through the heat conduction between the upper and lower sides of the billet sides. The discharging machine is used to move the billet at the furnace door forward by 30 cm to separate the adjacent billets, so that the heat conduction between the originally adjacent billet sides is changed to radiant heat transfer. The radiant heat transfer on the billet side increases the heat transfer amount and shortens the heating time.

[0043] When the billet moves to the discharging end and is about to be discharged from the furnace, the soaking section time of the billet in the furnace is collected as t = 0.6 h; calculate the difference in the heat transfer amount between radiant heat transfer and heat conduction under the same time.

[0044] ΔQ = (q2 - 2q1)t = 20146.92 KJ / m 2 。

[0045] The above calculation shows that the heat supply gap for the billet to meet the temperature uniformity requirement is ΔQ, and the time required for the billet to be heated to meet the temperature uniformity requirement is t x ,through calculation,

[0046] t x = ΔQ / q2 = 0.11 h.

[0047] The residence time of the billet in the furnace is 0.6 h > 0.11 h, which meets the requirement of the billet's outgoing furnace temperature.

[0048] The above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and its concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A method for improving the temperature uniformity of billets heated in a pusher-type reheating furnace, characterized in that, The method for improving the temperature uniformity of billets in a pusher-type reheating furnace specifically includes the following steps: S1. Collect the data of the soaking section furnace temperature T of the steel billet L ; S2. Through on-line temperature testing of the steel billet, it is obtained through testing that the average temperature T at the center of the soaking section of the steel billet z ; the surface temperature T of the steel billet b is calculated by the following empirical formula: T b = 0.995 × T L , T L < 1000 °C; T b = 0.95 × T L where 1000 < T L ≤ 1200 °C; T b = 0.9 × T L ,T L > 1200 °C; Establish T z The relational database with T b Through T b Obtain T z ; S3. The thermal conductivity of the steel billet at T z is λ z . The thermal conductivity of the steel billet at T b is λ b . The average thermal conductivity is λ: S4. The heat transfer amount by heat conduction from the surface to the center of the steel billet is where h is the thickness of the steel billet; S5. The radiative heat transfer amount of the reheating furnace to the billet is where C is the thermal radiation coefficient; S6. When the billet moves to the discharge furnace door, separate the adjacent billets to increase the heat radiation heat transfer on the side of the billets and shorten the heating time; S7. When the billet moves to the discharge end and is about to be discharged from the furnace, collect the residence time t of the soaking section of the billet in the furnace; calculate the difference in the amount of heat transfer between radiation heat transfer and heat conduction at the same time: ΔQ = (q2 - 2q1)t; The heat supply gap for the billet at the discharge end to meet the temperature uniformity requirement is ΔQ, and the heating time required for the billet to meet the temperature uniformity requirement is t X , and through calculation, it is obtained that: t X = ΔQ / q2; S9. When the heating time t of the steel billet in the furnace satisfies t ≥ t X , it meets the requirement of the steel billet's outgoing furnace temperature; when the heating time t of the steel billet is less than t X , the heating time of the steel billet in the heating furnace is extended to t X - t.

2. A method for improving the temperature uniformity of billets heated in a pusher-type reheating furnace according to claim 1, characterized in that, The specifications of the billets include the billet thickness h and the billet density ρ.

3. A method for improving the temperature uniformity of billets in a pusher-type reheating furnace according to claim 1, characterized in that, T in the step S2 described above z and T b The relationship is obtained through the on-line temperature test of the steel billet.

4. A method for improving the temperature uniformity of steel billets in a pusher-type reheating furnace according to claim 1, characterized in that, In step S6, the billets at the discharge furnace door move forward 30 - 40 cm to separate the originally adjacent billets, changing the heat transfer on the side from heat conduction to radiation heat transfer and increasing the amount of heat transfer.

5. A method for improving the temperature uniformity of steel billets in a pusher-type reheating furnace according to claim 1, characterized in that, The units of q1 and q2 are KJ / m 2 ·h.

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