CN1473945A - Locally reinforced heating method and device for hot rolling steel billet before discharging - Google Patents

Abstract

The local heating process for reinforced heating rolled steel billet includes the following steps: calculating the temperature distribution of discharged steel billet; calculating the reinforced heating time for the steel billet inside the furnace; establishing local reinforced heating area or chamber in the last end of the heating furnace based on the calculated data and heating the local 200-300 mm long areas in two ends of the steel billet at the temperature 80-120 deg.c higher than the average furnace temperature for 20-30 sec. The local heating apparatus features its at least one pair of burning nozzles installed on two side walls or top of the local heating area for the reinforced heating. The present invention can reduce the surface temperature difference in the steel billet to be rolled, raise the rolling temperature homogeneity and raise rolling quality.

Description

Local strengthening heating means and device before hot rolling steel billet is come out of the stove

Technical field

The present invention relates to a kind of hot rolling steel billet reheat, local strengthening heating means and device before particularly a kind of hot rolling steel billet is come out of the stove.

Background technology

Steel billet needs heating before hot rolling, steel billet temperature is heated even more well more before wishing to come out of the stove when heating finishes by existing technology.Before yet the uniform steel billet of tapping temperature is delivered to milling train by roller-way, because heat radiation makes the uniform steel billet of original temperature become inhomogeneous.This phenomenon is long more in fed distance, the cooling intensity of roller-way surrounding enviroment is big more, and temperature is inhomogeneous more during the steel billet feed mill.Fig. 1, Fig. 2 are the continuous casting steel billet of surveying and the continuous casting square billet surface temperature distribution curves at feed mill forward position steel billet length direction.Can get from measured curve, continuously cast bloom two ends temperature is lower than medium temperature, and the scene is commonly called as " pregnant " phenomenon, the temperature difference about 40～50 ℃ (slabs) and 50～70 ℃ (square billet).Such temperature difference steel grade (silicon steel etc.) higher to the rolling temperature uniformity requirement can cause rolling quality problems, even the difficulty of can nipping (as rolled wire time), and then influences steel rolling production.And at present, still do not have and a kind ofly can address this problem method and apparatus.

Summary of the invention

The objective of the invention is in order to reduce the surface temperature difference of steel billet, improve the rolling temperature homogeneity at feed mill forward position steel billet length direction, provide a kind of hot rolling steel billet to come out of the stove before local strengthening heating means and device.

The characteristics of method proposed by the invention are that it may further comprise the steps:

1, calculating steel billet tapping temperature distribution steel billet tapping temperature distribution requirement can press the biographies thermal model and obtain through numerical evaluation: $\mathrm{\λ}\frac{{\∂}^{2}T}{{\∂X}^2}-\frac{\mathrm{\ϵ\σ}}{b_1}(T^4-T_{\∞}^4)=\mathrm{\ρc}\frac{\∂T}{\∂t}$ $X=0\frac{\∂T}{\∂X}=0$ $X=L-\mathrm{\λ}\frac{\∂T}{\∂X}=\mathrm{\ϵ\σ}(T^4-T_{\∞}^4)$

T=τ T=f (x) wherein λ, ρ, c, ε is respectively thermal conductivity, density, specific heat and the blackness of blank, and σ is the Si Difen constant, b ₁Square billet is got half that size dimension, slab are got gauge, and T is a steel billet temperature distribution along its length, and X is a steel billet coordinate along its length, T _∞Be envrionment temperature, τ be steel billet from the required transmission time of the rolling mill of coming out of the stove, f (x) is the τ temperature distribution of steel billet constantly;

2, the Time Calculation steel billet of steel billet local strengthening heating in stove following heat transfer model of time of local strengthening heating in stove calculates $\mathrm{\ρcLS}\frac{\mathrm{dT}}{\mathrm{d\τ}}=\mathrm{\α}(T_{\∞}-T)$

τ=0 T=T ₁In the following formula ρ, c as described above, L=200mm, S are the blank sectional area, α is the rad equivalent coefficient of heat transfer, T _∞Be local strengthening heating furnace gas temperature, T is the blank end temperature, and τ is local strengthening heat-up time, T ₁Temperature when leaving soaking zone for blank;

3, obtain the steel billet two ends along in the subrange of length 200-300mm based on aforementioned calculation, Heating temperature needs these data than 4～10 ℃ of other steel billet scopes raisings, set up a local strengthening heating zone or local strengthening heating chamber at process furnace soaking zone end, heating is strengthened along the subrange of length 200-300mm in the steel billet two ends, make temperatures at localized regions (being the regional area furnace temperature) be approximately higher than 80～120 ℃ of soaking zone furnace temperature, 20～30 seconds heat-up times.

The device that designs in order to realize aforesaid method is:

1, the both walls of the local strengthening heating zone of setting up at process furnace soaking zone end is equipped with 1 pair of burning at least and chews, and strengthens heating to finishing the steel billet two ends that soaking is about to come out of the stove.

2, in soaking zone end, set up a local strengthening heating chamber, the both walls of local strengthening heating chamber or furnace roof both sides are equipped with 1 pair of burning at least and chew finishing the steel billet two ends reinforcement heating that soaking is about to come out of the stove.

Adopt the present invention, reduce the surface temperature difference of continuous casting steel billet at feed mill forward position steel billet length direction, improve the rolling temperature homogeneity, improve the product rolling quality, reduce scrap rate, rolling rate improves, and reduces production costs.

Description of drawings

Fig. 1 is the slab that is of a size of 10000 * 2000 * 230mm temperature distribution history along its length;

Fig. 2 is the square billet that is of a size of 11000 * 140 * 140mm temperature distribution history along its length;

Fig. 3 need strengthen the heated perimeter synoptic diagram for the slab two ends;

Fig. 4 need strengthen the heated perimeter synoptic diagram for the square billet two ends;

Fig. 5 is a local strengthening heating zone structural representation;

Fig. 6 is the A-A sectional view of Fig. 5;

Fig. 7 is a local strengthening heating chamber structural representation;

Fig. 8 is the A-A sectional view of Fig. 7.

Embodiment

Present method is based on calculating and the steel billet Time Calculation that local strengthening heats in stove that the steel billet tapping temperature distributes and requires, and details are as follows:

1, the calculating of tapping temperature distribution requirement

Steel billet tapping temperature distribution requirement can be pressed the biographies thermal model and be obtained through numerical evaluation: $\mathrm{\λ}\frac{{\∂}^{2}T}{{\∂X}^2}-\frac{\mathrm{\ϵ\σ}}{b_1}(T^4-T_{\∞}^4)=\mathrm{\ρc}\frac{\∂T}{\∂t}$ $X=0\frac{\∂T}{\∂X}=0$ $X=L-\mathrm{\λ}\frac{\∂T}{\∂X}=\mathrm{\ϵ\σ}(T^4-T_{\∞}^4)$

T=τ T=f (x) wherein λ, ρ, c, ε is respectively thermal conductivity, density, specific heat and the blackness of blank, and σ is the Si Difen constant, b ₁Square billet is got half that size dimension, slab are got gauge, and T is a steel billet temperature distribution along its length, and X is a steel billet coordinate along its length, T _∞Be envrionment temperature, τ be steel billet from the required transmission time of the rolling mill of coming out of the stove, f (x) is the τ temperature distribution of steel billet constantly.

Calculated example: is 140 * 140mm to length for 12m, cross section ²45 ^#Wire blank, the temperature distribution when getting it to milling train is: T=1000 ℃ at x=0 place; T=960 ℃ at x=6m place.The situation that gets blank end temperature and adjacent regions temperature as calculated is as follows: (℃)

Transmit cooling time	25 seconds	35 seconds	40 seconds	45 seconds
					The blank end temperature	????988	????1001	????1007	????1014
Temperature from end 200mm place	????984	????994	????998	????1004

Can obtain in transmission is 25～45 seconds time range cooling time from the data of last table, the blank end temperature should be than high 4～10 ℃ from the temperature at end 200mm place.

2, strengthen the Time Calculation of heating

Steel billet following heat transfer model of time of local strengthening heating in stove calculates $\mathrm{\ρcLS}\frac{\mathrm{dT}}{\mathrm{d\τ}}=\mathrm{\α}(T_{\∞}-T)$

τ=0 T=T ₁In the following formula ρ, c as described above, L=200mm, S are the blank sectional area, α is the rad equivalent coefficient of heat transfer, T _∞Be local strengthening heating furnace gas temperature, T is the blank end temperature, and τ is local strengthening heat-up time, T ₁Temperature when leaving soaking zone for blank.

Calculated example: the temperature the when temperature of getting the L=200mm place is left soaking zone as blank, T _∞Get 1100 ℃ by experience, the time following (second) that the local strengthening heating is required

Temperature when blank leaves soaking zone (℃)	????984	????994	????998	????1004
					The time that the local strengthening heating is required	????20	????25	????27	????30

3, obtain steel billet two ends these data based on aforementioned calculation along 4～10 ℃ of the raisings of length 200-300mm, set up a localization heating zone or a local strengthening heating chamber at the soaking zone end, to the steel billet two ends along length 200-300mm, indicate shown in the oblique line part as Fig. 3, Fig. 4, subrange is strengthened heating, make temperatures at localized regions (being the regional area furnace temperature) be approximately higher than 80～120 ℃ of soaking zone furnace temperature, 20～30 seconds heat-up times.

Enforcement of the present invention is example with the three-stage heating furnace, and as Fig. 5, shown in Figure 7, process furnace is made up of preheating section 1, heating zone 2, soaking zone 3, for realize hot rolling steel billet come out of the stove before its characteristics of local strengthening heating method device be:

1, sets up a local strengthening heating zone 4 at process furnace soaking zone 3 ends, promptly will go out the both walls of fire door,, be equipped with 1 pair of burning at least and chew 5, finishing the steel billet two ends reinforcement heating that soaking is about to come out of the stove according to the steel billet kind at stove soaking zone end.Under the preceding topic that does not change the existing type of furnace, the both walls (from 0.3～2 meter of outlet) that is about to out fire door at the stove soaking zone is reconstructed into half garden arc indent side wall 6 with the stove inwall, as Fig. 5, shown in Figure 6, and in the indent furnace wall of both sides, respectively be equipped with 1 when square billet (heating), 2～3 burnt and chew (during the heating slab).Strengthen heating to finishing the steel billet two ends that soaking is about to come out of the stove, the furnace temperature of strengthening heating region is greater than 80～120 ℃ of soaking zone furnace temperature, 20～30 seconds heat-up times.

2, in soaking zone end, set up a local strengthening heating chamber 7, the both walls of local strengthening heating chamber or furnace roof both sides according to the steel billet kind, are equipped with 1 pair of burning at least and chew 5 pairs and finished the steel billet two ends that soaking is about to come out of the stove and strengthen heating.The burning of local strengthening heating chamber is chewed and is placed in both walls or arc inner concavity place, half garden, furnace roof both sides, installs that 1 pair of burning is chewed when square billet (heating), 2～3 pairs of burnings are chewed (during the heating slab), as Fig. 7, shown in Figure 8.The furnace temperature of strengthening the heating chamber both sides is greater than 80～120 ℃ of soaking zone furnace temperature, 18～30 seconds of heat-up time.It is to form even thermal radiation that the advantage of chewing is burnt in the installation of arc inner concavity place, above-described half garden.

Claims (2)

1, local strengthening heating means before a kind of hot rolling steel billet is come out of the stove is characterized in that method steps is:

(1) calculating the steel billet tapping temperature distributes

Steel billet tapping temperature distribution requirement can be pressed the biographies thermal model and be obtained through numerical evaluation: $\mathrm{\λ}\frac{{\∂}^{2}T}{{\∂X}^2}-\frac{\mathrm{\ϵ\σ}}{b_1}(T^4-T_{\∞}^4)=\mathrm{\ρc}\frac{\∂T}{\∂t}$ $X=0\frac{\∂T}{\∂X}=0$ $X=L-\mathrm{\λ}\frac{\∂T}{\∂X}=\mathrm{\ϵ\σ}(T^4-T_{\∞}^4)$

T=τ T=f (x) wherein λ, ρ, c, ε is respectively thermal conductivity, density, specific heat and the blackness of blank, and σ is the Si Difen constant, b ₁Square billet is got half that size dimension, slab are got gauge, and T is a steel billet temperature distribution along its length, and X is a steel billet coordinate along its length, T _∞Be envrionment temperature, τ be steel billet from the required transmission time of the rolling mill of coming out of the stove, f (x) is the τ temperature distribution of steel billet constantly;

(2) Time Calculation of steel billet local strengthening heating in stove

Steel billet following heat transfer model of time of local strengthening heating in stove calculates $\mathrm{\ρcLS}\frac{\mathrm{dT}}{\mathrm{d\τ}}=\mathrm{\α}(T_{\∞}-T)$

τ=0 T=T ₁In the following formula ρ, c as described above, L=200mm, S are the blank sectional area, α is the rad equivalent coefficient of heat transfer, T _∞Be local strengthening heating furnace gas temperature, T is the blank end temperature, and τ is local strengthening heat-up time, T ₁Temperature when leaving soaking zone for blank;

(3) obtain the steel billet two ends along in the subrange of length 200-300mm based on aforementioned calculation, Heating temperature needs these data than 4～10 ℃ of other steel billet scopes raisings, set up a local strengthening heating zone (4) or local strengthening heating chamber (6) at process furnace soaking zone (3) end, heating is strengthened along the subrange of length 200-300mm in the steel billet two ends, making temperatures at localized regions is that the regional area furnace temperature is higher than 80～120 ℃ of soaking zone furnace temperature, 20～30 seconds heat-up times.

2, plant hot rolling steel billet come out of the stove before the device of local strengthening heating means, the both walls that it is characterized in that the local strengthening heating zone (4) set up at process furnace soaking zone (3) end is equipped with 1 pair of burning at least and chews (5); The both walls of the local strengthening heating chamber of setting up in soaking zone end or furnace roof both sides are equipped with 1 pair of burning at least and chew (5).

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