JPS629712A - Estimating method for mean temp. inside cross section of rolling stock in continuous hot rolling of steel bar and wire - Google Patents

Abstract

PURPOSE:To correctly estimate the average temp. inside the cross section of a rolling stock by making in advance the table showing the relation between the surface temp. of the rolling stock and average temp. inside the cross section under the representative operation conditions and by estimating based on the extract temp. of a billet from a heating furnace measured actually and others. CONSTITUTION:The average temp. inside he water cooling finished cross section after forcible cooling of the case executing a control cooling in a rear step cooling zone 25 is found. In this case the temp. distribution state is determined by the temp., cooling water flow and cooling time of the rolling stock at the inlet side of the rear step cooling zone 25. The temp. of the rolling stock at the inlet side of the rear step cooling zone 25 is determined by the extraction temp. and rolling speed of the billet fed from a heating furnace 20. The average temp. inside the water cooled finishing cross section of the rolling stock can be therefore correctly estimated by measuring the surface temp. of the rolling stock after knowing of the water cool finishing temp. distribution state by the extraction temp. and rolling speed of the billet and cooling water flow in one of pass schedule of the rolling stock.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for estimating the average temperature within a cross section of a rolled material during continuous hot rolling of steel bars and wire rods.

(Prior technology) Heat is used to continuously roll rolled materials such as steel bars and wire rods through a large number of rolling mills that pass the fillets and throats heated in a heating furnace through a rough rolling mill train, an intermediate rolling mill, and a finishing rolling mill train. In continuous continuous rolling, controlled rolling in which the rolled material is forcedly water-cooled after the intermediate rolling mill row and controlled cooling in which the rolled material is forcedly water-cooled after the finishing mill row are performed to improve the material quality of the rolled material. It will be done.

By the way, in the past, with regard to water-cooling temperature during controlled rolling or after controlled cooling, only the surface temperature was mainly determined using a radiation thermometer, and temperature control such as finishing temperature was performed based on the surface temperature. However, various controls (mainly water cooling control) were not performed based on understanding the average temperature within the cross section, which is important for ensuring the quality of rolled materials.

That is, in the past, only the surface temperature was used.

The temperature of the rolled material was known, and based on this measured surface temperature, the water cooling temperature during controlled rolling and after controlled cooling was known.

(Problems to be Solved by the Invention) However, in the continuous hot rolling process, billets and rolled materials suffer from process heat generation, contact with rolls, cooling by forced water cooling, etc., and subsequent reheating. Due to the repeated rolling process, the rolled material has a temperature distribution within its cross section, and its surface temperature is influenced by the measurement position in the continuous hot rolling line, that is, the reheating time, etc. Therefore, the surface temperature of the rolled material is not representative of the temperature of the rolled material, and various controls based on this actually measured surface temperature are not sufficient to obtain the target quality.

This is particularly important during controlled rolling and controlled cooling.

In other words, in controlled rolling and controlled cooling, forced water cooling is usually used to obtain the target finishing temperature and water cooling temperature, but the water cooling temperature of the rolled material after forced water cooling is determined by the temperature within the cross section of the rolled material. The temperature difference in the distribution is large, and the surface temperature of the rolled material changes rapidly with the reheating time.

Therefore, in the above case, simply grasping the surface temperature of the rolled material is extremely insufficient for controlling the material quality of the rolled material, and it is extremely difficult to always obtain the target material quality.

Therefore, it is possible to estimate the average temperature within the cross section from the surface temperature of the rolled material and grasp this temperature as the representative temperature of the rolled material.In this way, it is possible to obtain the target material quality. It becomes extremely easy.

By the way, the relationship between the surface temperature of the rolled material and the average temperature within the cross section varies depending on the temperature distribution within the cross section of the rolled material.

The temperature distribution within the cross section of the rolled material changes depending on the pass schedule (dimensions of the rolled material) of the rolled material, the extraction temperature of the billet from the heating furnace, the rolling speed, and the cooling conditions during controlled rolling and controlled cooling.

Therefore, depending on the various operating conditions mentioned above,
Calculating the temperature distribution within a cross section of a rolled material and determining the relationship between the surface temperature and the average temperature within the cross section is extremely difficult online due to problems such as calculation time and complexity of operations.

Another possible method is to use a simple formula or the like to determine the average temperature within the cross section from the measured surface temperature.

However, in continuous hot rolling, various operating conditions are wide-ranging, so calculating the average cross-sectional temperature using the above-mentioned simple formula is not appropriate in terms of accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for estimating the average temperature within a cross section of a rolled material during continuous hot rolling of steel bars and wire rods, which can solve the above-mentioned problems.

(Means for solving the problems) In order to achieve the above object, the features of the present invention are as follows:
The billet extracted from the heating furnace 20 is continuously hot-rolled into rolling materials such as steel bars and wire rods through rolling mills 1 to 16, and
In the case where the rolled material is forcedly water-cooled by the cooling devices 27 and 28 provided between the intermediate rolling mill 22 and the finishing rolling mill row 23 and after the finishing rolling mill row 23, the average cross-sectional temperature of the rolled material after forced water cooling is A method for estimating a plurality of representative operating conditions in which representative values of billet extraction temperature and rolling speed from the heating furnace 20 are combined in one pass schedule out of a plurality of planned pass schedules. Below, Tables A and B showing the relationship between the typical surface temperature of the rolled material and the average temperature within the cross section are created in advance, and the actually measured extraction temperature of the billet from the heating furnace 20, rolling speed, and Based on the surface temperature of the rolled material, from the above tables A and B,
The point is to estimate the average temperature within the cross section of the rolled material by taking into account the reheating time.

(Example) Hereinafter, the present invention will be described in detail with reference to the illustrated example.
The figure shows a hot continuous rolling line, where 20 is a heating furnace for heating the billet, and a rough rolling mill row 21, an intermediate rolling mill row 22, and a finishing rolling mill row 23 are provided in series at the subsequent stage. These rolling mill rows 21, 22, 23 are the first to sixteenth rolling mill rows.
It is composed of rolling mills 1 to 16. 24 is a front cooling zone provided between the intermediate rolling mill row 22 and the finishing rolling mill row 23; 25 is a rear cooling zone provided between the finishing rolling mill row 23 and the cooling bed 26; Obi 24.25
Cooling devices 27 and 28 are provided for supplying cooling water to the rolled material, and the amount of cooling water in each of the cooling devices 27 and 28 is controlled by a control device including a process control computer 29. 30 is a thermometer that measures the surface temperature of the rolled material on the entry side of the ninth rolling mill 90; 31 is a thermometer that measures the surface temperature of the rolled material after forced water cooling on the exit side of the finishing rolling mill row 23;
2 is a thermometer for measuring the surface temperature of the rolled material after forced water cooling on the exit side of the latter cooling zone 25.

When rolling steel bars, wire rods, etc., controlled rolling is performed in which the temperature is controlled by supplying cooling water to the rolled material in an intermediate cooling zone 24 under automatic control by a computer 29, and cooling water is supplied to the product after this controlled rolling in a subsequent cooling zone 25. Controlled cooling is performed by supplying and cooling each material to improve the material quality of the rolled material.
In these cases, in order to obtain the desired material quality, it is necessary to accurately grasp the water-cooling temperature of the rolled material during controlled rolling or after controlled cooling.

Therefore, in conventional continuous hot rolling, only the surface temperature of the rolled material is known.

However, since a rolled material has a temperature distribution within its cross section, this measured surface temperature is not representative of the temperature of the rolled material.

Moreover, the surface temperature can be measured at the measurement position of the continuous hot rolling line.
That is, since the surface temperature varies greatly depending on the reheating time, etc., it is extremely insufficient to grasp the surface temperature in order to constantly obtain the target material quality through controlled rolling and controlled cooling.

For this reason, it is necessary to know the representative temperature of the rolled material, that is, the cross-sectional circular average temperature, during controlled rolling or after controlled cooling.

Next, a method for determining the finished water-cooled cross-sectional circle average temperature after forced water cooling when controlled cooling is performed in the latter cooling zone 25 will be described.

First, if the cooling device 28 of the downstream cooling zone 25 has a single cooling zone or the number of cooling zones used is always the same, that is, the difference in recuperation time from the cooling zone exit side to the temperature measurement position is not considered. Let me explain a good case.

The rising temperature of the rolled material after controlled cooling is determined by the water cooling temperature of the rolled material after controlled cooling.
This is determined by the temperature of the rolled material on the worker's side and various cooling conditions (cooling water flow rate, cooling time). It is determined by the temperature of the rolled material, the flow rate of cooling water, and the cooling time.

In addition, the temperature of the rolled material in the 25-man side of the latter cooling zone depends on the pass schedule of the rolled material (rolled material dimensions), the extraction temperature of the billet from the heating furnace, and the rolling speed.Furthermore, the cooling time also depends on the rolling speed. It will be decided individually.

Therefore, in one pass schedule for rolled material,
The water-cooling temperature distribution state within the cross section of the rolled material after controlled cooling can be known from the extraction temperature, rolling speed, and cooling water flow rate. Then, by measuring the surface temperature of the rolled material, it is possible to accurately estimate the circular average temperature of the water-cooled section of the rolled material.

FIG. 2 is a basic table for estimating the circular average temperature of the water-cooled upward cross section of the rolled material, in which the pass schedule D of the rolled material as input data and the average temperature of the billet extracted from the heating furnace 20, that is, the extracted From the temperature d, the actual rolling speed Vfm, the actual surface temperature jfffi of the rolled material measured by the thermometer 32, and the actual cooling water flow rate W1, estimate the circular average temperature of the water-cooled up cross section of the rolled material. It is something.

By the way, since there are many types of pass schedules in continuous hot rolling lines, we created an index table ■ as shown in basic table A in Figure 2 independently for each schedule, and An estimation table (2) is created for each operating condition combining the multiple values of the index table T.

First, in the index table I, for example, three representative extraction temperatures 〒d, ~T d 3 and the ratio of three typical rolling speeds to the maximum rolling speed are expressed as percentages Vr + ~
Operating conditions ① to ② are set in combination with VRS.

In addition, estimation table ■ for each of the operating conditions from ■ to ■ above.
is created, and the estimation table (■) shows the surface temperatures tfl to tf4 of four representative rolled materials, and the circular average temperature of the water-cooled up cross section of the rolled materials when the surface temperature has the above multi-values.
, 1 to 〒f4 and the cooling water flow rate W, to W4 are displayed.

In addition, the surface temperature t fl"" t f4, the cross-sectional circular average temperature 〒f.

~〒f4, at cooling water flow rates W1 to W4, tfl>
1. , >1. , >1. ,,〒fl＞〒、2〉〒f3＞〒
, 4, W l<Wz<W3<Wa.

Next, a procedure for estimating the cross-sectional circular average temperature from the surface temperature of the rolled material under each of the operating conditions (■) to (■) of the index table (■) of the basic table A will be described.

First, if the actually measured surface temperature tea is one of the surface temperatures tf+-t (4) in the estimation table (4), the cross-sectional circular average temperature can be estimated immediately, but in many cases this is not the case.

Therefore, the measured surface temperature tfM is the above-mentioned surface temperature tfl~t
If it is not the value of f4, the cross-sectional circular average temperature tm is estimated by linear interpolation as described below.

That is, now, for example, t fil<t flI< t f
2, Wa<W, <W3, and the cross-sectional circular average temperature fM in this case is determined by the following formula.

tf2 trot Next, a case where the number of cooling zones used in the cooling device 28 of the rear cooling zone 25 is not always the same, that is, a case where it is necessary to take into account the difference in recuperation time will be described.

For example, in the case of linear interpolation as described above, the cooling water flow rate W, , W, of the index table ■ of the basic table A,
When the number of cooling zones used is different in the case of
Table values (tri, 〒12), (tf:l, 〒) corresponding to the cooling water devices W2, W in the estimation table ■
By interpolating from f3), it is not possible to accurately estimate the cross-sectional circular average temperature 〒1M corresponding to the actually measured surface temperature tl++.

Therefore, when the actual measured surface temperature tf is a value between the table values (tfl to tf4) of the index table ■, and the number of cooling zones used is different in the case of two sets of table values used for interpolation, Interpolation is performed by using correction table B as shown in FIG. 2 together with estimation table (2).

Correction table B in FIG. 3 is for the case where the cooling device 2 of the second stage cooling zone 25 is configured as shown in FIG. 4.

That is, in FIG. 4, the cooling device 28 of the rear cooling zone 25 is
Consisting of first to third cooling zones 34.35.36, each cooling zone 34x35.36 has a flow meter 37.38.
Cooling water is supplied via 39.

In the latter cooling zone 25, when the flow rate of cooling water for cooling the rolled material is small, only the first cooling zone 34 is used, and as the flow rate of cooling water increases, the second cooling zone 34 is used. .35 and three cooling zones 34, 35, and 36, first to third, are used.

By the way, in the correction table B, W, B, the cooling water flow rate range when only the first cooling zone 34 is used, and the cooling water flow rate range when using both the first and second cooling zones 34,35. The boundary cooling water flow rate is shown, and WB2 is the cooling water flow rate range when both the first and second cooling zones 34.35 are used, and when the first to third three cooling zones 34, 35.36 are used. It shows the boundary cooling water flow rate between the cooling water flow rate and the cooling water flow rate.

Also, to. ~t04, 〒f,. ～〒fb4 is each used cooling zone when the cooling water flow rate is O, W□, WB□
The surface temperature and cross-sectional circular average temperature are shown respectively.

Incidentally, the correction table B is also created for each of the operating conditions (■) to (■) of the index table (■).

If the extraction temperature and rolling speed are different, the second stage cooling zone 2
The cross-sectional temperature distribution state of the rolled material on the 5-person side will be different, and even if the same cooling water flow rate and the same number of cooling zones are used, the cooling time will also differ depending on the rolling speed.
Therefore, the temperature distribution state within the cross section after forced water cooling becomes largely different.

Now, for example, the measured surface temperature Lfm is between tfl and triO in the estimation table (i.e., 1,2<1f
m<j fl), cooling water flow rate W corresponding to j fl,
is in the cooling water flow rate range when only the first cooling zone 34 is used (that is, W+ < We+), and the cooling water flow rate W2 corresponding to trz is within the range of the cooling water flow rate when only the first cooling zone 34 is used.
It is within the cooling water range when using WB
, <W2<W, □), and the cooling water flow rate W1 when the measured surface temperature is jfn is both the first and second cooling zones 34.
If the cooling water flow rate is within the range when using 35 (in addition, to<tflI<tf, so W□<W,<
), and the cross-sectional circular average temperature 〒fm corresponding to this actually measured surface temperature jfn is determined as follows.

That is, in the above case, the cross-sectional circular average temperature 〒, H is the table value (11〒fl) of the estimation table ■ and (trz,
Instead of interpolating from 〒, 2), the table values (ttz, 〒f
Z) and correction table B, the boundary cooling water flow rate Wl+ of the used cooling water flow rate range of the first cooling zone 34 and both the first and second cooling zones 34, 35['') is calculated as follows. Table value when used with 35 (11, □,
From ↑7, t), by a formula similar to the above formula (1), -
Estimate by next interpolation As mentioned above, even if the measured surface temperature is located between the surface temperatures where the number of cooling zones used differs in the estimation table ■, by using the correction table B, the number of cooling zones can be Interpolation from the same two sets of table values becomes possible, and the cross-sectional circular average temperature can be accurately estimated from the measured surface temperature.

In addition, the cooling water flow rate listed in estimation table ■ is not very important when estimating the cross-sectional circle average temperature under operating conditions where there is no need to consider differences in recuperation time, but it is When estimating the cross-sectional circle average temperature under operating conditions that require consideration of differences, the surface temperature in the estimation table ■ can be calculated by comparing the cooling water flow rate listed in the estimation table ■ with the boundary cooling water flow rate. Which cooling zones 34, 35.
This is important because it is used to determine whether the value is the value when 36 is used.

Note that each table value of the basic table A and the correction table B is calculated using a temperature distribution analysis model of a hot rolling line and an empirical formula for cooling capacity during forced water cooling.

By the way, the actual extraction temperature during rolling is 6, and the rolling speed is Vf.
If vl, which is the ratio of m to maximum rolling speed vfm*x expressed as a percentage, is other than the standard operating conditions in index table ■, for example, 〒4□< Ta〒d3,
When vfm <vfm” <V f:I, each estimation table ■ corresponding to ■■■■ of the traction table ■ and, if necessary, each correction table B corresponding to ■■■■ of the index table ■ Using, the measured surface temperature tf,...
Find the average temperature of the four cross-sectional circles corresponding to .

Next, the above four cross-sectional circle average temperatures are further added to the extraction temperature,
By interpolating the rolling speed, it is possible to obtain the correct cross-sectional circle average temperature fM corresponding to the actually measured surface temperature t0 under the actual rolling conditions (extraction temperature d, rolling speed vrs).

In actual operation, when estimating the cross-sectional circle average temperature, the table values of the basic table A and the correction table B are stored in the auxiliary storage device of the process control computer 29, and the actually measured extraction temperature, The rolling speed, the surface temperature of the rolled material, etc. are input into the computer, and the cross-sectional circular average temperature of the rolled material is estimated using the calculation method described above.

In addition, in the embodiment, a method for determining the water-cooling up cross section circular average temperature after forced water cooling when controlled cooling is performed in the downstream cooling zone 25 has been described. It is also applicable to the method of determining the circular average temperature of the finished cross section after forced water cooling when implemented.

As mentioned above, it is possible to accurately and easily obtain the corresponding cross-sectional circle average temperature from the actual measured value of the surface temperature after forced water cooling for controlled rolling and controlled cooling in the continuous hot rolling process. Therefore, by performing various controls such as water cooling control based on the cross-sectional circle average temperature, the material of the rolled material can be made to be the target material.

In addition, in the example, in the index table, a plurality of typical operating conditions are set by combining typical extraction temperatures and values expressed as percentages of the ratio of typical rolling speed to maximum rolling speed. However, instead of the ratio of the typical rolling speed to the maximum rolling speed expressed as a percentage,
The typical rolling speed itself may be used.

(Effects of the Invention) As detailed above, according to the present invention, representative values of the billet extraction temperature and rolling speed from the heating furnace are determined in one bus schedule out of a plurality of planned pass schedules. A table showing the relationship between the typical surface temperature of the rolled material and the cross-sectional circular average temperature under multiple typical operating conditions combining Based on the extraction temperature, rolling speed, and surface temperature of the rolled material, the cross-sectional circle average temperature of the rolled material is estimated from the table above, taking into account the reheating time, so the cross-sectional circle, which is the representative temperature of the rolled material after forced water cooling, is estimated. The average temperature can be estimated accurately and easily in a short time, so there is no problem even if it is done online.Also, by using this cross-sectional circle average temperature for various controls such as water cooling control, it is possible to estimate the temperature of steel bars and wire rods. The material quality of the rolled material can be well controlled by controlled rolling controlled cooling in the intermittent continuous rolling process, which can contribute to improving the quality of the rolled material and expanding the variety of products. The present invention has the above advantages and is of great practical benefit.

[Brief Description of the Drawings] The drawings show one embodiment of the present invention, and Fig. 1 is a schematic diagram of a continuous hot rolling line, and Fig. 2 and Fig. 3 show cross-sectional circle average temperatures of rolled materials. Diagram showing a table for estimation, 4th
The figure is a schematic diagram of the post-cooling zone. 1 to 16-1st to 16th rolling mills, 20-heating furnace, 21,
22.23 - Roughing, intermediate and finishing mill rows, 24.2
5--Pre-stage/rear-stage cooling zone, 27.28--Cooling device, 34.35.36-First to third cooling zones.

Claims (1)

[Claims] 1. The billet extracted from the heating furnace 20 is transferred to rolling mills 1 to 16
Through the continuous hot rolling into rolled steel bars, wire rods, etc., the rolled materials are forcibly rolled by cooling devices 27 and 28 installed between the intermediate rolling mill row 22 and the finishing rolling mill row 23 and after the finishing rolling mill row 23. A method for estimating the average cross-sectional temperature of a rolled material after forced water cooling in the case of water cooling, in which the extraction temperature of the billet from the heating furnace 20 and the Create tables A and B in advance that represent the relationship between the typical surface temperature of the rolled material and the average temperature in the cross section under a plurality of typical operating conditions combining typical values of rolling speed, Based on the actually measured billet extraction temperature from the heating furnace 20, rolling speed, and surface temperature of the rolled material,
A method for estimating the average temperature within a cross section of a rolled material during hot continuous rolling of steel bars and wire rods, the method comprising estimating the average temperature within the cross section of the rolled material in consideration of reheating time.