JPS60413B2 - Heating temperature control method in continuous heating furnace - Google Patents

Description

[Detailed description of the invention] The present invention relates to a heating temperature control method in a continuous heating furnace,
In particular, during unsteady operations in multi-zone continuous heating furnaces where extraction of heat-treated materials is scheduled to be suspended, the heating conditions of the heating furnace can be appropriately controlled to reduce fuel consumption and increase the amount of heat-treated materials. The present invention relates to a method that allows heat treatment and subsequent secondary treatment to be carried out smoothly.

In general large-scale rolling mills, most of the steel pieces to be processed move within the heating furnace, given the current situation such as the number of continuous heating furnaces, the furnace length, and the number and dimensions of steel materials to be processed per roll unit. The reality is that the mill encounters at least one stoppage during this time due to roll changes, etc., and at this time, the extraction of steel pieces is naturally also stopped. In addition, if direct rolling is being carried out in parallel, or if a batch furnace or soaking furnace is being used in parallel, the rolling of steel pieces from these will be interrupted, so extraction from the continuous heating furnace must be suspended during this time. No. In this way, when operating a continuous heating furnace, there is an extraction downtime that can be set in advance, but if the heating condition in the furnace is maintained as it is when heating with a normal heat pattern during this period, the steel to be processed will continue to flow during the downtime. As the temperature rises, the temperature of the steel material extracted from the heating furnace after restarting extraction will be considerably higher than the target heating temperature, which will not only result in overheating and over-soaking, but also in terms of thermal efficiency. This will result in huge losses.

Therefore, conventionally, as shown in Fig. 1, for example, when extraction is stopped, the burner output of each zone in the heating furnace is lowered to maintain the temperature of the steel to be heated at that time, and when extraction is resumed, the steady heating pattern is returned to. The solution is to heat it up. The temperature rise line of the steel to be heated in the furnace can be understood as a quadratic or multidimensional function with the time spent in the furnace as a variable.
Here, it is shown as a linear function for convenience. However, with the above measures, maintaining the fracture-heated steel material at a constant temperature during the extraction suspension period means that the high-temperature scarlet gas is continuously discharged outside the furnace, resulting in considerable heat loss. Setting the heating conditions is also surprisingly difficult.

The inventors of the present invention have focused on the above-mentioned circumstances, and in particular, when an extraction stop time is scheduled, by setting a corresponding heat pattern in advance, it is possible to reduce heat loss and set heating conditions. I thought it might be possible to simplify it,
We have been conducting intensive research to realize this idea.

As a result, the inventors found that the above object could be successfully achieved by employing the method shown below, and were able to complete the present invention. That is, the configuration of the heating temperature control method according to the present invention is a heating temperature control method in a continuous furnace that involves a scheduled extraction stop of the material to be heated, and consists of the following: , (corresponding to each pause time of the tosa that involves an extraction pause, and at the end of the pause time, the steady heating temperature corresponding to the pause position of the material to be heated in the furnace is reached, and the average temperature increase rate is increased from the steady heating pattern. A slow heating pattern for resting is set in advance, and the material to be heated that involves resting is heated according to the heating pattern for resting described in (2) until the end of the resting time, and after the resting time is over, heating is performed according to the heating pattern for resting described in (2) above. The gist lies in raising the temperature along a steady heating pattern.

The structure and effects of the present invention will be explained below based on the drawings showing examples, but the following does not limit the present invention like the embodiments described in the claims, but the gist of the preceding and following. It is also possible to change the heating pattern, etc., as appropriate, and all of these are within the scope of the technology of the present invention.

Fig. 2 is a diagram corresponding to Fig. 1 illustrating the heating pattern adopted in the present invention, and each heat source control section of the heating furnace has two types: ■ Steady heating pattern when no extraction pause is involved, and ■ Scheduled heating pattern. A heating pattern for rest that is adopted when the extraction is stopped is stored.The heating pattern for rest corresponds to each scheduled rest time and reaches the heating temperature Ts at the end of the rest time. At the same time, the average temperature increase rate is set to be slower than the steady heating pattern in (2).By the way, the conventional method is as shown in Figure 1, but to explain in more detail, Until the stopping time t, heating is performed at the normal heating rate C to reach the temperature Ts, and during the extraction stopping time, heating is carried out to the extent that the temperature Ts is maintained, and when the extraction restart time t2 is reached, the original heating rate C is increased. , to raise the temperature of the material to be heated.In other words, even though the extraction stop time is scheduled, there is a problem that the scheduled time is not fully utilized.In contrast, in the present invention, the extraction stop time is When a pause is scheduled, the pause heating pattern (3) is adopted in advance, but this pattern is set so that the above-mentioned steady heating temperature Ts is reached at the extraction restart time t2.
The temperature is raised at a relatively slow rate C2, and this temperature increase continues during the extraction pause time, and when the extraction restart time t2 is reached, the temperature is returned to the steady heating pattern (2) above and the temperature is raised at a rate C. The lower part of FIG. 2 conceptually shows the amount of fuel used in each of these patterns. The amount of fuel used after the extraction restart time is the same for both the conventional method and the method of the present invention, but up to time t2, it was easy to make the method of the present invention more advantageous. In other words, the amount of fuel used to maintain the heated material at temperature Ts during the extraction pause time is [〇], and the amount of fuel used to raise the temperature at the rate C, C2 is [C,'], [C2']. The amount of fuel used by the conventional method and the method of the present invention are compared, and C2', that is, C2 in the following equation is determined. C'. (Sh-t.

)〉D'(t2-t,)〉C'2(t2-t,)〉C'2(t2-t, etc.) Further, as a result of further research, the heating pattern up to the extraction restart time t2 was divided into a heating pattern before a pause and a heating pattern during a pause, It has been confirmed that the total amount of fuel used can also be reduced by making the temperature increase rate of the pre-pause heating pattern smaller than the temperature increase rate of the during-pause heating pattern. That is, FIG. 3 is a similar correspondence diagram for explaining this situation, where the temperature increase rate of the pre-pause heating pattern is C3, and the fuel consumption at this time is [C3].
'3], the temperature increase rate of the heating pattern during suspension is C4, and the amount of fuel used at this time is [C'4], then the total amount of fuel used from the time to in the furnace until the extraction restart time t2 is C' 3(
ra-to)+C'4(r-chi), but this value is also the fuel consumption amount of the dependent method, C', (t,-to)+
It is easy to control it so that it is less than D(t2-t,). However, when adopting the above-mentioned two-stage heating pattern, if the temperature increase rate C4a of the heating pattern before rest is too slow, as shown by the dashed line in FIG. This results in an increase in total fuel consumption in terms of thermal efficiency. Therefore, taking these points into consideration, the above 03(t, -
to)+〇4(t2-t,) is C',(t,-to
)+D(t2-chi).
It is desirable to set C4 and C4 appropriately. In addition, the appropriate heating rate for the entrustment varies depending on the size, shape, and material of the material to be heated, as well as the performance of the continuous furnace (heat retention, mass heat capacity, etc.), so select the optimal heating conditions according to these conditions. Should. According to Naoko, the extraction stop time and stop time will vary depending on the roll change, direct rolling, rolling process of the material to be processed from the batch furnace or scorching furnace, etc., as mentioned earlier. Although there are cases where the furnace is paused twice or more, heating patterns for each pause may be stored in accordance with the pauses, and a heating pattern corresponding to each extraction pause time may be selected and adapted.

The present invention is generally configured as described above, but the key point is to continue heating the temperature at a relatively slow rate during the extraction pause time, and to control the temperature increase rate so that the steady heating temperature is reached at the time when the extraction is resumed. This made it possible to reduce the total amount of fuel used.

Moreover, since there is no process of holding the temperature at a constant temperature, it is relatively easy to set the heating conditions, and the heat treatment can be performed as evenly as possible without the risk of overheating or overheating the material to be heated. , various practical benefits can be enjoyed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional heating pattern when the extraction is stopped, and FIGS. 2 and 3 are explanatory diagrams showing the heating pattern employed in the present invention in comparison with the amount of fuel used. Figure 3 Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A heating temperature control method in a continuous heating furnace with a scheduled extraction stoppage of a material to be heated, comprising: (1) a steady heating pattern when no extraction stoppage is involved; ) Corresponding to each pause time when accompanied by an extraction pause, and at the end of the pause time, the steady heating temperature corresponding to the pause position of the material to be heated in the furnace is reached, and the average temperature increase rate is increased from the steady heating pattern. A slow heating pattern for resting is set in advance, and the material to be heated that involves resting is heated according to the heating pattern for resting in (2) above until the end of the resting time, and after the resting time is over, the heating pattern is set in advance. (1) A heating temperature control method in a continuous heating furnace, characterized by heating with the steady heating pattern. 2 In claim 1, the heating pattern for rest is divided into a heating pattern before rest and a heating pattern during rest, and the heating rate of the heating pattern before rest is smaller than the temperature rise rate of the heating pattern during rest. Temperature control method. 3. A heating temperature control method according to claim 2, in which the temperature increase rate of the heating pattern during rest is smaller than the temperature increase rate of the steady heating pattern.