JPS61283411A - Descaling method for hot rolling - Google Patents

Abstract

PURPOSE:To descale efficiently by injecting high-pressure water to a rolling material at several positions on the rolling stage and by interrupting the injection with a priority lower ranking of to moderate the lowering of the injection pressure of high-pressure water, when the injections are conducted parallelly. CONSTITUTION:In the hot rolling stage of the rolling material traveling to the direction of arrow A, the injection nozzles 4-6 are disposed on a scale breaker 1, roughing mill 2 and finishing mill 3 respectively and the descaling of the rolling material is performed by the injections of high-pressure water from a piping system equipped with several pumps 8 and an accumulator 7. Then the preferential orders (1) front and rear surfaces of the finishing mill 3, (2) the scale breaker 1, (3) front and rear surfaces of the roughing mill 3, etc. are set in due consideration of the conditions such as effectiveness and influence. When the injections of high-pressure water are simultaneously carried out, the injections are interrupted by said priority of lower ranking. In this way, the lowering of injection pressure is moderated and the descaling is performed efficiently by minimum number of pumps.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a descaling method in hot rolling, and more specifically, to a method for determining the injection order when high-pressure water is injected almost simultaneously at multiple locations on a rolling line. This relates to a control method.

[Conventional technology]

Steel plate scale removal during hot rolling is usually 100 to 15
Before the start of rolling, high-pressure water raised to 0 kV- or higher (heating furnace ~
This is done by injecting it into the rolled material at multiple locations, such as between the rolling mills) and during rolling (at the front and rear descaling sections of the rolling mill such as rough rolling and finishing rolling).

The pressure of this descaling water is increased using multiple boost pumps, and an accumulator is installed to maintain a high pressure state at all times, but if it is injected from multiple locations at the same time, In the past, the discharge pressure decreased and descaling became impossible, so conventional measures were to increase the number of booster pumps in operation to prevent an abnormal drop in pressure even when descaling work was performed at multiple locations in parallel.

FIG. 5 shows an example of conventional descaling operation.

In the figure, (1) is a scale breaker, (2) is a rough rolling mill, (3) is a finishing mill, and the rolled material flows in the direction indicated by the arrow. (4) is the injection nozzle of the scale breaker (1), (5) is the injection nozzle of the rough rolling mill (2), and (6) is the injection nozzle of the finishing mill (3). (7) is an accumulator, and (8) is a pump. As shown in the figure, descaling work is performed at three locations: the scale breaker (1), the front and rear parts of the rough rolling mill (2), and the front and rear parts of the finishing mill (3), and the average injection amount is However, as shown in the discharge pressure change diagram in FIG. 5(b), it can be seen that the discharge pressure is significantly lower during parallel descaling.

[Problem that the invention seeks to solve]

As a result, approximately 25 to 30% of normal operations are handled by increasing the number of booster pumps in operation from one to two.
The operation is extremely inefficient.

In addition, in the conventional case, the timing of injection and stop at each telescaling point was limited to reducing losses by using sensors such as HMD and other detectors, and there were no improvement measures that considered simultaneous injection at multiple points. [Means and actions for solving the problem] The descaling method in hot rolling according to the present invention takes into consideration the descaling effect and the conditions that affect the quality of the steel sheet in advance. Priority compensation is given to the injection points, and when high-pressure water is injected at multiple points, the injection is interrupted starting from the one with the lowest priority. However, since descaling is performed at the nine locations interrupted in this way during the next rolling pass, descaling at those locations is not omitted.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a descaling piping system diagram, and since it is the same as the conventional one, the same reference numerals are given and the explanation will be omitted. FIG. 2 is a control flowchart of the present invention.

In this embodiment, as in FIG. 5(a), the scale breaker (1), the front and rear surfaces of the rough rolling mill (2) and the finishing mill (
3) is a case in which descaling work is performed at a total of six locations on the front and rear surfaces. The priority order of injection at each location is determined by considering conditions such as the descaling effect and the impact on steel sheet quality.
■The order is from the front and back of the rough rolling mill. According to this priority order, when descaling operations are being performed in parallel at multiple locations, the descaling operations at lower locations are interrupted (interlocked). Here, the timing to interrupt the injection, that is, to interlock, is determined by setting a nine-timer, taking into account the discharge pressure of the pump (8), the detection of the water level of the puccumulator (7), or the discharge pressure drop characteristics for each combination of multiple pumps. is determined so that the value does not fall below a certain value.

Table 1 shows the interlock timing procedure, and FIG. 2 shows the control flowchart.

Further, FIG. 3 is an explanatory diagram of a timer setting method for the injection patterns shown in Table 1. As for the interlock timing, as shown in FIG. 3, a timer is set for each injection time that corresponds to 60% of the permissible fluctuation range of the pump discharge pressure. However, in the case of simultaneous injection at all locations, the pressure drop will be significant, so the timer setting will be much shorter.

The present invention is intended to prevent a pressure drop due to simultaneous injection by smoothing parallel descaling operations at a plurality of locations, and is based on the premise that scale removal will not be hindered. Therefore, for example, if the descaling of the front and rear surfaces of a rough rolling mill is interrupted, the nine lamps will be installed in each operator's cab as shown in Figure 2 and a buzzer will sound to alert the operator and prevent the descaling from being interrupted. The ninth rolling bus (
In the case of thick plate rolling, descaling is always performed during reverse rolling (there are several passes of the rolling bath). Maku,
If the injection in the front stage of the scale breaker is interrupted, descaling must be performed at the start of rough rolling and before the first pass of the part is bitten.

In normal operations, descaling operations are rarely performed in parallel, and the rolling cycle is about 1 to 2 V, so high-efficiency operations can be achieved by performing descaling using the method described above.

FIG. 4 is a graph showing the discharge pressure drop characteristics during injection at all locations in order to show the effect of this embodiment, where the solid line shows the case of the present invention and the broken line shows the case of the conventional case. As is clear from the figure, in the conventional method, the accumulator is shut off and descaling becomes impossible approximately 4 seconds after the parallel operation, whereas in the present invention, the injection at the front and rear surfaces of the rough rolling mill occurs t1 seconds after the parallel operation. 1. Scale breaker on the sand diameter - Injection at the front stage is interrupted. At the 9th stage, the drop in discharge pressure is eased, and it takes about 90 minutes to reach the accumulator continuous cutoff pressure.
It takes about 2.6 seconds, which is about 2.6 times longer than the conventional method.

〔Effect of the invention〕

As described above, according to the present invention, descaling work in hot rolling can be performed with high efficiency using a minimum number of pumps even when the descaling work is performed at a plurality of locations in parallel.

[Brief explanation of drawings]

FIG. 1 is a descaling piping system diagram of an embodiment of the present invention.
2 is a control flowchart, FIG. 3 is a discharge pressure change diagram, FIG. 4 is a comparison diagram of discharge pressure changes between the present invention and the conventional example, and FIG. 5 is the descaling piping system of the conventional example. It is an explanatory view showing changes in a jet pattern, total amount of water, and discharge pressure. (4) (5) (6)...Injection nozzle, (7)...
・Accumulator, (8)...pump. Agent Patent Attorney Masaru Sato M3 Figure 4

Claims (1)

[Claims] A method for removing scale from a rolled material by injecting high-pressure water from a piping system equipped with a plurality of pumps and accumulators at multiple locations in a rolling process, comprising: 1. A descaling method in hot rolling, which comprises prioritizing and, when jetting high-pressure water in parallel, interrupting the jetting starting from the one with the lowest priority to alleviate a drop in discharge pressure.