JPS5814489B2 - Billet charging control method for hearth rotary billet heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a steel billet heating furnace with a rotary hearth as a line equipment that is connected to subsequent equipment such as a hot rolling mill, such as round billets for producing seamless steel pipes. The present invention relates to a single charging control method, and in particular to a method for controlling the charging interval of steel billets in order to obtain optimum heating efficiency and working efficiency when the hearth is continuously rotating.

As is well known, a seamless steel pipe manufacturing line is constructed as a continuous process line from a billet heating furnace to a sizer, and processing of each billet is performed under the control of a predetermined mill schedule.

Therefore, the pitch of the billet extraction work from the heating furnace is determined by the above mill schedule, and therefore the rotation of the hearth of the heating furnace is set in accordance with the above extraction work pitch determined by the mill schedule so that a predetermined uniform heating is achieved. determined.

In order to make effective use of the hearth space, the distance between the charging position and the extraction position is set close to the entire circumference of the hearth.
Therefore, the charged billet is extracted after going around the furnace approximately once.

The heating time is the average rotational speed of one rotation of the hearth (for example, 0
．． Conventionally, the hearth is controlled at a speed of about 6 m/min), and the hearth is stopped and extracted at every extraction pitch, and the hearth is rotated bit by bit at the above-mentioned average rotation speed.

In this case, when charging billets of the same size, the charging machine tongs are brought to the furnace loading position in advance while the hearth is rotating, taking into account the timing of the above-mentioned inching, and when the hearth stops at the extraction timing. The pitch of the billets is adjusted by placing each billet on the hearth.

In reality, an operator is attached to the charging machine, and while reading the charging interval work table, which is determined based on the billet diameter and length, minimum heating time, capacity of the succeeding line, etc., the operator performs charging according to billet size. Set the operation of the charging machine by setting the digital setting device at intervals, count the number of pulses of the pulse generator from the hearth rotation system with a counter, and when the above setting value is counted, start the charging machine. A command is issued, and the driver operates the charging machine based on this command.

It is fine as long as the billets to be charged are the same size, but in general, billets of various sizes are handled, so the charging timing changes each time, and the set value must be adjusted based on the driver's intuitive judgment. The reality is that there are.

Therefore, it is essentially difficult to charge the billet at the correct time to achieve accurate heating, and the billet may have to be charged onto a rotating hearth.

If billets are charged onto such a rotating hearth by the operator's operation, the charging interval will inevitably vary due to the influence of the hearth rotation speed, and the charging interval will inevitably vary due to the effect of the hearth rotation speed. The delay until the start of the machine changes each time, making it impossible to make the charging interval VITNA, which determines the heating conditions, uniform.

It is also true that in the past, billets were charged at unspecified positions in the radial direction of the hearth, resulting in a waste of hearth space due to short billets.

This invention aims to provide a method for automatically charging steel billets at predetermined charging intervals without wasting space while the hearth is rotating at an average rotational speed determined by heating conditions. This eliminates the operator's visual confirmation and operations based on it, and makes it possible to automatically charge billets at the optimum pitch according to the billet size without leaving wasted space in the hearth.

This invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the control system according to the present invention together with the rotational position of the hearth, where 1 is a rotary hearth, 2 is a motor for driving its rotation, 3 is a speed reducer, and the motor 2 is a separate motor (not shown). The rotation is controlled by a control device 5 by human control 5 corresponding to the operating conditions of the extractor 4 and the like.

Reference numeral 6 denotes a charging machine, which is equipped with opening/closing tongs each driven by a fluid pressure cylinder device and a boom for inserting the tongs into the furnace. The drive mechanism 9 moves the required stroke to the furnace front charging position.

The drive mechanism 9 is rotatably driven by a motor 11 via a speed reducer 10, and the rotation speed of the motor 11 is controlled by a speed control device 12 of, for example, a Thyris-Cléonard type.

In one example, the charging machine 6 is equipped with a limit switch, a photo cell, etc., for detecting the tail end position of the charging billet B held by the tongs and always specifying the starting point position of the insertion boom. A tail end detector 13 is installed so that when a certain billet B is picked up from the billet pit by the tongs of the charging machine 6, the tail end of the billet B is always located above a point on the body of the charging machine. When the boom is operated and the charging machine is stopped at a predetermined position with a stopper 8, the distance L1 from the hearth peripheral wall to the tail end of the billet is always constant.

Incidentally, instead of using the tail end detector 13 described above, the charging machine or the boom may be retreated until the billet tail end hits a fixed object and that point may be used as the starting position.

A tachometer 14 for measuring the rotational speed of the hearth and a pulse transmitter 15 for measuring the rotation angle of the hearth are attached to the motor 2 for rotating the hearth. has been entered.

The length l and outer diameter d of each billet in the pit to be picked up by the above-mentioned charging machine 6 are individually measured in advance, and these measured value data are set as billet data at each point in time when the tongs pick up the billet. from the device 17 to the arithmetic device 1
6.

In addition, in the charging machine 6, after the charging machine 6 aligns the tail end of the billet B with the above-mentioned distance L1 and stops at a fixed position, the billet is always inserted into the furnace from the above-mentioned fixed position by a start command signal, which will be described later. The boom operates at a constant speed, and inside the furnace it is at a constant distance L from the hearth peripheral wall.

The boom will stop at the position where the tail end of the billet has penetrated deeply.
At that position, the billet is lowered at a constant speed, waits at a predetermined standby position, and is automatically placed on the hearth in response to a charging signal, which will be described later, thereby starting the operation of the boom, i.e. The time required from the time the start command signal arrives to the time the billet finishes lowering to a predetermined height, that is, the time it reaches the standby state where it can accept the charging signal, is mechanically determined to be a constant time T1. do.

The above-mentioned rice and T1 are each set by the setting devices 18 and 19 and inputted to the arithmetic unit 16, and the distance L from the center of rotation of the hearth to the peripheral wall of the hearth and the total number of pulses N for one rotation of the hearth are constants. is given in advance in the arithmetic unit 16 as .

The total number of pulses obtained from the pulse transmitter 15 by one rotation of the hearth 1 is N as described above, and therefore the number of pulses obtained from the transmitter 15 when the hearth rotates by a unit angle (n
o) is.

A billet of length l is placed on the hearth along the radial direction at intervals of rotation angle θ of the hearth, and its tail end is L.

The distance a between the tips of the billets when placed according to the position of
becomes.

Therefore, the number n of pulses from the pulse generator 15 representing the charging pitch to give the spacing a to a billet of length l
is .

In the above formula (3), the billet tip spacing a is the minimum required in order to efficiently heat the billet from the flow of combustion gas on the hearth, and to take into account the shape restrictions required for opening and closing the tongs of the charging machine. A value is determined, which is empirically related to the outside diameter value d of the billet, and a=md...
It is expressed as (4).

(e) in this equation (4) is a setting value called a selection coefficient, which is a function of the outer diameter d and has a tendency as shown in FIG. It is assumed that the value is set and given to the arithmetic unit 16.

The calculation device 16 calculates the number of pulses <n) that gives the charging pitch based on the above equations (1) to (4) using the given setting values and constants, and the charging machine transfers the front billet to the furnace. When the number of pulses actually counted (n') from the pulse transmitter 15 after the placement on the floor matches the value of (n) above, a charging signal is sent to open the tongs of the charging machine 6. Send to machine 6.

In the charging machine 6, the tongs that have gripped the next billet must be kept waiting at a predetermined position on the hearth before that, and for this reason, in order to insert the tongs of the charging machine into the furnace prior to the above-mentioned charging signal. The above-mentioned start instruction signal is sent from the calculation device 16 to the charging machine 6.

That is, the calculation device 16 receives the hearth rotation angle Δθ corresponding to the time T1 required for the tong movement and descent of the charging machine, and the hearth rotation angular velocity (f) up to that point from the tachometer 14, △θ=ω・T1 ・・・・・・・・・
・・・・・・・・・・・・In order to calculate by (5) and replace it with the number of pulses (△n), perform the calculation as follows, and calculate the number of pulses (n) according to the above formula (35).
When the number of pulses from the pulse transmitter 15 reaches the number of pulses obtained by subtracting the above Δn, that is, the number of pulses from the pulse generator 15 (rO), a start command signal is issued to the charging machine 6.

The charging machine 6 receives the start signal, inserts the boom into the furnace from the standby position, and moves the tongs to a predetermined position above the hearth at a predetermined height from the hearth through a series of operations. position and wait for the arrival of the next charging signal.

The operation up to this standby state is performed by predictive position control based on the rotational speed of the hearth (preferably the maximum speed up to that point), so the next billet is placed before the next billet charging position reaches just before the charging machine. can be reliably kept on standby at a predetermined position within the furnace.

Next, a pulse corresponding to the actual length measurement value from the pulse transmitter 15 enters the calculation device 16, and when the count result of this matches the calculation result, a charging signal enters the charging machine,
This causes the tongs to open and place the billet at the correct and most efficient pitch position, and this opening of the tongs is electrically detected and clears the computation unit's calculations for the next billet. Start pulse counting.

The above sequence of operations is shown as a process diagram in FIG.

If the billet length and outer diameter dimensions are within the allowable variation range, the above calculation process may be further simplified to give a constant pitch a, or conversely, if the billet length is short, If the pitch a is maintained within a certain tolerance range, a selective control operation may be performed so that two short billets are placed side by side in the same row in one charge.

As described above, according to the control method of the present invention, the billet is placed so that the tail end is positioned at a constant distance L0 from the peripheral wall of the furnace body of the rotary furnace to the maximum possible distance without causing any hindrance. The maximum number of billets can be charged to the top, and the heating efficiency is also maintained at a good level.Since the charging machine operates fully automatically, there is no need for manpower for charging work, and the heating efficiency is maintained at a high level. Billets of various sizes can be charged in accordance with the extraction pitch at an efficient pitch, and the maximum capacity of the furnace can be exerted.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the control system according to the present invention together with a part of the rotary hearth, Fig. 2 is a diagram illustrating the relationship between the selection coefficient and the billet outer diameter, and Fig. 3 is the process of the present invention. It is a diagram. 1: Rotating hearth, 6: Charging machine, 8: Stopper, 9: Drive device, 11: Motor, 12: Speed control device, 13: Tail end detector, 14: Tachometer, 15: Pulse transmitter, 16 : Arithmetic device, 17.18, 19.20: Setting device.

Claims (1)

[Claims] 1. A charging operation in which steel pieces are placed at intervals on a hearth by a charging machine along the radial direction of a hearth which is rotated at a constant rotation speed based on a predetermined extraction work pitch. In this case, the separation distance L of the tail end of the charging steel from the inner peripheral wall of the furnace above the hearth. is set to a constant value, the furnace inner circumferential wall radius L, and the separation distance L. , and the distance a between the tips of adjacent steel billets after charging determined by the pre-measured length l and outer diameter d of the billet is determined by the heating efficiency considering the flow of the heating fluid and the charging and The rotation angle θ of the hearth to achieve a predetermined distance based on the dimensions and shape of each tong for extraction is calculated, and after charging the pre-charged billet, the rotation angle of the hearth based on the above calculation result is calculated. θ
The time required for the hearth to rotate by the distance L is determined from the rotational speed ω of the hearth, and the charging machine that receives the next charged billet is separated from the standby position by the distance L. Pre-charging for a predetermined time corresponding to the time required by subtracting the sum T1 of the time required to move to the charging position determined by and the time required for the tongs of the charging machine to descend to the charging height from the required time. A start command signal is issued to start the above-mentioned movement and lowering operation of the charging machine after the billet has been charged, and the actual rotation angle of the hearth, which has been pulse-measured since the charging of the pre-charged billet, is issued. is the hearth rotation angle θ of the above calculation result
A method for controlling billet charging in a hearth rotary billet heating furnace, characterized in that charging is carried out by issuing a charging signal to release the tongs of a charging machine at a time when this coincides with the timing.