JPS5841926B2 - Rolling length measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rolling length measuring method for measuring rolling elongation length, and more particularly to a rolling length measuring method used in rolling production of seamless steel pipes.

In the manufacturing process of seamless steel pipes, it is extremely important to keep the steel pipe wall thickness within a predetermined range for reasons such as ensuring a predetermined quality and improving material yield and product yield.

Conventional methods for measuring the wall thickness of seamless steel pipes include the radial transmission method, the contact method using a measuring roller, and the method of calculating the average wall thickness of the entire length of the steel pipe. The material to be measured has a high temperature of about 1,000 to 1,300°C, and there are plugs inside the tube, and it is moving in a spiral or straight line. Continuous and accurate measurement during the manufacturing process is extremely difficult and difficult to employ as a practical technique.

Therefore, a common method for controlling the wall thickness of a steel pipe in the manufacturing process of seamless steel pipes is to control the wall thickness of the steel pipe by accurately measuring the rolling elongation length of the steel pipe being rolled.

The conventional technology for measuring the rolling elongation length of steel pipes during this rolling process has two devices that integrate the output of a tachometer that is driven at a speed proportional to the speed of the rolling mill. Those controlled by signals (Japanese Patent Publication No. 39-688), those that generate a signal for each moving unit length of a moving object and count by controlling a passing detector (Japanese Patent Publication No. 39-2184), and the rotation of rolling rolls. A method that converts the number into pulses, corrects the roll diameter using a specified pulse counter, and calculates the length using another counter (Japanese Patent Publication No. 39-21013
(No. 42-4060), a pulse counting length meter that uses a speed calculation counter to calculate including neutral point correction (No. 4060), a pulse counting length meter that uses a speed calculation counter to calculate the neutral point 45-32506.32507) Calculating the number of pulses equivalent to unit length (Japanese Patent Laid-Open No. 48-7
6764), or with a narrow-field position detector that detects one end and a rotating field-of-view scanning position detector that detects the other end with a detection field of view that is greater than the maximum installation interval of the detectors. Some examples include a long one (Special Publication No. 50-47647).

To summarize the problems of these conventional techniques, for example, optical means for directly measuring the pipe moving speed have been found, but stable measurement is difficult because the response speed is slow and the temperature on the surface of the rolled steel pipe is non-uniform.

Furthermore, due to poor site conditions where the measuring device is installed, for example, a measuring means using a contact roll causes fluctuations in the slip ratio, making accurate measurement difficult.

Furthermore, the advance rate of a rolled steel pipe that occurs during rolling is determined by the originally existing pipe wall thickness in the longitudinal direction of the steel pipe, the difference in outer diameter, the temperature distribution in the longitudinal direction, changes in working degree due to expansion of the plug, temperature expansion of the rolls, etc. It is impossible to measure in advance because it changes depending on various rolling conditions, such as changes in the coefficient of friction between the plug and the inner surface of the tube, and between the roll and the outer surface of the tube.Measuring the change in the advance rate accurately is incomplete, so measurement is difficult. This is an error.

In particular, with recent rolling mills, the ratio of the minimum diameter to the minimum diameter of steel pipes that can be rolled has increased, making it even more difficult to accurately measure the rolling elongation length.

Incidentally, the advance ratio is expressed as the moving speed of the rolled steel pipe/the roll speed, and since the roll speed is controlled to be constant, a change in the moving speed of the rolled steel pipe directly appears as a change in the advance ratio.

The present invention was made in view of the many problems in conventional rolling elongation length measurement technology, and it uses correction using changes in the moving speed of rolled steel pipes that actually occur during real-time processing in the seamless steel pipe manufacturing process. The present invention provides a rolling length measurement method in which the measurement is completed when the steel pipe passes through the rolling rolls.The present invention will be described in detail below with reference to the drawings.

The figure is an explanatory diagram showing the overall configuration of a measuring device for implementing the method of the present invention during operation.

In a rolling mill for producing seamless steel pipes, a perforated billet 1 is sandwiched between rolling rolls 2 and 2', and its inner diameter is determined by a plug 4 at the tip of a mandrel bar 3, and the diameter is determined by the arrow 5.
Rolled in the direction of

The measuring device installed in such a rolling mill for producing seamless steel pipes includes a plurality of tip detectors 6, which are activated by detecting the tip of the steel tube being rolled, on the exit side of the rolling rolls 2, 2'. 7
, 8.9 will be installed.

The installation position of each tip detector is the distance (Lo), (Li-2), (L
i-1) and (Li), which are installed at predetermined length reference points.

On the other hand, a load detector 11 such as a load cell that detects changes in rolling load is installed on the rolling roll 2', and detects the load change at the time when the billet 1 is rolled and passes through the rolling rolls 2, 2'. Gives the ash removal signal.

Instead of the load detector 11, a current relay 13 may be used that provides an ash removal signal in response to a change in the current of the rolling roll drive motor 12, or the load detector 11 and the current relay 13 may be used together.

Detection signals from each tip detector 6 , 7 , 8 , 9 , weighted detector 11 and current relay 13 are input to a counting circuit 14 .

The counting circuit 14 counts the count pulses from the count pulse oscillator 15 and gives this pulse count number to the arithmetic circuit 16, and the count contents are as follows: a. Pulse count number (Ni) until the ash removal signal is given by the detector 11, b, Pulse count number (Ni-1) from the activation of the tip detector 7 until the activation of the tip detector 6, C0 tip The number of pulse counts (Ni-2) from when the detector 8 is activated until when the tip detector 7 is activated is counted by the counting circuit 14.

The arithmetic circuit 16 calculates each count pulse number (Ni) 1. Using (Ni-1) and (Ni2),
Calculate the rolling elongation length 1) of the steel pipe.

The arithmetic circuit 16 calculates the distance (Li) (Li-1) (Li-2) to the length reference point where each tip detector is installed.
) is set in advance.

First, the number of pulse counts (Ni
2), the number of pulse counts (N
i,), the steel pipe moving speed in each section (ai,),
(ai,) is calculated using the following equation.

Steel pipe moving speed (ai-1) (ai
-2), the steel pipe moving speed (ai) when pulse Curran) (Ni) is given is calculated using the following formula.

This formula can be obtained as follows.

That is, as shown in FIG. 2, the number of pulses between detectors 6 and 7 is Ni1, the average speed in that section is ai1, the number of pulses between detectors 7 and 8 is Ni, and so on. Since the average speed of is ai, , in this case, assuming that the speed changes linearly, the triangle
can be created, and the unknowns ai can be found using the straight line wave technique.

Since △ADE and △DBF are similar shapes, the following holds true.

When calculating the rolling speed in equation (3), when there is a change in the moving speed between two sections, the rate of change is estimated to be the same in other sections, that is, the moving speed is On the condition that it changes linearly, the final tip detector 6
The steel pipe moving speed in the immediately preceding two sections is determined, and the steel pipe moving speed after the section is calculated.

Therefore, the final rolling elongation length 1) is calculated as follows, where C=corrected length.

The calculation of these equations (IX2X3X4) is carried out by the weighted detector 1
It is executed when the ash removal signal from 1 is given to the counting circuit 14 and the pulse count number (Ni) is obtained, and is immediately given to the display panel 17 to display the rolling elongation length of the steel pipe 1) in real time processing. let

In the above embodiment, the measurement was carried out when the change in the advance rate was linear, but when the moving speed of the steel pipe changes non-linearly, the counting circuit 14 further performs measurement when the change in the advance rate is linear. The pulse count number (Ni-3) is given, and the arithmetic circuit calculates the average speed a between the tip detectors 8 and 9.
i 3 is calculated, and replaced with the above equation (3), the tip detector 6
Steel pipe movement speed (ai-,), (ai-
2), from (ai - s), find the steel pipe moving speed (ai) when the pulse count number (Ni) is given by the quadratic curve approximation method, etc., and calculate the rolling elongation length 1) from the above equation (4). It is used for calculation output.

As explained above, the rolling length measuring method of the present invention calculates the steel pipe moving speed in the remaining sections based on the actual steel pipe moving speed in a plurality of predetermined distance sections, and obtains the ash removal signal. Since the distance calculation is executed and output at the time when the rolling elongation length is calculated, it is possible to measure the rolling elongation length with high accuracy according to the advance rate that changes for each billet.

As described above, by accurately measuring the rolling elongation length of a steel pipe using the measuring method of the present invention, the following effects are achieved.

In other words, by measuring the elongation length of the steel pipe during rolling, the billet weight has been measured in advance with a weighing machine, so the wall thickness of the rolled steel pipe can be calculated, and the production of defective steel pipes can be prevented. It is possible to understand the amount of rolling processed for each pass in the machine and prevent uneven thickness of steel pipes.

Furthermore, since the average wall thickness can be measured by measuring the elongation length of the steel pipe during rolling, automatic steel pipe wall thickness control can be performed by feeding this back to the rolling mill.

Furthermore, since the equipment configuration of the measuring device for carrying out the method of the present invention is simple, it is easy to install the equipment, especially since it is only necessary to install a tip detector on the exit side of the rolling mill.

[Brief explanation of the drawing]

The figure is an explanatory diagram showing the configuration of an apparatus and the dimensions of each part for carrying out the rolling length measuring method of the present invention, and FIG. 2 is an explanatory diagram for determining the steel pipe moving speed ai. 1... Billet, 2. z... Rolling roll, 3... Mandrel bar 4... Plug, 5... Arrow indicating rolling direction, 6, 7, 8,
9... Tip detector, 10... Ash removal point, 11... Weight detector, 12... Roll drive motor, 13... ...Current relay, 1
4... Counting circuit, 15... Count pulse oscillator, 16... Arithmetic circuit, 17...
...Display board.

Claims (1)

[Scope of Claims] 1. A rolling length measuring method for measuring the rolling elongation length of a rolled steel pipe manufactured by a seamless steel pipe rolling mill, which includes determining at least three length reference points on the exit side of the rolling mill, and a tip detector provided at each of the reference points to detect the passage of the rolled steel pipe; a bottom removal detector that detects the end of the rolled steel pipe from changes in the load of the rolling roller of the rolling mill or changes in the current of the drive motor; The detection signal of each of the tip detectors gives a pulse count number corresponding to the rolling steel pipe transit time between each reference point, and the rolling steel pipe transit time from the activation of the tip detector at the final end to the activation of the bottom removal detector. The number of pulse counts corresponding to (
The steel pipe moving speed between the reference points is calculated by using each pulse count obtained by the counting circuit and the reference point length preset by installing the detector as calculation parameters. Find the average value of at least two pieces, and then, based on these average moving speeds and each pulse count number, calculate the average value of the steel pipe moving speed when the pulse count number (Ni) is given (
ai), and the rolling elongation length l is determined by the following formula Li; The distance C from the point to the reference point of the tip detector at the final end of the steel pipe bottom removal of the rolling roll is determined by the corrected length. Extended measurement method.