KR20030054632A - Detection method and apparatus for skid mark of hot strip - Google Patents

Abstract

PURPOSE: A method and an apparatus for detecting skid marks formed on hot rolled strip by using only thickness deviation signals and rolling speed signals of the hot rolled strip fundamentally generated in hot rolling process are provided. CONSTITUTION: The method comprises first step (S201) of measuring thickness deviation and rolling speed of the hot rolled strip sampled at certain time intervals; second step (S202) of converting the thickness deviation sampled at certain time intervals into thickness deviation sampled in a length unit by multiplying the thickness deviation sampled at certain time intervals in the first step (S201) by rolling speed corresponding to measuring time; third step (S203) of sampling the thickness deviation sampled in a length unit in the second step (S202) in a certain length unit again; and fourth step (S204) of Fourier transforming the function sampled in a certain length unit again in the third step (S203) into spatial frequency and judging that thickness of the hot rolled strip is changed by skid marks if size of skid mark frequency components exceed a certain value.

Description

Detection method and apparatus for skid mark of hot rolled sheet

The present invention relates to a method and apparatus for detecting a skid mark in a hot rolled sheet in a rolling process, and in particular, a skid mark appearing on a hot rolled sheet using only a thickness deviation signal and a rolling speed signal of a hot rolled sheet, which are fundamentally generated in the hot rolled sheet. It relates to a device for detecting.

In the hot rolling process, the slab manufactured in the casting process is uniformly heated to a rollable temperature, and the heated slab is rolled in a rough rolling mill to form a sheet bar having a thickness of 60 mm or less. Finally, the rolling mill makes the product and width of the specification required by the customer.

By the way, an iron beam called a skid for supporting and moving the slab is uniformly arranged at regular intervals in the heating furnace in which the slab is uniformly heated. On the other hand, since the inside of the furnace is hot, the skid itself is also heated. Thus, the skid needs cooling to perform its function. To this end, the skid is configured to allow cooling water to flow inside the skid. However, due to this, the surface of the slab in contact with the skid drops relatively, and the area in contact with the skid during rolling exhibits a thickness variation of a certain period in the hot rolled sheet because the thickness is not controlled.

The conventional skid mark detection method of hot rolled sheet was dependent on manual labor. In other words, the number of peaks and valleys of a certain period was confirmed by looking at the thickness deviation signal of the hot-rolled sheet. However, the detection by the manual labor was delayed and the accuracy decreased.

1 shows a configuration diagram of a skid mark detection apparatus according to the present invention,

2 is a flowchart showing a skid mark detection method according to the present invention;

3A is a thickness deviation signal of a hot rolled sheet sampled by a predetermined time unit;

Figure 3b shows an example of the waveform of the rolling speed signal of a certain time unit,

FIG. 4A illustrates a thickness deviation signal resampled by a predetermined length unit by compensating the thickness deviation signal of FIG. 2 at a rolling speed.

4B shows an example of the Fourier transform of FIG. 4A.

※ Explanation of code about main part of drawing ※

101: thickness meter 102: speedometer

103: operating computer 104: data acquisition device

105: processor 106: display unit

According to the present invention for solving such a problem, a thickness meter which is installed at the end of the finishing process rolling to measure the thickness of the final product and outputs a deviation signal from the target thickness, and a speedometer to output the rolling speed of the final stand And an operation computer that outputs the length value of the rolled steel and a thickness deviation signal from the thickness gauge, a rolling speed from the speedometer, a sampling rate at a predetermined time interval, and a digitized value of the steel material from the operation computer. It includes a data acquisition device for storing the value, and a processor for converting the thickness deviation signal and the rolling speed signal sampled at a predetermined time interval into a thickness deviation signal according to the rolling length, and approximating it with a continuous function, and Fourier transforming this function. Provided is a skid mark detection apparatus for a hot rolled sheet constructed.

In addition, the thickness deviation sampled at a predetermined time interval is measured, the thickness deviation sampled at a predetermined time interval is multiplied by the rolling speed corresponding to the measurement time, and converted into a thickness deviation sampled by the length unit, and sampled by the converted length unit. After re-sampling the thickness deviation by a certain length unit, Fourier transforming the transformed function to spatial frequency, if the size of the skid mark frequency component exceeds a certain value, it is judged that there is a thickness variation due to the skid mark on the hot-rolled sheet. A skid mark detection method of a hot rolled sheet is provided.

Hereinafter, a skid mark detection apparatus and method according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a skid mark detection apparatus according to the present invention. The skid mark detection apparatus according to this embodiment includes a thickness gauge 101 for measuring thickness deviation of a hot rolled sheet, a speedometer 102 for measuring a rolling speed of a hot rolled sheet, and a thickness interval and a rolling speed at regular intervals (eg, , 50 msec) to store and to receive and store the slab length value from the operating computer 103, and the processor 105 for processing the collected signal to detect the presence of skid marks And a display unit 106 showing the detection result.

2 is a flowchart for exemplarily describing a method for detecting a skid mark according to a preferred embodiment of the present invention.

The thickness meter 101 is installed at the end of the finishing rolling process, and measures the deviation (x [nT], n = 0,1,2, .. N) from the target rolling thickness at a predetermined time interval and measures the speedometer ( 102 measures the rolling speed (v [nT], n = 0, 1, 2, ..., N) (S201).

The rolling speed measured at the time of measuring the thickness deviation signal from the speedometer 102 is multiplied by the rolling thickness deviation measured at a predetermined time interval, and converted into a rolling thickness deviation converted in units of length (S202).

.

Using the method of interpolation or the like of the converted thickness deviation signal, the rolling thickness deviation sampled again at a predetermined length interval D is calculated (S203). D is defined by Equation 2 below.

.

The thickness deviation signal sampled again at a predetermined length interval is transformed into a spatial frequency region through Fourier transform, and when the magnitude of the skid mark frequency component exceeds a predetermined value, it is determined that there is a skid mark on the hot rolled sheet (S204). . The method of calculating the spatial frequency Fs of the skid mark is represented by Equation 3 below.

Fs = (length of steel before rolling) / (length of coil after rolling × skid spacing in the furnace) [1 / m]

3A graphically illustrates thickness deviations sampled at time intervals of 50 milliseconds (msec). Thickness variations can be seen oscillating between approximately -20 to 20 micrometers (μm). 3B is a graph showing the speed at the time of measuring the thickness deviation signal.

4A shows a graph of resampling of the thickness deviation to a constant rolling length. Since the length of steel before rolling is about 10m, the length of coil after steel rolling is about 1000m, and the skid spacing for supporting steel in the furnace is about 1m, the skid spacing after rolling is 100m It can be expected that the results of Fig. 4a shows that the present invention properly detects a skid mark, as shown in FIG.

4B shows a spatial frequency obtained by Fourier transforming the graph of FIG. 4A.

Since the length period of FIG. A is about 100 m, the Fourier transformed spatial frequency can be expected to be 0.01 (1 / m), and when the spatial frequency of the circle region representing the largest spatial frequency is represented, it is represented as 0.01. can see.

As described above, according to the present invention, there is an effect of automatically detecting a thickness abnormality due to the skid mark of the hot rolled sheet using only a signal basically provided in the hot rolling process without installing an additional sensor.

Although the technical spirit of the present invention has been described above with reference to the accompanying drawings, it is intended to exemplarily describe the best embodiment of the present invention, but not to limit the present invention. In addition, it is obvious that any person skilled in the art may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (2)

In the skid mark detection device of the hot rolled sheet, A thickness meter installed at the end of the finishing process rolling to measure a thickness of the final product and output a deviation signal from a target thickness; A speedometer for outputting the rolling speed of the final stand; A data collection device configured to receive a thickness deviation signal from the thickness meter, receive a rolling speed from the speedometer, and store a value obtained by sampling and digitizing the data at a predetermined time interval; And A processor for converting the thickness deviation signal and the rolling speed signal sampled at a predetermined time interval into a thickness deviation signal according to the rolling length, and approximating it with a continuous function; Skid mark detection device of the hot rolled sheet comprising a. In the skid mark detection method of a hot rolled sheet, A first step of measuring a thickness deviation and a rolling speed sampled at regular time intervals; A second step of converting the thickness deviation sampled in the first step into a thickness deviation sampled in units of length by multiplying the rolling speed corresponding to the measurement time by the thickness deviation sampled at a time interval; A third step of resampling the thickness deviation sampled by the length unit in the second step by the predetermined length unit; And Fourth transforming the function resampled by the predetermined length unit in the third step to the spatial frequency, and if the size of the skid mark frequency component exceeds a certain value, it is determined that the thickness variation due to the skid mark in the hot rolled sheet 4 steps; Skid mark detection method of the hot rolled sheet comprising a.