Method for detecting ingot cracks

(54) Method for detecting cracks in ingots

The present invention relates to a method for detecting cracks in ingots.

It is known that surface breaks and cracks in ingots can be detected by heating their surface with a high frequency current, along with their displacement in longitudinal direction through a high frequency induction coil. The part of the ingot that passed through the coil is immediately subjected to analysis with the help of infrared equipment for recording the temperature distribution along the ingot. The temperature distribution is recorded in the form of a striped pattern that indicates the superficial ingots or cracks in the ingot. By such a recording of the temperature profile in the ingot, during an analysis a temperature increase will be detected near the breaks. The increases of. temperature which are repeated from one analysis to another, when combined, forms a corrugated path indicating the crack.

By using the infrared scanner (the infrared emission pyrometer), temperatures are obtained that deviate from the real surface temperature, due to the emission coefficient of the respective surface, which depends on the nature of the surface and which varies between 0 and 1.

In order to obtain the best conditions during the analysis of the ingots and as few anomalies in the temperature profile, it is necessary that the surface be as clean as possible5. This can be achieved, for example, by strong surface blowing. This insufflation creates an undesirable side effect of surface brightness, which alters the emission conditions. Consequently, the over-temperatures recorded in the cracks are reduced to the ingots rolled with the rolling train which result in different interpretations of the depth of the cracks, depending on the emission coefficient and requiring the recalibration of the equipment for each new one. type of surface, to obtain correct results. This determines the increase of the operating time, the method / becomes complicated and; unsuitable for use but industrial. ;

The method for detecting cracks in ingots, according to the invention, removes the above disadvantages through the aisle. it, in order to increase the coefficients of_;broadcasting ¹ of the different ingots and of the compensation, the differences between them, provides for the wetting of the face of the ingot with a suitable liquid, for example water, possibly with addition. of components that reduce the surface tension, the liquid / being,. by the PRICE OF LEI 15.47

I have holes in front of the detection unit, and for the purpose of analyzing ingots at temperatures below 0 ° C 'it is possible for the wetting fluid to be provided with components for reducing the freezing point, such as ordinary anti-freeze or alcohol liquids. ₅

The following is an example of the application of the method according to the invention, in relation to the figure which is a graphical representation of the temperature measurements with the contact pyrometer and with the infrared emission for different surfaces.

The term "ingot" refers to the present invention both to metal parts first subjected to rolling, as well as to parts to be subjected to rolling processes, 15 as well as to finished products, such as bars, pipes, profiles, etc. subjected to lamination treatment.

The present invention aims to record very small surface cracks (with depths below 1 mm) and to obtain uniform emission conditions for all surfaces, with the simultaneous reduction of anomalies in the temperature profile.

According to the invention, for all types of 25 ingot surfaces, the emission coefficients can be equalized by moistening the respective surfaces with a suitable liquid, for example water, to which are added components to reduce the surface tension, in order to obtain a better wetting. in the case of analyzing ingots at temperatures below 0^pC frost-reducing components can also be added. Experiences have shown that by wetting the surface of the ingot with water to which were added components to reduce surface tension all surfaces, regardless of the previous treatment will have the same emission coefficient that will only deviate to a small extent, practically, unimportant. at the value of the emission coefficient of a dry ingot laminated with the rolling train. Also, prjn. 4 ",, The wetting of the ingots, in the temperature profile creates fewer anomalies, because the differences between the emission coefficients of the different zones are equalized, obtaining an important improvement of the ratio of anomalous signal to the signals of the pyrometer of infrared emission. In the insufflated ingots that have not been moistened, the signal / anomaly ratio is so low that on certain types of surfaces, problems of detecting very small cracks occur.

In the following table, the results of the temperature measurements with the contact pyrometer and the infrared emission pyrometer for different types of surfaces, dried or moistened.

Sample A refers to a rolled ingot in the rolling train. Sample B refers to an ingot with corroded surface, and samples CSA 1, 2 and CSA 2 1/2 are cleaned by insufflation. T represents the temperature read at the contact pyrometer and IR represents the temperature read at the infrared emission pyrometer. As mentioned, the readings were made on the damp and dry surface. Analyzing the column "dry, we observe an important temperature deviation between the two measurements and this deviation increases with the degree of insufflation that is designated, CSA 1 - 2, CSe 2 and CSe 21/2 respectively. The deviation between the two measurements. it increases with the brightness of the ingot. As a result, in the measurements with the infrared emission pyrometer in the insufflated ingots, too low a temperature is recorded and, consequently, a lower increase of the temperature on the scale, in these cases, to obtain the desired results, the equipment must be calibrated according to by the emission coefficient of the surface, which is a major disadvantage, as the coefficient varies from ingot to ingot.

<td></td><td colspan="3">A</td><td colspan="4">B</td><td colspan="2">CS 1</td><td colspan="2"> —2</td><td colspan="2">CSA</td><td colspan="2"> 2</td><td colspan="2">CSA</td><td colspan="2"> 2 1/2</td>

<td colspan="2">Dry</td><td colspan="2">Wet</td><td colspan="2">Dry</td><td colspan="2">Wet</td><td colspan="2">Dry</td><td colspan="2">Wet</td><td colspan="2">Dry</td><td colspan="2">Wet</td><td colspan="2">Dry</td><td colspan="2">Wet</td>

<td>T</td><td>IR</td><td>T</td><td>IR</td><td>Th</td><td>IR</td><td>T</td><td>IR</td><td>T</td><td>IR</td><td>T</td><td>IR</td><td>T |</td><td>IR</td><td>T</td><td>IR</td><td>T</td><td>IR</td><td>T</td><td>IR</td>

<td> 23,9</td><td> 21,0</td><td> 22,4</td><td> 19,0</td><td> 24,1</td><td> 20,0</td><td> 22,3</td><td> 18,0</td><td> 22,7</td><td> 19,5</td><td> 21,9</td><td> 18,5</td><td> 23,4</td><td> 20,0</td><td> 22,3</td><td> 18,5</td><td> 32,4</td><td> 19 0</td><td> 22,0</td><td> 18,5</td>

<td> 25,8</td><td> 23,0</td><td> 24,7</td><td> 22,0</td><td> 25,4</td><td> 21,5</td><td> 26,1</td><td> 22,5</td><td> 25,1</td><td> 21,0</td><td> 25,3</td><td> 22,5</td><td> 26,6</td><td> 21,0</td><td> 25,0</td><td> 22,5</td><td> 24,9</td><td> 20,0</td><td> 25,4</td><td> 23,0</td>

<td> 30,7</td><td> 28$</td><td> 29,7</td><td> 27,5</td><td> 30,1</td><td> 27,0</td><td> 30,2</td><td> 27,5</td><td> 30,1</td><td> 24,0</td><td> 30,0</td><td> 27,5</td><td> 29,8</td><td> 22,5</td><td> 29,7</td><td> 27,5</td><td> 30,0</td><td> 22,0</td><td> 31,4</td><td> 29,5</td>

<td> 35,6</td><td> 34,0</td><td> 30,7</td><td> 35,5</td><td> 35,5</td><td> 33,5</td><td> 35,6</td><td> 33,5</td><td> 35,0</td><td> 27,5</td><td> 34,5</td><td> 32,5</td><td> 34,8</td><td> 24,5</td><td> 35,8</td><td> 34,5</td><td> 35,(1</td><td> 24,0</td><td> 34,7</td><td>33, Q</td>

<td> 40,4</td><td> 38,0</td><td> 41,3</td><td> 40,0</td><td> 40,1</td><td> 38,0</td><td> 40,0</td><td> 38,5</td><td> 40,0</td><td> 30,5</td><td> 40,0</td><td> 38,5</td><td> 39,4</td><td> 26,5</td><td> 40,0</td><td> 38,5</td><td> 40,0</td><td> 26,0</td><td> 40,0</td><td> 38,0</td>

<td>47.7 50, Q</td><td> 45,0 47,0</td><td> 47,2</td><td> 45,5</td><td> 46,0 50,1</td><td> 45,0 48,0</td><td> 44,6</td><td> 43,5 1 ·</td><td> 44,3</td><td> 34,5</td><td> 45,3</td><td> 44,0</td><td> 45,7</td><td> 29,0</td><td> 46,0</td><td> 45,0</td><td> 45,8</td><td> 28,0</td><td> 44,7</td><td> 42,5</td>

cracking surfaces, obtaining a redone sign 1 / anojnalie, which is unfavorable.

Experience has shown that coefficients.

The reduction of the temperature peaks in the case of the insufflated surfaces also has a lower tolerance between the temperature peaks at the cracks and the emission temperature for the different surfaces can be made approximately equal for all the surfaces by wetting the surface.

By approximately equal it is understood that the surface emission coefficients are within an acceptable range for the results of the analysis method. The ingot can be wetted before passing through the induction coil, and the wetting fluid is provided as evenly as possible on the surface, 10 either through an opening nozzle or similar arrangement or by leaking along the surface. The effect of wetting is shown in the table in the column "moistened¹¹.

The results of the measurements on the dry or wet surface 15 are also graphically represented in the figure through the CSA 2½ curves. CSA 2, CSA 1-2, B, A for dry surfaces and CSAU 1 - 2, CSAU 2,

CSA 2½. AU, BU for wet surfaces. 20

According to the diagrams, the emission coefficients for wetted surfaces CSAU 2%,

CSAU 2, CSA 1 - 2 are all at the same level as for the laminated dry ingot with rolling mill, ingot A. It can also be observed that by wetting all surfaces have approximately the same emission coefficient which is close of the maximum level 1.

As mentioned, by humidity the level of anomaly for the surface without cracks, defined as the variation of temperature on the surface is reduced, because the increase of temperature caused by a crack, defined with the over-temperature along the 35 surface without cracks is amplified, which means that the signal / anomaly ratio is improved.

The method for detecting cracks in ingots, according to the invention, has the following 40 advantages:

Chairman of inventions committee - reduction of anomalies in temperature profile;

- obtaining the equalization of the emission coefficients;

- the possibility to perform the control on several types of ingots without re-calibrating the control equipment;

- the possibility of carrying out the control at low temperatures.