SU1562818A1 - Method of detecting cracks in external surfaces of steel articles - Google Patents

Abstract

The invention relates to non-destructive methods for monitoring the integrity of the outer surfaces of products and can be used to detect hidden defects such as "cracks". The purpose of the invention is to increase the reliability of the method and its simplification. After mechanical cleaning of the test surface, the zone of the supposed crack is heated locally to the temperature of flowers of tinge. The heat is produced by a burner with a flame temperature above the melting point of the metal of the product. 7 il.

Description

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The invention relates to non-destructive methods for monitoring the integrity of the external surfaces of products, mainly large steel, for the detection of microcracks and can be used in various fields of engineering.

The purpose of the invention is to increase the reliability of the method and its simplification.

Local heating of the zone of suspected cracks with a burner with a flame temperature above the melting point of the metal of the product increases the crack opening width, and the formation of tinge colors on the surface under study contributes to the release of the crack.

The method is implemented in the repair work of the detachable bottom of the working cylinder of the stamping press.

Figure 1 - shows a detachable bottom-, with the area C of the alleged microcrack, general view; figure 2 - section aa in figure 1; in FIG. 3, node I on f of FIG. 2; figure 4 - view B in figure 1, when heated; figure 5 - the same, when cooled; figure 6 is a section bb In figure 5; Fig. 7 shows a final split, a slit.

The detachable bottom of the working cylinder is a round plate with

insert central part. Mother J Al is steel 35. Periodic preventive ultrasonic testing of the face of the part operating at a working fluid pressure of 320 kg / cm2 showed the presence of a defect in one place. After dismantling the central part of the bottom with seals in diameter D, a visual inspection of the defective zone revealed a crack along the generatrix of the inner cylindrical surface 120 mm long and, as shown by ultrasonic testing, a depth of 22 mm. After cutting the crack zone with drill holes with emery circles to a depth of 21 mm, the crack disappeared and could not be detected by any Known methods. However, doubts remained, since the ultrasonic, control showed before cutting the depth of the crack to 22 mm. Then the proposed method was applied. With its use, the remnants of a crack immediately appeared, were cleaned to a depth of 22 mm. After reapplication of the proposed method, the remnants of the crack reappeared and only after cutting the crack zone, to a depth of 23 mm, the crack was not detected by the proposed method.

Next, the crack zone was mechanically processed with the expectation that the boundaries of the crack zone and the bottom of the sample had smooth radius transitions, as shown in Fig. 7. With the crack zone divided in such a way, the bottom was allowed for further exploitation.

When the crack zone was heated, a conventional oxy-acetylene cutting torch was used. The highest temperature of the flame of the cutter at a distance of 3-5 mm from the flame core is 3100-3150 ° C, and on both sides of this point it is much lower, but above the melting temperature of steel 1510 ° C. The mechanism for detecting a hidden microcrack by the proposed method can be explained as follows.

When the microcrack zone is treated with an abrasive wheel, it is tightened by the plastically deformed metal as separate micropets (Fig. 2) and the discontinuity of the metal on the surface thus treated (Fig. 3, size a) is so small that it cannot be detected by known methods.

When exposed to microcrack zones with a thermal field of a burner with a flame temperature above 1510 ° C, the microchips and microcrack edges above the crack are melted (Fig. 6), and the zone itself is compacted by local thermal expansion, being surrounded by a powerful corset of cold metal bottom

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(Fig. 4), local raising of the microcrack edges occurs.

The determining factor for increasing the size of a crack is primarily the melting of the micro-visor over the crack and melting of its edges, therefore, the burner with a flame temperature higher than the melting point of the metal of the product is chosen. The rubbing of the edges of a microcrack during heating of the controlled zone due to thermal deformation accompanies the processes of melting and is inseparable from them, since thermal stresses at

warming up the crack zone to the colors of the shoots,

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The pity (400 C) to which this zone is heated is very significant.

During the heating of the crack zone, the melted edges of the cracks against the background of the colors of the tinge are sharply highlighted with an exclusively black color, therefore, they cannot be overlooked.

When cooled, a reverse movement of the crack zone metal occurs (Fig. 5), due to which the black oxide film breaks and the crack appears particularly contrasting.

The invention makes it possible to simplify the method of detecting microcracks, to reduce the time and cost. The method does not require the use of various indicator liquids and is available for any company.

The microcrack at the bottom with the method of heating with a burner flame allowed us to qualitatively and with guarantee repair the bottom, put it in place for further operation and thereby reduce the simple unique press.

Claims (1)

Invention Formula The method of detecting cracks on the outer surfaces of steel products, including mechanical cleaning of the surface under study with its subsequent visual inspection, characterized in that, in order to increase the reliability of the method and simplify it, after cleaning, the zone of the alleged crack is heated to the temperature of the poker color of the burner with the flame temperature above the melting point of the metal of the product, and after the zone cools, a crack is judged. warming up the crack zone to the colors of the shoots, 0 five 0 five 0 five 0 five The pity (400 C) to which this zone is heated is very significant. During the heating of the crack zone, the melted edges of the cracks against the background of the colors of the tinge are sharply highlighted with an exclusively black color, therefore, they cannot be overlooked. When cooled, a reverse movement of the crack zone metal occurs (Fig. 5), due to which the black oxide film breaks and the crack appears particularly contrasting. The invention makes it possible to simplify the method of detecting microcracks, to reduce the time and cost. The method does not require the use of various indicator liquids and is available for any company. The microcrack at the bottom with the method of heating with a burner flame allowed us to qualitatively and with guarantee repair the bottom, put it in place for further operation and thereby reduce the simple unique press. Invention Formula The method of detecting cracks on the outer surfaces of steel products, including mechanical cleaning of the surface under study with its subsequent visual inspection, characterized in that, in order to increase the reliability of the method and simplify it, after cleaning, the zone of the alleged crack is heated to the temperature of the poker color of the burner with the flame temperature above the melting point of the metal of the product, and after the zone cools, a crack is judged. rvj l one "ABOUT FIG 6 7