SU703274A1 - Method of evaluating the tendency of metals to crack formation at welding - Google Patents

Description

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The invention relates to welding, in particular to methods for the technological assessment of the tendency of metals to form hot cracks during welding, and can be used in the engineering, shipbuilding and other industries.

There is a known method of testing metals for cracking by stitching a specimen with decreasing stiffness, in which welding is performed at a constant speed, and the intensity of the heat sink from the weld pool is increased as the arc 1 moves.

However, the need to change the heat sink during the test complicates the execution of the sample and introduces uncertainty in the assessment, since under actual conditions for the manufacture of welded structures, an increase in the intensity of the heat conductor in the process of moving the arc does not occur.

The known method tehnoprogicheskoy assessment of the tendency of metals to obrazovaniyu

hot cracks during reconciliation, in which a sample is made from an edge to the middle in the form of a rectangular plate with a slit, and the smallest specimen of a series of similar ones in which a crack occurs 2 is taken as an indicator of technological strength.

However, the presence of a slit leads to the fact that the rigidity of the sample is reduced compared to the rigidity of real structures, and the presence of the slit and the need to manufacture samples of different widths makes it difficult to execute the sample and evaluate the results.

A known method for the technological evaluation of the tendency of metals to form hot cracks during welding, in which a series of identical plates, tightly adjacent to each other, is laid on a gasket and carried out in the direction perpendicular to their joints.

However, due to the uncertainty of the conditions of fixation of the sample, its deformation arises, which creates uncertainty for the O77432 HOCTb test conditions and reduces the accuracy of the assessment. In addition, the method allows the test metals to be divided only into hot cracks prone to three tests for this sample and non-compliant, although bb1, assigned to one category: d, may differ in terms of technological strength. The purpose of the invention is to increase the exact estimate by preventing deformations of the plates. To do this, in the process of welding, the plates are pressed to the lining of permanent and equal in length over the series, and the ratio of the sum of the lengths of the longitudinal cracks that occur at the joints, to the number of joints is taken as an indicator of the tendency of metals to crack the hot cracks. 1 shows a sample for testing according to a known method; aai FIG. 2 - test scheme. The method is as follows. Plate 1 of the same stiffness is placed on a smooth lining 2, tightly pressed to each other. The plates are then pressed against the lining with a constant, constant over the length of the series, a force P sufficient to ensure that the plating is lost in the process. not two. In a mode that ensures the normal formation of a weld, in one pass, the plates are cut through, and the seam 3 is placed in the direction from the first to the last pasline of this series. TbttiiKM -t is the germs of hot T | cracks in welding (T) mrcpmst from UTp.; carrying the sum of tregaine lengths ((n}: number of transverse joints. HG7. As experiments conducted under laboratory conditions showed, with a little laboriousness and simplicity of execution and evaluation, the sample ensures good reproducible results. Example: 4mm thick plates were cut out of extruded AMGB alloy rods made from single-ingot ingots, but with 5 a hydrogen content. They tested a series of plates from 5-7 cm. The plates with milled ends were placed on a stainless steel lining. The plates were pressed to the lining is made of pneumatic clamps, which ensure the pressing force unchanged along the series. The pressure in the pneumatic system was 4 MPa and did not change during the testing process. The penetration was carried out by automatic srgano-arc welding with a tungsten electrode on a USPO-900 installation.

The table shows the test results. As can be seen from the data in the table, the tendency of the metal of the bars to the formation of hot cracks during welding depends on the hydrogen content in them.

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The method for the technological assessment of the tendency of metals to form hot cracks during welding is more precise due to the reduction in the scatter of the data on the length of the cracks and the MacManVvHoro approaching the real time of welding. Formup of the invention. Method of a pedicological evaluation of metal sheetness to hot cracks at. welding, in which a series of identical plates, tightly adjacent to each other, are laid on the lining and welding is carried out in the direction perpendicular to their joints, about and yen so that, with increasing accuracy of assessment by preventing {jurmatia plates, in the process of welding plas

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ig.2 tines are pressed to the lining by a constant and equal in length series of force, and the ratio of the sum of the lengths of the longitudinal cracks arising at the joints to the number of joints is taken as an indicator of the tendency of metals to form cracks; Sources of information taken into account during the examination 1. USSR author's certificate No. 399329, cl. B 23 K 28 / OO, 1973. 2. Author's testimony of the USSR No. 337690, кп. G 01 N 3/20, 1972. 3. Welding handbook, vol. 3, Ed. V. A. Vinokurova. M., 197O, p. 205 (prototype).