SU1613282A1 - Method of testing alloys for tendency to form cold cracks - Google Patents

Abstract

The invention relates to welding, in particular to the determination of the technological strength of welded joints. The purpose of the invention is the expansion of technological capabilities by providing an assessment of the tendency of alloys to form cold cracks in the heat-affected zone (3TB) of the base metal and increase the reliability of the test results. The sample is assembled, loaded. The test specimen is manufactured as a composite, connecting all its parts with one control weld. Part of it is made massively than monolithic. The occurrence of a cold crack in the right place of 3TV is ensured by the difference in cooling rates in different zones of 3TV (and, accordingly, the difference in structure) and asymmetrical arrangement of the grooves, ensuring the concentration of stresses in a given place of 3TV. AFTER WELDING A SAMPLE, ITS ELEMENTS WILL BE LOADED WITH VARIOUS BENDING EFFORTS AND DETERMINATE THE REQUIRED INDICATOR - CRITICAL VOLTAGE CAUSING DESTRUCTION. 3 IL.

Description

The invention relates to welding production, in particular to the determination of the technological strength of welded joints, and can be used in mechanical engineering.

The aim of the invention is the expansion of technological capabilities by providing an assessment of the tendency of the base metal of the heat-affected zone of a welded joint to the formation of cold cracks and increase the reliability of the test results.

FIG. 1 shows a test setup; in fig. 2 is a view I in FIG. one; in fig. 3 - auxiliary part of the test specimen.

The method is carried out as follows.

The sample part of the sample is assembled from the same plates (parallelepipeds) 1 of the test material and between them install spacers-plates 2 of an alloy that is not prone to the formation of cold cracks, i.e. possessing a large stock of technological strength. The dimensions of the plates 1 of the test material t width (along the axis X. figure 1) and height (along the axis Z) should be significantly greater than their thickness (size along the axis Y). for example, 5-15 times in order to ensure the necessary heat removal in the heat-affected zone and the formation of quenching structures in this zone. The dimensions of the gaskets 2 in thickness (in the direction of the Y axis) are taken within 0.5-1 of the thickness of the test plates 1. The size of the gaskets in the direction of the Z axis can be chosen

with

Yu

00

1st

It is equal to 1-1.5 of the thickness of the plates 1, and the size along the X axis is equal to or less than the corresponding size of the plates 1, but not less than the length of the supporting tooth 3 (Figures 1 and 3).

The monolithic part of the sample, the 4-plates, for the convenience of manufacture, is recommended to choose the same thickness as for the plates 1. In part 4, weld cutting is performed, for example, with a bluntness in the root. When applying a weld, it is necessary to provide a non-melting, which, when loading the welded joint, performs the functions of a concentrator. Such an embodiment of a welded joint with an asymmetrical with respect to the parts being joined with a groove ensures the concentration of stresses in the desired part of the heat affected zone. When testing a sample, its monolithic part is fixed in the housing 5 with bolts 6. At the same time, the plate 4 and the plate-gasket 2 are supported on a special comb-lining 7 with teeth 3. (FIG. 3). The dimensions of the comb 7 are chosen such that the loaded plate elements do not have support and, when the seam is deformed, bend down freely. At the same time laying

2 must be reliably supported on the teeth 3 of the comb 7 in order to ensure that the shims do not move vertically. The groove 8, formed on the comb 7, is intended to eliminate the support on the comb, reinforce the seam and prevent the gaskets 2 from hanging over the teeth.

3 (in accordance with the position in FIG. 1).

The loading of the plates 1 of the composite sample is effected, for example, by means of grips 9 connected to the lever 10, to which forces P are applied on the arm I. In FIG. 1 shows one gripper on the last plate 1. By the indicated (or different) method, a bending moment is applied to each of the plates 1, and the magnitudes of the moments are chosen such that the critical force Pcr (or the corresponding critical voltage (7cr) can be detected, ensuring the formation of a cold crack in the heat affected zone of the seam 11 after the time tKp. The magnitudes of these points can be adjusted by selecting the force P or the shoulder I (Fig. 1).

When using the proposed test method, the characteristics of the formation of a welded joint are as follows.

When applying a welded seam due to the difference in the sizes of the parts connected by the seam, the heat retraction in them becomes different. At the same time the cooling rate

Metal plates 1, including in the temperature range of phase transformations, turn out to be higher than in plate 4. When testing, for example, hardening steels, this leads to an increase in the percentage of the martensitic phase and an increase in the probability of cold cracks in the heat affected zone. plates 1.

The location of the plates 1 across the length of the seam helps to reduce the required length of the seam and, consequently, the welding time. Therefore, the time from the moment of welding of each plate 1 to its loading can be kept for a minimum and

the same for all loaded elements, which is a necessary factor for ensuring the reliability of the test results.

When testing by the proposed method it is possible to perform a weld without cutting edges.

In addition, when testing steels that are prone to the formation of cracks of the type of spallation, it is possible to use the lining 7

without teeth and assembling a package of plates 1 without gaskets 2 (FIG. 3). In those cases where a fracture trajectory is possible (a crack) can pass through the heat affected zone and along the seam, the use of a comb

with teeth 3 and grommets 2 necessary. This is due to the fact that during the development of deformations in the seam during the bending of one of the elements 1, these deformations do not affect the development of the stress-strain state in the seams connecting the other (adjacent) elements 1 with the plate 4.

Example. Collected samples from ZOHNMA steel. The elements 1 had dimensions 70x50x10 mm, plate 4 - dimensions 136x50x10 mm, gaskets 2 were made of low carbon steel and measured 50x12x8 mm. The number of plates 1 was 8 pcs. Welding cuts were made by chamfering on plate 4 at an angle of 45 ° 4 mm in depth. Welding was performed using Sv-08GN2M electrode wire. To ignite the arc and output it used the lead-in and lead-out bars. Assembly and

Welding was carried out in a special snap-in, providing the specified shape of the sample. The welding current is 300 A, the voltage is 24 V, the welding speed is 0.65 cm / s. After welding, the sample was fixed and each of the elements JOB 1 was loaded with bending moment of 34, 45, 57, 68, 80, 91.103, 114 Nm, respectively, which corresponded to the stresses in the weld and OSH approximately 225, 300, 375, 450, 525, 600 , 675, 750 MPa.

As a result of exposure at specified loads, 6 samples were destroyed. Processing the results of the experiment showed the desired critical voltage (for Tcr 20 h), equal to 340 MPa.

The use of the proposed method ensures the occurrence of cold cracks of the type of spallation in the heat-affected zone of the base metal and allows to obtain reliable test results with good reproducibility. This increases the reliability of detecting the propensity of materials to form this type of defects associated with delayed fracture and decreases therefore, the reject rate of welded joints.

Form l and 3 about b The method of testing alloys for the tendency to cold cracking, which consists in welding two halves of the sample — one monolithic and the other composite — both of the tested alloy, and in the typesetting part of the sample parallelepiped elements alternate alloy pads

not prone to cold cracking, and immediately after welding, the weld is loaded with various loads, and the tendency to delayed fracture is judged by the magnitude of the load causing the fracture, which is different in that, in order to expand technological capabilities by providing an estimate of the tendency of the base metal weld to cold formation

cracks in the near-weld zone and increase the reliability of the test results, a monolithic part of the sample is made with a side smaller than the side facing the component part of the sample, and

This side of the monolithic part is cut for welding with blunting at the root of the seam.

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Claims (1)

Claim A method for testing alloys for the tendency to form cold cracks, which consists in welding two half of the sample — one monolithic and the other component — both of the test alloy, and in the type-setting part of the sample, parallelepiped elements are interspersed with alloy spacer plates which is not prone to the formation of cold cracks, and immediately after welding the welded joint is loaded with various loads, and the tendency to delayed fracture is judged by the magnitude of the load causing fracture, which differs We note that, in order to expand technological capabilities by providing an assessment of the tendency of the welded joint base metal to form cold cracks in the heat-affected zone and increasing the reliability of the test results, the monolithic part of the sample is made with a side smaller than the side of the component of the sample facing it, and This side of the monolithic part is cut for welding with blunting at the root of the seam. Fig. 1 Fig. 3 Compiled by L. Nazarov Editor A. Lezhina Tehred M. Morgenthal Corrector V. Girnyak Order 3856 Circulation 631 Subscription VNIIIPI of the State Committee for Inventions and Discoveries at the State Committee for Science and Technology 113035, Moscow, Zh-35, Raushskaya nab., 4/5 Production and Publishing Combine Patent, Uzhgorod, 101 Gagarin St.