SU747658A1 - Method of investigating properties of welded joint - Google Patents

Description

one

The invention relates to welding, in particular to methods for researching the properties of a welding joint in the end zone during electroslag welding.

There is a known method for studying the properties of a welding joint in electroslag welding 1, in which an inwardly grooved, perpendicular seam line is performed in the product to be welded. Standard grooves are installed in these grooves with the edges joined for welding. In the process of welding the product, as the gap between the weld edges 15 of the metal bath is completed, the samples are exposed to external tensile forces.

At. The implementation of this method creates conditions that are identical to the thermal cycle during welding real detonation, and the external applied force is significantly reduced by applying them not to the product being welded, but to the samples installed in pairs of products.

However, the use of samples or real parts for the implementation of cnocoeSa is not economically feasible, but due to the significant costs of metal -30

and laborious machining. In addition, the implementation in the product of the grooves under the samples also necessitates the use of time-consuming machining.

The closest in technical essence and the achieved effect to the described invention is a method of studying the properties of a welded joint, mainly during electroslag welding, in which the sample under test is subjected to external tensile forces across the weld axis that apply a higher level to the weld edges. metal bath.

In the process of welding the sample, the crystallized part of the weld is cut from the bottom by gas cutting to the place where the metal is still hot and has significant ductility. The sample is then exposed to external tensile forces in the transverse direction.

This method saves metal during research and also significantly reduces the use of laborious machining.

However, this method of investigating the properties of a welded joint, like the previous one, allows to obtain only a general assessment of the quality of welded joints. At the same time, in practice, there is a need in the process of slag welding of high-strength metals to obtain information on the resistance of the welded metal against the formation of cracks and tears in the heat-affected: zone.

The known methods do not allow conducting a qualitative study of the n4 resistance of the single-seam welded joint zone against the formation of tensile scars.

The purpose of the invention is the ability to determine the resistance of the heat-affected zone of the welded joint against the formation of cracks and tears, as well as to maximally approximate test conditions to real ones.

The goal is to reach the target body that the specimen under test is additionally exposed to compressive forces at the level of the metal bath.

The application of compressive forces in the direction opposite to the influence of external tensile forces, butts against the specimen above the level of the metal bath creates a bending mvTeHT simulating the conditions for closing the welding joint.

In the process of electroslag welding K | Of these products, conditions are created when the brew seam, which undergoes shrinkage deformation, forms a rigid connection. At the same time in | as a result of heating of not yet welded edges, they are rotated relative to the level of the metal bath. The turning of the edges is accompanied by their bending. Moreover, the maximum value of the bending moment is created in the sections of the heat-affected zone at the level of the metal bath. In this connection, longitudinal tensile stresses are formed in the heat-welded zone (at the fusion site of the base and electrode metals), which contribute to the formation of cracks-tears in the metal to be crystallized.

The invention is illustrated in the drawing.

The drawing shows the test subjects: sample 1, on which the method of studying the properties of the welded joint is implemented, the water-cooled copper pocket (chill mold) 2, the weld 3, which is subjected to compressive forces Q at the # points at the level of glutanic janna 4. Ir-expanding forces N applied to the ends of the edges to be welded at points C and D, located above the level of the slag bath 5, electrode b, melted parts 1, cracks-tears 8.

Example. Electric welding sample 1; consisting of two workpieces with dimensions 80 x 80 x 200 mm, started with electrode 6 in a chill mold 2 in order to eliminate the distorting effect of the initial part of the seam 3. Electroslag, the device was welded in the following mode: welding wire feed speed 250 m / h ; The welding voltage is 40 ... 42 V, the number of electrode wires with a diameter of 3 mm is 1 pc., the gap between the weld edges is 30 mm.

Welding materials - wire SV-20HNZMF (EI-62) and flux AN-8.

After welding 40 ... 50 mm of the length of the sample at the level of the metal bath, a compressive load was applied by abutment, and above the level of the slag bath, a tensile force was applied to the sample using a gripping device, this. ensured the creation of the necessary deformations and stresses in the studied areas of the heat-affected zone.

After welding of the sample and removal of external loads, a longitudinal macrosection was made, as a result of an external inspection of which a qualitative and quantitative characteristic of resistance to the formation of cracks and tears was determined.

The timing of time showed that it took 2 ... 3 hours to install, weld, make a macro section and analyze its external inspection.

“Thus, the laboriousness of the research on the proposed method is reduced in comparison with the known one, due to the use of small samples, the application of external forces, and the maximal approximation of test conditions to real ones.

The proposed scheme of application of external forces creates a bending moment in the studied areas of the heat-affected zone lying in the vicinity of the melted edges 7 (areas most suitable for the formation of cracks

eight).

The forced movement of the edges to be welded as a result of this N action can be carried out at different speeds, and the magnitude of the bending moment is controlled by changing the points of application of N forces relative to the level of the meticholic bath, which simulates the conditions for fixing the welded standard items and maximally approximates the test conditions to real ones.

After removing the loads from external forces, cutting the specimen, making and viewing the micro-pyphs, the presence of cracks in the research sections of the peritoneal zone is determined.

In the absence of cracks, shrinkage moves

the process of the next sample is increased, and in the presence of - reduced.

In this way, the critical strain rate is determined, which is a quantitative criterion for assessing the tendency of a welded joint to crack formation at a constant welding speed and other mode parameters.

Claims (2)

1. USSR author's certificate number 421910, cl. At 23: 25/00, 1972. 2. Authors certificate of the USSR 285747, cl. At 23: 25/00, 1969.