SU1199815A1 - Method of controlling process of cyclic heat treatment of welds - Google Patents

Abstract

METHOD OF CONTROLING THE PROCESS OF THERMOCYCLIC TREATMENT OF WELDED CONNECTIONS, includes thermal cycling of the welded joint with measuring the background of the internal friction of its various zones before and after processing and comparing the results obtained, in order to improve the quality and shorten the processing time, periodically measure the amplitude of independent high-frequency background, internal friction and when it reaches the minimum value, the heat treatment is stopped (L with from 00 U Ch.}

Description

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This invention relates to the machining of welded joints.

Uejib invention - improving quality and reducing processing time.

FIG. 1 shows the dependence of the internal friction background on the number of thermal cycles; in fig. 2 - the relationship between impact, viscosity and internal friction.

The measurement of the background of the internal friction is carried out by installing their standard instruments: a quartz transducer, a measuring instrument of the light frequency and an electronic counting clock in the frequency range 5-10 MHz.

The method is implemented as follows.

In the welded joint zone, a measuring plane with an area of 1-5 mm is prepared by machining. After conducting a certain number of thermal cycles on the measuring plane using an acoustically permeable glue, a quartz transducer is connected, connected to a Q-meter, and the background friction value is measured. It was established experimentally that the magnitude of the amplitude independent high-frequency background of the internal friction in welded joints decreases with an increase in the number of thermal cycles. This is due to the processes of substantial restructuring of various zones during thermal cycling, grain grinding, polygonization, intensive movement of dislocations to energetically favorable zones, to the grain boundaries. Periodically, these measurements, while increasing the number of thermal cycles, determine when the minimum value of the internal friction background value is reached, and the number of thermal cycles corresponding to this value is considered optimal. If it is necessary to establish the numerical values of standard parameters, for example, toughness, experimentally obtained dependences, such as the background of the internal

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friction is the impact viscosity for the materials studied.

So, for example, heat-treated steel weld 40, made by electroslag welding, is subjected to heat treatment. The quality of thermocyclic processing is controlled by the background of the internal friction. The resulting dependence of the background of the internal friction — the number of thermal cycles for the seam (curve 1) and the overheating zone (curve 2) showed (Fig. 1) that the minimum value of the background of the internal friction is reached at five thermocycles. A further increase in the number of thermal cycles (up to 7-8) leads to an increase in the amount of internal friction, and, consequently, to a deterioration in the mechanical properties of the welded joint. Testing samples for impact bending under similar heat treatment conditions showed that the optimal number of thermal cycles is 7–9. it

25 is associated with lower structural sensitivity of toughness and reliability of test results. In order to obtain standard parameters of mechanical properties, a relationship is established between standard parameters, such as impact toughness, and the amount of internal friction for a number of grades of materials to be welded (3-curve steel 3, 40-curve steel 4, 40x-curve steel 5, 23Г- steel curve 6). This allows, if necessary, determining the values of the standard parameters without carrying out destructive tests.

dd So, in the above case, the value (the background of the internal friction of the overheating zone 0 100 corresponds to the impact strength and c 110 J / cm. Thus, the structural sensitivity of the internal friction is high, the simplicity of the experiments and the ability to evaluate the properties of individual weld zones can reduce the complexity and increase the reliability of the results

50 quality control thermal cycling without conducting destructive testing of specially manufactured samples.

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Claims (1)

METHOD FOR CONTROLING THE PROCESS OF THERMOCYCLIC PROCESSING OF WELDED COMPOUNDS, including thermal cycling of the welded joint with measuring the background of internal friction of its various zones before and after processing and comparing the results obtained, characterized in that, in order to improve quality and reduce processing time, the amplitude-independent high-frequency background is periodically measured, internal friction and upon reaching its minimum value stop the heat treatment. _about SS SU <„, 1199815