SU408731A1 - METHOD OF CONTROL QUALITY OF CONNECTION IN THE PROCESS OF CONTACT WELDING - Google Patents

Description

one

This invention relates to the field of quality control of joints made by contact Hoii welding.

Known drift quality control welding time.

However, the known methods of control do not provide sufficient accuracy due to the imposition of certain errors.

In order to increase the reliability of control according to the proposed method, the duration of time during which the welded joint is under pressure below a predetermined welding compressive force is determined.

As parts heat up under the action of the welding current, the yield strength of the material being welded decreases and by some point in time it becomes less than the stresses created by the compressive force. As a result, the actual pressure in the contact becomes lower than the established one, and the difference between these pressures accelerates the mass of the sliding parts of the compression mechanism, which causes the parts to settle down. As the mass of the moving parts of the squeeze mechanism accelerates, the heated volumes of the metal are squeezed out of the joint, and the contact area is dispersed. In addition, by the end of the current pulse, the heating intensity is reduced. As a result, the actual pressure in the contact increases again.

Having determined the time interval during which the actual pressure in the contact during the precipitation process was lower than the previously selected for this type of parts, one can judge the strength of the joints with sufficient accuracy, since the degree of pressure reduction on the one hand depends on the known parameters — mode rigidity and inertia of the mechanism compression, and on the other hand, from the temperature field of the contact area of the parts to be welded.

FIG. Figure 1 shows a block diagram of a device, the method of which is used to implement the proposed method; in fig. 2-characteristic oscillogram of the actual pressure at the contact c of the welded current over time for capacitor welding of parts according to the T-shaped scheme.

The circuit consists of a pressure measurement unit 1, a time measurement unit 2, a comparison unit 3, a signal unit 4, a unit 5 of the informational mechanism, a unit 6 of the reference signal and a software device 7.

Welding quality is determined as follows.

By means of fusion welding and reading of this type of parts, the optimal value of the minimum compression ratio Py ,,,, and the limits of the time tc are determined at the optimum mode, the bw of which ensures sufficient strength of the connection. The selected values are Ryny and K are transmitted to a software device. When the weld current pulse is turned on / due to the heating of pressure P at the contact, the melada by the parts being welded begins to decrease and by some time ti reaches the value PINN- The signal on reaching this pressure from the pressure gauge is fed to the time measurement unit, which starts counting. When the pressure starts to rise again, a second signal is applied to the time meter. The duration of the time between signals enters the comparison unit, where it is compared with the duration of the reference signal. The result of the comparison is applied to a signaling device, which in the case of insufficient heating intensity is less than the allowable) or excessive penetration of the contact zone (/ k is more than the allowable), gives the operator a corresponding signal. In addition, when operating in the automatic mode, the result of the comparison may be fed to the block of the actuating mechanism, which either terminates the operation of the machine or closes the path of the low-quality part to the bunker.

10 of the invention

A method of controlling the quality of a joint in the process of contact welding over time, characterized in that, in order to increase the reliability of control, the duration of the time during which the welded joint is under pressure below a predetermined welding compressive strength is determined.