SU452456A1 - Arc welding method - Google Patents

Description

one

There is a known method of arc welding, in which the dp of preventing the formation of defects in the weld (cracks, quenching structures) is carried out by heating the welded products.

The known method does not allow the rate of heating and subsequent cooling of the product after welding to be controlled within the spine limits.

The proposed method eliminates the indicated disadvantages.

This goal is achieved by the fact that during the welding process the product is heated by passing an electric current through it in a direction perpendicular to the axis of the joint, while the force of the transmitted current constantly increases in proportion to the cross section of the joint.

The method is carried out as follows.

The parts to be welded are connected to the current source, for example, constant or industrial frequency.

In the process of welding, the seams and the heat-affected zone due to a sharp increase in temperature are much painful.

neck electrical resistance than the surrounding cold areas according to the equation:

 Rt R2af / (i-20) J,

2D - resistance at 2., ohm

where: fvt is the resistance at t ° C, ohm (TO is the temperature coefficient of resistance.

; With the passage of current through the weld; My parts in these areas predominantly generate heat, since the amount of heat released as a result of the passage of current linearly depends on the resistance due to the following level:

Q C / ftt

where: (amount of heat, j Y - current strength, and f - resistance, ohm i - time, sec.

In the process of welding, the resistance of the seam decreases due to an increase in the area of its longitudinal section.

Therefore, to maintain a constant weld temperature during welding, the strength of the supplied current is changed according to the law:

: /, - 00 Vee-i

 - the force of the supplied current in the process. se welding and

Jo- initial current strength, a / sy - welding speed, m / s. B - time, sec.

The initial current strength is chosen such that when a quasi-stationary temperature field is established, the heat loss is equal to the heat released by the passage of a current equal to.

In the same way, it is possible to produce heating even after the end of welding of an article that is not yet cold, which is especially important for hardening steels.

Simultaneously with the prevention of the formation of quenching structures, the occurrence of cold cracks and the elimination of deficiencies in the known methods of heating products

The proposed method provides an increase in the productivity of welding. Due to the release of additional energy. Decrease in the probability of the formation of slag inclusions by reducing the rate of crystallization.

 The effectiveness of this method can be enhanced by applying heat insulation of the seam, heat affected zone and forced cooling of the remaining areas.

The method of arc welding, in which the accompanying heating of the welded products is carried out, characterized in that, in order to improve the quality of the welded joint and productivity,

Concurrent heating is carried out by passing an electric current through the product in the direction perpendicular to the axis of the weld, and the strength of the transmitted current is changed during the welding process in proportion to the increase in the area of the longitudinal section of the weld.