The assessment methods of the weld metal tendency to hot cracking (Part 2).

During the process of crystallization the weld metal continuously undergoes to lateral deformations, due to which the longitudinal crystallizational crack can be formed in the weld metal.

The initial strain rate A is selected so large that the crack initiation was guaranteed, and in process of movement the arc along a sample decreases monotonically (Fig. 1). The crack which has occurred at the beginning of the weld develops deep into the crystallizing metal after the moving arch. The effort necessary to deform the samples, in this case is insignificant as the weld behindthe arch is completely divided by the longitudinal crack, the liquid bathtub deforms freely and the deformation resistance is provided only by the metal layer.

Since in the process of welding the strain rate A constantly decreases, at some point of time t it will become so small that the metal will withstand such deformation without crack formation. There will be set and the plastic deformation of the strengthened metal as a result of cooling will begin.

The advantage of this method over others is, first of all, in the purity of the experiment, as the test is exposed to only one layer of weld metal, the properties of which we are interested and in those conditions, which are very close to reality. It is important to emphasize that in the process of testing the main metal samples and the weld metal aren’t exposed to deformations and their properties aren’t imposed on results of testing.

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