ABSTRACT

Nitrogen, oxygen and metallographical structure are regarded as the main factors for impact properties low carbon steel weld deposits. Especially the influence of the variable amounts of nitrogen and oxygen on impact properties of different welds were tested. Furthermore, on the basis of the results of the influence of the variable amounts of nitrogen, oxygen and metallographical structure on impact properties, mathematical equations regarding those relationships have been given.

INTRODUCTION

The influence of nitrogen contents in weld metal deposit on impact properties was well analyzed in the last 15 years (1,2,3,4,5,6,7,8). Authors of the main publications present that the optimal content of nitrogen should not be ~eater than 100 ppm. The lowest amount of nitrogen in all weld metal gives the best impact results of the weld metal deposit. However also amount of oxygen and metallographical structure could be regarded as the important factors on impact properties and metallographical structure (3,4,5,6,7,8,9,10).

EXPERIMENTAL PROCEDURE
Welding Procedure

To asses the effect of nitrogen and oxygen on mechanical properties of deposited metals there were used basic electrodes prepared in experimental way. The electrode contained constant or variable proportions of the following components in powder form. The principal diameter of the electrodes was 4 mm. The standard current was 180A, and the voltage was 22V. A typical weld metal deposited had following chemical composition: 0.08% C, 0.9% Mn, up to 0.35% Si, 0.02%P, 0.02% S, up to 0.035% A1, up to 0,07 Yi and a variable composition of nitrogen (from 63 to 287 ppm) and oxygen (from 262 to 804 ppm). In order to prepare weld metals containing different concentration of nitrogen, nitrided ferromanganese was added to the coatings of electrodes. A variation in the nitrogen amount in the deposited metals was analyzed from the extra low-nitrogen weld metals containing 63 ppm up.

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