Improvement of materials for gas welding of cast iron

Abstract

The aim of the study is to create a bar for gas welding of cast iron parts, with improved mechanical characteristics and lower hardness of the weld metal.
A disadvantage of the known welding rods is the high hardness and low mechanical properties of the weld metal. This does not allow the use of the mentioned filler rods for welding critical structures and surfacing of parts to be machined in industrial volumes.
As a filler material in gas and electric arc welding of cast iron, rods with a diameter of 8-10 mm from cast iron of grade A or B according to GOST 2671-80 were used. As a flux in gas welding, we used a technical drill according to GOST 8429-77, calcined at a temperature of 300350 ° C for 2 hours.
Yttrium and erbium were used as an alloying and rare-earth metals additives in iron bars.
The welding-technological properties of the investigated rod compositions were checked during gas (acetylene-oxygen) and electric arc welding of high-strength cast iron of grade VCh 40.
Based on the tests of the welding and technological properties of the rods under study, it was determined that rod No. 2 is optimal, which ensures good wettability of the weld pool with molten metal. Slags are fusible and do not impede the conduct of the welding process for cutting large volumes. No weld defects.
The structure of the deposited metal on the surface of the weld at a depth of 1.5-2 mm is pearlitic with small areas of austenite of dendritic orientation. Further along the height of the weld to the fusion line, perlite prevails in the structure. The inclusion of ferrite and cementite are single. Spherical graphite of medium size, slightly smaller than in the base metal.
The hardness in this zone is 220-229 HB and allows easy machining of welds with conventional metal cutting tools.