On 25 January 1955, the colleagues of the special workshop of the Machine and Tractor Station (MTS) Nauen celebrated the "Day of the Soviet innovator".
On this day, welders from the Experimental and Training Welding Workshop (Schweißtechnische Versuchs- und Lehrwerkstatt ) in Berlin-Adlershof demonstrated the method of the Soviet innovator Nazarov to colleagues in Nauen in the German Democratic Republic and those of other MTS Workshops, who had been invited.
The Nazarov method for arc welding of cast iron is a cold welding procedure for grey cast iron parts using electrode bundles consisting of a thickly flux-coated stick electrode and two copper wires. The dissemination and exploitation of this method was intended to save material costs and reduce the downtimes of machines in need of repair.
The Nazarov method for arc welding of cast iron with an electrode bundle consisting of a thickly flux-coated stick electrode and copper wire according to H. Thömke
In November 1955, the engineer H. Thömke from Leipzig reported on the "cold welding of cast iron according to the Nasarov method", and his report is reproduced here in excerpts as a suggestion
for scientific investigation and further development:
A KbXs of 3 to 4 mm diameter is used as steel electrodes and two copper wires are added so that the copper content is about 55%.
Electrode bundle according to H. Thömke
The electrode bundle must be manually moved in an arc shape (similar to a spiral). The larger arcs shown in the picture should be about two to three times the bundle diameter.
Spiral movement of the electrode bundle during welding according to H. Thömke
The spiral movements distribute the heat over a larger area and result in a better alloying of the cast iron with the copper. De; The base material itself may only be melted to a small extent.
Therefore it is wrong to keep the electrode bundle in one place for a long time. On the other hand, if the electrode bundle is moved away too quickly, the metal to be welded on will only bond
poorly with the base material, because there may be spots in the base material which have not been sufficiently melted.
The welder must therefore never be tempted to wait for the casting to cool down to hand heat after each welding section, even when carrying out urgent jobs. To achieve a good weld it is necessary not to melt the base material too deeply and to cover the whole weld with copper. For this purpose, the copper is firmly fused with the base material. Violations of this rule very often ruin all efforts to achieve a perfect weld.
When welding workpieces that work under pressure, one should work with an excess of borax. Acid-resistant cast iron with about 10 percent silicon cannot be welded using the Nasarov method. because silicon promotes graphite formation. When cold welding according to the Nazarov method with very short heating of the welding point, the graphite evaporates and thus the porous welding points are formed. Such castings with a silicon content of more than 5% can only be welded with hot welding under red heat. The weld is then so deep and thin that the gases that form have enough time to escape and the formation of pores is avoided.
However, even cracks in workpieces with a wall thickness of 2 mm can be welded with the combined electrode bundle. Of course, the welding process must be carried out all the more carefully when welding thin walls. It is best to use bundles of electrodes with a diameter of up to 3 mm for this purpose.
For wall thicknesses up to 3 mm, cracks are welded without preparing the edges. In this case, the welder guides the electrode bundle away from himself. The weld seam length is 50 to 70 mm. In order to prevent the material from melting through, which less experienced welders occasionally do, it is recommended to use a copper backing.
Furthermore, cracks in wall thicknesses of 3 to 5 mm can also be welded without pretreatment if two-sided welding is possible. However, it is absolutely necessary to let the workpiece cool down after welding a section. Only after cooling down can the next section be welded.
Cracks are best welded from the inner sections towards the outer edge. The welding bead should cover the end of the crack by about 15 to 20 mm in the first section of the seam.
Branched cracks are welded by first welding the shorter branches and then turning towards the main crack. In thick-walled workpieces, crack welding usually requires several layers. The quality of the weld depends on the preparation of the seam. If the material is 5 to 30 mm thick, the end of the crack must be drilled with a drill whose diameter is two thirds of the material thickness.
For material thicknesses above 30 mm, the end of the crack must be chiselled out. The chamfer angle of the V-shaped joint for the weld shall not exceed 50 to 60°. It is best to use a grinding wheel for preparation. Straight sections of cracks can be chamfered by milling during preparation.
The joint is seam
welded in two, three or more layers. The normal height of the welding beads is about 4 mm for each layer.
When laying the bead, the welder guides the electrode bundle away from himself. The length of the weld seam sections is 50 to 60 mm.
Weld sequence of laying the bead when the welder moves the electrode bundle away from himself
The welded-on material can be machined without pretreatment by grinding or by milling with carbide-tipped tools. Brackets, pins, etc. can also be welded onto the workpieces in addition to repairing cracks. Cladding (i.e. overlay welding) is also possible.
H. Thömke predicted that the application of the Nasarov cold welding method in the field of repair welding could save the economy of the German Democratic Republic large sums of money every year, because broken and worn grey cast iron workpieces, and even small casting defects could be restored by this welding method. However, the foundry industry must not draw the conclusion that welding technology can eliminate all grey cast iron defects and that generating casting defects should no longer be avoided.
The cold welding method should rather be regarded as a repair method and should be used mainly by repair shops. Of course, the material question also plays a not insignificant role, as copper was in short supply in the GDR. But often the advantage of repairing castings will be greater than that of saving non-ferrous metals and for this reason the Nazarov method will be used as a repair method for cast iron machine parts.