It is known that welding wires are used, mainly in the form of activated solid wire or fluxed-core wire with a core consisting of a mixture of alloying and other components.
The welds made with the use of such wires should meet a variety of requirements. They should have a dense macrostructure free of cracks, pores, undercuts, rolls, and other defects. Besides, such mechanical properties of the weld as its ultimate strength, yield strength, impact strength, etc., should not be inferior to the same parameters of the base metal of the welded structure.
Welding of metal structures and elements from carbon and low-alloy steels with welding wires is accompanied by intensive splashing of the molten metal. The degree of splashing and the mechanical properties of the weld depend to a great extent on the composition of the welding wire.
Known in the prior art is a composition of a solid-section welding wire (Inventor's Certificate of the USSR No. 664797) comprising the following components, mass %:
______________________________________ carbon 0.03 to 0.25 manganese 0.8 to 2.2 silicon 0.7 to 2.2 chromium 0.03 to 1.0 nickel 0.03 to 0.45 zirconium 0.05 to 0.3 calcium 0.001 to 0.02 copper 0.05 to 0.6 aluminium 0.01 to 0.5 iron the balance. ______________________________________
Said composition of the welding wire is good for welding carbon and low-alloyed steels and ensures high resistance of the weld to corrosion and cold. However, the employment of said wire is accompanied by heavy sputtering of the molten metal. The splashes stick to the work and clog the nozzle of the welding torch. This calls for a labor-consuming operation of cleaning the metal structures from splashes, restricts the passage through the gas nozzle thus interfering with the protection of the arc.
There is another known composition of a solid-section welding wire consisting of the following components, mass %: (Inventor's Certificate of the USSR No. 863264):
______________________________________ carbon 0.02 to 0.12 manganese 0.3 to 1.0 silicon 1.0 to 1.5 aluminium 0.01 to 0.2 chromium 10 to 14.9 copper 0.3 to 1.2 titanium 0.01 to 0.2 rare-earth metals 0.01 to 0.06 nickel 4 to 8 calcium 0.001 to 0.05 vanadium 0.05 to 0.35 zirconium 0.01 to 0.2 molybdenum 2.4 to 3.5 iron the balance. ______________________________________
The use of the wire of this composition is inexpedient, since it contains a large amount of such costly and scarce elements as chromium, nickel, copper, vanadium, zirconium, molybdenum.
Besides, the release of copper in an amount of more than 0.6 mass % in the form of epsilon phase (.epsilon.-phase) impairs the quality of the weld as a result of cracking. The use of this wire also results in heavy losses of metal due to splashing. Said composition of the wire enjoys but a limited field of application, being suitable for welding metal structures made from stainless and alloyed steels only.
The utilization of the known compositions of welding wire entails the necessity for cleaning the metal structures from the stuck splashes. Up to 12% of metal of the welding wire is lost for splashing, while the amount of labor spent in stripping the work from splashes runs to 30-35% of the welding work proper.
The mechanical properties of the welds produced with the use of welding wires of known compositions fail to meet the imposed requirements for impact strength, at subzero temperatures to quote but one. The macrostructure of the produced welds does not guarantee against crystallization cracks and other defects.