Flux-cored wire for welding in shipbuilding


Published at "The Paton Welding Journal" 2005 №06

Analysis of the state of welding in the world shipbuilding has shown a steady and dynamic growth of the use of mechanized and automatic welding with flux-cored wire. Shipyards of the largest shipbuilding companies of Japan, South Korea, Finland perform about 80 % of the whole volume of welding operations by the gas-shielded flux-cored wires of small diameter (1.0--1.2 mm). Advantages of using flux-cored wire include high productivity of works, marketable style of the weld and high welding-technological characteristics; simplification of the welding technique in different spatial positions and easiness of its mastering; a possibility to provide necessary mechanical properties.
     Efficiency of the flux-cored wire application should be estimated not by separate stages but by an increase of the total productivity of the technological process of production of the metalwork. Manual welding with coated electrodes and mechanized gas-shielded welding with solid wire prevail in shipbuilding of the CIS countries. A noticeable growth of using import flux-cored wires of small diameter is observed in the recent years. The latter is connected first of all with the absence of the equivalent domestic analog and the presence of the number of factors making it difficult to apply domestic flux-cored wire. These factors include the lack of a reliable specialized welding equipment; a probability of the appearance of porosity; a problem of feed by hoses; increased release of welding aerosol; insufficient mechanical properties of welds.
     Welding technologies in the shipbuilding of Russia and Ukraine are subject to revision in the last years: a noticeable growth of the use of gas-shielded flux-cored wires instead of coated electrodes and solid wire of grade Sv-08G2S is observed. Demand of shipbuilding is met by import of flux-cored wires of the leading world producers: ESAB (Sweden), Welding Alloys (England), Filarc (the Netherlands), Kobeko (Japan), Hyundai (South Korea) and others. At the same time production capacities of domestic producers of flux-cored wire allow completely meeting the demand of the domestic shipbuilding in flux-cored wire of small diameter (1.2 mm).
     Problems on creation of flux-cored wire on par with the best foreign specimens as to its technical data and provision of the domestic shipbuilding with gas-shielded wires of small diameter are solved by TM.WELTEC Ltd., one of the leading producers of flux-cored wire in Ukraine. In 1994--1996 a comprehensive research was carried out, which allowed developing and mastering production of gas-shielded flux-cored wire of new generation (grade FCW-TMW7) 1.0--2.5 mm in diameter (TUU 19369185.008--96). The flux-cored wire FCW-TMW7 and its production were adopted by the Russian Marine Navigation Register and Lloyds Register.
     The latest achievements in the sphere of arc welding metallurgy were employed in developing a wire composition. Quickly setting rutile slag of increased basicity allows performing welding in all spatial positions. An alloying system provides mechanical properties of the deposited metal corresponding to the type E7T1 according to the standard AWS A5.20--95. The use of FCW-TMW7 wire is especially effective in welding of fillet and butt welds in vertical, horizontal and overhead positions with CO2 or Ar + 18 % CO2 mixture. In this case the deposition efficiency achieves 3.5 kg/h (Table 1).

Table 1. Welding conditions with wire PPs-TMV7 for producing fillet and butt welds (shielding gas is CO2 or Ar + 18 % CO2 mixture)

     The use of this flux-cored wire is highly effective in making root pass of the butt joints in all spatial positions using ceramic backing. Typical chemical composition of the deposited metal has the following content, wt.%: 0.05C; 0.32Si; 1.45Mn; 0.015S; 0.015P. Implementation of the gas-slag shielding of the welding pool leads to the minimal sensitivity of porosity caused by the grounds. Complex alloying of weld metal in combination with a low content of harmful impurities provides the required strength and plastic properties with high level of impact strength of the weld metal (Table 2).

Table 2. Mechanical properties of deposited metal at the testing temperature -20 °C

     The improved production technology provides a stable quality of flux-cored wire. It is easily adapted to any types of semi-automatic machines for mechanized gas-shielded welding, characterized by an easy feed by hoses of semi-automatic machines. The flux-cored wire FCW-TMW7 is certified by UkrSEPRO. Tests of the manufactured products are controlled by the quality system TUF at the Open Joint Stock Company «Dneprometiz». The wire is supplied in bundles in the calcinated state in the standard cassettes K200 and K300 fully ready for application. The wire is packed in metallic drums 50--70 kg in mass by the GOST 26101--84. As requested by the consumer it may be packed in the paperboard boxes with one bundle or cassette in the box with preliminary packing into polyethylene package.
     The TM.WELTEC Ltd. Company delivers flux-cored wire on the following conditions: free carrier FCA or through its dealers in the Russian Federation.