Posco won a bronze prize in the annual ISSF Awards for its laser welded duplex stainless (329J4L) tube for gas gas heaters. In Korea, thermal power plants are being upgraded to improve atmospheric environmental problems. In particular, plate heat exchangers are being replaced with tube heat exchangers due to the problem of flue gas leakage. For the tube heat exchanger, seamless duplex stainless steel tubes were mainly applied in Korea. However, the seamless duplex stainless steel tube is expensive and has a long delivery period, so heat exchanger manufacturers needed a welded tube with equivalent characteristics, low price, and short delivery time.
The Posco team selected the LBW welding process as the most suitable and the welding and heat treatment conditions were optimized to improve the corrosion resistance of the weld. Various evaluation methods were used to prove that the welded tube has characteristics equivalent to that of the seamless tube. After inducing artificial pitting electrochemically, it was proved that the frequency of pitting occurrence was the same in the base metal and the welded part.
This product can be mass-produced through laser welding and post-heat treatment by domestic manufacturing companies, and the corrosion resistance of the produced product meets the requirements of the customer through the ASTM corrosion evaluation method. The product can be widely applied to various industrial fields such as power plant, petrochemical, construction, and automobiles where seamless tubes are used.
The newly developed 329J4L LBW tube was applied to a new thermal power plant in Samcheok, Korea, and through this, GGH manufacturers were able to reduce manufacturing costs by more than 30% and shorten delivery time by 1.5 months.
