Influence of Addition of Fe2O3 and CaO on the Performance of Manual SHS Welding Slag

Fe2O3、CaO have been added into the combustion system of manual SHS welding as slagging elements and the effects of their addition have been studied. Results showed that the combustion velocity and the adiabatic combustion temperature both became lower as the amount of the additives increased. The additives have dropped the density and the solidification temperature of the slag, which accelerated the separation of the slag and gas from the weld pool. (0.2~2.0) g of Fe2O3 and (0.2~1.2) g of CaO have been added into the rod. Experiments showed that the appropriate added amounts of Fe2O3 and CaO for each combustion weld rod were 1.2g and 0.6g respectively. The weld slag was honeycomb, brittle and easy to be removed from the weld metal. Analysis of the microstructure and composition showed that the matrix of the weld slag was glass, with some ceramics distrabuting on it. The ceramics had high content of Al2O3, which was created in the combustion reaction. The matrix of the weld alloy was α-Cu solid solution, on which a second phase with high content of Fe precipitated. There were no non-metallic inclusions in the weld metal ultimately. The weld joint had favorable mechanical performance, which tensile strength reached 400MPa, that fulfil the requirement of emergency welding.

Design on Cleaning Device for Slag of Narrow Gap Submerged Arc Welding

At present, the Narrow Gap Submerged Arc Welding is an advanced welding technology. As the weld is very deep and narrow, the slag is difficult to clean and will have impact on the quality of welding seam. Therefore, a new kind of narrow gap submerged arc welding slag cleaning device is designed to clean the welding slag. It is consisted of welding walking tractor, height adjuster, slag masher, slag cleaner and slag collector. The narrow gap submerged arc welding slag removal device used for the welding process can realize the cleaning that manpower cannot finish. It is a kind of time-saving, energy-saving and high efficient welding cleaning method.

Corrosion of 304L Stainless Steel Tube in Power Plant Condenser

Before being put to use, a new condenser of 600 MW unit was found corrosion leakage of a large number of 304L stainless steel tubes during the water leakage test. Through field investigation, sampling, chemical composition and mechanical properties test, metallographic analysis, corrosion area surface morphology and micro area component analysis, corrosion reasons were analyzed. The main reason for corrosion is improper installation. Stainless steel tubes were polluted by rain, soil, welding slag during the installation process. Carbon steel members cut the tubes when wore tubes, and was placed in such condition for a too long time. Moreover, the electric current occurred in repair welding with water may accelerate pitting holes.