The Research Of Failure Reason And Countermeasures For Stainless Steel In Power Plant

In this article, investigations are made to two failure accidents of boiler's martensitic stainless steel and turbine's austenitic stainless steel at a power plant, and also modern methods and means are applied by macro check, tube's thickness measuring, determination of chemical composition, mechanical properties testing, microstructure inspection, electro-microscopic scanning of the fracture, X-phase scan ,etc to the samplings in order to separately find out the reasons of failures to boiler's martensitic stainless steel and turbine's austenitic stainless steel, put forward the responding solutions to provide technical basis for guaranteeing the long-term safe operation of equipment, preventing similar accidents.The failure analysis shows that one of the main reasons for heating surface tube's leakage is under over-temperature operation for boiler's martensitic stainless steel., as new units, over-temperature is from block of additional material in tubes. So check should be enhanced for header, heating surface tube during erection of power plant equipment, the manufacture's equipment should be completely checking with internal pipe's climber as soon as they arrival on site, re-check again after assembling. All these measures ensure the leakage will not take place for the block of additional material in tubes; on the other hand, the turbine's austenitic stainless steel pipe crack out during early operation because internal-crystal corrosion rapidly develop under stress, and the internal-crystal corrosion exist in welding of shopping.As one word, we should absorb the experience from above accidents, one is strictly performed the quality check and accept stipulation, specially the check of internal-crystal corrosion should be done to austenitic stainless steel. The other is to enhance the checking of clear degree during boiler manufacture and erection. These measures can ensure the long-term safe operation of equipment.