No abstract

No abstract

No abstract

No abstract

Cadmium-coated type 410 martensitic stainless steel 14-14 self-drilling tapping screws fractured during retorquing tests within a few weeks after installation. The screws were used to assemble structural steel frames for granite panels that formed the outer skin of a high-rise building. Fractographic and metallographic examination showed that the fractures occurred in a brittle manner from intergranular crack propagation. Laboratory and simulated environmental tests showed that an aqueous environment was necessary for the brittle fracture/cracking phenomenon. The cracks were singular and intergranular with little branching. Secondary subsurface cracks suggested possible hydrogen embrittlement. The 410 screws had been introduced to replace conventional case-hardened carbon steel screws that conform to SAE specification J78. Carbon steel screws had a proven record of acceptable performance for the intended application. It was recommended that use of the 410 screws be discontinued in preference to the case-hardened carbon steel screws.

No abstract

A stainless steel pipe transferring hot white liquor solution of sodium hydroxide and sodium sulfite, developed leaks adjacent to the welds within four years of service. The stainless steel pipe was AISI type 304 and welded with E308 weld electrodes. The service temperature was 190 deg C (375 deg F) and the solution contained approximately 700 ppm chlorides. Liquid penetrant inspection of the pipeline showed the leaks were numerous and confined adjacent to the welds. A metallographic specimen from the circumferential weld showed the cracks initiated at the inside surface. In addition to the base metal, SCC also had initiated at a notch at the weld root due to improper welding procedures. Failure was attributed to chloride-induced SCC with secondary contributory factors, including improper welding procedures. It was recommended that the pipeline be replaced with a material more resistant to SCC. The candidate materials are commercial grade unalloyed titanium or Inconel 600, which have superior resistance to SCC compared to austenitic stainless steels.

No abstract