Cov yeeb nkab fittings
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Qhov kev txiav txim siab no npog cov hlau thiab cov hlau sib txuas hlau ntawm kev sib khi thiab kev tsim kho welded. Cov fittings no yog siv rau hauv cov kav dej siab thiab hauv siab ntsha ntaub ua rau kev pabcuam thaum muaj qhov kub thiab txias. The material for fittings shall consist of killed steel, forgings, bars, plates, seamless or fusion-welded tubular products with filler metal added. Forging or shaping operations may be performed by hammering, pressing, piercing, extruding, upsetting, rolling, bending, fusion welding, machining, or by a combination of two or more of these operations. The forming procedure shall be so applied that it will not produce injurious imperfections in the fittings. Fittings, after forming at an elevated temperature, shall be cooled to a temperature below the critical range under suitable conditions to prevent injurious defects caused by too rapid cooling, but in no case more rapidly than the cooling rate in still air. The fittings shall be subjected to tension test, hardness test, and hydrostatic test.