(1) Gb3087-2008 seamless steel tubes for low and medium pressure boilers. Tensile test shall comply with GB / t228-87, hydrostatic test with GB / t241-90, flattening test with GB / t246-97, flaring test with GB / t242-97 and cold bending test with gb244-97. In general, after the stainless steel pipe is treated by the ordinary thermosetting furnace (milk stove), the oxide scale on the inner and outer surfaces of the pipe needs to be pickled, which destroys the internal and outer surface finish of the original cold-rolled pipe, resulting in slight unevenness, which can not meet the surface finish standard of sanitary pipe. Therefore, the gas protected bright annealing furnace should be selected.
(2) Gas shielded bright annealing furnace: it is composed of two parts: bright annealing furnace body and complete ammonia decomposition device.
Bright annealing furnace body: the main structure is a muffle tank with circular section, which adopts the heating method of arranging high-temperature heating wires on both sides and bottom, and ammonia decomposition gas is used as protective gas and circulating cooling gas. Compact structure, safe operation, reliable control and convenient maintenance, The furnace temperature is uniform (the temperature can reach 1150 ℃), the source loss is low, the protective gas can be fully used, and the cooling speed is fast, which ensures the prevention of re precipitation and precipitation of chromium carbide, so that all chromium carbide is completely dissolved into the austenitic matrix, changes the hard state and metallographic structure of the original cold rolled pipe, and truly achieves the purpose of solid solution treatment.
Complete ammonia decomposition unit: use pure liquid chlorine to decompose into 70% hydrogen and 30% ammonia, fill it into the furnace and drive away air (oxygen), and the smaller the air as much as possible.
After being treated by gas shielded bright annealing furnace, the stainless steel pipe is soft, there is little oxide scale on the inner and outer surfaces, pickling treatment is not required, and the inner and outer surface finish of the cold rolled pipe is maintained.