Annealing equipment and process

1, tight tight roll of bell type annealing annealing were annealed plate volume in tight condition. Plate volume by convection heat transfer and radiation heat through the inner cover when heated, plate roll center achieve specified temperature need long time, however, does not need to like the back of loose coil annealing and continuous annealing open book, and the surface is not easy to scratch, cheap investment, etc. The chassis has a blower to make protective atmosphere circulation, and insert the convection between the volume and the volume, the main role is to plate heat transfer, have protective gas in convection. Furnace connected to control instrument, such as temperature can be selected regulations and can detect plate roll temperature. At the same time, the furnace temperature and the plate roll temperature can be automatic control. In annealing cycle, cooling takes a long time, in order to promote cooling, using the chassis of special gold tube with water, or through a heat exchanger to protect gas pumping out outside the cooling method. Furnace form a single crib annealing furnace and buttress annealing furnace. Single crib every crib annealing furnace has a hood. Crib annealing furnace of a few more crib ( 3 ~ 4) Could fit in a hood, which is suitable for small variety, large production. 2, typical annealing heat treatment process is composed of three heating, heat preservation, cooling process. According to different specifications and equipment and there are all sorts of rules, but in general, to comply with the following rules: ( 1) Insulation range is 600 ~ 750 ℃, the higher the annealing temperature, the longer the time of heat preservation, steel will be soft, elongation increase, processing performance is improved. ( 2) If the annealing temperature is too high, would lead to recrystallization grain overgrowth of, often rough machined surface ( The so-called granular surface) 。 ( 3) In order to make the solid solution of carbon and nitrogen in steel sufficient precipitation, the slow cooling method, form of soft steel plate. Small tight coils annealing, cooling speed, basic no problem. Shown below for tight coils annealing heat treatment process is one of the cases. 3, gas shielded bright annealing, to prevent the strip oxidation and decarburization, commonly used ammonia decomposition atmosphere for their own protection. Liquid ammonia ( NH3） Under the high temperature, using nickel as catalyst, decomposition of 75% hydrogen ( H2） And 25% of nitrogen ( N2） , thus reducing the air in the furnace gas ( O2） And the reaction of the strip. Ammonia decomposition should be paid attention to: ammonia decomposition temperature should be controlled in 800 ~ 850 ℃, the decomposition of ammonia can fully; The gas dew point should be controlled in - after decomposition About 20 ℃, make gas dry, prevent moisture from entering the furnace steel strip oxidation; Liquid ammonia input pressure of 0. 2 to 0. 4 mpa, decomposition furnace pressure control in 0. About 5 mpa.