How,treat,hot-rolled,seamless, business, insurance How to treat hot-rolled seamless steel pipe scale
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How to treat hot-rolled seamless steel pipe scale1, three acid (sulfuric acid, nitric acid and hydrochloric acid) pickling: three acid pickling is made from three acid according to certain proportion, is a more effective method to remove stainless steel oxide skin.Three acid pickling can well remove stainless steel oxide coating, but the disadvantage is that due to a large amount of nitrogen precipitation during the dioxide pickling process, worsening working conditions and polluting the environment. In addition, it’s quite easy to produce over acid pickling phenomenon, so widely use this method to remove scale is not advisable.2, Hydrofluoric acid + nitric acid pickling: this method is one of the acid pickling of stainless steel method. Common used ratio is as follows: HF 4% - 6%,HNO3 8% -12%, using temperature 50-600, pickling time depends on the material scale on the surface of steel: general for 20 to 40 minutes. Operation process must be frequently watched, to prevent the phenomenon of pickling.Advantage is: the acid pickling process with fast speed, easy operation andgood quality, but the drawback is: hydrofluoric acid is toxic, need good ventilation condition and wastewater treatment.3, alkali cooking, pickling after legal, mainly in order to overcome the shortcoming of three acid acyl. This compound method not only can improve the quality of pickling, and metal consumption is less. Alkali cooking can loose scale, and then by pickling method to remove oxide skin of the seamless steel pipe. Soda boiling liquid ingredients commonly adopt the mixture of NaOH and NaNO. Alkali cooking time is related to the steel grade, specification, quantity, the product state of scale and so on.Soda boiling steel shall be immediately immersed in the sink after blasting to scale, and then use three acid pickling method to remove oxide skin. Especially it is important to note: soda boiling steel material should be dry and without water, in order to avoid hot alkali liquor spattered cuts.Operation process need to be careful, must be seeing much, record the changes to achieve the purpose of safe operation.
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