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What are the ways to remove Duplex Stainless Steel Pipe?

Oct. 31, 2019

  As a Seamless Stainless Steel Tubing Supplier, there is some information to share with you. Duplex stainless steel pipe removal method of organic, chemical and electrochemical methods. Because of the complexity of the scale composition of the stainless steel tube, it is not easy to clean the surface scale and make the surface high and clear. The removal of the scale of the stainless steel tube is usually carried out in two steps, the first step is pretreatment, and the second step is deashing.

Duplex Stainless Steel Pipe

Duplex Stainless Steel Pipe

  The Duplex Stainless Steel Pipe pre-treatment allows the scale to become loose and then pickled for easy removal. The pretreatment can be further divided into the following methods: alkaline nitrate melting treatment. The alkaline melt contains 87% hydroxide and 13% nitrate. The ratio of the two in the molten salt should be strictly controlled so that the molten salt has the strongest oxidizing power, the lowest melting point, and the smallest viscosity. In the manufacturing process, only sodium nitrate was studied to contain no less than 8% by weight. The treatment was carried out in a salt bath furnace at a temperature of 450 to 470 ° C, ferritic stainless steel for 5 minutes, and austenitic stainless steel for 30 minutes. Similarly, iron oxides and spinels can also be oxidized by nitrates to become loose trivalent iron oxides, which are easily removed by pickling. Because of the high-temperature effect, the oxides partially peel off and sink into the bath in sediment form. Bottom. Alkaline nitrate melt pretreatment process: steam degreasing → preheating (150 ~ 250 ° C, time 20 ~ 30min) → molten salt treatment → water quenching → hot water washing. Molten salt treatment is not suitable for the assembly with a weld gap or crimping. When the parts are taken out from the molten salt furnace and then water quenched, an irritating alkali and salt spray will be splashed. Therefore, water quenching should adopt a deep type. Splash-proof water quenching tank. When water quenching, first hang the parts basket into the trough, stop above the water level, close the trough cover, and then lower the parts basket into the water until it is submerged.

  Alkaline potassium permanganate pretreatment: the treatment solution contains sodium hydroxide 100→125g/L, sodium carbonate 100→125g/L, potassium permanganate 50g/L, solution temperature 95~105°C, treatment time 2~4 hours. Although alkaline potassium permanganate treatment is not as good as molten salt treatment, it has the advantage of being suitable for assemblies with welds or crimps.

  Pretreatment by dipping: In order to loosen the scale, the following strong acids are directly adopted.

  Immersion pretreatment: In order to prevent the dissolution of acid on the base metal, it is necessary to strictly control the acid leaching time and the acid temperature.

  So what method should ASTM A312 TP304 Stainless Steel Pipe use to clean it?

  1. Stainless steel tube cleaning, using solvent and emulsion to clean the steel surface to remove oil, grease, dust, lubricant and similar organic matter, but it can not remove the rust, scale, flux, etc. of the steel surface, so it is in anti-corrosion production. Only used as an auxiliary technique.

  2. Stainless steel pipe pickling, generally chemical and electrolytic two methods of pickling, pipeline anti-corrosion only use chemical pickling, can remove oxide scale, rust, old coating, and sometimes can be used as sandblasting and rust removal deal with. Although the chemical cleaning can make the appearance reach a certain degree of cleanliness and roughness, its anchor pattern is shallow and it is easy to pollute the environment.

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