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Surface oxide removal of TC4 titanium alloy

                         


                              TC4 titanium alloy


TC4 titanium alloy has excellent corrosion resistance, low density, high strength and good toughness and


 welding of a series of advantages and has been successfully applied in aerospace, petrochemical, 


shipbuilding, automobile and medicine departments. 



TC4 titanium alloy in hot forming process, the surface will form a layer of oxide, hot forming temperature is different, the oxidation of skin color is not the same. 


In the process, the temperature of the hot forming is blue when the temperature is about 600 degrees 


centigrade, and the temperature of the hot forming is about 850 degrees centigrade, and the oxide skin is 


gray, and the temperature of the hot forming is gray. With the increase of temperature, the removal of the 


oxide scale gradually increased. At home and abroad on titanium alloy oxidation skin to remove most of the 


two-step, first molten alkali wash, pickling and; however, molten alkali wash medium temperature is higher,


 to about 450 DEG C and is easy to cause the alpha + beta and beta titanium alloy semi-finished products of


 premature aging strengthening, for further processing difficult. In addition, hot alkali washing with 


nitric acid and hydrofluoric acid cleaning may lead to hydrogen embrittlement of titanium alloy surface


corrosion.



Researchers for the scale in 590, 850 and 920 are three DEG C temperature, low temperature alkaline solution


 after washing, then the pickling process to remove the oxide layer on the surface of. Using optical 


microscopy were used to characterize the morphology of oxide scale, the research time on the removal of 


oxide skin and through the international advanced the LECO axle fixed determination to after removal of the oxide titanium alloy hydrogen mass fraction of hydrogen analyzer.


Experiment with lye is a blend of industrial pure NaOH and industrial pure NaNO2 supersaturated solution, 


pickling with hydrofluoric acid and nitric acid mixed solution (volume ratio for HF: HNO3: H2O=1: 1: 3). 


After the hot alkali washing and water washing of TC4 titanium alloy after complete immersion in the acid 


solution of 20s was removed, and then washed with tap water. Finally, the samples with acetone or alcohol


 after ultrasonic cleaning and drying weighing, using electronic balance in hot alkali washing, the quality of the sample were measured before and after acid treatment, the precision is 0.001g. The analysis shows 


that the first hot alkali washing after pickling process, oxide TC4 titanium alloy surface can be removed 


completely. The conclusions are as follows:


(1) TC4 titanium alloy hot forming surface oxide thickness is less than 2 m.



(2) by hot alkali washing, pickling process, TC4 titanium alloy surface oxide can be removed completely, 


alkali ratio of 700g / L or NaOH + 250 g / L sodium nitrite, the boiling temperature of about 160 DEG C, 


supersaturated hot lye soaked for 6 h can be reached removal effect.



(3) TC4 titanium alloy with oxide by hot alkali washing, acid pickling process of hydrogen concentration 


changes little, meet the needs of production.


Shaanxi Yunzhong Industry Development Co.,Ltd