Investigation On The Nitriding Process Of The Low Temperature Slab Reheating Hot Rolling High Permeability(HiB) Silicon Steel

Low temperature slab reheating hot rolling high permeability(HiB)silicon steel which have an advantage of lower temperature in casting billet reheating,reducing loss of than high temperature HiB steel.Therefore,both domestic and foreign have become a hot spot in the study o And,Japanese has successfully developed a more mature technology and put into application?Wuhan Iron and steel and Baosteel have developen the low temperature HiB steel until 2014?This paper investigated the organizational principle?the composition of steel,nitriding process,nitriding equipment of the low temperature HiB steel.By Researching simulation environment,we reducing the casting billet hot rolled the highest heating temperature from 1380? to 1180??we have made the low temperature HiB steel successly by the new process in this paper.The production been tested by means of an Epstein frame measurements.the result showd it reach the leve of HiB.and could be used into industrial production.In the study of this paper,through a laboratory used for oriented silicon steel nitriding process experiment of three section type controlled atmosphere heat treatment furnace,the use of the device will continuously complete decarburization,reduction and nitriding three different atmosphere heat treatment,provides reliable data for the trial production of the scene.The results showed the restraining ability of high temperature HiB steel is 1.57 times more than which of low temperature HiB steel under the same heating condition.this paper calculate the nitrogen content of the low temperature HiB steel.Nitriding process show that the oriented silicon steel decarburization annealing in 0.1 um films 0.018um a silica based dense layer,the compact layer is the strong resistance area of nitriding.The hydrogen can be reduced to 18%of the thickness of the oxide film in the nitriding atmosphere.The inner layer FeO is reduced,and the FeO in the Fe2Si04 is partially reduced,while the Si02 can not be restored.The hydrogen in the mixed gas can be characterized by a dual character,which can be reduced by reducing the oxidation film on the other hand.When the oxide film is Si02 mainly,the ability of hydrogen reducing oxidation is weak.On the other hand,when the oxide film is FeO-based,hydrogen can be reduced by a large reduction of the oxide film,the nitriding speed is accelerated.When the Low temperature HiB steel nitride in short time,nitrogen reactive nitrogen can penetrate into the silicon steel.Nitriding method has a great influence on the amount of nitriding.The method of direct injection to the steel plate is 2.5 times of the conventional nitriding.In this paper,the optimum magnetic energy and the performance requirements of HiB steel were obtained by the nitrogen content of 110?150ppm in the steel plate,it is different with than that of the 200ppm steel abroad.The analysis of different temperature of the normal tissue shows that the grain structure of the HiB steel is Ferrite + Pearlite.When the temperature is 960??1130?,it can be known that with the increase of temperature,the ratio of re crystallization is increased,and the band structure in the matrix can be reduced but will not disappear completely.When the normalizing annealing temperature is 1130?,the surface and subsurface grain size of the sample is obviously raised,and the grain growth is not uniform along the direction of the rolling direction and the vertical direction.Using transmission electron microscopy(TEM)to low temperature Hib steel hot rolled plate and normalized slab is studied,analysis of both the precipitation that with low temperature Hib steel normalized the increase of annealing temperature,enhance the AIN quantity of precipitation series,precipitate size gradually reduced,in 1030? often precipitates the smallest in size,with normalizing annealing temperature rises to 1130? and gradually grow up precipitates grew up,cloud be influenced by Ostwald ripening.The morphology of the precipitates was different,and the morphology of the hot rolled plate and under 960 ?,the common plate was not regular,it is globular until the normalizing annealing temperature rises to 1030??1130?.The formation measure of AIN compound phases is different in different normalizing annealing temperature.The AIN formed during 960? are mainly the accumulating and growing from the original secong phases;one section of the AIN formed during 1030? is isothermally precipitates from the original matrix,the other section is soild solution firstly and precipitates;While the AIN formed during 1130?mainly precipitates after solid solution.The best temperature range of HiB steel for low temperature in normalizing annealing is 1030??1130?.