In recent years, under the background of energy conservation and emission reduction, major countries in the world have issued mandatory high efficiency distribution transformer standards.Our country issued the new standard GB 20052-2013 in 2013, which was updated on May 29th 2020 and will be enforced in 2021. To meet the updated transformer standards and energy efficiency upgrade, it is important to enhance the magnetic properties of core materials. Baosteel had developed new products B18R055 and B20R060 in the fourth intelligent factory of silicon steel, which were successfully used for grade S15 energy efficiency distribution transformers. The typical properties of B20R060 product were two grades higher than the highest grade of international  silicon steel with the same thickness, and the B18R055 product is the lowest iron loss oriented silicon steel in the world. In this paper, the properties and transformer performance of B18R055 and B20R060 are introduced, expecting favorable for material selection of transformer manufacturers.

The effect mechanism of chromic anhydride in tension coating of oriented silicon steel was systematically analyzed and studied through the design of experimental research programs and the use of XPS, XRD, TGDSC and FESEM and other analysis and detection techniques. The results showed that the chromic anhydride adding into ingredients of tension coating can help to form gelatinous membrane materials, by using the lowmeltingpoint characteristic of chromic anhydride in the initial stage of heating and curing. And in the indurating stage, the small molecule filmforming materials of phosphates and silica will fill into the trivalent chromium skeleton structure generated by the REDOX reaction of chromic anhydride itself, which can reduce the coating microporous structure and make the coating film more dense. The tension coating combined with magnesium silicate bottom layer can exert tension stress on iron substrate, which can refine magnetic domains and greatly reduce iron loss of silicon steel.

The energy efficiency upgrade of energy saving distribution transformer is an important measure to implement the basic national policy of energy saving and emission reduction in China and promote the technological progress of transformer industry.The manufacturing technology of transformer core and its superposition structure are directly related to the noload loss, noload current and noise.By comparing the main indexes of four kinds of transformer core manufacturing technology,the advantages and disadvantages of them were analyzed, and different design methods or magnetic materials or new materials were put forward to realize energy saving and consumption reduction of distribution transformer, reaching the standard of energy efficiency grade, which can be popularized and applied vigorously.

The effects of oxidizing atmosphere on the electromagnetic properties, microstructure and surface state of Fe2 %Si nonoriented electrical steel during annealing were investigated by using multi atmosphere continuous annealing furnace. The results showed that, when the oxygen content in the furnace increased from 3×10-6 to 52×10-6, the hysteresis loss in the iron loss P1.5/50 increased from 1.78 W/kg to 2.14 W/kg, the eddy current loss remained basically unchanged, the anisotropy of iron loss increased from 9.3 % to 11.5 %, and the magnetic induction B50 decreased from 1.731 T to 1.727 T. During annealing, the oxidizing atmosphere in the furnace caused the generating of oxide layer and inner nitriding layer on the surface of electrical steel, and the increasing internal stress in the steel, which led to the increase of hysteresis loss.

The effect of coiling temperature after hot rolling on the microstructure, texture evolution and magnetic properties of 0.4 % Si nonoriented silicon steel was investigated under laboratory conditions. The results showed that the increase of the coiling temperature from  630 ℃ to 700 ℃ was conductive to the nucleation and growth of the hot rolled coiled sheet, leading to coarse the microstructure of the steel before cold rolling.The mean grain size of the annealed plate was increased from 26.1 μm to 41.5 μm, and the iron loss was decreased from 5.634 W/kg  to 4.825 W/kg. In the case of the coiling temperature at 630 ℃，the volume fraction of unfavorable {111} oriented grains in annealed plates was 31.6 %, and the favorable {001} and Goss oriented grains was 4.6 %. By contrast, in the case of the coiling temperature at 700 ℃, the volume fraction of {111} oriented grains was decreased to 21.2 %, and {001} and Goss oriented grains was increased to 5.9 %.With the increase of the coiling temperature, the favorable textures were enhanced while the unfavorable textures were significantly weakened, thus increasing the magnetic induction from 1.754 T to 1.774 T.

The cold rolling strip breakage fault of highefficiency nonoriented silicon steel made in Ansteel was analyzed, of which the hot rolled coil was annealed in a ring furnace before cold rolling. Many inclusions were found on the subsurface of hotrolled steel plate by metallographic observation of steel plate section. And by SEM observation, it was showed that the inclusions were AlN. The main reason of the cold rolling strip breakage was the nitrogen in protection atmosphere permeated into steel during annealing of hot rolled coil, which was then generated into AlN combining with the aluminum in steel, causing the abnormal increase of inclusions and broking the continuity of steel. The nitrogen content in steel had a gradient along the direction of the plate thickness, and the nitrogen content in the edge of steel plate was evidently higher than that in the core, which had a strong corresponding relationship with the oxide scale distribution on the surface of the steel plate, and it is indicated that the oxide scale played a catalytic role in nitrogen infiltration during the annealing process. Meanwhile, the infiltrated nitrogen escaped from the weld and form bubbles, which affected the welding quality seriously.

The technology of high efficiency utilization of pure water in continuous annealing coating unit of nonoriented electrical steel was introduced in this paper. Through the gradual overflow recovery and utilization of pure water in each circulating tank and circulating tank in the precleaning and postcleaning section, and further using the pure water, which was in the high pressure spray tank before its utilization at the end, to configure a certain concentration of alkali, and meanwhile adjusting and optimizing the startup and shutdown conditions of the tranfer pump from postcleaning to precleaning and the interlocking conditions, the postcleaning pure water can be of no overflow and completely transport to the front cleaning section, achieving water balance, and greatly improving the rate of pure water utilization.

The composition and the causes of the roller ring nodule in CSP soaking furnace of Wuhan Iron and Steel Corporation Strip Mill were analyzed. Then the control measures to reduce roller nodulation were put forward from the aspects of heating control, decreasing roller ring temperature, improving stress uniformity of roller ring and cleaning roller.