In this paper, the control targets for the process of adding rare earth after VD are defined through the industrial test of adding rare earth into U75V heavy rail steel of Baotou Steel as well as the effects of rare earth on modification of typical inclusions in heavy rail steel are defined by sampling on the rail, analyzing the components of rare earth and characteristics of inclusions.

In the paper, the differences of phosphorus content in coking coal of each region were studied based on the phosphorus content in coking coal of Baotou Steel as well as the phosphorus contents in blended coal and coke under the same production condition were tested and analyzed to obtain the data transformation relation between them. Meanwhile, the mode of occurrence of phosphorus in coal was analyzed to study the correlation between phosphorus content, ash content and sulfur content. The results showed that there were significant regional differences for coking coal of Baotou Steel as well as there was a positive correlation between phosphorus contents in blended coal and coke, which provide important support for predicting the phosphorus content of coke and controlling the phosphorus load of coke of blast furnace.

In the experiment of producing 25CrMoBVRE and U76CrRE, the ladle input method was used to add rare earth alloy. After pretreatment of hot metal, converter smelting, deoxidization and alloying process, deep desulfurization process in LF ladle refining, the sulfur and oxygen contents in molten steel were very low, which had positive effects on improving the yield of rare earth. The rare earth La-Si-Ca-Fe alloy and Ce-Fe alloy were added into ladle before and after VD by effectively controlling the oxygen and sulfur contents in molten steel as well as the amount added were 0.012% and 0.003% respectively. The test results showed that there was no nozzle clogging, the production process was trouble－free, operations were convenient, yields of rare earth could reach 15% and 40% respectively as well as costs were reduced by 60% and 50% respectively by taking corresponding protective pouring measures. The distribution of rare earth in steel is uniform, which can improve inclusions. The properties of products can fully meet the requirements of product standards and customer use.

After the 7^# and 8^# blast furnaces were put into operation one after the other, the water slag treatment system was put into use at the same time. Due to the serious corrosion and wear of water slag treatment equipment, there are more sudden failures in production run and the operating rate of blast furnace water slag is low. It is effectively improved through optimizing the corrosion and wear of equipment as well as continuously practising and reforming technologies to solve problems in productions.

In the paper, it is introduced the process flow and operation conditions for cooling system of 6^# blast furnace as well as the reasonability and accuracy for cooling regime of blast furnace are improved by strengthening the daily management for closed cooling system of soft water and careful maintenance combining with the actual situations for operations of cooling system of 6^# blast furnace. Moreover, the problems and improvement suggestions are put forward to prolong the service life of blast furnace.

In the paper, the control for each process of smelting rare earth is introduced. The test results showed that the rare earth was still with deoxygenation and desulfuration when the contents of oxygen and sulfur in steel were ultra low as well as the inclusions in steel were mainly tiny rare earth oxysulfides with the size of 3~5 μm. There is serious nozzle clogging during pouring process and the blockage is mainly cold steel. Such measures as improving the cleanness of molten steel and rare earth alloy, increasing pouring temperature and developing new-type nozzle are proposed by analyzing the mechanism of nozzle clogging to solve the problem of pouring nozzle clogging for rare earth steel.

The originally designed iron influx for main channel before 4 150 m³ blast furnace of Baotou Steel is about 0.16 million tons. In the use process, it is found that only the refractory in jet impingement zone is eroded so seriously that cannot be used anymore, while the refractory in other parts of main channel keeps basically intact. If the main channel is disassembled, the cost of pig iron will be greatly increased. The iron influx of main channel could be up to 0.22 million tons through partial spraying with improving the spraying material, particle size and binder so that the cost of molten iron is decreased effectively.

In this paper, it is introducrd the pre-remained 240 mm × 240 mm section for 6^# casting machine of Baotou Steel is commissioned as well as such technical parameters as the electromagnetic stirring of crystallizer of casting machine, final electromagnetic stirring, secondary cooling water, nozzle type and water pressure of nozzle are mainly regulated and controlled. During the commissioning period, the low, medium and high carbon steels such as Q195, Q235, 45^# and SWRH82B were produced as well as the scab and cracks were not found on the surface of casting blank. The ratio of grades of 0 and 1 could reach 94% by sulphur print and macroscopic examination, so the quality control of casting blank is good and can meet rolling demand of Steel Rolling Plant.

Based on the experiment of adding rare earth into interstitial free(IF) steel of Baotou Steel, the changes of cleanliness of IF liquid steel were studied. The results showed that no rare earth oxides were found in the slag when steel ladle left RH. CeO and Ce₂O₃ were found in the slag during casting as well as the valence states were + 2 and + 3. The effects on oxidability and Ca-Al rate in slag were not great with and without adding rare earth. The content of TFe in tundish is about 5% and CaO/Al₂O₃ is stabilized at about 1.3. The size of Al₂O₃ along the thickness direction of casting blank for the heats without adding rare earth is larger and increases from inner and outer arc to the center of casting blank as well as it decreases and the quantity of Al₂O₃ increases after add rare earth.

In the paper, it is elaborated the development method for each working procedure of phosphorated high－strength IF steel BT170P1, studied the effects of C and N atoms on drawability, analyzed the reinforcing mechanism of such elements as Si, Mn and P, explained the mechanism of action of hot rolling process such as the finish rolling temperature and coiling temperature, continuous annealing process of cold rolling on microstructure and mechanical property as well as analyzed the inclusions, annealed structure of recrystallization for cold rolling, forms and distribution of precipitated phase in the microstructure. As a result, the product performances could meet the technical requirements.