The microstructure and mechanical properties of parent metal for 700L beam steel with different titanium contents and specimens with metal active gas (MAG) welding are compared and studied. The results showed that the ferrite grains in the microstructure of test steel were 3~5 μm, there were a small quantity of deformation bands, yield strength was 678 MPa, tensile strength was 760 MPa and elongation was 17.0% when Ti content was 0.11%; the ferrite grains in the microstructure was 4~8 μm, there were a small quantity of pearlite grains, yield strength was 658 MPa, tensile strength was 734 MPa and elongation was 24.0% when Ti content was 0.07%; the strength of the two types of test steel was increased by about 10 MPa, but elongation was decreased by 1.0 and 3.0 percent points respectively and property of root bending of 180° (d = 2a) was qualified after MAG welding; the content of low carbon martensite was increased and microstructure of heat affected zone for test steel was refined with the increase of Ti content.

The maximum concentration of nitrogen oxide emissions in the flue gas of four compressor-turbine units with low heating values using blast furnace and coke oven gas in a steel enterprise is about 250 mg/m³, which could not meet the requirements of limiting values for ultra-low emissions of the steel industry, so the denitration modification is needed. Three different denitration modification schemes are proposed based on studying frequently-used flue gas denitration technologies at home and abroad. The modification scheme of built-in double-layer SCR catalyst in waste heat boiler is finally implemented by comparing such factors as the technology maturity, use risks and operating economy as well as the expected effects are achieved. This study could provide the feasible and effective technical methods for the compressor-turbine unit with low heating values and more nitrogen oxides while without prepared denitration space on site in our country.

The chemical composition of wire rod for 2 200 MPa ultra-high strength steel strand is designed based on the chemical composition of SWRH82B. The Φ14 mm wire rod is rolled by second heating and cogging with 280 mm×380 mm continuous casting billet. The tensile strength of hot rolled wire rod is increased from 1 150 MPa to over 1 450 MPa by optimizing the cooling rate of wire rod. The target that the strength of steel strand reaches over 2 200 MPa after drawing is realized. The results of industrial trial production showed that the time of soft blow and deep vacuum was the key to control the size of non-metallic inclusions and oxygen content in steel as well as it should be more than 15 min; under the condition of constant casting speed and the degree of superheat is below 35 ℃, the center macrosegregation index could be controlled below 1.15; the ideal microstructure of sorbite could be obtained by controlling moderate cooling rate and optimum cooling rate was 4.89~5.62 ℃/s.

The 5th generation American Morgan technology was introduced in the early 1990s for a production line of high speed wire rod and its design capacity was 0.38 million tons. With the constant improvement of production technology and efficiency for the deep processing industry of wire rod, the requirements of dimensional accuracy, surface quality and mechanical properties for wire products in the market are higher. In order to satisfy the market changes and improve product competitiveness, the size reducing mill is added in the production line of high speed wire rod. In the paper, it is introduced the construction transformations of such types of equipment as mechanical, electrical and power as well as the roll gaps of finishing rolling unit and size reducing mill are redesigned. Moreover, the R values of each stand are given as well as different accident types and solutions after the mill put into production are summarized.

In the paper, the production technology process and process control system of wide and thick plate mill in Baotou Steel are briefly introduced. The wide and thick plate mill is the important component for production line of wide and thick plate of Baotou Steel as well as its process control system is between the production management system and basic automation system in the plant, which is mainly responsible for managing production process data. The process control system model of rolling mill is generally divided into control part and non-control part. The emphasis of this paper is to research, analyze, optimize and adjust the rolling moment model of control part. After the optimization, the setpoint accuracy of secondary system model of roughing mill is improved and capacity of roughing mill is further increased.

The process of blowing out by lowering the charge level is smooth. Moreover, the whole process without detonation, rapid blowing out with safety and environmental protection are realized through activating the furnace hearth, calculating and analyzing loading of light load materials, adopting high blowing rate in early stage to make coke burnt as quickly as possible, improving atomization device to reduce the amount of water injected into furnace top, refining tapping in stokehole, reasonably controlling the relationship between air pressure and blowing rate, shortening the time of gas release, efficiently organizing, safely placing residual iron and coordinating various systems.

In the paper, the restraining factors affecting recycling fly ash of sintering machine head and blast furnace bag are discussed as well as the key technologies of extracting such valuable elements as Zn, K and Na from the fly ash are studied by analyzing its characteristics and disposal status. The technical plans for comprehensive utilization of fly ash of sintering machine head with high alkali metal content as well as fly ash of blast furnace bag with high zinc and alkali metal contents are proposed combining with such cases as salt extraction technology by washing for fly ash with high alkali metal content, zinc extraction technology with pyrogenic and wet processes for fly ash with high zinc content and reduction technology of electric arc furnace for iron-bearing dust as well as evaluating their merits and demerits. After implement the plans, the disposed fly ash could be recycled for sintering as well as products of Zn, K and Na could be sold externally so that the economic benefits are considerable and the problems of land occupation and environmental pollutions could be solved.

The stock of medium-lean oxidized ore in Bayan Obo is huge as well as its degree of oxidation and impurity content are high. Among them, iron and rare earth are the main recovered components. The grade of iron is 28.74%, content of FeO is 1.99% and grade of rare earth is 5.45%. The iron in the ore mainly exists in forms of hematite and limonite and magnetic iron as well as the distribution ratios are 48.54% and 43.84% respectively. The qualified iron concentrate with grade of iron concentrate of 66.07% and gross recovery of iron of 87.47% is obtained by studying the ore properties of medium-lean oxidized ore in Bayan Obo as well as exploring and recycling its iron resource with the process of “preconcentration-hydrogen-based mineral phase transformation-stage grinding-stage magnetic separation”. This method is beneficial to the full utilization of iron resources and improving the utilization rate of mine resources.

The rare earth oxides of lanthanum and cerium are high-value rare earth products, they are usually packed in the packing bags of 500 kg or 1 000 kg and the bagging error is required to be less than 0.05%. At present, the manual bagging is adopted, followed by the charging mode of weighing and compensating. There are such steps for the charging process of each ton bag as hanging bag, charging, carrying, weighing and compensating, so at least 4~5 workers are needed. There are such problems as high labor cost and low production efficiency. The automatic charging machine whose charging error is less than 0.05% and supporting charging basket are developed by adopting such technologies as automation and high-precision measurement and weighing. As a result, the automatic charging for the rare earth oxide products of lanthanum and cerium is realized as well as the problems that complex process of charging rare earth oxide products and several workers needed to operate are solved so that the working efficiency is improved and labor costs are reduced.

In this paper, the oxidation and decarbonization as well as formation rule of heterogeneous particles around cracks of web for SS400B hot rolled H beam are studied. The experiment is designed based on the actual working conditions on site as well as oxidation and decarbonization and performance distribution of heterogeneous particles with different processes are analyzed qualitatively and quantitatively with metallographic analysis and energy spectrum. The results showed that there was decarburization around cracks of SS400B hot rolled H beam in the stage of rough rolling, but no heterogeneous particles appeared. It is systematically and comprehensively explained that the oxidation and decarbonization and precipitation of silicon containing heterogeneous particles around cracks are closely related to the composition of steel, process location and thermal regulation combining with domestic study results.