The main causes for strength fluctuation are determined to be abnormal microstructure and length differences of furnace area in the two continuous annealing production lines by analyzing the causes aiming at the problems of great strength fluctuation and low qualified rate for HC500LA steel with small batch trial production of Rare Earth Steel Plate Plant. The abnormal microstructure and strength fluctuation caused by incomplete recrystallization are reduced by optimizing the compositions. The design of differentiated annealing temperature and speed of steel strip for the two continuous annealing production lines is carried out so that the strength fluctuation of steel strip is significantly improved and qualification rate of performances is increased from 87.8% to 98.2%.

In this paper, the products of 685 and Armox 500T, armor plate BTP500 are selected to compare and analyze. The results showed that the microstructure of armor plate BTP500 produced by Baotou Steel was tempered martensite, original austenite grain was fine, average grain size was 10.5 μm and grain size was uniform. The average hardness of BTP500 steel plate (HBW) is 291~296, which is about 30 higher than that of 685 steel plate. The mechanical performance indexes could fully reach the levels of Armox 500T protective plate, average low-temperature impact absorbing energy at -40 ℃ is 51.6 J, which is higher than that of Armox 500T. The BTP500 steel plate is still with good bullet proof property in the case that it is thinner, which provides the ideal protective material for lightweight of armored vehicles.

The chemical compositions of wire rod for large heat input welding are designed, its continuous cooling transformation (CCT) curves are determined, key control parameters of smelting process are established and industrial trial production is carried out with twice-heating production by analyzing the influences of chemical elements on welding performances of wire rod. The results indicated that the Ti content needed to be controlled over 0.15% in order to increase the input quantity of welding energy; the non-metallic inclusion of TiN in steel was controlled effectively in smelting process to ensure the pouring in continuous casting process is trouble-free; the optimum cooling rate was controlled at around 1 ℃/s, microstructure obtained was ferrite+pearlite+a small amount of bainite; the performance examination results of wire rod could fully meet the requirements of technical agreement and its welding performances were good, there were no welding cold cracks after drawing by user.

The development and trial production of high corrosion-resistant products with Zn-Al-Mg coating for photovoltaic applications are carried out after transform Zn-Al-Mg production line of Baotou Steel. The microstructure of coating for Zn-Al-Mg products is analyzed, neutral salt spray test and surface defects of the products with Zn-Al-Mg coating are analyzed, controlled and studied. The analysis results showed that the microstructure of the coating was composed of Zn-rich phase, ternary eutectic phase of Zn/MgZn₂/Al and binary eutectic phase of Zn/MgZn₂ as well as the elements of Al and Mg were with uniform distribution in the coating; the neutral salt spray test results showed that the products with Zn-Al-Mg coating manufactured by Baotou Steel were with good corrosion resistance, processability, formability and self-healing ability of notch. The trial production results showed that the process control of Zn-Al-Mg production line of Baotou Steel was stable, stable batch productions of products with Zn-Al-Mg coating were realized, qualified rate of products reached 95.33% and yield reached 97.84% so that all performances could meet the technical requirements.

With the environmental protection and production limitation, the output of sinter is becoming increasingly tense after 1^# and 2^# sintering machines in 1^# sintering workshop are not in the production sequence as well as the addition of large proportion of pellets into blast furnace has become new development trend of iron-making. During this test, 5^# blast furnace is with trouble free operations through regulating charge level, adjusting central coke quantity and discharging sequence of feed zone, optimizing parameters of tuyere and area of inlet air, increasing heat reserve of hearth, adjusting and controlling basicity of slags as well as actively coping with various changes of furnace conditions after increase the proportion of pellets. The smelting production is successfully realized in the 1 500 m³ blast furnace of Baotou Steel with structure of furnace charge of large proportion of pellets and use ratio of pellets reaches 52%, so the fuel ratio is stable with a slight decline.

In this paper, the continuous cooling transformation (CCT) curve of X80 pipeline steel researched and developed in laboratory is determined. The determination results showed that the ideal microstructure of X80 pipeline steel could be obtained when cooling rate was 5~30 ℃/s, which was granular bainite + ferrite bainite + a small quantity of martensite/austenite island; the microstructure transformation was basically completed when finish cooling temperature was 450 ℃. The determination of CCT curve could provide references for subsequent optimization of composition design, establishment of process parameters and control of microstructure.

Phosphating and silane treatments are the common surface pretreatment technologies for cold rolled sheet. In this paper, the two conversion coating technologies are compared and analyzed from such aspects as the process flow, mechanism of film formation and evaluation methods as well as the morphologies of the two conversion coatings are compared and analyzed by scanning electron microscopy. Moreover, the influences of pretreatment technology on the surface roughness and peak density of cold rolled automobile steel DC04 are studied. The results showed that the surface conditioning and double washes after phosphating were omitted for silane treatment process compared with phosphating process as well as process flow was short and environmental; the mode of phosphate precipitation was adopted for film formation of phosphating, while covalent bond was adopted for film formation of silane treatment. Since the phosphating phase is crystal structure, so its phase composition and proportion could be evaluated by X-ray diffractometer. The phosphating film is composed of phosphate of 2~4 μm, while silane film is composed of finer round or irregular particles analyzed by scanning electron microscopy. After phosphating or silane treatment, the surface roughness of sample of cold rolled sheet DC04 remains unchanged, but peak density is increased slightly.

The frequent quality defect of corner crack for casting blank of carbon structural steel with conventional composition design of medium carbon and low manganese seriously affects the hot charge rate of products. With the original equipment and working conditions, composition optimization design is carried out. The mechanical properties of products are ensured through replacing part of C with microalloying element Ti as well as replacing solution strengthening with fine-grain strengthening and precipitation strengthening. Meanwhile, the high temperature plasticity and corner crack of casting blank are improved through liquation of second phase particle for TiN with the high temperature of Ti microalloying to fix free nitrogen atom in liquid steel. The rate of corner crack for carbon structural steel Q235B with new composition design is controlled effectively through the evaluations of mass production and applications.

With the continuous development of industry, the requirements of steel quality for various countries in the world are higher and higher. It has been current research emphasis how to improve the corrosion resistance of steel. The effects of rare earth elements on improving corrosion resistance of steel have been proved. In the paper, it is mainly elaborated the influence mechanisms of rare earth elements on modification of inclusions, causes of pitting, change of structure and components of rust layers as well as electrochemical corrosion resistance of low alloy steel through investigating a large number of literatures, which could provide the theoretical basis for promoting applications of rare earth elements in steel.

In this paper, it is comprehensively introduced the energy consumption is reduced by automatically controlling feed pressure based on the drum pressure by frequency converter and stand by pump is ensured to be put into automatic interlocking when the unit is started and in the condition of low load through optimizing control logics under the working condition of “one with two” for frequency converter of high pressure feed pump in the gas-steam combined cycle unit, which lay the foundation for stable operations of the unit.