The old horse of 7^# blast furnace of Baotou Steel is deeper. In order to shorten the project duration and reduce workload of removing residual slag iron in furnace hearth after blowing out, the mode of dropping stockline and discharging residual liquid iron is adopted. It is one of the most important links in blowing out operation of blast furnace to discharge residual liquid iron and its effect directly affects the clearance time of furnace hearth. In the paper, the process of discharging residual liquid iron for 7^# blast furnace of Baotou Steel during blowing out is mainly introduced. The previous preparation work mainly includes such as activating furnace hearth, confirming position of residual liquid iron notch, calculating amount of residual liquid iron and making residual liquid iron runner. The cutting of shell of blast furnace and cooling stave, manufacture of mud sleeve for residual liquid iron notch as well as the whole process of discharging residual liquid iron after blowing out are introduced in detail. The process of discharging residual liquid iron of 7^# blast furnace is safe and ordered. After blowing out, it is found that there is basically no residual iron in the furnace hearth when cleaning it, which indicates that the effect of discharging residual liquid iron this time is good and experiences are gathered for discharging residual liquid iron in future heavy and medium repairs of blast furnace.

In this paper, the production practices on improving automatic casting ratio of ladle are introduced as well as various improvement measures are proposed through deeply analyzing the factors influencing automatic casting of ladle combining with production practices. The practices showed that the automatic casting ratio of ladle could be increased to over 99.5% so that the goal of reducing unplanned products produced by cast billets with burning oxygen is achieved through improving the quality of stuffing sand, optimizing sand filling device, formulating plan of replacing nozzle, strictly controlling time of steel filling according to steel grade, preventing back flow of steel slag and shortening standing time of liquid steel.

The continuous cooling transformation laws of X120M pipeline steel is studied with Gleeble 1 500 thermal simulated test machine as well as it is with controlled rolling and controlled cooling in laboratory. The results indicated that the microstructure of test steel was mainly lower bainite and martensite when cooling rate was at 20~50 ℃/s. When the finish cooling temperature of test steel is at 380 ℃, its yield strength is 900 MPa, tensile strength is 1 015 MPa, elongation is 18%, impact energy at -30 ℃ is 180 J and shearing area of drop weight tear test at -20 ℃ is 100%. The mechanical properties could meet the standard requirements.

The transformation structure and critical points of phase transformation for rare earth alloyed high carbon wear resistant steel as well as continuous cooling transformation (CCT) curve of undercooled austenite at different cooling rates are studied by metalloscope, field emission scanning electron microscopy and quenching dilatometer. The results showed that the critical points of phase transformation were Ac₁=742.6 ℃, Ac₃=816.5 ℃ and Ms=307.0 ℃. When cooling rate is less than 0.4 ℃/s, the microstructure is a small amount of ferrite+pearlite; when cooling rate is 0.4 ℃/s, the microstructure is single-phase pseudo eutectoid pearlite; when cooling rate is greater than 0.5 ℃/s, the microstructure is gradually transformed to martensite; when cooling rate is greater than 4 ℃/s, there is only the microstructure of martensite+retained austenite in the steel.

The characteristics of continuous cooling transformation of fire-resistant test steel are analyzed as well as its microstructure at different cooling rates within 1~100 ℃/s are observed through drawing the continuous cooling transformation(CCT) curve of 345 MPa grade fire-resistant test steel. The results showed that there were ferritic and perlitic transformations of test steel when cooling rate was 1 ℃/s; there were ferritic and bainite transformations of test steel when cooling rate was 8~20 ℃/s, pearlite completely disappeared, grain size was reduced and proportion of bainite structure was increased; microstructure transformation of test steel was mainly bainite transformation, proportion of ferritic transformation was very low and grain size was further reduced when cooling rate was 50~100 ℃/s; ferrite disappeared completely, all the microstructure was changed to bainite and was with obvious tendency of lath when cooling rate was increased to 100 ℃/s. The analysis of CCT curve and microstructure for fire-resistant test steel provides theoretical basis for formulating cooling processes in the production process of 345 MPa grade fire-resistant test steel.

The feedback of user is that the elongation of cold rolled sheet with cold rolled base material SPCC manufactured by 2 250 mm production line after cold rolling and annealing is low, part of flow forming is not easily to form in punch forming process and cracking rate is higher. The cause analysis showed that its high Mn content was one of the causes for slightly higher strength of steel strip so that elongation was low and steel strip was easy to crack; cooling modes of the two production lines were different, the cooling mode of preconcentration was adopted by 2 250 mm production line and the cooling mode of predispersion was adopted by CSP production line so that the strength of hot rolled steel strip manufactured by 2 250 mm production line was slightly higher, elongation was low and steel strip was easy to crack. The elongation of hot rolled steel strip manufactured with raw materials with thickness of 3.0~5.0 mm by 2 250 mm production line is lower than that of hot rolled steel strip manufactured by CSP production line so that the elongation of cold rolled steel strip after cold rolling and annealing is also slightly higher due to the “heredity” of rolling.

The drop weight tear test (DWTT) is used to test the toughness of materials, mainly for studying the low-temperature toughness of metal materials. In the paper, the microstructure and morphology of samples corresponding to different area proportions of brittle fracture are compared and analyzed with optical microscope aiming at the unqualified DWTT properties of products during trial production process of heavy gauge X80M hot rolled steel strip. The composition segregation in thickness direction of casting blank is tested. It is found that the severe segregation in thickness direction of steel strip is the main factor influencing the DWTT properties by analysis. The center segregation of casting blank and DWTT properties of product are improved effectively by adjusting the arc alignment precision of segment and optimizing the specific water amount of continuous casting machine so that the goal of stable production of hot rolled steel strip for heavy gauge X80M pipeline steel is realized.

In this paper, the continuous casting billet of low temperature Hi-B steel, metallographic structure and texture of plates after such processes as hot rolling, normalizing, cold rolling, decarburizing annealing and high temperature annealing are observed with metallographic microscope and X-ray diffractometer (XRD) as well as the evolution laws of microstructure and texture in the whole process are analyzed. The results showed that the macrostructure of continuous casting billet was mainly columnar crystal and proportion of equiaxed crystal zone was 7%~12%; microstructure of hot rolled plate was composed of alternant banded structure of ferrite and pearlite; microstructure of normalized pickled plate was composed of fine crystal zone and recrystal microstructure. The textures at 1/8 of thickness of hot rolled plate and normalized plate are mainly Goss texture and brass texture as well as strong Goss texture is formed with the secondary recrystallization after high temperature annealing.

The coupling is an important part of oil casing and oil tube as well as they are connected into tubing string by coupling with the mode of screw joint. In order to improve the anti-galling property of thread of coupling, the high temperature manganese phosphating is usually adopted for coupling so that it is corrosion resistant, the friction is reduced and lubrication performance is improved. In this paper, the effects of free acidity, total acidity and acid ratio on the quality of phosphating film and phosphating reaction time are studied by experiments. The phosphating process parameters are further optimized to control the phosphating film weight to be within certain range so that more compact and homogeneous phosphating film is obtained.

In China, the steel for steel structure is mainly plate and applications of hot rolled H beam (RH) in steel structure is growing slowly. The use level of RH accounts for only 15% of total amount of H beam, which is relatively lower and the rest is welded H beam (BH). In this article, the specifications, types, production processes, residual stresses, microstructure at R corner, advantages and disadvantages as well as future development trends of BH and RH are compared and analyzed. Moreover, several countermeasures for the application bottleneck of RH in construction steel structure are proposed.