The key influence factors of the entire process of pretreatment, phosphating and electrophoresis are studied through system experiments as well as the influencing mechanisms of such key parameters as surface roughness of plaque, peak density, processing modes of rust preventive oil and pH values of washing process on coating performances are revealed aiming at the coating compatibility issues of deep drawing automobile steel. The research results showed that pH value of washing process over 8.5, cooperating effects of reasonable surface roughness of plaque (Ra≈1.2 μm) and peak density (RPc≥90 cm^-1), avoiding manual oiling treatment of plaque are the core of forming high-quality phosphating film and improving corrosion resistance of electrophoretic coating film. This study provides universal process optimization directions and key points of quality control for optimizing the coating compatibility of automobile steel sheets.

In this paper, the causes of surface blistering of electrophoretic coating plate for DC04 cold rolled automobile steel after 60-cycle cyclic corrosion resistance test are analyzed with scanning electron microscope and energy dispersive spectrometer. The test results showed that the size of phosphating phase in blistering area was approximately 10~25 μm, while that in non-blistering area was about 2~3 μm; such characteristic elements of phosphating phase as Zn and P were not detected in blistering area, while the phosphating film was bound tightly with matrix and electrophoretic coating film in non-blistering area as well as there were such characteristic elements of phosphating phase as Zn and P in phosphating film. The binding force of matrix, phosphating film and electrophoretic coating film is reduced by coarse phosphating phase as well as the channel for extension of corrosive liquid is provided so that there is surface blistering of electrophoretic coating plate for DC04 cold rolled automobile steel after 60-cycle cyclic corrosion resistance test finally. The incomplete degreasing during pretreatment of automobile steel and there is residual oil on the surface may be the causes for the abnormal growth of phosphating phase.

The 300 MPa grade enamel steel is with low-carbon composition design, such alloy elements as Mn, Nb and Ti are added, tapping temperature of heating furnace in hot rolling is controlled at 1 200~1 230 ℃, finishing temperature≥890 ℃, coiling temperature≤580 ℃, cold rolling reduction ratio≥65% as well as continuous annealing temperature is selected to be 830 ℃. The yield strength of developed high strength enamel steel is 367 MPa, which is still over 300 MPa after enameling as well as its microstructure mainly consists of uniform equiaxed ferrite with Fe₃C and dispersed TiC precipitates. The TiC could effectively pin grain boundaries to prevent grain coarsening during high temperature treatment process. TH (sensitivity of resistance to scute burst) is 6.80~7.23 min/mm², which could meet the requirements of EN 10209—2013 standard (TH>6.7 min/mm²).

In order to study the weldability of wind power steel Q420ME, the SH-CCT (simulated heat-affected zone continuous cooling transformation) curve is determined, temperatures of A_c1 and A_c3 for wind power steel Q420ME are 690 ℃ and 920 ℃ separately. The SH-CCT curve analysis shows that the bainite transformation occurs first, followed by martensite transformation during cooling process as well as the microstructure is bainite and martensite when cooling rate is 10~40 ℃/s. With the increase of cooling rate, the content of bainite is decreased, while content of martensite and hardness of wind power steel Q420ME are increased.

In this paper, the effects of different chloride ion (Cl^-) concentrations on corrosion behavior of T91 steel treated by indentation method in the neutral salt spray environment are studied. The corrosion test of 48~288 h for indentation specimens is carried out with NaCl solutions of concentrations of 10% and 15% under the standard neutral salt spray test conditions. It is found that the corrosion weight loss in the environment of 15% NaCl is higher than that in the environment of 10% NaCl through analyzing the corrosion weight loss, corrosion morphology and corrosion products as well as the difference between them is increased with the extension of corrosion time, which reaches the maximum value (0.008 5 g) at 288 h. This proves that the corrosion effects of environment with high Cl^- concentration on T91 steel are stronger and they are obvious with time accumulation. The observation results of scanning electron microscope showed that the indentation was more easy-corrosive and the more the Cl^- concentration, the more serious the corrosion was, which indicates that the corrosion resistance in this area is significantly reduced by stress concentrations (dislocations, microcracks etc.) introduced by indentation so that it becomes the sensitive area where corrosion occurs preferentially.

In this paper, the effects of different heating temperatures and holding time on original austenite grain size are studied by taking X80 pipeline steel as the research object. The results showed that the original austenite grain size of X80 pipeline steel holding for 1 hour at different heating temperatures was gradually increased with the increase of heating temperature; the austenite grain was coarsened rapidly with the effect of driving force of high grain boundary at initial stage of holding under the soaking condition of 1 180 ℃ as well as the average size was increased from 15 μm to 50 μm within 1 hour, which showed the high sensitivity to time.

In this paper, the design of new economical steel grade, laboratory researches and industrial trial production of BNS line pipe in sour service are carried out. The results showed that such properties as the yield strength, tensile strength, elongation, impact properties and Vickers hardness of trial-produced steel pipe (as-hot-rolled and after normalizing treatment of 890 ℃) could meet the requirements of API 5L standard. After normalizing treatment of 890 ℃, the low temperature impact toughness of steel pipe is significantly improved and its ductile-brittle transition temperature is reduced from -10 ℃ (as-hot-rolled) to -50 ℃ (as-normalized condition) as well as its banded structure is improved and grain size of matrix is refined from grade 7(as-hot-rolled) to grade 8.5 with normalizing treatment.

In this article, the construction technology of synchronous sliding for steel box girder of Lanzhou Chaijiaxia Yellow River Bridge is comprehensively summarized. The construction scheme of “assemble on both shores, incremental launching toward each other and accumulate sliding section by section” is systematically proposed through researching the synchronous sliding technology for steel box girder. Moreover, such technical problems as the sliding route, setting of temporary piers, assembly of sections for girder of slippage and length of steel launching nose are solved through the BIM (building information modeling) technology. The control measures for key technologies of sliding construction are sorted out in this paper, which could provide references for sliding constructions of girder for cross-river cable-stayed bridge under complicated conditions.

The mobile robot is widely applied in various complicated terrain environments, so the requirements of travelling speed and capacity of passing complicated terrain for travelling mechanism are higher. In the paper, the interactions and problems existing between components are determined with function analysis tool as well as the key problems are determined with causal chain analysis tool in modern TRIZ (Theory of Inventive Problem Solving) theory system by taking wheeled travelling mechanism as the prototype system as well as analyzing its advantages and disadvantages. The above problems are solved and 10 conceptual proposals are obtained through combining such tools as ideal final result, cropping, substance-field model, physical and technical contradictions with inventive principles. Finally, the scheme of deformable tire is determined to be the optimal technical scheme and modeling design is carried out.

The traditional detection robot of water surface environment is limited by such problems as difficult deployment of vessel and susceptibility to effects of weather conditions so that the operation costs are high. In the paper, a solution is proposed. The detection robot of water surface environment autonomously enters water to perform underwater operation tasks after deploying it on land. The solution does not need vessels to support, allows rapid response to operational requirements in lakes, reservoirs and shallow areas, which is suitable for replacing conventional detection robot of water surface environment to perform underwater operations when it is difficult to deploy vessel as well as it could provide the solution with light weight and high maneuverability for underwater task operations.