In this paper, it is mainly introduced the research and development of figured steel for expansion joint of highway bridge (π profile steel) in Rail and Beam Rolling Plant of Baotou Steel to meet the market demands. In order to improve the safety of expansion joint device of highway bridge, the BG355BRE rare earth steel is designed independently to improve strength and toughness of steel. The special pass system is designed aiming at the complex cross section of π profile steel and seriously uneven deformation during rolling process. In the production process, the problem of rolling bending for asymmetric cross section are effectively solved by optimizing pass design and distributing rolling reduction of every pass reasonably. All the mechanical properties of finished products could meet the requirements of technical agreement as well as dimension and surface quality could meet the operating requirements of users so that batch supply is realized.

In the paper, the dimension parameters of sizing mill and its corresponding hot tool, sizing mill stand are optimized and designed with the software, ultimate machining dimension of sizing mill stand is calculated as well as pass design of rolling specifications within ultimate dimension and theoretical analysis on optimization of rolling parameter are carried out with the numerical simulation technology and existing equipment status. The ultimate specifications of replacing stretch reducing mill with sizing mill are obtained by comparing relevant parameter design of stretch reducing mill for rolling with the same specification as well as comprehensively analyzing the status of host of equipment and production efficiency, which could provide reliable theoretical support for promoting replacing stretch reducing mill with sizing mill for rolling.

During the process of producing welding wire with BGER60Ti-1 welding wire steel, there is drawing fracture and faint yellow hard block phase is found to be direct cause through metallographic analysis of fracture sample. It is obtained according to formation mechanism of the microstructure that the faint yellow hard block phase is mixture of bainite and martensite. In the paper, such measures as extending holding time of wire rod and improving heat-retaining capacity of temperature holding hood are proposed based on studying from the perspective of controlled cooling after rolling. There is not any hard block phase in the improved matrix structure so that the problem of fracture of wire for BGER60Ti-1 welding wire steel is solved.

There is drawing fracture during the process of drawing SWRH82B hard wire rod for users. Its chemical composition, gas content, macrostructure with hot acid of base material and sample of drawing fracture are tested. Moreover, the micro analysis of sample of drawing fracture is carried out with metallographic microscope and scanning electron microscope. The analysis results indicated that since there were abnormal network ferrite structure and band structure of ferrite in the core, their combined action caused fracture of core of SWRH82B during drawing process.

In the paper, it is systematically elaborated the product defects when rolling H beam with universal pass as well as mainly discussed and analyzed from such two aspects as the steel defects and rolling defects of H beam aiming at the rolling process of H beam with universal pass in 1^# production line of Rail and Beam Rolling Plant of Baotou Steel. The steel defects include inclusions, scabs and cracks of product as well as rolling defects include dimension deviation, scratch and bending of product. The treatment methods and optimization measures are put forward according to different types of defects. The amount of waste products caused by unqualified H beam is reduced by taking such measures as reasonably controlling rolling reduction, optimizing guide and controlling rolling speed as well as optimizing control process. As a result, the first pass yield and yield of H beam are improved so that economic benefits are increased.

In order to meet the requirements of carbon equivalent and low temperature toughness, the chemical composition of low temperature Q355C hot rolled H beam for steel structure is designed and reasonable process route is formulated according to the functions of Nb element in steel as well as the mechanical properties of test steel are analyzed based on industrial production data. The test results showed that the yield strength of test steel was 355~465 MPa, tensile strength was stabilized at 525~620 MPa, elongation after fracture was stabilized at over 22% and low temperature impact energy at 0 ℃ was stabilized at 60~160 J by adding Nb element. Finally, the low temperature Q355C hot rolled H beam for steel structure mainly with ferrite and pearlite is obtained as well as all the properties of product could meet standard requirements.

The field observations and collection of relevant information of curves with different radii are carried out aiming at the rolling contact fatigue (RCF) of U75V heat-treated rail on the curved section of Tangshan-Baotou heavy haul railway. The important characteristics of rolling contact fatigue of rail are obtained through statistics and comparative analysis. Further, the model for initiation of rolling contact fatigue of rail integrating heavy haul train dynamics and damage function model is established to predict the effects of axle load, speed and adhesion coefficient on rolling contact fatigue of rail. It is found that the rolling contact fatigue of rail for up going heavy haul railway is alleviated with the increase of curve radius, there is severe peeling on R600 and R800 curves, the peeling on R1000 curve disappears by and large, while there is just slight cracks on R1600 curve as well as the rail damages of up going heavy haul railway are more serious than those of down going line at no-load. On the section of entering transition curve of up going railway R600, there is obvious peeling when excess of height of inner rail is 55 mm, while there is just sporadic small-size peeling on corresponding outer rail. The numerical simulation results could well explain the phenomena of field observation, which provides the key research tools for further treatment. The curve radius, axle load and profile after wear are determined to be the main influencing factors for rolling contact fatigue of rail in Tangshan-Baotou railway combining with the previous research results.

In the paper, the composition design and industrial trial production process of BNS, X60QS and X65QS grade acid corrosion-resistant line pipe are introduced, the effects of normalizing, quenching and tempering processes on metallographic structure and mechanical properties of the hot rolled steel pipe are studied as well as acid corrosion resistance of the product is analyzed. The trial production results showed that the mechanical properties and acid corrosion resistance of BNS grade line pipe produced with normalizing process as well as X60QS grade and X65QS grade line pipes produced with quenching and tempering process could fully satisfy the API Spec 5L standard requirements.

As a type of very important soft magnetic material, non-oriented silicon steel is widely used in such electrical equipment as motor and transformer. In recent years, with the continuous development of science and technology, the requirements of energy conservation and emission reduction are increasing so that the requirements for performances of iron core material are higher. As an important alloying method, the addition of rare earth elements has significant effects on the properties of non-oriented silicon steel and has been widely concerned. In this paper, the effects of rare earth elements on inclusions, texture and magnetic property of non-oriented silicon steel are summarized as well as the future development direction is proposed according to present research status.

The hardness of hardened layer for rails after quenching is with hardness gradient and it is difficult to accurately calculate the threshold value ΔK_th of fatigue crack growth for rails. In the paper, the detection of threshold value ΔK_th is carried out through software optimization based on the fatigue crack growth software. The threshold values ΔK_th of U75V and U71Mn quenched rails with different stress ratios are obtained by national standard method and actual measurement method respectively. As a result, the threshold values ΔK_th of quenched rails obtained by actual measurement method are more accurate through comparative analysis of data.