The method of testing recrystallization temperature for cold rolled sheet with thermal simulated test machine in laboratory is introduced in this paper. The thermal simulation experiment schemes with a series of annealing temperatures and time are designed combining with on-site production conditions. The recrystallization temperature of test steel is obtained through thermal simulation experiments of SPFC390 cold rolled sheet at a series of temperatures, hardness test and microstructure analysis. The recrystal activation energy and coefficients are obtained by calculation as well as the relational model of recrystallization temperature and annealing time for test steel is established, which could provide the basis for formulating or optimizing annealing process on site.

In this paper, the digital twin model for production process of rare earth products is established based on digital twin technology and its visual representation in virtual space is realized. The full-process integration from data collection, transmission to model establishment and visualization is realized with the system through the design of layered architecture. In practical applications, the real-time collection of key equipment data for production line of rare earth oxide could be realized with the system as well as running status of equipment and production process could be visually displayed through the three-dimensional visualization technology. The implementation results showed that the monitoring efficiency in production process was significantly improved, production processes were optimized, production costs were reduced and product quality was improved by applying digital twin technology.

The rare earth in baiyuneboite is recovered with the process of concentration-flotation-concentration-filtration in Baoshan Mining Co.. During the concentration process of concentrate, about 4% of rare earth resources are run off from overflow of concentrate, their grade is 26.17% by detection and most of their particle sizes are 5~20 μm so that they are micro-fine particles. In this paper, the overflowed concentrate of large well of concentrate in Baoshan Mining Co. is with sampling analysis. The rare earth resources are recovered with various methods as flotation, desliming flotation, magnetic concentration and gravity concentration. Finally, the rare earth ore concentrate with grade of 50.72% and recovery rate of 30.82% is obtained with the gravity concentration method, which is with significant guiding function for comprehensive recovery of rare earth resources in Bayan Obo.

The causes on lower impact toughness of weld for 10 mm thick 700 MPa grade square and rectangular welded pipe welded with high frequency resistance are analyzed with such inspection and analytical equipment as metallographic microscope, impact testing machine, scanning electron microscope and energy dispersive spectrometer. The results showed that there were such endogenous inclusions as silicate and titanium nitride as well as foreign inclusion that is mainly manganese oxide at the weld, the combined effect of which causes impact absorbing energy at room temperature of weld to be less than 8 J. Subsequently, the weld quality of square and rectangular welded pipe is improved, impact absorbing energy of weld is increased to about 20 J by taking such measures as strengthening control level of steelmaking process and increasing upset force of high frequency resistance welding. In straightening and sizing process, cracking rate of square and rectangular welded pipe is decreased from 8% to 3%.

The spatial detection of rolling mill housing is the difficulty in rolling mill measurement. In the past, the measurement was with total station and inside micrometer, however, the measurement accuracy and technical indexes of this method could no longer meet the requirements of operating maintenance for rolling mill. In this paper, the method of measuring rolling mill housing with laser tracker is summarized. The centerline of rolling mill row is fitted according to the data of rolling mill housing collected by laser tracker as well as the coordinate system is established by taking the centerline of rolling mill row as the baseline so that such spatial position relationships as the centering size, window size and deflection of rolling mill housing could be obtained. The installation precision of rolling mill housing is recovered by adjusting the rolling mill housing based on the measurement data of laser tracker. This method is so reliable that it could be popularized.

The scale generated on polyurethane sieve mesh caused by long-term use could be effectively removed with the acid leaching method so as to recover its screening efficiency. The efficient descaling could be realized by soaking polyurethane sieve mesh in 2% oxalic acid solution for 12 h so that the screening efficiency could be recovered to 62.33%; although the descaling efficiency of sieve mesh with hydrochloric acid is high, treatment costs of waste acid is high, so it is not recommended for long-term use; the screening efficiency of soaking sieve mesh in the mixed solution of 0.5% hydrochloric acid and 0.5% oxalic acid for 12 h is similar to that of sieve mesh after using 15 days, but the operations of preparing acid solution are complex, so it is not recommended for long-term use. The 2% oxalic acid solution is used to soak the sieve mesh after using 180 days for 12 h to remove its scale considering the impacts of waste acid after descaling on the environment.

In the paper, the study on influences of quenching temperature, holding time of quenching, tempering temperature and holding time of tempering on microstructure and properties of test steel is carried out by taking as-hot-rolled 10Cr5MoVRE seamless steel pipe as the object of study. The study results showed that the yield strength, tensile strength and hardness (HRC) of test steel were first increased and then decreased while elongation and impact energy were decreased with the increase of quenching temperature; yield strength, tensile strength and hardness (HRC) of test steel were decreased while elongation was increased as well as impact energy was first increased and then decreased with the extension of holding time of quenching; yield strength of test steel was increased by about 17.5%, tensile strength was increased by about 18.2% and impact energy was decreased by 8.1% with the increase of tempering temperature; strength and hardness of test steel were decreased while impact energy was gradually increased with the extension of holding time of tempering.

The ultrasonic flaw detection of fixed flash welding joints for 60 kg/m-U75V rail is carried out in a welded rail base. It is found that there is excessive alarm of flaw detection at the rail bottom corner at welding line. The joints with defects are analyzed through metallographic observation, detections with scanning electron microscope and energy dispersive spectrometer (EDS). The results showed that the lack of fusion and hole defect were observed at weld bond at rail bottom of welded joint at the position marked by rail detecting as well as there were gray spots and abnormal bulk inclusions at fracture of bending. Analysis suggested that the main causes of flaw detection alarm were the lack of fusion and hole defects caused by formulating improper welding process parameters as well as excessive inclusions in base material. The defects could be reduced by optimizing welding process and improving metallurgical quality of base material.

The hardness of cross section and longitudinal section of rail head for 75 kg/m hot rolled bainite rail and heat treated bainite rail is tested as well as the reasons are analyzed combining with microstructure and energy dispersive spectrometer (EDS). The results showed that the change laws for hardness of cross section and longitudinal section of rail head were consistent from rail head to rail web for both states of rail. The hardness of rail head for hot rolled rail is decreased first and then increased from tread to rail web, hardness fluctuation is smaller from top surface of rail head to 13 mm below tread, microstructure is granular bainite+ lath bainite+ lath martensite as well as local hardness is abnormally high due to the existence of martensite segregation band or hard phase inclusions; the hardness of rail head for heat treated rail is decreased first and then increased from tread to rail web. The outliers of high hardness are because indentation contains hard phase inclusions and outliers of low hardness are because there is granular bainite structure in micro region. The rail is with more uniform duplex structure of bainite and martensite as well as both of them are existed in the form of lath so that segregation is significantly improved from the macroscopical view.

For the laser cladding technology, metal powder is melted by high energy laser beam to form metallurgical bonding layer with base material, which could prepare functional coating. Its performances could be optimized through adjusting and controlling process parameters. In the iron and steel industry, the technology is applied for strengthening components and parts, corrosion prevention of equipment as well as repair of high value equipment. Such problems as peeling of cladding layer and cracks are solved by optimizing the pretreatment, process parameters and material adaptation as well as high-quality repair of complex components is realized combining the technology with such technologies as 3D scanning and robot, which could promote the intelligence of repair processes.