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 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 this paper, the process flow and problems in process of production and operation for desulfurization and denitrification system of flue gas of coke oven are introduced in detail. The operation of the system is stable, emission indexes of flue gas are acceptable, repair cycle of the system is extended so that repair frequency is reduced and hourly qualified rate per month of emission for flue gas of coke oven is guaranteed to be over 95% through taking such measures as adjusting the heating schedule of coke oven, grouting of coke oven, sealing desulfurization and denitrification system, reforming denitrification system, strengthening heat preservation of gas pipeline as well as reducing impurities in gas.

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.

There is alarm signal in the ultrasonic flaw detection of PZ100 grade expansion pipe. The detected defects those trigger alarm signal are found through cutting open the area where there is alarm on pipe body. The defects of alarm of flaw detection are determined to be big inclusions of aluminium oxides with main components of O, Al, Mg and Ca through such methods as microstructure observation and scanning electron microscope energy spectrum analysis. The continuity of matrix for PZ100 grade expansion pipe is destroyed by cinder inclusions under surface of pipe and interlayer is formed, so cracks are formed under the action of rolling force so that flaw detector is alarmed. The product quality of PZ100 grade expansion pipe is ensured by strictly implementing technological operation regulation as well as strengthening macroscopic examination of steel billet and detection of inclusions of finished product.

The chemical compositions of X52QH seamless steel pipe for hydrogen compressed natural gas transportation are designed with microalloying design based on low carbon manganese steel. The results of laboratory studies and industrial trial productions showed that the pipe was with excellent low temperature toughness and strength, its microstructure was mainly bainite +ferrite, grain size of microstructure was grade 9.0 as well as low temperature impact energy at -90 ℃ of material was 200 J when the quenched-tempered heat treatment process of “910 ℃ quenching+640 ℃ tempering” was adopted. The CTOD (crack tip opening displacement) test (-10 ℃) results showed that crack tip opening displacement>0.9 mm (required to be≥0.254 mm). In the environments with and without hydrogen, the reduction of area and elongation of slow strain rate test materials are all over 90% so that they are with good crack extension resistance and hydrogen embrittlement resistance.

The composition and production process of hot rolled steel strip for CT70 grade corrosion resistant coiled tubing are independently designed and formulated as well as small batch industrial trial production is carried out. For the trial product, the yield strength is 520~522 MPa, tensile strength is 575~584 MPa, elongation is 33%~34%, microstructure is mainly ferrite +pearlite with a small quantity of bainite, banded structure is grade 1.0 and total of inclusions is grade 1.0 so that non-metallic inclusions are well controlled. The mechanical properties, resistance to hydrogen induced cracking (HIC) and welding performance indexes of steel strip for CT70 as well as the mechanical properties and hardness of coiled tubing manufactured with steel strip for CT70 could all meet the user requirements.

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 defect with morphology of rolling skin is found on the internal surface of Φ406 mm×8.8 mm seamless tube for gas cylinder, but longitudinal ultrasonic testing does not give an alarm, so probe of transverse flaw detector is started to detect defects and the proportion of alarm is found to be higher. The cause of transverse defect on internal surface is that the lubrication effect in rolling process of continuous mill is not good through the macro analysis, chemical composition analysis, metallographic analysis and energy spectrum analysis of defective products as well as the improvement measures for rolling method of reducing arresting force are proposed.

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.

The effects of heat treatment process on the microstructure and properties of 60Cr2MnMoNi steel are studied as well as the changes of microstructure and properties of samples at different states are compared and analyzed with TV-4X metallographic microscope, R(D)-150A1 material hardness tester, N1500C material impact testing machine and INSTRON5989 electronic universal material testing machine. The results showed that the as-cast microstructure of 60Cr2MnMoNi steel was P+B+A(residual)+carbide, average hardness was 28.1 HRC, average impact toughness was 15.4 J/cm², tensile strength was 795.9 MPa, yield strength was 458.1 MPa, elongation was 2.6% and reduction of area was 1.1%; the annealed microstructure was F(a little)+P+carbide, average hardness was 24.5 HRC, average impact toughness was 193.4 J/cm², tensile strength was 846.6 MPa, yield strength was 443.1 MPa, elongation was 17.5% and reduction of area was 25.3%; the quenched microstructure was B+M+A(residual)+carbide, average hardness was 58.1 HRC, average impact toughness was 14.5 J/cm², tensile strength was 1 442.6 MPa, yield strength was 1 186.4 MPa, elongation was 2.7% and reduction of area was 1.8%; the tempered microstructure was S(temper)+B+carbide, average hardness was 45.1 HRC, average impact toughness was 64.9 J/cm², tensile strength was 1 389.5 MPa, yield strength was 1 004.4 MPa, elongation was 7.4% and reduction of area was 10.9%. The microstructure and properties of 60Cr2MnMoNi steel are changed through different heat treatment processes so that the performance requirements of spare parts for equipment in service under different operating conditions could be met.

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 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.

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.

The stable operation of heavy duty mining truck is beneficial to safe production of mines. The failure rate of heavy duty mining truck in a mine is high and it is even higher in winter. It is found through analysis that the main causes are structural designs of accumulator and steering pump themselves for hydraulic system are not reasonable as well as control of mixture ratio of fuel to oil for engine is not accurate. The seal wear is reduced through changing single-point support to oriented multi-point support for piston of accumulator and adding unload groove; such problems as high pressure and temperature rise are solved as well as loss of parts is reduced through adding unloading valve on steering pump; temperatures of solidification point for different mixing ratios of 0^# and -35^# diesel are determined through experiments as well as auxiliary fuel tank is installed to choose different mixture ratios of fuel to oil and oil supply modes based on weather conditions. The failure rate of heavy duty mining truck is reduced through implementing the above measures.

The integrated control platform system of special steel requires to adopt industrial private cloud architecture. The upper monitoring system needs to establish virtual machines in the private cloud as well as install the Windows 7 operating system and WinCC7.0 SCADA. The private cloud server and switch in central control room are connected to the two core switches separately to establish redundant network structure in core layer. The systems in control layer and switch in central control room form ring network through respective switches, which takes into account the economical efficiency and security of network.

The rare earth inclusions in rare earth steel sample are separated from the matrix by electrolysis. The separations of rare earth sulfides, rare earth sulfur oxides and rare earth oxides are studied through different solvents, water bath time and chemical tests so that the scientific and reliable analytical method is established. The verification tests indicated that the results of precision for sample detection were good and relative standard deviation was less than 10%; for the comparative experiment of inductively coupled plasma mass spectrometry and spectrophotometry, detection results of the two methods were consistent. The analytical method could provide important technical supports for mechanism studies of rare earths in steel.

In the paper, the simultaneous determination for elements of vanadium, manganese, phosphorus and silicon in vanadium-carbon alloy is carried out with inductively coupled plasma-atomic emission spectrometry (ICP-AES), calibration curve is drawn with matrix matching method to eliminate the effects of matrix effects as well as instrument parameters are optimized. The precision experiment results showed that relative standard deviation (RSD, n = 11) for elements of vanadium, manganese, phosphorous and silicon was 0.5%~3.0%. The recovery rate experiment results showed that recovery rate was 95%~110% through adding standard solutions of different concentrations. The accuracy experiment results showed that the experimental results of each determination element were consistent with standard values, which could meet the requirements of detection method so that rapid and accurate determination for elements of vanadium, manganese phosphorus and silicon in vanadium-carbon alloy is realized.

In this paper, the current situations of implementation, advantages, challenges and optimization strategies for co-investment mechanism of employees in state-owned enterprises are discussed. Its connotation, characteristics and application situations in state-owned enterprises are elaborated through literature research and case analysis. It is found in the research that the co-investment mechanism of employees is with significant advantages in motivating employees, promoting enterprise innovation and optimizing governance structure, however, it is also facing such challenges as imperfect improvement and difficult risk control of co-investment mechanism in enterprises. In this paper, such suggestions as perfecting relevant systems of enterprises, optimizing system design as well as strengthening risk management and control are proposed, which could provide references for deepening reform of co-investment mechanism of employees in state-owned enterprises.

In this article, it is introduced the nitrogen content and oxygen concentration in heating furnace are reduced to inhibit NO_x to be generated through taking such specific measures as strictly implementing cooling system for rolling delay, improving hot charging rate and strengthening furnace body maintenance from the aspect of strengthening management of heating furnace as well as such means as taking minimum coefficient of excess air, refining air-fuel ratio, reasonably distributing thermal load, accurately controlling combustion temperature, prohibit negative pressure operations and increasing preheating temperature through analyzing the generation mechanism and influencing factors of NO_x based on current thought and methods of treatment for NO_x combining with working principle and characteristics of regenerative heating furnace. As a result, the accuracy of production operation is improved, generation of NO_x is reduced so that ultra low emission of NO_x is achieved.