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 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.

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.

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.

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 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.

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.

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 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.