In the paper, the microstructure and mechanical properties of test steel are analyzed aiming at the additional technical requirements for impact property and grain size of hot rolled J55 steel grade casing based on the Technical Specification for Seamless Casing Procurement published by China National Petroleum Corporation as well as the steel grade design of microalloying of titanium for restraining abnormal growth of austenite structure and the scheme for cooperative control of hot continuous rolling temperature are proposed. The industrial production of J55 steel grade casing with the specification of Φ244.48 mm × 8.94 mm has been carried out, the results showed that the grain size, impact energy and tensile property could all meet the requirements of Technical Specification for Seamless Casing Procurement.

In the paper, the improvement and practical application of slag retaining with sliding plate and detecting technology of roughing slag with infrared ray for 120 t converter of Baotou Steel are introduced as well as they are compared with present common slag retaining ways and analyzed. The results showed that the success rate of slag retaining could reach over 99%, the quantity of roughing slag was controlled within 80 mm and average rephosphorization of molten steel could be controlled within 0.001% with the improvement so that the cleanliness of molten steel was improved to lay a good foundation for manufacturing steel grades with high added value and reducing production costs.

The characteristics of continuous casting process for round billet and distribution of carbon element in round billet are analyzed as well as the causes of carbon segregation are analyzed and discussed. The optimum measures are put forward from such two aspects as degree of superheat of molten steel and cooling regime of continuous casting combining with the technological characteristics and equipment condition of continuous casting for round billet. Moreover, the industrial test results showed that the carbon segregation in round billet with large section could be effectively improved when the current of mold electromagnetic stirring was controlled at around 300 A, degree of superheat of molten steel was controlled at around 25 ℃ and specific water flow was controlled at 0.20~0.22 L/kg.

The quenching and tempering process with the quenching temperature of 900 ℃ and tempering temperature of 670 ℃ is determined by taking the upgraded BT135VRE process parameters provided by laboratory as references, on-site adjustment and determining the reasonable on-site heat treatment process parameters combining with reality. The yield strength, tensile strength, elongation and metallographic structure of steel tube are tested as well as the results could meet the product requirements.

The problems of misrun on surface of three-section mandrel for large diameter continuous rolling mill and fracture at joint of bolt are solved through such measures as controlling the cooling effect of mandrel, adjusting the thickness of lubricating layer of graphite, reducing the coefficient of elongation for rolling ultra-thin-wall steel pipe with maximum diameter mandrel, designing the function of "mandrel avoidance" in servo system of continuous rolling mill and adding gasket unit at the joint of connecting rod and working section so that the service life of mandrel is significantly improved and the use cost of mandrel is reduced by about 8%.

In the production process of 12CrMoV pearlitic heat resistant steel carrier rod, there are such problems as poor weldability and great welding difficulty caused by using the v-groove electrode arc welding and horizontal fixed all position butt joint welding, such defects as incomplete penetration, slag inclusion and cracks are effectively avoided by standardizing the welding process and welding quality control to ensure the welding quality.

The axle steel with large bulging rate is designed and developed as well as the trial production and evaluation of seamless steel tube are carried out aiming at the problem of cracking in bulging area when produce axle with large bulging rate using seamless steel tube in a domestic axle manufacturing enterprise. The results showed that the elongation of seamless steel tube for axle produced with the designed and developed steel grade was 28%~31%, its longitudinal impact energy at-60 ℃ could reach 80 J as well as it was with good plasticity and low temperature impact toughness. With the batch use by users, there is not the cracking problem when it is bulging.

The alloy composition design based on V and Cr is carried out through analyzing the performance requirements and technological characteristics of seamless steel tube for hydraulic cylinder as well as the corresponding control measures of smelting, rolling and heat treatment technology are formulated so that the seamless steel tube with excellent comprehensive performance is successfully developed. The yield strength, tensile strength and longitudinal low-temperature impact value at-20 ℃ of trial-manufacture steel tube are more than 480 MPa, 650 MPa and 100 J respectively.

The load-bearing axle tube for low-temperature working condition is developed and offered to user on trial with the beneficial effects of rare earth in steel aiming at the problem that there are cracks on axle tube XCQ16-1 produced by Baotou Steel in process of forming at low temperature of -5 ℃. The results showed that the products could completely meet the manufacture requirements at low-temperature working condition of -5 ℃, there were no cracks on them in use procedure, they had passed fatigue test of axle and had been supplied in batch stably.

The rotary hearth furnace with gas of Φ180 mm plant unit in Steel Tube Co. of Baotou Steel is the most important equipment in the process of producing and rolling steel tube. In this paper, it is analyzed such defects as unstable calorific value of gas, inaccurate flow element measurement and deviated flow characteristic of valve for combustion control system of rotary hearth furnace with gas as well as adopted such reformation measures of its intelligent upgrade as upgrading the temperature control program, introducing strategy of autocorrection for coefficient of excess air, reserving automatic regulation interface of air fuel ratio, newly increasing automatic control of pressure in air main, automatic control software of furnace pressure, functions of automatic starting up and air-tight test, basic alarm of loop and interlock. Finally, the stable intelligent combustion system is realized.

In this paper, the heat treatment schedule which is easy to generate yellow block of martensite is obtained through observing and analyzing the metallographic structure of samples of tube for 12Cr1MoVG boiler after different heat treatments. Moreover, the method for eliminating yellow block of martensite is obtained through exploring the heat treatment schedule, which provides technical reference for heat treatment production on site.

In the paper, the microstructures of BT-65MnRE steel at different cooling rates are observed with the metalloscope by determining its continuous cooling transformation (CCT) curves at different cooling rates. The results showed that the phase transition points of test steel BT-65MnRE, A_c1 was 707 ℃ and A_c3 was 764 ℃, the microstructure at room temperature was pearlite + proeutectoid ferrite when the cooling rate was 1~4 ℃/s, it was pearlite + bainite + martensite + a small number of ferrite when the cooling rate was 5~8 ℃/s, it was pearlite + martensite + a small number of ferrite when the cooling rate was 10~30 ℃/s and it was martensite when the cooling rate was greater than 40 ℃/s.

In the paper, the effects of different quenching and tempering temperatures on the microstructure and mechanical properties of chrome-molybdenum steel are studied. The results showed that the tensile strength, elongation and impact energy of test steel were not changed much with the tempering temperature increased. The yield strength was more sensitive to tempering temperature and it decreased with the temperature increased. The optimum quenching and tempering temperatures were 900~920 ℃ and 690~710 ℃ respectively for hardening and tempering C90 steel grade steel tube with this grade of steel.

After the heat treatment of normalizing + tempering, the hardness value of P22 high pressure boiler tube with specification of Φ325 mm × 10 mm exceeds the upper limit of standard due to thinner wall thickness and faster cooling rate. A new heat treatment process of "slow cooling after normalizing + air cooling + tempering" is proposed through experimental research. The P22 steel pipe is with the microstructure of ferrite + pearlite after heat treatment by controlling the cooling rate after normalizing, which is the key to ensure its good comprehensive mechanical properties.

In this paper, it is introduced the micro analysis of microstructure for Q345B high pressure fertilizer pipe with metalloscope aiming at the problem of its unqualified longitudinal impact property and found out its cause is the existence of a large number of Widmanstatten structure. The sample tube was treated with the heat treatment of normalizing process and the results showed that the Widmanstatten structure in steel could be eliminated by normalizing treatment as well as the longitudinal impact energy is greater than 120 J, reaching 3 times of the lower limit value of impact in standard GB 6479-2013.

The reasonable heat treatment process parameters are formulated in view of the problem that the time of full annealing for 1Cr5Mo seamless steel tube for high pressure fertilizer facility is longer and its mechanical properties cannot meet the standard requirements with normalizing and tempering process. Finally, the heat treatment process of isothermal annealing with heating temperature of 880 ℃ is adopted through trial and error so that the products with stable performances meeting the requirements of standard GB/6479—2013 are successfully produced with volume production.

In this paper, the continuous cooling transformation (CCT) curve of test steel is determined with FORMAS-TOR-F full automatic phase transformation instrument by taking low carbon medium manganese steel as the object of study. The results showed that the microstructure at room temperature was proeutectoid ferrite + pearlite when the cooling rate was 0.1~0.5 ℃/s; when the cooling rate was 1~2 ℃/s, there was granular bainite and the microstructure at room temperature was ferrite + pearlite + granular bainite; when the cooling rate was 5~10 ℃/s, the bainite gradually transformed to martensite, so the martensite increased continuously and it was the mixed microstructure of martensite + bainite at room temperature; when the cooling rate was greater than 10.0℃/s, it was martensite structure at room temperature, which provide references for formulating heat treatment process.

In this paper, the structure, working principle, characteristics and performances of silicon controlled rectifier are summarized as well as its advantage of controlling high power with low power for metallurgical hoisting crane is introduced through examples. It can control the 160 kW motor of main coil with milliampere current, it is with such functions superior to those of contactor as it can be turned on and off in microsecond, noncontacting operation, no spark and noises, high efficiency as well as low costs and failure rate.

With the continuous development of medium frequency power supply of thyristor technology, the medium frequency smelting furnace has become very important equipment in the field of casting and steelmaking at present. In this paper, the working principle and electrical faults easy to occur of medium frequency smelting furnace are analyzed and studied, the emphasis is to study the main common electrical faults of rectifier and inverter electric control systems as well as load circuit, which provide the references for relevant practitioners.

In this article, the composition of main machine system for tube gang saw and logic control process of sawing are introduced, the hydraulic operation scheme of clamping mechanism for control system of sawing for tube gang saw as well as the composition of hardware and design thought of software for sawing of main machine are mainly described.

In this paper, it is mainly analyzed and introduced the causes of internal hexagonal defect in super thick walled tube rolled with sizing mill in production of seamless steel pipe. Moreover, it is controlled by such means as increasing the rolling pass as well as reducing the reduction rate of each frame and coefficient of ovality so that the wall thickness accuracy of thick walled tube, ratio of first-grade products and yield of metal are improved.

This article starts with the product quality problem that the stand off between two sides of coupling is out of tolerance in production process of coupling thread processing. Moreover, it is introduced two process plans of coupling thread processing, lathe threading after boring of both sides and direct lathe threading after boring of single side. The times of chuck rolling-over can be reduced and the out-of-tolerance waste products of stand off for coupling and lathe threading caused by large axiality deviation of chuck can be avoided by direct lathe threading after boring of single side. It is mainly introduced the problem of stand off out of tolerance is solved with optimizing the coupling thread processing technology by technician and the effects are satisfactory.

In the paper, it is introduced the materials of coated tool and ceramic tool as well as matters needing attention in the process of using them, described the materials of two superhard material tools as well as summarized the development direction of cutter materials in our country.

In view of the shrinkage defect often appears in the process of casting V-type roll, the solidification process of casting shape for V-type roll is simulated with the casting process simulation software ProCAST. The area of casting defects is predicted and their causes are analyzed. As a result, the casting processes such as improving the pouring modes and riser of V-type roll are obtained so that the problem of shrinkage could be effectively solved and the casting process is optimized, which provide the effective guideline for production.

The tolerance rate of additional wall thickness for mandrel pipe mill is an important parameter to control the accuracy of wall thickness for steel pipe and main basis of selecting corresponding mandrel series for a pass. In the paper, the calculation formula for tolerance rate of additional wall thickness for three-roll mandrel pipe mill is derived as well as the additional tolerance values of reducing and increasing diameter of pass are simulated in pass detail and the simulated results are consistent with the calculated values. The result of variation for wall thickness calculated by this formula is basically the same as that calculated by external mathematical model.

In the paper, the research and development and application of non-standard oil casing in such four domestic large steel pipe production enterprises as China Baowu Steel Group, Tianjin Pipe Corp., Baotou Steel Group and Hengyang Pipe Group are introduced. With the increasingly harsh exploitation conditions in domestic oil and gas fields, its demand is increasing, while there are obvious differences between blocks and wells of oil and gas fields in China as well as a lot of work needs to be done further to evaluate its applicability, so the development direction of its research field is to formulate the unified standard and specification recognized by the industry on this basis.