The experiment with 14MnCrMoNiNb steel was for studying quenching + quenching in two-phase region + tempering process (QQ'T). The experimental results showed that the multiphase microstructure of tempered sorbite + a small amount of ferrite could be obtained with the QQ'T process. On the premise of without losing the strength and toughness of material, the yield ratio of material could be reduced to about 0.80 so that the serviceability safety performance of material could be improved greatly.

The metallographic structure of hot-rolled TC4 titanium alloy seamless tubes with different specifications was studied with the light microscope and scanning electron microscope as well as the mechanical properties of titanium alloy tube were tested. Moreover, the effects of different heat treatment and pickling processes on the microstructure and properties of tube were also studied. It was found that the differences of as-hot-rolled microstructure of titanium alloy tubes with different specifications were significant as well as the outer diameter and wall thickness of the head of tubular billet after perforation were larger than those of the tail. The annealed microstructure obtained by the two-phase region annealing process at different temperatures did not change significantly. Although the oxidation products on the surface of titanium tube could be effectively removed with the pickling process, the time parameters of pickling process were very important, otherwise, the surface quality of titanium tube would be deteriorated.

In the paper, the effects of reheating temperature in the on-line normalizing process on yield strength and impact energy of steel tube were explored with industrial experiments based on the indexes of yield strength and impact toughness for Φ139.7 mm × 7.72 mm N80-1 casing in the Q/YS 1572.1 standard. The results showed that the yield strength of steel tube could reach 570~620 MPa and the half-size longitudinal impact energy at 0 ℃ is ≥40 J if the temperature of steel tube before entering reheating furnace was≤550 ℃ and reheating temperature was controlled at 870~900 ℃, which could meet the requirements of the Q/YS 1572.1 standard.

The instrument of production in Steel Tube Co. of Baotou Steel, mandrel, is damaged during use, so different repair plans are put forward based on the different forms and degrees of damages. The effects are remarkable through practical applications so that its repair problems are solved fundamentally, its service life is prolonged and the production costs are reduced.

In this paper, the design for key technological parameters of hot continuous rolling process of producing TA2 seamless titanium tube with MPM unit is introduced. The trial production showed that the plastic deformation was better and the surface of hot tool was not sticky when the heating temperature was controlled at 1 010~1 020 ℃, the surfaces of top and guide plate were coated with the self-developed viscous resistance agent as well as the initial rolling temperature was controlled at 940~960 ℃. The inspection results of TA2 seamless titanium tube produced with the hot continuous rolling process showed that its internal and external surface quality was good as well as the outer diameter and wall thickness were controlled within the dimensional deviations so that the process could be used for producing the titanium tube and titanium alloy tube.

With the change of application environment for tubular products, the requirements for impact energy and grain size of J55 casing are continuously increased. The growth of grain size during heating is controlled through the micro Ti processing during steel making. The shape of precipitation of ferrite is changed through applying the controlled rolling and controlled cooling technology with tandem mill of hot-rolling seamless pipe so that the product performances are improved.

The service environment of high-pressure boiler tube is harsh, so the requirements for inclusions of tube bloom are very strict. In the actual production process of 12Cr1MoVG, the inclusions are often over proof, which is solved by such measures as improving the control target of end-point carbon content in converter, optimizing refining slag system and narrow component control.

The defect of infolding is one of the main problems during hot perforation of 1Cr5Mo alloy steel tube blank, which could not only influence the qualified products ratio, but also the yield of steel tube. In the paper, it is mainly introduced the heating schedule of circular furnace, rolling pace, perforation technology and application of hot tools are optimized as well as analyzed the defects of infolding in the production of 1Cr5Mo alloy steel tube of our company so that the effects are good.

The stress concentration is generated in the processes of cooling, stretching and straightening for continuous casting tube bloom with large diameter as well as the stress cracks are formed on the interior and surface of continuous casting tube bloom when the stress is too large. In this paper, it is analyzed their causes and mechanisms as well as summarized the types of defects for steel pipe caused by them in the process of hot rolling seamless steel tubes. Moreover, the guiding suggestions for controlling and solving stress cracks of continuous casting tube bloom and defects of seamless steel pipe are proposed by analyzing their relevance, which conduce to controlling the related elements pointedly in practices and reduce the defects in the process of rolling seamless steel pipe.

In the production process of round billet with Φ430 mm section, the original current direction ("single direction rotation") of electromagnetic stirring of mould was adjusted to "alternate rotation with positive and negative rotation" mode. The experimental results showed the equiaxial crystal ratio of section center was increased and the carbon segregation was obviously improved.