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Ning B.Q.,Tianjin University of Technology | Ning B.Q.,Tianjin Pipe Group Corporation | Jiang H.,Tianjin University | Yan Z.S.,Tianjin Pipe Group Corporation
Journal of Materials Science: Materials in Electronics | Year: 2010

Combined with thermal analysis and phase identification, the sintering process of Ag-doped MgB 2 superconductor was investigated. It is found that the Ag doping could form Mg-Ag liquid through the eutectic reaction at low temperature (about 470 °C) and then obviously accelerated the formation of MgB 2 phase. Moreover, a sintering model is also proposed to illustrate the liquid activated sintering mechanism present in the sintering process of Ag-doped MgB 2 samples. The sintering model is supposed to provide theoretic guidance for optimizing the sintering condition in the synthesis of doped MgB 2 superconductors. © Springer Science+Business Media, LLC 2009.

Qiao Z.-X.,Tianjin University of Commerce | Qiao Z.-X.,Tianjin University | Liu Y.-C.,Tianjin University | Yan Z.-S.,Tianjin Pipe Group Corporation Ltd | And 2 more authors.
Cailiao Kexue yu Gongyi/Material Science and Technology | Year: 2012

Martensitic phase transformation characteristics in the 30CrNi3MoV low-alloy ultra-high strength steel were investigated by means of microstructure observation and dilatometric measurements. The results showed that the transformation products in the quenched 30CrNi3MoV steel were two kinds of martensite with different morphologies, lath martensite and acicular martensite, formation of which clearly separate each other in transformation dynamics curves. Lath martensites form in the relatively high temperature range (310°C~260°C) below the Ms, during which diffusion of carbon atoms occurred and resulted into carbon-rich austenite micro regions around martensite lath bunches. Acicular martensites form in the relatively low temperature range (260°C~170°C) below the Ms, which are transformed from the carbon-rich austenite micro regions retained after the formation of lath martensites. Transformation rate of the lath martensite is obviously higher than that of the acicular martensite.

Qiu H.,Japan National Institute of Materials Science | Qi J.G.,Liaoning University of Technology | Wang L.N.,Tianjin Pipe Group Corporation | Yin F.X.,China First Heavy Industries | Hiraoka K.,Osaka University
Materials Science and Technology (United Kingdom) | Year: 2013

As environmental temperature decreases, the amount of retained austenite is more likely to greatly reduce due to the thermal austenite-martensite transformation caused by the decreased thermal stability of retained austenite, probably making its amount lower than the required content. In the present study, the thermal stability of retained austenite in Cr-Ni weld metals was investigated to see whether sufficient retained austenite can be maintained at low temperatures. The specific experimental procedure is as follows: briefly, the samples were cooled in turn from room temperature to 0,-20,-40,-60,-80,-100 and-196°C; the amount of retained austenite at the above temperatures was measured using X-ray diffraction. Through investigating the dependence of the content of retained austenite on temperature, it was revealed that when the content of retained austenite is <20%, retained austenite can be maintained until-196°C. © 2013 Institute of Materials, Minerals and Mining.

He C.-L.,University of Science and Technology Beijing | Zhu R.,University of Science and Technology Beijing | Dong K.,University of Science and Technology Beijing | Qiu Y.-Q.,University of Science and Technology Beijing | Sun K.-M.,Tianjin Pipe Group Corporation
Journal of Iron and Steel Research International | Year: 2011

A transient three-dimensional mathematical model has been developed to analyze the three-phase flow in a 150 t EAF (electric arc furnace) using oxygen. VOF (multiphase volume of fluid) method is used to simulate the behaviors of molten steel and slag. Numerical simulation was conducted to clarify the transient phenomena of oxygen impingement on molten bath. When oxygen jet impinges on the surface of molten bath, the slag layer is broken and the penetrated cavity in molten steel is created. Simultaneously, the wave is formed at the surface of uncovered steel on which the slag layer is pushed away by jet. The result of numerical simulations shows that the area and velocity of uncovered steel created by impingement, jet penetration depth change from 0.10 m 2, 0.0125 m/s, 3.58 cm to 0.72 m 2, 0.1445 m/s, 11. 21 cm, when the flow rate of an oxygen lance varies from 500 to 2000 m 3/h. The results have been validated against water model experiments. More specially, the relation between the penetration depth and oxygen flow rate predicted by numerical simulation has been found to agree well with that concluded by water model. © 2011 Central Iron and Steel Research Institute.

Zhang C.,Yanshan University | Zhang C.,Tianjin Pipe Group Corporation Ltd | Wang Q.,Yanshan University | Wang Q.,Tianjin Pipe Group Corporation Ltd | And 5 more authors.
Materials and Design | Year: 2012

The microstructures of lath martensite in 25CrMo48V steel quenched at 900°C and tempered at 600-700°C for 5-105min were characterized by field emission scanning electron microscopy (FESEM), electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM). The tensile properties of 25CrMo48V martensitic steel were evaluated from the specimens subjected to various tempering temperature and time. The result shows that with the tempering temperature and time decreased, the refinement of martensitic packet, block and lath can take place and induce the enhancement of the yield strength. The yield strength follows the classical formula of Hall-Petch relationship with the packet size and block width, and the value of ky is 102.7Nmm-3/2 and 46.6Nmm-3/2 respectively. The yield strength is more dependent on the packet size than the block width, while the martensitic lath is the minimum structure unit controlling the yield strength of the steel. © 2011 Elsevier Ltd.

Tianjin Pipe Group Corporation | Date: 2011-09-22

A threaded connector including female thread and male thread. The female thread is symmetrically disposed on both ends of a coupling. The male thread is disposed at an end of a pipe. The female thread includes buttress thread. A torque shoulder is disposed in front of the buttress thread. The female thread is connected to the torque shoulder via a tool withdrawal groove. A protruding threaded segment is disposed on any one of a fourth to seventh tooth of the female thread to prevent high pressure gas from leaking.

Qiu H.,Japan National Institute of Materials Science | Wang L.,Tianjin Pipe Group Corporation | Hanamura T.,Japan National Institute of Materials Science | Torizuka S.,Japan National Institute of Materials Science
ISIJ International | Year: 2013

A study was conducted to demonstrate physical interpretation of grain refinement-induced variation in fracture mode in ferritic steel. Tensile tests were performed at room temperature and at a crosshead rate of 0.4 mm/min with specimens of 4 mm in diameter and 10 mm in gage length to investigate the dependence of critical fracture strain on ferrite grain size. Round smooth tensile specimens were applied to conduct the investigations where they were in uniaxial stress state before the onset of necking and turned into triaxial state after necking. The stress triaxiality in the region ahead of the crack was higher than that in the round smooth tensile specimen for a sample with a crack as the crack tip was sharp. The fracture strain obtained from tensile tests was larger than the critical fracture strain in the local region ahead of the crack.

Tianjin Pipe Group Corporation | Date: 2010-05-11

Poles of metal; common metals, unwrought or semi-wrought for further manufacture; steel sheets; laths of metal; elbows of metal for pipes; junctions of metal for pipes; pipes of metal; building boards and panels of metal; steel pipes; casings of metal for oilwells.

Tianjin Pipe Group Corporation | Date: 2014-10-29

Steel pipes; casings of metal; seamless steel pipes.

Tianjin Pipe Group Corporation | Date: 2016-03-04

Metal cylinder pipes; Steel pipes; seamless steel pipes; metal mechanical pipes.

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