Papers by Keyword: High Temperature Tensile

Abstract: In recent years, the oil and gas well casing is confronted with more complex service environment, and the casing is subjected to higher service load and temperature. In this study, the strength and plasticity of Cr - Mo low alloy casing steel of 80, 90 and 110 steel grades commonly used under high temperature service conditions was studied. The results show that with the increase of temperature, the yield strength and tensile strength of casing steel decreased. The sensitivity of high steel grade to temperature change was higher than that of lower steel grade; with the increase of steel grade, the fracture mechanism of casing steel changed from microporous polymerization fracture induced by large size second phase particles to shear propagation fracture induced by sub grain boundary microporous polymerization. This study has important guiding significance for the service safety and strain design of high grade steel under high temperature conditions.

Abstract: The high temperature tensile behavior of Mg-13Gd-4Y-2Zn-0.5Zr alloy was investigated at deformation temperature of 400-520 °C and strain rate of 0.001-0.5 s^-1, and the stress-strain curves were obtained by using INSTRON 3382. The high temperature tensile constitutive model and hot processing map of the alloy were established, and the reliability of the hot processing map was further verified by analyzing the microstructure of the deformed alloy. The results showed that the dynamic recrystallization (DRX) occurred of Mg-13Gd-4Y-2Zn-0.5Zr alloy during the tensile tests under high temperature conditions, and its peak stress decreased with the increase of deformation temperature or strain rate. The Arrhenius equation can be used to fit the rheological behavior of the alloy. The thermal deformation activation energy Q was 259.13kJ/mol, and the maximum error between the model and the experimental data was less than 9%. It can be concluded that the optimum deformation parameters of the alloy were temperature of 500-520 °C and strain rate of 0.01-0.001 s^-1 based on the dynamic material model and hot processing map.

Abstract: In this study, high temperature tensile test was conducted on the specimen of superalloy GH4169 coated with wt8%-YSZ under the conditions of 950°C and 80MPa. By using finite element (FE) simulation method, the failure initiation and evolution of the metal substrate and YSZ coating were predicted. It was found that stress concentration originally occurred in the YSZ ceramic top coating, causing an axial stress and triggering severe debonding failure in the center region of the specimen at t=180s. With increased load, further interfacial debonding failure of the residual coating occurred due to the presence of oblique tensile stress and at t=900s, and only a few residues can be seen at the arc transitional region. Subsequently, the metal substrate was subjected to uniform tensile deformation and finally ruptured at t=76min with apparent necking. In addition, it was notable that YSZ coating can relieve stress significantly (nearly 40% lower), thus helping prolong the substrate's service life in the same environment. Simulated results were consistent with observed behavior.

Abstract: GH3230 is a new type of superalloy,it is the first study about it. This paper studied the high temperature mechanical properties of the GH3230 base metal and argon-arc welding joints by high temperature tensile test,high temperature creep test and SEM analyses. The results showed thatthe ultimate tensile strength of GH3230 argon-arc welding joints is about 85.6% of that of base metal under the same conditions. In the high temperature creep test, GH3230 argon-arc welding joints had a longer creep life than that of base metal. Both GH3230 base metal and argon-arc welding joints showed a ductile fracture. High temperature tensile fracture is cavities fracture and high temperature creep fracture is intergranular fracture. The deformation of GH3230 argon-arc welding joints is much more uniformited and smaller than that of base material, and GH3230 argon-arc welding joints has less cracks.

Abstract: In this paper, the high temperature tensile properties of the LAZ532-2RE alloy prepared by hot extruded processing after vacuum casting was investaged. The tensile properties of the extruded LAZ532-2RE alloy specimens were tested at different temperature with different strain rate. The microstructures near the fractured surfaces were observed using microscope in order to investigate the dominant deformation mechanism. The activation energy was calculated to explain the high temperature deformation mechanism. The result indicated that the strength of LAZ532-2RE alloy was high at the temperature range from 398K to 423K. Meanwhile, the fracture elongation of the alloy reaches 121% at 523K under strain rate 1×10^-3s^-1.

Abstract: High temperature tensile properties of Ti-4Al-6V material were obtained through high temperature tensile test, and processing maps of the material were drawn by Matlab, then strain rate sensitivity exponent m was calculated. The value of m obtained through constant strain rate stretching method was compared to the former. The results showed that processing map could not only predict the good workability region and flow instability region but also calculate the value of m accurately.

Abstract: Q390 steel owns lots of good mechanical properties, it is used in many fields. By means of Gleeble 1500D thermal simulation machine, high temperature tensile tests were carried out; by OM,SEM, the fracture pattern and the microstructure of different distance from the fracture were watched and analyzed; by means of hardness test, the micro-hardness of different distance from the fracture was measured. The results show that the rupture at different temperature belongs to ductile rupture, with distance increasing from the fracture, the microstructure changes from composition structure of martensite, bainite, residual austenite into base metal structure, the grain size is smaller and smaller. The fracture hardness increases firstly and decreases secondly when tensile temperature increases, it is up to the max when temperature is 1200°C, the value is 395HV; the micro-hardness increases firstly and decreases secondly with distance increasing from the fracture, the hardness is the max when distance is 10mm,8mm,10mm at 800°C,1000°C,1200°C tensile temperature, the max value is respectively 330HV,340HV,370HV.