High-Temperature Tensile and Creep Behavior in a CrMoV Steel and Weld Metal

The 2.25Cr1Mo0.25V steel is a vanadium-modified 2.25Cr1Mo steel and is being widely used in the manufacture of heavy-wall hydrogenation reactors in petrochemical plants. However, the harsh service environment requires a thorough understanding of high-temperature tensile and creep behaviors of 2.25Cr1Mo0.25V steel and its weld for ensuring the safety and reliability of hydrogenation reactors. In this work, the high-temperature tensile and creep behaviors of base metal (BM) and weld metal (WM) in a 2.25Cr1Mo0.25V steel weldment used for a hydrogenation reactor were studied experimentally, paying special attention to its service temperature range of 350–500 °C. The uniaxial tensile tests under different temperatures show that the WM has higher strength and lower ductility than those of BM, due to the finer grain size in the WM. At the same time, the short-term creep tests at 550 °C reveal that the WM has a higher creep resistance than that of BM. Moreover, the creep damage mechanisms were clarified by observing the fracture surface and microstructures of crept specimens with the aid of scanning electron microscopy (SEM). The results showed that the creep damage mechanisms of both BM and WM are the initiation and growth of creep cavities at the second phase particles. Results from this work indicate that the mismatch in the high-temperature tensile strength, ductility, and creep deformation rate in 2.25Cr1Mo0.25V steel weldment needs to be considered for the design and integrity assessment of hydrogenation reactors.

Hot Deformation Behavior and Strain Rate Sensitivity of 33MnCrB5 Boron Steel Using Material Constitutive Equations

In this paper, the constitutive equation parameters (Johnson–Cook parameters) of the 33MnCrB5 material were determined with the help of tensile tests. Initially, Johnson–Cook (JC) model was used for performing the simulations of the sample with finite element analysis with the help of ANSYS software. For these operations, the sample was first used at a certain temperature (24 °C) and low strain rates (10−1, 10−2, 10−3 s−1) and quasi-static tensile tests were performed. Then, high temperature tensile tests were performed with strain rate values of 10−3 s−1 at temperatures of 300 °C, 600 °C, and 900 °C, respectively. Finally, JC parameters belonging to test materials were found in accordance with the results obtained from the high temperature tensile and quasi-static tests. In the last stage, the results obtained from the simulation software for the yield stress, maximum stress, and elongation values were compared with the experimental results. As a result, deviation values for quasi-static tests are calculated as 5.04% at yield stress, 5.57% at maximum stress, and 5.68% at elongation, while for high temperature, yield stress is 9.42%, maximum stress is 11.49% and the elongation value is 7.63%. The accuracy of JC parameters was verified with the comparison made with the obtained data.

Effects of Heat Treatment on High Temperature Mechanical Property and Corrosion Resistance of Hastelloy X Manufactured by Selective Laser Melting

In previous studies, the microstructure, mechanical properties and corrosion resistance of Hastelloy X fabricated by selective laser melting (SLM) have been investigated; however, it is hoped that heat treatment will effect on its properties. Therefore, this study is to discuss heat treatment effect on Hastelloy X fabricated by SLM. It is interestingly found that fracture strain greatly increases with heat treatment, and the yield ratio decreases, which demonstrates the material is more reliable. High temperature tensile behavior is discussed; it is worth mentioning that not only fracture strain of the HT sample increases greatly at 550∘C in comparison with SLM sample, but also ultimate tensile strength increases from 632 MPa to 639 MPa; the results show that the mechanical property can be improved at medium and high temperature by heat treatment. The corrosion resistance of HT sample deteriorates slightly, which can be explained by Cr-rich precipitates. In conclusion, the material after heat treatment is suitable for applications requiring high mechanical reliability and medium and high temperature occasions, but it is not befitting for corrosive environments.

Study of Factors Affecting Tensile Strength of Grey Cast Iron

Tensile strength of a material is the capacity of material to withstand tensile force without failure. Tensile strength is important mechanical property of material which gives direction to use it for proposed application safely. It is very important parameter considered in designing sound product. Grey cast iron carries properties like high compressive strength, castable, good machinability, good abrasion resistance, high thermal conductivity, resist to expand under high temperature. Tensile strength of grey cast depends mainly on carbon content, steel scrap % used, inoculation, graphite morphology, cooling time. Present paper summarizes study of factors affecting tensile strength of grey cast iron. With the study of factors affecting the tensile strength of cast iron it is very helpful to achieve required tensile strength by controlling the factors affecting strength of the material. While studying and experimenting on the behavior of tensile strength, clear idea comes into the picture how the strength is affected.

The High-Temperature Tensile Test of Quartz Fiber Fabric- Reinforced Resin Composites

The tensile properties of quartz fiber fabric-reinforced resin composites at high temperature were studied. The effects of specimen type and dimension, temperature loading procedure, holding time and loading rate on the tensile properties of the composites at high temperatures were analyzed through series of comparative experiments, the tensile test parameters were determined. Chinese national standard for high-temperature tensile property testing of the composites was compiled based on the data collected. According to the established standard, the tensile testing at 500°C was carried out. Compared with the tensile properties at room temperature, the tensile strength and tensile modulus of the composite at high temperature decreases significantly, with the tensile strength decreasing by about 42.32% and the tensile modulus decreasing by about 24.18%. This is mainly due to the high temperature which causes part of the resin matrix to pyrolyze and detach from around the fiber, thus losing the integrity of the material. In addition, this national standard for high-temperature tensile properties has some general applicability to different types of fiber-reinforced resin composites.

Effects of Stabilizing Heat Treatment on Properties of Simulated Microstructures in the Heat-Affected Zone of 347H Stainless Steel

In this paper, two kinds of heat affected zone (HAZ) simulation structures of 347H stainless steel, which are coarse grain zone (CGZ) and unmixed zone (UZ), were prepared by thermal simulator. The material properties of toughness, reheat crack susceptibility and intergranular corrosion susceptibility of the two kinds of HAZ simulation structures were studied by impact test, high temperature tensile test, electrochemical potentiodynamic reactivation (EPR) test and micro morphology test. The result shows that CGHAZ had better toughness. But after the stabilizing heat treatment, it was weakened while that of the UZ was enhanced. The reheat crack susceptibility of the CGZ and UZ both increases after stabilization heat treatment, and the tendency of the UZ are more obvious. Stabilizing heat treatment has a certain effect on the prevention of sensitization process, which can improve the intergranular corrosion resistance of the material. Stabilizing heat treatment is double-edged to 347H HAZ, and it needs combined with the specific situation to used.