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Types of Corrosion in the Offshore Environment
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
Let’s start from the first condition: tensile stress. The type of tensile stress could be applied or residual or a combination of both. As explained above, residual stresses are those that are locked inside a material due to mechanical or thermal loads. As an example, welding can cause thermal stress as well as residual stress inside a material. A heat-affected zone (HAZ) is defined as an area adjacent to welding that is not melted, but in which the microstructure and properties of the material are altered because of the welding. HAZ areas are shown in Figure 1.44 around the welding and are different in color from the base metal. Many crack failures happen in HAZs close to welding areas when the stress value exceeds certain limits. The outcome of stress is strain, which is defined as the ratio of a material’s expansion to its initial length. Strain is another parameter that is taken into account in the HISC study and evaluation.
Design of Welded Joints
Published in Harold Josephs, Ronald L. Huston, Blake’s Design of Mechanical Joints, 2018
Harold Josephs, Ronald L. Huston
There are certain similarities between the casting and welding of steel. The most significant problem with the HAZ is that the metal adjacent to the weld develops a coarse microstructure leading to reduction in fatigue resistance. Single- and double-fillet tee joints can act as built-in stress risers.
Basic Materials Engineering
Published in David A. Hansen, Robert B. Puyear, Materials Selection for Hydrocarbon and Chemical Plants, 2017
David A. Hansen, Robert B. Puyear
A heat affected zone (HAZ) is a volume of the parent metal in which the mechanical properties and/or the microstructure have been changed by the heat of welding or thermal cutting. For most welds in carbon and low-alloy steels, the HAZ is a band, usually about 1/8” (3 mm) wide, adjacent to the fusion line of the weld. In austenitic stainless steels, a narrow, secondary HAZ may be generated at some distance from the fusion line, as a result of welding-induced sensitization. This effect is illustrated in Figure 2-5.
Laser and hybrid laser welding of type 316L(N) austenitic stainless steel plates
Published in Materials and Manufacturing Processes, 2020
The HAZs are formed due to the welding heat source, and the width of the HAZ depends on the intensity of heat input. The HAZ grain size is influenced by the cooling rate and peak temperature-induced by the welding processes. HAZ contains coarse grains when compared with the base metal (40 µm), which can be easily distinguished by using the optical microscope. The average grain size in different HAZs, measured by an optical microscope utilizing the ASTM E112 standard, are shown in Table 3. The fusion boundary and HAZs of laser and hybrid laser welding processes are shown in Fig. 3.
Effect of Welding Speed and Post-Weld Heat Treatment on Microstructural and Mechanical Properties of Alpha+Beta Titanium Alloy EB Welds
Published in Fusion Science and Technology, 2023
Vamsi Krishna K, Gopi Krishna C, Ateekh Ur Rehman, Kishore Babu Nagumothu, Mahesh Kumar Talari, Prakash Srirangam
Additionally, the welds made with the 800 mm/min welding speed (low heat input) exhibit the highest hardness in the FZ as compared to the 500 and 700 mm/min welding speeds. This increase in the hardness is due to the formation of fine densely packed α´ martensite in the FZ due to higher cooling rates. On the other hand, the higher hardness in the HAZ region compared to that of the BM is due to traces of α´ martensite in the as-welded conditions of all the welding speeds. It is noted that as the welding speed increases, the heat input decreases, which in turn reduces the width of the HAZ.
Dealing with Defects and Strengthening Historical Steel Bridges
Published in Structural Engineering International, 2023
Jakub Vůjtěch, Pavel Ryjáček, Jose C. Matos
The Chromium content should not exceed 0.2%, in order to avoid affecting weldability. Chromium improves the corrosion resistance and increases the hardenability of steel. In higher contents, it may cause excessive hardness of the steel and cold cracking in the HAZ.