Steel pipelines are commonly used in the petroleum industry where high strength and durability values are required. In oil installations, the problems of corrosion, especially with crude oil, appear clearly and dramatically, in dealing with API 5L series. Improving the corrosion protection and mechanical properties are a genius goal for steel manufacturers, the heat treatment processes are familiar with this field. In this study, experimental investigations were executed to find the heat treatment influence on the corrosion rate, microstructure, and mechanical properties behavior of API 5L X60 pipeline steel in the presence of three different environments: seawater, freshwater, and crude oil. Two austenitizing temperatures 900°C and 800°C were prepared followed by quenching at 600°C, 450°C, and 300°C respectively, where the corrosion rate was estimated by the mean weight loss method. In this study, more than 60% of the corrosion rate in both seawater and freshwater was improved at 900 ºC austenitizing tempered at 300ºC for the selected pipeline specimens while only 22% reduction was achieved in crude oil. Different microstructure phases appeared in the heat-treated specimens such as tempered martensitic at 300°C and fine-grained ferrite with polygonal ferrite at 600°C. The microhardness values decreased with increasing the tempering temperatures while impact toughness values increased with tempering temperature increasing from 300°C until it was reached 450°C and then return to decrease again in 600°C.

Enhancing corrosion resistance in stainless-ssteel alloys is a paramount objective in the petroleum industry. This study investigated the effects of the previous cold working and welding processes on the mechanical properties and corrosion rates of 204 Cu stainless steel in different aggressive environments (crude oil, freshwater, and seawater). The experimental sets were supported by microstructure analysis. The mean weight loss method was employed to determine the corrosion rates, which were optimized using the Taguchi method. The ferrite and austenite phase bands, as well as the deformed portions of austenite, are pushed to flatten out during cold working, which increases the material’s hardness. Cold-worked steels were welded, creating an annealed area around the HAZ in addition to the usual weld zones, which demonstrated partial microstructure recovery and hardness reduction. HAZ showed signs of iron overload and chromium nitride precipitation. Cold-worked specimens only showed reduced corrosion resistance to 30% of the initial rate and reduced thickness. Moreover, the Taguchi optimization technique indicated that the corrosion environment has the most effect on the corrosion rate compared to the cold work ratio for welded and non-welded stainless-steel specimens.

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The aim of this study is to investigate the effect of heat treatments on the impact properties of hot rolled high strength steel and describes the effect of tempering temperature and quenching media on the microstructure, hardness, and impact resistance of plates. In the present study a high strength steel was austenitized at 900 °C with different quenching medium and followed by tempering at 300 °C, 500 °C. After thermal treatments, the values of Charpy impact resistance, hardness, and microscopic structure were evaluated from mechanical and metallographic analysis of metals respectively. The change of mechanical properties and microstructure of the metal with the existence of heat treatment with the ballistic performance of high-strength steel. Experimental results showed that tempering at 500 °C for 2 hours after water quenching medium it provides the best mechanical properties in conjunct on with an improved in microstructure.

Submerged Arc Welding (SAW) is a safe and efficient process for joining thick plates AISI 1020. A high-quality weld joint is a critical objective in a series of optimization studies. The current study focuses on maximizing the ultimate tensile strength and minimizing the peak temperature using Taguchi, Genetic Algorithm (GA), and Simulated Annealing (SA) algorithms. The input parameters in the three techniques were voltage (V), welding speed (S), and wire feed rate (F). At a 95% confidence level, the regression models were combined using the ANOVA to predict tensile strength and peak temperature. The maximum ultimate tensile strength was 599MPa achieved at a welding speed of 30 mm/s, an arc voltage of 30 V, and a wire feed rate of 120 mm/s, while the minimal peak temperature was 417C under the same conditions. With the increase of the welding parameters (welding speed, arc voltage, and feed rate), the ultimate tensile strength was increased. Furthermore, the average hardness achieved was 250 at welding metal and 292 at HAZ, while it was 275 at the base metal. The results were supported with an examination of microstructure. In the heat-affected zone (HAZ), the grain was finer while its grain size was larger in specimens with high tensile strength. It was noticed that the HAZ contains pearlite and some colonies of ferrite.