Effect of Heat Treatment on Microstructure and Mechanical Properties of High-Strength Steel for in Hot Forging Products

Abstract

High-strength steel is widely used in hot forging products for application to the oil and gas industry because it has good mechanical properties under severe environment. In order to apply to the extreme environment industry requiring high temperature and high pressure, heat treatments such as austenitizing, quenching and tempering are required. The microstructure of high-strength steel after heat treatment has various microstructures such as Granular Bainite (GB), Acicular Ferrite (AF), Bainitic Ferrite (BF), and Martensite (M) depending on the heat treatment conditions and cooling rate. Especially in large forged products, the difference in microstructure occurs due to the difference in the forging ratio depending on the location and the temperature gradient according to the thickness during post-heat treatment. Therefore, this study attempted to quantitatively analyze various phases of F70 high-strength steel according to the austenitizing temperature and hot forging ratio using the existing EBSD analysis method. In addition, the correlation between microstructure and mechanical properties was investigated through various phase analysis and fracture behavior of high-strength steel. We found that various microstructures of strength steel depend on the austenitizing temperature and hot forging ratio, and influence the mechanical properties and fracture behavior.

Partial austenitisation and TBF steel composed of ferrite, bainitic ferrite, and austenite

“…Based on recent studies on microstructural analysis on steels [20,[27][28][29][30], the GOS map can be used for separating BCC components such as ferrite, bainite, and martensite. Figure 10(c,g,k) presents the GOS maps of ferrite.…”

Effect of Cooling Rate on Microstructure and Mechanical Properties According to Heat Treatment Temperature of Inconel 625

“…inconel 625, a ni-based superalloy, is typically used in extreme environments due to excellent mechanical properties such as high strength, corrosion resistance, abrasion resistance and lowtemperature toughness [1][2]. in order to be applied to piping systems in extreme environments, forged flanges manufactured by hot forging are mainly used and have the advantage of obtaining excellent mechanical properties such as high strength and ductility [3][4]. however, when manufacturing a hot forged flange with a thick and complex shape, the cooling rate varies depending on the location due to the difference in thermal gradient during the cooling process after hot forging [5][6].…”

Microstructure and Hardness of Cold Forged 42CrMo4 Steel Hollow Component with the Outer Flange

“…Interesting results have been obtained by Li et al [19], who proposed a formula that describes the full range strain hardening behavior of steels. Besides, microstructure analysis is crucial for the evaluation of the effects of initial heat treatment for plastic processes [20,21], the quality of plastic forming processes [22], or identifying the macro-and microstructure nonuniformities [23,24]. Therefore in the current paper, all mentioned features were considered while evaluating the quality of the fabricated hollow part.…”