Continuous cooling transformation behavior in the weld coarse grained heat affected zone and mechanical properties of Nb-microalloyed and HY85 steels

Effect of cooling rate and composition on microstructure and mechanical properties of ultrahigh-strength steels

“…The toughness properties including impact toughness at room temperature and -40°C and ductile fracture (DF) percentage are increased when the cooling rate increased from 0.01 to 1°C/s and then decreased when CR increased to 60°C/s. The same trend was observed by Kumar et al [20]. The decrease in toughness at the highest cooling rate (60°C/s) may be attributed to the very high strength values, and the presence of less retained austenite compared with the other cooling rates [35].…”

“…5a. This behavior may be due to the increasing loss of carbon from the martensite laths into an increasing volume fraction of retained austenite as explained below [20]. Increasing the cooling rate from 0.01 to 0.08°C/s has no effect on the microhardness of the bainite as shown in Fig.…”

Isothermal Transformation Behavior and Microstructural Evolution of Micro-Alloyed Steel

“…The base metal micrograph consists of pro-eutectoid ferrite and pearlite as shown by arrow in Figure 2a. The pearlite structure is found to be in banded form in the direction of rolling [6]. The average grain size of pro-eutectoid ferrite is found to be in range of 10 ± 3 μm.…”

“…However, carbide precipitates precipitate inside ferrite plates in lower bainite [11]. Engineering Steels and High Entropy-Alloys 6 As there is a decrease in temperature (500°C), the amount of upper bainite is found to be decreasing and more refined due to the lower transformation temperature, and subsequently lower bainite reveals (Figure 3a). At 450°C, the fraction is fully transformed into lower bainite with small amount of upper bainite as can see in Figure 3b.…”

Determinação dos diagramas de aquecimento e resfriamento do aço API 5L X70Q através do calor latente de transformação de fase

“…Porém, no caso do limite inferior (início das transformações), a taxa de aquecimento teve uma ligeira interferência. .25 0,056 0,180 1,820 0,020 0,213 0,208 0,005 0,020 0,013 0,086 0,450 0,206 Figura 6.27 0,130 0,250 1,530 0,010 0,056 0,043 0,387 0,496 Figura 6.28 0,065 0,290 1,550 0,280 0,086 0,379 0,171 Figura 6.29 0,040 0,250 1,710 0,006 0,202 0,000 0,156 0,214 0,112 0,391 0,158 Figura 6.27 -Diagrama CCT de um aço microligado de composição com 0,13% C, 0,25% Si, 0,007% S, 1,53% Mn, 0,003% P, 0,043% Nb e 0,002 Al, levantado por Kurma et al (2015): as taxas de resfriamento foram de 0,5 até 120 °C/s, com formação de ferrita (F) e perlita (P) entre as taxas de resfriamento de 0,5 a 3 k/s, formação de bainita (B) entre as faixas de 3 até 40 k/s e para taxas de resfriamento maiores do que 40 k/s formação de martensita (M) Figura 6.28 -Diagrama CCT para um aço API 5L X80 de composição 0,065% C, 0,29% Si, 1,55% Mn, 0,015% P, 0,003% Al, 0,28% Mo, 0,076%Nb e 0,020%Ti levantado por Cizek et al (2005): com taxas de resfriamento extremamente baixa ocorreu formação de perlita de 0,1 a 1 °C/s, enquanto para as taxas de resfriamento de 1 até 34 °C/s verificase formação de ferrita acicular (GF), classificando como: (B) bainita, (QF) ferrita quase poligonal, (P) perlita, (PF) ferrita poligonal, (M) martensita, (BF) bainita fina.…”