Carbide precipitation in austenite of Nb–Mo-bearing low-carbon steel during stress relaxation

Zhang, Zhengyan; Sun, Xinjun; Wang, Zhenqiang; Li, Zhaodong; Yong, Qilong; Wang, Guodong

doi:10.1016/j.matlet.2015.06.111

Cited by 22 publications

(6 citation statements)

References 15 publications

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“…Therefore, the interfacial structural energy of the matrix/carbide changes. On the other hand, the continuity of carbidizing elements reduces the contribution of chemical bonding energy to surface energy, which is a factor that reduces the surface chemical energy [ 30 ].…”

Section: Resultsmentioning

confidence: 99%

The Effect of Adding V and Nb Microalloy Elements on the Bake Hardening Properties of ULC Steel before and after Annealing

et al. 2023

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Bake hardening (BH) is a vital part of special steel production. Studies in this field have focused on steels under homogeneous yielding, but until now, none have been conducted on the phenomena that occur for steels under heterogeneous yielding. In the current study, the effect of adding Nb and V alloying elements on the strength of ultra-low carbon (ULC) steel after bake hardening was investigated. The effects of pre-strain, grain size, and recrystallization annealing temperature were analyzed, as well as the effect of Nb and V on the yield stress caused by the bake hardening process. For this purpose, five types of alloys with different V and Nb contents were melted, cast in an induction furnace, and subjected to hot hammering and hot rolling. Then, cold rolling was applied to the samples by ~80%. To eliminate the effects of cold working, tensile samples were subjected to recrystallization annealing at 750 and 800 °C for 30 min, and the samples were quickly quenched in a mixture of a NaCl solution and ice. The annealed samples were subjected to a pre-tensile strain in the range of 2–12% and then aged in a silicone oil bath at 180 °C for 30 min. Then they were subjected to a tensile test. The obtained results showed that with the increase of the pre-strain and the annealing temperature, the values of baking hardness increased. The presence of V in the composition of steel reduced the annealing temperature.

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Section: Resultsmentioning

confidence: 99%

The Effect of Adding V and Nb Microalloy Elements on the Bake Hardening Properties of ULC Steel before and after Annealing

et al. 2023

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“…Through the statistical analysis, (V, Nb, Ti) C had a higher volume fraction of fine precipitates in the steel, and the precipitation strengthening of the steel was greater. According to [ 29 , 30 ], Nb nano precipitates mainly formed during rolling and cooling at austenite grain boundaries or ferrite matrix.…”

Section: Results and Analysismentioning

confidence: 99%

Effect of Thermal Simulation Process on Microstructure of Seismic Steel Bars

Huang

et al. 2022

Materials

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Thermal deformation has a significant influence on the microstructure of high-strength antiseismic steel. The effect of hot deformation on the microstructure of experimental steel was studied by the Gleeble-3800 thermal simulator. The microstructure of the steel was characterized by the metallographic microscope, microhardness, tensile test, field emission scanning electron microscope, electron backscatter diffraction, and high-resolution transmission electron microscope. The results show that the core microstructure of the test steel is composed of polygonal ferrite and lamellar pearlite. The test steel is mainly ductile fracture. Tensile strength and hardness increase with the decrease of temperature. At 650 °C isothermal temperature, the ferrite distribution was uniform, the average grain size was 7.78 μm, the grain size grade reached 11, the pearlite lamellar spacing was 0.208 μm, and the tensile fracture was distributed with uniform equiaxed dimples. Polygonal ferrite grain boundaries have high density dislocations that can effectively block the initiation and propagation of cracks. However, there are some low dislocation boundaries and subgrain boundaries in ferrite grains. Precipitation strengthening is mainly provided by fine precipitates of V-rich carbonitride in experimental steel. The precipitates are round or narrow strips, about 70–100 nm in size, distributed along ferrite grain boundaries and matrix.

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“…Owing to the high coherency between MC nano-carbides and matrix in the HWD700 steel, the nano-carbides have lower elastic strain energy and interface energy, increasing the thermal stability of the MC nano-carbides at high temperatures. [39] An equilibrium-phase calculation of the HWD700 steel was performed in our earlier study. [20] The precipitation of MC carbides is strongly encouraged while the precipitation of M 23 C 6 carbides is inhibited by the addition of V, Mo, and W. Instead of precipitation of MC carbides, the combination of Cr and C increases the precipitation of M 23 C 6 carbides.…”

Section: Discussionmentioning

confidence: 99%

Microstructure Stabilities of Newly Developed Hot‐Working Die Steel and H13 Steel at Elevated Temperature

Zhang

Cao

Chen

et al. 2023

steel research int.

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Hot-working die steels have an important role in the development of the industry and society, and they are widely used in industrial manufacturing due to their good mechanical properties, wear resistance and thermal resistance. [1][2][3][4] With the rapid increase in industrial and manufacturing requirements, dies need to operate under severe conditions of high temperature and pressures. The peak temperature at the surface of dies can reach even 700 °C, and exceed the tempering temperature. This inevitably leads to an evolution of the microstructure and degradation of mechanical properties, such as the hardness, strength, and thermal fatigue properties, strongly related to the service life of dies. [4,5] Therefore, the microstructure stability of hot-working die steels is of significance.The martensite lath structure is in a metastable state with a low thermal stability. The strength and hardness of the steel rapidly decrease with the recovery and disappearance of the lath structures in a martensitic steel. [6][7][8] Alloying with high levels of alloying elements is usually regarded as an effective approach to improve the thermal stability of a metallic material, but it is not a universally applicable method and is not conducive to some important properties of steels. For example, Cr is an important alloying element in a heat-resistant steel, and 9-12% Cr is usually added in the heat-resistant steel to form M 23 C 6 carbides always distributed along lath boundaries and grain boundaries to hinder their migration and recrystallization during creep. [9,10] However, the M 23 C 6 carbide is not conducive to the thermal fatigue performance and thermal stability of hot-working die steels owing to its fast coarsening. [5,11] The growth rate of M 7 C 3 in low-Cr alloys is slower than that of M 23 C 6 , which can be used as a type of precipitation pinning the microstructure interface. [12,13] Owing to the excellent thermal stability, the MC carbide can effectively hinder the recovery and recrystallization of the microstructures at temperatures lower than 600 °C. [14] Moreover, at a temperature below 0.5 T m , the deformation mechanism of steel materials is still the slip of dislocations. The stable and fine MC carbide can provide an excellent strengthening effect for the matrix under high-temperature conditions. [15,16] Therefore, the typical microstructures of hot-working die steels contain carbide forming elements such as Cr, Mo, and V to form the fine dispersed MC or M 2 C nano-carbides. [17] However, the microstructures of the present commercial hot-working die steels still becomes unstable when the temperature is increased to 600-650 °C. [6,11] In a previous study, a Cr-Mo-W-V HWD700 steel was developed, which exhibits a high strength as well as excellent fatigue performance at temperatures up to 700 °C strengthened by MC (M = V, Mo, W) nano-carbides. [18][19][20] However, the microstructure stability of the HWD700 steel at an elevated temperature has not been extensively investigated. In this study, the

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Carbide precipitation in austenite of Nb–Mo-bearing low-carbon steel during stress relaxation

Cited by 22 publications

References 15 publications

The Effect of Adding V and Nb Microalloy Elements on the Bake Hardening Properties of ULC Steel before and after Annealing

The Effect of Adding V and Nb Microalloy Elements on the Bake Hardening Properties of ULC Steel before and after Annealing

Effect of Thermal Simulation Process on Microstructure of Seismic Steel Bars

Microstructure Stabilities of Newly Developed Hot‐Working Die Steel and H13 Steel at Elevated Temperature

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