Improved Toughness of a High‐Strength Low‐Alloy Steel for Arctic Ship by Ni and Mo Addition

Self Cite

Keeping through‐thickness homogeneity of mechanical properties has been a great challenge for producing heavy gauge steel plates. Herein, a superior homogeneity of microstructure and hence strength and toughness achieved in a quenched and tempered (QT) 210 mm‐thickness steel plate produced by advanced electroslag remelting casting and roller quenching (ESR–RQ) technologies are reported. Some comparisons are made with a QT 178 mm steel plate produced by conventional mold casting and immersion quenching in the water tank (MC‐IQ). The martensite of the as‐quenched ESR–RQ steel is distributed homogeneously across the thickness with a fraction of 39% at the 1/2 thickness, remarkable higher 34% than that of MC‐IQ steel. ESR–RQ steel appears excellent comprehensive mechanical properties even for the as‐quenched samples, as well as QT samples. Comparing with the MC‐IQ steel, the Charpy impact energy at −60 °C is 150 J (278%) higher for the samples tempered at 650 °C, and the yield strength is 137 MPa (18%) higher for the samples tempered at 600 °C than those of MC‐IQ steel, respectively. The considerable improvement can be attributed to homogeneous through‐thickness microstructures, including refined prior austenite grains, effective grain size, and carbide precipitates.

Section: Precipitation Behaviormentioning

confidence: 99%

Superior Through‐Thickness Homogeneity of Microstructure and Mechanical Properties of Ultraheavy Steel Plate by Advanced Casting and Quenching Technologies

Wang

et al. 2021

Self Cite

“…According to Figure 5c, it is evident that the solution strengthening of the T-630, T-650, and T-670 specimens gradually increases. The grain boundary strengthening of the specimens can be calculated based on the Hall-Petch equation as follows: [36] Δσ gb ¼ k y d À1=2 EGS (6) where k y is the Hall-Petch coefficient, for tempered martensitic steel, k y = 120 MPa μm 1/2 , [37] and d EGS is the equivalent grain size (EGS), μm. The finer the equivalent grain size of the specimens, the greater its ability to withstand deformation under external loads.…”

Section: Strengthening Mechanismmentioning

confidence: 99%

“…[ 1–3 ] In response to the growing demand for exploring deep‐sea resources, research on marine materials worldwide is increasingly focused on achieving high strength and high toughness, particularly at cryogenic temperatures. [ 4–6 ] In general, the high strength of steel often results in limited impact toughness, especially at low temperatures, which restricts the application of high‐strength steel in specific fields. To achieve a better balance between strength and toughness, metallurgists have conducted extensive research.…”

Section: Introductionmentioning

confidence: 99%

Study on Microstructure and Mechanical Properties of Marine 10Ni5CrMoV Steel during Tempering

Zou,

Dong,

Jiang

et al. 2024

The microstructure and mechanical properties of marine 10Ni5CrMoV steel are systematically investigated at tempering temperatures ranging from 630 to 670 °C. With increasing tempering temperature, several key parameters exhibit notable changes: the volume fraction of reversed austenite decreases from 17.36% to 13.39%. The equivalent grain size increases from 0.91 to 1.09 μm. The equivalent diameter of precipitates increases from 59 to 79 nm. The dislocation density decreases from 0.82 × 10−15 to 0.51 × 10−15 m−2. As the tempering temperature increases, the pinning effect of precipitates on dislocations and martensite laths decreases. This leads to reductions in both dislocation strengthening and precipitation strengthening mechanisms. Consequently, the yield strength of the specimen decreases from 876 to 683 MPa. The increase in the ductile‐brittle transition temperature of the specimens from −116 to −95 °C can be attributed to several factors. First, the increase in precipitate size reduces the critical nucleation stress of cleavage cracks and promotes the nucleation of such cracks. Additionally, the decrease in dislocation density mobility leads to a reduction in the dimple nucleation rate, thereby diminishing the role of dimples in hindering crack propagation.

“…For example, the presence of microstructure inhomogeneity along the thickness direction (TD) results in a reduction in mechanical properties. [ 3 ] In addition, for body‐centered‐cubic metal materials, the toughness is sensitive to temperature change and decreases with decreasing temperature, and the ductile–brittle transition will occur when the temperature is below a certain level. [ 4 ] Therefore, to ensure the secure utilization of large equipment, the enhancement of low‐temperature toughness is crucial as it signifies the overall resistance of the materials to brittle fracture failure.…”

Section: Introductionmentioning

confidence: 99%

The Low‐Temperature Toughness Improvement of High‐Strength Low‐Alloy Steel Due to the Microstructural Changes Caused by the Reheating/Rolling Temperature

Liu,

Zhao,

Tian

et al. 2024

Self Cite

Herein, the microstructure, low‐temperature toughness, and fracture characteristics of high‐strength low‐alloy (HSLA) steel prepared by various thermomechanical control processes are systematically studied. Three different reheating/rolling temperatures are designed to obtain microstructures with different prior austenite grain sizes: 20.12 μm (S810), 27.58 μm (S910), and 35.19 μm (S1010). After hot rolling, S810 steel with smaller prior austenite grain size can provide high‐density deformed grain boundaries that promote ferrite phase transformation. The S910 and S1010 steels predominantly undergo bainite transformation as the prior austenite grain size and rolling temperature increase. Also, excellent low‐temperature toughness is obtained by reducing the reheating/rolling temperature (i.e., S810 steel), reflecting that Charpy impact energy of the core of the steel plate is 118.53 J at −120 °C. High performances is mainly attributed to the higher ferrite content, grain refinement, lower dislocation density, and higher proportion of high‐angle grain boundaries. Furthermore, fracture morphology analysis demonstrates that the S810 steel exhibits ductile fracture and noticeable plastic deformation at −120 °C, while S910 and S1010 steels exhibit brittle fracture and rapid crack propagation. These findings manifest the applicability of the suggested technique in preparing HSLA steel with excellent low‐temperature toughness.