Toughness Of Steel Research Articles

Application of Surface-Cracking Process to Improve Impact Toughness of High-Strength BCC Steel at Low Temperatures

At very low temperatures, typically ductile materials, especially body-centered cubic (BCC) steels, often exhibit an abrupt transition to brittle fracture, significantly limiting their applicability in cryogenic and low-temperature environments. This challenge arises from the inherent properties of BCC steels, where ductility is drastically reduced, leading to unexpected failures under mechanical stress. Despite the advantages of high-strength BCC steels, including cost-effectiveness and mechanical robustness, their susceptibility to brittle fracture restricts their use in demanding low-temperature applications. To address this limitation, we developed an innovative surface-cracking process to enhance the impact toughness of BCC steels. The introduction of controlled surface cracks redistributes stress and energy dissipation mechanisms, improving the toughness of high-strength BCC steels at cryogenic temperatures. Microscopic observations and finite element analyses reveal that these surface cracks not only dissipate crack formation energy but also alter stress triaxiality at crack tips. This causes the stress state to transition toward a plane stress condition, effectively mitigating stress concentrations typically observed in plane strain states. By reducing localized stress severity and promoting uniform energy distribution, the surface cracks encourage failure mechanisms favoring ductile behavior over brittle fracture.

Precipitation-controlled grain boundary engineering in a cast & wrought Ni-based superalloy

Grain boundary engineering (GBE) describes the various approaches to control the fraction and composition of special boundaries in designing engineering materials. For example, complex thermo-mechanical processing routes are harnessed to increase the fraction of Σ3 twin boundaries, bringing about improvements to strength, toughness, and corrosion properties in austenitic stainless steels. However, high-temperature gas turbine engine components designed for the most demanding applications must be manufactured from Ni-based superalloys. To provide the required high-temperature strength, their microstructures are highly complex and consist of an austenitic γ-matrix, γ' precipitates, and grain boundary (GB) carbides, and/or borides. GBE approaches for Ni-based superalloys have been reported to reduce in-service GB cracking via targeted engineering of the GB microstructure. However, the same complex microstructures severely limit the processability of the most advanced Ni-based superalloys required to develop the next generation gas turbine engines.To tackle this challenge, we propose precipitation-controlled GBE for Ni-based superalloys with limited formability, via formation of GB serrations and precipitation upon slow cooling. We showcase our approach by achieving controlled GB precipitation of GB-γ' and M6C carbides in the cast & wrought Ni-based superalloy René 41 via a simple heat treatment. Ductility improvements are predicted via crystal plasticity modeling due to increased slip transmission compatibility. Instead of generating additional Σ3 twin boundaries only, these interfaces are directly incorporated into the GB network. It is shown that precipitation-controlled GBE is enabled by GB-γ' nucleating heterogeneously on M6C whereby competitive coarsening of GB-γ' provides the driving force. The fundamental mechanisms of our GBE approach are discussed and summarized in a qualitative microstructural model.

Modelling the geometry constraints on the cleavage fracture toughness in ferritic steels

Modelling the geometry constraints on the cleavage fracture toughness in ferritic steels

Effects of (Ti, Mo)C precipitation on the microstructure, impact toughness, and sulfide stress corrosion cracking resistance of linepipe steels

Effects of (Ti, Mo)C precipitation on the microstructure, impact toughness, and sulfide stress corrosion cracking resistance of linepipe steels

Study of the mechanical and tribological behaviour of a low-alloy steel treated by nitriding

This study investigates the effects of plasma nitriding treatment on the mechanical surface properties of 25Cr2Ni4W low alloy steel, using Charpy test specimens. Plasma nitriding is a surface modification process that introduces nitrogen into the steel, enhancing its hardness and wear resistance. The experimental setup involved a comparative analysis of treated and untreated specimens to evaluate the impact of the nitriding process on the material’s mechanical performance.Optical microscopy (OM) analysis of the nitrided specimen revealed the formation of a nitride zone at the surface, confirming successful nitrogen implantation. The Charpy impact test showed that the treated specimen required 72.8 Joules of energy to fracture, a significant increase of 10.3 Joules compared to the untreated specimen, which required only 62.5 Joules. This indicates that plasma nitriding improved the material’s toughness and resistance to crack propagation. Additionally, the nitriding process led to an increase in nano-hardness, as measured using nanoindentation techniques. The treated specimen exhibited a higher surface hardness compared to the untreated sample, further enhancing its wear resistance and durability. These results suggest that plasma nitriding effectively improves both the hardness and toughness of 25Cr2Ni4W low alloy steel, making it a promising treatment for applications requiring enhanced mechanical performance, particularly in high-stress environments.

Unraveling the significance of cobalt on transformation kinetics, crystallography and impact toughness in high-strength steels

Unraveling the significance of cobalt on transformation kinetics, crystallography and impact toughness in high-strength steels

Effect of Pore Size on the Precipitation of Iron-Rich Phase and Impact Toughness in Copper-Infiltrated Steel

Effect of Pore Size on the Precipitation of Iron-Rich Phase and Impact Toughness in Copper-Infiltrated Steel

Design and Manufacture of Intelligent Filter Processing System of Modular Cutting Fluid

For the needs of ecological protection and high-quality development in the Yellow River Basin, the project plans to design and produce the intelligent filtration treatment system of modular cutting fluid, which is caused by the massive application of cutting wastewater and the improper treatment will cause serious damage to the environment. Through the study of the action mechanism of semiconductor inorganic film on cutting liquid, the development and application verification of cutting liquid filtration system and the development of cutting liquid online monitoring system, a complete set of semiconductor inorganic film high strength toughness steel cutting liquid filtration technology and equipment is formed, providing technical support for green, high efficiency, energy saving and environmental protection cutting fluid treatment. To solve the problem of improper treatment of cutting waste liquid after the processing process of deep hole parts of high strength and toughness steel. Keywords: modularization, online detection, semiconductor inorganic film.

Fracture Toughness Behaviour of Nickel Alloy Steel 1.5662.

Nickel significantly increases the toughness of steel and makes it ideal for use in applications that require high impact and fracture resistance at low temperatures. These inherent advantages position nickel steel as indispensable material in various domains, with a pronounced presence in stationary Liquefied Natural Gas (LNG) tanks and in the shipbuilding industry, particularly for tanks in vessels intended for the transport of liquefied ethane and LNG. The presented study focuses on assessing the fracture toughness behaviour of nickel alloy steel 1.5662+QT640 under sub-zero and cryogenic temperatures. The fracture performance of the material was evaluated, specifically emphasizing the impact toughness and fracture toughness characteristics of the material. Moreover, it was discussed if the transferability of the experimental results to the well-known fracture mechanics-based concept of EN 1993-1-10, which relies on the master curve concept, is possible. The results show that the master curve concept is not applicable to the nickel alloy steel 1.5662+QT640 due to its exceptional fracture toughness behaviour at very low temperatures.

Experimental Investigation of the Effect of Input Control Variables and Thermal Treatments on the Impact Toughness of EN-31 Steel

To meet the engineering applications, mechanical and physical properties of materials especially steels and their alloys are improved through thermal treatments. This research aimed to augment the impact toughness of EN-31 steel by picking the combinations of different levels of Charpy impact test control variables and thermal treatments built in three-level (L9) Orthogonal Arrays (OAs). For this reason, the experimental runs were conducted to examine the influence of varying V-notch angles (30°, 45° and 60°), heights of the hammer (1370 mm, 1570 mm, and 1755 mm), temperatures (-196°C, -50°C, and 28°C), and heat treatments (hardening followed by cryogenic treatment and low-temperature tempering - HCTLTT, hardening followed by cryogenic treatment and medium-temperature tempering - HCTMTT, and hardening followed by cryogenic treatment and high-temperature tempering - HCTHTT) on the impact toughness of EN-31 Steel specimens. Several patterns of thermal treatment sequences were executed with an aim to modify the material properties. Cryogenic treatment (CT) was conducted through a cryocan at 77K. The hardness of specimens were measured by employing a Brinell hardness tester. The results reported that height of the hammer and thermal treatments enhanced the toughness and hardness of the specimens most significantly.

Revealing the Role of Pre-Strain on the Microstructure and Mechanical Properties of a High-Mn Austenitic Steel

The effects of different pre-strain levels on the dislocation density, twinning behavior, resultant tensile properties, and cryogenic impact toughness of a high-manganese austenitic steel for low-temperature service were investigated. The results indicate that the dislocation density and volume fraction of twins are sharply increased when the pre-strain exceeds 15%, leading to an increase in yield strength and a decrease in impact toughness. At a 5% pre-strain level, few mechanical twins are observed while the dislocation density increases, resulting in enhanced yield strength whilst maintaining the toughness. The dislocation and grain refinement strengthening effects dominate the yield strength at various pre-strain levels. The initial mechanical twins and increased dislocations induced by pre-straining adversely affect the impact toughness. These findings validate the potential of controlling the mechanical twins and dislocations via pre-strain treatment as an effective approach to tailoring the mechanical properties of high-manganese austenitic steel.

Study on the effects and mechanisms of ultrasonic impact treatment on impact toughness of Q345 steel welded joints

Study on the effects and mechanisms of ultrasonic impact treatment on impact toughness of Q345 steel welded joints

Effect of tempering temperature on low-temperature impact toughness of 35MnB steel

Effect of tempering temperature on low-temperature impact toughness of 35MnB steel

Corrosion, Impact Toughness and Tensile Properties of Duplex Stainless Steels Manufactured by Directed Energy Deposition

Duplex stainless steels provide a desirable combination of corrosion resistance, strength and toughness. Additive manufacturing of duplex stainless steels can be challenging due to high cooling rates and repeated reheating, which can produce detrimental microstructural constituents. In this study, a coaxial directed energy deposition system with laser and wire was used to deposit 2205, 2209 and 2509 duplex stainless steels. Corrosion resistance, strength and impact toughness in both as-built and solution annealed condition was tested and the microstructure was characterized. Solution annealing improved impact toughness considerably, produced a slight increase in corrosion resistance and a slight decrease in tensile strength. The 2205 material surpassed all common requirements and exhibited better corrosion resistance than 2209 due to less segregation between austenite and ferrite. Segregation of alloying elements was lower in intragranular austenite than grain boundary allotriomorph and Widmanstätten austenite. The 2209 and 2509 materials provided relatively low strength, especially in the solution annealed condition. For the 2509 material, sigma phase caused low as-built corrosion resistance and impact toughness. Overmatching welding consumables were found to be less suitable as feedstock for additive manufacturing due to high austenite content in the deposited material and lower corrosion resistance than conventional duplex compositions.

Design and control the selection of martensitic variant to simultaneously improve strength and toughness of low-carbon martensitic steel

In this paper, the microstructure evolution and mechanical properties of low carbon steels during direct quenched and rolling followed by water-cooled processes were studied. Two experimental steels, which were directly quenched at 900 °C (Q900) and 1000 °C (Q1000), were compared with steels that were water-cooled after rolling at the same temperatures (R900 and R1000). Microstructural analyses using EBSD and TEM revealed that rolling reduced the size of prior austenite grains (PAGs), resulting in an average width of 3.6 μm, which influenced grain boundary distributions and variant selection. The best combination of strength, ductility and toughness was obtained in R900 steel, including tensile (with the yield strength of 1304 MPa, the total elongation of 22.95 %), Charpy impact (with the impact energy at 20 °C is 182 J), and fracture toughness evaluations (with the J1c is 326.28 KJ/m2), this demonstrates that R900 steel exhibited significantly enhanced strength and ductility compared to Q900 steel. Moreover, EBSD analysis of crack propagation paths highlighted the role of high-angle grain boundaries (HAGBs) in enhancing fracture toughness by deflecting cracks. These findings underscore the critical role of PAGs size in tailoring microstructures to achieve superior mechanical properties in low carbon martensitic steels, offering insights for advanced material design and application in demanding structural and industrial contexts.Keyworks.low-carbon martensitic steel; strength and toughness; martensitic transformation; ductile-to-brittle transition phenomenon; selection of martensitic variants.

Mechanistic understanding of banded microstructure and its effect on anisotropy of toughness in low carbon-low alloy steel

In this study, the relationship between the anisotropy of toughness and microstructure in low carbon low alloy steel treated by quenching and tempering (QT) heat treatment was investigated with the aid of scanning electron microscope, electron back-scattered diffraction and transmission electron microscope combined with energy disperse spectroscopy techniques. Results show that the impact toughness of the quenched steel plate along the longitudinal and transverse directions are little different. However, after tempering, the longitudinal impact toughness of QT steel plate is improved by 88 %, while the transverse impact toughness is slightly decreased, leading to a significant anisotropy of toughness. Microstructural characterizations reveal that banded microstructure with coarse grain size exists along longitudinal direction (i.e., rolling direction) of steel plate, which is attributed to co-segregation of Mn and C and the resulting uneven recrystallization during hot rolling. After tempering, fine and dispersed carbides are precipitated in matrix microstructure, but high-density coarse carbides are formed within banded microstructure. It is suggested that the coarse grains and high-density coarse carbides significantly deteriorate the resistance against crack propagation along banded microstructure, leading to the anisotropy of toughness of QT steel plate. The findings of this study will aid to design metallurgical processes including chemical composition design, hot rolling, and heat treatments to eliminate the anisotropy of toughness of low alloy steels with high strength and toughness.

Production of improved quality steel in highscale basic oxygen furnaces using vacuum treatment

The article presents the results of the converter steel technology development using ladle treatment including portion vacuum degassing at vessel UPVS-350 and pouring at continuous casting machine. In order to improve the quality of metal products, steels of grades 3sp, 08sp, 20k, 20sp, 09G2S, 10G2S1D, 09G2S, 08GT, 17G1SU, 17G1S, 17GS, 10HSND, 15HSND, E36, pipe steels of type 09G2FB were treated by vacuum. Steel was smelted in basic oxygen furnaces with a capacity of 350 ton using technical pure oxygen (99,2–99,5% О2). The article shows that with a UPVS-350 vacuum chamber dilution to133 Pa (1 mm Hg), a metal portion weight of 20–40 tons, the number of vacuum ing cycles less than 25 and a circulation coefficient from 2 to 5, a degree of oxygen removal of up to 40%and hydrogen up to 50% can be achieved. There is an improvement in the pouring ability of vacuum treated steel, a decrease in the axial discontinuity (stratification)at the central part of the slabs from 3 to 2–2.5 grades, decrease of the nonmetallic inclusions content in the billets by 0,2–2,3 grade and their distribution in the volume of metal is more uniform. When exhaustion in a vacuum chamber reach of 1–2 mm Hg level, the impact toughness and elongation of steel in crease. For carbon steel, the production of inappropriate quality metal according to the ultrasonic control decreased by about 3 times (from 0,39 to 0,12%), and the total degree of the rejected metal decreased from 1,06 to 0,65%. During vacuuming of 08GT steel using for chemical reactors, there is a more compact and greater uniformity of the ferrite-perlite structure with the value of the actual grain no. 7–9. The internal structure at the liquation central zone of the sheets produced of this steel is also improved

Synergistic regulation of nano-precipitates and reversed austenite in titanium-free maraging steel by low-temperature solution treatment and double aging treatment

To synergistically enhance the strength and toughness of titanium-free maraging steel, a multi-scale characterization method was used to illustrate the effects of low-temperature solution treatment and double aging treatment on the microstructure of titanium-free maraging steel in this paper. After the low-temperature solution treatment and the double aging treatment, the tensile strength of titanium-free maraging steel increased from 1954 MPa to 2160 MPa and the elongation increased by 8.95 %. By the low-temperature solution treatment, the original austenite grain size of the titanium-free maraging steel was refined to 0.69 μm. The double aging treatment promoted the diffusion of Mo and Ni elements, increased the volume fraction of ω phase, Ni3Mo nano-precipitation phase and reversed austenite, and refined the size of ω phase and Ni3Mo by 14.2 % and 7.9 %, respectively. The nanoparticles of titanium-free maraging steel mainly include the ω phase, Ni3Mo and Laves phase. The strengthening mechanism of nanoparticles was quantitatively evaluated from the shear mechanism and Orowan dislocation loop mechanism. The mechanism shows that the ω phase is the main contributor to the overall precipitation strengthening. Therefore, low-temperature solution treatment and double aging treatment provide a potential solution for achieving high strength and high toughness in maraging steel.

Influence of Intercritical Annealing on Microstructure, Ductility, and Toughness of Medium Mn Steels

Influence of Intercritical Annealing on Microstructure, Ductility, and Toughness of Medium Mn Steels

Microstructure and mechanical properties of austenitic stainless steels manipulated by trace TiC–TiB2 nanoparticles

It is difficult to simultaneously increase strength and toughness of austenitic stainless steels through traditional heat treatment and alloying. However, adding nano-sized ceramic particles is a potential method to manipulate the microstructure and mechanical properties of austenitic stainless steels. In this study, TiC–TiB2 nanoparticles were introduced into austenitic stainless steel using an aluminum master alloy. Adding 0.02 wt% nanoparticles effectively refined the substrates including the dendritic ferrite and austenite and reduced the grain size from 23.7 μm to 18.4 μm. The edge-to-edge model indicated that the nanoparticles act as heterogeneous cores to facilitate the nucleation rates. For mechanical properties, the addition of nanoparticles simultaneously enhanced the hardness, yield strength, tensile strength and impact toughness of the austenitic stainless steels without sacrificing the ductility. The yield strength and tensile strength of as-cast austenitic stainless steels were enhanced by 4.8% and 2.1%, 7.2% and 3.9%, 10.0% and 5.7% at the temperatures of 20 °C, 200 °C, and 400 °C, respectively. The impact toughness was improved by 4.2%, 5.9%, and 4.3% at the temperatures of −20 °C, 0 °C, and 20 °C. Also, the presence of nanoparticles increased the yield strength and tensile strength of forged austenitic stainless steels by 16.6% and 5.9%, 17.7% and 7.7%, 18.5% and 12.2% at the temperatures of 20 °C, 200 °C, and 400 °C, respectively. The impact toughness was increased by 11.6%, 8.6% and 11.3% at the temperatures of −20 °C, 0 °C, and 20 °C. The nanoparticles refined the grains, inhibited dislocation movement, scattered large cracks and distributed the external loads more uniformly to strengthen and toughen the austenitic stainless steels. In wear tests, the nanoparticle reinforced austenitic stainless steels showed higher wear resistance against adhesive wear and abrasive wear by impeding the nucleation and growth of cracks, retarding the dislocation migration and plastic deformation and bearing the external loads. The wear volumes of as-cast and forged austenitic stainless steels were reduce by 15.7% and 21.5%. This innovative approach provided a promising strategy to produce high-performance austenitic stainless steels and serve as a reference in the development of other nanoparticle reinforced ferrous materials.