Charpy V-notch Research Articles

Assessment of the impact behavior of CLF-1 steel with Charpy V-notch testing and miniature Charpy V-notch testing

China Low-activation Ferrite steel (CLF-1), as one of the structural materials developed in China for fusion reactors, is a Reduced activation Ferritic/Martensitic (RAFM) steel modeled after the traditional T91 steel (9Cr-1Mo-0.2V-0.08Nb). For fusion reactor materials, the Charpy impact testing is an important method to assess their notch sensitivity. In this study, Charpy impact tests were conducted on CLF-1 steel using Charpy V-notch specimens (CVN) and Miniature Charpy V-notch specimens (Kleinstprobe, KLST) to assess the impact behavior of CLF-1 steel, and data normalization was performed on the KLST specimen. The results show that as the specimen size of CLF-1 steel decreased, the curves of impact absorbed energy, lateral expansion, and shear fracture appearance shifted towards lower temperatures, and the impact absorbed energy significantly decreased. Both the macroscopic and microscopic characteristics of the specimens obtained from the experiments indicated that KLST specimens could achieve the same fracture characteristics as CVN specimens. Additionally, at the same experimental temperature, KLST specimens exhibited a higher proportion of ductile fracture regions.

Effect of Tempering on Phase Transformations in Low-Alloy Steel with 1.6%Si

Low temperature tempering of a 0.53%C–1.6%Si–0.9%Mn–0.76%Cr–0.14%V–0.05%Nb steel provides combination of high yield stress σ0.2=1890 MPa with elongation-to-failure δ=6% and Charpy V-notch (CVN) impact energy of 11 J/cm2 due to precipitation of non-stoichiometric η-carbide Fe2C. Silicon suppresses precipitation of para-equilibrium cementite both from martensite and retained austenite. Orthoequilibrium cementite precipitate upon tempering at 500°С providing combination of σ0.2=1360 MPa with δ=9% and CVN impact energy of 18 J/cm2.

Thick-wire GMAW for fusion welding of high-strength steels

The paper describes a high-current Gas Metal Arc Welding (GMAW) process using wire electrodes with diameters up to 4.0 mm for single-pass full penetration butt joint welding of 20 mm thick steel plates. Fundamental research aims to develop thick-wire GMAW into a high-efficiency method by identifying the limits of welding performance and achievable deposition rates. Current gaps in understanding include equipment requirements, process properties, application fields, and weld quality. The research project addresses these gaps through systematic investigations of basic technological analyses, application sample welding, and quality evaluations. The objective was to create a robust, cost-efficient gas-shielded high-performance welding technology with deposition rates comparable to Submerged Arc Welding. The fully mechanized, automatic welding setup included two parallel-connected welding power sources, one wire feeder and one high-power welding torch. Welding parameters and conditions were evaluated with the aim of achieving a high-quality weld. Optimal parameters were identified for one-sided single-pass welding on 20 mm thick plates. Validation of thick-wire GMAW for 20 mm thick high-strength steels was conducted via two-sided single-pass welding on S690Q grade plates. Testing of the weld joint included static tensile strength test (3x tensile specimen), a Charpy impact test at −40 °C (6x Charpy V-notch specimens respectively with notch position in weld metal, base material and heat-affected zone (HAZ)), microstructure examination and a hardness test. The lowest recorded impact energy was observed to be 50 J within the weld metal, in combination with hardness peaks in the HAZ reaching 415 HV1, and all tensile specimens failing outside the HAZ within the base material. The process achieved reliable, reproducible, and economical joint welding, meeting necessary mechanical-technological quality standards. The paper enhances the understanding of selected welding techniques tor thick plate joining and offers valuable industrial insights, demonstrating the technique's applicability and feasibility for high-strength applications.

Microstructural Dependence of the Impact Toughness of TP316H Stainless Steel Exposed to Thermal Aging and Room-Temperature Electrolytic Hydrogenation.

This work deals with the effects of two individual isothermal aging experiments (450 °C/5000 h and 700 °C/2500 h) and the subsequent room-temperature electrolytic hydrogen charging of TP316H stainless steel on its Charpy V-notch (CVN) impact toughness and fracture behavior at room temperature. Microstructural analyses revealed that aging at 700 °C resulted in the abundant precipitation of intermediary phases, namely, the Cr23C6-based carbide phase and Fe2Mo-based Laves phase, whereas aging at 450 °C resulted in much less pronounced precipitation of mostly intergranular Cr23C6-based carbides. The matrix phase of 700 °C-aged material was completely formed of austenitic solid solution with a face-centered cubic (FCC) crystal structure, whereas an additional formation of ferritic phase with a base-centered cubic (BCC) structure was detected in 450 °C-aged material. The performed microstructure observations correlated well with the obtained values of CVN impact toughness, i.e., a sharp drop in the impact toughness was observed in the material aged at 700 °C, whereas negligible property changes were observed in the material aged at 450 °C. The initial, solution-annealed (precipitation-free) TP316H material exhibited a notable hydrogen toughening effect after hydrogen charging, which has been attributed to the hydrogen-enhanced twinning-induced plasticity (TWIP) deformation mechanism of the austenitic solid solution. In contrast, both aging expositions resulted in significantly lowered hydrogen embrittlement resistance, which was likely caused by hydrogen trapping effects at the precipitate/matrix interfaces in thermally aged materials, leading to a reduced TWIP effect in the austenitic phase.

A prediction model of brittle crack arrest toughness in TMCP heavy plates

Micro-alloyed low carbon MnCrNiCuMo steels were proposed to produce heavy plates with a maximum thickness of 100 mm. An integrated industrial route including a thermo-mechanical control process (TMCP) based on a study on continuous cooling transformation was applied in industrial production. Comprehensive mechanical properties tests including the measurement on resistance against crack initiation using crack tip opening displacement (CTOD) approach were conducted. Large scale wide-plate temperature gradient double tension (DT) technique was employed to evaluate the crack arrest toughness Kca in the heavy plates under different conditions. Nil-ductility transition temperature (NDTT) was also tested across the entire thickness section of the plates. The results showed that heavy steel plates were qualified being brittle crack arrest (BCA) products at EH47 grade with yield strength high than 460 MPa. High crack initiation toughness was exhibited by both Charpy-V notch impact property and CTOD values. Crack arrest toughness at −10 °C greater than 253 MPa √m was achieved in a plate even with thickness of 100 mm. The mean value of crack arrest toughness at different temperature measured by the DT approach can be indexed by the highest NDTT in the interior section of the heavy plates leading to an empirical prediction model. Further, fracture mechanics based master curve approach was used to statistically predict crack arrest toughness distribution over a wide range of temperatures showing improved predictability over the empirical model and an existing model in the literature.

The effects of heat treatment on the mechanical properties of 450 HB wear resistant steel

The effects of heat treatment on the mechanical properties of 450 HB wear resistant steel produced by Usiminas steelworks in the form of heavy plates were investigated. The results showed that when tempering temperature is lower than 200°C, there are no significant changes in hardness, tensile properties and absorbed energy in Charpy V-notch test. With further increase in temperature up to 400°C, hardness, tensile strength, total elongation and impact toughness exhibited a slight downward trend. For heating carried out from 400°C to 600°C, a very significant drop in hardness and tensile strength and an increase in total elongation and absorbed energy values were observed. The abrasive wear resistance, evaluated by dry-sand rubber wheel test, increased with the heating up to 500°C. With the additional rise in temperature to 600°C, the abrasive wear resistance decreased, reaching a similar level to the reference state (steel in as-delivered condition).

Carbon distribution in lath martensite and quench embrittlement

Effect of water quenching and low-temperature tempering (LTT) at T≤280 °C on fracture mechanisms upon tension and during the Charpy V-notch (CVN) impact test of a 0.53%C-1.6%Si-0.9%Mn-0.76%Cr-0.14%V-0.05%Nb steel was studied. The steel exhibits quench embrittlement (QE). Tensile specimens fractured in elastic region after quenching due to easy crack initiation by intergranular fracture mechanisms. CVN impact toughness was ∼5 J/cm2. Low fracture toughness is attributed to superposition of intergranular fracture and transgranular quasi-cleavage fracture within packets during crack propagation; crack initiation occurs locally at the notch surface. QE is attributed to carbon segregations on high-angle boundaries if a sufficient portion of bulk carbon could not be consumed for the formation of Cottrell clouds on dislocations. LTT provides precipitation of transition carbides that leads to depletion of carbon from martensite and boundary segregations that decreases severity of QE due to suppression of intergranular fracture, increase of fracture brittle stress and contribution of dimple fracture to overall fracture process. The onset of fracture takes place after yielding in tension and fracture toughness increases by a factor of ∼2 after LTT.

Laser Welding of ARMOX 500T Steel.

The article describes the results of the study on laser welding of armor plates with a nominal thickness of 3.0 mm. The plates were made of Armox 500T steel characterized by a hardness of up to 540 HB, a minimum yield strength of 1250 MPa, an ultimate strength of up to 1750 MPa, and an elongation A5 minimum of 8%. The laser used for the welding tests was a solid state Yb:YAG laser. The influence of basic parameters such as laser output power, welding speed, and focal plane position on the weld geometry was determined during bead-on-plate welding tests. The optimal conditions for butt joint welding were determined, and the test joints were subjected to mechanical and impact tests, metallographic analysis, and hardness measurements. It has been shown that it is possible to laser weld Armox 500T armor plates, and at the same time it is possible to provide high quality butt joints, but this requires precise selection of welding parameters. A decrease in HAZ hardness of about 22-35% in relation to the hardness of the base material, ranging from 470 to 510 HV0.2, was found. The ultimate tensile strength of the test joints was approx. 20% lower than the Armox 500T steel. The bending tests revealed the low plasticity of the tested joints because the bending angle was just 25-35°. The results of Charpy V-notch test revealed that the impact toughness of the weld metal at -20 °C was approx. 30% lower than at room temperature.

Tailoring the strength and low-temperature toughness of HSLA structural steel by adding trace Ce

In this study, the trade-off between strength and low-temperature toughness of high-strength low-alloy (HSLA) structural steel was solved by adding trace Ce, which increased yield strength by 5.4 % and Charpy V-notch (CVN) impact energy at −40 °C by 57.9 %. The strengthening and toughening mechanism was revealed by multi-scale characterization. The results show that the strain hardening ability is improved after adding Ce. The grain size is refined and the geometrically necessary dislocation (GND) density increases to ensure the strength improvement. The CVN impact specimens change from cleavage fracture to quasi-cleavage fracture. The grain size, inclusions and high angle grain boundaries (HAGBs) are refined and optimized, which enhances the resistance to impact crack propagation and improves the low-temperature impact toughness.

Microstructural and mechanical characterization of electron beam welded low-nickel nitrogen-strengthened austenitic stainless steel

In this paper, the Electron Beam Welding (EBW) was used to join thin plates of low-nickel nitrogen-strengthened austenitic stainless steel (LNiASS), a material valued for its superior mechanical properties and cost-effectiveness. Traditional welding techniques often lead to issues such as hot cracking, reduced toughness, and undesirable microstructures. The objective was to address these challenges using EB·W., which offers precise control, minimal heat input, and deeper penetration.Methodology included joining LNiASS plates with E.B.W. and analyzing the resulting microstructures and mechanical properties through optical microscopy, tensile testing, microhardness testing, and scanning electron microscopy (SEM). The findings indicated the presence of various ferrite morphologies without significant precipitation of deleterious phases like carbides and sigma phase. The weldment strength was ∼90 % of the base alloy, with fractures occurring near the weld cord due to nitrogen loss and grain coarsening in the (HAZ). Microhardness increased by ∼12.9 %, attributed to microstructural evolution and a fine-grained structure. Impact testing in Charpy V-Notch (CVN) configuration showed the weld absorbed ∼50 % more impact energy than the base material, due to refined Microstructure and enhanced hardness. Longitudinal residual stress analysis indicated compressive nature below mid-thickness, resulting from thermal expansion and contraction during welding. These results demonstrated E.B·W.'s effectiveness in preserving mechanical properties and enhancing the performance of nitrogen-strengthened stainless steel welds.

Study on Fracture Behavior and Toughening Mechanisms of Ultra-High-Strength Pipeline Steel

In this paper, a series of low-temperature CVN (Charpy V-notch impact test) and DWTT (drop-weight tear test) experiments were carried out to deal with the intensifying contradiction of strength and toughness of ultra-high-strength pipeline steel. The fracture behavior and toughening mechanisms of ultra-high-strength pipeline steel were investigated using scanning electron microscopy, transmission electron microscopy and backscattered electron diffraction systems. The results show that DWTT fractures in ultra-high-strength pipeline steel had a variety of unconventional morphological features compared to CVN fractures, including ridge protrusion in ductile fracture conditions and a large-size fracture platform in brittle fracture conditions. Therefore, DWTT fractures contained more information about the material fracturing process, and could better reflect the actual process of material fracturing. In ultra-high-strength pipeline steel, fine-grained granular bainite caused cracks to undergo large deflections or frequent small transitions, which consumed additional energy and improved toughness. In contrast, large-sized granular bainite, which consisted of low-angle grain boundaries, did not effectively prevent crack propagation when it encountered cracks, which was not conducive to improved toughness. Moreover, the M/A constituents in large-sized granular bainite aggregated, cracked, or fell off, which could easily lead to the formation of microcracks and was also detrimental to toughening.

Study of The Microstructure and Mechanical Property Relationships of Gas Metal Arc Welded Dissimilar Protection 600T, DP450 and S275JR Steel Joints

The need for combining dissimilar materials is steadily increasing in the manufacturing industry, and the resulting products are expected to always have high performance. While there are various methods available for joining such material pairs, one of the commonly preferred techniques is fusion welding. In this study, three different steel materials (Protection 600T, DP450, and S275JR) were joined using gas metal arc welding (GMAW) in different combinations (similar/dissimilar). The microstructure and mechanical properties of the joints were evaluated. Tensile test, Vickers microhardness (HV 0.1), bending, Charpy V-notch impact testing, and microstructure examinations were conducted to analyze the weld and heat-affected zone. The tensile strengths of the base metal materials Protection 600T, DP450, and S275JR were found to be 1524.73 ± 18.7, 500.8 ± 10.4, and 508.5 ± 9.5 MPa, respectively. In welded samples of similar materials, the highest efficiency was found to be 103.05% for DP450/DP450, while in dissimilar welded joints, it was 105.5% for the DP450/S275JR pair. Hardness values for the base materials Protection 600T, DP450, and S275JR were measured as 526.5 ± 10.5, 153.8 ± 1.8, and 162.5 ± 5.2, respectively. In all welded samples, there was an increase in hardness in the weld zone (due to the welding wire) and the heat-affected zone (due to grain size refinement). While the impact energy values of similar material pairs were close to the base material impact energy values, the impact energy values of dissimilar material pairs varied according to the base materials. In addition, in joints made with similar materials, the bending force was close to the base materials, while a decrease in bending force was observed in joints formed with dissimilar materials. As a result, the welding of DP450 and S275JR materials was carried out efficiently. Protection 600T was welded with other materials, but its welding strength was limited to the strength of the material with low mechanical properties.

Investigation of Hydrogen Embrittlement Effect on Microstructure Mechanical Properties and Fracture of Low-Carbon Steels

Investigation of Hydrogen Embrittlement Effect on Microstructure Mechanical Properties and Fracture of Low-Carbon Steels

Effect of Heat Treatment on Magnetic Properties of EN8D Steel Used in Automotive Applications

The present study focuses on achieving the optimum combination of mechanical and magnetic properties for EN8D steel. SAE 1010 and EN8D steels are the candidate materials to manufacture the fixed nucleus of the disk-type electro-mechanical horn. Both materials have either good magnetic or mechanical properties. The main function of fixed nucleus is to get magnetized and pull the mobile nucleus towards it. However, as magnetization and demagnetization take place in the range of 300-500 Hz, fixed and mobile nucleus continuously strikes each other at high frequency. Due to such high frequency working condition, fixed nucleus is prone to failure under wear and tear or under fatigue. For this kind of application, a combination of magnetic and mechanical properties is required in the material used to manufacture fixed nucleus. Thus, in current paper, the effects of chemical composition, microstructure, hardness, strength and toughness of EN8D steel before and after austenizing and tempering heat treatment are evaluated and compared with as-rolled EN8D and SAE 1010 steels, which are mostly used for manufacturing fixed nucleus. Magnetic permeability was evaluated using JMatPro software and compared. Austenizing treatment is performed at 900 °C for 1 hour, followed by water quenching. Tempering treatment of the same was performed at 550 °C for 2.5 hours. The Ultimate Tensile Strength (UTS) and hardness of EN8D after heat treatment decreased from 917 to 781 MPa and 269 to 233 HV0.1 respectively. Charpy V-Notch (CVN) toughness of EN8D steel after heat treatment increased from 12 to 45 joules. It indicates that the decrease in strength and hardness resulted into increase in toughness. Microstructure changes from ferrite and pearlite to combination of tempered martensite, ferrite and bainite. Magnetic permeability evaluated by JMatPro software shows increment from 450 to 564 Gauss/Oersted in EN8D steel after heat treatment.
 Keywords: Electro-mechanical horn, fixed nucleus, magnetic permeability, JMatPro, SAE1010 steel, EN8D steel

Achieving ultrahigh yield strength and decent toughness in an in-situ alloyed H13 steel via laser powder bed fusion

It is highly challenging to simultaneously achieve ultrahigh yield strength (YS) and decent toughness in the H13 steel via laser powder bed fusion (L-PBF). In this contribution, a double tempering strategy is used to optimize the microstructure and mechanical performance of an in-situ alloyed H13 steel fabricated via L-PBF. The primary tempering can result in the formation of fresh martensite and the relatively unstable retained austenite (RA), which substantially deteriorates impact toughness and yield strength (YS). The appropriate double tempering can effectively eliminate fresh martensite and reduce the fraction of the unstable RA to below 5%, successfully realizing decent mechanical properties with an ultrahigh YS of ∼1.8 GPa, an ultimate tensile strength (UTS) of ∼2.05 GPa, and a Charpy V-notch (CVN) value of 17 J in an in-situ alloyed H13 steel via L-PBF, which is comparable with those of the wrought H13 steel. The current study demonstrates that the elimination of fresh martensite and optimization of austenite stability are the key to improve the mechanical performance of L-PBF ultra-high strength steels with medium carbon content.

Взаимосвязь микроструктуры с ударной вязкостью металлов сварного шва трубных высокопрочных низколегированных сталей (обзор исследований)

Introduction. The modern pipeline industry requires the development of materials of high strength and toughness for the production of steels for oil and gas pipelines. Changes in steel production and rolling technologies have become a challenge for welding consumables and joining technologies. This is more critical for strength levels above 830 MPa, where there are no specific regulations for the approval of welding consumables. Research methods. The failure of stainless steel pipeline welds is becoming a serious problem in the pipeline industry. Multiphase microstructures containing acicular ferrite or an acicular ferrite-dominated phase exhibit good complex properties in HSLA steels. This paper focuses on the results obtained using modern methods of scanning electron microscopy for microstructural analysis, backscattered electrons (BSE) for electron channel contrast imaging (ECCI) and orientation microscopy based on electron backscatter diffraction (ORM), as well as characteristic X-rays for compositional analysis using energy-dispersive X-ray spectroscopy (XEDS) and secondary electrons (SE) for observing surface morphology. Results and discussion. This paper analyzes the characteristics of the microstructure of the weld and its relationship with impact toughness. It is shown that predicting impact toughness based on the microstructural characteristics of steel weld metals is complicated due to the large number of parameters involved. This requires an optimal microstructure of the steel. Satisfactory microstructure depends on several factors, such as chemical composition, hot work processing, and accelerated cooling. Alloying elements have a complex effect on the properties of steel, and alloying additives commonly added to the steel composition include Mn, Mo, Ti, Nb and V. From a metallurgical point of view, the choice of alloying elements and the metallurgical process can greatly influence the resulting microstructure. A longer cooling time tend to improve the toughness and reduce the mechanical strength of weld deposits on high-strength steels. Welding thermal cycles cause significant changes in the mechanical properties of the base material. The analysis showed that impact toughness strongly depends on the microstructure of the multi-pass weld of the material under study, which contains several sources of heterogeneity, such as interdendritic segregation, and the effective grain size can also be a significant factor explaining large deviations in local impact toughness values. Acicular ferrite nucleated in intragranular inclusions has been shown to produce a fine-grained interlocking arrangement of ferrite plates providing high tensile strength and excellent toughness, and is therefore a desirable microstructural constituent in C-Mn steel weld metals. At the same time, discussion regarding the relationship between acicular ferrite and toughness is very complex and still open at present. Relating impact toughness to acicular ferrite, taking into account the top bead, is not a reliable procedure, even for single-pass deposit welding. Impact strength depends on several factors, and the strong effect of acicular ferrite is generally recognized due to its fine-grained interlocking structure, which prevents the propagation of brittle cracks by cleavage. The large-angle boundaries and high dislocation density of acicular ferrite provide high strength and toughness. However, for the same amount of acicular ferrite, different viscosity values may be observed depending on the content of microalloying elements in the steel. An analysis of the results of various studies showed that other factors also affect the impact strength. For example, microphases present along the Charpy-V notch are critical for the toughness of weld metals. The combination of OM, SEM and EBSD techniques provides an interesting method for metallographic investigation of the refined metal microstructure of stainless steel pipeline welds. Conclusion. This review reports the most representative study regarding the microstructural factor in the weld of pipe steels. It includes a summary of the most important process variables, material properties, regulatory guidelines, and microstructure characteristics and mechanical properties of the joints. This review is intended to benefit readers from a variety of backgrounds, from non-welding or materials scientists to various industrial application specialists and researchers.

Tempering behavior of an ultra-high-strength steel with 1.6 wt% Si at low to medium temperatures

Tempering behavior of a 0.53%C-1.6%Si-0.9%Mn-0.76%Cr-0.14%V-0.05%Nb steel was examined. Water quenching produced lath martensite structure with a 10.5% volume fraction of retained austenite (RA) with film-like shape. Low temperature tempering (LTT) leads to precipitation of transition carbides and carbon partitioning between martensite and RA. The following precipitation sequence was found: martensite →non-stoichiometric η-carbide→stoichiometric η-carbide→Fe3C. Highest density of non-stoichiometric Fe2C η−carbides was found after isochronal tempering at 280 °C that provided attractive combination of high yield stress (YS) (1890 MPa) with a ductility of ∼6% and a Charpy V-notch (CVN) impact energy of ∼10 J/cm2. At 400 °C, the replacement of non-stoichiometric η-carbide by the stoichiometric one decreases strength and increases ductility due to 30% decrease in its volume fraction. No tempered martensite embrittlement was found due to the fact that Si effectively suppresses the precipitation of cementite at T ≤ 400 °C. The replacement of transition η-carbide by boundary cementite after isochronal tempering at 500 °C leads to considerably decrease in YS down to 1360 MPa, while elongation to failure increases up to 9.3%. Effect of decomposition of RA on strength, ductility and fracture toughness is insignificant.

Inelastic Deformation and Local Slenderness Requirements for Rectangular HSS Braces

Rectangular hollow structural sections (HSS) are commonly used as bracing in concentrically braced frames (CBFs) designed and detailed for seismic design requirements. As the primary yielding component in CBFs, braces are expected to sustain large inelastic axial deformation during earthquake loading. It is well known that their deformation capacity depends on the width-to-thickness ratio (local slenderness). Until 2013, HSS sections were produced to meet ASTM standard A500/A500M; after 2013, the ASTM 1085 specification was implemented, and since that time, HSS sections have also been produced to meet ASTM A1085/A1085M standards. Where the ASTM A500/A500M specification requires minimum yield and tensile stress values as well as a minimum elongation and tolerances on the wall thickness, the ASTM A1085/A1085M specification also requires a minimum Charpy V-notch (CVN) toughness, a maximum yield stress of the steel, and tighter tolerances on the wall thickness and radius of curvature of the corner. These requirements offer a more reliable brace for CBFs in seismic regions. Yet there has been limited research investigating the cyclic axial response of these members. A research study was undertaken to investigate the response of ASTM A1085/A1085M tubes using the response of ASTM A500C tubes as their reference. Forty-one brace specimens were tested under cyclic inelastic axial deformation. Comparison of the data shows that most of the ASTM A500/A500 M Grade C and ASTM A1085/1085M braces meet the respective requirements of their respective ASTM standard and that the differences between the performance of ASTM A500/A500M and ASTM A1085/1085M braces are not dramatic. In addition, the study investigated the impact of width-to-thickness ratio, global slenderness, and displacement history on the response of the braces. The data show that the current AISC 341-22 high-ductility slenderness limit for special concentrically braced frame (SCBF) braces is slightly conservative. However, the data suggest that the moderate ductility slenderness limit used for ordinary concentrically braced frame (OCBF) braces is significantly more conservative than required for consistent seismic safety. Further research is required to determine appropriate limits; this paper provides some initial recommendations based on this dataset.

Study of mechanical properties of RPV base and weld material using SPT technique

Small Punch Test (SPT) is one of the miniature test techniques used for evaluating tensile properties when limited dimension of material is available for standard mechanical test or handling of large specimen is difficult, especially while dealing with irradiated materials. In order to use SPT for determination of mechanical properties, it is crucial to establish correlation coefficients by comparing results obtained by SPT with that from standard tensile tests. Present work involves developing correlation coefficients and evaluation of tensile properties of reactor pressure vessel (RPV) steel using SPT technique. Specimen dimensions used for SPT was 10x10x0.5 mm3. These specimens were prepared from Charpy V-Notch specimens, which were earlier subjected to standard impact testing. Correlation coefficient for RPV material was established by comparison of SPT data with the tensile properties obtained using standard tensile test. Subsequently, SPT data was acquired on RPV thermal material and tensile properties were obtained using the correlation coefficient for validation. This paper describes the SPT set-up used during the current studies and methodology used for establishing the correlation coefficient on RPV base material.

Improving the Weld Heat-Affected-Zone (HAZ) Toughness of High-Strength Thick-Walled Line Pipes

The low-temperature fracture toughness of double-V weld seams is a well-known challenge due to the essential increased heat input for heavy-wall pipelines. A thorough investigation was conducted to explore the impact of the heat input on the grain size and precipitate coarsening, correlating the microstructure with the heat-affected-zone (HAZ) toughness. The results indicated that the actual weldments showed a toughness transition zone at −20 °C, with considerable scattering in Charpy V-notch (CVN) tests. Gleeble thermal simulations confirmed the decreased toughness of the coarse-grained HAZ (CGHAZ) with increasing heat input and prior austenite grain size (PAGS). A specially designed thermal treatment demonstrated its potential for enhancing the toughness of the CGHAZ, with the recommended thermal cycle involving peak temperatures of 700 and 800 °C, holding for 1 s, and rapid cooling. The toughness of the intercritically reheated CGHAZ (ICCGHAZ) improved with higher intercritical reheating temperatures and the removal of necklace-type M–A constituents along the PAG. Despite various thermal treatments, no significant improvements were observed in the toughness of the ICCGHAZ. Future work was suggested for optimising the use of tack welds to reduce the effective heat input (HI) associated with double-sided submerged arc welding (SAW).