Effect Of Tempering Research Articles

The effect of quenching/double quenching and tempering heat treatment cycles on the microstructure, impact energy and hardness of AISI H13 tool steel

ABSTRACT In this study, microstructure modifications of AISI H13 steel were studied with different heat treatments such as conventional quenching, quenching + tempering/double tempering and double quenching + tempering/double tempering. Carbide volume ratio analyses were performed. The XRD analysis was used to determine the type of carbide, the average crystallite size, and the dislocation density in the samples. Charpy impact tests were performed. The hardness values of the samples were measured with the Rockwell C scale. The presence of MC, M23C6, and M7C3 type carbides was determined in the microstructures. Heat treatment cycles caused a high dislocation density in martensite laths. The dislocation density of martensite laths decreased with double quenching. The tempering process caused the formation of fine carbide particles in the microstructure. In addition, tempering processes gave rise to an increase in the volume ratio of M23C6-type strip carbides. The length/width ratio of the strip-type carbides increased with the effect of double tempering. As a result of the applied heat treatments, the impact energies of the samples decreased. The tempering process caused a secondary hardening of the samples. While the double quenching process increased the impact energy value by approximately 2%, it caused a decrease in hardness by 24%.

Effect of microwave drying and tempering on color attributes, fissure formation, and cooking characteristics of fortified rice kernels.

The online version contains supplementary material available at 10.1007/s13197-023-05871-4.

11 The Moderating Effect of Depression on Workload Perception in Traumatic Brain Injury

Objective:Individuals who have experienced traumatic brain injury (TBI) are at an elevated risk for worsened physical and psychological outcomes. Increased rates of anxiety and depression, along with cognitive issues, are common post-TBI. While there is some evidence that anxiety and depression may affect objective cognitive performance, less is known about their effect on other factors that are associated with the individual’s capacity to complete the task, such as perceived workload of the cognitive task. Workload represents an individual’s perception of task difficulty and serves as a proxy for the magnitude of mental demands a given task places on an individual. Preliminary findings in the literature suggest that individuals with TBI commonly report greater workload when completing cognitive tasks compared to neurotypical peers, but the influence of anxiety and depression on survivors’ workload remains unclear. Considering the elevated rates of psychological and cognitive problems in individuals with TBI, the present study examined the moderating role of anxiety and depression on TBI survivor workload perception of a stress-inducing working memory task.Participants and Methods:Ten participants with moderate to severe TBI and eight neurologically healthy controls performed the Paced Auditory Serial Addition Task (PASAT). After completing the PASAT, participants reported their subjective workload using the NASA task load index (NASA-TLX). Participants also completed measures of psychological functioning, including the Chicago Multiscale Depression Inventory (CMDI) and the State-Trait Anxiety Inventory (STAI). Relationships between workload and depression and trait anxiety were examined using linear regression.Results:Linear regression was employed for both the TBI and the healthy control groups to assess the influence of trait anxiety and depression on perceived workload. There was no significant difference between the TBI and HC NASA perceived workload scores. Within the TBI group, there was a significant anxiety by depression interaction (b = -.015, p < .001). Simple slopes analyses revealed that for TBI participants reporting low depression, perceived workload increased with increased anxiety (b = .093, p < .001). For TBI participants reporting high depression, perceived workload decreased as anxiety increased (b = -.38, p = .03). While there was also significant anxiety by depression interaction in the healthy control group (b = .033, p = .04), simple slopes analyses revealed that there were no significant associations for healthy controls.Conclusions:These results demonstrate that in TBI, level of depression moderates the relationship between anxiety and workload perception. The pattern observed in the TBI group was unique from controls. The present findings suggest that post-TBI, higher depression may temper the influence of anxiety on stressful cognitive task performance and workload rating. The tempering effect of high depression in TBI may represent a biased reporting style or impaired assessment of task difficulty, which may ultimately affect the individual’s capacity to accomplish a task well.

A novel multiscale process simulation to predict the impact of intrinsic heat treatment on local microstructure gradients and bulk hardness of AISI 4140 manufactured by laser powder bed fusion

ABSTRACT Although finite element model based process simulations for the laser powder bed fusion additive manufacturing process have become more common in the recent years, the proposed approaches are often only viable for materials without complex phase transformations. Process simulations for materials such as the quench and tempering steel AISI 4140 typically lead to higher computational cost due to the finer mesh and time steps needed for more complex material models. This study proposes a novel multiscale approach to combine the advantages of the macroscale and mesoscale models into one framework, in order to reduce computational cost while retaining the high accuracy. The implementation of these multiscale methods was validated by experimentally analyzing multiple parameter combinations regarding bulk hardness and local microstructure differences. The results show an accurate prediction of bulk hardness and localised tempering effects while reducing the computational cost in order to simulate the component scale.

The effect of enzymatic tempering of wheat on the extraction rate and the quality of the resulting flour

Enzymes are widely used as flour aids to improve the properties of flour, but their optimum use and application at the tempering stage were limited. This method is an excellent tool to ensure a good distribution of the resulting flour's enzymes, control dosage during milling, and obtain flour of specific characteristics according to its final use. Therefore, the effect of enzymatic tempering on flour yield and quality of the resulting flour was investigated in the present study, where different concentrations of cellulase enzyme were used at (24, 60, 96) units / 100 gm of wheat, and the concentration 60 units / 100 gm of wheat gave the best results, The results of the statistical analysis witnessed a significant increase in the extraction rate (Flour yield), which amounted to 74.6% for the enzymatic conditioning, compared to the control treatment, which was 70%, and a significant decrease in the percentage of fibers with an increase in the concentration of the enzyme, so it reached 0.78% for the enzymatic conditioning compared with the control treatment, which was 1.44%., There was an insignificant increase in the proportion of ash and, protein and carbohydrates, and the degree of flour color was not affected by the increase in the enzyme concentration. Keyword: Enzymatic tempering, extraction rate (Flour yield), Flour quality.

Effect of tempering process on elastic modulus of soda-lime-silica glass

The tempering process strengthens the bending strength and impact strength of the glass, but it alters the elastic modulus of glass as well. Aim of this study is to investigate the variations in the elastic modulus of soda-lime-silica (SLS) glass after tempering. The elastic modulus of intact SLS glass is measured using the elastic support-free end beam test method. Additionally, the elastic modulus of broken SLS glass that had released the tempering stress is measured using nanoindentation. The experimental results show the tempering process reduces the elastic modulus of SLS glass, the reduction is related to the tempering level and glass thickness, the existence of tempered stress does not influence the elastic modulus of tempered SLS glass. Finally, the mechanism of variation in the elastic modulus of tempered glass is elucidated. Ignoring the effect of tempering will lead the elastic modulus of the SLS glass to be wrongly estimated.

Effect of intrinsic thermal cycles on the microstructure and mechanical properties of heat affect zones in laser cladding coatings on full-scale rails

Laser cladding (LC) wear-resistant alloy on the surface of pearlite rails has been proven to be able to improve their wear resistance significantly. However, the rapid cooling rate in LC will result in the formation of martensite structures with high hardness but low toughness in heat affected zone (HAZ), making the rails' service safety endangered. In this paper, a novel method was proposed to eliminate the un-tempered martensite in U71Mn rail based on the in-situ gradient tempering (IGT) effect induced by the intrinsic thermal cycles in multilayer LC. The influence mechanisms of interlayer and inter-track thermal cycles on the evolutions of microstructure and mechanical properties of HAZs were studied systematically. The results illustrate that the martensite in HAZs can be gradually tempered within the optimal IGT temperature range, and the tempering processing mechanisms are as follows: firstly, the ε-carbides precipitate from HAZs and then dissolve to form granular cementites. Then, the cementites form colonies of lathlike particles with similar orientations. Finally, a composite structure consisting of fine-tempered sorbite and granular cementites forms, in which the lamellar spacing of sorbite is <1/5 of that of the original pearlite, and the proportion of the high angle grain boundaries has increased by 2.2 times. During the tempering process, the microhardness of HAZs gradually decreases, accompanied by the increase of the bending properties therein. The ultimate bending strength and fracture strain of the specimens with fully tempered HAZs are enhanced to be about 1.6 and 5.5 times as much as those of the specimens with fully quenched HAZs, even much better than the substrate.

Effect of physical tempering on the mechanical properties of aluminosilicate glass

Research on factors that influence the physical tempering of glass is important for further exploration of the toughening mechanism and the development of new toughened glasses. In this study, the glass properties, viz., the elastic modulus and linear thermal expansion coefficient of aluminosilicate glass, were found to have a positive linear relationship with tempered strength. When the linear thermal expansion coefficient was (50 ± 2) × 10−7/K, the average bending strength of the tempered aluminosilicate glass with a high elastic modulus increased from 88 to 305 MPa, which was 2.5 times higher than that of the annealed glass. When the elastic modulus was (85 ± 1) GPa, from 73 MPa to 272 MPa, the average bending strength of the tempered glass with a high linear thermal expansion coefficient increased to 2.7 times that of the annealed glass. By optimising the tempering process of the glass specimen with an elastic modulus of 85 GPa and linear thermal expansion coefficient of 48.2 × 10−7/K, the average bending strength was improved by a maximum of 1.5 times. Moreover, a positive linear relationship was found between the surface compressive stress and tempered strength.

Embrittlement mechanism of ferrite-martensite dual-phase steel during strain-baking

Press forming and paint curing are necessary in automobile production. However, strain and baking effects induced by these processes cannot be ignored in steel plates. Previously researchers have focused on the baking hardening effect but neglected the embrittlement issue. Baking embrittlement occurs when the elongation of ferrite-martensite dual-phase (DP) steel decreases significantly after strain-baking. In this work, the baking embrittlement value (ΔE) was defined for the first time as an evaluation index, and the baking embrittlement mechanism of DP steels was clarified. The baking embrittlement process of DP steels was divided into two stages. The first stage consisted of dislocations pinned by C clusters or low-temperature carbide, while the second stage was the tempering effect of martensite. Furthermore, the volume contraction of martensite led to the release of internal stress, resulting in an increase in the critical stress for dislocation movement. Both processes reduced dislocation mobility. In addition, by calculating the geometrically necessary dislocation (GND) densities before and after strain-baking, we found that the multiplication ability of dislocations was weakened.

Study on the effect of tempering on the impact abrasive wear performance of 45Si2MnCr2Mo ultra-high strength steel

In this paper, three-body impact abrasive wear tests of 45Si2MnCr2Mo ultra-high strength steel (UHSS) at different tempering temperatures were carried out by using the MLD-10 impact abrasive wear machine. The effects of different tempering temperatures on the wear weight loss and the depth of the hardened layer of UHSS were investigated. The results show that the weight reduction rate of the steels tempered at 150 and 220 °C decreases at first and then increases with time, but the steels tempered at 290 and 360 °C gradually increase with time. The surface and subsurface areas of UHSS are strengthened by work hardening after wear. The wear performance of UHSS should consider the change of weight reduction rate with time rather than just considering short-term weight loss. UHSS tempered at 150 °C has the best comprehensive surface hardness, hardening percentage, and effective hardened layer depth, and the wear process is more uniform.

High-speed manufacturing-driven strength-ductility improvement of H13 tool steel fabricated by selective laser melting

ABSTRACT H13 tool steel was additively manufactured by selective laser melting (SLM). The sample printed at a higher laser scan speed exhibited higher strength and ductility than those of the sample printed at a lower speed. The samples were repeatedly exposed to a massive heat input during the SLM. The in-situ tempering effect was applied to the sample; the phase fraction is changed by varying the heat input by controlling the laser scan speed. The microstructure analysis showed that the sample printed at a higher scan speed had a higher fraction of retained austenite than at a lower speed. The former was affected by deformation-induced martensitic transformation with enhanced strain-hardening ability. This study entailed the control of process parameters to improve the mechanical properties and the productivity of SLM-printed H13 tool steel. It investigated the relationship between the laser scan speed and the phase fraction, whose effect on the mechanical properties was confirmed.

Thermodynamic prediction of precipitations behaviour in HAZ of a gas metal arc welded S690QL with varying Ti and Nb content

For a significant increase in the strength of high-strength fine-grained structural steels with a nominal yield strength ≥690 MPa, the addition of microalloying elements such as Nb and Ti is required. The standard specifications for the chemical composition of these steels (e.g., in EN 10025-6) often only give the manufacturer limit contents to achieve the defined properties. The effect of the alloying elements in the heat affected zone (HAZ) is sometimes completely contrary. This makes it difficult to adequately predict the batch dependency regarding weldability and the load-bearing behaviour of the welded joint. Three different micro-alloyed steels of the grade S690QL were produced on a laboratory scale, focusing on different Nb and Ti contents. To investigate the tempering effect, these were gas metal arc welded in three layers. In addition to metallographic investigations of individual HAZ areas, thermodynamic phase calculations were carried out using Thermo-Calc, following variations in the chemical composition. This provides an understanding of phase transformation, precipitation growth, and dissolution during welding as a function of temperature and cooling conditions. The results show a divergent metallurgical behaviour in the HAZ of the three different micro-alloyed steels. Thereby, the Ti micro-alloyed grade showed a strong softening of the HAZ in contrast to the Nb micro-alloyed grade. This can be attributed to a contrary precipitation behaviour during welding.

Effects of High Temperature Tempering on Microstructure and Hardness Distribution on 18Cr2Ni4WA Alloy Steel Heavy-duty Gears: Numerical Simulation and Experiments

In the present work, simulations of gas carburizing heat treatment of heavy-duty gears on a coal-cutting machine fabricated by a 18Cr2Ni4WA alloy steel were carried out by using a finite element method software. The physical property database of the 18Cr2Ni4WA alloy steel was constructed in the software. The effects of the high temperature tempering process on the microstructure and hardness distributions were simulated and studied. The hardness distribution results obtained by simulation are in good agreement with the experimental results, which verifies the accuracy of the simulation. The evolution of the volume fractions of the austenite, martensite, and bainite microstructure after high temperature tempering was simulated, while the change of the retained austenite varying with the number of high temperature tempering was studied. The results show that with the increase of the number of high-temperature tempering, the content of retained austenite in the gear decreases, and it could reduce the surface carbon concentration. The hardness variation, calculated by the Maynier equation through secondary development, is shown to be governed by the joint influence of carbon concentration and microstructure distribution. The hardness distribution from the surface layer to the core is 62HRC-32HRC after the heat treatment process with twice high tempering, which meets the needs of the practical application of the gears.

Investigation of the Effect of Tempering and Cryogenic Treatment on Mechanical Properties of Boron Steels

Boron steels are a group of steels that stand out with their high wear resistance and hardenability. In this study, 33MnCrB5-2 boron steel was shaped by applying hot forging process. After the hot forging process, the microstructure examinations and mechanical tests of the materials were carried out. A group of materials was cryogenically treated at -80 °C for 2 hours. Then, a different group of materials was austenitized at 890 °C and quenched, and then tempered at 400 °C for 90 minutes. In the last group of materials, after tempering heat treatment, cryogenic treatment was applied at -80 °C for 2 hours. Hardness and abrasion tests were carried out on the samples that were subjected to cryogenic treatment and tempering heat treatment. Microstructure analyzes were examined with the help of scanning electron microscope (SEM) and optical microscope. Element distributions from different regions in the microstructure were analyzed with energy-dispersive X-ray spectrometry (EDS). The crystallite size of the materials were calculated by X-ray diffraction. The results showed that the hardness value and wear resistance of the samples that were cryogenically treated after tempering gave higher values compared to the other samples.

Continuous tempering effect induced PWHT alternative technology using wire arc additive manufacturing for application in replacing nuclear pressurized water reactor system repairing: CALPHAD, FEM simulation, and EBSD investigation

This study proposes an effective repair technology using arc additive manufacturing for pressurized water reactors (PWRs) in nuclear power plants (NPP) aimed at avoiding complete replacements and post-weld-heat treatments (PWHTs) of component parts while ensuring safety and reliability. Effective repair technology is defined as economic and process efficiency, because of maintenance costs and radiation exposure, and it is critical in related industries. The technology is designed to relieve the hardness and martensite fraction of the welding heat affected zone (HAZ) of low alloy steels (SA508) in PWRs penetration/nozzles by heat source generated in the WAAM process, thus ensuring structural integrity. In the first layer of wire arc additive manufacturing processes, 89.6% of the martensite phase was formed in the HAZ of SA508, which was significantly reduced to 45.7% due to repetitive thermal behaviors at the third layer. The resulting process dramatically reduced hardness from 450Hv in the initial layer additive manufacturing to 320Hv in 3 layers without additional heat treatments. Moreover, the study quantitatively investigated the martensite starting temperature (Ms) and bainite starting temperature (Bs) and analyzed the microstructure and mechanical behavior of the developed process using thermodynamic calculation (CALPHAD), finite element method (FEM) simulation, and microstructure quantitative analysis by electron backs-catter diffraction (EBSD). The proposed technologies and their quantitative analysis results can be a substantial alternative to the repair technology for penetration/nozzles in nuclear primary water cooling reactor applications, complying with ASME Sec.IX Qw-462.12 and ISO 15614-1.

Arctic ecosystem restoration with native tundra bryophytes

ABSTRACT Bryophytes are ecologically essential to northern ecosystem restoration after disturbance. In this study, native bryophytes were used to revegetate two Arctic restoration sites. Different propagation types (small, medium, large fragments) and substrates (crushed rock, lake sediment, processed kimberlite in Canada; volcanic silt loam and crushed lava rock in Iceland) with two erosion control treatments (with and without cheesecloth) were evaluated. After two growing seasons, large bryophyte fragments resulted in the greatest density and total and live cover with erosion control and medium fragments resulted in the highest density and species occurrence without erosion control. Erosion control significantly increased live cover, total cover, species occurrence, and density, including a tempering effect on soil volumetric water content and temperature. Substrates with more heterogeneous surfaces (crushed rock, volcanic silt loam, crushed lava rock) yielded higher live cover, density, and spontaneous colonization than more homogeneous substrates (processed kimberlite, lake sediment) and can be more suitable for use in arctic ecosystems revegetation. The positive outcomes in both Canada and Iceland led to the conclusion that bryophyte propagation with large to medium fragments, erosion control with cheesecloth, and substrates with heterogeneous surfaces would be effective restoration approaches where bryophyte revegetation is a focus.

Anisotropic fracture toughness of a selective laser melted martensitic stainless steel

Anisotropic fracture toughness of selective laser melted AISI 420 built in two build directions was investigated. Post-process heat treatments were performed at 200 °C and 400 °C to study the tempering effect. The parallel group exhibited better fracture toughness than the perpendicular group in both as-built and tempered states. KIC value of the 400 °C tempered state was superior to that of other states due to a coarser martensite phase. Elongated cellular structure was responsible for the anisotropic behavior because of a build direction effect, while the anisotropy was barely changed by the tempering treatments.

Developing practical and small-scale radio frequency technology for tempering minced chicken breast at home

Radio frequency (RF) tempering, as a new tempering method suitable for overall heating applications, has been widely used for meat processing industry. However, an effective and uniform tempering process in a suitable RF system is still lacking for household applications. The cylindrical chicken breasts (Φ75 mm × 60 mm, Φ100 mm × 60 mm, and Φ125 mm × 60 mm) in a cubic polypropylene container were tempered in a newly self-built small-scale 50 Ω domestic RF heating system. Crushed ice was applied to surround the medium-size sample to improve the temperature distribution by matching the electric field behaviors in the RF tempering process. This study explored the effects of crushed ice assisted RF tempering (CIRFT) on heating behavior of test samples under three input power levels (300, 500, and 700 W) and three electrode gaps (80, 90, and 100 mm). The tempering performance between CIRFT and crushed ice assisted microwave tempering (CIMWT) were compared. The product quality [drip loss, color, pH value, and total volatile base nitrogen (TVBN) content] obtained through CIRFT, RFT, CIMWT, and MWT were compared. Results demonstrated that at the optimum CIRFT condition (500 W, 80 mm) the tempering rate and the heating uniformity of samples were improved as compared to RFT. In addition, the drip loss and TVBN content of the samples were relatively better with CIRFT than with RFT. Moreover, the better-quality attributes were obtained in RF treatments compared to MW tempering. Thus, CIRFT showed a positive effect on chicken tempering for household applications resulting in a rapid and uniform heating with a relatively greater retention of product quality.

Tempering and enabling ambition: how equity is considered in domestic processes preparing NDCs

The considerations of how Nationally Determined Contributions (NDCs) to global climate action under the Paris Agreement are ambitious and fair, or equitable, is expected to guide countries’ decisions with regards to the ambition and priorities of those contributions. This article investigates the equity aspect of the NDCs of four cases (Canada, the EU, Kenya, and South Africa) utilizing a combination of document analysis and expert interviews. It interrogates both the NDC documents themselves and, uniquely, the role of international and domestic equity considerations within the domestic policy processes that led to the formulation of the NDCs. For this, 30 participants and close observers of these processes were interviewed. We find countervailing effects of equity on ambition, with an enabling, or ambition-enhancing, effect resulting from international equity, in that these four Parties show willingness to do more if others do, too. In contrast, tempering effect appears to result from domestic equity concerns, for example with regards to real, perceived, or anticipated adverse distributional impacts of climate action across regions, sectors, and/or societal strata. Political cultures differ across the four case studies, as do the key actors that influence domestic policies and the preparations of NDCs. This paper also demonstrates that research on equity in NDCs can benefit from expanding its scope from the contents of NDC submissions to also examine the underlying decision-making processes, to generate insights that can contribute to future NDCs being both equitable and ambitious.

Fatigue Properties of Spring Steels after Advanced Processing.

This article deals with the effect of strain-assisted tempering (SAT) on the fatigue properties of 54SiCr6 steel used for spring steel wires in a wide variety of automotive applications, including coil springs. This steel spring wire is extremely strong, having a high elastic limit and yield point, giving the steel excellent energy accumulation and fatigue properties. This combination opens up new possibilities in helical and cylindrical coil spring design, resulting in the reduction of both size and weight. Lightweight coil springs lead to improvements in fuel consumption, stability and vehicle traction. A large plastic deformation and SAT were applied to enhance the yield point of the study material. Improvements in the static and cyclic properties of steel springs were investigated using tensile tests and 3PB fatigue tests at ambient temperature. In addition, an advanced laser shock peening (LSP) process was employed to increase the fatigue resistance of the SAT material. The results presented here show great improvements in the static and fatigue properties over commercial steel treatment. The material quality of the wires was evaluated to be insufficient for further processing with cold coiling.