Heat Treatment Simulation Research Articles

Numerical simulation of electron beam welding and local heat treatment of TC4 titanium alloy sheet

Numerical simulation of electron beam welding and local heat treatment of TC4 titanium alloy sheet

Failure analysis and heat treatment process optimization of NOS525 rotary flat binaural hot forging die

A NOS525 steel rotary flat binaural hot forging die frequently failed too early due to collapse and wear in service. In this paper, the rotating planar binaural failure die was taken as the research object. Firstly, the sample design and sample processing of the failure die with different depths and directions were carried out. The material composition, hardness and metallographic structure of the samples were analyzed, and the tensile and impact properties were tested by direct-reading spectrometer, Rockwell hardness tester, optical microscope, scanning electron microscope, MTS testing machine and impact testing machine, etc. Meanwhile, with the help of Deform-HT software and JMatPro software, the coupling simulation of hardness, temperature and structure of the heat treatment of NOS525 steel was realized, and the hardness change of the material after heat treatment was predicted and verified by heat treatment test. The research results show that the composition of the die material is abnormal, especially the excessive P and C elements, at the same time, there is a phenomenon of quenching overheating and insufficient tempering, resulting in insufficient strength, toughness and hardness of the die material, in addition, the die surface is subjected to the cold and hot alternating load, and finally, the die surface collapses and wear too soon, resulting in its failure. Through the combination of heat treatment simulation optimization and test, the optimal heat treatment temperature of NOS525 steel was finally determined, that is, the quenching temperature of 1090℃, the first tempering temperature of 560℃, the second tempering temperature of 600℃, the third tempering temperature of 600℃, so that the mechanical properties of the material have been significantly improved.

Comprehensive Distortion Analysis of a Laser Direct Metal Deposition (DMD)-Manufactured Large Prototype Made of Soft Martensitic Steel 1.4313

Additive manufacturing (AM) by using direct metal deposition (DMD) often causes erratic distortion patterns, especially on large parts. This study presents a systematic distortion analysis by employing numerical approaches using transient–thermal and structural simulations, experimental approaches using tomography, X-ray diffraction (XRD), and an analytical approach calculating the buckling distortion of a piston. The most essential geometrical features are thin walls situated between massive rings. An eigenvalue buckling analysis, a DMD process, and heat treatment simulation are presented. The eigenvalue buckling simulation shows that it is highly dependent on the mesh size. The computational effort of the DMD and heat treatment simulation was reduced through simplifications. Moreover, artificial imperfections were imposed in the heat treatment simulation, which moved the part into the buckling state inspired by the experiment. Although the numerical results of both simulations are successful, the eigenvalue and DMD simulation cannot be validated through tomography and XRD. This is because tomography is unable to measure small elastic strain fields, the simulated residual stresses were overestimated, and the part removal disturbed the residual stress equilibrium. Nevertheless, the heat treatment simulation can predict the distortion pattern caused by an inhomogeneous temperature field during ambient cooling in an oven. The massive piston skirt cools down and shrinks faster than the massive core. The reduced yield strength at elevated temperatures and critical buckling load leads to plastic deformation of the thin walls.

Stress relief simulation for post-weld heat treatment process of pressure equipment: Creep constitutive equation considering temperature and stress variations

Due to the limited testing methods and high costs, researches on the evolution law of residual stress in the post-weld heat treatment (PWHT) process of pressure equipment are mainly by numerical simulation, in which the selection of a reasonable and reliable creep constitutive model is crucial to ensure the accuracy of numerical predictions. It is worth noting that the temperature changes and residual stress variation during the heat treatment process result in the following creep characteristics: the creep occurs under different temperatures during the heat treatment processes of heating, holding, and cooling; the creep occurs under different residual stress level where the residual stress varies during the heat treatment stages. Thus, to accurately simulate the stress release behavior during the PWHT process, the proper creep constitutive model must involve the influences of the temperature and the stress state. Meanwhile, current heat treatment simulation usually adopts simplified qualitative approaches, and the creep constitutive models often ignore the physical mechanisms and characteristics of actual creep processes, such as the Norton, the Norton-Bailey, and the Omega models. As a result, the accuracy of heat treatment simulation is limited. In this paper, a new creep constitutive relation under varying temperature and stress is proposed. The hyperbolic-sinusoidal function is used to represent the complete three stages of creep, which compensate the inaccuracy prediction at the first and the third creep stages. Moreover, the Arrhenius function is introduced to characterize the creep response under varying temperature conditions, which enables the prediction of residual stress evolution throughout the entire heating-holding-cooling process of heat treatment. Then, a typical pressure vessel cylindrical circumferential weld is simulated. The stress release during the heat treatment is calculated, and the efficacy of the proposed model is validated through surface residual stress testing. It is found that the creep behavior is a crucial factor in numerical simulation of heat treatment, and the creep constitutive relation can significantly affect the accuracy of heat treatment simulation. The simulation utilizing the hyperbolic-sinusoidal temperature-dependent creep model is much more accurate compared to the classical simulation. The simulation results are much more consistent to the experimental results. Specifically, the traditional model often underestimates the stress state, the residual stress drops abruptly during the heating stage. The residual stress evolution mechanism is simulated using the new model: The majority of residual stress are released during the heating process which primarily relies on the creep strain transformation (contributes up to 85%). The stress state does not change during the holding stage and slight higher at the cooling stage.

Simulation of Solidification, Microsegregation, and Heat Treatment of Cr-Based Fe–xMn–7.5Al–1.0C Lightweight Steels

Simulation of Solidification, Microsegregation, and Heat Treatment of Cr-Based Fe–xMn–7.5Al–1.0C Lightweight Steels

Prediction of Cross-Section-Dependent ADI Microstructures by Experimental Heat Treatment Simulation

Heavy section Austempered Ductile Iron (ADI) components may contain pearlitic or a mixed microstructure (mixture of pearlite and ausferrite) in their centres besides ausferrite. As a result, mechanical properties are not homogeneously distributed across the thicknesses of the components. The oversizing of the components therefore leads to unnecessary material expenses in foundries. In order to avoid the complex manufacturing process of heavy section ADI components and subsequent investigations, preliminary tests were performed with smaller test samples. Here, temperature-time curves were detected during heat treatment at different depths. Material samples of the customised composition were heat treated in a dilatometer under the same heat treatment conditions according to different sections of the cast component. A variation of the quenching rates was conducted to investigate the influence on the mixed microstructure formation and ratio of pearlitic and ausferritic microstructures. A comparison of the conventionally heat-treated and dilatometer produced microstructures proved the successful application for heavy section parts and enables microstructure predictions with small samples only. In this way, there is no requirement of expensive tests with high-mass components.

A finite element model with multi-flow fields for the quenching process of mill liner component made of bainite and martensite: simulation and experimental validation

Controlling the type and location of microstructure transformation through heat treatment processes is the key to improving the property of workpieces, especially they are large-sized and highly thick irregular. Such as mill liner, the worst wear in mining machinery, of which microstructure inhomogeneity is key to developing cost-efficient mining process. In order for advanced high strength steel (AHSS) to be used in mining machinery, its microstructure uniformity must be optimized, usually by adjusting the process parameters of the heat treatment process to optimize the microstructure distribution uniformity. However, the research on the simulation of large-sized and highly thick irregular heat treatment process is limited. Previous studies usually controlled the heat transfer process by using the heat transfer coefficient as the boundary condition, but only applied to small size and simple structure of the workpiece. As the heat transfer coefficient is a process quantity, its size depends on the thermal property parameters of the fluid on both sides of the wall, the flow rate, the shape of the solid surface, the thermal property number of the material and other factors, which is not suitable for large-sized and highly thick irregular. Therefore, for the large-sized and highly thick irregular heat treatment simulation process, the equivalent heat transfer coefficient of flow field was introduced as the boundary condition, and the temperature field, microstructure field and stress field were coupled to improve the accuracy of the numerical model. The accuracy of the finite element model is verified by comparing the temperature simulation error of less than 10% through temperature measurement experiments of the quenched workpiece. The evolution process of heat transfer in large-sized and highly thick irregular water bath quenching is obtained through the finite element model data. The difference in the flow rate of the wall fluid is the fundamental reason for the difference in cooling effect, and the wetting process of the wall is the secondary reason. At the same time, the corresponding microstructure and surface hardness distribution of different cooling regions are obtained, which can provide more accurate guidance for the optimization of heat treatment process of large size and thick special-shaped parts.

Combined CFD and Heat Treatment Simulation of High-Pressure Gas Quenching Process

Abstract To improve the process development for high pressure gas quenching a digital quenching simulation model combining the fields of computational fluid dynamics and heat treatment process simulation has been developed. It was found that the gas flow and hence the quenching properties depend on both local (geometry of parts, carrier and chamber) as well as global influencing factors (fan characteristics, system pressure and hydraulic resistances). Therefore, a computational fluid dynamics model that includes all these factors was realized. The approach includes a heat transfer analysis to determine the local heat exchange coefficients on a component level. By connecting the computational fluid dynamics model and heat treatment simulation the local quenching characteristics are used to compute the temperature history of the quenched part. Based on a thermo-metallurgical heat treatment simulation the computed local cooling curves and metallurgical phase compositions are used to accurately predict the part properties like microstructure and hardness. The applicability of the model has been confirmed by hardness measurements. Hardness results for different batch positions, batch setups or tray systems can now be computed enabling an efficient virtual development of the gas quenching process.

Simulation of Porosity Regrowth during Heat Treatment after Hot Isostatic Pressing in Titanium Components

Abstract Additive manufacturing (AM) is driven by design freedom, having fewer process constraints than traditional manufacturing processes. It requires careful process control and qualified parameters to create dense metal parts. However, defects in the form of cavities can be detected in as-built specimens by computed tomography. Post-processing techniques such as hot isostatic pressing (HIP) are applied to eliminate porosity, but regrowth of argon gas pores is observed after additional heat treatment. In this work, a mesoscopic heat treatment simulation of an argon-filled gas pore in titanium components is presented. A combination of HIP and high-temperature heat treatment for β-annealing is simulated. Calculated pore regrowth is qualitatively consistent with experimental observation from the literature. Simulation results support the hypothesis of argon not dissolving in the titanium matrix by assuming a constant amount of argon particles in the pore. Mesoscopic heat treatment simulations may be a part of a simulation-driven optimization of thermal post-processing to improve the quality and performance of AM components.

Heat Treatment Simulation of Aluminum Alloy Wheels and Investigation of Process Steps

Heat Treatment Simulation of Aluminum Alloy Wheels and Investigation of Process Steps

Analysis of the Distortion of the Bearing Rings after Quenching

Bearings are usually used at high-speed and high-load conditions, so the bearing sleeve must be able to withstand large contact stress, which requires heat treatment. However, during the quenching process of the bearing sleeve, a vapor film is formed on the surface. Since the vapor film is not uniform along the axial direction during the process of boiling and breaking, it will cause uneven distortion of the bearing sleeve. This uneven distortion will cause the outer ring of the bearing to have elliptical distortion after heat treatment. However, the mechanism of this problem and how to reduce the elliptical distortion has not been completely solved. In this paper, two points on the inner wall and outer wall of the bearing sleeve in the orthogonal direction are measured by means of experiments, and the mechanism of the ellipticity distortion during the quenching process is revealed. Additionally, through its horizontal placement, oblique placement, and vertical placement, the cooling curve and cooling rate curve changes in the process of entering the quenching agent are studied; based on the cooling curve, the heat transfer coefficient of the bearing sleeve during quenching is obtained by the heat transfer equation. Input the heat transfer coefficient into the CAE heat treatment simulation software COSMAP, according to the Metallo-Thermo-Mechanics theory and the method of multi-field coupling, simulating the quenching process of GCr15 and 16MnCr5 materials. By comparison, the ellipticity value of the bearing placed at a 45° angle is smaller than that of the horizontally and vertically placed bearings, with the 16MnCr5 material having the smallest ellipticity value of 0.00016. The simulation results verified the distortion mechanism of the bearing sleeve during the quenching process and how to reduce the solution of elliptical distortion.

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.

Numerical modelling of the process chain for aluminium Tailored Heat-Treated Profiles

Lightweight construction in modern car design leads to an increased usage of various aluminium semi-finished products. Besides sheet material, aluminium extrusion profiles are frequently used due to their high stiffness and variety of possible cross-sections. However, similar to sheet material, aluminium profiles exhibit limited formability in comparison to mild steel materials. One possibility to increase the forming limits of precipitation hardened aluminium alloys is the so-called Tailored Heat Treatment technology. By a local short-term heat treatment, the material is softened and the material flow can be controlled to reduce stresses in critical forming zones. The purposeful definition of the heat treatment zones is mandatory to improve the forming results. Therefore, numerical methods are necessary. In this investigation, a numerical process chain is presented. It combines the thermo-mechanical simulation of a local laser heat treatment with a subsequent bending process of the heat-treated profile using the alloy EN AW-6082. The temperature distribution, mechanical properties, and finally, the bending result of the numerical model are validated by experimental tests.

Study on thermal deformation behavior and microstructure evolution of P550 high nitrogen austenitic stainless steel

The high nitrogen austenitic stainless steel is widely used as power generation and geological exploration equipment materials because of its excellent strength, corrosion resistance and non-magnetic. In this paper, the mechanical behavior and microstructure evolution of P550 steel in the range of 900 °C–1200 °C and 0.001–10 s−1 deformation conditions were studied by physical and heat treatment simulations, metallographic observations and thermal processing maps. The results showed that the flow curves quickly reach the peak and then soften to a steady state, which indicates dynamic recrystallization (DRX) behavior. DRX is easy to occur when the deformation temperature is above 1080 °C. The activation energy of the forged P550 stainless steel was calculated as 519 kJ mol−1. There is a positive correlation between the peak stress, DRX critical stress, strain and Z value of the tested steel. The instability of the tested steel is easy to produce in the high strain rate region and low temperature region during hot working. Crack germinates and expands preferentially at the ‘necklace structure’ of inadequate dynamic recrystallization. Under the deformation state of 0.001 s−1, coarse crystals and mixed crystals are easily emerged during subsequent heat treatment. Combining the hot working map, the maximum deformation resistance and the grain evolution behavior during hot working and heat treatment, the suggested working window is T = 1020 °C–1200 °C and έ = 0.01–1 s−1.

Integrated property predictions during casting and heat treatment of Al-Si-Cu-Mg alloys by precipitation simulation

The production and manufacture of aluminium castings typically involves multiple heat treatment process steps. Simulation tools are very useful to help predict the evolution of mechanical properties, to improve process parameters and as a guideline for casting design. In this study, a kinetic model, based on Nucleation and Growth Theory (CNGT), was developed and implemented for modelling heat treatment in a casting process simulation tool. Starting from information generated from the simulation of solidification and cooling of the casting, simulation was carried out to predict further precipitation behaviour of multiple Cu or Mg-Si -containing phases during solution treatment, quenching, and artificial ageing processes in heat treatment of Al alloys. Model validation was carried out within the research cluster “Advance Metals and Processes” in Aachen, Germany. Heat treatments were performed on two different Al-Si-Cu-Mg alloys with different quench methods and at different ageing temperatures. Experimental investigations including atom probe, wavelength dispersive X-ray spectroscopy, and tensile tests were conducted to calibrate and validate the model. The simulations showed good agreement for the studied conditions and a promising modelling approach for integrated simulation of casting and heat treatment for industrial applications.

코일전류 계산 및 AISI 1552 상변태를 고려한 주차기어의 고주파 열처리 시뮬레이션

This study performed high-frequency heat treatment experiments and simulations of the park gear of an automobile transmission. The heating temperature and hardening depth were measured during high-frequency heat treatment. Moreover, by applying the resonance RCL circuit, the current value of the coil during high-frequency heat treatment, the electromagnetic and heat transfer material properties dependent on the temperature, and the phase transformation function were all applied to the simulation. In the high-frequency heat treatment experiment, the heating temperature was 977.4℃ and the 1st direction hardening depth was 1.5 mm, the 2nd direction hardening depth was 3 mm, and the 3rd direction hardening depth was 2.5 mm, and the reliability was verified by comparing the simulation heating temperature of 1,097℃ and the 1st direction predicted hardening depth of 1.6 mm, the 2nd direction predicted hardening depth of 2.8 mm, and the 3rd direction predicted hardening depth of 2.7 mm. The error rate of the heating temperature results was 12.2% whereas that of the hardening depth results was 7.1%.

Mechanism of Residual Stress Generation in Quenched Fe-Ni Alloy Cylinders Using Simulated Strains-Based Approach*

Abstract To elucidate the mechanisms of residual stress generation in quenched steel parts has been a longstanding problem. Qualitative explanations for the changes in the stress distribution in quenched cylinders appeared in the 1930s when it became possible to measure residual stresses in specimens. The explanation at that time used the concept of thermal and transformation stresses, which is still included in current textbooks. This concept is referred to here as the estimated stresses-based approach. To simplify the explanation of stress generation due to the combined effects of temperature change and phase transformations, quenching experiments were devised using Fe-Ni alloys in which only martensitic transformation occurs. On the other hand, since heat treatment simulations provide strains resulting from thermal, phase transformation, plastic, transformation plastic, and creep phenomena, a method to elucidate the mechanism using these strains was devised in the early 2000s and named the simulated strains-based approach. This paper contrasts the estimated stresses-based and simulated strains-based approaches to the mechanism of residual stress generation in quenched Fe-Ni alloy cylinders and highlights the superiority of the latter.

Computer simulation of preliminary heat treatment and radial-shear rolling of copper

Computer simulation of preliminary heat treatment and radial-shear rolling of copper

Influence of 3D printing on compressor impeller fatigue crack propagation life

Taking a compressor impeller with a pressure ratio less than 3 as the research object, the influence of 3D printing on the fatigue crack propagation life of the compressor impeller is analyzed under the combined action of 3D printing residual stress and external load. The impeller is printed by selective laser melting (SLM) technology. Finite Element Method (FEM) is used to simulate the 3D printing process of the impeller, and the residual stress, residual deformation and other mechanical quantities are comprehensively analyzed. The numerical simulation results are in good agreement with the crack location in 3D printing experiment. The heat treatment and numerical simulation of the printed impeller significantly reduce the residual stress. According to the experimental results and the magnitude and direction of the first principal stress, the position and orientation of the macroscopic crack are determined. The FEM of linear elastic fracture mechanics (LEFM) and the Forman-Newman-de Koning (FNK) model are used to give the propagation law and fatigue crack propagation life of the cracked compressor impeller under different working conditions. The results show that the crack initiation position is affected by the maximum residual stress of the printed impeller after heat treatment. When only the external load is applied, the stress intensity factor (SIF) of the initial crack front varies with the rotational speed as a quadratic power. When the external load and 3D printing residual stress act at the same time, the law will no longer be satisfied. The general trend of the crack propagation path is along the radial direction. The speed has a linear influence on the critical crack size and a nonlinear influence on the fatigue crack propagation life. The research work in this paper can provide a basis for damage tolerance analysis of 3D printing compressor impeller, and also provide a reference for maintenance work.

Experiment and simulation of heat treatment for disinfection in the chicken farm using IR irradiation

Chicken meat is widely consumed worldwide and in order to supply the growing demand, chickens are raised in large factory farms. To prevent contaminated chicken meat being released into the market, a good hygiene practice must be strictly followed. Materials utilized in chicken farming must be completely sanitized including the rice husks that are normally being used as a floor covering material. Aiming to improve rice husk disinfection protocol, infrared radiation (IR) was utilized as an effective, time-saving, and environmental friendly method. A proof-of-concept prototype of rice husk disinfection apparatus equipped with IR source and a rotating conveyor belt was developed. Finite element analysis using COMSOL Multiphysics to simulate heat transfer of IR irradiation to rice husk was performed. The effectiveness of IR irradiation method was analysed using the rice husks that were spiked with Salmonella typhimurium. The total aerobic bacteria plate count showed that the most effective IR rice husk treatment was at 120 ºC for 3 min of exposure time.