Heat Treatment Distortion Research Articles

Determination of Transformation Plasticity Coefficient of Structural Steel Sheet by Oil Quenching and Improvement in Prediction Accuracy of Distortion in Heat Treatment

Determination of Transformation Plasticity Coefficient of Structural Steel Sheet by Oil Quenching and Improvement in Prediction Accuracy of Distortion in Heat Treatment

Validation of a digital twin: Part distortion in heat treatment

This paper presents a study on multi-process manufacturing optimisation, employing a sophisticated data analytic model based on Gaussian Processes. Through strategically designed aluminium trials and rigorous model evaluation using leave-one-out cross-validation, the efficacy of the model in identifying optimal parameters is demonstrated. An interactive dashboard, powered by the Anaconda Panel(c) library, enables real-time insights into the impact of varying parameters on outcomes. Experimental validation showcases the model’s ability to reduce distortions yet highlights the dynamic nature of manufacturing processes. The iterative refinement of optimal parameters based on real-world observations underscores the adaptability of the model. This study emphasises the importance of combining advanced data analytics with practical experimentation for enhanced precision in modern manufacturing, paving the way for further advancements in the field. Real-world validation of predicted optimal parameters reveals unexpected distortions, highlighting the dynamic nature of manufacturing processes and the necessity for continuous refinement. Further analysis uncovers a discrepancy in distortion outcomes, emphasising the need for vigilant investigation and iterative refinement. By incorporating the latest experimental findings, the data analytic model has generated updated optimal parameters, effectively minimising part distortion. This study underscores the significance of data-driven decision-making and the continuous integration of new experimental results in the pursuit of optimal manufacturing parameters, paving the way for further advancements in manufacturing optimisation.

Mitigation of heat treatment distortion of AA 7075 aluminum alloy by deep cryogenic processing using the Navy C-ring test

Abstract Heat treatment is a promising approach to advance the mechanical properties of AA 7075 aluminum alloy for aerospace structural applications. Quenching is commonly performed after solutionizing of AA 7075 aluminum alloy to impart supersaturated solid solution condition. It involves rapid cooling of the previously solutionized part to room temperature with water as a quenching medium. It leads to severe distortion of the structural part and deteriorates its surface integrity due to the high thermal residual stresses. This paper reports the distortion behavior of heat-treated AA 7075 aluminum alloy by implementing the standard Navy C-ring test. For precise measurements, the coordinate measuring machine (CMM) was used. Deep cryogenic treatment (DCT) was executed after conventional heat treatment (CHT) to reduce the tensile residual stresses and mitigate the distortion potential of AA 7075 aluminum alloy. Results showed significant improvement in surface finish and hardness of deep cryogenically treated AA 7075 aluminum alloy. It is attributed to the precipitation of fine spherical second phase particles distributed uniformly in the matrix. The distortion potential of heat-treated AA 7075 aluminum alloy is minimized by 30.7 % by deep cryogenic processing. It is correlated to the counterbalancing of tensile residual stresses in the heat treated part by compressive residual stresses ensued by deep cryogenic quenching.

Finite element analysis on shape deformation of the macro‐structure region during hot‐rolling process for gear steel FAS3420H and its modification

AbstractThe rectangular macro‐segregation region in the core of hot‐rolled steel bar has a great influence on the heat treatment distortion of an automotive gear steel FAS3420H. In order to understand the distortion process of the segregation region during hot‐rolling process, a finite element (FE) analysis of the whole hot‐rolling process was carried out by software DEFORM‐3D, and a constructed constitutive model was embedded into DEFORM‐3D to describe the deformation process. The results show there is an inhomogeneous strain distribution at the cross‐section of hot‐rolled round bar, which results in uneven distortion of the segregation region in different directions. A square segregation region, which can reduce inhomogeneous distortion of gear in the subsequent heat treatment, is obtained after being rolled by simulation calculation verified through experiment.

Comparison of microstructure and heat treatment distortion of gear steels with and without Nb addition

In order to research the effect of microalloying Nb, the microstructure and heat treatment distortion of case carburizing steels with and without Nb addition are compared. Results show that a uniform and fine prior austenite grain size was obtained for the steel with the addition of 0.03 wt.% Nb even after being carburized at 980 °C for 37 h, resulting in a very deep hardened layer of about 4 mm. Nb is an effective microalloying element to hinder austenite grain growth of gears during high-temperature carburizing. Theoretical calculation and experimental observation of NbC precipitates indicate that fine NbC precipitates have not evidently dissolved at 980 °C, and thus they can act as grain refiners due to pinning effect. Heat treatment distortion of Nb-added steel is much lower than that of the steel without Nb addition. It may be contributed to its fine and uniform grain size, which presumably influences stress during martensitic transformation.

Tailoring the residual stress and mechanical properties by electroshocking treatment in cold rolled M50 steel

The residual stress and mechanical anisotropy caused by cold rolling (CR) seriously deteriorate the heat treatment distortion and final service performance of M50 steel. In this work, the effect of electroshocking treatment (EST) on the microstructure, residual stress and mechanical properties of cold rolled M50 steel has been investigated. The microstructure was characterized by X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The mechanical properties were measured by Vickers hardness, uniaxial tensile and Charpy impact test. The results show that the EST accelerates the movement and annihilation of dislocation and thus promotes the local recrystallization. The dislocation density of treated specimen decreases from 2.37 × 1015 m−2 to 1.96 × 1015 m−2 and the typical deformation texture is obviously weakened after EST treatment. It is also found that the residual stresses in the rolling and transverse direction of the EST specimens decrease by more than 50% with a more homogeneous distribution. In addition, the anisotropy of tensile strength and impact toughness decreases remarkably after EST treatment, which could be ascribed to the local rapid recrystallization and the weakened intensity of deformation texture. Furthermore, due to the release of concentrated stress, the average elongation of EST specimens is increased by 25.5% without loss of tensile strength.

Determination of transformation plasticity coefficient of steel by horizontal quenching of shaft

Shape accuracy of steel gears and shafts depends on the heat treatment distortion in the oil quenching condition of those parts. The distortion is mainly caused by the inhomogeneous cooling in oil quenching. The deformation by heat treatment can be estimated by the numerical simulation considering transformation plasticity. The key material property for the simulation is the transformation plasticity coefficient. The coefficient is conventionally measured by tensile or bending test under controlled temperature and stress, however the determination of the coefficient is not easy. In this study, the authors propose a simple method to determine the coefficient using horizontal quenching of a steel shaft. Horizontal quenching tests of chrome steel shafts were conducted to demonstrate inhomogeneous deformation by experiments and numerical simulations. The specimen was uniformly heated at 850 °C, and then quenched into oil with 100 °C. The direction of deflection has changed depending on the diameter of the specimen. Through the comparison between the predicted deformation by simulation and the experimental results, the transformation plasticity coefficients were determined as 3.0 x 10-5 MPa-1 (austenite -> martensite) and 4.0 x 10-5 MPa-1 (austenite -> bainite).

Effect of boiling heat transfer on heat treatment distortion while relative flow quenching

Effect of boiling heat transfer on heat treatment distortion while relative flow quenching

Research for Utility of Combination Calculation Method between Heat Treatment Simulation and Computer Fluid Dynamics

Abstract For vehicle drivetrain system parts such as gears, case hardening heat treatment with carburizing is well used to improve wear and rolling contact fatigue properties. However, distortion would occur during heat treatment processes, which may be a problem in improving the precision of the gear shape. Predicting distortion behavior accurately by heat treatment simulation method could help us achieve a good heat treatment quality and parts’ shape accuracy. In this article, heat treatment simulation that is the predicting method from cooling situation to heat treatment distortion and computer fluid dynamics that is the predicting method from flow condition to cooling phenomena are combined. This combined method can estimate heat treatment quality on mass production treatment, especially in stable flow condition or some cooling conditions. However, especially for a continuously variable transmission pulley quenched in high-speed flow oil condition, the accuracy of heat treatment simulation is lower than other conditions. We estimated this to be the effect of turbulence generated in the flow.

Experimental Analysis about Heat Treatment Distortion in Bearing Race

It’s well known that the vehicle fuel economy is improved by reducing the weight of their structural and mechanical components. Therefore, there is a demand of bearing race with thin thickness for weight reduction. But, this thickness reduction also causes a large oval distortion in bearings after Heat Treatment (HT). The factors affecting the HT distortion are extremely complicated, which makes it difficult to do rectification only by experimental analysis. There is also a limitation in numerical analysis due to the lack of workable model for HT distortion. Therefore, the aim of this study is to identify the effective factors of HT distortion by experimental approach in order to build suitable numerical simulation model that can estimate HT distortion. The material used in this study is a conventional case-hardened steel (Fe-0.4mass%C-Cr-Mn). The ring with the diameter of 100mm is heat treated and quenched. The resulting HT distortion is evaluated by measurement of maximum and minimum diameter of the race. A jig was developed to correct the ring shape during heat treatment, which helped in identifying that the quenching affects more than 50% of HT distortion. From these results, we developed a cooling equipment to reproduce inhomogeneous cooling rate by controlling oil flow toward the exterior of the ring. The quenching with this equipment reveals that inhomogeneous flow with opposite side (0 degree and 180 degree) reproduces a large oval distortion. The data obtained from the experimental analysis is suitable for developing the numerical model for HT distortion.

Data-driven operation and compensation approaches to tooth flank form error measurement for spiral bevel and hypoid gears

In the actual design and manufacturing of spiral bevel and hypoid gears, the real tooth flank form geometry inevitably deviate from their theoretical or master target one, due to machine tolerances and systematic flexibility, heat treatment distortions, variation of cuttings forces and other noise factors. This deviation in normal direction is tooth flank form error which can cause some detrimental effects on tooth contact performances. Particularly, once the edge contact or highly concentrated stresses occurs, it will result in noisy operation and premature failure. This paper presents an accurate systematic CMM measurement method to prescribe and data-driven control the tooth flank form error. Firstly, the accurate measurement positioning is developed as an important step in whole measurement. And then, a data-driven programming is performed to prescribe a flank grid in CMM measurement. Where, this programming includes: (i) UMC machine settings are used to establish a universal tooth flank model, (ii) NURBS fitting and stitching approach is employed to accurate explicit flank expression, and (iii) flank parameterization using the steepest descent method with Newton step is proposed to identify flank grid points. Moreover, to distinguish with the conventional methods, a high-order machine setting modification considering residual tooth flank form error is proposed to get a flexible compensation of tooth flank form error. Given numerical test can verify the proposed methods.

Investigation of Analytical Prediction of Heat Treatment Distortion for Transmission Shaft

Investigation of Analytical Prediction of Heat Treatment Distortion for Transmission Shaft

Investigation of Shape Effect of Transmission Shaft for Heat Treatment Distortion

Investigation of Shape Effect of Transmission Shaft for Heat Treatment Distortion

低熱処理変形高強度肌焼鋼ECOMAX4の開発

低熱処理変形高強度肌焼鋼ECOMAX4の開発

Coupled process simulation of cold extrusion and heat treatment distortion of steel shafts

A simulation study will be presented regarding effects of cold extrusion – a forming process – on heat treatment distortion of a 20MnCr5 (SAE 5120) steel. Therefore, both cold extrusion and heat treatment simulations with transferring the geometry and the stresses from the cold extrusion to the heat treatment were done. The influence of two degrees of deformation, two friction coefficients, and two heat transfer coefficients between workpiece and tool on the heat treatment distortion was studied. Additionally, heat treatment simulations were done regarding only the geometry without transferring the stress (as machined state). Stress relief annealing and case hardening were applied as heat treatment. Finally, the simulated length changes of the shafts were compared with experimentally determined length changes using different lubricants, degrees of deformation, and heat treatments.

Study of an Alternative Novel Cold Forging Process

Deformation behavior was investigated in detail from cold extrusion and upsetting tests on medium carbon steel. A new “cold forging after quenching and tempering” (CFAQT) process was proposed. Compared with conventional processes, including annealing before cold forging, plus quenching and tempering after forging, the CFAQT process could shorten the process chain and avoid subsequent heat treatment distortion with clear energy-saving and cost-reduction benefits. The CFAQT process was applied successfully in the mass production of a lock set for industrial automobile wheels and in laboratory spline extrusions.

Distortion Control: Quenching Apparatus for Hardening Parts: An Overview

Abstract During the production and quality control of heat treatment, especially during drastic cooling operations, avoiding heat-related distortions is critical if relatively stringent geometrical requirements stipulated by industrial manufacturing specifications are to be achieved. Therefore, specialized distortion minimization procedures are often used, which includes: the use of clamps and spreaders for fixturing workpieces in a designated position, and/or to controlling the flow direction and flux of coolants as they impinge on to the cooling workpiece surface. In addition, some assistive devices are required to implement designed movement of workpieces during the quenching process in order to meet the technical requirements of workpieces undergoing heat treatment. Quenching apparatuses are also used to fix workpieces to avoid any possible damage due to unexpected mutual contact or collision between them, and more importantly to ensure uniform heating and reasonable quenching of workpieces. On many occasions, some specially designed accessories are also considered as quenching apparatus to form a complete set with available heating or cooling equipment. Therefore, the quenching apparatuses are discussed in this paper for their role and function both in heat treatment production and especially for controlling quenching distortion. The main principles of the apparatus design are briefly described, and some apparatuses for typical heat treatment purposes are introduced, such as core rods, quenching machines, fixtures for press quenching, copying mould for quenching of aluminum alloy structural components, and apparatuses for induction hardening, and the use of quenchant flow tunnels. The management and the development trends of quenching apparatus are also briefly discussed. Characterization by digital technology, CFD, and computer control quenching apparatus has already become an important part of modern heat treatment production, and the synchronous increases of both production cost and heat treatment quality has been achieved. The popularization of the use quenching apparatuses implies that the fundamental solution to heat treatment distortion, which is based on effective movement constraints of workpiece upon quenching, suggests the programming cooling of workpiece and the reasonable design of quenchant flow tunnel for hardening is approaching. In the meantime, quenching apparatus design is becoming less empirical by increasing the use of established quenching theory and technology.

Consideration of residual stress and geometry during heat treatment to decrease shaft bending

In automotive industry, heat treatment of components is implicitly related to distortion. This phenomenon is particularly obvious in the case of gearbox parts because of their typical geometry and precise requirements. Even if distortion can be anticipated to an extent by experience, it remains complex to comprehend. Scientific literature and industrial experience show that the whole manufacturing process chain has an influence on final heat treatment distortions. This paper presents an approach to estimate the influence of some factors on the distortion, based on the idea of a distortion potential taking into account not only geometry but also the manufacturing process history. Then the idea is developed through experiments on an industrial manufacturing process to understand the impact of residual stress due to machining on shaft bending and teeth distortion during heat treatment. Instead of being measured, residual stress is being neutralized. By comparing lots between each other, connections between gear teeth geometry and manufacturing steps before heat treatment are obtained. As a consequence, geometrical nonconformities roots can be determined more easily thanks to this diagnosis tool, and corrective actions can be applied. Secondly, the influence of product geometry on bending is experimentally considered. Moreover, metallurgical observations enable to explain the influence of workpieces geometry on shaft bending. Thanks to the obtained results, process and product recommendations to decrease shafts bending are proposed.

Hot Forming-quenching Integrated Process with Cold-hot Dies for 2A12 Aluminum Alloy Sheet

A novel process called hot forming-quenching integrated process with cold-hot dies was proposed to improve the formability and avoid thermal distortion in solution heat treatment. In this process, the heated lower dies were used to improve the forming temperature and the cooled upper dies were utilized to accomplish quenching and reduce thermal distortion. The effects of temperatures of the hot dies ranging from 100 to 450°C on strengthening were systematically investigated. The strengths were measured by Vickers hardness test and uniaxial tensile test. It was found that the temperature of heated lower dies could be improved to 450°C to slow the temperature decrease of heated sheet besides obtaining excellent strength. The temperature of both hot dies could only be improved to 250°C. The strengthening phase was the dispersed lath-shaped S precipitate with an average cross-section of approximately 50×100nm.

Distortion and residual stress measurements of induction hardened AISI 4340 discs

10 Induction hardened discs with two initial hardness levels were used for exploring the influences of the variation of initial hardness as well as induction hardening (IH) recipes on the heat treatment distortions and hardening depth. The results show that for the same initial hardness, the larger the energy input, the higher the distortion size as well as the hardening depth. For a given induction hardening recipe, the increase in initial hardness leads to a deeper hardening depth but a smaller distortion. One disc was selected for the residual stress investigation in three orthogonal directions by neutron diffraction (ND). The corresponding stress-free lattice spacing d0 was measured from the same material using both ND and X-ray diffraction (XRD) methods. The ND results show that the variation of d0 in the hardened layer is significant and should be taken into account for stress calculation. However, regarding the core region, the d0 value measured by XRD is more reliable. Accordingly, a combination of the ND-measured d0 profiles in the hardened layer and the XRD-measured d0 value in the core was adopted for the determination of residual stress distributions.