Induction Hardening Research Articles

The Effect of Temperature in Induction Surface Hardening on the Distortion of Gear

One way to extend the lifetime of gear is minimizing the distortion during the manufacturing process. One of the most important processes in gear manufacturing is induction surface hardening. Induction hardening causes a geometric distortion in gears. This study aimed to analyze the distortion of the gear after induction surface hardening. The material of gear that used in this research is S45C, and it was designed with the a module (m) of 1.75, and 29 teeth (z). In the experiment, the gear was heat-treated using induction hardening at variations of temperatures of 820, 880, and 920 °C with holding time was 35, 45, and 55 s, respectively. Then the gear quenched in water at room temperature. The microstructure analysis was conducted to explore the phase change in gear teeth. Hardness test was also performed on the gear using Rockwell test, and finally, the gear dimension was evaluated. The results showed that the hardness of gear at the teeth surface was 64.9 HRC at the case depth of 5 mm is proper to be used. The microstructure of gear at the surface is martensitic, and the deeper area is pearlite. Gear distortion of all teeth with average thickness was reduced and the highest value was 1.593% at the austenite temperature of 820 °C. While the highest reduction was produced at the temperature of 920 °C and generated the highest shrinkage. The induction surface hardening of the gear was not high, and the highest distortion was found in the outside diameter.

Influence of Austenitizing Heat Treatment on the Properties of the Tempered Type 410-1Mo Stainless Steel

The modified 410-1Mo stainless steel has been developed with higher tensile strength and elongation compared to the standard 410 stainless steel. This paper reports the influence of austenitizing temperature on the microstructure, hardness, impact resistance and corrosion resistance of the modified 410-1Mo steel. The steel samples were prepared by a process sequence of induction melting, hot forging, annealing, hardening, and tempering. The microstructure of the tempered steels revealed additional phase of delta ferrite at pre-austenitizing temperatures of 950 to 1050 °C and disappeared at a temperature of 1100 °C. The steels which underwent pre-austenitizing at 1100 °C showed the largest sized lath martensite and the largest amount of retained austenite. The tempered steels maintained hardness at austenitizing temperatures of 950 °C to 1000 °C and showed an increasing hardness at austenitizing temperatures from 1000 to 1100 °C. At a range of austenitizing temperatures, it was investigated that the steels exhibited higher impact resistance at 1050 °C. The tempered steels that were pre-austenitized at 950 °C and 1100 °C showed the lowest pitting potential due to the existence of carbides and coarse-high carbon martensite, respectively.

Formula omitted]–[formula omitted] formulation of a mathematical model for the induction hardening process with a nonlinear law for the magnetic field

We derive and analyze a mathematical model for induction hardening. We assume a nonlinear relation between the magnetic field and the magnetic induction field. For the electromagnetic part, we use the vector–scalar potential formulation.The coupling between the electromagnetic and the thermal part is provided through the temperature-dependent electric conductivity and the joule heating term, the most crucial element, considering the mathematical analysis of the model. It acts as a source of heat in the thermal part and leads to the increase in temperature. Therefore, in order to be able to control it, we apply a truncation function.Using Rothe’s method, we prove the existence of a global solution to the whole system. The nonlinearity in the electromagnetic part is handled by the theory of monotone operators. To supplement our theoretical results we provide a numerical simulation using real physical constants.

Effect of Curved Surface Shape and Feed Velocity on Microstructure and Mechanical Performance of Gray Cast Iron After Spot Continual Induction Hardening

Spot continual induction hardening (SCIH) is a surface heat treatment process, which can strengthen more than one small area or relative large area on complicated component surface. In order to investigate the microstructure and mechanical properties of gray cast iron with curved surface after SCIH, the microstructure, microhardness and residual stresses were analyzed under different process conditions. The results showed that the martensite grain in hardened region of concave surface was larger than that of convex surface. The domain sizes of concave and convex surfaces were smaller than that of matrix region due to the high heating rate in SCIH process. The phase transformation depth increased with the increasing of convex surface radius but decreased with the increasing of concave surface radius. The maximum values of residual tensile and compressive stresses increased with the increasing of feed velocity for convex and concave surfaces, respectively. The appearance positions of maximum tensile and compressive stresses were closer to center for convex and concave surfaces, respectively, when feed velocity increased from 1 to 5 mm/s. The achieved results indicated that the SCIH with relatively low feed velocity was more suitable for improving the mechanical properties of gray cast iron. Compared with convex surface, the concave surface of workpiece can obtain better mechanical properties under the same feed velocity of inductor.

Effect of Spot Continual Induction Hardening on the Tribological Performance of Grey Cast Iron with Curved Surface

ABSTRACTIn order to investigate the effect of a spot continual induction hardening (SCIH) process on the tribological performance of grey cast iron with a curved surface, dry sliding wear tests were performed under different loads. The curved surface structure of the workpiece and feed velocity of the inductor were considered important influence factors. X-ray diffractometry (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) were used to investigate the phases, compositions, and morphologies of grey cast iron after the SCIH process and tribological tests. The results showed that the wear mechanism of grey cast iron was always adhesive and abrasive wear at different loads when the workpiece was not strengthened. In the case of partial strengthening, the wear mechanism changed from adhesive and abrasive wear to fatigue–exfoliative wear with increasing load. Oxidative wear always appeared as the dominant wear mechanism when the workpiece was completely strengthened. The wear resistance of the concave surface was always larger than that of the convex surface under the same feed velocity of the inductor. Relatively low feed velocity of the inductor in the SCIH process can optimize the wear resistance of grey cast iron with a curved surface.

Numerical simulation of induction hardening of a cylindrical part based on multi-physics coupling

An induction hardening process was simulated based on an electromagnetic-thermal-transformation coupled numerical model. Calculation of the microstructure fraction was introduced using a coupled electromagnetic-thermal field during heating and the temperature field of the subsequent cooling process. The isoconversional method was used to formulate the austenitization process during heating, model parameters were determined by continuous heating dilatometric curves, and JMAK and K–M equations were adopted to calculate the fraction of new phases formed during cooling. The temperature and microstructure evolution in a cylindrical part of JIS-SCM440 steel were simulated during the induction hardening process and the simulated temperature and final microstructure distribution fit well with experimental data. Simulation results also showed that the free cooling prior to spray quenching could be optimized to decrease the temperature gradient in the surface layer to avoid decomposition of austenite into non-martensite microstructure.

Induction hardening of tool steel for heavily loaded aircraft engine components

Abstract Induction hardening is an innovative process allowing modification of the materials surface with more effective, cheaper and more reproducible way to compare with conventional hardening methods used in the aerospace industry. Unfortunately, high requirements and strict regulation concerning this branch of the industry force deep research allowing to obtain results that would be used for numerical modelling of the process. Only by this way one is able to start the industrial application of the process. The main scope of presented paper are results concerning investigation of microstructure evolution of tool steel after single-frequency induction hardening process. The specimens that aim in representing final industrial products (as heavily loaded gears), were heat- -treated with induction method and subjected to metallographic preparation, after which complex microstructure investigation was performed. The results obtained within the research will be a basis for numerical modelling of the process of induction hardening with potential to be introduced for the aviation industrial components.

The Effects of Austempering and Induction Hardening on the Wear Properties of Camshaft Made of Ductile Cast Iron

6th Congress and Exhibition on International Advances in Applied Physics and Materials Science (APMAS) -- JUN 01-03, 2016 -- Istanbul, TURKEY

The Effect of Quenching Temperature and Polishing Force on the Residual Stress and Deformation of Rack Bar Semi-Products

In the present study, the residual stress state and macroscopic deformation of automotive rack bar semi-products were examined. The rack bars were taken from the original production line after induction hardening, burnishing and polishing. Induction hardening was performed at 860°C, 880°C and 900°C and the polishing step was performed with standard and increased polishing force. Thus, the effect quenching temperature and polishing force are described. Non-destructive residual stress mapping was performed after which macroscopic deformation measurements were carried out on the same rods. It was shown that the variation of quenching temperature had no effect on the residual stress state and deformation of the components. The increased polishing force did not change the average stress state of the rods, however, it resulted in higher stress asymmetry and deformation of the rods. Stress asymmetry was shown to be the cause of bending of the rods.

Effects of the Inductive Hardening Process on the Martensitic Structure of a 50CrMo4 Steel*

Abstract This study focuses on the influence of a fast heat treatment, as occurring with induction heating processes, on the microstructural features, and their effect on the mechanical properties of a 50CrMo4 steel. To this end, three different heating rates (1 K/s, 10 K/s, and 100 K/s) and three different austenitizing temperatures (950 °C, 1000 °C, 1050 °C) were applied to a ferritic-pearlitic steel. After quenching, the resulting martensitic microstructures were investigated and compared to a conventional furnace heat treating sequence using electron back scattered diffraction (EBSD). Thus, the effect of variable heating rates during austenitization on the resulting martensitic microstructure, including the evaluation of packet and block sizes and orientations, was analyzed. Through the investigations of this work, it could be shown, that the adaption of the Kurdjumov-Sachs (K-S) variants is changing with the prior heat treatment. The occurrence of all 24 K-S variants in the same intensity increases and the misorientation angle across a martensite block decrease with higher austenitizing temperatures, despite fast heating rates. Therefore, it is suggested, that the austenitizing temperature has more impact on the martensitic structure than the heating rate.

Bending Distortion Analysis of a Steel Shaft Manufacturing Chain from Cold Drawing to Grinding

Shafts are usually manufactured from bars that are cold drawn, cut machined, induction hardened, straightened, and finally ground. The main distortion is characterized by bending that appears after induction hardening and is corrected by straightening and/or grinding. In this work, the consequence of the variation of manufacturing parameters on the distortion was analyzed for a complete manufacturing route for production of induction hardened shafts made of Grade 1045 steel. A DoE plan was implemented varying the drawing angle, cutting method, induction hardening layer depth, and grinding penetration depth. The distortion was determined by calculating curvature vectors from dimensional analysis by 3D coordinate measurements. Optical microscopy, microhardness testing, residual stress analysis, and FEM process simulation were used to evaluate and understand effects of the main carriers of distortion potential. The drawing process was identified as the most significant influence on the final distortion of the shafts.

Induction hardening treatment and simulation for a grey cast iron used in engine cylinder liners

In this research, a technical study of induction hardening in a grey cast iron used in engine cylinder liners manufactured by LAVCO Ltda., a Colombian foundry company, was carried out. Metallurgical parameters such as austenitization temperature, cooling rate, and quenching severity were determined. These factors are exclusively dependent on chemical composition and initial microstructure of grey cast iron. Simulations of induction heating through finite elements method were performed and, the most appropriate experimental conditions to achieve the critical transformation temperature was evaluated to reach a proper surface hardening on the piece. Preliminary results revealed an excellent approximation between simulation and heating test performed with a full bridge inverter voltage adapted with local technology.

HARDENING OF CRANE RAILS BY PLASMA DISCRETE-TIME SURFACE TREATMENT

Crane wheels and rails are subjected to intensive wear in the process of operation. Therefore, improvement of these components’ performance can be considered a task of high importance. A promising direction in this regard is surface treatment by highly concentrated energy flows such as laser beams or plasma jets. This thesis suggests that the use of gradient plasma surface treatment can improve the performance of crane rails. A research was conducted, according to which hardened zones were deposited on crane rails under different treatment modes. Microhardness was measured both at the surface and in depth using custom-made microsections. The article includes the results of study of plasma surface hardening effects on wear resistance of crane rails. Change of plasma surface treatment parameters (current, plasma torch movement speed, argon gas flow rate) allows for desired steel hardness and structure, while the choice of optimal location for hardened zones makes it possible to significantly improve wear resistance and crack resistance. As a result of plasma surface hardening, the fine-grained martensite structure is obtained with mainly lamellar morphology and higher hardness rate compared toinduction hardening or overlaying. Wear test of carbon steels revealed that plasma surfacing reduces abrasive wear rate compared to the irinitial state by 2 to 3 times. Enough sharp boundary between hardened and non-hardened portions has a positive effect on the performance of parts under dynamic loads, contributing to the inhibition of cracks during the transition from solid to a soft metal. For carbon and low alloy rail steels, the properties achieved by plasma surface hardening can effectively replace induction hardening or overlaying.The mode range for plasma surface treatment that allow sobtaining a surface layer with certain operating properties has been determined.

Effect of induction hardening of Fe-C-Ni-Cu-Mo-B metal matrix composites by powder metallurgy for gear production

Purpose: In this study, mechanical behavior of iron base (Fe-0.8 C-2.0 Cu-1.5 Ni-X Mo-YB (%wt.), x=0.6, 1.2 and 1.8; Y=0.2, 0.6 and 1.0) metal matrix composite (MMC) by powdermetallurgy was investigated for gear production. Effect of Mo and B elements on surfacehardness, density and microstructure of the composite samples.Design/methodology/approach: MMC has produced by warm compaction methodfollowed by free sintering in controlled Ar gas atmosphere. Green composite has producedunder 650 MPa pressure at 160ºC temperature. The green products have been sinteredat temperature of 1150ºC and 60 min sintering time. Hardness test have been conductedbefore and after induction hardening. The microstructure of the samples have beenexamined before and after induction hardening under optical microscopy.Findings: The results have showed that the highest surface hardness has been obtainedX=1.8 and Y=1.0 composition. Addition of Mo and B elements does not affect on the densityof the sample.Research limitations/implications: The ability of induction hardening to compositematerial has been investigated.Originality/value: The studies were carried out in experimental composition with warmcompacting method.

The Microstructure and Mechanical Properties of Cylindrical Elements from Steel 38Mn6 after Continuous Induction Heating

Abstract The paper deals with the influence of induction surface hardening on the microstructure and mechanical properties of cylindrical elements made of steel 38Mn6. The first stage was based on computer simulation of the induction hardening process. The second stage - experiments were provided on laboratory stand for induction surface hardening located at the Silesian University of Technology. Microstructure tests were conducted on light and scanning microscopes. The hardness penetration pattern and thickness of hardened layer were marked. It was found that due to properly chosen parameters of the process, the appropriate properties and thickness of hardened layer were achieved.

Effects of Microalloy Additions and Thermomechanical Processing on Austenite Grain Size Control in Induction-Hardenable Medium Carbon Steel Bar Rolling

Three AISI 1045 steels: a base steel, one modified with vanadium (V), and one modified with V and niobium (Nb) were studied to evaluate microstructural conditioning prior to induction hardening. Simulated bar rolling histories were evaluated using fixed-end hot torsion tests with a Gleeble® 3500. The effects of chemical composition and thermomechanical treatment on final microstructures were examined through analysis of laboratory simulations of steel bar rolling and induction hardening processes in order to provide additional insights into the morphological evolution of austenite of microalloyed steels. Analysis of prior austenite grain size (PAGS) is complemented with analysis of austenite recrystallization and pancaking during rolling. The potential for utilizing TMP, in conjunction with microalloy additions, to enhance bar steel microstructures and subsequent performance is assessed by evaluating the induction hardening response of each steel systematically processed with different preconditioning treatments.

Properties and Commercial Application of Manual Plasma Hardening

A new method and a device for plasma hardening of various parts are considered. Installation of the new device does not require too much investment (the active mechanical productions are appropriate for its accommodation) and special choice of personnel (welders train to use it without difficulty). Plasma hardening does not deform and worsen the smoothness of the surface, which makes it possible to employ many hardened parts without finishing mechanical treatment required after bulk or induction hardening. The hardened layer (about 1 mm) produced by plasma hardening exhibits better wear resistance than after bulk hardening with tempering, which prolongs the service life of the parts.

Bearing Steels for Induction Hardening – Part II

Abstract Surface induction hardening, through induction hardening, and induction tempering of components like rolling elements or rings are established in production and are further developed in research and development. Among others, the used steel grade for induction hardening is one important factor affecting the induction hardening result. The present study benchmarks potential and existing bearing steels in terms of their induction hardening response. Steel grades with low to high carbon contents and different alloying strategies were selected. The robustness of the heat treatment result depending on the selected steels and their conditions prior to induction hardening, shall be pointed out. A dilatometer study was used to compare the sensitivity of martensite start temperature (MS), hardness after quenching, prior austenite grain size, and appearance of non-martensitic transformation products, for varied process parameters. The study showed the pronounced effect of the steels prior microstructure, prior to induction hardening, on the hardening response. The alloying with silicon and manganese reduced the amount of non-martensitic transformation products after hardening. Increasing amounts of alloying elements led in general to larger changes in MS temperature and lower hardness after hardening.

Induction hardening of steel with restrained Joule heating and nonlinear law for magnetic induction field: Solvability

We study a coupled system of Maxwell’s equations with nonlinear heat equation. We start with derivation of a mathematical model assuming a nonlinear dependency of magnetic field H on magnetic induction B. Moreover the electric conductivity σ is supposed to be temperature reliant. The coupling between the thermal and electromagnetic equations is provided via the Joule heating term and σ. Next we use time discretization based on the Rothe’s method to provide energy estimates for discretized system. We prove the existence of a weak solution {u,B} to this coupled system with controlled Joule heating term.

Simulation of multi-frequency-induction-hardening including phase transitions and mechanical effects

Induction hardening is a well known method for the heat treatment of steel components. With the concept of multi-frequency hardening, where currents with two different frequency components are provided on a single inductor coil, it is possible to optimize the hardening zone to follow a given contour even in the case of complicated 3D geometries like gears.In this paper, we consider the simulation of multi-frequency induction hardening in 3D. The equations to solve are the magneto-quasistatic approximation of Maxwell׳s equations describing the electromagnetic fields, the balance of momentum to determine internal stresses and deformations arising from thermoelasticity and transformation induced plasticity (TRIP), a rate law to determine the distribution of different phases and the heat equation to determine the temperature distribution in the workpiece.The equations are solved using adaptive finite element methods. The simulation results are compared to experiments for discs and for gears. A very good agreement for the hardening profile and the temperature is observed. It is also possible to predict the distribution of residual stresses after the heat treatment.