Скачать или смотреть Scanning Induction Hardening Simulation

Scanning induction hardening is used to case harden shafts. Induction heating coils austenitize the shaft surface to a predetermined depth. A water cooling jacket quenches the shaft and transforms the austenite into martensite.


Product: DEFORM Premier; DEFORM-2D / Microstructure Module; DEFORM-HT

Summary:

Scanning induction hardening processes are commonly utilized to case harden shafts in manufacturing flowpaths. The 2D DEFORM-HT simulation predicts how induction heating coils austenitize a shaft surface to a predetermined depth. A water cooling jacket quenches the shaft and transforms the austenite into martensite. The simulation results plot temperature, austenite phase volume fraction and martensite phase volume fraction throughout the process.

Case Study:

Engineering components must have specific mechanical properties to achieve acceptable performance in service. A common way to improve mechanical properties in metal parts is through heat treatment.

Induction hardening is a popular and efficient method for rapidly heating and cooling a workpiece to achieve desired microstructural and mechanical properties. The surface hardening of long, slender components may be carried out by scanning the part through an induction hardening unit. The unit is comprised of an induction heating coil and a water quench jacket.

Tight control of process conditions is important, otherwise problems such as an insufficient case depth might result. Also, phase transformations and local thermal response within the metal inevitably result in some amount of distortion.

Additional problems can be caused by an insufficient balance between the heating and cooling operations. For example, a quenched surface comprised of martensite could soften due to the tempering effect produced by a still-hot core.

A SAE-1055 steel shaft was analyzed in DEFORM-HT with a two turn copper induction coil and a water quench jacket. All components were axisymmetric and the analysis was carried out in 2D.

The workpiece and coil were each modeled with an FEM mesh. The water jacket was represented by a user-defined heat transfer window. The induction Boundary Element Method (BEM) solution was coupled to the deformation and thermal Finite Element Method (FEM) solutions. Relative movement was applied between the coil and workpiece.

Material data consisted of elastic, plastic, thermal, and electro-magnetic properties for each steel phase. Electromagnetic properties were also specified for the copper coil. Diffusion-type phase transformations were predicted by coupling isothermal transformation (TTT) diagrams and the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The calculation of non-diffusion types of transformations were modeled using a martensitic relationship.

15 kW of power was applied to heat the workpiece. A frequency of 20 kHz, concentrated heating at the surface layer of the shaft. A local cooling window represented the quench water jacket. It was set to a temperature of 20 °C and a convection coefficient of 20 kW/(m2*K). The heat transfer temperature field was governed by the Laplace equation. The governing equations for the electromagnetic field solution incorporated magnetic permeability, electric conductivity, source current density, and magnetic vector potential.

The DEFORM-predicted temperature-time variations at the exit of the coil were very close to those measured via optical pyrometer in the actual process. Axial dilation measurements were facilitated by applying boundary conditions, which locked one end of the shaft in place while the other end was free to move.

Effective case depth is defined as the region containing over 50% martensite volume fraction. It was measured across a radial section of the simulated shaft. Predictions were taken after cooling the workpiece to room temperature.

Induction heating, hardening and microstructure modeling are available in DEFORM Premier, DEFORM-HT or the Microstructure Module add-ons to DEFORM-2D and DEFORM-3D.

Process simulation provides designers and metallurgists with valuable, predictive information about heat treatment processes. Temperature, case depth, residual stress and part distortion are just a few of the critical outputs. It also enables induction coil design efforts to incorporate the modeling and optimization of electromagnetic influences on the end product.

Induction hardening simulations have been applied to a wide range of products including shafts, stub axles, gears,and bearing components. Such analyses allow automotive, aerospace, oilfield and specialist industries to evaluate their processes on the computer, thus reducing shop floor trial and error.