Identification of process parameters affecting distortion of disks for gear manufacture ‐ Part II: heating, carburizing, quenching

Self Cite

Distortion is an effect of inhomogeneous strain behavior. It can be initiated by plasticity due to thermal or transformation stresses (such as yielding, creep and transformation plasticity), phase transformations or strains during phase transformations. Inhomogeneities in microstructure and anisotropies constitute a distortion potential. Based on this knowledge several investigations were carried out on forged disks with a centered hole made of low alloy steel SAE 5120 (EN 20MnCr5) because both inhomogeneity and anisotropy have been observed in the microstructure of this material. Disks have been forged from continuous cast and hot rolled bar material. They show an inhomogeneous banded microstructure that is explicitly orientated in the direction of the two manufacturing processes. By forging, the initial microstructure of the bar material is influenced significantly: the segregation bands parallel to the rolling direction are deformed into a typical pattern. Besides this inhomogeneity in microstructure also the inhomogeneities of the bar material, such as center segregations from continuous casting, can still be observed in the deformed material. Gear blanks were machined from these disk blanks. It has been shown that the original position of the gear blank inside the disk blank influences the distortion [1]. The underlying reason remained unclear and investigations on this topic are discussed in this paper.

Section: Discussionmentioning

confidence: 95%

“…Relevant shape changes were also identified for the ovality of disks [1,12] and have been presented at the IDE 2008. Analysis using the design of experiment (DoE) method showed a high significant influence of hardenability on the phase angle of the ovality.…”

Section: Introductionmentioning

confidence: 99%

Anisotropies and inhomogeneities in the microstructure of the case hardening steel SAE 5120

Eisbrecher

Clausen²,

Hunkel

et al. 2012

Self Cite

“…Both approaches led to a reduced scatter of the change of dishing as well (for more details [4]. However the influences of the material properties and other processes of the manufacturing chain are being analyzed and have been presented elsewhere [2,6].…”

Section: Materials Flow and Distortion Of The Gear Wheel Blanksmentioning

confidence: 99%

Parameters of distortion in forging gear wheel blanks

Rentsch

2012

The gear wheel manufacture is one of the key technologies for power train systems and in automotive industry. These complex high performance parts require stable processes and narrow tolerances in order to control the manufacturing costs. Experimental analyses show that the material flow in disk-like gear wheel blanks made of 20MnCr5 can vary significantly. This is of significance as a correlation between the dishing after case-hardening of the gear wheel blanks and the material flow was found. Besides experimental findings, finite element (FE) analyses of the influence of process parameters and perturbations on the distortion of forged gear wheel blanks have been carried out. A temperature gradient over the height of the workpiece is assumed to be largely responsible for the observed material flow variations and the related dishing of the forged gear wheel blanks.

“…Derived from these measurements the dishing is calculated as documented by Clausen [5]. The toothing is characterised by the tooth alignment error, profile angle error and adjacent pitch error.…”

Section: Coordinate Measurementmentioning

confidence: 99%

Methodical investigation of distortion biasing parameters during case hardening of spur wheels

Steinbacher

Surm

Clausen

et al. 2012

Self Cite

Highly stressed gears are typically heat treated to satisfy operational demands. Case hardening is a common heat treatment associated with power train components. In the heat treatment process complex distortion processes take place, which were studied in these examinations. Object of the actual investigations were spur wheels with module 2.557 and 42 teeth on the wheel with a helix angel of 23 8. The case hardening was realized utilizing low pressure carburisation with subsequent high pressure gas quenching in a heat treatment furnace of industrial proportion. The systematic analysis was guided using design of experiment methods. In strategic focus were the three contributing heat treatment steps of heating, carburisation and quenching. Heating related factors were the batch design, the heat transfer and the preheating temperature. During carburisation the temperature, carburisation depth and surface carbon content as well as the atmosphere during diffusion were altered. Finally the quenching related variation was the hardening temperature. The identified main factors on size as well as shape changes of the base body and the toothing will be presented and discussed.Keywords: Case hardening / gear wheels / heat treatment / heating / carburising / quenching / SAE5120 (EN20MnCr5) / Chargenaufbau, der Wärmeübergangsmechanismus sowie die Temperatur der ersten Haltestufe für den Temperaturausgleich in der Charge. Die in der Aufkohlung variierten Größen sind die Aufkohlungstiefe und der Randkohlenstoffgehalt, sowie die Atmosphäre während der Diffusionsund Haltephasen. In Bezug auf die Abschreckung wurde der Einfluss der Härtetemperatur auf den Verzug der Zahnräder betrachtet. Durch eine 3-D-Koordinatenmessung des Grundkörpers und der Verzahnung vor und nach der Wärmebehandlung konnte eine ¾nderung der Maß-und Formabweichungen durch die Wärme-behandlung abgeleitet werden. Diese ¾nderungen wurden hinsichtlich der einzelnen beschriebenen Parameter und deren Variationen mittels der Auswertung des DoE-Plans analysiert, um die signifikanten Einflussgrößen auf den Verzug zu identifizieren. Im Folgenden werden die Ergebnisse der Untersuchungen dargestellt und diskutiert.