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Identifying process parameters influencing gear runout
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0002-0288-0238
Scania CV AB.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The hardening distortions with respect to base body, clutch teeth and helical gears are investigated for a serial-produced main shaft gear of a 20NiCrMoS6-4 steel. The influences of casting geometry, annealing heat treatment and stress relief annealing of blanks, as well as vertical and horizontal loading arrangements during case hardening, are studied. The concentricity, roundness and runout of clutch teeth and helical gears are measured in the soft machined, hardened and hard-machined conditions.

The Brinell hardness is measured on blanks obtained from different manufacturing routes showing differences in hardness and scatter. Stress relief annealing lowers the hardness and the scatter for all groups, but has no significant effect on distortions. The case depth, core hardness and surface hardness are measured after hardening. The study shows that the surface hardness correlates with the oil flow measured in the quench tank.

The effect of casting geometry is stronger for the clutch teeth compared to the helical gears. For the clutch-teeth roundness and runout, significantly lower values are found for square geometry compared to rectangular. It is also seen that the major part of the runout comes from roundness errors which are mainly induced by the hardening. Horizontal loading reduces roundness errors and runout but produces conical base-bodies with worse backplane flatness.

Keywords [en]
Hardening distortions, main shaft gear, gear runout
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-207123OAI: oai:DiVA.org:kth-207123DiVA, id: diva2:1095944
Funder
VINNOVA, 2015-03723
Note

QC 20170516

Available from: 2017-05-16 Created: 2017-05-16 Last updated: 2017-05-16Bibliographically approved
In thesis
1. Hardening Distortions of Serial Produced Gears
Open this publication in new window or tab >>Hardening Distortions of Serial Produced Gears
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Hardening distortions are unwanted changes in shape and dimension that arise during hardening of steel components. Uncontrolled distortions induce random errors to the manufacturing process, and have a strong negative impact on manufacturing costs. The distortions are not only caused by the hardening process, several factors from previous manufacturing steps including the component geometry itself contribute to varying extent. The aim of the current work is to investigate the main influencing factors on hardening distortions for serial produced gears.

The investigations were done on two different types of gears for heavy-duty transmissions, crown wheels for the rear axle central gear and main shaft gears for the gearbox. The steel was produced using either continuous casting or ingot casting. For rectangular continuously cast steel, the effect of disabling magnetic stirring of the steel melt during casting was investigated, finding a strong reduction of gear runout for crown wheels. Segregations in crown wheels produced from the top and bottom of ingots were shown to go in opposite directions, producing opposite back-face tilts.

For crown wheels quenched one at a time, influences of stacking level on the hardening tray were found, indicating an impact from small variations in the carburizing process, despite identical quenching conditions. For main shaft gears, horizontal loading gave considerably less roundness and runout errors but increased flatness errors compared to vertical loading.

This thesis shows the complexity of the distortion phenomenon and how several factors interact and contribute to the final result. It is shown that factors with significant impact on hardening distortions for one component may be less important for another component. With this in mind, each type of component to be hardened should be produced by a manufacturing chain where each process step is carefully chosen with respect to minimizing distortions.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. p. 33
Keywords
hardening distortions, crown wheel, main shaft gear, gear runout, back-face tilt, macrosegregation, ingot casting, continuous casting, case hardening
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-207087 (URN)978-91-7729-449-8 (ISBN)
Presentation
2017-06-12, Hörsalen byggnad 260, Scania, Södertälje, 14:30 (Swedish)
Opponent
Supervisors
Note

QC 20170516

Available from: 2017-05-16 Created: 2017-05-16 Last updated: 2017-05-19Bibliographically approved

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