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A quasi-3D method used for increasing the material yield in closed-die forging of a front axle beam
KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Materials Forming.
KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Materials Forming.
2005 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 160, no 2, 119-122 p.Article in journal (Refereed) Published
Abstract [en]

The aim of the work is to increase the material yield in closed-die forging of a front axle beam meant for heavy trucks. The amount of flash obtained in production constituted 35% of the total workpiece weight, which was equal to 115.4 kg. The strategy for improving the material yield was to modify the initial forging workpiece geometry, keeping the pre- and finishing die geometries constant. Recommending new shapes for certain cross-sections of the reducer-rolled billet did this. The goal was reached by using a quasi-3D analysis. Three critical cross-sections that showed close to plane strain conditions during forging were chosen for the analysis. The FE-code Form2D was used. The losses of material in the sections caused by axial material flow were measured from full-scale experiments and added to the optimised cross-sectional areas established from the FE-analysis. Because of advice front industry the initial cross-sections used in the 2D-forging simulations were chosen to be circular. Also the final results, after compensation for the axial material flow are presented as circular cross-sections. Utilising the results from the quasi-3D approach the theoretical material yield was increased by 2.58-7.59% for the cross-sections. Results from this work have facilitated the development of adequately shaped grooves in the reducer rolling mill so that the flash volume obtained in production has been reduced. The investigation was carried out with data from IMATRA KILSTA AB.

Place, publisher, year, edition, pages
2005. Vol. 160, no 2, 119-122 p.
Keyword [en]
quasi-3D; material yield; closed-die forging; front axle beam; FE-analysis
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-8194DOI: 10.1016/j.jmatprotec.2004.05.007ISI: 000227689700003Scopus ID: 2-s2.0-13844297035OAI: oai:DiVA.org:kth-8194DiVA: diva2:13450
Note
QC 20100720Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Closed-die forging and slab hot rolling with focus on material yield: some industrial problems analysed by FEM
Open this publication in new window or tab >>Closed-die forging and slab hot rolling with focus on material yield: some industrial problems analysed by FEM
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The thesis is focussed on improving the material yield in closed-die forging and rolling. The former is restricted to the manufacturing of heavy crown wheels and front axle beams and the latter to the hot rolling of steel slabs. To enhance the yield the commercial FE-codes Form2D and Dyna3D are used. Results from forging simulations are strengthened by full scale experiments. The research is carried out in near contact with the Swedish steel and engineering industry. In closed die forging, two bulk forming problems are treated: How to improve the tool design and how to change the pre-form geometry for decreasing the amount of material exiting the flash gap? In slab rolling, two problems related to material defects are considered: How to eliminate existing surface cracks and how to prevent the formation of voids around macro-inclusions embedded in the steel matrix? Internal voids might be the reason for scrapping the whole workpiece.

Considering the forging of crown wheels, a new concept is proposed. For making the central hole of the product, the traditional method was forging a thin circular plate which was then sheared off and scrapped. Using the new technique this operation is replaced by forging a conical tap in the centre, which is then discarded. Doing so, the inner scrap material decreased with about 15%. The idea has been used in production for seven years. – Regarding the forging of front axle beams, a quasi-3D method is used comprising full scale measurements of the axial material flow. Here the theoretical material yield increased 2-7%.

Regarding rolling, the initial surface cracks in the simulations are V-shaped with a crack angle of 6o and of depth 5-20 mm. The inclusions are cylindrical and either three times harder or three times softer than the matrix. The behaviour of the cracks and the inclusions are studied as influenced by process parameters. Current industrial input data are used as a reference. – It is concluded that longitudinal cracks cannot be totally eliminated. During rolling their V-shape gradually changes to Y-shape and a remaining oxide flake separates the crack bottom surfaces. For minimizing the detrimental influence of the entrapped oxide, an early closure of the crack bottom is important. Throughout the remaining rolling schedule the entrapped oxide is then torn to pieces with large areas of virgin metal in between ensuring a strong bond. The following recommendations are given for the longitudinal cracks: Light drafts/pass at the beginning of the rolling schedule followed by heavy ones. – Contradictory to longitudinal cracks it is concluded that transversal cracks are possible to eliminate. When eliminated, the initial bottom of the crack coincides with the slab surface. No folds are formed. For the transversal cracks light drafts/pass are proposed together with reversal rolling, the latter for avoiding crack folding. – Voids are easiest formed around hard macro-inclusions in the centre of the slab. Large rolls and heavy drafts are recommended to avoid this.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 41 p.
Series
Trita-IIP, ISSN 1650-1888 ; 08-01
Keyword
Material yield, Closed-die forging, Hot rolling, Cracks, Macro-inclusions, Steel, FEM
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:kth:diva-4690 (URN)978-91-7178-871-9 (ISBN)
Public defence
2008-04-25, Sal M311, KTH, Brinellvägen 68, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100720Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-07-20Bibliographically approved

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