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| Pernis R. |
| DRAW DIE WITH TRACTRIX CURVE |
| Keywords: deep drawing|draw die|draw curve|tractrix|equidistance equation|equidistance tractrix| |
| No 1 (2006), p. 33-41 |
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| Molnárová M., Leško A., Vlado M. |
| DETERMINATION OF CRITICAL TIN PLATE THICKNESS FOR SURFACE PENETRATION OF ROLLED IN OXIDES |
Abstract
Surface defects of tin plates and methods of their detection were analyzed. For individual points in technological production process of flat rolled semi-products, in this case the tin plate, several types of characteristic defects were described. Formation of most of these defects can be avoided by observing the technological terms in production process. It is important to avoid mainly the formation of embedded oxides in push heating furnaces by selecting the right heating temperatures, heating period and also the content of oxygen in heating atmosphere. Thick layers of scales, containing different types of oxides, which went into original grain boundaries of slab surface layer, these can be very compact, adhesive and hardly removable. Under the surface scale layers in material grains interior, the small globular particles of internal oxidation can form at elevated temperature, according to the published data above the temperature of 1100°C. Non removed scales with high degree of cohesion, which formed in pushing reheating furnace and are anchored in cracks, surface defects and in the primary grain boundaries can be rolled in during the following production operation. During the cold rolling process and gradual reduction of sheet thickness, the rolled in oxides approach the material surface and after reaching the critical thickness they penetrate it.
In the experimental part there is presented the optical microscopy using the „Olympus DP-SOFT“ software application and SEM and EDX analysis using „EDAX GENESIS“ software application. In this paper Subsurface rolled in oxides are monitored during cold rolling and critical plate thickness for their surface penetration is estimated. In the conclusion recommendations are formulated for reduction of these oxides formation.
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| Keywords: tin plate|surface defects|hot rolling|cold rolling|critical plate thickness|structure|optical microscopy|SEM|EDX| |
| No 1 (2006), p. 59-68 |
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