Metal treatment – Process of modifying or maintaining internal physical... – With measuring – testing – or sensing
Patent
1999-01-11
2000-11-28
Kastler, Scott
Metal treatment
Process of modifying or maintaining internal physical...
With measuring, testing, or sensing
148645, 148646, 266259, C21D 154
Patent
active
061530263
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for tempering flat metallic products comprising station with an upper surface orientated upwardly and a lower surface orientated downwardly, substantially horizontal lower support table of the tempering station, tempering liquid simultaneously on all its upper and lower surfaces, and tempering apparatus for the implementation of such a process.
Tempering processes of this type, intended to temper flat metallic products, such as sheets, strips and similar products, have been known for a long time. They are batch processes in which an upper pressing table is lowered on the flat product to be tempered and is either pressed or placed down on it. The apparatuses implementing this type of process are called tempering presses.
These processes enable the simultaneous spraying of the whole upper and lower surfaces of the flat product exiting out of the furnace with a tempering liquid, for example water. However, they have the major drawback of producing scratches on the surface of the tempered sheets. In effect, at the time of tempering, the sheets are subjected to a sudden shrinkage whilst they are gripped between support elements of the upper and lower tables in the shape of fingers. Another drawback is the fact that at the time of tempering, the forward portion of the sheet exhibits a difference in temperature relative to the rear portion which has just exited from the furnace. The stresses caused by tempering are not therefore uniform over the whole surface of the tempered sheets.
Continuous tempering processes are also known in which the sheets are tempered progressively as they exit from the furnace. Each portion of the sheet is therefore always cooled under the same conditions. However, such a sheet exhibits with this process enormous differences in temperature between a portion already tempered and one which has exited from the furnace but is not yet tempered. These differences lead to stresses and deformations in the sheets, to such an extent that this type of process has been virtually abandoned, especially for large sheets (see on this subject patents FR-1415912, U.S. Pat. No. 3,423,254, U.S. Pat. No 3,420,083, NL-135696, BE-A-758799, BE-A-789130 and U.S. Pat. No. 4,149,703).
The object of the present invention is to provide a batch tempering process and apparatus which does not appreciably exhibit the major drawbacks described above. In particular it has for its object to allow tempering or hyper-tempering of fine flat products, for example stainless steel sheets with a thickness of 3 to 30 mm, or carbon steel sheets with a thickness of 3 to 10 mm, to produce flat sheets which are substantially without scratches.
To solve this problem according to the invention, a process is provided similar to the one described above which comprises, before the sudden cooling, a transference of retaining elements, which form together a substantially horizontal upper holding table, into a horizontal retaining plane located a predetermined distance above the upper surface of the flat product, and during sudden cooling a possible retention of the flat product by the upper retaining table in the limits imposed by the said horizontal retaining plane. This process, therefore, is no longer tempering under compression and thus no longer has the drawbacks of the latter. On the contrary, the advantages of a simultaneous and uniform spraying on the whole of the upper surface and the whole of the lower surface of the sheet to be cooled are retained.
Advantageously, the above mentioned retaining plane is located at a distance of the order of 0.5 to 2.5 mm from the upper surface of the flat product to be tempered, preferably of the order of 0.8 to 1.2 mm, in particular of 1 mm.
In one embodiment of the invention the transference comprises a comprises a continuous measurement of the position of the retaining table in relation to a fixed reference and a stoppage of the transference when the said measurement reaches a predetermined value, in which the retaining table is located at the said pre
REFERENCES:
patent: 541422 (1895-06-01), Carpenter
patent: 3423254 (1969-01-01), Safford et al.
patent: 3534947 (1970-10-01), Lenz
patent: 4371149 (1983-02-01), Takeuchi et al.
patent: 5885522 (1999-03-01), Giannini et al.
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