Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Patent
1994-09-14
1997-11-25
Sheehan, John
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
148579, C21D 802
Patent
active
056907575
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention concerns a method relating to the manufacturing of steel strips, comprising continuous treatment of the steel strip in an annealing furnace at a temperature between 1000.degree. C. and 1250.degree. C.
BACKGROUND OF THE INVENTION
The rolling of steel strips usually is carried out for several reasons. A primary objective is to afford the steel strip a desired thickness. The rolling usually is performed as hot rolling down to a thickness in the dimension range 1-12 mm, preferably 1-mm, whereupon continued reduction of the thickness to desired final thickness is performed through cold rolling. In connection with the cold rolling, usually one or more annealing operations are included for the recrystallization of the steel structure.
In connection with this technique, it is difficult to achieve the desired final thickness in a simple and practical way.
Another problem concerns the breadth of the strip. The end product shall have a certain desired strip breadth, which must at least be reached. In order to meet with this requirement it is conventional to use, as starting material for the cold rolling operation, hot rolled strips having a breadth which substantially exceeds the desired final breadth. This implies that larger amounts of edge scrap are formed at the manufacturing than what is required for the more or less unavoidable conditioning of the edges of the strip. The formation of this scrap material from the edge portions, which is due to poor adaptation of the breadth of the raw strips to the breadth required by the customer and also due to the fact that there are no possibilities to adjust the breadth of the strips in the cold roll mills, represents very large losses.
BRIEF DESCRIPTION OF THE INVENTION
The purpose of the invention is to solve the above mentioned problems. This can be achieved by the method of the present invention wherein steel strip is fed continuously into an annealing furnace at a certain feed-in rate and drawn out of the furnace at a rate higher than the feed-in rate while subjecting the steel strip to a pulling force in the annealing furnace at a temperature above the recrystallization temperature of the steel in the region of 1000.degree. to 1250.degree. C. This results in the introduction of a permanent stretch of the steel strip corresponding to the difference between the feed-out and feed-in rates as well as a reduction in the cross-section of the strip corresponding to the elongation and a reduction of the strip thickness and strip width. The method of the invention has been developed particularly for austenitic stainless steels but can be used also for other steel grades, stainless as well as other alloyed steels, and also for carbon steels. The principles of the invention per se also can be utilized for the manufacturing of metal strips, which do not consist of steel, particularly metals which are subjected to cold hardening during cold working, as for example copper and copper alloys. Further features and aspects of the invention will be apparent from the following description of a preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention, various aspects of the invention, and performed experiments will be described in the following with reference to the accompanying drawing, which illustrates a production plant, in which facilities for performing the method of the invention are integrated.
DETAILED DESCRIPTION OF THE INVENTION
In the drawing, a roll of hot rolled steel strip is generally designated 1. As an alternative the starting material--the steel strip 1--may consist of a cold rolled, annealed strip. A cutter is designated 2, and a welding apparatus for welding together strip sections is designated 3. The steel strip, consisting of sections which have been welded together, and which shall be treated according to the invention, is designated 4. The plant shown in the drawing also includes the following members, namely a strip store or accumulator 5, a first braking mill 6, a cold rolling mil
REFERENCES:
patent: 3388011 (1968-06-01), Zacksy et al.
Derwent's Abstract, accession number 74-16917v/09, SU-384903, publ week 7409, Orbit Search Service, File WPAT Aug. 1978.
Avesta Sheffield
Sheehan John
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