Metal treatment – Stock – Ferrous
Patent
1998-12-04
2000-11-28
Jenkins, Daniel J.
Metal treatment
Stock
Ferrous
148334, 420100, 420101, 420104, 420105, C22C 3822, C22C 3818
Patent
active
061530247
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to steel wire stocks making it possible to obtain ready-to-use wires which can be used to reinforce articles, made of plastics or made of rubber, especially tire covers, plies, belts, hoses, etc.
The expression "ready-to-use wire" is employed here in its usual assertion in the metallurgy field, namely that this wire can be used, for the intended application, without having to subject it beforehand to a heat treatment capable of altering its metallurgical structure and without deforming it, for example in a wire-drawing operation capable of altering its diameter.
PRIOR ART
International Patent Application WO-A-92/14811 describes a process for obtaining a "ready-to-use" wire of this type, which comprises a steel substrate whose structure comprises, by weight, more than 90% work-hardened tempered martensite, the steel having a carbon content at least equal to 0.05% and at most equal to 0.6%, this substrate being coated with a metal alloy other than steel, for example brass. The process for obtaining this wire includes a quenching treatment on work-hardened wire by heating the wire above the AC.sub.3 transformation point in order to give it a homogeneous austenitic structure and then by rapidly cooling it to below the martensite transformation finish point at a rate at least equal to 150.degree. C./second. After this quenching treatment, at least two metals are deposited on the wire, then the wire is heated to form, by diffusion, an alloy of these metals, generally brass, and then the wire is subsequently cooled and work-hardened.
The process described in this document has, in particular, the following advantages: a pearlitic steel, ready-to-use wires thus obtained, fewer breakages, and wire, which reduces the manufacturing costs.
However, this known process has the following drawbacks: coating does not always correspond specifically to that necessary for obtaining sufficient mechanical strength before wire drawing; temperature variations introduced as a result of the inevitable dispersion in the heating systems; and is necessary to cool at a high rate in order to obtain a completely, or almost completely, martensitic structure. If the cooling rate is too low, phases other than martensite may appear, such as bainite for example. This high quench rate is a major manufacturing constraint.
It is known in general that, in processes for producing components made of martensitic steels, the addition of an alloying element, such as vanadium or chromium, makes it possible to improve the hardenability and the strength as the result of the precipitation of vanadium or chromium carbonitrides and/or carbides during the tempering. However, the usual treatment times for allowing precipitation are several tens of minutes, or even several hours.
The Applicant has completely unexpectedly found that the precipitation, in the form of carbonitrides and/or carbides, of an alloying element such as vanadium, molybdenum or chromium could take place rapidly in wires having a diameter smaller than 3 mm. This precipitation during tempering makes it possible to avoid the aforementioned drawbacks a) and b) and the presence of these alloying elements during the quench makes it possible to avoid the aforementioned drawback c), thereby making a softer quench possible.
SUMMARY OF THE INVENTION
Thus, the subject of the invention is a wire stock intended to obtain, by deformation and heat treatment, a ready-to-use wire, this wire stock being distinguished by the fact that it is made of a microalloyed steel having a carbon content, by weight, of between 0.2% and 0.6%, the steel furthermore containing at least one alloying element selected from the group consisting of vanadium, molybdenum and chromium, the steel containing at least 0.05% and at most 0.5% by weight of the alloying element or of the combination of alloying elements.
The "ready-to-use" wire obtained from the wire stock according to the invention has the following characteristics: equal to 0.2% and at most equal to 0.6% by weight. Th
REFERENCES:
patent: 5229069 (1993-07-01), Shemenski et al.
Arnaud Jean-Claude
Depraetere Eric
Francois Marc
Serre Raoul
Cole Thomas W.
Coy Nicole
Ispat-Unimetal
Jenkins Daniel J.
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