Metallurgical apparatus – Means treating a continuum of work – With heating means
Patent
1988-07-22
1991-01-15
Kastler, S.
Metallurgical apparatus
Means treating a continuum of work
With heating means
266115, C21D 956
Patent
active
049847708
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the partial tempering of rolled wire products made of steel.
2. The Prior Art
In the production of bars, quenching directly from the rolling heat, and thus partially tempering the steel, is known. With bars of finite lengths, the bars, after being cut, are moved axially and in so doing are treated with a cooling medium. This method has gained wide application and has proved itself many times.
In the partial tempering of rolled wire, this method cannot be used without great difficulty, because at the typical rolling speed and with a necessary cooling period of from 0.5 to 1 s, the cooling line can be up to 120 m long. Such a long cooling line is vulnerable to malfunction, and both an initial and a final length of the rolled product remain uncooled, so there is considerable waste.
The term "partial tempering" is understood to mean a process that affects only the peripheral region of the tempering material, in which the peripheral zone is converted completely to martensite and after the quenching process is ended is annealed again by the residual heat present in the center of the cooling material. The important factor is the peripheral zone is converted completely and homogeneously to annealed martensite.
It is known for wires to be cooled down first from the heat of the rolling mill, and then delivered to a winding layer. Examples of this are described in British patent application No. 1,128,35, German examined patent application No. 1,262,323 and German unexamined patent application No. 1,452,343. Such methods were offered in order to improve the cold drawing capability. The hot-rolled wire here is subjected to an intermediate-stage tempering, and martensite formation during the cooling process is very consciously avoided, because it considerably impairs the drawing capability.
In contrast to that, German unexamined patent application No. 2,829,428 discloses an apparatus for producing wires usable for concrete reinforcing bars. Here, following the final rolling pass, cooling to approximately 750.degree. C. is supposed to take place, so that after the following winding layer the cooling can be completed to 600.degree. to 500.degree.. As indicated in this published reference, a complete conversion of the peripheral region to a martensitic structure is not sought; this is dictated by the first cooling stage, in which the precipitation of perlite already takes place, and only the remaining amount of austenite can be converted into martensite.
SUMMARY OF THE INVENTION
Even if these disadvantages were accepted as a necessary compromise, the great lengths involved present still further problems, because the wires have to be shaped into wire windings by winding layers immediately following the cooling, or in other words when their surface is hardened. Accordingly, the winding layer must work against great resistance, and must therefore be equipped with heavy-duty motors. On the other hand, the hardened surface acts like a file and quickly wears down the equipment parts required. Finally, the internal strains generated by the cooling and subsequent bending have a deleterious effect on laying the wire uniformly, which can cause problems and disrupt operation during an ensuing processing operation.
It is therefore the object of the invention to devise a method and an apparatus for performing the method with which the above-mentioned disadvantages can be overcome, and with which rolled wire products can be partially tempered with equal ease, and with a quality comparable to that of bars.
It is an object of the invention to produce a rolled wire product in which the peripheral region comprises fully annealed martensite, so as to attain high final strength in combination with good fatigue properties, high durability and conductability, with favorable corrosion resistance.
According to a preferred embodiment a method is provided for partial tempering of rolled wire products made of steel from the rolling heat by quenching with a coo
REFERENCES:
patent: 4016009 (1977-04-01), Economopoulos et al.
patent: 4108695 (1978-08-01), Paulitsch et al.
patent: 4168993 (1979-09-01), Wilson et al.
patent: 4236551 (1980-12-01), Worgt et al.
Simon et al., "Tempcore: A New Process for the Production of High-Quality Reinforcing Bars", Iron and Steel Engineer, Mar. 1984, pp. 53-57.
Economopoulos et al., "Application of the Tempcore Process to the Fabrication of High Yield Strength Concrete-Reinforcing Bars", Steel Furnace Monthly, Feb. 1977, pp. 57-73.
Balzli Samuel
Syfrig Werner
Kastler S.
Von Moose Stahl AG
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