Metal founding – Including vibrator means – In continuous casting mold
Patent
1985-11-19
1987-06-02
Lin, Kuang Y.
Metal founding
Including vibrator means
In continuous casting mold
164478, B22D 1104
Patent
active
046695257
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates generally to the casting of metals, and more particularly, to the continuous casting of metals having a high melting point, i.e., above about 2600.degree. F.
In the continuous casting of high temperature metals, it is essential that the cast metal be prevented from adhering to the mold as the cast metal cools and solidifies.
2. Background Art
In conventional continuous steel casting, molten steel is passed throuqh a vertically oriented, usually curved, mold tube. The mold tube is preferably made of copper and typically has a square or rectangular cross-sectional shape. As the molten steel passes through the mold tube its outer shell hardens. As the steel strand continues to harden, it is bent through an angle of 90.degree. so that it moves horizontally upon leaving the casting machine, and it is subsequently cut into individual billets.
The temperature of molten steel is typically 2850.degree. F., although with certain grades of steel the temperature may be as low as 2600.degree. F. In general, although most references herein are to steel casting, the invention contemplates the casting of any metal or metal alloy whose liquid temperature exceeds about 2600.degree. F.
The mold tube is oscillated in conventional continuous casting machines to prevent adherence of the molten metal to the walls of the mold tube. If the oscillation of the mold tube is interrupted or stopped the steel will adhere to the copper mold tube and will eventually form a complete shell surrounding a liquid steel core. When this stationary shell has formed, heat transfer ceases and the strand shell cracks, allowing the liquid steel core to pour out (termed a "break out" in the art). When a break out occurs, the casting operation must cease and the cast steel is ruined.
In addition to oscillation of the mold tube, a lubricating material such as Rapeseed Oil or high melting point powder composition is applied either automatically or manually to the meniscus of the liquid steel in the mold.
Strand oscillation, through research and experimentation conducted during the development of the continuous casting process, was found necessary in order to permit the flow of the lubricating medium onto the walls of the copper mold tube. This lubricating material ensures that the steel will not adhere to the walls of the mold. Heretofore, the most effective frequency and amplitude of the oscillation was believed to be from about 60 to about 120 cycles per minute and from about 0.375 to about 0.750 inch, respectively. Further, the oscillation was rigidly controlled so as to be in the vertical direction only - or parallel to the direction in which the steel strand is moving.
Lateral movement of the mold tube was strictly avoided since it was found that lateral motion caused severe surface cracks on the solidifying steel due to high strand shell stresses arising from this motion. Consequently, large, complex machines were designed and developed to prevent the possibility of any lateral motion of the mold tube during the casting process.
In order to design an oscillating system that will smoothly lift and lower a casting mold requires a very complex mechanical arrangement (a typical casting mold weighs in excess of 1000 pounds). It has, therefore, been very difficult to build a system which ensures that all lateral motion is eliminated. In fact, most oscillators do contain significant lateral motion (as high as 0.625 inch) which, when coupled with an oscillation stroke length in the range of from about 0.375 to about 0.750 inch, results in transverse billet cracks an excessive wear on the copper mold tube. Poor surface quality thus results. All designers and operators of continuous steel casting machines therefore strive to eliminate any form of lateral motion of the mold tube when designing or constructing casting machines.
Since conventional mold oscillation systems require large stroke length, typically 0.375 to 0.750 inch, when lateral motion occurs the strand binds against the copper mold tube wall
REFERENCES:
patent: 2578213 (1951-12-01), Welblund
patent: 3075264 (1963-01-01), Wognum
patent: 3386494 (1968-06-01), Yearley et al.
patent: 4438803 (1984-03-01), Takeuchi et al.
patent: 4483385 (1984-11-01), Kurzinski
"Spray-Tech Mold System Boosts Steel Production", in Iron and Steel Engineer, vol. 59, No. 7, Pittsburgh, Jul. 1982, pp. 59 and 60.
AMB Technology, Inc.
Batten, Jr. J. Reed
Lambert Dennis H.
Lin Kuang Y.
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