Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Patent
1998-11-13
2000-11-14
Lin, Kuang Y.
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
164459, B22D 1104
Patent
active
061455792
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to a liquid-cooled chill mold that is used for continuous casting of thin steel slabs whose cross-sectional length is a multiple of its cross-sectional width.
BACKGROUND OF THE INVENTION
A liquid-cooled chill mold of the type in question is used for continuous casting of thin steel slabs whose cross-sectional length is a multiple of its cross-sectional width. At least each wide side wall is composed of a copper liner bordering the mold cavity and a steel backing plate. The copper liner is attached to the backing plate by metal studs projecting laterally. The metal studs therefore pass through bore holes in the backing plate. At the ends of the bore holes are enlarged areas where nuts can be screwed onto the threaded ends of the metal studs. With their help the copper liner is tightened against the backing plate.
Within the scope of U.S. Pat. No. 3,709,286, it is known that the metal studs may be made of stainless steel. However, metal studs made of stainless steel yield poor welded joints with the copper liner because coarse-grained structures develop at the welds, which have a low elasticity and therefore are very sensitive to flexural stresses.
From the Patent Abstracts of Japan JP-A 3258440, it is known that threaded bushings can be inserted into rear bore holes in the copper liner bordering the chill mold space, and longer rods passing laterally through a cooling box can be screwed into these bushings, and the copper liner tightened against the stainless steel backing plate. To do so, bore holes are also provided in the backing plate. In addition, short fastening studs are attached to the rear side of the copper liner by stud welding. These sort fastening studs are provided with bushings into which the rods passing through the cooling box can be screwed.
Against the background of this related art, the object of the present invention is to create a liquid-cooled chill mold for high casting rates, in particular for continuous steel casting in close-to-final dimensions, with a great reduction in strength problems in areas where the metal studs are joined to the copper liners.
SUMMARY OF THE INVENTION
The object of the present invention is achieved with a liquid-cooled chill mold for continuous casting of thin steel slabs whose cross-sectional length is a multiple of the cross-sectional width, having two opposing wide side walls, each with a copper liner and a backing plate, and narrow side walls delimiting the width of the slab, with the copper liners that delimit the mold cavity being detachably attached to the backing plates by metal studs made of a CuNiFe alloy and the metal studs being welded to the copper liners.
At the core of the present invention is the measure of producing the metal studs specifically of a CuNiFe alloy. Because of such metal studs, in particular hard-drawn metal studs, a considerable increase in strength is achieved with only a narrow scattering in strength in the welded joints with the copper liner. The latter may be made of pure copper, e.g., SF--Cu (oxygen-free copper ASTM C12200), or a copper alloy with a high temperature stability, e.g., a hardenable copper alloy containing chromium and/or zirconium additives. This eliminates the previously unreliable handling and the many influencing factors during welding which entail 100% testing.
In an especially advantageous embodiment, the metal studs are made of a CuNi30Mn1Fe material.
To attach the metal studs to the copper liners, the essentially known stud welding method is used to advantage.
To improve the strength and toughness of the welded joint, the metal studs are welded to the copper liners using a filler material.
Nickel is used in particular as a filler material here. The filler material may be applied as a thin plate between the metal studs and copper liners. It is likewise possible to provide the copper liners with filler material at the connecting points or to plate the end faces of the metal studs. Furthermore, it is possible to use nickel rings around the
REFERENCES:
patent: 4834167 (1989-05-01), Streubel
Hugenschutt Gerhard
Keiser Franz
Stagge Wolfgang
KM Europa Metal AG
Lin Kuang Y.
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