Lubricant for improved surface quality of cast aluminum and method

Abstract

In an oxidation inhibiting lubricant composition suitable for use in the manufacture of aluminum alloys comprising lubricant base selected from the group consisting of solid lubricants, liquid lubricants, grease lubricants, emulsion lubricants, and dispersion lubricants, the improvement wherein the lubricant composition further comprises: an effective amount of a fluorine-containing passivating compound.

Description

FIELD OF THE INVENTION [0001] The invention relates to coolant and lubricant formulations for use in the casting of aluminum or aluminum alloy ingots or bodies. In particular, lubricants and coolants containing a fluorinated species are used to improve surface quality of cast ingots or bodies, resulting in enhanced product recovery. A method for producing aluminum or aluminum alloy ingots with enhanced surface quality is also disclosed. BACKGROUND OF THE INVENTION [0002] The casting of alloys may be done by any number of methods known to those skilled in the art, such as direct chill casting (DC), electromagnetic casting (EMC), horizontal direct chill casting (HDC), hot top casting, continuous casting, semi-continuous casting, die casting, roll casting and sand casting. [0003] Each of these casting methods mentioned above has a set of its own inherent problems, but with each technique, surface imperfections can be an issue. It is well known in the aluminum alloy casting art that mol...

AI Technical Summary

Benefits of technology

[0018] In the present invention it has been discovered that when fluorine-containing compounds are added to conventional casting lubricants, the improved lubricant formulation can protect the surface of aluminum alloys from oxidation, and in particular from runaway magnesium or lithium alloying element oxidation, even in high humidity atmospheres.

[0020] When used in continuous casting operations, effective fluorine-containing compounds added to the casting lubricant are able to prevent oxidation from occurring at the meniscus, or where the melt contacts the mold wall. Existing continuous casting equipment for aluminum alloys can be used for this invention.

[0030] In one more preferred embodiment of this invention, an oxidation inhibiting lubricant formulation of this invention is supplied to the oil ring of a cooled continuous or semi-continuous casting mold, which subsequently lubricates the inner wall of the continuous casting mold. Molten aluminum alloy is cast into the mold. The oxidation inhibiting lubricant reduces the oxidation of the molten aluminum base alloy at the meniscus of the lubricated inner mold wall and the molten aluminum base alloy.

Problems solved by technology

Each of these casting methods mentioned above has a set of its own inherent problems, but with each technique, surface imperfections can be an issue.

It is well known in the aluminum alloy casting art that molten metal (or melt for brevity) surface oxidation can result in various surface imperfections in cast ingots such as pits, vertical folds, oxide patches and the like, which can develop into cracks during casting or in later processing.

A crack in an ingot or slab propagates during subsequent rolling, for example, leading to expensive remedial rework or scrapping of the cracked material.

Certain alloys, such as 7050 and other 7xxx alloys as well as 5182 and 5083 are especially prone to surface defects and cracking.

However, beryllium has been banned from aluminum products used for food and beverage packaging.

Further, there have been increased concerns over the health risks associated with factory workers using beryllium and products containing beryllium.

Despite the use of continuous lubrication during casting, a limitation of current ingot casting practice exists in the inadequate control of oxide growth at the meniscus of molten metal at the mold interface.

Uncontrolled oxide growth at the meniscus of the molten metal and mold interface is particularly problematic of alloying elements that rapidly oxidize in air or in air containing moisture.

Images