System for releasing gas into molten metal

Abstract

A device for releasing gas into molten metal includes a base having a discharge. The discharge has a first section including a first cross-sectional area and a second section including a second cross-sectional area, wherein the first section is upstream of the second section and the first cross-sectional area is smaller than the second cross-sectional area. A gas-release opening is positioned so that it can release gas into one or more of the first section or the second section. As the molten metal moves from the first cross-sectional area to the second cross-sectional area gas is released into the molten metal and the molten metal flow helps to draw the gas into the flow, thereby lowering the pressure required to release gas into the molten metal. Metal-transfer conduits other than a discharge incorporated in a pump base are also disclosed, as are pumps including either a discharge or other metal-transfer conduit according to the invention.

Description

FIELD OF THE INVENTION [0001] The invention relates to releasing gas into molten metal and more particularly, to a device for releasing gas into a stream of molten metal utilizing the flow of the molten metal stream to assist in drawing the gas into the stream. In this manner, the gas may be released at a relatively low pressure as compared to known devices. BACKGROUND OF TH INVENTION [0002] As used herein, the term “molten metal” means any metal or combination of metals in liquid form, such as aluminum, copper, iron, zinc and alloys thereof. The term “gas” means any gas or combination of gases, including argon, nitrogen, chlorine, fluorine, freon, and helium, which are released into molten metal. [0003] Known pumps for pumping molten metal (also called “molten-metal pumps”) include a pump base (also called a housing or casing), one or more inlets, an inlet being an opening to allow molten metal to enter a pump chamber (and is usually an opening in the pump base that communicates wi...

AI Technical Summary

Benefits of technology

[0014] As molten metal moves through the metal-transfer conduit from the first section to the second section, its velocity slows when it enters the second section because of the larger cross-sectional area. Gas is released in either the first section or the second section through a gas-release opening into the molten metal stream and the molten metal stream tends to help draw the gas out of the gas-release opening and into the molten metal stream. This reduces the amount of pressure required to force gas out of the gas-release opening and into the molten metal stream, thereby reducing the stress and wear on components caused by higher pressures and increasing component life.

Problems solved by technology

One problem with releasing gas into a metal-transfer conduit is that, in some systems, the conduit that transfers the gas from a gas source into the molten metal stream (called a gas-transfer conduit) typically extends into the metal-transfer conduit, usually extending downward from the top of the metal-transfer conduit, and disrupts the flow of molten metal passing through the conduit thereby creating a low-pressure area behind the portion of the gas-transfer conduit extending into the metal-transfer conduit.

The low-pressure area can interfere with the released gas mixing with molten metal passing through the metal-transfer conduit because, among other things, the gas immediately rises into the low-pressure area instead of mixing with molten metal throughout the metal-transfer conduit.

One problem with releasing gas into a molten metal stream outside of a pump casing or metal-transfer conduit connected to the pump casing is that one or more of the components used to transfer the gas into the molten metal may be susceptible to breakage since they are not typically as well supported as if they had been inserted into the pump base or a metal-transfer conduit extending from the base.

Another problem is that if the gas is released and is not constrained within a metal-transfer conduit, this may lessen the interaction between the gas and the molten metal.

A problem with known systems, regardless of whether they release gas into or outside of a pump casing or metal-transfer conduit connected to the pump casing is that the gas must be pumped into the molten metal at a relatively high pressure.

The high pressure can cause damage to the components through which the gas passes.

Images