CN105710346A - Aluminum alloy casting method - Google Patents

Abstract

The invention relates to a method for casting aluminum alloy containing about at least 0.1% of magnesium and/or about at least 0.1% of lithium. In most of the solidification process, the liquid-state surface of alloy is made to make contact with dry gas containing about at least 2% (in volume) of oxygen and with moisture pressure less than about 150 Pa. The method can be used for safely casting the aluminum alloy with the high oxidability degree without using beryllium and/or calcium additives and using expensive devices and/or gases, especially aluminum alloy containing magnesium and/or lithium. Thus, casting ingots without surface defects and surface contamination can be obtained.

Description

The casting method of aluminium alloy

Technical field

The present invention relates to the casting of aluminium alloy, specifically, relate to the casting containing magnesium and/or the alloy to oxidation-sensitive of lithium.

Background technology

The oxidation of liquid aluminium alloy can produce the result being harmful in casting process.In smelting furnace and transmission sprue-way, first the oxidation of metal can cause the net loss of metal, is called loss on ignition.It addition, in casting process, the over oxidation of liquid metal can produce surface defect on ingot casting, and the use of prepared product is had detrimental effect by it.These problems are especially pronounced to the alloy containing magnesium and/or lithium.

One main defect is be particularly due to the wrinkling vertical fold caused of oxide-film on the surface of collecting tank.In some cases, particularly during casting 7xxx alloy, this problem meeting especially severe, because these folds, especially when they are long and deeply, it is easy to cause that crackle occurs in surface.Fold and crackle generally must eliminate before the ingot casting deformation of gained in casting process.These defects can be eliminated by machining, and in some cases, the existence in crack makes ingot casting not use, and must again melt.

Summary of the invention

It is an object of the invention to provide a kind of containing at least about 0.1% magnesium and/or at least about 0.1% the casting method of aluminium alloy of lithium, wherein in most of process of solidification, the liquid surface making described alloy contacts with the dry gas of one, this dry gas contains the oxygen of at least about 2 volume %, and its water partial pressure is lower than about 150Pa.

Detailed description of the invention

The inventive method can be used for the magnesium containing at least about 0.1% and/or at least about 0.1% the aluminium alloy of high oxidability of lithium, the inventive method can be especially useful for the alloy of 2XXX, 3XXX, 5XXX, 6XXX, 7XXX or 8XXX series, especially when these alloys without the beryllium deliberately added and/or calcium time.The inventive method is particularly conducive to containing less than 3ppm beryllium or even less than 1ppm beryllium and/or less than 15ppm calcium or even less than the alloy of 5ppm calcium.The example of the particularly advantageous alloy of the inventive method is: the alloy AA2014 in 2XXX series alloy, AA2017, AA2024, AA2024A, AA2027, AA2139, AA2050, AA2195, AA2196, AA2098, AA2198, AA2214, AA2219 and AA2524；Alloy AA3003 in 3XXX series alloy, AA3005, AA3104 and AA3915；Alloy AA5019 in 5XXX series alloy, AA5052, AA5083, AA5086, AA5154, AA5182, AA5186, AA5383, AA5754 and AA5911；And alloy AA7010 in 7XXX series alloy, AA7020, AA7040, AA7140, AA7050, AA7055, AA7056, AA7075, AA7449, AA7450, AA7475, AA7081, AA7085, AA7910 and AA7975.

Described dry gas must contain the oxygen of at least about 2 volume %, and its water partial pressure is lower than about 150Pa, it is preferable that lower than 100Pa, more preferably less than 70Pa.In particularly advantageous embodiment of the present invention, water partial pressure is even below 30Pa, it is preferable that lower than 5Pa, is even more preferably less than 1Pa.The water partial pressure of gas is also referred to as vapour pressure.Ideal gas i dividing potential drop in the perfect gaseous mixture that gross pressure is P, is defined as when gas i occupies alone the accessible whole volume of this mixture, the molecule pressure applied of this gas.The temperature when dew point of gas refers to this gas current gas pressure condition remains unchanged by steam-laden.It can also be defined as vapour pressure and saturated vapour pressure temperature time equal.The water partial pressure of 150Pa corresponds to the dew point of-17.9 DEG C and the water content of the 0.0013kg/m3 at this temperature.The water partial pressure of 100Pa corresponds to the dew point of-22.6 DEG C and the water content of the 0.0009kg/m3 at this temperature.The water partial pressure of 70Pa corresponds to the dew point of-26.5 DEG C and the water content of the 0.0006kg/m3 at this temperature.

Dry gas advantageously possibly together with at least one selected from following gas: air, helium, argon, nitrogen, carbon dioxide, carbon monoxide, combustion of natural gas product, methane, ethane, propane, natural gas, organic fluoride-containing compound, organic chlorine-containing compound.In dry gas, add carbon dioxide under certain conditions can improve antioxidant effect.In one embodiment of the invention, described dry gas contains the carbon dioxide of 1 to 10 volume %.But, because this effect is limited, and adds carbon dioxide and can increase cost, therefore in another favourable embodiment of the present invention, the content of dry carbon dioxide in gas is less than 1 volume %, even less than 0.1 volume %.In a favourable embodiment of the present invention, described dry gas is mainly the means by any appropriate and dries to reach the air of required water partial pressure.

According to the present invention, dry gas contacts with the liquid surface of described alloy in most of process of aluminum alloy solidification.Described gas preferably realizes with contacting of surface in the way of one atmosphere of square one-tenth on a surface, water content in this atmosphere is roughly equal with the water content of described dry gas, difference is generally less than 10% or 20%, namely avoids steam significantly the spreading in described atmosphere from surrounding air.

It addition, in order to obtain advantageous effects in the surface quality of cast article, all can contact with described dry gas typically without the wholly liquid state surface enabled aluminum alloy to.Advantageously, the liquid surface of the aluminium alloy contacted with dry gas preferably accounts at least the 10% of the wholly liquid state surface of described aluminium alloy, it is preferable that at least 25%, more preferably at 50%.

The liquid surface of aluminium alloy all keeps in touch with dry gas in most of process of solidification.Therefore, although without making liquid surface contact with dry gas at liquid metal in Casting Equipment once introducing, but preferably steady statue one is formed and does like this.Such as, when directly cooling down semicontinuous vertical casting, it is preferable that when at least beginning to decline at the false end, or do when the region at least will not being cut in casting subsequently operation starts like this.Casting process can change the flow of dry gas stream, particularly when surface defect occurs.So, in some cases, the flow increasing dry gas stream can make the fold in cast article disappear.Contacting between liquid surface with dry gas is optionally removed before casting terminates, particularly when arriving cut region in operation subsequently.In general, the liquid surface of aluminium alloy keeps in touch with dry gas in the process of solidification at least 50% or even at least 90%.

Claims (4)

1. a casting containing 0.1% magnesium and/or 0.1% the method for aluminium alloy of lithium, wherein make the liquid surface of described alloy in most of process of solidification, contacting with the dry gas of one, this dry gas contains the oxygen of at least about 2 volume %, and its water partial pressure is lower than about 150Pa.

2. method according to claim 1, the water partial pressure of wherein said dry gas is less than 100Pa, it is preferable that less than 70Pa.

3. method according to claim 1, wherein said gas realizes in the way of one atmosphere of square one-tenth on said surface with contacting of described surface, and the water content of this atmosphere is roughly equal with the water content of dry gas.

4. method according to claim 1, the liquid surface wherein bearing the described aluminium alloy of described dry gas stream accounts at least the 10% of described aluminium alloy wholly liquid state surface, it is preferable that at least 25%, more preferably at 50%.