CN109746422A - A kind of casting method of aluminium alloy - Google Patents

Abstract

The present invention relates to a kind of casting methods of aluminium alloy containing at least about 0.1% magnesium and/or at least about 0.1% lithium, wherein during the major part of solidification, contact the liquid surface of the alloy and the dry gas containing at least about oxygen of 2 volume % and water partial pressure below about 150Pa.In the case that the present invention can be especially useful in the additive without using such as beryllium and/or calcium and not use the device and/or gas of valuableness, safely cast the very high aluminium alloy of oxidable degree, the especially aluminium alloy containing magnesium and/or lithium, and obtain the ingot casting of no surface defect and pollution.

Description

A kind of casting method of aluminium alloy

Technical field

The present invention relates to the castings of aluminium alloy, specifically, are related to a kind of conjunction to oxidation-sensitive containing magnesium and/or lithium The casting of gold.

Background technique

The oxidation of liquid aluminium alloy can generate harmful result in casting process.The metal in smelting furnace and transmission sprue-way Oxidation will lead to the net loss of metal, referred to as loss on ignition first.In addition, the excessive oxidation of liquid metal exists in casting process Surface defect can be generated on ingot casting, and there is detrimental effect to the use of prepared product.These problems are to containing magnesium and/or lithium Alloy it is especially pronounced.

One main defect is the vertical fold caused by surface of collecting tank is particularly due to oxidation film corrugation.? In some cases, when especially casting 7xxx alloy, this problem meeting especially severe, because of these folds, especially when them When long and deep, it is easy to cause surface cracked.Fold and crackle generally must deform it in ingot casting obtained in casting process Preceding elimination.These defects can be eliminated by being machined, and in some cases, the presence in crack prevents ingot casting from using, And it must re-melt.

Summary of the invention

It is closed the purpose of the present invention is to provide a kind of containing the aluminium of at least about 0.1% magnesium and/or at least about 0.1% lithium The casting method of gold, wherein make liquid surface and a kind of contact of dry gas of the alloy during major part of solidification, The dry gas contains the oxygen of at least about 2 volume %, and its water partial pressure is below about 150Pa.

Specific embodiment

The method of the present invention can be used for the high oxidability containing at least about 0.1% magnesium and/or at least about 0.1% lithium Aluminium alloy, the method for the present invention can be especially useful for the alloy of 2XXX, 3XXX, 5XXX, 6XXX, 7XXX or 8XXX series, especially When these alloys are free of the beryllium and/or calcium deliberately added.The method of the present invention 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 reality of the particularly advantageous alloy of the method for the present invention Example are as follows: alloy AA2014, AA2017, AA2024, AA2024A, AA2027, AA2139, AA2050 in 2XXX series alloy, AA2195, AA2196, AA2098, AA2198, AA2214, AA2219 and AA2524；Alloy AA3003 in 3XXX series alloy, AA3005, AA3104 and AA3915；Alloy AA5019, AA5052, AA5083, AA5086, AA5154 in 5XXX series alloy, AA5182, AA5186, AA5383, AA5754 and AA5911；And alloy AA7010, AA7020 in 7XXX series alloy, AA7040、AA7140、AA7050、AA7055、AA7056、AA7075、AA7449、AA7450、AA7475、AA7081、AA7085、 AA7910 and AA7975.

The dry gas must be containing at least about oxygen of 2 volume %, and its water partial pressure is below about 150Pa, preferably Lower than 100Pa, more preferably less than 70Pa.In a particularly advantageous embodiment of the present invention, water partial pressure is even lower than 30Pa, preferably shorter than 5Pa, even more preferably less than 1Pa.The water partial pressure of gas is also referred to as vapour pressure.Perfect gas i is in gross pressure For the partial pressure in the perfect gaseous mixture of P, it is defined as when gas i occupies alone the accessible whole volume of the mixture, The molecule pressure applied of the gas.The dew point of gas refer to the gas by steam-laden and current gas pressure condition keep not Temperature when change.It can also be defined as temperature of the vapour pressure with saturated vapour pressure when equal.The water partial pressure of 150Pa correspond to- The water content of 17.9 DEG C of dew point and the 0.0013kg/m3 at a temperature of this.The water partial pressure of 100Pa corresponds to -22.6 DEG C of dew The water content of point and the 0.0009kg/m3 at a temperature of this.The water partial pressure of 70Pa is corresponding to -26.5 DEG C of dew point and this temperature The water content of 0.0006kg/m3 under degree.

Dry gas is advantageously also containing at least one gas selected from the following: air, helium, argon gas, nitrogen, titanium dioxide Carbon, carbon monoxide, combustion of natural gas product, methane, ethane, propane, natural gas, organic fluoride-containing compound, organic chloride containing close Object.Carbon dioxide is added into dry gas under certain conditions can improve antioxidant effect.In an implementation of the invention In scheme, the dry gas contains the carbon dioxide of 1 to 10 volume %.But since this effect is limited, and add two Carbonoxide will increase cost, therefore in another advantageous embodiment of the invention, carbon dioxide contains in dry gas Amount is less than 1 volume %, even less than 0.1 volume %.In an advantageous embodiment of the invention, the dry gas master It to be to pass through the dry air to reach required water partial pressure of any appropriate means.

According to the present invention, dry gas connects during the major part of aluminum alloy solidification with the liquid surface of the alloy Touching.Contact of the gas with surface preferably by a surface it is rectangular at an atmosphere in a manner of realize, the water in the atmosphere The water content of content and the dry gas is roughly equal, and difference is generally less than 10% or 20%, that is, avoids from surrounding air Significant diffusion of the vapor in the atmosphere.

In addition, in order to obtain advantageous effects in terms of the surface quality of cast article, it is entire typically without what is enabled aluminum alloy to Liquid surface can all be in contact with the dry gas.Advantageously, the liquid surface for the aluminium alloy being in contact with dry gas is excellent It selects and accounts at least the 10% of the wholly liquid state surface of the aluminium alloy, preferably at least 25%, more preferably at least 50%.

The liquid surface of aluminium alloy is all kept in contact with dry gas during the major part of solidification.Therefore, although nothing As soon as need to be introduced into Casting Equipment in liquid metal contacts liquid surface with dry gas, but preferably stable state one is formed It does so.For example, in the case where directly cooling down semicontinuous vertical casting, preferably at least when false bottom is begun to decline, or at least It is done like this when starting in the region that will not be cut in casting then operation.It can change dry gas stream in casting process Flow, especially when there is surface defect.So in some cases, the flow for increasing dry gas stream can make to cast Fold in product disappears.Contact between liquid surface and dry gas is optionally removed before casting terminates, especially When reaching the region that will be cut in subsequent operation.In general, the liquid surface of aluminium alloy is in solidification at least 50% Or it is kept in contact during even at least 90% with dry gas.

Claims (4)

1. a kind of method for casting the aluminium alloy containing 0.1% magnesium and/or 0.1% lithium, wherein making the liquid of the alloy Surface is in contact during the major part of solidification with a kind of dry gas, which contains the oxygen of at least about 2 volume % Gas, and its water partial pressure is below about 150Pa.

2. according to the method described in claim 1, wherein the water partial pressure of the dry gas is less than 100Pa, preferably smaller than 70Pa.

3. according to the method described in claim 1, wherein the gas is with the contact on the surface with rectangular on said surface It is realized at the mode of an atmosphere, the water content of the atmosphere and the water content of dry gas are roughly equal.

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