CN109207758B

CN109207758B - Aluminum alloy workpiece smelting and casting process

Info

Publication number: CN109207758B
Application number: CN201811224449.0A
Authority: CN
Inventors: 张平娟; 江龙; 陈雪
Original assignee: Suzhou Alutech Auto Parts Co ltd
Current assignee: SUZHOU ALUTECH AUTO PARTS Co.,Ltd.
Priority date: 2018-10-20
Filing date: 2018-10-20
Publication date: 2021-05-04
Anticipated expiration: 2038-10-20
Also published as: CN109207758A

Abstract

A smelting and casting method for an aluminum alloy workpiece comprises the steps of smelting, refining, degassing and deslagging, mold assembling, casting, demolding, heat treatment and processing, wherein pinholes for preparing the aluminum alloy workpiece can be reduced, the air tightness of the aluminum alloy workpiece can be improved, the quality of cast aluminum alloy can be ensured, and the final use performance of the aluminum alloy workpiece can be improved through the arrangement of rotary blowing in the degassing and deslagging.

Description

Aluminum alloy workpiece smelting and casting process

Technical Field

The invention relates to the technical field of metal casting, in particular to a smelting and casting process of an aluminum alloy workpiece.

Background

Aluminum is a metal element with the highest content in the earth crust, and the aluminum alloy has a series of excellent characteristics of light weight, good thermal conductivity, good ductility, high strength, excellent corrosion resistance and the like, so that the aluminum alloy is used as a non-ferrous metal structural material and has been widely applied in various industries of modern construction such as mechanical engineering, energy chemical industry, control equipment, house building and the like, and particularly has irreplaceable effects in the process of energy conservation, emission reduction and light weight.

Aluminum is relatively reactive due to its chemical nature. In the preparation process of the aluminum alloy, the aluminum alloy is easy to react with water vapor, oxidize and absorb hydrogen in the smelting process. The gas component in the aluminum liquid is mainly hydrogen (about 80-90 percent), and the rest is nitrogen, oxygen, carbon monoxide and the like. About 90% of hydrogen dissolved in the aluminum liquid is in an atomic state. The saturated solubility of hydrogen in the aluminum alloy from liquid to solid differed by a factor of 17. During the solidification process, hydrogen tends to escape from the molten liquid to form bubbles, so that the casting often generates metallurgical casting defects such as shrinkage porosity, air holes, shrinkage cavities and the like, and the performances such as tensile stress, elastoplasticity, ductility, stress fatigue, hot cracking sensitivity and the like of the cast alloy material are obviously reduced.

In order to reduce the influence of an excessively high gas content in the aluminum melt on the quality of the final ingot, degassing and cleaning processes are generally carried out on the aluminum alloy melt. Obviously, the advanced degassing technology has very important significance for ensuring the quality of the cast aluminum alloy and improving the final service performance of the product.

The rotary blowing method is an adsorption refining degassing method, and is characterized by that it utilizes a rotating head to introduce inert gas (nitrogen gas, argon gas, etc.) into the interior of aluminium melt, and the hydrogen in the melt can be diffused into the bubbles under the action of partial pressure difference, and floated up and discharged with the bubbles so as to attain the goal of degassing. The bubbles can absorb impurities through physical adsorption while taking away hydrogen due to the dissolution in the floating process, thereby removing the impurities and achieving degassing and impurity removal. Compared with the single purification effect of other methods, the rotary blowing can simultaneously remove hydrogen and impurities, and has small environmental pollution, so that the method is widely applied to industry.

The degassing effect of the rotary blowing method depends on the dispersion uniformity of bubbles in the melt, the size of the bubbles, the residence time of the bubbles in the melt and the like. The smaller the bubbles are, the more uniform the bubbles are dispersed, and the slower the floating speed is, the better the hydrogen removal efficiency is. In addition, the aluminum alloy melt has certain viscosity, a certain resistance needs to be overcome when the argon bubbles are separated out, a certain time is needed when the argon bubbles are completely separated out, and the degassing effect is better after the argon bubbles are required to be kept stand for a period of time; however, the standing time is not preferably too long, because the reaction of the gas with the melt is a dynamic process during standing. The gas in the melt is separated out along with the inert gas, meanwhile, the liquid metal absorbs the water vapor in the atmosphere and reacts with the water vapor to continuously form hydrogen, the dehydrogenation purification process actually consists of a dehydrogenation purification process inside the aluminum liquid and an oxidation-hydrogen absorption process, namely a pollution process, on the surface of the aluminum liquid, the reaction of the water vapor and the aluminum melt is carried out along with the increase of the standing time, the hydrogen generated by the reaction is dissolved in the aluminum melt through adsorption and diffusion, so that the hydrogen absorption amount in the aluminum melt is larger than the dehydrogenation purification amount inside the aluminum melt, and the hydrogen absorption amount of the aluminum melt is increased.

Disclosure of Invention

The invention provides a smelting and casting process of an aluminum alloy workpiece, which can reduce and uniformly disperse bubbles during rotary blowing degassing in the smelting and casting process of the aluminum alloy, and has enough standing time without increasing the hydrogen absorption amount of a melt.

As one aspect of the present invention, there is provided a method for melt casting an aluminum alloy workpiece, comprising the steps of: (1) putting an aluminum ingot with the purity of more than or equal to 99.9% into a smelting furnace, heating to 660-670 ℃ for melting, heating to 720-730 ℃ and adding intermediate alloy metal for melting to obtain alloy melt; (2) transferring the melt in the smelting furnace into a standing furnace for refining, heating to 740-780 ℃, adding a flux, stirring and purifying the alloy liquid; (3) degassing and deslagging the refined melt; (4) assembling a die, and preheating the die to 300 ℃; (5) continuously casting the cleaned aluminum alloy liquid, controlling the casting temperature to be 690-700 ℃, and casting in a horizontal casting mode to obtain a cast workpiece; (6) after demoulding, the workpiece is subjected to heat treatment strengthening; (7) machining and surface treating the workpiece to finally form a required workpiece; the step (3) comprises the following steps: (3.1) introducing inert gas into the standing furnace, and exhausting air in the standing furnace; (3.2) sealing the standing furnace, and introducing high-pressure inert gas to the upper part of the melt through a gas input channel above the melt to enable the gas pressure in the standing furnace to be in a high-pressure state; (3.3) heating the melt in the standing furnace to enable the temperature of the melt to be greater than a threshold temperature; (3.4) introducing inert gas from the lower part of the melt through a rotary spray head to blow off the bottom of the furnace; (3.4) after a certain time, reducing the temperature to the pouring temperature; (3.5) exhausting the high-pressure inert gas in the standing furnace through an exhaust port; (3.6) opening a slag removing door to clean the aluminum slag floating on the surface of the aluminum alloy liquid; and (3.7) arranging a covering agent layer on the surface of the aluminum alloy liquid.

Preferably, the threshold temperature is greater than 800 degrees.

Preferably, the specific time is more than 30 minutes.

Preferably, the pressure of the high pressure inert gas is greater than three times atmospheric pressure.

Preferably, in the step (2), the solvent includes potassium chloride and/or magnesium chloride.

Preferably, the master alloy metal in step (1) includes aluminum manganese copper or aluminum magnesium copper.

Preferably, the inert gas is nitrogen or argon.

Detailed Description

In order to more clearly illustrate the technical solutions of the present invention, the present invention will be briefly described below by using embodiments, and it is obvious that the following description is only one embodiment of the present invention, and for those skilled in the art, other technical solutions can be obtained according to the embodiments without inventive labor, and also fall within the disclosure of the present invention.

The method for smelting and casting the aluminum alloy workpiece, provided by the embodiment of the invention, can reduce pinholes for preparing the aluminum alloy workpiece, improve the air tightness of the aluminum alloy workpiece and obtain a high-quality casting, and comprises the following steps: smelting, refining, degassing and deslagging, assembling a mold, casting, demolding, heat treatment and processing.

In the smelting process, determining the content of each component in the aluminum alloy according to the requirement of a cast workpiece, firstly, putting an aluminum ingot with the purity of more than or equal to 99.9 percent into a smelting furnace, heating to 660-670 ℃ for melting, heating to 720-730 ℃, adding intermediate alloy metal for melting, and obtaining aluminum alloy melt; wherein the intermediate metal can be aluminum manganese copper or aluminum magnesium copper, etc.

Transferring the molten aluminum alloy obtained by smelting in the smelting furnace into a standing furnace for refining, raising the temperature of the molten aluminum alloy to 740-780 ℃, adding a flux, stirring and purifying the molten aluminum alloy, and removing oxides and harmful gases in the alloy; the solvent may include potassium chloride and/or magnesium chloride, and for example, a solvent containing potassium chloride-magnesium chloride as a base component may be used in an amount of 2 to 6%. Furthermore, in order to avoid oxidation of the aluminum alloy melt, a covering agent can be uniformly scattered on the melt during refining, so that the liquid metal is prevented from being exposed and oxidized.

Degassing and deslagging the refined aluminum alloy melt, comprising the following steps: (3.1) introducing inert gas into the standing furnace, and exhausting air in the standing furnace; if the covering agent layer is arranged on the solution during refining, the covering agent layer on the solution needs to be cleaned before the inert gas is introduced; (3.2) closing the standing furnace, and introducing high-pressure inert gas to the upper part of the melt through a gas input channel above the melt to enable the gas pressure in the standing furnace to be in a high-pressure state, wherein the high pressure can be, for example, more than three times of atmospheric pressure, so that the pressure inside the aluminum alloy liquid in the standing furnace is increased, and the bubble volume of the inert gas sprayed into the melt is reduced; (3.3) heating the melt in the holding furnace to a temperature greater than a threshold temperature, which may be, for example, greater than 800 ℃; (3.4) introducing inert gas from the lower part of the melt through a rotary spray head to blow off the bottom of the furnace, wherein after the inert gas is introduced into the melt, hydrogen in the melt is diffused into bubbles under the action of partial pressure difference, floats upwards along with the bubbles and is discharged; the inert gas may be argon or nitrogen; (3.5) because air and water vapor do not exist above the melt, and the oxidation-hydrogen absorption process on the surface of the aluminum liquid does not exist, the melt can be kept still for a long enough time to fully perform the dehydrogenation purification process in the aluminum liquid, and after a long enough specific time, for example, 30 minutes, the temperature is reduced to the pouring temperature; preferably, in order to avoid the adsorption of the precipitated hydrogen on the surface of the aluminum liquid, in the step (3.5), an air inlet and an air outlet can be intermittently opened above the melt in the degassing process, and high-pressure inert gas is introduced to discharge the precipitated hydrogen out of the standing furnace; (3.6) exhausting the high-pressure inert gas in the standing furnace through an exhaust port; (3.7) opening a slag removing door to clean the aluminum slag floating on the surface of the aluminum alloy liquid; and (3.8) arranging a covering agent layer on the surface of the aluminum alloy liquid.

Before casting of the aluminum alloy solution, a mold needs to be assembled, and the mold is preheated to 300 ℃; and continuously casting the cleaned aluminum alloy liquid, controlling the casting temperature at 690-700 ℃, casting in a horizontal casting mode, allowing the aluminum alloy liquid to enter a cavity of a mold, then starting to solidify and cool, and demolding after the cooling time is reached. After demoulding, the workpiece is subjected to heat treatment strengthening, so that the internal structure is more uniformly distributed, and the microscopic stress and the machining residual stress in the quenched workpiece are eliminated or reduced. Then, the workpiece is machined and surface treated to eliminate surface defects and stress concentration, and finally the required workpiece is formed.

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and are intended to be within the scope of the invention.

Claims

1. A smelting and casting method of an aluminum alloy workpiece comprises the following steps: (1) putting an aluminum ingot with the purity of more than or equal to 99.9% into a smelting furnace, heating to 660-670 ℃ for melting, heating to 720-730 ℃ and adding intermediate alloy metal for melting to obtain alloy melt; (2) transferring the melt in the smelting furnace into a standing furnace for refining, heating to 740-780 ℃, adding a flux, stirring and purifying the alloy liquid; (3) degassing and deslagging the refined melt; (4) assembling a die, and preheating the die to 300 ℃; (5) continuously casting the cleaned aluminum alloy liquid, controlling the casting temperature to be 690-700 ℃, and casting in a horizontal casting mode to obtain a cast workpiece; (6) after demoulding, the workpiece is subjected to heat treatment strengthening; (7) machining and surface treating the workpiece to finally form a required workpiece; the method is characterized in that: the step (3) comprises the following steps: (3.1) introducing inert gas into the standing furnace, and exhausting air in the standing furnace; (3.2) sealing the standing furnace, and introducing high-pressure inert gas to the upper part of the melt through a gas input channel above the melt to enable the gas pressure in the standing furnace to be in a high-pressure state, wherein the pressure of the high-pressure inert gas is more than three times of the atmospheric pressure; increasing the pressure inside the aluminum alloy liquid in the standing furnace, so that the volume of the bubbles of the inert gas sprayed into the melt is reduced; (3.3) heating the melt in the standing furnace to enable the temperature of the melt to be greater than a threshold temperature; the threshold temperature is greater than 800 degrees; (3.4) introducing inert gas from the lower part of the melt through a rotary spray head to blow off the bottom of the furnace; (3.5) after a certain time, lowering the temperature to the casting temperature; the specified time is greater than 30 minutes; (3.6) exhausting the high-pressure inert gas in the standing furnace through an exhaust port; (3.7) opening a slag removing door to clean the aluminum slag floating on the surface of the aluminum alloy liquid; and (3.8) arranging a covering agent layer on the surface of the aluminum alloy liquid.

2. The aluminum alloy workpiece smelting and casting method of claim 1: the method is characterized in that: in the step (2), the flux includes potassium chloride and/or magnesium chloride.

3. The aluminum alloy workpiece smelting and casting method of claim 2: the method is characterized in that: the intermediate alloy metal in the step (1) comprises aluminum manganese copper or aluminum magnesium copper.

4. The aluminum alloy workpiece smelting and casting method of claim 3: the method is characterized in that: the inert gas is nitrogen or argon.