CN116240416A - Low-foam low-smoke refining agent for rare earth magnesium alloy and preparation method thereof - Google Patents

Abstract

The invention discloses a low-foam low-smoke refining agent for rare earth magnesium alloy and a preparation method thereof. The refining agent is characterized by comprising the following components in percentage by mass: caCl (CaCl) ₂ 20～36％；BaCl ₂ 5～15％；NaCl 0.5～3％；CaF ₂ 1～5％；BaF ₂ 2-8%; KF 5-20%; KCl balance. The preparation method is characterized by comprising the following steps: s1, proportioning: caCl is added with ₂ 、BaCl ₂ 、NaCl、CaF ₂ 、BaF ₂ Uniformly mixing KF and KCl according to a proportion to obtain mixed salt; s2, smelting: heating the crucible to 100-150 ℃, adding the mixed salt into the crucible, and heating the crucible to 800-850 ℃ until the mixed salt is completely melted; s3, pouring: pouring the liquid mixed salt into a mould after fully stirring, and obtaining a massive flux after solidification and cooling; s4, crushing and sieving: crushing and sieving the massive flux to obtain the refining agent. The invention adjusts the proportion of inorganic salt to leadThe fluoride is used for replacing part of chloride, so that the content of the specific gravity agent is properly increased, and on the basis of ensuring the refining effect of the refining agent, the release of corrosive smoke in the refining process is effectively reduced, and the damage to personnel, equipment and plants is reduced.

Description

Low-foaming and less-smoke refining agent for rare earth magnesium alloy and preparation method thereof

technical field

The invention belongs to the technical field of metal materials and metallurgy, and in particular relates to a low-foaming and less-smoke refining agent for rare earth magnesium alloys and a preparation method thereof.

Background technique

Magnesium alloy has high specific strength, high specific stiffness, and excellent damping performance. As a metal material, it has the characteristics of vacuum resistance, radiation resistance, and atomic oxygen resistance. It has broad application prospects in aerospace, transportation, 3C digital and other fields. Rare earth magnesium alloy is an important part of magnesium alloy. This type of alloy uses rare earth as the main addition element, and utilizes the characteristics of large solid solubility of rare earth elements in magnesium alloys, causing strong lattice distortion, and forming dispersed precipitates during aging. It has achieved excellent solid solution and aging strengthening effects, breaking through the bottleneck of insufficient absolute strength and toughness of magnesium alloys. Rare earth elements can also be enriched at the front of the solute interface during the solidification process of the magnesium alloy to cause supercooling of the composition, refine the alloy grains, and further improve the creep resistance and room temperature strength of the magnesium alloy. At present, rare earth magnesium alloys represented by VW63Z and WE43B have been widely used in aerospace products such as cabins and receivers.

However, the chemical properties of magnesium and rare earth are very active. The P-B ratio of the surface film formed on the surface of the melt at high temperature is less than 1, which cannot fully protect the melt. In the process, violent combustion is caused, which seriously affects the safety of production. Filling the alloy melt with flux is the most commonly used protection method in actual production, with low cost, easy operation and high efficiency of impurity removal. Flux can be subdivided into covering agent and refining agent: covering agent forms a complete and continuous covering layer on the surface of magnesium melt, thereby inhibiting the oxidation and combustion of magnesium melt, and reducing the formation of inclusions during smelting; refining agent is used in magnesium alloy refining Adding in the process, using the refining agent to wet and capture the inclusions is better than the characteristics of the magnesium melt, so that the inclusions spontaneously migrate, adsorb, aggregate, and settle to the flux to achieve the removal of the inclusions. The quality of refining effect will directly affect the quality of magnesium alloy products.

Traditional magnesium alloys mostly use RJ2 flux for refining, but the rare earth magnesium alloy melt has a high density, and it is difficult for RJ2 flux to fully settle in the melt, and it is easy to produce flux inclusions in castings. At present, rare earth magnesium alloys are mostly refined by JDMJ or RJ6. JDMJ has a good purification effect for rare earth magnesium alloys with low rare earth content such as ZM6, but MgCl ₂ will react with rare earth as follows: 3MgCl ₂ +2[RE]→2RECl ₃ +3Mg, resulting in the loss of rare earth atoms, so for VW63Z and other high rare earth content of rare earth magnesium alloy, the preferred refining agent is RJ6 flux. The main components of RJ6 flux are chloride salts of Ca, K and Ba, and the specific mass fractions are: 54-56% KCl, 27-29% CaCl ₂ , 14-16% BaCl ₂ , 0-5% CaF ₂ . The melting point of chlorine salt is low, and it will be liquefied rapidly when sprinkled into the magnesium alloy melt. During the smelting process, HCl, Cl ₂ and other gases will be generated. The proportion of chlorine salt in the RJ6 component is too high, and the corrosive gas produced will be harmful to the operator's body. It has adverse effects on health, causes serious corrosion of foundry equipment and smelting workshops, and is not conducive to environmental protection. In addition, the density of RJ6 is also low,

In view of the above situation, the patent CN103468976A has prepared a covering agent and refining agent that adds 5-10% MgF ₂ to MgCl ₂ , CaCl ₂ , BaCl ₂ , NaCl and CaF ₂ , which can effectively reduce melt inclusions and reduce harmful gases. produce. But the flux still contains MgCl ₂ , which is not suitable for rare earth magnesium alloys. Patent CN105349816A prepares a covering flux containing BaCO ₃ , CaSO ₄ , LiCl, hydroxyapatite and magnesium silicate, which reduces the content of chlorides, uses foaming materials such as carbonates to decompose by heat to release pollution-free gases, and covers the The melt surface plays a role in protecting the melt. But this flux is not suitable for the refining of magnesium alloy.

Contents of the invention

In order to overcome the above defects, the present invention provides a low-foaming and less-smoke refining agent for rare earth magnesium alloy, which is characterized in that it comprises the following components in mass percentage:

The present invention also provides a preparation method of a low-foaming and less-smoke refining agent for rare earth magnesium alloy, which is characterized in that it comprises the following steps:

S1 ingredients: mix CaCl ₂ , BaCl ₂ , NaCl, CaF ₂ , BaF ₂ , KF and KCl uniformly according to the proportion to obtain mixed salt;

S2 Melting: Heat the crucible to 100°C-150°C, add the mixed salt into the crucible, raise the temperature of the crucible to 800°C-850°C, stir the mixed salt during the heating process until the mixed salt is completely melted;

S3 pouring: After fully stirring the liquid mixed salt, pour it into the mold, solidify and cool to obtain a block flux;

S4 crushing and sieving: crush the bulk flux, grind it to obtain powdery flux, and obtain refining agent after sieving.

Further, the ratio of raw materials added in the step S1 is by mass percentage:

Further, in the step S1, CaCl ₂ , BaCl ₂ , NaCl, CaF ₂ , BaF ₂ , KF and KCl are dried and dehydrated at 220° C. to 250° C. before mixing according to the proportion.

Further, in the step S1, the obtained mixed salt is placed in a dry airtight container or sealed in an ordinary airtight container and stored in an environment with low relative humidity.

Further, the rare earth element in the rare earth magnesium alloy includes one or more combinations selected from Gd, Y, Nd, La, Ce, Sm, Sc, Er, Dy, Ho, Yb or Eu, and the rare earth The total atomic mass percentage is ≥6%.

Further, in the step S2, the material of the crucible is graphite, corundum, or cast iron, and the stirring method is mechanical stirring with a ladle.

Further, in the step S2, after adding the mixed salt into the crucible, the heating rate of the crucible is 200°C/h-400°C/h.

Further, in the step S3, the material of the mold is graphite.

Further, in the step S4, the mesh size of the sieve is 10 mesh to 20 mesh.

The invention adjusts the ratio of inorganic salts, uses fluoride to replace part of chloride, and appropriately increases the content of specific gravity agent, which can effectively reduce the release of corrosive fumes during the refining process on the basis of ensuring the refining effect of the refining agent, and reduce the impact on personnel. , equipment, plant damage.

Description of drawings

Fig. 1 is the exterior view of the block flux that obtains after pouring in the embodiment 1 that adopts the inventive method;

Fig. 2 is a cooling curve of refining agent A obtained in Example 1 using the method of the present invention.

Detailed ways

The following describes the present invention in detail, and the features and advantages of the present invention will become more clear and definite along with these descriptions.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or better than other embodiments. While various aspects of the embodiments are shown in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The refining agent of the present invention aims at the problem that the traditional refining agent of rare earth magnesium alloy has high _chloride salt content and easy release of corrosive gas during the refining process. The type and content of inorganic salt components reduce the proportion of chloride in the refining agent and increase the fluoride salt corresponding to the cation, which appropriately increases the melting point of the flux, slows down the melting rate of the refining agent during the refining process, and reduces the amount of HCl and Cl in the refining process. ₂ release of harmful gases.

The optimized refining agent composition has good slagging ability and refining ability. Due to the high content of fluorine salts, the refining agent has a higher density, which improves the settling rate of the refining agent in the melt and ensures that the refining agent-inclusion polymer can Settling is completed in a short time, which reduces the possibility of flux inclusions and shortens the time for melt processing. It is especially suitable for the refining treatment of rare earth content magnesium alloys with high melt viscosity and high density.

The components of the refining agent of the present invention include CaCl ₂ , BaCl ₂ , NaCl, CaF ₂ , BaF ₂ , KF and KCl.

Aiming at the problem that the traditional refining agent of rare earth magnesium alloy has high content of chloride salt and easy release of corrosive gas during the refining process, the present invention proposes a low-foaming and less-smoke refining agent for rare earth magnesium alloy. The mass percentage range of the components contained is: CaCl ₂ : 20-36%; BaCl ₂ : 5-15%; NaCl: 0-3%; CaF ₂ : 0.5-5%; BaF ₂ : 0-8%; KF: 0.5-20%; The purity of components is technical purity and above.

The refining agent of the present invention can be used in the refining treatment of removing impurity elements and non-metallic inclusions in the smelting process of rare earth magnesium alloy, and has the advantages of good refining effect, less corrosive fume generated in the refining process, and less pollution to personnel, equipment and the environment, and can be used in The refining treatment of the rare earth magnesium alloy can be realized within a short standing time, and can be effectively applied to industrial production. The rare earth elements added to the rare earth magnesium alloy include one or more combinations selected from Gd, Y, Nd, La, Ce, Sm, Sc, Er, Dy, Ho, Yb or Eu, and the total mass percentage of rare earth atoms is is ≥6%.

The invention is suitable for refining treatment of rare earth magnesium alloy.

The present invention also provides a preparation method of the above-mentioned refining agent.

The preparation method of the above-mentioned low-foaming and less-smoke refining agent for a rare earth magnesium alloy comprises the following steps:

S1 ingredients: mix CaCl ₂ , BaCl ₂ , NaCl, CaF ₂ , KF and KCl according to the ratio to obtain mixed salt, and place it in a dry airtight container; in this step, the dry airtight container can be a drying dish or a sealed plastic bottle , and can also be sealed in ordinary airtight containers and stored in an environment with low relative humidity. In this step, the ratio of raw materials added is in the following ranges according to the mass percentage of the components: CaCl ₂ : 20-36%; BaCl ₂ : 5-15%; NaCl: 0.5-3%; CaF ₂ : 1-5% ; BaF ₂ : 2-8%; KF: 5-20%; KCl: balance. In this step, CaCl ₂ , BaCl ₂ , NaCl, CaF ₂ , BaF ₂ , KF and KCl should be dried and dehydrated at 220°C to 250°C before proportioning.

S2 Melting: Heat the crucible to 100°C-150°C, add the mixed salt into the crucible, raise the temperature of the crucible to 800°C-850°C, stir the mixed salt with a ladle during the heating process until the mixed salt is completely melted; in this step, The material of the crucible is preferably graphite, or corundum or cast iron, as long as the temperature resistance level can reach 900°C; in this step, after the mixed salt is added to the crucible, the heating rate of the crucible is preferably 200°C/h～400°C/h , there is a risk of bumping if the heating rate is too fast, and the production efficiency is affected by a too slow heating rate, and there may be volatilization of molten salt during the heating process; in this step, the stirring method is mechanical stirring, and the material of the ladle is not specified. It only needs to ensure that it does not react with the molten salt and can withstand the high temperature of the molten salt.

S3 Pouring: After the liquid mixed salt is fully stirred, it is poured into the mold, solidified and cooled to obtain a block flux. In this step, the mold material is preferably graphite.

S4 Crushing and sieving: crush the bulk flux, put it into a grinding bowl to crush, and grind to obtain a powdery flux, which is sieved to obtain a refining agent, which is stored in a dry airtight container for later use. In this step, the mesh size of the sieve is preferably 10 mesh to 20 mesh, but it can also be lower than 10 mesh or higher than 20 mesh. Too fine a mesh will result in low efficiency of flux sieving, and too coarse a mesh will cause flux.

The present invention has obtained following technical effect:

(1) The low-foaming and less-smoke refining agent for rare earth magnesium alloys of the present invention does not contain MgCl ₂ , which will not cause loss of rare earth elements;

(2) In the low-foaming and less-smoke refining agent for rare earth magnesium alloys of the present invention, the specific gravity of chlorides such as KCl, CaCl ₂ , and BaCl ₂ has been reduced, and fluorine salts such as KF, CaF, and BaF ₂ have been increased. The polarity is greater than that of chloride ion, the ionic radius is smaller, and the polarity between the ionic compounds is stronger, so the melting point of the obtained refining agent is higher, and the melting is slowed down after being sprinkled into the magnesium melt, which reduces the intensity of the interaction between the refining agent and the melt. The absolute content of chloride ions is also reduced, and the activity of [Cl] decreases, which reduces the tendency of the reaction of 2[Cl]→Cl ₂ ↑, thereby reducing the release of corrosive and harmful gases during the refining process;

(3) In the low-foaming and less-smoke refining agent for rare earth magnesium alloys of the present invention, the types and contents of chlorides and fluorides in inorganic salts are optimized. On the basis of ensuring good slagging ability and refining ability, due to the high density The higher the mass fraction of fluoride salts, the higher the density of the refining agent, the higher the separation between the refining agent and the melt, reducing the possibility of flux inclusions, and the adsorption, sedimentation and separation of inclusions can be completed in a short period of time. The time for melt processing is shortened. It is especially suitable for the refining treatment of rare earth content magnesium alloys with high melt viscosity and high density.

Example 1

Prepare a low-foaming and less-smoke refining agent for rare earth magnesium alloys according to the following steps, its components and mass fractions are: CaCl ₂ : 27%; BaCl ₂ : 5%; NaCl: 1%; CaF ₂ : 5%; BaF ₂ : 8%; KF: 18%; KCl: 36%.

The preparation steps of the low-foaming and less-smoke refining agent for rare earth magnesium alloys in this example are as follows: mix the above-mentioned raw materials according to the above-mentioned ratio to obtain a mixed salt, and place it in a dry airtight container; heat the crucible to 120°C, add the mixed salt In the crucible, raise the temperature of the crucible to 810°C, and stir the mixed salt with a pouring spoon during the heating process until the mixed salt is completely melted; after fully stirring the liquid mixed salt, pour it into the mold, solidify and cool to obtain a block flux (see Figure 1 ), breaking the lumpy flux, putting it into a grinding bowl, crushing, and grinding to obtain a powdery flux, which is sieved through a sieve with a mesh number of 10 to obtain refining agent A and put in a dry airtight container for subsequent use.

Fig. 1 is the exterior view of the block flux obtained after pouring in Example 1 using the method of the present invention. The appearance of block solvent is shown in Figure 1. Fig. 2 is a cooling curve of refining agent A obtained in Example 1 using the method of the present invention. Fig. 2 shows a flux cooling curve obtained by measuring the melting point of refining agent A, as shown in Fig. 2, from which the melting point was measured to be about 670°C.

When using the refining agent A obtained above, sprinkle the covering agent in the painted iron crucible, add pure magnesium and raise the temperature to 780°C, during which the covering agent is sprinkled to prevent flames, and then add the master alloy to the melt composition distribution The ratio is Mg-4Y-2Nd-1Gd, stirring until the intermediate alloy is fully melted; during refining, while stirring the alloy liquid, add 1.5wt.% of the above refining agent, and the refining time is 10 minutes; after the refining process, remove the slag and let it stand After 20 minutes, gravity cast the metal sample, the T6 tensile strength is 255MPa, and the elongation is 2.2%.

Example 2

Prepare a low-foaming and less-smoke refining agent for rare earth magnesium alloys according to the following steps, its components and mass fractions are: CaCl ₂ : 30%; BaCl ₂ : 10%; NaCl: 2%; CaF ₂ : 4%; BaF ₂ : 6%; KF: 16%; KCl: 32%.

The preparation steps of the low-foaming and less-smoke refining agent for rare earth magnesium alloys in this example are as follows: mix the above-mentioned raw materials according to the above-mentioned ratio to obtain a mixed salt, and place it in a dry airtight container; heat the crucible to 130°C, add the mixed salt In the crucible, raise the temperature of the crucible to 825°C, and stir the mixed salt with a ladle during the heating process until the mixed salt is completely melted; after fully stirring the liquid mixed salt, pour it into the mold, solidify and cool to obtain a block flux; The flux is crushed, placed in a grinding bowl, crushed, and ground to obtain a powdery flux, which is sieved through a sieve with a mesh size of 10 to obtain refining agent B and stored in a dry airtight container for later use.

When using the refining agent B obtained above, sprinkle the covering agent into the painted iron crucible, add pure magnesium and raise the temperature to 780°C, during which the covering agent is sprinkled to prevent flames, and then add the master alloy to the melt composition distribution The ratio is Mg-2.8Nd-1.4Gd-0.4Zn-0.5Zr, stir until the intermediate alloy is fully melted; when refining, add 1.5wt.% of the above refining agent while stirring the alloy liquid, and the refining time is 8 minutes; the refining process is completed After removing the slag and standing still for 30 minutes, reverse gravity casting and pouring resin sand mold large-scale castings. The body sampling T6 tensile strength is 280MPa, and the elongation is 3%.

Example 3

Prepare a low-foaming and less-smoke refining agent for rare earth magnesium alloys according to the following steps, its components and mass fractions are: CaCl ₂ : 32%; BaCl ₂ : 12%; NaCl: 2%; CaF ₂ : 3%; BaF ₂ : 8%; KF: 19%; KCl: 24%.

The preparation steps of the low-foaming and less-smoke refining agent for rare earth magnesium alloys in this example are as follows: mix the above-mentioned raw materials according to the above-mentioned ratio to obtain a mixed salt, and place it in a dry airtight container; heat the crucible to 120°C, add the mixed salt In the crucible, raise the temperature of the crucible to 840°C, stir the mixed salt with a spoon during the heating process, until the mixed salt is completely melted; after fully stirring the liquid mixed salt, pour it into the mold, solidify and cool to obtain a block flux; The flux is crushed, placed in a grinding bowl, crushed, and ground to obtain a powdery flux, which is sieved through a sieve with a mesh size of 10 to obtain refining agent C and stored in a dry airtight container for later use.

When using the refining agent C obtained above, sprinkle the covering agent into the painted iron crucible, add pure magnesium and raise the temperature to 780°C, during which the covering agent is sprinkled to prevent flames, and then add the master alloy to the melt composition The ratio is Mg-6Gd-3Y-0.5Zr, stirring until the intermediate alloy is fully melted; during refining, while stirring the alloy liquid, add 2wt.% of the above-mentioned refining agent, and the refining time is 8 minutes; After 30 minutes, anti-gravity casting cast resin sand mold large castings, body sampling T6 tensile strength 332MPa, elongation 4.2%.

The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent replacements, modifications or improvements can be made to the technical solutions and implementations of the present invention, all of which fall within the scope of the present invention. The protection scope of the present invention shall be determined by the appended claims.

The content that is not described in detail in the description of the present invention belongs to the well-known technology of those skilled in the art.

Claims (10)

1. The low-foam low-smoke refining agent for the rare earth magnesium alloy is characterized by comprising the following components in percentage by mass:

KCl balance.

2. The preparation method of the low-foam low-smoke refining agent for the rare earth magnesium alloy is characterized by comprising the following steps of:

s1, proportioning: caCl is added with ₂ 、BaCl ₂ 、NaCl、CaF ₂ 、BaF ₂ Mixing KF and KCl according to a certain proportionEvenly mixing to obtain mixed salt;

s2, smelting: heating the crucible to 100-150 ℃, adding the mixed salt into the crucible, heating the crucible to 800-850 ℃, and stirring the mixed salt in the heating process until the mixed salt is completely melted;

s3, pouring: fully stirring the liquid mixed salt, pouring the liquid mixed salt into a mold, and solidifying and cooling to obtain a massive flux;

s4, crushing and sieving: crushing the massive flux, grinding to obtain powdery flux, and sieving to obtain the refining agent.

3. The method for preparing the low-foam low-smoke refining agent for the rare earth magnesium alloy according to claim 2, wherein the raw materials added in the step S1 are in a ratio of mass percent:

KCl balance.

4. The method for producing a low-foaming low-smoke refining agent for a rare earth magnesium alloy according to claim 2, wherein in said step S1, caCl is selected from the group consisting of ₂ 、BaCl ₂ 、NaCl、CaF ₂ 、BaF ₂ Drying and dehydrating KF and KCl at 220-250 ℃ before mixing according to the proportion.

5. The method for producing a low-foaming low-smoke refining agent for a rare earth magnesium alloy according to claim 2, wherein in the step S1, the obtained mixed salt is placed in a dry sealed container or sealed in a normal sealed container and stored in an environment with low relative humidity.

6. The method for preparing a low-foam and low-smoke refining agent for rare earth magnesium alloy according to claim 2, wherein the rare earth elements in the rare earth magnesium alloy comprise one or more of Gd, Y, nd, la, ce, sm, sc, er, dy, ho, yb and Eu, and the total mass percentage of rare earth atoms is more than or equal to 6%.

7. The method for preparing a low-foaming and low-smoke refining agent for rare earth magnesium alloy according to claim 2, wherein in the step S2, the crucible is made of graphite, corundum or cast iron, and the stirring mode is mechanical stirring of a ladle.

8. The method for producing a low-foaming low-smoke refining agent for a rare earth magnesium alloy according to claim 2, wherein in the step S2, the crucible temperature rise rate is 200 ℃/h to 400 ℃/h after adding the mixed salt into the crucible.

9. The method for preparing a low-foaming and low-smoke refining agent for rare earth magnesium alloy according to claim 2, wherein in the step S3, the mold material is graphite.

10. The method for producing a low-foaming low-smoke refining agent for a rare earth magnesium alloy according to claim 2, wherein in the step S4, the number of the sieves to be sieved is 10 to 20 mesh.

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