Flame-retardant composite flux suitable for magnesium-aluminum alloy casting and preparation method of flame-retardant composite flux

Abstract

The invention provides a composite flux suitable for Mg-Al magnesium alloy and a preparation method of the composite flux. The alloy comprises the following components in percentage by mass: 30 to 40 percent of MgCl, 24 to 30 percent of KCl, 4 to 8 percent of NaCl, 6 to 12 percent of BaCl2, 3 to 6 percent of CaCl2, 6 to 12 percent of CaF2, 0.5 to 2 percent of C powder, 1 to 6 percent of Ti powder and 1 to 10 percent of rare earth carbonate. And the rare earth element is one or combination of lanthanum, cerium, praseodymium, neodymium, gadolinium, terbium, scandium and yttrium. The rare earth composite flux with uniform components and granularity is obtained by melting, crystallizing, crushing, grinding and milling, and ball-milling. The density of the composite flux is slightly larger than that of magnesium alloy (1.8-2.0 g / cm < 3 >), the composite flux is low in melting point, moderate in viscosity and high in chemical stability, and the composite flux has the functions of melt protection and flame retardance, magnesium alloy melt purification and magnesium alloy grain refinement.

Description

Technical Field

[0001] The invention relates to the technical field of new metallurgical materials, and in particular to a flame retardant composite flux suitable for magnesium-aluminum alloy smelting and casting and a preparation method thereof. Background Art

[0002] As the lightest metal structural material in engineering applications, magnesium alloy has high specific strength, high specific stiffness and good damping performance. It is widely used in aviation, aerospace, communications, automobile and other industries. In the non-ferrous metal planning forecast for the apparent consumption demand and output of major non-ferrous metals in 2020, magnesium is included in the five major products. It can be seen that the country recognizes the future development space of magnesium and sets the tone for the future development of magnesium.

[0003] The flame retardancy, purification, grain refinement and homogenization of magnesium alloys in the melting and casting process have always been hot topics of research. Clean molten metal is the prerequisite for obtaining high-quality ingots and castings. Due to its active chemical properties, magnesium alloys are prone to chemical reactions or even combustion with oxygen, water, nitrogen and other gases in the air during the smelting process, forming non-metallic inclusions. These non-metallic inclusions have serious harm to the mechanical properties and corrosiveness of the material. Therefore, it is very necessary to purify the melt during the preparation of magnesium alloys.

[0004] The flux purification method is a commonly used method, which uses the full contact between the flux and the molten metal to wet the inclusions, so that the inclusions agglomerate and combine with the flux to form large particles, which are precipitated at the bottom of the crucible to achieve the purpose of separation from the molten metal. However, the existing flux has problems such as low flame retardancy, insignificant purification effect, single function, and harm to the environment. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a flame retardant composite flux suitable for magnesium-aluminum alloy casting and a preparation method thereof, which solves the problems of existing fluxes such as insignificant flame retardant and purification effects, single function, and harm to the environment.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The magnesium-aluminum alloy flame retardant composite flux and the preparation method thereof disclosed in the present invention are characterized by comprising the following steps:

[0008] (1) The composite flux has the following components in mass fraction: MgCl: 30%-40%, KCl: 24%-30%, NaCl: 4%-8%, BaCl: 6%-12%, CaCl: 3%-6%, CaF2: 6%-12%, C powder: 0.5%-2%, Ti powder: 1%-6%, rare earth carbonate: 1%-10%.

[0009] (2) The rare earth element of the rare earth carbonate is one or a combination of lanthanum, cerium, praseodymium, neodymium, gadolinium, terbium, scandium and yttrium.

[0010] (3) The preparation method of the composite flux of the present invention is as follows: magnesium chloride, potassium chloride, sodium chloride, calcium chloride, barium chloride and calcium fluoride weighed in a good proportion are heated to 850-900°C for melting, stirred evenly, cast into a crystallizer and then cooled to obtain a block material, which is then mechanically crushed and loaded into a ball mill for mixing with C powder, Ti powder and rare earth carbonate according to a proportion, and the mixture is ball milled, and the ball-to-material ratio, rotation speed and time are set to obtain the flame retardant composite flux of the present invention.

[0011] (4) The method of using the composite flux of the present invention is as follows: the crucible resistance furnace is heated to 700-800°C, the preheated magnesium-aluminum alloy is added, and 0.5-3% of the mass of the composite flux of the melt is spread on the surface for melting. After all the melt is melted, the composite flux is stirred until a mirror effect appears on the surface of the melt, and the melt is allowed to stand for 10-30 minutes, and the temperature is lowered to 680-720°C for casting.

[0012] Compared with the prior art, the present invention has the following advantages and technical effects:

[0013] (1) The present invention has a simple preparation process and low cost, and has significant flame retardant, purification and refinement effects. It is a composite flux. The chloride and fluoride in the composite flux can play the role of adjusting density and surface tension and refining and removing impurities.

[0014] (2) Rare earth carbonate: Rare earth carbonate can decompose into CO2 and rare earth oxides at temperatures above 500°C. The generated CO2 gas can block the contact between air and the melt to a certain extent, reduce the generation of oxide inclusions and participate in flame retardancy. On the one hand, rare earth oxides combine with magnesium oxide on the surface of the melt to form a dense oxide layer, further hindering the contact between air and the magnesium alloy melt to cause further oxidation or even combustion. On the other hand, rare earth oxides can wet inclusions in the melt and use the density difference to cause rapid sedimentation of inclusions, which is beneficial to the purification and removal of impurities from the melt. Finally, the rare earth oxides that fail to capture inclusions can serve as nucleation particles during the solidification process and play a role in grain refinement.

[0015] (3) C powder: C powder and Ti powder are combined together during the ball milling process, with moderate density, which reduces the floating burning loss of C powder and the sedimentation of Ti powder, and improves the refinement effect and raw material utilization rate; C powder can form an insoluble compound Al4C3 with aluminum in the magnesium alloy melt, which can serve as an in-situ particle for grain nucleation and play a role in grain refinement.

[0016] (4) Ti powder: Ti powder is a poorly soluble substance in the melt. After being kept warm for a certain period of time, it can form compounds with C and Al elements, which has a refining effect. During the solidification process, the slow migration rate of Ti elements can inhibit the growth of dendrites. DETAILED DESCRIPTION

[0017] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below in conjunction with the embodiments.

[0018] It should be noted that all components in the technical solution of this application require the necessary additional facilities of water supply, oil supply, electricity supply and gas supply to be driven and / or controlled. If there is no further explanation, it is assumed that the existing technology is used and equipped without special explanation.

[0019] It should be noted that, in order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific implementation methods.

[0020] Example 1

[0021] The invention provides a magnesium alloy composite flux, which comprises the following components in mass fraction: MgCl: 40%, KCl: 20%, NaCl: 5%, BaCl: 5%, CaCl: 5%, CaF2: 10%, C powder: 1%, Ti powder: 4%, and rare earth carbonate: 10%.

[0022] The preparation method of the composite flux of the invention comprises the following steps: melting magnesium chloride, potassium chloride, sodium chloride, calcium chloride, barium chloride and calcium fluoride in a weighed proportion, stirring the mixture evenly, casting the mixture into a crystallizer, mechanically crushing the obtained block material, grinding the obtained block material into powder, and finally charging the block material into a ball mill, mixing the obtained block material with C powder, Ti powder and rare earth carbonate according to a proportion, and ball milling the mixture, wherein the ball-to-material ratio is 20:1 and the ball milling time is 20 minutes, so as to obtain the flame retardant composite flux of the invention.

[0023] The method for using the composite flux of the present invention is as follows: a crucible resistance furnace is heated to 720°C, a Mg-9Al-1Zn-0.5Mn alloy is melted under the protection of a CO2+SF6 mixed gas, after all the alloy is melted, the alloy is stirred once, the temperature is raised to 800°C, 1% of the composite flux by mass of the melt is added, the alloy is stirred until a mirror effect appears on the surface of the melt, the alloy is left to stand for 10 minutes, the alloy is cooled to 680°C, and the alloy is poured.

[0024] Example 2

[0025] The invention provides a composite flux, which comprises the following components in mass fraction: 35% of MgCl, 25% of KCl, 6% of NaCl, 6% of BaCl, 6% of CaCl, 10% of CaF2, 1% of C powder, 4% of Ti powder and 7% of rare earth carbonate.

[0026] The preparation method of the composite flux is as follows: magnesium chloride, potassium chloride, sodium chloride, calcium chloride, barium chloride and calcium fluoride are weighed and proportioned, melted and stirred evenly, cast into a crystallizer, the block material is mechanically crushed and then ground into powder, and finally loaded into a ball mill and mixed with C powder, Ti powder and rare earth carbonate according to the proportion, and the mixture is ball milled, the ball-to-material ratio is 20:1, and the ball milling time is 30 minutes, so as to obtain the flame retardant composite flux of the present invention.

[0027] The crucible resistance furnace was heated to 720°C, and the Mg-9Al-1Zn-0.5Mn alloy was melted under the protection of CO2+SF6 mixed gas. After all the alloys were melted, they were stirred once and heated to 780°C. 1% composite flux by mass of the melt was added and stirred until a mirror effect appeared on the surface of the melt. The alloy was allowed to stand for 10 minutes, cooled to 680°C, and poured.

[0028] Example 3

[0029] The invention provides a composite flux, which comprises the following components in mass fraction: MgCl: 35%, KCl: 30%, NaCl: 4%, BaCl: 6%, CaCl: 5%, CaF2: 10%, C powder: 2%, Ti powder: 2% and rare earth carbonate: 6%.

[0030] The preparation method of the composite flux is as follows: magnesium chloride, potassium chloride, sodium chloride, calcium chloride, barium chloride and calcium fluoride are weighed and proportioned, melted and stirred evenly, cast into a crystallizer, the block material is mechanically crushed and then ground into powder, and finally loaded into a ball mill and mixed with C powder, Ti powder and rare earth carbonate according to the proportion, and the mixture is ball milled, the ball-to-material ratio is 20:1, and the ball milling time is 60 minutes, so as to obtain the flame retardant composite flux of the present invention.

[0031] The crucible resistance furnace was heated to 720°C, and the Mg-9Al-1Zn-0.5Mn alloy was melted under the protection of CO2+SF6 mixed gas. After all the alloys were melted, they were stirred once and heated to 800°C. 1% composite flux of the melt was added and stirred until a mirror effect appeared on the surface of the melt. The alloy was left to stand for 20 minutes, cooled to 680°C, and poured.

[0032] Example 4

[0033] The invention provides a composite flux, which comprises the following components in mass fraction: MgCl: 40%, KCl: 30%, NaCl: 4%, BaCl: 6%, CaCl: 4%, CaF2: 8%, C powder: 2%, Ti powder: 1% and rare earth carbonate: 5%.

[0034] The preparation method of the composite flux is as follows: magnesium chloride, potassium chloride, sodium chloride, calcium chloride, barium chloride and calcium fluoride are weighed and proportioned, melted and stirred evenly, cast into a crystallizer, the block material is mechanically crushed and then ground into powder, and finally loaded into a ball mill and mixed with C powder, Ti powder and rare earth carbonate according to the proportion, and the mixture is ball milled, the ball-to-material ratio is 20:1, and the ball milling time is 60 minutes, so as to obtain the flame retardant composite flux of the present invention.

[0035] The crucible resistance furnace was heated to 720°C, and the Mg-9Al-1Zn-0.5Mn alloy was melted under the protection of CO2+SF6 mixed gas. After all the alloys were melted, they were stirred once and heated to 750°C. 2% composite flux by mass of the melt was added and stirred until a mirror effect appeared on the surface of the melt. The alloy was allowed to stand for 30 minutes, cooled to 700°C, and poured.

[0036] Example 5

[0037] The invention provides a composite flux, which comprises the following components in mass fraction: MgCl: 35%, KCl: 30%, NaCl: 6%, BaCl: 8%, CaCl: 8%, CaF2: 10%, C powder: 1%, Ti powder: 1% and rare earth carbonate: 1%.

[0038] The preparation method of the composite flux is as follows: magnesium chloride, potassium chloride, sodium chloride, calcium chloride, barium chloride and calcium fluoride are weighed and proportioned, melted and stirred evenly, cast into a crystallizer, the block material is mechanically crushed and then ground into powder, and finally loaded into a ball mill and mixed with C powder, Ti powder and rare earth carbonate according to the proportion, and the mixture is ball milled, the ball-to-material ratio is 20:1, and the ball milling time is 30 minutes, so as to obtain the flame retardant composite flux of the present invention.

[0039] The crucible resistance furnace was heated to 720°C, and the Mg-9Al-1Zn-0.5Mn alloy was melted under the protection of CO2+SF6 mixed gas. After all the alloys were melted, they were stirred once and heated to 750°C. 3% composite flux by mass of the melt was added and stirred until a mirror effect appeared on the surface of the melt. The alloy was allowed to stand for 20 minutes, cooled to 700°C, and poured.

[0040] Table 1 Comparison of purification and refinement effects of Mg-9Al-1Zn-0.5Mn alloy

[0041] Instance serial number Inclusion area fraction / ‰ Grain size / μm Unrefined 1.035 480 RJ-2# 0.6126 465 Example 1 0.3532 357 Example 2 0.2137 315 Example 3 0.4930 402 Example 4 0.4320 370 Example 5 0.3012 402

[0042] Furthermore, the best effect is achieved when the mass fraction ratio of Ti to C is 4:1, the atomic ratio is close to 1:1, and the mass fraction of rare earth carbonate is 7%.

[0043] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A composite flux suitable for Mg-Al magnesium alloy and a preparation method thereof, characterized in that: The composite flux is composed of the following components in percentage by weight: Composition: MgCl: 30-40%, KCl: 24-30%, NaCl: 4-8%, BaCl: 6-12%, CaCl: 3-6%, CaF2: 6-12%, C powder: 0.5-2%, Ti powder: 1-6%, rare earth carbonate: 1-10%.

2. The composite flux according to claim 1, characterized in that: The rare earth element in the mixed rare earth is one or a combination of lanthanum, cerium, praseodymium, neodymium, gadolinium, terbium, scandium and yttrium.

3. A method for preparing a composite flux according to any one of claims 1 to 2, characterized in that: The following steps are involved: (1) The crucible is preheated to 850°C-900°C, magnesium chloride, potassium chloride, sodium chloride, calcium chloride, barium chloride, and calcium fluoride are weighed and mixed, melted, stirred evenly, and cast into a crystallizer to obtain a bulk material. (2) After the block material is mechanically crushed, it is put into a ball mill and mixed with C powder, Ti powder and rare earth carbonate according to the proportion and ball milled. The ball-to-material ratio, rotation speed and time are set to obtain the composite flux of the present invention.

4. A method for using the flame retardant composite flux according to any one of claims 1-2, characterized in that: The following steps are involved: The crucible resistance furnace is heated to 700-800℃, preheated magnesium-aluminum alloy is added, and 0.5-3% of the composite flux of the melt mass is spread on the surface for melting. After all the melt is melted, it is stirred until a mirror effect appears on the surface of the melt, and then it is left to stand for 10min-30min, cooled to 680℃-720℃, and then cast.