CN1587425A - Magnesium alloy smelting method using difluoromethane as protective atmosphere - Google Patents
Magnesium alloy smelting method using difluoromethane as protective atmosphere Download PDFInfo
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- CN1587425A CN1587425A CN 200410052617 CN200410052617A CN1587425A CN 1587425 A CN1587425 A CN 1587425A CN 200410052617 CN200410052617 CN 200410052617 CN 200410052617 A CN200410052617 A CN 200410052617A CN 1587425 A CN1587425 A CN 1587425A
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- magnesium
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- methylene fluoride
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Abstract
The present invention relates to magnesium alloy smelting method with difluoromethane as protecting atmosphere. In the gas mixer, 1, 1-difluoroethane of content 0.05-5 vol% and dry air and/or CO2 are mixed to form the magnesium melt protecting agent. Pure magnesium or magnesium alloy inside closed crucible is heated white the mixed gas is introduced into the crucible to form compact antioxidant protecting film covering the surface of pure magnesium or magnesium alloy, with the mixed gas flow rate being 0.05-10 % of the closed volume. After refining, the pure magnesium or magnesium alloy is gravitationally cast of pressing cast. The method of the present invention can prevent pure magnesium or magnesium alloy from being oxidized or burnt during smelting, in excellent protecting effect, low cost and low green house effect.
Description
Technical field
The present invention relates to high temperature oxidation and burning guard technology in a kind of pure magnesium or the conventional magnesium alloy smelting process; being specifically related to adopt the gas mixture that contains methylene fluoride (its trade name is R32) is the pure magnesium of protective atmosphere or the melting method of magnesium alloy, belongs to the material metallurgical technology field.
Background technology
Because the oxytropism of MAGNESIUM METAL, pure magnesium or magnesium alloy be very easily oxidation in air, because its oxidation products-magnesian density coefficient is less than 1, this oxide film that generates naturally can not constitute the further oxidation that effective blocking layer stops interior metal, and at high temperature pure magnesium or magnesium alloy also easily burn.Therefore, the gas mixture that industrial general normal employing contains sulfur hexafluoride is that protective atmosphere carries out magnesium alloy smelting and production, and this is one of the most effective magnesium alloy smelting guard method at present.In recent years, along with developing rapidly of magnesium industry, shielding gas consumptions such as sulfur hexafluoride required when pure magnesium or magnesium alloy smelting and production are increasing.Yet; the global warming potential of sulfur hexafluoride (GWP) reaches 23900 (the GWP value of carbonic acid gas is 1); and atmospheric lifetime reaches 3200; be a kind of long-life, high-temperature chamber effect gas; forbidding pressure from the environment protection tissue is increasing; classified as the material that needs to reduce discharging by the international environmental protection tissue; the Kyoto Protocol of signing in the meeting of the 5th UNFCCC (United Nations Framework Convention on Climate Change) require industry member in following 10 years in the discharging that reduces sulfur hexafluoride gas as far as possible; to realize by 2015 sulfur hexafluoride zero release (U.S.EPA, 2003b).Therefore, international magnesium association (IMA) requires to reduce by the raising service efficiency consumption of sulfur hexafluoride, and definite magnesium industry circle was realized the zero release of sulfur hexafluoride before 2015.
For realizing that above target does not influence the development of magnesium industry simultaneously again, striving to find the substitute of sulfur hexafluoride in the world and developing the melting protection technology of pure magnesium or magnesium alloy.The finding that the protective atmosphere of novel low environmental impact carries out is found to have only a few alternative atmosphere to be suggested at present, and most typical representative is just by three kinds of surrogate: AMCover of international magnesium association's its protection effect of assessment and carrying capacity of environment
TM(HFC-134a), HFE7100 (C
4F
9-O-CH
3) and Novec
TM612 (C
3F
7COC
2F
5).The former is by the invention of Australian CAST research centre, and both are invented the back by 3M company.Although these three kinds of gases and melting protection technology has been effectively by tentative confirmation to pure magnesium or magnesium alloy, and the influence of their Greenhouse effect has only sulfur hexafluoride
More friendly more to environment than sulfur hexafluoride, but the GWP value of these three kinds of gases is still higher, all above 1000, and the protection effect of back two kinds of gases does not also obtain affirmation also in the middle of evaluation at present; Simultaneously, HFE7100 and Novec
TM612 price is higher, and domestic still do not have production, obviously will limit the feasibility of its industrial application.Therefore it is cheaper to continue to seek price, and place of gas that environmental influence is littler and melting protection technology thereof are the targets of magnesium industry always.
Summary of the invention
The objective of the invention is at the deficiencies in the prior art; a kind of magnesium alloy smelting method is provided; adopt a kind of protection effect and sulfur hexafluoride suitable to the magnesium melt; and being better than the material of sulfur hexafluoride, environmental protection effect replaces the atmosphere protection agent of sulfur hexafluoride as the magnesium melt; reduce the technology cost; the melting protection is respond well, can not pollute environment.
For realizing such purpose, the present invention adopts methylene fluoride to replace the atmosphere protection agent of sulfur hexafluoride as the magnesium melt, and melting technology mainly may further comprise the steps:
1, methylene fluoride (its trade name is R32) is mixed in gas mixing device with auxiliary diluent gas, the volume content of methylene fluoride in mixed gas is 0.05-5%.Wherein auxiliary diluent gas can be dry air, dry carbonic acid gas or other rare gas element, also can be their mixture.
2, pure magnesium or magnesium alloy are placed sealing crucible heat temperature raising.
3, when pure magnesium or magnesium alloy temperature reach 400 ℃, begin mixed gas is fed crucible, make gas cover pure magnesium or Mg alloy surface, the mixed gas per minute flow of feeding is confining gas volumetrical 0.05-10%.
4, continue heat temperature raising to pure magnesium or magnesium alloy fusing, make shielding gas form oxide film one deck densification, that good protection is arranged rapidly at bath surface.
5, when pure magnesium or magnesium alloy fused mass are warming up to 700～850 ℃, under gas shield, carry out refinement and denaturation, leave standstill 30～40 minutes then after, carry out gravity casting or pressure die casting.
In the smelting and pouring process of whole pure magnesium or magnesium alloy; contain the gas mixture of methylene fluoride and the fresh magnesium liquid surface of fusing complicated chemical reaction takes place; improved the structure of natural oxide film; make surface film become fine and close, complete, flexible; be closely linked with the melt metal, and cover bath surface fully, magnesium melt and air are separated; reduce the oxidation or the combustionvelocity of magnesium melt greatly, pure magnesium or magnesium alloy are protected when melting.Remove old oxide film in melting or casting process, bath surface will form the new oxide film of protectiveness of one deck densification rapidly, be covered in the magnesium bath surface again, the not oxidized or burning of protection magnesium melt with remaining valid.
Characteristics of the present invention are: (1) contain methylene fluoride atmosphere to the protection effect of magnesium melt with to contain sulfur hexafluoride atmosphere suitable, in whole melting temperature range, the content of methylene fluoride has good protection effect to the magnesium melt when 0.05-5% (volume).(2) under optimal conditions, the density of the surface film of formation, smooth finish, thickness and to contain the formed surface film of sulfur hexafluoride atmosphere very similar, also about the same to the protection effect of magnesium melt.(3) methylene fluoride all be at normal temperatures stablize, nontoxic, non-corrosive material, at high temperature can decompose, its degradation production can consume with magnesium generation chemical reaction, the discharging gas can not produce harm to environment and operator; (4) global warming potential of methylene fluoride (GWP) is about 650 (is about sulfur hexafluoride
), atmospheric lifetime only is 5 years, even discharge methylene fluoride in atmosphere in the magnesium alloy smelting process, the influence of its Greenhouse effect is also well below sulfur hexafluoride.(5) the domestic suitability for industrialized production that realized of methylene fluoride is buied easily, and cheap, its market value is sulfur hexafluoride approximately
Compare with sulfur hexafluoride, the former consumption and the efficient when the magnesium melting is about the same, and melting protection technology is simple.Therefore, replacing sulfur hexafluoride with methylene fluoride is very considerable as the economic benefits of the protective atmosphere of pure magnesium or magnesium alloy.
Embodiment
With reference to following specific embodiments narration, can be well understood to technical scheme of the present invention and plurality of advantages.
Embodiment 1: methylene fluoride is to the protectiveness melting of AM60 magnesium alloy
Implementation step is: mix methylene fluoride in gas mixing device with dry air or carbonic acid gas (1) by the various ratio of mixture that provide in the table 1; (2) with 3 kilograms of clean AM60 magnesium alloy heat temperature raising in 5 kilograms of electrical crucibles; (3) when alloy temperature surpasses 400 ℃, begin mixed gas is fed crucible, gas mixture is fed crucible by the flow parameter that table 1 provides, make gas cover alloy surface; (4) magnesium alloy continues heat temperature raising to fusing, makes shielding gas form oxide film one deck densification, that good protection is arranged rapidly at bath surface; (5) magnesium alloy fused mass is warming up to 70～850 ℃, and carries out refinement and denaturation under this gas shield, leave standstill 30～40 minutes then after, carry out gravity casting or pressure die casting.
Protection effect when in whole fusion process, constantly observing various melting technology parameter, and observations also is recorded in the table 1.From table 1 as seen; when the AM60 magnesium alloy carries out melting under containing the protection of methylene fluoride mixed atmosphere; each smelting temperature that sets in table 1, various air blowing flow and under the hold-time even surface agitation takes place, can both form fine and close, incombustible sealer quickly.
Table 1
| Sequence number | The protection processing parameter | Melting protection effect | ||||||||
| Melt temperature ℃ | Ratio of gas mixture (volume) | Mixed gas flow (%/min) | Diluent gas | Hold-time (minute) | Surface agitation | Film color, slickness | Rate of film build | Film thickness | Incendivity | |
| 1 | ??670 | ????0.05％ | ????0.05 | Air | ????1 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| 2 | ??700 | ????0.12％ | ????0.5 | Air | ????19 | Have | Light, gauffer arranged | Hurry up | Thin | Do not fire |
| 3 | ??720 | ????0.05％ | ????1 | Carbonic acid gas | ????14 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| 4 | ??750 | ????0.05％ | ????1 | Carbonic acid gas | ????11 | Have | Bright, smooth | Hurry up | Thicker | Do not fire |
| 5 | ??780 | ????0.1％ | ????2 | Carbonic acid gas | ????7 | Have | Light, gauffer arranged | Hurry up | Thick | Do not fire |
| 6 | ??800 | ????2％ | ????2 | Air+carbonic acid gas | ????4 | Have | Light, gauffer arranged | Hurry up | Thick | Do not fire |
| 7 | ??820 | ????2％ | ????3 | Air+carbonic acid gas | ????5 | Have | Light, gauffer arranged | Hurry up | Thick | Do not fire |
| 8 | ??820 | ????5％ | ????10 | Air+carbonic acid gas | ????10 | Have | Burnt hair, gauffer is arranged | Hurry up | Thick | Do not fire |
Embodiment 2: methylene fluoride is to the protectiveness melting of AZ91 magnesium alloy
Implementation step is: mix methylene fluoride in gas mixing device with dry air or carbonic acid gas (1) by the various ratio of mixture that provide in the table 2; (2) with 3 kilograms of clean AZ91 magnesium alloy heat temperature raising in 5 kilograms of electrical crucibles; (3) when alloy temperature surpasses 400 ℃, begin mixed gas is fed crucible, gas mixture is fed crucible by the flow parameter that table 2 provides, make gas cover alloy surface; (4) magnesium alloy continues heat temperature raising to fusing, makes shielding gas form oxide film one deck densification, that good protection is arranged rapidly at bath surface; (5) magnesium alloy fused mass is warming up to 700～850 ℃, and carries out refinement and denaturation under this gas shield, leave standstill 30～40 minutes then after, carry out gravity casting or pressure die casting.
Protection effect when in whole fusion process, constantly observing various melting technology parameter, and observations also is recorded in the table 2.From table 2 as seen; when the AZ91 magnesium alloy carries out melting under containing the protection of methylene fluoride mixed atmosphere; each smelting temperature that sets in table 2, various air blowing flow and under the hold-time even surface agitation takes place, can both form fine and close, incombustible sealer quickly.
Table 2
| Sequence number | The protection processing parameter | Melting protection effect | ||||||||
| Smelting temperature ℃ | Ratio of gas mixture (volume) | Mixed gas flow (%/min) | Diluent gas | Hold-time (minute) | Surface agitation | Film color, slickness | Rate of film build | Film thickness | Incendivity | |
| ??1 | ??650 | ????0.05％ | ????0.05 | Air | ????40 | Have | Light, gauffer arranged | Hurry up | Thin | Do not fire |
| ??2 | ??700 | ????0.15％ | ????0.5 | Air | ????17 | Have | Light, gauffer arranged | Hurry up | Thin | Do not fire |
| ??3 | ??720 | ????0.4％ | ????1 | Carbonic acid gas | ????25 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| ??4 | ??750 | ????1％ | ????1 | Carbonic acid gas | ????10 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| ??5 | ??780 | ????1％ | ????2 | Carbonic acid gas | ????25 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| ??6 | ??800 | ????5％ | ????10 | Air+carbonic acid gas | ????10 | Have | Light, gauffer arranged | Hurry up | Thin | Do not fire |
Embodiment 3: methylene fluoride is to the protectiveness melting of pure magnesium
Implementation step: mix methylene fluoride in gas mixing device with dry air or carbonic acid gas (1) by the various ratio of mixture that provide in the table 3; (2) with 3 kilograms of clean pure magnesium heat temperature raising in 5 kilograms of electrical crucibles; (3) when the temperature of pure magnesium surpasses 400 ℃, begin mixed gas is fed crucible, gas mixture is fed crucible by the flow parameter that table 3 provides, make gas cover the surface of magnesium; (4) pure magnesium continues heat temperature raising to fusing, makes shielding gas form oxide film one deck densification, that good protection is arranged rapidly at bath surface; (5) the magnesium melt is warming up to 700～850 ℃, and carries out refinement and denaturation under this gas shield, leave standstill 30～40 minutes then after, carry out gravity casting or pressure die casting.
Protection effect when in whole fusion process, constantly observing various melting technology parameter, and observations also is recorded in the table 3.From table 3 as seen; when pure magnesium carries out melting under containing the protection of methylene fluoride mixed atmosphere; each smelting temperature that sets in table 3, various air blowing flow and under the hold-time even surface agitation takes place, can both form fine and close, incombustible sealer quickly.
Table 3
| Sequence number | The protection processing parameter | Melting protection effect | ||||||||
| Smelting temperature ℃ | Ratio of gas mixture (volume) | Mixed gas flow (%/min) | Diluent gas | Hold-time (minute) | Surface agitation | Film color, slickness | Rate of film build | Film thickness | Incendivity | |
| 1 | ?680 | ????0.05％ | ????0.05 | Air | ????1 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| 2 | ?680 | ????0.2％ | ????0.5 | Air | ??40 | Have | Light, gauffer arranged | Hurry up | Thick | Do not fire |
| 3 | ?700 | ????0.1％ | ????0.5 | Carbonic acid gas | ??17 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| 4 | ?720 | ????0.4％ | ????1 | Carbonic acid gas | ??25 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| 5 | ?750 | ????0.4％ | ????1 | Carbonic acid gas | ??10 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| 6 | ?780 | ????5％ | ????2 | Air+carbonic acid gas | ??15 | Have | Bright, smooth | Hurry up | Thin | Do not fire |
| 7 | ?800 | ????5％ | ????10 | Air+carbonic acid gas | ??20 | Light, gauffer arranged | Hurry up | Thicker | Do not fire | |
Above embodiment explanation; it is that protective atmosphere carries out smelting operation to pure magnesium or magnesium alloy fused mass that employing contains the methylene fluoride gas mixture; good protection effect is all arranged in the whole temperature range of its melting; suitable with the protection effect of sulfur hexafluoride; and melting technology is simple, has more environmental protection and economic advantages than sulfur hexafluoride.
Claims (2)
1, a kind of methylene fluoride that adopts is the magnesium alloy smelting method of protective atmosphere, it is characterized in that may further comprise the steps:
1) methylene fluoride is mixed in gas mixing device with auxiliary diluent gas, the volume content of methylene fluoride in hybrid protection gas is 0.05-5%;
2) pure magnesium or magnesium alloy are placed sealing crucible heat temperature raising;
3) when pure magnesium or magnesium alloy temperature surpass 400 ℃, begin mixed gas is fed crucible, make gas cover magnesium or Mg alloy surface, the mixed gas per minute flow of feeding is confining gas volumetrical 0.05-10%;
4) continue heat temperature raising to pure magnesium or magnesium alloy fusing, make shielding gas form the protective oxide layer of one deck densification at bath surface;
5) when pure magnesium or magnesium alloy fused mass are warming up to 700～850 ℃, under gas shield, carry out refinement and denaturation, leave standstill 30～40 minutes then after, carry out gravity casting or pressure die casting.
2, the employing methylene fluoride as claimed in claim 1 magnesium alloy smelting method that is protective atmosphere is characterized in that described auxiliary diluent gas is dry air, dry carbonic acid gas or its mixture.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200410052617 CN1587425A (en) | 2004-07-08 | 2004-07-08 | Magnesium alloy smelting method using difluoromethane as protective atmosphere |
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|---|---|---|---|
| CN 200410052617 CN1587425A (en) | 2004-07-08 | 2004-07-08 | Magnesium alloy smelting method using difluoromethane as protective atmosphere |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101142043B (en) * | 2005-04-27 | 2010-05-19 | 中央硝子株式会社 | Protective gas composition for preventing melt magnesium or magnesium alloy from quickly oxidation or combustion and the method therefor |
| CN101135005B (en) * | 2006-08-28 | 2011-03-23 | 贵州世纪天元矿业有限公司 | Method for generating metal vacuum smelting protective gas |
| CN103820653A (en) * | 2014-02-19 | 2014-05-28 | 上海交通大学 | Magnesium alloy melt gas protection method |
-
2004
- 2004-07-08 CN CN 200410052617 patent/CN1587425A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101142043B (en) * | 2005-04-27 | 2010-05-19 | 中央硝子株式会社 | Protective gas composition for preventing melt magnesium or magnesium alloy from quickly oxidation or combustion and the method therefor |
| CN101135005B (en) * | 2006-08-28 | 2011-03-23 | 贵州世纪天元矿业有限公司 | Method for generating metal vacuum smelting protective gas |
| CN103820653A (en) * | 2014-02-19 | 2014-05-28 | 上海交通大学 | Magnesium alloy melt gas protection method |
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