CN105033181A - Grain refiner for investing ferritic stainless steel and application method of grain refiner - Google Patents

Grain refiner for investing ferritic stainless steel and application method of grain refiner Download PDF

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CN105033181A
CN105033181A CN201510364587.9A CN201510364587A CN105033181A CN 105033181 A CN105033181 A CN 105033181A CN 201510364587 A CN201510364587 A CN 201510364587A CN 105033181 A CN105033181 A CN 105033181A
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stainless steel
grain refiner
ferritic stainless
casting
model casting
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CN105033181B (en
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盛晓波
江坤华
董寅生
储成林
郭超
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Southeast University
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Southeast University
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Abstract

The invention discloses a grain refiner for investing ferritic stainless steel and an application method of the grain refiner. The grain refiner is armco iron powder and nearly spherical, wherein the grain size of the grain refiner ranges from 30 meshes to 50 meshes, and the purity of the grain refiner is that the content of Fe is larger than or equal to 98%. The grain refiner can be evenly and quantitatively added to stainless liquid steel along with flowing of the stainless liquid steel in the investing pouring process, and grains of the ferritic stainless steel can be refined; nearly-isometric grains are obtained, and the mechanical properties and high-temperature and corrosion resistance performance of the materials are improved. Ferrite grains can be refined effectively after refining, and isometric grains are promoted to be generated, and the strength, toughness, corrosion resistance and high temperature oxidation resistance of the materials are improved. The influences on fluidity and mold-filling capacity of liquid steel are low. The grain refiner is fully fused with a casting in a casting mould, rich in source, low in cost and capable of being added easily.

Description

A kind of model casting ferritic stainless steel grain refiner and using method thereof
Technical field
The invention belongs to technical field of metal, be specifically related to a kind of grain refiner and using method thereof of model casting ferritic stainless steel.
Background technology
Ferritic stainless steel refers to all have complete ferrite at high temperature and room temperature or be agent structure with ferrite, and a series of low C ferrous alloy that Cr content is greater than 10.5%, in order to obtain different particular characteristic, often adds the elements such as appropriate Mo, Ni, Nb, Ti.In recent years, the raising of the Ni prices of raw and semifnished materials makes to increase containing the stainless steel-making cost of Ni, the develop rapidly of auto industry makes again vehicle exhaust gas extraction system stainless steel consumption figure increase, and these are do not contain or only provide the wide market space containing the development of the ferritic stainless steel of a small amount of Ni.Due to China Ni shortage of resources, more than 80% required dependence on import, expensive, therefore develop ferritic stainless steel, few with even not using Ni, be one of direction of domestic stainless steel industry development.Ferritic stainless steel experienced by the evolution from 409 types to 430 series.C content≤0.12wt%, the Cr content of 430 ferritic stainless steels is between 16.0wt%-18.0wt%, and generally not containing Ni, shrinkage coefficient is 1.4%-1.6%, and casting character is poor.This kind of alloy is cheap, and have well anti-oxidant and sulfuration resistant performance, its foundry goods is mainly used in valve gap, vehicle exhaust gas extraction system etc.But this kind of alloy has σ phase fragility, 475 DEG C of fragility, high-temperature brittleness, martensite fragility and casting fragility, and notch sensitivity is high, to shortcomings such as intercrystalline corrosion are more responsive.Casting fragility wherein mainly comes from solidified structure in casting solidification process and keeps ferritic phase always, there is not the phase transformation of α → γ, therefore in solidified structure, column crystal is more flourishing, even do not have Center Equiaxial Crystal district, again because the foundry goods such as valve gap, vehicle-exhaust exhaust pipe joint are thin-wall part, the general investment casting method that adopts is shaped, mold temperature is high, cooling velocity is slow, and make crystallite dimension thicker, therefore particularly Toughness is poor for the intensity of foundry goods.In order to solve the problem of ferritic stainless steel as-cast structure coarse grains, people constantly explore the method for crystal grain thinning.At present, in producing and studying, the method for crystal grain thinning mainly contains electromagnetic agitation, cooling twice, interpolation rare earth and Nb, Ti alloy etc., but the limited efficiency of crystal grain thinning, often reduce the mold-filling capacity of thin-wall part molten steel while micronization processes.These make the grain refinement of model casting ferritic stainless steel thin-wall part become an insoluble technical barrier, seriously have impact on the quality of ferrite stainless product made from steel and apply.
Summary of the invention
In order to overcome the deficiencies in the prior art, the invention provides a kind of model casting ferritic stainless steel grain refiner, with the limited efficiency that the method solving existing crystal grain thinning exists, while micronization processes, often reduce the problem of the mold-filling capacity of thin-wall part molten steel.
For achieving the above object, the present invention is by the following technical solutions:
A kind of model casting ferritic stainless steel grain refiner, described fining agent is iron powder.
Further, described fining agent is technical pure iron powder, and its shape is subsphaeroidal, and its granularity is 30 order-50 orders, and its purity is Fe content >=98%.
Another object of the present invention is to provide a kind of using method of above-mentioned model casting ferritic stainless steel grain refiner, can the stainless crystal grain of fining ferrite, and obtains nearly equiaxed grain structure, improves mechanical property and the high-temperature corrosion resistance performance of material.Its technical scheme is as follows:
A using method for model casting ferritic stainless steel grain refiner, comprises the following steps:
(1) prepare molten stainless steel, adopt plycast cast iron ferritic stainless cast steel part;
(2) according to the molten stainless steel quality of model casting, fining agent addition is determined;
(3) fining agent is dried and the pre-heat treatment;
(4) in pouring cast part process, iron powder is added casting mold;
(5) by after casting cleaning to heat treating castings.
Further, in described step (2), the addition of fining agent is the 2%-6% of molten stainless steel quality.
Further, in described step (3), fining agent is dried and the temperature of preheating is 120 DEG C-150 DEG C.
Further, in described step (4), evenly add with stream in molten stainless steel in casting process.
Further, in described step (4), the pouring temperature of molten stainless steel is 1600 DEG C-1650 DEG C.
Further, in described step (5), heat-treating methods is: carry out 800 DEG C of insulation 1.5h-2.5h water-cooled again to foundry goods.
The invention has the beneficial effects as follows:
Add iron powder and can accelerate cooling velocity, shorten setting time, improve nucleation rate; Bring external nucleus into; Change solidification processing temperature field, namely reduce molten steel section temperature gradient in the degree of superheat of molten steel and casting mold.Above-mentioned effect is all conducive to crystal grain thinning, promotes to generate equiax crystal, improves intensity, toughness, corrosion resistance, the high temperature oxidation resistance of material.Iron powder again owing to adding with stream is mutual independently subsphaeroidal particle, is different from the dendritic crystal in normal freezing, therefore can not cause too large impact to the mobility of molten steel and mold-filling capacity, avoid grain refinement and mold-filling capacity reduce between contradiction.In addition, by controlling addition and the granularity of iron powder, iron powder fully being fused as foundry goods normal structure, does not produce combination interface.Iron powder abundance, with low cost, adition process is simple to operation, good in refining effect.The product quality of ferrite stainless steel casting can be improved after enforcement, rate of reducing the number of rejects and seconds, improve economic benefit and the market competitiveness of enterprise, promote the extensive use of ferritic stainless steel.
Detailed description of the invention
Below in conjunction with specific embodiment, the present invention is further described.
Embodiment 1
1) aluminium alloy prepares: melting 430 molten stainless steel in medium-frequency induction furnace, its composition is 0.065wt%C, 0.29wt%Si, 0.67wt%Mn, 0.023wt%P, 0.012wt%S, 16.19wt%Cr, 0.10wt%Ti.
2) casting mold prepares: adopt model casting casting wall thickness to be the foundry goods of 3mm, during cast, shell mould temperature is 800 DEG C.
3) fining agent prepares: be 40 object subsphaeroidal atomization technical pure iron powder to granularity, by 4% weighing of quality of molten steel, dries and preheating for 120 DEG C.
4) cast and micronization processes: pouring temperature is 1640 DEG C; Evenly add with stream in molten stainless steel in casting process.
5) after cleaning, foundry goods is carried out to the heat treatment of 800 DEG C of insulation 1.5h water-cooleds.
Testing result: compared with the foundry goods not adding fining agent,
Ferrite crystal grain average equivalent circular diameter is reduced to 198 μm by 521 μm, and circularity increases to 0.89 by 0.67.
Percentage elongation, the contraction percentage of area, ballistic work are substantially suitable, and tensile strength brings up to 569MPa by 458MPa.
Electrochemical etching experimental result is: the cyclic voltammetry curve characteristic value R (Ia/Ir) of reflection intercrystalline corrosion susceptibility is reduced to 4.45 by 14.55; At the 50%H of boiling 2sO 4+ 5.5g/LFe 2(SO 4) 3soaking 24h result in solution is: weightlessness is reduced to 4.15g from 4.29g; 850 DEG C of air oxidation 200h results are: increase weight from 9.16% and be reduced to 8.44%.
Embodiment 2
1) aluminium alloy prepares: melting 430 molten stainless steel in medium-frequency induction furnace, its composition is 0.07wt%C, 0.30wt%Si, 0.63wt%Mn, 0.021wt%P, 0.021wt%S, 17.35wt%Cr, 0.11wt%Ti.
2) casting mold prepares: adopt model casting casting wall thickness to be the foundry goods of 3mm, during cast, shell mould temperature is 800 DEG C.
3) fining agent prepares: be 50 object subsphaeroidal atomization technical pure iron powder to granularity, by 2% weighing of quality of molten steel, dries and preheating for 140 DEG C.
4) cast and micronization processes: pouring temperature is 1600 DEG C.Evenly add with stream in molten stainless steel in casting process.
5) after cleaning, foundry goods is carried out to the heat treatment of 800 DEG C of insulation 2h and then water-cooled.
Testing result: compared with the foundry goods not adding fining agent,
Ferrite crystal grain average equivalent circular diameter is reduced to 201 μm by 521 μm, and circularity increases to 0.87 by 0.67.
Percentage elongation, the contraction percentage of area, ballistic work are substantially suitable, and tensile strength brings up to 567MPa by 458MPa.
Electrochemical etching experimental result is: the cyclic voltammetry curve characteristic value R (Ia/Ir) of reflection intercrystalline corrosion susceptibility is reduced to 4.43 by 14.55; At the 50%H of boiling 2sO 4+ 5.5g/LFe 2(SO 4) 3soaking 24h result in solution is: weightlessness is reduced to 4.20g from 4.29g; 850 DEG C of air oxidation 200h results are: increase weight from 9.16% and be reduced to 8.25%.
Embodiment 3
1) aluminium alloy prepares: melting 430 molten stainless steel in medium-frequency induction furnace, its composition is 0.054wt%C, 0.32wt%Si, 0.60wt%Mn, 0.019wt%P, 0.015wt%S, 16.50wt%Cr, 0.09wt%Ti.
2) casting mold prepares: adopt model casting casting wall thickness to be the foundry goods of 3mm, during cast, shell mould temperature is 800 DEG C.
3) fining agent prepares: be 30 object subsphaeroidal atomization technical pure iron powder to granularity, by 6% weighing of quality of molten steel, dries and preheating for 150 DEG C.
4) cast and micronization processes: pouring temperature is 1650 DEG C.Evenly add with stream in molten stainless steel in casting process.
5) after cleaning, foundry goods is carried out to the heat treatment of 800 DEG C of insulation 2.5h and then water-cooled.
Testing result: compared with the foundry goods not adding fining agent,
Ferrite crystal grain average equivalent circular diameter is reduced to 191 μm by 521 μm, and circularity increases to 0.86 by 0.67.
Percentage elongation, the contraction percentage of area, ballistic work are substantially suitable, and tensile strength brings up to 565MPa by 458MPa.
Electrochemical etching experimental result is: the cyclic voltammetry curve characteristic value R (Ia/Ir) of reflection intercrystalline corrosion susceptibility is reduced to 4.56 by 14.55; At the 50%H of boiling 2sO 4+ 5.5g/LFe 2(SO 4) 3soaking 24h result in solution is: weightlessness is reduced to 4.23g from 4.29g; 850 DEG C of air oxidation 200h results are: increase weight from 9.16% and be reduced to 8.40%.
The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (8)

1. a model casting ferritic stainless steel grain refiner, is characterized in that: described fining agent is iron powder.
2. model casting ferritic stainless steel grain refiner as claimed in claim 1, it is characterized in that: described fining agent is technical pure iron powder, its shape is subsphaeroidal, and its granularity is 30 order-50 orders, and its purity is Fe content >=98%.
3. a using method for model casting ferritic stainless steel grain refiner as claimed in claim 1 or 2, is characterized in that: comprise the following steps:
(1) prepare molten stainless steel, adopt plycast cast iron ferritic stainless cast steel part;
(2) according to the molten stainless steel quality of model casting, fining agent addition is determined;
(3) fining agent is dried and the pre-heat treatment;
(4) in pouring cast part process, iron powder is added casting mold;
(5) by after casting cleaning to heat treating castings.
4. model casting ferritic stainless steel crystal fining method as claimed in claim 3, it is characterized in that: in described step (2), the addition of fining agent is the 2%-6% of molten stainless steel quality.
5. model casting ferritic stainless steel crystal fining method as claimed in claim 3, is characterized in that: in described step (3), and fining agent is dried and the temperature of preheating is 120 DEG C-150 DEG C.
6. model casting ferritic stainless steel crystal fining method as claimed in claim 3, is characterized in that: in described step (4), evenly adds in casting process in molten stainless steel with stream.
7. model casting ferritic stainless steel crystal fining method as claimed in claim 3, it is characterized in that: in described step (4), the pouring temperature of molten stainless steel is 1600 DEG C-1650 DEG C.
8. model casting ferritic stainless steel crystal fining method as claimed in claim 3, is characterized in that: in described step (5), heat-treating methods is: carry out 800 DEG C of insulation 1.5h-2.5h water-cooled again to foundry goods.
CN201510364587.9A 2015-06-26 2015-06-26 A kind of model casting ferritic stainless steel grain refiner and its application method Expired - Fee Related CN105033181B (en)

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Cited By (4)

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CN106001514A (en) * 2016-06-29 2016-10-12 宣达实业集团有限公司 Casting process of high-silicon austenitic stainless steel casting
CN107008872A (en) * 2017-03-10 2017-08-04 东北大学 Grain refiner for ferritic stainless steel continuous casting and preparation method thereof and application method
CN108031788A (en) * 2017-12-12 2018-05-15 中国兵器工业第五九研究所 A kind of aluminium alloy casting compound sand core of high heat conduction and preparation method thereof
CN117026068A (en) * 2023-10-08 2023-11-10 中北大学 Investment precision casting ferrite stainless steel and preparation method and application thereof

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106001514A (en) * 2016-06-29 2016-10-12 宣达实业集团有限公司 Casting process of high-silicon austenitic stainless steel casting
CN107008872A (en) * 2017-03-10 2017-08-04 东北大学 Grain refiner for ferritic stainless steel continuous casting and preparation method thereof and application method
CN107008872B (en) * 2017-03-10 2019-07-02 东北大学 Grain refiner for ferritic stainless steel continuous casting and preparation method thereof and application method
CN108031788A (en) * 2017-12-12 2018-05-15 中国兵器工业第五九研究所 A kind of aluminium alloy casting compound sand core of high heat conduction and preparation method thereof
CN117026068A (en) * 2023-10-08 2023-11-10 中北大学 Investment precision casting ferrite stainless steel and preparation method and application thereof
CN117026068B (en) * 2023-10-08 2023-12-22 中北大学 Investment precision casting ferrite stainless steel and preparation method and application thereof

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