CN102554174B - A kind of method reducing gravity segregation in centrifugal casting - Google Patents
A kind of method reducing gravity segregation in centrifugal casting Download PDFInfo
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- CN102554174B CN102554174B CN201110440203.9A CN201110440203A CN102554174B CN 102554174 B CN102554174 B CN 102554174B CN 201110440203 A CN201110440203 A CN 201110440203A CN 102554174 B CN102554174 B CN 102554174B
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Abstract
The invention discloses a kind of method reducing gravity segregation in centrifugal casting, comprise following content: ready METAL HEATING PROCESS is melted; By melted molten metal, inject selected special bottom pour ladle, stir in advance when reaching predetermined altitude H, make molten metal form whirlpool; Then the plunger of special bottom pour ladle is extracted, negative pressure is formed when special bottom pour ladle inner metal liquid is flowed down, by the effect of siphon and gravity, the molten metal in special bottom pour ladle is made to form downward eddy current in central axial direction, aspirate upper strata light metal and lower floor's heavy metal simultaneously, each alloying element is uniformly distributed again together flow down, enters casting mold, complete cast.Additionally provide its special bottom pour ladle.The inventive method is simple, and cost is low, can improve inherent quality and the mechanical performance of foundry goods, makes organizing of foundry goods finer and close.
Description
Technical field
The present invention relates to a kind of method reducing gravity segregation in centrifugal casting, belong to casting technology field.
Background technology
So-called casting aliquation is exactly after aluminium alloy solidifies in casting mold, casting section various piece and there is the non-uniform phenomenon of chemical composition between crystal grain and crystal boundary.Because foundry goods each several part chemical composition is inconsistent, certainly will make its machinery and physical property also different, working effect and the service life of foundry goods will be affected like this.Therefore, in Foundry Production, should prevent alloy from process of setting, producing segregation as far as possible.
Segregation is a kind of casting flaw, is generally divided into three types, i.e. microsegregation, regional segregation and gravity segregation.So-called microsegregation, also known as dendritic crystal segregation, is characterized in that, in same crystal grain, each several part chemical composition is inconsistent, and often many compared with high composition containing fusing point on first crystal axial line.So-called regional segregation, namely on whole casting section, the phenomenon that each several part chemical composition is inconsistent, it carries out selecting solidifying caused mainly due to alloy., namely because two constituent element proportions in alloy are different, and in same foundry goods, there is the phenomenon that top and the bottom composition is inconsistent in so-called gravity segregation.For a certain alloy-steel casting, the segregation of generation often has a kind of broad form, but due to the impact of various casting condition, several segregation also may occur simultaneously.
Because each component proportion is different in alloy-steel casting, usually cause gravity segregation.When there is this segregation, for the foundry goods of gravitational casting, the alloy constituent element that in the alloy of top, proportion is less is more, and proportion larger alloy constituent element in bottom is more.Particularly when centrifugal casting cover class foundry goods or pipe fitting, no matter be alloy steel casting, or non-ferrous metal is as copper alloy, aluminium alloy castings, its foundry goods is shaping under the influence of centrifugal force and solidifies, because various alloying element density is different, in centrifugal casting process, easily produce the more serious gravity segregation of force of gravity casting, serious also can produce layering (as Allen's metal, phosphor bronze), thus affects casting quality.This is a more scabrous problem, and manufacturer is mostly from the angle consideration changing the centrifugal casting parameter such as casting mold preheat temperature, pouring temperature, poring rate, casting mold rotating speed, Optimizing Technical; The interpolation trace element also had is to change coagulating property.Above-mentioned measure is to the gravity segregation problem solving centrifugal casting, and tool has certain effect, but all there is the limitation of doing to use.
Summary of the invention
For the deficiency that prior art exists, technical problem to be solved by this invention is, provides a kind of method reducing gravity segregation in centrifugal casting, and the pouring technology of improvement conventional centrifugal casting, reduces the gravity segregation problem in centrifugal casting, improve the internal quality of casting.
For solving the problems of the technologies described above, the technical solution used in the present invention is: a kind of method reducing gravity segregation in centrifugal casting, comprises following content:
1, ready METAL HEATING PROCESS is melted;
2, by melted molten metal, inject selected special bottom pour ladle, stir in advance when reaching predetermined altitude H, make molten metal form whirlpool; Then the plunger of special bottom pour ladle is extracted, negative pressure is formed when special bottom pour ladle inner metal liquid is flowed down, by the effect of siphon and gravity, the molten metal in special bottom pour ladle is made to form downward eddy current in central axial direction, aspirate upper strata light metal and lower floor's heavy metal simultaneously, each alloying element is uniformly distributed again together flow down, enters casting mold, cool and be frozen into foundry goods fast in centrifugal casting mould; If casting quality is large, molten metal consumption is many, can pour into a mould one side and the molten metal of preparation is injected special bottom pour ladle, and the height maintaining its alloy fluid column is close to predetermined altitude H, until all molten metals enter casting mold, completes cast.
Above-mentioned special bottom pour ladle, comprises bottom pour ladle and cup, and cup one end connects bottom bottom pour ladle, and one end is communicated with casting mold; Described bottom pour ladle, its inner chamber is inversed taper platform shape, and tapering is 1: 4-1: 7.5; Its bottom centre has orifice, and in bottom pour ladle, centrally axis direction arranges plunger, plunger and orifice interference fit.
Above-mentioned special bottom pour ladle, according to the quality of alloy liquid, its bottom inner diameter D1, predetermined altitude H place internal diameter D2, predetermined altitude H and orifice diameter d meet the following requirements:
D2＝n×D1；
d＝m×D1；
H＝(1.2--1.5)×D1；
Wherein:
N is footpath difference coefficient, value 1.2-1.3; Take large values when density contrast is greater than 5 between each constituent element in alloy, get the small value when density contrast is below 3; With this coefficient value of interpolation calculation when density contrast is between 3-5, density unit is 10
3kg/m3;
M is orifice coefficient, value 0.07-0.08; Casting quality gets the small value when being greater than 5t, takes large values when being less than 5t; Casting ladle orifice diameter is not less than 30mm.
The present invention is under the prerequisite retaining existing part centrifugal casting technique, change the method for cast, molten metal is utilized to have certain head, negative pressure is formed when the design of casting ladle makes casting ladle inner metal liquid flow down, under the effect of negative pressure, produce siphonage, by casting ladle upper strata molten metal lighter for proportion and the larger lower metal liquid of proportion with together flow down, make each alloying element under siphon and Action of Gravity Field, redistribution, plays the effect of uniform stirring.Stir in advance pulling out plunger advancement row in addition, form whirlpool, be more conducive to the formation of axis place cavity.By in centrifugal casting mould due to pole cold-working with and solidify very fast, the formation of gravity segregation can be greatly reduced, obtain the foundry goods of composition and even tissue.Casting ladle used in the present invention is different from common casting ladle, and orifice diameter is larger than usual cast bottom pour ladle, is convenient to form central negative pressure district, accelerates flow rate of metal, and suction upper strata light metal and lower floor's heavy metal together enter cup simultaneously.In addition, different molten metals, because difference in specific gravity is different, selects the casting ladle of different size, to obtain better effect.
Traditional centrifugal casting cast, generally after Metal Melting completes, directly pours cup into, and with cup direct current quantitative pouring, cast steadily, quantitatively accurately, can control poring rate.But because density metal is different, once melt for liquid phase completely, for albronze, copper-rich phase sinks to the bottom, and rich aluminium floats mutually; Even if stir energetically before cast, but slightly standing, and result is still.So very easily cause rich aluminum portions (light metal) to be introduced into centrifugal casting mould during cast, centrifugal cold mould makes it solidify very soon, form shell, and enter after rich copper part (heavy metal), although gravity is large, because outside forms shell, and fusing point is high, usually concentrate on internal layer, form gravity segregation.
For solving the serious gravity segregation problem that existing centrifugal casting technique exists, through studying for many years, the invention provides a kind of centrifugal casting placingJi Shu, this technology remains the process characteristic of part centrifugal casting, overcome again the remarkable shortcoming wherein existed, when making steel alloy, non-ferrous alloy pipe fitting, pipe, cover class foundry goods, solve the defect of gravity segregation, the performance of foundry goods is significantly increased.Compared with prior art, the present invention has the following advantages: one be foundry goods mechanical performance improve, due to gravity segregation Resolving probiems, improve the internal quality of casting, make organizing of foundry goods finer and close.Two is that method is simple, and cost is low, only need change the pattern of cast.
Accompanying drawing explanation
Below in conjunction with drawings and the specific embodiments, the present invention is described in further details.
Fig. 1 is the structural representation of the special bottom pour ladle of the embodiment of the present invention.
Detailed description of the invention
Embodiment 1
The ZCuAl9Fe4 copper alloy cover of centrifugal casting 9 tons of weights, comprises following content:
1, various metal is got out and heat fused according to the CuAl9Fe4 copper alloy cover of casting 9 tons of weights.
2, selected special bottom pour ladle: this its bottom inner diameter of special bottom pour ladle D1, predetermined altitude H place internal diameter D2, predetermined altitude H and orifice diameter d meet the following requirements: D2=n × D1; D=m × D1; H=(1.2-1.5) × D1;
Wherein: n is footpath difference coefficient, value 1.2-1.3; Take large values when density contrast is greater than 5 between each constituent element in alloy, get the small value when density contrast is below 3; With this coefficient value of interpolation calculation when density contrast is between 3-5, density unit is 10
3kg/m3;
M is orifice coefficient, value 0.07-0.08; Casting quality gets the small value when being greater than 5t, takes large values when being less than 5t; Casting ladle orifice diameter is not less than 30mm.
Because the density contrast of copper and aluminium is greater than 5, casting quality is greater than 5t, thus n, m two coefficient get 1.3 and 0.07 respectively.
Now casting ladle inner cavity size is, getting D1 is φ 900mm, then:
D2＝1.3×900＝1170mm，
d＝0.07×900＝63mm；
Now calculate the averag density of alloy, the mean value ρ consulting and using solid metallic density is equal:
ρ all=0.87 × ρ copper+0.09 × ρ aluminium+0.04 × ρ iron=8.3;
According to circular cone cubature formula, calculate H=1280mm, namely 1.42D1, meet requirement for height.
Then by melted molten metal, inject selected special bottom pour ladle, stir in advance when reaching predetermined altitude H, make molten metal form whirlpool; Then the plunger of special bottom pour ladle is extracted, negative pressure is formed when special bottom pour ladle inner metal liquid is flowed down, by the effect of siphon and gravity, make the molten metal in special bottom pour ladle form downward eddy current in central axial direction, aspirate upper strata light metal and lower floor's heavy metal simultaneously, each alloying element is uniformly distributed again and together flows down, enter casting mold, cool and be frozen into foundry goods fast in centrifugal casting mould, completing cast, obtaining the ZCuAl9Fe4 copper alloy cover of 9 tons of weights.
Embodiment 2
The ZCuPb30 copper alloy cover of centrifugal casting 6 tons of weights.Comprise following content:
1, various metal is got out and heat fused according to the ZCuPb30 copper alloy cover of casting 6 tons of weights.
2, selected special bottom pour ladle: this its bottom inner diameter of special bottom pour ladle D1, predetermined altitude H place internal diameter D2, predetermined altitude H and orifice diameter d meet the following requirements: D2=n × D1; D=m × D1; H=(1.2-1.5) × D1;
Wherein: n is footpath difference coefficient, value 1.2-1.3; Take large values when density contrast is greater than 5 between each constituent element in alloy, get the small value when density contrast is below 3; With this coefficient value of interpolation calculation when density contrast is between 3-5, density unit is 10
3kg/m3;
M is orifice coefficient, value 0.07-0.08; Casting quality gets the small value when being greater than 5t, takes large values when being less than 5t; Casting ladle orifice diameter is not less than 30mm.
Because copper and plumbous density contrast are less than 3, therefore n gets the small value 1.2, and casting quality is greater than 5t, and m gets 0.07.
Now casting ladle inner cavity size should be, and getting D1 is φ 800mm, then:
D2＝1.2×800＝960mm，
d＝0.07×800＝56mm。
Now calculate the averag density of alloy, with reference to using, the mean value ρ of solid metallic density is equal:
ρ all=0.7 × ρ copper+0.3 × ρ is plumbous=9.62;
According to circular cone cubature formula, calculate H=1070mm, it is 1.34D1, meets requirement for height.
Then by melted molten metal, inject selected special bottom pour ladle, stir in advance when reaching predetermined altitude H, make molten metal form whirlpool; Then the plunger of special bottom pour ladle is extracted, negative pressure is formed when special bottom pour ladle inner metal liquid is flowed down, by the effect of siphon and gravity, make the molten metal in special bottom pour ladle form downward eddy current in central axial direction, aspirate upper strata light metal and lower floor's heavy metal simultaneously, each alloying element is uniformly distributed again and together flows down, enter casting mold, cool and be frozen into foundry goods fast in centrifugal casting mould, completing cast, obtaining the ZCuPb30 copper alloy cover of 6 tons of weights.
The foundry goods of the various embodiments described above, all avoids gravity segregation, and cast structure is fine and close, improves the internal quality of casting.
Claims (1)
1. reduce a method for gravity segregation in centrifugal casting, comprise following content:
1, ready METAL HEATING PROCESS is melted;
2, by melted molten metal, inject selected special bottom pour ladle, stir in advance when reaching predetermined altitude H, make molten metal form whirlpool; Then the plunger of special bottom pour ladle is extracted, negative pressure is formed when special bottom pour ladle inner metal liquid is flowed down, by the effect of siphon and gravity, the molten metal in special bottom pour ladle is made to form downward eddy current in central axial direction, aspirate upper strata light metal and lower floor's heavy metal simultaneously, each alloying element is uniformly distributed again together flow down, enters casting mold, cool and be frozen into foundry goods fast in centrifugal casting mould; If casting quality is large, molten metal consumption is many, can pour into a mould one side and the molten metal of preparation is injected special bottom pour ladle, and the height maintaining its alloy fluid column is close to predetermined altitude H, until all molten metals enter casting mold, completes cast;
Wherein, special bottom pour ladle comprises bottom pour ladle and cup, and cup one end connects bottom bottom pour ladle, and one end is communicated with casting mold, and its inner chamber is inversed taper platform shape, and tapering is 1: 4-1: 7.5; Its bottom centre has orifice, and in bottom pour ladle, centrally axis direction arranges plunger, plunger and orifice interference fit;
According to the quality of aluminium alloy, special bottom pour ladle bottom inner diameter D1, predetermined altitude H place internal diameter D2, predetermined altitude H and orifice diameter d meet the following requirements:
D2＝n×D1；
d＝m×D1；
H＝(1.2-1.5)×D1；
Wherein:
N is footpath difference coefficient, value 1.2-1.3; Take large values when density contrast is greater than 5 between each constituent element in alloy, get the small value when density contrast is below 3; With this coefficient value of interpolation calculation when density contrast is between 3-5, density unit is 10
3kg/m
3;
M is orifice coefficient, value 0.07-0.08; Casting quality gets the small value when being greater than 5t, takes large values when being less than 5t; Casting ladle orifice diameter d is not less than 30mm.
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| CN102554174B true CN102554174B (en) | 2016-04-13 |
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| JP2001191159A (en) * | 1999-12-28 | 2001-07-17 | Daido Steel Co Ltd | Vertical centrifugal casting method |
| JP2001212658A (en) * | 2000-02-04 | 2001-08-07 | Kubota Corp | Centrifugal casting method and liquid metal supply device |
| JP4314207B2 (en) * | 2005-03-15 | 2009-08-12 | 株式会社日本製鋼所 | Casting method and casting apparatus |
| CN101722289B (en) * | 2008-11-01 | 2011-09-28 | 吴为国 | Vacuum centrifugal casting machine |
| CN101704083A (en) * | 2009-09-08 | 2010-05-12 | 新兴铸管股份有限公司 | Pouring device for centrifugal ductile cast iron pipes |
| CN101875096A (en) * | 2009-12-11 | 2010-11-03 | 武昌船舶重工有限责任公司 | Method for preventing centrifugal casting of large and medium-size copper bush castings from generating cold shut defects |
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Address after: Kowloon Zhen Kuang Jia Ling Cun of Jiaozhou city 266300 Shandong city of Qingdao Province Applicant after: QINGDAO ZHENGDA HEAVY INDUSTRY CO., LTD. Address before: Kowloon Zhen Kuang Jia Ling Cun of Jiaozhou city 266300 Shandong city of Qingdao Province Applicant before: Qingdao Zhengda Foundry Co., Ltd. |
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