原标题：教你如何设计铸铁件的冒口-不看后悔
ComputerDesign of Feeding Systems for Iron Castings
Or,How to Avoid Years of Problems with 20 Minutes of Analysis
利用计算机设计铸铁件的补缩系统
如何利用20分钟的分析计算避免多年困扰的问题
L ESmiley
Finite Solutions Inc, Hamilton, OH
D CSchmidt
Finite Solutions Inc, Slinger, WI
翻译：张新宇
ABSTRACT摘要
Iron foundries usea variety of methods for design of feeding systems for iron castings. Many ofthese methods are based on non-scientific principles, or principles whichneglect the actual behavior of the cast metal during solidification.
铸铁厂使用多种方法设计铸铁件的补缩系统，其中的许多种方法是基于非科学原则的，或者使用了一些忽略了铸件凝固过程中实际行为的原则
There is nowavailable a set of tools and principles which, if applied correctly, willreduce or eliminate the vast majority of feeding problems encountered in ironfoundries.
现在有一套可用的工具和原则，如果将其正确应用，将会减少或者消除铸造厂遇到的大多数补缩方面的问题。
Application ofthese techniques to a given casting may often require only 20 or 30 minutes ofhuman and computer time, yet this may eliminate years of problems in subsequentproduction of the castings.
将这些技术应有到给定的铸件上面，仅需要大约20-30分钟的人工和计算机计算时间，就可能会消除铸件后续生产中出现多年的问题。
Considerable cost savings in terms of reduction ofscrap and customer returns can be realized. This paper will explain the principles and the use of computerizedtools, as well as present multiple examples where these methods have beensuccessfully applied in actual foundries to improve quality and reduce defects.
在减少废品和客户退货方面可以实现可观的成本节约。本文将解释计算机化工具的原理和使用方法，并提供多个案例，这些方法已经成功应用到了铸造厂中，帮助他们提升了铸件质量，减少了缺陷的发生。
INTRODUCTION介绍
Proper design offeeding systems for iron castings (grey and ductile, also called nodular orspheroidal graphite, iron) requires an understanding of how these alloys differfrom other alloys such as steel.
要设计合格的铸铁件的补缩系统，就需要了解铸铁与其他合金的差异，如与铸钢的差异。
If these differences are not properly taken intoaccount, then the feeding systems may be less than adequate and casting qualitywill suffer. It has been our experiencethat many iron foundries do not properly take into account the solidificationcharacteristics of iron when designing feeding systems; in many cases, feedersfor iron castings are designed essentially as feeders for steel castings andthe result is the presence of defects in the production castings.
如果这些差异没有得到适当的考虑，那么补缩系统的设计就不会太成功，铸件质量将会受到影响。根据我们的经验，许多铸造企业在设计补缩系统时，没有恰当的考虑铸铁的凝固特性。在许多情况下，他们将铸铁件的冒口是和铸钢件的冒口一样的想法设计的，结果就是生产出来的铸件出现缺陷。
Often thesuggested remedies for these defects worsen the situation, due to the same lackof understanding. It is the intention ofthis paper to present a few relatively simple design rules which, if followed,will help the iron foundry engineer to design casting processes which have ahigher degree of success.
通常针对这些缺陷提出的补救措施会使情况更糟，因为同样缺乏对正确理论的理解。本文旨在提出一些相对简单的设计规则，如果遵循这些规则，将有助于铸铁企业的铸造工程师设计出成功率更高的铸造工艺。
The design methodsexplained in this paper are generally quite easy to implement and require onlya minimal investment of time. We haveseen a number of castings in ongoing production in foundries where defects werea continuing problem for the foundry and the customer, resulting in excesscosts, delays and in some cases loss of business. Most of these problems could have beenprevented had the foundry engineers applied correct design methodology from thestart, and in most cases this methodology would have taken no more than 15 or20 minutes of time to implement. Spending such a short amount of time to prevent ongoing problems infoundry production over months or years results in an extremely high return oninvestment.
本文介绍的设计方法一般都很容易实现，而且只需要花费最少的时间。我们已经看到在铸造厂的持续生产中，许多铸件的缺陷一直是铸造厂和客户的问题，导致成本过高、延误交付，有时甚至失去订单。如果铸造工程师从一开始就采用正确的设计方法，可以避免大多数问题的发生，大多数情况下，这种方法的实施时间不会超过15或20分钟。花这么短的时间来防止铸造生产中几个月或几年的持续问题，会带来极高的投资回报。
DESIGN PRICIPLES FORCAST IRON
铸铁件的设计原则
The mostfundamental difference between iron and other alloys is the expansion thatoccurs in the iron as graphite precipitates during solidification. This expansion is significant in that, inmost situations, the casting can become “self-feeding” after the onset ofexpansion, meaning that no further feeding is required. Thus, the object of designing a feedingsystem for iron castings is to provide feed metal only for the contraction ofthe liquid alloy as well as the contraction of the solidifying iron prior tothe start of expansion;
铸铁和其他合金之间最根本的区别在于，在凝固过程中，当石墨析出时，在铸铁中发生膨胀。这种膨胀是很重要的，因为在大多数情况下，铸件在膨胀开始后会变成“自补缩”，这意味着不需要进一步补缩。因此，设计铸铁件补缩系统的目的是仅为液态金属的收缩以及开始膨胀前铸铁凝固时的收缩提供进给补缩金属；
once the expansionbegins, a well-designed feeding system should control the expansion pressure toensure that the casting is self-feeding during the remainder ofsolidification. This is in contrast toother alloys such as steel, where feed metal must be supplied to the castingduring most or all of solidification and there is no expansion involved.
一旦膨胀开始，良好的补缩系统应能控制膨胀压力，以确保铸件在剩余的凝固过程中实现自补缩。这与其他合金（如铸钢）不同，其他合金如铸钢在大部分或全部凝固过程中，必须向铸件提供补缩金属，并且不存在膨胀。
Another majordifference between cast irons and other alloys has to do with the mechanisminvolved in “piping”, or the onset of feeding behavior in the feeder. Cast irons (particularly ductile iron) do notreadily form a solid skin during solidification; rather the freezing mechanismis often described as “mushy” or “pasty”.This freezing pattern is what rendersatmospheric cores (Williams’s cores) ineffective with these alloys.
铸铁和其他合金的另一个主要区别在于“收缩”中涉及的相关机制，或者冒口中补缩行为的出现。铸铁（特别是球墨铸铁）在凝固过程中不易形成坚硬的外壳；相反，凝固机理通常被描述为“糊状””。这种凝固模式使得大气核心（威廉姆斯的核心）对这些合金无效。
For blind feedersto pipe effectively, atmospheric pressure must be able to collapse the weakplastic skin after the internal pressure drops below atmospheric. Once onefeeder punctures, the internal pressure is equalized so there is no longer ahigher external pressure to cause other feeders to pipe. In practice, this means that only one feedershould be used on each “feeding zone” within an iron casting; if multiplefeeders are placed on the same zone of a casting, then typically one feederwill begin piping while the other feeders will not.
为了使暗冒口有效补缩，当内部压力降到大气压力以下时，大气压力必须能够使脆弱的凝固外壳破裂。一旦一个冒口被穿透，内外部压力将会平衡，因此不再有更高的外部压力导致其他冒口出现收缩。实际上，这意味着在铸铁件内一个补缩区仅需要使用一个冒口。如果在铸件的同一补缩区上放置多个冒口，则通常会出现一个冒口收缩，其他冒口不缩的情况。
Often, porositywill be seen at the contact point of non-piping feeders.With alloys such assteel, solidification is strongly directional; a relatively strong solid skinrapidly forms which over time increases in thickness towards the thermalcenter. When blind feeders are used in steel castings, it is essential thatatmospheric cores are employed to allow a passage for atmospheric pressure toact on the internal liquid. In effect the atmospheric core creates the surfacepuncture and allows atmospheric pressure to act on the liquid interior of thefeeder(s) for an extended time. In thiscircumstance, multiple feeders may effectively be used within the same zone ofthe casting.
通常情况下，在没有收缩的冒口的冒口颈处会发现缩松，对于铸钢等合金，凝固具有很强的方向性；随着时间的推移，向热中心方向的厚度会迅速增加，快速形成相对坚固的凝固壳。当钢铸件中使用暗冒口时，必须使用大气压型芯，以允许大气压作用于内部液体。实际上，大气压核心使得表面出现穿透，并允许大气压力作用于冒口的内部液体一段时间。在这种情况下，可以在铸件的同一补缩区域内使用多个冒口。
The requirementfor a single feeder within a single zone of the casting is probably the designrule which is violated most often within iron foundries. We often see designs where two or morefeeders are feeding the same zone within a casting, and the resulting castingexhibits porosity, often at the contact point of one of the feeders. The tendency of many foundry engineers is toadd more feeders to try and resolve the porosity issue; in fact, this isexactly the wrong approach and will worsen the situation.
铸件内一个补缩区需要一个冒口可能是一个经常在铸铁厂违背的设计原则。我们经常看到工艺设计人员会在铸件内的设置两个或者多个冒口来补缩相同的区域。结果出现缩松缺陷。经常在其中一个冒口根部发现这些缩松缺陷，许多铸造工程师倾向于增加冒口来解决缩松问题；事实上，这完全是错误的做法，而且会使情况恶化。
In order tocorrectly design a feeder system for iron castings, it is necessary to be ableto analyze the cast shape and determine the location and size of feed zoneswithin the casting. We must answer thequestion: Is this casting composed of asingle feed zone, or are there multiple zones and, if so, what is the locationand size of each zone? In order to makethis determination, we introduce the concept of the Transfer Modulus.
为了正确设计铸铁件的补缩系统，有必要能够分析铸件的形状，确定铸件内补缩区的位置和尺寸。我们必须回答这个问题：这个铸件是由一个单一的补缩区组成，还是有多个补缩区，如果有的话，每个区的位置和大小是多少？为了确定这一点，我们引入了 传递模数的概念。
Feed zones withinthe casting are defined by knowing where within the casting it is possible forliquid metal to flow from one point to another in response to expansionpressures. If there is no possibility ofmetal flowing from one area of the casting to another as expansion begins, theneach of these areas forms a separate feed zone and each may require its owncorrectly-designed feeder (but no more than one).
铸件内的补缩区是通过知道铸件内液态金属在膨胀压力下从一点流向另一点的可能性来定义的。如果在开始膨胀时，液态金属不能从铸件的一个区域流向另一个区域，则每一个区域都形成一个单独的补缩区，并且每个区域可能需要单独正确设计的冒口（注意每个区域不能超过一个冒口）。
Such an analysisof a casting begins with consideration of the Casting Modulus. This is defined as the volume:surface arearatio of various areas of the casting, and has been used for many years toestimate the order of solidification of different parts of the casting. TheCasting Modulus (M c ) allows us to estimate which part of the castingwill solidify first and which will solidify last.
对铸件的这种分析从考虑铸件模数开始。模数指铸件各区域的体积与表面积的比值，多年来一直用来估计铸件不同部位的凝固顺序。铸造模数（Mc）允许我们评估铸件的哪个部分首先凝固，哪个部分最后凝固。
In steel castings, this information is immediately useful to indicatewhere feeders should be placed and what size they should be (the Modulus of thefeeder should be greater than the Modulus of the casting).
在铸钢件中，此信息可立即指导出，应在何处放置冒口以及冒口的尺寸（冒口的模数应大于铸件的模数）。
In iron castings, the Casting Modulus is used toestimate when expansion will begin, expressed as a percentage of completesolidification.
在铸铁件中，铸件模数用于评估何时开始膨胀，表示为完全凝固的百分比。
Prior todevelopment of computers and software, calculation of M c was tediousand time-consuming; it required the foundry engineer to estimate volumes andsurface areas by approximating various parts of the casting to relativelysimple shapes. With modern castingsimulation software, solidification of a casting can be simulated, often in amatter of minutes. The result data fromthis simulation can be converted to Modulus values within the casting. This means that Modulus data is now availableat every point within a 3D representation of the casting; this also means thatthe Modulus data is more accurate, as effects such as local superheating of themold material are accurately taken into account by the simulation, which is notpossible with manual methods.
在计算机和软件开发之前，Mc的计算是繁琐和耗时的；它要求铸造工程师通过将铸件的各个部分近似成相对简单的形状来估计体积和表面积。利用现代铸造模拟软件，可以模拟铸件的凝固过程，通常只需几分钟。此模拟的结果数据可以转换为铸件的模数值。这意味着模数数据现在可以在铸件的三维表示中的每个点上使用；这也意味着模数数据更精确，因为模拟精确地考虑了造型材料的局部过热等影响，而这在手动方法中是不可能的。
With the Modulusdata for the casting, as well as the chemistry and temperature data, the pointat which expansion begins can be calculated. Castings which have a higher Modulus (heavy section castings) will beginto expand earlier and will undergo more expansion than castings with lowModulus (light section castings). Thispoint at which expansion begins is expressed as a percent of fullsolidification and is often referred to as the Shrinkage Time( ST)point.
利用铸件的模数数据以及化学成分和温度数据，可以计算出开始膨胀的点。模数较高的铸件（大截面铸件）比模数较低的铸件（薄截面铸件）会更早开始膨胀并经历更多的膨胀。膨胀开始的点表示为完全凝固的百分比，通常称为 收缩时间（ST）点。
Knowing the STpoint for the iron in a casting, it is possible to calculate an equivalentModulus value which then corresponds to the Modulus at which contraction of theiron stops and expansion begins. ThisModulus value is known as the TransferModulus (M TR ) , because it defines for us the areas of thecasting where liquid metal transfer is possible. The calculation of M TR is asfollows:
知道铸件中铁的ST点，就可以计算出等效模数值，该值对应于铸铁停止收缩和开始膨胀时的模数。这个模数值被称为 传递模数（MTR），因为它为我们定义了铸件中可能发生液态金属传递的区域。计算如下：
M TR = SQR ( ST /100) * M C
By post processing(or plotting) the value of M TR in our casting simulation, we areable to visualize the feed zone(s) within the casting and determine whether theentire casting is a single feed zone (M TR is continuous throughoutthe casting) or whether there are multiple zones (M TR is discontinuous). This then allows us to determine the numberof required feeders, using the rule of one feeder per feed zone.
通过在铸件模拟中绘制MTR值，我们能够观察到铸件内的补缩区，并确定整个铸件是单个补缩区（MTR在整个铸件中是连续的）还是有多个补缩区（MTR是不连续的）。这样，我们就可以使用每个补缩区放置一个冒口的原则来确定冒口的数量。
The value of M TR can be understood as representing the Modulus value below which feeding of thecasting in the traditional way (from feeders) is no longer effective, and theiron becomes self-feeding due to expansion. M TR is thus critical in designing the feeding system for thecasting. The basic premise in all designwork for feeding iron castings is that the expansion pressure must becontrolled.
MTR的值可以理解为表示以传统方式（从冒口）补缩铸件的模数值不再有效，并且铸铁因膨胀而成为自补缩。MTR是设计铸件补缩系统的关键点。控制膨胀压力是所有铸铁件补缩设计工作的基本前提。
This means that,assuming the mold is rigid enough, all contacts with the casting (gates andriser contacts) should essentially be solid enough to ensure that the expansionpressure is contained within the casting after the onset of the graphiteexpansion. This leads to another simplerule: The Modulus of the feeder contactneck should be equal to M TR.
This ensures thatfeeding of the liquid contraction will be able to occur, and also that theexpansion pressure will be contained within the casting due to freezing of thefeeder contact at just the correct point in solidification.
这意味着，假设外模足够坚硬，与铸件的所有接触位置（浇口和冒口颈）基本上应该足够坚固，以确保在石墨膨胀开始后，铸件内的膨胀压力得到控制。这引出了另一个简单的规则：冒口颈的的模数应等于MTR。这确保了液体收缩的补缩能够发生，并且由于冒口颈在正确的凝固点凝固，膨胀压力将被控制在铸件内。
If the mold issoft and is unable to resist the pressure of expansion, then some allowancemust be made to relieve that portion of the pressure which the mold is unableto resist. This is generally done bysizing the feeder neck contacts so that the expansion pressure is allowed tobackfill the feeder; in this case the feeder neck must be designed for aModulus value greater than M TR . In general, for successful production of iron castings, the foundryshould attempt to ensure that molds are as rigid as possible given theconstraints of the production machinery employed. For larger castings, this typically will meanchemically-bonded sand in steel flasks with top weights and parting-lineclamps.
如果外模刚度低，无法抵抗膨胀的压力，则必须留出一定的余量，以释放外模无法抵抗的部分压力。这通常是通过调整冒口颈的尺寸来实现的，以便允许膨胀压力回填给冒口；在这种情况下，冒口颈必须设计为大于MTR的模数值。一般来说，为了成功地生产铸铁件，铸造厂应考虑到所使用的生产机械的限制，尽量确保外模的刚性。对于较大的铸件，这通常意味着使用化学粘结剂的型砂，并且用压铁和砂箱紧固装置。
CASE STUDY 1案例1
As an example ofboth the incorrect and the correct feeding approach, we consider first of theall the ductile iron control arm as shown in Figure 1.
找一个不正确的和正确的补缩系统的设计方案，我们首先想到了图1中显示的球铁控制臂。
Figure1. Ductile iron control arm casting.
图1球铁控制臂
Figure 2 shows thelocation of this casting in the production vehicle.
图2显示了该控制臂在在制车辆中的位置
Figure2. Location of the casting in the vehicle.
图2 铸件在车辆中的位置
The foundryoriginally approached the feeding design for this iron casting by placing twosymmetrical feeders as shown in Figure 3. This was, perhaps, understandable as the two sections to which thesefeeders were attached are the heaviest sections of the casting.
铸造厂最初批准了如图3的设计方案，如图3所示的两个对称冒口来补缩。这也许是可以理解的，因为这些冒口连接的两个部分是铸件中最厚重的部分。
Figure3. Original pattern layout and feeder design.
图3，原始的工艺设计图
During initialproduction of this casting, it was found that porosity occurred at one feedercontact on a consistent basis, as shown in Figure 4. The porosity was not always at the samecontact, but on almost all castings one contact showed evidence of porosity andthe other did not. No acceptablecastings were produced with this pattern design.
在该铸件的初始生产过程中，发现在批量生产过程中，在一个冒口颈处出现缩松，如图4所示。缩松并不总是在同一个冒口的冒口颈上，但在几乎所有铸件上，一个冒口颈显示有缩松，另一个则没有。用这种工艺设计方案没有生产出合格的铸件。
Figure4. Feeder contacts with original design(2 feeders).
图4 最原始设计方案的冒口颈（两个冒口）
In order toresolve this problem, it was decided to analyze this casting using the approachdescribed previously to determine the feeding requirements. First, a solidification simulation of thecasting without gating or feeders was performed. The results of this simulation are shown inthe plot of Solidification Time (in minutes) in Figure 5.
为了解决这个问题，决定使用前面描述的方法来分析这个铸件，以确定补缩要求。首先，对铸件进行了无浇口和冒口的凝固模拟（裸件）。该模拟结果显示在图5中的凝固时间（分钟）云图。
Figure5. Plot of solidification time:Simulation of casting without feeders.
图5 凝固时间云图：纯铸件模拟
The result datafrom the simulation is now converted to Modulus data so that the feedingcalculations can be performed. Figure 6shows a plot of the areas of highest Modulus in the casting. From viewing this plot, the foundry engineermight be tempted to conclude that the original feeder design was correct, asthere are two areas of high Modulus value in the casting and these are adjacentto the feeder contacts in the original design.
模拟的结果数据现在转换为模数数据，以便可以进行补缩计算。图6显示了铸件中模数最高的区域。从图中可以看出，铸造工程师可能会得出这样的结论：原来的补缩设计是正确的，因为铸件中有两个高模数值区域，它们与原来设计中的冒口颈位置相邻。
Figure 6. Areas of high modulus value in the casting.
图6 铸件中模数高的位置
However, it isnecessary to further analyze this casting to determine the Shrinkage Time andfrom this the Transfer Modulus (M TR ) in order to understand thelocation and size of the feeding zones within the casting. Figure 7 shows the calculation performedwithin the software of values for both ST and M TR .
然而，有必要进一步分析该铸件，以确定收缩时间，并由此确定传递模数（MTR），以便了解铸件补缩区的位置和尺寸。图7显示了在软件中对ST和MTR值进行的计算。
Figure 7. Calculation of Shrinkage Time and TransferModulus for the Casting
图7 铸件收缩时间和传递模数的计算
Analysis of theiron characteristics for this casting indicates that the value of the TransferModulus is 0.645 cm. Creating a plot ofthis value within the casting will indicate the location of feed zone(s); thisis shown in Figure 8.
对该铸件的铸铁性能分析表明，传递模量为0.645cm。在铸件中创建此值的云图将显示出补缩区的位置；如图8所示。
Figure8. Plot of transfer modulus of 0.645 cmin the casting.传递模数是0.645时铸件内的补缩区位置
Examination ofthis plot shows us that the entire casting is actually a single feed zone. The areas of higher modulus are connected by asection of the casting in which the Modulus is above the value of MTR ,thus allowing liquid transport for feeding throughout the casting.
This means that only a single feeder should beused on this casting. With thetwo-feeder design, both feeders were connected to the same zone of the casting;when this is done, typically one feeder will pipe and the other feeder will notpipe, resulting in porosity at the contact of the non-piping feeder.
从图中可以看出，整个铸件实际上是一个单一的补缩区。模数较高的区域通过铸件的一段连接，这段的模数高于高于MTR值，从而允许液体流动，补缩整个铸件。这意味着在这个铸件上只能使用一个冒口。采用两个冒口设计时，两个冒口都连接到铸件的同一区域；完成此操作时，通常一个冒口将会缩，而另一个冒口不缩，从而导致不缩的冒口出现缩松
It should be notedthat the computer simulation in this case took 16 minutes to perform, andwithin less than 5 minutes after that the calculation of ST, M TR ,and the plot shown in Figure 8 were created. This means that with about 20 minutes of analysis, the correct feederdesign was arrived at. Had this beendone before the original pattern equipment was created, several months of timeinvolved with production of defective castings would have been avoided. The costs involved were far greater than thecost of the software and training to perform this analysis.
应该注意的是，在这种情况下，计算机模拟需要16分钟才能完成，并且在这之后不到5分钟内，ST、MTR的计算和图8所示的绘图就被创建出来了。
这意味着，经过大约20分钟的分析，得出了正确的补缩系统设计。如果这是在原始的模具被生产之前完成的，那么就可以避免几个月的时间生产有缺陷的铸件。所涉及的成本远远大于购买此分析软件和培训成本。
After thisinformation was presented to the foundry, the pattern was revised to reflect asingle feeder as shown in Figure 9.
在将此信息提交给铸造厂之后，对模具进行了修改，如图9所示的单个冒口。
Figure9. Revised pattern with single feeder.
图9 修改后单个冒口的工艺
Figure 10 is aphotograph of the revised pattern showing a single feeder.
图10是修改后的模具
Figure10. Photo of revised pattern with singlefeeder.
It should be notedthat the feeder in this case is not connected to the casting at one of theareas of high Modulus. This illustratesthe point that in iron castings, the location of the feeder is not as criticalas in steel castings. This is due to theexpansion pressure which acts throughout the casting once precipitation ofgraphite begins.
应注意的是，在这个案例中的冒口没有放置在高模数区域的位置。这说明了在铸铁件中，冒口的位置不如在钢铸件中重要。这是由于一旦石墨开始析出，膨胀压力作用于整个铸件。
Finally, Figure 11shows a photograph of the contact area with a single feeder. In this case there is no porosity at thefeeder contact, and no porosity elsewhere within the casting. Thus, a simple and quick analysis of thecasting has produced the correct feeder design for making a sound casting.
最后，图11显示了一张单冒口工艺的冒口颈的照片。在这个案例中，冒口颈位置没有缩松，铸件内其他地方也没有缩松。因此，一个简单而快速的铸件分析产生出了正确的补缩设计方案，从而生产出了一个合格的铸件。
Figure11. Photo of the contact area with a singlefeeder.
图11，单个冒口方案的冒口颈图
CASE STUDY 2案例2
A second exampleof an incorrect feeding approach is the ductile iron bracket casting shown inFigure 12. Again, the design forproduction of this casting was performed without adequate consideration of thesolidification properties of the iron.
第二个不正确补缩案例是图12所示的球墨铸铁支架铸件。这个工艺也犯了一样的错误，生产这种铸件的设计没有充分考虑铸铁的凝固特性。
Figure12. Ductile iron bracket casting.
图12 球铁支架铸件
In this case thefoundry decided to produce the casting with two top feeders as shown in Figure13.
在这个案例中，铸造厂决定用两个顶冒口生产这个铸件，如图13所示
Figure13. Bracket casting with 2 top feeders:Only 1 feeder has piped.
图13，支架铸件用了两个顶冒口，只有一个冒口收缩
Examination of thecasting results shows very clearly that one of the feeders shows pipingbehavior and the other does not. Whenthe non-piping riser was removed from the casting, porosity was visible at thecontact surface.
铸件结果的检查非常清楚地表明，一个冒口显示收缩，而另一个没有。当将没有收缩的冒口从铸件上移除时，接触面上可见缩松。
This illustratesan important tool for the iron foundry engineer. Much information can be gained by examining acomplete casting with all feeders and gating still attached. In many foundries we see that the feeders andgates are removed before the casting is examined for defects; this practiceeliminates some important information which can guide the foundry engineer tothe root cause of defects.
这说明了铸铁厂的铸造工程师的一个重要工具。通过检查一个完整的铸件（所有的冒口和浇口仍然连接）可以获得很多信息。在许多铸造厂，我们看到在检查铸件是否有缺陷之前，已经切掉了冒口和浇口；这种做法消除了一些重要的信息，这些信息可以指导铸造工程师找出缺陷的根本原因
In this case, thefact that one feeder pipes while the other does not should suggest stronglythat both feeders are attached to the same zone within the casting. This can be verified by performing asolidification analysis of the casting and, from that analysis, creating a plotof Transfer Modulus within the casting as shown in Figure 14.
在这个案例中，一个冒口缩而另一个没有，强烈表明两个冒口都连接到铸件内的同一区域。这可以通过对铸件进行凝固分析来验证，并根据该分析，在铸件内绘制传递模数图，如图14所示。
Figure14. Solidification time and transfer modulusplots in the bracket casting.
图14，支架铸件的凝固时间和传递模数
The calculatedvalue for of M TR in this casting is 0.612 cm. The plot of M TR illustrates veryclearly that the entire casting consists of a single feed zone and thus only asingle feeder should be used to produce the casting. In this case, the complete analysis requiredless than 15 minutes of time.
该铸件的MTR计算值为0.612cm。图非常清楚地表明，整个铸件由一个单一的补缩区组成，因此只能使用一个冒口来生产铸件。在这个案例中，完整的模拟分析需要的时间不到15分钟。
CASE STUDY 3案例3
A third exampleinvolves a 210 Kg ductile iron casting used as a bearing connector for a windpower generator. This casting is in theshape of a large ring as shown in Figure 15.
第三个例子是一个210公斤的球墨铸铁铸件，用作风力发电机的轴承连接器。这个铸件是一个大环的形状，如图15所示
Figure15. Ductile iron bearing connector (210Kg).
图15 球铁轴承连接器210kg
The foundryinvolved in producing this casting approached feeding design as a steel castingrather than an iron casting.
铸造厂批准的设计方案是当做铸钢件看的，而不是铸铁件。
Figure 16 shows two alternate feeder designs whichwere being used to produce this casting. The original design specified five feeders with insulating sleeves. When the results of this design wereunsatisfactory, the design was changed to include six feeders.
图16展示了生产此铸件的两种工艺，最初的工艺是5个保温冒口，当发现对结果不行以后，改成了6个冒口
Figure16. Original design with 5 feeders and redesignedprocess with 6 feeders.
图16 原始是用了5个冒口，后来有改成了6个
This is typical ofthe approach to design and problem solving that one might encounter in a steelfoundry;
if a casting cannotbe successfully produced with a given set of feeders, then the next decision isto add more feeders. In actuality, thisapproach did not resolve the problem, instead the quality of the casting wasworse. This one casting represented themost costly scrap problem of all production castings in the foundry.
这是一种铸钢厂普遍采用的设计和解决问题的方法，如果当前的工艺结果不好的话，下一个决定就是增加更多的冒口，实际上，这种办法解决不了问题，反倒使铸件质量变得更糟
Examination of thedefective casting showed that porosity was exposed on the top surface of thecasting after machining 6 mm of iron off the surface, as shown in Figure 17.
对有缺陷铸件的检查表明，顶面加工掉6mm后，铸件的顶面上露出了缩松，如图17所示。
Figure17. Appearance of porosity on machined surface.
图17 加工面的缩松
Close-upinspection of the areas of porosity showed what appeared to be primaryshrinkage as shown in Figure 18. A verystrong clue as to the cause of this porosity is contained in the fact thatthese defective areas were found at the location of the feeders on top of thecasting (which were removed after the casting operation). This suggests the phenomenon which has beendiscussed earlier in this paper, that multiple feeders are being used on asingle common feed zone and only one feeder is showing piping behavior withporosity formation under the non-piping feeders.
对缩松区域进行的近距离检查显示，如图18所示，出现的初始收缩。关于产生这种缩松的原因有一个非常有力的线索，即这些缺陷区域是在铸件顶部冒口的位置发现的（冒口被移除）。这表明了本文前面讨论过的现象，即在一个补缩区使用多个冒口，仅仅一个冒口收缩，其他不缩的冒口根本发现缩松。
Figure18. Porosity on machined face, under feederlocation.
图18 冒口位置加工后发现缩松
An analysis ofthis casting was performed, involving a solidification simulation andcalculation of the M TR . Thevalue of M TR was determined to be 0.96 cm. A plot of M TR in the casting isseen in Figure 19.
对该铸件进行了分析，包括凝固模拟和MTR计算。MTR值为0.96cm。铸件中的MTR图如图19所示。
Figure19. Plot of M TR at a value of 0.96cm.
This image showsvery clearly that the entire casting consists of a single feed zone, and thatonly a single feeder should be used on this casting. The final revised design for this casting isshown in Figure 20.
这张图片非常清楚地显示，整个铸件由一个单一补缩区组成，并且在这个铸件上只能使用一个冒口。该铸件的最终修改设计如图20所示。
Figure20. Single feeder design.
图20 单一冒口方案
When this designwas adopted in the foundry and the feeder and contact were sized correctly, thefinal result was a casting without porosity defects. It is worth noting that the cores which wereoriginally used by the foundry to create the contact between the feeders andthe casting were intended for production of steel castings, where the contactdiameter was 50% of the feeder diameter. Consideration of the fact that the Modulus value in the contact shouldbe equal to MTR resulted in a much smaller contact diameter. In this case the foundry produced coreswhich were specialized for this particular casting to ensure the correctcontact size.
当这种设计在铸造中被采用，并且冒口和冒口颈的尺寸正确时，最终的结果是铸件没有缩松缺陷。值得注意的是，最初由铸造厂用于制造冒口颈型芯是用于生产钢铸件的，其直径为冒口直径的50%。考虑到冒口颈的模量值应等于MTR，因此冒口颈的直径要小得多。在这个案例中，铸造厂生产专用于这种特殊铸件的型芯，以确保正确的接触尺寸。
It is also worthmentioning that the analysis of this casting to produce the correct feederdesign required 15 minutes of time. Thefoundry could have saved considerable costs over a long period of time had theyperformed this quick and simple analysis before finalizing the productiondesign for the casting.
值得一提的是，分析这一铸件以确定正确的补缩设计需要15分钟的时间。如果铸造厂在最终确定铸件的生产设计之前进行这种快速简单的分析，那么在很长一段时间内就可以节省相当大的成本。
SUMMARY结论
Understanding thesolidification mechanisms of graphitic iron alloys in terms ofexpansion/contraction behavior, feeding mechanisms and control of expansionpressure is critical to correct design of feeding systems. Quick and simple analysis is available whichwill help the foundry engineer to design the production process correctly atthe beginning of production, thereby avoiding the potential for major costsinvolved in production of defective castings.
从膨胀/收缩行为、补缩机理和膨胀压力的控制等方面了解石墨铸铁件的凝固机理，是正确设计补缩系统的关键。快速简单的分析有助于铸造工程师在生产开始时正确地设计生产工艺，从而避免潜在的废品浪费。
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