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Rio Tinto Iron & Titanium
DUCTILE IRONThe essentials of gating
and risering system designRevised in 2000
DUCTILE IRONThe essentials of gating
and risering system design
Published by:
770 Sherbrooke Street West – Suite 1800Montréal (Québec) CanadaH3A 1G1
Rio Tinto Iron & Titanium Inc.
FOREWORD .......................................................... 4
1.0 GATING SYSTEM DESIGN ........................ 6
1.1 Requirements .............................................. 6
1.2 Essential Components ................................ 6
1.3 Planning ...................................................... 6
1.4 The Role of “Choke” .................................... 6
1.5 Selection of Gating System Type ................ 7
1.6 Friction ........................................................ 7
1.7 Pouring Time ................................................ 8
1.8 Choke Cross Sectional Area ........................ 8
1.9 Choke Configuration .................................... 9
1.10 Sprue Design .............................................. 11
1.11 Runner Bar .................................................. 12
1.12 Gate Connection .......................................... 13
1.13 Pouring Basin and Sprue Well .................... 13
1.14 Common Defects Relating to Poor GatingSystem Design ............................................ 14
1.15 Case History ................................................ 15
1.16 Molten Metal Filtration .................................. 17
2.0 RISERING SYSTEM DESIGN .................... 19
2.1 Objectives .................................................... 20
2.2 Essential Components ................................ 20
2.3 The Following are Suggested by Researchand Supported by Industrial Experience .... 20
2.4 Typical Volume Change Patterns ................ 21
2.5 Planning ...................................................... 21
2.6 Cooling Rate ................................................ 22
2.7 Mould Quality .............................................. 23
2.8 Liquid Iron Processing ................................ 23
2.9 Selection of Risering Method ...................... 24
2.10 Pressure Control Risering ............................ 25
2.11 Bottle Riser .................................................. 28
2.12 Riserless Design .......................................... 30
2.13 Directly Applied Risering Design (DAR) .... 30
2.14 Selection of Pouring Temperature Basedon Risering Method .................................... 32
2.15 Pressure Control Risering & Bottle RiseringCase Histories ............................ 33-37, 41-43
2.16 Metallurgical Quality Control ...................... 38
2.17 Methods to measure Metal Quality .............. 38
2.18 Other Risering Aids .................................... 39
2.19 Chills ............................................................ 40
BIBLIOGRAPHY ...................................................... 44
3
TABLE OF CONTENTS
The importance of casting soundness and produc-tion economy, as influenced by gating and riseringpractice, has been recognized for many years byRIT’s producers of high purity iron QIT - Fer et TitaneInc. (QIT) and Richards Bay Iron and Titanium (Pty)Limited (RBIT). Indeed, it can be accurately describedas being a RIT tradition of interest and involvement inthis area of castings production. The pioneer in thiswork was Dr. Stephen I. Karsay and his book entitled“Ductile Iron III – Gating and Risering” has formed thebasis for this present seminar/lecture notes book.
In addition to Karsay’s groundwork, a number of otherRIT technical service personnel have made valuablecontributions towards RIT’s present approach to thetask of gating and risering. True to tradition, RIT hasclosely followed the results and experiences of othersworking in this field and, where appropriate, has incor-porated some of these into its presentations on thesubject.
This set of seminar/lecture notes forms the basis forgating and risering presentations which are regularlygiven around the world to groups of foundrymen atseminars and meetings organized either by RIT and itsagents or in conjunction with foundry organizations.The notes are not intended to be a comprehensivetreatment of the subject but rather to give the essen-tial features of RIT’s approach in a form, that is easy touse and apply. For those who require a more detailed,in depth, treatment of the subject, see the bibliography.RIT is indebted to the foundries and foundrymen whohave contributed in many ways over the years during the
continuing quest to arrive at a generally acceptable andsuccessful approach to the task of gating and riseringDuctile Iron castings.
RIT makes no claim to “have discovered the ultimateformulae”, but suggests that these notes provide a sen-sible and logical approach to a problem which dailyconfronts foundrymen – namely, the economic pro-duction of clean, sound Ductile Iron castings.
RIT has made every reasonable effort to ensure thatthe data presented accurately represents the informa-tion contained in the many sources from which it wasobtained and, when necessary, attempts have beenmade to reconcile data from different sources whichdo not agree. Therefore RIT believes that all informationgiven is accurate and is provided in good faith, butwithout any warranty, either express or implied. Thisbook is protected by copyright and no part of it can bereproduced, stored in a retrieval system or transmittedin any form or by any means without the prior writtenpermission of Rio Tinto Iron & Titanium Inc.
Copyright 2000 by Rio Tinto Iron & Titanium Inc.
4
FOREWORD
Section one
Gating System Design
Please note:
The reader should note that the risering of a casting mustbe done before the gating system is designed or calculationsmade.
1.0 GATING SYSTEM DESIGN
1.1 Requirements:• Fast pouring to: Minimize temperature loss during
mould filling.Minimize metallurgical “fade”.Minimize oxidation.
• Clean pouring to: Avoid slag (dross) generation duringpouring.Screen out slag from first iron poured into mould.
• Economic Design: Maximize casting yield.
1.2 Essential Components:All components shown are necessary to minimize
occurence of slag defects.
1.3 Planning:Generate a basic layout by considering: optimum
space utilization for castings; chosen risering method;place parting to minimize need for cores; castingslocated in cope, fill quietly; simple, symmetrical system;identical gating and risering for identical castings; useone riser for more than one casting if possible; LEAVEROOM ON PLATE FOR ADEQUATE GATING ANDRISERING SYSTEM.
Detailed design follows planning.
1.4 The Role of “Choke”:• Definition: Choke is that cross sectional area in a
gating system which determines mould filling time.
• There are two “correct” locations for the choke,hence two basic gating system types:
6
Choke located at junction ofrunner and gate in a simpleGATE-RUNNER (pressuriz-ed) system.
Choke located at junction ofsprue and runner in a simpleSPRUE-RUNNER (non-pressurized) system.
1.5 Selection of Gating System Type:• In a GATE-RUNNER system castings are choked
individually by one or more chokes or gates. With aSPRUE-RUNNER system it is possible for severalcastings to share a common choke.
• Use SPRUE-RUNNER system for large number of small castings in one mould where it is impracticalto choke the castings individually – where chokedimensions are very small – very demanding onmoulding technique and pouring temperature.
• Use GATE-RUNNER system on most other occa-sions.
• Features of GATE-RUNNER and SPRUE-RUNNERSYSTEMS can be combined to form a HYBRID sys-tem. This is normally used where a complicatednetwork of runners is required to deliver iron tocasting cavities.
1.6 Friction:• Not all potential energy of liquid at top of sprue is
converted to mechanical energy at casting cavity.
• Some potential energy lost to friction (heat) as li-quid moves against mould wall and liquid movesagainst liquid.
• Energy loss due to friction extends mould fillingtime and must be taken into account whencalculating choke cross sectional area and pouringtime.
• Energy loss estimated by selecting value of “fr”,frictional loss factor.
• for thin “plates”, fr 0.2
• for heavy “cubes”, fr 0.8
7
CASTING WEIGHT Kg.
CASTING WEIGHT lbs
fr
1 10 100 1,000 10,000.9
.8
.7
.6
.5
.4
.3
.2
.1
1 10 100 1000 10000 100000
1.7 Pouring Time:
• As fast as possible consistent with human abilityand production routine.
• Recommended pouring times:
• very approximate guide, t sec = (W. lb)(W = weight of castings + risers)
1.8 Choke Cross Sectional Area (Ac.):• Select fastest practicable pouring time (t.) (sec.) for
total poured weight (section 1.7).
• Select suitable “fr” value. (Section 1.6)
• Determine total poured volume/choke (V.)(in.3, cm.3)
• V is volume of all castings plus risers, downstreamof a particular choke.
• Volume = weight/density.For liquid iron, density = 0.25 lb/in3 or 0.007 Kg/cm3.
• Determine effective ferrostatic head in sprue (H.)(in., cm.)
• Determine height of casting in cope (b.) (in., cm.)
• From Torricelli, velocity of iron stream at choke is,vc = fr 2gH
• When casting located entirely in drag,
VDAc = (b = 0)t.fr 2g. H
(g = acceleration of gravity = 386 in/sec2 or981 cm/sec2)
• When casting located entirely in cope,
1.5 (b) VCAc =fr.t. 2g [ H3 – (H – b)3]
• When casting located in cope and drag,1 VD + 1.5 (b)
VcAc =fr.t. 2g H H3 – (H – b)3
8
Total Poured Weight (Incl. Risers) Per Choke. lbs.
Po
uri
ng
Tim
e S
ec.
100
10
11 10 100 1,000 10,000
Total Poured Weight (Incl. Risers) Per Choke. Kg.
Po
uri
ng
Tim
e S
ec. 100
10
11 10 100 1,000 10,000
• A reasonably accurate guide to suitable Ac can beselected from these plots:
• Plot data is based on average cope heights whichwill vary from foundry to foundry. In the majority ofcases this introduces negligable error.
• Mould filling process should be timed and if actualfilling time is significantly different from selected fill-ing time, choke should be redesigned according toabove equations.
1.9 Choke Configuration:GATE-RUNNER: The total choke cross sectional area
is the sum of individual gate cross sectional areas:
• Total choke = Ac = A1 + A2 + ... An
• Ac chosen according to casting weight. For multiplechokes (A1, A2), individual choke cross sectionalarea chosen according to(weight of castings + risers)
number of chokes from section 1.8.
• Individual gate dimensions: let choke dimensions= 4a wide x a thick. 4a2 = A1 = A2 hence, a, 4a.
9
Total Poured Weight (Incl. Risers) Per Choke. lbs.
Ch
oke
Cro
ss S
ecti
on
al A
rea
in2
10.0
1.0
0.11 10 100 1,000 10,000
Casting in Cope Casting in Drag
Total Poured Weight (Incl. Risers) Per Choke. Kg.
Ch
oke
Cro
ss S
ecti
on
al A
rea
cm2
100
10
11 10 100 1,000 10,000
Casting in Cope Casting in Drag
• Total choke = Ac1 + Ac2
• Ac1 = A1 + A4; Ac2 = A2 + A3
• A1, A2, A3, A4, chosen according to casting weight(section 1.8)
• Individual gate dimensions:A1 = A2 = A3 = A4 = 4a (a), as before.
Note: when using filters the design of the runner andgates can be changed (volume reduced) since thechoke will be at the filter.
• SPRUE-RUNNER: The total choke cross sectionalarea is the sum of individual choke cross sectionalareas downstream of the sprue:
• Ac chosen according to W1 + W2 + W3 + ... + WN(section 1.8)
• Total choke, Ac = 4a (a)
• (a = choke thickness; 4a = choke width)
10
• Ac1 chosen according to W1 + W2 + W3 + W4 +W5 + W6
• Ac2 chosen according to W7 + W8 + W9 + W10 +W11 + W12 + W13
• Ac1 = 4a (a) = Ac2 hence a, 4a
1.10 Sprue Design:• Ensure sprue does not act as choke.
• Design according to As = Ac H (minimum)h
• Ac = sum of all choke cross sectional areas.
• This design holds for upward taper, downward taperand parallel sprues. As relates to the smallest crosssection in a tapered sprue. In the case of downwardtapered sprues, “h” is measured to the smallestcross section of the sprue, which normally is at therunner / sprue junction.
• Avoid use of standard sprue diameter.
If you must use standard sprue diameter, designaccording to
Ac = As h (maximum)H
This invariably slows down mould filling incurring highertemperature loss and increased risk of casting defects.
11
W1
W4
W1
W4
W5 W6
W2 W3 W7
W10 W11 W12
W8 W9
CXD
W2
W5
W3
W6
W7
Choke cross sectional area AC1 chosen according toW1 + W2 + W3 + W4 + W5 + W6
or AC2 chosen according toW7 + W8 + W9 + W10 + W11 + W12
AC1 AC2
W10
W8
W11
W9
W12
1.11 Runner Bar:Exists to reduce flow velocity of iron stream thus
allowing slag particles to float out of iron stream.
• Avoid use of curved runners.
• Avoid use of stepped runners.
• GATE-RUNNER: use tall narow runners with crosssectional area (AR) about 2 to 4 times total crosssectional area of gates attached to runner.
AR = 2a (a) = 3 (Ac)
• Use tapered extension or where space does notpermit, use drag well
• Gate location should not be too close to sprue orrunner bar end
• Branch gates at 90° to runner and don’t staggergates on opposite sides of runner.
• SPRUE-RUNNER: Square runner cross section atchoke end tapering to rectangular section towardsend of runner.
• Taper determined by making cross sectional areajust beyond last gate, equal to choke cross sec-tional area C.
12
1.12 Gate Connection:GATE-RUNNER: always connect to side of runner
• Ensure that bottom of runner and bottom of gate(s)are in the same horizontal plane.
• SPRUE-RUNNER: Place runner in drag, gates incope.
• Total area of gate overlap should be slightly morethan choke cross sectional area. (+ 10%)
• Gates overlap top of runner by slightly more thangate thickness.
• Always connect gate to top of runner.
1.13 Pouring Basin and Sprue Well:Worst shape for pouring basin is conical – much
splashing at start of pour.
• Best shape is “sump” where L = 2 x W
• Sprue well required to avoid aspiration at sprue-runner junction. Shape square or rectangular, flatbottom.
13
Poor GoodGood
1.14 Common Defects Relating to Poor GatingSystem Design:
• GAS-HOLES at or near cope surface.
• Poor design allows slag, metallic oxides (M0, majorslag component) to enter casting cavity.
• Oxides react with carbon dissolved in iron.
• M0 + C = C0 + M
• C0 bubble floats to cope surface or is trappedunder core.
• Remedy by examining gating system for violationsor simple rules presented previously.
• MAGNESIUM SILICATE defects act as cracks whenlocated at or near casting surfaces. These drasticallyreduce dynamic mechanical properties (impact, fa-tigue, fracture toughness).
• Most common cause is use of too small a sprue forselected choke. (Refer to section 1.10.)
• Low pouring temperature can increase problem.
14
• LAP TYPE defects and “ELEPHANT SKIN”.
• Extreme case of magnesium silicate contaminationwhere several liquid streams entering casting cavi-ty are covered with magnesium silicate film. Whenseparate streams meet, the surface films will notallow complete fusion.
• Check sprue size (section 1.10).
• Check design of gating system for componentslikely to cause undue turbulence.
• True cold lap defects are not very common in duc-tile and grey iron castings.
• LUSTROUS CARBON defects occur as “wrinkles”or “peel” which are partially detached from the castsurface.
• Occurence due to excessive carbonaceous matterin moulding sand. Defect encouraged by slow mouldfilling.
• Remedy by decreasing pouring time (section 1.7)and adjusting composition of moulding sand.
1.15 Case History:• High incidence of scrap castings due to lap type
defects and cope surface “peel” (Ductile ironcastings).
• Micro section showed gross lap type defect con-taining magnesium silicate film. Cope surface “peel”typical of lustrous carbon defect.
• Examination of original gating showed a gate-runnersystem, but without correctly designed gates.
15
• Implication: The first iron poured contained relativelyhigh concentration of slags. This is unavoidable inspite of meticulous ladle practice, skimming, etc.Since the runner leads directly to the riser (no gates)the first, slag rich iron poured, entered the riser andsubsequently the casting cavity. (See next page).
• Implication: The “choke” in the original system isthe smallest cross section between the sprue andthe casting cavity, i.e. the runner cross section. Thisviolates the design criteria:
As ≥ Ac H (here Ac = AR)h
leading to generation of magnesium silicate slag inthe gating system, extended pouring time, hightemperature loss.
• Redesign: Total poured weight (casting + riser)= (15 + 2) = 17 lb (7.73 kg).
• Gate runner system will be used.
• Casting located 50% in drag, 50% in cope.
• fr = 0.4 (section 1.6)
• recommended pouring time, t = 4 secs. (section1.7)
• Ferrostatic head in sprue (approx. cope height),H = 8 in. (20.3 cm)
• Pouring basin depth, h = 3 in. (7.62 cm)
• Height of casting in cope, b = 2 in. (5.1 cm)
• Total choke cross sectional area, (section 1.8), forcasting located in cope and drag:
• for given conditions, selected Ac value from plot onpage 9 is Ac = 0.37 in.2 (2.38 cm2)
• sprue design (section 1.10),
AS ≥ Ac H = 0.37 (8) 0.5h 3
AS = 0.60 in.2 (3.88 cm2)hence DS = 0.88 in.
minimum sprue diameter = 0.88 in. (2.24 cm)
• individual choke dimensions, (section 1.9)Ac = 0.37 in.2 and gate dimensions are 4a x asince there is one gate,
4a (a) = 0.37 in.2 (2.38 cm2)hence a = 0.30 in. (0-71 cm)
4a = 1.22 in. (3.1 cm)
• Runner area, (section 1.11),2a2 = 3(0.37) a = 0.75 2a = 1.49 in.
3(2.38 cm) (1.91 cm) (3.78 cm)
• Due to space restrictions on the pattern plate, theriser was moved to the opposite side of the castingsince the runner, gate and riser could not all beaccomodated on one side.
• In the re-design, the riser is “cold”, with a exother-mic sleeve whereas the original design showed a“hot” riser. This appears not to be detrimental tocasting integrity. Probably because the redesignedsystem permits faster filling of the mould hence lessiron temperatures loss during mould filling.
16
• The re-design reduced scrap levels thereby improv-ing casting yield from 16% to 67%.
casting yield =weight of good castings sold
weight of iron poured
55% scrap slag < 5% scrapand lustrous carbon 70% pattern yield72% pattern yield
Before After
• Alternative system designs could include filters andother types of risers to further improve yield.
1.16 Molten Metal FiltrationThe use of molten metal filters is becoming estab-lished practice for an increasing number of foundriesto improve casting quality, yield, machinability andproperties. With this growth in use there is a need foran increased technical understanding of filtering tech-nology in general. It is not enough for a filter to justhave good filtration efficiency. It must also have a highand consistent flow rate, good strength, high capaci-ty, good dimensional accuracy and low cost. Some ofthese parameters are in conflict with each other, forexample if a filter has a very large capacity, the filtra-tion efficiency may be compromised. The most effec-tive filters are therefore ones that have beenengineered to give the optimum performance over allof these parameters.
17
There are several established filter technologies pre-sently on the market. These include strainer cores, wovencloth or mesh, and ceramic tile filters. Ceramic tile fil-ters are generally considered to be the most effectiveand used for smaller molds & pours. The most popularof these are pressed cellular, extruded cellular and foamfilters. Pressed cellular are generally characterized bytheir round cells, extruded filters generally have squarecells, whilst foam filters have a random dodecahedrontype structure.
• Filtration Efficiency is important to remove slag anddross from the iron to prevent them from enteringthe mold cavity.
• Metal Capacity must be adequate for the castingbut it should also be consistent. The capacity shouldnot vary from filter to filter. This may lead to prema-ture blockage in some cases.
• Flow Rate must be high and consistent. Wide vari-ations in flow rate may in some cases, lead to moldfill problems, or a requirement to use a larger filterthereby increasing cost and decreasing yield.
• Dimensional Accuracy is important because the fil-ters should fit into their print cavity correctly eachtime.
• Strength (hot or cold) is important for shipping andhandling purposes and so the filter remains intactwhen molten metal is poured onto it.
Filters do a good job of removing inclusions using avariety of mechanisms. Some types may be more effi-cient at one mechanism than another. Filters will collect
dross particles and inclusions by screening, that arelarger than the filter hole or pore size, on their upstreamface. These particles are unable to pass through to thecasting cavity due to their physical size. Secondly, largedross particles collected on the upstream face duringthe screening phase will form what is known as a “fil-ter cake”. This cake acts as an efficient filtrationmedia. This mechanism is able to collect particlessmaller than the cells of the filter. In ductile iron, it ispossible that the mechanism for the removal of micro-inclusions, (<1% of the cell size), is through the for-mation of “inclusion bridges”. Small eddy currents,formed when the metal stream splits on the activeface of the filter, are generated. These eddy currentswill encourage small non-metallic particles to makecontact with the edges of the cell. As the pour pro-gresses these particles will continue to adhere to eachother and will eventually form an “inclusion bridge”.
The use of the filters has increased dramatically in thepast 10 years as the cost per unit has decreased whilecasting wall thickness has been reduced and generalquality requirements for castings have increased. How-ever, as always, some experimentation must be donein the foundry to establish proper filter sizes, ladle des-lagging practices and pouring temperature ranges sothat good casting yield is maintained.
18
19
Section two
Risering System Design
Please note:
Risering must be done before gating system can be calculated.Bottle shaped (Heine) risers are now the riser of choice in themajority of systems.
2.0 RISERING SYSTEM DESIGN
2.1 Objectives:• castings without shrinkage defects
• economic production – maximize casting yield
2.2 Essential Components• Riser – always “blind” (closed top).
Riser contact – generally as short as possible.Designed dimensions always measured at thenotch.
• Gate – thin and wide for fast freezing (see p. 28).
• Vents – to assist fast mould filling.
2.3 The Following are Suggested by Research andSupported by Industrial Experience
• Volume change patterns of cooling and solidifyinggraphitic irons result in net volume increase of ironin the mould.
• The net volume increase can produce liquid pres-sure in the mould of several hundred p.s.i. (2 MPa).
• This pressure always exceeds the elastic limit ofthe mould, except for very rigid moulds, leading tomould enlargement and swollen castings, oftencontaining shrinkage defects.
• Green sand moulds are not considered to be rigidin this context.
• Riser function is very sensitive to pouring tempera-ture and pouring time.
• Volume change pattern is not constant but variesaccording to cooling rate and liquid iron process-ing route (superheat, charge composition, meltingmethod, inoculation, etc).
• Due to the high pressures experienced by themould during pouring and solidification, mouldhalves should be clamped together. Weightingalone is not sufficient.
20
2.4 Typical Volume Change Patterns• General volume change pattern for steel, white
iron, brass, etc.
• Volume change patterns for graphitic irons.
• Cooling liquid initially contracts then expands. Towardsthe end of solidification, last remaining liquid solidifieswith contraction.
• Shape of volume change pattern influenced bycooling rate and by changes in liquid iron process-ing. This directly affects the extent of contractionand expansion.
2.5 PlanningThe detailed design principles will be presented in
the following order:
• Determine significant modulus of the castings (MS).
• Evaluate mould and iron quality, then select appro-priate risering method.
• Determine corresponding liquid transfer modulus(MN) and number of risers required for each casting.
• Select riser type and compute dimensions (MR).
• Select riser contact (neck) type and computedimensions.
• Check that available feed volume in riser(s) is suffi-cient for casting’s requirements.
• Select pouring temperature based on selectedrisering method.
21
Pri
mar
y (L
iqu
id)
Co
ntr
acti
on
Rate of solidState Contraction
Temperature Intervalof Solidification
Temperature of theLiquid after CompletedPouring.(Ty)
Temperature (˚C, ˚F)
Solidification (Freezing)Contraction
SpecificVolume(cm3/g)(in3/ lb)
2.6 Cooling Rate• Casting weight or wall thickness not sufficiently ac-
curate to describe cooling rate.
• Simple shapes: cube, plate, bar etc, all 1 inch (25 mm)thick but all cool at different rates.
• Use modulus (M) to describe cooling.
• Modulus = volumeeffective cooling surface area
• More complicated shapes should be broken downinto simple shapes and the moduli of the individualsimple shapes, determined.
• Note in the example that the connecting surfacesbetween adjacent segments are not considered tocontribute to cooling (variable “c” below).
Where:V = total casting volume.CSA = total cooling surface area of the casting
Example for the calculation of Modulusa = any sideb = any sidec = non-cooled side
2. Modulus = V M = a • bCSA 2 (a + b) – c
• all dimensions in cmM1 = 5 • 2.5 = 1.0 cm
12.5
M2 = 5 • 3 = 1.5 cm10
M3 = 5 • 4 = 1.8 cm11
Significant Modulus = M3 = 1.8 cm
Note: See example on page 36.
22
• When hollow sections are involved, the coolingeffect of cores may be approximated as shown.
ADJUSTMENTS TOTHE COOLING SURFACE AREA
If d < 1/3 D, ASSUME 0% COOLING FROM CORE
If d > 1/3 D and d < 2/3 D, ASSUME 50% COOLINGFROM CORE
If d > 2/3 D, ASSUME 100% COOLING FROM CORE
2.7 Mould Quality• Objective is to avoid enlargement of the mould from
high liquid pressures exerted by the cooling andsolidifying graphitic iron.
• Green sand and shell moulds will not withstand thesolidification pressure.
• Chemically bonded sand moulds will resist solidifi-cation pressure if they are properly prepared. Thisrequires mechanical compaction of sand duringmould preparation and adequate curing.
• Cement sand and dry sand moulds will normallywithstand the iron solidification pressure.
2.8 Liquid Iron Processing• All aspects of iron processing have some influence
on the magnitude of volume change during coolingand solidification, hence the shrinkage characteris-tics of the iron.
• Some of the factors which increase shrinkage ten-dency:
• high melt superheat temperatures
• long holding times in the furnace
• high proportion of foundry return scrap or steelscrap in the charge
• presence of carbide stabilizing elements in meltchemistry (including high Mg)
• variable carbon equivalent of the iron
• inadequate inoculation.
• Combined effect of these (and other) process vari-ables can be assessed, very approximately, bymeasuring nodule count of standard test piece(Nodule count increases with faster cooling).
• Irons which show low tendency to shrinkage alwaysseem to show low tendency to form as-cast car-bides i.e. they graphitise well. Such irons are saidto possess good “metallurgical quality”.
• The presence of any type of carbides in the as-caststructure should be considered as an indicationthat the iron has poor metallurgical quality. Conse-quently problems with shrinkage defects should beexpected.
23
• Plot shows range of expected nodule counts forgood metallurgical quality ductile irons in depen-dance of modulus (cooling rate).
• For example, a 1 in (25 mm) ‘Y’ block has a modu-lus of 0.33 in (8 mm). For good metallurgical qualityiron, range of nodule counts is 140-280/mm.
• See also 2.16 and 2.17.
2.9 Selection of Risering Method• CONVENTIONAL RISERING – The test bar blank
or ‘Y’ block is one example. Use of a large (open)riser encourages directional solidification ensuringdefects appear in the riser not the test bar blank(parallel sided portion).
• Problem with conventional risering is low yield. Inthis example, about 23%. Not economical.
• APPLIED RISERING –
Use this “family tree” to select risering method foryour production conditions.
24
MODULUS cm
MODULUS inch.
MO
DU
LE
CO
UN
T p
er m
m2
0 0.5 1.0
1000
500
400
300
200
100
20
0 0,3 0,8 0,9 1,2 1,5 1,8 2,1 2,4
INCREASEDSHRINKAGETENDENCY
EXCESSIVEPRESSURECREATED
RISERINGLIQUID CONTRACTIONWITH GATING SYSTEM
RISERINGLIQUID CONTRACTION
WITH RISER
PARTIAL RISERINGWITH
GATING SYSTEM
PRESSURECONTROLRISERING
RISERLESSDESIGN
DIRECTLY APPLIED RISERING
SAFETY RISERNO RISER
APPLIED RISERING METHODS
MOLD
WEAK
MODULUS in.
> 3/16 < 3/16
STRONG
MODULUS in.
< 1 > 1
• Selection based on mould strength and castingmodulus.
• Methods take advantage of the fact that graphiticirons expand during cooling, unlike steel, whiteiron, malleable iron etc.
• WEAK MOULD: Green sand, shell, non-compactedchemically bonded sand.
• STRONG MOULD: Well compacted chemicallybonded sand, cement sand, dry sand, permanentmould.
• There are three basic applied risering methods:
• pressure control risering (PCR) or bottle riser
• directly applied risering (DAR)
• riserless
• Application of each method:
• when mould is weak and casting modulus isgreater than 0.16 in. (4 mm) use PCR.
• when mould is strong and casting modulus isless than 1.0 in. (25 mm) or when mould is weakand casting modulus is less than 0.16 in. (4 mm)use DAR.
• when mould is strong and casting modulus isgreater than 1.0 in. (25 mm) use RISERLESS.
2.10 Pressure Control Risering• Most green sand and shell moulded castings should
be risered by this method.
• Objective is to control the pressure generated dur-ing cooling and solidification, between a minimum
pressure level, which will prevent the occurenceof secondary contraction defects and a maximumlevel, at which the mould will enlarge.
• Principles of PCR (necks not used to simplify):
A. after pouring completed, liquid contracts.
B. riser compensates for liquid contraction.
C. when expansion starts, mould deformation avoi-ded by pressurized liquid from casting, “bleed-ing back” to refill the (blind) riser.
25
• ideally riser should refill just before expansion ceases.
• this puts all remaining liquid under slight positivepressure and prevents secondary shrinkage defect.
• Design Sequence:
• determine casting significant (largest) modulus(MS) (Section 2.6).
• determine Modulus – Riserneck (MN)
• determine Modulus – Riser (MR)
• see Card #3 metric or english.
Card #3
Relationship between significant modulus (MS), riser-head neck modulus (MN) and riser-head modulus (MR) inpressure-control riser-system design. Includes factor (f).See page 28.
• select blind riser type and compute dimensions.
• Also see section “bottle riser design”.
• main riser dimensions expressed in terms of diam-eter, D; height = 1.5 x D or with neck located indrag riserheight = 1.5 x D + neck heigth.
• Find riser neck dimension on Card #4 english ormetric.
• Round or square necks = 4 x MN
• Rectangular necks = 3 x MN + 6 x MN.
26
PRESSURE CONTROL RISERING METHOD
Sig
nif
ican
t M
od
ulu
s (M
S)
cm
Riser Neck Modulus (MN) cm
Riser Modulus (MR) cm (MR = MN x 1.2)
10.0
5.0
4.0
3.0
2.0
1.5
1.0
0.5
0.5 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0
I II III
0.6 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
Poo
r Qua
lity
Goo
d Qua
lity
• Riser neck dimensions are measured at the bottomof the radius between riser and casting.
• Additional notching of the contact may be introducedproviding the additional notch depth is not more thanone fifth contact thickness.
• Determine volume (weight) of riser(s) for yield andgating system design calculations.
• Only that portion of the riser which is higher thanthe highest point of the casting to which it is attached,will compensate for liquid contraction in the casting.See Card #5.
• Feeding distance should be assumed to be a max-imum of 10 x MN.
Card #5
27
1,500
1000900800700
600
500
400
300
200
10090807060
50
40
30
20
109876
5
4
3
2
10.90.80.7
0.6
0.5
0.4
0.3
0.20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
"X" (cm or in.)
Eff
ecti
ve F
eed
Met
al V
olu
me
(cm
3 o
r in
.3)
Topmost point of riserEffective feed metal(shaded volume)Topmost point of casting
Riser Diameter at Parting(cm or in.)
CXD
D (dia)
1.5
x D
x
12
11
10
9
8
7
6
5
4
3
2
1
• Determine effective feed volume of riser(s) andcheck against casting requirements. “X” is the ef-fective riser height. (See Card #5)
• If the effective volume of riser(s) is less than the vol-ume required by the casting(s), larger or multiplerisers should be used.
• In order for the PCR system to function correctly,the gating system must be isolated from the castingand riser very soon after mould pouring is complete.This can be achieved by ensuring the gate has alow modulus MG, (fast freezing) compared to theliquid transfer modulus (MN).
• For design purposes,MG ≤ 0.2 MN. If MG does not satisfy this condition,increase the number of gates but maintain thesame total gate cross sectional area. Individualgate dimensions and modulus will be reduced butmould filling time will be unchanged.
Origin of the riser neck calculation factor (f).
2.11 Bottle Riser DesignIt is very important that a primary shrinkage hole (pipe)is created quickly in a riser, so that the riser can feedmetal into the casting. If the liquid metal in the riser isnot open to the atmosphere (skins over), the riser will notfunction. Atmospheric pressure is necessary to pushmetal into the casting.
The classical riser shape with a rounded or flat top, evenwith a “v” or a dimple on the top, may not always guar-antee that the riser will pipe. Temperature control is alsovery important with this design, since these risers workwell at higher pouring temperatures, but not at lowones.
Ductile Iron tends to form a thin stable skin quite quicklyand especially at lower temperatures due to the mag-nesium content contributing to an oxidized surfacelayer. Once this skin forms the liquid metal is not opento the atmosphere and a vacuum can be created in-side the riser. At this point the riser will not feed at allunless it begins to collapse.
A bottle riser (also known as a “Heine Riser”) has sucha small area at the top diameter that it will begin to pipevery quickly. So in order to have sufficient feed metalvolume these risers must be taller than classical designs,which were normally 1.5:1 height:diameter. The heightto diameter ratio for a bottle riser will vary accordingto the amount of feed metal required. This is usuallytaken to be about 4%, which includes a safety factor.This type of riser is also not as dependent upon pour-ing temperature for it to function. Since this riser is soefficient it can improve the overall yield by as much as2% or more.
28
The determination of the riser size for the bottle typeriser is very simple. The size is calculated from thesignificant modulus of the casting and the weight of thecasting, which determines the amount of feed metalrequired. Classical methods use the metal quality andthe significant modulus to find the transfer (riser) modu-lus and then calculating the riser diameter and the feedmetal required so that it can be compared to the riserfeed metal volume. The riser neck calculations are donethe same way for both risering methods. All risersshould be blind.
BOTTLE RISER FORMULASRiser diameter = 4 (MS) + Riser top diameterCasting feed metal required = 4% of pouring weightRiser feed volume – determined by riser top diameterand height to diameter ratio. See table. Use tallest riserpossible for flask size.Riser height = H.D ratio x riser top diameter
EXAMPLE:Casting weight = 187 lbs (85 kg)Cope height = 13 inches (330 mm)Significant modulus of the casting (MS) = .6 in (15 mm)
* Feed metal required = .04 (187 lbs) = 7.5 lbs(3400 g)
* Choose from table a riser with a 2 in (50 mm) topdiameter and 5:1 ratio to give 7.6 lbs (3434 g) of feedmetal.
* Riser diameter = 4 x .6 in + 2 in = 4.4 in (110 mm)* Riser height = 5 x 2 in = 10 in (250 mm)
29
8:1 6:1 5:1
Top Dia. Feed Wt. Top Dia. Feed Wt. Top Dia. Feet Wt.in (mm) lbs (g) in (mm) lbs (g) in (mm) lbs (g)
.4 (10) .10 (44) .4 (10) .07 (32) .4 (10) .06 (28)
.8 (20) .78 (352) .8 (20) .58 (264) .8 (20) .48 (219)1.2 (30) 2.6 (1186) 1.2 (30) 2.0 (890) 1.2 (30) 1.6 (741)1.6 (40) 6.2 (2813) 1.6 (40) 4.6 (2110) 1.6 (40) 3.9 (1758)2.0 (50) 12.1 (5495) 2.0 (50) 9.1 (4121) 2.0 (50) 7.6 (3434)
FEED METAL TABLE
Ratio (Height: Diameter at top)
2.12 Riserless DesignPrinciples of Riserless Design:
• Pour at relatively low iron temperature to avoid (pri-mary) liquid contraction.
• Allow the (rigid) mould to contain all the expansionpressure during iron cooling and solidification.
Production conditions necessary for successful riser-less design:
• High metallurgical quality of the liquid iron.
• Very rigid moulds. Green sand and shell moulds notstrong enough. Chemically bonded sand mouldsmay be used providing the sand is mechanicallycompacted before curing. Mould halves must beclamped or bolted together.
• Minimum casting significant modulus of 1.0 in.(25 mm).
• Pouring temperature range 2,320 – 2,460°F(1,270 – 1,350°C).
• Fast pouring. See Card #2.
• Casting cavity should be well vented.
• Casting cope surface depression will occur if pour-ing temperature not carefully controlled. Remedymay be effected by using a small blind riser oncasting cope surface. Riser volume should beabout 2% of casting volume.
• Gating system design should follow the rulesdescribed in section 1. Providing fast filling isachieved, gate thickness may be as low as 0.4 in.
(10 mm) for the minimum pouring temperature of2,370°F (1,300°C).
2.13 Directly Applied Risering Design (DAR)Principles of DAR;
• Use a riser, or the gating system, to compensate forliquid contraction.
• Allow the mould to contain all the expansion pres-sure during iron cooling and solidification.
• Since the design allows compensation for liquidcontraction, thinner sections, poured at higher tem-peratures, can be produced than is possible withriserless design.
Production conditions necessary for successfulDAR design:
• Very rigid moulds if casting significant modulus(MS) is greater than 0.16 in (4 mm).
• Excellent control of iron pouring temperature whichshould not vary by more than ± 25°F (± 14°C).
• DAR can be used with weak moulds if MS ≤ 0.16 in.(4 mm).
Design Sequence for DAR:
• Determine casting significant modulus (MS). In con-trast to PCR design, MS in DAR design may well bethe modulus of the smallest segment of the casting,where solidification and expansion begins.
30
• Select suitable pouring temperature bearing inmind the value of MS.
• Select contact modulus value, MN, dependant uponMS and desired pouring temperature.
• For round or square contact, contact diameter= 4 (MN) contact side length = 4 (MN).
• For rectangular contact, short side = 3 (MN) longside = 6 (MN).
• Where MS ≤ 0.16 in. (≤ 4 mm) and the mould isweak, the sprue can be used to compensate for li-quid contraction in casting cavity. To achieve this,gate dimensions should be 4 (MN) x 4 (MN) for rec-tangular section.When MS ≥ 0.16 in. (>4 mm) and the mould is strong,a similar arrangement can be used.
• Gate length should be at least 5 times the gatethickness.
• Alternatively, a riser can be used to compensate forliquid contraction in strong moulds when MS >0.16in. (>4 mm) (when MS exceeds 1.0 in. (25 mm) con-sider using RISERLESS technique). Riser contact(neck) should be constructed according to the MS/MNplots on the following page. Riser volume should(obviously) be large enough to satisfy the volumecontraction requirements of the casting.
Porosity resulting from secondary shrinkage.
31
2.14 Selection of Pouring Temperature Based onRisering Method
• PCR: 2,500 – 2,600°F (1,380 – 1,425°C) to “guar-antee” formation of a shrinkage void in the riserduring initial liquid cooling.
• RISERLESS: 2,320 – 2,460°F (1,270 – 1,350°C) toavoid liquid contraction in the mould.
• DAR: Dependent on casting modulus. (see p. 31)
32
Ms (inches)
Mn
(in
ches
)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4
2700°F2650°F2600°F2550°F2500°F2450°F
2400°F
2350°F
20
15
10
5
05 10 15 20 25 30
Ms mm.
Mn
mm
.
Tp°C.1,5001,450
1,400
1,350
1,300
2.15 Pressure Control RiseringCase Histories
ROTOR: Material GGG 40.3; casting weight 26.0 kg;pouring weight 45.6 kg; yield 58%; moulding material,greensand; MS 1.90 cm; modulus A/A = 1.30; modu-lus B/B = 1.25; f = 0.60; MN 1.14; feeder neck =45/45 mm; MR = 1.37 cm; feeder = 70 mm dia; pour-ing temperature 1,400°C min; pouring time 11 sec;gate cross-section 6.5 sq cm; photograph by courtesyof Emmenbrücke foundry, Switzerland.
PULLEY WHEEL: Material GGG 40; casting weight 40 kg;pouring weight 65 kg; yield 62%; moulding material,greensand; MS 1.0 cm; modulus A/A = 0.70; f = 0.80;MN 0.80 cm; feeder neck = 32/32 mm; MR = 0.96 cm;feeder = 70 mm dia; pouring time 12 sec; pouring temp.1,400°C min; gate cross-section 6.0 sq cm; photographby courtesy of Emmenbrücke foundry, Switzerland.
33
FRONT WHEEL HUB: Material GGG 40; casting weight:5.8 + 5.8 = 11.6 kg; pouring weight: 19 kg; yield: 61%;MS = 1.0 cm; MR = 0.8 cm; feeder = 50 mm dia; x =4.6 cm; MN = 0.66 cm; feeder neck 40 by 20 mm;pouring temperature 1,370/1,420°C; gate area 2.64 sqcm; sprue area 4.5 sq cm; produced on a Disamaticmoulding machine by BFL-Karachi/Pakistan.
34
Bottle risering case histories
HUB PLATE: Ductile Iron grade 420/12; casting weight2.85 kg; riser weight 2.85 kg; total poured weight 25.3kg; yield 67.6%.
Green sand mould; MS = 0.61 cm; feed metal required4% x 2.85 kg x 3 = 342 g; riser 14 cm high, 2 cmtop diameter. Base 10 cm diameter (increased be-cause of 3 castings per riser); riser ratio 7:1; riser neckM = 0.55 cm. Riser neck 4.5 cm x 1.5 cm; ingates(2) 3.5 cm x 0.5 cm x 12 cm long; runner 3 cm highx 1.5 cm wide; downsprue 2.5 cm diameter x 25 cmhigh; pouring temperature 1400°C; pouring time 9 sec;photo and data courtesy Bolan Engineering Foundry,Pakistan.
35
1 cm
1.3 cm
MS
20.5 cm
CASE HISTORY [ENGLISH SYSTEM (INCH: LB)]• Heavy truck wheel hub casting. Weight 150 lb.
(68 kg).
• Very high scrap due to shrinkage defect located at‘A’. (Segment M3)
• Green sand mould (weak).
• Significant modulus, MS = 0.77 in.
• PCR method applies.
GATE / RISER SYSTEMPart No: 770 Company: ABCEstimated Casting Weight: 150 lb
1. Layout:
2. Modulus = VCSA
MS = 0.77 in3. MN see Card #3 MN = 0.40 in4. Riser modulus (MR) MR = M1 MR = 0.50 in5. Blind Riser Type
Type 2 D1 = 4.91 x MR (2.46) = 3.0 in*
NOTE: Max. MT = M1 = 0.5 inAssumes good metallurgicalquality of the liquid iron.
* Use a 3.0 indiameter riserto obtain adequatefeed volume.
36
M1 = 21/2 x 11/4 = 0.50 in61/4
M2 = 21/2 x 13/4 = 0.87 in5
M3 = 11/4 x 2 = 0.77 in31/4
6. Riser Contact modulus (Mn) = .40 inSee Card #4.
6b. Contact ShapeSquare Side Length = 4 (Mn) = 1.6 inRound Diameter = 4 (Mn) = 1.6 inRectangular Short Side = 3 (Mn) = 1.2 in
Long Side = 6 (Mn) = 2.4 in7. Check Feed Volume
Estimated Casting weight (each) = 150 lbEstimated Casting volume =
150 ÷ 0.25 = 600 in3
Required feed volume =3% of 600 = 18 in3
Available feed volume “X” dimension = 4-1/2 inAvailable feed volume 25 in3
Number of risers required/casting 18. Total choke cross sectional area (section 1.8) per
casting. Ac = 0.65 in2 (from chart)Number of gates. n1 = 1 (per casting)Gate dimensions (4/1):n (4a2) = Ac 4a2 = 0.65 a= 0.4 in
4a= 1.6 in9. Runner Bar:
Cross sectional area, AR = 2 to 4 (Ac)= 3 (2) (0.65) = 3.9 in2 (2 chokes)
Height = 2 x width, 2a2 = AR = 2 to 4 (Ac) (2)a = 3 (0.65)a = 1.4 in
2a = 2.8 in
10. AS ≥ Ac H or Ac ≤ AS hh H
AS ≥ 2(0.65) 10 D2S = 4 (2) (0.65) 10/3
3 πSprue diam. = 1.74 in
or, total choke ≤ 0.43 in2
11. Pattern Yield:Volume of castings 2 x 600 1200 in3
risers & contacts 100sprue & basin 62runner 50gates 1sprue well 10Total volume poured = 1423 in3
Pattern Yield =Casting Volume 1200 = 84%
Total volume poured 1423
37
2.16 Metallurgical Quality Control and theimportance of the nucleation condition
One of the most important factors involved in therisering of a casting is to understand and exercisesome control over the way in which the solidificationprocess takes place.
The schematic representation of the volume changeswhich accompany the cooling and solidification of duc-tile iron are shown above. As can be seen from the plotsA, B, and C the volume changes are not constant, evenfor ductile irons of identical chemical composition, therecan be differences in the degree of nucleation whichwill affect the volume change pattern. It is the “metal-lurgical quality” of the iron which is important and isdirectly related to the self-feeding characteristics (smallvolume changes) of the ductile iron.
There is no universally accepted measure of metallur-gical quality at the present time. Nevertheless we dohave knowledge about the important features of rawmaterials selection, melting practice, magnesium treat-ment and inoculation – all of which influence metallur-gical quality. From a practical view point also it isimportant to maintain all conditions as constant aspossible in order to ensure consistent volume changebehaviour with consistent and predictable feed metalrequirements.
2.17 Methods to measure the Metallurgical Quality• Base Iron:
chemistry and wedge test (check undercooling)
• After treatment and inoculation:chemistry (including Mg content), cooling curve ana-lysis, and nodule count/modulus. (See page 24).
38
0.06
0.05
0.04
0.03
0.02
0.5 1 1.5 2 2.5 3 3.5
Modulus (cm)
% M
g -
res
idu
al
Tendency to shrinkage formation
Less shrinkage problems
Recommended
Mg content
2.18 Other Risering AidsThe reasons for using exothermic or insulating risersis that you can sometimes use smaller risers where theapplication dictates that the riser be cold (not gatedinto – such as a top riser and isolated risers). Normalrisers use only a small portion (around 14%) of theirvolume for feed metal. Exothermic and insulating ris-ers can give up to 80% and more as feed metal to thecasting. These risers are also designed in relation tothe significant modulus of the casting to be fed. In thiscase you can normally use relatively small risers tofeed the castings even in heavy castings. The normalexothermic and insulating risers have, by their nature;an increased effective modulus of about 1.4 to 1.5times in relation to sand molded riser. Another type ofspecial riser system is called a “Mini-Riser” which is asmall exothermic riser. This type will have an in-creased modulus of approximately 2.3 times.
To calculate the size of the risers, normally you shouldmeasure or calculate the significant modulus andcasting weight. The actual feed metal required isabout 3 – 5% of metal by weight. This is depending onthe mould-hardness, metallurgical quality of the ironand pouring temperature. One should also consult themanufacturer’s recommendations on the use of thesespecial types of risers. Maximum utilization of this“mini-riser” should be no more than 70% of its volume.
Example:If we have a casting with a significant modulus of2.5 cm and a weight of 20 kg you get the followingriser: Weight of the riser = 3% minimum x 20 kg =0.60 kg or 600 gr. ÷ 70% = 857 gr. of feed metal
would be supplied. The riser modulus should be 1.1 x2.5 cm = 2.75 cm.
The neck is also very important when using these ris-ers. A breaker core is necessary between the castingand the riser. The diameter of the hole in the breakercore should be maximum 1/3 of the diameter of theriser. This has the advantage to avoid shrinkage holesin the riser neck and also it reduces finishing costs.
One further advantage of the “Mini-Riser” is that thepressure, which is created during the growth andexpansion of the graphite, is not going on the mould,it is relieved by the riser because there is still liquidmetal and a void in the riser. This type of riser wasinvented in a foundry where they produce hydrauliccastings. This foundry has had great problems withpenetration and cracking of the cores. After using the“Mini-Risers” the problem nearly disappeared, becausenow the feeding system was a pressure control system.During solidification the riser was feeding the castingswith liquid iron and during the formation of graphiteiron was forced back into the open riser and the pres-sure was released.
All exothermic risers contain aluminum and other ele-ments to provide the reaction. These elements can oftencause graphite degeneration. To avoid this problem youhave to increase the height or length of the riser neck.There are also other elements that can cause castingdefects if they get into the sand system especially inthe unburned condition. Defects such as “Fish eyes”can be produced.
39
2.19 The use of chills
Since there are more methods of non-destructive test-ing performed on castings, foundries are forced tofind economical ways to make completely sound cast-ings. Ductile Iron has an expansion phase during soli-dification. If you have a slow solidification and a strongmould you can make sound castings riserless andmost often with some chills. However the majority ofcastings are smaller and made in relatively soft greensand moulds. During the expansion of graphite themould walls will yield and so it is not possible to usethe expansion of the iron for the feeding of the cast-ings. Ductile Iron is also a eutectic alloy. All eutecticalloys are liquid very long during solidification. Theydon’t form a skin during solidification. When usingchills we quickly form a solid skin in the area where wehave placed the chill. We also increase the density inthe matrix producing fine structure in this area. This canhelp improve wear resistance and pressure tightness.
Most foundries are using chills made from Grey iron.The thickness of the chill should be at least the samesize as the thickness of the section to be chilled. Addingchills to one side of a section can reduce the modulusby up to 50%. Grey iron chills can be used until they getcracks. Using chills with cracks may produce blow-holesin the area were you placed the chills. To avoid thisproblem foundries are using more SiC-bricks or gra-phite blocks as chills. They do not have as strong achilling tendency as Grey iron chills, but they have notendency to absorb moisture. Applying chills can reducethe number of risers and normally also the scrap rate.These things can increase yield and reduce finishingcosts.
Reduce section modulus with chill(s).
Eliminate risers by using chills (minimum modulus > 1 in(25 mm)).
40
T
RISER
t = T
tCHILL
65 mmGATES
RAM UPCHILLS�
���
More bottle riser examples
41
LINK CASTING: GGG80; casting weight 5 kg; greensand mould; MS = 1.5 cm; modulus riser neck = 1.05 cm;riser diameter at parting 4 x 1.5 cm + 3 cm = 9 cm;riser height 15 cm (5:1 ratio); feedmetal 741 g (needed5 kg x 4% x 2 = 400 g); riser neck dimensions 2.5 cmx 6.4 cm.
Cross section through links and riser. Link castings connected by a bottle riser.
42
HUB CASTING: GGG40; one riser for 4 castings; MS =1.0 cm; casting weight each = 2.5 kg; green sandmould; Mneck = 0.7 cm; neck dimensions 1.8 cm x6.0 cm; riser modulus 0.8 cm; riser dimensions (5:1ratio) 3.0 cm top diameter; 15.0 cm high, diameter atparting 14 cm; feedmetal required 400 g; feedmetalsupplied 741 g.
4 hub castings - one bottle riser.
43
Use of bottle risers.
1. Chvorinov, N.Giesserei vol. 27 1940 page 177
2. Wlodawer, R.Directional Solidification of Steel Castings– Pergamon Press 1966
3. Karsay, S.I.Ductile Iron vol. 1 – Production published byQIT – Fer et Titane Inc. 1976
4. Karsay, S.I.Ductile Iron vol. 3 – Gating and Risering publishedby QIT – Fer et Titane Inc. 1981
5. Corlett, G.A. & Anderson, J.V.Experience with an Applied Risering Technique forthe Production of Ductile Iron CastingsAFS Transactions 90, 1983, 173-182
6. Gerhardt Jr., P.C.Computer applications in Gating & Risering SystemDesign for Ductile Iron CastingsAFS Transactions 1983, 73, 475-486
7. Karsay, S.I.International Foundry Congress, Budapest 1978paper 28
8. Karsay, S.I.“The practical foundryman’s guide to feeding andrunning Grey, CG and SG iron castings”Published by Ferrous Casting CentreAvailable form AFS HeadquartersDes Plaines, U.S.A.
9. Anderson, J.V. & Karsay, S.I.Pouring rate, pouring time and choke design for S.G.Iron Castings”.British Foundryman, December 1985
10. Rödter, H.“An alternative method of pressure control riseringfor Ductile Iron castings.QIT – Fer et Titane Inc., June 1984
September 2000
PRINTED ON RECYCLED AND RECYCLABLE PAPER
Copyright Rio Tinto Iron & Titanium inc.
PRINTED IN CANADA BY TRANSCONTINENTAL, MÉTROLITHO DIVISION
44
BIBLIOGRAPHY
Comments to and criticism of this work are welcome.Please write to:
Rio Tinto Iron & Titanium Inc.Technical Services770 Sherbrooke St. WestSuite 1800Montreal, QuebecH3A 1G1CANADA
Total Poured Weight (Incl. Risers) Per Choke. lbs.
Ch
oke
Cro
ss S
ecti
on
al A
rea
in2
10.0
1.0
0.11 10 100 1,000 10,000
Casting in Cope Casting in Drag
CARD #1 ENGLISH
Total Poured Weight (Incl. Risers) Per Choke. Kg.
Ch
oke
Cro
ss S
ecti
on
al A
rea
cm2
100
10
11 10 100 1,000 10,000
Casting in Cope Casting in Drag
CARD #1 METRIC
Total Poured Weight (Incl. Risers) Per Choke. lbs.
Po
uri
ng
Tim
e S
ec.
100
10
11 10 100 1,000 10,000
CARD #2 ENGLISH
Total Poured Weight (Incl. Risers) Per Choke. Kg.
Po
uri
ng
Tim
e S
ec. 100
10
11 10 100 1,000 10,000
CARD #2 METRIC
CARD #3 ENGLISH
PRESSURE CONTROL RISERING METHODS
ign
ific
ant
Mo
du
lus
(MS)
in
Riser Neck Modulus (MN) in
Riser Modulus (MR) in (MR = MN x 1.2)
5.0
4.0
3.0
2.0
1.5
1.0
.1
.1 1.0 1.5 2.0 3.0 4.0
0.12 1.2 1.8 2.4 3.6 4.8 6.0
Poo
r Qua
lity G
ood Quality
0.36 0.60 0.84 1.08
I II III
PRESSURE CONTROL RISERING METHODS
ign
ific
ant
Mo
du
lus
(MS)
cm
Riser Neck Modulus (MN) cm
Riser Modulus (MR) cm (MR = MN x 1.2)
10.0
5.0
4.0
3.0
2.0
1.5
1.0
0.5
0.5 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0
I II III
0.6 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
Poo
r Qua
lity
Goo
d Qua
lity
CARD #3 METRIC
USE OF CARDCurved lines represent riser neck modulus (MN). To find neck dimensions, follow diagonal line to MN (curved line).Where these lines meet read dimensions on a and b scales for neck size.
b(in)
a (in)
4.0
2.0
1.2
0.80
0.400.40 0.80 1.2 2.0 4.0
1.38
1.0
0.79
0.55
0.40
0.28
0.20
CARD #4 ENGLISH
USE OF CARDCurved lines represent riser neck modulus (MN). To find neck dimensions, follow diagonal line to MN (curved line).Where these lines meet read dimensions on a and b scales for neck size.
b(cm)
a (cm)
30
20
108
7
6
54
3
2
11 2 3 4 5 6 7 8 10 20 30
9
9
7,06,05,04,5
4,0
3,5
3,0
2,5
2,01,8
1,6
1,4
1,21,00,9
0,8
0,7
0,60,5
CARD #4 METRIC
1,500
1000900800700
600
500
400
300
200
10090807060
50
40
30
20
109876
5
4
3
2
10.90.80.7
0.6
0.5
0.4
0.3
0.20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
"X" (cm or in.)
Eff
ecti
ve F
eed
Met
al V
olu
me
(cm
3 o
r in
.3)
Topmost point of riserEffective feed metal(shaded volume)Topmost point of casting
Riser Diameter at Parting(cm or in.)
CXD
D (dia)
1.5
x D
x
12
11
10
9
8
7
6
5
4
3
2
1
CARD #5
