Split Pattern of Green Sand Molding and Hollow Casting Production

8/13/2019 Split Pattern of Green Sand Molding and Hollow Casting Production

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Machine Shop (2)

Experiment Report Foundry Workshop

Experiment: Split Pattern of Green Sand

Molding and Hollow Casting Production

Report by:

Jorge Sance!

Student "umber: #$%&$'()

Report *ue *ate: June )%+ ,&))


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1. Introduction

Sand astin!is a metal process caracteri!ed by using sand as te mold material-

.t is ceap and retains its strengt at ig temperature- /e sand is moistened wit

water to de0elop strengt+ plasticity and ma1e it suitable for molding- Sand castings

are produced in speciali!ed factories called foundries- 2unny fact: o0er $&3 of allmetal castings are produced 0ia sand casting process-

2or our process we use "reen Sand- Green Sand is called li1e tis because it is

wet+ not because it is green in color+ and it is a type of molding sand+ or foundry

sand+ and it is not a type of sand per se+ but is actually a mixture of silica+ clay+

water+ inert sludge and antracite+ and terefore must fulfill some conditions#

re$ractoriness% chemica& inertness% permea'i&ity% sur$ace $inish% cohesieness%

$&oa'i&ity% co&&apsi'i&ity% and finallyaai&a'i&ity*cost- "ow we sall define eac of

tese caracteristics-

Re$ractoriness: tis means te sand can witstand 0ery ig temperatures+ tis

would be from te li4uid metal being cast+ and it will not brea1 down- 5ou a0e to

ta1e into consideration tat wen casting+ different types of sand can a0e different

temperature limits- /is is important because if te sand as too low refractoriness+

it will melt and fuse to te casting-

hemica& inertness: te sand mustn6t react wit te metal being cast- /is is

important because some metals are igly reacti0e- Examples are al1ali metals in

te periodic table suc as magnesium and titanium-

+ermea'i&ity: tis refers to te ability of te sand to exaust gases- /is is

important+ because during te casting process+ gasses are produced and tey must

lea0e te mold or else tere will be casting defects+ suc as blow oles and gas

oles-

Sur$ace Finish: tis is defined by te si!e and sape of te sand particles7 finer

particle+ better finis- 8ut you must ta1e into consideration tat permeability

decreases as particles are finer-

ohesieness: tis refers to te ability of te pattern to retain its sape after te

mold is remo0ed-

F&oa'i&ity: tis is te ability of te sand to flow into complex details and corners

witout special processes or e4uipment-

o&&apsi'i&ity: tis means te easiness wit wic a casting can be remo0ed from

te sand mold after it solidifies- Poor collapsibility means tat te sand aderes

strongly to te casting-


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,ai&a'i&ity*cost: tis is important because for e0ery ton of metal poured+ you need

%9 tons of sand- ;nd anoter point to consider is tat most of te sand cannot be

reused+ because it migt be damaged in te process- So to reduce cost+ , types of

sand migt be used+ one type wic will be te facing sand+ wic is te sand in

direct contact wit te casting- ;nd ten te bac1ing sand+ wic can be any type of

normal sand+ wit no special properties-

2. +rincip&es

Casting is a solidification process+ wic means tat most of te properties are

controlled by solidification penomena- ;lso+ most of te casting defects occur in te

solidification process- Solidification occurs in , steps+ wic are nuc&eationand

crysta& !roth- "ucleation is wen solid particles from witin te li4uid material-

/e internal energy of tese particles is lower tan tat of its surrounding medium+

and so tere is an interface between te two- /e formation of te surface at tis

interface re4uires energy+ so as nucleation occurs+ te material undercools+ becauseof te extra energy needed to form te internal surface- .t ten eats up again to te

free!ing temperature+ so tere crysta& !roth- ;ll nucleation represents a crystal+

wic grows as te eat of fusion is extracted from te li4uid until tere6s no li4uid

left- /e direction+ rate and type of growt can be controlled to get te best results-

.n general+ oo&in! urescan be used to control te 4uality of a casting- .n

general+ an area of te casting tat cools rapidly will a0e fine grain structure and if it

cools slowly+ it will a0e coarse grain structure-

/ere are , metods wic are te most widely used today: te "reen Sandand

,ir Setmetods-


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/e "reen Sandmetod consists of ma1ing molds wit wet sand+ ence te name

/e ,ir Setmetod uses dry sand wit no clay but instead fast curing adesi0es- .t

is also 1nown as no ba1e mold casting- .n tis process+ te sand is not rammed to

te flas1+ but ?ust poured in+ and ten because of te resin+ it solidifies at room

temperature- .t gi0es off a better finis tan oter types of sand molds- .t is

considered a cold setting process+ since no eat in in0ol0ed- /is process is mostly

used for brass+ ferric and aluminum alloys-

@en te process is finised+ some irregularities can present- Suc an irregularity is

called a Casting *efect+ wic is any irregularity in te casting process tat is

undesired- Some defects can be tolerated+ wile oters+ if tey can6t be fixed+ te

cast must be disposed of completely- /ere are ( main categories of defects: "as

+orosity+ Shrinka!e+ Mo&d Materia&+ +ourin! Meta&+ and Meta&&ur!ica&defects-

Gas Porosity Srin1age Porosity


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.nclusion Mold Sifting

2las Sort Casting

Hot Tears


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-. +rocedure

Commonly+ te basic process consists of steps:

)A Place a pattern in sand and create a mold- /e facing sand sould be strained

first+ to get finer particles and better finis-

,A Put te pattern and sand in a gating system- if tere are any crac1s andBor oles+

fix tem- ;dd te coating powder- /en place te upper part of te mold- Place

te upper part of te pattern- Redo te process- /en ma1e oles on top- Ma1e

te top smoot-


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%A ;dd water to te sides of te pattern- Remo0e te pattern- .f tere are any crac1s

andBor woles+ fix tem-


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/e next steps would loo1 someting li1e tis:

'A 2ill te mold ca0ity wit molten material

(A ;llow it to cool

A 8rea1 away te sand mold and remo0e te casting- 2or example in te picture+

we can see door andles-

Split Pattern of Green Sand Molding and Hollow Casting Production

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