AFS Casting Defect Handbook

Phone: (800) 537-4237

Appendix Title Page

Chapter Page

1 Broken or Cracked Castings... 5

2 Crushes, Pushups and Clamp-offs... 8

3 Cuts and Washes ... 12

4 Dirt, Slag and other Inclusions ... 16

5 Drops ... 25

6 Erosion Scabs ... 30

7 Expansion Defects ... 33

8 Gas Defects ... 38

9 Gross Segregation and ... 46

Carbon Flotation (Kish) 10 Hard Spots, Hard Areas and Chilled Spots ... 49

11 Hot Tears ... 55

12 Inverse Chills... 58

13 Mass Hardness... 61

14 Metal Penetration and Fusion... 63

15 Misruns and Cold Shuts... 68

16 Off Dimensions Related to Cores ... 75

17 Open Grain Structure ... 79

18 Poured Short ... 82

19 Ramoffs or Ramaways ... 83

20 Rough Surface... 85

21 Runouts and Bleeders ... 88

22 Scars, Seams and Plates ... 93

23 Shifts... 96

24 Shot Metal or Cold Shots ... 100

25 Shrinkage Cavities and Depressions ... 102

26 Stickers... 106

27 Swells, Strains, Sags and Core Fins ... 108

28 Veins and Fins... 113

American Foundrymen’s Society, Inc.

Des Plaines, IL 60016

Reprinted 1998

The American Foundrymen’s Society as a body Is not responsible for the statements and opinions advanced in this publication. Nothing contained in any publication of the American Foundrymen’s Society is to be construed as granting any right, by implication or otherwise, for manufacture, sale or use in connection with any method, apparatus or product covered by Letters Patent, nor as insuring anyone against liability for Infringement of Letters Patent.

Copyright 1972, 1984, 1997

Credits

This manual was prepared by the Molding Methods and Materials Group, Special Publications Committee 80-G, Section 2, Casting Defects:

George W. Anselman, Victor Rowell, Vice-Chairman Chairman Sales Representative Consultant, Anselman Foundry Construction Aggregates Corp. Services

Albert M. Prewitt, Edwin H. Phelps Secretary Research Supervisor Campbell, Wyant & Cannon American Cast Iron Pipe Co. Foundry Co.

Joseph Cunningham LeRoy E. Taylor Cunningham Patterns Sales Representative Manley Brothers Richard A. Green Charles W. Ward Foundry Sales Mgr. Foundry Consultant International Minerals & Benjamin Harris Co.

Chemical Corp.

James C. Lee AFS Staff Superintendent Ezra Kotzin Frank Foundries Corp. Technical Director

This software version was prepared by:

Clifford E. Couture Peter M. Wendt Vice President President Datalab, Inc. Datalab, Inc. Software & Imaging Software & Imaging

Introduction

Quality control implies both prevention and cure of casting defects. This text deals with the diagnosis and correction phases of quality control in the area of rejected castings or castings that require costly repair, grinding or cleaning.

Every business prefers a minimum of rejects. Intelligent effort in this direction will yield excellent returns on the investment of time and energy needed to make every producing individual zero-reject conscious.

There are correct and incorrect methods of approaching any problem. The steps in corrective procedure are expressed in the following outline:

1) Identify the defect

2) Obtain the facts. The record should answer such pertinent questions as where? when? how? how often?

3) Research for missing facts 4) Verify the defect

5) Try corrective action-one change at a time 6) Follow up.

Broken or Cracked Castings - Chapter 1

Description

This refers to castings, which have been broken or cracked by mechanical action, rough handling, or thermal shock.

Causes

I.

Casting and Pattern Design

1) Irregular sections, sections, such as isolated heavy sections, light sections or projections require careful handling at shakeout, cleaning, finishing and heat- treating.

2) Lack of fillets

3) Lack of proper reinforcing ribs, tie bars or stress relieving

II.

Pattern Equipment

1) Failure to provide proper break-off notches on the gates and risers

2) Flask bars that extend into deep pockets, not allowing normal collapse of the sand.

III.

Gating and Risering

1) Lack of adequate fillets

2) Incorrectly placed or dimensioned cracking strips and tie bars

3) A gating system which promotes stresses or segregation due to turbulence

Early rough shakeout of this gray iron casting broke the gates into the castings while they were hot and weak.

VI.

Core Practice

1) Poor collapsibility due to excessive hot compression strength 2) Low hot deformation when coupled with poor collapsibility 3) Rods or arbors that are too close to the surface of cores 4) Over-reinforced cores

VII.

Molding Practice

1) Mold rammed too hard

2) Rods, arbors, and gaggers which are too close to the mold surface 3) Risers or sprues too close to a flask bar

4) Excessive swabbing or sponging

5) Improper use of chills or excessive chilling

Poor design of the cracking strip increased the breakage of this malleable casting in the hard iron condition

VIII.

Metal Composition

1) Improper metal composition for the application

2) A composition having too high a shrinkage characteristic

IX.

Melting Practice

1) Excessive carbide stabilizers which promote high shrinkage 2) Composition having too high a shrinkage characteristic 3) Gaseous or over oxidized metal

4) Contamination

Careless finning caused this casting to break in the gate area.

The protruding section of bar on the casting shown tended to break off during cleaning, milling or shake out.

X.

Pouring Practice

1) Insufficient pouring temperature to promote proper collapsibility of sand and cores

XI.

Miscellaneous

1) Shakeout too hot or too rough

2) General carelessness in handling at shakeout 3) Improper packing in tumbling barrels or barrel blast

4) Careless and rough handling in loading or tumbled with light thin section castings 5) Careless and rough handling in loading or tumbled with light thin section castings 6) Improper piling or stacking

7) Banding too tight on pallets

8) Any mechanical handling that drops castings any distance into containers

Tight banding of pallets broke this casting.

Crushes, Pushups and Clamp-offs - Chapter 2

Careless handling of the mold during assembly caused this crush on the cope section.

Description

Crushes, pushups and clamp-offs are indentations in the casting surface. These defects are caused by disruption of the mold surface due to external or internal force or weight. The major cause of these defects is carelessness particularly related to flask equipment, rigging, and molding practice.

Causes

I.

Casting and Pattern Design

None

II.

Pattern Equipment

1) Worn patterns and core boxes. A worn pattern can result in the core print

being too small for the normal core. Conversely, a worn core box results it the core being too large for a normal print

2) Insufficient draft

3) Pattern not correctly mounted

4) Misalign cope and drag patterns, or plates 5) Worn pins and bushings

6) Core prints not properly marked 7) Lack of crushing strips

8) Core print too small to support the core

9) Warped or untrue pattern plate (cope and drag) 10) Excessive flexibility of matchplate

Crush caused by poor pin alignment.

11) Flask landing strips too high above parting line. This creates a condition of excessive loading at the sand-to-sand contact

III.

Flask Equipment and Rigging

1) Misalignment of flask equipment, pins, and bushings 2) Weights too heavy or uneven

3) Insufficient sand bearing surface 4) Warped or uneven flask joints

5) Worn stripping plate on molding machine 6) Improperly fitting, dirty, or crooked jackets 7) Worn pins and bushings

8) Uneven, dirty or burned bottom boards 9) Weak bottom boards

10) Improperly barred cope

IV.

Gating and Risering

1) Gating and risering do not, by themselves, create a crush although mounting gate runners too close to the pattern can result in an inadequate sand bearing surface.

V.

Molding Sand

1) Weak sand

2) Low green tensile strength may permit the cope to sag

3) Low green deformation causes the sand to crush rather than give during closing of flask 4) Low dry strength in a dry sand mold may fail to support the normal load

VI.

Core Practice

1) A core too large for the core print will fail to seat properly and cause a crush 2) A misaligned assembly will cause incorrect contact when the flask is closed 3) Core sagged out of shape may be the result of:

a. Rough handling while green b. Soft ram

c. Low green strength

d. Excessive water in the core mix e. Warped driers

f. Low warm strength such as from excessive solvent g. Improper cure

h. Reinforcement i.e.: rods, wires, or arbors 4) Warped cores (including shell)

3) Faulty bedding of molds on bottom boards or plates 4) Improper setting of the jackets

5) Careless core setting

6) Use of wrong chaplets or failure to use chaplets 7) Setting dirty jackets

A lump of sand on bottom caused this pushup.

Crush on camshaft gear blank; finished casting on left.

8) Stem chaplets not properly wedged or seated 9) Unshaved core prints and joints

10) Failure to wedge flask joints

11) Careless handling of molds during carry-out or on the conveyor 12) Dropping of the weights

VIII.

Metal Composition

None

IX.

Melting Practice

None

X.

Pouring Practice

1) Resting ladles or heavy objects on molds

XI.

Miscellaneous

1) Rough handling during any part of the molding process can break or crush a mold 2) Resting heavy objects on the mold

Uneven clamping of the small mold crushed one side of the mold face.

Cuts and Washes - Chapter 3

Description

Cuts or washes are rough spots and areas of excess metal caused by erosion of the mold or core surface by metal flow. This definition differentiates between a cut and an erosion scab, in spite of the fact that the two defects are often similar or identical in general appearance. It is necessary to make such a distinction because the cure for the two defects may be diametrically opposed.

Causes

I.

Casting and Pattern Design

1) A design that promotes excessive metal flow over any given area of the mold surface 2) A design which includes unavoidable nozzle effects within the casting

II.

Pattern Equipment

1) Pattern layouts which prevent correct gating. Equalized flow is essential if excessive localized heating of sand in mold or core is to be avoided.

III.

Flask Equipment and Rigging

1) Flask too small to permit proper gating 2) Flask bars too close to pattern

IV.

Gating and Risering

1) A gate which forces metal to impinge on a mold or core surface as in the case of gating into a thin wall of a casting

Drag view of cuts or washes caused by low strength sand.

2) A downsprue which does not provide a pool or well of metal ahead of the gating system

3) Too much metal across any mold surface will eventually redissolve the metal skin which is formed during early stages of pouring

4) Excessive metal velocity across a given mold surface 5) Unequal distribution of metal through the gating system

Inclusions caused by the cuts and washes on drag side.

V.

Molding Sand

1) Inadequate hot strength 2) Insufficient clay

3) Inadequate water to properly activate the clay and improper mixing 4) Excessive use of certain additives such as cellulose

5) Hot molding sand

6) Low hot strength self-curing binders

VI. Core Practice

1) Soft core surface

2) Overcuring or undercuring 3) Insufficient binder or water 4) Improper mixing

5) Improper application and control of core wash 6) Vents or reinforcements too close to the surface 7) Poorly patched cores or filled hook holes 8) Nonuniformly made cores

9) Low density

10) Damage in handling

11) Soft cores (rising self-curing binders) a. Overmixing

b. Improper sand temperature c. Use beyond bench life d. Stripping too early

e. Excessive variation of acid demand of sand

VII.

Molding Practice

1) Soft or nonuniformly rammed molds. Hot strength varies greatly depending on the mold Hardness or moisture

2) Mold edges burned by excessive drying temperatures 3) Gaggers, bars or soldiers set too close to mold surface

VIII.

Metal Composition

IX.

Melting Practice

None

X.

Pouring Practice

1) Excessive pouring temperature for molding or core materials used 2) Hard pouring

XI.

Miscellaneous

1) Excessive parting or solvent such as kerosene can materially change the hot and dry strength 2) Hard pouring

Cut caused by low strength sand.

Dirt, Slag and Other Inclusions - Chapter 4

Description

Inclusions are surface or subsurface particles of sand, slag, dross, oxides or other materials imbedded in the metal. They may originate from the molds, cores, metal, ladles or careless practices.

Causes

I.

Casting and Pattern Design

1) Those design factors which contribute to scabs, cuts, washes and erosion will intensify the tendency toward inclusions in a casting

II.

Pattern Equipment

1) Improper coating for materials involved. Some pattern coatings produce a tendency towards sticking of the sand

2) Insufficient clearance for setting cores and closing 3) Lack of fillets

4) Insufficient draft

5) Loosely mounted pattern or gating system

6) Worn flask landing areas can create a crush or disrupt sand gains 7) Inaccurate partings

Use of excessive liquid parting material on the pattern left these kish tracks (classified as inclusions).

III.

Flask Equipment and Rigging

1) Any factor in the rigging which creates a rubbing or gouging effect during the closing of the mold, or setting of cores

2) Warped or dirty flasks

3) Worn or crooked pins or bushings

4) Inaccurate core setting assembly or inspection jigs 5) Dirty pins and bushings

6) Inadequate locators

IV.

Gating and Risering

1) Factors causing scabs, cuts and washes

2) Gating systems that create slow pouring can cause scabs particularly on cope surfaces

3) Gating systems which create a non-filled runner should be avoided since the cope of such runners will eventually scab and drop sand into the gating system

Ineffective slag trap permitted ladle slag to locate at top of the boss.

4) Gating which promotes high velocity metal flow

5) The choke or the area of the choke core in the gating system may be inadequate to stop the flow of slag or dross

6) Exothermic materials if used in such a way as to permit the by-product of the reaction to enter the mold or casting

Defect caused by contaminant (boric acid) in molding sand.

V.

Molding Sand

1) Sands with low physical properties, such as low green, dry and hot compressive strength 2) Mold gas-metal reaction

3) Low fusion point materials

4) Coatings too heavy, not dried, or wrong for the purpose

VI.

Core Practice

1) Improperly bonded or cured cores 2) Excessive core gas-metal reaction 3) Improperly cleaned cores

4) Premature collapse of cores in molds and gating system 5) Core wash too heavy, not dried, or wrong for the application 6) Broken cores

Result of broken core

.

VII.

Molding Practice

1) Any molding factor which contributes to displaced or loose sand in the mold cavity 2) Sloppy or careless molding

3) Excessive use of liquid parting 4) Loose sand from cores or molds

Result of coarse seacoal in molding sand.

Broken edge of mold caused by low strength sand, which permitted sand grains to wash into other sections of the casting.

Loose sand left in the mold caused these sand inclusions on the drag face.

Inclusions of aluminum in a copper alloy caused by contamination during melting.

VIII.

Metal Composition

1) In many metals, it is possible for off-analysis to create a separation of slag or slag-like materials 2) In cast irons, high sulfur may lead to sulfide slag, which could separate during cooling

3) Oxides and intermetallic compounds in steel, copperbase or light alloys

IX.

Melting Practice

1) Undissolved alloy addition, inoculant, or deoxidizer 2) Dross resulting from alloy addition or inadequate fluxing

3) Too low a melting temperature may result in the inability of the slag or dross to separate 4) Insufficient slag cover during melting to maintain metal cleanliness

5) Thin watery slag

6) Refractory-metal reaction can easily release impurities into the metal 7) Excessive fluxes or deoxidizers

X.

Pouring Practice

1) A wet or boiling lip on a ladle can promote, or interfere with proper separation of slag 2) Careless skimming of the ladle can result in excess slag being carried into the mold 3) Low pouring temperature

4) Intermittent or slow pouring 5) Dirty ladles

6) Ladle linings must be adequate, to avoid mechanical or chemical loss

XI.

Miscellaneous

\

Metallic oxides from ladle entered the mold to cause this (can be corrected by proper gating).

Section of a centrifugal casting showing slag inclusions originating from refractory lining material.

Intermittent pouring trapped slag in the metal stream and permitted it to enter the mold.

View of an inclusion caused by a rag left in mold.

View of an inclusion caused by a rag left in mold.

Core wires in casting cavities.

Core wires in casting cavities.

Poorly designed pouring basin prevented proper choke and permitted slag to enter mold

.

Poorly skimmed ladle permitted slag to enter the mold cavity.

Drops - Chapter 5

Typical result of the drop of one part of a green sand pocket.

Description

A drop is a casting defect due to the loss of a portion of sand from the cope or other overhanging section. In appearance, the defect resembles a sticker.

Causes

I.

Casting and Pattern Design

1) Deep pockets or inadequate draft 2) Protruding or overhanging sections

II.

Pattern Equipment

1) Insufficient draft or backdraft

2) Improperly designed parting creating narrow pockets

III.

Flask Equipment and Rigging

1) Too many patterns for the flask size 2) Insufficient cope height

3) Weak, loose, or springy flasks and bars

4) Misaligned, bent, or sprung bands can result in the lack of rigidity 5) Not enough bars, or bars improperly designed

6) Rough handling due to faulty equipment 7) Improperly fitted, dirty, or crooked jackets

Backdraft on the cracking strip weakened sand pocket and permitted a drop.

IV.

Gating and Risering

1) Any placement of runners and risers that results in narrow sand pockets.

V.

Molding Sand

1) Inadequate green properties

2) Inadequate mold properties related to sand moldability 3) Low mold Hardness or insufficient mold strength 4) Low dry strength (dry sand molding)

5) Poorly prepared sand

VI.

Core Practice

1) A weak or inadequately secured core or core assembly 2) Core failure in centrifugal casting appears as a drop

VII.

Molding Practice

1) Nonuniformly rammed or soft rammed molds

2) Gaggers, nails, soldiers, bars, etc. too close to the mold cavity 3) Insufficient mold reinforcement

4) Careless core setting may fracture a portion of the mold surface 5) Improper closing of the mold

6) Rough handling

7) Separation of molded layers of sand such as a separation between a facing and backing sand 8) Insufficient venting

Inadequate draft in the pocket contributed to a drop, with this result.

A nonuniform ram was the major cause of drop in this large mold section.

None

X.

Pouring Practice

1) Bumping molds with ladle

Inadequate green compressive strength in molding sand.

XI.

Miscellaneous

1) Foreign material in sand

2) Mold explosions which occur when the gas ignites

Low green sheer strength of molding sand permitted

pocket to shear under the drop and float.

3) Vibration caused by heavy jolt machines or other equipment 4) Rough handling

Sand broke off the core during setting and dropped into the drag. During pouring the sand section floated to the cope.

Weight carelessly dropped on mold.

Erosion Scabs - Chapter 6

Typical scab on cope surface caused by excessive slicking

Description

An erosion scab is a defect usually occurring in the drag, in which the loosened sand has been eroded away by the motion of the metal, and has left a solid junction between the casting and the defect. The defect can be removed usually leaving a solid surface. The erosion scab may result in sand holes or sand inclusions in some other part of the casting.

Causes

I. Casting and Pattern Design

1) A design which necessitates gating through thin sections

II. Pattern Equipment

1) Insufficient fillets on gates and abrupt section changes 2) Parting the pattern to necessitate gating through thin sections

III. Flask Equipment and Rigging

1) Bars improperly placed, preventing uniform ramming

2) Bars, soldiers, and gaggers coated with wet clay and too close to the mold surface 3) Rigging in too small a flask so that the vertical pattern wall is too close to flask or bar 4) Plugged flask vents

Typical scab on cope surface caused by excessive slicking

Scab caused by metal impingement on sand surface (gates located on inside of the two bosses).

IV. Gating and Risering

1) Gating which creates interrupted metal flow 2) Metal impinging on and disrupting sand surface

3) Gating which creates localized overheating of the sand

There is a fine line of distinction between an erosion scab and a cut or wash. As far as metal flow alone is concerned, the two defects have the same cause. In the case of an erosion scab there is not enough impingement to actually cut, in the absence of expansion, but is enough when expansion stresses exceed the strength of the sand

V. Molding Sand

1) High moisture content 2) Excessive volatile material

3) Insufficient carbonaceous (or cellulose) material for expansion control 4) Insufficient hot deformation

5) Improper conditioning of the sand, such as clay or moisture not uniformly distributed 6) Under tempered sand

VI. Core Practice

1) Excessive moisture in or on the core

2) A core blow may cause an erosion scab on the adjacent mold surface 3) Insufficient hot deformation

4) Core wash not properly dried 5) Insufficient penetration of the wash 6) Undercured cores

7) Excessive core wash

Excessive pouring temperature caused erosion scab on the cope surface.

VII. Molding Practice

1) Nonuniform ramming 2) Gaggers too close to pattern 3) Excessive clay on gaggers 4) Excessive slicking

Erosion scab caused by wet sand, aggravated by hard ramming.

5) Moldwash, not properly dried 6) Insufficient penetration of wash 7) Excessive wash

VIII.

Metal Composition

None

IX. Melting Practice

None

X.

Pouring Practice

1) Excessive pouring temperatures 2) Interrupted, or slow pouring

XI.

Miscellaneous

Expansion Defects - Chapter 7

Typical expansion defect on cope surface.

Description

Stage one in this family of defects is RATTAILS which are irregular lines caused by low temperature expansion of the mold surface resulting in a fault in the mold surface.

Stage two is BUCKLES which are V-shaped indentations which may occur by themselves or under an expansion scab.

Stage three is EXPANSION SCABS, which are rough layers of metal connected to the main body of the casting by a vein of metal.

Stage four is COPE SPALLS or pull downs which are indentations in the cope surface of the casting. Depending on the time of formation they may have the appearance of a buckle, rattail, shrink, or blow. Blackening scabs are a special form of a scab in which the defect is related to the coating rather than to the sand.

Since sand surfaces go through the process of expansion and contraction during the pouring and solidification of the casting, it is a common practice to assume that the sand is the principal cause. This is a mistake, as these defects are all closely related to all practices.

Typical rattail from interrupted metal flow.

Causes

I. Casting and Pattern Design

1) Large uninterrupted flat surfaces 2) Inadequate radii

3) Large, smooth uninterrupted concave or convex surfaces

II. Pattern Equipment

1) Inadequate fillets

III. Flask Equipment and Rigging

1) Bars or flask too close to pattern surface 2) Rigging which prevents proper pouring speed 3) Flask too shallow

IV. Gating and Risering

Buckle (which had a scab before cleaning) caused by inadequate carbonaceous or cushioning material.

Scab (with buckle underneath) related to inadequate hot deformation.

VI. Core Practice

1) Low hot deformation

2) Green sand or green top cores (See “Molding Sand”) 3) Nonuniform shell thickness

4) Rods or arbors too close to the core surface 5) A nonuniform ram

6) Insufficient penetration of wash 7) Improper type of wash

8) Excessive wash

9) Insufficient drying of wash 10) Poor sand grain distribution

VII.

Molding Practice

1) Nonuniform or hard ramming 2) Insufficient penetration of wash 3) Excessive wash

4) Insufficient drying of mold or wash

5) Gaggers, soldiers, and bars too close to mold surface 6) Excessive trowelling and slacking

7) Downsprue and risers too close to bars and flask

Expansion scab in dry sand mold after removal from casting. Defect caused by excessive clay wash of a gagger close to the costing surface.

Uneven ramming of drag mold permitted pattern

plate to bend and prestress the mold surface, (defect corrected by hard ramming the drag.

VIII. Metal Composition

1) Metals vary in their tendency toward expansion defects as they vary in temperature and pouring rate

IX. Melting Practice

1) Factors which control fluidity

X. Pouring Practice

1) Pouring too slow 2) Pouring too hot

XI. Miscellaneous

1) Foreign material between centrifugal mold and sand, which appears similar to and expansion type defect

Gas Defects - Chapter 8

Pinholes caused by excessive moisture in molding sand combined with low permeability and poor grain distribution (6 screen sand).

Description

“Blows” or gas holes in castings are cavities, either spherical, flattened or elongated. They are related to localized gas (including entrapped air) pressure that exceeds metal pressure in any locality during

solidification of the metal. One of the greatest problems with core blows is the ease with which they may be confused with mold blows. Since gas travels upwards in the mold it is quite possible for a gas bubble to form from a core and then travel toward the cope surface.

Pinholes, blisters, and body scars as well as certain types of porosity are variations of gas holes. In gas defect problems, there are several possible sources, among which are cores, molding sand and metal. The volume of gas may be kept unchanged but offset by providing easier escape or by providing more metal pressure, forcing gas through existing vents.

Causes

I.

Casting and Pattern Design

1) Insufficient print or outlet provided for venting 2) Design that prevents adequate metal pressure 3) lnsufficient vents at the parting line

II.

Pattern Equipment

None

Pinholes from excessive permeability and moisture remedied by lowering permeability from 140 to 90-110 and reducing moisture from 4.2% to 2.8-3.3%.

Gas blows caused by clay balls (excess fines).

III.

Flask Equipment and Rigging

1) Bars too close to the mold surface 2) Flask wall too close to mold surface 3) Cope too shallow

4) Sprues and risers too close to bars or flask walls 5) Insufficient venting in flasks

IV.

Gating and Risering

1) Insufficient cope height 2) Gating causing turbulence

3) Gating design that causes interrupted flow of metal 4) Inadequate riser height or size

5) Improper sprue or gate design allowing air or mold gas to enter metal stream 6) Insufficient spinning speed in centrifugal casting of pipe

7) Insufficient vents and flow-offs

V.

Molding Sand

1) High moisture content

2) Inadequate permeability for the volatile materials involved 3) Foreign material in sand-shot, nails, coke, cinders, etc. 4) Clay balls

5) Poorly mixed sand

6) Coarse particles of gas-producing materials

7) Coatings containing excessive gas-producing materials

8) Excessive permeability in skin-dried molds, allowing sweat-back 9) Excessive or insufficient reducing volatile materials

Blow due to excessive moisture in molding sand.

VI.

Core Practice

1) Underbaked or undercured cores 2) Excessive binder

3) Inadequate permeability for conditions involved 4) Inadequate venting

5) Excessive or wet core paste

6) Core wash too heavy, skin broken or not dried

7) Excessive gas-producing material either in the core sand or wash 8) Cores that absorb moisture either in storage or in the mold 9) Exposed hooks, wires or hangers

10) Chill or sealing materials not dried

11) Hooks or hanger holes filled and not dried

12) Foreign materials, such as roots, leaves, coke, coal, etc. 13) Excess nitrogen content in resin binders

14) Poorly mixed core sand

Improperly conditioned core sand (lumps of cereal

binder and excessive moisture are potential sources of gas and can cause blows).

Vents plugged with iron during pouring caused a major defect on the cope surface.

Blow in manifold at a hot spot, caused by a hard core.

Close-up of the blow shown above.

VII.

Molding Practice

1) Combinations of hot and cold materials 2) Improper venting in green or dry sand molds 3) Insufficiently dried molds

4) Hard spots caused by improper ramming for conditions involved 5) Gagger, soldiers, arbors, or bars too close to pattern

6) Clay wash too heavy on gaggers

7) Excessive slicking and patching of green sand 8) Dough roll too wet or too close to mold cavity 9) Wet pouring basins and gating systems 10) Insufficient sand in flask

11) Excessive liquid parting (especially in pockets or depressions) 12) Mold wash or coating too heavy or not dried

13) Failure to lead core vents out of molds 14) Vents too close to surface causing sweatback

Gas blows-cold iron, high moisture.

Blow in the cope side of a pump impeller caused by wet sand and hard ramming.

Result of aluminum in iron.

VIII.

Metal Composition

1) Gas dissolved in molten metal

2) Metallic impurities e.g. aluminum, bismuth, lead, tin, antimony and boron 3) Greasy or rusty scrap

4) Enameled scrap containing boron

Blister on casting caused by hard ramming and wet sand.

Upper section shows a chaplet blow caused by improper coating material or a damp chaplet. Lower section shows a good fusion.

Blows due to cold melted metal.

IX.

Melting Practice

a. Too short a boil b. Insufficient deoxidation c. Wet refractories 2) Iron

a. Cold melted metal b. Oxidized iron

c. Tramp elements (e.g. aluminum, lead, tin, antimony, boron, bismuth, enameled iron d. Stripping too early

e. Excessive variation of acid demand of sand 3) Non-ferrous

a. Improper fluxing or degassing procedures b. Excessive melting temperatures

c. Wet refractories

d. Wet or cold melt addition e. Wet or cold skimmer

f. Metallic impurities or tramp elements g. Oxidized metal

X.

Pouring Practice

1) Cold, damp, or green crucibles or ladles 2) Pouring cold metal

3) Interrupted pouring

4) Ladle or crucible too high above mold 5) Slow or fast pouring

6) Improperly cleaned ladles 7) Heel of metal left in ladle

8) Insufficient spinning speed in centrifugal casting

XI.

Miscellaneous

Gross Segregation and Carbon Flotation (Kish) - Chapter 9

Dross in ductile iron.

Description

Segregation is the metallurgical or mechanical separation of one or more elements during solidification. Normally this is a function of metal composition and cooling rates. Kish is free graphite separated from molten iron.

Causes

I.

Casting and Pattern Design

1) Too great a difference in metal sections causes segregation due to slow cooling in the larger sections if the composition is planned for the more rapid cooling sections

2) A section of mold or core that promotes heat retention and could promote localized segregation

II.

Pattern Equipment

None

Ill. Flask Equipment and Rigging

1) Rough running flask (out of balance) in centrifugal castings have been known to promote segregation

IV.

Gating and Risering

1) Distribution of gates and risers promoting heat retention in localized area

2) Localized hot spots at the gate or riser junction could slow down cooling to the point that gross segregation is found in the gate junction or riser neck

3) Turbulent flow of metal changes the normal cooling rate

V.

Molding Sand

1) Abnormally slow heat transfer due to the use of insulating materials or molding aggregates can change the cooling rate of a given section

VI.

Core Practice

1) Underbaked oil-bonded cores which create an exothermic reaction causing excessive heating of the core could change the cooling rate of an adjacent metal section

2) Insulating gas films such as in shell cores may act to change the rate of heat transfer from the metal section into the sand

VII.

Molding Practice

1) Introduction of any insulating material such as asbestos or perlite can produce localized slow cooling 2) Incorrect use of exothermic molding materials changes the cooling rate of metal sections adjacent to

these materials

VII Metal Composition

1) Gray iron and malleable. The carbon equivalent may be too high for the cooling rate involved. The eutectic point in these systems is seldom found exactly at 4.3 percent carbon equivalent

Kish caused by high carbon equivalent.

2) Phosphorus too high for the application has an influence on the eutectic formation.

3) Insufficient carbide stabilizers permit free carbon to segregate in high carbon equivalent irons 4) Excessive use of graphitizers may have a direct effect on kish formation in addition to their

obvious influence on carbon equivalent

5) Spheroidal graphite iron (ductile iron) . There is an added influence from the use of either excessive magnesium treatment or excessive secondary inoculation

6) High sulfur can contribute to segregation of magnesium sulfide and other segregations which are thrown out of solution by the nodularizing treatment

7) Aluminum plus titanium in excess of .10 percent produces a segregation of ternary carbide eutectics in iron

8) Steel does not usually exhibit gross segregation except in high or special alloys. High sulfur or leaded steels can show segregation. Special high copper steels may also show segregation if the copper is in excess of approximately .6 percent

9) In aluminum, copper or other alloy additions exceeding the solubility limit may show as gross segregation

IX. Melting Practice

1) Cupola melted gray iron and ductile iron may develop segregation as a result of faulty melting practice which produces an unintended change in composition. Improper balance of air to coke promoting carbon pickup will produce an undesirable level of carbon equivalent

2) Melting too hot causing excessive carbon pickup at the beginning of a heat can produce an off- analysis and kish.

3) Nonuniform chemical composition, due to variation in size of materials charged, produces variations in carbon and possible segregation

5) Malleable: Melting too hot, too fast, or with a carbonizing flame can result in excessive carbon equivalent, or may result in a direct seeding effect which then starts kish accumulations 6) Steel: Improper melting or deoxidation

7) Aluminum: Excessive superheat starts a grain growth phenomenon which may induce or show as segregation

8) Magnesium: Careless makeup of the charge introduces undesirable and segregating type impurities

9) Brass and Bronze: Leaded bronzes not adequately stirred will show segregation of the lead 10) Dirty or skulled ladles causing contamination introduce segregation either because of a composition change or because the impurities are only partially absorbed by the melt 11) Carelessness in segregating returned scrap permits the alloy to be melted with an incorrect

analysis

X.

Pouring Practice

1) Pouring below the temperature of solubility is most apt to occur when alloying elements differ widely in their solubility temperature

2) Cooling before pouring permits some components to come out of solution even though the original melt was adequately blended and alloyed

3) Pouring too hot in the case of leaded bronze permits the lead to segregate during the

solidification process. These alloys must be poured as close to the solidification temperature as possible and be stirred immediately before pouring

XI.

Miscellaneous

Hard Spots, Hard Areas and Chilled Spots - Chapter 10

Flask bar close to casting surface caused hard spot, corrected by cutting out one section of the bar (see diagram).

Brinell hardness indentations indication nonuniform hardness.

Description

Hard spots, hard areas and chilled spots in a casting are localized zones of excessive hardness.

Causes

I.

Casting and Pattern Design

1) Thick and thin sections

2) Metal chemistry, as related to casting section thickness

II.

Pattern Equipment

1) Worn or warped patterns and core boxes cause thin sections 2) Mismatched pattern equipment causing thin sections

III.

Flask Equipment and Rigging

1) Mold cavity too close to bars or wall of flask 2) Shift created by worn flask pins and bushings 3) Weak or warped flasks and bottom boards

1) Gating that fails to provide adequate heat to thin sections

Hard spots caused by use of core wash contaminated with tellurium.

V.

Molding Sand

1) Wet spots 2) Tramp materials

VI.

Core Practice

1) Wires or rods too close to surface 2) Improper or wet coating

3) Warped cores (causing thin sections) 4) Improper print size (causing thin sections)

VII.

Molding Practice

1) Careless core setting (causing thin sections) 2) Arbors, rods, gaggers, bars too close to mold cavity 3) Excessive nailing

4) Wash too thick and not dried 5) Excessive or improper chills

VIII.

Metal Composition

1) Metal composition not suitable for section size 2) Tramp elements from the charge

Nonuniform section, which required dense hub, promoted chilled edges on the outer sections of the vanes.

Nonuniform casting hardness.

Nonuniform casting hardness.

Typical hard spot that showed up on machining.

Hard spots from undissolved ferroalloy additions.

Nonuniform section, which required dense hub, promoted chilled edges on the outer sections of the vanes.

IX.

Melting Practice

1) Cold melting that results in poor alloy distribution 2) Excessive Superheat and oxidation

3) Wet refractories in furnaces and ladles

4) Crucibles or ladles containing residue from prior heats 5) Incorrect inoculation

a. Wrong inoculant

b. Inoculant added at the wrong time c. Failure to use inoculant when required

d. Improper inoculant that does not go into solution readily. e. Metal too cold to dissolve inoculant

X.

Pouring Practice

1) Cold metal because of cold or wet ladles 2) Skull left in ladles

XI.

Miscellaneous

1) Shaking out too hot (insufficient sand for insulation on casting) 2) Localized heating from cut-off torch or grinding

3) Failure to heat treat after welding 4) Wrong composition of welding rod 5) Uneven temperature of metal mold

View of hot tear in chilled casting caused by low phosphorus content.

Hot Tears - Chapter 11

View of hot tear in chilled casting caused by low phosphorus content.

Description

A hot tear is a crack in the casting which occurs while it is still hot, or either solid or semisolid.

Causes

I. Casting and Pattern Design

1) Lack of adequate fillets

2) Abrupt change in section thickness

3) Any design which causes the mold to resist metal contraction

II. Pattern Equipment

1) Incorrectly placed or sized cracking strips and tie bars

III. Flask Equipment and Rigging

1) Flask bars too near the riser or sprue 2) Flask bars preventing casting contraction 3) Pattern too large for the flask

IV. Gating and Risering

1) Gates and risers that prevent normal contraction

V.

Molding Sand

1) Poor collapsibility

2) Low sintering-point materials which form a ceramic bond

VI. Core Practice

1) Poor collapsibility

2) Low hot deformation with poor collapsibility (high hot strength) 3) Reinforcement rods too close to core surface

4) Failure to shake out reinforced core soon enough

VII. Molding Practice

1) Hard ramming

2) Rods, gaggers, etc., too close to mold surface

Cracked casting caused by failure of core to collapse.

Crack in drag section due to excess amount of pitch binder in core.

Core rods too close to casting surface.

3) Riser or sprue too close to bars or flask wall 4) Excessive swabbing or sponging

5) Failure to use chill when specified

6) Uneven ramming that causes swell and prevents contraction

VIII.

Metal Composition

1) Wrong composition for the design

IX.

Melting Practice

1) Excessive carbide stabilizers

2) Wrong composition due to careless charging 3) Presence of tramp elements

4) Charging contaminated scrap

X.

Pouring Practice

1) Pouring temperature too low to promote collapsibility

XI.

Miscellaneous

1) Shakeout too soon

2) Cooling too fast after shakeout-fans at shakeout 3) Spinning speed too high in centrifugal casting 4) Rough flask or mold in centrifugal casting

Inverse Chills - Chapter 12

Inverse chill on test bar caused by cold metal and wet sand.

Description

Inverse chill, also known as reverse chill. This condition is common in gray iron, ductile iron and malleable castings. Casting sections where the interior is chilled or white, while the outer sections are mottled or gray.

Causes

I. Casting and Pattern Design

1) Thin sections adjacent to heavy sections in malleable iron

II. Pattern Equipment

1) None

III. Flask Equipment and Rigging

1) None

IV. Gating and Risering

1) None

V. Molding Sand

1) Wet sand and cold metal

VI. Core Practice

Inverse chill caused by cold metal on wet sand.

VII.

Molding Practice

1) Any practice involving excess or free water

VIIl. Metal Composition

1) (carbon equivalent too high for casting design 2) The presence of non-ferrous metals in the iron 3) Carbide stabilizers, such as tellurium, chrome, etc. 4) Sulfur content not balanced with manganese

IX

Melting Practice

1) Any condition which would allow or lend itself to the solution of free Hydrogen gas in the metal 2) Hydrogen atmosphere from low coke bed in the cupola

3) Wet linings in cupola, electric, or air furnace

4) Use of contaminated metals in charge, such as die cast non-ferrous metals 5) Boiling metal caused by wet runners or spouts

6) Wet bottom sand in the cupola

7) Moisture in the blast, particularly in hypereutectic iron, such as piston rings 8) Inadequate inoculations for the conditions of the melting previously described

X. Pouring Practice

1) Wet ladles or ladle lips

Mass Hardness - Chapter 13

Chill sequence indicates occurrences of charge material contamination

when stainless steel scrap was inadvertently charged instead of regular steel scrap.

Chill sequence indicates occurrences of charge material contamination when stainless steel scrap was inadvertently charged instead of regular steel scrap.

Description

Mass Hardness is a condition in which the entire casting is too hard for the application.

None

II.

Pattern Equipment

None

Ill.

Flask Equipment and Rigging

None

IV.

Gating and Risering

None

V.

Molding Sand

1) Wet sand in combination with off analysis

2) Use of other material, such as zircon sand or chromite sand that has a more rapid transfer of heat

VI.

Core Practice

1) Excessive use of chill coat

2) Too thin a layer of sand over arbors

VII.

Molding Practice

1) Improper use of chill techniques 2) Misapplied chill washes

3) Low temperature of the molds in die casting or permanent molds 4) Inadequate insulation in permanent mold

VIII.

Metal Composition

1) Incorrect metallurgy

2) Steel-excessive carbide stabilizing alloys 3) Gray and ductile iron-too low carbon equivalent

a. Tramp element

4) Lack of inoculation in thin sections

5) Malleable-tramp elements that prevent nodulizing or malleablizing

6) Aluminum-alloys that increase mass hardness, e.g. iron, magnesium or other trace alloys 7) Magnesium-excessive silicon or aluminum

8) Brass and Bronze-incorrect composition, excessive impurities a. Wrong combination

b. Contamination

c. Careless control of various alloy returns

IX.

Melting Practice

1) Off analysis

2) Oxidizing melting conditions 3) Super heating of most metals 4) Careless charging

5) Low coke bed in cupola

X.

Pouring Practice

1) Oxidized metal

2) Wet, dirty and contaminated ladle spouts and runners 3) Pouring too cold in thin sections

XI.

Miscellaneous

1) Air quench due to early shakeout 2) Improper heat treatment

3) Over-chilling with water-cooled permanent molds 4) Unintentional water quench

Metal Penetration and Fusion - Chapter 14

Penetration due to soft-rammed core.

Description

Metal penetration is a condition in which the metal or metallic oxides have filled the voids between the sand grains without displacing them or by chemically changing the silica or binder. In conventional molds or cores this can take place because of an open grain or surface porosity. In high density molds iron oxide readily combines with the silica to form a fayalite which is fluid at several hundred degrees lower temperature than that of the original metal. Generally, the higher the free moisture content at the metal sand interface the greater will be this phenomena.

Fusion is a related surface defect having a rough glossy appearance resulting from metallic oxides acting as a flux on the sand or low fusion binders which melt leaving voids on the surface. Controlled fusion may result in a hard cake or fused layer which peels away from the casting leaving a smooth finish. As the fusion

progresses it results in penetration.

Causes

I.

Casting and Pattern Design

1) Sharp corners

2) Overhanging or protruding sections

3) Thin core or sand section surrounded by heavy metal

II. Pattern Equipment

1) Pattern equipment constructed so as to promote uneven or soft ramming 2) Improper location of parting line which induces soft ramming

3) Improper location of the pattern on the plate causing narrow pockets 4) Multiple patterns mounted too close together

5) Improper location of sprues, risers, and runners 6) Inadequate draft

7) Pattern equipment constructed to promote excessive metal pressure such as a vertical rather than horizontal mounting.

1) Design and construction of flask equipment which promotes uneven or soft ramming 2) Excessive cope height

3) Lack of venting of flask and bottom boards in high density molding 4) Metal inserts or chills which act as condensers for moisture

IV. Gating and Risering

1) The location of gates and risers which promote localized overheating of the sand 2) Incorrect ratio of sprue, runner, and gate permitting metal oxidation during pouring 3) Pouring cup or sprue designed so as to permit aspiration of air

4) A riser neck which overheats the sand

Photomicrograph showing type of metal structure often found between sand grains and at a considerable distance from mold / metal interface; original photo 400X.

V.

Molding Sand

1) A low sintering or low fusion sand or binder

2) Any sand condition that promotes nonuniform density

3) Improper distribution of the sand grains which induce poor ramming

4) Poor flowability or moldability caused by: moisture segregation; poorly mixed sand; excessive moisture;

excessive cereal; excessive green deformation; and prepacked or lumpy sand 5) Nonuniform coating of shell sand

6) Insufficient carbonaceous or deoxidizing material which will prevent the water vapor from reacting with

the metal

7) Excessive mold permeability or, in the case of high density molding, insufficient permeability

VI.

Core Practice

1) Too low a sintering or fusion point of sand or binders

A typical hard mold penetration caused by using a green sand mold rammed to 85-90 hardness.

3) Soft rammed cores 4) Plugged vents

5) Improperly tucked sand under loose pieces 6) A rough or porous core surface

7) Core surface which is bruised or abraded 8) Improper or insufficient release agent

9) A partially disintegrated core surface due to overbaking 10) A broken or disturbed core wash due to rough handling 11) A dirty core box

12) In self curing binders; improper ratio of catalyst to binder 13) Poorly mixed core sand

Fusion of silica on steel and ductile iron.

Complete fusion of iron into the core because the core was underbaked.

Insufficient drying of mold wash created a penetrated area.

16) Low hot compressive strength 17) Poorly cleaned or finished cores

18) Dipped or sprayed cores that are not redried 19) Cores that have picked up moisture during storage

20) Low air pressure for core blower or rammer which results in soft-rammed cores

VII. Molding Practice

1) Soft or uneven ramming 2) Excessive ramming or density 3) Poorly patched areas

4) Loose fitting stop-off

5) Uneven or insufficiently dried mold coatings 6) Excessive use of parting compounds 7) Insufficient facing to cover the pattern

8) Low air pressure on molding machine or rammer

9) Any combination of hot and cold materials which can cause condensation

10) Combining high permeability facing sand with a low permeability backing sand particularly in high density molding

VIII. Metal Composition

1) Metals which form fluid oxides

2) Low melting constituents such as lead or tin 3) Excessive phosphorus in copper alloys

4) Metal oxides which readily react chemically with sand 5) Metals requiring high pouring temperature

IX. Melting Practice

1) Oxidized metal

2) The excessive use of any fluxing-type material such as 3) limestone, soda ash, and fluorspar

4) Melting too hot.

X. Pouring Practice

1) Excessively high pouring temperature 2) Excessive pouring height

3) Poor skimming practice

XI. Miscellaneous

1) Any factor involving free moisture in the mold cavity

2) Shaking out too cold or too late-particularly in high density molding 3) Sand coated with low fusion materials

4) Sand or binder reacting chemically with metal oxides 5) Insufficient venting in high density molding

Misruns and Cold Shuts - Chapter 15

Laps or cold shuts caused by pourer missing pouring cup for a matter of seconds.

Description

A misrun casting is one which lacks completeness due to failure of the metal to fill the mold cavity. There may be a smooth rounded-edge hole through the casting wall. One or more extremities may be only partially filled out.

A cold shut casting is one in which a definite discontinuity exists due to imperfect fusion where two streams of metal have converged. This defect may have the appearance of a crack or seam with smooth, rounded edges.

Both defects may be related to insufficient fluidity of the metal or excessive gas pressure in the mold. It is well to check the chapter on Gas Defects before assuming that cold metal is the only cause.

Causes

I.

Casting and Pattern Design

1) Non-uniform casting sections resulting in interrupted metal flow 2) Metal sections too thin for area involved

3) Isolated thin sections

II.

Pattern Equipment

1) Worn patterns or core boxes causing thin metal sections 2) Patterns not made according to blueprint

Typical misrun; one tooth completely missing.

3) Pattern equipment not properly reinforced 4) Misalignment of pattern or core equipment

III.

Flask Equipment and Rigging

1) Cope or drag shift causing too thin metal sections 2) Worn flask pins or bushings

3) Patterns not properly mounted

4) Failure to tilt molds causing interrupted metal flow 5) Flask insufficiently barred allowing cope to sag 6) Distorted or dirty jackets causing a crush 7) Weak or improperly reinforced flasks 8) Distorted bands

9) Cope flask too shallow

IV.

Gating and Risering

1) Improper sizing of gates, runner and sprue-ingates too small or too few 2) Gates not properly located

3) Improper distribution or balance of gates 4) Too low head pressure

V.

Molding Sand

1) Excess moisture

2) Sand too high in volatile matter

3) Sand too weak allowing mold distortion 4) Permeability too low

5) Too rapid heat transfer of molding material

Typical cold shut on impeller casting, the defective vein is broken away from the casting to demonstrate the cold shut section.

Cold shut caused by small ingates.

VI.

Core Practice

1) Excess organic core binders 2) Under cured or green cores 3) Insufficient permeability 4) Insufficient vents

5) Cores not properly sized or fitted allowing decreased metal sections

6) Excess wash, mudding compound or paste. Metal sections may be reduced and/or excess gas formed

7) Raised or sagged cores

8) Core shift causing too thin metal sections 9) Cores warped or distorted-thermoplastic binders 10) Reinforcing rods too close to core surface chilling effect

VII.

Molding Practice

1) Excessive ramming causing low mold permeability 2) Soft ramming permitting mold distortion or sagging 3) Mold insufficiently reinforced

4) Improperly bedded or clamped bottom boards 5) Excessive sticking or patching

6) Molds for thin flat castings set level instead of tilting 7) Too few or too small chaplets allowing core to raise 8) Core prints too tight

9) Excessive wash 10) Misalignment of sprue

VIII.

Metal Composition

1) Gray, malleable or nodular irons with low

Same casting as in previous example after correction.

Misrun caused by cold metal.

1) Carbon equivalent or excess carbide stabilizers 2) Low phosphorus in gray iron or brasses

3) Steel-composition changes affect fluidity 4) Inadequate fluidity in brass or bronze alloys 5) Low silicon or iron in aluminum alloys 6) Improper degassing of aluminum alloys 7) Magnesium-improper metal composition

IX.

Melting Practice

1) Wrong composition due to careless weighing or charging 2) Cold melting

3) Oxidized or gassy metal

4) Over reduced metal-hydrogen reduces fluidity in all metals especially aluminum 5) Excessive ladle additions

6) Damp ladle additions

X.

Pouring Practice

1) Pouring temperature too low 2) Interrupted pouring

3) Reducing the rate of pour too soon

4) Boiling metal from wet spout, wet lining, etc. 5) Cold ladles

6) Thin castings poured on the level 7) Low head pressure

8) Slag, dross or ladle refractory which plugs the gate 9) Poured short

10) Pouring too slow

XI.

Miscellaneous

1) Chills and chaplets too large for metal section

2) Reduced metal section from any cause, e.g. excessive mold weights, careless weight shifting, etc. 3) Condensation from warm sand on cold cores, chills, inserts, or chaplets

Misrun caused by gates so small they froze before casting filled.

Off Dimension Related To Cores - Chapter 16

Result of failure to clean core assembly prior to setting the mold (boss was intended to be solid).

Description

An off dimension defect is an incorrect dimension occurring as a result of the wrong core being used, correct cores improperly set, cores omitted, cores incorrectly assembled, or thermal instability of cores.

Causes

I.

Casting and Pattern Design

None

II.

Pattern Equipment

1) Unidentified locators or prints 2) Improper or broken telltales

3) Improperly marked core boxes and patterns 4) Faulty core box construction, causing distortion 5) Core prints too large or too small

6) Chaplet location not marked 7) Chaplet size not marked

Improper marking of pattern caused molder to leave out required cores.

Excessive metal pressure caused core to warp during pouring.

The large core print permitted metal flow around entire core.

III.

Flask Equipment and Rigging

1) Core setting jig or fixture worn or inaccurate

IV.

Gating and Risering

None

V.

Molding Sand

None

VI.

Core Practice

1) A wrong core Used 2) Cores improperly set 3) Sagged or distorted cores 4) Too much or lack of paste 5) Wash coating too thick or too thin 6) Improper rodding

7) Conversion of oil sand core to self cure core resulting in lack of compensation for stability 8) Under cured cores

9) Improper grain distribution 10) Too rapid heat transfer of cores