Papineni.Satheesh, BVB0911002

MSRSAS - Postgraduate Engineering and Management Programme - PEMP

Metal casting and joining technologies

i

ASSIGNMENT

Module Code AMT 503

Module Name Metal casting and joining technologies

Course M.Sc in Advanced Manufacturing Technology

Department Mechanical and Manufacturing Engineering.

Name of the Student Papineni.Satheesh

Reg. No BVB0911002

Batch Full-Time 2011

Module Leader Mr. K.N. Ganapathi

PO

STG

RA

DU

ATE

EN

GIN

EER

ING

AN

D M

AN

AG

EM

EN

T P

RO

GR

AM

ME –

(P

EM

P)

M.S.Ramaiah School of Advanced Studies Postgraduate Engineering and Management Programmes(PEMP)

#470-P Peenya Industrial Area, 4th Phase, Peenya, Bengaluru-560 058

Tel; 080 4906 5555, website: www.msrsas.org


ii

Declaration Sheet Student Name Papineni.Satheesh

Reg. No BVB0911002

Course AMT Batch Full-Time 2011.

Batch FT-11

Module Code AMT-503

Module Title Metal casting and joining technologies

Module Date 19-03-2012 to 17-04-2012

Module Leader Mr. K.N. Ganapathi

Extension requests: Extensions can only be granted by the Head of the Department in consultation with the module leader.

Extensions granted by any other person will not be accepted and hence the assignment will incur a penalty.

Extensions MUST be requested by using the „Extension Request Form‟, which is available with the ARO.

A copy of the extension approval must be attached to the assignment submitted.

Penalty for late submission Unless you have submitted proof of mitigating circumstances or have been granted an extension, the

penalties for a late submission of an assignment shall be as follows:

Up to one week late: Penalty of 5 marks

One-Two weeks late: Penalty of 10 marks

More than Two weeks late: Fail - 0% recorded (F)

All late assignments: must be submitted to Academic Records Office (ARO). It is your responsibility to

ensure that the receipt of a late assignment is recorded in the ARO. If an extension was agreed, the

authorization should be submitted to ARO during the submission of assignment.

To ensure assignment reports are written concisely, the length should be restricted to a limit

indicated in the assignment problem statement. Assignment reports greater than this length may

incur a penalty of one grade (5 marks). Each delegate is required to retain a copy of the

assignment report.

Declaration The assignment submitted herewith is a result of my own investigations and that I have conformed to the

guidelines against plagiarism as laid out in the PEMP Student Handbook. All sections of the text and

results, which have been obtained from other sources, are fully referenced. I understand that cheating and

plagiarism constitute a breach of University regulations and will be dealt with accordingly.

Signature of the student P.Satheesh Date 17-04-2012

Submission date stamp (by ARO)

Signature of the Module Leader and date Signature of Head of the Department and date



iii

Abstract ____________________________________________________________________________

In this Metal casting and joining technologies assignment we have three different sets of parts.

In the Part-A, it is discussed about a debate topic on “cast components designed for

functionality, regardless of manufacturability is the main reason for high rejections in foundry”.

To support this debate an industrial case study is taken and explained about what actually the

cast product design engineers will do while designing the cast components, and what design

engineer should perform while designing the cast component and the main reason for these

defects is due to the lack of communication between the product designers and casting experts.

To overcome these how to apply the Design for Manufacturability in the cast design is

explained.

In the Part-B, it will be seen about the simulation of casting model using pro cast

software and using this software critical analysis of the fluid velocity, temperature during

filling, solidification time, pressure of liquid metal while filling the mould cavity and fraction

of solid in the gate junction and center of the castings. In the same casting the defects are

identified and explained the reason for the defect and calculated the riser dimensions for the

given model.

In the Part-C, welding process is selected for high alloy steel materials to manufacture

the pressure vessels. The selected welding process is capable of good corrosion resistance and

weld will be able to with stand the pressure given by the pressure vessel and weld should be of

no porosity. By considering all the above factors Sub merged Arc Welding process is selected

and explained about the complete process with process parameters of selected welding process.

For checking the quality of weld a non-destructive testing method is also explained which is

suitable for this application.


iv

Contents ____________________________________________________________________________

Contents Declaration Sheet ......................................................................................................................... ii

Abstract ....................................................................................................................................... iii

Contents ........................................................................................................................................iv

List of Tables ................................................................................................................................vi

List of Figures ............................................................................................................................ vii

Nomenclature ............................................................................................................................ viii

PART-A ......................................................................................................................................... 1

1.1 Casting: .................................................................................................................................... 1

1.2 Analysis of the case and build of opinion: .............................................................................. 1

1.3 Examples: ................................................................................................................................ 1

1.4 Conclusion: .............................................................................................................................. 3

PART-B ......................................................................................................................................... 4

2.1 Pro CAST: ............................................................................................................................... 4

2.2 Given model: ........................................................................................................................... 4

2.3 Simulation process: ................................................................................................................. 5

2.4 Defects identified: ................................................................................................................. 14

2.5 Riser calculation for given model: ........................................................................................ 16

2.6 Conclusion: ............................................................................................................................ 16

PART-C ....................................................................................................................................... 17

3.1 Welding: ................................................................................................................................ 17

3.2 Suitable welding process for fabrication of pressure vessel from high alloy steel for LPG

storage: ........................................................................................................................................ 17

3.2.1 Process features: ............................................................................................................. 17

3.2.2 Advantages of SAW: ...................................................................................................... 18

3.3 SAW Process and process parameters: ................................................................................. 19

3.3.1 Power source: ................................................................................................................. 19

3.3.2 SAW head: ..................................................................................................................... 20

3.3.2.1 Manual welding: ...................................................................................................... 20

3.3.2.2 Mechanized welding: .............................................................................................. 20

3.3.2.3 Wire stick out or electrode extension: ..................................................................... 20

3.3.2.4 Gun angle: ............................................................................................................... 21



v

3.3.3 Flux handling: ................................................................................................................. 21

3.3.4 Electrode wires: .............................................................................................................. 23

3.3.5 Protective equipment: ..................................................................................................... 23

3.4 NDT techniques for pressure vessels: ................................................................................... 24

Comments on learning outcomes ................................................................................................ 25

4.1 Comments on learning outcomes: ......................................................................................... 25

References ................................................................................................................................... 26

Bibliography ................................................................................................................................ 27


vi

List of Tables ____________________________________________________________________________

Table No. Title of the table Pg. No.

Table 3. 1 Maximum stick out lengths and wire diameters [12] ................................................. 21


vii

List of Figures ____________________________________________________________________________

Figure No. Title of the figure Pg. No.

Figure 1. 1 Part designing features which affects quality [1] ........................................................ 2

Figure 2. 1 Gravity casting process, given casting model with complete mold and casting

assembly ........................................................................................................................................ 5

Figure 2. 2Actual given casting model with gating system .......................................................... 5

Figure 2. 3 Material assigning tool bar .......................................................................................... 6

Figure 2. 4 Interfacing tool bar ...................................................................................................... 7

Figure 2. 5 Boundary conditions assigning tool bar ...................................................................... 8

Figure 2. 6 Flow rate and filling time calculator ........................................................................... 8

Figure 2. 7 Initial gravity condition assigning tool ....................................................................... 8

Figure 2. 8 Initial conditions tool bar ............................................................................................ 9

Figure 2. 9 Run parameters tool bar .............................................................................................. 9

Figure 2. 10 Simulation status window ....................................................................................... 10

Figure 2. 11 Fluid velocity in the gating junction ...................................................................... 10

Figure 2. 12 Critical fluid velocity of casting ............................................................................. 11

Figure 2. 13 Molten metal filling temperature during filling ...................................................... 11

Figure 2. 14 Solidification temperature ....................................................................................... 12

Figure 2. 15 Solidification time of casting .................................................................................. 13

Figure 2. 16 Fraction of solid in the casting ................................................................................ 13

Figure 2. 17 Molten metal pressure while filling the casting ...................................................... 14

Figure 2. 18 Shrinkage porosity defect in the casting ................................................................. 14

Figure 2. 19 Shrinkage porosity in the casting ............................................................................ 15

Figure 2. 20 Casting volume and surface area ............................................................................ 15

Figure 3. 1 Schematic diagram of submerged arc welding process [11] .................................... 18



viii

Nomenclature ____________________________________________________________________________

Acronyms Description

AC Alternate Current

DC Direct Current

DFM Design for Manufacturability

DECN Direct Current Electrode Negative

LPG Liquid Petroleum Gas

OEM Original Equipment Manufacturer

SAW Submerged Arc Welding

PART-A

1.1 Casting:

Metal casting is one of the direct methods of manufacturing the desired geometry of

component. The method is also called as near net shape process. It is one of the primary processes

for several years and one of important process even today in the 21st century. The principle of

manufacturing a casting involves creating a cavity inside a mould and then pouring the molten

metal directly into the mould. Casting is a very versatile process and capable of being used in mass

production. The size of components is varied from very large to small, with intricate designs. Out of

the several steps involved in the casting process, moulding and melting processes are the most

important stages. Improper control at these stages results in defective castings, which reduces the

productivity of a foundry industry.

1.2 Analysis of the case and build of opinion:

I agree with given stance, cast components designed for functionality regardless of

manufacturability is the reason for high rejections in foundry.

Casting rejections as high as 8-15% in jobbing foundries cannot be attributed to poor

methoding and process variability alone. Most castings are designed for manufacture, not for

manufacturability. Many defects like shrinkage porosity, hot tear, and cold shut originate from

poorly designed part features like isolated junction, constrained internal feature, and long thin

section, respectively. Foundry engineers partially tackle the problem by tweaking the part design

for example; increasing a fillet radius or padding a thin wall, but incur additional and avoidable

costs of machining and productivity loss [1].

To overcome these, design for manufacturability (DFM) should be carried out early by

product design engineers, instead of late DFM. In practice, casting product designers need to

communicate with casting experts in order to ensure that the casting being designed is

manufacturable and the most appropriate casting process is chosen. Lack of communication

between these parties or lack of expertise support can lead to erroneous design and extensive design

lead times. The problems originated in such scenarios are considerably magnified when the design

engineer is as yet inexperienced [2].

1.3 Examples:

(1) According to technical paper for 59th

Indian foundry congress, a series of industrial

studies and discussions with major original equipment manufacturers (OEMs) revealed that most

parts are designed for manufacture, not for manufacturability [1]. The origin of major casting

defects like shrinkage porosity, crack, and cold shut discovered at the manufacturing stage can be



2

traced back to part design. This is because product designers usually limit their focus to achieving

the desired functionality through a suitable combination of part material, geometric features and

manufacturing tolerances. They may not be aware of the extent to which part features affect quality

and cost issues later. In the figure 1.1, we can see some of the part design features which cause the

defect in casting.

Figure 1. 1 Part designing features which affects quality [1]

Foundry engineers try to achieve the desired quality through appropriate design of tooling

and process parameters. Minor changes to part design is needed in most cases: draft for faces along

draw direction, plugging drilled holes, increasing fillet radius, padding thin walls, and other

changes. These increase the weight of as-cast parts by 10-15% compared to the original design.

Machining the additional volume leads to an unnecessary increase in cost. Still, a large number of

castings are rejected, recycled or repaired, implying further avoidable costs. The above mentioned

wastage of resources could be avoided by early evaluation of part design in terms of product quality

and cost, and modifying the design to achieve the desired manufacturability without compromising

the required functionality. [1]

(2) Case study on Brock Metal Company limited, Zinc die casting defects. The need for

high quality decorative finishes will invariably mean that the finishing criteria will become more

critical and this will affect the cost and the prospect of higher reject rates must be taken into



3

account. It therefore follows that the elimination of surface defects is a key requirement when

manufacturing parts which require high quality surface finishes [3].

In the zinc die casting, casting design is a major controlling factor in the instigation of

casting defects. Section thickness changes, lack of fillet radii, surface textures and profiles may all

promote surface defect problems if the casting design does not follow recognized design guidelines.

Here the some of the cast design guidelines for achieving better surface finish in the casting, lack of

these knowledge only most of the casting defects occurring in the zinc die casting [3].

Failure to use adequate fillet radii and soft external edges.

Failure to control section changes, and adopt the accepted guidance.

Failure to adopt curved surfaces and other design aids which disguise plating and polishing

blemishes.

Deep blind pockets or holes.

Gate scars and part line defects.

Vertical part line changes.

1.4 Conclusion:

Casting design and manufacture is, however, a complex problem and involves the

interactions of many interdependent casting process variables. Designing cast components and

determining the correct casting process requires extensive knowledge of various casting processes

and their practical capabilities and limitations. Quite an extensive experience curve is necessary in

order for one person alone to be able to acquire all the knowledge and experience needed. It is,

therefore, highly unlikely that a casting product designer will have all the knowledge needed to

solve a whole range of casting design problems. Product designers usually design the cast

components for functionality; regardless of manufacturability is the reason for high rejections in

foundry. To overcome these Design for Manufacturability should be carried out early by product

design engineers, instead of late DFM.



4

PART-B

________________________________________________________________________________

2.1 Pro CAST:

The Pro CAST is leading Finite Element solution for casting process simulation software.

Throughout the manufacturing industry, casting process simulation is now widely accepted as an

important tool in product design and process development to improve yield and casting quality.

Based on powerful Finite Element solvers and advanced specific options developed with leading

research institutes and industries, Pro CAST provides an efficient and accurate solution to meet the

casting industry needs. Compared to a traditional trial-and-error approach, Pro CAST is the key

solution to reduce manufacturing costs, shorten lead times for mold developments and improve the

casting process quality. [4]

Pro CAST provides a complete software solution allowing for predictive evaluations of the

entire casting process including mold filling, solidification, and microstructure and thermo-

mechanical simulations. It enables to rapidly visualize the effects of mold design and allows for

correct decision making at an early stage of the manufacturing process [4].

Pro CAST covers a wide range of casting processes and alloy systems including:

High and low pressures die casting.

Sand casting, gravity die casting and tilt pouring.

Investment casting, shell casting.

Lost foam and centrifugal casting.

2.2 Given model:

Gravity casting process in a sand mold:

Filling time 9sec.

Material to fill the casting AlSi7Mg03-A356.

Percentage of filling should be 95%.

Given model shown in the figure number 2.1.

Given actual casting and gating system shown in

the figure number 2.2.



5

Figure 2. 1 Gravity casting process, given casting model with complete mold and casting

assembly

Figure 2. 2Actual given casting model with gating system

2.3 Simulation process:

Here the given file to simulate the model is complete assembly of casting and mold

in the meshed file.

These meshed file to assign the material properties, boundary conditions opened in

the precast tool in the pro cast software.

In the precast tool by the use of material assigning tool applied given materials to the

given model and here in the assigning of material to the casting that casting area

should be kept empty and mold area should be filled. Material assigning tool with

assigned materials shown is in the figure number 2.3



6

Figure 2. 3 Material assigning tool bar

After assigning the material give interface between mold, internal cores and casting.

In the interface tool the model will be pre grouped before in the mesh cast only.

Here we have to define the interfacing type like if it is equal material in the casting

and gating should give EQUIV connection and it is not equal the material like mold

and casting should give COINC connectivity and in the COINC interface should

assign temperature variation heat coefficient.

In the given model (1) Mold (2) Casting (3) Gating system (4) Internal cores (5)

Internal cores.

Here the interfacing between 2 & 3 that is casing and gating system is given EQUIV

connection because of its same material in the interface of both.

Interface between 1 & 5 and 1 & 4 given EQUIV connection because mold and

internal core material are same.

Interface between 2 & 1, 2 &4, 2 &5, 3 & 1 given COINC connection because of

casting, mold, cores having different materials and here given the temperature

variation heat coefficient given as h=500.

The interfacing of given model assigned tool shown in the figure number 2.4



7

Figure 2. 4 Interfacing tool bar

After interfacing we should specify the boundary conditions and this is done with

boundary conditions menu.

In the boundary condition menu with use of surface boundary tool can be applied

mold cooling type and inlet conditions.

By using add option in the side menu, add the heat and select the entire model and

add the cooling medium like air cooling or water cooling and assign the properties.

Next should add the inlet conditions, here by add option, add the inlet and select the

inlet portion in the given model and store it and next should give inlet parameters.

Inlet parameter can be applied by add option in the down menu; add the inlet give

the inlet parameters like material flow rate and temperature at which material should

flow and here only we can able to calculate the fill time and according to that we can

able to assign the proper flow rate to the metal.

After giving the all inlet conditions should assign to the inlet conditions to the

model.

In the figure number 2.5 & 2.6 shows the boundary condition tools and flow rate

calculator.



8

Figure 2. 5 Boundary conditions assigning tool bar

Figure 2. 6 Flow rate and filling time calculator

After assigning of boundary conditions should apply the material filling process.

In the process menu by selecting the gravity option add the initial gravity to the

model according to the axis of filling. The gravity tool shown in the figure number

2.7.

Figure 2. 7 Initial gravity condition assigning tool



9

After applying the gravity conditions next should apply the initial conditions to the

model.

In the initial conditions menu by selecting constant option should give initial

temperatures to the assigned material.

Hear in the given model I assigned initial temperatures as mold and cores 30 deg C

and casting metal 780 deg C. The figure number 2.8 shows the initial condition tool

bar.

Figure 2. 8 Initial conditions tool bar

After assigning the initial conditions we should run the given conditions in the run

parameters.

In the run parameters menu we should select the gravity filling option in the

preference of filling the material and should give final temperature to stop and

should give time step in general tool bar. Figure number 2.9 shows the run

parameters tool bar.

Figure 2. 9 Run parameters tool bar

By assigning all the above options pre casting will be finished then it should be

saved.

After saving the precast should run the data cast for error checking in the assigned

properties.

If there are no flaws in the assigned parameters we should run the pro cast for actual

simulation of the casting.



10

Next in the status window we can able to see the percentage of filled material,

percentage of solid fraction and time step.

In the figure number 2.10 shows the status of given model filling details.

Figure 2. 10 Simulation status window

After the completion of percentage of filling and solid fraction we can able to

simulate the model in the visual cast tool.

In the visual cast tool we can able to simulate the model in different conditions like

thermal flow, fluid velocity, solidification time, temperature during solidification

and temperature during filling.

In the simulation itself we can able to find out the shrinkage porosity and other

defects.

Fluid velocity of the given model in the gating junction shown in the figure number

2.11.

Figure 2. 11 Fluid velocity in the gating junction

In the figure number 2.11 shows the fluid velocity of the gating junction, here we

have to select a node point on the gating junction, at that node point we can able to

see the critical fluid velocity with respect to Z-direction of 0.531 m/sec.



11

In the figure number 2.12 shows the fluid velocity of the casting, here we have to

select one node point to show the fluid velocity of the casting, that node point shows

the critical fluid velocity of the casting with respect to the Y-direction of 0.349

m/sec.

Here in the both places compare to fluid velocity in the casting and fluid velocity in

the gating junction, inlet entry in the gating junction fluid velocity is high.

By this we can able to tell that gating system can able to control the inlet fluid

velocity to avoid turbulent flow of liquid metal.

Figure 2. 12 Critical fluid velocity of casting

In the figure number 2.13 shows that temperature during filling.

Figure 2. 13 Molten metal filling temperature during filling

In the figure number 2.13 we can able to observe that molten metal filling

temperature and here we have selected one node point to show the temperature



12

where it is decreased below the melting point while filling. The node temperature

shows 740.6 deg C this temperature is below the melting temperature.

In the figure number 2.14 shows the solidification temperature.

Figure 2. 14 Solidification temperature

In the figure 2.14 we are able to observe that solidification temperature. Here in the

model casting area is reached the temperature up to 558 deg C and raiser

temperature reached up to 422 deg C.

From these temperatures the casting starts solidification.

In the figure 2.15 we can able to see the total solidification time of the casting and

gating system.

In the solidification time of casting, we are able to observe where exactly maximum

time as taken to solidify the casting.

In the figure 2.15 we have selected the node point where exactly the casting

solidification time taken more, as much as 1593.5 sec. Because at this node area of

casting where it‟s having more material and in-gates are coming contact with this

point and this point is last to fill area compare to other areas in casting because of

these reasons this area will solidify last.



13

Figure 2. 15 Solidification time of casting

Figure 2.16 shows the fraction of solid in the casting. Here in the selected node point

we can able to see the where exactly fraction of starts.

Figure 2. 16 Fraction of solid in the casting

In the figure 2.17 we can see the fluid pressure differences in filling the casting.

Here in the bottom portion of the casting we can observe that it‟s having more

pressure compare to the top portion.



14

Figure 2. 17 Molten metal pressure while filling the casting

2.4 Defects identified:

In the figure 2.18 we can able to see the shrinkage porosity in the casting area.

In the figure 2.18 we can observe that shrinkage occurs where the area of

solidification has taken more time and in the same area we can see the shrinkage

porosity. Here proper riser is not available to compensate this shrinkage, because of

this shrinkage porosity came in the casting area.

Here in the figure 2.18 & 2.19 selected node areas we can see the shrinkage porosity

percentage as maximum as 81.94 to 85.31%

Figure 2. 18 Shrinkage porosity defect in the casting



15

Figure 2. 19 Shrinkage porosity in the casting

Figure 2. 20 Casting volume and surface area



16

2.5 Riser calculation for given model:

According to given drawing and pro cast results casting volume 5730.03 CC and surface

area of casting 2.280 e+5 mm2. In the figure 2.20 we can see the pro cast results for volume and

surface area.

Modulus of casting = casting volume /surface area

Mc=5730030/228000=25.13 mm.

The modulus of casting =25.13mm, according to this modulus of riser is 1.2 of Mc.

Mr= 25.13*1.2= 30.156 mm.

The diameter of the riser is 4 times of modulus of riser.

d= 30.156 * 4 = 120.624mm.

The length of the riser is l/d=1.5.

L = 1.5 * 120.624 = 180.936 mm.

According to this for given casting model (d) 120 mm * (l) 180 mm riser should be used.

2.6 Conclusion:

For the given casting model major defect occur in the casting because of no riser in the

casting to avoid the shrinkage porosity and for the given model we should use 120 mm diameter.

By observing the simulation details where the defect has occurred, at the same area solidification

time has taken more and this is the place of last to fill area and thick ness of the casting here is high

compare to other. In the entire casting area first solidification is started on the gating system and

gradually it moved to the casting. Here the most of the incoming velocity of the molten metal is

reduced in the gating system to avoid turbulent flow in the casting.

PART-C

________________________________________________________________________________

3.1 Welding:

The process of joining together two pieces of metal`s so that bonding accompanied by

appreciable interatomic penetration takes place at their original boundary surfaces. The boundaries

more or less disappear at the weld, and integrating crystals develop across them. Welding is carried

out by the use of heat or pressure or both and with or without added metal. The integrity of a

welded component, which has metallurgical continuity across the joint, is also characterized by

properties such as pressure tightness or heat and corrosion resistance. These properties have

contributed to the rapid development, both technical and economic, in all fields including nuclear

power, chemical engineering, bridge building, offshore engineering, shipbuilding and the

manufacture of cars, railway locomotives and rolling stock, aero engines, domestic appliances, and

military hardware from small arms to main battle tanks. There are many types of welding including

Metal Arc, Atomic Hydrogen, Submerged Arc, Resistance Butt, Flash, Spot, Stitch, Stud and

Projection.

3.2 Suitable welding process for fabrication of pressure vessel from high alloy steel for LPG

storage:

Here I suggest a suitable welding process for fabrication of pressure vessel from high alloy

steel for LPG storage as Submerged Arc Welding process with reference to the below case studies,

Process features and advantages of Submerged Arc Welding process (SAW).

PPS group of companies, one of the leading manufacturers of LPG cylinders. In the LPG cylinder

manufacturing process they first take high alloy steel sheet and deep draw on the hydraulic press by

two half cylinder bodies. Then both the top and bottom halves are joined by the backing strip and

are welded together by submerged arc welding process by using 3.15mm MSCC wire [5].

In the Case study of Raya Technical services, they prefer submerged arc welding process for

fabrication of petro chemical pipelines and gas cylinders because of its various advantages [6].

In the Case study of BOC India limited leading manufacturers of pressure vessels, they use

submerged arc welding process for LPG cylinder welding [7].

3.2.1 Process features:

Similar to MIG welding, SAW involves formation of an arc between a continuously-fed

bare wire electrode and the work piece. The process uses a flux to generate protective gases and



18

slag, and to add alloying elements to the weld pool. A shielding gas is not required. Prior to

welding, a thin layer of flux powder is placed on the work piece surface. The arc moves along the

joint line and as it does so, excess flux is recycled via a hopper. Remaining fused slag layers can be

easily removed after welding. As the arc is completely covered by the flux layer, the molten weld

and the arc zone are protected from atmospheric contamination by being “submerged” under the

blanket of granular fusible flux, heat loss is extremely low. Distortion is much less and welds

produced are sound, uniform, ductile, and corrosion resistant and have good impact value. Single

pass welds can be made in thick plates with normal equipment. The arc is always covered under a

blanket of flux, thus there is no chance of spatter of weld. This produces a thermal efficiency as

high as 60% (compared with 25% for manual metal arc). There is no visible arc light, welding is

spatter-free and there is no need for fume extraction [8,9]. The Schematic representation of

submerged arc welding process is shown in the figure 3.1.

Figure 3. 1 Schematic diagram of submerged arc welding process [11]

3.2.2 Advantages of SAW:

High deposition rates (over 100 lb/h (45 kg/h) have been reported).

High operating factors in mechanized applications.

Deep weld penetration.

Sound welds are readily made (with good process design and control).

High speed welding of thin sheet steels up to 5 m/min is possible.

Minimal welding fume or arc light is emitted [10, 8].

Practically no edge preparation is necessary.



19

The process is suitable for both indoor and outdoor works.

Distortion is much less.

Welds produced are sound, uniform, ductile, and corrosion resistant and have good impact

value [10, 8].

Single pass welds can be made in thick plates with normal equipment.

The arc is always covered under a blanket of flux, thus there is no chance of spatter of weld.

50% to 90% of the flux is recoverable.

3.3 SAW Process and process parameters:

Essential equipment components for SAW are:

Power source

SAW head

Flux handling

Electrode wires

Protective equipment

3.3.1 Power source:

SAW can be operated using either a DC or an AC power source. DC is supplied by a

transformer-rectifier and AC is supplied by a transformer. Current for a single wire ranges from as

low as 200Amp, (1.6mm diameter wire) to as high as 1000Amp (6.0mm diameter wire). In practice,

most welding is carried out on thick plate where a single wire (4.0mm diameter) is normally used

over a more limited range of 600 to 900A, with a twin wire system operating between 800 and

1200A [12].

In DC operation, the electrode is normally connected to the positive terminal. Electrode negative

(DCEN) polarity can be used to increase deposition rate but depth of penetration is reduced by

between 20 and 25%. For this reason, DCEN is used for surfacing applications where parent metal

dilution is important. The DC power source has a 'constant voltage' output characteristic which

produces a self-regulating arc. For a given diameter of wire, welding current is controlled by wire

feed speed and arc length is determined by voltage setting [12].

AC power sources usually have a constant-current output characteristic and are therefore not self-

regulating. The arc with this type of power source is controlled by sensing the arc voltage and using

the signal to control wire feed speed. In practice, for a given welding current level, arc length is

determined by wire burn off rate, i.e. the balance between the welding current setting and wire feed

speed which is under feedback control [12].

http://en.wikipedia.org/wiki/Flux_(metallurgy)#Flux_Recovery



20

Square wave AC square wave power sources have a constant voltage output current characteristic.

Advantages are easier arc ignition and constant wire feed speed control.

3.3.2 SAW head:

SAW can be carried out using both manual and mechanized techniques. Mechanized

welding, which can exploit the potential for extremely high deposition rates, accounts for the

majority of applications [12].

3.3.2.1 Manual welding:

For manual welding, the welding gun is similar to a MIG gun, with the flux which is fed

concentrically around the electrode, replacing the shielding gas. Flux is fed by air pressure through

the handle of the gun or from a small hopper mounted on the gun [12]. The equipment is relatively

portable and, as the operator guides the gun along the joint, little manipulative skill is required.

However, because the operator has limited control over the welding operation (apart from adjusting

travel speed to maintain the bead profile) it is best used for short runs and simple filling operations.

3.3.2.2 Mechanized welding:

Single wire: - As SAW is often used for welding large components, the gun, wire feeder

and flux delivery feed can be mounted on a rail, tractor or boom manipulator. Single wire welding

is mostly practiced using DCEP even though AC will produce a higher deposition rate for the same

welding current. AC is used to overcome problems with arc blow, caused by residual magnetism in

the work piece, jigging or welding machine [12].

Twin wire: - SAW can be operated with more than one wire. Although up to five wires are

used for high deposition rates, the most common multi-wire systems have two wires in a tandem

arrangement. The leading wire is run on DCEP to produce deep penetration. The trailing wire is

operated on AC which spreads the weld pool, which is ideal for filling the joint. AC also minimizes

interaction between the arcs, and the risk of lack of fusion defects and porosity through the

deflection of the arcs (arc blow). The wires are normally spaced 20mm apart so that the second wire

feeds into the rear of the weld pool [12].

3.3.2.3 Wire stick out or electrode extension:

The distance the wire protrudes from the end of the contact tip is an important control

parameter in SAW. As the current flowing between the contact tip and the arc will preheat the wire,

wire burn off rate will increase with increase in wire stick out. For example, the deposition rate for

a 4mm diameter wire at a welding current of 700A can be increased from approximately 9 kg/hr at

the normal 32mm stick out, to 14 kg/hr at a stick out length of 178mm. In practice, because of the



21

reduction in penetration and greater risk of arc wander, a long stick out is normally only used in

cladding and surfacing applications where there is greater emphasis on deposition rate and control

of penetration, rather than accurate positioning of the wire [12]. Recommended and maximum stick

out lengths shown in the table no 3.1

Table 3. 1 Maximum stick out lengths and wire diameters [12]

3.3.2.4 Gun angle:

In manual welding, the gun is operated with a trailing angle, i.e. with the gun at an angle of

45 degrees (backwards) from the vertical. In single wire mechanized welding operations, the gun is

perpendicular to the work piece. However, in twin wire operations the leading gun is normal to the

work piece, with the trailing gun angled slightly forwards between an angle of 60 and 80 degrees.

This reduces disturbance of the weld pool and produces a smooth weld bead profile [12].

3.3.3 Flux handling:

Flux should be stored in unopened packages under dry conditions. Open packages should be

stored in a humidity-controlled store. While flux from a newly-opened package is ready for

immediate use, flux which has been opened and held in a store should first be dried according to

manufacturer's instructions. In small welding systems, flux is usually held in a small hopper above

the welding gun. It is fed automatically (by gravity or mechanized feed) ahead of the arc. In larger

installations the flux is stored in large hoppers and is fed with compressed air. Unused flux is

collected using a vacuum hose and returned to the hopper [12]. Care must be taken in recycling

unused flux, particularly regarding the removal of slag and metal dust particles. The presence of

slag will change the composition of the flux which, together with the wire, determines the

composition of the weld metal. The presence of fine particles can cause blockages in the feeding



22

system. The flux has to be designed and selected to incorporate Thermodynamics, Kinetics &

Transport phenomenon.

It must [6]:

Melt just below the temperature of the steel being welded via Material balance & phase

diagrams to achieve the ideal eutectic point (Thermodynamics).

Mix with the parent material in the molten zone & refine the weld metal, adding elements

such as Mn, Si, Cr, etc & removing rust & nonmetallic oxide inclusions from the heat

affected weld zone, by enveloping the oxides in a Silicate-aluminate matrix (Kinetics).

Float up (Transport the oxides) to the surface before the steel solidifies & to peel off

automatically (self-lifting slag).

Two main types of fluxes are available: fused and agglomerated. Fused fluxes are manufactured by

fusing together a mixture of finely ground minerals, followed by solidifying, crushing and sieving

the particles to the required grain size. Fused fluxes do not deteriorate during transportation and

storage and do not absorb moisture. Agglomerated fluxes are manufactured by mixing finely

ground raw materials with bonding agents such as sodium or potassium silicates followed by

baking to remove moisture. This type of flux is sensitive to moisture absorption and may require

drying before use. Agglomerated fluxes are more prone to mechanical damage which can cause

segregation of some of the constituents [13].

Fluxes are classified as acid, neutral, or basic, the last being subdivided into semi-basic or

highly basic. The main characteristics of the fluxes are as follows [13]:

Acid fluxes: High content of oxides such as silica or alumina. Suitable for high welding currents

and fast travel speeds. Resistant to porosity when welding rusty plate, Low notch toughness, and

not suitable for multi pass welding of thick material`s.

Neural fluxes: High content of calcium silicate or alumina-rutile. Suitable for fairly high welding

currents and travel speeds and also for multi pass welding.

Basic fluxes: High content of chemically basic compounds such as calcium oxide, magnesium

oxide and calcium fluoride. Highest weld metal quality in respect of radiographic soundness and

impact strength. Lower welding currents and travel speeds are suitable for multi pass welding of

thick sections.



23

3.3.4 Electrode wires:

The electrode for submerged-arc welding is a bare wire in coil form usually copper coated.

They two types are available solid wire and tubular wire. The solid wire is widely used for general

fabrication of mild and low-alloy steels, stainless steels and non-ferrous metals. The tubular wire

(made by forming narrow strip into a tube) carries alloy powders which permit the economical

production of a wider range of weld compositions than is possible by using the solid wire type.

Tubular wires are widely used for hard-facing [13]. With coated manual electrodes, wire and

coating is one unit so that such electrodes can be classified according to the type of coating and its

effect on weld mechanical properties. In submerged-arc welding, any wire may be used with a

number of different fluxes with substantially different results in respect of weld quality and

mechanical properties. Consequently, BS 4165 grades wire flux combinations according to the

tensile and impact strengths obtained in the weld metal. A number of tubular wires are available,

particularly for surfacing and hard-facing. These contain alloy powders which produce weld metals

consisting of low-alloy steels, martensitic and austenitic stainless steels, chromium and tungsten

carbides, and various cobalt- and nickel-based heat- and corrosion-resistant alloys. Some corrosion-

resistant alloys, including stainless steel, are available in the form of coiled strips from 100 mm to

150 mm wide, 0.5 mm thick for high deposition rate surfacing by a submerged-arc welding process

known as strip cladding [13].

ASTM A240 Type 316 or 316L, electrode wire is best suitable for joining the more

common austenitic stainless steel grades referred to as "18-8" steels for very good corrosion

resistance in acid environments [14].

3.3.5 Protective equipment:

Unlike other arc welding processes, SAW is a clean process which produces minimum fume

and spatter when welding steels. Normal protective equipment is required for ancillary operations

such as slag removal by chipping or grinding. Special precautions should be taken when handling

flux - a dust respirator and gloves are needed when loading the storage hoppers [12, 15].



24

3.4 NDT techniques for pressure vessels:

The following welds shall be tested by NDT process:

All butt welds in the pressure structure shall be subjected to X-ray radiographic

inspection over their entire length. In addition, at least 10 % of the weld length shall

be tested for surface cracks.

Fillet welds at the joint between the central longitudinal bulkhead and the tank

casing of twin tanks or similar structures shall be subjected to ultrasonic or, where

this is not possible, X-ray radiographic inspection over their entire length. In

addition, at least 10% of the weld length shall be tested for surface cracks.

10 % of the butt-welded joints of supporting rings in tanks shall be subjected to X-

ray radiographic inspection. In the case of fillet welds between the web and the

tank wall and between the web and the girder plate, at least 10 % of the weld

length shall be tested for surface cracks.

All butt and fillet welds of nozzles weldments, e.g. sockets, domes, sumps, rings,

and of reinforcing plates around cutouts shall be tested for surface cracks over their

whole length.

Fillet welds of fitments welded to the tank which may induce stresses in the tank

wall, e.g. lifting lugs, feet, brackets, shall be tested for surface cracks over their

whole length.

Full root penetration nozzle connections in the pressure structure shall undergo

ultrasonic or radiographic inspection if the attachment wall thickness at the

pressure structure is > 15 mm and the inside diameter of the nozzle is ≥ 120 mm.

If pressure vessels are to be mechanically de stressed, all points with geometry-

related stress concentrations, such as the seams of socket weldments or fitments,

shall afterwards be tested for cracks by the magnetic particle or dye penetrant

method [16].



25

Comments on learning outcomes ________________________________________________________________________________

4.1 Comments on learning outcomes:

By undertaking this assignment now I am able to justify that what are all the casting defects

and by which process these casting defects will occur. The main casting defects arise from the

foundry because of inefficient communication between product designer and foundry engineer and

product design engineers who don‟t perform DFM early in the product design. This debate helped

me to get the complete knowledge about casting and casting defects.

By doing simulation of given model I have understood that how the simulation software is

helpful in the foundry to eliminate the casting defects and here we can able to see the virtual model

of casting and simulate the model in different conditions like fluid velocity, fluid pressure,

solidification time and fluid flow in the casting where the turbulence effect appears.

In the selection process of welding high alloy steel for the manufacturing of pressure

vessels I came to an understanding that the conditions essential for selecting the welding process

,suitable weld quality that can be identified, process parameters for selected welding process and its

limitations in carrying out the welding.



26

References

________________________________________________________________________________

1. Author unknown, http://www.foundryinfo-india.org/images/pdf/TS-2C-II.pdf, retrieved on

25th March 2012

2. Author unknown, http://www.sciencedirect.com/science/article/pii/S0950705100000757,

retrieved on 25th March 2012

3. Author unknown,

http://www.brockmetal.com/downloads/documents/EB4IB5ELA9_Web_Tech_Resource__

_Zinc_die_casting_defects_cause_and_elimi.pdfl, retrieved on 25th March 2012

4. Author unknown, http://www.esi.com.au/Software/ProCAST.html, retrieved on 26th March

2012

5. Author unknown, http://www.pps-india.com/lpg.htm, retrieved on 27th March 2012

6. Author unknown, http://rayatechnicalservices.com/case_studies, retrieved on 28th Mar 12

7. Author unknown, http://www.boc-india.com/business_area/case_study.php, retrieved on

28th March 2012

8. Author unknown, http://www.wolfrobotics.com/products/images/SAWbro.pdf, retrieved on

29nd March 2012

9. Author unknown, http://www4.hcmut.edu.vn/~dantn/TWI/jk5.html, retrieved on 29th

March 2012

10. Author unknown,

http://cmapspublic2.ihmc.us/rid=1151380771906_867522767_14912/Submerged%20Arc%

20Welding.doc, retrieved on 30th March 2012

11. Author unknown, http://www4.hcmut.edu.vn/~dantn/TWI/jk5.html, retrieved on 30th March

2012

12. Author unknown, http://www4.hcmut.edu.vn/~dantn/TWI/jk16.html, retrieved on 30th

March 2012.

13. Edward H. Smith, Mechanical engineers Reference book, Twelfth edition.

14. Author unknown, http://www.lincolnelectric.com/en-us/consumables/submerged-

arc/Pages/submerged-arc.aspx, retrieved on 4th Apr 2012.

15. Author unknown, http://www4.hcmut.edu.vn/~dantn/TWI/jk20.html, retrieved on 4th Apr

2012.

16. Author unknown, http://www.gl-group.com/infoServices/rules/pdfs/english/werkstof/teil-

3/kap-3/englisch/abschn03.pdf, retrieved on 5th Apr 2012.



27

Bibliography

________________________________________________________________________________

1. Edward H. Smith, Mechanical engineers Reference book, Twelfth edition.

2. Author unknown,

http://www.twi.co.uk/services/technical-information/job-knowledge/job-knowledge-87-

submerged-arc-welding-consumables-part-1/.

3. Dr.N.S.Mahesh, Weld metallurgy Weld design, AMT 503, MS Ramaiah School of

Advance Studies.

4. Mr.K.N. Ganapathi, Casting process, AMT 503, MS Ramaiah School of Advance Studies.

5. Author unknown,

http://www4.hcmut.edu.vn/~dantn/news/Jk-view.


1

Industrial visit Report on Bangalore Metallurgical Pvt, Ltd ___________________________________________________________________________

Bangalore metallurgical Pvt Ltd is one of the leading cast component manufacturing

industries. It produces a wide variety of sand castings ranging from 0.5 kg to 3000kg which

includes housing clutches ,motor parts, flywheel housings, eccentric housings, bearing shields

etc.,.

In the sand casting process they use silica sand for mould making and in the mould

making 70% old sand and 30% new sand. The process they use in the binding of sand is no-

bake binder system. The binding process is based on the ambient temperature cure of two or

more binder components on sand. The resin binder used at this industry is the fural-alcohol.

The concentration of this fural alcohol is about 0.9-1 percent of the sand. Along with this the

sulphonic acid is mixed around 30-40 percent of one percent fural alcohol. All these

ingredients are mixed with silica sand and water in right proportion. Curing of the binder

system begins immediately after all the components are combined. Furon binder can be

modified with urea, formaldehyde, phenol and wide variety of other reactive and non-reactive

additives. The choice of specific binder depends on the type of metal to be cast. The speed of

the curing action can be adjusted by changing the catalyst type. Furon or No bake binder

process provides high dimensional accuracy and high degree of resistance to sand or metal

interface casting defects. After the completion of all the above processes now the sand is

ready for mould making. After making of required mould geometry, the mould surface

should be applied the refractory coatings like zirconia and graphite coating of 20 microns.

For curing and removal of water content from zirconia and graphite coatings preheating will

done to the mould for easy removal of pattern from the mould strip coating will done to the

pattern. Here the compaction process of moulds will do manually for the small moulds and

for the big moulds hydraulic gaggers will be used for achieving the better strength in the

moulds.

Next after preparation of mould cope and drag they will arrange the internal cores

with the help of chaplets to support and hold the cores at the right position during the taping

of molten metal to the mould. After arrangement of all the cores in the mould cope and drag

the cope and drag portion will be assembled. After arrangement of all the cope and drag

assembly next process will be the pouring of molten metal to the mould. Here for melting of

metal done using of induction furnace and here the sum amount of pure iron and scrap will be

used for ingot. This molten ingot will be transferred to the crucible and through the crucible


2

molten metal will be poured in to the mould. After solidification of metal the casting will be

removed and the broken mould will be collected in to the vibrator or reclamation impeller. In

the vibrator or impeller this material will be further broken into fine particles and refined.

Here the refined sand will be reused for mould making again for reduction of cost. This

process is called as the reclamation of the sand.

The poured material properties will be checked using a spectro meter. The use of

electrical supply produces a high spark in the sample material and by reading of this spark

light the spectro meter will be able to display the different composition of the metals in the

material according to this display the material ingot properties will be changed in the shop

floor by the engineer to achieve the better material properties in the casting. For the achieving

of better surface finishes in the casting they will pre check the sand properties like moisture

content, sand strength and grain size controlling in the frequent manner.

These are the observations made by me during the visit to the Bangalore metallurgical

Pvt Ltd.Hoskote. By visiting of this foundry I got the clear knowledge about the how the

foundry functions and where actually the chaplets, chills will be used how it will helpful in

achieving directional solidification process.

M. S. Ramaiah School of Advanced Studies 1

Metal casting and joining process

Module leader:

M.r. K.N. Ganapathi

MSRSAS, Bangalore

Avoid turbulent entrainment

(the critical velocity requirement)

Papineni.Satheesh BVB0911002

Bushan Yadav.B BVB0911003


Contents

Maximum velocity requirement

The `no fall' requirement

Surface tension controlled Filling

Filling system design

Gravity pouring of open-top moulds

Gravity pouring of closed Moulds

Pouring basin and down sprue design

Horizontal transfer Casting


The key aspect of the critical velocity is that at velocities

less than the critical velocity the surface is safe. Above the

critical velocity there is the danger of entrainment damage.

The criterion is a necessary but not sufficient condition for

entrainment damage.

If the whole, extensive surface of a liquid were moving

upwards at a uniform speed, but exceeding the critical

velocity, clearly no entrainment would occur.

Maximum velocity requirement


If the melt is travelling at a high speed, but is constrained

between narrowly enclosing walls, it does not have the room to

fold-over. Thus no damage is suffered by the liquid despite its

high speed, and despite the high risk involved. This is one of the

basic reasons underlying the design of extremely narrow

channels for filling systems (Gating system).


The `no fall' requirement

the no-fall requirement applies to the design of the

filling system downstream of the base of the sprue.

The critical fall heights for all liquid metals are in the

range 3 to 15 mm.

For example, if liquid aluminium is allowed to fall

more than 12.5mm then it exceeds the critical 0.5m/s.

with a good sprue and pouring basin design this initial

fall damage can be reduced to a minimum.

The `no fall' requirement may also exclude some of

those filling methods in which the metal slides down a

face inside the mould cavity, such as some tilt casting

type operations.


Narrow filling system geometries are valuable in their

action to conserve the liquid as a coherent mass, and so

acting to push the air out of the system ahead of the

liquid.

A good filling action, pushing the air ahead of the

liquid front as a piston in a cylinder, is a critically

valuable action. Such systems deserve a special name

such as perhaps `one pass filling (OPF) designs'


Surface tension controlled filling

This is interesting situation that the liquid may not be able to enter the

mould at all.

This is to be expected if the pressure is too low to force melt into a narrow

section. It is an effect due to surface tension.

If the liquid surface is forced to take up a sharp curvature to enter a non-

wetted mould then it will be subject to a repulsive force that will resist the

entry of the metal.

Even if the metal enters, it will still be subject to the continuing resistance

of surface tension, which will tend to reverse the flow of metal, causing it

to empty out of the mould if there is any reduction in the filling pressure.

These are important effects in narrow section moulds (i.e. thin-section

castings) and have to be taken into account.


Filling system design

The liquid metal as it travels through the filling system

indicates that most of the damage is done to castings by

poor filling system design.

The filling system design can be of two types:

Gravity pouring of open-top moulds.

Gravity pouring of closed moulds.


Gravity pouring of open-top moulds

Generally moulds consists of cope and drag but in open-top moulds

only drag is required. This means the mould cavity is open so that

metal can be poured directly.

The skill of the foundry man plays vital role in the gravity

pouring system


Gravity pouring of closed moulds

Gravity pouring of closed moulds consists of pipes, channels

to guide the metal from the ladle into the mould.

In poor filling system designs, velocities in the channels can

be significantly higher than the free-fall velocities.

There fore it encourages surface turbulence, bubbles and bi-films.

In the gravity pouring system of closed moulds, bottom gating system

design is much efficient compared to top gating system.


Pouring basin and down sprue design

The offset blind end of the basin is important in bringing the vertical

downward velocity to a stop. The offset also avoids the direct inline type of

basin, such as the conical basin, where the incoming liquid goes straight

down the sprue, its velocity unchecked, and taking with it unwanted

components such as air and dross, etc.


An oversize sprue that has suffered severe erosion damage because of air

entrainment during the pour.

A correctly sized sprue shows a bright surface free from damage.

Greater the sprue diameter greater the turbulence.


Runner

The runner is that part of the filling system that acts to distribute the melt

horizontally around the mould, reaching distant parts of the mould cavity

quickly to reduce heat loss problems.

For products whose reliability needs to be guaranteed, the arrangement of

the runner at the lowest level of the mould cavity, causing the metal to

spread through the running system and the mould cavity only in an uphill

direction is a challenge that needs to be met.


Horizontal transfer Casting

Tilt casting is a process with the unique feature that, in principle, liquid

metal can be transferred into a mould by simple mechanical means

under the action of gravity, but without surface turbulence.

The problem of horizontal transfer is that it is slow, sometimes resulting in

the freezing of the `ski jump' at the entrance to the runner, or even the non-

filling of the mould. This can usually be solved by increasing the rate of

tilt after the runner is primed.


References

1. John Campbell, Castings Practice, The 10 Rules of Castings,

published 2004.

Papineni.Satheesh, BVB0911002

Documents

Transcript of Papineni.Satheesh, BVB0911002