COST REDUCTION IN MELTING- A SQC & SIX SIGMA APPROACH

ARUN KUMAR.S,

B.E.MECHANICAL ENGINEERING

FINAL YEAR

RAJA COLLEGE OF ENGG.&TECH.

FOUNDRY

• A Foundry is a factory that produces metal, castings.• Metals are cast into shapes by melting them into a

liquid, pouring the metal in a mould, and removing the mould material or casting after the metal has solidified as it cools.

• The most common metals processed are aluminium and cast iron.

• However, other metals, such as bronze, brass, steel, magnesium, and zinc, are also used to produce castings in foundries. In this process, parts of desired shapes and sizes can be formed.

FOUNDRY-PROCESSES

PATTERN MAKINGMETHODINGMOULDINGMELTINGLAB TESTSFETTLINGQUALITY CONTROLDESPATCH

ARUNA ALLOY STEELS(AAS)-COMPANY PROFILE

The temple city of Madurai houses a world class foundry “ARUNA ALLOY STEELS PVT LTD.”, a versatile company which laid down its roots in the memorable year of 1961 as a small scale industry.

Down the years of its growth, the company became the suppliers to our country’s prestigious Indian Railways for more than 3 glorious decades.

When the Vacuum brake system in the Railways became obsolete, the company also changed tracks in Manufacturing to Automotive castings, Flywheel, brake drum, and Gear & Clutch Housings.

ARUNA ALLOY STEELS(AAS)-COMPANY PROFILE

From 1998 ARUNA is forging ahead to dedicate itself exclusively to VALVE industry.

ARUNA has excelled itself in the faultless supply of high performance of widely varied valves for maximum pressure rating up to “5000 PSI and size 30 Inch.”

ARUNA is manned by Mr.SV. Arunachalam who is a proud recipient of the “All India Best Foundry Man of the Year 2003-2004 award.”

The company is now a World-class certified supplier of steel castings to reputed valve manufacturers both in the domestic and international arena.

MELTING

Melting is a physical process that results in the phase transition of a substance from a solid to a liquid.

The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the ordering of ionic or molecular entities in the solid breaks down to a less ordered state and the solid liquefies.

An object that has melted completely is molten.

MELTING

Melting Techniques:There are a variety of methods used in foundries for

melting the metal for casting.  The selection of an appropriate technique is

dependant on factors such as the metal being melted, the amount of molten metal required for the production run and the area available to house the melting equipment. 

The range of melting equipment typically used can be categorised as follows:

MELTING

Electric Arc Furnaces Induction FurnacesVacuum Induction meltingHearth FurnacesCrucible FurnacesCupola FurnacesVacuum Arc Skull Melting and Casting

INDUCTION FURNACES

 A water cooled copper coil carrying alternating current produces a magnetic field, which in turn induces eddy currents in the charge. 

These eddy currents heat and eventually melt the metal.  A second magnetic field is generated by the induced current

in the charge.  The opposed magnetic fields result in a mechanical force,

which stirs the molten metal.  The benefits of this stirring include the production of a

thermally and chemically homogeneous melt and excellent alloy and charge absorption.

POURING

In a foundry, molten metal is poured into moulds. Pouring can be accomplished with gravity, or it

may be assisted with a vacuum or pressurized gas. Many modern foundries use robots or automatic

pouring machines for pouring molten metal. Traditionally, moulds were poured by hand using 

ladles.

LAB TESTS

The following are some of the tests being carried out in chemical lab: Micro structure of Scraps; Compression strength; Permeability and Moisture content of Mould

& Core Sand. Chemical composition of Castings(Bath1&2 and final).

The following are some of the tests being carried out in mechanical lab:

Hardness; Yield Strength; Ultimate Tensile Strength; Elongation%; Reduction%.

FETTLING

• The foundry Cleaning Room is collection processes where castings are ‘finished’ to meet the customers specifications.

• Once poured, the moulds are allowed to cool before next being sent to the shakeout.

• At the shakeout, the castings are separated from the sand mould.

• The sand is sent to a reclamation system so that it can be reused in the moulding process.

FETTLING

• For some metal types, and with some gating system designs, the sprue, runners and gates can be removed by breaking them away from the casting with a sledge hammer or specially designed knockout machinery.

• The gating system required to produce castings in a mould yields leftover metal, including heads, risers and sprue, sometimes collectively called sprue, that can exceed 50% of the metal required to pour a full mould.

• Since this metal must be remelted as salvage, the yield of a particular gating configuration becomes an important economic consideration when designing various gating schemes, to minimize the cost of excess sprue, and thus melting costs.

FETTLING

• Heat treating is a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of a material.

• Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material.

• Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering and quenching.

PROBLEM DEFINITION

• Usage of more scraps leads to more cost.• This can be controlled by using SQC(Statistical

Quality Control) and Six Sigma.• Some of tools that can be used are:Pareto chartsFish-Bone DiagramHypothesis testingControl charts…

EXPERIMENTAL DATA

Taken melts of WCB without returns.Taken melts of WCB with returns.Taken melts of CK3MCuN without

returns.Taken melts of CK3MCuN with returns.

CK3MCuN GRADE WITH& WITHOUT RETURNS

Heat No SCRAP Status RT NSD % WELD Chem Mech

K7748 406.75 Rejection 50   Ok Ok

K7837 416.35 Rejection 50   Ok Ok

K7668 413.41 Rejection 75   Ok Ok

K7715 406.23 ok 100 1.87% Ok Ok

K7502 413.71 ok 100 0.82% Ok Ok

K7378 409.1 Rejection     Ok Ok

K7432 413.59 ok 100 0.89% Ok Ok

CK3MCuN GRADE WITH& WITHOUT RETURNS

Heat No SCRAP+RET Status RT NSD % WELD Chem Mech

K7868 390.44 ok 100   Ok Ok

K7906 391.27 ok 100   Ok Ok

K7629 364.62 Rejection 50   Ok Ok

K7643 392.54 Rejection 50   Ok Ok

K7513 408.99 Rejection 50   Ok Ok

K7521 401.01 R ok 100 0.93% Ok Ok

WCB GRADE WITHOUT RETURNS

HEAT NO: NSD% WELD%

K6739 78.90% 3.22%

K6740 81.50% 1.78%

K6741 82.90% 5.11%

WCB GRADE WITH RETURNS

HEAT NO: NSD% WELD%

K6748 63% 15.17%

K6751 81.50% 1.66%

K6752 75.30% 9.66%

K6756 89.50% 0.52%

K6761 63.20% 3.67%

K6762 73.70% 3.18%

K6764 48.60% 3.54%

K6765 94.60% 0.78%

K6766 83.80% 1.81%

WCB GRADE WITHOUT RETURNS

K6739 K6740 K67410.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

NSD% WELD%

WCB GRADE WITH RETURNS

K6748K6751

K6752K6756

K6761K6762

K6764K6765

K67660%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

NSD% WELD%