About Fomas Group And Bay Forge Ltd Engineering Essay

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Fomas Group is a world leader in critical forging. Fomas Group's mission is to manufacture open die forgings and seamless rings with the ultimate in quality standards that few would match. Fomas Group has a vast reputation for product and technological innovations to offer new advantages to a worldwide clientele.

Bay Forge Ltd

Bay Forge, a subsidiary of the renowned Fomas Group of Italy, has grown to be an undisputed leader in the realm of open die forging and large seamless rings in India. Since its inception in 1996, it is a pioneer in large volume critical forging and ring rolling. At Bay-Forge, quality and innovation have always been the watchwords. Its commitment to quality has put it way ahead of others. Over the years, Bay-Forge has been upgrading its workmanship by incorporating the latest in technological developments around the world. Today, it is the most sought for name when it comes to large forged components and seamless rings used in critical areas like aerospace, power generation, wind power, general engineering, oil and gas application, among host of others.

Customers:

The technological focus and commitment to quality have earned Bay-Forge some of the most renowned names as customers. The customers list includes...

VIKRAM SARABHAI SPACE CENTRE

ALSTOM / VA TECH / JP HYDRO

BARC / NPCIL / IGCAR

BELLELI HEAVY INDUSTRIES, SAUDI ARABIA

BHEL / SIEMENS /TRIVENI

BHPV / KCP

DRESSER RAND

DRDL / ASL / RCI

GODREJ & BOYCE

HAL

JINDAL STEEL AND POWER

KSB / SULZER

LARSEN & TOUBRO

MIDHANI

RRB VESTAS / SUZLON / PIONEER WINCON / NEG MICON

TISCO / SAIL

WALCHAND NAGAR INDUSTRIES

Products manufactured by Bay-Forge Ltd:

Bay-Forge has been a forerunner in high quality

components for critical applications. Some of the highly specialized forgings manufactured are:

Rings in Carbon/ Alloy/ Stainless Steel up to dia 5500mm.

Convergent & Divergent Nozzles for Aerospace applications

Large Rings for Aerospace applications in Aluminium and High Strength Alloy Steels

Bucket Flange for Aerospace applications

Pinions for Steel Industries

Seal Housing /Barrel Casings for Pump Industries

Wind Mill Shafts and Flanges

Steam Turbine Rotor Shafts

Dished End with Integral Nozzle for Nuclear applications

INTRODUCTION

TO

ALUMINIUM

ALLOYS

Aluminium alloys can be divided into nine groups:

Designation Major Alloying Element

1xxx Unalloyed (pure) >99% Al

2xxx Copper is the principal alloying element, though other elements (Magnesium) may be specified

3xxx Manganese is the principal alloying element

4xxx Silicon is the principal alloying element

5xxx Magnesium is the principal alloying element

6xxx Magnesium and Silicon are principal alloying elements

7xxx Zinc is the principal alloying element, but other elements such as Copper, Magnesium, Chromium, and Zirconium may be specified

8xxx Other elements (including Tin and some Lithium compositions)

9xxx Reserved for future use

1xxx Series

These grades of aluminium are characterized by excellent corrosion resistance, high thermal and electrical conductivities, low mechanical properties, and excellent workability. Moderate increases in strength may be obtained by strain hardening. Iron and silicon are the major impurities.

2xxx Series

These alloys require solution heat treatment to obtain optimum properties; in the solution heat-treated condition, mechanical properties are similar to, and sometimes exceed, those of low-carbon steel. In some instances, precipitation heat treatment (aging) is employed to further increase mechanical properties. This treatment increases yield strength, with attendant loss in elongation; its effect on tensile strength is not as great.

The alloys in the 2xxx series do not have as good corrosion resistance as most other aluminium alloys, and under certain conditions they may be subject to intergranular corrosion.  Alloys in the 2xxx series are good for parts requiring good strength at temperatures up to 150 °C (300 °F). Except for alloy 2219, these alloys have limited weldability, but some alloys in this series have superior machinability.

3xxx Series

These alloys generally are non-heat treatable but have about 20% more strength than 1xxx series alloys. Because only a limited percentage of manganese (up to about 1.5%) can be effectively added to aluminium, manganese is used as major element in only a few alloys.

4xxx Series

The major alloying element in 4xxx series alloys is silicon, which can be added in sufficient quantities (up to 12%) to cause substantial lowering of the melting range.  For this reason, aluminium-silicon alloys are used in welding wire and as brazing alloys for joining aluminium, where a lower melting range than that of the base metal is required.  The alloys containing appreciable amounts of silicon become dark gray to charcoal when anodic oxide finishes are applied and hence are in demand for architectural applications.

5xxx Series

The major alloying element is Magnesium an when it is used as a major alloying element or with manganese, the result is a moderate-to-high-strength work-hardenable alloy. Magnesium is considerably more effective than manganese as a hardener, about 0.8% Mg being equal to 1.25% Mn, and it can be added in considerably higher quantities. Alloys in this series possess good welding characteristics and relatively good resistance to corrosion in marine atmospheres. However, limitations should be placed on the amount of cold work and the operating temperatures (150 degrees F) permissible for the higher-magnesium alloys to avoid susceptibility to stress-corrosion cracking.

6xxx Series

Alloys in the 6xxx series contain silicon and magnesium approximately in the proportions required for formation of magnesium silicide (Mg2Si), thus making them heat treatable. Although not as strong as most 2xxx and 7xxx alloys, 6xxx series alloys have good formability, weldability, machinability, and relatively good corrosion resistance, with medium strength. Alloys in this heat-treatable group may be formed in the T4 temper (solution heat treated but not precipitation heat treated) and strengthened after forming to full T6 properties by precipitation heat treatment.

7xxx Series

Zinc, in amounts of 1 to 8% is the major alloying element in 7xxx series alloys, and when coupled with a smaller percentage of magnesium results in heat-treatable alloys of moderate to very high strength. Usually other elements, such as copper and chromium, are also added in small quantities. 7xxx series alloys are used in airframe structures, mobile equipment, and other highly stressed parts.  Higher strength 7xxx alloys exhibit reduced resistance to stress corrosion cracking and are often utilized in a slightly overaged temper to provide better combinations of strength, corrosion resistance, and fracture toughness.

Introduction to 7075 Aluminium Alloy

Alloy 7075 has been the standard workhorse 7XXX series alloy within the aerospace industry ever since. It was the first successful Al-Zn-Mg-Cu high strength alloy using the beneficial effects of the alloying addition of chromium to develop good stress-corrosion cracking resistance in sheet products. Although other 7XXX alloys have since been developed with improved specific properties, alloy 7075 remains the baseline with a good balance of properties required for aerospace applications. This heat treatable alloy is considered high in strength. Corrosion resistance and machinability is fair. Rated low on workability and welded only by the resistance process.

7075 is an aluminium alloy, with zinc as the primary alloying element. It is strong, with a strength comparable to many steels, and has good fatigue strength and average machinability, but has less resistance to corrosion than many other Al alloys. Its relatively high cost limits its use to applications where cheaper alloys are not suitable.

7075 aluminium alloy's composition includes 5.1-6.1% zinc, 2.1-2.9% magnesium, 1.2-2.0% copper, and less than half a percent of silicon, iron, manganese, titanium, chromium, and other metals. It is commonly produced in several heat temper grades, 7075-O, 7075-T6, 7075-T651.

7075 Aluminium Alloy Applications:

Alloy 7075 sheet and plate products have application throughout aircraft and aerospace structures where a combination of high strength with moderate toughness and corrosion resistance are required.

Typical applications are alclad skin sheet, structural plate components up to 4 inches in thickness and general aluminium aerospace applications.

Material Overview:

7075 is the most popular of the aluminium-zinc (7xxx series) alloys. Properties are representative of the entire series.

Aluminium Association (US) grade 7075 is equivalent to: ISO AlZn6MgCu; German AlZnMgCu1.5; British L95 or L98; Spanish L-371; French A-Z5GU; and Canadian ZG62.

The term "aerospace-grade aluminium" typically refers to 7075, but may also refer to any 2xxx or 7xxx alloy.

Used in aircraft parts, high-end sporting goods, and moulds for small runs of plastic parts.

Nominal composition: 1.6% copper, 2.5% magnesium, 0.23% chromium, 5.6% zinc, and a remainder of aluminium.

Baseline properties given for temper T6. Mechanical properties of the T6 and T651 tempers are nearly identical.

CHEMICAL COMPOSITION LIMITS

(WT. %):

Si . . . . . . . . . . . . .0.40

Zn . . . . . . . . . . . . 5.1-6.1

Fe . . . . . . . . . . . . .0.50

Ti . . . . . . . . . . . . .0.20

Cu . . . . . . . . . . . . 1.2-2.0

Mn. . . . . . . . . . . . 0.30

Mg. . . . . . . . . . . . 2.1-2.9

Cr . . . . . . . . . . . . 0.18-0.28

Others, each . . . . 0.5

Others, total . . . . 0.15

Balance . . . . . . . Aluminium

Direct chill casting:

Aluminium and aluminium alloy ingots and billets are routinely formed by the direct chill (DC) casting process. In this process, molten metal is fed to a mould having a bottom portion thereof which is lowered as the metal solidifies, forming the ingot or billet from a molten pool of metal at the top of the mould. Solidification of the molten metal results from water spray cooling of the mould and the outer surface of the metal ingot or billet.

The DC casting method is not without its limits. Surface cracks and other surface imperfections require that a significant portion of the outer surface of the ingot or billet be removed or scalped from the ingot or billet after casting and prior to rolling or extrusion into a final product.

With certain aluminium alloys, notably the relatively hard aluminium can body stock alloys, such as aluminium alloy 7075, these surface irregularities are often pronounced. It is evident from close examination of finished ingots of this material that a major cause of the surface irregularities comes from the metal solidifying in a series of horizontal layers, rather than in a continuous vertical freeze pattern. This requires even more extensive scalping of the ingots, resulting in excessive scrap.

Other surface defects in aluminium ingots and billets as they are formed by the DC casting method include tearing of the surface resulting from sticking of the surface of the ingot to the surface of the mould.

In the past, various lubrication schemes have been attempted to improve aluminium ingot and billet casting surface quality. Such methods as coating the mould surface with a release agent prior to casting, supplying a soluble oil to the mould during casting and applying carbon powder to the molten metal surface of the ingot during casting have met with mixed results.

It is desirable, therefore, to provide an improved method for direct chill casting of aluminium and aluminium alloy ingots and billets which will substantially reduce or eliminate surface cracks, tearing, and other surface defects, such as black ingots, so that reduced levels of scalping prior to final forming are required.

By means of the present invention, the desirable result has been obtained.

The method of the present invention involves applying to the molten metal surface of an aluminium or aluminium alloy ingot or billet being cast an insulating and nonreactive powder selected from the group consisting of boron nitride, amorphous silica, diatomaceous earth and talcum. The powder migrates to the edges and corners of the mould, resulting in reduced levels of tearing and surface cracking, reduction in or elimination of black surface ingots and solidification of the ingot in a vertical direction, rather than as horizontal layers.

The resulting ingot or billet is more easily scalped, with less metal having to be removed and scraped from the ingot or billet.

Process flow:

Manufacturing of AA 7075 rings:

Pancaking:

Pancake is a rough, flat, forged shape made quickly with a minimum of tooling. The billet is heated up to forging temperature. Then, it is mechanically worked (forged) until a rough cylinder of less height when compared to the billet is achieved.

Then the pancake is placed in a punching press and a hole is punched in its centre such that a ring of high wall thickness is achieved. This is then sent for ring rolling.

Ring Rolling:

This method is characterized by two pairs of tools. One of them acts in the radial, the other one in axial ring direction. In a radial-axial ring rolling machine, the ring is rolled simultaneously in the radial pass and the axial pass, which is typically located directly across from the radial pass. During rolling, the ring is kept in the proper position using centring rolls. These rolls position the rings correctly between the radial roll and the axial roll during rolling. The positions of the centring rolls are carefully controlled during the rolling process so that there are no unwanted stresses on the ring during rolling. In this ring rolling process the ring undergoes height reduction, decrease in wall thickness as well as increase in the outer diameter.

In this process

The motor torque causes the rotation of the ring.

The axial rolling force causes reduction of the height.

The radial rolling force causes the reduction of wall thickness.

The reduction of wall thickness and the height at the total ring circumference causes the ring growth.

Heat treatments:

This process comprises of solution treatment and ageing.

Solution treatment:

If the slowly cooled alloy is preheated to produce a complete solid solution, and then quenched in water or oil, precipitation will not occur and a supersaturated solid will be produced. The temperature and duration of this solution treatment depend on its thickness. At the end of this stage of the heat treatment, the alloy is soft and weak, which is convenient stage to do cold working. Solution treatment is done at a temperature of 470ËšC.

Precipitation treatment:

The supersaturated solid solution treatment is only stable at lower temperatures, and if the alloy is given a further heat treatment, called precipitation treatment, precipitation will start; provided the temperature is not too high the copper (or the other alloying additions) will not leave the solid solution, but will form regions of "high population" within it. The temperature to which the alloy is heated (between 100 & 200ËšC) depends on its composition. The duration of the treatment (between 2 & 30 hours) depends on its composition and its thickness.

Ageing:

Hardening is followed by ageing in which the alloy is held at a temperature of about 120˚C for about 24 hours. In this process of ageing, the oversaturated solid solution decomposes. This actually strengthens the alloy. At these ageing temperatures the copper atoms move only within the crystal lattice of the α-solid solution over extremely small distances.

In between the solution treatment and ageing, the compression process is carried out. In this process, the ring is compressed by 2 - 3% of its height. This process is carried out to relieve the internal stresses.

EXPERIMENTS

AND

OBSERVATIONS

Separate test piece testing results:

UTS vs. Hardness:

As the hardness increases, the Ultimate tensile strength increases and vice-versa.

Yield strength/UTS vs. Hardness:

As the YS/UTS increases, the hardness increases and vice-versa.

Yield strength vs. Hardness:

As the hardness increases, the Yield strength increases and vice-versa.

UTS vs. Conductivity:

As UTS increases, the conductivity decreases and vice-versa.

YS vs. Conductivity:

As YS increases, the conductivity decreases and vice-versa.

Conductivity vs. Hardness:

As hardness increases, the conductivity decreases and vice-versa.

Production ring test results:

UTS vs. Hardness:

As the hardness increases, the Ultimate tensile strength increases.

Yield strength/UTS vs. Hardness:

As the YS/UTS increases, the hardness increases.

Yield strength vs. Hardness:

As the hardness increases, the Yield strength increases.

UTS vs. Conductivity:

No correlation.

YS vs. Conductivity:

No correlation.

Conductivity vs. Hardness:

No correlation.

Lab trial No: 2 testing results:

At 115-24 hrs:

UTS vs. Hardness:

As the hardness increases, the Ultimate tensile strength increases and vice-versa.

Yield strength/UTS vs. Hardness:

As the hardness increases, the YS/UTS increases and vice-versa.

Yield strength vs. Hardness:

As the hardness increases, the Yield strength increases and vice-versa.

UTS vs. Conductivity:

As UTS increases, the conductivity increases and vice-versa.

YS vs. Conductivity:

As YS increases, the conductivity increases and vice-versa.

Conductivity vs. Hardness:

As hardness increases, the conductivity increases and vice-versa.

Lab trial No:2 testing results:

At 120-16 hrs:

UTS vs. Hardness:

As the hardness increases, the Ultimate tensile strength decreases and vice-versa.

Yield strength/UTS vs. Hardness:

No correlation.

Yield strength vs. Hardness:

As the hardness increases, the Yield strength decreases and vice-versa.

UTS vs. Conductivity:

As UTS increases, the conductivity increases and vice-versa.

YS vs. Conductivity:

As YS increases, the conductivity decreases and vice-versa.

Conductivity vs. Hardness:

As hardness increases, the conductivity decreases and vice-versa.

SUGGESTIONS

FOR

FUTURE

DEVELOPMENT

Spray deposition:

Three 7xxx series aluminium SS70, N707 and 7075 alloys have been produced by the spray deposition process. The alloys were extruded and subsequently heat treated in the T6 and T7 temper conditions. Texture analysis of as-received and solution treated alloys revealed <111> and <100> fibre textures leading to higher mechanical properties in the longitudinal direction. Anisotropic behaviour was observed in these alloys. In addition, the influence of recrystallizing, heat treatment, stretching, and processing techniques (IM, PMand spray casting) as well as techniques of forming (extrusion, rolling and forging) on the anisotropic behaviour of the 7xxx series aluminium alloys was examined.

Introduction:

Recently, the spray deposition technique has been developed to produce high density, near net shaped preforms of materials directly from the liquid state as an alternative production method to PM. Spray casting was developed from work carried out by Singer at the University of Swansea, U.K., during the early 1970s (Singer, 1970, 1972). The process was explained schematically in detail (Salamci, 2001). Spray deposition processing generally consists of two steps: the energetic disintegration of a molten metal by inert gas jets into micron-sized droplets (atomization) and the subsequent deposition of a mixture of solid, liquid, and partially solidified droplets on a surface (deposition) (Lengsfeld, 1995). The spray deposition technique differs from established PM technology in that both the atomization and consolidation processes are combined in a single operation. The reduction in the number of manufacturing steps can lead to significant financial savings. Furthermore, this process is carried out under an inert (typically nitrogen) atmosphere, and therefore the embrittling oxide content can be reduced and thus the ductility and fracture toughness can be improved. Compared to conventional casting spray casting involves a much more rapid solidification which gives the added benefits of extending the maximum solute content of alloying elements, as well as allowing reduced macrosegregation and refinement of the alloy grain size (Lavernia and Grant, 1988). Anisotropic mechanical properties are important for designers, who can often use a material with enhanced strength in one direction. Little attention has been focused on the anisotropic behaviour of spray cast 7xxx series aluminium alloys. The objective of the present research was to investigate the texture mechanism of spray cast 7xxx series aluminium alloys and the anisotropic behaviour of the alloys.

Experimental Procedure:

The alloys, namely SS70, N707 and 7075, investigated in the present study were produced by Alcan Cospray Ltd. at Banbury, U.K., using the spray deposition process. SS70 was spray cast as a cylindrical preform with a diameter of 240 mm and height of 1100 mm and extruded down to a 25 mm diameter rod. The N707 was also spray cast as a preform, which was 235 mm in diameter and 790 mm in height, extruded down to 63 x 25 mm rectangular section. The 7075 alloy was similarly processed, i.e. spray cast to a ~ 240 mm diameter cylindrical preform and extruded to a 65 x 30 mm rectangular section. The chemical compositions of the alloys are given in Table 1. Compared to 7075, the zinc contents of SS70 and N707 were significantly increased from 5.4% to 11.5 and 10.9% , respectively, in order to increase strength. In order to control recrystallization and grain growth 0.2% Zr was added to SS70 and N707 instead of Cr, which was used in 7075. SS70 had a slight increase in Zn and Mg content compared to N707. The SS70 and N707 had lower iron and silicon contents (around 0.05-0.03% Fe and 0.02-0.01% Si) compared to the conventional 7075 alloy.

Table 1: Chemical composition of SS70, N707 and 7075 alloys

(Weight percentage).

ALLOY

Zn

Mg

Cu

Zr

Cr

Fe

Si

Mn

Al

SS70

11.50

2.64

1.16

0.26

<0.01

0.05

0.02

-

Bal.

N707

10.90

2.16

1.01

.22

<0.01

0.03

0.01

-

Bal.

7075

5.6

2.5

1.6

-

0.2

0.4

0.5

0.3

Bal.

Table 2: Average room temperature tensile test results in the T6 condition

ALLOY

TEMPER

ORIENTATION

σYS (MPa)

σUTS (MPa)

ELONG.(%)

SS70

T6

L

775

803

5

N707

T6

L

711

740

5

T

635

673

5

7075

T6

L

590

656

11

T

524

588

8

Table 3: Average room temperature notch tensile strength results in the T6 condition

ALLOY

TEMPER

ORIENTATION

σYS (MPa)

σN (MPa)

σN/σYS

SS70

T6

L

755

666

0.88

N707

T6

L

711

674

0.94

T

635

314

0.5

7075

T6

L

590

687

1.16

T

524

560

1.07

Table 4: Yield strength values in L and T orientations from spray deposited 7000 series aluminium alloys in the T6 and T7 conditions

ALLOY

ORIENTATION

T6 TEMPER

T7 TEMPER

Al-Zn-Mg-Cu (7000 series)

L, σYS

705

503

T, σYS

620

482

N707

L, σYS

711

590

T, σYS

635

524

7075

L, σYS

544

513

T, σYS

513

481

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