127.study The Effect Of Welding Parameters Of Tig Welding Of Plate.docx

STUDY THE EFFECT OF WELDING PARAMETERS OF TIG WELDING OF PLATE

1

ABSTRACT

The object of the present work is to research the dissimilar material welding of Aluminium alloy 6063 and different types of weld using stainless steel filler metals. Gas tungsten arc welding with identical parameters and procedures was used to carry out single V groove butt welding. The mechanical properties were performed. And to evaluate Toughness and hardness analysis to performed in the weld region. And evaluate the tensile strength of the material.

2

CHAPTER 1

INTRODUCTION

3

CHAPTER 1 INTRODUCTION The requirements for the pharmaceutical and biotechnology industries are relatively high and the materials of construction for processing vessels and piping systems must demonstrate outstanding corrosion resistance and clean ability to ensure the purity and integrity of the drug product. Materials must be capable of withstanding the temperature, pressure, and corrosive nature of the production environments as well as all sanitizing and cleaning procedures. In addition, candidate materials must have good weldability and must be capable of meeting the industry’s surface finish requirements.

The primary material of construction for processing equipment in the pharmaceutical and biotechnology industries is Type 316L austenitic stainless steel and inconel steel. The corrosion resistance, weldability, electro polishing properties, and availability of the 316 grade and alloy steel P12 make it an ideal candidate for most pharmaceutical applications. Although Type 316 performs well in many process environments, users are continually looking to enhance the properties of When process environments are too aggressive for Type 316, users have either accepted the increased maintenance costs of a 316 system and aluminium alloy 6061 steel.

The project starts with chemical analysis of materials and preparation of WPS based on thermal and mechanical properties. Finally the strength of material is calculated and compared with the ASME and AWS value. In welding by controlling the parameters of thermal property mechanical 4

deviations are reduced and so weld with fewer defects could be obtained and also the service life of material will be increased.

DISSIMILAR MATERIAL WELDING: In modern steel constructions it is extremely important, and sometimes unavoidable, to perform a durable dissimilar metal weld between low alloyed or carbon steel and stainless steel. A schematic picture of a dissimilar metal weld is presented. When welding such dissimilar metal welds the choice of filler metal plays a big role and usually has a composition differing from both of the parent metals. The composition of the weld metal will therefore be a mix of the parent metals and the filler metal at some specific ratio. During welding of dissimilar metal welds it is important to control the composition of the weld metal. From assumptions that the weld metal consists of a mix of the parent metals and the filler metal the composition can be estimated. Narrow control of the resulting weld metal composition is important to decrease the risk of defects in the weld, such as hot cracks or sigma phase formation. The composition is also important to control so that the weld metal properties corresponds the required ones. The filler metal normally used in dissimilar metals welds. If the welds are exposed to high temperatures or an intense thermal cycle, nickel based alloys are usually used as filler metal. In a dissimilar metal weld between carbon steel and stainless steel it is important to reduce the dilution with the carbon steel, in order to obtain a good microstructure. It is therefore common to not point the arc directly on the carbon steel side, but rather to angle the torch slightly toward the stainless steel. Another important factor to optimize during welding of a dissimilar metal weld is the inter pass temperature, i.e. the actual temperature in the already present weld bead before welding starts during multi pass welding. Welding dissimilar 5

metal welds faces many characteristic problems caused by structural changes and several constitutional changes can occur during welding. Changes in the dilution ratio of the parent metals are possible and affected by the welding conditions. During welding a stable manufacturing and good crack resistance is important. If the dilution between the filler metal and parent metals increases, the ferrite content will decrease in the case of welding low alloyed or carbon steel to stainless steel with a filler metal of over-alloyed austenitic stainless steel. If the amount of stainless steel diluted to the weld metal increases the structure can be fully austenitic and the risk of hot cracking increases significantly. On the other hand, if the dilution with the low alloyed steel increases a structure with more martensite is created which is a hard and brittle structure. If the ferrite content becomes too high, thermal ageing during operation at elevated temperatures may lead to a transformation of the ferrite to sigma phase or as spinodal decomposition. The sigma phase is very brittle, due to this joints used in systems that operates at high temperatures should have as low ferrite content as possible. Factor for dissimilar metal welding: The weld metal composition is usually not uniform throughout the weld, especially in multi pass welds. A composition gradient is likely to arise in the weld metal between the two parent metals. The solidification procedure of the weld metal is influenced by the dilution and the composition gradients, this is important with respect to hot cracking. When designing a dissimilar metal weld final weld metal and the mechanical properties must be considered. The factors that usually are responsible for failure of dissimilar metal welds are:  Alloying problems and formation of brittle phase and limited mutual solubility of the two metals  Widely differing melting points 6

 Differences in thermal expansion coefficients  Differences in thermal conductivity When designing a butt weld to a dissimilar metal weld, attention must be given to the melting characteristics of the both parent metals and the filler metal, as much as to the dilution effect. Large joints will permit better control of the molten weld metal, decrease the dilution and provide room for control of the arc for good fusion. It is important that the joint design provides appropriate dilution for the first few passes. It is not unusual for dissimilar metal welds to have a failure in shorter time than the expected lifetime. Most of the failures of a dissimilar metal weld between austenitic steel and low alloyed steel occur in the HAZ on the low alloyed steel side, close to the weld interface. These failures usually fulfill one or more of the following criteria:  High stresses resulting in creep at the interface between the weld metal and parent metals due to differences in thermal expansion.  A weakening in the HAZ on the low alloyed or carbon steel side due to carbon migration from the low alloyed steel side to the austenitic steel side.  Oxidation at the interface that is accelerated by the presence of the stresses induced by the welding. A chemical composition gradient is likely to arise in the weld metal and especially close to the parent metals. If the dissimilar metal weld is operating at an elevated temperature inter diffusion between the parent metals and weld metal is possible which could result in a modified microstructure. This is can happen when an austenitic stainless steel is used as a filler metal. Chromium that has a greater affinity to carbon than iron, therefore it is likely for the carbon to diffuse from the parent metal to the weld metal during temperatures above 425 °C. Carbon migration usually takes place during post-weld heat treatment or when operating at elevated temperatures or cryogenic environment. The 7

parent metals and the weld metal has different corrosion behaviors that must be considered when producing a dissimilar metal weld. For example a galvanic cell could be created and trigger corrosion of the most anodic metal or the most anodic phase in the weld. Corrosion at a micro structural level is possible in the weld metal that usually consists of several different micro structural phases. To avoid galvanic corrosion the composition of the weld metal could be changed to provide a cathodic protection to the parent metal that is the most vulnerable to corrosion attack. A cathodic protection is a good option as long as it does not threaten the mechanical properties of the dissimilar metal weld.

Properties of various Materials: Material

Young’s

Density(kg/m³)

Poisson’s ratio

Modulus(GPa) Steel

7850

210

0.30

Stainless Steel

8000

190

0.30

Cast Iron

7300

110

0.26

Aluminium

2700

70

0.33

Copper

8800

110

0.34

Magnesium

1800

45

0.35

Titanium

4500

110

0.34

Nickel

8900

200

0.31

Inconel

8800

200

0.32

Monel

8400

180

0.31

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Thermal Properties of Various materials: Material

Thermal

Thermal

Expansion

conductivity

Specific Heat

W\mK Steel

11

50

486

Stainless Steel

11

20

550

Cast Iron

11

40

544

Aluminium

23

208

900

Copper

17

385

385

Magnesium

26

90

1050

Titanium

9

10

550

Nickel

14

70

450

Inconel

13

10

410

Monel

14

20

427

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CHAPTER 2

LITERATURE SURVEY

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CHAPTER 2 LITERATURE SURVEY MIKE WILSON, (Banbury, UK) (2007) “TIP TIG: new technology for welding”, industrial robot: an international journal, vol. 34 Iss : 6, pp.462 – 466. DOI: 10.1108/01439910710832057. The paper aims to report a new technology on TIG. The study finds that the technology provides significant cost savings to the user. TIG provides improved quality of their product and reduces their cost BHEL JOURNAL VOLUME 27 No.2 (SEP 2006).ISSN 0970-1540. “Advances in Materials for Advanced Steam cycle power Plants” by Kulvir singh. Development of stronger high temperature materials is the prime requirement. This article reviews the potential benefits, operational experiences, the present trend and the advances in materials that require special attention, in respect to power plants with super critical steam conditions. “STANDARD TECHNICAL FEATURES OF BTG SYSTEM FOR SUPERCRITICAL 660/800MW THERMAL UNITS”, Government of India Ministry

of

Power

Central

Electricity

Authority

New

Delhi

.July

2013.”Supercritical technology is an established and proven technology with 500 supercritical units. Ultra supercritical parameters with pressure of 250300Kg/cm2 and main steam temperature 600-610oc. Research is underway to further increase the stream temperature to 700oC DAVID A. METZLER, supplement to the welding journal, June 2012 Sponsored by the American Welding Society and the Welding Research Council. Strain-Age Cracking Susceptibility of Ni Based Super alloys as a Function of Strain Rate, Temperature, and Alloy Composition. 11

Gyun Na et al. aluminium alloy 6061 Stated that residual stress is one of the most important factors but its effect on high-cycle fatigue is of more concern than the other factors. Residual stress is a tension or compression that exists in a material without any external load being applied, and the residual stresses in a component or structure are caused by incompatible internal permanent strains. Welding, which is one of the most significant causes of residual stress, typically produces large tensile stresses, the maximum value of which is approximately equal to the yield strength of materials that are joined by lower compressive residual stresses in a component. The residual stress of welding can significantly impair the performance and reliability of welded structures.

Chengwu et al.

In their work on weld interface microstructure and

mechanical properties of alloy steel dissimilar welding, the microstructure near the interface between Cu plate and the intermixing zone was investigated. Experimental results showed that for the welded joint with high dilution ratio of copper, there was a transition zone with numerous filler particles near the interface. However, if the dilution ratio of copper is low, the transition zone is only generated near the upper side of the interface. At the lower side of the interface, the turbulent bursting behaviour in the welding pool led to the penetration of liquid metal into Cu.

Khan et al.

aluminium alloy 6061

Came to the conclusion that

formation of ferrite along the austenite grain boundary in the heat affected zone on austenite side is observed. At the same time, microstructures are composed of two-phase ferrite and martensite with intra-granular carbide on ferrite side. Also the variation in local micro-hardness observed across the weld depends on 12

the fraction intermix of each base metal and the redistribution of austenite- and ferrite-promoting elements in the weld. Itoh et al. Got a patent on the joined structure on the metallic materials. This invention relates generally to a joined structure of dissimilar metallic materials having different characteristics. More specifically, the invention relates to a joined structure of a current carrying contact or arching contact which are used for, e.g., a power breaker, or a coating end structure of a metal base and a coating material for improving conductivity and heat resistance. Delphin et al. aluminium alloy 6061 stated that the choice of hardening model is important. It is believed that kinematic hardening is a better choice than isotropic hardening in low cycle simulations i.e. in a few-pass welding process, as in the present study. For the case of weld residual stresses in combination with high thermal stresses, it is found that the plasticity induced by the thermal stresses is not sufficient to suppress the influence of weld residual stresses on CTOD, even for very high thermal loads. The residual stresses can be relaxed by unloading from a primary tensile load. Mai and Spowage did their work on characterisation of dissimilar joints of steel kovar, copper-steel and aluminium-copper.

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CHAPTER-3

SELECTION OF MATERIAL

14

CHAPTER-3 SELECTION OF MATERIAL

 ALUMINIUM ALLOY 6063

1. ALUMINIUM ALLOY 6063

Fig. Aluminium alloy Aluminium is a light metal ( = 2.7 g/cc); is easily machinable has wide variety of surface finishes; good electrical and thermal conductivities; highly reflective to heat and light.  Versatile metal - can be cast, rolled, stamped, drawn, spun, roll-formed, hammered, extruded and forged into many shapes. Aluminium can be riveted, welded, brazed, or resin bonded.  Corrosion resistant - no protective coating needed, however it is often anodized to improve surface finish, appearance.

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 Al and its alloys - high strength-to-weight ratio (high specific strength) owing to low density.  Such materials are widely used in aerospace and automotive applications where weight savings are needed for better fuel efficiency and performance.  Al-Li alloys are lightest among all Al alloys and find wide applications in the aerospace industry.

History, properties and alloys The history of the light metal industry, as that of many other industries in this century, is one of notable and ever accelerating expansion and development. There are few people today who are not familiar with at least some modern application of aluminium and its alloys. The part it plays in our everyday life is such that it is difficult to realise that a century ago the metal was still a comparative. The excellent corrosion resistance of pure aluminium is largely due to its affinity for oxygen; this results in the production of a very thin but tenacious oxide film which covers the surface as soon as a freshly cut piece of the metal is exposed to the atmosphere. This oxide coating is of great significance in the production of practically every type of surface finish for the metal. It is, of course, the basis of what is probably the most corrosion-resistant finish of all, namely, that group of finishes which involves the technique of anodic oxidation in its varied forms.

Development of aluminium alloys The chief alloying constituents added to aluminium are copper, magnesium, silicon, manganese, nickel and zinc. All of these are used to increase the strength of pure aluminium. Two classes of alloys may be considered. The first 16

are the 'cast alloys' which are cast directly into their desired forms by one of three methods (i.e., sand-casting, gravity die casting or pressure die casting), while the second class, the 'wrought alloys', are cast in ingots or billets and hot and cold worked mechanically into extrusions, forgings, sheet, foil, tube and wire. The main classes of alloys are the 2000 series (Al-Cu alloys), which are high-strength materials used mainly in the aircraft industry, the 3000 series (AlMn alloys) used mainly in the canning industry, the 5000 series (Al-Mg alloys) which are used unprotected for structural and architectural applications, the 6000 series (Al-Mg-Si alloys) which are the most common extrusion alloys and are used particularly in the building industry, and the 7000 series (Al-Zn-Mg alloys) which are again high strength alloys for aircraft and military vehicle applications. The alloy used in any particular application will depend on factors such as the mechanical and physical properties required, the material cost and the service environment involved. If a finishing treatment is to be applied, then the suitability of the alloy for producing the particular finish desired will be an additional factor to be taken into account. The great benefit of aluminium is that such a wide variety of alloys with differing mechanical and protection properties is available, and these, together with the exceptional rang e of finishes which can be used, make aluminium a very versatile material

Aluminium alloy selection and applications This monograph contains an outstanding introductory description of the properties of wrought and cast aluminium alloys and the enormous variety of their applications. From transportation

and

packing to

construction,

infrastructure and aerospace, the versatility of aluminium as a practical material is amply documented. The text is richly illustrated with numerous applications which demonstrate the enormous flexibility and the wide range of applications for aluminium alloys. This publication will be invaluable to engineers, designers 17

and students unfamiliar with the variety of aluminium alloys and to those faced with an alloy selection decision. It outlines many of the issues to consider in selecting an alloy for a specific application and environment. Starting with a description of the aluminium alloy designation system, the text describes the major alloy series, outlines their primary chemical constituents, mechanical properties and major characteristics, and provides numerous examples of specific alloys in use. In summary, this monograph provides a lot of clarity to the process of selecting alloys for various applications.

Effect of aluminium Aluminium and aluminium alloy are gaining huge industrial significance because of their outstanding combination of mechanical, physical and tribological properties over the base alloys. These properties include high specific strength. High wear and seizure resistance, high stiffness, Better high temperature strength, controlled thermal expansion coefficient and improved damping capacity. Corrosion of aluminium Whilst aluminium and its alloys generally have good corrosion resistance, localised forms of corrosion can occur, and it is important to understand the factors contributing to these of corrosion. Corrosion may be defined as the reaction between a metal and its immediate environment, which can be natural or chemical in origin. The most recognisable form of corrosion is, perhaps, the rusting of iron. All metals react with natural environments but the extent to which this happens can vary; for noble metals like gold the amount is insignificant whereas for iron it is considerable. Aluminium is no exception but, fortunately, it has the propensity of self passivation and for many applications corrosion is not a problem.

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PROPERTIES OF AL-ALLOY (i) Heat treatable and age hardenable. (ii) High strength efficiency due to high strength to weight ratio (iii) Good weldability (iv) Good corrosion resistance (v) Good thermal conductivity APPLICATIONS OF AL- ALLOY Alloy 6063 is perhaps the most widely used because of its extrudability, it is not only the first choice for many architectural and structural members, but it has been the choice for the Audi automotive space frame members. A good example of its structural use was the aluminum bridge. (Gilbert Kaufman, 2000). The alloy has versatile application as given below  Pressure vessels  Pipelines  Cryogenic tanks  Door beams, seat tracks, racks, rails  Electrical cable towers  Petroleum

and

Chemical

Industry

Components

(The

excellent

combination of high strength combined with superior corrosion resistance plus weldability makes a number of aluminum alloys ideal for chemical industry applications, even some involving very corrosive fluids)

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MATERIAL PROPERITIES OF ALUMINIUM ALLOY 6063 Properties Elastic Modulus Poisson's Ratio Thermal Expansions Co-efficient Thermal Conductivity Specific Heat

Value 69000 N/mm2 0.33 2.4x10-5 /K 170 w/mk 1300 J/kg k

WELDING PROCEDURE SPECIFICATIONS: Gas

:

ARGON

Rod

:

ER304L (Filler Rod)

Flow Rate

:

4-6L/min

Current

:

60-110A

Speed

:

LOW SPEED

Class Diameter Range

:

1.6mm

Voltage

:

10-12V

Polarity

:

DCEN-Direct Current Electrode Negative

Bead

:

Weaving Bead

Heat Input

:

Medium Heat Input

20

NEED OF WPS In the existing system the WPS, it does not contain any details regarding the mechanical and thermal properties for the welding process. Hereby we are going optimize the WPS for TIG and SMAW based on the mechanical and thermal properties considerations in order to reduce the Stress, Thermal stress, Residual stress achieve good weld strength. Welding could be done without preparation of WPS, but which may results in improper weld or with defects like weld decay, knife line attack and stress corrosion cracking. To avoid such cases WPS is followed in all industries. Sometimes improper welding will increase the strength due to this the life time of materials may be changed. To overcome those weld defects WPS is optimized, use extra low carbon electrode, avoiding hylogen family

21

Chapter-4

WELDING PROCESS

22

Chapter-4 WELDING PROCESS Welding is a fabrication process that joins materials by causing coalescence in which heat is supplied either electrically or by mean of a gas torch,. This is often done by melting the work pieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld. This is in contrast with soldering and brazing, which involve melting a lower-melting-point material between the work pieces to form a bond between them, without melting the work pieces. Welding is also the least expensive process and widely used now a days in fabrication. Welding is also called as secondary manufacturing process. WELDING PARAMETERS Tungsten inert-gas arc welding Tungsten inert-gas arc welding (TIG) is a fusion welding method that was developed in the late 1930’s. The TIG-method is characterized by its high quality weld metal deposits, great precision, superior surfaces and excellent strength. TIG is the most common welding method used for pipes and tubes with a wall thickness from 0.3 mm and upward. In the TIG-method a nonconsumable electrode of tungsten or tungsten alloy is used, in comparison to other common welding methods where the filler metal also is the electrode. Filler rod (Ref-A.W.S) E 304

Corrosion resistant

E 316, 304L, 330 High and low temperature strength

23

E 410, 420

Abrasion resistant

E304-16 electrodes are used to weld unstabilized 18-8 stainless steels such as Types 301, 302, 304, 305, and 308. E308-16 electrodes provide corrosion resistance and physical properties equal to or greater than the steels for which they are recommended. Typical applications include dairy, distillery and restaurant equipment, and chemical tanks.

To prevent oxygen in the air from oxidizing the weld pool and the heated material, a shielding gas is used during TIG-welding. The shielding gas is also important to promote a stable metal transfer through the arc, the shielding gas commonly used for TIG-welding is argon. The root side of the weld also needs protection from oxidizing in form of a backing gas during the production of the first weld beads. The backing gas helps the weld bead to form correctly and keep the weld bead from becoming porous or crack.

The TIG-welding method has some great advantages, they are:  Produces a high quality and a low-distortion weld  Free of splatter that is associated with other methods  Can be used with or without filler metal  Can be used in a wide range of power supplies  Can weld almost all metals, including dissimilar metal welds  Gives precise control of welding heat.

24

SELECTION OF FILLER RODS E304 l filler rod properties:  All position stainless steel electrode for 304L or equivalent steels  Excellent corrosion resistance in oxidizing environments such as nitric acid  High resistance to inter granular corrosion  Smooth bead appearance  Easy slag release  High Toughness and strength.

TIG-METHOD IS A VERY HIGH QUALITY WELDING METHOD THERE ARE SOME LIMITATIONS :  Creates lower deposition rates than consumable electrode arc welding processes  Demands somewhat more skill and welder coordination than gas metal arc welding or shield metal arc welding when welding manually  Less economical than consumable electrode arc welding for sections thicker than 9.5 mm  Challenging in draughty environments due to difficulty in shielding the weld zone properly  Tungsten inclusions can be created if the electrode make contact with the weld pool

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INFLUENCE OF CURRENT

Dc electrode negative (DCSP) is one in which the work piece is connected to positive and the electrode is connected to negative. In this type 70% of heat goes to work and 30% to electrode. In this type we can get deep and narrow penetration. Dc electrode positive (DCNP) is one in which the work piece is connected to negative and the electrode is connected to work piece. In this type 35% of heat goes to work and 65% to electrode. In this type we can get wide and shallow penetration. Alternating current (AC BALANCED) is one in which the 50% of heat goes to work and 50% to electrode. In this type we can get medium penetration. But the capacity of electrode is good when compared to DCEP.

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WELDING POSITION PIPE

1G pipe rotated / welder fixed

5G pipe fixed welder rotated

45.

2G pipe vertically Fixed welder rotated

Pipe inclined fixed welder rotated

HORIZONTAL POSITION The horizontal welding position is also known as the 2G or 2F. It is slightly harder to do than the flat weld as gravity is trying to pull the molten metal down towards the ground. But it is still easy to do.

27

VERTICAL POSITION This is the one that we all have trouble with the dredded vertical up weld. This is also called the 3G or 3F, and you can go up or down. As mention before going up in this position is called the vertical up weld and going down is the vertical down.

OVERHEAD POSITION The overhead welding position is just that, overhead. The welding position here is also known as the 4G or 4F.

DOWNHAND POSITION The flat welding position when welding like this is called the 1G or 1F. It is the most basic and easiest welding position.

28

CHAPTER-6

MECHANICAL PROPERTY TEST

29

CHAPTER-6 MECHANICAL PROPERTY TEST

AFTER WELDING STRENGTH MEASUREMENT TENSILE TEST Tensile test is used to determine the tensile strength of the specimen, % elongation of length and % reduction of area. Tensile test is usually carried out in universal testing machine. A universal testing machine is used to test tensile strength of materials. It is named after the fact that it can perform many standard tensile and compression tests on materials, components, and structures. The specimen is placed in the machine between the grips and an extensometer if required can automatically record the change in gauge length during the test. If an extensometer is not fitted, the machine itself can record the displacement between its cross heads on which the specimen is held. However, this method not only records the change in length of the specimen but also all other extending / elastic components of the testing machine and its drive systems including any slipping of the specimen in the grips. Once the machine is started it begins to apply an increasing load on specimen. Throughout the tests the control system and its associated software record the load and extension or compression of the specimen. Tensile Specimens and Testing Machines Consider the typical tensile specimen. It has enlarged ends or shoulders for gripping. The important part of the specimen is the gage section. The crosssectional area of the gage section is reduced relative to that of the remainder of the specimen so that deformation and failure will be localized in this region.

30

The gage length is the region over which measurements are made and is centered within the reduced section. The distances between the ends of the gage section and the shoulders should be great enough so that the larger ends do not constrain deformation within the gage section, and the gage length should be great relative to its diameter. Otherwise, the stress state will be more complex than simple tension. Detailed descriptions of standard specimen shapes are given in Chapter 3 and in sub-sequent chapters on tensile testing of specific materials. Tensile Strength The tensile test of the composites was performed as per the ASTM D3039 standards. The test was done using a universal testing machine (Tinius Olsen H10KS).The specimen of required dimension was cut from the composite cast. The test was conducted at a constant strain rate of 2 mm/min. The tensile test arrangement is shown in figure

31

Tensile test is used to determine the tensile strength of the specimen, % elongation of length and % reduction of area. Tensile test is usually carried out in universal testing machine. A universal testing machine is used to test tensile strength of materials. It is named after the fact that it can perform many standard tensile and compression tests on materials, components, and structures. The specimen is placed in the machine between the grips and an extensometer if required can automatically record the change in gauge length during the test. If an extensometer is not fitted, the machine itself can record the displacement between its cross heads on which the specimen is held. However, this method not only records the change in length of the specimen but also all other extending / elastic components of the testing machine and its drive systems including any slipping of the specimen in 32

the grips. Once the machine is started it begins to apply an increasing load on specimen. Throughout the tests the control system and its associated software record the load and extension or compression of the specimen. Tensile test is used to find out Tensile strength Yield strength % Elongation % Reduction HARDNESS TEST A simple and economical way to characterize the mechanical properties and microstructure is by performing hardness measurements. By performing hardness measurements the highest and lowest levels of hardness can be determined. In dissimilar metal welds the hardness level of parent metals and weld metal are determined. The most interesting part is where the transition from parent metal to weld metal takes place and in the root bead of the weld. A cross-section from each sample is taken transverse the weld by mechanical cutting. It is important that the preparations of the samples do not affect the surface metallurgical by hot or cold work. After the samples are cut they are grinded and polished in order to make as good preparation as possible

33

The numbers of indentations need to be enough to assure that hardened and softened zones are tested, i.e. that the indentations do not affect each other. This gives the metals ability to show resistance to indentation which show it’s resistance to wear and abrasion. Hardness testing of welds and their Heat Affected Zones (HAZs) usually requires testing on a microscopic scale using a diamond indenter. The Vickers Hardness test is the predominant test method with testing being applied to HAZ testing in some instances. Hardness values referred to in this document will be reported in terms of Vickers Number, HV.

34

INDENTOR

WORK PIECE

TABLE ARM

TOUGHNESS TEST: It is well understood that ductile and brittle are relative, and thus interchange between these two modes of fracture is achievable with ease. The term Ductile-to-Brittle transition (DBT) is used in relation to the temperature dependence of the measured impact energy absorption. For a material, as the temperature is lowered, the impact energy drops suddenly over a relatively narrow temperature range, below which the energy has a considerably lower value as a representative of brittle fracture. The principal measurement from the impact test is the energy absorbed in fracturing the specimen. Energy expended during fracture is sometimes known 35

as notch toughness. The energy expended will be high for complete ductile fracture, while it is less for brittle fracture. However, it is important to note that measurement of energy expended is only a relative energy, and can not be used directly as design consideration. Another common result from the Charpy test is by examining the fracture surface. It is useful in determining whether the fracture is fibrous (shear fracture), granular (cleavage fracture), or a mixture of both.

36

Chapter-7

ADVANTAGES AND APPLICATIONS

37

CHAPTER-7 ADVANTAGES AND APPLICATIONS  Non-ferrous metals with high strength and toughness  Higher creep stress and rupture properties when compared with 304  Ideal for high temperature services  Overcomes sensitization and inter granular corrosion concerns  Can be used in elevated temperature applications for ASME boiler and pressure vessel code application  Corrosion resistance, wear resistance  Aerospace aircraft gas turbines  Steam turbine power plants, medical applications  Chemical and petrochemical industries  Strength at elevated temperatures and Excellent Mechanical properties  Magneto striction is a property of ferromagnetic materials that causes them to change their shape when subjected to a magnetic field.  Nickel-based alloys are used in many applications where they are subjected to harsh environments at high temperatures. Nickelchromium alloys or alloys that contain more than about 15% Cr are used to provide both oxidation and carburization resistance at temperatures exceeding 760°C.

38

Chapter-7

CONCLUSION

39

CHAPTER-7 CONCLUSION AND DISCUSSION In raw materials before welding the Strength calculated and also Micro and chemical test is made to get the exact values of material composition. During Welding Strength will be decreased as because due to the change of properties and behavior of materials. After Welding Heat treatment is to be carried out to maintain the strength of material. Finally Tensile, Toughness and Hardness test are to be carried out.

40

Chapter -8

REFERENCES

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CHAPTER -8 REFERENCES  Parmar.R.S. “Welding Engineering and Technology”, Khanna publishers, Delhi. (1997)  O.P.Khanna,“Text book material science & metallurgy” Dhanpatrai publications (1999)  C.P.Sharma, “ Engineeringv material properties and application of metals and alloys” PHI Learning Pvt Ltd, delhi 2013  R.B.Choudry, “ Material science and metallurgy” Khanna publications 2011  N.K.Srinivasan, “ Welding technology” Khanna publications 2012  P.R.RAMANATHAN “ Piping and welding technology”, 2014.  Wen-chun Jiang and Xue-wei Guan “A study of the residual stress and deformation in the welding between half-pipe jacket and shell” Materials and Design, Vol. 43, 2013, PP 213-219.  Man Gyun Na, Jin Weon Kim and Dong Hyuk Lim “Prediction of Residual Stress for dissimilar metals welding at nuclear plants using Fuzzy Neural Network Models” Nuclear Engineering and Technology, Vol. 39, 2007, PP 337-348.  M.M.A. Khan, L. Romoli, M. Fiaschi, G. Dini and F. Sarri “Laser beam welding of dissimilar stainless steels in a fillet joint configuration” Journal of Materials Processing Technology, Vol. 212, 2012, PP 856-867.  Yoshiyasu Itoh and Kabushiki Kaisha Toshiba “Joined structure of dissimilar metallic materials” Patent Publication Number, EP0923145A2, 1999.

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