Weld Cons Sojam

7/27/2019 Weld Cons Sojam

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PRESENT TRENDS IN WELDING CONSUMABLES

R.D.PENNATHUR, MAILAM INDIA LIMITED

ABSTRACT

Demands for properties of materials being used in fabrication include properties such as

strength, toughness, fatigue property, corrosion resistance and heat resistance. On theother hand, demands for welding consumables become critical with these demands for

properties. Consumable & process selection is based on high efficiencies, high qualities,high productivity , labor saving and economical application..

Application of welding technologies in the fields of ship buildings, bridges, automobiles,tanks, pressure vessels, pipelines and power plants are fast growing & high productiveconsumable are in great demand.Problems in the field of welding technologies are very wide, for example,

application of newly developed steels and welding procedures in the field of engineering.

Further development is needed continuously in the field of welding to keep pace withnewer materials being introduced.

1. INTRODUCTIONFabrication materials are required to have a wide variety of properties according toenvironment, design and assembly methodology and weld joints of the materials.Therefore materials must satisfy widely varied and demanding quality requirements forwelded structures.

Furthermore labour saving and lower costs are also required for welding work. Therequirements for materials and welding consumables have become increasingly

sophisticated and demanding. In response to these increasingly demandingrequirements, welding consumable manufacturers have developed and suppliedconsumables suitable for various steel materials of high functionality and high quality foreach of application.

2.0: MATERIAL OF CONSTRUCTION:

The global economy has compelled Fabricators to use newer materials of higher strengthto reduce cost of material & reduce Fabrication time. This has posed challenge tomanufacturer of welding consumable manufacturer to develop newer consumables tomeet the industrial needs. Here below ,some of the present types of materials being used

by specific industries are indicated.

2.1: METHODOLOGY:

Whereas steel plates were either as rolled or quenched and tempered conventionally.The development of high strength materials are based on improved manufacturing

practice such as :

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By the TMCP, they are produced through thermo-mechanical rolling(TMR) and

accelerated cooling (AcC). The microstructure of theTMCP products is finer andtheir toughness is higher than those of conventional products.

Lowering carbon equivalent (Ceq) s; and grain refining

Micro structures refining using different kinds of oxides; and decreasing embrittled

structures.

This makes it possible for welding of such joints with higher heat input & still retain themechanical properties across weldment .

Typical examples of such products include heavy plate products such as :

Temp.Resistant steels(Cr-Mo Type) that maintain high strength at high

temperatures.

High toughness steels

High-strength plates for large container carriers for higher transportation efficiency

for shipbuilding

Weathering steels, resistant to salt contamination in coastal locations for bridges

Steel pipes of 120-ksi-class yield stress for line pipes

All the above types of steels are required to meet Mechanical properties & also besuitable for ultra-high-heat-input welding

The modification in micro structure makes it possible to weld such joints with narrowgroove application & achieve required mechanical properties in the weldment.

Fig. 1 High efficiency welding and the embrittlement zone

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2.1.1: SHIPBUILDING

To transport more cargo , the size of container carriers is increasing lately, and as

a result, heavy plates of YP 500MPa /590MPa steels up to 50 mm or more inthickness have come to be used.

Low-temperature steel plates for LPG carriers and their weld joints must have hightoughness at low temperatures .

The selection of proper high strength material & weld metal can achieve required

mechanical properties without resorting to stress relieving.

2.1.2: PRESSURE VESSELS

Steels for high-temperature use are used for boilers and pressure vessels to

enhance their operating efficiency.

As the operating temperature becomes higher, steel must have better high-

temperature strength, and for this purpose, Cr and Mo contents of steel areincreased.

The advanced 2.25Cr-Mo steel with improved high-temperature stre2ngth and

resistance to hydrogen corrosion was developed by adding V to conventional2.25Cr-Mo steel .

Recently, V and Nb are added to 9Cr-1Mo steel , which has improved high-

temperature strength through precipitation hardening, and thus, the steel can beused now at temperatures up to 575 C.By addition of W, the operating temp .canbe increased to 600 C

2.13: .LARGE TANKS

Notch toughness at low temperature & resistance to crack propagation, is required

for steels for low-temperature tanks of liquefied gasses such as LPG and LNG1. ; Al-killed carbon steels2. Ni-containing steels and 2.5%-, 3.5%-, 5%-, and 9%-Ni steels) are used for

these

2.1.4: PIPELINESX120 (800 MPa YP) line pipes have been presently being used in a commercial

pipelines.

Because of the very high material strength, care must be taken to secure high

toughness and good resistance to low-temperature cracking at the welding ateither the steelworks or the sites.

The material of X120 line pipes is a low-C steel with a lower bainitic structure, andthe weld metal has to have a microstructure of fine acicular ferrite to secure goodweldability.

2.1.5: STAINLESS STEELS:

Specific material for corrosion Application.

Nitrogenated SS for High Strength application

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TABLE 1: PROPERTIES OF MATERIAL IN EACH INDUSTRIAL FIELD

AND AVAILABILITY OF DEVELOPED STEELS

INDUSTRY APPLICATION PROPERTIES REQD. DEVELOPED STEELS

Ship

Building

Liquefied gas carrier ship

Container shipCorrosion resistance forcrude oil carrier

Weld, HAZ toughness

Controlled H2High heat input weldabilityHigh tensile strengthCorrosion resistance

Low temperature steels for

LPG, LNG tanksHigh strength Heavy plateswith YP upto 600 MPaCorrosion resistant steels

BoilerPressurevessels

High temperatureoperationHigh pressure operation

Higher strengthEfficient weldingfabricationCreep resistance

Advanced Cr-Mo steels

Tanks Growth in sizeLowering temperature

Higher strengthCorrosion resistancelow ten, Toughness

Steels for combination tankerof LPG and liquid ammonia9%Ni steels High corrosion

resistant stainless steel

Pipe lines High pressure operationOperation .Corrosion resistance

Higher strengthLow temperaturetoughnessSour gas resistance

X-100, X-120 steel pipesHigh HAZ toughness-highstrength thick line pipes

Offshorestructure

Growth in sizeOperation at arctic region

High strengthLow temperaturetoughness

YP460, 500 MPa steels foroffshore fabrication

3.0: CONSUMABLES:

Keeping above development of material in view, it has to be agreed that Consumablemanufacturers have responded positively by developing suitable consumable for each of theapplication.The demand of Welding Engineer for availability of reliable Consumable whichcan give higher Productivity & Consistent Quality have been met. .The basic selection of

process is based on following factors in addition to availability of suitable consumables. ..

METALLURGICAL

MECHANICAL

The developments of newer consumables have to take into consideration followingfactors:

Chemical Composition

Achievable Mechanical Properties.

Effect of Heat Input on Mech. Properties.

PWHT requirement ,if any

Corrosion Properties

Any other special requirements

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In the present scenario, keeping in view rapid pace of development of newer materialswith enhanced mechanical properties, the most commonly adopted are SMAW &FCAW.This is mainly due to response time required for development of newer consumables tomeet TDC of newer Material.

We will now look at various process options available such as SMAW, SAW, GMAW& FCAW Advantages & Limitation of each of above as indicated in Table 2 ..TABLE 2:ADVANTAGES & LIMITATION OF VARIOUS WELDING PROCESS

PARAMETER SMAW SAW GMAW FCAW TYPE OF CONSUMABLE FINITE CONTINUOU

SCONTINUOUS

CONTINUOUS

VARIETY/SPECIFICATION

V.GOOD GOOD LIMITED V.GOOD

AVAILABILITY V.GOOD GOOD GOOD GOOD

POSITIONAL CAPACITY EXCELLENT

LIMITED GOOD V.GOOD

DEPOSITION RATE POOR EXCELLENT GOOD V.GOODAUTOMATION NOT

AMENABLEMOSTSUITABLE

SUITABLE SUITABLE

EQUIPMENT SIMPLE SPECIAL SPECIAL SPECIAL

PORTABILITY V.GOOD LIMITED GOOD GOODWELDERS SKILL HIGH LOW AVERAGE AVERAGE

4.0: ANALYSIS:Taking into consideration various process advantages & limitations, following points can behighlighted.

For welding of CS/LAS & SS in most cases as all the process consumable arereadily available, the process limitation is finally dictated by following criteria.

Taking into consideration deposition rate, even though SAW is the first choice,

the availability, positional capability & ease of application does not favour it as

automatic choice. The introduction of Newer material & need to weld with higher Heat input for

productivity requires consumables developed with Micro Alloying.

The development of such consumables are easily achieved with SMAW &

FCAW consumables due to ease of controlled alloying addition through fluxingmaterial.

Also both SMAW &FCAW consumables can be supplied in economic quantity

for initial trails.

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To achieve higher productivity, if required, FCAW consumables can also be

used with neutral flux for SAW application.

Positional welding capability makes SMAW/FCAW as most favoured process,

with FCAW having advantage of much higher deposition rates.

For field joints/difficult to reach joint, even though SMAW is most ideal

process, FCAW is making definite inroads in this area also. In the field of Hard Facing & reclamation, FCAW has definite edge as it is only

high deposition process catering wide range of requirements .

TABLE 3: AVAILABILITY OF VARIOUS TYPES OF CONSUMABLES:

MATERIAL SMAW SAW GMAW FCAW

CORBON STEEL EXCELLENT

EXCELLENT EXCELLENT EXCELLENT

HSLA EXCELLEN T

GOOD LIMITED EXCELLENT

LOW ALLOYCr-Mo

EXCELLENT

LIMITED VERY LIMITED

EXCELLENT

LOW ALLOY WITH SPL.PROP

EXCELLENT

LIMITED NO EXCELLENT

NOTCHTOUGHNESS

EXCELLENT

LIMITED LIMITED EXCELLENT

SS EXCELLEN T

GOOD GOOD EXCELLENT

NICKEL ALLOYS EXCELLEN

T

LIMITED GOOD EXCELLENT

HF EXCELLEN T

LIMITED NO EXCELLENT

4.1: THE PRESENT TRENDThe success in todays competitive business is Productivity & two ways to improve Productivityare,

0 Reducing Labor Cost1 Increasing Production Speed

FCAW wires are capable of achieving the same in all position & also maintain good quality. InIndian scenario more than 70 % of welding is still being done with SMAW (Stick) & about 8 % by

automatic process i.e. SAW. The share of FCAW &GMAW Process is about 20% leaving 2% toother processes. As compared to this, the global scenario regarding application of Process isindicated here below.(Table 5)

TABLE 4: PROCESS SHARE APPLICATION INTRERNATIONAL SENERIO

JAPAN EUROPE USA INDIA

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SMAW 20% 30% 35% 70%

GTAW 2% 2% 2% 2%

SAW 8% 8% 8% 8%

GMAW/FCAW 70% 60% 55% 20%

5.0: FINAL REVIEW:

A wide variety of materials with properties such as high strength, toughness,

fatigue resistance, corrosion resistance and heat resistance are being developed& used for fabrication.

Arc welding by conventional equipment and work practice still remains to be the

main assembling method for steel structures made of heavy plates.

Even though the SAW is established process with reasonable market share, due

to positional limitation, FCAW is playing major role as high productivity processcombined with availability of suitable consumables.

GMAW process is also gaining in importance with specific application particularlywith use of mixed gas which reduces spatter & enhances finish.

Increasing awareness of the improved productivity, higher metal deposition rates and reduced fumes offeredby wired consumables is driving the total consumables market . .

Metal-cored wires are more popular for robotic welding while the rising preference for automation ispromoting the use of flux cored wires among several end user Industries.

In higher end process, the use of laser welding has increased significantly, and

the method is being applied to heavy plates.

Consumable Manufacturers should invest in R&D and develop their product

range,. They should introduce different metal alloys that suit varied end-user applications even whilefocusing on quality and value-added services.

Respond to customers need based on understanding of their field practice ofjoint design, welding work and control.

Increasingly, the key competitive factors that are likely to be critical to success

are price, quality, value, reputation, and the development of close customerrelationships .

E-commerce will enable suppliers to cut costs, streamline the supply chain and

broaden their reach of the market. It will also foster healthy competition byensuring adequate supply sources.

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