tubular fon- thermal

7/27/2019 Tubular Fon- Thermal

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PRESENT INTERNATIONAL STATUSOFTUBULAR ELECTRODES

FORHARDFACING APPLICATIONS

ADOR FONTECH LIMITED


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Hardness Vs. Wear (cont)

A Micro Hardness test on the other hand measuresthe individual hardness of each grain or particle.

Although, macro hardness indicates resistance to

wear, but the actual micro-hardness of the hardparticles in the the matrix of hardfacing material

which imparts such high average macro-hardness is

the important criteria for determining wear

resistant properties. This knowledge eventually helpsto select most suitable alloy for a specific type of

WEAR.


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Universal recognition of nature of alloying elements &its total contents (approx) in Weld-Metal for best

WEAR RESISTANCE

Alloying elements &

its total content

(approx) in %age

Abrasion Erosion High

Temp

Abration

Impact Corro

sion

Friction

C,W,Cr65 9 5 5 3 3 8

C,Cr,B,Mo,V34 7 9 4 3 4 4

C,Cr,Mo,Nb,W,V - 54 7 7 9 4 3 4

Mn,Cr30 4 2 2 9 4 2

C,Cr,Nb,Mo- 38

8 7 5 7 3 5C,Cr,Mo,Ni- 37 7 7 6 7 3 2

C,Cr- 40 6 6 6 6 3 2

C,Cr,Mo,Ni - 35 5 4 4 4 8 4

Maximum 10 points allotted in each type of WEAR RESISTANCE


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CONCEPT OF TUBULAR ELECTRODE The advent of Solid-Core electrode for joining took place about 100 years

ago.Then, came Solid-Core electrode for Hardfacing where such high alloy

contents in the weld-metal were the primary conditions to impart wear-resistant surfaces on base metal.

Since high alloying elements need to be transferred across the arc to the

weld-metal, thick flux coatings for such Hardfacing Solid-core Electrodes

became the necessity. As a result of such thick flux coating the

characteristics likei) high operating current

ii) high slag volume

iii) spatter etc were associated with such Solid- Core Hardfacing

electrodes.

To get over such difficulties of operations the concept of making of high-

alloys containing electrodes through Powder-metallurgical method came to the

minds of Developers which has finally given rise to the present form of

Tubular Hardfacing Electrodes.


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Constructional Features of Tubular Electrode

lead to:-

Low operating current Low heat-inputLess distortion No burn-through

Hardfacing on thin sections Low dilution

Uniform alloy distributionWeld deposit richer in carbides

No deslagging Un-limited shelf life

No special storage No pre-drying

Universal grip for all sizes High recovery

High deposition rate


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Spatter loss- nil

Slag negligible

Deslagging-not required

Recovery: 80 85%

Spatter loss- high

Slag Volume high

Slag removal-essential

Recovery: 47 -55%


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Deposition Efficiency 55%

Kg of electrode required 1.82

Deposition Efficiency 85%

Kg of electrode required 1.18

Electrode Savings 35% approx.


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Shortcomings of THF electrodes inEarlier Years

1. Open Arc.

2. Restricted to Down hand & Horizontal

welding (Limitation in Positional Welding).

3. Restriction of Size.

(non-availability below 6.3 mm).

4. Limitation to manufacture low alloy


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Developments in the International

Scenario to Overcome Shortcomings1.Available with almost identical arc characteristics of solid core

electrode i.e close arc and touch types.

2.Vertical and Overhead position welding in certain type of THFElectrodes are claimed today by few Manufacturers.

3.Minimum size of 5.0mm available.

4.Low alloy (containing 12-16%) giving martensitic / austeniticmicrostructure are available.

5. Besides Hardfacing, Joining type THF Electrodes for ColdWelding of Cast iron are now available conforming to ENiFe-CI

and ENiFeMn-CI. These varities of THF Electrodes also enjoy theEconomic Advantages in comparison to equivalent Solid-core

Electrodes.


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Conclusions It is heartening to note that the Indian Industries are now

taking advantage of these Techno-Economic benefits of

Tubular Electrodes and are at present using these electrodeson larger scale since the earlier shortcomings were overcome.

Thereby, the Industries demand of THF electrodes is felt

by the Electrode manufacturers in the country today. Hence,

the established manufacturers of Solid-core hardfacing

electrodes are now either Manufacturing or Importing THF

electrodes to cater to the demands of these Industries.

From our experience we find that the demand of these

products in the International Market is growing day by day.

It is an universally accepted fact that THF electrodes give

greater wear resistance & twice the value for Money of

Solid-Core Hardfacing Electrodes.


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