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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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