Dispersed and granulated carbides of transition metals in welding materials for arc welding nickel and its alloys
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Dispersed and granulated carbides of transition metalsin welding materials for arc welding nickel and itsalloysM N Ignatov a , V P Korablev a & A M Khanov ba Perm' State Technical University ,b Institute of Technical Chemistry, Ural'sk Division , Russian Academy of Sciences ,Published online: 09 Dec 2009.
To cite this article: M N Ignatov , V P Korablev & A M Khanov (1995) Dispersed and granulated carbides of transitionmetals in welding materials for arc welding nickel and its alloys, Welding International, 9:3, 225-227, DOI:10.1080/09507119509548784
To link to this article: http://dx.doi.org/10.1080/09507119509548784
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Welding International 1995 9 (3) 225-227Selected from Svarochnoe Proizvodstvo 1994 41(6) 21-23: Reference SP/94/6/21; Translation 1734
Dispersed and granulated carbides of transition metals inwelding materials for arc welding nickel and its alloys
M N I G N A T O V a n d V P K O R A B L E VPerm' State Technical University
A M KHANOVInstitute of Technical Chemistry, Ural'sk Division of the Russian Academy of Sciences
As a result of a unique combination of certain physico-mechanical properties such as high melting points, highmechanical strength at elevated temperatures, and cor-rosion and thermal resistance, carbides are used on a largescale in various areas of technology.
The carbides of transition metals are added to struc-tural alloys as dispersion-hardening additions and areused in welding materials (fluxes, flux-cored wires, elec-trodes) for modifying and alloying the weld metal. Thisalso results in considerable interest when examiningdifferent properties of carbides.
The properties of composite materials and coatingsbased on dispersed systems are determined by the initialcharacteristics of the powders (particle size, specificsurface).
To control the course of metallurgical reactions inwelding and reactions in the solid phase in the formationof welding materials, it is necessary to disperse andgranulate carbides of transition metals.
In this work, the authors discuss the processes ofwelded joints produced using dispersed welding ma-terials, and their properties.
Investigations were carried out into the process ofdispersion of carbides of transition metals in a planetary-centrifugal system with a working volume of the drums of2 x 150 cm3.1
Table 1 gives the characteristics of equipment in rapidand fine grinding the powder of titanium carbide.
It is characteristic that an increase of the energyparameters (see grinding conditions 400 m/sec2, 5min + 600 m/sec2 > 5 10 min) of the treatment doesnot increase greatly the specific surface with a correspond-ing reduction of the particle size.
Thus, dispersion of the powdered titanium carbide inthe planetary-centrifugal system makes it possible toproduce a titanium carbide powder with a particle size of1-2 jim and a specific surface of 14.4 m2/g, instead ofrespectively 2-30 nm and 0.41+0.1 m2/g for the powdersupplied by the producer. It is obvious that titaniumcarbide powder with these characteristics makes it poss-ible to produce welding materials with new physico-chemical properties.
However, further improvement of dispersed carbidepowders makes it necessary to ensure that they havecertain processing properties (flowability, etc). Conse-quently, these powders must be granulated.
The authors developed a granulator/mixer of periodic
Milling conditions* Specific surface, m2/g
Initial400/5400/10400/15400/20400/5 + 600/2.5400/5 + 600/10400/5 + 600/15
0.41 + 0.019.4 + 0.111.6 + 0.112.3 + 0.113.9 + 0.110.4 + 0.111.2 + 0.114.4 + 0.1
*The numerator gives the energy state, xn2/sec, the denominator theduration, min.
1 Diagram of design of a periodic action granulator/mixer.
action for producing homogeneous mixtures of powdersof the required composition (Author's cert No. 4797793,USSR), Fig. 1.
The granulator/mixer operates using the followingprocedure. When the regulated drive 1 is switched on,rotation is transferred through the clutch 2 to the shaftwith the blades 3. The powder systems travel through thehole 4 of the chamber 5 to the working zone, where, underthe effect of three types of motion generated by blades,they are intensively mixed with the binding compoundintroduced into the working chamber through the nozzle6. A mixture of the powders and the binding compound ismixed in the chamber where granulation also takes place.
226 Ignatov et al
Content of fractions,of the corresponding
Comment, a angle of inclination of working part of the blade tobottom of the working chamber of the granulator,0; p angle ofrotation of working part of the blade in the radial plate,".
The resultant granules are removed through a gate devicein the lower part of the chamber.
The use of the proposed high-speed granulator/mixermakes it possible to carry out high-quality granulation offinely dispersed welding materials in a controlled me-dium. This is because the internal surface of the workingchamber is coated with a fluoroplastic layer approximate-ly 15 nm thick, the width of the working blade is (0.2-0.3)r (r is the radius of the internal part of the workingchamber), the angle of inclination of the working blade tothe bottom is 35-45 and the angle of rotation of the bladein the radial plane is 5-20 .
The solution of the equations of the amount of motion,kinetic energy and rate of its dissipation has made itpossible to determine, with an allowance made for the
experimental data, that the process of granulation cantake place in the near-wall zone with a width (0.2-0.3)r. Ata width of the working part of the blades less than 0.2 r it isnot possible to obtain the required grain size composition.
To determine the service conditions of the granulator/mixer, tests were carried out on a prototype of the devicewith a working volume of 5 1. Granulation was of adispersed mixture based on titanium carbide. Paraffinwas used as a binder. Falling into the working zone of thechamber, this mixture was intensively mixed for 2-3 minand liquid paraffin was supplied through the nozzle. Therotation speed of the working blades was 1500 rev/min.
The technological characteristic was the parameter offlowability of the powder of the given granule grain sizecomposition. Flowability was determined using the stan-dard method, i.e. on the basis of the flow of 50 g of powderthrough a hole in a conical container. The composition offractions and the test results are presented in Table 2.
It may be seen that, at an angle of inclination of theworking part of the blade to the bottom part of < 30 and>45 and at an angle of rotation of the working part ofthe blade with a radial plane of 45 and > 20 , the ratio ofthe fractions of the grain size composition resultantgranulated product changes. This reduces its flowabilityand, in the final analysis, its technological properties.
The working part of the granulator/mixer of periodicaction generates an air flow with technical characteristicsensuring the most extensive granulation.
The diagrams of X-ray spectral microanalysis of thedistribution of titanium and welded joints produced withexperimental flux-cored nickel wires containing, as thefiller charge, granulated (PPNT-1 wire) and dispersed(PPNT-2 wire) titanium carbide, are shown in Fig. 2.
so too /so zoo
ATOO t50 200 1/
2 Distribution of titanium in weld metal for arc welding using a flux-cored wire with granulated (a) and dispersed (b) titanium carbide.
Carbides of transition metals 227
3 Distribution of hardness in metal of welded joints in NP-2 nickelproduced with flux-cored nickel wires with granulated (broken line)and dispersed (solid line) titanium carbides.
Analysis of the diagrams shows that the amount anduniformity of the distribution of titanium in the weldmetal of nickel depends on the grain size of titaniumcarbide, both as regards the content and the componentsof the structure.
When producing welded joints with a wire containingin the charge granulated titanium carbide with a particlesize of 5-30 jan (Fig. 2(a)), the destruction of Ti is highlynon-uniform both in respect of the content and in thestructure at a higher content of these elements. Themaximum and minimum content of titanium differs fromthe mean content by more than a factor of two. Themaximum titanium content is obtained inside the grainsand reaches 6%, at the grain boundaries it is around