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Section 8. Mechanics
Norkhodjaev Fayzulla Ramazanovich, Associate Professor of a Tashkent State technical University Yakubov Lazizkhon Ergashkhanovich, Assistant Teacher of a Tashkent State technical University,
E-mail: bjd1962@mail.ru
Actual prospects of application of metal layered composition of type "Fss-an intermediate alloy-solid working element" in manufacture of drill tools
Abstract: The basic directions of development of Uzbekistan are conditioned by acceleration of scientific and technical progress at advancing rates of development of mechanical engineering and oil and gas complex. Implementation of these plans assumes strengthening and an intensification of tool manufacture, demands increase in the nomenclature and complexity of applied tools for realization of the newest technological processes at simultaneous increase of their reliability, durability and decrease in labor input, power intensity and material capacity of their manufacturing.
Keywords: technological processes, drilling of blast, metal layered composition, mechanically-by press fitting, steel melt, Materials science and materials technology.
In this aspect, undoubtedly, working out and introduction of the new technological processes directed on creation of new materials, possessing a complex of set valuable properties is perspective. Thereupon working out scientific basis of creation and research of metal layered composition (MLC) of type "FSS-an intermediate alloy-solid working element" possessing high ruggedness is actual. Application of investigated MLC is perspective in manufacture of the tools of exploited under conditions of percussive perforating drilling of blast holes in medium-abrasive rocks with strength factor f >10 and other tools, applied at carrying out of drilling works, including in oil and gas complex.
The purpose of the present researches is studying of composition, structure and properties of the forming bimetallic compound and its behavior under operating conditions as the drill tool depending on technological parameters of its manufacture.
The method essence consists in placing in polystyrene foam models of inserts from the tool materials forming a working surface tool by melting or formation of connection at contact with melt. Formation ofbimetallic connection allows raising working capacity and longevity of the tool, cutting down thus expenses of materials, work and energy expenses. Depending on modular inserts can be carried out from powder green compositions or compact materials.
Various tools applied recently not meet completely the requirements of technological processes, in particular -low ruggedness, high prices, etc. [1; 2]. Now the bimetallic structure of the tool is reached by connection with the body by welding, the soldering ofworking elements [1], mechanically-by press fitting or by means of the special device [2]. Constructively such tool demands separate manufacturing and the body, and working elements with their subsequent connection. Besides complication at the expense of introduction of additional operations, technological processes is distinguished in this case by high labor input and low use factor of metal, and also, high cost product. For elimination of these lacks in practice the "know-how" of the tool was used by molding [3], but it conditions low accuracy of received castings, great volumes of the
subsequent machining and low durability of formed connection. Last years it is offered to apply a method ofprecision to the decision of these problems in metal forms. However for reception of reliable and strong connection in this case the preliminary warming up of the die-casting tool and creation of regenerative atmosphere in it is required. All this complicates and raises the price of the process of tool manufacturing.
Considering all listed lacks, the "know-how" of the cast bimetallic tool of various special-purpose designations by molding method on lost models [4] is developed. The essence of the method consists in formation of polystyrene foam models in specially made mold, with model dressing, model assemblage on a collector, installation of collectors on a post in cast, sanding-up, its vibrato compaction, filling-in with steel melt. At contact with melt polystyrene is gasified, the formed cavity is filled with melt which after crystallization completely and with high accuracy reproduces the form and the sizes of the initial foam model.
Distinctive features of the method are:
- Possibility of reception of complex one-piece models;
- Reception of casts on II class of accuracy;
- Creation in the course of filling-in of the melt in a form of regenerative atmosphere during all period of its crystallization.
These features defined a choice of way as basis for working out the "know-how" of the drill tool from bimetallic systems. Specification and grounding for of technological process of reception of the cast bimetallic tool needed the decision ofvariety of problems:
- An establishment of formation conditions of cast bimetallic compound depending on modular state of inserts;
- Studying of influence of formation conditions on composition, structure and properties of bimetallic compounds;
- Reliability estimation, working capacity and durability of bimetallic connections;
- Grounding for and a choice of ways and directions ofperfec-tion of technological process of reception of the cast bimetallic tool with a view of increase of its technical and economic indexes.
Actual prospects of application of metal layered composition of type "Fss-an intermediate alloy-solid working element"
It is established, that for a class tools, with corresponding geometrical parity of an insert and a bearing base, the crust in a contact zone remains prior to the beginning of volumetric crystallization.
In this situation for reception of solid tie formation of liquid phase at the expense of fusion of the intermediate layer material put on an insert, or fusion of the insert is necessary.
The variant with intermediate layer practically unique for compositions hitch components essentially differ under physical characteristics. Solid alloys-steel concern these compositions, molybdenum alloys-steel. Practical realization of similar compositions has found the embodiment at the manufacturing of the drill tool applied in oil and complex (Fig. 1, 2).
For the drill tool inserts from the solid alloys, intended for soldered tool were used. Transitive layer was put by a method of plasma spraying. Structures of sprayed alloys are presented in table, the thickness of coverings is in limits of 0,1-0,5 mm. MLC with solid working element from solid alloys of group VK and TK differ by presence of fusible intermediate layer between composition components. As intermediate layers various fusible alloys were approved:
- Alloys for soldering of solid alloys P-100, P-102, brass L60;
- Self fluxing alloys of the system Cu-Ni-Mn Vpr-2, Vpr-4.
As well as in the previous cases, as criterion of quality served a continuity of connection. To this criterion the group of alloys not concerns such as: P-100, P-102, which is conditioned by occurrence of cracks in formation of compositions. Therefore all researches have been spent on compositions with use of self fluxing alloys of system Cu-Ni-Mn (VPr-2 and VPr-4) where has been reached continuity of ties. For revealing of parity of content Cu and Ni (% weight) on quality of formation of a compound, compositions with transitive layer from alloy PR-N55P on Ni-Mn- base and brass L62 (Table 1) were in addition investigated.
Fig.1. Polystyrene foam models
Fig. 2. Casts MLC type casting bore bits. a - one arrow; b - three arrow
Fig. 3. Cast mills of type MLC for drilling bits. a - for three cone bit; b - for one cone bit
Table 1. - Chemical composition of self-fluxing alloys system Cu-Ni-Mn used as intermediate alloys at creation MLC
Alloy grade Chemical composition, weight %
Ni Mn Si Мо Others
VPr-2 base 5,2 25,7 2,5 - -
VPr-4 base 29,5 28,4 1,1 - -
VPr-33 4,1 base 19,5 7,7 10,4 10,6% Cr
VP-N55R 55
a b
Fig. 4. A microstructure of transitive zone MLC solid alloy T5K10-LKC 40HL with transitive layer from alloy Vpr-4. I-Migration zone; II- a zone on the base of transitive layer material 8=0,2mm (a), 8=0,3mm (b), III- a crust; IV- a zone of carburizing increase x100
b
a
b
a
Metallographic researches of compositions have elicited following facts:
- Presence of well distinguishable border on solid alloy (edging) on all interface with steel (Fig. 3) with characteristic thickness of 0,5-1,0 mm.
- Complexity of microstructure of the transitive zone including four subbands (Fig. 4):
I subband-from the side of solid alloy differs in the increased distance between carbide particles. A thickness is to 0,1mm.
II subband- is formed on the base of material of intermediate alloy. Characteristic signs-dendrite skeleton with fine-grained structure of inter dendrite zones. A thickness is 0,2-0,3 mm.
III subband — a crust with fine-grained structure. A thickness is from 0,02 to 0,05 mm.
IV subband — area of carburizing material of a bearing base by products of polystyrene gasification with paelite-cementite or parlite structure gradually turning into ferrite-pearlite structure of hypereutectoid steel. A thickness is 0,3-0,5 mm.
Prominent feature of composition with transitive layer is an influence of structure and a thickness of covering on the sizes of subbands.
Changes of Ni in transitive layer, depending on used material from 5% weights to 55% weights increases a thickness of I subband for group VK8 alloys approximately twice and for alloys T5K10 1,8 times (Fig. 5). Accurate correlation between thickness of coated covering and I subband is traced, namely to smaller thickness of covering, the smaller sizes of I subband correspond and on the contrary.
a b
Fig.5. A microstructure of transitive zone MLC solid alloy VK8-FSS 40HL with transitive layer from alloy VPr-2. I - Migration zone; II - a zone on the base of transitive layer material; 8=0,2mm (a), 8=0,3mm (b), III - a crust IV - a zone of carburizing. Increase x100
The sizes of II subband formed on a basis of material melt of a transitive zone are defined by the sizes of coated covering. The thickness of III subband (crust), and also subband of carburizing practically not depend on a thickness of transitive layer. The wavy relief of a crust testifies to its dissolution in a material of an intermediate layer and fusion in metal-of the base. Results ofmicro sounding ofall zones on samples of composition VK-8-VPr-2-steel 40HL are resulted on Fig. 3, 4.
Attracts attention the fact of the great paths of diffusion of tungsten and cobalt from solid alloy in intermediate layer and further, reaching 400 microns, i. e. practically in all subbands there is a tungsten and cobalt content decreases. Penetration Ni into solid alloy and Cu in steel is characterized by diffusion-200 microns and 150-200 microns; Mn penetrates into solid alloy, more strongly than in a steel 40HL.
Thus, possibility of forecasting with high probability of creation MLC with higher level of set mechanical properties is established, purposefully to introduce corrective amendments in manufacturing techniques of tools on base of MLC, in particular-bits and mills, subjected while in service to a friction that allows to prolong accident-free operation of the drilling equipment.
Results of researches MLC are introduced in technology OJSC "Uzbek factory of refractory and heat resisting" materials. The received scientifically-practically results are entered into educational process on department "Materials science and materials technology" of Tashkent State Technical University named after Abu Rayhan Beruni for students of undergraduate and postgraduate students.
References:
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2. Zubtsov M.E, Korsakov V. D. Firmness of stamps/Machine building, - 1991. P. 200 p.
3. Lenezemovsky A. V. Bimetallic casts/Machine building, - 2004. P. 180 p.
4. Stepanov U. A. Moulding on gasified models/Machine building, - 1996. P. 224 p.
5. Norhodjaev F. R. Cast bimetallic compositions of molybdenum alloys-steel for pressing tool. Thesis of candidate of technical sciences. -Tashkent. 1993. P. 168 p.
