Konstantin Borodianskiy and Michael Zinigrad

Transcription

1 OMPUTATIONAL METHODS for REQUIRED MATERIAL'S OMPOSITION and STRUTURE. Konstantn Borodansky and Mchael Zngrad Laboratory for Metallc and eramc oatngs and Nanotechnology, Arel Unversty enter of Samara, Arel, 40700, Israel. Abstract The mathematcal modelng of real hgh temperature processes, such as weldng, castng, jonng technologes, based on a physcochemcal analyss of the nteracton between the phases s n the focus of the present work. The model s based on the fundamental equatons of thermodynamcs and knetcs of hgh-temperature metallurgcal reactons and factors whch take nto account the thermal and hydrodynamcs condtons of the real process. The model can be used to predct the chemcal composton of the metal matrx, as well as the quanttatve and qualtatve composton of the strengthenng carbde phases formed durng prmary and secondary crystallzaton processes. The correctness of the developed model calculaton was expermentally examned n a real technologcal problem,.e., the development of a new flux-cored wre for formng a buld-up layer wth certan shock-abrason resstance propertes. The nverse problem of flux-cored wre computaton was solved, and can provde us wth the requred chemcal composton of a buld-up metal and ts structure. These requred propertes are acheved by an austente-martenste matrx structure wth a low percentage of carbdes phases unformly dstrbuted theren. The buld-up metal was prepared and tested to determne ts chemcal composton, structure and mechancal propertes. The obtaned chemcal composton structure and mechancal propertes were compared wth the expermentally results. It was found that the expermental results confrm the adequacy of the computer calculatons usng ths model. 1. State of the art. One of the most mportant and complcated problems n modern ndustry s to obtanng materals wth the requred chemcal composton, structure and mechancal and physcal propertes. Solvng ths problem nvolves great deal of tme and expense, and the results obtaned mght be far from the optmal soluton. The development of computer technology and ts accessblty have made t possble to solve problems for whch there were prevously unknown solutons or these methods were so tedous that they proved to be unsutable for practcal applcaton. There are some works where models were developed to predct the chemcal composton [1, 2] and the structure [3-20] of the requred depost metal durng hgh temperature processes, such as weldng, jonng, and buld-up processes. These complcated models nclude the physcal and chemcal parameters of sold, lqud and gas phases, phase transton parameters, hydrodynamcs parameters, etc.

2 2 Materals Scence It s also necessary to be aware of the materal s phase structure, whch has a sgnfcant nfluence on ts fnal propertes. Predctng the phase-structure composton of a metal has been the subject of numerous papers [21-27] that ncluded graphcal representatons of the phase-structure composton of the metal as a functon of ts chemcal composton, as well as computatonal methods for determnng the percentage of ts phase. Such a method s poorly suted to complex systems and processes descrbed by systems of equatons. In the case of mathematcal modelng, the process s studed on a mathematcal model usng a computer, and not on a physcal object. The nput parameters of the mathematcal model are fed nto the computer, and the computer supples the output parameters calculated n the process. The frst stage n the mathematcal modelng of physcochemcal systems s generally the constructon of thermodynamc models. Ths stage s very mportant both for ascertanng the fundamental possblty of the combned occurrence of partcular chemcal processes and for lstng the most mportant thermodynamc characterstcs. In recent years mathematcal modelng has been appled not only to the nvestgaton of theoretcal aspects of physcochemcal processes, but also to the analyss of real technologes. The areas of the predcton and optmzaton of the composton and propertes of materals obtaned n dfferent technologcal processes are especally promsng. Some of the results were obtaned from the modelng of the process of the formaton of a weld pool, from modelng of weld metal transformatons. Important results were obtaned from the studes of the physcal and chemcal parameters of hgh temperature processes, such as weldng or castng, and development of knetc model of alloy transfer. By determnng the chemcal composton of the weld metal researchers have developed the knetc model [3-9]. Based on ths model, the authors descrbed the transfer of alloyng elements between the slag, whch s the resdue left on a weld from the flux conssts mostly of mxed metal oxdes, sulfdes and ntrdes, and the metal durng arc weldng. The model takes nto consderaton the practcal weld process parameters such as voltage, current, travel speed, and weld preparaton geometry, and t was expermentally tested. 2. Structural composton. Structural approach s only a method development tool,.e., a means to structurze a problem, to establsh connectons and the order of prortes, to structurze data, etc., usng structural analyss. A bref revew of the major stages of structural analyss of the weldng materals desgn problems s presented below: 1. Determnng the composton (structure) of the desgn object subject doman. 2. Establshng functonal relatonshp between the desgn object and the subject doman elements (drect and reverse connectons). 3. Establshng connectons between the subject doman and the desgn tool (expert system). 4. Determnng the operatonal algorthm structure and the subject doman representaton method for the desgn tool. 5. Desgn stages structurzaton. Settng prortes. 6. Establshng functonal relatonshp between the desgn stages, tools and desgn object. 7. Determnng nput and output parameters of the desgn tool. Ths s schematcally shown n Fg. 1.

3 Materals Scence 3 Expert Expert system Intellectual nterface Logcal nput module Kernel Logcal output module Internal nterface Knowledge base management system Knowledge base Knowledge model Soluton Doman of possble solutons Subject doman Fg. 1. Smplfed flow-chart of the expert system. 3. Mathematcal modelng of phase nteracton n real technologcal process. A detaled analyss of a welded jont and ts nteracton wth the envronment are presented n the followed part. It was shown that an effectve method for developng a new weldng materal nvolves solvng the nverse problem of fndng the formula of the materal as a functon of the servce characterstcs of the weld metal. The most mportant problems for the new methodology n the area of determnng the electrode formula of a new weldng materal nclude devsng a model of the requred structure of the weld metal under servce condtons and calculatng the prmary structure

4 4 Materals Scence and chemcal composton of the weld depost. The chemcal composton of the weld metal s determned by the ntal chemcal composton of the weldng materal and the base metal and by the nature of the physochemcal processes accompanyng the nteracton between the molten metal and slag. Predcton of the chemcal composton of a weld depost and, consequently, determne ts mechancal propertes, s based on a knetc analyss of the smultaneous dffuson-controlled reactons that occur between the molten metal and slag [5]. The mutual nfluence of the reactons and the dffuson of all the reactants n the metal and slag are also taken nto account. The analyss of the knetcs and mechansm of ndvdually occurrng reactons does not present any specal dffcultes at the present tme and that, as a rule, ts results fathfully descrbe the real processes. A knetc analyss of the nteracton of mult-component metallc and slag melts wth consderaton of the mutual nfluence of reactons takng place n parallel s consderably more complcated. The theoretcal bass of the method conssts of two assumptons: under dffuson-controlled condtons the concentraton rato at the phase boundary for each reacton s close to the equlbrum value; the rate of transfer of the reactants to the phase boundary or away from t s proportonal to the dfference between ther concentratons n the bulk and on the boundary of the metallc and oxde melts. The oxdaton of elements n a metallc melt can be represented by the reacton. n 1 [ ] (FeO) ( Om) Fe n m m (1) where E denotes the elements dssolved n the molten metal (Mn, S, W, Mo, V, etc.), and E n O m denotes the oxdes n the molten slag. A calculaton of the rates of reactons of type (1) for each element does not present any dffcultes. However, a separate analyss of each reacton does not correspond to the real ndustral processes occurrng n the weld pool. The mutual nfluence of both the components of the nteractng molten phases and the heterogeneous reactons takng place n these complex systems must be consdered. Wthn the approach developed, the rate v of mass transfer of any element (mol/cm 2 s) for reactons of type (1) for all the metal components wth consderaton of ther mutual nfluence are defned by the expresson: at n=1. V m m ( nom ) x K [ ] (2), m m x K( E O ) v [ ] v lm n m lm nom V v lm v 1 b 4v where b s defned by the equaton: lm lm 2Om v 1 b 4v lm lm 2Om 2 1 b (3),

5 Materals Scence 5 m K( O ) b (4), m x [ E 2 m 2 ] at n=2. Here K s the equlbrum constant of reacton (1) for the -th component of the molten metal, and n and m are stochometrc coeffcents, x s the rato between the concentraton of ron oxde n the slag and the concentraton of ron n the molten metal on the boundary between the nteractng phases: ( FeO)' x (5), [ Fe]' v lm and v lm nom are the lmtng dffuson fluxes of the components (j) of the molten metal or slag phases, [] and (E n O m ) are the ntal concentratons (wt.%) of the elements and oxdes n the molten phases, respectvely calculated by: v lm 1 j D 2 j (6) j where β s the mass-transfer coeffcent (cm/s), D j s a dffuson coeffcent (cm 2 /s), and j s a reagent's concentraton at the phase boundary (mol/cm 3 ). The rate V FeO of mass transfer of ron monoxde (mol/cm 2 s) whch s the second reagent n reactons of type (1) defned by the expresson: V FeO ( FeO) x [ Fe] x ( FeO) v [ Fe] v lm Fe lm FeO (7). It follows from the stochometry of the reacton (1) that: V k FeO 1 m V V n Havng substtuted V FeO and V n expresson (8), we wll have an equaton wth one unknown x. Havng found x from (2) and (3) we can fnd V. The scheme of the analyzed technologcal process of fuson weldng process s presented n Fg. 2. (8).

6 6 Materals Scence Fg. 2. Scheme of the fuson weldng process. On the scheme, fgures denote the drecton of materal transfer, and letters denote the nteracton of phases: meltng of the electrode bare and formaton of a drop (1); meltng of the electrode coatng and formaton of slag flm over the drop (2); transfer of the drop metal (whch has reacted wth slag flm at the stage of transfer) to the metal pool (3); transfer of the slag flm (whch has reacted wth the drop metal at the stage of transfer) to the slag pool (4); meltng of base metal (5); crystallzaton of the slag pool (6); crystallzaton of the metal pool (7); a, b redox reacton at slag metal boundary n a weldng drop; c, d redox reacton at slag metal boundary n a weldng pool.

7 Materals Scence 7 The fnal composton of the drop n general case s determned by the concentratons n each of the powdered components n the flux of the flux-cored wre or n the electrode coatng [] l pd and, accordngly, by the meltng rates of these components v l pd, the concentraton of each element n the metal sheath or n the electrode bare [] b and ts meltng rate v b, as well as by the rates of passage of the elements through the nterface V of the drop and the slag flm on ts surface, whch can be calculated n accordance wth the methods descrbed above. The values of v l pd and v b are found from emprcal relatons as functons of the technologcal parameters of the process. Thus, the concentraton of the -th element n the drop at any moment n tme s, can be calculated from the equaton: L l l v b [ ] b d v l pd d M pd Ad V d [ ] [ ] (9), md where A d s the surface area of the lqud drop, l labels the type of powder, L s the number of types, M molar mass of the -th element, and m τ d s the mass of the metal drop at the tme s. The fnal drop composton thus calculated [] d s used to calculate the concentraton of the -th element n the weld pool at any tme s. The composton of the pool and therefore the composton of the weld metal are determned by the concentratons of the elements n the lqud drop [] d and accordngly by the rate of descent of the drops nto the lqud pool v d, the concentraton of each element n the base metal [] bm, the meltng rate of the base metal v bm and, as n the case of the drop stage, by the rate of passage of each element through the nterface between the metal and slag pools. In accordance wth the foregong, the expresson for calculatng the fnal composton of element n the crystallzed metal can be wrtten n the form: v [ ] d v [ ] d 100 M A V d [ ] (10) d d bm bm p 0 mp where A p s the nterfacal nteracton area between the metal and the slag, and m τ p s the mass of the weld pool at the tme s. Thus, the proposed method can be used to fnd the chemcal composton of the molten metal n the weld pool,.e., of the metal n a welded jont. Ths chemcal composton s the startng pont for determnng the quanttatve and qualtatve composton of the phases of the weld depost. 4. Physcochemcal analyss of prmary crystallzaton and carbde formaton. The subsequent transformatons of the molten metal are assocated wth the prmary and secondary crystallzaton processes,.e., the phase transformatons n the mult-component alloy. After determnng the chemcal composton of the -th component n the sold phase at the crystallzaton tme τ, we should determne ts dstrbuton between the austente and the carbde phases that have formed at the prmary crystallzaton process. Let us use the chemcal composton of the lqud molten metal n the weld pool as a startng pont for examnng the prmary crystallzaton process. As we know from the theory of weldng processes, crystallzaton of the weld pool proceeds under hghly non-equlbrum condtons n the absence of convectve strrng of the metal n the "tal" of the weld pool,.e., at the crystallzaton

8 8 Materals Scence front. Therefore, the process of dstrbutng the components between the lqud and sold phases s controlled only by dffuson. Another mportant factor that determnes the dstrbuton of the components s the concentraton buldup occurrng at the crystallzaton front. These factors produce concentraton-nduced supercoolng, whch, together, wth thermal supercoolng, s responsble for the cyclc character of weld pool crystallzaton and the chemcal nonunformty of the crystallzed weld metal. At any moment durng crystallzaton of the weld pool, the amount of the -th component that has passed from the lqud phase nto the sold phase can be defned as: s t L v 0 cryst [1 (1 Keff )exp( )] (11) l D where s s the concentraton of the -th component n the sold phase at the crystallzaton tme τ, 0 s the ntal mean concentraton of the -th component n the molten phase, K eff s the effectve dstrbuton coeffcent, L t s the dstance from the crystallzaton startng pont (the length of the crystallte at the crystallzaton tme τ), v cryst s the crystallzaton rate, and D l s the dffuson coeffcent of the -th component n the molten phase. After determnng the concentraton of the -th component n the sold phase at the crystallzaton tme t, we stll cannot determne ts dstrbuton between the austente and the carbde phases that have formed at the crystallzaton process. The factors that nfluence carbde formaton can be dvded nto two groups: physcochemcal factors, whch drectly determne the nature of the carbde-formaton process. technologcal factors, whch ndrectly nfluence the carbde-formaton process by alterng the physcochemcal factors parameters. In our work, the prncples governng carbde formaton n an alloyed ron-carbon weld depost were formulated on the bass of a detaled physcochemcal analyss of the formaton of prmary carbdes as compounds of carbon wth d metals accordng to the quantum-chemcal theores of the electronc structure of d metals and prmary carbdes. The carbde formng reacton can be descrbed as follows: x (12). y ( ) x y Accordng to these prncples, the amount of carbon that s used to form the carbde of the -th metal s proportonal to the atomc radus of the metal (R ) and s nversely proportonal to the number of electrons n the d sublevel of the metal (d ). We ntroduce the concept of the absolute arbde Formng Ablty (FA) tendency of the -th d metal (Θ ) as the rato: R (13). d It follows from an analyss of (12) that the carbde-formng tendency ncreases along the seres consstng of: Fe, Mn, r, Mo, W, Nb, V, Ta, T, Zr, and Hf, n good agreement wth the results n [24, 25]. The dstrbuton of the alloyng elements and carbon between the lqud and the sold phases s gven by (11). Dffusonless decomposton of the supersaturated sold soluton to austente and carbde phases occurs durng crystallzaton. The amount of carbon bound by any carbde-formng element s determned by the stochometry of the compound (Me x y ) and can be found from the followng expresson:

9 E ya (14), xa Materals Scence 9 where x and y are stochometrc coeffcents, A and A are the atomc weghts of carbon and the carbde-formng element, respectvely, and E (c) s the concentraton of the carbde-formng element n the carbde phase. For prmary carbdes, the value of x s always equal to 1, and y takes values from 0.4 to 1.0, dependng on the homogenety regon of the respectve carbde. It s logcal to assume that only the porton of the alloyng elements and carbon that cannot be dssolved n austente at the respectve temperature s used for carbde formaton: E t k ( s) (lm) E E (15) where E (c) s the concentraton of carbon that s not dssolved n austente, E (s) s the carbon concentraton gven by (13) at the crystallzaton tme, and E (lm) s the solublty lmt of carbon n austente at the respectve crystallzaton temperature at the tme t k. The dstrbuton of carbon between the carbde phases and the alloy wll be proportonal to the relatve carbde-formng tendency of the respectve transton element l 1 and ts concentraton n the alloy a. It s now clear that the proportonalty factor for the -th carbdeformng element s: 1 a n (16). Then the concentraton of the -th carbde-formng element bound n the correspondng carbde phase at the tme t kt can be defned as (wt.%): E xa ya (17), and the concentraton of the -th carbde-formng element dssolved n austente at the tme t k determned by (wt.%): ( s) (18). The concentraton of carbdes formed at the tme t k (wt.%) s the sum of the carbon concentraton and the total concentraton of the carbde-formng elements that have partcpated n carbde formaton: Q k E l 1 (19).

10 10 Materals Scence Then the austente content (wt.%) s: S 100% Q I (20) The mean concentratons (wt.%) of carbon and the alloyng elements n the austente phase can be found, respectvely, as: E z E k 1 100% (20), zs z k 1 100% (21). zs Thus, at the end of prmary crystallzaton, we know the mean chemcal composton of the austente phase, as well as the quanttatve and qualtatve composton of the carbde phases n dfferent zones of the formed metal. Equatons (11) and (13)-(22) comprse a phenomenologcal model of the prmary non-equlbrum crystallzaton of the weld pool and the formaton of the weld metal. At the end of prmary crystallzaton, we have a weld depost of complex phase and structural composton that conssts of prmary carbdes and of austente phases. 5. Physcochemcal analyss of secondary crystallzaton. Secondary crystallzaton s accompaned by dffuson-controlled evenng of the composton of the crystallzed metal to the composton specfed by expressons (21) and (22), and partal coagulaton of the prmary carbdes along ther gran boundares durng coolng. When the temperature for the lmtng solublty of carbon and the alloyng elements n austente s reached, the sothermal decomposton of austente occurs, and the dstrbuton of carbon between the carbde phases s proportonal to the FA of the respectve transton element. The evoluton of the system n ths stage could be predcted theoretcally on the bass of the correspondng phase dagrams. However, the constructon of such phase dagrams s extremely dffcult for the mult-component alloys under consderaton, n whch the concentratons of the alloyng elements can vary from several percent to tens of percent by weght. Takng nto account the features of the crystallzaton of a weld metal noted above, we should be able to predct ts phase consttuton on the bass of pseudo-bnary phase dagrams on the level of a qualtatve estmate. There wll stll be a probablty of a hgh degree of devaton from realty. Ths s because equlbrum phase dagrams do not take nto account the real nature of the crystallzaton of a weld metal and the effects of the thermal-stranng cycle durng hgh temperature processes, such as weldng, as well as the cyclc nature of prmary crystallzaton, whch results n chemcal non-unformty of the crystallzng metal. More than 70 years, a smlar problem has been solved for certan types of molten metals n a weld pool usng the phenomenologcal Schaeffler consttuton dagram [21]. The Schaeffler dagram s a real emprcal dagram that s constructed for the weld metal n the ntal state after weldng for ordnary averaged manual arc weldng regmes are shown n Fg. 3.

11 Materals Scence 11 Fg. 3. Schaeffler dagram. Schaeffler dagram ndcates a real metal mcrostructure formed after secondary crystallzaton for hgh alloy steel welds but can be appled for a hgh varety of hgh temperature processes n steel makng processes. The mcrostructure composton conssts of the ferrte, austente and martenste phases can be calculated by the followng equatons whch are called equvalents. hromum equvalent s calculated usng the weght percentage of ferrte stablzng elements: r eq % r % Mo1.5 % S 0.5 % Nb 0.8 % V 4% T ) 22(, and nckel equvalent s calculated usng the weght percentage of austente stablzng elements: N eq % N 30% 0.5 % Mn1.6 Al 19 N 0. 3u (23). However, when a metal contans a consderable amount of carbon (more than 0.12 wt. %) and ferrte-formng elements, are also carbdes (Nb, T, V, etc.) form n the metal mcrostructure. The possblty of ther formaton must be taken nto account because the equvalent values of chromum and nckel can devate sgnfcantly n ths case from the values calculated usng equatons (22) and (23) proposed by Schaeffler wthout consderaton of the formaton of carbdes phases. The decomposton of austente begns at K and s accompaned by the precptaton of secondary carbdes, whch form manly wth chromum and ron (carbdes wth the general formulas Me 3, Me 23 6, Me 7 3, and Me 6 ). Emprcal relatons for predctng the type of carbde formed were determned usng lterature data [28, 29] and the results of our own research 4-7, 9] on the bass of the rato between the atomc concentratons of the carbde-formng element and carbon n austente and the parameters of the thermal-stranng cycle durng weldng. In analogy to (17), we can wrte: k ( d ) xa w j E (24). ya j1

12 12 Materals Scence Here w j s the fracton of carbon n the j-th carbde phase relatve to the total amount of carbon used to (d) form carbdes of the -th alloyng element, E s the concentraton of carbon n the austente decomposton products, and s the coeffcent defned by (16). Then the concentratons (wt.%) of the carbde-formng element dssolved n the matrx are gven by the expresson: ( b) (25), and of the carbon dssolved n the matrx are gven by the expresson: n k ( b) ya E E w j (26) xa 1 j1 The concentraton (wt.%) of the carbde phases formed as a result of secondary crystallzaton s: Q II E E ( b) n 1 (27), and the total concentraton (wt.%) of the carbde phases n the weld metal s: Q I II Hd Q Q (28). The concentraton (wt.%) of the matrx n the weld depost s determned from the expresson: ( b) S 100% Q Hd (29). The concentratons (wt.%) of carbon and n the matrx s: and of the alloyng elements n the matrx s: ( b) b E E 100% (30), ( b) S ( b) b 100% (31) ( b) S Equatons (24)-(31) comprse a phenomenologcal model of the secondary crystallzaton process n the weld metal whch enables us to predct the phase consttuton of the weld depost. 6. Technologcal experments usng modelng approach. The task of the followng step s developng of a new flux-cored wre for formng of buld-up layer wth shock-abrason resstance propertes. The nverse problem of flux-cored wre computaton has been solved (usng mentoned model) whch can provde us wth the requred chemcal composton of buld-up metal and as the result t can gve us the requred mechancal propertes. These requred propertes are acheved by austente-martenste matrx structure wth 10 wt. % of carbdes unformly dstrbuted n t.

13 Materals Scence 13 Austente has a F structure allows holdng a hgh proporton of carbon n ts soluton. In our case austente s used for shock resstance thanks to ts mpact energy absorbance ablty. Martenste has a BT structure where the carbon atoms consttute a supersaturated sold soluton and as a result t has the hardest and strongest propertes. Therefore martenste serves as abrason resstant accordng to ts mechancal propertes. The stable carbde phase brngs the better toughness and addtonal abrason resstance and also ensures unform dstrbuton of the hardness propertes. Under ntensve mpact loadng, some amount of metastable austente absorbs part of the mpact energy and transforms nto addton martenste phase. The mathematcal model permts predcton of the composton of the weld metal as a functon of the compostons of the startng materals and the technologcal parameters of the weldng process. Predcton of the mcrostructure of the weld metal s based on computer smulaton of a Schaeffler dagram and the process of carbde formaton n steels. A cold-rolled rbbon (1008 steel) was flled wth a powder mxture calculated usng the mentoned model. The man alloyng elements, n fnal wre, were: graphte, ferrottanum, chromum and nckel powders. From Hume-Rothery rules t s known that the crystal structures of the solute and the solvent must be the same. Here the mentoned alloyng elements should be dssolved n F structure (austente phase). It s also known that the sze dfference between solute and solvent must be < ~15%. Austente and carbde are the only phases crystallze durng prmary crystallzaton process. hromum and nckel dssolves well n the austente formed matrx. However, ttanum, because of ts hgh dfference n atomc rad as compared to γ-ron, and because of ts dfferent lattce structure, poorly dssolves n austente. Some amount of non dssolved n austente chromum and ttanum forms carbdes. By the end of the secondary crystallzaton, the stable carbde phases wll be stay and resdual amount of the alloyng metals wll be dssolved n the metal matrx. The requred propertes for shock-abrason resstance were the nput, and the output are the needed alloyng elements and ther wt.% of the flux and wt.% of the fnal wre. The output s presented n Table 1 whch presents chemcal composton of the base metal (A516), wre band (coldrolled rbbon, 1008 steel) and alloyng elements the band was flled wth. omponent Densty (g/cm 3 ) ore composton (quantty Relaton n the dray n 100 kg of FE, kg) mxture of the flux (%) Fer FeT N powder af omposton of the base materals and the buld-up layers, wt% S Mn r Mo T Fe N A Electrode bend

14 14 Materals Scence Requred weld Layer Layer Layer Table 1. Flux cored wre for shock-abrason resstance output. Buld-up samples were produced usng flux cored wre wth dameter 1.7 mm by process whch was performed by weldng machne Kempp FU 30, PS The samples were prepared by 3 layers buld-up metal. The technologcal parameters of the process were: urrent: 250A. Voltage: 35V. Feed speed: 180 m/h. Travel speed: 30 m/h. Polarty: Reverse. The samples were tested on home-made shock-abrason resstance measurng devce. The samples were subjects of the mechanc mpact loadng wth the smultaneous contnuous sea sand strew (85 g/mn) of the 60 Mesh. A 12.5 mm thckness sheet of low carbon steel, A516, consstng of 73% ferrte and 27% pearlte phase mcrostructure, was used as the base metal. The obtaned surface (3-rd layer buld-up metal) conssts from martenste and austente mxed phase mcrostructure and carbde stable phase, nvestgated by Scannng Electron Mcroscopy (SEM) and shown on Fg. 4. Fg. 4. SEM mage of surface buld-up metal mcrostructure.

15 Materals Scence 15 hemcal analyss of the matrx was made wth Energy Dspersve X-ray Analyss (EDS) and the receved results are shown n Table 2 and compared wth the calculated, usng the descrbed model, results. Element EDS results (wt.%) alculated results (wt.%) S Mn r Fe N T Table 2. hemcal composton of the weld obtaned by EDS analyss and model calculaton. A lttle dfferences as seen n Table 2, caused as the result of technque lmtaton. The detected chemcal elements must be rounded to 100% and ths lmtaton doesn't take nto account some chemcal nclusons that usually found n steels. As we see from the presented results, the calculated and the real chemcal composton results are closed, that emphasze the correctness of the calculatons performed by the model. Hardness tests were made by Rockwell Hardness Tester. The hardness obtaned on the 3-rd layer of buld-up metal was 56 HR as compare to the hardness of the base A516 metal - 90 HRB. The dfference between base metal and buld up-metal for shock-abrason resstance results obtaned by shock-abrason tests usng specal home-made devce are presented n the plot shown n Fg. 5. The results of tested specmens presented as the plot of the weght loss per shocked area as a functon of tme: Shock-abrason test results Base metal Buld up metal surface m/a (gr/mm^2) 4.5E E E E t (mn) Fg. 5. Shock-abrason test results as a functon of tme.

16 16 Materals Scence It s seen from the plot that the buld-up metal has an mproved shock-abrason resstance. It s found that effcency ncreased by 29%, what s n a good agreement wth the declared am of the work. 7. onclusons. A phenomenologcal model for predctng the chemcal composton and structure of the nonequlbrum prmary and secondary crystallzaton whch takes nto account the carbde phase formaton has been developed. Ths allows the realzaton of the quanttatve predcton of the metal structure and ts mechancal propertes. The dffculty whch was solved n the purposed model s a knetc analyss of the nteracton of mult-component metallc and slag melts wth consderaton of the mutual nfluence of reactons takng place n parallel. Full-scale testng and nvestgaton have been performed. The obtaned results have been analyzed and treated to verfy the equvalence of the model. The model was tested for solvng the real technologcal problem, whch s developng a new flux-cored wre for formng a buld-up layer wth shock-abrason resstance propertes. The expermental results confrm the adequacy of the calculatons usng ths model. References [1] Kettner U.R. The Thermodynamc Modellng of Mult-component Phase Equlbra. Journal of the Mnerals, Metals and Materals Socety 1997; 49 (12) [2] Ansara I., Sundman B., Wllemn P. Thermodynamc Modellng of Ordered Phases n the N-Al System. Acta Metallurgca 1988; 36 (4) [3] Zngrad M., Mazurovsky V., Borodansky K. Physco-chemcal and Mathematcal Modelng of Phase Interacton Takng Place durng Fuson Weldng Processes. Materal Scence and Engneerng Technology 2005; 36 (10) [4] Zngrad M. omputatonal Methods for Development of New Weldng Materals. omputatonal Materal Scence 2006; 37 (4) [5] Borodansky K., Mazurovsky V., Zngrad M., Gedanken A. reaton of Shock-Abrason Resstance Buld-up Metal Usng a Physcochemcal Model of Hgh-Temperature Processes. Israel Journal of hemstry 2007; 47 (3-4) [6] Borodansky K., Mazurovsky V., Gedanken A., Zngrad M. Developng a Requred Structure of Metals Usng omputatonal Methods. Materal Scence A 2008; 497 (1-2) [7] Mazurovsky V., Zngrad M., Leontev L., Lsn V., Borodansky K., Quanttatve Estmaton of arbde-formng Abltes of d-elements: proceedngs of the Jublee Scentfc onference on Physcal hemstry and Technology n Metallurgy, 2005; Yekaternburg, Russa, [8] Zngrad M., Mazurovsky V., Borodansky K., Physco-hemcal and Mathematcal Modelng of Phase Interacton takng place durng Fuson Weldng Processes: proceedngs of the 1-st Internatonal conference on Dffuson n Solds and Lquds, 2005; Avero, Portugal 2, [9] Boronenkov V., Zngrad M., Leontev L., Pastukhov E., Shalmov M., Shanchurov S. Phase Interacton n the Metal-Oxde Melts-Gas System. Sprnger, [10] Elmer J., Palmer T., Zhang W., Wood B., DebRoy T. Knetc Modelng of Phase Transformatons Occurng n the HAZ of -Mn Steel Welds Based on Drect Observaton. Acta Materala 2003; 51 (12) [11] Zhang W., Elmer J., DebRoy T. Knetc of Ferrte to Austente Transformaton Durng Weldng of 1005 Steel. Scrpta Materala 2002; 46 (10)

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