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Доклад на д-р инж. Богомил Великов Колев на международен конгрес публикуван в Сараево
Автор: bogomil
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Последна промяна: 23.06.2010 09:46
Dr.Eng.Bogomil Velikov Kolev - Institute of Metal Science, Bulgarian Academy of Sciences, 67 "Shipchesky prohod "str., 1574 Sofia, Bulgaria- member of Balkan Union of Metallurgists and the Scient. Technical Union of Mechanical Engineering (STUME)
NEW HIGH STRENGTH WEARRESISTANT ALLOYS
ON Fe-C BASE WITH FERROMAGNETIC MATRIX,
INTENDED FOR CASTINGS
Bogomil Velikov Kolev
Abstract, E-mail;b.v.kolev@abv.bg
The objective of this study is the production of new qualities of alloys with original ferromagnetic matrix, of the Fe-Cr-C-(N) systems, having very high hardness, increased strength parameters, high penetration hardness, improved mashinability combined with high HRC and high (top) wear resistance in the abrasive, hidroabrasive, impact and corrosion abrasive conditions, the structure and property investigations of alloys in as-cast conditions and after various thermal treatment and on the basis of the achieved results, the determination of the application trends for martensitic quenched alloys, etc.
1. Introduction
The world wide recognition of the developed in the Institute of Metal Science N containing alloys has been confirmed by the investigation activation in all advanced countries during recent years: first world congress on high N steels (HNS) in France (1988), followed by conferences: in Bulgaria (1989), Germany (1990), Ukraine (1993), Japan (1995), Sweden and Finland (1998) and India (2002). Information on steels for shaped castings are not or practically not available. The former studies of the executive of the project and his collaborators have shown that the possibilities for producing casting alloys are considerably grater than the wrought ones [1-5]. The better part of details in industrial condition work not only under abrasive, hydroabrasive, corrosion mechanic wearing, but also under complex dynamic wear. That"s why the study of mechanic characteristics of these alloys aiming to search possibilities for their improvement as well as to chose the appropriate composition is very important for the quality and efficiency of the alloys. This is connected with the solving some topical problems: lightening of machines and apparatuses decreasing the need of about, resources and energy, which become less on the earth Global ecology. [6] The mechanic characteristics of Cr. alloyed casting alloys depend on many factors of which very significant are: chemical composition, crystallisation and thermal treatment conditions. These factors determine the character of the carbide (K) and nitride (N) and carbonitride (KN) phases and the basic metal matrix. The pressure, resp. the absorbed under its influence. N sharply refine structure along with the increase of cooling rate. [7,8] The information about mechanic characteristics of casting alloys of Fe-Cr-C system connected with influence of chemical composition and thermal treatment is very scarce and for casting alloys of Fe-Cr-C-N system there are no data. One of the basic problems is that high C casting alloys of that system N free are difficulty to treating cutting instruments. The long years of observation show that N improves mashinability and sharply decreases the affinity towards crashes and slots, since under crystallisation N-phases are formed which have bigger hardness, than K and take stresses easily from phase transitions. We suppose that in cutting N phases have an lubricant role very much like graphite. In patent RB49451 there is a concrete worked-out regime which allows cutting wearing, making aperture, etc. These alloys aren"t used in practices without thermal treatment. On importance for it are 3 factors: austeitization, duration, situation of critic points and T°C of quenching. First factor depends an alloying degree with elements making solid solutions for replacement. N doesn"t influence. The rest factor dependable on N.We studied a larg number of cast alloys contaiig (wt%): 0,6-4,2%C; 0,2-2,5%Si; 0,2-9%Mn; 6-34%Cr; 0,02-2,5%N; 0,01-3%Mo; 0,001-0,3%B; 0,01-1% Ti; 0,01-l%V; 0,01-2,5%Ni and/or Cu; 0,001-0,3%Nb; 0,01-l,0%W; 0,001-0,5%Ce and/or Mg and/or Zr.
2.Sumurized results
3.1. Influence of chemical composition on mechanic characteristics
There are results presented of the research on influence on basic components (Cr, C, N) on mechanic characteristics of alloyed and heat treated wearresistant complex alloys of the Fe-Cr-C-(N) system: Rockwell"s hardness (HRC), strength tensile (crB), strength bending( abend-) and impact strength (ak). The regularities drawn during testing enable the right choice of a proper chemical composition for specific casts according to specific working conditions: the type of wearing and pressure. Determine [9] l.HRC increases, whil tensile strentgh aB, bending strength - cBend and impact strength- ak decrease, when the content of C increases from 1 to 4 % in the undereutectic alloys - 12-14% Cr.
2. N up to 0,2-0,4% tends to increase HRC by some units after quenching. In further its
increase HRC decreases due to in-crease of quantity and stability of austenite. In spite
of that fact ak, tends to preserve constant values of N content increase of content up to
the studied values - 0,89% in alloy C200Cr20MoCu. We obtained casting austenite
(non magnetic) alloys of the Fe-Cr-C-N system which have higher HRC and mechanic
characterictics, than cast austenite alloys of the Fe-Cr-Mn-(Ni)-C-N, Fe-Cr-Ni-C
systems. This makes them competitive even to replace some traditional steel
instruments. Advantage is the good machinability compared to austenite Cr-Mn steels
for details that require high mechanic workability. 3. N increase hardness of casting austenite alloys of the system with 1-3.10"^ Pa every
0,1% N after quenching of 950-1000°C and low treatment. Basic influence has
according to conclusions 1 and 2 C and Cr content neverttheless N increases carbide
(K), nitrides (N), carbonitrides (KN) quantity. The change in type, shape, size, quantity,
distribution. C influence is bigger than N and Cr, because the K phase role is determined
than that of the N phases. The problem of KNremains open. 4. Increasing C content the basic role of the basic matrix on mechanic characteristics
decreases and increases the role of K, N and KN phases with their characteristics. The
bearing cross-section of the tested samples decreases and hardness cha-racteristic
deteriorate. Nitrides are more soft than K. 5. T°C quenching and increase quantity and holding times and C, N increase quantity
and stability of austenite- changes that reflect in properties. 6. The invers relationship between HRC and a^ influenced by C necesitates taking
compromise decisions about C content at (12-24% Cr) and thermal treatment regime as
a function of concret demands of practice and esp. loading of casting in use. 3.2. Influence of termal treatement on mechanic characteristics Hardness (HRC) and strike resilience(ak) are the most-important mechanic indicators wich determine the application of complex alloyed cast alloys of the Fe-Cr-C-N system.. They are determining choice of alloys to work in concrete conditions of wear abrasive, hydroabrasive or strike abrasive. An opposite influence of T°C during tempering on the variation of HRC and ak has been determined. This necessitates a choice of thermal treatment rates, i.e. compromise decisions about the values of HRC and ak according to working conditions in production, resp.to pressure Tempered Cr alloyed steels (cast irons) are better in mechanic characteristics and resistance to .fracture them Grey and modified cast irons with ferrite or perlite basic matrix. This makes them suitable of phacettes opening (casting) working in these conditions .If hardness is important to wear resistance of those class casting alloys in practices it is often to see impact strength determines exploits. These alloys aren"t used in practices without thermal treatment. Of importance for it are 3 factors: austenitization, duration, situation of critic points and T°C of quenching. First factor depends on alloying degree with elements making solid solutions for replacement. N doesn"t influence. The rest factors are dependable on N [10,11]. Study of T°C influence on HRC and ak is significant to form reliable and quality melts.for high strike pressure. Difficult working with cutting instruments ligature data, esp, opposition to strike destruction of alloys of Fe-Cr-C system are scares and for alloys of Fe-Cr-C-N system there are almost no data [7,13,14]. Aim of this work is to presents the effect of T°C of quenching (and tempering) on HRC and ak of basic characteristic components of alloys of Fe-Cr-C-(N) system to compare these data with some wear-resistant alloys of Fe-Cr-Ni-(Mn)-C system. We know that N, Mn, Ni are austenitizators and N replaces them. Besides N is residue product of many industries. Unlike Ni and Mn it is common and cheap. Study is due to our patent RB 4945. More importat coclusions [12]: 1. The influence of T°C of quenching and tempering on HRC and ak of some typical
casting alloys of the Fe-Cr-C-(N ) system(cotaining 12-22%Cr,0,15-0,4%N) has been
studied and we. determined that its influence is opposite of HRC and ak. a) for every alloy there is T°C quenching which obtains max. in HRC and resp. min in ak.
This practically imposes the necessity of compromise choice of the T°Cquenching
according to the concrete configuration working conditions and sample pressure. b) N influence comes over C influence. To the right of HRC maximums (min for ak) the
austenite is stabilised by N. c) Increasing T°C of tempering to 400-500°C there is almost no deterioration of HRC
resp. of ak after which the further increase of HRC decreased and ak is does not change
and tends to increase. d) N containing casting alloys of Fe-Cr-C-N system tend to harden in tempering in the
range up to 400-5 00°C in comparison to N-free and alloyed with austenite forming Mn,
Ni. The effect of hardening in tempering is bigger in low C steels, those containing N.
N replaces C. 2. We studied the influence of holding time (of quenching) and tempering (annealing) on
HRC (ak) and determined that the first 1-2 hours carry out active diffusion processes
connected, with solid-phase reactions reflecting in the change of HRC in variation of
values. After 2-4 hours HRC values are retained and are practically constant (samples
14 xl4mm). 3. The influence of increasing T°C of quenching and time of tempering (holding time)
can be said to be simultaneous complex alloying of the matrix with all elements
included in carbide, nitride, karbonitride. 4. The studied cast alloys of the Fe-Cr-C-(N) system have resp. better HRC and ak after
quenching and tempering (annealing) compared to classic wear resistant with Mn, Ni:
Nicherd, cast iron of the Fe-Cr-Ni-(Mn)-C system: C300C414Ni3Mn4, C315Cr28Ni2.
This show that the alloys of studied system can be replace these alloys, resp. for casting
of details working in abrasive and hydroabrasive wear and impact loading. 3.3 Hardenability of new wearresistant complex alloyed cast alloys Hardenability is a quite important requirement for castings, particularly thick walled, operating in conditions of various types of abrasion wear, because possessing good hardenability a large part of the components remain fit for work after wearing of up to 40 - 80 cm depth. In the development of alloys of optimum wear resistance and impact strength the aim is production of structures having high HRC: martensite or martensite-austenite (with unstable austenite). Proceeding from the above said, in the present paper under "hardenability" it is understood the ability of wear resistant cast alloys (cast irons) to harden as well as their property to possess similar structures of the metal base and HRC all over the cross-section of the casting. For a quantitative measure of hardenability production hardness not lower than 55-60 HRC referred to the casting thickness can be accepted. For laboratory and pre-industrial tests the optimum is 58-60 HRC. According to published data cast iron containing 10-15% Cr has a not high hardenability, up to 20-40 mm [15]. Unlike the carbon and low alloyed deformed steels the published data about hardenability of high hardened cast alloys (steels and cast irons) are quite scarce [13-15]. The available methods do not allow exact modeling of hardenability test [13-17], On the basis of the author"s methods, equipment and installation for hardenability testing of high hardening alloys the experimental results obtained comprise a wide range of wear resistant complex alloyed alloys of the Fe-Cr-C-(N) system summarized in several generalized graphical dependencies [17]. The researches have been granted a patent RB Claim RB49451. More important summarized results [17] 3.4. Wear resistance of complex alloyed alloys The basic exploitation means of complex alloyed founded alloys the systems Fe-Cr-C and Fe-Cr-C-N with and without additional alloying is wear resistance [18-19]. During last round 15 years data show cast iron of system Fe-Cr-C (without N) are said to be alternative of wearresistance materials for working in abrasion conditions.[20]. Data for their physicomechanic and exploitation are rare, especially by observation [18-20]. There are no data for wear resistance complex alloyed cast alloys of system Fe-Cr-C-N, as well as influence of basic components on it. The work presents develop, of patent RB 49451. Results of laboratory study are confirmed by tests in industrial conditions on concrete casts. It is obtained a series of cast alloys in the systems Fe-Cr-C and Fe-Cr-C-N with and without additional alloying with other carbon or nitride forming (V, W, Mo, Ti, B, Nb ) introduced together or separately in combinations with stabilising austenite elements in controllable quantities (Mn,Ni,Cu,N) and modifying (Mg,Ce,Zr, ) having to 6-10 times better wear resistance under friction in comparison with Hatfield steel Cl 10Mnl3. After thermal treatment the alloys possess strength tensile ctb 50-110.107Pa, impact strength ak=0,3-l,2.105Pa J/m2, 40-67HRC, hardenability-over 200mm. There are created also complex alloyed founded wear resistant alloys of the systems Fe-Cr-C; Fe-Cr-C-N, protected with patents (claim) and innovations RB49451, RB26110, RB23669 which have much better treatability with, cutting instruments than Hatfield steel C110Mnl3 and better impact strength than practically non treatable with cutting instruments cast irons: Nichard, Cr28Ni2, than austenite cast iron. Crl4N(0,95)Mnl2; Crl4Ni3Mn4 and austenite cast iron from the systems Fe-Cr-Mn-C-(N). It is studied the wear resistance of cast complex alloying alloys from the systems Fe-Cr-C and Fe-Cr-C-N under abrasive, hydroabrasive wearing with moderate impact pressure and under friction by the method "Skoda-Savin" in a wide range of variation of components, patent RB49451. We determined that [21]: 1. Increasing C content, resp., the ratio Cr/C the wear resistance of under compositions improves and of above eutectic it deteriorates. On the characters of regularities between wear resistance and C, Cr/C big influnce exert the properties of the building and changing in size, form, distribution and type carbide (carbo-nitride ) phase and of the basic matrix. The best wear resistance is obtained under formation of chromium carbides of the type Cr7C3, Cr7C3+Cr23C6, (Cr23C6) plus special carbides of the type Me2C, MC tighly attashed in martenzite or martensite-austenite matrix. 2 Increasing temperature of quenching wear resistance improves up to reaching maximum hardness HRC, where upon because of increasing austenite quantity it deteriorates. Chemical elements stabilising austenite (C, N, Mn, Ni) except Cu after the Maximum of hardness HRC deteriorate wear resistance Cu does not increase residual austenite quantity. 3. Wear resistance of cast complex alloying alloys of the system Fe-Cr-C can be
improve through additional alloying with pre-equilibrium and certain (optimum) above
equilibrium quantities of N, inducing increasing of hardness. N influence is most
effective under quenching at T°C around the HRC max. or on its left. On its right wear
resistance deteriorates until the extent of increasing the quantity and stability of
austenite. N influence is summed with that of C and the other alloying elements.
Although high temperatures are not technological on the right of HRC maximum they
could be effective (especially for alloys of the system Fe-Cr-C-N) in a secondary
strengthening and improvement of wear resistance, i.e. after a primary or several
temperings. 4. Significant influence on cast complex alloying alloys of the system Fe-Cr-C-(N) wear
resistance has C, resp. C, since the forming carbide phases have better thermal; and
mechanical stability and are harder than nitride phases. The effect from N influence is
basically displayed in strengthening the matrix in introducing in the solid solution,
improvement of hardenability, regulation of austenite quantity and stability, resp. in
maintaining constant value of impact strength and improvement of slotting resistance.
The forming after crystallisation secondary nitride phases in the form (mould) or after
appropriate thermal treatment help improve treatability with cutting tools. They could
probably be used in "metal-metal" friction. 5. On the basis of laboratory research industrial testing and other analyses certain
decisions can be taken, including compromise ones about the choice of appropriate
chemical composition and thermal treatment depending on the cast configuration,
working conditions and pressure, wearing type: a) for abrasive wearing most appropriate are cast irons containing 12-22%wt Cr., 2,5-
3,5%wtC and ration Cr/C=4-7 without or with additional alloying, including N. b) most appropriate for impact abrasive wearing under high impact pressure (combined
with pushing) as a substitute for the Hatfield steel of the type Cl 10Mnl3 (non-corrosive
and other steels used in practices) are alloys containing 2-2-4%wtC up to l-l,5%wtC
and 12-15%wtCr. to 18-24%wtCr and ratio Cr/C 8-12 without and with additional
alloying. N- containing have some advantages over N-free alloys. c) most appropriate for hydroabrasive and corrosion machining wearing are cast alloys
of the systems Fe-Cr-C; Fe-Cr-C-N with increased Cr content above 24%wtCr up to 30-
35%wtCr and C depending on pressure according to items : a) and b) of conclusion 5.
Under impact pressure Cr/C ratios above 12-16 are preferable N substitutes for
expensive and deficit elements-Ni, Cu, Mo. d) thin wall casts (up to 15-30mm) can be
used without thermal treatment or after quenching in oil and air. Thick wall -after
quenching in air. Tempering -depending on exploitation conditions. 6. We obtained a range of cast alloys in the systems Fe-Cr-C; Fe-Cr-C-N without and
with additional alloying with carbide and nitride forming (V, W, Mo, Ti, B, Nb)
introduced separately or togheder in combinations with stabilizators of austenite in
combinations with stabilizators of austenite in controllable quantities (Ni, Mn, Cu, N)
and modificators (Mg, Ce, Zr) possessing up to 6-10 times better wear resistance than
the Hatfield steel C110Mnl3 under abrasive and hydroabrasive wearing and moderate
impact pressure and up to 18-28 times better on friction and hardenability up to 200 mm.
Unlike C110Mnl3 the studied alloys pressure good volume perseverance under impact
pressure. N alloyed have advantages .7. We created complex alloying cast wear resistant
alloys of the systems wear resistant alloys of the systems Fe-Cr-C; Fe-Cr-C-N protected
by patent claim RB49451 and innovations RB26110, RB 23669. They have good
treatability with cutting tools, better wear resistance and comparable and better impact
toughness and comparable and better impact toughness that practically untreatable cast
irons Nichard, C320Cr28 Ni2, C310Cr30Ni3, austenite cast irons C240Crl4NMnl2,
300Crl4Ni3Mn4 and steels of the type C110Mnl3, Nichard possess worse impact
toughness stabilizators of "substitution" austenite (Ni, Mn) and carbide forming special
carbides of the type Me2C and MeC deteriorate treatability, whereas N improves, it. Deterioration of treatability with cutting tools is not observed under the influence of copper. Referenses [1] National Conf. with Inter. Part."High Nitrogen Steels", HNS-89, Proc, Varna, 1989 [2] 3"rd Intern.Conf. "High Nitrogen Steels "HNS-93, Proceedings, Kiev, Ureaina, 1993 [3] 4"* Intern.Conf. "High Nitrogen Steels "HNS-95, Proceedings,Kyoto, Japan, 1995 [4] 5"* Intern.Conf. "High Nitrogen Steels "HNS-98, Proceed, Helsinky-Stokholm, 1998. [5] 6"* Intern.Conf. "High Nitrogen Steels "HNS-98, Proceed., Kalpakkam, India, 2002 [6] Kolev B.V. Study on wearresistance of complex alloyed alloys of the systems Fe-Cr-C-(N).10"th Itern.Metallurgy and Materials Cogr., Istanbul, 2000, vol.11, pp.901-909. NEW HIGH STRENGTH WEAR RESISTANT ALLOYS ON Fe-C BASE WITH FERROMAGNETIC MATRIX, INTENDED FOR CASTINGS Bogomil Velikov Kolev We studied a large number cast alloys with different ratio of components in wt%;C=0,6-4,2%, Cr.=4-34%, N=0,02-2,5%, Si=0,2-2,5%, Mn=0,2-9,%, Mo=0,01-3%,V=0,001-l%, Ni and/or Cu=0,01-2,5%, Nb=0,001-0,3%, W=0,01-l%, Ti=0,01-1%, B=0,001-0,3%, Ce and/or Mg and/or Zr=0,01-0,5% and the rest Fe: patent claim RB49451, RB26110, RB23669. Cast wear resistance alloys of the systems Fe-Cr-C and Fe-Cr-C-N can be obtained in atmospheric conditions as well as under pressure (MOMGP). It is determined that N lowers critical points, decreases the quantity of ferromagnetic phases, increases the y-area and stabilises austenite, makes grains smaller acting in one direction with the velocity of cooling during crystallization in shape and pressure and slows down the diffusion process, suppresses disintegration, especially in tempering (ageing), strengthening the matrix with its two basic forms (installed in the solid solution and chemically connected) i.e. increases the strength characteristics and hardness to certain optimum values depending on duration, temperature, cooling and solid phase reactions, preserves its strike elasticity and unlike C does not deteriorate it (in the studied values to 0,8-0,9%N), improves possibilities for quenching, hardeability , wear resistance and can substitute expensive and deficit elements austenite formers (Ni, Cu, Mn) even carbide and nitride- forming increasing hardness (quenching, V, Mo, W etc. improves resistibility to slotting and treatibility with cutting instrument. Alloys have been obtained having up to 6-10 times better wear resistance than that of Hatfield steel Cl 10Mnl3, under conditions of hydroabrasive impact wear resistance under friction. They have good hardness penetration (hardenability above 150-2220 mm) and high hardness up to 60-67 HRC [25-27,31]. E-mail:b.v.kolev@abv.bg NEW HIGH STRENGTH WEARRESISTANT ALLOYS ON Fe-C BASE WITH FERROMAGNETIC MATRIX, INTENDED FOR CASTINGS Bogomil Velikov Kolev Abstract, E-mail;b.v.kolev@abv.bg The objective of this study is the production of new qualities of alloys with original ferromagnetic matrix, of the Fe-Cr-C-(N) systems, having very high hardness, increased strength parameters, high penetration hardness, improved mashinability combined with high HRC and high (top) wear resistance in the abrasive, hidroabrasive, impact and corrosion abrasive conditions, the structure and property investigations of alloys in as-cast conditions and after various thermal treatment and on the basis of the achieved results, the determination of the application trends for martensitic quenched alloys, etc. 1. Introduction The world wide recognition of the developed in the Institute of Metal Science N containing alloys has been confirmed by the investigation activation in all advanced countries during recent years: first world congress on high N steels (HNS) in France (1988), followed by conferences: in Bulgaria (1989), Germany (1990), Ukraine (1993), Japan (1995), Sweden and Finland (1998) and India (2002). Information on steels for shaped castings are not or practically not available. The former studies of the executive of the project and his collaborators have shown that the possibilities for producing casting alloys are considerably grater than the wrought ones [1-5]. The better part of details in industrial condition work not only under abrasive, hydroabrasive, corrosion mechanic wearing, but also under complex dynamic wear. That"s why the study of mechanic characteristics of these alloys aiming to search possibilities for their improvement as well as to chose the appropriate composition is very important for the quality and efficiency of the alloys. This is connected with the solving some topical problems: lightening of machines and apparatuses decreasing the need of about, resources and energy, which become less on the earth Global ecology. [6] The mechanic characteristics of Cr. alloyed casting alloys depend on many factors of which very significant are: chemical composition, crystallisation and thermal treatment conditions. These factors determine the character of the carbide (K) and nitride (N) and carbonitride (KN) phases and the basic metal matrix. The pressure, resp. the absorbed under its influence. N sharply refine structure along with the increase of cooling rate. [7,8] The information about mechanic characteristics of casting alloys of Fe-Cr-C system connected with influence of chemical composition and thermal treatment is very scarce and for casting alloys of Fe-Cr-C-N system there are no data. One of the basic problems is that high C casting alloys of that system N free are difficulty to treating cutting instruments. The long years of observation show that N improves mashinability and sharply decreases the affinity towards crashes and slots, since under crystallisation N-phases are formed which have bigger hardness, than K and take stresses easily from phase transitions. We suppose that in cutting N phases have an lubricant role very much like graphite. In patent RB49451 there is a concrete worked-out regime which allows cutting wearing, making aperture, etc. These alloys aren"t used in practices without thermal treatment. On importance for it are 3 factors: austeitization, duration, situation of critic points and T°C of quenching. First factor depends an alloying degree with elements making solid solutions for replacement. N doesn"t influence. The rest factor dependable on N.We studied a larg number of cast alloys contaiig (wt%): 0,6-4,2%C; 0,2-2,5%Si; 0,2-9%Mn; 6-34%Cr; 0,02-2,5%N; 0,01-3%Mo; 0,001-0,3%B; 0,01-1% Ti; 0,01-l%V; 0,01-2,5%Ni and/or Cu; 0,001-0,3%Nb; 0,01-l,0%W; 0,001-0,5%Ce and/or Mg and/or Zr. 2.Sumurized results 3.1. Influence of chemical composition on mechanic characteristics There are results presented of the research on influence on basic components (Cr, C, N) on mechanic characteristics of alloyed and heat treated wearresistant complex alloys of the Fe-Cr-C-(N) system: Rockwell"s hardness (HRC), strength tensile (crB), strength bending( abend-) and impact strength (ak). The regularities drawn during testing enable the right choice of a proper chemical composition for specific casts according to specific working conditions: the type of wearing and pressure. Determine [9] l.HRC increases, whil tensile strentgh aB, bending strength - cBend and impact strength- ak decrease, when the content of C increases from 1 to 4 % in the undereutectic alloys - 12-14% Cr. 2. N up to 0,2-0,4% tends to increase HRC by some units after quenching. In further its
increase HRC decreases due to in-crease of quantity and stability of austenite. In spite
of that fact ak, tends to preserve constant values of N content increase of content up to
the studied values - 0,89% in alloy C200Cr20MoCu. We obtained casting austenite
(non magnetic) alloys of the Fe-Cr-C-N system which have higher HRC and mechanic
characterictics, than cast austenite alloys of the Fe-Cr-Mn-(Ni)-C-N, Fe-Cr-Ni-C
systems. This makes them competitive even to replace some traditional steel
instruments. Advantage is the good machinability compared to austenite Cr-Mn steels
for details that require high mechanic workability. 3. N increase hardness of casting austenite alloys of the system with 1-3.10"^ Pa every
0,1% N after quenching of 950-1000°C and low treatment. Basic influence has
according to conclusions 1 and 2 C and Cr content neverttheless N increases carbide
(K), nitrides (N), carbonitrides (KN) quantity. The change in type, shape, size, quantity,
distribution. C influence is bigger than N and Cr, because the K phase role is determined
than that of the N phases. The problem of KNremains open. 4. Increasing C content the basic role of the basic matrix on mechanic characteristics
decreases and increases the role of K, N and KN phases with their characteristics. The
bearing cross-section of the tested samples decreases and hardness cha-racteristic
deteriorate. Nitrides are more soft than K. 5. T°C quenching and increase quantity and holding times and C, N increase quantity
and stability of austenite- changes that reflect in properties. 6. The invers relationship between HRC and a^ influenced by C necesitates taking
compromise decisions about C content at (12-24% Cr) and thermal treatment regime as
a function of concret demands of practice and esp. loading of casting in use. 3.2. Influence of termal treatement on mechanic characteristics Hardness (HRC) and strike resilience(ak) are the most-important mechanic indicators wich determine the application of complex alloyed cast alloys of the Fe-Cr-C-N system.. They are determining choice of alloys to work in concrete conditions of wear abrasive, hydroabrasive or strike abrasive. An opposite influence of T°C during tempering on the variation of HRC and ak has been determined. This necessitates a choice of thermal treatment rates, i.e. compromise decisions about the values of HRC and ak according to working conditions in production, resp.to pressure Tempered Cr alloyed steels (cast irons) are better in mechanic characteristics and resistance to .fracture them Grey and modified cast irons with ferrite or perlite basic matrix. This makes them suitable of phacettes opening (casting) working in these conditions .If hardness is important to wear resistance of those class casting alloys in practices it is often to see impact strength determines exploits. These alloys aren"t used in practices without thermal treatment. Of importance for it are 3 factors: austenitization, duration, situation of critic points and T°C of quenching. First factor depends on alloying degree with elements making solid solutions for replacement. N doesn"t influence. The rest factors are dependable on N [10,11]. Study of T°C influence on HRC and ak is significant to form reliable and quality melts.for high strike pressure. Difficult working with cutting instruments ligature data, esp, opposition to strike destruction of alloys of Fe-Cr-C system are scares and for alloys of Fe-Cr-C-N system there are almost no data [7,13,14]. Aim of this work is to presents the effect of T°C of quenching (and tempering) on HRC and ak of basic characteristic components of alloys of Fe-Cr-C-(N) system to compare these data with some wear-resistant alloys of Fe-Cr-Ni-(Mn)-C system. We know that N, Mn, Ni are austenitizators and N replaces them. Besides N is residue product of many industries. Unlike Ni and Mn it is common and cheap. Study is due to our patent RB 4945. More importat coclusions [12]: 1. The influence of T°C of quenching and tempering on HRC and ak of some typical
casting alloys of the Fe-Cr-C-(N ) system(cotaining 12-22%Cr,0,15-0,4%N) has been
studied and we. determined that its influence is opposite of HRC and ak. a) for every alloy there is T°C quenching which obtains max. in HRC and resp. min in ak.
This practically imposes the necessity of compromise choice of the T°Cquenching
according to the concrete configuration working conditions and sample pressure. b) N influence comes over C influence. To the right of HRC maximums (min for ak) the
austenite is stabilised by N. c) Increasing T°C of tempering to 400-500°C there is almost no deterioration of HRC
resp. of ak after which the further increase of HRC decreased and ak is does not change
and tends to increase. d) N containing casting alloys of Fe-Cr-C-N system tend to harden in tempering in the
range up to 400-5 00°C in comparison to N-free and alloyed with austenite forming Mn,
Ni. The effect of hardening in tempering is bigger in low C steels, those containing N.
N replaces C. 2. We studied the influence of holding time (of quenching) and tempering (annealing) on
HRC (ak) and determined that the first 1-2 hours carry out active diffusion processes
connected, with solid-phase reactions reflecting in the change of HRC in variation of
values. After 2-4 hours HRC values are retained and are practically constant (samples
14 xl4mm).
increase HRC decreases due to in-crease of quantity and stability of austenite. In spite
of that fact ak, tends to preserve constant values of N content increase of content up to
the studied values - 0,89% in alloy C200Cr20MoCu. We obtained casting austenite
(non magnetic) alloys of the Fe-Cr-C-N system which have higher HRC and mechanic
characterictics, than cast austenite alloys of the Fe-Cr-Mn-(Ni)-C-N, Fe-Cr-Ni-C
systems. This makes them competitive even to replace some traditional steel
instruments. Advantage is the good machinability compared to austenite Cr-Mn steels
for details that require high mechanic workability. 3. N increase hardness of casting austenite alloys of the system with 1-3.10"^ Pa every
0,1% N after quenching of 950-1000°C and low treatment. Basic influence has
according to conclusions 1 and 2 C and Cr content neverttheless N increases carbide
(K), nitrides (N), carbonitrides (KN) quantity. The change in type, shape, size, quantity,
distribution. C influence is bigger than N and Cr, because the K phase role is determined
than that of the N phases. The problem of KNremains open. 4. Increasing C content the basic role of the basic matrix on mechanic characteristics
decreases and increases the role of K, N and KN phases with their characteristics. The
bearing cross-section of the tested samples decreases and hardness cha-racteristic
deteriorate. Nitrides are more soft than K. 5. T°C quenching and increase quantity and holding times and C, N increase quantity
and stability of austenite- changes that reflect in properties. 6. The invers relationship between HRC and a^ influenced by C necesitates taking
compromise decisions about C content at (12-24% Cr) and thermal treatment regime as
a function of concret demands of practice and esp. loading of casting in use. 3.2. Influence of termal treatement on mechanic characteristics Hardness (HRC) and strike resilience(ak) are the most-important mechanic indicators wich determine the application of complex alloyed cast alloys of the Fe-Cr-C-N system.. They are determining choice of alloys to work in concrete conditions of wear abrasive, hydroabrasive or strike abrasive. An opposite influence of T°C during tempering on the variation of HRC and ak has been determined. This necessitates a choice of thermal treatment rates, i.e. compromise decisions about the values of HRC and ak according to working conditions in production, resp.to pressure Tempered Cr alloyed steels (cast irons) are better in mechanic characteristics and resistance to .fracture them Grey and modified cast irons with ferrite or perlite basic matrix. This makes them suitable of phacettes opening (casting) working in these conditions .If hardness is important to wear resistance of those class casting alloys in practices it is often to see impact strength determines exploits. These alloys aren"t used in practices without thermal treatment. Of importance for it are 3 factors: austenitization, duration, situation of critic points and T°C of quenching. First factor depends on alloying degree with elements making solid solutions for replacement. N doesn"t influence. The rest factors are dependable on N [10,11]. Study of T°C influence on HRC and ak is significant to form reliable and quality melts.for high strike pressure. Difficult working with cutting instruments ligature data, esp, opposition to strike destruction of alloys of Fe-Cr-C system are scares and for alloys of Fe-Cr-C-N system there are almost no data [7,13,14]. Aim of this work is to presents the effect of T°C of quenching (and tempering) on HRC and ak of basic characteristic components of alloys of Fe-Cr-C-(N) system to compare these data with some wear-resistant alloys of Fe-Cr-Ni-(Mn)-C system. We know that N, Mn, Ni are austenitizators and N replaces them. Besides N is residue product of many industries. Unlike Ni and Mn it is common and cheap. Study is due to our patent RB 4945. More importat coclusions [12]: 1. The influence of T°C of quenching and tempering on HRC and ak of some typical
casting alloys of the Fe-Cr-C-(N ) system(cotaining 12-22%Cr,0,15-0,4%N) has been
studied and we. determined that its influence is opposite of HRC and ak. a) for every alloy there is T°C quenching which obtains max. in HRC and resp. min in ak.
This practically imposes the necessity of compromise choice of the T°Cquenching
according to the concrete configuration working conditions and sample pressure. b) N influence comes over C influence. To the right of HRC maximums (min for ak) the
austenite is stabilised by N. c) Increasing T°C of tempering to 400-500°C there is almost no deterioration of HRC
resp. of ak after which the further increase of HRC decreased and ak is does not change
and tends to increase. d) N containing casting alloys of Fe-Cr-C-N system tend to harden in tempering in the
range up to 400-5 00°C in comparison to N-free and alloyed with austenite forming Mn,
Ni. The effect of hardening in tempering is bigger in low C steels, those containing N.
N replaces C. 2. We studied the influence of holding time (of quenching) and tempering (annealing) on
HRC (ak) and determined that the first 1-2 hours carry out active diffusion processes
connected, with solid-phase reactions reflecting in the change of HRC in variation of
values. After 2-4 hours HRC values are retained and are practically constant (samples
14 xl4mm). 3. The influence of increasing T°C of quenching and time of tempering (holding time)
can be said to be simultaneous complex alloying of the matrix with all elements
included in carbide, nitride, karbonitride. 4. The studied cast alloys of the Fe-Cr-C-(N) system have resp. better HRC and ak after
quenching and tempering (annealing) compared to classic wear resistant with Mn, Ni:
Nicherd, cast iron of the Fe-Cr-Ni-(Mn)-C system: C300C414Ni3Mn4, C315Cr28Ni2.
This show that the alloys of studied system can be replace these alloys, resp. for casting
of details working in abrasive and hydroabrasive wear and impact loading. 3.3 Hardenability of new wearresistant complex alloyed cast alloys Hardenability is a quite important requirement for castings, particularly thick walled, operating in conditions of various types of abrasion wear, because possessing good hardenability a large part of the components remain fit for work after wearing of up to 40 - 80 cm depth. In the development of alloys of optimum wear resistance and impact strength the aim is production of structures having high HRC: martensite or martensite-austenite (with unstable austenite). Proceeding from the above said, in the present paper under "hardenability" it is understood the ability of wear resistant cast alloys (cast irons) to harden as well as their property to possess similar structures of the metal base and HRC all over the cross-section of the casting. For a quantitative measure of hardenability production hardness not lower than 55-60 HRC referred to the casting thickness can be accepted. For laboratory and pre-industrial tests the optimum is 58-60 HRC. According to published data cast iron containing 10-15% Cr has a not high hardenability, up to 20-40 mm [15]. Unlike the carbon and low alloyed deformed steels the published data about hardenability of high hardened cast alloys (steels and cast irons) are quite scarce [13-15]. The available methods do not allow exact modeling of hardenability test [13-17], On the basis of the author"s methods, equipment and installation for hardenability testing of high hardening alloys the experimental results obtained comprise a wide range of wear resistant complex alloyed alloys of the Fe-Cr-C-(N) system summarized in several generalized graphical dependencies [17]. The researches have been granted a patent RB Claim RB49451. More important summarized results [17] 3.4. Wear resistance of complex alloyed alloys The basic exploitation means of complex alloyed founded alloys the systems Fe-Cr-C and Fe-Cr-C-N with and without additional alloying is wear resistance [18-19]. During last round 15 years data show cast iron of system Fe-Cr-C (without N) are said to be alternative of wearresistance materials for working in abrasion conditions.[20]. Data for their physicomechanic and exploitation are rare, especially by observation [18-20]. There are no data for wear resistance complex alloyed cast alloys of system Fe-Cr-C-N, as well as influence of basic components on it. The work presents develop, of patent RB 49451. Results of laboratory study are confirmed by tests in industrial conditions on concrete casts. It is obtained a series of cast alloys in the systems Fe-Cr-C and Fe-Cr-C-N with and without additional alloying with other carbon or nitride forming (V, W, Mo, Ti, B, Nb ) introduced together or separately in combinations with stabilising austenite elements in controllable quantities (Mn,Ni,Cu,N) and modifying (Mg,Ce,Zr, ) having to 6-10 times better wear resistance under friction in comparison with Hatfield steel Cl 10Mnl3. After thermal treatment the alloys possess strength tensile ctb 50-110.107Pa, impact strength ak=0,3-l,2.105Pa J/m2, 40-67HRC, hardenability-over 200mm. There are created also complex alloyed founded wear resistant alloys of the systems Fe-Cr-C; Fe-Cr-C-N, protected with patents (claim) and innovations RB49451, RB26110, RB23669 which have much better treatability with, cutting instruments than Hatfield steel C110Mnl3 and better impact strength than practically non treatable with cutting instruments cast irons: Nichard, Cr28Ni2, than austenite cast iron. Crl4N(0,95)Mnl2; Crl4Ni3Mn4 and austenite cast iron from the systems Fe-Cr-Mn-C-(N). It is studied the wear resistance of cast complex alloying alloys from the systems Fe-Cr-C and Fe-Cr-C-N under abrasive, hydroabrasive wearing with moderate impact pressure and under friction by the method "Skoda-Savin" in a wide range of variation of components, patent RB49451. We determined that [21]: 1. Increasing C content, resp., the ratio Cr/C the wear resistance of under compositions improves and of above eutectic it deteriorates. On the characters of regularities between wear resistance and C, Cr/C big influnce exert the properties of the building and changing in size, form, distribution and type carbide (carbo-nitride ) phase and of the basic matrix. The best wear resistance is obtained under formation of chromium carbides of the type Cr7C3, Cr7C3+Cr23C6, (Cr23C6) plus special carbides of the type Me2C, MC tighly attashed in martenzite or martensite-austenite matrix. 2 Increasing temperature of quenching wear resistance improves up to reaching maximum hardness HRC, where upon because of increasing austenite quantity it deteriorates. Chemical elements stabilising austenite (C, N, Mn, Ni) except Cu after the Maximum of hardness HRC deteriorate wear resistance Cu does not increase residual austenite quantity. 3. Wear resistance of cast complex alloying alloys of the system Fe-Cr-C can be
improve through additional alloying with pre-equilibrium and certain (optimum) above
equilibrium quantities of N, inducing increasing of hardness. N influence is most
effective under quenching at T°C around the HRC max. or on its left. On its right wear
resistance deteriorates until the extent of increasing the quantity and stability of
austenite. N influence is summed with that of C and the other alloying elements.
Although high temperatures are not technological on the right of HRC maximum they
could be effective (especially for alloys of the system Fe-Cr-C-N) in a secondary
strengthening and improvement of wear resistance, i.e. after a primary or several
temperings. 4. Significant influence on cast complex alloying alloys of the system Fe-Cr-C-(N) wear
resistance has C, resp. C, since the forming carbide phases have better thermal; and
mechanical stability and are harder than nitride phases. The effect from N influence is
basically displayed in strengthening the matrix in introducing in the solid solution,
improvement of hardenability, regulation of austenite quantity and stability, resp. in
maintaining constant value of impact strength and improvement of slotting resistance.
The forming after crystallisation secondary nitride phases in the form (mould) or after
appropriate thermal treatment help improve treatability with cutting tools. They could
probably be used in "metal-metal" friction. 5. On the basis of laboratory research industrial testing and other analyses certain
decisions can be taken, including compromise ones about the choice of appropriate
chemical composition and thermal treatment depending on the cast configuration,
working conditions and pressure, wearing type: a) for abrasive wearing most appropriate are cast irons containing 12-22%wt Cr., 2,5-
3,5%wtC and ration Cr/C=4-7 without or with additional alloying, including N. b) most appropriate for impact abrasive wearing under high impact pressure (combined
with pushing) as a substitute for the Hatfield steel of the type Cl 10Mnl3 (non-corrosive
and other steels used in practices) are alloys containing 2-2-4%wtC up to l-l,5%wtC
and 12-15%wtCr. to 18-24%wtCr and ratio Cr/C 8-12 without and with additional
alloying. N- containing have some advantages over N-free alloys. c) most appropriate for hydroabrasive and corrosion machining wearing are cast alloys
of the systems Fe-Cr-C; Fe-Cr-C-N with increased Cr content above 24%wtCr up to 30-
35%wtCr and C depending on pressure according to items : a) and b) of conclusion 5.
Under impact pressure Cr/C ratios above 12-16 are preferable N substitutes for
expensive and deficit elements-Ni, Cu, Mo. d) thin wall casts (up to 15-30mm) can be
used without thermal treatment or after quenching in oil and air. Thick wall -after
quenching in air. Tempering -depending on exploitation conditions. 6. We obtained a range of cast alloys in the systems Fe-Cr-C; Fe-Cr-C-N without and
with additional alloying with carbide and nitride forming (V, W, Mo, Ti, B, Nb)
introduced separately or togheder in combinations with stabilizators of austenite in
combinations with stabilizators of austenite in controllable quantities (Ni, Mn, Cu, N)
and modificators (Mg, Ce, Zr) possessing up to 6-10 times better wear resistance than
the Hatfield steel C110Mnl3 under abrasive and hydroabrasive wearing and moderate
impact pressure and up to 18-28 times better on friction and hardenability up to 200 mm.
Unlike C110Mnl3 the studied alloys pressure good volume perseverance under impact
pressure. N alloyed have advantages .7. We created complex alloying cast wear resistant
alloys of the systems wear resistant alloys of the systems Fe-Cr-C; Fe-Cr-C-N protected
by patent claim RB49451 and innovations RB26110, RB 23669. They have good
treatability with cutting tools, better wear resistance and comparable and better impact
toughness and comparable and better impact toughness that practically untreatable cast
irons Nichard, C320Cr28 Ni2, C310Cr30Ni3, austenite cast irons C240Crl4NMnl2,
300Crl4Ni3Mn4 and steels of the type C110Mnl3, Nichard possess worse impact
toughness stabilizators of "substitution" austenite (Ni, Mn) and carbide forming special
carbides of the type Me2C and MeC deteriorate treatability, whereas N improves, it. Deterioration of treatability with cutting tools is not observed under the influence of copper. Referenses [1] National Conf. with Inter. Part."High Nitrogen Steels", HNS-89, Proc, Varna, 1989 [2] 3"rd Intern.Conf. "High Nitrogen Steels "HNS-93, Proceedings, Kiev, Ureaina, 1993 [3] 4"* Intern.Conf. "High Nitrogen Steels "HNS-95, Proceedings,Kyoto, Japan, 1995 [4] 5"* Intern.Conf. "High Nitrogen Steels "HNS-98, Proceed, Helsinky-Stokholm, 1998. [5] 6"* Intern.Conf. "High Nitrogen Steels "HNS-98, Proceed., Kalpakkam, India, 2002 [6] Kolev B.V. Study on wearresistance of complex alloyed alloys of the systems Fe-Cr-C-(N).10"th Itern.Metallurgy and Materials Cogr., Istanbul, 2000, vol.11, pp.901-909. NEW HIGH STRENGTH WEAR RESISTANT ALLOYS ON Fe-C BASE WITH FERROMAGNETIC MATRIX, INTENDED FOR CASTINGS Bogomil Velikov Kolev We studied a large number cast alloys with different ratio of components in wt%;C=0,6-4,2%, Cr.=4-34%, N=0,02-2,5%, Si=0,2-2,5%, Mn=0,2-9,%, Mo=0,01-3%,V=0,001-l%, Ni and/or Cu=0,01-2,5%, Nb=0,001-0,3%, W=0,01-l%, Ti=0,01-1%, B=0,001-0,3%, Ce and/or Mg and/or Zr=0,01-0,5% and the rest Fe: patent claim RB49451, RB26110, RB23669. Cast wear resistance alloys of the systems Fe-Cr-C and Fe-Cr-C-N can be obtained in atmospheric conditions as well as under pressure (MOMGP). It is determined that N lowers critical points, decreases the quantity of ferromagnetic phases, increases the y-area and stabilises austenite, makes grains smaller acting in one direction with the velocity of cooling during crystallization in shape and pressure and slows down the diffusion process, suppresses disintegration, especially in tempering (ageing), strengthening the matrix with its two basic forms (installed in the solid solution and chemically connected) i.e. increases the strength characteristics and hardness to certain optimum values depending on duration, temperature, cooling and solid phase reactions, preserves its strike elasticity and unlike C does not deteriorate it (in the studied values to 0,8-0,9%N), improves possibilities for quenching, hardeability , wear resistance and can substitute expensive and deficit elements austenite formers (Ni, Cu, Mn) even carbide and nitride- forming increasing hardness (quenching, V, Mo, W etc. improves resistibility to slotting and treatibility with cutting instrument. Alloys have been obtained having up to 6-10 times better wear resistance than that of Hatfield steel Cl 10Mnl3, under conditions of hydroabrasive impact wear resistance under friction. They have good hardness penetration (hardenability above 150-2220 mm) and high hardness up to 60-67 HRC [25-27,31]. E-mail:b.v.kolev@abv.bg NEW HIGH STRENGTH WEARRESISTANT ALLOYS ON Fe-C BASE WITH FERROMAGNETIC MATRIX, INTENDED FOR CASTINGS Bogomil Velikov Kolev Abstract, E-mail;b.v.kolev@abv.bg The objective of this study is the production of new qualities of alloys with original ferromagnetic matrix, of the Fe-Cr-C-(N) systems, having very high hardness, increased strength parameters, high penetration hardness, improved mashinability combined with high HRC and high (top) wear resistance in the abrasive, hidroabrasive, impact and corrosion abrasive conditions, the structure and property investigations of alloys in as-cast conditions and after various thermal treatment and on the basis of the achieved results, the determination of the application trends for martensitic quenched alloys, etc. 1. Introduction The world wide recognition of the developed in the Institute of Metal Science N containing alloys has been confirmed by the investigation activation in all advanced countries during recent years: first world congress on high N steels (HNS) in France (1988), followed by conferences: in Bulgaria (1989), Germany (1990), Ukraine (1993), Japan (1995), Sweden and Finland (1998) and India (2002). Information on steels for shaped castings are not or practically not available. The former studies of the executive of the project and his collaborators have shown that the possibilities for producing casting alloys are considerably grater than the wrought ones [1-5]. The better part of details in industrial condition work not only under abrasive, hydroabrasive, corrosion mechanic wearing, but also under complex dynamic wear. That"s why the study of mechanic characteristics of these alloys aiming to search possibilities for their improvement as well as to chose the appropriate composition is very important for the quality and efficiency of the alloys. This is connected with the solving some topical problems: lightening of machines and apparatuses decreasing the need of about, resources and energy, which become less on the earth Global ecology. [6] The mechanic characteristics of Cr. alloyed casting alloys depend on many factors of which very significant are: chemical composition, crystallisation and thermal treatment conditions. These factors determine the character of the carbide (K) and nitride (N) and carbonitride (KN) phases and the basic metal matrix. The pressure, resp. the absorbed under its influence. N sharply refine structure along with the increase of cooling rate. [7,8] The information about mechanic characteristics of casting alloys of Fe-Cr-C system connected with influence of chemical composition and thermal treatment is very scarce and for casting alloys of Fe-Cr-C-N system there are no data. One of the basic problems is that high C casting alloys of that system N free are difficulty to treating cutting instruments. The long years of observation show that N improves mashinability and sharply decreases the affinity towards crashes and slots, since under crystallisation N-phases are formed which have bigger hardness, than K and take stresses easily from phase transitions. We suppose that in cutting N phases have an lubricant role very much like graphite. In patent RB49451 there is a concrete worked-out regime which allows cutting wearing, making aperture, etc. These alloys aren"t used in practices without thermal treatment. On importance for it are 3 factors: austeitization, duration, situation of critic points and T°C of quenching. First factor depends an alloying degree with elements making solid solutions for replacement. N doesn"t influence. The rest factor dependable on N.We studied a larg number of cast alloys contaiig (wt%): 0,6-4,2%C; 0,2-2,5%Si; 0,2-9%Mn; 6-34%Cr; 0,02-2,5%N; 0,01-3%Mo; 0,001-0,3%B; 0,01-1% Ti; 0,01-l%V; 0,01-2,5%Ni and/or Cu; 0,001-0,3%Nb; 0,01-l,0%W; 0,001-0,5%Ce and/or Mg and/or Zr. 2.Sumurized results 3.1. Influence of chemical composition on mechanic characteristics There are results presented of the research on influence on basic components (Cr, C, N) on mechanic characteristics of alloyed and heat treated wearresistant complex alloys of the Fe-Cr-C-(N) system: Rockwell"s hardness (HRC), strength tensile (crB), strength bending( abend-) and impact strength (ak). The regularities drawn during testing enable the right choice of a proper chemical composition for specific casts according to specific working conditions: the type of wearing and pressure. Determine [9] l.HRC increases, whil tensile strentgh aB, bending strength - cBend and impact strength- ak decrease, when the content of C increases from 1 to 4 % in the undereutectic alloys - 12-14% Cr. 2. N up to 0,2-0,4% tends to increase HRC by some units after quenching. In further its
increase HRC decreases due to in-crease of quantity and stability of austenite. In spite
of that fact ak, tends to preserve constant values of N content increase of content up to
the studied values - 0,89% in alloy C200Cr20MoCu. We obtained casting austenite
(non magnetic) alloys of the Fe-Cr-C-N system which have higher HRC and mechanic
characterictics, than cast austenite alloys of the Fe-Cr-Mn-(Ni)-C-N, Fe-Cr-Ni-C
systems. This makes them competitive even to replace some traditional steel
instruments. Advantage is the good machinability compared to austenite Cr-Mn steels
for details that require high mechanic workability. 3. N increase hardness of casting austenite alloys of the system with 1-3.10"^ Pa every
0,1% N after quenching of 950-1000°C and low treatment. Basic influence has
according to conclusions 1 and 2 C and Cr content neverttheless N increases carbide
(K), nitrides (N), carbonitrides (KN) quantity. The change in type, shape, size, quantity,
distribution. C influence is bigger than N and Cr, because the K phase role is determined
than that of the N phases. The problem of KNremains open. 4. Increasing C content the basic role of the basic matrix on mechanic characteristics
decreases and increases the role of K, N and KN phases with their characteristics. The
bearing cross-section of the tested samples decreases and hardness cha-racteristic
deteriorate. Nitrides are more soft than K. 5. T°C quenching and increase quantity and holding times and C, N increase quantity
and stability of austenite- changes that reflect in properties. 6. The invers relationship between HRC and a^ influenced by C necesitates taking
compromise decisions about C content at (12-24% Cr) and thermal treatment regime as
a function of concret demands of practice and esp. loading of casting in use. 3.2. Influence of termal treatement on mechanic characteristics Hardness (HRC) and strike resilience(ak) are the most-important mechanic indicators wich determine the application of complex alloyed cast alloys of the Fe-Cr-C-N system.. They are determining choice of alloys to work in concrete conditions of wear abrasive, hydroabrasive or strike abrasive. An opposite influence of T°C during tempering on the variation of HRC and ak has been determined. This necessitates a choice of thermal treatment rates, i.e. compromise decisions about the values of HRC and ak according to working conditions in production, resp.to pressure Tempered Cr alloyed steels (cast irons) are better in mechanic characteristics and resistance to .fracture them Grey and modified cast irons with ferrite or perlite basic matrix. This makes them suitable of phacettes opening (casting) working in these conditions .If hardness is important to wear resistance of those class casting alloys in practices it is often to see impact strength determines exploits. These alloys aren"t used in practices without thermal treatment. Of importance for it are 3 factors: austenitization, duration, situation of critic points and T°C of quenching. First factor depends on alloying degree with elements making solid solutions for replacement. N doesn"t influence. The rest factors are dependable on N [10,11]. Study of T°C influence on HRC and ak is significant to form reliable and quality melts.for high strike pressure. Difficult working with cutting instruments ligature data, esp, opposition to strike destruction of alloys of Fe-Cr-C system are scares and for alloys of Fe-Cr-C-N system there are almost no data [7,13,14]. Aim of this work is to presents the effect of T°C of quenching (and tempering) on HRC and ak of basic characteristic components of alloys of Fe-Cr-C-(N) system to compare these data with some wear-resistant alloys of Fe-Cr-Ni-(Mn)-C system. We know that N, Mn, Ni are austenitizators and N replaces them. Besides N is residue product of many industries. Unlike Ni and Mn it is common and cheap. Study is due to our patent RB 4945. More importat coclusions [12]: 1. The influence of T°C of quenching and tempering on HRC and ak of some typical
casting alloys of the Fe-Cr-C-(N ) system(cotaining 12-22%Cr,0,15-0,4%N) has been
studied and we. determined that its influence is opposite of HRC and ak. a) for every alloy there is T°C quenching which obtains max. in HRC and resp. min in ak.
This practically imposes the necessity of compromise choice of the T°Cquenching
according to the concrete configuration working conditions and sample pressure. b) N influence comes over C influence. To the right of HRC maximums (min for ak) the
austenite is stabilised by N. c) Increasing T°C of tempering to 400-500°C there is almost no deterioration of HRC
resp. of ak after which the further increase of HRC decreased and ak is does not change
and tends to increase. d) N containing casting alloys of Fe-Cr-C-N system tend to harden in tempering in the
range up to 400-5 00°C in comparison to N-free and alloyed with austenite forming Mn,
Ni. The effect of hardening in tempering is bigger in low C steels, those containing N.
N replaces C. 2. We studied the influence of holding time (of quenching) and tempering (annealing) on
HRC (ak) and determined that the first 1-2 hours carry out active diffusion processes
connected, with solid-phase reactions reflecting in the change of HRC in variation of
values. After 2-4 hours HRC values are retained and are practically constant (samples
14 xl4mm).
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