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paper of B.V.Kolev in "Asia steel-2000" Conference, Beijing
Автор: bogomil
Категория: Технологии
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The Chinese Society for Metals
46 Dongsixi Dajie Tel: 86 10 65133925
Beijing100071, China Fax: 86 10 65124122
E-mail: csm@public.bta.net.cn http://www.org.cn
Dr. Bogomil Velikov Kolev Institute of Metal Science Bulgarian Academy of Sciences Bulgarian
Date: March 23,2000
Dear Dr. Bogomil Velikov Kolev,
I am very pleased to inform you that the Program Committee of the Asia Steel International Conference-2000 has accepted your papers titled POSSIBILITIES FOR (ECOLOGICAL) PRODUCING OF NEW WEAR RESISTANT Fe-C BASED ALLOYS and HARDENABILITY OF NEW WEAR RESISTANT CAST ALLOY for this conference to be held in Beijing, September 26-29, 2000.
Now you are kindly requested to send two copies of your manuscript in English with the filled Copyright Transfer Form to the secretariat of ASIA STEEL"2000 before
May 31,2000.
Before preparing your manuscript, please carefully read the instructions as followings:
1.The text should be typed in Times New Roman font with font size 10 and on paper
of A4 size with margins of 3cm. 2. It would be expected that your paper does not exceed 8 pages in length. 3. The title page should contain the following: title of paper (all caps, center,
boldface); author"s name (Center); author"s affiliations (center); and the address with
city or state and country (center). All pages should be numbered consecutively
beginning with the title page. 4. Each heading should be in capital letters and centered. Secondary headings, if any,
should be flush with the left margin and have the first letters of all main words
capitalized.
Additionally, I am very glad to inform you that preparations for this Conference are proceeding well. Up to now, the organization committee of Asia steel 2000 in Beijing has received about 100 abstracts out off China and some 120 domestic ones. Now we send you the second circular for Asia Steel 2000 that is edited into a MS-word97 file and attached in the email. Thank you for your kind cooperation. We are looking forward to welcoming you in Beijing. Sincerely yours.
Prof. Huang Wudi Deputy Secretary General Asia Steel"2000 Conference-Proceedings, pp.309-319
POSSIBILITIES FOR ECOLOGICAL PRODUCTION OF NEW WEAR RESISTANT Fe-C BASED ALLOYS- Dr.Eng. Bogomil Velikov KOLEV Institute of Metal Science - Bulgarian Academy of Sciences, 67 Shipchensky prohod.str., Sofia 1574, Bulgaria,
E-mail:b.v.kolev@abv.bg ABSTRACT We present in general framework a part of by now obtained results of the authors studies in the period 1968-99 about possibilities for obtaining new high-alloyed and wear-resistant founded alloys on Fe-C basis grey cast iron and complex alloyed steels and cast iron of different systems with different structure, reflected inover 110 publications, innovations, patents and other scientific studies. The results of the studies make possible to determine not only the directions for application of the obtained alloys in practices, but also to outline ecological and technical directions for obtaining of new high strong and wear-resistant alloys with N, using the possibilities of the new gas metallurgy with gaseous elements under pressure. Key words: new cast alloys, grey cast iron, complex alloyed steels and cast iron alloying with N,mechanic characteristics,wearresistance, Ecology, application, perspectives, prognostication. INTRODUCTION The intensive progress of world science imposes the necessity to create new materials and alloys with high physico-mechanic and exploitation characteristics with simultaneous decrease in material energy and other expenses for achieving high quality. Development of machine building as a strategic sector is inevitably connected to the creation of ever newer and more effective technologic and ecological processes in foundry. At the end of the 20! century tradition metallurgic and founding technologies are exhausted in their possibilities to solve these complex issues. From the three thermodynamic factors (composition, temperature and pressure), characterising and defining processes and phenomena in substances (the Nature), resp.structure and properties of materials (alloys) in classic technologies are practically used only the first two. If studying and applying of the possibilities of vacuum technologies are developed well enough vacuum technologies are developed well enough, then the study and application of the possibilities of pressure, still at an initial stage seems to be very perspective, having in mind the challenges of the 21-sl century [4]. Bulgarian methods with gas counter pressure(MOMGP) presents a fundamental innovation for great potential possibilities to develop and solve actual-priority Global problems of Mankind; creation of technologic and ecological as well as economically profitable machines and devices, new materials (alloys) and their products [4]. One of the most perspective directions of MOMGP is creation of new machine-building materials(steels and cast iron), alloyed with gaseous elements [5-8]. Of all known methods for improvement of structure and properties of the alloys on ierro-basis the most effective is alloying. MOMGP outlined the principal fundamental possibilities and directions for development of the new gaseous metallurgy with volatile elements and substances. Nitrogen as the most common in Nature gas and residual product of a number of industrial production, processing the unique property to substitute expensive and deficit elements like: Ni, Cu, Co, (Mn) etc. and to improve some physic-mechanic and exploitation characteristics in times, not in percentage, completely corresponds to some of the challenges and the outlined Global problems of Mankind for the present and future. Yet for unknown reasons the efforts of scientist are directed towards studying of possibilities to create most of all non-corrodible deformable steels. For cast alloys many restrictions in alloying with C and Ν come down as well as for other carbon-nitride forming elements, which imposes requirements for enough and high technological plasticity of deformable steels, treattability with cutting instruments, corrosion resistance etc. This shows that possibilities for obtaining of new N-containing alloys aimed at casts are many times bigger [7-12, 15-29]. With the increase of productivity of machines the wearing of details through friction increases. This leads to increase of capital investments for amortisation and for producing spare parts. The needs for wear-resistant materials for details in conditions of abrasive, hidroabrasive, strike abrasive and other types wearing are constantly growing in world range. This is due to constant decrease in ores, resp. raw materials traditionally used for obtaining of high-quality products, for enhancing all activities linked to treatment and processing of Earth crust and bowels as well as the constant development of mechanisation in industry agriculture and transport. The building of ever more power full and automatic new machines and devices for digging making smaller, grinding mixing enriching, separating transport etc. requires and justifies the use of ever
more qualitative and reliable and with longer life materials in order to minimize the defection and amortisation of spare parts.Ecologic problems are also topical 1-4] In the institute of Metal Science are carried out profound studies not only on possibilities for obtaining new Ν alloyed deformable steels, but new cat steels and cast irons as well. SUMMARISED RESULTS AND DISCUSSION 1. Possibilities for obtaining new N-containing high-strong and wear resistant ordinary grey pre-eutectic cast iron Of cast alloys used in modern machine building dominating position have grey cast iron microalling with Ν is possible trough introduction of gaseous as well as solid N-carriers[7, 9] The treatment of melts of grey cast iron with 0,8-0,9 grade of eutectics with Ν through N-treated FeMn, without introduction of other elements is possible in founding under pressure (MOMGP), as well as in atmospheric conditions [4, 10, 11]. Thus both of the two absorbed elements (Mn and N) act stabilizingly for increase of N- content, since the treatabiliry with cutting instruments sharply deteriorates. To prevent whitening is necessary quantity of the introduced N-treated FeMn to be restricted (to 0,5-1% towards weight of treated metal). To prevent stabilising influence of Mn is needed additional metallurgical treatment with FeB. Introduction of β and Ν in stoichometric quantities securing formation of nitrides of B(with crystal lattice wear to that of graphite being conductive to crystallisation and graphitization processes without thermal treatment, sharply decreases the affinity towards whitening and allows obtaining of grey cast iron, with increased Mn and Ν content [10-11].Summarised Mn and Ν content of patent Claim RB23345: [.Treatment of melts of grey cast iron with exit composition; C=2,0-3,4%; Si= 1,7-2,2%; Mn=0,4-0,5%; S up to 0,04%, Ρ up to 0,08%, Ν up to 0,005-0,007% through N-treated FeMn (containing influence of absorbed Mn and Ν leads to whitening (sample rain 0 50 mm): a)after treatment under
pressure (6/18.105Pa; 6-pressure when introducing N-carrier, 18-pressure of melt crystallisation [7, 12, 15,22].
Whitening starts at lower Mn content above 1,1-1,3%) and lower content (above 0,010-0,0160%). 2.On statistical basis are worked out mathematics models which help determine the influence of quantity of introduced N-treated FeMn ,,q",resp of the absorbed Mn (CMn) after treating under pressure 6/!8.105Pa; a) on quantity of absorbed Ν (CN); lg 58,8CN=0,14CMn; b) on the extent of Ν absorption (ηΝ); r]N=20,4+14,578q- 4,456q2 3.We obtained grey cast iron containing high content of Mn and N, thanks to the modifying and graphitizing influence of the products of "N-B" interaction; without applying long-iasting and expensive thermal treatment; a)in founding under pressure 6/18.105Pa-up to 2,5-3%Mn and 0,05%N; b) in founding in atmospheric conditions- up to 1,5-2% Mn and up to 0,025%N 5.The effect of the action of the products from the "N-B" interaction is bigger when the quantity of introduced Ν and Β is bigger. It is visible even at low content; of Ν below 0,04-0,06% of B-below 0,1-0,15%. The optimum quantity FeB (containing 20-22%B) depends on Mn and Ν content and is within the range-0,025-1,5% towards metal weight; a) in founding under pressure 6/18.105Pa-0,5-l,5%; b)in founding in atmospheric conditions-0.25- 1%. 6.To decrease the losses of Ν (N-carrier) is possible a change of part of the N-treated FeMn with ordinary, without particular deterioration mechanic characteristics; a) in founding under pressure 6/18.105Pa up to 25-30%; b) in founding in atmospheric conditions-up to 50%. 7.On statistic basis are developed mathematics models which can help evaluate the influence of absorbed Mn (resp. accordings to conclusion 2, N) on mechanic characteristics of cast iron, contain 55.10"3 - 150.10 3%B, after treatment under pressure 6/18.105Pa; b) for strength tensile; σΒ= 18,3 + 10,6CMn; b) strength of bending; aBcngmg = 38,58 + 20,260^; c) for hardness, HB = 204,86 + 23,025.CMn. 8.The obtained grey pre-eutectic after treatment as melt with N-treated FeMn and FeB under pressure in atmospheric conditions have small grain and fine grain structure density and high mechanic properties and very good wear-resistance with satisfactory treatabiliry with cutting instruments [7, 8, 10, II]. Influence of Β is basically concluded in decreasing the cimentite quantity. N-treating of melt underpressure 6/18. 103 Pa in Ν medium increases the strength of tensile with 17-25% in comparison with analogous treatment in atmospheric conditions and more than 2 times towards exit non-treated cast iron. Wear resistance of obtained under pressure 6/18.105) grey N-treated cast iron with higher Mn content is with 15-35% better than that of analogous treated cast iron in atmospheric conditions and depends on Mn content of Mn and satisfactory treteabality with cutting instruments which have comparable and better strength characteristics than the renound." Mihanite" cast iron and with many times better wear resistancre than it, consisting in; a)in founding in atmospheric conditions-up to l,5-l,8%Mn and 210-250HB. Experimentally it was determined that in atmospheric conditions to decrease the whitening in a sample body with 3-5 mm it is necessary to introduce 0,2-0,4%FeSi-75. Observations show that introduction of 0,018-0,025% Ν and up to 0,01%B is equivalent of modification with 0,6-0,8%FeSi-75.wear
resistance of N-treated grey cast iron under equal other conditions is with 30-5)% better than the modified with FeSi. As a cryterion for research of wear resistance we used the loss in the weight of tested bodies of η-treated grey cast iron under friction with lubrication. To this end we used laboratory mashine"Amsler".The tested rolls have diameter 35mm and are 4omm wide the sample is worked out of bearing steel and is quenched. Yhe tested cast iron body is smashed to the samples with a force of 100kg. Stiding-15%. The results of the carried industrial testing with grey cast iron from a special type show that the developed technology with patent RB23345 can breach quality Grade 17 according to British standard BS1452, required in production of some details for engines with internal combustion and for some details for hydraulic machines [30]. These details are usually founded from the famous modified cast iron "Mihanaite". The results from the laboratory and industrial observations show that the developed compositions of cast iron and technologies for casts from which is required high strength and wear resistance as well as to make cutting machines lighter metallurgic treatment can be carried out by existing conditions in founding factories in an ordinary founding bucket i.e no additional complex devices are needed. This makes technology easy to apply [30] .[n point of view of technological utility and economic profit the future belongs to cast iron obtained in closed heat aggregates [4-12], By now obtained results show that a wide range of grey cast iron with high strength and wear resistance can be created.They contain Ν and are produced in atmospheric conditions as well as under higher pressure according to Bulgarian processes for gas counter pressure(MOMGP) [7-12, 30]. 2. Possibilities of formation of new austenite N-containing high strength and wear resistant complex alloyed cast alloys of the systems Fe-Cr-Mn-C-N and Fe-Cr-Mn-C Austenite is the most economic basis for creation of new alloys with special properties: wear resistance, heat resistance, corrosion resistance, non magnetism etc., combined with high mechanic characteristics and plasticity. Topical and very perspective is the problem about attempts to substitute for expensive and deficit austenite forming elements like: Ni, Cu, Co etc. with other cheaper ones Mn, N, C. In other words, the systems Fe-Cr-Mn-C-N and Fe-Cr-Mn-C as a whole and as a basis for creating new alloys with special properties are not studied enough. Researches boil down to mainly attempts to substitute Ni with Mn or Mn with Ν in C content below 0,ΙΟ,3% making possible a good plastic deformation. For more than 2-3 decades we studied those systems with a wice range of variation of basic components without additional alloying with other elements. As a result we obtained series of cast steels and cast iron with high mechanic properties and wear resistance in conditions of abrasive, hydroabrasive, strike abrasive wearing under cavitation and erosion. Some of them have good resistance towerds oxidation at high temperature and good corrosion resistance, which makes them applicable for short work at higher temperatures or in conditions of wearing and oxidation wearing in certain aggressive media etc We studied possibilities to obtain new austenite complex alloyed cast alloys through treating the steel under pressure with MOMGP in order to obtain alloys with above equilibrium contents of Ν of the system Fe-Cr-Mn-C-N and atmospheric conditions: 2#obtaining alloys with equilibrium contents Ν and N-free alloys of the system Fe-Cr-Mn-C. Below we present results of some economic alloys. 2.1. Summarized results of studies on possibilities to obtain high strength austenite wear resistant alloys of the systems Fe-Cr-Mn-C-N and Fe-Cr-Mn-C: The problem linked to obtaining of cast austenite alloys of the austenite class with high values of the yield strength (σΟ2) is wry topical. The values of σ02 of classic austenite wear resistant) steels of Hatfield type (C110Mnl3) are low (to 35-40.107 Pa [13]. Values ofa02 in classic Cr-Ni austenite steels of the type C10Crl8Ni9Ti are lower [14]. Under control regulation and observation of ratios between components forming solid solutions of substitution (most of all of Cr.and Mn) and of introduction (C and N) very good conditions of creation are created for effective action on structure. As a result we obtain high strong alloys with valuable properties. Improvement is in times not percentage. Stable austenite structure in Ni -free alloys can be obtained only at certain ratios between basic components: Cr, Μη, Ν and C. [7,12, 15-16, 22]. We studied cast austenite alloys in wide range of variation of the basic components; securing after high temperature austenitization (1100-1200°C) austenite and austenite-carbide structure [7, 12, 15]. C=0,09 -3,5%, below l%Si, to 10-30% Mn, to 3-14%Cr, 0,05-l%N, below 0,09% Ρ and S. Some of the steels and cast iron are additionally alloyed with V, Mo, Al, Pb at general sum to 2,5% austenitization and quenching of 1100-1200 C that austenite can be strengthened with Ν and C separately or together with both elements. Ν increases the strength of stretching under equal other conditions with 4-6.107Pa every 0,1%N. On statistical basis we obtained mathematics models which help evaluate the influence of the sum ZC+N in the range 0,18-1,8% on the strength of stretching and the relative border of sprawling (σ02) in cast alloys containing 12-14%Mn, 4-6%Cr, 0,4-0,6%V, 0,25-0,5%Mo, 0,15-0,2%Al. Carbon has been changed within the range 0,09-1,15% and N=0,08-0,9%. The following regression equations have been obtained after 47-48 experiments: l.For the strength tensile σΒ = 36,66+45,28 (C+N) -10,24% (C+N)2; for the yield strength σ02 = 17,035 + 50,95 (C+N) -13,97 (C+N)2. The elongation δ5 varies within the range 10-13% up to 30-35%, impact strength (ak) from 4-6 to 17-20.105Pa j/m2.
The hardness varies within the range 200-300HB. The influence of plastic characteristics higher than that of nitrogen [7, 15-17], In nitrogen, nitro-carbon austenite alloys (steels) can be reached higher plastic characteristics compared to only carbon steels. This reveals possibilities and perspectives for regulation of strength and plastic characteristics when introducing C and Ν in the melt separately or together in EC+N at different ratios C/N or N/C[7, 14-20]. We obtained high and medium-alloyed with Cr cast austenite steels, which after high temperature homogenisation and quenching possess yield strenrgt up to 3-4 times higher than that of classic austenite Cr-Ni steel of the type C10Crl8Ni9Ti and up to 1,5-2 times higher than that of the famous Hatfield steel C110Mnl3, patent claim RJB31141. Cast alloys of the system Fe-Cr-Mn-C-(N) with austenite-carbide structure after high temperature austenitization and quenching possess high mechanic properties (σΒ reaching 80-90.107Pa, hardness to 500 -600HB) and lower plasticity (δ5 and a^ depending on quantity, shape, size, distribution and type of residual carbide phase. Decreasing Mn quantity first come the unstable under deformation steels, then we reach martenzite (ferrite) class, at Mn content below 1-3%. Table I presents some generalised data on strength tensile (σΒ), yield strength (σοι), elongation (δ5) impact strength (a^) and hardness of N-free and N-containing cast austenite alloys from the different phase areas of the systems Fe-Cr-Mn-C-N and Fe-Cr-Mn-C. The advantages of alloys in the respective phase areas (γ, γ+k.k -carbide)) are obvious-steels and cast iron, containing Ν in comparison with alloys of the same phase areas with C, without Ν [7, 12]-patent claim RB3 1141and RB49451. At one and the same sum EC+N for steels of y-area. better strength characteristics and especially plasticity have those containing less C. This shows that Ν creates conditions for obtaining better plastic characteristics towards C, and up to higher content, irrespective of the fact that both elements form solid solutions of introduction. The mechanism of influence of both element on strength and plastic characteristics has been theoretical presented in [7, 16-17, 22]. It is determined by the similarities and differences in the influence of C and Ν [7, 12, 18]. For example: at the sum ΣΟΝ =1,5-1,6%and 4-7% Cr, σΒ is 1.55-1,65 times better than Ν free steels with the same sum Σ C+N, i.e containing I,5-I,6%C; σΟ2 is 1.35-1.5 times better and δ5 under the same conditions is 9-14times better than that of alloys not containing Ν or at 1,5-!,6%C. Impact strength (ak) under the same conditions is 3-5 times better. The differences in hardness are minor. Hardness of high carbon steels without Ν at 1,5-1,6%C is with 45-87 HB higher than that of Ν
of A4 size with margins of 3cm. 2. It would be expected that your paper does not exceed 8 pages in length. 3. The title page should contain the following: title of paper (all caps, center,
boldface); author"s name (Center); author"s affiliations (center); and the address with
city or state and country (center). All pages should be numbered consecutively
beginning with the title page. 4. Each heading should be in capital letters and centered. Secondary headings, if any,
should be flush with the left margin and have the first letters of all main words
capitalized.
Additionally, I am very glad to inform you that preparations for this Conference are proceeding well. Up to now, the organization committee of Asia steel 2000 in Beijing has received about 100 abstracts out off China and some 120 domestic ones. Now we send you the second circular for Asia Steel 2000 that is edited into a MS-word97 file and attached in the email. Thank you for your kind cooperation. We are looking forward to welcoming you in Beijing. Sincerely yours.
POSSIBILITIES FOR ECOLOGICAL PRODUCTION OF NEW WEAR RESISTANT Fe-C BASED ALLOYS- Dr.Eng. Bogomil Velikov KOLEV Institute of Metal Science - Bulgarian Academy of Sciences, 67 Shipchensky prohod.str., Sofia 1574, Bulgaria,
E-mail:b.v.kolev@abv.bg ABSTRACT We present in general framework a part of by now obtained results of the authors studies in the period 1968-99 about possibilities for obtaining new high-alloyed and wear-resistant founded alloys on Fe-C basis grey cast iron and complex alloyed steels and cast iron of different systems with different structure, reflected inover 110 publications, innovations, patents and other scientific studies. The results of the studies make possible to determine not only the directions for application of the obtained alloys in practices, but also to outline ecological and technical directions for obtaining of new high strong and wear-resistant alloys with N, using the possibilities of the new gas metallurgy with gaseous elements under pressure. Key words: new cast alloys, grey cast iron, complex alloyed steels and cast iron alloying with N,mechanic characteristics,wearresistance, Ecology, application, perspectives, prognostication. INTRODUCTION The intensive progress of world science imposes the necessity to create new materials and alloys with high physico-mechanic and exploitation characteristics with simultaneous decrease in material energy and other expenses for achieving high quality. Development of machine building as a strategic sector is inevitably connected to the creation of ever newer and more effective technologic and ecological processes in foundry. At the end of the 20! century tradition metallurgic and founding technologies are exhausted in their possibilities to solve these complex issues. From the three thermodynamic factors (composition, temperature and pressure), characterising and defining processes and phenomena in substances (the Nature), resp.structure and properties of materials (alloys) in classic technologies are practically used only the first two. If studying and applying of the possibilities of vacuum technologies are developed well enough vacuum technologies are developed well enough, then the study and application of the possibilities of pressure, still at an initial stage seems to be very perspective, having in mind the challenges of the 21-sl century [4]. Bulgarian methods with gas counter pressure(MOMGP) presents a fundamental innovation for great potential possibilities to develop and solve actual-priority Global problems of Mankind; creation of technologic and ecological as well as economically profitable machines and devices, new materials (alloys) and their products [4]. One of the most perspective directions of MOMGP is creation of new machine-building materials(steels and cast iron), alloyed with gaseous elements [5-8]. Of all known methods for improvement of structure and properties of the alloys on ierro-basis the most effective is alloying. MOMGP outlined the principal fundamental possibilities and directions for development of the new gaseous metallurgy with volatile elements and substances. Nitrogen as the most common in Nature gas and residual product of a number of industrial production, processing the unique property to substitute expensive and deficit elements like: Ni, Cu, Co, (Mn) etc. and to improve some physic-mechanic and exploitation characteristics in times, not in percentage, completely corresponds to some of the challenges and the outlined Global problems of Mankind for the present and future. Yet for unknown reasons the efforts of scientist are directed towards studying of possibilities to create most of all non-corrodible deformable steels. For cast alloys many restrictions in alloying with C and Ν come down as well as for other carbon-nitride forming elements, which imposes requirements for enough and high technological plasticity of deformable steels, treattability with cutting instruments, corrosion resistance etc. This shows that possibilities for obtaining of new N-containing alloys aimed at casts are many times bigger [7-12, 15-29]. With the increase of productivity of machines the wearing of details through friction increases. This leads to increase of capital investments for amortisation and for producing spare parts. The needs for wear-resistant materials for details in conditions of abrasive, hidroabrasive, strike abrasive and other types wearing are constantly growing in world range. This is due to constant decrease in ores, resp. raw materials traditionally used for obtaining of high-quality products, for enhancing all activities linked to treatment and processing of Earth crust and bowels as well as the constant development of mechanisation in industry agriculture and transport. The building of ever more power full and automatic new machines and devices for digging making smaller, grinding mixing enriching, separating transport etc. requires and justifies the use of ever
more qualitative and reliable and with longer life materials in order to minimize the defection and amortisation of spare parts.Ecologic problems are also topical 1-4] In the institute of Metal Science are carried out profound studies not only on possibilities for obtaining new Ν alloyed deformable steels, but new cat steels and cast irons as well. SUMMARISED RESULTS AND DISCUSSION 1. Possibilities for obtaining new N-containing high-strong and wear resistant ordinary grey pre-eutectic cast iron Of cast alloys used in modern machine building dominating position have grey cast iron microalling with Ν is possible trough introduction of gaseous as well as solid N-carriers[7, 9] The treatment of melts of grey cast iron with 0,8-0,9 grade of eutectics with Ν through N-treated FeMn, without introduction of other elements is possible in founding under pressure (MOMGP), as well as in atmospheric conditions [4, 10, 11]. Thus both of the two absorbed elements (Mn and N) act stabilizingly for increase of N- content, since the treatabiliry with cutting instruments sharply deteriorates. To prevent whitening is necessary quantity of the introduced N-treated FeMn to be restricted (to 0,5-1% towards weight of treated metal). To prevent stabilising influence of Mn is needed additional metallurgical treatment with FeB. Introduction of β and Ν in stoichometric quantities securing formation of nitrides of B(with crystal lattice wear to that of graphite being conductive to crystallisation and graphitization processes without thermal treatment, sharply decreases the affinity towards whitening and allows obtaining of grey cast iron, with increased Mn and Ν content [10-11].Summarised Mn and Ν content of patent Claim RB23345: [.Treatment of melts of grey cast iron with exit composition; C=2,0-3,4%; Si= 1,7-2,2%; Mn=0,4-0,5%; S up to 0,04%, Ρ up to 0,08%, Ν up to 0,005-0,007% through N-treated FeMn (containing influence of absorbed Mn and Ν leads to whitening (sample rain 0 50 mm): a)after treatment under
pressure (6/18.105Pa; 6-pressure when introducing N-carrier, 18-pressure of melt crystallisation [7, 12, 15,22].
Whitening starts at lower Mn content above 1,1-1,3%) and lower content (above 0,010-0,0160%). 2.On statistical basis are worked out mathematics models which help determine the influence of quantity of introduced N-treated FeMn ,,q",resp of the absorbed Mn (CMn) after treating under pressure 6/!8.105Pa; a) on quantity of absorbed Ν (CN); lg 58,8CN=0,14CMn; b) on the extent of Ν absorption (ηΝ); r]N=20,4+14,578q- 4,456q2 3.We obtained grey cast iron containing high content of Mn and N, thanks to the modifying and graphitizing influence of the products of "N-B" interaction; without applying long-iasting and expensive thermal treatment; a)in founding under pressure 6/18.105Pa-up to 2,5-3%Mn and 0,05%N; b) in founding in atmospheric conditions- up to 1,5-2% Mn and up to 0,025%N 5.The effect of the action of the products from the "N-B" interaction is bigger when the quantity of introduced Ν and Β is bigger. It is visible even at low content; of Ν below 0,04-0,06% of B-below 0,1-0,15%. The optimum quantity FeB (containing 20-22%B) depends on Mn and Ν content and is within the range-0,025-1,5% towards metal weight; a) in founding under pressure 6/18.105Pa-0,5-l,5%; b)in founding in atmospheric conditions-0.25- 1%. 6.To decrease the losses of Ν (N-carrier) is possible a change of part of the N-treated FeMn with ordinary, without particular deterioration mechanic characteristics; a) in founding under pressure 6/18.105Pa up to 25-30%; b) in founding in atmospheric conditions-up to 50%. 7.On statistic basis are developed mathematics models which can help evaluate the influence of absorbed Mn (resp. accordings to conclusion 2, N) on mechanic characteristics of cast iron, contain 55.10"3 - 150.10 3%B, after treatment under pressure 6/18.105Pa; b) for strength tensile; σΒ= 18,3 + 10,6CMn; b) strength of bending; aBcngmg = 38,58 + 20,260^; c) for hardness, HB = 204,86 + 23,025.CMn. 8.The obtained grey pre-eutectic after treatment as melt with N-treated FeMn and FeB under pressure in atmospheric conditions have small grain and fine grain structure density and high mechanic properties and very good wear-resistance with satisfactory treatabiliry with cutting instruments [7, 8, 10, II]. Influence of Β is basically concluded in decreasing the cimentite quantity. N-treating of melt underpressure 6/18. 103 Pa in Ν medium increases the strength of tensile with 17-25% in comparison with analogous treatment in atmospheric conditions and more than 2 times towards exit non-treated cast iron. Wear resistance of obtained under pressure 6/18.105) grey N-treated cast iron with higher Mn content is with 15-35% better than that of analogous treated cast iron in atmospheric conditions and depends on Mn content of Mn and satisfactory treteabality with cutting instruments which have comparable and better strength characteristics than the renound." Mihanite" cast iron and with many times better wear resistancre than it, consisting in; a)in founding in atmospheric conditions-up to l,5-l,8%Mn and 210-250HB. Experimentally it was determined that in atmospheric conditions to decrease the whitening in a sample body with 3-5 mm it is necessary to introduce 0,2-0,4%FeSi-75. Observations show that introduction of 0,018-0,025% Ν and up to 0,01%B is equivalent of modification with 0,6-0,8%FeSi-75.wear
resistance of N-treated grey cast iron under equal other conditions is with 30-5)% better than the modified with FeSi. As a cryterion for research of wear resistance we used the loss in the weight of tested bodies of η-treated grey cast iron under friction with lubrication. To this end we used laboratory mashine"Amsler".The tested rolls have diameter 35mm and are 4omm wide the sample is worked out of bearing steel and is quenched. Yhe tested cast iron body is smashed to the samples with a force of 100kg. Stiding-15%. The results of the carried industrial testing with grey cast iron from a special type show that the developed technology with patent RB23345 can breach quality Grade 17 according to British standard BS1452, required in production of some details for engines with internal combustion and for some details for hydraulic machines [30]. These details are usually founded from the famous modified cast iron "Mihanaite". The results from the laboratory and industrial observations show that the developed compositions of cast iron and technologies for casts from which is required high strength and wear resistance as well as to make cutting machines lighter metallurgic treatment can be carried out by existing conditions in founding factories in an ordinary founding bucket i.e no additional complex devices are needed. This makes technology easy to apply [30] .[n point of view of technological utility and economic profit the future belongs to cast iron obtained in closed heat aggregates [4-12], By now obtained results show that a wide range of grey cast iron with high strength and wear resistance can be created.They contain Ν and are produced in atmospheric conditions as well as under higher pressure according to Bulgarian processes for gas counter pressure(MOMGP) [7-12, 30]. 2. Possibilities of formation of new austenite N-containing high strength and wear resistant complex alloyed cast alloys of the systems Fe-Cr-Mn-C-N and Fe-Cr-Mn-C Austenite is the most economic basis for creation of new alloys with special properties: wear resistance, heat resistance, corrosion resistance, non magnetism etc., combined with high mechanic characteristics and plasticity. Topical and very perspective is the problem about attempts to substitute for expensive and deficit austenite forming elements like: Ni, Cu, Co etc. with other cheaper ones Mn, N, C. In other words, the systems Fe-Cr-Mn-C-N and Fe-Cr-Mn-C as a whole and as a basis for creating new alloys with special properties are not studied enough. Researches boil down to mainly attempts to substitute Ni with Mn or Mn with Ν in C content below 0,ΙΟ,3% making possible a good plastic deformation. For more than 2-3 decades we studied those systems with a wice range of variation of basic components without additional alloying with other elements. As a result we obtained series of cast steels and cast iron with high mechanic properties and wear resistance in conditions of abrasive, hydroabrasive, strike abrasive wearing under cavitation and erosion. Some of them have good resistance towerds oxidation at high temperature and good corrosion resistance, which makes them applicable for short work at higher temperatures or in conditions of wearing and oxidation wearing in certain aggressive media etc We studied possibilities to obtain new austenite complex alloyed cast alloys through treating the steel under pressure with MOMGP in order to obtain alloys with above equilibrium contents of Ν of the system Fe-Cr-Mn-C-N and atmospheric conditions: 2#obtaining alloys with equilibrium contents Ν and N-free alloys of the system Fe-Cr-Mn-C. Below we present results of some economic alloys. 2.1. Summarized results of studies on possibilities to obtain high strength austenite wear resistant alloys of the systems Fe-Cr-Mn-C-N and Fe-Cr-Mn-C: The problem linked to obtaining of cast austenite alloys of the austenite class with high values of the yield strength (σΟ2) is wry topical. The values of σ02 of classic austenite wear resistant) steels of Hatfield type (C110Mnl3) are low (to 35-40.107 Pa [13]. Values ofa02 in classic Cr-Ni austenite steels of the type C10Crl8Ni9Ti are lower [14]. Under control regulation and observation of ratios between components forming solid solutions of substitution (most of all of Cr.and Mn) and of introduction (C and N) very good conditions of creation are created for effective action on structure. As a result we obtain high strong alloys with valuable properties. Improvement is in times not percentage. Stable austenite structure in Ni -free alloys can be obtained only at certain ratios between basic components: Cr, Μη, Ν and C. [7,12, 15-16, 22]. We studied cast austenite alloys in wide range of variation of the basic components; securing after high temperature austenitization (1100-1200°C) austenite and austenite-carbide structure [7, 12, 15]. C=0,09 -3,5%, below l%Si, to 10-30% Mn, to 3-14%Cr, 0,05-l%N, below 0,09% Ρ and S. Some of the steels and cast iron are additionally alloyed with V, Mo, Al, Pb at general sum to 2,5% austenitization and quenching of 1100-1200 C that austenite can be strengthened with Ν and C separately or together with both elements. Ν increases the strength of stretching under equal other conditions with 4-6.107Pa every 0,1%N. On statistical basis we obtained mathematics models which help evaluate the influence of the sum ZC+N in the range 0,18-1,8% on the strength of stretching and the relative border of sprawling (σ02) in cast alloys containing 12-14%Mn, 4-6%Cr, 0,4-0,6%V, 0,25-0,5%Mo, 0,15-0,2%Al. Carbon has been changed within the range 0,09-1,15% and N=0,08-0,9%. The following regression equations have been obtained after 47-48 experiments: l.For the strength tensile σΒ = 36,66+45,28 (C+N) -10,24% (C+N)2; for the yield strength σ02 = 17,035 + 50,95 (C+N) -13,97 (C+N)2. The elongation δ5 varies within the range 10-13% up to 30-35%, impact strength (ak) from 4-6 to 17-20.105Pa j/m2.
The hardness varies within the range 200-300HB. The influence of plastic characteristics higher than that of nitrogen [7, 15-17], In nitrogen, nitro-carbon austenite alloys (steels) can be reached higher plastic characteristics compared to only carbon steels. This reveals possibilities and perspectives for regulation of strength and plastic characteristics when introducing C and Ν in the melt separately or together in EC+N at different ratios C/N or N/C[7, 14-20]. We obtained high and medium-alloyed with Cr cast austenite steels, which after high temperature homogenisation and quenching possess yield strenrgt up to 3-4 times higher than that of classic austenite Cr-Ni steel of the type C10Crl8Ni9Ti and up to 1,5-2 times higher than that of the famous Hatfield steel C110Mnl3, patent claim RJB31141. Cast alloys of the system Fe-Cr-Mn-C-(N) with austenite-carbide structure after high temperature austenitization and quenching possess high mechanic properties (σΒ reaching 80-90.107Pa, hardness to 500 -600HB) and lower plasticity (δ5 and a^ depending on quantity, shape, size, distribution and type of residual carbide phase. Decreasing Mn quantity first come the unstable under deformation steels, then we reach martenzite (ferrite) class, at Mn content below 1-3%. Table I presents some generalised data on strength tensile (σΒ), yield strength (σοι), elongation (δ5) impact strength (a^) and hardness of N-free and N-containing cast austenite alloys from the different phase areas of the systems Fe-Cr-Mn-C-N and Fe-Cr-Mn-C. The advantages of alloys in the respective phase areas (γ, γ+k.k -carbide)) are obvious-steels and cast iron, containing Ν in comparison with alloys of the same phase areas with C, without Ν [7, 12]-patent claim RB3 1141and RB49451. At one and the same sum EC+N for steels of y-area. better strength characteristics and especially plasticity have those containing less C. This shows that Ν creates conditions for obtaining better plastic characteristics towards C, and up to higher content, irrespective of the fact that both elements form solid solutions of introduction. The mechanism of influence of both element on strength and plastic characteristics has been theoretical presented in [7, 16-17, 22]. It is determined by the similarities and differences in the influence of C and Ν [7, 12, 18]. For example: at the sum ΣΟΝ =1,5-1,6%and 4-7% Cr, σΒ is 1.55-1,65 times better than Ν free steels with the same sum Σ C+N, i.e containing I,5-I,6%C; σΟ2 is 1.35-1.5 times better and δ5 under the same conditions is 9-14times better than that of alloys not containing Ν or at 1,5-!,6%C. Impact strength (ak) under the same conditions is 3-5 times better. The differences in hardness are minor. Hardness of high carbon steels without Ν at 1,5-1,6%C is with 45-87 HB higher than that of Ν
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