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23.06.2010 18:00 - Доклад изнесен от д-р инж. Богомил Великов Колев и публикуван в Атина Гърция . Международен конгрес
Автор: bogomil Категория: Технологии   
Прочетен: 696 Коментари: 0 Гласове:
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Последна промяна: 23.06.2010 18:19


ΤΕΧΝΙΚΟ ΕΠΙΜΕΛΗΤΗΡΙΟ ΕΛΛΑΔΑΣ 3ο ΣΥΝΕΔΡΙΟ ΟΡΥΚΤΟΥ ΠΛΟΥΤΟΥ ΟΡΥΚΤΕΣ ΠΡΩΤΕΣ ΥΛΕΣ ■ ΥΠΟΓΕΙΑ ΕΡΓΑ ΜΕΤΑΛΛΟΥΡΓΊΑ ΠΡΑΚΤΙΚΑΣΥΝΕΔΡΙΟΥ ΤΟΜΟΣΒ" ΑΘΗΝΑ 22-23 & 24 ΝΟΕΜΒΡΙΟΥ 2000 ΞΕΝΟΔΟΧΕΙΟΜΕΓ. ΒΡΕΤΤΑΝΙΑ
NEW WEAR RESISTANT AUSTENITE CAST ALLOYS Dr.Eng. Bogomil Velicov Kolev -Institute of Metal Sdcnce-B/YS. 67 Sliipchensky prohod sir, Sofia 1574, Bulgaria Abstract The paper presents part of the initial results of the investigations concerning the possbilities to produce wear resistent austenitic alloys of higher wear resistance than that of I latfield"s(of the type CllOMnl3). The effects of the basic components (C, N, ZC+N, Cr, Mn) and crycstalisation pressure on the wear resistance are studied. The results apply to states: after homogenization and quenching from 115Ο0 C, ageing at 7oo° C and after cooling at minus 65° C and they are protected by authors sertificates(patents). l.Inrtoduction The basic factor determining   wear resistance is phase composition , resp. chemical composition. At the present stage of research there is no common theory explaining the mechanisme of wearing processes: cutting, grinding, friction, wearing at high or negative temperatures, hidroerosion, cavitation, erosion and additional corrosion [1],Wearing   may be: pure abrasive, hydroabrasive, in media with different Ph, resp. with different pressure: striking, folding etc. influence exerts also the metallurgical treatment of the melt conditions of cristslization and the regime of thermal treatment. The diversity of wearing reflects on the structure formation, changes in which create difficulties in the determination of regularities between phase (structure) and chemical composition and wearing as well as in the choice of suitable composition in practice, regime and methods of treatment. Compomises between contradictory properties should often be made, e.g. hardness, resilience etrc. There are difficulties coming from the lack of standart experiment methods, environment effects, estimation of the economic usefulness of different  decisions. In rising wear-resistance phases and structure compositions go in the following order: ferrite, perlite, troostite, zorbite. Austenite has been insufficiently studied and is given contradictory estimates. Besides, austenite of the CrlSNilO type is corrosion-resistant, but poorly wear resistent and austenite of the Hatfield steel type Cl 10Mnl3 is highly resistant under strike wearing and possesses low corrosion and thermal resistance. The efforts to improve wear resistence   of ClIOMnl3   with carbide-formators   and   even   stabilizers gave   no important results. It seems that intil recently [6] scientiest have considered C the most Important and single element which determines wear resistance of steels of the Hatfield ype.   Hence,   it   is   expected   that   strengthening   [1-3,8)   should   improve   wear esistance.Strengthening   under   alloying(N   etc.),   additional   treatment   and   use. ccording to [1-3,8] combining Cr and Mn and C, Ν along with other elements very ucceful combination of strength and heat resistence, wear resistance etc. The iroduction of wear resistant alloys is a topical problem of national and world ignificance. Needs are rising. This is a resource and environmental issue. There are no ;ferences about wear-resistant non-nickel alloys of the studied system, about the ifluence of the basic factors, pressure and different types of heat treatment upon wear distance.
2.The aim and experimental procedurs. The aim of the work is to present to the scientific and technical public a part of the initial results of the studies on wear resistance of founded austenite non-nickel alloys of the Fe-Cr-Mn-C-N system the influence of basic components and pressure, heat treatment and on the basic of wear resistant and higly strong alloys with better wear resistance than that of the Hatfield steel (of the CllOMnl3 type) and of the first time [6]. Alloys have been obtained in an induction autoclave and have been poured into dry sand forms in sample bodies 22 mm in diametr under pressure Ρ =45. ΙΟ.5 Pa after the method of [1-2]. The wear resistance testing is carried out in a Skoda -Savin machine in Central Manifacturing Institute- Sofia. The results have been interpreted graphically and in tables and every point has been averaged of at last 3 samples. Results have been compared to those of Crl8NilF and CllOMnO. The teasting consits of: 4 hour homogenization at 115O° C and tempering in water followed by aging at 7OO° C for 15 hours after cooling down of homogenized samples at minus 65° C for 3Omin. A larg amount of samples has been studied in the γ and γ+Κ areas in fig.l. 3.Experimental results and discution. C(fig. 1, tabl.2), resp.I C +N (fig.3) improve wear resistance. For alloys of the γ area the influence of the strengthening effect of the alloyng with Ν and C and of the wearing is still importcnt. The explanation lies the dislocation theory [1-3,8]- For alloys of the γ+Κ area in fig 1. influence exerts the relation between the ustenite(y) and the characteristics of the carbide phase(K) [4]: For alloys γ / K1 the influence of Κ is importent, for γ/Κ



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