MOLDED DURABLE ALLOYS ON THE BASIS OF IRON FOR MANUFACTURING OF INSTRUMENT OF PRIMARY POLIMER GRANULATION A.G. Baginskyi, Yu.P. Egorov, O.M.

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1 METAL , Hradec nad Moravicí MOLDED DURABLE ALLOYS ON THE BASIS OF IRON FOR MANUFACTURING OF INSTRUMENT OF PRIMARY POLIMER GRANULATION A.G. Baginskyi, Yu.P. Egorov, O.M.Utiev Nowadays rapid development of the production of construction plastics and other polymer materials, stipulated by the market growing demand, is taking place. Since the beginning of 90-s plastic output has grown by,8,0 times, and equipment capacity by dozens of times. Granulation of polymers is a basic procedure of their production. The most problematic section in a granulator is a pair knife-draw plate (Fig.)., мм Полимерный поток Figure. A scheme of a cutting pair draw plate-knife : patch surface (alloy of the type WCo); internal heat-insulating layer; heating canals between outlets (oil, t=00 C); outlets; thermal pipe effect; knife; 7 granules; 8 water ring; 9 cutting edge The conducted research has shown that knives for cutting plastics work in conditions of a considerable wear-out at contact dragging with a draw plate surface, especially at grinding knives to the draw plate surface []. Grinding period is from 8 to hours and depends on wear-resistance of the materials and accuracy of the knives production. Table Manufacturers, chemical composition of knives and processed product «Berstorff», Great Britain «Farel Bridj», Great Britain «Napomcna», Japan «Werner und Pfleider», Germany «Trusioma», Germany Chemical composition, % C Mn Mo Ni Cr Ti V W Co HRC Processed product, 0, 0, , Polyethylene, 0,7 0, , -- 9± Polyethylene Машина, фирмаизготовитель 0,9,0 0,8 0, ± Polypropylene, 0,09,7 0,0 0,,,7 -- 0± alloy «ferrotic» Polypropylene 0,8 0, --, --,7 7, ± Polyethylene

2 METAL , Hradec nad Moravicí To manufacture knives for polyethylene processing steels with a high content of chromium are more often used (see table). Recently to process polypropylene an alloy ferrotic, obtained by the method of power metallurgy, is used. High durability of knives made from ferrrotic is provided by content of titanium carbides (about 0% by volume) with a high hardness (over 00 HV). Thus, the main requirement to the material for granulating instrument is a high durability. This is achieved due to high content of carbides (0 0% form а Figure. Microstructure of molded alloy with various content of vanadium (enlargement 00): а % vanadium; - 0% vanadium the volume). The material with this content of carbides can be obtained by the method of power metallurgy or molded technology. Research in development of a molded variant of the alloy with hardness of 8 HRC, received due to big quantity of hard vanadium carbides (with hardness of 800 HV), has been carried out at the TPU subfaculty Material science and technology of metals. Vanadium carbides are poorly soluble while heating for hardening, and their volume can be easily changed while molding, varying the content of carbon and vanadium in molding. Review of the publications in the field has shown that vanadium is a strong carbide-forming element. Thus, a high content of vanadium is possible only in the condition of simultaneous increase in carbon content, otherwise steel does not have a high hardness while hardening. That is why increase in vanadium content by % involves increase in carbon content by 0,% []. The present article summarizes the results of the research of molded ferricarbonic alloys with vanadium with the purpose of their use at manufacturing granulating knives. Alloys melting was done with the use of highfrequency plant in an acid bowl. Before pouring the alloys were deoxidized by silicocalcium and ferrosilicon. After molding and cooling in a still air the hardness varied from 8 HRC (alloy ) to HRC (alloy ). A microstructure of the alloys was visualized by etching a microsection with a % solution of nitric acid in ethyl alcohol. The alloy structure with % of vanadium is a pearlite with a discrete grid of a secondary cemenite and vanadium carbide (figure, а). With the further increase in vanadium content up to 0% isolated groups of carbides in the form of a flower, square and fan-shaped eutectic begin to appear (figure, ). Quantity of a carbide phase increases with the growth of vanadium content (figure ). Quantitative adjectives V% К V% Figure. Influence of the vanadium content in the alloys on inclusion volume fraction of a carbide phase: molded; Т hard =800 С; Т hard =0 С

3 METAL , Hradec nad Moravicí for the structure were determined with the use of metallographic microscope, digital camera МDС-00 and a software, developed by the TPU sub-faculty Material science and technology of metals [] T0 ЗАК ос Figure. Influence of the hardening temperature on the alloys hardness: %С;,%С, %V; -,8%С, %V; -,%С, %V; -,%С, 8%V; - %С, 0%V For this group of alloys research in hardening temperature impact on a structure and hardness was carried out. Samples hardening was performed within the temperature interval from 800 to 0 С. To prevent decarbonization heating was made in salt tanks with the further water hardening. Figure illustrates dependence of hardening change of molded vanadium alloys on hardening temperature. These vanadium alloys can be split into two groups. Hardness of the first group alloys with the increase in hardening temperature changes insignificantly. Hardness of the second group considerably decreases. Decrease is up to Т hard =0 С. Steels with a high content of vanadium (8 0%) have got more considerable hardening decrease. This is conditioned by the increase of the residual austenite portion []. Hardening at the temperature over 0 С growth of hardness, conditioned by vanadium carbides dissolution, takes place (figure, curves,.) T700 ОТП, С T700 ОТП, С a Figure. Influence of the hardening temperature ( 800 С; 900 С; 000 С; 00 С; 00 С; 0 С) and tempering on hardness of molded alloys with various vanadium content: а с %V; 8%V The samples were further processed at the temperature from 00 to 700 С with the interval of 0 С. Figures а, illustrate dependences of hardness of the hardened alloys with % and 8% of vanadium on the tempering temperature. Graphics show that hardness of the alloys, hardened from the reheat temperature to 000 С, is continuously decreasing while tempering. On the other hand, hardening at the temperature over 0 С involves hardness growth at 0 0 С (afterhardening). Thus, alloys hardened at high reheat temperatures will have higher heat endurance. 0 0

4 METAL , Hradec nad Moravicí On the basis of the conducted research a technology for production of molded granulating instrument of the primary polymer granulation has been developed. The body for experimental alloys is instrumental production waste, additionally alloyed with vanadium and carbon. To manufacture granulating knives a molded technology with forming into a shell mold or by investment patterns was used. Knives of a simple form (figure а, without a threaded fitting) are advisable to manufacture in shell molds. To reduce labor intensiveness metal models were made from aluminum alloy. The models location was radial (figure 7). This molding method is very economical since it provides quite a high quality. Knives of a complex form (figure, ) were molded in the form, made by investment patterns. A mold for forming models was made. As a model composition was used a paraffinstearic mixture. Paraffin-stearic models were prepared for soldering into model blocks (figure 8). A refractory coating of the models is a hydrolized solution of ethyl silicate with marshalite. Quartz sand was used as a filling compound. This molding technology makes possible to considerably reduce costs for mechanical operation and decrease waste by 0%. Figure. Photo of the knives for polymer processing Figure 7. Shell mold Figure 8. Model block If it is necessary to use threaded fitting in granulating knives the following technique was used: before pressing-in of paraffin into a mold hexahedral steel locks (0,% С) were used (figure 9,а). The received knife molding from durable steel with the locks from constructional steel make possible to considerably reduce costs for drilling mounting holes and screwing thread (figure 9,). To set up locks in the mold correctly the locks were equipped with holders on both sides. A hexahedral form of the lock was chosen to avoid the lock slipping in the knife body in case of failure to weld it with the durable alloy while molding.

5 METAL , Hradec nad Moravicí a Фиксатор Figure 9. Drawing of the knife with the lock: а - lock; - knife Then finishing thermal processing, hardening at the temperature over 00-0 С and tempering at the temperature of 0 С were carried out during two hours. Finishing mechanical operation involved polishing of base and contact instrument plates. Instrument manufactured according to this technology widely applied for granulators of the companies «Berstorff», «Werner und Pfleider», «Trusioma» and others. Durability of knives manufactured form experimental alloys with the use of this technology meets the demand of consumers []. REFERENCES. Utiev O.M. Analysis and development of the material for granulating instrument used for plastic processing// Proceeding book «Mechanics and machine building». -Tomsk: TPU P.0-.. Egorov Yu.P., Utiev O.M., Martushev N.V. Computer analysis of metals structure.//metal processing. 00. (0). P-.. Kostarev A.B., Korchmit A.V. Utiev O.M. Metallographic and x-ray-structural research of molded instrument steel with vanadium Proceedings of V-ой Regional scientific conference of students, post-graduate students and young scienticts «Modern technique and technolgies» TPU public house, P0.