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IMPROVEMENT OF THE TECHNOLOGY OF PRODUCING HIGH-STRENGTH CAST IRON FOR THE MANUFACTURING OF CRITICAL PARTS OF
RAILWAY TRANSPORT
Tursunov Nodirjon Qayumjonovich Toshkent davlat transport universiteti "Materialshunoslik va mashinasozlik" kafedrasi t.f.d professor
E-mail: u_nadir@mail. ru
Rahimov Uchqun Toshniyoz o'g'li Toshkent davlat transport universiteti "Materialshunoslik va mashinasozlik" kafedrasi tayanch doktaranti
E-mail: uchqun.raximov. [email protected]
Urazbayev Talgat Tileubayevich "Materialshunoslik va mashinasozlik" kafedrasi katta o'qituvchisi, PhD
E-mail: [email protected]
Annotasiya. Ushbu maqolada ikkilamchi po'lat chiqindi xomashyolaridan foydalanib induksion tigel pechida sintetik cho'yanni eritish, yuqori mustahkam cho'yanning mexanik xossalari va strukturasini yaxshilash maqsadida modifikatorlar q o'llab cho'yanni modifikatsiyalash va D49 silindr qopqog'ini qumliy qolipning quyish tizimiga modifikatorlarni o'rnatish.
Аннотация. Данная статя посвящена выплавке синтетического чугуна из вторичного сталного лома в индукционной тигелной печи, модифигация чугуна в ковше с применением модификаторов и установка модификаторов в литниковую систему песчано-глинистой формы для крышки цилиндра Д49 с целю улучшения механических свойств и структуры высокопрочного чугуна.
Abstract. This article is devoted to the smelting of synthetic cast iron from secondary steel scrap in an induction crucible furnace, modification of cast iron in a ladle using modifiers and installation of modifiers in a gating system of a sand-clay mold for the D49 cylinder cover in order to improve the mechanical properties and structure of high-strength cast iron.
Kalit so'zlar: yuqori mustahkamlikka ega bo'lgan cho'yan, modifikator, mexanik xususiyatlar, induksion pech, kovsh, sintetik cho'yan, mikrotuzilishi.
Ключевые слова: высокопрочный чугун, модификатор, механические свойства, индукционная печ, ковш, синтетический чугун, микроструктура.
Key words: ductile iron, modifier, mechanical properties, induction furnace, ladle, synthetic cast iron, microstructure.
High-strength cast iron with spherical graphite, which are new materials for mechanical engineering, combine the high mechanical properties of steel with the simplicity of cast iron production. These materials can replace steel casting, forging, and non-ferrous alloys. The use of high-strength cast iron instead of gray and modified cast iron improves performance, increases the reliability and durability of machine parts, and in some cases reduces their weight and reduces the cross section. The production process of high-strength cast iron includes modification of its liquid alloy with magnesium or cerium [1].
In the production of high-strength cast iron with spherical graphite, the method of placing a modifier at the bottom of the ladle is used to modify the melt using the sandwich process technology using a complex modifier based on iron and silicon dioxide. For successful
modification in a bucket, the dimensions of the bucket itself and the correct location of the modifiers are important. Bucket modification is one of the most effective methods for producing high-strength cast iron castings with spherical graphite, as it allows you to achieve stable results with minimal consumption of modifiers.
The technology of modifying high-strength cast iron in a ladle consists in adding modifiers directly into a ladle with molten cast iron to improve the structure and mechanical properties of the metal. The main task of this process is to transform the shape of graphite in the melt from lamellar to spherical, which significantly increases the strength, ductility and wear resistance of cast iron [2].
The developed technological processes for the production of high-strength cast iron of the (Bch 50) brand:
Melt preparation: Research smelting was carried out at JSC Foundry and Mechanical Plant using a medium-frequency induction crucible furnace from OTTO JUNKER with a capacity of 6 tons and a neutral lining (Fig. 1). Scrap steel with a high carbon content is used as charge materials, and graphite is added to carburize the melt in order to obtain synthetic cast iron. To bring the chemical composition of cast iron, for example, ferrosilicon FS45 or FS65 is added. [3] As is known, sulfur (S) complicates the graphitization process, increases brittleness and worsens the fluidity of cast iron. Therefore, when smelting synthetic cast iron in an induction crucible furnace, desulfurization is carried out to a sulfur content of 0.02%. Then the molten synthetic cast iron is
Figure 1. General view (a) and diagram (b) of the ITP with a capacity of 6 tons of JSC
"LMZ"
The chemical composition of the experimental smelting of synthetic cast iron is shown in Table 1. At the same time, the temperature of the metal must be strictly controlled to ensure optimal modification conditions.
Table 1. Chemical composition of synthetic cast iron
№ melt № melt The content of the elements by weight, %
C Si Mn S P Cr Ni Cu Mg Ti Al
1 1 3,039 0,916 0,552 0,020 0,030 0,104 0,090 0,080 0,0010 0,007 0,003
2
2 3,467 0,882 0,568 0,021 0,029 0,106 0,088 0,080 0,0010 0,008 0,004
bucket 3,380 2,213 0,570 0,009 0,032 0,111 0,088 0,082 0,054 0,010 0,025
1 2,554 1,085 0,683 0,026 0,057 0,193 0,140 0,158 0,0012 0,008 0,014
2 3,054 1,140 0,685 0,028 0,052 0,189 0,139 0,157 0,0012 0,008 0,012
bucket 2,979 2,094 0,667 0,023 0,051 0,197 0,137 0,154 0,056 0,010 0,021
Introduction of modifiers: Modifiers are added to a special bucket at the bottom of the reaction chamber using the "sandwich process" technology, in which the modifier is filled with layers between the melt layers for uniform distribution. To achieve the best result, metal modification is performed in a bucket of special processing, the main difference between which and buckets traditionally used in foundry production are geometric proportions and the presence of a reaction chamber at the bottom (Fig.2) [4].
Figure 2. A rotating bucket for modifying the solution and a sketch of the modifier placed at the bottom of the bucket.
Sferomag ®620L with a fraction of 1.0-10.0 mm were used as modifiers, to eliminate cementite, SIBAR®4 is used for uniform distribution of the casting section over the surface of the structure. INOCSIL SM180 is used for early graphite fraction and late graphite. It is recommended to cover the top. These materials ensure stable production of high-strength cast iron with spherical graphite by modification in a bucket. The chemical composition of the modifiers is shown in Table 2.
Table 2. Chemical composition of modifiers
The brand of the The mass fraction of the main elements, %
modifier Mg Al Si Са Ba La Fe
Sferomag ®620L 5,7-6,5 0,6-1,2 44,0-49,0 1,6-2,5 - 0,35-0,6 res.
SIBAR®4 - 1,0-2,0 65,0-75,0 0,8- 1,5 3,5-5,0 - res.
INOCSIL - 3,2-4,5 70,0-78,0 0,3-1,5 - - res.
SM180
QURILISH
Reaction with modifiers: As a result of the interaction of the modifier with the melt, the shape of graphite changes - it is transformed from lamellar to spherical. This improves the mechanical properties of high-strength cast iron, such as strength and ductility.
Pouring into molds: After modification, cast iron is poured into sandy clay molds to obtain castings of the cylinder cover D49. The INOCSIL SM80 modifier is placed at the bottom of the lower half-mold gate system for late graphitization (Fig. 3) [5,6].
Figure 3. The lower half of the shape of the cylinder cover D49 with a diagram of the installation of the modifier at the bottom of the gate system.
The results of mechanical tests of samples of high-strength cast iron of the (BCh 50) grade are shown in Table 3.
№ melt № samples Temporary resistance Cb, MPa Relative elongation, ô %, Brinell hardness, HE^HI
rOCT 729385 He менее 500 He MeHee 7 153-245
1 1 575 10 200
2 602 7 205
3 595 8 208
4 606 9 210
2 1 580 7 202
2 606 8 208
3 585 10 212
4 600 10 210
As can be seen from Table 3, the mechanical properties of high-strengt i cast iron meet the
requirements of GOST 7293-85.
The structural analysis of high-strength cast iron of the (BCh 50) grade with a spherical graphite shape is shown in Figure 4.
1 melt 2 melt
Figure 4. Microstructure of high-strength cast iron of the (ech 50) grade with a spherical
graphite shape.
Microstructural analysis of the comprehensively modified samples showed the presence of a finely dispersed structure with a spherical shape of graphite. The test results confirmed the expediency of the combined use of Spheromag®620L, SIBAR®4 and INOCSIL SM180 modifiers to improve the properties of cast iron.
Conclusions
1. The developed new technology for producing synthetic cast iron from secondary scrap steel waste in an induction crucible furnace at JSC Foundry and Mechanical Plant is an appropriate method for producing high-strength cast iron.
2. The developed technological processes for modifying high-strength cast iron of the (BCh 50) grade in the bucket and at the bottom of the gate system of the lower half of the mold confirmed the expediency of the joint use of Spheromag®620L, SIBAR®4 and INOCSIL SM180 modifiers, ensuring compliance of the mechanical properties and microstructure with the spherical shape of graphite with the requirements of GOST 7293-85.
REFERENCES
1. Tursunov N.K.; Alimuxamedov, Sh.P.; Toirov, O.T. Development of an effective technology for producing synthetic cast iron in an induction crucible furnace. Universum: Technical sciences: electron. scientific Journal -2022. 6(99), June, 2022
2. Rakhimov, U. T., N. K. Tursunov, and S. E. Tursunov. "Improvement of production technology for spheroidal graphite cast iron with increased strength." American Institute of Physics Conference Series. Vol. 3045. No. 1. 2024.
3. Kren A.P.; Masulevich, O.V.; Protasenya T.A.; Tursunov N.K.; Urazbaev T.T.; Nikiforov A.V.; Delendik M.N. Justification of the choice of geometric parameters of the indenter and the energy of micro-shock deformation to achieve sufficient sensitivity and accuracy in measuring the hardness of cast iron. Technological support of machine-building production: electron. scientific Journal - 2024 (March 21-22).
4. U.T. Rakhimov, N.K. Tursunov, S.E. Tursunov. Improvement of production technology for spheroidal graphite cast iron with increased strength. AIP Conference Proceedings. AIP Conf. Proc. 3045, 060024 (2024) 12 March 2024.
5. Н.К. Турсунов, У.Т. Рахимов. Исследование технологии производства высокопрочного чугуна для изготовления крышки цилиндра. Инновaционное развитие транспортного и строителного комплексов. (Гомел, 16-17 ноyaбря 2023 г.)
Tursunov Nodirjon Qayumjonovich, Rahimov Uchqun Toshniyoz o'g'li, Urazbayev Talgat Tileubayevich. D49 turidagi dizeli dvigitel qopqogini tayyorlash uchun yuqori mustahkamlikka ega bo'lgan choyanlarni olish texnologiyasini takomillashtirish. № 4 (13), 2023.
