THE RESULTS OF ABRASIVE WEAR TESTS UNDER LABORATORY CONDITIONS OF CHISEL-CULTIVATOR PLOUGHSHARES WITH INCREASED DURABILITY, PRODUCED BY CASTING FROM WEAR-RESISTANT LOCAL RAW MATERIALS

ABSTRACT

The article presents modern methods for selecting wear-resistant steel grades to ensure the efficiency and long-term operation of soil tillage machines. Additionally, the use of high-carbon steels, special alloys, and chromium-molybdenum steels significantly increases the wear resistance of working parts, thereby considerably extending their service life. The use of such materials reduces production costs and ensures long-term durability. The methodology for selecting materials resistant to abrasive wear is based on studying their physical and mechanical properties, chemical composition, microstructure, and abrasive tests.

АННОТАЦИЯ

В статье приведены современные методы выбора марок стали, устойчивых к износу, для обеспечения эффективности и длительного срока службы почвообрабатывающих машин. Кроме того, использование высокоуглеродистых сталей, специальных сплавов и хромомолибденовых сталей значительно увеличивает износостойкость рабочих органов, что существенно продлевает их рабочий ресурс. Применение таких материалов снижает производственные затраты и обеспечивает длительный срок эксплуатации. Методика выбора материалов, устойчивых к абразивному износу, основывается на изучении их физических и механических свойств, химического состава, микроструктуры и абразивных испытаний.

Keywords: Raw material, ploughshare, equipment, wear resistance, resource, chisel cultivator, induction, furnace, material, abrasive wear, thermal treatment, standard.

Ключевые слова: сырье, лемех, оборудование, износостойкость, ресурс, строгальный культиватор, индукция, печь, материал, абразивное изнашивание, термическая обработка, стандарт.

INTRODUCTION. When selecting a material resistant to abrasive wear, it is important to consider the elimination of factors that accelerate the abrasive wear process and transition to a potential mechanical-chemical wear process. This can be achieved by using materials that differ in their chemical composition and properties (Figure 1). The following materials are considered resistant to abrasive wear:

1. Materials with a hardness greater than that of the abrasive particles;
2.  Austenitic materials capable of transforming into deformation martensite;

Materials that can absorb a significant portion of the kinetic energy of the abrasive particles through elastic deformation.

Figure 1. Ploughshare of chisel cultivator

Materials with a hardness greater than that of the abrasive particles belong to this group. These materials have a heterogeneous structure composed of a metal matrix with a certain hardness and high-hardness fillers (such as carbides, nitrides, carbonitrides, carboborides, etc.). The matrix with a specific hardness resists the penetration of the abrasive particle into the surface of the part, while the high-hardness fillers resist the movement of the abrasive particle across the surface. Steel and white cast iron are examples of matrix materials with specific hardness. Based on their increasing resistance to abrasive wear, steel can be arranged in the following sequence according to their metallurgical structure: ferrite → (ferrite + pearlite) → pearlite → bainite → martensite; pearlite → sorbite → troostite; tempered sorbite → quenched sorbite; low-carbon martensite → high-carbon martensite. Specifically, pre-eutectoid and quenched martensitic steels have higher wear resistance compared to tempered or normalized eutectoid or post-eutectoid steels.

METHODS.

A high-frequency JLZ-35KW induction steel melting furnace was used (Figure 2) in the production of chisel-cultivator ploughshares, which deeply loosen the soil. These ploughshares were cast from locally sourced raw materials. The research work to determine the abrasive wear of the ploughshare samples was conducted according to the sample testing program. Factors such as the pressure exerted on the sample, test duration, friction speed, and consumption of abrasive material were taken into account. The amount of wear was determined by measuring the difference in weight and dimensions of the samples before and after testing.

Figure 2. High-Frequency Induction Metal Melting Furnace, JLZ-35 KW

The wear resistance tests of the samples were conducted at the "Technological Machines and Equipment" department of Andijan machine building institute using an abrasive wear testing device (Figure 3). The tests were carried out according to the ГОСТ 23.208-79 standard. In the abrasive wear testing, the sample was subjected to friction against an elastic roller made of rubber, combined with abrasive particles.

Figure 3. Device for Testing Metal Samples for Abrasive Wear in an Abrasive Environment

As the abrasive material, quartz sand with a particle size of less than 0.1 mm was used. Weights of 1 kg, 2 kg, 3 kg, 4 kg, and 5 kg were used as the load exerting pressure on the sample. The loads applied to the sample surface via the arm of the wear testing machine corresponded to 35, 70, 105, 140, and 175 N, respectively. One cycle of wear in the abrasive environment lasted 120 minutes. A roller with a diameter of 50 mm operated at an angular speed of 60 rpm, covering a wear path of 1130 meters per cycle.

As a reference sample, unquenched steel of grade ШХ15СГ was selected. Various composition ploughshare materials cast from locally sourced raw materials were subjected to thermal treatment and tested, and the obtained results were compared with the reference sample's performance.Testing of samples was carried out according to the pressure force and friction speed corresponding to the surface unit of ploughshares based on plowing and tillage in an abrasive environment.

The average arithmetic value of the creep rate of the samples was compared with the sample selected as a standard. The rate of wearing within a unit of time was determined by the following expression.

 mass of the sample before the experiment, g;

 mass of the sample after the experiment, g;

t   -       experiment time, min.

Compared to the standard material, the relative wearing velocity was determined by the following formula

Here

Since the deflection expressed in masses for different materials is relatively imprecise, it is convenient to obtain it in relation to the density of the material, that is, in the unit of volume.

 amount of wearing per mass;

 density of the material, , kg/m3 (for example, the density of steel is equal to 7800 kg/m3).

RESULTS

The samples were tested in an abrasive environment with adjustments made to the pressure and friction speed to reflect the conditions of soil treatment and chiseling operations. Each sample was tested in the abrasive environment for 10 hours. The values of the obtained results are presented in Table 1.

Table 1.

Wear Characteristics of Samples Subjected to Laboratory Testing

From the table, it can be observed that the wear resistance of the tested samples compared to the unquenched steel of grade ШХ15СГ is, on average, 0.95 to 6.4 times

Figure 5. Relative wear resistance and amount of wearing

1) ШХ15СГ unquenched; 2) С255 unquenched; 3)45Г unquenched; 4) ШХ15СГ; 5) 40Г; 6) С245 quenched with water; 7) C255 quenched with water;8) C285 quenched with water; 9) 38Х2Н2МА quenched with water; 10) 5ХГМ quenched with water; 11) 35XГСЛ quenched with water; 12) ШХ15СГ quenched with water; 13) 45Г quenched with water; 14) T590; 15) 110Г13Л;

CONCLUSION

Based on the results of the conducted laboratory studies, it can be concluded that the wear resistance of ploughshares is dependent on the composition and hardness of their material. Considering that the wear resistance and hardness of ploughshares made from locally sourced raw materials and subjected to thermal treatment have been improved, it is recommended to subject those with the highest wear resistance observed in laboratory tests to comparative testing in production.

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