Developing model of mass-exchange processes in porous bodies on example of iron-ore pellets oxidation process

There is developed a model of magnetite oxidation in agglomeration of iron-ore pellets. Unlike the oxidation models proposed before, this model considers the porous structure of a pellet: the surface and the distribution of pores by sizes. The process of magnetite oxidation is considered as three-unit: diffusion by pores, diffusion through products of oxidation and proper chemical reaction. The model considers various limiting steps at different stages of the process. There were carried out pilot studies on the basis of SSMCC pellets for confirming the correctness of the proposed model. This model can be used in a broader aspect: for the description of the process of chemical reaction in polyporous bodies

Using high-chromium iron as material for production of the equipping components of mine shafts

This paper deals with service conditions of shaft equipment, in particular, inserts of sliding bearings for the purpose of increasing service life due to material substitution and wear resistance increase. As a new material high-chromium irons are offered. Studies are conducted on a microstructure and wear resistance of prototypes is measured. Experimental data are treated by methods of mathematical statistics which confirm reliability of results. The results obtained make it possible to suggest using high-chromium irons as the direct material to produce inserts of sliding bearings

Studying of properties and microstructure of 30 CrMnV9 steel on wear resistance

The properties and microstructure of 30 CrMoV9 steel after its treatment with ferronickel and ferromanganese with the aim of increasing the content of nickel and manganese in steel were studied. After the trial smelting, the samples were tested in four parameters: hardness, ultimate stress limit, wear resistance, and toughness. Experimental studies have shown that changing the composition of steel with increasing the nickel content up to 0,5 – 0,7 % and manganese up to 1,5 – 1,8 % leads to increasing strength, hardness and wear resistance of steel with slight decreasing its toughness

Heat treatment effect on the properties of vibration treated steel during crystalization

The effect of heat treatment on the structure and properties of 30HGSNMA steel that has been subjected to vibration treatment at the stage of primary crystallization is considered in the work. It is proposed to use normalization with accelerated cooling with a water-air mixture among possible treatment methods. The properties of steel after this heat treatment are investigated. It has been found that there is a significant increasing of hardness, tensile strength and impact strength, and the level of these properties is comparable with the level of properties after hardening and tempering. The introduction of one-stage heat treatment that consists in normalization with accelerated cooling, allows reducing the heat treatment cycle and increasing the equipment productivity

Studying the graphite phase in antifriction AChS-2 cast iron

The paper presents the data of studying the characteristics of graphite inclusions in various samples of AChS-2 cast iron. The metallographic analysis was carried out using the Thixomet Pro software, the length of the graphite inclusions, their shape and the occupied area were estimated. The slip coefficient and hardness were measured on the same samples. It was found that the characteristics of the graphite phase affect the antifriction properties of the alloy

Studying the graphite phase in antifriction AChS-2 cast iron

The paper presents the data of studying the characteristics of graphite inclusions in various samples of AChS-2 cast iron. The metallographic analysis was carried out using the Thixomet Pro software, the length of the graphite inclusions, their shape and the occupied area were estimated. The slip coefficient and hardness were measured on the same samples. It was found that the characteristics of the graphite phase affect the antifriction properties of the alloy

Studying microstructure of heat resistant steel deoxidized by barium ferrosilicon

The paper examined the nature and distribution of non-metallic inclusions in the heat-resistant steel 12H1MF (0,12 % С, 1 % Сr, 0,5 - 0,6 Mo, 0,5 % V), ferrosilicobarim. As a reference, used by steel, deoxidized silicon. Melting was carried out in a laboratory, research-metallic inclusions, their shape and distribution, pollution index were studied according to conventional methods. Studies have shown that ferrosilicobarim deoxidation in an amount of 0,1 - 0,2 %, reduce the overall pollution index of non-metallic inclusions and change the nature of their distribution

Studying titanium carbide effect on cast iron AChS-3 properties

The paper presents the results of studying microhardness and tribological characteristics of antifriction cast iron grade AChS-3 after modification with titanium carbide. Titanium carbide has been used as a nanomodifier to change the structure parameters by forming additional crystallization centers. It has been established that introducing titanium carbide in the amount of 0,2-0,3 % by weight with dispersion of 0,3-0,5 μm leads to increasing its hardness and wear resistance by about 20 %, while the friction coefficient decreases by almost 2 times

Investigation of heat-resistant properties and microstructure of experimental steel based on the Cr-Ni-Ti-Nb system obtained under industrial conditions

The Nb effect on long-term strength of Cr18Ni10Ti steel is considered. There is substantiated selecting this steel for obtaining cast parts for metallurgical furnaces. It is shown that introduction of Nb in the amount of 1 % into steel of a given composition increases tensile strength and long-term strength by 15 %. Improving the properties is associated with the formation of NbC carbides

Studying the properties and microstructure of parts obtained by different casting technologies

The paper presents some data of studying the microstructure, properties and surface quality of parts obtained in different modes. It is shown that in the case of quenching and tempering (QT) in the process of primary crystallization by vibration, in the future it becomes possible to replace QT with a simpler and cheaper method: normalization with accelerated air-water cooling. After this treatment, the steel structure is characterized by almost the same parameters as after QT. Tensile strength, hardness, average grain size are comparable with the performance of QT steels