As we noted earlier, for many years experience in grinding media market Energosteel Company specialists have conducted many industrial tests to evaluate the steel grinding balls performance produced by Energosteel at production bases of our customers. Industrial tests conducting is an activities complex aimed at organizing, implementation monitoring (observance of all conditions prescribed in the Methodology), and indicators calculation characterizing current and final test results, recommendations development for grinding process changes. As general rule, the customer’s technical and economic department completely revises the normative parameters of the material grinding process (most costly part the finished products production) following the results of such tests. This shows the importance of the various tests accuracy and quality. The main stages of industrial tests are below: The technical and economic negotiations conduction for research objects determination; Responsible person’s identification. They are directly involved in industrial tests; The industrial tests tasks and objectives definition; The testing place determination; The testing method determination; The testing technique preparation; The industrial tests conduction; The summing up of industrial tests. Each of the above-mentioned stage includes the technical and economic measures complex covering decision making on all possible factors that can directly and/or indirectly affect to the final result. […]
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Ball mills use in all industries needs a material grinding. Steel grinding balls use as grinding media in such mills. In this article, we will consider the steel grinding balls use in coal grinding. Coal grinding is preparatory process to a creating mixture for combustion in boilers at thermal power plants. To a high-quality fuel creation for the TPP units furnaces (fuel has the coal basis), needs to achieve the maximum material grinding degree and maximally reduce the coal dust moisture content. Fuel drying and fuel grinding can be carried out separately or jointly in one unit. If these processes occur separately, then coal dried in drying drums and ground in short ball mills. The ratio of drum length to the drum diameter is usually 1.5: 1. The 40 mm grinding balls of the 2nd and the 3rd hardness groups have used for coal grinding at thermal power plants in USSR. This is due to a fairly low hardness indicator of the grinded material and absence the grinding balls with higher hardness groups, in the past. Following the coal grinding world practice, Energosteel company specialists among the first offered for customers to use grinding balls the 4-th and 5-th hardness […]
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The metals and alloys structure distinguishes by: the macrostructure, the microstructure and the fine structure. There are three methods for their investigation: Macroscopic analysis Microscopic analysis X-ray diffraction analysis and X-ray flaw detection The macroscopic analysis. Macrostructure is the metals and alloys structure that can be visible with small magnifications by a magnifying loop (up to 30 times max). The macrostructure investigated by macro analysis. Metals are non-transparent substances and their structure investigated in the fracture or in specially prepared samples (macrosections). The sample cuts from a certain location in a certain plane, depending what examine (casting, forgings, stamping, rolling, welded or thermally processed details) and what needs to identify (primary crystallization, structural heterogeneity, defects breaking the metal continuity). Therefore, the samples cut from one or more ingot places (or billet, or detail) in the longitudinal and transverse directions. The sample (template) surface leveled on the emery wheel and then ground. The template etched in special reagents after grinding. The reagents differently dissolving the structural components and irritate the defects. Macroanalysis reveals: the fracture type (brittle, viscous); the size, shape and location of grains and cast metal dendrites; the ingots and castings defects(shrink sleeves, gas bubbles, cracks); the defects breaking […]
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Material science is an applied science studies the interrelationships between the metals and alloys composition, structure and properties under different conditions. Studying this discipline allows the rational selection of materials for a particular application. Metal science is a constantly developing science continuously enriched by new steels and alloys creation, which stimulate progress in all science and technology fields. Material science exists for about 200 years as a science, despite the humanity used metals and alloys for several millenary before our era. Scientific results allowing start meaningful study all accumulated knowledge by humanity for the whole time of using metals appeared only in the 18th century. Researches of French scientist René Antoine de Réaumur (1683-1757) has been great importance in the metals nature study. He conducted researches of the grains structure in metals in 1722. English scientist Grignon in 1775 drew his attention to the columnar structure formed during the iron solidification. He owns a well-known picture of dendrite obtained with the cast iron slow solidification. M.V. Lomonosov (1711-1765) was the first in Russia who has scientifically comprehended the metallurgy and foundry problems. He wrote a training manual “The First Metallurgy Fundamentals in Ore Mining”, where he described the metallurgical processes […]
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The steel tempering – is a heat treatment process, when steel heated to a critical temperature and rapidly cooled. This treatment purpose is to increase the hardness and strength of the detail with a decrease its plasticity. The steel tempering in one environment This tempering is easier to perform, but it can’t be used for all steels and steel products. Rapid cooling of products with variable cross-section in a large temperature range contributes to occurrence the temperature unevenness and high internal voltages, called thermal voltages. In addition to thermal voltages, the austenite transformation to martensite creates additional structural voltages, because this transformation occurs with a volume increase. If detail has a complex shape or a variable cross-section, then volume increase passes unevenly and induces the internal voltages occurrence. The high voltages presence can induce the product warpages, leashes, and sometimes cracking. Cracking occurs if the internal voltages magnitude exceeds the ultimate strength. The more carbon content in the steel composition means more volumetric changes and structural voltages, and greater cracks risk. Steel with a carbon content more than 0.8% tempered in one environment when products have simple shape (balls, rollers, etc.). Otherwise, the steel tempering preferred in two environments or […]
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The rolling process of “Energosteel” grinding balls corresponds to high-temperature thermomechanical treatment significantly increases the products strength and hardness. HTTT provides the austenite deforms in thermodynamic stability area and then conduct hardening for martensite. Low tempering follows after hardening. The main aim of simple heat treatment is to exclude special heating for hardening from deformation (rolling) heating. Thanks to this, we get an economic effect. HTTT main goal is to increase the steel mechanical properties. The martensite inherits the substructure of recrystallized austenite formed during hot deformation, under HTTT. The best complex of mechanical properties achieves if martensite formed from austenite with a well-developed polygonized structure. Martensitic crystals completely imitate the dislocation subbands of the hot-deformed austenite. Dislocations interlacing inherited by martensite, also. The strength threshold, the fluidity threshold and substructure martensite characteristics increase under HTTT, as a result of the martensite crystals fragmentation by subgrain boundaries. We are only talking about substructure martensite characteristics enhance plasticity by strength increasing. HTTP allows obtain higher plasticity indices at the same strength, in comparison with simple hardening and tempering. Temper brittleness can be abruptly weakened with the HTTT help. In this case, the intra-grain destruction occurs instead of intergrain destruction typical for […]
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The rolling consists in billet compressing between the rotating rolls. The billet retracts between the rollers by friction forces, and the pressure forces reduce the transverse billet dimensions. The pressure forces are normal to the rolls surface. There are three main types of rolling: longitudinal, transverse and cross- helical. The longitudinal rolling. The billet deformed between two rolls rotating in different directions, and moves perpendicular to the rolls axes. The flat billet produces this way. The transverse rolling. The rolls rotate in the same direction and impart the billet rotation. The billet moving along to the rolls axis and deforms. In this rolling way obtains the billet in the form of revolution body. The cross-helical rolling. The rolls located at an angle and report to the billet the rotational and translational motion during it deformation. In this rolling way obtains the billet with complex shapes. The rolling product profile is the shape of its cross-section. The profiles set of different sizes called a range. The rolling profiles range divided into 4 main groups: long products, sheets, pipes and special types of rolled metal. Long products profiles divided into simple shapes and complex shapes. Simple shapes are square, circle, hexahedron and […]
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The metals treatment by pressure based on their ability to plastically deform under certain conditions, as a result of external forces influencing on deformed body (billet). The metals treatment processes divided into two types by appointment: Type for billet production of constant cross-section by length (bars, wires, tapes, sheets) used in building structures or for the subsequent details manufacture. Treatment performs by cutting or by preliminary plastic shaping. The main types of such processes are rolling, pressing and dragging. Type for obtain parts or billets (semi-finished products) having approximately shapes and dimensions the finished details. They require treatment by cutting only to give them final dimensions and the set quality surface. Forging and stamping are the main varieties of such processes. The rolling The rolling consists in billet compressing between the rotating rolls. The billet retracts between the rollers by friction forces, and the pressure forces reduce the transverse billet dimensions. The pressure forces are normal to the rolls surface. The pressing The pressing consists in billet pressing at closed form through the matrix hole. A cross section shapes and dimensions of the billet pressed segment, correspond to the matrix hole shapes and dimensions. The dragging (drawing) The dragging […]
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As we have written it before, there are two methods for determining the grinding balls bulk weight in a mill: Method with complete grinding media discharge from the mill inner drum. Method without unloading grinding balls. In the previous article we considered the 1-st method for determining the bulk weight of grinding media. This article analyzes the second method. The 2-nd method is less labor-intensive, but has a small error, because the sampling is no more than 5% of total volume the grinding media in the mill. Unloaded grinding balls sorted by classes – gradation by diameters. The gradation scale selected in steps of 10 mm. Each class (diameter) is weighing after sorting. Next, determines the average grinding balls diameter in the mill by the weighted average value. The formula for calculating the average grinding balls diameter in the mill ∅ср – the average grinding balls diameter, mm; ∅i – the maximum grinding ball diameter in each class, mm; mi – the grinding ball mass of each class, kg. Then, selected samples placed in a container and re-weighed. Capacity should have no flaws (“waves”, protrusions, holes, etc.) and container form must be of the correct geometric shape (cube or parallelepiped). […]
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In the previous article we considered the method for determining the bulk weigh of new grinding media. Determination the grinding balls bulk weigh directly operating in a ball mill becomes necessary on practice. It is done in order to accurately definition the grinding ball mass during measuring in a ball mill and exclude the mill overloading with grinding balls possibility There are two methods for determining the grinding balls bulk weight in a mill: Method with complete grinding media discharge from the mill inner drum. Method without unloading grinding balls. Calculations by the first method are most accurate, but require a lot of labor costs and time. In this article, we will consider the technique for determining the grinding balls bulk weight in fully unloaded mill. This method used in the mills repair (armor plates replacement). The grinding balls unload from the mill into a special pit (needs to open hatches and pour the grinding balls from the drum during mill scroll). Then, need to definition maximum and minimum grinding balls diameter located in the mill. Unloaded grinding balls sorted by classes – gradation by diameters. The gradation scale selected in steps of 10 mm. Sorting can be done manually […]
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Technological process control of forged steel grinding balls production carried out by the shift supervisor and testing laboratory assistant in accordance with the technological control scheme shown in Table. 1 Table 1. Technological control scheme on ball-rolling complex SHPK 25-120 Technological operation Control location Controlled parameter Inspection method Control periodicity Responsible person for control 1 2 3 4 5 6 Billets acceptance: Conformity check information about incoming billet. Conformity check incoming billet to requirements of normative technical documentation and technological documentation Billets warehouse Melting number (batch number), Steel grade, Chemical composition, Batch weight Visually Constantly Shift supervisor, Laboratory assistant Loading billet into the furnace Billets warehouse, Boot device Nominating Rolgang Steel grade, dimensions, curvature, surface condition of the billet Billet displacement value Visually Visually Constantly Constantly Loading desk operator Melting stream Nominating and furnace Rolgang Different billet brands separation Visually Constantly Billet heating Heating regime Furnace Furnace temperature Metal temperature before rolling Control measuring instruments, VisuallyControl measuring instruments Constantly Periodically Constantly Operator, Laboratory assistant Acceptance of rolling rolls Billets warehouse Roll shop […]
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Metrological assurance the technological production process and quality control of steel grinding balls should comply with Table. 1. Table.1. Metrological assurance the technological production process and quality control of the grinding balls Technological operation Controlled parameter Measurement units Measuring tools Measurement range Accuracy class, graduation value Measuring tool error 1 2 3 4 5 6 7 Loading billet into the furnace Billet diameter Billet length Billet curvature mm mm mm Slide Calipers GOST 166 Measuring roulette GOST 7502 Measuring ruler GOST 427 0-300 0-10000 0-150 2class, 0,1 3 class, 1,0 1,0 ± 0,5 Billet heating at induction furnace Billet temperature at the furnace exit 0С Photo Pyrometer «Quartz-M» 0-1300 ± 1 Acceptance of rolling rolls Caliber dimensions in the calibration section – Cake Size Patterns ± 0,5 Rolling rolls setting Rolling rolls inclination angle 0С Arrowhead with a degree scale 0,5 The rolling: – Rolling temperature regime – Rolling control process Metal temperature before rolling Grinding balls diameter 0С mm Photo Pyrometer «Quartz-M» Slide Calipers GOST 166 0-1300 0-250 2 class, […]
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The quality control the grinding balls hardness and surface checked every hour of the mill’s work, as well as new steel grade rolling in the beginning. Quality control the grinding balls surface, dimensions and hardness carried out by a shift master or laboratory assistant in accordance with the requirements to current regulatory documentation. The grinding balls hardness control carried out in accordance with DSTU 3499-97. Ten grinding balls select from five different batch locations to check the dimensions, quality and surface hardness. If surface hardness control results are unsatisfactory, this indicator checked again on a doubled grinding balls quantity selected from the same batch. If more than two grinding balls don’t meet the requirements during the second test then batch transferred to a lower hardness group. Three balls select from three different locations in each 20-th batch for hardness control of grinding balls the 4th group on 0.5 R depth. If surface hardness control results are unsatisfactory at least for one grinding ball then provide test again on a doubled grinding balls quantity selected from the same batch. If repeated measurements show unsatisfactory results, then needs to perform tests on two consecutive batches until acceptable results. Requirements to normative documentation […]
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Grinding balls produced of steel round billets (according to DSTU 3499-97, DSTU 8538: 2015 or GOST 7524-2015 and TU U 27.1-26524137-1376: 2008). Received billet in the workshop must comply with the requirements to GOST 2590-2006 and regulatory documentation and it should comply to DSTU 3499-97 in terms of the carbon mass fraction and the carbon equivalent value (Table. 1). Table. 1. Ø Hardness group Carbon, % Equivalent, % 15-55 1,2 0,40 0,50 3 0,60 0,70 4,5 0,75 60-70 1,2 0,50 0,70 3,4 0,60 0,75 5 0,80 80-120 1,2 0,50 0,70 3,4 0,60 0,75 5 0,85 The 20mm, 25mm and 120mm grinding balls rolled by billet with a length from 3200 to 4000 mm on a ball rolling mill SHPK 20-120. The 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm and 100 mm grinding balls rolled by billet with a length from 4000 to 6000 mm on the ball rolling mill SHPK 20-120. Limit deviations by billet diameter and length must not exceed the values indicated in Table. 2 Table. 2. Nominal billet diameter, mm Limit deviations of the billet diameter, mm Limit deviations of the billet length, mm Weight 1m of the billet length, kg 30 + 0,3 – 0,7 +50 […]
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In the grinding material process at ball mills becomes necessary to calculate the bulk weigh of used grinding media. The bulk weigh of the grinding balls is necessary to understand the grinding balls mass in the cube, the grinding balls mass loaded into the mill, the prevention of mill overloading with grinding balls, etc. These data often used in operational management of grinding process. Consider a definition technique the bulk weight of new grinding balls. Methodological tables in specialized handbooks indicated the bulk weight of grinding balls different sizes. The indicators were calculated more than 20 years ago. Currently, these data can give an error more than 10%. This is a big error in production operational management. This error is caused by the fact that in the modern grinding balls production apply many materials (different grades of steel, “white” and “gray” cast iron) in contrast to past years. Besides, the actual diameter (size) and shape of grinding media affect the bulk weigh value. Experts of “Energosteel” company have developed a common methodology together with technical specialists of Ukrainian and CIS countries mining & processing enterprises. This methodology allows to accurately determining a bulk weigh of grinding balls. Below, we give […]
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The company “Energosteel” produced an experimental batch (110 tn) the 40mm grinding balls of high carbon steel alloyed by Chromium in January 2017. The batch showed highest hardness values throughout cross section of grinding ball with a surface hardness 65-69HRC and volumetric hardness – 64-66 HRC. Thus, these products comply with the fifth group of hardness (according to both DSTU 3499-97 and DSTU 8538: 2015). Grinding balls have been successfully tested for the impact resistance. 100 balls have been selected from a batch for the experiment. Each selected ball sustained the total impact energy of 64 312 J without destruction. At hardness check of batch grinding balls we have faced with the problem of surface preparation for measurement. Polishing surface by fine-grained stone with coolant even with a minimum machine infeed gave a “tan” on the surface and polishing micro-cracks which distort hardness result of grinding balls to 3-5 HRC measured on a stationary hardness tester. The problem was solved by ultrasonic hardness tester T-UD2 for measuring hardness. Using a suitable method, we achieved increase measurement accuracy, increase productivity control and ensure a high results reliability.
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The main technological process in steel grinding balls production is a hot rolling in helical calibers (see Picture 1) by two rolling rollers (1) deployed on feed angle and rotating in the same direction. Rulers (3) hold billet (2) and grinding balls on the rolling axis. Helical streams (4) are cut into rolling rolls. Helical streams formed by helical flanges (5). The height and width of the helical springs increases during rolling. The round billet is material for grinding balls rolling and has diameter slightly smaller than rolling ball. The rolling performed following way: the flange (5) grip the billet then rotated it and moved it along the rolling rolls gradually compressing the web (6) and formed the grinding ball (7). Grinding ball separates from the billet in end of forming section and protrudes from the calibrated gauge. Picture1. The rolling rollers scheme Streams and flanges hardness of the rolling rolls very important in grinding balls production and affects on products quality, so it must be controlled. Rolling rolls hardness control performed by combined hardness tester T-UD2. For normal rolling rolls operation the streams and flanges hardness should be 50-55HRC – for large diameters and 55-65HRC – for small diameters. […]
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The company “Energosteel” produced an experimental batch the 20mm grinding balls of high carbon alloy steel in the end of December 2016. The batch showed higher hardness values throughout cross section of grinding ball with a surface hardness 61-63HRC and volumetric hardness – 59-61 HRC. According to old national quality standard (DSTU 3499-97) current grinding balls correspond to the 4-th hardness group and according to the new national quality standard (DSTU 8538: 2015) they correspond to the 5-th hardness group. Grinding balls have been successfully tested for the impact resistance. Thirty balls have been selected from a batch for the experiment. Each selected ball sustained the total impact energy of 64 312 J without destruction. This batch of grinding balls was successfully shipped for export.
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