Search Documents

By Y Yamaguchi, S Nomura, M Matsumura, C Kamijo

In order to increase productivity and decrease reducing agent rate (RAR) of blast furnaces, slag content of sinter ore must be decreased. However, gangue content in iron ore tends to increase because of resource depletion. Therefore, amount of high-grade concentrate in sinter ore feeds should be increased, but this situation causes a decrease in permeability of the sintering bed so that the productivity of sinter process decreases. In order to increase the amount of concentrate, NSSMS has developed the P-type separate granulation method, RF-MEBIOS and SPEx II technologies. These technologies have been introduced to actual sintering machines. In this report, a new technology using microparticles of iron ore is proposed to increase the amount of concentrate in sinter blends. Basic experiments simulating the sinter making process using microparticles of iron ore were undertaken. Crushed pisolite, containing >60 wt per cent -10 µm was prepared for binder. The pisolite microparticle binder was mixed with another Australian sinter feed ore in a high-speed agitating mixer. They were mixed for about one minute, and then granulated using a pan pelletiser. After that, they were added to another raw material mixed by a drum mixer, and then charged in a pot for a sinter pot test. As a result, when the amount of concentrate increased from 13 wt per cent to 20 wt per cent, productivity was almost kept constant using pisolite microparticle binder.CITATION:Kamijo, C, Yamaguchi, Y, Matsumura, M, Kawaguchi, T and Nomura, S, 2017. Development of an iron ore microparticle binder for increasing the concentrate content of sinter blends, in Proceedings Iron Ore 2017, pp 69–74 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By Robert J. McNally

There are three primary plant nutrients-nitrogen, phosphorus, and potassium--expressed in any fertilizer compound as percent N, percent P2O5, and percent K20, in that order. This article will be concerned with the first two. The chief source of P205 is phosphate rock. As found in the western states phosphate rock is essentially tricalcium phosphate-calcium fluoride (fluorpatite). As such, it is quite water insoluble. The principal phosphate fertilizer used is single superphosphate, produced by reacting sulfuric acid with phosphate rock in the proper proportions.

Oct 1, 1956

By A. B. Irwin

"Discussion at MeetingDR. D. DERRY (Ventures Limited) referring to the diagram (Figure 15) which shows a transverse structure section across the Central Slocan area, asked what the assumed structure at depth was, remarking that dips are steeper and more uniform at depth and that the contortions with gently-dipping axial planes are at higher elevations. He wondered whether the section represented ,part of a very large fold with steeply-dipping axial plane.MR. J. D. LITTLE (Canadian Exploration, Limited) replied that E. B. Mayo (Kelowna Exploration Company) and others had considered that the entire section illustrated faces to the southwest and represents part of the lower limb of a great overturned •syncline which is concave toward the southwest.DR. R. DEWIT (Geological Survey) remarked that the photograph of a ripple mark (Figure 7) showed internal lamination conformable to the ripple mark and wondered if the structure was not due to slumping during consolidation, since the normal mode of formation of ripple mark would seem to preclude the possibility of such internal stratification.MR. LITTLE remarked that in his opinion such structures should not be depended upon alone with-out other confirmatory evidence of the direction of tops of beds."

Jan 1, 1952

Accretions of dust on the walls of the offtakes from furnaces and in the waste heat boiler are a cause of significant operating and maintenance problems in non-ferrous smelters. The dust originates from entrained solids in the gas stream and vaporised species that condense during gas cooling. Control of dust formation is very important for minimising the formation of accretions and reducing the severity of environmental problems caused by toxic species, such as those containing arsenic, in the dust. The present paper discusses the formation of accretions and the condensation of dust in copper smelting from a thermodynamic viewpoint. Changes, in gas composition and the amounts and identities of the condensed species in the dust are calculated using computational thermodynamics. Interactions between dust species to form accretions are considered in the light of appropriate phase equilibria. The results show that the nature of the dust formed varies greatly, depending on the temperature and the amount of oxygen present during cooling. Control of the amount of oxygen is required if offtake and waste heat boiler accretion problems are to be minimised.

Jan 1, 2002

By Jean-Luc Cornet

As modern conveyors are increasing in size and complexity, their control requirements are becoming more and more critical. In addition to the safety and equipment protection requirements, control systems are now called to implement intelligent drive controls derived from dynamic analysis modelling, as well as to provide fast and accurate diagnostics while keeping operator controls simple. These requirements led to the development of a new and innovative approach to control system development. This paper describes the control philosophy used by Conveyor Dynamics, Inc. (CDI) and some of the key features of our approach to the architecture of control systems.

Jan 1, 1993

By Ishwar G. Mulani

In conveyor design, the first step is capacity and the second step is belt width and speed. The third step is decision on 'ff," where distinction arises between DIN/ISO and CEMA for calculating resistances. Then again, both the methods are virtually similar. This topic helps in understanding Dm design style and its comparison to CEMA. This topic is from the book Engineering Science and Application Design for Belt Conveyor wherein the issue has been analysed in detail. It presents a workable calculation model to calculate the value off in design office, based on conveyor parameters. CEMA uses Kx, Ky and 0.01 5 instead off. Thus, f is a sum effect of Kx, Ky and 0.015. Hence, knowledge on f is also applicable to Kx and Ky. This helps to understand their relationship.

Jan 1, 2004

By N. Saracoglu, J. P. Golightly, R. H. Wallis, J. J. Brummer

"The McClean uranium deposits are located 11 km west northwest of the Rabbit Lake Mine. Their average grade is 1.8 % U3O8 , and they contain 6. 350 tonnes of uranium oxide in seven pods of variable grade and mineral assemblage. They are hosted by both basal Athabasca Group and the regolith developed on the underlying crystalline basement. The major mineral facies are: sulphide, arsenide, 'bleached', and hematite, with the important uranium minerals being coffinite, uraninite and pitchblende. Abundances of carbon and sulphur isotopes are consistent with their derivation from pyritic graphite in basement gneisses. Isotopes of oxygen and hydrogen suggest equilibration at temperatures of about 200°C. Ar39/ Ar40 age determination of illite associated with ore suggest mineralization began about 1300 m.y. ago and that significant alteration had ceased by about 1170 m.y. ago though Pb/ U data suggest the deposits continued to evolve into the Mesozoic.IntroductionThe McClean deposits lie on the eastern side of the Athabasca Basin of northern Saskatchewan where they are part of a cluster of uranium deposits lying west of Wollaston Lake (Fig. 1). The general stratigraphy is schematically portrayed in Figure 2 which emphasizes that mineralization is hosted by both the Athabasca Group and the underlying regolith and also that the deposits are preserved at depth and have not suffered from preand post-Pleistocene weathering and erosion. This circumstance, combined with their simple shape and the presence of seven separate zones of mineralization (pods) allows a description, based on over 450 fully cored drill holes, to be made of the wide variation in chemistry, grade, alteration patterns and position relative to the sub-Athabasca Group unconformity. Ar39 / Ar40 age determinations have been made of illites associated with regolith, Athabasca Group and mineralization and studies are in progress on C, S, 0 and H isotopes of mineralized material and host rocks. Only some of these data have been published; Brummer et al., (1981); Golightly et al., (1982); Bray et al., (1982); and Saracoglu et al., (1983). The only other published data on McClean geology are by Tremblay (1982, 1983)."

Jan 1, 1986

By McHenry Mosier

This progress report on a national survey of the use of detachable bits in metal mines covers 10 mines. It presents comparative costs for drilling with conventional and detachable bits, describes the reconditioning of drill steel, and gives various data on rock drilling at these particular mines. Reports to follow will include similar data on drilling at other metal mines in the United States. ACKNOWLEDGMENTS This report is based on costs and data developed and furnished by the operators of the mines visited. The author is greatly indebted to the officials and staff members at these mines for their cooperation and assistance.

Jan 1, 1936

By R. V. Ramani, R. Srikanth, R. Zhao

"A two-pan study was conducted to understand the factors affecting respirable dust generation potential or dustiness of coal seams. In the first part, the data from three prior comprehensive laboratory studies was analyzed to establish quantitative relationships between respirable dust generation potential and coal characteristics. This analysis indicates that respirable dust generation rate is positively correlated with Hardgrove Grindability Index (HGI), fuel ratio (fixed carbon/volatile matter), Vitrinite Reflectance (VR), and Level of Organic Metamorphism (LOM). In the second part, specially-designed single breakage experiments were conducted to determine the primary dust generation potential of 17 coal samples obtained from four continuous miner sections, three longwall sections, and the Penn State Coal Data Bank. The single breakage study indicates that primary dust generation rate is positively correlated with fixed carbon content, fuel ratio (fixed carbon/volatile matter), VR, and LOM. Since VR and LOM are strongly influenced by the process of coalification, differences in respirable dust generation rates in different coal seams may be explained by the thermal metamorphism of sedimentary organic matter during subsurface burial.Mineral particles in the range of one to five microns, if inhaled in sufficient amounts, lead to a number of lung diseases generally referred to as pneumoconiosis. A priori knowledge of the mechanisms and rates of fine particle generation during mining can aid in the development of more effective technology for controlling primary dust generation. Unfortunately, the data and knowledge currently available are not adequate for this purpose. In fact, a committee of the National Academy of Sciences on the measurement and control of dust concluded that the knowledge of the fundamental mechanisms by which coal mine dust is generated and a part of it is entrained in the mine atmosphere as respirable dust is not sufficient to clarify, let alone control, the processes involved (Anon., 1980). Under a research contract from the U.S. Bureau of Mines, Stecklein et al. (1982) have identified a number of fundamental research issues for understanding the coal fragmentation and entrainment processes.Reduction of dust generation is the best means of control since fine particles are difficult to control once they become airborne. Therefore, considerable research efforts have been directed to understand the factors influencing dust generation and entrainment, including machine design, water sprays, and ventilation. Laboratory studies have been conducted on the mechanical action of bits and machine power requirements (Evans and Pomeroy, 1966; Roepke, 1984). Since the physical characteristics of coal play an important role in the process of breakage, a number of laboratory studies have been conducted to study the relationship between coal characteristics and respirable dust generation (Baafi, 1977; Moore, 1986; Polat, 1990; Thakur, 1971). Several studies have been conducted on the relationships between coal characteristics and airborne dust concentrations (Hamilton and Knight, 1958; Khair and Xu, 1991; Organiscak and Page, 1993; Page et al., 1993). A limited number of studies have also been conducted on the relationships between coal characteristics and airborne dust concentrations in mines (Organiscak et al., 1990). Yet, no reliable method has been developed to rank coal seams according to their respirable dust generation potential. The conclusions derived from previous studies can be summarized as follows:"

Dec 1, 1996

Accurately modeling and predicting long term mill throughput is one of the challenges facing metallurgists, geologists and mine engineers in their quest to consistently deliver accurate life of mine business plans. Batu Hijau has systematically improved long and short term mill throughput predictions since feasibility and commissioning in 1999. This has been achieved through a combination of ongoing improvement to the geology ore hardness and grade characterisation model, drill and blast optimisation and, by application of these data to model mill throughput. Batu Hijau has demonstrated the ability to consistently estimate long term mill throughput within ±2% accuracy. Aside from reliably predicting expected production rates with the existing plant configuration, this predictive ability provides a solid foundation for identifying operating and design criteria for short term grinding circuit optimisation and future expansions. This paper discusses ongoing throughput prediction model development at Batu Hijau based on geo-metallurgical characterisation. Also discussed are tools used for day to day production performance management. This includes on line "Mine to Mill" variable monitoring to improve operations parameter ecision making and performance assessment.

Nov 1, 2011

By V. Runkana, N. K. V. Nadimpalli, S. Sahu

"IsaMill™ has been in operation in the recent past for fine grinding of low grade ores to extract non-ferrous minerals. IsaMill™, typically, consists of a series of uniformly spaced identical disks mounted on a rotating shaft which is encased in an outer shell. The mill offers high energy efficiency for fine grinding and an inherent scalability. But, it encounters certain operational challenges such as non-uniform distribution of grinding media coupled with high wear rate of the disks and solid walls of the mill at specific locations—which adversely affect the mill performance. To circumvent these operational challenges, design modification of the disks through heuristics, by introducing a reduced diameter disk (RDD) at specific locations, is a common practice in industry. But there is no systematic scientific study in this regard. In the current work, we developed a discrete element method (DEM) based model and simulated for the IsaMill™ operation to study the effect of RDD on the efficiency of the mill and wear rate of the solid walls and disks. Since the first set of disks experience the high wear rate due to the high loading of the charge, the RDD was introduced at the first two disks. The simulations were performed at different diameters of the RDDs and at different media loadings. The performance of the mill was analyzed based on the power consumption, the wear rate on disks and the distribution of media particles inside the mill. Besides, the performance variables such as mean velocity of media particles and total impact energy provided useful insights into the milling operation. It was observed that the reduction in disk diameter yields lower wear rate of the disks at the cost of decrease in power draw at a constant high media loading. Whereas, when the media loading was decreased, the amount of wear and power drawn was comparable for both the most reduced and least reduced disk diameters. Therefore, there is an optimum choice of RDD for a given mill loading to maximize the mill performance while reducing the wear rate of the disks."

Jan 1, 2018

By T. Kawai

Japan Oil, Gas and Metals National Corporation (JOGMEC) has started an exploration program for Seafloor Massive Sulfides (SMS) in the EEZ of Japan, and launched an investigation program for mining, processing and environmental impact on SMS development. With regard to the mining aspect, the mining system consists of three units: a mining unit on the sea floor, an ore lift-up unit to surface, and a mining support vessel unit which has an ore unloading system that unloads onto a shuttle ship. Regarding the mining unit, JOGMEC and certain Japanese mining and machinery companies developed two types of state of the art mining testing tools. Excavation tests on the actual SMS site in the Okinawa Trough, south-west of Japan, were conducted in 2012. In these tests, the functions of the testing tools, such as cutting ore, moving on the seafloor and climbing up slopes having steeper than a 25 degree gradient, were confirmed. The physical characteristics of the ore, which are key parameters for establishing a mining system, are yet to be fully understood as the exploration program has been undertaken simultaneously. Hence, those examinations have been carried out by ground cutting experiments, analysis of drilling core data, and the like. This paper describes the outline of a proposed mining system, mining testing tools and results of the on-site mining testing.

Aug 1, 2013

By B. C. Paul, R. Q. Honaker, K. Ho

Recent research has shown that froth flotation is not effective at treating fine coals (-28 mesh) containing a large portion of middling particles. Due to their relatively large density differences, middling particles can be separated more efficiently using gravity-based processes. The ability of gravity separators to treat fine particles has been limited by the lack of particle inertia relative to the surface drag forces. However, particle inertia can be enhanced by the application of a centrifugal field. A commercial-scale centrifugal Falcon concentrator capable of treating a mass flow rate of greater than 1 tph continuously has been used to evaluate its feasibility for treating fine coal as an alternative to froth flotation. Tests conducted on a -28 mesh fine coal circuit feed have found the Falcon concentrator to be very effective at cleaning the 28 x 325 mesh size fraction. For an Illinois No. 5 coal sample, the ash content was reduced in the 100 x 325 mesh size fraction from about 18% to 8% while achieving a high combustible recovery value of nearly 97%. In addition, the total sulfur content was substantially decreased from 2.6% to 1.7%. The effects of the critical operating parameters on separation performance have been studied and their values optimized.

Jan 1, 1995

By Frank R. Hunter

Introduction Scope of Work This paper represents the results of an investigation of the presence, amounts, and degree of concentration of heavy minerals found in the pulp of the phosphate flotation plant at Peace Valley, Fla., which is operated by the International Minerals and chemical Corporation of Chicago. In this paper, heavy minerals are those, excepting collophane, that sink in acetylene tetrabromide with a specific gravity of 2.95. Percentages of heavy minerals at several points of the flowsheet and the species of minerals have been determined. Some information as to the screen size of the minerals has been acquired. Previous Work All previous published reports or investigations of the deposits of heavy minerals in Florida have been limited to present beach sands. The mining operations conducted by the Humphreys Gold Corp. about seven miles east of Jacksonville along an ancient shore line have been described in trade journals, but descriptions of the minerals have been lacking. Commercial grades of ilmenite, zircon, and rutile are produced on a large scale. Papers have been published on heavy minerals found on the Florida beaches.1-6 Location "International's" Peace Valley flotation plant is in south-central Polk County, Fla. about eight miles south of Bartow and along the Atlantic Coast Line Railroad. The mine surrounds the plant and includes about 1500 acres of the phosphatic lands in this area. Geology General Setting All of the rock underlying the area is almost horizontal. The oldest bed exposed is part of the Hawthorn phosphatic limestone of Miocene age. This outcrops in the stream bed of the Peace River about one mile east of the plant. Elsewhere the Hawthorn is covered except where it has been exposed by mining operations. The Bone Valley formation of Pliocene age, which is the phosphatic stratum extensively mined in this area, unconforma-bly overlies the Hawthorn. Resting unconformably upon the Bone Valley formation are Pleistocene (?) terrace deposits of unconsolidated quartz sand which comprise the overburden of the phosphate ore. Stratigraphy Hawthorn formation: "Bedrock" of the pebble phosphate deposits is a cream to white colored, sandy, dense limestone containing varying amounts of small grains and nodules of collophane. The upper surface of the formation is undulating and irregular showing evidence of former

Jan 1, 1949

By M. Hall, Y. P. Chugh, A. Okunola

Effects of moisture absorption on the behavior of the Dykersburg shale overlying Harrisburg coal seam in Southern Illinois are presented in this paper. Cylindrical samples of the shale 2.5 cm in diameter and 5.0 cm long were studied for weight gain and swelling strains at 90, 95, and 100 percent relative humidity and under immersed water conditions. After attaining equilibrium conditions, the samples were studied for changes in the strength and deformation behavior. The depth of moisture penetration was measured using the Vickers microhardness measurements. Using the basic mass transfer concepts, effective diffusion coefficients were computed for the shale.

Jan 1, 1981

By P. Stantke

In recent years the CollaMat process has been used successfully worldwide in a number of copper electrorefining tankhouses as an instrument for measuring the glue concentration and optimizing cathode quality. Owing to its measuring principles the CollaMat can be used not just for measuring the concentration of active glue but also the activity of other substances, which have an impact similar to glue on the copper deposition. In SX-EW plants guar is frequently used instead of glue as a levelling additive. In our laboratory the effect (activity) and the decomposition rate of guar in copper electrolyte was examined. As expected, the results show that guar has an effect similar to glue on the copper deposition. However, at the same temperature, a greater quantity of guar is required to achieve the same results. As with glue, the decomposition rate (due to hydrolysis) of guar is strongly dependent on the temperature. Therefore, in practice, its on-line monitoring is necessary to guarantee the same guar activity at any time.

Jan 1, 1999

By A J. Nick, I I. Townsend, J M. Schuler, J D. Smith, R P. Mueller, L Sibille, K Leucht, J J. Fox

The first steps for in situ resource utilisation (ISRU) on target bodies such as the Moon, Mars and near-Earth asteroids (NEA), and even comets, involve the same sequence of steps as in the terrestrial mining of resources. First exploration including prospecting must occur, and then the resource must be acquired through excavation methods if it is of value. Subsequently a load-haul-dump sequence of events occurs, followed by processing of the resource in an ISRU plant, to produce useful commodities.While these technologies and related supporting operations are mature in terrestrial applications, they will be different in space since the environment and indigenous materials are different than on Earth. In addition, the equipment must be highly automated, since for the majority of the production cycle time, there will be no humans present to assist or intervene. This space mining equipment must withstand a harsh environment which includes vacuum, radical temperature swing cycles, highly abrasive lofted dust, electrostatic effects, van der Waals forces effects, galactic cosmic radiation, solar particle events, high thermal gradients when spanning sunlight terminators, steep slopes into craters / lava tubes and cryogenic temperatures as low as 40 K in permanently shadowed regions. In addition the equipment must be tele-operated from Earth or a local base where the crew is sheltered. If the tele-operation occurs from Earth then significant communications latency effects mandate the use of autonomous control systems in the mining equipment. While this is an extremely challenging engineering design scenario, it is also an opportunity, since the technologies developed in this endeavour could be used in the next generations of terrestrial mining equipment, in order to mine deeper, safer, more economical and with a higher degree of flexibility. New space technologies could precipitate new mining solutions here on Earth.The NASA Kennedy Space Center (KSC) Swamp Works is an innovation environment and methodology, with associated laboratories that use lean development methods and creativity-enhancing processes to invent and develop new solutions for space exploration. This paper will discuss the Swamp Works approach to developing space mining and resource extraction systems and the vision of space development it serves. The ultimate goal of the Swamp Works is to expand human civilisation into the solar system via the use of local resources utilisation. By mining and using the local resources in situ, it is conceivable that one day the logistics supply train from Earth can be eliminated and Earth independence of a space-based community will be enabled.CITATION:Mueller, R P, Sibille, L, Leucht, K, Smith, J D, Townsend, I I, Nick, A J, Schuler, J M and Fox, J J, 2015. Swamp works – a new approach to develop space mining and resource extraction technologies at NASA’s Kennedy Space Center: prospecting, excavation, load, haul and dump for in situ resource utilisation, in Proceedings Third International Future Mining Conference, pp 297–304 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By Harpal Parmar

This paper evaluates dynamic methods of pile capacity prediction by comparing their results to static load test results. Dynamic and static pile load test data were assembled from four southeastern states of the U.S. End-of-drive and restrike capacities were evaluated using the Pile Driving Analyzer (PDA) and by wave equation (WEAP) analyses. These were compared to static (Davisson criterion) loads. The best comparison was obtained for restrike PDA results; restrike wave equation analyses values also compared well. The end-of-drive results for both methods-showed relatively poor comparisons. The PDA was recognized as an important tool to measure energy transferred to the pile; this transferred energy was recognized as an uncertainty when conducting wave equation analyses. A statistical analysis showed restrike capacity results to be associated with higher precision and accuracy as compared to end-of-drive methods. The authors believe that restrike dynamic testing is essential to establish long term static soil strength and that it will lead to accurate and cost-effective design of piles.

Jan 1, 1996

By P. E. Demmler

PHOSPHORUS combines with copper in various proportions, forming true alloys, some of which are of commercial importance. These materials find wide application as deoxidizers and as a means of introducing phosphorus into other alloys, as in phosphor-bronze. Phosphor-coppers containing 10 and 15 per cent. of phosphorus are the commercial grades that are most generally offered. Each has certain advantages when used in making other alloys. The 10 per cent. grade of phosphor-copper has an advantage over the 15 per cent. in that it has a much lower melting point and can be prepared by certain methods with a much lower loss in phosphorus. The 15 per cent. grade has the advantage of lower freight rates per unit of phosphorus and, by the method to be described, a uniform product can be prepared with practically no loss of phosphorus. Alloys of copper and phosphorus containing any desired percentage of phosphorus lower than 15 per cent. can be prepared by melting together the requisite amounts of copper and 15 per cent. phosphor-copper. Processes for making phosphor-copper may be divided into two classes as follows: (1) Those depending on the smelting of phosphate rock or superphosphate of calcium with copper or copper-bearing materials, and coal or other carbonaceous material; (2) those depending on the direct combination of metallic copper and elemental phosphorus. A number of formulas for preparing phosphor-copper according to the first method have been published. The Metal, Industry' gives-the following: Superphosphate of calcium, 60 lb.; granulated copper, 301b.; finely powdered coal, 10 lb. Similar formulas are given by Brannt2 and others, and detail 'variations are covered by patents, such as those of L A Jeffs3 and H A Webster.4

Jan 8, 1920

By C. F. Riisness, E. R. Parker

THAT grain size has a great effect on the mechanical properties of metals has been recognized for a long time. Bassett and Davis1 in 1919 did excellent work in [ ] determining the effect of grain size on the hardness of brass. About the same time Jeffries2 and Sykes3 ascertained the effect of grain size on the strength and ductility of several metals at temperatures ranging from 80°K. to their melting points. When creep was recognized as an important property of metals, those engaged in the study of this property tried to determine the effect of grain size 4-9 on creep rates. Unfortunately, most of the investigations were conducted on only two grain sizes, often designated simply as "fine" and "coarse." It is well known that at high temperatures coarse-grained test bars creep less than fine-grained bars. The relation between grain size and size of test bar, [ ] however, has been frequently overlooked. In his early work, Jeffries2 showed that the number of grains in the cross section has a more important influence on the properties of the material than the actual grain size. More recently Hanson and Sandford10 and Pell-Walpole,11 in their measurements of the creep and tensile properties of tin, tested a wide range of grain sizes and correlated the grain size with the strength. Hanson9 later established the relation between the number of grains in the cross section and the. creep rate: At high temperatures, generally a coarse-grained structure is considered superior in creep to a fine-grained structure, but it is evident that for a given bar size continuously increasing the grain size will

Jan 1, 1944