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By S. Saeb, C. Francke

Introduction Although mining in one form or another has existed for millennia, the use of numerical methods for mine design is a relatively recent development. The basic physics that control the behavior of rock or soil have been known for centuries, but it wasn’t until the last half of the twentieth century that analytical methods that could accurately predict the behavior of a large, irregular rock mass were developed. Before the advent of modern computers combined with differential and integral analytical methods, numerical methods available to mining engineers were limited to closed form solutions for simple excavation geometries. Today, mine-scale three-dimensional stress analyses can be performed on a relatively inexpensive personal computer. Many of the recent advances in rock mechanics modeling are the result of research funded as part of nuclear waste repositories around the world. The large scale exacting performance requirements of waste repositories are frequently very different from traditional rock mechanics projects. These facilities are designed and built under tighter control and scrutiny because of the potential hazards they present to the public. Therefore, a great deal of research towards advancing rock mechanics and numerical modeling resulted from these projects. Much of the repository research is applicable to commercial mines. The advances in modeling programs have been paralleled by advances in computer equipment. Today, a moderately equipped personal computer can handle most mine geomechanical modeling projects in a reasonable period of time. While the learning curve varies, an engineer with modeling experience can develop a medium sized model in a few days. The relatively low investment cost of geomechanical modeling today makes it accessible to most mining operations. The benefits of a solid geomechanical modeling program include reduced operating costs, improved safety, and reduced design costs.

Jan 1, 2007

AXTAT is a computerised system developed by the Western Australian Department of Minerals and Energy in conjunction with the local mining industry for recording and retrieving information about fatalities and work related injuries. Since its inception, the system has gained considerable recognition by consistently demonstrating its usefulness as a tool, not only to the Department, but for the entire industry nationwide. AXTAT has played an important role in the continuous improvement process in management of occupational health and safety in the Western Australian mining industry with gains in both human and financial terms, by regularly providing timely and accurate statistical feedback on fatalities and lost time injuries to industry.

Jan 1, 1996

By A. W. Allen

Progress in the art of amalgamation in recent years has been negligible, partly because a copper plate, though it occupies extensive floor space, requires frequent attention and invites theft, is a simple piece of apparatus that gives visible results; partly because the impression prevails that amalgamation is too primitive a process to merit consideration by an up-to-date metallurgist. Both these objections can be overruled. Plates can and will be superseded by more efficient, theft-proof amalgamating units. Improved methods of application other than by settlement or by impact, neither of which is effective for removal of fine gold, will be developed, and the process given wider opportunity. As A. F. Crosse aptly remarked, neglect to utilize amalgamation when free gold can be recovered thus is comparable to the decision of a storekeeper to deal only with credit customers. Usual practice is to follow amalgamation with cyaniding. Rarely is attention paid to the possibility of reversing the order—of extraction of the fine gold first by cyaniding; the coarse, subsequently, by amalgamation. Such a sequence avoids the alleged hazard that amalgamated gold particles may be unacted upon by cyanide, whereas cyanided gold particles are readily amalgamated. Research has indicated, however, that the mercury coating on a gold particle is easily soluble in cyanide solution, probably because such coating is a compound of gold and mercury. Comparative-test results at one plant, of cyaniding a ground concentrate before and after amalgamation, showed total extractions of about 90 and 100 per cent, respectively, indicating high solubility of the mercury-gold particle, if present, or the advantage of preliminary impoverishment before cyaniding, or both. The contention that a loss in residue from an amalgamation-cyanidation plant is occasioned by presence of amalgamated gold that escapes action by solution is not supported by adequate evidence. The function and scope of mercury as an aid to extraction of gold by cyanide is deserving of attention. It is a powerful desulfurizer. To restrict an extractive process to a concentrated product is logical and economical, if preliminary concentration will segregate a high per-

Jan 1, 1935

It is self evident that in many cases mining disrupts communities, however, community reaction to mining varies enormously. This is due to a whole host of factors, some physical, some financial, some political and some a direct result of the projected mining company attitude towards the community at large. Physical and political factors are increasingly being dealt with realistically and financial aspects are to a significant extent determined by profit margins. If the acceptable profit margin canÆt accommodate all necessary costs (which now includes a variety of community considerations unheard of even a decade ago), then the project is just not viable. Despite major commitments now made by many mining companies to their affected communities, corporate attitudes, and their projection, remain as the most outstanding factor in mining project development where real gains can still be made in effectively reducing social risk. This paper addresses both international and domestic experience gained in managing this aspect of mining development risk, including initiatives implemented by multilateral institutions.

Jan 1, 2003

The French research institute, INERIS, requested the assistance of the CSIR?s Division of Mining Technology in developing further precautionary measures against explosions in their collieries. In response to this approach, an on-board active suppression system was adapted to meet their mining requirements. This system is used on tunnelling machines in Germany where the machine is positioned in the middle of the tunnel, which is therefore not much wider than the machine itself. With this configuration, the machine is never away from the tunnel face during the cutting cycle. As a result, the possible volume in front of the machine of combustible gas requiring suppression is less than 50 m3. In South Africa this technology has been adapted to suit a two-cut mining method which entails greater distances from the face and thus much larger volumes of methane mixtures requiring suppression. The particular configuration of the Explo-Stop® system being investigated required the suppression of possible methane ignition volumes of up to 180 m3of a 9% per volume methane/air mixture. The volume is a consequence of the large cross-sectional area of French underground workings and of the two-cut mining method used in France. In order to take the second cut in the coal seam, the machine is pulled back a maximum distance of 4 m, leaving an air pocket in which gas can accumulate. The machine-mounted system is required to effectively suppress any flame ignited by such a large accumulated volume of methane. The results of the protocol tests done at Kloppersbos showed that the system was capable of suppressing all simulated methane ignitions for the prescribed conditions. This was achieved with a temperature increase of less than a 100°C at the operator?s position and without any flame being detected at this position.

Jan 1, 2001

By T. W. H. Parker, S. B. Sadleir

ABSTRACT A comprehensive program of air flush core and reverse circulation drilling, trial mining and beneficiation test work was carried out in 1980-1982 to re-assess the potential of the Mitchell Plateau bauxite deposit. The results generally confirm previous work by Amax Corporation. The bauxite is a medium available alumina and reactive silica deposit which responds well to wet screen beneficiation. High grade pockets have developed locally, with the potential for refractory grade extraction. A major feasibility study of the Mitchell Plateau bauxite deposit was completed in 1983. Due to the unexpected severity of the downturn in the alumina market, development of the project has been deferred.

Jan 1, 1984

By Toshio Suzuki, Machiko Ode, Won Tae Kim, Seong Gyoon Kim

"The Ostwald ripening and growth and coarsening of the secondary dendrite arm are studied using a phase-field model. The phase-field parameters are obtained at a thin interface limit proposed by Kim et al. In Ostwald ripening analysis, the difference of the concentration due ·to· the curvature effect is shown. The third power of the average particle radius Rav is proportional to time and the ripening constant shows a good agreement with the value by Deppers et al. The particle radii distribution shows the transition behavior to attain a self-similar stationary shape. The growth and coarsening behavior of the secondary dendrite arm is also analyzed using a phase-field model. The estimated arm spacing and its dependence on time are in good agreements with experimental data.IntroductionThe ripening or coarsening process controls the microstructure during the late stage of solidification. The ripening phenomena are recognized firstly by the Ostwald [1]. The first quantitative analysis for the Ostwald ripening in the limit of vanishing solid fraction was provided by Lifshitz, Slyozov and Wagner (LSW) [2,3]. In their study, that the mean radius grows proportional to the cubic root of time and the size distribution of precipitations shows a ""self-similar"" shape are shown. Most of the studies for the Ostwald ripening confirm or predict these two general rules above. In case of finite solid fraction, the general rules are observed but the ripening constant is larger and the self-similar shape is wider than the LSW prediction respectively [4-6]. To analyze· the high solid fraction system, the theories that consider the solute field correlation are proposed [4,7-8]. In the theory, however, since the particle is treated as the point, the effect of the concentration field deviation from the monopole field should be taken into account. Recently the numerical simulation, in which not only diffusive transportation of solute but also convection effect is considered, has been done using a phase-field model [9]."

Jan 1, 2000

By J. C. Uy, A. A. Burr

IN the primary solid solutions of zirconium-base alloys, there is a striking regularity of the effect of solute valence on the stabilization of the allotropic phases.1 The valences derived by pauling2 are for elements as they are bonded in the solid metallic state. Effects of variations in isotopes, alloying elements, and allotropes on their valences are difficult to determine and such data are presently unavailable. Pauling's values are somewhat empirical and approximate, but if some definite correlations can be found between those values and experimental observations, this will lend support to the tacit assumption that the possible variations in valence mentioned above are small. Pauling has amassed a large amount of evidence of such correlations. It is the purpose of this technical note to show another application of the Pauling valences and to offer a possible explanation for this observation. The relationship between the Pauling metallic valence of the solute and the stabilization of allotropic phases in zirconium is shown in Table I, which has been compiled from available data in the literature3 plus the results of work done at Rens-selaer Polvtechnic Institute.' The chemical valences are included for comparison. It can be seen that a solute whose metallic valence is lower than that of the solvent tends to stabilize the a phase while one whose metallic valence is higher than that of the solvent tends to stabilize the 0 phase. It should be noted that, inasmuch as the Pauling valences are periodic with atomic number, this is tantamount to saying that the elements in groups I-A, 11-A, III-A, III-B, IV-B, V-B, and VI-B are a stabilizers while those in groups IV-A, V-A, VI-A, VII-A, VIII-A, I-B, and 11-B are ß stabilizers. The chemical valences do not show such consistency. Although the zirconium-rich end of the Zr-Au diagram is not available, it call be expected that gold, having a metallic valence of 5.56, would stabilize the ß phase. At absolute zero, the Fermi energy level is the criterion of equilibrium, i.e., the structure having the lower Fermi level will be more stable. Conse- quently, allotropic transformation occurs in a metal when thermal excitation raises the Fermi level to a point at which the atoms can be better accomodated by a different structure which yields a lower Fermi level.4-6 Thus in allotropic transformation, a change in structure occurs as a result of the change in the energies of the bonding electrons. Since the Pauling valence is the number of bonding electrons per atom, and these are the only electrons whose energies are affected by thermal excitation,* it can be inferred that the introduction of a solute which has a higher Pauling valence than that of the solvent raises the initial Fermi level; consequently, the transformation temperature is lowered. The converse is also true. The fact that at the transformation temperatures this statement is still fairly valid implies that the contribution due to the difference in specific heat terms of the two allotropes is comparatively small.

Jan 1, 1962

The first geological maps of parts of Australia were produced in the 1830s and 1840s, many being for purely practical purposes, such as indicating the occurrence of coal, iron and other essential materials. Mineral location maps were also first made about the same time.More systematic geological mapping commenced in the 1850s when large parts of New South Wales and Victoria were studied in government-sponsored surveys by geologists such as Samuel Stutchbury, Alfred Selwyn and Reverend William B. Clarke. Their work coincided with the opening up of most of the major goldfields of eastern Australia, which led to the establishment of Departments of Mines in the separate Colonies (later States within the Commonwealth of Australia).A few companies employed consultant geologists at this time, and the mapping by Frederick Odernheimer is particularly notable. Geological study of Australian ore-deposits and mineralisedareas was influenced by the continental European geological ideas of men such as Odernheimer as well as by those from England. Both geological and mineral maps were a feature of Colonialdisplays presented at major international exhibitions during the second half of the nineteenth century. The maps accompanied rock and mineral collections which showed the known and potential mineral wealth of the Colonies. Such displays raised interest in the potential for development amongst government officials, entrepreneurs and investors in Australia and abroad.By the 1880s most of the Colonies had produced basic geological maps, and several maps of the whole continent had been published. Although systematic mapping of the continent become a reality only in the 1950s, the nineteenth century geological and mineral mapping formed the basis for the development of the major coal, artesian water, and metalliferous mining regions of Australia.

Jan 1, 1990

By N Bianco, D Drinkwater

The professional skills shortage is intensifying, and commentators are predicting a shortfall in supply of qualified professionals for the mining industry, ranging from thousands to tens-of-thousands by 2020 (Tuckwell, 2011; Scoble, 2011; Laurence and Hebblewhite, 2011). Human resources are already stretched, and university graduates arriving in the workplace are often moved rapidly into management positions where there is limited scope to develop their engineering proficiency. This process may well be developing excellent young managers, but our industry is producing fewer excellent young engineers (Munro and Tilyard, 2009). Many believe that it is engineering excellence that is likely to be the key to our industryÆs success in the decade to come. An innovative in-house graduate development program has been created by specialists at the JK Centre in partnership with two mining companies. This program, known as MetSkill«, has been running throughout 2012. Groups of graduates have had to identify a process plant optimisation opportunity and embark on a structured program of data collection and analysis, facilitated by a æteaching teamÆ of researchers and consultants from the Julius Kruttschnitt Mineral Research Centre (JKMRC) and JKTech. This group project culminates in a report-back session to senior company officials. Along the way, a series of short workshops and other activities provide opportunities to work on specialist skills, and support is also offered by senior technical specialists from the companies involved.This paper outlines key features of the MetSkill« program, along with a report-card on progress in 2012 and plans for further program development in 2013.CITATION:Drinkwater, D and Bianco, N, 2012. Developing minerals industry leaders by encouraging metallurgical excellence, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 287-290 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By C. R. Fischrupp, M. D. Helfrick, W. A. Straw

In the manufacture of telephone apparatus a number of nonferrous sheet metals arc blanked and formed to produce a wide variety of parts, which are generally small in size because of space and weight requirements. Many are given sharp bends in forming, so that they may be assembled into compact units. This study covered sheet metal of the alloys of brass, phosphor bronze and nickel silver that are most extensively used by our company. In general, the sheets range from 0.005 to 0.100 in. in thickness and from 1/4 hard to extra spring temper in hardness. As many parts function as flat springs, and others require the maximum stiffness for structural reasons, a large percentage of the metal is used in the hard and spring tempers. So, because of the necessity for the minimum radius of bend consistent with the maximum in hardness, there has been a need for information as to the forming characteristics of these sheet metals in the various alloys, tempers and thicknesses. The literature yields relatively little regarding such forming characteristics, so that designers of apparatus and tools have been largely dependent upon past experience or tool tryouts for guidance. In presenting tabular data intended as a basis for selecting the temper of the metal and radius of the bend, we recognize the influence of many other factors which are not covered in this study. For example, the angle of the bend and conditions of the metal, such as grain size and presence of impurities, as well as conditions of the fabricating process, such as rate of forming and adjustment of the tools, may all affect the result. In addition, a bumping operation subsequent to forming, which is frequently used to set the bend, increases the strain on the metal. We wish to emphasize the fact that this is not considered a scientific investigation of the formability of materials or an attempt to correlate forming characteristics with various other properties of the metals, except in so far as such properties are controlled by commercial limits on composition and temper. It is expected, however, that the data presented may serve some useful purpose in estimating the relative formability of different thicknesses

Jan 1, 1931

By Thomas M. Gurtowski

The New Pacific Northwest Baseball Park, now known as Safeco Field, is located directly south of the Kingdome in Seattle, Washington, and will be the new home of the Seattle Mariners baseball team. The location of the ball field is shown on Figure 1, Vicinity Map. The seating capacity is 45,600, and outfield distances are 331 feet in left, 405 feet in center, and 326 feet in right field. The overall dimensions of the stadium are 680 by 800 feet. It is bordered on the east by the Burlington Northern Santa Fe Railroad main line. A unique aspect of this ballpark is the retractable roof with a north-south span length of 660 feet. The roof consists of three separate sections that roll on elevated rails running east-west on the north and south sides of the stadium. The soil conditions consisted of near-surface fill underlain with alluvial and Estuarine deposits to depths of 60 to 80 feet. The bearing soils consisted of very dense, glacially overridden deposits. Groundwater is 4 to 7 feet below the ground surface, and the alluvial deposits are subject to liquefaction during a strong motion earthquake.

Jan 1, 1998

By Luca de Sanctis

The analysis of piled raft foundations in layered soils may be performed by 3D finite elements or by approximate procedures. Among the latter, the code NAPRA (Russo, 1998) is based on the method of the interaction factors and accounts for soil layering by the so called Steinbrenner approximation. A comparison between the results of 3D FEM and NAPRA for some reference layered soil profiles shows that the approximation is fully acceptable for engineering purposes, provided the stiffness of the single pile is properly selected. The interest of the conclusion lies in the fact that the amount of work needed to model a practical problem by NAPRA is but a fraction of that needed by FEM modelling.

Jan 1, 2002

Arthur Jarman, Sydney, New South Wales, Australia (communication to the Secretary*):—All designs for modern metallurgical and chemical laboratories should provide each student's desk with a hood or cupboard for the removal of fumes, but I doubt the advisability of placing air-baths and similar apparatus close to the hot plate. It seems to me that unless the draft be exceptionally strong the fumes from ordinary wet assay work will corrode the iron-work of the fittings, in which case the baths would have to be removed to a general desk in order to lighten the work of the laboratory attendant. Since the laboratory described by Mr. White has been in use for two years, I should like to ask if any inconvenience has resulted from this corrosion. If not, it is certainly an important improvement to have the air-baths and similar apparatus placed on the student's desk. The hoods described by Mr. White are supplied with a good draft by means of a fan, which gives them a great advantage

Jan 1, 1905

The ready solubility of gold in dilute aqueous solutions of the cyanides of the alkalies or alkaline earths provides a convenient method for the separation of the precious metal -from the large surplus of associated materia1. The finely ground ore is pulped with a weak solution of cyanide, agitated to dissolve the gold, filtered and washed. The lowgrade filtrate is then clarified and the gold precipitated by some electronegative agent, the most usual being finely divided zinc or zinc dust. The slight precipitate is collectedon some form of filter coated with a filter aid, the filter cake being then known as "gold slime".A typical analysis of this slime is given in Table 1.

Jan 1, 1956

A new system for granting access to mineral rights is proposed in the recently released White Paper, ?A Minerals and Mining Policy for South Africa?. Official policy states that ?Government?s long-term objective is for all mineral rights to vest in the State for the benefit of and on behalf of all the people of South Africa?. In order to achieve this objective, government is presently investigating the feasibility of imposing a financial or tax-related disincentive to holding mineral rights. The paper aims to present the pros and cons and to examine the alternatives which will cause minimal disruption to the minerals industry in the period during which mineral rights are transferred to the State. South Africa is a country whose economic and political history is embedded in the development of its mineral resources and has inherited a system which cannot simply be wished away. Hasty or radical decisions will compound the problem, rather than provide a lasting and widely acceptable solution. Mineral rights ownership and its impact on access to mineral deposits are discussed. Taxation as a possible economic disincentive is also evaluated. Finally, the value of mineral resource related information as a prerequisite to mineral policy decisions and as an alternative to mineral rights taxation is emphasized.

Jan 1, 1999

By Bruce F. Grant

"INTRODUCTION The future of oil production in the part of the Appalachian region included in southwestern Pennsylvania; West Virginia, and southeastern Ohio is directly dependent on the maintenance of existing wells. This report presents an analytical study of the methods used in oil-well reconditioning in this area. The study is part of a research program designed to evaluate those means of stimulating oil production that can effectively and economically maintain present oil-production rates and make it possible to keep existing wells in operation. Well-reconditioning work was curtailed during the war; therefore, an abnormally large number of wells in the Appalachian Region is now in need of repair. Because the lubricant content of Appalachian crude: oils is high and the refined lubricating oils an; particularly suited to use in high speed, high-temperature engines, the demand for these crude oils during the war exceeds, the maximum rate of production obtainable under wartime operating conditions. Increases in operating, expenses, inability to meet war-time reconditioning costs, and inflexible price structures caused the abandonment of an alarming number of wells during the past 4 or 5 years.As a means of increasing regional oil-production rates, new drilling in the older fields for primary production generally is uneconomical because reservoir pressures in most of the fields have virtually been depleted and the production rates of newly drilled wells are small."

Feb 1, 1948

By John. C. Reed

THIS paper presents briefly some of the principal results of 3 ½ months field work during the summer of 1938 in the Chichagof mining district, southeastern Alaska. The report is preliminary and presumably will be followed later by a more complete report to be published by the Geological Survey. The paper is concerned principally with the structural geology of a block of steeply dipping graywacke as revealed underground in the Hirst Chichagof and the Chichagoff mines, the two principal mines of the district. The two mines have produced about $16,000,000 worth of gold and silver. The attitude of the graywacke, which is locally cut by dikes and sills of aplite, is remarkably uniform and trends about N. 62° W. The average dip is about 67° SW. The graywacke is cut by large faults, the best known of which are the Hirst and the Chichagof, whose average trends are about N. 30° W. and average dips about 75° SW. The faults at some places split into the bedding of the graywacke and at others are deflected from their normal trends for considerable distances along the bedding. The relative movements along the faults was northwest and up at about 30° for the south-west or hanging-wall sides. The ore bodies are elongate quartz lenses in the faults. Most of the quartz is mineralized but locally large quartz masses are too low grade to be mined. The emplacement of the ore bodies appears to have been structurally controlled in large part by the intersections of the faults with the bedding surfaces. Places where the faults split or are deflected appear to have been particularly favorable places for ore deposition. There has been some post-quartz movements along the faults but it is thought that such movements have not been extensive enough to greatly modify the original positions and shapes of the ore bodies.

Jan 1, 1939

THIS paper presents briefly some of the principal results of 3 ½ months field work during the summer of 1938 in the Chichagof mining district, southeastern Alaska. The report is preliminary and presumably will be followed later by a more complete report to be published by the Geological Survey. The paper is concerned principally with the structural geology of a block of steeply dipping graywacke as revealed underground in the Hirst Chichagof and the Chichagoff mines, the two principal mines of the district. The two mines have produced about $16,000,000 worth of gold and silver. The attitude of the graywacke, which is locally cut by dikes and sills of aplite, is remarkably uniform and trends about N. 62º W. The average dip is about 67º SW. The graywacke is cut by large faults, the best known of which are the Hirst and the Chichagof, whose average trends are about N. 30ºW. and average dips about 75º SW. The faults at some places split into the bedding of the graywacke and at others are deflected from their normal trends for considerable distances along the bedding. The relative movements along the faults was northwest and up at about 30º for the south- west or hanging-wall sides. The ore bodies are elongate quartz lenses in the faults. Most of the quartz is mineralized but locally large quartz masses are too low grade to be mined. The emplacement of the ore bodies appears to have been structurally controlled in large part by the intersections of the faults with the bedding surfaces. Places where the faults split or are deflected appear to have been particularly favorable places for ore deposition. There has been some post-quartz movements along the faults but it is thought that such movements have not been extensive enough to greatly modify the original positions and shapes of the ore bodies.

Jan 1, 1939

By J. A. Roberson, A. M. Adair

A plate of an 18 pct Ni (250 grade) maraging steel was homogenized, cold rolled, and re crystallized to produce a fine grained, homogeneous structure. The strength properties were then measured as a function of cold rollinq prior to aging. Material in the solution heat treated condition exhibited substantial strengthening from cold rolling. The strength increase and the rate of strengthening were proportional to the amount of cold work. This benefit, of up to 50 ksi, was retained during aging for 3 hr at 900°F. The structures produced by cold rolling and aging have been systematically investigated by transmission electron microscopy. The dislocation debris produced by cold work influences the morphology and distribution of precipitate particles as well as the rate of precipitation. An essential feature of the high nickel maraging steels is a martensitic transformation from y to a with the resultant production of a supersaturated bcc solid solution. This solution decomposes to form precipitates during a subsequent aging treatment.' The martensitic transformation in low carbon Fe-Ni alloys and the mechanical properties of these alloys have been studied extensively.2"4 The carbon content of maraging steel is kept very low to avoid the embrittling Fe3C phase and to minimize the acicular, or twinned martensite common to high carbon steels. Maraging steels are usually strengthened only by heat treatment, but cold working is also quite effective in this respect as was shown by Decker, Eash, and Goldman,' Kula and Hickey,5 and the present work. There is, however, some disagreement between the present results and those of Kula and Hickey. Because of their unusual combination of strength and toughness, the maraging steels are suitable for applications where reliability at high stress levels is required. The strength level is achieved through a combination of solid solution hardening,' substructure hardening,3 and precipitation hardening,6 of which the last is the most important. The toughness of these steels has been reported to be a result of the absence of brittle grain boundary precipitates,7 and the fact that the matrix is a massive martensite rather than a twinned martensite.' One of the problems in the manufacture and use of maraging steel has been its tendency to develop laminations in sheets parallel to the rolling plane.9,10 The present investigation was intended to determine whether or not an improvement in the microstructure of this steel by thermomechani-cal processing would improve mechanical properties. I) EXPERIMENTAL PROCEDURES A plate ($ in. thick) of an 18 pct Ni-250 grade maraging steel* was obtained and examined metallo- "Analysis, wt pct: 18.1 Ni, 8.6 Co, 5.3 Mo, 0.4 Ti, 0.07 Mn, 0.05 Cr, 0.05 Si, 0.002B. 0.1 Cu. 0.05 Al. 0.002 Zr, 0.016 C, balance Fe. graphically. It was found to contain laminations as described by previous investigators. This plate was then annealed at 2100°F for 24 hr to promote homogeneity. Pilot studies on small coupons had shown that this was the minimum temperature required to accomplish homogenization in 24 hr. Since this treatment caused excessive grain growth, the steel was subsequently cold rolled and recrystallized. Cold rolling was accomplished at about 5 pct per pass to a total reduction of 66 pct. The standard solution annealing treatment (1 hr at 1500°F) was adequate to cause recrystallization of the cold worked steel. The recrystallized steel was then cold rolled and ground by various amounts to produce specimens with uniform thickness and selected amounts of cold rolling. All tensile specimens with less than 90 pct cold reduction were ground to a thickness of 0.050 in. Specimens with 90 pct cold reduction were 0.025 in. thick. All

Jan 1, 1970