Search Documents

By Yoshii Y

Many kinds of shield machines are being driven in the soft ground of Tokyo metropolitan area. Tunnel alignments for underground power transmission lines are generally planned to pass under public roads where facilities, especially life-line facilities, are densely located. Therefore, it is frequently required to drive the shield machines along very sharply curving routes. This paper reports on the performance of the new shield machine - the Sharp Curve Excavation Shield Machine - developed by Tokyo Electric Power Co., Inc., which can freely drive along a much sharper curve than conventional machines. Some of features of the developed devices of this machine are, maximum flexing angle of 6.5 degree in all deirection at the middle of shield body, maximum bending angle of 3.5 degree in all direction at the cutter disc, and so on. This shield machine can there- fore drive along curve of minimum radius 15m. The machine was confidently applied to the const- ruction of tunnel in soft clay strata at N values 2 to 5. Outer diameter 3.7m. Length 202m. Horizontal curve; radius 15m, length 20m x 2. Vertical curve; radius 30 m, inclined driven up 29%. The behaviors of the shield machine, segments and surrounding ground were monitored during construction for safety and efficiency check of this machine.

Jan 1, 1987

By Veal FL

Technological changes in Portland cement manufacturing during past years have reflected changes in the economics and availability of various types of fuel such as coal, fuel oil and natural gas. The industry consumes a sig- nificant quantity of both thermal and electric- al energy. The nature of the process and its chemical constraints does however permit the use of comparatively low grade fuels such as high ash coal and high sulphur oil. In striving for increased daily kiln outputs and conservation of energy, there is a worldwide trend towards the use of dry process plants. Wet process kilns of about 2 500 tonnes per day assume massive component sizes which present difficulties in manufacture, and transport to plant sites. Large capacity dry process units in excess of 8 000 tonnes per day are now in operation using precalcination techniques in which part of the fuel is introduced in the static preheater section ahead of the kiln while the balance is added to the kiln in a conventional manner. This technique has virtually doubled the potential output of any given single kiln.

Jan 1, 1976

By Holla L

There exist several legislative provisions in N.S.W. which work together to control surface subsidence due to extraction of coal by underground methods. The important ones are the Coal Mining Act, Coal Mines Regulation Act, Mine Subsidence Compensation Act and Dams Safety Act. In addition, there are guidelines laid down by the Chief Inspector of Coal Mines for mining under and in the vicinity of tidal waters and the ocean. There are also conditions of coal mining leases and conditions of approvals given to undertake various methods of mining which stipulate further controls. The legislative provisions and relative controls are designed to minimise surface damage, ensure safety , of major public utilities, control- surface land use and compensate damage caused by subsidence as a result of coal mining operations. They aim at balanced and responsible development of our valuable coal resources consistent with adequate safeguards to surface improvements and natural features. The paper discusses in detail these legislative provisions and the mechanics of their operation with a view to emphasising the fact that underground coal mining operations are undertaken responsibly and in a planned and rational manner for the overall benefit of the community. Further, the paper aims to demonstrate the need for legislative measures and conditioning of mining operations to keep abreast of developments in the knowledge and skills of mining and subsidence engineers and continuing improvements in mining technologies. Likewise there is a need on the part of engineers and those associated with introduction of new technologies to appreciate the requirements and existence of legislative and other measures having a direct or indirect association with surface subsidence as a result of coal mining operation.

Jan 1, 1986

By K Thompson

The Diavik Diamond Mine is a world-class operation located in an extreme environment 220 km south of the Arctic Circle in CanadaÆs Northwest Territories. The mine has a number of distinctive characteristics û such as limited winter access via an ice road, mine infrastructure being located on an island, with mining taking place behind dykes holding back a lake, temperatures at the mine that get down to -45¦C in winter, and the presence of bears, wolves, foxes and wolverines! One thing that Diavik does have in common with other mines around the world is the need for reconciliation. In late 2005 Diavik implemented SnowdenÆs Reconcilor software system to facilitate the process of reconciling geological models, mine plans, production data and plant results. This paper provides a case study of the reconciliation system implementation. It outlines the migration of Diavik away from a comprehensive and effective spreadsheet-based reconciliation process to a commercial grade, automated and web-based information management system. This paper documents the reasons for moving away from the spreadsheet system, the key parameters used for reconciliation, and the benefits gained by closing the loop between reconciliation and ongoing process improvement.

Jan 1, 2006

By L C. Thompson

Biomineralisation is the process by which microorganisms mediate and catalyse inorganic reactions so as to form new mineral assemblages. The goal of biomineralisation as a remediation tool is to control microbial processes and their environment so as to sequester and immobilise specific toxic metals within exceptionally strong bonds of neo-formed mineral assemblages. In this way, the bound metals are no longer mobile within a geological time-scale. Applied biomineralisation uses microorganisms, which are isolated from a metal waste environment and are selected for their ability to rapidly catalyse neo-mineral development from dissolved or leachable metals. A typical waste environment will contain microbes that contribute to the mobilisation of metal contaminants as well as microbes that possess the potential for remineralising available metals. Selection and augmenting the correct combination of bacteria and eliminating the competing mineral degrading reactions are the key to applying biomineralisation as an in situ remediation process. Applied biomineralisation harnesses the microbesÆ ability to stabilise toxic soluble metals into non-mobile mineralassemblages. This paper will discuss and demonstrate the biomineralisation process through several case studies including the Summitville mine site in Colorado, the McCoy-Cove mine in Nevada, the Argonaut mine in California, and an historic lead site in Crooksville, Ohio.

Jan 1, 2004

By Bogar D. V

Often dewatering of coal tailings is inhibited by the presence of clays, making it difficult to obtain a high concentration, handleable coal tailings. The net result can be a low concentration, chocolate mousse-like tailings which poses significant sedimentation problems in a tailings dam and represents a significant environmental problem. This paper examines the coal tailings from a Hunter Valley colliery where the tailings properties are influenced significantly by the presence of montmorillonite clay. The influence of the calcium ion on the rheology and sedimentation/compression behaviour of coal tailings . containing montmorillonite already dispersed in water was investigated and revealed that very little improvement in the properties is achieved through the coagulation. The preliminary investigations also indicated that the properties of the tailings were dominated by the presence of the montmorillonite clay. Thus investigations were carried out on the clay alone in water. Investigations into the effect of dispersing samples of the clay alone in water and then coagulating with calcium compared with dispersing the clay directly into calcium ion solutions at the same calcium concentration showed huge improvements in the rheology, compressibility, sedimentation rates and sediment solids concentrations for the second dispersion method, which can be called controlled dispersion. The sediment volume fraction solids improved by more than a factor of two by controlling the dispersion of the clay. The reason for the improved properties lies in the suppression of the initial swelling of the clay, which is initially in the sodium form, thus maintaining the parallel orientation of the platelets that is present before wetting. While swelling is being suppressed, ion exchange occurs with the calcium which results in permanent swelling suppression. In the uncontrolled dispersion case where swelling is uninhibited, the clay is allowed to break up and despite the powerful coagulating nature of the calcium ion, the random orientation of the high aspect ratio clay platelets inhibits effective coagulation. Results indicate that the initial electrolyte concentration of the washwater in a coal washery is the critical factor controlling the dewaterability of clay tailings and the handleability of the dewatered product rather than the actual act of coagulating with the calcium ion. The results presented are of clear practical significance and indicate how coal tailings problems where clay dominates the rheology can be improved considerably by knowledge of the surface chemistry.

Jan 1, 1995

By D Craw

The Hyde Macraes Shear Zone is a mineralised low-angle shear within the Otago Schist traceable for ~30 km with a NW strike. It is been actively mined along 12km of this strike, producing >6 Moz of gold. The shear zone consists of greenschist facies rocks with a mineralogy only subtly different from that of the host schist. Pervasive fluid flow has occurred along grain boundaries and within microshears which have been enhanced by the deposition of hydrothermal graphite. We model the development of these microshears using a threedimensional numerical code. For an inhomogeneous initial rock with lithostatic fluid pressures and a dynamic permeability deformed under dextral non-coaxial flow, deformation is distributed into weak shear bands. Graphite deposition and associated reaction-softening has a dramatic effect on the development of model shear zones. Graphite is deposited into a shear band, weakening it and further localising the deformation into that shear band, producing an anastomosing and interconnected shear zone structure such as observed in the HMSZ. The degree of graphite precipitation and graphitic-induced weakening are varied in the models. More graphite precipitation with a low degree of reaction-softening results in more diffuse shear bands. In contrast less graphite deposition but with a high degree of reaction-softening more leads to the development of more focused shear bands. Graphite deposition has clearly controlled the formation of the HMSZ structure, and is an important indicator of potentially mineralised structures elsewhere.

Jan 1, 2007

By S Gannon, J Abols, T Hughes

In the past year, two very innovative gold ore processing plants have been designed, built and commissioned by Gekko Systems Pty Ltd. The first plant in Vietnam utilises conventional crushing and ball milling followed by gravity concentration (Inline Pressure Jig (IPJ) and Falcon concentrator), flotation, intensive leaching (GFIL), the first industrial scale use of AuRIX«100å ion exchange resin and a cyanide destruction circuit. The second plant, in Australia, uses a three-stage crushing circuit to crush the gold ore to minus 1 mm, followed by gravity concentration utilising a rougher, scavenger, cleaner circuit of IPJs and a Falcon concentrator. A direct smeltable gold concentrate is produced as well as a lower grade concentrate for future intensive leaching or sale. Both plants were designed and built within very tight time frames and budgetary constraints. The experience gained during the plantsÆ design, commissioning and operation are discussed.

Jan 1, 2006

Upper Cretaceous and Eocene coal measures of the Ohai Coalfield are stratigraphically complex, and coal seam geometry and quality are influenced by washouts and partings resulting from accumulation in a fluvially active environment. Mining efficiency is influenced by these seam discontinuities, which are difficult to predict in the absence of refined paleoenvironmental models of peat accumulation. Petrographic variations between the Upper Cretaceous and Eocene coals indicate differences in the environments of peat accumulation. Seams in the Upper Cretaceous Morley Coal Measures accumulated autochthonously (in situ) in predominantly forest swamps with a high water table. These swamps were occasionally subject to brief floods. No significant changes in swamp vegetation, as indicated by petrography, have been detected between seams. In contrast, the greater content of mineral matter and maceral detritus within the Eocene Beaumont Coal Measure seams indicates hypautochthonous (locally transported) peat accumulation under more frequently flooded conditions. A precursor forest-moor is again indicated but the greater resin content of these coals compared with the Upper Cretaceous examples may suggest a greater contribution from conifers. Integration of coal petrography with investigation of other seam characteristics and coal measure sedimentology is expected to result in a detailed understanding of original depositional controls on peat accumulation. Paleoenvironmental models derived in this way should facilitate prediction of seam geometry, roof and floor conditions, and variations in coal quality, with obvious benefits to exploration and mine development.

Jan 1, 1983

By G Showers, R Triglavcanin

The complexity of understanding the whole thickening process to achieve real performance improvements cannot be underestimated. The last significant change in feedwell design was more than 15 years ago with the introduction of self-dilution systems û firstly with OutotecÆs Autodil, followed by FLSmidthÆs E-Duc. Now, following many years of extensive in-house research, including close collaboration with AMIRA and the CSIRO, Outotec has launched the next generation Vane Feedwell. The Vane Feedwell has been globally patented and installed at various sites. This paper briefly outlines the feedwellÆs development using CFD modelling and its subsequent performance in a æreal lifeÆ site installation. Plant results of the first commercial Vane Feedwell, in a mineral sands application, are discussed. The Vane Feedwell was retrofitted so comparative data of pre- and post-installation is shown.

Jan 1, 2009

By R-H Yoon

Increasing the upper particle size limit of flotation would allow operators to increase mill throughput, save operating costs, simplify flow sheets, and increase rate of return. However, coarse particle flotation is difficult for various reasons, of which bubble-particle detachment has been identified as the major limiting factor. In the present work, the process of bubble-particle detachment has been studied by directly measuring the forces required to detach air bubbles from hydrophobic solids. The measurements were conducted using a hanging balance apparatus. The measured forces were converted to detachment energies that can be compared with the work of adhesion, which in turn is a function of hydrophobicity, surface tension and contact area. The results were converted to detachment energies using the Young-Laplace equation for capillarity. In the present work, the solid surfaces were hydrophobised by coating them with octadecyltrichlorosilane and cetyltrimethylammonium bromide. The results show that bubble-particle detachment occurs in two steps. In the first step, air bubbles are deformed, while the three-phase contact (TPC) line is pinned, until contact angle reaches advancing angle. In the second step, the TPC line moves along the surface until solid/air interface is replaced by solid-liquid interface. In general, the energies of detachment measured in the second step are in good agreement with calculated work of adhesion. Thus, the energy required during the first step effectively represents an energy barrier for bubble-particle detachment. It has been found that the energy barrier varies with surface roughness and surface tension. The results of the present investigation suggest, therefore, that coarse particle flotation can be improved by control of particle hydrophobicity, surface roughness, and surface tension.

Jan 1, 2005

By R Piper

The Yabulu Nickel Refinery commissioned in 1974, processes lateritic ore via a modified Caron process to produce high quality nickel and cobalt products. The Greenvale orebody provided the sole source of feed to the plant until 1990 and with well-blended mineralogy, it resulted in stable and predictable plant performance, allowing the operating focus to be on reducing energy consumption and increasing ore throughput. This approach provided better economics than pursuing increased reduction efficiency. From 1990, increasing quantities of lateritic ore were imported from Indonesia, Philippines and New Caledonia. This introduced considerable variation in ore blends and instability in plant operation but also provided the opportunity to treat higher grade ore blends which yielded higher reduction efficiencies. Ore reduction is conducted using 12 Herreshoff multiple hearth reduction furnaces, using heavy fuel oil as reductant. The æROASTERÆ Project was approved in November 2000 with the primary objective of improving Nickel reduction efficiency by: Stabilising Roaster Operation via a structured program including focused maintenance efforts, capital equipment upgrades, new process measurements, process re-design and improvements to operating skills and process troubleshooting. A structured technical program including laboratory and plant studies using one plant furnace as a pilot unit to develop improved knowledge of how the reduction process proceeds in the Herreshoff furnace. Armed with this knowledge, optimised process conditions and a reduction process model were developed contributing to a significant demonstrated reduction efficiency improvement. Technical input to the project was provided by QNI with Hatch providing the engineering and project management for the $8.5 M capital work. Execution of the work included extensive consultation with the plant operators and close cooperation between the Hatch project team and QNI operations personnel ensuring installations were completed with minimal production disruption. A strong focus on safety management resulted in a number of brownfields project relevant safety initiatives being implemented resulting in project completion without a serious injury.

Jan 1, 2002

The South Ghorveh Batholith (SGB) and the Almoughlagh Batholith (AB) intruded the volcanosedimentary sequence of Songhor Series (Triassic-Jurassic), during the Oligo-Miocene orogenic phase. The granitoids of the AB belong chiefly to the quartz-syenite and syenogranite clans while those constituting the SGB can be generally characterised as quartz monzonite varying towards quartz monzodiorite, and diorite. Granitoids constituting both the batholiths are low in free quartz, and possess characteristics of the æmagnetite seriesÆ, mostly of I-type, metaluminous to marginally peraluminous and calk-alkaline type. Adjacent to them are located the magnetite skarn deposits of Baba Ali and Gelali. In the light of petrography, geochemistry, mineralogy and field geology investigations they could be classified as Fe-skarn and mainly bear characteristics of calcic skarn deposits.

Jan 1, 2005

An account of milling "methods and costs at Mount Isa Mines Limited up to the year 1938 has been published. The present paper outlines the methods since adopted in the milling of lead-zinc ores and presents a description of the equipment now being provided for the milling of copper ore.The programme approved for the mining, milling and smelting of both lead-zinc and copper ores involves the milling 9f 50,000 tons of lead-:-zinc ore and 35,000 tons of copper ore per month.The crushed ores will be delivered to the surface from alternate levels through No. 2 Ore shaft and conveyed to their respective crude ore bins at the crushing plant. The ores will be crushed and milled in separate circuits in common buildings and the tailings will be stored on a common tailings dump. The water services to the two circuits will be separate.LEAD ZINC PLANTCrushing PlantThe crushing plant described in the previous paper was located adjacent to the Urquhart shaft. The crushing plant had grown considerably over the years by the addition of a 4ft. BY-mons shorthead crusher and a set of Traylor 72 in. x 20 in. crushing rolls and, whilst operating satisfactorily, was difficult to maintain and cramped in many places. As a satisfactory layout for the new copper crushing plant could not be made in the vicinity of the, existing plant, it was decided to construct a new plant on the western side of theconcentrator building and provide identical equipment in...

Jan 1, 1953

A broad zone of intra-plate volcanism occurs for some 3000 km along the E. Australian coastal regions, extending from far northern Queensland southwards to Tasmania, westwards to western Victoria, and into southeastern South Australia. The age range, taken over the whole region, extends from Eocene to Holocene. Wellman & McDougall (1974) recognised the occurrence of three distinct types of volcanic occurrences: (a) Lava field provinces, dominantly basaltic and commonly strongly undersaturated, but of variable size. Large lava fields are especially exemplified by the younger provinces in northern Queensland (e.g. Nulla, McBride), and western Victoria. (b) Central volcano provinces, in which a reasonably well defined volcanic edifice is discernable. Such provinces are built of mildly undersaturated to saturated mafic lavas, but are also characterised by felsic volcanism (and often substantial mafic and felsic intrusive phases). Examples are the Springsure-Minerva Hills province, the Tweed and Focal Peak Shields (southeastern Queensland to northeastern N.S.W.), and the Nandewars, Warrumbungles, and Canobolas volcanic centres (N.S.W.). (c) A single leucitite province in N.S.W. Wellman and McDougall (1974) were able to show that the central volcano provinces exhibit a remarkably regular southward age migration pattern, the calculated migration rate being 66 + 5 mm yr , and these authors interpreted this in terms of the northward passage of the Australian plate across a fixed 'hotspot' within the upper mantle. The leucitite province also fits this migration pattern. The lava field provinces apparently exhibit more erratic regional age distribution patterns, but Sutherland (1981) has interpreted the data in terms of a multiple 'hotspot' model. It is noted, however, that the youngest areas of volcanism (Pleistocene 1. Department of Geology and Mineralogy, University of Queensland, St. Lucia, Brisbane, Queensland

Jan 1, 1987

By Wang S

Fragmentation is the basic concern in rock blasting and serves as the main measure of blasting effectiveness. A good estimation of fragment size distribution before blasting is very useful and helpful for selecting the proper equipment for loading, transporting, and crushing rocks. A fragmentation model is presented that is based on a hole by hole analysis and correlates the rock properties, burden, spacing, and explosive column with the blasted volume and fragmentation obtained. The drill bench is divided into three separate areas corresponding to different breakage mechanisms. They are: 1) a main breakage or casting area, 2) a secondary breaking area, and 3) an overbreak area. The boundary of the main breakage area is found from the magnitudes of strains in the stress waves and the tensile strength of the rock. The secondary breaking area is determined by stress wave reflections at discontinuities and interactions between colliding stress waves from adjacent boreholes. The overbreak area is that beyond the main breakage area "where the reflected tensile waves no longer break the rock. This analysis is applied on a hole by hole basis to locate the breaking points. Then connecting the breaking points on each side of a borehole forms the triangle of the main breakage area. This is repeated for the next hole and the remaining area is the secondary breakage area. After the angle and area for each hole are found the Kuz-Ram model is used to predict the fragmentation size distribution for each hole. Then summing up the size distribution for each hole gives the total fragmentation distribution. This analysis has been successfully applied to field tests performed in a limestone bench where the entire spoil pile was screened to determine the fragment size distribution. Knowing the explosive and rock properties the breaking area was found for each hole, the strain and stress values, the breaking point, and angle of breakage (104 degrees). The fragmentation size distribution was then calculated and compared to the field data with excellent agreement.

Jan 1, 1990

By V Ser, I Smit, C Robertson

Anglo American has been researching the potential benefits of inter-particle comminution techniques for several years. Inter-particle comminution has additional benefits in terms of milling circuit performance such as energy consumption and stability. This paper focuses on the flotation benefits. Inter-particle comminution leads to selective breakage, mineralogical analysis has shown that this leads to improved liberation of the valuable minerals. In addition to selective breakage, the relatively short residence time experienced in typical inter-particle comminution machines allows more efficient classification which contributes to a æsharperÆ product size distribution. The effect of particle size in flotation has been well documented in literature. In general, it is has been shown that there is an optimal particle size range for flotation, and that both above and below this range, flotation recovery is adversely affected. Results show that the narrow size distribution which results from inter-particle comminution improves flotation recovery. Furthermore, the absence of excessive fine gangue material which typically results from conventional fine (-75 ¦m) milling of talcaceous ores, can lead to 100 per cent savings in depressant consumption when such ores are subjected to inter-particle comminution. To-date, this technology has been evaluated on more than ten ores. This paper will focus on one set of results which demonstrates a number of common differences that exist between material that has been milled conventionally and using inter-particle comminution technologies, with emphasis on what the impact of these differences is on flotation performance. A pilot scale (200 kg/h) vertical roller mill (VRM) was used to produce the material, and the results shown will describe conventional laboratory batch, locked cycle and pilot plant flotation testwork.

Jan 1, 2005

By B A. Wake, G G. Lowder, M J. White

The Tooloom gold field is located within the New England Fold Belt in the far northeast of New South Wales, approximately 130 km south southwest of Brisbane. Gold was first discovered at Tooloom in 1857. Within a few years up to 10 000 people were mining placer gold deposits in the Tooloom valley and a few tried their hand at mining hard rock occurrences as well. Mining of alluvial gold continued in a small way at Tooloom until very recently, but only in the last few years, since Malachite Resources acquired its interest at Tooloom (now 100 per cent), has the full potential of this large, reduced intrusion-related gold field been appreciated. By the mid 1870s, once the alluvials were largely worked out, most of the early miners had made the 270 km trek north to the newly discovered Gympie gold field and Tooloom slipped into obscurity. Such was this obscurity that the Tooloom gold field was not recorded on published Government geological maps until 2001, four years after Malachite became involved. The many hard rock prospects that Malachite has identified in recent years were largely or completely unknown. Tooloom is a good example of blinkered thinking when it comes to modern mineral exploration. The New England province in NSW has long been the æpoor relationÆ to the much better known and more highly favoured Lachlan Fold Belt in NSW. It has also suffered serious neglect compared with the Queensland part of the New England Fold Belt that hosts such major gold deposits as Mt Morgan (>7 Moz), Gympie (>3 Moz) and Cracow (>1 Moz). Tooloom is proof that prospective geology does not stop at state borders.

Jan 1, 2004

An investigation was made into the mineralogical characteristics of the upper portions of the 650 and 750 copper lodes. The investigation was based on a comprehensive suite of geological specimens representing all types of mineralization encountered during mining until the end of 1954 and the chief aims of the investigation were to determine (a) the minerals present and their textures and associations, (b) the paragenetic sequence of deposition of minerals in the orebodies, (c) significant changes, if any, which could be found in the orebodies with depth, and (d) the nature and mode of occurrence of nickel in the ore. The general structure of the orebodies is outlined and their mineral composition given. 10 textures exhibited by the ore minerals are described and a paragenetic sequence of events in the formation of the copper orebodies is outlined. No decrease in the complexity of the sulphide mineral textures with depth could be seen and no evidence was found to suggest that the tenor of the ore would decrease with depth although some factors which may eventually limit the extent of the orebodies are noted. The mode of occurrence of minor elements in the orebodies is described. Notes on the occurrence of pyrite, aikinite and berthierite in the orebodies is given and the orebodies are considered to be identified with LiIidgren's mesothermal type of sulphide ore deposit in which considerable replacement of older by younger generations of sulphide minerals occurred.INTRODUCTIONA mineragraphic study was made by Stillwell and Edwards (1945) of a suite of specimens submitted by Mount Isa Mines Limited from the Mount Isa Black Star copper orebodies with a view to determining 1. the nature, extent and association of arsenic, antimonyand bismuth minerals, 2. the mode of occurrence of silver and 3. whether galena and sphalerite occurred in minute forms and below the sizes readily observed in hand specimens.

Jan 1, 1961

The scope of this paper has been restricted to the manufacture in Australia of seamless steel tubing, as the subject of buttweld tubing has already been dealt with by A. N. Hamilton in a paper delivered before the Institute in 1935.The earliest attempts to produce seamless steel tubes were based on the extrusion of lead piping, a process developed by Thomas Burr in 1820. However, the problems associated with the extrusion of white hot steel had to await the metallurgical knowledge of the twentieth century, and these early attempts were unsuccessful.The years 1840 and 1845 were noteworthy for the introduction of the first practical methods of making seamless steel tubes. In one process, a large circular plate was 'cupped' in a vertical press; in the other, a round steel billet was pierced for its entire length.The product from both these methods was then elongated by repeated reheating and rolling over an internal mandrel, in a circular pass mill.At this juncture, it should be noted that every process developed for the manufacture of seamless steel tubing can be divided into two parts. In the first part of the process, attention is centred on the conversion of the heated bloom into a short, thick-walled, hollow cylindrical forging; this product is then elongated in the second section of the process. It will be noted that these two sections are actually quite distinct, and in practice numerous methods exist for carrying out both functions. The first stage is generally referred to as 'piercing', the second stage being termed 'elongating.' In this paper, the author proposes to outline the various methods adopted for piercing and elongating; the reader is asked to note that although certain methods of piercing are almost invariably associated with only one method of elongating, the distinction between the two functions is, nevertheless, a vital one and should be noted accordingly.

Jan 1, 1947