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By P. R. A. Andrews

"Garnet occurs in schists and gneisses in all provinces of Canada, all mainly in Quebec and Ontario. There is currently a renewed interest in exploration for economic sources of garnet for abrasive applications because of the inherent dangers from exposure to ground silica from sandblasting operations.High-quality garnet is used for lapping and grinding of glass and ceramics; for coated and bonded products such as sandpaper and cloth; and abrasive wheels for grinding and finishing various metals, woods, rubber and plastics. Low-quality garnet is used for cleaning and conditioning aluminum and other soft mewls, particularly by aircraft manufactures. Garnet may be added to grouting cements for oil-well drilling applications, and it has also been used for low- to medium-level radiation shielding. Garnet has been studied extensively by CANMET and its predecessor, Mines Branch, between 1917 and 1990. Twenty-nine studies relating 10 various aspects of beneficiation are presented and a review of the more important studies is presented. The information includes mineralogy, beneficiation methods, product sizes and analyses."

Jan 1, 1995

By P Kovacs, D. L. Flock

For the purpose of reservoir-performance calculations a balance can be made between the materials with-in the reservoir and the production from the reservoir. The material balance equation, a relationship which holds under or near equilibrium conditions, has been used in many forms by the Petroleum Engineer for the determination of initial oil-in-place in the reservoir and the calculation of performance into the future. One of the more recent methods developed by Tracy, utilizes a modified form of the Schilthuis material balance. In the latter case, values of incremental production are assumed for a particular pressure drop, a value of the gas-oil ratio found and a check of this estimate made by calculation"' the initial oil-in-place. Tracy's method utilizes an estimation of the instantaneous gas-oil ratio and by trial and error a value of the gas-oil ratio is

Jan 1, 1961

By C. -M. Katsari, G. N. Anastassakis

"Copper is considered one of the most important industrial metals because of its properties (conductivity, malleability) and variety of uses. Approximately 70% of the global copper is used for various electrical applications, with a significant part of copper originating from recycling, since copper can be recycled and re-used countless times, without any loss of performance and difference in the quality of recycled copper in comparison to that from ore. Copper recycling significantly contributes to natural resources conservation, waste minimization, energy saving, and overall cost reduction. Approximately, 35% of the globally produced copper originates from recycled copper.The objective of the current work is to investigate the recovery of copper from electric wire scraps using wet shaking table as an alternative to air separation methods that prevail over the wet ones in recycling processes. The tests were carried out using feed of correspondingly high- and low-grade in copper. In the first case, the wire scraps had been subjected to shredding only, prior to tabling separation; in the later, the low-content tailing of prior air separation was used as feed ?n table separation.In regard to testing, the following factors were examined: table tilt, water flow-rate, and reciprocating speed. The results of the tests clearly denote that copper wire separation from plastic polymer is feasible, as in most cases, table separation resulted in heavy products of high purity in copper and high recovery, and tailings of very low copper grade. The results of the current work clearly denote that wet tabling can be applied efficiently for the separation of recycled copper wire from plastic, as an alternative to air separation methods, as well as for the recovery of copper from the low-grade tailings derived from air separation methods."

Jan 1, 2016

By Paul J. Beck

The impact of mining development on the environment can be minimized through comp careful construction and accurate monitoring. Key to meeting these objectives is t information at all stages of design, development, operation and decommissioning. This paper will describe cost-effective means of gathering and managing reliable fiel groundwater flow and surface water regime within and surrounding the mine site, as localized contaminant plumes associated with mine operations, and monitoring ground quality. Recent research has led to the development of inexpensive, easy to install syst sampling/monitoring from different zones within a single borehole. Advances in elect developed small diameter probes and pumps for measuring water levels and taking wat continuous monitoring stations in remote areas can be colldeacttaeldo gaguetrosm aatnidc adlolwyn luosaidnegd from a central facility using telemetry systems powered by direct, battery or solar radio frequency, landline or cellular telephones, and satellite. Two case studies will illustrate the use of datalolgagregres sacnadl et eblaesmient rwyi dien mao nitoring sc and the use of multilevel samplers for managing a contaminant plume.

May 1, 2004

By Yve Aymong

"The objective of this paper is to help readers benefit from the practical experience of persons who have been engaged for several year s in the testing and repair of power transformers. Power transformers are known to be reliable pieces of equipment with expected usage of 25 to 30 years, but simple problems such as leaking radiators, or a bad contact on a tap changer, could shorten the life of a transformer. To ensure a longer life span, transformers should be checked on a regular basis.What is a Power Transformer?It can be a 90 MVA transformer for Hydro-Québec or a power transformer can be a 500 KVA unit in a small hospital. Generally a power transformer is an oil -filled type of 3 to 5 MVA. It can also be a dry type transformer, that should be treated in the same manner as oil-filled transformers, and some of the tests explained in this paper also apply."

Jan 1, 1984

By N. Katsikaros, R. Agius, B. Adaszynski

"With stricter limits globally being imposed on cyanide discharge levels in plant tailings, having a reliable and well designed cyanide detoxification circuit is critical for any operation. The INCO SO2/Air method is most commonly used for cyanide detoxification where sulfur dioxide and oxygen combine to oxidize cyanide to the much less toxic cyanate. This paper discusses the steps involved with the development, from laboratory through to design, of a robust cyanide detoxification circuit. The goal is to produce a cyanide detox circuit that reliably meets discharge target with the lowest operating and capital cost.Design begins in the laboratory where continuous tests simulate full scale operation of a detoxification circuit. Detailed design relies on several design parameters, based on theory and experience, to ensure the reactor can satisfy requirements of the cyanide destruction reaction. Selection of the correct reagents and their supply to the reactor is important to an operable process with minimal operator workload. The operability of the system relies on correct process control strategies to maintain optimal reagent addition and chemical conditions in the reactor. These design factors are critical to providing a robust plant that will consistently meet cyanide discharge levels, ensuring uninterrupted production and plant profitability."

Jan 1, 2014

By D. Mraz

"In certain instances, rocks around underground excavations behave as a plastic mass. This paper offers several solutions to predicting the mode of plastic flow around cavities and designing mining pillars where plastic conditions exist.IntroductionWhen stresses around underground cavities exceed yield limits of the host rock, the material often behaves as a plastic mass. The best example of this phenomenon is the behaviour of salt rocks in deep salt and potash deposits (more than 500 m deep).However, many other soft rocks exhibit similar properties. For example, Jeremic(1) described certain types of coal yielding plastically under high pressure. Alder suggested that granulated rock behaves plastically.The object of this paper is to propose a de sign procedure for mining pillars exhibiting plastic flow due to the combination of rock properties and in-situ stresses.Prandtl(3) mathematically defined a concept of a generalized, perfectly plastic substance, not possessing the property of strain hardening (Fig. I). He had in mind, a solid with a quasi quasi-isotropic , polycrystalline structure having a well defined yield point, and he postulated that its material elements start and continue to deform plastically when the maximum shearing stress ""'MAX"" reaches a sharp limit, dependent on the mean value of the sum of the major and minor principal stresses:"

Jan 1, 1984

By Franc R. Joubin, Donald H. James

"The Algoma (or Blind River) uranium district is centred in an area of some 600 square miles on the north shore of Lake Huron, about half way between Sudbury and Sault Ste. Marie, Ontario (Figure 1). Its favourable location, adjoining the main provincial highway and Canadian Pacific Railway line which follow the lake shore, has contributed greatly to its rapid development.By Canadian standards, the district has long attracted geological attention, beginning with the discovery of the Bruce mine in 1846. It has been repeatedly prospected at intervals since then, chiefly for copper and nickel but also for lead, zinc, cobalt, silver, iron, and gold. Numerous discoveries have prompted the suggestion by Yates (13) and others that one metal-logenic province embraces the entire mineralized area from Michigan through Sudbury and Cobalt.Geological mapping was initiated by Murray in 1847, and the area attracted much interest as the type locality of the Huronian, the correlation and stratigraphic position of which are still not entirely agreed on. Subsequent contributors to the geological literature of the area have been very numerous, and the bibliography at the end of this paper includes only some of the more modern reports.The history of uranium in this part of Ontario also dates from 1847, when J. L. LeConte identified as uranium-bearing a pitchblende-like mineral which he named ""coracite"". The specimens came from Theano Point, north of Sault Ste. Marie. In 1948 a search for the source of these specimens led to the discovery of the Camray uranium field. Occurrences in this field consist of numerous small and locally rich pitchblende-bearing fractures, within or along the contacts of diabase dykes cutting Archaean granite and gneiss.None of the showings explored proved large enough to justify production, but they stimulated prospecting of adjoining areas and thus led to the Algoma discoveries.The first find of radioactive conglomerate in place was made in 1949 in Long township, and it was partially staked as the Fisher-Audette-Breton property. Rusty, overgrown rock-cuts indicated that the pyrite-bearing conglomerate had been investigated years before, probably during searches for base metals and gold. Examinations were made at this time by a number of geologists, including the senior author. In spite of high radioactivity, sampling returned only negligible uranium. The claims were allowed to lapse and the showings reverted to obscurity."

Jan 1, 1949

By Chris V. Sellathamby

Condition-based maintenance is replacing preventive maintenance in many industrial operations as a result of gains in productivity. Preventive maintenance is strictly time-based which means that as long as the prescribed time is sufficiently short, failures are prevented. The trade-offs between shorter cycles and increased downtime is a fine balancing act. Condition-based maintenance is gaining momentum as the more cost-effective and green solution to finding the optimal maintenance cycle and improving overall productivity. In the mining industry, various parameters of heavy equipment are monitored continuously to provide feedback for maintenance events. However, strain, shock, and vibration, key factors which lead to yielding and fatigue of metal parts, are not generally monitored by built-in systems, mainly due to the complexity of sensor installation and computational intensity of data processing. Scanimetrics has developed a stand-alone, add-on wireless system for measuring strain, shock, and vibration in heavy equipment and components, the data from which can be directly used to trigger maintenance events. The present system is being deployed in tar sands mining equipment. The system consists of a portable display and control unit, a software platform consisting of data management, sensor instrumentation and data analysis, and wireless strain sensor units, which can be easily installed on equipment. Data from the sensors can be gathered throughout the mine site, processed instantly, and used to generate condition-based maintenance events, improving overall uptime of the equipment and overall productivity of the mining operation.

Oct 1, 2010

By A. Khan, C. Ciriello, W. Oliveira

"The purpose of this paper is to demonstrate the value of Operational Readiness (OR) in the successful delivery of capital projects. OR can be captured using several technical and practical definitions:• To ensure that the capital project being delivered is capable of an effective start up, ramp-up as planned and a sustainable productive operation.• To function as intended when started, with the appropriate people able to run it.• To increase the value in delivering the product/service through established systems, processes and procedures, while simultaneously minimize risk to both the project and the business.Historically, mining and metallurgical capital projects concentrate efforts on cost and scheduling during the implementation and design phases. The completion and subsequent handover of the operational unit is the main objective.When reviewing the mining and metallurgical industry’s capital projects, it seems many poor results and errors in terms of project design and ramp-up are self-inflicted, with the project neglecting to account for key aspects of the future operational plant. Interestingly, if the problems for the future plant occur during project implementation, they can be prevented during the project phase. It is required to connect the operational knowledge with the project in order to ensure an effective start up and operation.The benefits of OR will be shown to be applicable not only to mining capital projects but also to sustaining and business transformation projects. The paper also includes industrial examples showing both proper and improper use of OR techniques.The paper will cover 3 main areas of Operational Readiness: the OR model, OR related risk elements (i.e., risks associated specifically with the improper execution of OR) and conclude with OR specific case studies."

Jan 1, 2016

By Curtis Rempel, John Bartlett, Alex Holtzapple

METSIM is a powerful program capable of modelling and simulating every known metallurgical and inorganic chemical process. METSIM is used by companies throughout the world to design, simulate and control operations from mine to tailings and everything in between. At its absolute simplest, METSIM can be used to create a process flowsheet. METSIM modules and built-in unit operations cover mass and energy balances for either steady-state or dynamic simulations of mine, stockpile, heap leach, material handling, comminution, beneficiation, hydrometallurgy, pyrometallurgy, gas and steam handling, and tailings management processes. Data for the material being processed can include mineralogy, particle size analysis, grade by size or multicomponent size analysis, washability data, mechanical, physical and thermodynamic properties. METSIM is written in APL (A Programming Language). Unlike C++, APL is simple and easy to learn, allowing the user to program whatever they can imagine, without first obtaining a degree in computer science. METSIM can also interface with EXCEL and other software through dynamic data exchange (DDE), allowing data to be imported and exported for viewing, analyzing and controlling. METSIM can answer simple or complex metallurgical and process questions allowing the user to predict and engineer without the issues of clumsy and tortuous spreadsheets.

Jan 1, 2014

By A. G. Beer

The evolution of microstructure is examined during the annealing of hot worked magnesium alloy AZ31. The influences of deformation and annealing conditions on the developed microstructures are assessed. It is found that annealing at a low temperature (300 °C), after deformation at a low temperature and strain rate (300 °C and 0.001 5-1 respectively), results in the development of abnormally large grains. With increasing values of Z (lower temperatures, higher strain rates), static recrystallization of the dynamically recrystallised structure takes place; smaller annealed grain sizes are attained and the time at which coarsening begins is reduced. Whilst both the deformation and annealing conditions influence the time it takes to reach a stable annealed microstructure, the grain size attained is governed solely by the prior deformation conditions employed.

Jan 1, 2006

By J. R. Perumareddi, V. S. Sastri, M. Elboujdaini

It is well known that high strength steels used in aerospace industry, are generally susceptible to hydrogen embrittlement during surface treatment such as electroplating with zinc on cadmium. Hydrogen embrittlement reduces ductility and results in brittle fracture rather than failure by plastic deformation. Hydrogen embrittlement of high strength steels is mitigated by surface treatment such as plating with other metals. Data on the hydrogen contents of steels before and after surface treatment by hot extraction-thermal conductivity, secondary ion mass spectrometry (SIMS) and UV-visible spectroscopy along with the mechanism are presented.

Jan 1, 2006

By G. Dodbiba, A. Otsuki, T. Fujita, J. Ponou, A. Shibayama

"The different types of nano to submicron particles, which are well-dispersed nano particles, coagulated nano particles or settled submicron particles, have been measured by the interactive force apparatus (IFA). The information is very useful for mineral processing treatment. The IFA can measure the particle size distribution in low to high concentration of particles in liquids and non-light transparent liquids. Here, mainly the emulsion and bubble size measurements are described.Emulsion (w/o type) is prepared with oil and water mixture. The nano to micro emulsion particle size is usually measured by light scattering method. The particle size distribution of emulsion of light oil measured by IFA agreed well with the one by the dynamic light scattering (DLS) method. The water size distribution in emulsions of gasoline is difficult for the small reflection index and C heavy oil is difficult for the black color by DLS method. The IFA can measure both emulsions.There are many methods to measure fine air bubbles, however, the finer nano size measurement apparatuses are DLS method and IFA. A “ghost” peak appeared in the large particle micron meter size in DLS method. The mean diameter in IFA is similar with DLS for the nano meter size. INTRODUCTIONParticle size distribution measurement of nano to submicron particle, emulsion and bubble size distribution are very useful for ultrafine particle separation and characterization of fine particles by the necessity of recent fine minerals separation (For example, Li et al.2016, Mikhlin et al.2016, Wang et al.2013). As for the size measurement of solid particles in liquids, three different types of nano to submicron particles, that are well-dispersed nano particles, coagulated nano particles or settled submicron particles, have been measured by the interactive force apparatus (IFA). The particle size distributions are compared with the one of dried particles measured by TEM or SEM. The well-dispersed nano particle size distribution by IFA is influenced by the nano size surfactant micelles and becomes smaller, when compared with the TEM result. The size distribution of nano size of magnetite particles in water is influenced by the isoelectric point and the mean diameter of coagulation becomes larger. The particle coagulation in diluted suspension is about 2nm smaller when compared with the higher concentration. The submicron nickel particle size distribution is well agreed the result by SEM. The coagulation effect is small in the submicron size of nickel powder in water (Fujita et al., 2013). In this paper, the emulsion and bubble size measurements are mainly described."

Jan 1, 2016

"Batch flotation testwork demonstrated that a low-grade chromite ore from Bird River, Manitoba, was best floated at pH 2 using Armac C (coco amine acetate) collector and sulphuric acid as pH modifier. A grind of 100% minus 150 um was necessary for liberation, and flotation selectivity was greatly enhanced by prior desliming. A concentrate analyzing 24.2% Cr203 with a recovery of 90.2% was obtained, after three cleaning stages, from ore grading 6.05% Cr203. Total rougher collector concentration was 500 g/t and cleaner collector concentration 380 g/t. Similar grade and recovery were obtained during the pitot-plant evalualion, when a concentrate analy zing 22.3% Cr203 with a recovery of 93% (based on deslimed feed) was obtained for a total collector addition of 630 g/t.Selective flotation in a region of positive surf ace charge implies anionic activation, and a possible flotation mechanism is suggested.IntroductionIn an earlier study(1) of the beneficiation of chromite ore from Bird River, Manitoba, several methods of beneficiation were explored. These included ore sorting, heavy-media separation, and gravity concentration with flotation using Armac C (coco amine acetate) collector at pH 2, and sulphuric acid as pH modifier. Because flotation was not fully evaluated, a laboratory study was undertaken to determine the optimum parameters of chromite flotation. Optimization of parameters was established first on a laboratory scale followed by confirmation a t the pilot -plant level. Flotation of chromite using Armac C and sulphuric acid as a pH modifier has been reported as being selective for low-grade chromite ores(2)."

Jan 1, 1990

By X. Cao, X. -G. Chen, K. Liu

As is well known, the standard Al-Cu 206 cast alloys have extremely low iron contents, usually less than 0.15 wt. %. Recently it is found that the iron contents of the 206 cast alloys can be extended up to 0.5 wt. % through the precise control of the iron-rich intermetallic phases. In the present work, the tensile fracture surfaces of the 206 cast alloys with various iron contents are systematically analyzed to understand the failure mechanisms. Results show that higher iron contents can reduce the tensile properties (especially the ductility) of the alloys mainly due to the increasing volume percent and size of the iron-rich intermetallics. Tensile failure mainly occurs at the iron-rich intermetallics/matrix interfaces for the platelet ß-Fe, but by the self-disassociation for the Chinese script a-Fe and Alm(FeMn). Cracking is easier to initiate and propagate along the longitudinal axis of the platelet intermetallics, but it can be deflected along the branches/arms of the Chinese script iron-rich phases, making the alloy more resistant to the propagation of the cracks, and thus the Chinese script iron-rich intermetallics are less harmful than platelet ß-Fe. In addition, it was also found that the Chinese script a-Fe has even a less damaging effect compared to the Chinese script Alm(FeMn) due to the relatively small size and compact morphology.

Jan 1, 2014

By G. E. Bogin, C. Strebinger, J. F. Brune

"Evidence shows that methane gas emanates from the mined-out area or gob of a longwall coal mine and can travel towards the working face, posing an explosion risk. Since the gob consists of varying levels of compacted rock, many researchers have modeled fluid flow through the gob as a Darcy-type porous media with a specified porosity and permeability. When studying methane gas explosions near the gob fringe, the Darcy flow assumption may not be applicable to describe the methane flame interaction with the gob. Computational fluid dynamic studies were performed modeling methane flame propagation across a simulated gob which was modeled as both a Darcy porous medium and as discrete rock objects with varying sphericity. Modeling the gob as a Darcy porous medium results in unrealistic methane flame propagation since the porous media assumption does not consider any differences in rock size and/or distribution. Additionally, the porous media model does not allow for ignition within and subsequent flame propagation through the porous medium, which must be modeled to understand the potential for methane gas explosions in the gob area. Modeling the gob as discrete rock objects produces more realistic methane flame dynamics and agrees with experimental observations. Modeling results show flame propagation across circles, hexagons, and squares, meant to represent rock rubble in the gob, produce different levels of turbulence which affects methane flame propagation velocity. This research demonstrates that modeling methane gas explosions in a longwall coal mine environment, specifically near the gob area, requires modeling obstacles, such as rock rubble, as discrete physical objects to capture the complex coupling of fluid dynamics, thermodynamics, and heat transfer. INTRODUCTION Although there are methods to mitigating methane accumulations in a longwall coal mine, explosive gas zones (EGZs) of methane and air may exist and pose an explosion risk to nearby miners and equipment (Brune, 2014) (Karacan, Ruiz, Cote, & Phipps, 2011). In the event of an explosion, the resulting methane flame and pressure wave can be catastrophic as evidenced by the Upper Big Branch explosion in 2010 that killed 29 miners (Page, et al., 2011). Since the mining process is transient, it is difficult to determine exactly where these EGZs exist, but investigative reports show in many cases, these EGZs can be near the working face, behind the shields, or within the gob area (Brune, 2014) (McKinney, et al., 2001). Additionally, miners have recounted seeing flames moving back and forth within the gob and under the roof supports (McKinney, et al., 2001) and in other cases, anecdotal evidence of hearing small pressure pops deep within the gob area (Brune, 2014)."

Jan 1, 2019

By A. Malfliet, A. Van den Bulck, D. Willems, M. Guo

The feed stock of copper fire refining processes consists of two major constituents: blister copper and high-Cu secondary scrap. A large fraction of this secondary scrap, originating from urban mining, is quite high in impurities such as Fe, Ni, Pb and Sn. Problems arise in electro-refining when these elements exceed certain limits. As a consequence, transformation of the secondary copper raw materials into high grade copper has become troublesome. However, the behavior of impurities relevant to fire refining conditions, essential for anode refineries, has not been studied in detail. Furthermore, limited research has been performed on the distribution of Ni between copper metal and slag. In this study, equilibration at 1300°C of liquid Cu-1wt.% Ni alloy and CaO-CuOx- FeOy-SiO2 slag in vacuum sealed quartz ampoules was performed for 12 hours, followed by water quenching. Electron Probe X-ray Microanalysis was employed to investigate the composition of the equilibrated alloy and slag. The distribution coefficients of Ni between slag and alloy were determined as a function of oxygen partial pressure and CaO concentration. INTRODUCTION Europe’s initiatives for a circular economy, pushing for resource-efficient ways for a sustainable future, puts Europe at the forefront of the globe. In Europe, 50% of the copper originates from recycling, being an excellent example of Europe’s circular economy (Juncker, 2018; Lacasse, 2018). High-grade copper recyclates are made available which regularly contain impurities like Fe, Ni, Sn and Pb. Aurubis Belgium is responsible for recycling these types of recyclates to anodes, cathodes and copper products. However, after fire refining of copper, the aforementioned impurities remain in the anode copper, leading to problems in electrorefining. During the fire refining of copper, a CaO-“Cu2O”-“Fe2O3”-SiO2 slag is used. Fundamental information of the distribution of impurities between the copper and this slag system is therefore essential to understand and improve the copper fire refining process at Aurubis Belgium.

Jan 1, 2019

Concentrator Improvements -1990-1995Back to Basics ?pilot plant versus plant opportunities identified ?understand process fundamentals & baseline -1996-2000Point ?C?Projects ?strategy to improve global competitiveness ?structure implemented to generate & drive ideas ?capital investment for life of mine asset renewal - 2001-200?Six Sigma Methodologies ?emphasis on data, measurements & analyses ?dedicated, highly trained personnel on projects 1990-1995 Improvement Phase??Philosophy??back to basics?approach?understand what each piece equipment needed to do?understand reagents, control variables?confirm operating strategies ??probe, stabilize, institutionalize??test theories, confirm with lab and plant trials?process stability (equipment reliability, controls)?enhanced operator guidelines, operator training?focus on continuous improvement?optimize existing equipment capability?stop looking for ?magic?solutions 1990-1995 Improvement Phase??Technical?finer grind, same equipment?optimize media size/shape to grinding application?balanced available ball mill power to applications?lowered cyclone feed densities where possible?improved selectivity, same equipment?balanced available cells to applications?streamlined process (eliminate process steps)?added cleaning stages where required?understanding pulp/mineral surface chemistry?lowered flotation pulp densities 1990-1995 Improvement Phase??Effort?numerous studies to understand process?liberation and mineralogical characterization?pulp and mineral surface chemistry?flotation kinetics and entrainment?extensive internal and external manpower?Brunswick, Noranda Technology Centre?CanMet, AMTEL, MinnovEx, Lakefield Research, McGill University?small capital expenditure

May 1, 2002

By E. Essadiqi, P. Poruks, D. Boyd, D. Emadi, I. Yakubtsov, T. Turi

This paper reviews the results of an extensive study of microstructures and mechanical properties in bainitic linepipe steels. The research was carried out as a collaborative project between Queen's, Stelco and CANMET. Basic studies of phase transformations and mechanical properties in these steels established important relationships between processing schedule and microstructure evolution, and between final microstructure and mechanical properties. The best combination of strength and toughness properties is obtained with a microstructure comprising a matrix of intragranularly-nucleated bainite (`acicular ferrite - AF') and small (~ 0.5 µm) dispersed particles of martensite (`M/A'). We describe this as a dual-phase AF+M/A microstructure. An experimental study on 15-mm thick plate determined the window of steel composition and processing parameters which gives the dual phase AF+M/A microstructure. The minimum strength and toughness properties for Grade 621 (X90) linepipe steel can be achieved by either a lean steel composition (0.04C-1.77Mn-0.04Cr¬0.32Mo-0.31Ni-0.29Cu-0.08Nb) with extreme processing parameters, or by a higher alloy composition (0.04C-2.07Mn-0.50Cr-0.51Mo-0.04Nb) with a more industrially realistic processing schedule. It is proposed how this approach could be extended to obtain higher strength linepipe grades.

Jan 1, 2005