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By Muhammed Şener, Ahmet Gültek

The flotation chemicals are important in mineral processing, and new progress is made in this area day by day. For sanidine purification, some commercial collectors, which can be harmful to the environment, are used. In that respect, the poly(amidoamine) (PAMAM) dendrimers, which are non-toxic for the environment, are good candidates for flotation applications. In this study, the second-generation PAMAM dendrimer was used as a collector to remove magnetite from sanidine by microflotation method, and obtained results were compared with commercial collectors. The results showed that the PAMAM dendrimer is an efficient and selective collector for magnetite. PAMAM adsorption mechanism was determined by zeta potential and FTIR spectra. According to the microflotation results, 87.76% of magnetite recovered at pH 8 by using PAMAM as a collector. It was found that the flotation recovery with the PAMAM dendrimers is similar to the Aero 704 between pH 2 and 6 but less between pH 6 and 9 and more between pH 9 and 12. All experiments were carried out five times and the standard deviation of all results was evaluated with p = 0.05 confidence interval. The second-generation PAMAM dendrimers can be an alternative flotation chemical to the commercial ones concerning usability at a wide pH range, recovery potential, and environmentally benign.

Apr 28, 2023

By Remo Grandori

"INTRODUCTIONDouble Shield TBMs were introduced in the market in the early seventies with three main targets:• Increase the TBM performances in term of advance per day thanks to the ability to erect a segmental lining simultaneously with the excavation phase.• Be able to advance through unstable and disturbed rocks under the protection of the shields• Provide a finished tunnel by installing a precast lining as the TBM advance.In 2003 SELI developed the design of the Double Shield Universal (DSU) TBM as an evolution of the original Double Shield TBM design.This new TBM design was targeted to improve: the TBM capability to advance through squeezing/converging rock formations under high cover, the telescopic joint design (allowing by such to operate the machine in double shield mode in very weak rock), the capability of the TBM to investigate and treat the ground around and ahead of the tunnel face.In the same lapse of time Single Shield TBMs, originally utilized for soft ground tunnelling, extended progressively their range of application to mix rocks and finally to hard rock tunnelling with increasing performances.This also thanks to the substantial reduction in the installation time of the segmental lining ring that contributed to minimize the TBM stand by time between two consecutive boring strokes.Today the choice between the two types of TBMs needs to be carefully evaluated project by project since one type of TBM may “prevail” in certain geologies and diameters and vice versa.THE VISHNUGAD PIPALKOTI TUNNELThe Vishnugad Pipalkoti Tunnel is part of the 444 MW Vishnugad Pipalkoti Hydro Electric Project (VPHEP) on Alaknanda river in Uttarakhand (India).The Owner is the Indian electric company “Tehry Hydro Development Corporation” (THDC) and the World Bank finances the project.The Headrace Tunnel total length is 13.4 Km and a section of about 12,3km will be excavated by TBM by SELI Overseas (Italy) in subcontract to HCC (India) the General Contractor for the project. The TBM will be delivered ex workshop in March 2016 and it is foreseen to start boring in the second half of 2016.Figure 1 below shows the location of the project and the following Table 1 summarizes the geometrical characteristics of the TBM tunnel."

Jan 1, 2016

By K. K. Panthi, P. K. Shrestha

"Displacement of rock mass around a tunnel opening varies according to the rock mass properties, insitu stress conditions and applied support in the tunnel. Such displacement is also altered by presence of bands of rock mass that differ in properties. This paper focuses on the deformation behavior of rock mass around tunnel openings at four tunnel sections in Kaligandaki headrace tunnel where extensive instrumentation was done. Based on the actually measured tunnel displacement records and actually measured support pressure; back analysis has been done to estimate rock mass properties and insitu stresses. Numerical analysis has been done to analyze and assess the deformation behavior of the rock mass around the tunnel sections.INTRODUCTION Instrumentation and monitoring of tunnel convergences have significant importance in evaluation of tunnel stability. One of the key aspects of monitored data is that early convergences can be used in estimation of long term convergence. In addition, these data can also be used in evaluation of rock mass parameters and in-situ stresses around the tunnel. Convergence around a tunnel periphery may vary according to rock mass quality. Presence of bands of different rock mass may hinder the displacement pattern in the tunnel. Particularly, displacement characteristic of tunnel periphery in schistose, foliated and deformed rock mass is altered by presence of bands of comparatively stronger rock mass, e.g., quartz veins or presence of shear seams or faults. Similar observations were also recorded in monitored tunnel sections in Kaligandaki headrace tunnel, located in the Nepal Himalayas. Extensive monitoring was done by installing multiple point borehole extensometers (MPBX) at three different locations of the tunnel periphery at four different tunnel sections. In addition, convergence measurements by tape extensometers and installation of pressure cells to record support pressures were also carried out at each of the tunnel sections. Observations showed that the tunnel convergences varied according to rock mass quality, in-situ stress and effective support pressure.Rock mass parameters and stresses have significant role in the extent of tunnel deformation, but these parameters are often unknown or difficult to predict. Back analysis based on actual tunnel displacement records and known support pressure is believed to be an important method in such endeavor. This paper performs back analysis to evaluate rock mass parameters and discusses correlation of rock mass behavior with tunnel deformation and applied support. For this purpose, the rock mass parameters are estimated from actual tunnel displacement records, mapped rock mass quality records and laboratory tested data. Then, numerical modelling is conducted to correlate post peak behavior of the rock mass with actual tunnel displacement."

Jan 1, 2015

By Adrian Dance

Newmont Mining Corporation?s Carlin (?Carlin?) operation processes roaster feed through a double rotator, dry grinding mill following secondary crushing. Metso Process Technology & Innovation (?PTI?) was involved in a review of crushing and dry grinding circuit operations in August 2009. A number of opportunities for increased throughput were identified in the PTI study. Extended plant trials were conducted in July 2010 to provide justification for possible circuit modifications and if needed, additional equipment. The trials confirmed that a finer crusher product would reduce the build-up of material ahead of the coarse grinding chamber in the double-rotator. Also revealed were material transport and airflow restrictions in the dry grinding circuit that resulted in a high circulating load. The secondary crushing plant demonstrated it was capable of reducing the amount of +¾? material in the mill feed thus increasing dry grinding throughput. However, wet and sticky feed affected screening efficiency resulting in low utilisation of the existing crusher capacity. The open circuit configuration also made it difficult to control crushing circuit product size. For the dry grinding circuit, changes in grinding media size, transfer grate design and increased airflow were recommended to reduce circulating load issues and increase circuit capacity. This paper summarises the crushing and grinding circuit review, the extended site trials performed by PTI and the improvements in dry grinding operation that resulted from this study.

Jan 1, 2012

By J. Worden, D. Hughes, S. Smart, H. Zughbi

The enterprise wide optimization (EWO) of steelmaking and manufacturing is a multi-level, hierarchical problem which spans higher level corporate planning and scheduling through to the lower level operations of processes that produce and manufacture steel. External and internal system dynamics combined with process unit co-ordination create complex changing circumstances for the enterprise. This paper presents a scoping study as a prelude to enterprise wide considerations at an integrated steelworks to help inform the choice of appropriate model types and optimization techniques. The hierarchical, multi-level structure of the enterprise and the important spatial-temporal scales to consider are defined. Insights into the system were gained by analyzing a large set of dynamic operational data. Over two years of data were subject to both univariate and multivariate analysis with the intent of understanding the complex interrelations of energy flows on site, the inherent system dynamics of the energy network, system operational modes, aspects of planning and scheduling and the coordination between major processing units. This analysis was further used to evaluate the performance of the system in regards to energy utilization and understand the potential economic benefits derived from improved operational decisions.

Jan 1, 2015

By Reichmuth, Donald R.

Most brittle solids are relatively weak in tension and this weakness can be very significant in determining their performance in structures and excavations. Consequently, accurate knowledge of the tensile strength of brittle materials has long been recognized as important. In the past, measurements of the tensile strength of materials such as concrete, ceramics, and particularly rock have been hindered by problems encountered in fabricating test specimens and in accurately loading them. These difficulties have resulted in a scarcity of published tensile strength data. This can be readily seen in tabulations such as Wuerker's "Annotated Tables of Strength and Elastic Properties of Rocks.

Jan 1, 1968

By M Frenzel

At the last MassMin Conference in Sudbury, Caterpillar’s vision of a continuous mining concept for block caving operations was presented on the background of global raw material demand and its continuous increase. By analysing today’s structure of mining processes in block caving, the paper (Krings, Steinberg and Frenzel, 2012) highlighted the main bottlenecks in the process chain and identified conceptual solutions by help of a case study. The main focus was the paradigm shift from discontinuous batch type operation to a continuous mining process of the blocks.In 2016, the strategic vision has taken major strides forwards and remote continuous operation has become a reality. Caterpillar’s continuous operation system – the Rock Flow system – was successfully installed in Codelco’s Andina mine and start of operation is scheduled in the first half of 2016.Based on continuous product developments, this paper sets the focus on two main aspects of continuous mining. First, field experiences of the Rock Flow system will be shared, highlighting the Andina project course from system installation, to commissioning and successful system start. The second aspect concentrates on the system and mine layout as discussed in the case study scenario in MassMin 2012 (Krings, Steinberg and Frenzel, 2012).Based on Caterpillar`s continuous product development, the Rock Flow system set-up and panel design were modified for a general roadway design and drawpoint layout. The new design allows an optimised use in block preparation phase (spreading) and full production phase (reaping), operating a fleet of load-haul-dumps (LHDs) and Rock Flow systems. The combined use of the two technologies optimises the mining process in every stage of block life and significantly increases the performance of the continuous block caving operation in the production panel to pave the road for the next generation of super caves.CITATION:Frenzel, M, 2016. New continuous production system in block cave mining – the rock flow system, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 543–548 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By C M. Stewart, P Bowen

McArthur River Mine, in the Gulf Country of the Northern Territory, exploits one of worldÆs largest deposits of zinc, lead and silver. It was officially opened in September 1995, 40 years after its discovery in 1955. This paper describes the geological, engineering and metallurgical assessments which made up the feasibility study. It then relates how these study components compare with the first two years of operation. The challenges that had to be overcome before the McArthur River Mine became economically viable included the metallurgical problems associated with extremely fine grained ore and the development of an effective mining process.

Jan 1, 1998

By K C. Corin, N Ndamase, M Tadie

Mining operations in arid regions are compelled to reduce their consumption of fresh water. Closed water circuits are an attractive solution and, in addition to reducing freshwater consumption, have the added benefit of reducing reagent consumption as well as the environmental impact by eliminating effluent discharge. Accumulating ionic species have been shown to hinder collector adsorption which reduces the recovery of valuable minerals. Numerous studies have investigated the effect of degrading water quality on collector adsorption however there is very limited understanding as to how this takes place from an electrochemical perspective. This study therefore aims to investigate how the presence of accumulating ionic species at varying concentrations affects the electrochemical adsorption of sodium ethyl xanthate onto galena. The synthetic plant water used in this study comprised of single salt solutions to isolate the effects of the ionic species of interest. The ionic strengths were varied between 0.0242 M, 0.0727 M, 0.1212 M and 0.2426 M which correspond to University of Cape Town (UCT) Centre for Minerals Research (CMR) synthetic plant waters of 1, 3, 5 and 10SPW, respectively. Mineral rest potentials indicated how changing water quality affected xanthate-mineral interactions. Microflotation observed the impact of changing water quality on mineral floatability.

Aug 24, 2022

By AIME AIME

AMONG the European nations Germany is the center of interest economically as well as politically, and of prime importance for Europe as a whole is Germany's capacity to produce mineral products for armament and for export in exchange for the import of the essential supplies to maintain its industries. So far as minerals are concerned, Germany is worse off than any other great power except Italy, and deficiencies are being met by attempts to increase output from local deposits and by greater use of substitutes derived from domestic raw materials to replace imported metals, petroleum products, and other minerals.

Jan 1, 1939

By Catharine L. VanOmmeren

Emulsion quality characteristics such as shelf life, handling, and sensitivity are critical to the end-user. It is therefore important that the consumer be prepared to ask his supplier specific questions. To do so, he needs to have a basic understanding of what an emulsion is and how emulsion properties can affect safety, performance, and environmental impact. The criteria to be covered include: energy, velocity, sensitivity, minimum priming, shelf life, pumpability, effect of AN quality, over-the-road handling, and formulation The consumer will learn how each of these properties can directly affect him. The information will enable him to set minimum standards in product selection, blending, and application.

Jan 1, 1989

By S J. Loach

F-Series reconciliations are formal comparisons of estimates and measurements of ore quantity and quality made at pre-determined points along the mining value chain. F1 is the ratio of ‘Depleted Grade Control Ore/Depleted Long-term Model Ore’ and validates the models upon which Resource and Reserve statements are based. F2 is the ratio of ‘Produced Tonnes and Grade/Depleted Grade Control Ore (-) Changes in Pre-Crusher Stockpiles’ and validates that the ore tonnes and grade delineated in the pit are being accurately extracted and correctly delivered to the processing plant. These factors provide important corporate assurance for a mining company by providing quantitative feedback on model-predicted tonnes and block grade estimates. Since 2009, BHPs Western Australian Iron Ore F-Series reconciliations have been calculated in a single, centralised sequel-server database. This software routinely collates data regarding mineral resource block model depletions, grade control model depletions, pre-crusher stockpile inventories and production tonnes and grade measurements and then calculates F-Series factors for both tonnes and product quality. This paper will present case studies where reconciliation factors were used to identify improvement opportunities leading to projects that improved our models and subsequent forecasts of production tonnes and quality. In addition, it will show how reconciliation factors are tools that monitor control during periods of rapid change and provide feedback on the effectiveness of improvement projects.

Sep 18, 2023

By J. -M. Lalancette, D. Lemieux, C. Chouinard

"A gold bearing concentrate containing 107 g/T of gold, 9.3% copper and 706 ppm of mercury was processed at the demonstration scale for the extraction of gold and copper using a cyanide free process. The concentrate was generated through flotation to upgrade the gold and copper grade, but also showed contamination with mercury. This concentrate was submitted to the DST process demonstration plant. The concentrate was first oxidized using a fluidized bed to produce a calcine. The mercury was volatilized during the oxidation stage with an efficiency higher than 98%. The mercury was condensed and removed from the sulfuric acid using a thiosulphate process. Copper was extracted from the calcine as copper sulphate using diluted sulfuric acid. The solid remaining after acid leaching was submitted to the DST chlorination process for gold extraction. Under optimized conditions, a gold extraction of 97.3% was achieved in the chlorination reactor. Gold was recovered from the pregnant brine by precipitation on silica using a DST proprietary process.INTRODUCTION Dundee Sustainable Technologies Inc. (DST) offers proprietary metallurgical processes for the treatment of material from the mining industry. DST processes enable the extraction of precious metals and for the removal and stabilization of contaminants, such as arsenic, from ores and concentrates. DST provides environmentally-friendly, viable and efficient processes, capable of handling complex and refractory ores which cannot be processed with conventional approaches due to metallurgical issues or environmental considerations. Several mining jurisdictions around the world have banned or restricted the use of cyanide. DST has developed a closed loop chlorination process as an alternative to the conventional cyanidation process for the extraction of precious metals from minerals. The tailings from the process are inert from toxic substances such as cyanide and organic compounds, are sulphide depleted which means they do not generate acid, and thus, meet and/or exceed environmental norms. The process has demonstrated excellent gold recoveries within a fraction of the time needed for cyanidation to obtain similar results. Moreover, the closed loop process does not generate any liquid effluent and does not consume much water: it only requires a water make-up to compensate for moisture leaving with the tailings and by-products, and seawater may be used. The improved environmental footprint of the DST process has been certified by the Environment Technology Validation program (ETV) which provides an independent evaluation of the performance claims of innovative technologies."

Jan 1, 2017

By G. J. Perrott, H. W. Clark

During the course of the cooperative smoke abatement investigation carried on by the Bureau of Mines , the city of Salt Lake and the University of Utah during 1919-1920 , a study was made as to the suitability of Utah coals for by-product coking with particular reference to low temperature coking . was done because it was realized that a smokeless fuel for domestic consumers was the best remedy for this class of smoke producer . A report of the technical side of the work was included in the final report of the cooperative investiga- Since this report was written (June 1 , 1920) further work has been done by other investigators .

Apr 1, 1922

By D Connelly

Quartz deposits are common in nature but the presence of quartz suitable for yielding high purity quartz is exceedingly rare. This paper describes a test work study on producing high purity quartz (HPQ) product to meet the tight product specifications of greater than 99.97per cent, including four and even five nines, for uses including, lighting and fibre optics and modern-day high efficiency solar panels. Due to demand in renewable energy applications the market for high purity silica solar panels known for their increasing efficiency and durability is rapidly growing. Demand continues to rise for the use of high purity quartz in semiconductors, electronics, imaging and sensor markets. Microelectronic components are created by chemically fabricating wafers of semiconductors such as silicon to obtain the desired transport of electrical charge and control of the current. The production of silicon metal from high purity quartz has been designated a Strategic Mineral by the European Commission and by the US Department of Justice due to the growing significance of this metal in various industries. The subsequent processing of quartz is the key step to adding value and aiding technological advances. Overall, the high purity quartz market is a highly secretive, specialised market with increasing opportunities for stakeholders. The attempt to produce HPQ in this work was carried out using an Australian quartz ore following a typical HPQ process flow sheet. The unit processes included primary crushing, scrubbing, magnetic separation, flotation, acid leaching followed by hot chlorination. The results indicate that grinding of quartz requires specialist equipment due to the hardness and extreme abrasiveness of the ore leading to additional iron contamination in the ground ore. The critical impurities were aluminium, iron, sodium, potassium, lithium, titanium, zircon, calcium and magnesium. The chemical refining was found effective. The hot chlorination process needed to be done at 1200°C in a chlorine – hydrogen chloride gas atmosphere. The risk of any gas being released during this stage is very serious and only specialist companies should and can carry out this step. More recent studies reported many new options that appear to facilitate the production of HPQ with the requisite purities more easily, but costly equipment along with highly trained operators are required and hence unlikely to become available in standard metallurgical laboratories any time soon.

Sep 1, 2024

By William F. Tanner

A river delivers a given load of sand, and hence of heavy minerals, into the sea into which it empties. This load is fixed by drainage basin characteristics and processes. Wave energy available for redistributing that load is fixed in an entirely different way. An equilibrium diagram of these two parameters (load versus energy) permits a tentative prediction of what will happen to the heavy minerals. The Chattahoochee River delivers a load which, over the past few thousand years, appears to have been greater than the available coastal energy could handle. As a result, much of the sand has been accumulated in various delta-margin features: barrier islands, beach ridges, and large furrowed off-shore shoals. The bulk of the trapped sand is found today in the shoals, which are attractive deposits for possible exploitation. If coastal energy levels are high enough to move the total load delivered by the river, accumulations of sand (and hence of heavy minerals) should be sought in the down-drift direction. Energy levels are rarely constant over any great length of coast. Decreases in energy may be due to widening of the shelf, convexity of, the shore, restrictions on the fetch, wave decay, or other causes. Such decreases result In deposition. Hydrodynamic mapping of coastal areas, as outlined here, should prove useful in the location of additional reserves. Part of this type of work can be done on maps, charts, and air photos.

Jan 1, 1962

By K. Boakye, T. Newman, P. Bláha, M. B. Toelle

"This paper presents a quarry optimization plan using a block model and an in-house development quarry scheduling and optimization software (QSO Expert) to help improve quarry operations at Crystal River. The Crystal River Quarry is an underwater quarrying operation that barges limestone via the Gulf of Mexico, as the main source of raw material to a cement plant in Theodore, Alabama. To improve the quarry operation, an evaluation was completed to optimize the quarry planning and extraction procedures of the quarry. In order to achieve this, additional exploration drilling campaign was implemented, a new block model was re-calculated and the latest version of QSO Expert software was used. The primary economic impact is a higher recovery of limestone reserves; sustainability of resources, corresponding longer quarry life. Secondarily as the limestone is mined underwater and stockpiled above water, drainage reduces moisture content achieving direct cost reduction on limestone shipping. In addition, a considerable reduction in operational cost was achieved due to a significant decrease in consumption of electrical energy, reduced dragline maintenance costs and reduced dragline movements within the operation. INTRODUCTION Holcim is a Swiss-based global building materials and aggregates company. Founded in 1912, the company expanded into France and then throughout Europe and Middle East during the 1920s. In 1922, Holderbank, as the company was then known, expanded beyond the Swiss borders into France. By the end of the decade Holderbank held stakes in Belgium, Germany, the Netherlands, and Egypt (Holcim History 1912-2012) Positions in Lebanon and South Africa soon followed.. Holder bank later expanded in North America in the 1950’s. In the late 1970s and early 1980s, Holderbank continued its expansion in Latin America, Asia and Spain for the first time. The company expanded into Eastern Europe and experienced a boom in Spanish construction preceding the 1992 Summer Olympics. By 1986, Holderbank was the world's largest cement manufacturer. In the 1990s, the company consolidated its European holdings as the American market drove growth. Expansion into Eastern Europe and Russia continued (Holcim History 1912-2012). In 2001, the company changed its name from ""Holderbank Financière Glaris"" to Holcim (short for Holderbank ciment) (Holcim History 1912-2012). Holcim expanded by purchasing Aggregate Industries entering into the United Kingdom for the first time. That year, the company also expanded into India by acquiring a stakes in The Associated Cement Companies (ACC) and Ambuja Cement Eastern. In 2008, Holcim became the largest shareholder of China's Huaxin Cement with a 40% stake. In 2009, they acquired Cemex Australia. In 2014, Holcim and Lafarge announced they had agreed to terms on a ""merger of equals"" valued at nearly $50 billion in 2015. The new company LafargeHolcim based in Switzerland has a manufacturing capacity of 427 metric million tons a year."

Jan 1, 2017

In high stress mining environments, production drill rigs are often employed for rapid drilling of boreholes for systematic cable bolting. One outcome of this drilling method is the need for larger boreholes than would normally be drilled using customised bolting machines, such as the Tamrock Cabolter. Past laboratory studies indicate that, under ideal grouting conditions, borehole diameter has little effect on the pull-out strength of cable bolts with high bulb densities. However, the sensitivity of pull-out strength to large boreholes and less ideal variations of grout strength have not been investigated. To explore these sensitivities, industry standard single embedment tests were conducted on large boreholes simulated using steel pipes. Four borehole diameters were tested, namely: 42 mm, 52 mm, 81 mm and 106 mm. In each case the grout water to cement ratio was varied from 0.35 to 0.45 and two cable bolt bulb spacings were considered, namely: one and three bulbs per metre. The results indicate that, across the range of parameters tested, variations in peak axial load at failure corresponding to changes in hole diameter were statistically insignificant.

Nov 25, 2010

By Alban Lynch, Benigno Aquino, Hakan Dündar, Alexander Kalugin, Marco Delgado, Alberto Palomino, Ali Türkistanli

Dynamic separators are efficient dry classifiers because new designs during the last 50 years have reduced the by-pass and improved the partition curve. By contrast cyclones have been used as classifiers in wet grinding circuits for 50 years but without serious change and the early problems which were caused by high and variable by-pass, and different mineral specific gravities, still exist. High frequency screens are now used for wet separation and the operating characteristics of closed grinding circuits using cyclones or screens are discussed. Data come from circuits at the Condestable, Cerro Lindo, El Brocal and Catalina Huanca mines in Peru, the Eczacibasi mine in Turkey, and the Apatit mine in central Kola Peninsula in Russia. All classifier data are described by their partition curves and all mill data by their breakage rates. With cyclones the by-pass, d50, and sharpness of the partition curve change as operating conditions change but with high frequency screens the values vary little because the by-pass is low, the sharpness is high, and d50 depends on the aperture size. Data from all plants indicate that lower by-pass and sharper separation improve breakage rates and throughputs. An initial model of the screen is proposed.

Jan 1, 2014

By L. Wilfley, G. A. Calboreanu

"Wear resistant 25% Cr hard cast iron is a heterogeneous material containing 1,600 HV hard chromium carbides embedded into martensitic matrix. It is the most used cast alloy in wear operations of mining industry, chemical industry, fracking, etc. During the last decade the hard iron manufacturers increased wear resistance in the following ways: • Reduce / eliminate harmful retained austenite and chromium + carbon depleted areas especially within eutectic carbide cells. In Max5A the improved 25% Cr alloy brittle carbide eutectic cells are removed which increases toughness. • Delay delamination between chromium carbides and matrix particularly during sliding abrasion wear. Delamination commences at the weakest chromium carbide – matrix contact lines exposing chromium carbide to localized bending stresses which gradually chip carbides away. Once the chromium carbide base is removed accelerated wear degradation occurs. • Evenly randomize and avoid discontinuities in the chromium carbide network. When chromium carbides are perpendicularly positioned to the wear surface wear rate is minimized. On the contrary the highest wear rate takes place when 3D oriented chromium carbides are parallel with the wear surface. In this case chromium carbides cover top network discontinuities being just matrix supported which leads to rapid carbide cracking. The new hard iron discussed in this paper fulfils and exceeds the above requirements increasing the casting service life around 250% in various wear operations. Physical and mechanical properties of Max5A are compared with well manufactured Industry Standard 25% Cr hard iron. The paper presents practical accomplishments obtained in the USA, South America and India. INTRODUCTION The chemical composition of Max5A and Industry Standard 25% Cr are identical like specified by ASTM A532 Class III Type A requesting C = 2.0-3.3% and Cr = 23.0-30.0%. Manganese, silicon, nickel, molybdenum and copper contents are limited by maximum accepted quantities.[1] According to published data the eutectic chromium carbides chemical composition of 25% Cr hard iron is Cr = 54% and C = 8% which indicates strong depletion of chromium and carbon along chromium carbide - matrix interfaces. [2] The optimized Max5A microstructure has minimized retained austenite, is devoid of harmful carbide eutectic cells and has the most advantageous chromium carbide and secondary chromium carbide morphology. This favorable microstructure increases wear resistance, mechanical properties and corrosion resistance. The paper compares the Max5A microscopic features and mechanical – physical properties with similar properties of high quality Industry Standard 25% Cr."

Jan 1, 2017