Metallurgical Quality Research Articles

Fracture Analysis of the Chain Pin Shaft of an Escalator Ladder

This study analyzed the cause of fracture for the chain pin shaft of an escalator ladder, and found that the pin material satisfied the chemical composition content requirements of the GB 20CrMo steel standard and similar to ASTM A29/A29M-2012 grade 4120. Abnormal metallurgical quality defects were not found in the pin. The pin shaft was carburized, and internal oxidation defects were not observed on the surface as a result of carburization. The internal structure of the material was uneven, there existed a mixed grain structure, and the martensite structure was coarse at particular regions, to seven grade. Additionally, the martensite structure in the carburized layer was slightly coarser, four to five grade, which had an adverse effect on the pin strength. The pin break was a fatigue fracture caused by multiple cumulative damages. The fracture originated on the surface of the pin, and may have been caused by indentation on the pin’s surface.

Study on micro-structure, solid solubility and tensile properties of 5A90 Al–Li alloy cast by low-frequency electromagnetic casting processing

In this paper, the low-frequency electromagnetic casting (LFEC) processing was introduced as an efficient pollution-free casting technique, and how it influenced the micro-structure and mechanical properties of 5A90 Al–Li alloy was investigated. The mechanical properties of the alloy had a close connection with the casting metallurgical quality and the precipitation phases. Compared to the conventional direct chill casting (DCC), the LFEC could promote the precipitate of the δ′ (Al3Li)/β′ (Al3Zr) and reduce the width of PFZ, which enhanced the effect of the precipitation strengthen and alleviated the strain localization. Meanwhile, the micro-structure of the ingot was refined significantly and the metallurgical quality was improved after LFEC treatment due to the modification of the flow and temperature field of the sump that caused by the application of low-frequency electromagnetic field. Maximum yield strength and ultimate tensile strength of as-aged alloy cast by LFEC with 150 A/15 Hz could reach 371.85 MPa and 495.5 MPa, while elongation remained at 9.82%.

Effect of solid solution phase constitution on dissimilar Al/Cu FSW using Zn as an alloying element at the joint interface

The effect of Al/Zn/Cu binary and ternary solid solution phase constituents on metallurgical and mechanical properties of Al/Cu dissimilar friction stir welding using Zn as an alloying element was investigated. Because of Zn interlayer material binary intermetallic compounds (IMCs) such as AlCu, Al2Cu, Al.71Zn.29, CuZn5 and ternary IMCs such as Al4.2Cu3.2Zn.7 are formed. These solid solution alloying phase constituents improved the weld properties of the joint. The tensile strength was enhanced by 13% for Zn alloying specimens compared with non-alloyed weld specimen and 104% of the Al base material due to the formation of thin and controlled IMCs and solid solution phase constitution strengthening as well as Orowan strengthening. The fractured surface with Zn alloying element suggested combination of ductile–brittle fracture and indicated transgranular failure. Micro-hardness with Zn alloying specimen is higher compared to the non-alloyed specimen for the existence of different IMCs at the stir-zone. The mapping analysis indicated that the thickness of the IMCs with Zn alloying was at micro-meter level. Phase constituent revealed that thin continuous and uniformly distributed binary and ternary phases are beneficial for the enhancement of mechanical and metallurgical qualities. Macrostructural views revealed variation in IMCs flows at non-alloyed and Zn alloying cases. Different weld zone reflected grain variations and finer grain at the weld nugget due to the nucleating effect of Zn interlayer.

AFM Study of Pyrite Oxidation and Xanthate Adsorption in the Presence of Seawater Salts

The effect of seawater ions presents a great challenge to theories about mechanisms of pyrite oxidation, collector adsorption, and surface reactions. As the use of seawater is key to the sustainability of the mining industry in regions without fresh water, there is a need to study the surfaces of minerals and products that are formed in the presence of seawater salts. In this study, atomic force microscopy (AFM) was used to analyze the topography of pyrite surfaces subjected to treatments, including oxidation and exposure to xanthate and solutions of seawater salts and xanthate, at pH 8.5. Topographic details were related to surface products. The results showed that xanthate was adsorbed without hindrance on oxide-free pyrite which validated one well-known model. The results also showed that pyrite oxidized forming a structure of interconnected pillars and that xanthate was adsorbed on the top and skirt of these pillars; the experimental evidence on the increase in the height and width of these pillars validated another well-known model. In the presence of seawater salts, the cations covered the surface of the pyrite, suppressing collector adsorption regardless of the dose. The results are expected to help in decisions about the flotation of sulfide minerals in water with limited metallurgical quality.

Effect Of Temperature And Micro structural Evolution Of Magnesium And Aluminium Alloy Using Vacuum Diffusion Bonding

This work is directed to acquire better understanding and portrayal of the dissemination holding of comparable and disparate metals. It additionally meant to get ideal parameters for dispersion holding of aluminum covering over magnesium compound with Aluminum composite. This work targets building up a basic strategy to get dispersion holding joints at moderately not ease. On one hand, the exploration is expected to set up a strategy. This technique is concocted to contemplate the physical wonders that have huge effect on dissemination holding, for example, time, temperature, weight on joints and metallurgical qualities. Elastic and shear tests are to be directed. This work is directed to acquire better understanding and portrayal of the dispersion holding of comparable and unique metals. It likewise intended to ge t ideal parameters for dissemination holding of aluminum covering over magnesium combination with aluminum composite. These two metals are jointed inside the kick the bucket in the wake of completing surface treatment. At that point the bite the dust is kept inside the dispersion holding machine by shifting the time, temperature, weight by methods for burden.

TES-PS10 postmortem tests: Carbon steel corrosion performance exposed to molten salts under relevant operation conditions and lessons learnt for commercial scale-up

Abstract Postmortem tests were performed over components removed from the TES-PS10 pilot plant after almost four years of continuous operation being exposed to solar salts under representative commercial operation conditions. Accordingly, corrosion performance of plates sections extracted from both storage tanks and samples cut from the hot molten salts pump were evaluated. Corrosion damage extension, oxides layers morphology, and corrosion products chemistry were analyzed by X-ray diffraction, energy dispersive X-ray spectrometry, optical microscopy, and SEM. In addition to materials compatibility with molten salts, mechanical tests were carried out over the storage tanks plates sections. Although the corrosion damage extension over the plates extracted from storage tanks was low and the mechanical properties were according to the standard, some interesting observations were seen. For example, a sample extracted from the hot storage tank and exposed to intermittent contact with molten salts showed some areas characterized by the growth of a non-protective oxide scale. Moreover, localized corrosion with slight penetration through the base material was identified for all storage plates samples under evaluation. On the other hand, the molten salt pump parts under study showed adherent and uniform oxides layers without detecting corrosion–erosion phenomena. Some cavities were found in the discharge elbow, and these imperfections were associated to a bad metallurgical quality during casting. Summarizing, corrosion phenomena suffered by the components under evaluation could be corrected in future plants by applying the lessons learned discussed in this study. As conclusion, materials selection analyzed within this postmortem evaluation is valid from the corrosion point of view to be used in the design of commercial TES systems in PTC plants.

Solderability of AZ31B Magnesium Alloy Coated by Copper and Strength of the Solder Joints

Magnesium alloys are promising as light materials, while their high chemical reactivity makes them difficult to be soldered. In this study, the AZ31B alloy was pretreated by zincification and coated by an electrodeposited Cu layer, and then soldered with Sn-58Bi solder in air furnace. The microstructure and properties of the AZ31B/Cu(Zn)/SnBi solder joints were characterized to evaluate the solderability of the Cu-coated Mg alloy and the influence of soldering on the Cu coating. It was found that the Cu coating is dense, and little defect exists along the Cu(Zn)/AZ31B interface. The soldering process has little negative effect on the bonding between the Cu coating and the AZ31B substrate, and the AZ31B/Cu(Zn)/SnBi solder joints of high metallurgical quality were obtained. Tensile fracture of the solder joint occurs mainly in the solder, with no peeling of the Cu coating. Under shear loading, cracks initiate inside the SnBi solder and the final fracture of the joint occurs around the Cu6Sn5/solder interface or along the Cu(Zn)/AZ31B interface. The tensile and shear strength of the AZ31B/Cu(Zn)/SnBi solder joints are close to that of the SnBi/Cu solder joints. It is demonstrated that the Cu-coated Mg alloy shows superior solderability and can be soldered by the Sn-based low-melting solder in air.

Study on Solidification Process of ZL114A Wheel Casting

In this paper, three different solidification process design schemes of the ZL114A wheel casting are discussed, in according with the comparative analysis of metallurgical quality statistics, a solidification order from bottom to top and from outside to inside is attained by adjusting the chiller material and reducing the pouring temperature, which meets the HB963-2005IIcasting standards. The average tensile strength, yield strength and elongation of the T6 state are 340MPa, 260MPa and 6.5% respectively after the T6 heat treatment and the low temperature stabilization process. The average grain size of the primary α-Al matrix is about 86μm after adding 0.11%Sb element, the morphology of the binary and ternary eutectic Si phases that distributed nearby the grain boundary are spherical and elliptical, the fracture mechanism of T6 state shows a typical dimple fracture.

Experience in the Development of Production of Rolled Stock from Microalloyed Steels for Shipbuilding by NLMK DanSteel

Due to general trends in the development of the heavy plate market in the segments of shipbuilding and marine engineering, as well as on the base of the rolling mill 4200, NLMK DanSteel has developed chemical compositions and mastered the production technology of rolled products with a thickness up to 55 mm from low carbon microalloyed steels of grades D36, D40, and D420 in the state of delivery after normalizing rolling (+NR). The developed gauge is actively used in the process of construction of cruise liners. The following aspects have been tested: the metallurgical quality of experimental-industrial, certification, and production lots of heavy plates that have a required strength level, low-temperature impact toughness at –20°C over the entire thickness; a high level of joint mechanical characteristics during welding with the use of various methods at a heat range from 15 ± 1 to 50 ± 2 kJ/cm. The developed steels remain at the required level of strength characteristics after the heat treatment at a soaking temperature above Ac3; and they are recommended for warm (580–600°C) and hot (900–940°C) forming. The results of the examinations have enabled NLMK DanSteel to pass certification tests according to the IACS rules and to confirm the quality of rolled products in accordance with the requirements of DNV-GL, RINA, and other maritime certification societies.

Contribution to the quality improvement of manganese steel Z120 MC12

Manganese steel, known by the name of its inventor, steel Hedfield is deemed by its high mechanical shock resistance, it is used in the field of crushing and grinding. This type of steel is obtained by adding manganese (Mn) between (12 & 18%) to get a metallographic structure austenitic. For a very good quality of the manufactured parts, and to prevent crack initiation intergranular generated by the presence of pre-cipitates or clusters of carbides in the areas near the grain boundary, it is necessary to conduct a treatment hyper thermal quenching at 1050°C to dissolve these clusters. On all treated samples, we find the presence of an austenitic structure with a homogeneous distribution of grains having a size to be correct [1]. However, it appears as a network, the presence of a network of black dots (as precipitates) we find abnormal, and which we know neither the nature nor its impact on the metallurgical quality of the material. To solve this problem, we con-ducted a specific analysis by scanning electron microscopy (SEM) to explain the nature of these blackheads and subsequently, tried to judge when its influence on the structure of austenitic manganese steel

Importance of representative metallurgical sampling and testwork programmes to reduce project risk – a gold case study

ABSTRACTWhen developing a process flowsheet, the risks in achieving positive financial outcomes are minimised by ensuring representative metallurgical samples and quality testwork. A case study is presented based on an underground gold operation, where poor metallurgical sampling led to grade and recovery underperformance. Sampling-related issues included: poor liaison between geologists and metallurgists; poor domaining; too few metallurgical samples collected and tested; unrepresentative sample composites and sub-samples; poor laboratory practice; and a lack of documentation and QAQC. These issues led to disruption over four years and are estimated to have cost around US$115M in lost revenue and US$7.5M in corrective expenditure. After an initial characterisation programme, a variability mini-bulk sampling and testwork phase was undertaken. This was followed by a pilot programme, progressing to trial mining and production. The paper emphasises the need for fit for purpose metallurgical sampling and testwork, and the early application of variability sampling.

Effect of Turning Amount on Metallurgical Qualities and Mechanical Properties of GH4169 Superalloy.

The determination of an appropriate amount of turning for superalloy ingot surfaces, in a scientific and reasonable manner, is vital to the improvement of the metallurgical quality and comprehensive performance of superalloy ingots. In the present study, scanning electron microscopy with energy-dispersive spectroscopy, a high-temperature testing machine, a Brinell hardness tester and the Image-Pro Plus software were used to analyze and compare the types and amounts of inclusions, the average area of the (Al,Mg)O inclusions, and the mechanical properties of points at different distances from the edge of the GH4169 superalloy vacuum arc remelting (VAR) ingot edge. The effects of the amount of turning to which the superalloy is subjected, the metallurgical qualities, and the mechanical properties were systematically studied. The results showed that the five inclusion types did not change as the sampling locations moved away from the ingot edge, but the amount of inclusions and the average area of the (Al,Mg)O inclusions first decreased and then stabilized. Similarly, the tensile strength, elongation, section shrinkage, hardness, and fatigue life first increased and then stabilized. Finally, this experiment tentatively determined that an appropriate amount of turning for a GH4169 superalloy ingot is 36–48 mm.

Recovered polyvinyl alcohol as an alternative binder for the production of metallurgical quality coke breeze briquettes

ABSTRACT Coke breeze briquettes are promising low-cost substitute to metallurgical coke, prepared by adding binder to the coke breeze to form briquettes. At present, pregelatinized starch is used as binder in the preparation of briquettes, but its food and confectionary applications restrict its usage on account of high cost and ease of availability. Subsequently, there is a necessity to develop alternative binders for the briquetting process, without affecting the briquette properties. Polyvinyl alcohol (PVA) could be one such possible binder. The textile industry generates waste streams with significant amounts of PVA that can be recovered by membrane filtration. The present work, therefore investigates the possibility of using pure polyvinyl alcohol (pPVA), recovered polyvinyl alcohol (rPVA), and mixtures of rPVA with pregelatinized starch as binders for coke breeze briquetting. Weak green briquettes were produced by rPVA binder. The quality of briquettes improved after addition of pregelatinized starch to rPVA and this was found to be equivalent to pure polyvinyl alcohol (pPVA) binder briquettes. The mixed (rPVA+ Pregelatinized starch) binder produced briquettes with UC strength 1347 kPa. The study demonstrates the fact that good quality briquettes can be formed by rPVA when used in combination with minimal quantities of pregelatinized starch.

Parametric appraisal of mechanical and metallurgical behavior of butt welded joints using pulsed Nd:YAG laser on thin sheets of AISI 316

In the era of miniaturization, welding of thin sheets find wide spread applications in developing micro-scale products essentially used in bio-medical, aerospace and automobile industries. During welding of thin sheets, welding deformation needs to be addressed to obtain sound and strong joints. Experimental investigation has been made on laser butt welding using pulsed Nd:YAG laser. Specifically, the study attempts to examine the influence of laser parameters such as laser current, pulse width, and scanning speed on weld quality of thin sheets of 0.45 mm. The quality of weld beads have been analyzed by scanning electron microscope (SEM), optical microscope, and radiography and fractographic inspection. Further, mechanical characterization of the weld beads is made by estimating micro-hardness, residual stress, surface roughness, and welding strength. The study indicates that laser current is the most importance parameters in welding of thin sheets because it helps in obtaining good mechanical and metallurgical qualities of welded joints. The welding strength increases with increase in scanning speed to a certain level and then it reduces. Spot overlapping significantly influences on surface integrity (surface roughness) and welding strength of welded joints. Micro-hardness in fusion zone (FZ) is comparatively higher than that in the heat affected zone (HAZ) because of the difference in grain structure (coarseness) attributed to cooling rate. The study further indicates that there is significant effect of laser pulse energy on development of residual stresses in welded joints. The study is extended to develop empirical relationship between laser parameters and welding strength using non-linear regression analysis. The adequacy of the empirical model is checked by comparing the results obtained from empirical model and experimental values. A new meta-heuristic approach known as simple optimization (SOPT) algorithm has been adopted to obtain optimum parametric setting for welding strength. A relative error of 8.79% is obtained when welding strength at optimal parameter setting is compared with confirmatory experiment.

An efficient method of foundry and metallurgical coke quality improvement

At foundry coke production, introduction into a coal burden comparatively small amount of non-sintering carbonaceous additives is one of effective methods of the coke mechanical, physical and chemical properties intended control. A review of industrial tests on coal burdens coking with different thinning additives, carried out at coking plants of Western Siberia and the Urals, presented. Coke dust of coke dry quenching facility was used as additives, as well as oil-coke and semi-coke fines, and rubber crumb. Under industrial conditions of JSC “Altaj-koks” and JSC “Koks” coke dust of coke dry quenching facility was tested as a thinning additive. After introduction into the burden of 1.6–3.0% of coke dry quenching facility dust, the coarseness and mechanical strength of foundry coke increased. The industrial burden coking with oil-coke fines was accomplished at JSC “Altajkoks” Nos 1 and 2 coke-oven batteries. Oil-coke fines in the amount of 5% was added to a burden (у = 15–16 mm) without change of coking regime (the period of coking is 15–16 h). Strength of foundry coke (М40) increased by average 0.5%, of BF coke – by 1.2%, ash content decreased by 0.3%, sulfur content increased by 0.03–0.06%, reaction ability decreased by 19% (rel.). At the OJSC “Gubakhinsky koks” it was determined by industrial tests, that it is possible to produce a metallurgical coke, meeting requirements of non-ferrous metallurgy, providing up to 5% of oil-coke fines are added instead of the same amount of low-sintering coals. VUKHIN’ studies showed, that still higher effect in improving foundry and BF coke quality can be reached by introducing into the coal burdens “modified” oil coke up to 50% as a coking additive. During industrial tests at JSC “Altaj-koks” semi-coke fines were introduced into production burden instead of KCH coal in the amount of 3–7%. At its utilization a burden crushing degree decreased down to 76.5%, dust content (class 0.5–0 mm) decreased down to 39.1%, its bulk density increased up to 780 kg/m3 . At that the coke mechanical strength corresponds to that for coke made of industrial burden, and its coarseness increased. Results of successful industrial tests of foundry coke made of burdens with coke dry quenching facility dust and oil coke fines at smelting in cupola gray cast iron and malleable cast iron.

Transformations in the Si-O-Ca system: Silicon-calcium via solar energy

The production of silicon-calcium alloy is energy intensive (>10,000 kWh/t). This means that energy cost has a relevant influence in the price of the alloy. The utilization of concentrated solar energy in the synthesis of silicon-calcium alloy is proposed in this paper. Metallurgical quality silicon and limestone are used as starting materials (25 wt.%, 50 wt.% and 75 wt.% Si). After a 12 min treatment under power values of around 1 kW and without using special atmosphere, silicon-calcium was detected in all samples, although mixed with the products of reaction (Ca3Si2O7, Ca10O25Si6, SiO2). This last question means that there was not proper separation metal-slag, and it should be improved in future investigations. However, the basic knowledge presented in this paper could be of great interest for an industrial process based on the solar energy. This way, the energy costs could be reduced, the pollutant emissions could be minimized, and the competitiveness of the ferroalloys industry could be increased.

Development of energy saving technology of coke dry quenching

Application of coke dry quenching technology provides saving of energy resources, decreasing of environment pollution and increase of metallurgical coke quality. Despite of advantages of coke dry quenching facilities, an additional quantity of circulating gas is generated because of quenching technology peculiarities. This additional circulating gas must be released out of the cooling agent circuit resulting in environment pollution. Existing and proposed methods of reduction of emissions into atmosphere of excess circulating gas considered. It was shown, that utilization of the excess circulating gas as a fuel is the most effective solution of the considered problem. The solution comprise stabilization and support of combustible components composition in the circulating gas at the level of approved indices, joining of excess gas flows out of the dry quenching facility chambers, it enrichment by some amount of high calorie gas (coke or natural) and supply to gas uses. This technical solution was first realized by ArcelorMittal at the coke plant of the steel-works after E. Zendzimir in Krakov, Poland. In 2017 at the EVRAZ NTMK coke plant a project of the dry coke quenching facility modification was realized, comprising utilization of excess circulating gas, which has a considerable technical difference comparing with ArcelorMittal project. According to technology flowsheet, the excess circulating gas is collected out of operating chambers into a collector, cleaned of dust in a bag filter, chilled, enriched by a high calorie gas and delivered into the gas pipe of BF gas for further utilization as a fuel. To increase efficiency of the technology and to reduce the natural gas consumption for calorie content of enriched gas stabilization and supply it into the BF gas pipe line, the CO and H2 content in the circulating gas of the coke dry quenching facility is kept at the level of 12–15 and 4–5 % correspondently. Implementation of the technical modification of the coke dry quenching facility with elimination of harmful substances emissions within the excess circulating gas provided decrease of harmful substances emissions at JSC EVRAZ NTMK – 4 kg per ton of steel.

Metallographic Examinations Performed on Automotive Parts Through Several Case Studies

Abstract Metallurgical analysis is widely used in the field of heat treatment of metals to ensure the quality of the treatments carried out on a wide variety of industrial parts and treatments carried out. It is therefore a valuable tool for subcontractors of the heat treatment industry to monitor their production and treatment response on various parts. Through different examples, we will present actual cases that involve in particular automotive parts. We show that there is a strong interdependence between material and heat treatment, one being related to each other, a successful treatment depends both on the metallurgical quality of the material and the production quality of the heat treatment process. We will discuss the type of treatments like: vacuum hardening or under protective atmosphere, surface induction hardening, carburizing, nitriding and brazing.

Contributions of the High Frequency Dynamic Wire Feeding in the GTAW Process for Increased Robustness

Abstract: The GTAW process is recognized as a process of high metallurgical quality, being widely used in the pipelines welding, mainly in the root pass. The relative independence between the heat delivered to the melting pool and the amount of material added helps to control the melting of the material and to avoid the appearance of welding discontinuities such as lack of fusion and lack ok penetration. When orbital welding is carried out, mainly in the overhead position, there is a tendency of electrode contamination by the melted wire, reducing process productivity and quality. In this scenario, there are some strands of the GTAW process that aim for increased productivity, reconciled with the already present high metallurgical quality. These includes low and high frequency dynamic wire feeding, preheating wire and tangential wire insertion. The present work deals with the contribution of the high frequency dynamic wire feeding for the increase of robustness in the GTAW process, evidencing through voltage monitoring and high speed filming the formation of regular and uniform drops for the process stability.

Corrosion testing of experimental steels for oilfield pipelines

Emergency equipment failures at oilfield pipelines are often associated with corrosion damage of the pipe material. Optimization of the chemical composition of the used steel can play a significant role in increasing the corrosion resistance under the condition of ensuring the metallurgical quality of pipes. This article presents a comparative assessment of the corrosion resistance of the used Fe-Cr-Cu-Mn-V steel and experimental compositions, basing on the results of electrochemical studies and tests for general corrosion.