Carbon Equivalent Values Research Articles

Investigation of the effect of thermo-mechanical processing orientation on the final material performance in 6xxx aluminium alloys produced with high recycling rates

Recycling of aluminium alloys is crucial due to its effects on environment, economy and social situations. It is also a popular research topic for aluminium producers and aluminium end users like automotive industry due to its tremendous effects on final carbon equivalent value and price. This scientific study emphasizes the critical importance of recycling in alloys used in the automotive sector, investigating the effects of thermo-mechanical processing orientation on the final material performance of 6XXX aluminium alloys with high recycling rates. Specifically, materials obtained using high recycling rates on 6063 and 6082 alloys produced for the automotive industry have been examined. The study aims to evaluate the mechanical properties of materials under thermal load through methods such as anisotropic strength correlations and bake-paint testing. The central focus of the study is to establish correlations between mechanical properties in different orientations based on thermal inputs. Data obtained through mechanical tests and bake paint tests conducted at 0, 45, and 90-degree orientations to extrusion direction play a crucial role in determining the material's performance. The findings contribute to our understanding of the impact of 6XXX aluminium alloys produced with high recycling rates on the final material performance in industrial applications.

Analysis of the possibilities to increase abrasion resistance of welded joints of Hardox Extreme steel

This paper presents a heat treatment process designed to enhance the abrasion resistance of welded joints of Hardox Extreme steel, which is known for its high hardness (>600 HBW) and tensile strength (>2000 MPa). Despite these properties, the steel's weldability, characterized by a Carbon Equivalent Value (CEV) of 0.70, limits its use in applications like mining machinery where welding is essential. The key challenge in welding martensitic boron steels, such as Hardox Extreme, is the reduction in hardness and abrasion resistance in the heat-affected zone, along with cold cracking due to increased hardenability. This study investigates the abrasion resistance and microstructural properties of welded joints made with submerged arc welding (SAW) under different heat treatment conditions. The developed process achieved a uniform tempered martensite microstructure across all welded zones, increased hardness to over 550 HV in the weld material zone and improved the relative abrasion resistance by 25 % compared to the as-welded state.

Microstructure Characteristics and Mechanical Properties of Grey Cast Iron at Varied Ferrosilicon Addition

Inoculation is an essential metallurgical route for controlling solidification conditions of cast iron, consequently, in this study, the influence of varied percent ferrosilicon (FeSi) addition on microstructure and mechanical properties of grey cast iron (GCI) was investigated. A 50Kg capacity rotary furnace was used to melt the charge (Auto engine block scrap, graphite, ferrosilicon (FeSi) and limestone). The casting was produced in a greensand mold with wooden rectangular pattern of length 50 mm and breadth 30 mm. Chemical compositions and carbon equivalent values (CEVs) of the samples were determined, using Optical emission spectrometry (AR 4 metal analyzer) and the expression respectively. Microstructures of the samples were obtained, using metallurgical microscope (model number NJF-120A). The tensile and hardness properties were measured, using Universal tensile tester and Rockwell hardness tester respectively. From the results, C and Si were the major elements. Other trace elements were Mn, P, S and Al. CEVs of both the control and inoculated samples were less than 4.3%. Microstructure of the control sample was comprised of primary dendrites and graphite flakes, while those of the inoculated samples were characterized by varied amount of more developed primary dendrites, longer graphite flakes and austenite dendrites. Also, a number of small MnS particles were observed in relative amount within the microstructures. Tensile and hardness properties of the FeSi inoculated samples were superior to the control sample. Highest tensile strength and hardness values of 76.62 MPa and 99.89 HRB respectively were obtained at the optimum inoculation of 1.5 wt. % FeSi.

Microstructure Characteristic and Mechanical Properties of Copper Influenced Grey Cast Iron

Grey cast iron (GCI) is characterized by brittleness, making it unsuitable for use in applications requiring high impact loading. Hence, efforts were made in this study to produce GCI with improved mechanical properties by addition of copper. Four samples were produced, the first sample was not alloyed (control), and the second, third and fourth were alloyed with 1.4wt.%Cu, 1.8wt.%Cu and 2.2wt.%Cu respectively. The samples were characterized using scanning electron microscope with EDS, and tested in tensile, hardness and impact. From the results, silicon contents of the alloyed samples are high relative to the control sample. The control and 2.2wt.%Cu alloyed samples are hypereutectic with carbon equivalent values (CEVs) of 4.391% and 4.200% respectively, while the 1.4wt.%Cu and 1.8wt.%Cu alloyed samples are hypoeutectic with CEVs of 3.940% and 3.600% respectively. The control sample is characterized by long graphite flakes, which are uniformly distributed within ferritic - pearlitic matrix. Graphite flakes of the 1.4 wt.% Cu and 1.8 wt.% Cu alloyed samples are uniformly distributed within pearlitic - ferritic matrix, while graphite flakes of the 2.2wt.%Cu alloyed sample are uniformly distributed within ferritic-pearlitic. Average graphite flake length of the control sample is high as compared to the copper alloyed samples, while graphite flake count of the control sample is low relative to the copper alloyed samples. Tensile strength characteristics of the copper alloyed samples are superior to the control sample. Optimum tensile strength characteristics (165.9 Nm2) was obtained at 1.4wt.%Cu. Ductile characteristic of the of control the sample is superior to ductile characteristics of the copper alloyed samples. Optimum ductility characteristic (3.82%) was obtained at 2.2 wt. %Cu. Hardness characteristics of the copper alloyed samples are superior to hardness characteristic of the control sample. Optimum hardness characteristics (61 HRB) was obtained at 1.4wt.%Cu. Impact strength characteristic of the control sample is low relative to impact strength characteristics of the copper alloyed samples. Optimum impact strength characteristics (78.93 KJ/m2) was obtained at 2.2wt.%Cu.

Experimental Investigation into Strength Properties of Ribbed Mild Steel Reinforcing Bars (RMSRBs) Produced by Local Companies in Ghana

The construction of high-rise buildings has increased the production and demand of ribbed mild steel reinforcing bars (RMSRBs) in Ghana. This study aimed at investigating the strength properties of RMSRBs manufactured in Ghana from scrap metals. Three steel-producing companies were considered for this study. A total of 90 samples of 12, 16, and 20mm diameters with lengths of 500, 50, and 20mm were used for the study. The prepared specimens were subjected to tensile strength test, chemical composition analysis, micro-hardness test, and microstructure analysis. The results indicate that the average tensile strength of between 576.00 and 768.40N/mm2 were above the minimum tensile strength of 250N/mm2 recommended by ASTM E8/E8M-16a. The carbon equivalent values (CEVs) of between 0.287 and 0.333% obtained were almost within the range of 0.3 to 0.55% recommended by ASTM A706/A706M-09b. It was also identified that the average Vickers hardness values of between 255.76 and 295.38HV were acceptable. The microstructural images showed good distribution of the pearlite and ferrite of the core. One Way ANOVA results indicated that the differences in the tensile strength values for 12mm (p-value ˂0.000) and 16mm (p-value =0.001) were statistically significant, however, the 20mm (p-value =0.138) was not statistically significant. The study, therefore, concludes that the strength properties of the 12, 16, and 20mm diameters of the RMSRBs produced by the three different companies in Ghana meet the standard requirements, and are recommended for use by contractors for the production of reinforced concrete.

Effect of Post-Weld Treatment on the Microstructure and Mechanical Properties of Austempered FeNiCr Steel Welded Joint

This study investigated isothermally treated FeNiCr structural steel welded joints. The base metal contains various phases which are dominated by a mixture of bainite and martensite. Joining this steel can be challenging since it has high carbon equivalent values and high hardness. Shielded metal arc welding (SMAW) with austenitic stainless-steel electrodes is used to avoid cold cracking. After the welding process, the samples were subjected to three various post-weld temperatures: 425°C, 475°C, and 525°C. From the tensile test results, the tensile strength of welded joint shows an increase as the temperatures increase. The highest value is reached for a joint sample which treated at 525°C, with a tensile strength of 680 MPa. Conversely, the highest elongation is obtained by the 425°C post-treated sample, which is 14%. The microstructure in the weld metal (WM) area shows a formation of δ-ferrite, whereas the HAZ and BM areas show the presence of bainite and martensite tempered phases with various plate densities, plate size, and plate shapes depending on its post-treatment temperatures, which then affect the value of the hardness.

Оцінка підходів до прогнозування властивостей синтетичного чавуну у ливарному виробництві

An overview of approaches to assessing the dependence of the mechanical properties of products made of synthetic iron smelted in induction crucible furnaces on the content of carbon and the content of silicon in its chemical composition, as well as on the carbon equivalent, the degree of eutecticity, and the ratio of the carbon content to the silicon content is given. The statistical parameters of the percentage distributions of the specified elements in the chemical composition of cast irons with lamellar graphite produced in accordance with the requirements of DSTU 8833-2019 were analyzed. The values ​​of the carbon equivalent of the chemical state of these cast irons and the values ​​of their degree of eutecticity were calculated according to common formulas for determining these indicators using the Monte Carlo method and using a probabilistic approach taking into account the content of each element in the chemical composition of cast iron. It is emphasized that, from a probabilistic point of view, the values ​​of the carbon equivalent and the degree of eutecticity may not coincide in different batches of cast iron, even with the same values ​​of the percentage content of chemical elements in its composition. It is shown that with an increase in the carbon equivalent and the degree of eutecticity, the strength and hardness of cast iron produced in accordance with DSTU 8833-2019 decrease. As the carbon content and carbon equivalent increase, the ratio of carbon content to silicon content decreases. In industrial batches of cast iron brake pads and «Khanin wedge» manufactured in accordance with GOST 30249-97 and GOST 34503-2018, the hardness of these products does not depend on the carbon equivalent due to the small range of the carbon equivalent values. Keywords: foundry products, cast iron, chemical composition, carbon equivalent, ratio of carbon content to silicon content, degree of eutecticity, hardness, strength

Microstructural analysis of some reinforcement steel rods used for concrete reinforcement and their effect on the mechanical properties, and carbon equivalent values of the reinforcement steel rods

Microstructural analysis of some reinforcement steel rods used for concrete reinforcement and their effect on the mechanical properties, and carbon equivalent values of the reinforcement steel rods

Microstructural analysis of some reinforcement steel rods used for concrete reinforcement and their effect on the mechanical properties, and carbon equivalent values of the reinforcement steel rods

The microstructural analysis of some reinforcement steel rods used for concrete reinforcement and their effect on the mechanical properties, and carbon equivalent values of the reinforcement steel rods have been studied. The work subjected the samples to test specimen preparation as required by standard specification for each test. Samples from five different mini mills were investigated for hardness, impact strength, composition, and microstructure. The result obtain from the work, has clearly shown that the microstructure of all the samples investigated reflected the hardness, impact strength, and the CEV of the samples. The microstructure of sample D with spheroidal pearlite dark areas, and a ferrite matrix had the highest hardness value of 34.61BHN, impact strength of 274.7J and CEV of 0.545. These values correlate with the microstructure. The work showed that as the CEV is increased the hardness and the impact strength of the material also increased. The work also show that as the total carbon (TC) % in the samples increased the microstructure becomes darker and the hardness and the impact strength also increased. In conclusion the microstructure of the reinforcement steel rods had effect on the hardness, impact strength properties, and carbon equivalent value of the reinforcement steel rods.

Data Science to Determine Mechanical Properties of Low Carbon Steel During In-Process Inspections

Carbon steel is a widely used category of engineering metal, mainly due to its attractive mechanical and fabrication properties and low cost. The chemical composition, physical parameters, and mechanical properties of carbon steel are maintained as per the specified standards, and local steel should be complied with Sri Lankan Standard 375: 2009. Generally, the chemical composition is tested during melt stages, and mechanical properties are tested for finished products. Since it is necessary to ensure products comply with the standard, mechanical properties are tested during in-process inspections as well. When the results are not within the acceptable range, a considerable amount of production has to be rejected, causing a loss to the manufacturers. If the results of the in-process inspection are instant, it will help make suitable adjustments to process conditions and thereby prevent rejection of products, while reducing quality assurance costs, as well. Therefore, the objective of this study is to predict tensile properties with chemical composition, as input variables, to be used for in-process inspections. Forty mechanical test reports were collected from a steel manufacturing factory for 12 mm diameter, thermo-mechanically treated (TMT) steel bars. Each test report is of 15 samples from the respective batch, and consists of corresponding chemical composition and physical parameters. Multiple linear regression analysis was applied to each batch, using Statistical Package for the Social Sciences (SPSS) software, to predict yield strength (YS), ultimate tensile strength (UTS), elongation at break (EB) with carbon equivalent value (CEQ) and percentage of Sulphur as inputs. Relationships between variables were not significant, even though those relationships can be used to predict tensile properties. The predictions may not be reliable, due to the limited conditions of the study and assumptions made. It is therefore recommended to apply multivariate regression analysis or Artificial Neural Network (ANN) techniques, with other chemical elements, process temperature and water flow rate etc. also as input variables. KEYWORDS: Chemical composition, In-process inspection, Low carbon steel, Multiple linear regression analysis, Tensile properties

STRENGTH OF BUTT WELDED BUTT JOINT OF REINFORCEMENT OF CLASS A500C

The paper presents the results of experimental studies of the strength of cross-shaped welded joints of types К1-Кт and К3-Рр [1] of thermomechanically hardened reinforcement of class A500C [2] for hardening during welding of the main bar [3].
 Experimental studies included testing three series of samples of welded joints and reinforcement samples in the initial state. The first series included testing welded joints of type К1-Кт to strengthen the main bar during welding. Reinforcement Ø14A500С was accepted as the main (working) bar, and reinforcement Ø12A500С and Ø8A240С were accepted as the transverse bar. For each joints, 6 samples were tested on the lower and upper limits of the carbon equivalent values of the grade steel class Ст3пс, 0.245% and 0.346%, respectively. The second series included testing of welded joints of the K3-Pp type to strengthen the main bar during welding. To directly compare the test results of different types of cross-shaped welded joints, the diameter of the main and transverse rods, the number of samples and the value of equivalent were the same as in the first series. The third series included testing welded joints of type К1-Кт for cutting. Reinforcement Ø14A500С was taken as a longitudinal bar, and reinforcement Ø12A500С and Ø8A500С was taken as a transverse rod. For each joints, 12 samples were tested at the lower and upper limits of the carbon equivalent values.
 As a result of testing samples of welded joints of types К1-Кт and К3-Рр of reinforcement A500C for strengthening during welding, it was established that the destruction occurs along the main bar and in the zone of thermal exposure, the amount of hardening was up to 4% for the К1-Кт compound, and for the К3-Рр type connection - 4... 10%.
 Failure of samples of welded joints of type К1-Кт reinforcement A500C with reinforcement Ø12A500C and Ø8A240C during the cut test usually occurred in the zone of thermal exposure, or in some cases, in the presence of both rods from reinforcement of class A500C - directly at the welding site. The average value of cut strength for a sample of 24 samples of reinforcement connections of class A500C with reinforcement A240C was 356.5 MPa, or 0.89 of the temporary resistance of the reinforcement in the initial state, with a coefficient of variation - 0.08 and a span of 107.4 MPa. The average cut strength for a sample of 24 samples of reinforcement connections of class A500C with reinforcement A500C was 541.1 MPa, or 0.80 of the temporary resistance of the reinforcement in the initial state, with a coefficient of variation – 0.152 and a span of 280.0 MPa.
 The first series included fittings Ø12A500C, Ø14A500C, Ø16A500C from steel of the ST3ps brand and Ø18A500C, Ø20A500C, Ø22A500C from steel of the Ст3пс brand. A total of 278 samples of welded joints were tested. The second series included samples of C1-Co welded joints from the rest of the nomenclature of diameters and grades of steel reinforcement class A500C, namely Ø16A500C from steel grade St3ps, Ø20A500C, Ø22A500C from steel grade St3Gps and Ø25A500C, Ø32A500C, Ø32A500C, Ø32A500C. For each of the diameters, 6 samples were tested in the initial state and 6 samples of C1-Co welded joints.
 It was found that the destruction of the butt contact connection type C1-Co thermomechanically reinforced reinforcement class A500C of all diameters, from 12 to 32 mm, and steel grades, takes place in the zone of thermal impact and is plastic.
 Experimental data on the strength of the butt contact weld type C1-Кo reinforcement class A500C for the entire range of diameters and grades of steel produced in Ukraine. It is established that the greatest degree of hardening within 19-20% takes place at diameters of armature of 12… 16 mm from steel of the Ст3пс brand, at diameters of armature of 18… 22 mm from steel of the Ст3Гпс brand of marking made 15-17%, and at diameters of 25… 32 mm from steel of the 25Г2С brand - 2,5… 8%.

EFFECT OF ANTIMONY ON THE WEAR RESISTANCE AND IMPACT TOUGHNESS OF CARBIDIC AUSTEMPERED DUCTILE IRON (CADI)

This work investigated the effect of antimony on the impact toughness and wear resistance of carbidic austempered ductile iron (CADI). Six alloys with a carbon equivalent value of 4.44 (hyper-eutectic composition) were used to evaluate the produced CADI, with antimony content ranging from 0.096 to 0.48 wt. %. The produced carbidic ductile irons (CDI) were heated to austenitic temperature of 910oC and held for 1 hour, then austempered at temperature of 325oC and held at different times (1-3 hours) to obtain carbidic austempered irons. Microstructural characterization was then carried out. The wear resistance was evaluated using a wear tester, it was noted that the wear resistance values of the CADI ranged from 2.35E8 cm-2 to 3.74E9 cm-2. The impact toughness of the CADI was determined using Charpy method, the results obtained ranged from 46.5 – 55J. It was observed that the as-cast CDI has graphite nodules, blocky carbides with a pearlitic matrix, the samples with antimony addition had granular carbides, the heat-treated samples had their matrix transformed to ausferrite while other structures remained unchanged. Sample with antimony content of 0.288 wt. % has the highest wear resistance value while sample with 0.096 wt. % has the best impact toughness value.

Визначення вуглецевого еквівалента і ступеня евтектичності чавуну в ливарному виробництві

The issues related to the essence of the concepts of carbon equivalent, an indicator of the degree of eutecticity and the ratio of carbon content to silicon content for characterizing the chemical composition and properties of gray cast iron were analyzed. The results of studies of the carbon equivalent value, the degree of eutecticity and the C/Si ratio of the chemical composition of synthetic cast iron, which is used for the manufacture of brake pads and the «Khanin wedge» of railway rolling stock, are presented. Examples of different approaches and formulas for determining the limits and methods of using the carbon equivalent of the chemical composition of cast iron to characterize the weldability of steels, coefficient of friction, wear, other operational indicators of cast iron brake pads, and evaluation of the quality of cast iron as a whole are given and analyzed. Within the standards-regulated ranges of the content of chemical elements in cast iron, the value of its carbon equivalent in individual smelting batches of products can differ significantly (by 30 %). With certain ratios of the main elements in the chemical composition of cast iron, the values of the carbon equivalent can be the same, but the mechanisms of crystallization of cast iron and its properties do not coincide. The parameters of the distribution of the content of carbon, silicon, manganese, phosphorus, sulfur, carbon equivalent, and the degree of eutecticity in cast iron СЧ350, from which the friction «Khanin wedge» for railway rolling stock is made, were analyzed. Cleaning the factory arrays of indicators of chemical composition, hardness, carbon equivalent, degree of eutecticity of cast irons intended for the production of brake pads and the friction «Khanin wedge» from gross erroneous values practically did not affect the general characteristics of the statistical analysis, which indicates the reliability of the results. It is shown that when smelting in induction crucible furnaces gray synthetic cast iron intended for the production of brake pads and the «Khanin wedge», the ranges of variation in the content of C, Si, Mn, P, S are much narrower than those regulated by the standards for these foundry products. The fundamental possibility of introducing appropriate clarifications to the requirements of the standards regarding the content of chemical elements in synthetic gray cast iron intended for the production of brake pads of the «M» type and the friction «Khanin wedge» for railway rolling stock was noted, in particular, reducing the sulfur content to 0,05 % to increase stability of its quality. Keywords: cast iron, chemical composition, carbon equivalent, degree of eutecticity, properties, castings, brake pads, operational characteristics.

Hot Deformation Behavior of Non-Alloyed Carbon Steels.

The hot deformation behavior of selected non-alloyed carbon steels was investigated by isothermal continuous uniaxial compression tests. Based on the analysis of experimentally determined flow stress curves, material constants suitable for predicting peak flow stress σp, peak strain εp and critical strain εcrDRX necessary to induce dynamic recrystallization and the corresponding critical flow stresses σcrDRX were determined. The validity of the predicted critical strains εcrDRX was then experimentally verified. Fine dynamically recrystallized grains, which formed at the boundaries of the original austenitic grains, were detected in the microstructure of additionally deformed specimens from low-carbon investigated steels. Furthermore, equations describing with perfect accuracy a simple linear dependence of the critical strain εcrDRX on peak strain εp were derived for all investigated steels. The determined hot deformation activation energy Q decreased with increasing carbon content (also with increasing carbon equivalent value) in all investigated steels. A logarithmic equation described this dependency with reasonable accuracy. Individual flow stress curves of the investigated steels were mathematically described using the Cingara and McQueen model, while the predicted flow stresses showed excellent accuracy, especially in the strains ranging from 0 to εp.

The State of the Art of Underwater Wet Welding Practice: Part 2

Developments in underwater wet welding (UWW) over the past four decades are reviewed, with an emphasis on the re-search that has been conducted in the last ten years. Shielded metal arc welding with rutile-based coated electrodes was established as the most applied process in the practice of wet welding of structural steels in shallow water. The advancements achieved in previous decades had already led to control of the chemical composition and microstructure of weld metals. Research and development in consumables formulation have led to control of the amount of hydrogen content and the level of weld porosity in the weld metal. The main focus of research and development in the last decade was on weldability of naval and offshore structural steels and acceptance of welding procedures for Class A weld classification according to American Welding Society D3.6, Underwater Welding Code. Applications of strictly controlled welding techniques, including new postweld heat treatment procedures, allowed for the welding of steels with carbon equivalent values greater than 0.40. Classification societies are meticulously scrutinizing wet welding procedures and wet weld properties in structural steels at depths smaller than 30 m prior to qualifying them as Class A capable. Alternate wet welding processes that have been tested in previous decades — such as friction stir welding, dry local habitat, and gas metal arc welding — have not achieved great success as originally claimed. Almost all of the new UWW process developments in the last decade have focused on the flux cored arc welding (FCAW) process. Part 1 of this paper covered developments in microstructural optimization and weld metal porosity control for UWW. Part 2 discusses the hydrogen pickup mechanism, weld cooling rate control, design, and qualification of consumables. It ends with a description of the advancements in FCAW applications for UWW.

The State of the Art of Underwater Wet Welding Practice: Part 1

Developments in underwater wet welding (UWW) over the past four decades are reviewed, with an emphasis on the research that has been conducted in the last ten years. Shielded metal arc welding with rutile-based coated electrodes was established as the most applied process in the practice of wet welding of structural steels in shallow water. The advancements achieved in previous decades had already led to control of the chemical com-position and microstructure of weld metals. Research and development in consumables formulation have led to control of the amount of hydrogen content and the level of weld porosity in the weld metal. The main focus of research and development in the last decade was on weldability of naval and offshore structural steels and acceptance of welding procedures for Class A weld classification according to American Welding Society D3.6, Under-water Welding Code. Applications of strictly controlled welding techniques, including new postweld heat treatment procedures, allowed for the welding of steels with carbon equivalent values greater than 0.40. Classification societies are meticulously scrutinizing wet welding procedures and wet weld properties in structural steels at depths smaller than 30 m prior to qualifying them as Class A capable. Alternate wet welding processes that have been tested in previous decades — such as friction stir welding, dry local habitat, and gas metal arc welding —have not achieved great success as originally claimed. Al-most all of the new UWW process developments in the last decade have focused on the flux cored arc welding (FCAW) process. Part 1 of this paper covers developments in microstructural optimization and weld metal porosity control for UWW. Part 2 discusses the hydrogen pickup mechanism, weld cooling rate control, design, and qualification of consumables. It ends with a description of the advancements in FCAW applications for UWW.

Solidification, Macrostructure and Shrinkage Formation of Ductile and Compacted Irons

This manuscript summarizes recent investigation of the authors into the solidification and shrinkage defect formation of ductile and compacted graphite cast irons. The study makes use of the DAAS (direct austempering after solidification) technique, developed earlier by some of the authors, to reveal the solidification grains. In addition, color metallography is used to reveal the microsegregation pattern. The formation of shrinkage defects is related to both the solidification macrostructure and the microsegregation pattern. The examination of the macrostructure shows that large solidification grains, composed by dendritic austenite and graphite, characterize the solidification of compacted graphite irons of carbon equivalent values ranging from hypoeutectic to hypereutectic. Similar results are observed for ductile iron, but in this case, the hypereutectic irons display a finer macrostructure. The characteristics of the primary austenite dendrites are revealed by the microsegregation pattern, which is exposed by the color etching reagent. This pattern also clarifies the nature of the interaction between the growing austenite and the compact and spheroidal graphite particles. The microshrinkage cavities in both ductile and compacted graphite irons form at the interior of the austenite grains, where fluid feeding cannot compensate the contraction of the last-to-freeze portions of the melt. Schematics of the solidification of ductile and compacted irons are proposed, accounting for the experimental observations.

Effect of water flow on the microstructure, mechanical performance, and cracking susceptibility of underwater wet welded Q235 and E40 steel

Abstract Underwater wet flux-cored arc welding was investigated varying water flow velocities. Q235 and E40 steel, which have different carbon equivalent (CE) values, were used for these experiments. At the same flow conditions, the joint with E40 (a higher CE value steel) contained more side plate ferrite, acicular ferrite, and even martensite microstructures in the weld metal. The coarse grain heat-affected zone (CGHAZ) in the Q235 joints was dominated by Widmanstatten ferrite and some bainite, while lath martensite and acicular martensite were dominant in E40 joints. The side plate ferrite in the weld metal and acicular martensite in the CGHAZ were the most probable locations for the formation of cold cracks owing to their brittle characteristics. In the E40 weld joints, the mechanical properties showed a slight increase initially and then decreased dramatically with increasing flow velocity. In this study, the joints with higher CE values demonstrated a higher susceptibility for cold cracking, resulting in narrower process parameter ranges limited by cold cracking in the underwater environment.

The influence of the carbon equivalent on the weldability of high-strength low-alloy steel in the water environment

From many years, the high strength low alloy steels are often used for offshore constructions. This constructions, due to the environment in which they work, require more frequent repairs than the constructions from the land. For economic reasons, repairs take place in the underwater conditions, however water significantly decreases the weldability of steel. The paper presents the results of the CTS weldability test for S460ML and S460 steels, which have a similar value of the yield point, but different carbon equivalent (CeMIS) values. The welded joints were cut into specimens, which were then subjected to Vickers HV10 hardness measurements. The experiment has shown that as the CeMIS value increases, the hardness in the heat affected zone (HAZ) of joints and in the weld metal increases.

Study of the structure and properties of welded joints of micro-alloyed reinforcing steels made in the atmosphere of carbon monoxide

The structure and properties of welded joints of reinforced steel micro-alloyed with vanadium were investigated. The reasons for the formation of cold cracks are given. It has been established that welding at negative ambient temperature in the near-weld zone of rebar class A500C forms quenching structures with a hardness of up to 470 HV. Preheating of the rods by gas welding leads to a decrease in the temporary tensile strength. The technology of mechanized welding in carbon monoxide is proposed. It has been established that in multilayer welding in a reducing atmosphere, the carbon equivalent value of the weld metal increases. The hardness of the heat-affected zone decreases to 200… 260 HV. Mechanical properties of welded joints made in carbon monoxide environment comply with the requirements of regulatory documents.