Quenching Heat Treatment Research Articles

Effect of Quenching Post‐Intercritical Austenitizing on the Microstructure and Tensile Properties of an K55 Grade Steel for Oil and Gas Industry

The API K55 grade steel is widely utilized in seamless pipes for oil and gas exploration, especially as casing pipes for wellbores. Traditionally, this steel is processed using hot rolling followed by quenching and tempering to achieve the desired dimensional and microstructural characteristics, balancing high strength with ductility. This article introduces an alternative method to attaining the required tensile properties for API K55 grade steel by employing a biphasic microstructure (ferrite/martensite) achieved through quenching post‐intercritical austenitizing heat treatment to high‐strength‐low‐alloy steel. Thermodynamic simulations and dilatometric experiments revealed that increasing the austenitizing temperature enhances austenite formation, decreasing significantly its carbon content, which facilitates martensitic transformation and increases the Ms and Mf temperatures. A complete phase transformation mapping was presented, highlighting how the austenitizing temperature influences martensitic transformation kinetics during the quenching heat treatment. It was concluded that austenitizing at 750 °C, followed by quenching and short tempering at 650 °C, produced a biphasic microstructure with 30% ferrite and 70% martensite, providing a favorable balance between mechanical strength and ductility that meets the API K55 grade requirements, surpassing traditional methods in the industry.

Study on the Friction Characteristics and Fatigue Life of Carbonitriding-Treated Needle Bearings

Being a key component of the transmission system, the needle bearing’s performance and service life affects the overall service life of mechanical equipment. This study takes needle bearings composed of AISI 52100 steel as the research object and studies the effect of carbonitriding surface strengthening treatment on the bearing friction, wear, and fatigue life. The carbon and nitrogen co-infiltration surface-strengthening method was employed to prepare cylindrical and disc samples. The surface hardness, residual austenite content, microscopic morphology and organization composition, coefficient of friction, and wear scar were studied to analyze the effect on the wear performance of the material. The bearing fatigue wear comparison test was conducted on a test bench to compare the actual fatigue life and surface damage of the needle bearing through conventional martensitic quenching heat treatment and carbonitriding treatment. The results demonstrate that the carbonitriding strengthening method enhances the toughness of the material while improving its surface hardness. It also improves the wear resistance of the needle roller bearings, and the fatigue life of the bearings is significantly improved. In conclusion, carbon and nitrogen co-infiltration treatment is a strengthening method that effectively extends the service life of needle roller bearings, indicating its high practical value.

Controlling the optimal phase transition temperature of wires during quenching in salt bath through process parameters

Performing isothermal quenching heat treatment on austenitizing wires in a molten salt-bath can produce high-performance products. Meticulous regulation of the cooling process is essential for enhancing the performance of the wires. The research of this paper is based on the previous achievements of our research group. A three-dimension physical model is built to simulate the cooling process of the wires in the salt-bath. Through this model, this study first designs three new controlling flow hats and compares them with the original controlling flow hats from three perspectives: flow fields, entropy generations, and wire cooling rates, and finally selected the best performing hats. Subsequently, several groups of simulations are conducted under the boundary conditions of different salt capacities, temperatures and wires’ speeds to address the demand for increased capacity of the salt pump in the actual production. The main innovation of this article is to explore the synergistic effect of the salt temperature, capacity and wire speed on the optimal phase transition temperature, and determine the ideal salt temperature under the different salt capacities. In addition, the impact of the salt capacities on the wires’ thermo-uniformity and the range of phase transformation temperature is also studied. Finally, this article provides the molten salt-bath temperatures and wire speeds required to maintain the optimal phase transition temperature under three different salt capacities. This is of great significance for the renovation in actual production.

Application of Intercritical Austenitizing in a Commercial CMnSi Steel as a Tool for Optimizing a One‐Step Quenching and Partitioning Cycle Aiming to Achieve a Third‐Generation Advanced High‐Strength Steel

Advanced high‐strength steels (AHSS) have been extensively studied to develop its third generation from relatively low‐cost alloys, but seeking optimized mechanical properties. In this context, the effects of quenching heat treatments are evaluated in this work after intercritical austenitizing (IA) on microstructure, alloying elements partitioning, and Ms temperature for a commercial CMnSi alloy. Applying dilatometric data and microstructural characterization, different heat cycles are evaluated. The obtained experimental results are compared with those ones obtained by computer simulations at equilibrium conditions. Based on this characterization, an optimized one‐step quenching and partitioning (Q&P) cycle (after IA) is proposed and applied to tensile test specimens. Then, the specimen microstructure is characterized by scanning and transmission electron microscopy as well as by X‐ray diffraction. Using the proposed methodology, it is possible to produce a Q&P steel with a product of tensile strength and elongation of 29.5 GPa% and a 7% volumetric fraction of retained austenite. It is concluded that the precise knowledge about the IA effects on the phase transformations and microstructure evolution in a commercial CMnSi alloy has great potential to be applied in defining a one‐step Q&P heat treatment that favors a multiphase microstructure, which meets mechanical properties requirements for a third‐generation AHSS.

Archeometallurgical Investigation of a Fragment from a Medieval Sword Blade

A fragment from a medieval sword blade was investigated by metallography, Vickers microhardness tests and slag inclusions analysis are to extract technological information about its manufacturing process. Optical microscopy observations and microhardness measurements indicated that the sword blade was forged via hammer welding, combining different steel bars for an optimal balance of hardness and toughness. A steeling technique involved wrapping a steel bar around a composite billet, crafted by enclosing a hypoeutectoid steel bar around a near-eutectoid steel core. Moreover, it was found that the hardness of the cutting edges was increased with a quenching heat treatment. After quenching, the blade exhibited martensitic microstructure with Vickers microhardness ranging from 500 to 640 HV0.3. The compositional data of a large set of nonmetallic inclusions were collected by scanning electron microscopy coupled with X-ray dispersive spectroscopy. Slag inclusion analysis and multivariate statistics confirmed the blade's composite nature and revealed distinct smelting and forging-related SI groups. Liquidus temperatures indicated smelting temperatures of at least 1156°C for the external section and 1031°C for the internal. The forging temperature was estimated at a minimum of 1143°C. These findings provide insight into the blade’s metallurgical history.

Discussion on the Free Quenching Heat Treatment Process of Automotive Leaf Springs

Free quenching of automotive leaf springs is a new technology that has gradually started to be applied in the industry in China in recent years. Only a few manufacturers are applying it in the industry. Through more than half a year of on-site practice, the changes in the hot forming of spring plates before free quenching have been explored, and finally a heat treatment process that meets the production requirements of our company has been developed, achieving normal production.

Effect of austenitizing temperature on isothermal quenching microstructure and mechanical properties of 52100 bearing steel

In general, isothermal quenching heat treatment in salt bath can improve the toughness but sacrifice the strength and hardness of 52100 bearing steel. Many previous studies focusing on the isothermal quenching process have been carried out to balance the strength and toughness. And the optimal mechanical properties are limited to approximately 60–61 HRC hardness and 100 J impact toughness. In this study, in order to further improve the mechanical properties, the influences of austenitizing temperature on microstructural evolution and strengthening-toughening mechanism in isothermal quenched bainite in 52100 bearing steel have been systematically investigated. The increase of austenitizing temperature decreases the volume fraction of undissolved carbides, and increases the carbon concentration in austenite matrix. These changes not only strongly influence the kinetics of bainite phase transformation and bainite microstructure, but also cause the conflict between the coarsening of prior austenite grains, as well as bainite sheaves, and the refining of substructure of lower bainite. Austenitizing at 870 °C can balance this conflict well and obtain a good combination of hardness and toughness. It is found that the carbon content and dislocation density in bainite ferrite reach the peak value at 870 °C austenitized specimens, which effectively strengthens the bearing steels. At the same time, the 870 °C austenitized specimens retain appropriate content of undissolved carbides, which avoids stress concentration and inhibits crack propagation, and finally improve the impact toughness. Therefore, the optimal austenitizing temperature (870 °C) achieves the improvement of mechanical properties with the hardness and toughness of 59.7 HRC and 273 J, respectively.

Inductive Heating and Quenching of Planetary Shafts for Diesel Engine Starters

High mechanical and temperature cyclic loading of the final products for automotive, transport, construction and agriculture mechanization industry, demands sufficient mechanical properties of all of their components during its exploitation. Majority of the components is made of steel, by different cold forming processes. Their main demanded characteristics are surface wear resistance and fatigue strength under pulsating stress in combination with cyclic temperature loading, which could be achieved only by appropriate heat treatment. The efficiency of the combined inductive heating and water quenching heat treatment and quality of the planetary shafts were analyzed, with the use of thermographic analysis, hardness measurements, and metallographic examination. Combination of inductive heating and water quenching is the most effective heat treatment process of carbon steel planetary shafts for the diesel engine starters. Long life span of carbon steel planetary shafts it’s essential for their economical production. The replacement of starter is expensive from both: money and working time point of view. Surface temperature measurements during the inductive heating process were performed in the industrial environment. The intensity and homogeneity of the planetary shaft surface temperature field was measured by thermographic camera. On the base of theoretical knowledge and measurements, a mathematical model for temperature conditions determination in the shaft during the entire process of heating and quenching was carried out, and used for analyses and optimization of planetary shafts induction hardening process.

Comparative Study of Quench and Partition Processes in High Si and High Al Steels

The quench and partition process is a means to develop third-generation high-strength steels using many possible process variants. In this work, two variants of quench and partitioning heat treatments, one-step and two-step, were carried out for high Si and high Al steel alloys. The kinetics of isothermal transformation occurring during the one-step quench and partition process were analysed using dilatometry. Experimental analysis revealed the swing-back phenomenon in high Si steel, and the transformation characteristics above and below the Ms temperature differed. The high Al alloy resulted in higher retained austenite (19%) compared to high Si steel (17%) during the one-step quench and partition process. Aluminium addition favoured bainite formation more than silicon addition. A comparison of two heat treatment variants shows the two-step quench and partition heat treatment seemed preferable as it produced more retained austenite (22%) in the high Si steel.

Toughening mechanism and delayed fracture analysis of 4145H steel under intercritical quenching heat treatment process

Tuning thermal treatment schedule has been confirmed as an effective technical route for achieving optimum properties of steels. In the present work, the intercritical quenching tempering(IQT) process was applied to steel 4145H for oil drilling tools, and the performance enhancement and delayed fracture mechanism of the IQT process were comprehensively elucidated using multiscale characterization methods and various mechanical tests. Compared with the quenching and tempering(QT), the IQT process results in a separate island ferrite plus finely tempered sostenite organization, which reduces the dislocation density in the tempered organization and increases the proportion of recrystallized grains. Due to the grain refinement effect of multiple quenching, the pristine austenite grains were refined by 58 %. At the same time, the proportion of large-angle grain boundaries increased from 68.6 % to 80.3 %. The results of the mechanical property tests show that the intercritical 790 °C quenching treatment and tempering at 600 °C exhibits a tensile strength of 1087 MPa, a high elongation of 21.72 %, and a high impact work of 104 J compared to QT. The improved impact toughness is mainly attributed to the grain refinement effect of multiple quenching and the large-angle grain boundaries provided by the composite ferrite organization and M23C6 carbides. The impact of different ratios of large-angle grain boundaries on crack extension was also evolved by means of the crystal phase field, and the delayed fracture effect of large-angle grain boundaries was verified.

Effect of Heat Treatment of Beverage Cans Remelting on Mechanical Properties

This study compared the mechanical properties of the repeated melting of beverage cans. From the effects of the first melting, a chemical composition test was held out, which turned out that the aluminum produced was not explicitly admitted in the aluminum alloy series 2xxx, 3xxx, 4xxx or 6xxx. The semelting process I have increased the element Fe, as well as the addition of elements of Pb and Sn. Part of smelting I and II were annealed and quenched at 400?C with a holding time of 2 hours. The highest tensile strength is held from the first smelting product that has received quenching heat treatment, 9.67 kg/mm2. After remelting, it decreased to 9.07 kg/mm2. Products that have received quenching heat treatment have the most significant impact value, both for the first and second melting products, namely 74.34 BHN and 101.86 BHN. The most significant impact value was obtained from the first smelting product that received annealing heat treatment, which was 0.0388 J/mm2, and after receiving quenching heat treatment, the impact value became 0.0379 J/mm2.

In Situ Crystallization of SiO Spherical Nanocrystals in Optical Fibers

Extreme synthesis conditions can lead to discover materials and phenomena that are unknown under standard synthesis laboratory conditions. The particularities of the optical fiber fabrication, such as extreme temperatures, quenching heat treatments and the pressure generated during fiber drawing, among others, can be leveraged to explore novel phenomena at the nanoscale when optical fibers are engineered by nanoparticle doping. In this work, we demonstrate that starting from tetragonal cubic-shaped YPO4 nanocrystals contained into a silica-based optical fiber core, with a silica-based glass composition slightly modified with Ge P, and Al, it is possible to nucleate isolated spherical-shaped SiO nanocrystals by controlling fiber drawing temperature. This work demonstrates the existence of crystalline SiO, discussing the possible formation mechanism in detail, which addes new knowledge to silicon oxide family. Moreover, we show the suitability of using SiO nanocrystals for fabricating Rayleigh scattering enhanced optical fibers that can be applied for distributed sensing applications.

Experimental and Numerical Process Design for Press Partitioning of the New Q&P Steel 37SiB6

Quenching and partitioning (Q&P) heat treatments of low-alloy steels with exceptional property combinations are particularly promising. In this study, we characterize for the first time a new low-alloy steel to be processed using Q&P heat treatments. In combined experimental and numerical studies, we design a novel approach that effectively combines the short cycle times of press hardening with the excellent property profiles of Q&P-treated steels. We identify an appropriate austenization temperature of 950 °C and a portioning temperature of 250 °C for Q&P heat treatments through dilatometric studies. We adjust a number of reference conditions with fractions of 2.1 to 6.3 wt.% of retained austenite, resulting in tensile strengths up to 1860 MPa and elongations to failure up to 7%. Initial numerical designs of the process can identify varying temperature profiles and cooling rates depending on the position in the die. The results show that the geometry of the part plays a minor role, but the die temperature of 200 °C is the dominant factor for successful partitioning directly in the press hardening process.

Experimental Analysis of the Stability of Retained Austenite in a Low‐Alloy 42CrSi Steel after Different Quenching and Partitioning Heat Treatments

Quenching and partitioning (Q&P) steels are characterized by an excellent combination of strength and ductility, opening up great potentials for advanced lightweight components. The Q&P treatment results in microstructures with a martensitic matrix being responsible for increased strength whereas interstitially enriched metastable retained austenite (RA) contributes to excellent ductility. Herein, a comprehensive experimental characterization of microstructure evolution and austenite stability is carried out on a 42CrSi steel being subjected to different Q&P treatments. The microstructure of both conditions is characterized by scanning electron microscopy as well as X‐ray diffraction (XRD) phase analysis. Besides macroscopic standard tensile tests, RA evolution under tensile loading is investigated by in situ XRD using synchrotron and laboratory methods. As a result of different quenching temperatures, the two conditions considered are characterized by different RA contents and morphologies, resulting in different strain hardening behaviors as well as strength and ductility values under tensile loading. In situ synchrotron measurements show differences in the transformation kinetics being rationalized by the different morphologies of the RA. Eventually, the evolution of the phase specific stresses can be explained by the well‐known Masing model.

The Effect of Quenching and Tempering Heat Treatment on Abrasive Wear Behavior of Vanadis4 Extra and AISI D2 Steels

Bu çalışma, toz metalürjisi ile üretilen Vanadis4 Extra malzemesi ve AISI D2 (1.2379) soğuk iş takım çeliklerinin aşınma davranışı üzerinde su verme-temperleme ısıl işleminin etkisini araştırmıştır. Her iki çelik için aşınma testleri SiC bazlı bir aşındırıcı üzerinde 3,2 m/s sabit kayma hızında ve üç farklı kayma mesafesinde (100, 200 ve 300 m) gerçekleştirilmiştir. Deneysel sonuçlar, AISI D2 (1.2379) ve Vanadis4 Extra çeliğinin aşınma dirençlerinin benzer olduğunu göstermiştir. Aşınma testi sonuçlarına göre darbe dayanımı düşük olan AISI D2 (1.2379) çeliği yerine mükemmel tokluk özelliklerine sahip Vanadis4 Extra çeliğinin kullanılabileceği belirlenmiştir. Isıl işlem parametrelerinin AISI D2 (1.2379) ve Vanadis4 Extra çeliklerinin aşınma direncini optimize edebildiği belirlenmiştir

EFFECT OF QUENCHING HOLDING TIME ON MICROSTRUCTURE AND PROPERTIES OF HIGH SILICON HYPEREUTECTIC HIGH CHROMIUM CAST IRON

In this paper, the effects of different quenching holding times on the microstructure and properties of high-silicon hypereutectic high-chromium cast iron (Fe–4.0C–35.0Cr–1.9Si) were investigated. The effect of quenching holding time on the microstructure of high silicon hypereutectic high chromium cast iron was analyzed by optical microscope, scanning electron microscope and X-ray diffractometer. The hardness and wear resistance of high-silicon hypereutectic high-chromium cast iron quenched at 1150∘C for different time were tested by Rockwell hardness tester, microhardness tester and wear tester. The results show that the microstructure of as-cast high-silicon hypereutectic high-chromium cast iron is mainly composed of pearlite matrix and M7C3 carbide. Quenching heat treatment makes part of the matrix transform from pearlite to martensite, and precipitate a small amount of M[Formula: see text]C6 type secondary carbide. With the increase of quenching holding time from 1[Formula: see text]h to 6[Formula: see text]h, the amount of martensite transformation gradually increases, the primary carbide has no obvious change, the eutectic carbide tip dissolves, and the morphology gradually becomes smooth. The hardness and wear resistance both increase first and then decrease. After 4 hours of insulation, the hardness reaches the highest 60.5HRC, which is increased by 3 HRC compared to 1 hour of insulation. The wear resistance increases by 22.1% compared to 1 hour of insulation. At this time, the wear resistance is the best.

Strength Analysis of ST 41 Steel as Propeller Shaft with Quenching Heat Treatment and Tempering after Carburizing Carbon Media Variations

ST 41 steel is a low carbon steel which can be used for propeller shafts because it is categorized as a carbon steel permitted by BKI with a tensile strength requirement of 400 to 800 N/mm2. The propeller shaft deteriorates due to its surface frequently rubbing against the bearings. Carburizing is a technique used to increase the surface hardness by heating the specimen in a closed container containing mixture of carbon and a catalyst. The main objective of the subsequent quenching and tempering processes is to increase toughness and ductility while eliminating residual stresses. The achieved results are based on tests conducted on ST 41 steel with a measured carbon layer thickness of 229.12 μm, namely coal carbon media. Based on the results of wear tests, coal carbon media possesses a minimum value of 6.38287E-05 mm2/kg. In torsional testing, the maximum shear stress value for carbon media made from coconut shell charcoal is 429.79 MPa. When measuring hardness, coal carbon media has the highest value, which is 340.918 VHN. And metallographic testing shows that pearlite is the main phase in coal carbon media. The media with the most carbon is coal carbon, which 0.729% on the surface of the steel. Keywords: St 41 Steel, Carburizing, Wear, Hardness, Torsion, Chemical Composition, Micrograph.

Hot-forming of a 980 MPa third generation advanced high strength steel

This paper considers the effect of processing route on the final microstructure hardness and tensile behavior of a 980 MPa third generation advanced high strength steel (3G-AHSS). Of particular interest is the use of a hot stamping thermal schedule that mimics a quench and partition (Q&P) heat treatment process normally used to produce Q&P grade steel sheet. For comparison purposes, samples were also produced using a quench and temper (Q&T) processing history. The experiments were performed using a Gleeble 3500 thermo-mechanical simulator system. Large coupons were produced using both processing routes from which microstructure, hardness, and tensile samples were extracted. Mechanical properties results were compared with the as-received material. Both processing routes resulted in strength levels that were close to that of the as-received material; however, the total elongation of the Q&P processed samples was 52% higher than that of the Q&T processed material.

Effect of a modified quenching on impact toughness of 52100 bearing steels

In order to improve the uniformity of microstructures, and thus enhance the mechanical properties, especially the impact toughness, of 52100 bearing steels, modified quenching heat treatments with different austenitizing processes have been designed. The results show that 740 °C is the optimal holding temperature (approaching Ac1 = 750 °C) to improve the impact toughness of the steel by 37% after quenching and low-temperature tempering. Microstructure observations reveal that 740 °C holding shortens the nucleation incubation period of austenitization phase transformation, and inhibits the overfast growth of austenite in some regions, which leads to simultaneous nucleation and growth of austenite during austenitizing, and homogeneous dissolution of carbides in different austenite grains. The changes in microstructure evolution improve the microstructure uniformity (carbide and grain size) after quenching. Uniformly distributed carbides and grain size effectively reduce stress concentration and retard crack propagation during impact loading, thus resulting in high impact toughness.

Cubic-Shaped and Rod-Shaped YPO4 Nanocrystal-Doped Optical Fibers: Implications for Next Generation of Fiber Lasers

Engineering silica optical fibers by nanoparticle doping is a promising technology that allows the introduction of new functionalities and extends their applicable fields. However, the knowledge gap about the impact of the extreme fabrication temperatures on the nanoparticle features prevents field progress. Herein, we demonstrate that the particularities of fiber fabrication, such as fast-heating rates and quenching heat treatments, can be leveraged to explore unlikely phenomena at the nanoscale under standard laboratory conditions. Tetragonal cubic-shaped and monoclinic rod-shaped YPO4 nanocrystals are in situ nucleated in a silica-based fiber core glass, slightly modified with Ge and P, which shows for the first time, the possibility of doping optical fibers with this type of nanostructures, in terms of shape, composition, and structure of the nanocrystals. Structural and anisotropic differences allow engineering differently their shape and composition in the fiber core by tailoring the drawing temperature, as revealed by a thorough study consisting of scanning electron microscopy (SEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), electron energy loss spectroscopy (EELS), and high-resolution transmission electron microscopy (HRTEM). This work demonstrates, for the first time, the possibility of doping optical fibers fabricated by modified chemical vapor deposition (MCVD) with anisotropic nanostructures, as well as the stability of the monoclinic YPO4 phase. These findings open up new avenues to study shape-dependent properties of rare-earth orthophosphate (REPO4) nanostructures in optical fibers which will allow incorporating unprecedented functionalities and will have an impact in several fields of application, such as fiber lasers and optical fiber amplifiers, among others.